JP2019072857A - Molded body and working method - Google Patents

Abstract

To provide a molded body with a stable shape even after secondary working.SOLUTION: There is provided a molded body obtained by subjecting a synthetic resin to secondary working. Provided that the temperature of the temperature at which the loss tangent (tanδ) of the synthetic resin reaches the maximum+15°C is defined as T1(°C) and the temperature of the T1+30°C is defined as T2(°C), the storage elastic modulus (E') of the synthetic resin in the range from the T1 to the T2 being within ±10% of the storage elastic modulus (E') of the synthetic resin in the T1, and it is a molded body obtained by subjecting the synthetic resin to heating at a temperature of T1+15°C or more and to secondary working.SELECTED DRAWING: Figure 1

Description

  The present application relates to a molded body obtained by processing a synthetic resin, and a method of processing a synthetic resin.

Conventionally, products in which a resin-made tubular body is bent are widely sold.
As a method for bending a resin-made tubular body, it is generally performed as follows. First, the tubular body to be the original pipe is heated to a temperature that allows bending and deformation, and then a core material for preventing crushing is inserted into the tubular body, and a mold having a cavity conforming to the desired shape is used. The tubular body is clamped and deformed. After deformation, the tubular body is cooled inside the mold and then opened to extract the core from the tubular body. This results in a tubular body bent at the desired bending angle.
About the processing method of such a tubular body, it describes in patent documents 1-3, for example.

Japanese Examined Patent Publication No. 4-42974 Unexamined-Japanese-Patent No. 5-69480 Japanese Examined Patent Publication 6-55430 JP-A-7-223274 JP 2008-284714 A

At present, a tubular body made of a crosslinkable resin is being developed, and a method of bending the tubular body is being studied.
The crosslinkable resin is characterized in that the thermal stability such as heat resistance, oil resistance and creep resistance, chemical stability and mechanical properties are improved and stabilized by crosslinking.
However, since the crosslinkable resin has the above-mentioned characteristics, there is a problem that processing such as bending is extremely difficult if it is crosslinked. For example, in the methods disclosed in Patent Documents 1 to 3, it is difficult to bend a tubular body made of a crosslinkable resin.

Therefore, conventionally, bending of the tubular body is performed in a state before crosslinking or in a state in which the degree of crosslinking is reduced. For example, Patent Literatures 4 and 5 disclose a bending method of a tubular body made of a crosslinkable resin.
In Patent Document 4, bending is performed in a non-reacted state before crosslinking, and then, a heat medium is allowed to pass through the tube to react the base material and the crosslinking material, thereby bending the tubular body made of the crosslinkable resin. It is disclosed. Patent Document 5 discloses that the tubular body is crosslinked by heating to a certain degree of crosslinking without melting, and then the tubular body is heated and bent.
However, the methods disclosed in Patent Documents 4 and 5 require a step of crosslinking to the final degree of crosslinking after bending, and therefore, there is a risk that the shape may collapse if an extra load is applied to the tubular body in the crosslinking step. There is. Therefore, a holder and a safety fitting that match the shape after processing are required. In addition, it is necessary to control the time and temperature from the bending process to the crosslinking process.
Therefore, in the methods described in Patent Literatures 4 and 5, time management and temperature management between processes are required while taking into consideration the shape change from the bending process to the crosslinking process.

  Thus, the present application discloses a molded body having a stable shape after secondary processing such as bending and a processing method that does not require post-processing after secondary processing.

One aspect of the present invention for solving the above problems is
A molded body obtained by secondary processing of a synthetic resin, wherein the temperature + 15 ° C. at which the loss tangent (tan δ) of the synthetic resin is maximized is T1 (° C.), and the temperature T1 + 30 ° C. is T2 (° C.) And the storage elastic modulus (E ') of the synthetic resin in the range from T1 to T2 is within. +-. 10% of the storage elastic modulus (E' _T1 ) of the synthetic resin at _T1 , and the synthesis It is a molded article in which the resin is heated to a temperature of T1 + 15 ° C. or higher for secondary processing.

Preferably, the synthetic resin is heated and subjected to secondary processing in a temperature range in which the storage elastic modulus (E ′) of the synthetic resin is within ± 10% of the storage elastic modulus (E ′ _T1 ) at the _T1 . It is a molded body.

  Moreover, it is preferable that the said molded object is a tubular body. The outer diameter of the tubular body is preferably 35 mm or less, and the thickness of the tubular body is preferably 10 mm or less.

In addition, one aspect of the present invention for solving the above-mentioned problems is
A processing method for secondarily processing a synthetic resin, wherein the temperature + 15 ° C. at which the loss tangent (tan δ) of the synthetic resin is maximized is T1 (° C.), and the temperature T1 + 30 ° C. is T2 (° C.) Storage elastic modulus (E ') of the synthetic resin in the range of T1 to T2 is within. +-. 10% of the storage elastic modulus (E' _T1 ) of the synthetic resin at T1; Processing temperature by heating to a temperature of T1 + 15 ° C. or higher for secondary processing.

  The processing method is a method for processing a tubular body containing at least the synthetic resin, and the tubular body is installed along a shaping mold engraved in a shaping shape covering the entire outer periphery of the tubular body, Preferably, pressure is applied from the inside of the tubular body in a state where the tubular body is installed in the shaping mold.

  According to the molded article of the present invention, it is possible to provide a molded article having a stable shape after secondary processing. Moreover, according to the processing method of the present invention, post-processing after secondary processing is unnecessary.

It is the figure which showed the representative example of the viscoelastic behavior of bridge | crosslinking polyethylene resin. It is the figure which showed the representative example of the viscoelastic behavior of ultra-high molecular weight polyethylene. 10 is a flowchart of a processing method 10; FIG. 7 is a view showing the relationship between each process and temperature in the processing method 10. It is a figure explaining the method to install a synthetic resin pipe in the shaping type which covers the whole synthetic resin pipe. It is a figure explaining the method to install a synthetic resin pipe in the shaping type which covers only the heated part of a synthetic resin pipe. It is the schematic of the shaping | molding type which has a parting surface direction orthogonal to bending shape. It is a figure explaining the method to install a synthetic resin pipe in the shaping type which bends a plurality of places. It is a figure for demonstrating change amount (epsilon) to a bending shape. It is the figure which showed the temperature behavior of the synthetic resin pipe in internal pressure load process S13. It is a figure explaining giving processing of curve shape to the outer surface of a synthetic resin pipe. It is a figure explaining that a process of curve shape is given to the outer surface of the end of a synthetic resin pipe. It is the figure which showed the relationship of the heating temperature of a synthetic resin pipe and bending angle in an Example.

  Although the molded object and the processing method of this invention are demonstrated below, this invention is not limited to this.

<Molded body>
The molded body of the present invention is a synthetic resin heated and subjected to secondary processing. The secondary processing is to further process a synthetic resin formed by extrusion molding or injection molding into a desired shape, and includes, for example, bending, drawing, burring, diameter enlargement, and the like.
In addition, although the effect in the case of performing a bending process to a synthetic resin may be demonstrated below, such an effect is exhibited also in other secondary processing.

The shape of the molded body is not particularly limited, and examples thereof include a tubular body, a flat body, a curved plate and the like. Among them, a tubular body is preferable. Moreover, when a molded object is a tubular body, it is preferable that the synthetic resin before secondary processing is also a tubular body.
When the molded body is a tubular body, the lower limit of the outer diameter of the tubular body is preferably 5 mm or more, more preferably 7 mm or more, and preferably 35 mm or less, preferably 30 mm or less. Is more preferred. The lower limit of the thickness of the tubular body is preferably 1 mm or more, more preferably 1.5 mm or more, and the upper limit is preferably 10 mm or less, more preferably 7 mm or less, 5 mm It is more preferable that it is the following.

[Synthetic resin]
The synthetic resin is a visco-elastic body, and has storage elastic modulus (E ′) and loss elastic modulus (E ′ ′) as physical parameters representing its properties. Further, the ratio of loss elastic modulus (E ′ ′) to storage elastic modulus (E ′) is referred to as loss tangent (tan δ = E ′ ′ / E ′).

In the synthetic resin in the present invention, these physical parameters exhibit the following behavior. That is, when the temperature + 15 ° C. when the loss tangent (tan δ) of the synthetic resin is maximum is T1 (° C.) and the temperature T1 + 30 ° C. is T2 (° C.), the synthetic resin in the range of T1 to T2 It shows the behavior that the storage elastic modulus (E ') is within ± 10% of the storage elastic modulus (E'T1) of the synthetic resin at _T1 . This will be described in detail with reference to FIG. In addition, FIG. 1 is the figure which measured the viscoelastic behavior of the bridge | crosslinking polyethylene resin used in the Example mentioned later.

  The vertical axis of FIG. 1 represents the storage elastic modulus (E ′) or the loss elastic modulus (E ′ ′), or the loss tangent (tan δ), and the horizontal axis represents the temperature. The storage elastic modulus (E ′) is a line, the loss elastic modulus (E ′ ′) is a chain line, and the loss tangent (tan δ) is a two-dot chain line. When the temperature at which the loss tangent (tan δ) is maximized is T0 (120 ° C.), the temperature at T0 + 15 ° C. is T1 (135 ° C.) and the temperature at T1 + 30 ° C. is T2 (165 ° C.).

Focusing on storage elastic modulus (E ′) and loss elastic modulus (E ′ ′), storage elastic modulus (E ′) and loss elastic modulus (E ′ ′) gradually decrease from the low temperature side to around T0 Tend to decrease rapidly at around T0. Then, in the vicinity of T1, the storage elastic modulus (E ′) and the loss elastic modulus (E ′ ′) become stable in a very low state. This stabilization lasts at least from T1 to T2. That is, in the synthetic resin having the viscoelastic behavior shown in FIG. 1, the storage elastic modulus (E ') of the synthetic resin in the range from T1 to T2 is within ± 10% of the storage elastic modulus (E'T1) of the synthetic resin at _T1. Show the behavior of Furthermore, the storage elastic modulus (E ') of the synthetic resin in the range of T1 to T2 is within ± 1% of the storage elastic modulus (E'T1) of the synthetic resin at _T1 .

In a synthetic resin having such a viscoelastic behavior, the effect of bending on the temperature of the synthetic resin is as follows.
First, the synthetic resin has high storage elastic modulus (E ′) and loss elastic modulus (E ′ ′) below T1 and has a large bending difficulty and an amount of bending back at the time of bending. Moreover, it is unstable near T1, and the amount of bending back is large. Therefore, it is important to heat the synthetic resin to T + 15 ° C. or more from the viewpoint of reliably performing bending. By heating the synthetic resin to a temperature of T1 + 15 ° C. or more, the storage elastic modulus (E ′) and the loss elastic modulus (E ′ ′) become sufficiently lowered, and the storage elastic modulus (E ′) and the loss elastic modulus Since (E ′ ′) is in a stable state, the amount of return after bending is small, and a stable bent product can be obtained. In addition, the amount of return due to the subsequent change with time is stable.

On the other hand, as shown in FIG. 1, the synthetic resin starts to deteriorate when the temperature becomes too high, and the storage elastic modulus (E ′) increases. As a result of investigations by the present inventors, when the storage elastic modulus (E ') of the synthetic resin is heated to exceed the value of ± 10% of the storage elastic modulus (E' _T1 ), the synthetic resin is excessively deteriorated, and the quality of the molded product Was found to drop significantly.
Therefore, a more preferable heating temperature of the synthetic resin is a temperature range of T1 + 15 ° C. or more, and the storage elastic modulus (E ′) of the synthetic resin is within ± 10% of the storage elastic modulus (E ′ _T1 ). More preferably, T1 + 15 ° C. or higher, and the storage elastic modulus of the synthetic resin (E') is the temperature range within ± 5% of the storage modulus _(E'T1), particularly preferably, T1 + 15 ° C. or more, the storage modulus of the synthetic resin (E') is within ± 1% of the temperature range of storage elastic modulus _{(E'T1) (150 ℃ ~310} ℃). By heating the synthetic resin pipe within the above temperature range, it is possible to obtain a stable secondary processed product with a small amount of return after secondary processing.
However, even if it is the said temperature range, when appearance and quality, such as discoloration by heating, are affected, it is preferable to set to the temperature range except the temperature range.

  As a synthetic resin having such a viscoelastic behavior, ultra-high molecular weight polyethylene can be mentioned in addition to the above-mentioned crosslinked polyethylene.

FIG. 2 shows a representative example of the viscoelastic behavior of ultrahigh molecular weight polyethylene.
As apparent from FIG. 2, the storage elastic modulus (E ') of the synthetic resin in the range of T1 to T2 of the ultrahigh molecular weight polyethylene is within ± 10% of the storage elastic modulus (E'T1) of the synthetic resin at _T1. It shows the behavior that it is. Furthermore, the storage elastic modulus (E ') of the synthetic resin in the range of T1 to T2 is within ± 1% of the storage elastic modulus (E'T1) of the synthetic resin at _T1 .
Here, specific numerical values of T0, T1, and T2 in FIG. 2 are as follows.
T0 = 125 ° C
T1 = 140 ° C
T2 = 165 ° C.
In addition, the temperature range of T1 + 15 ° C. or higher and within ± 1% of the storage elastic modulus (E ′) of the synthetic resin within ± 1% of the storage elastic modulus (E ′ _T1 ) is 155 ° C. to 175 ° C.

  As described above, the molded article of the present invention is a secondary resin obtained by heating a synthetic resin having the above-described viscoelastic behavior to T1 + 15 ° C. or higher. In the prior art, when such a synthetic resin was used, a cross-linking step was required to cross-link to the final degree of cross-linking in use after bending, but in the present invention it is cross-linked to the final cross-degree in used Since it is possible to process from the crosslinkable resin, it is not necessary to consider the disfigurement of the shape processed in the crosslinking step or the treatment for shape maintenance. Therefore, according to the present invention, it is possible to provide a molded body having a stable shape after secondary processing.

The molded product of the present invention is obtained by heating a synthetic resin to T1 + 15 ° C. or more and performing secondary processing as described above. That is, the synthetic resin which has been crosslinked to the final crosslinking degree is heated, the resin is softened by breaking the crystal structure of the synthetic resin once, and then the secondary processing is performed. On the other hand, the conventional molded object is produced by processing the shape of the resin before crosslinking to the final crosslinking degree and crosslinking the resin to the final crosslinking degree after processing.
Therefore, although it is thought that the molded object of this invention and the molded object of a prior art may have a difference in the crystal structure, in order to discriminate the difference of the structure and the difference of a characteristic, It is necessary to repeat a great deal of trial and error, which is not nearly practical.

<Processing method>
Next, the processing method will be described.
The processing method of the present invention is a processing method for secondarily processing the synthetic resin having the viscoelastic behavior described above.
In the following, a processing method 10 for bending a synthetic resin (synthetic resin pipe) of a tubular body, which is a preferred embodiment of the present invention, will be described. However, the present invention is not limited to this.

[Processing method 10]
The processing method 10 is a method of heating and bending a synthetic resin pipe. Specifically, the following steps are provided.
In the processing method 10, a heating step S11 of heating a synthetic resin pipe to a temperature of T ₁ + 15 ° C. and a synthetic resin pipe heated from the heating step S11 are engraved in a shaped shape covering the entire outer periphery of the synthetic resin pipe. In the mold installation step S12 installed along the formed shaping mold and in the synthetic resin pipe in the state installed in the shaping mold by the mold installation step S12, an internal pressure loading step S13 for applying pressure from the inside of the synthetic resin pipe And a cooling step S14 for ventilating gas from the inner side of the tube to the shape holding temperature of the synthetic resin tube and cooling the gas, and a taking-out step S15 for taking out from the shaping mold after the cooling step is completed.
Here, FIG. 3 shows a flowchart of the processing method 10, and FIG. 4 shows the relationship between the temperature (surface temperature) of the synthetic resin pipe in the processing method 10 and the process.
In addition, as for the synthetic resin pipe | tube used in the processing method 10, it is preferable to consider the thickness reduction in a bending part previously, and to use the thing of the dimension which thickness was thickened.

[Heating step S11]
In the heating step S11, the synthetic resin tube having the viscoelastic behavior described above is heated to a temperature of T ₁ + 15 ° C. or higher.
By heating the synthetic resin tube to a temperature of T1 + 15 ° C. or more, the storage elastic modulus (E ′) and the loss elastic modulus (E ′ ′) are sufficiently reduced, and the storage elastic modulus (E ′) and the loss elastic modulus Since the ratio (E ′ ′) is in a stable state, the amount of return after bending is small, and a stable bent product can be obtained. In addition, the amount of return due to the subsequent change with time is stable.
The heating temperature is preferably T1 + 15 ° C. or higher, and the storage elastic modulus (E ′) of the synthetic resin tube is within ± 10% of the storage elastic modulus (E ′ _T1 ), more preferably T1 + 15 ° C. or higher And, the storage elastic modulus (E ′) of the synthetic resin is within a temperature range of ± 5% of the storage elastic modulus (E ′ _T1 ), more preferably, the storage elastic modulus of the synthetic resin (T1 + 15 ° C. or higher) E ') is a temperature range within ± 1% of storage elastic modulus (E' _T1 ). By heating the synthetic resin pipe in the above temperature range, it is possible to obtain a bent product having a small amount of return after bending and stable.
However, even if it is the said temperature range, when appearance and quality, such as discoloration by heating, are affected, it is preferable to set to the temperature range except the temperature range.

  The synthetic resin pipe may be heated by charging the synthetic resin pipe into a heating tank or the like such as a heating oven or the like, or by pressing it against a contact heater. In addition, the synthetic resin tube may be heated entirely, or only a portion to be bent may be heated.

[Die setting process S12]
In the mold installation step S12, the synthetic resin pipe heated in the heating step S11 is installed along the shaping mold which is engraved in the shaping shape covering the entire outer periphery of the synthetic resin pipe. Since the synthetic resin pipe heated in the heating step S11 is in a state in which the elastic modulus is lowered, it is easy to maintain the shape by using the shaping type that covers the entire circumference of the pipe.

Moreover, in heating process S11, when heating the whole synthetic resin pipe, it is preferable to install in the shaping type | mold which covers the whole synthetic resin pipe, and to perform mold closing, and when heating only the part to bend, It is preferable that the mold closing be performed by installing in a shaping mold designed in advance so that the boundary between the heating portion and the non-heating portion which does not heat is contained in the shaping mold.
Below, it divides into mold installation process S12 at the time of heating the whole synthetic resin pipe, and mold installation process S12 at the time of heating only the part to bend-process, and demonstrating it.

One example of a schematic view of the mold setting step S12 when the entire synthetic resin pipe is heated is shown in FIG. FIG. 5 (a) is a state before installation of the synthetic resin pipe 1, and FIG. 5 (b) is a state after installation of the synthetic resin pipe 1 and mold closing. Although the shaping type | mold of FIG. 5 is for processing of one curve shape, this invention is not limited to this, You may use the shaping shape for processing of two or more places of curve shape.
Further, as shown in FIG. 5, the shaping mold 2 has a shaping shape that covers the entire outer periphery of the synthetic resin pipe 1, and the split mold shape of the division for installing the heating pipe (FIG. 5 is horizontal to the bending It is preferable to set it as a split mold shape. In the following, one of the parting molds of the shaping type 2 is referred to as a shaping type 2a, and the other is referred to as a shaping type 2b.

In the heating step S11, when the entire synthetic resin pipe 1 is heated, it is preferable that the shaping mold 2 be sized and structured such that the end portion 1a of the synthetic resin pipe is contained in the shaping mold 2. In this way, in the subsequent step, the internal pressure loading step S13, by applying the internal pressure loading from the inner diameter side of the synthetic resin pipe 1, the entire outer periphery of the synthetic resin pipe adheres closely to the shaped shape covering the entire circumference. It becomes possible to form.
The distance x from the tube end 1a to the outside of the shaping type is preferably a distance twice or more the outer diameter of the synthetic resin tube. This is to prevent the end portion 1a of the synthetic resin pipe 1 from coming out of the shaping mold.

Next, one example of a schematic view of the mold installation step S12 in the case of heating only the portion to be bent is shown in FIG. FIG. 6 (a) is a state before installation of the synthetic resin pipe 1, and FIG. 6 (b) is a state after installation of the synthetic resin pipe 1 and mold closing. Although the shaping mold 2 of FIG. 6 is a shaping mold for processing a bending shape at one place, the present invention is not limited to this, and a shaping mold for processing a bending shape at two or more places is used. You may use.
Also, as shown in FIG. 6, the shaping mold 2 has a shaping shape that covers the entire circumference of the heating range 1b of the synthetic resin pipe 1, and the split mold shape of the division for installing the heating pipe (FIG. It is preferable to set it as a horizontal split type.

  About the non-heating part which is not heated, it does not deform | transform by the internal pressure applied by internal pressure load process S13 of the following process. Therefore, since it is not necessary to cover a heating object part with shaping die 2, when heating only a portion which carries out bending processing in heating process S11, a shaping die can be made small. However, since the boundary 1c between the heating part and the non-heating part is easily deformed by the influence of heating, the distance x from the end of the heating range 1b to the outside of the shaping mold is the outer diameter of the synthetic resin pipe The distance is preferably 2 or more, and more preferably 3 or more.

  The direction of the parting plane of the shaping mold shown in FIGS. 5 and 6 is horizontal to bending, but may be horizontal or perpendicular to the bending direction as long as it covers the entire circumference of the pipe. . FIG. 7 shows a shaping mold having a dividing surface in the direction perpendicular to bending.

  Moreover, although the shaping type | mold 2 shown by FIG. 5, FIG. 6 is a shaping type which performs a bending process of one place, you may use the shaping type which performs a bending process of multiple places. An example of the structure of a shaping type that performs bending at a plurality of places is shown in FIG. At this time, the structure and shape of the shaping mold 2 may be appropriately set according to the shape to be bent.

  The shaping type is not particularly limited as long as it is not a material that causes an abnormality such as deformation or the like due to the contact of the heated synthetic resin pipe. However, in the case of a material with good heat conductivity such as a metal material, the temperature of the heated tube is likely to decrease until the internal pressure is applied after the heated tube is installed and closed, so In this case, it is desirable to heat the shaping type in advance or to select a material which is less likely to conduct heat.

[Internal pressure loading step S13]
In the internal pressure loading step S13, pressure is applied from the inside of the synthetic resin pipe in a state of being installed in the shaping mold in the mold installation step S12.
Specifically, jigs for sealing are attached to both ends of the synthetic resin pipe so that the internal pressure can be loaded from the inner diameter side of the synthetic resin pipe, the pressure medium is fed from one end, and the outer diameter of the pipe is shaped Load the internal pressure so as to be in close contact with the mold. The pressure medium is not particularly limited, but is preferably compressed air. In the following, the case where the pressure medium is compressed air will be described.
Further, the internal pressure load step S13., The temperature of the synthetic resin pipe is preferably performed to below at least the temperature T _1. Furthermore, jig attachment for sealing at both ends may be performed in advance at the heating step S11.

  The internal pressure of the compressed air can be appropriately set depending on the elastic modulus of the heated synthetic resin pipe, the outer diameter and thickness of the pipe, and the bending angle. For example, in the case of a synthetic resin tube having a viscoelastic behavior shown in FIG. 1, the outer diameter of the tube is 14.6 mm and the thickness is 2.4 mm, preferably 0.05 MPa to 0.2 MPa .

As a method of setting the internal pressure of the synthetic resin pipe 1, it is preferable to actually process and set the transfer state to the shaping type, but it is set based on the following calculation formula as an example of a simple method. It can also be done.
Minimum stress required to deform a tube to form a bending shape: σ
Amount of deformation to bending shape: ε
Elastic modulus during bending (elastic modulus of material at installation of shaping type): E
Outer diameter of pipe: D
Tube thickness: t
Minimum required internal pressure: P
If you
σ = εE ..... (1)
P ≧ 2σt / (D−t) (2)
From equations (1) and (2), ∴P ≧ 2εEt / (D−t)
Here, the amount of deformation ε to the bending shape is the amount of change of the outer portion of the synthetic resin pipe when observed from the direction perpendicular to the bending direction for the synthetic resin pipe contained in the inside of the shaping mold . Specifically, this will be described with reference to FIG. FIG. 9 is a view of the synthetic resin pipe contained in the inside of the shaping mold as observed through the shaping mold from a direction perpendicular to the bending direction. The amount of deformation ε to the bending shape at this time is (l2−l1) /, where l1 is the length of a part of the synthetic resin pipe before loading of the internal pressure and l2 is the length of the part after loading of the internal pressure. It becomes l1.

  In the internal pressure loading step S13, both ends may be completely sealed and internal pressure loading may be performed, or the pressure medium may be discharged from the other end and the pressure medium may be allowed to pass while maintaining a predetermined internal pressure ( When using compressed air, it is ventilation.) As a method of discharging the compressed air from the other end while maintaining a predetermined internal pressure, there is a method of discharging the compressed air simultaneously with the close contact shaping from the inner diameter side to the shaping type by the internal pressure. Thereby, the cooling effect by the ventilation from the inner diameter side can be exhibited, and the time until the cooling process in the mold can be shortened, which is desirable. The details will be described with reference to FIG.

FIG. 10 shows the result of examination using the synthetic resin pipe having the viscoelastic behavior of FIG. 1, and when the temperature of the synthetic resin pipe after the mold setting step S12 is 200 ° C., the synthetic resin pipe in the internal pressure loading step S13 The result of the case where the both ends are completely sealed is compared with the result of the case where the compressed air is ventilated from one end of the synthetic resin pipe at a predetermined pressure in the internal pressure loading step S13.
As apparent from FIG. 10, in the internal pressure load step S13, it can be seen that the cooling effect is higher when the compressed air is ventilated. When the compressed air is ventilated, the higher the internal pressure of the synthetic resin pipe, the better the cooling effect.

Here, the difference between the internal pressure loading process 13 of the present invention and the conventional internal pressure loading process will be described.
The internal pressure loading step of the conventional bending method has employed a method of inserting a soft solid core or a method of inserting compressed air into a tube-shaped rubber core. However, in these methods, it is difficult to let the bent part pass when taking out the core material after bending, so it is necessary to make the diameter of the core material smaller than the inner diameter of the resin pipe or to make the core material Since it is necessary to make it low hardness, there is a limit in that part crushing prevention. In particular, removal of the core material in the case of complex bending at multiple locations in different directions was more difficult.
On the other hand, the internal pressure loading step S13 of the present invention is performed using a pressure medium as described above. That is, since the pressure medium is loaded from the inner diameter side of the pipe, there is no need to take out the core material, etc., and it adheres to the shapes along various shaping shapes and complex shaping shapes of multiple shapes. It can be done easily.
Moreover, since the synthetic resin pipe heated in the above-mentioned heating step S11 is in a state in which the elastic modulus is lowered, it is easily scratched, but by using a pressure medium such as compressed air as in the present invention, It is possible to form with certainty and prevent crushing without scratching. Further, since the heated synthetic resin pipe is in a state in which the elastic modulus is lowered, the pipe pressure loaded by the pressure medium does not have to be high.

[Cooling process S14]
In the cooling step S14, the gas is ventilated from the tube inner diameter side from the tube inner diameter side to the shape holding temperature of the synthetic resin tube and cooled. Specifically, a gas such as compressed air is fed from one end of the synthetic resin pipe, the other end is released and ventilated, and the pipe is cooled from the inner side of the pipe. At that time, the shaping mold may be cooled in addition.
Here, the “shape holding temperature” is a temperature at which the synthetic resin is not easily deformed when a load is applied by taking it out from the shaping mold, handling or the like, and the loss elastic modulus of the synthetic resin (E ′ ') Is the temperature at which it begins to decrease. For example, the shape stabilization temperature of the synthetic resin shown in FIG. 1 and FIG. 2 is about 50.degree.

[Extracting step S15]
In the take-out step S15, the tube subjected to bending and shaping is taken out from the shaping mold after the completion of the cooling step S14.

  As mentioned above, the bending method which is one embodiment of the processing method 10 was demonstrated. Conventionally, as a method of processing a synthetic resin having visco-elastic behavior as described above, a cross-linking step of cross-linking to the final cross-linking degree in use after bending is required, but in the present invention Since processing can be performed from the crosslinkable resin that has been crosslinked to the degree of crosslinking, time management and temperature management between processes taking into consideration the shape change from the bending process to the crosslinking process become unnecessary.

The above processing method 10 is a bending method for changing the pipe direction, but the present invention is not limited to this, for example, processing (processing to expand the diameter) in which the shape of the outer surface of the synthetic resin pipe is bent It may be a processing method to be performed. At that time, the shaping type is replaced with the above, for example, using the shaping type shown in FIG. 11a, FIG. 11b and FIG.
11a and 11b show an example in which the outer surface of a synthetic resin pipe is processed into a curved shape.
FIG. 12 shows an example of processing a curved shape into the outer surface shape of the end of the synthetic resin pipe.
The bending process for changing the pipe direction and the process in which the shape of the outer surface of the pipe is bent may be combined.

  Further, the molded article of the present invention described above can be manufactured from a synthetic resin by performing the processing method of the present invention.

  The following examples will be described, but the present invention is not limited thereto.

The following experiment was performed according to processing method 10 using a synthetic resin tube of a commercially available crosslinkable resin material (crosslinked polyethylene resin material) having the viscoelastic behavior of FIG.
The synthetic resin tube used had an outer diameter of 14.6 mm and a wall thickness of 2.4 mm.

[experimental method]
First, the synthetic resin pipe of each example was heated to the heating temperature shown in Table 1 in the heating step.
Then, in the mold setting process, a synthetic resin pipe was installed along the shaping mold. At this time, the shaping mold was of the shape shown in FIGS. 5a and 5b, and the bending angle was 90 °.
Next, in the internal pressure loading step, the internal pressure was loaded on the synthetic resin pipe using compressed air until the temperature of the synthetic resin pipe reached 100 ° C.
Then, in the cooling step, compressed air was ventilated and cooled from one end of the synthetic resin pipe until the temperature of the synthetic resin pipe reached 50 ° C.
Subsequently, in the take-out step, the synthetic resin pipe was taken out of the shaping mold.
Finally, it was placed in a heating furnace at 100 ° C. for 3 hours for annealing for accelerated evaluation of the bending angle after processing and the subsequent aging.
The above operation was performed three times for each example.

[Experimental result]
Table 1 shows the heating temperature of each example, the bending angle and appearance (color) after processing, and the storage elastic modulus at each heating temperature when the storage elastic modulus (E ' _T1 ) at _T1 is 100% ( The change rate of E 'was shown. 13 (a) and 13 (b) show graphs of the measurement results as the heating temperature on the horizontal axis and the bending angle on the vertical axis. FIG. 13 (b) is a graph obtained by enlarging FIG. 13 (a).
In addition, evaluation of the bending angle in Table 1 is “◎” when the average bending angle is 75 ° or more and 3σ (variation) is 2.0 or less, and the average bending angle is 75 ° or more And the case where 3σ was 3.0 or less was "○", and the others were "X". Of the evaluation after bending and the evaluation after annealing for 3 hours at 100 ° C., one with poor evaluation was adopted for the comprehensive evaluation of bending state.

According to FIG. 1, T1 of the synthetic resin pipe is around 135 ° C., and at temperatures below T1, the storage elastic modulus (E ′) and the loss elastic modulus (E ′ ′) are high, the bending back becomes large and reliable shaping can not be performed Is predicted.
For this, looking at Table 1 and FIGS. 13A and 13B, the bending angle is small in Comparative Example 1 where the heating temperature is 130 ° C. or less, and the bending angle after 100 hours of annealing in Comparative Example 2 Is small and the variation is also large.

  From FIG. 1, the bending return after processing should be stable above T1 (135 ° C.). However, in Comparative Example 3 where T1 = 135 ° C., it can be seen that the variation after 3 hours of annealing in a 100 ° C. heating furnace is large, and it is unstable with time.

On the other hand, in Examples 1 to 5 heated to 150 ° C. or higher, the bending angle after processing is stable, and after processing at 100 ° C. for 3 hours as an accelerated evaluation of the subsequent change with time, also after processing. The bending angle was stable although there was bending return.
However, in Example 5 heated to a temperature exceeding 300 ° C., although the bending angle after processing is almost stable, the variation tends to become large after the 100 ° C., 3-hour input annealing as accelerated evaluation. . This is because, in FIG. 1, the storage elastic modulus (E ') at a temperature exceeding 300 ° C. has a storage elastic modulus (E' _T1 ) at _T1 exceeding ± 1%, and the storage elastic modulus increases again and becomes unstable. It is consistent with becoming.

  As mentioned above, in the bending process in this experiment, in order to obtain the bending-processed goods in which the bending angle was stable, it turned out that the process at the heating temperature of 150 degreeC or more and 300 degrees C or less is good. Moreover, when the dispersion | variation in a process process is considered, it turned out that 200 degreeC-250 degreeC are more preferable.

1 Synthetic resin pipe 2 Shaped type

Claims (7)

A molded body obtained by secondary processing of a synthetic resin,
Assuming that the temperature + 15 ° C. at which the loss tangent (tan δ) of the synthetic resin is maximum is T1 (° C.) and the temperature T1 + 30 ° C. is T2 (° C.),
The storage elastic modulus (E ′) of the synthetic resin in the range from T1 to T2 is within ± 10% of the storage elastic modulus (E ′ _T1 ) of the synthetic resin at _T1 .
The molded object which the said synthetic resin was heated by the temperature of T1 + 15 degreeC or more, and was secondarily processed. The synthetic resin is heated and subjected to secondary processing in a temperature range in which the storage elastic modulus (E ') of the synthetic resin is within ± 10% of the storage elastic modulus (E' _T1 ) at the _T1. The molded body described.   The molded body according to claim 1, wherein the molded body is a tubular body. The molded article according to claim 3, wherein the outer diameter of the tubular body is 35 mm or less.   The molded article according to claim 3 or 4, wherein the thickness of the tubular body is 10 mm or less. A processing method for secondary processing of a synthetic resin,
Assuming that the temperature + 15 ° C. at which the loss tangent (tan δ) of the synthetic resin is maximum is T1 (° C.) and the temperature T1 + 30 ° C. is T2 (° C.),
The storage elastic modulus (E ′) of the synthetic resin in the range from T1 to T2 is within ± 10% of the storage elastic modulus (E ′ _T1 ) of the synthetic resin at _T1 .
A processing method in which the synthetic resin is subjected to secondary processing by heating to a temperature of T1 + 15 ° C. or higher. It is a processing method of a tubular body containing at least the above-mentioned synthetic resin,
Placing the tubular body along a shaping die engraved in a shaping shape covering the entire outer periphery of the tubular body;
The processing method according to claim 6, wherein pressure is applied from the inside of the tubular body in a state where the tubular body is installed in the shaping mold.