JPH0149101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for molding a synthetic resin with low fluidity.

(Prior Art) Since low fluidity resins cannot be kneaded, extrusion molding using a screw is impossible. For this reason, conventionally, a ram extrusion method or a paste extrusion method as disclosed in JP-A-56-38243 has been used.

In the ram extrusion method, a small amount of low-flow synthetic resin powder is loaded into an extrusion molding device, heated above the melting point of the synthetic resin, and pressurized by a ram to remove air between the powders. Then, the ram is moved back and a smaller amount of powder is loaded into the mold, and the same operation as above is repeated. However, in the above-mentioned ram extrusion method, the synthetic resin could only be molded in small quantities in order to remove internal air, and the molding time was extremely long.

Paste extrusion methods are widely used for molding fluororesins. Specifically, an organic solvent with a relatively low boiling point is mixed with a powder of a low-flow synthetic resin, and this mixed raw material is loaded into an extrusion molding device and pressurized with a relatively low pressure by a ram to prepare a billet. Shape. Next, the billet is pressurized by a ram and extruded from the die to obtain a molded product. next,
The molded article is dried and the organic solvent is removed by evaporation. Finally, the molded article is fired at a temperature higher than the melting point of the synthetic resin to obtain the final product. Although this paste extrusion method can improve the speed of extrusion molding, it requires the steps of extracting an organic solvent and baking, resulting in a large number of steps and low productivity.

(Objective of the Invention) The present invention was made based on the above-mentioned circumstances, and its object is to provide a method for molding a low-fluidity synthetic resin by which the low-flowability synthetic resin can be molded with good productivity.

(Summary of the Invention) The summary of the present invention is that the powder of a low-flow synthetic resin is
A liquid organic substance having a boiling point higher than the melting point of this synthetic resin is mixed, and this mixed material is heated at a temperature between the melting point of the synthetic resin and the boiling point of the liquid organic substance, and the mixture is charged into a cylinder and a small amount of By pressurizing the cylinder with a ram inserted with a gap of A method of molding a low fluidity synthetic resin, which is characterized by extrusion molding.

(Structure of the Invention) First, an example of an extrusion molding apparatus for carrying out the method of the present invention will be described with reference to the drawings. This device has a cylinder part 1 and a die part 2. The cylinder part 1 has a cavity 3 extending in the axial direction, and the die part 2 has a resin passage 4 communicating with the cavity 3. The resin passage 4 has a large diameter portion 4a and a reduced cross-sectional area portion 4 toward the exit side.
b. It has a parallel portion 4c whose cross-sectional area does not change.

In the cylinder part 1, a heater 6 as a heating means is embedded in a spiral shape so as to surround the cavity 3, and a cooling water passage 7 as a cooling means is formed in a spiral shape.

A heater 8 serving as a heating means is spirally embedded in the die portion 2 so as to surround the resin passage 4.

A ram 9 is inserted into the cavity 3 of the cylinder part 1 with a slight gap between it and the inner circumferential surface of the cylinder part 1, and is adapted to move in the axial direction.

The method of the present invention is carried out using the apparatus configured as described above. First, a mixed material 10 is prepared by mixing a liquid organic substance with a powder of a low-flow synthetic resin. Synthetic resins include ultra-high molecular weight polyethylene,
Aromatic polyamide, polyimide, aromatic polyester, etc. are used. The liquid organic substance has a boiling point higher than the melting point of the synthetic resin, and for example, aliphatic hydrocarbons, aromatic hydrocarbons, silicone oil, etc. are used, but liquid organic substances that easily wet the synthetic resin powder are preferred. The blending ratio (weight ratio) of the synthetic resin and the liquid organic substance is preferably in the range of 1:1 to 100:1. If the ratio of liquid organic matter exceeds 1:1, a large amount will remain in the molded product, causing a decline in physical properties.
This is because if the ratio is less than 100:1, desired effects (air removal effect and heating medium effect to be described later) cannot be achieved.

In the die part 2, a part 11a of the billet 11, which was solid-phase molded in the previous step, remains unmolded and blocks the resin passage 4 of the die part 2.

The mixed material 10 is loaded into the cylinder part 1 as shown in FIG. 1, heated by the heater 6, and pressurized by the ram 9 to form a billet 12 as shown in FIG. . The heating is carried out at a temperature above the melting point of the synthetic resin and below the boiling point of the liquid organic material, thereby fusing the powders together and preventing vaporization of the liquid organic material within the cylinder portion 1. Liquid organic matter is
Due to the pressurization of the ram 9, the mixed material 10 oozes out. Then, as shown by the arrow in FIG. 2, it leaks out from a small gap between the outer peripheral surface of the ram 9 and the inner peripheral surface of the cylinder part 1, and is removed from the powder.
As described above, forming the billet 12, fusing the powder, and removing the liquid organic matter can be performed simultaneously.

Liquid organic matter has the following effects. First, when mixed with powder, the air enters between the powder and eliminates the air between the powder, making it possible to reduce the air content in the mixed material 10. Furthermore, as described above, when the mixture leaks from between the ram 9 and the cylinder part 1 during pressurization, it leaks out while containing the air remaining in the mixed material. Therefore, when forming the billet 12, air can be removed quickly and reliably.

Further, the liquid organic substance acts as a heat medium that transfers the heat of the heater 6 to the synthetic resin powder. Therefore, it is possible to efficiently transfer heat to the powder, shorten the heating time of the mixed material, and
Powders can be fused together quickly and reliably.

As mentioned above, since the liquid organic substance allows air to be removed and powder to be fused quickly and efficiently, the molding speed of the billet 12 can be greatly improved. Furthermore, since air can be removed and powder can be reliably fused, the density of the billet 12 and, in turn, the density of the molded product can be increased.

In addition, since the liquid organic substance can efficiently transfer heat to the powder, the heating temperature of the mixed material can be adjusted to a temperature slightly higher than the melting point of the synthetic resin, for example 10℃ to 30℃.
℃ can be suppressed to a high degree, and the powder can be fused at a lower temperature compared to conventional methods.
Therefore, decomposition of the synthetic resin due to high temperatures can be prevented.

After forming the billet 12, cooling water is supplied to the cooling water passage 7 to cool the billet 12 to a temperature suitable for solid-phase molding, that is, a temperature range from the glass transition point to the melting point of the synthetic resin. In addition,
As described above, since the heating temperature during molding of the billet 12 is suppressed to a relatively low temperature, cooling can be performed in a short time and the cooling means can be simplified. On the other hand, the part 11a of the billet 11 formed in the previous step is maintained at a temperature suitable for solid phase forming by the heater 6 of the die section 2.

Next, by applying pressure with the ram 9, the billet 12 and a portion 11a of the billet 11 remaining in the die portion 2 are extruded in a solid state. Since molding is performed in a solid state, the cooling process after molding can be omitted, and dimensional accuracy can be improved by eliminating deformation and distortion caused by forced cooling.

Next, attach the ram 9 and a part of the billet 12 to the die part 2.
Stop at the position left and move back. The same operation is then repeated.

The present invention is not limited to the above embodiments, and various embodiments are possible. For example, when molding a hollow product, a ram with a mandrel may be used, and a product with any cross-sectional shape can be molded.

Further, the mixed material may be preheated before being loaded into the extrusion molding apparatus, and heating within the extrusion molding apparatus may be omitted or supplementary.

Furthermore, in the above embodiment, billet molding and extrusion molding were performed using one extrusion molding device, but the billet molding was performed in a cylindrical mold with one end closed, and the molded billet was It may also be taken out from the mold and loaded into an extrusion molding apparatus, where solid phase extrusion molding may be performed.

I tried the following molding. Mix 100 parts by weight of ultra-high molecular weight polyethylene with a melting point of about 130°C and 30 parts by weight of liquid paraffin with a boiling point of 200°C, preheat at 155°C for 2 hours, and then load it into an extrusion molding device.
A ram with a mandrel is used to maintain the above temperature using a heater installed in the extrusion equipment.
Extrusion pressure of 90MPa for about 3 minutes, outer diameter 50mm,
A tubular billet with an inner diameter of 21.5 mm was obtained. Next, after cooling the billet to 105℃ in the extrusion molding equipment,
Extrusion pressure 100MPa with ram again, molding speed 10cm/
Extrusion molding was performed at min. to obtain a final molded product in the form of a tube with an outer diameter of 30.5 mm and an inner diameter of 21.5 mm. The appearance of the molded product was good.

(Effects of the Invention) As explained above, according to the present invention, by mixing a liquid organic substance having a boiling point higher than the melting point of the synthetic resin with a powder of a low-flow synthetic resin,
It is possible to quickly and reliably remove the air between the powders, and also to quickly and reliably fuse the synthetic resin powders together, increasing the billet forming speed.
In addition, since the liquid organic matter is allowed to escape through the gap between the cylinder and the ram, billet forming, powder fusion, and liquid organic matter removal can be performed at the same time, simplifying the process and increasing productivity. You can improve.

[Brief explanation of drawings]

The drawings show an example of an extrusion molding apparatus for carrying out the present invention, and FIG. 1 shows a state filled with a mixed material,
FIG. 2 shows the state of the billet after the molding is completed. 10...Mixed material, 11,12...Billet.

Claims (1)

[Claims] 1. A powder of a low-flow synthetic resin is mixed with a liquid organic substance having a boiling point higher than the melting point of the synthetic resin, and this mixed material is mixed with the melting point of the synthetic resin and the boiling point of the liquid organic substance. By heating at a temperature between 1. A method for molding a low-flow synthetic resin, which comprises fusing bodies together to form a billet, and extruding the billet in a solid state. 2 The blending weight ratio of the synthetic resin and liquid organic substance is
The method for molding a low-flow synthetic resin according to claim 1, wherein the ratio is in the range of 1:1 to 100:1. 3. The method for molding a low fluidity synthetic resin according to claim 1 or 2, wherein the liquid organic substance is an aliphatic hydrocarbon. 4. The method for molding a low fluidity synthetic resin according to claim 1 or 2, wherein the liquid organic substance is an aromatic hydrocarbon. 5. The method for molding a low fluidity synthetic resin according to claim 1 or 2, wherein the liquid organic substance is silicone oil.