JP7389342B2 - Filament manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a filament that can be used in a thermofusion type 3D printer.

The filament for 3D printers (striated resin molded body) disclosed in Patent Document 1 includes an inner layer (first layer) and an outer layer (second layer) that covers this, and the physical properties of the outer layer are different from those of the inner layer. There is. By using such filaments, it has become possible to improve mechanical suitability and quality in 3D printing.

Japanese Patent Application Publication No. 2016-193602

By the way, depending on the purpose of 3D printing, it may be desirable to make the outer layer as thin as possible. The thickness of the outer layer can be reduced by reducing the speed at which the resin composition for forming the outer layer is extruded from the extruder. One method for reducing the extrusion speed of the resin composition is to reduce the rotational speed of the screw, but lowering the rotational speed of the screw destabilizes the extrusion speed of the resin composition, resulting in a decrease in the thickness of the outer layer. It was found that there may be variations in the quality.

The present invention has been made in view of the above circumstances, and provides a method for producing a filament that can stably produce a filament with a thin outer layer.

According to the present invention, there is provided a method for producing a filament in which an inner layer is coated with an outer layer, and the method includes a coating step, and in the coating step, the outer layer resin is extruded from the extruder by rotating a screw of the extruder. A method is provided, wherein the composition is used to form the outer layer covering the inner layer, and the screw has a [screw pitch/screw diameter] value of 0.1 to 0.9.

The value of [screw pitch P/screw diameter D] calculated from the screw pitch P and screw diameter D shown in Fig. 1 (hereinafter referred to as "P/D value") is generally set to 1. In the present invention, the P/D value is set to a relatively low value of 0.1 to 0.9. When the P/D value is lowered, the amount of resin composition extruded per one rotation of the screw decreases, and the extrusion speed of the resin composition is less likely to become unstable even when the rotational speed of the screw is lowered. Become. Therefore, according to the present invention, the extrusion speed of the resin composition for forming the outer layer can be easily reduced, and a filament with a thin outer layer can be stably manufactured.

Various embodiments of the present invention will be illustrated below. The embodiments shown below can be combined with each other.

Preferably, the method described above is a method in which the number of revolutions of the screw is 0.1 to 4.0 rpm.
Preferably, in the method described above, in the coating step, the inner layer is coated with the outer layer by coextruding an inner layer resin composition constituting the inner layer and the outer layer resin composition from an extrusion head. It's a method.
Preferably, in the method described above, the filament has a value of [average thickness of the outer layer/average diameter of the filament] of 0.1 to 3%.

FIG. 2 is an explanatory diagram of the screw pitch P and screw diameter D of the screw in the cylinder of the extruder. A filament 10 according to a first embodiment of the present invention is shown, with FIG. 2A being a perspective view and FIG. 2B being a sectional view. A manufacturing line 30 for manufacturing the filament 10 of the first embodiment of the present invention is shown, with FIG. 3A being a front view and FIG. 3B being a plan view. FIG. 3B is an exploded perspective view of the mold 32 in FIG. 3A. FIG. 3B is a plan view corresponding to FIG. 3B, showing a manufacturing line 30 for manufacturing a filament 10 according to a second embodiment of the present invention.

Embodiments of the present invention will be described below. Various features shown in the embodiments described below can be combined with each other. Further, the invention can be realized independently for each feature.

1. First embodiment 1-1. Configuration of filament 10 As shown in FIG. 2, filament 10 has an inner layer 21 and an outer layer 22 covering the inner layer 21. The outer layer 22 is made of a different material than the inner layer 21. The filament 10 is linear, the inner layer 21 is preferably cylindrical, and the outer layer 22 is preferably cylindrical.

The inner layer 21 and the outer layer 22 are composed of an inner layer resin composition and an outer layer resin composition, respectively. The inner layer resin composition and the outer layer resin composition each contain a thermoplastic resin and may also contain an additive. The inner layer resin composition and the outer layer resin composition differ in at least one of the composition of the thermoplastic resin, the type of additive, and the amount of additive added.

Examples of thermoplastic resins include amorphous resins such as ABS resin, polystyrene, polyvinyl chloride, polymethyl methacrylate, polycarbonate, and modified polyphenylene ether, polyolefin resins such as polyethylene and polypropylene, and crystalline resins such as polyester, polyamide, and polyvinyl alcohol. , olefin-based, styrene-based, polyester-based, urethane-based thermoplastic elastomers, and mixtures thereof.

Examples of additives include inorganic additives such as carbon black, carbon fiber, glass fiber, talc, mica, nanoclay, and magnesium, antioxidants, lubricants, and colorants.

The outer layer 22 is provided to impart functionality to the filament 10, such as weldability, formability, conductivity, and barrier properties. For example, if the weldability of the inner layer 21 is not good, the weldability of the filament 10 can be improved by forming the outer layer 22 using a composition that has better weldability than the composition constituting the inner layer 21. be able to.

During 3D printing, the filament 10 is transferred within the head by rotating a gear provided on the 3D print head with the gear biting into the filament 10. However, when the inner layer 21 is made of a soft material, In some cases, the inner layer 21 deforms as the gear rotates, making it impossible to transfer the filament 10. In such a case, forming the outer layer 22 using a harder composition than the composition constituting the inner layer 21 makes it easier to transport the filament 10 with a gear, improving moldability.

When imparting electrical conductivity to the filament 10, the outer layer 22 is formed using a conductive composition (for example, a resin containing a conductive material such as carbon) to impart electrical conductivity to the entire filament 10. Conductivity can be achieved with a smaller amount of conductor than when adding a conductor.

If the inner layer 21 is easily deteriorated by oxygen, water, etc., the weldability of the filament 10 can be improved by forming the outer layer 22 using a composition that has better barrier properties than the composition constituting the inner layer 21. can be done. In one example, the inner layer 21 is a shape memory polymer made of thermoplastic urethane, and the outer layer 22 is PETG (polyethylene terephthalate copolymerized with a material called cyclohexanedimethanol).

Although the outer layer 22 can provide various functionalities as described above, the functionality of the inner layer 21 may be difficult to express due to the outer layer 22. For example, if the inner layer 21 is made of a shape memory material and the outer layer 22 is not made of a shape memory material, the thicker the outer layer 22, the lower the shape memory properties of the filament 10. Furthermore, even if the outer layer 22 is thin, the functions of the outer layer 22 may be fully expressed.

In such a case, it is desirable to reduce the thickness of the outer layer 22. Specifically, the value of [average thickness Tav of outer layer 22/average diameter Dav of filament 10] (Tav/Dav value) is preferably 0.1 to 3%. If the Tav/Dav value is too small, the function of the outer layer 22 tends to be insufficient. If the Tav/Dav value is too large, the function of the inner layer 21 tends to be insufficiently expressed. Specifically, the Tav/Dav value is, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3%, and the range between any two of the numerical values exemplified here. It may be within. The average diameter Dav of the filament 10 is, for example, 1 to 3 mm, specifically, for example, 1, 1.5, 2, 2.5, 3 mm, and the range is between any two of the numerical values exemplified here. It may be within. The average diameter Dav of the filament 10 is calculated by measuring the diameter Da of the filament 10 at five points at 10 mm intervals along the longitudinal direction of the filament 10 and averaging the measured values. The average thickness Tav of the outer layer 22 is, for example, 5 to 60 μm, specifically, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 μm, where It may be within the range between any two of the illustrated numerical values. The average thickness Tav of the outer layer 22 is calculated by measuring the thickness Ta at each of 5 points at 10 mm intervals along the longitudinal direction of the filament 10 and at 4 points at 90 degree intervals, and averaging the measured values. .

1-2. Manufacturing method for filament 10 As shown in FIG. 3, the manufacturing line 30 for filament 10 includes extruders 31A and 31B, a mold 32, a sizing device 33, a water tank 37, a fixed roller 41, an outer diameter dimension measuring device 42, and a winding device. It includes a device 43.

The extruders 31A and 31B melt and knead the raw resin composition and continuously supply it to the mold 32, and include, for example, a cylinder with a built-in screw, hoppers 31a and 31b for inputting raw materials, and an injection nozzle. It is configured with the following. Extruders 31A, 31B are preferably arranged orthogonally. The screws of the extruders 31A and 31B are not particularly limited, but are preferably single screws.

The extruder 31A rotates a screw in the cylinder to melt and knead the inner layer resin composition and extrude it from the injection nozzle into the mold 32. The extruder 31B melts and kneads the outer layer resin composition and extrudes it from the injection nozzle. It is extruded into a mold 32. The inner layer resin composition and the outer layer resin composition extruded from the extruders 31A and 31B are combined in the mold 32, and the periphery of the inner layer 21 serving as the core is covered with the outer layer 22.

In order to reduce the thickness of the outer layer 22, it is necessary to reduce the extrusion speed of the outer layer resin composition from the extruder 31B. Even in a general extruder having a screw with a P/D value of 1, the extrusion speed can be reduced by lowering the rotation speed of the screw, but it is possible to reduce the rotation speed of such a screw to, for example, 4 rpm or less. Then, it was found that sufficient pressure was not applied to the resin composition in the cylinder, resulting in a problem that the extrusion speed was unstable. Therefore, when using a general extruder having a screw with a P/D value of 1, the filament 10 having an extremely thin outer layer 22 with a Tav/Dav value of 0.1 to 3% can be stably produced. It was difficult to manufacture it.

On the other hand, in this embodiment, an extruder having a screw with a relatively low P/D value of 0.1 to 0.9 is used as the extruder 31B. When the P/D value is lowered, the amount of resin composition extruded per one rotation of the screw decreases, and even when the rotational speed of the screw is lowered, the pressure applied to the resin composition in the cylinder becomes extremely high. It was found that the extrusion rate did not decrease and the extrusion rate was less likely to become unstable. For this reason, by extruding the outer layer resin composition little by little from an extruder having a screw with such a P/D value, an extremely thin outer layer 22 having a Tav/Dav value of 0.1 to 3% is formed. It was found that the filament 10 could be stably manufactured.

The P/D value of the screw of the extruder 31B is 0.1 to 0.9, preferably 0.4 to 0.8, and specifically, for example, 0.1, 0.2, 0. .3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and may be within the range between any two of the numerical values exemplified here. Further, the rotational speed of the screw of the extruder 31B is, for example, 0.1 to 4.0 rpm, specifically, for example, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 rpm, and may be within a range between any two of the numerical values exemplified here.

Note that the extruder 31A does not need to discharge a small amount like the extruder 31B, so a general extruder having a screw with a P/D value of 1, for example, can be used as the extruder 31A. .

The mold 32 horizontally extrudes the molten resin from the extruder 31, and the molten resin extruded from the mold 32 is cooled and becomes the filament 10. As the mold 32, for example, a multilayer mold as shown in FIG. 4 may be used. The multilayer mold of this example is a combination of three mold members 32A, 32B, and 32C, and each mold member 32A, 32B, and 32C has a central flow path N1, N2, and N3, respectively. .

The mold member 32B has an internal circular mold part CB surrounding the central channel N2, and has four through channels R1, R2, R3, and R4 around the circular mold part CB. The through channels R1, R2, R3, and R4 are each formed to penetrate the mold member 32B in the thickness direction. The circular mold portion CB has a central flow path N2 formed in its center, and is formed such that its circular surface recedes from the mold surface of the mold member 32B.

The mold member 32C has an annular passage CR surrounding the central passage N3, and has a semicircular intermediate passage HR outside the annular passage CR. This semicircular intermediate passage HR is connected to the annular flow passage CR at a 180° symmetrical position. Furthermore, the mold member 32C has a material supply passage X connected to one location of the intermediate passage HR. The annular channel CR faces the through channels R1, R2, R3, and R4 of the mold member 32B.

In the mold 32 in which the three mold members 32A, 32B, and 32C are combined, the inner layer resin composition is extruded from the extruder 31A, supplied to the central flow path N3 of the mold member 32C, and is fed to the mold member 32B. is pulled out from the mold 32 through the central flow path N2 of the mold member 32A and the central flow path N1 of the mold member 32A. On the other hand, the outer layer resin composition is extruded from the extruder 31B and supplied to the material supply passage X of the mold member 32C. The raw resin composition supplied from here flows into the annular channel CR through the semicircular intermediate channel HR, and each through channel of the mold member 32B provided opposite to the annular channel CR. It is supplied to R1, R2, R3, and R4. The raw resin material supplied to the through channels R1, R2, R3, and R4 flows into the space between the mold surface of the mold member 32A and the circular mold part CB that is formed in a receding shape. , coats the circumferential surface of the inner layer 21 drawn out from the central channel N2 provided in the circular mold part CB.

The water tank 37 is formed in a long box shape along the transport direction of the filament 10. The filament 10 is introduced into the water tank 37 from the wall of one end of the water tank 37, and is led out from the wall of the other end of the water tank 37. The water tank 37 stores water 37a for immersing the filament 10 and cooling the filament 10.

The sizing device 33 is disposed inside the wall of one end of the water tank 37, and has the function of making the cross section of the filament 10 a perfect circle and making the outer diameter of the filament 10 uniform to a predetermined size.

The fixed roller 41 stabilizes the posture of the filament 10 in the water tank 37 via the sizing device 33 and conveys the filament 10 toward the winding device 43 side.

The outer diameter measuring device 42 measures the outer diameter of the filament 10 cooled in the water tank 37 . The winding device 43 includes a pair of upper and lower winding rollers 43a that transport the filament 10 downstream after passing through the outer diameter measurement device 42, and a winding device that is arranged downstream of the winding roller 43a and winds the filament 10. A bobbin winder 43b having a take-up shaft 43c is provided.

Next, a method for manufacturing filament 10 using this manufacturing line 30 will be explained. The method for manufacturing filament 10 includes an extrusion process, a sizing process, a cooling process, a dimension measurement process, and a winding process.

As shown in FIG. 3, in the extrusion process, resin pellets introduced from a hopper 31a are melted in an extruder 31, and the molten resin is extruded from a mold 32. At this time, the inner layer 21 is extruded and the outer layer 22 is extruded so as to cover the inner layer 21, thereby extruding the multilayered filament 10. In this example, a filament 10 having an outer diameter (indicated by reference numeral D1) of 2.2 mm is extruded from the mold 32.

In the sizing process, the filament 10 is formed to have a uniform outer diameter in the sizing device 33. In this example, the filament 10 having an outer diameter D1 of 2.2 mm passes through the sizing device 33, so that its outer diameter (indicated by reference numeral D2) is made uniform to 1.80 mm in the transport direction.

In the cooling process, the filament 10 having an outer diameter (indicated by code D2) of 1.80 mm is cooled by passing through a water tank 37, and the outer diameter of the filament 10 (indicated by code D3) is reduced to 1.75 mm. Ru.

In the dimension measurement step, the outer diameter of the filament 10 is measured, and it is determined whether the measured value is an appropriate size. In this example, it is determined whether the outer diameter of the filament 10 is within a predetermined standard width centered around 1.75 mm. If the outer diameter of the filament 10 is outside the standard width range, each manufacturing condition is reviewed so that the outer diameter is within the standard width range.

In the winding process, when the outer diameter of the filament 10 is within the standard range, the winding roller 43a of the winding device 43 sends it to the bobbin winding machine 43b, and the continuous body of filament 10 is wound around the winding shaft 43c. To go. After a predetermined length of filament 10 has been wound onto the winding shaft 43c, the filament 10 is wound onto a new winding shaft 43c.

Through the above steps, the filament 10 wound around the winding shaft 43c can be manufactured.

2. Second Embodiment In the first embodiment, the inner layer 21 was made of the inner layer resin composition extruded from the extruder 31A, but in this embodiment, the inner layer 21 is made of continuous fibers. Continuous fibers are fibers that extend continuously along the longitudinal direction of the filament 10. The continuous fibers are preferably provided over the entire length of the filament 1. The continuous fiber may be a single fiber or a bundle of multiple fibers. Examples of continuous fibers include those containing at least one of continuous reinforcing fibers that do not melt during shaping and continuous resin fibers that melt during shaping. Examples of continuous reinforcing fibers include inorganic fibers such as glass fibers, carbon fibers, and metal fibers (such as steel fibers), and organic fibers such as aramid fibers. Examples of continuous resin fibers include the thermoplastic resin fibers listed in the first embodiment. Even in the filament 10 having such a configuration, it may be desirable to make the outer layer 22 thin, as in the first embodiment.

The filament 10 of this embodiment can be manufactured using a manufacturing line 30 shown in FIG. The production line 30 of this embodiment is the same as the first embodiment except that it includes a continuous fiber roll 45 instead of the extruder 31A and a continuous fiber coating die 46 instead of the die 32.

The continuous fiber roll 45 is a roll around which continuous fibers 45a are wound, and by unwinding the continuous fibers 45a from the continuous fiber roll 45, the continuous fibers 45a can be supplied to the mold 46.

The mold 46 is configured to cover the peripheral surface of the continuous fibers 45a with the outer layer resin composition extruded from the extruder 31B.

As explained in the first embodiment, the extruder 31B is configured to be able to extrude the outer layer resin composition little by little, so in this embodiment as well, the resin composition extruded from the extruder 31B By covering the inner layer 21 made of continuous fibers 45a, it is possible to stably produce a filament 10 having an extremely thin outer layer 22 with a Tav/Dav value of 0.1 to 3%. .

In the production line 30 of the first embodiment, the operating conditions of the extruder 31B were set as shown in Table 1, and the filament 10 was produced. As for the extruder 31A, an extruder having a screw with P/D=1.0 was used, and the screw was rotated under conditions such that the resin pressure in the cylinder was 14.2 MPa. As the inner layer resin composition, a polyurethane shape memory polymer (model: MM-3520, manufactured by SMP Technologies Co., Ltd.) was used, and as the outer layer resin composition, PETG (model: GN401, manufactured by Eastman Chemical Co., Ltd.) was used. there was.

In Examples 1 and 2, although the screw rotational speeds were set to low values of 1.3 rpm and 3.2 rpm, respectively, the resin pressure in the cylinder did not drop significantly. In Comparative Example 1, when the screw rotation speed was set to 4.5 rpm, the resin pressure in the cylinder became significantly lower than in the example. In Comparative Example 2, the number of revolutions of the screw was increased so that the resin pressure in the cylinder was at the same level as in the example.

Regarding the obtained filament 10, the average diameter Dav of the filament 10 and the average thickness Tav of the outer layer 22 were measured, and the Tav/Dav value was calculated. The results are shown in Table 1.

Furthermore, the filament formability was evaluated according to the following criteria. The results are shown in Table 1.
Good: All of the diameters Da measured at five points when determining the average diameter Dav were within the range of 1750 μm±100 μm.
×: One or more of the diameters Da measured at five points when determining the average diameter Dav was outside the range of 1750 μm±100 μm.

As shown in Table 1, in Examples 1 and 2, filaments 10 with very small Tav/Dav values were obtained. Moreover, these filaments had good formability.

In Comparative Example 1, the Tav/Dav value was larger than in Examples, and the filament 10 did not have good formability. In Comparative Example 2, the Tav/Dav value was significantly larger than in the Example.

From the above, by forming the outer layer 22 using the outer layer resin composition extruded from an extruder having a screw with a P/D value of 0.1 to 0.9, the filament 10 with a thin outer layer 22 can be formed. It was found that stable production was possible.

10: Filament 21: Inner layer 22: Outer layer 30: Production line 31A: Extruder 31B: Extruder 31a: Hopper 31b: Hopper 32: Mold 32A: Mold member 32B: Mold member 32C: Mold member 33: Sizing device 37: Water tank 37a: Water 41: Fixed roller 42: Outer diameter measurement device 43: Winding device 43a: Winding roller 43b: Bobbin winding machine 43c: Winding shaft 45: Continuous fiber roll 45a: Continuous fiber 46: Continuous Fiber-coated mold CB: Circular mold part CR: Annular channel HR: Intermediate passage N1: Central passage N2: Central passage N3: Central passage R1: Through passage R2: Through passage R3: Through passage R4: Through channel X: Material supply channel

Claims (4)

A method for producing a filament having an inner layer covered with an outer layer, the method comprising:
Equipped with a coating process,
In the coating step, forming the outer layer that covers the inner layer using the outer layer resin composition extruded from the extruder by rotating a screw of the extruder,
The screw has a [screw pitch/screw diameter] value of 0.1 to 0.9,
The method , wherein the rotation speed of the screw is 0.1 to 4.0 rpm . The method according to claim 1 , comprising:
In the coating step, the inner layer is coated with the outer layer by coextruding an inner layer resin composition constituting the inner layer and the outer layer resin composition from an extrusion head. A method for producing a filament having an inner layer covered with an outer layer, the method comprising:
Equipped with a coating process,
In the coating step, forming the outer layer that covers the inner layer using the outer layer resin composition extruded from the extruder by rotating a screw of the extruder,
The screw has a [screw pitch/screw diameter] value of 0.1 to 0.9,
In the coating step, the inner layer is coated with the outer layer by coextruding an inner layer resin composition constituting the inner layer and the outer layer resin composition from an extrusion head. The method according to any one of claims 1 to 3,
The method, wherein the filament has a value of [average thickness of the outer layer/average diameter of the filament] of 0.1 to 3%.