JP2006212973A - Extrusion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extrusion method which can effectively utilize a purge material and improve the moldability and mechanical properties of an extrusion material at the same time. <P>SOLUTION: The extrusion method conducts the preliminary process wherein a main raw material 81 containing a thermoplastic resin is extruded from an extruder 2 to obtain a preliminary material 82 and the extrusion process wherein the preliminary material 82 is added to the main raw material 81 to make a mixed raw material 83 and the mixed raw material 83 is extruded from the extruder 2 to obtain an extrusion material 8. The mixing ratio of the preliminary material 82 is within the range of 0.5-50.0 wt% to the whole of the mixed raw material 83. The main raw material 81 is used after selecting the one in which a re-extruded preliminary material, obtained by extruding the preliminary material 82 again from the extruder 2, shows an MFR value within the range of 1.03-1.30 times compared with an MFR value of the preliminary material 82. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an extrusion method for extruding a raw material containing a thermoplastic resin.

When a raw material containing a thermoplastic resin is melt kneaded and extruded in an extruder, the resin extruded material extruded when the extrusion is started does not have various physical properties. Products such as automobile interior materials, medical instruments, food containers and the like molded from the resin extruded material are required to comply with various strict product standards.
Therefore, the resin extruded material at the start of extrusion is purged (discharged) without being used in the product to be purged resin and discarded or reused for other purposes.

  And as a technique which reuses the purge resin at the time of an extrusion start, there exist some which were disclosed by patent document 1, for example. In Patent Document 1, when purging the molten resin, the purge resin discharged from the nozzle is filled in the receiving container in a molten state, and a molded product corresponding to the shape of the receiving container is formed. We use effectively.

However, the reuse application of the resin extruded material (purge resin) at the start of the extrusion is limited to applications where the product standards are moderate. Therefore, further ingenuity is required in order to use the resin extruded material at the start of extrusion more effectively.
On the other hand, for example, in automobile interior materials and the like, development of material blending techniques is actively performed in order to improve moldability. In particular, as moldability, it is essential to increase the fluidity (reduced viscosity) of the resin extruded material in order to enable thin-walled and high-speed molding in a low temperature state. However, the resin extruded material tends to generally decrease the mechanical properties due to high fluidization.

Japanese Patent Laid-Open No. 5-121723

  The present invention has been made in view of such conventional problems, and provides an extrusion method capable of effectively utilizing a purge material and simultaneously improving the moldability and mechanical properties of the extruded material. It is what.

The present invention includes a preliminary step of obtaining a preliminary material by extruding a main raw material containing a thermoplastic resin from an extruder;
The preliminary material is mixed with the main raw material to form a mixed raw material, and the mixed raw material is extruded from the extruder to obtain an extruded material.
The extrusion method is characterized in that the mixing ratio of the preliminary material to the whole mixed raw material is within the range of 0.5 to 50.0% by weight.

In the extrusion method of the present invention, the initial extruded material (purge material) extruded from the extruder at the start of extrusion is taken out as a spare material and is devised for effective use.
That is, in the present invention, first, as the preliminary step, the main raw material is extruded from an extruder to obtain a preliminary material. Next, in the extrusion step, the preliminary material is mixed with the main raw material to form a mixed raw material, and the mixed raw material is extruded from an extruder to obtain an extruded material.

Therefore, the extruded material is obtained by using a mixed raw material obtained by mixing the main raw material with a raw material which is extruded from the extruder and mixed with the main raw material having a modified formability (melt flowability). The moldability can be improved as compared with the conventional extruded material obtained by using. Thereby, when manufacturing a molded article using an extruded material, there is almost no molding unevenness (molding distortion), and a molded article having an excellent appearance can be obtained.
Moreover, the mechanical properties of the extruded material can be improved by mixing the above-mentioned preliminary material with the main raw material.

  In the present invention, the mixing ratio of the preliminary material is in the range of 0.5 to 50.0% by weight with respect to the entire mixed raw material. For this reason, it is possible to prevent the effect of improving the moldability from being reduced because the mixing ratio of the preliminary material is too small, and the mechanical properties from being deteriorated due to the excessive mixing ratio of the preliminary material. Thereby, both the moldability and mechanical properties of the extruded material can be improved.

Further, the initial extruded material (purging material) that has been conventionally discarded or used only for other applications can be used for the same application as the extruded material, and can be effectively utilized.
Therefore, according to the extrusion method of the present invention, the purge material can be effectively utilized, and the moldability and mechanical properties of the extrusion material can be improved at the same time.

A preferred embodiment of the present invention described above will be described.
In the present invention, when the mixing ratio of the preliminary material to the whole mixed raw material is less than 0.5% by weight, the moldability of the extruded material can hardly be improved. Further, in this case, when molding such as injection molding is performed from the above extruded material at a low temperature (200 ° C. or less), molding unevenness (molding distortion) occurs in the molded product, resulting in poor appearance. May occur.
On the other hand, when the mixing ratio of the preliminary material with respect to the whole mixed raw material exceeds 50% by weight, the mechanical properties of the extruded material may be significantly lowered. Further, in this case, when the molded product is molded by performing molding such as injection molding from the extruded material, the mechanical properties of the molded product may be significantly reduced.

The main raw material has a MFR value of a re-extrusion preliminary material obtained by extruding the preliminary material from the extruder again within a range of 1.03 to 1.30 times the MFR value of the preliminary material. It is preferable to use (Claim 2).
In this case, the main raw material has an MFR value (melt flow rate, melt) of the re-extruded preliminary material obtained by extruding this main raw material twice from the extruder as compared with the preliminary material obtained by extruding the main raw material once from the extruder. A value that appropriately increases the fluidity value) is used. Therefore, the moldability of the extruded material can be easily improved.

  Moreover, when the MFR value of the re-extruded preliminary material relative to the MFR value of the preliminary material is less than 1.03, the moldability of the extruded material cannot be improved much. On the other hand, when the MFR value of the re-extruded preliminary material exceeds 1.30 times the MFR value of the preliminary material, the mechanical properties of the extruded material may be significantly reduced.

The preliminary material is preferably mixed with the main raw material after pulverization, washing and dehydration.
In this case, impurities in the preliminary material can be appropriately eliminated, and the moisture content of the preliminary material can be adjusted appropriately.

The moisture content of the extruded material is preferably 0.2% by weight or less with respect to the entire extruded material (claim 4).
In this case, when molding the molded product by performing injection molding or the like on the extruded material, moisture contained in the extruded material is prevented from foaming and causing molding defects in the molded product. be able to. The water content of the extruded material is ideally reduced to 0% by weight, but it is considered that the water content is actually 0.01% by weight or more.

The thermoplastic resin is preferably a polyolefin resin.
In this case, it becomes easy to select a main raw material in which the MFR value of the re-extrusion preliminary material is in the range of 1.03 to 1.30 times the MFR value of the preliminary material. And it is easy to obtain the extrusion material which improved both the said moldability and mechanical property.

  The main raw material may contain an elastomer in addition to the thermoplastic resin. The content of the elastomer in the main raw material is preferably 10 times or less with respect to the content of the thermoplastic resin in the main raw material. If the elastomer content exceeds 10 times the thermoplastic resin content, it may be extremely difficult to grind the preliminary material.

  As the thermoplastic resin, a polyolefin resin such as polypropylene or polyethylene, or a thermoplastic resin such as polystyrene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polyamide, polycarbonate, or the like can be used alone. Two or more kinds of plastic resins can be mixed and used.

Moreover, as said elastomer, elastomers, such as an olefin type, a styrene type, or a vinyl chloride type, can be used independently, and 2 or more types of these elastomers can also be mixed and used.
Moreover, the said main raw material can contain the filler (filler) besides a thermoplastic resin. As this filler, fillers such as talc, mica, silica, calcium carbonate or glass fiber can be used alone, or two or more of these fillers can be mixed and used.

The main raw material can contain additives in addition to the thermoplastic resin. As this additive, an additive such as an antioxidant, an antistatic agent, a weathering stabilizer, a lubricant or an antiblocking agent can be used alone, or a mixture of two or more of these additives can be used. You can also.
The main raw material can also contain a colorant such as a pigment or a dye in addition to the thermoplastic resin.

Below, the Example concerning the extrusion method of this invention is described with FIGS.
In the extrusion method of this example, the initial extruded material (purge material) 820 extruded from the extruder 2 at the start of extrusion is taken out as a spare material 82 and is devised for effective use.
That is, as shown in FIG. 1, in this example, first, a preliminary process is performed in which a main raw material 81 containing a thermoplastic resin is extruded from the extruder 2 to obtain a preliminary material 82. Next, the preliminary material 82 is mixed with the main raw material 81 to form a mixed raw material 83, and the mixed raw material 83 is extruded from the extruder 2 to obtain an extruded material 8.

The main raw material 81 has a MFR value of the re-extruded preliminary material obtained by extruding the preliminary material 82 from the extruder 2 again, and is 1.03 to 1.30 times higher than the MFR value of the preliminary material 82. Select one that falls within the range.
Further, the mixing ratio of the preliminary material 82 is within a range of 0.5 to 50.0 wt% with respect to the entire mixed raw material 83 in order to define the mixing ratio and the mechanical properties of the extruded material 8 to be improved. To do.
The main raw material 81 refers to a pure raw material before being extruded from the extruder 2.
This will be described in detail below.

In the extrusion method of this example, as shown in FIGS. 2 and 3, an extruder 2 that performs extrusion, a raw material silo 21 that stores raw materials to be supplied to the extruder 2, a raw material received from the raw material silo 21, and an extruder An extruded material 8 is formed by an extrusion processing line 1 in which a raw material supply feeder 22 for supplying a raw material at a predetermined flow rate to 2 is disposed. The extrusion processing line 1 is provided with a raw material mixing mixer 23 for mixing the preliminary material 82 taken out from the extruder 2 with the main raw material 81 and supplying the mixed raw material 81 to the raw material silo 21.
The main raw material 81 in this example is obtained by mixing talc as a filler and an additive into a resin composite raw material 81A obtained by mixing a polyolefin resin as a thermoplastic resin and an olefin elastomer. The main raw material 81 may not contain an elastomer or a filler.

  2 and 3, the raw material silo 21 of the present example stores the first raw material silo 21A for storing the resin composite raw material 81A or the mixture 80 of the resin composite raw material 81A and the spare material 82, and the filler. Second material silo 21B. The raw material supply feeder 22 receives the resin composite raw material 81A or the mixture 80 from the first raw material silo 21A, and supplies the resin composite raw material 81A or the mixture 80 to the extruder 2 at a predetermined flow rate. It consists of a second raw material supply feeder 22B that receives the filler from the second raw material silo 21B and supplies the filler to the extruder 2 at a predetermined flow rate.

  Further, as shown in FIG. 2, the extrusion processing line 1 includes a cooling water tank 31 for cooling the strand-like extruded material 8 extruded from the extruder 2, a strand cutter 32 for cutting the extruded material 8 to a predetermined length, and a cut. A vibration sorter 33 that sorts and sorts the pelletized extruded material 8, a blend silo 34 that mixes the sorted extruded material 8, and a packaging machine 35 that packs the mixed extruded material 8 into a flexible container or a cassette can. Set up.

  Further, as shown in FIG. 4, the preliminary material 82 of this example is taken out from the extruder 2, pulverized, washed, and dehydrated, and then mixed with the resin composite raw material 81 </ b> A. That is, in the above extrusion method, the preliminary material 82 to be mixed with the resin composite raw material 81A is prepared by the preliminary treatment line 4 that pulverizes, cleans and dehydrates the initial extruded material (purge material) 820 taken out from the extruder 2. produce.

As shown in FIG. 4, the preliminary processing line 4 includes a dry pulverizer 41 for pulverizing the purge material 820, a cleaning dehydrator 42 for performing cleaning dehydration on the pulverized raw material pulverized in the dry pulverizer 41, and cleaning dehydration. And a catcher tank 43 for storing the pulverized raw material after being disposed.
The preliminary material 82 of this example is crushed, washed and dehydrated in the preliminary processing line 4 so that impurities are appropriately removed and the moisture content is appropriately adjusted. To the raw material mixing mixer 23.

Next, a method for extruding the extruded material 8 using the extrusion processing line 1 and the preliminary processing line 4 will be described in detail.
In starting the extrusion, first, as shown in FIGS. 1 and 3, as the preliminary process, in the extrusion processing line 1, the resin composite raw material 81A is introduced into the first raw material silo 21A, and the second The filler is charged into the raw material silo 21B.
Next, the resin composite raw material 81A is supplied from the first raw material silo 21A to the first raw material supply feeder 22A, and the filler is supplied from the second raw material silo 21B to the second raw material supply feeder 22B. Then, the resin composite raw material 81A adjusted to a predetermined flow rate is supplied from the first raw material supply feeder 22A to the extruder 2, and the filler adjusted to the predetermined flow rate is extruded from the second raw material supply feeder 22B. Supplied to the machine 2.

Next, the initial extruded material (purge material) 820 extruded from the extruder 2 at the start of extrusion is taken out. It should be noted that the amount of purge material 820 taken out can be the amount that is pushed out after the operation of the extruder 2 is started until the operation is stabilized.
Next, as shown in FIG. 4, in the preliminary processing line 4, the purge material 820 is charged into the dry pulverizer 41 and pulverized, and the pulverized raw material after the pulverization is conveyed to the washing and dehydrator 42. Next, the pulverized raw material is washed and dehydrated in the washing and dehydrator 42, and then the pulverized raw material after the washing and dehydration is stored in the catcher tank 43. In this way, the preliminary | backup material 82 which consists of a grinding | pulverization raw material after washing | cleaning dehydration is obtained.

  The purge material 820 is received in a rust-proof receiving box (in this example, a stainless steel receiving box), cooled, and then charged into the dry pulverizer 41. Further, when storing the purge material 820 before putting it into the dry pulverizer 41, a storage box having a drain hole for draining water at the bottom and an open / close lid for preventing foreign matter from being mixed at the top is used. be able to. Moreover, it is preferable that this storage box is rust-proofed.

Next, as the extruding step, an extruded material is obtained using a mixed raw material 83 obtained by mixing a preliminary material 82 obtained by pulverizing, washing and dewatering the purge material 820 with the main raw material 81.
That is, as shown in FIGS. 1 and 2, in the extrusion processing line 1, the resin composite raw material 81 </ b> A and the preliminary material 82 are introduced into the raw material mixing mixer 23 at a predetermined ratio. Mix. A mixture 80 of the resin composite raw material 81A and the spare material 82 is supplied to the first raw material silo 21A. In addition, the second raw material silo 21B is charged with a filler.

Next, the mixture 80 is supplied from the first raw material silo 21A to the first raw material supply feeder 22A, and the filler is supplied from the second raw material silo 21B to the second raw material supply feeder 22B. Then, the mixture 80 in a state adjusted to a predetermined flow rate is supplied from the first raw material supply feeder 22A to the extruder 2, and the filler adjusted to a predetermined flow rate is supplied from the second raw material supply feeder 22B to the extruder 2. To be supplied.
Thus, the mixed raw material 83 obtained by mixing the preliminary material 82 at a ratio of 5.0 to 50.0% by weight with respect to the total amount of the main raw material 81 including the resin composite raw material 81A and the filler is supplied to the extruder 2. .

Next, the mixed raw material 83 is extruded from the extruder 2 to obtain an extruded material 8. Further, in the extruder 2, unnecessary moisture is removed by evaporation, so that the moisture content in the entire extruded material 8 is 0.2% by weight or less.
Then, the strand-shaped extruded material 8 extruded from the extruder 2 passes through the two cooling water tanks 31, is cooled, and is cut into a predetermined length by the strand cutter 32. Next, in the vibration sorter 33, the pellet-shaped extruded material 8 cut by the strand cutter 32 is sorted and sorted, and the pellet-shaped extruded material 8 selected as a good product is mixed in the blend silo 34. Thereafter, the pellet-shaped extruded material 8 mixed in the blend silo 34 is conveyed to the packaging machine 35, and the pellet-shaped extruded material 8 is packed in a flexible container or a cassette can in the packaging machine 35 and shipped.

  Further, when the extruded material 8 is obtained by extruding the mixed raw material 83 and the preliminary material 82 is used up, the main raw material 81 can be extruded again to create the preliminary material 82. And the extrusion material 8 can be obtained from the mixed raw material 83 produced using this preliminary | backup material 82, and the extrusion material 8 can be obtained by repeating the same operation | work repeatedly after that.

As described above, the extruded material 8 uses the mixed raw material 83 formed by mixing the main raw material 81 with the preliminary material 82 whose formability (melt flowability) has been modified by extruding the main raw material 81 from the extruder 2. As a result, the moldability can be improved as compared with the conventional extruded material obtained using only the main raw material 81. Thereby, when a molded product is manufactured using the extruded material 8, there is almost no molding unevenness (molding distortion), and a molded product excellent in appearance can be obtained.
Moreover, the mechanical properties of the extruded material 8 can be improved by mixing the preliminary material 82 with the main raw material 81.

  In this example, the mixing ratio of the preliminary material 82 is in the range of 0.5 to 50.0% by weight with respect to the entire mixed raw material 83. For this reason, it is possible to prevent the mixing ratio of the preliminary material 82 from becoming too small and the effect of improving the moldability to be diminished, and the mixing ratio of the preliminary material 82 from being increased too much to deteriorate the mechanical properties. it can. Thereby, both the moldability and mechanical properties of the extruded material 8 can be improved.

Further, the initial extruded material (purging material) 820 that has been conventionally discarded or used only for other applications can be used for the same application as the extruded material 8 and can be used effectively.
Therefore, according to the extrusion method of this example, the purge material 820 can be used effectively, and the moldability and mechanical properties of the extrusion material 8 can be improved at the same time.

(Confirmation test)
In this example, a confirmation test for confirming the moldability and mechanical properties of the extruded material 8 extruded by the above extrusion method was performed.
In this confirmation test, the MFR value of the extruded material 8 obtained from the preliminary material 82 and the mixed raw material 83 was measured, and a molded product molded using the extruded material 8 obtained from the mixed raw material 83 (invention products 1 to 1). For 6), the appearance was visually evaluated and various mechanical properties were measured. Further, for comparison, the appearance of the molded products (comparative products 1 to 3) molded from the extruded material obtained without using the mixed raw material 83 was also visually evaluated and various mechanical properties were measured. .

(Invention 1)
Main raw material 81 contains 56.8% by weight of polypropylene (thermoplastic resin), 22.7% by weight of olefin elastomer and 20.5% by weight of talc (filler), and contains additives and the like. It was supposed to be.
And the MFR value of the preliminary | backup material 82 obtained by melt-kneading and extruding this main raw material 81 in the extruder 2 was 37.5 g / 10min.

Further, the MFR value of the re-extruded preliminary material obtained by melt-kneading and extruding the preliminary material 82 in the extruder 2 was 40.5 g / 10 minutes. And the MFR value of the re-extrusion preliminary material with respect to the MFR value of the preliminary material 82 was 1.08 times. In addition, the preliminary material 82 was mixed at a ratio of 5.0 wt% with respect to the main raw material 81 to obtain a mixed raw material 83.
The MFR values of the preliminary material 82 and the re-extruded preliminary material were measured under the conditions of a temperature of 230 ° C. and a load of 2.16 kgf (21.2 N).
Further, the extruded product 8 was dried, and the molded product obtained by injection molding under the condition of the cylinder temperature of 180 ° C. using the extruded product 8 having a moisture content of 0.1% by weight was referred to as invention product 1. did.

(Invention 2)
The preliminary material 82 of the invention 1 was mixed with the main material 81 of the invention 1 at a ratio of 10.0% by weight to obtain a mixed material 83. Also in this mixed raw material 83, the composition other than the above is the same as that of the invention product 1, and a molded product obtained by injection molding in the same manner as the invention product 1 was designated as the invention product 2.

(Invention 3)
The preliminary material 82 of the invention 1 was mixed at a ratio of 20.0 wt% with respect to the main material 81 of the invention 1 to obtain a mixed material 83. Also in this mixed raw material 83, the composition other than the above is the same as that of the inventive product 1, and a molded product obtained by performing injection molding in the same manner as the inventive product 1 was designated as the inventive product 3.

(Invention 4)
The preliminary material 82 of the invention 1 was mixed with the main material 81 of the invention 1 at a ratio of 30.0% by weight to obtain a mixed material 83. Also in this mixed raw material 83, the composition other than the above is the same as that of the invention product 1, and a molded product obtained by injection molding in the same manner as the invention product 1 was designated as the invention product 4.

(Invention 5)
The main raw material 81 was formed by adding an additive or the like to a polypropylene composite resin having a composition of 45.0% by weight of polypropylene (thermoplastic resin) and 55.0% by weight of olefin elastomer.
And the MFR value of the preliminary | backup material 82 obtained by melt-kneading and extruding this main raw material 81 in the extruder 2 was 13.0 g / 10min.

Further, the MFR value of the re-extruded preliminary material obtained by melt-kneading and extruding the preliminary material 82 in the extruder 2 was 13.9 g / 10 minutes. And the MFR value of the re-extrusion preliminary material with respect to the MFR value of the preliminary material 82 was 1.07 times. In addition, the preliminary material 82 was mixed at a ratio of 5.0 wt% with respect to the main raw material 81 to obtain a mixed raw material 83.
The MFR values of the preliminary material 82 and the re-extruded preliminary material were measured under the conditions of a temperature of 230 ° C. and a load of 2.16 kgf (21.2 N).
Further, a molded product obtained by drying the extruded material 8 and performing injection molding under the condition of a cylinder temperature of 180 ° C. using the extruded material 8 having a moisture content of 0.08% by weight is referred to as invention product 5. did.

(Invention 6)
The preliminary material 82 of the invention 5 was mixed at a ratio of 20.0 wt% with respect to the main material 81 of the invention 5 to obtain a mixed material 83. Also in this mixed raw material 83, the composition other than the above is the same as that of the invention product 5, and a molded product obtained by injection molding in the same manner as the invention product 5 is designated as the invention product 6.

(Comparative product 1)
A product obtained by extruding the same main raw material 81 as the invention product 1 from the extruder 2 is used as an extrusion material, and a molded product obtained by injection molding in the same manner as the invention product 1 is used as the comparison product 1 did.

(Comparative product 2)
The same main raw material 81 as that of the invention product 1 is extruded from the extruder 2 to be a spare material 82. The re-extruded preliminary material obtained by extruding the preliminary material 82 from the extruder 2 again is used as an extruded material, and this extruded material is used. A molded product obtained by injection molding in the same manner as the product 1 of the invention was used as a comparative product 2.

(Comparative product 3)
The same main raw material 81 as that of the inventive product 5 is extruded from the extruder 2 as an extruded material, and a molded product obtained by performing injection molding in the same manner as the inventive product 5 using the extruded material is compared with the comparative product 3 did.

  About the said invention products 1-6 and the comparative products 1-3, the moldability of the extrusion material 8 is evaluated by the external appearance (the presence or absence of shaping | molding nonuniformity) of the molded product shape | molded from the extrusion material, and the mechanical physical property of the extrusion material 8 is tensile. Yield point stress, Tensile strength at break, Tensile strength at break, Bending stress, Flexural modulus, Izod impact strength (23 ℃), Thermal deformation temperature (0.45MPa load), Rockwell hardness (R scale), Tear strength, It was evaluated by compression set.

About the said invention products 1-6 and the comparative products 1-3, the external appearance of a molded product was observed visually and the result of having measured various mechanical physical properties is shown in Table 1.
In the same table, it was found that Inventions 1 to 6 were excellent in appearance without molding defects such as molding unevenness in the appearance of the molded product. On the other hand, it was found that the comparative products 1 and 3 had molding defects such as molding unevenness in the appearance of the molded product, and the appearance was not so excellent.
Moreover, it turned out that the invention products 1-6 are excellent in the various mechanical physical properties of a molded article. On the other hand, it was found that the comparative product 1 is slightly inferior in various mechanical properties as compared with the inventive products 1 to 4, and the comparative product 2 is greatly inferior in various mechanical properties as compared with the inventive products 1 to 4.

Explanatory drawing which shows typically the extrusion method in an Example. Explanatory drawing which shows the state which manufactures an extrusion material in the extrusion process line in an Example. Explanatory drawing which shows the state which takes out a preliminary | backup material in the extrusion process line in an Example. Explanatory drawing which shows the preliminary processing line in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extrusion processing line 2 Extruder 4 Pretreatment line 8 Extrusion material 81 Main raw material 82 Spare material 820 Purge material 83 Mixed raw material

Claims (5)

A preliminary step of obtaining a preliminary material by extruding a main raw material containing a thermoplastic resin from an extruder;
The preliminary material is mixed with the main raw material to form a mixed raw material, and the mixed raw material is extruded from the extruder to obtain an extruded material.
An extrusion method characterized in that the mixing ratio of the preliminary material to the whole mixed raw material is in the range of 0.5 to 50.0% by weight.   2. The main raw material according to claim 1, wherein the MFR value of the re-extruded preliminary material obtained by extruding the preliminary material from the extruder again is 1.03 to 1.30 times the MFR value of the preliminary material. An extrusion method characterized by using a material that falls within the range.   3. The extrusion method according to claim 1, wherein the preliminary material is mixed with the main raw material after being pulverized, washed and dehydrated.   The extrusion method according to any one of claims 1 to 3, wherein the moisture content of the extruded material is 0.2% by weight or less based on the entire extruded material.   The extrusion method according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyolefin resin.

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