JPS59194819A - Molding die for crystalline resin pipe - Google Patents

Abstract

PURPOSE:To obtain the titled die giving a pipe product improved in dimensional stability and excellent in precision of diameter, thickness, etc., directly after extrusion by specifying the outer diameter of the inner die and the inner diameter of the outer die, of a set of circular dies fixed to an extruder. CONSTITUTION:When the temperature of resin, at the resin inlet, that is extruded in the Q-direction is given by T1, the surface temperature of resin at the outlet is given by T2, the specific volume in a melting phase M of crystalline resin that changes remarkably near the softening or melting temperature T3 is given by V1, the specific volume obtained by extending the specific volume curve of the melting phase M is given by V2, the specific volume in the solid phase at the softening or melting temperature T3 is given by V3, the specific volume of the solid phase S at the surface temperature of resin on the die outlet is given by V4, the inner diameter of an outside die 2 in the inlet section is given by D1 and the outer diameter of the inside die 1 is given by d1, the inner diameter D2 of the outside die 2 and the inner diameter d2 of the inside die 1 are decided by formulas I -III.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die for molding crystalline resin.
Generally, in Nonoib's extrusion molding, after extruding the product in a molten state at the exit of the die, the product was cooled with water, etc., but the dimensional stability was poor and the precision of the product was low. For this reason, production has been carried out by solid-phase extrusion, in which the inside of the die is cooled to a softening or melting temperature, but this causes swelling and drastic changes in volume due to the resin transitioning from a molten state to a solid state. As the resin tightened around the inner die, the frictional resistance rapidly increased and the extrusion pressure increased.

In addition, it inevitably results in forced rapid molding in the solid state,
Therefore, it is necessary to greatly increase the pressure resistance of the extruder.
Production was difficult and costs increased significantly.

Conventionally, methods to prevent a sudden increase in frictional resistance in solid-phase extrusion have been to reduce the coefficient of friction by injecting lubricating oil between the inner guide and the resin, or by mixing a lubricant into the resin, or by preventing the resin from solidifying. Based on experience, a tapered taper ξ was added to the inner die in the area where it was being formed. However, in the former case, lubricating oil remains on the inner surface of the pipe product, and -? There are drawbacks such as dirt and dust adhesion, and physical properties deteriorate due to lubricant contamination, and the latter has the drawback that it is extremely time consuming to determine the empirical taper and it is difficult to find the optimal taper. Ta. Conventionally, in dies for molding crystalline resin pipes, the tapered dimension has been set at a slope of approximately one cylinder, regardless of the resin, but this is often inappropriate and causes a drop in extrusion pressure, resulting in insufficient physical properties. There was something I couldn't get. Also, since it depends on experience/■Accuracy was also very high.

The present invention was developed by focusing on the change in the specific volume of the resin by focusing on the gradient of the tapered chi. Dimensional stability has increased, and the accuracy of pipe product diameter, thickness, etc. has improved. In addition, the flow of the resin becomes smoother, and the physical properties in the direction perpendicular to the flow, such as tensile strength, which was less than half of the tensile strength in the flow direction, have been instantly improved to the same level by using this die. did. .

・The skin on the surface and inner surface of ξ Eve is also a good example because the contact with the die can be controlled.

The present invention will be explained in detail below.

In FIGS. 1 and 4, the resin temperature TIs at the die port in the extrusion direction indicated by the arrow θ, the resin surface temperature T2 at the outlet, the aforementioned specific volumes ■l + V2 +v3 and v4, and the outer die at the inlet. Inner diameter D1% Outer diameter d of inner die
1, the inner diameter of the outer die at the outlet D2, the outer diameter of the inner die d
2 is determined as shown in the following equation.

2 d2/〈/ ・・・・・・・・・(3) d,
D.

At the exit of the tie, the pipe-molded resin is solidified on the surface, but the inside is not yet solidified due to heat generation due to crystallization, so the exit is in a so-called semi-solid/semi-molten state. Therefore, the specific volume is considered to be between v4 and ■2 in FIG. Therefore, the outer diameter of the inner die is larger than the value based on v4.

smaller than the value based on v2.

Further, the inner diameter of the outer die is mainly determined by the cooling rate calculated from the set temperature of the resin in the die and the extrusion rate of the resin.

When the cooling rate is the slowest, the resin is still in a molten state or very close to it at the die exit, and the inner diameter of the outer die at the exit is equal to that at the inlet, so that the resin and die are You can prevent it from getting caught on the inner wall.

In addition, when the cooling rate is the fastest, the resin at the goo outlet is
It is in the semi-molten/semi-solid state mentioned above, and the specific volume of the resin at that time is between v4 and ■2 as mentioned above, but as a result of examination, the value calculated from the specific volume between v4 and v3 is In the case, the resin is V! When it is in the v3 state, it gets stuck and the extrusion pressure increases rapidly.

In addition, the inner diameter of the outer die is a value calculated from the specific volume between ■2 and ■] in order to reduce the adhesive resistance between the resin and the die wall, which is considered to be one of the causes of increased extrusion pressure. Good results were also obtained in the case of

Further, even when the resin temperature at the die inlet is higher than Tl, formula (1) is used for calculation.

1. When entering with a specific volume larger than vl,
Also from the point of view of eliminating welding phenomenon and improving mechanical properties ■1
It may be better to calculate based on

As described above, as shown in Fig. 4, the die of the present invention is continuously reduced in size from the inlet to the outlet, and the pipe-shaped gap between the inner die and the outer die becomes larger toward the outlet. It is characterized by the fact that

Application of the present invention - A crystalline resin whose specific volume rapidly changes near the softening temperature or melting temperature T3, for example,
Typical crystalline resins among +5 polyethylene, polypropylene, f-lyacetal, nylon, etc. are exemplified by the above three formulas as follows.

As an example of polynylene 1-lene polyethylene, the one showing the specific volume change shown in FIG. 2 is used.

The resin temperature at the inlet of the annular die is 140°C, the specific volume is 1,253 Cm3/f, and the inner diameter of the outer die is 1.
001m, the outer diameter of the inner die is 90 sieve, the resin surface temperature at the outlet is 80℃, and the specific volume at that time is 1,078cm3/
In the case of "D", the inner diameter of the outer die is 98.8 mm to 100.0 mm, and the outer diameter of the inner die is 87.411111 mm to 88.9 mm.

When the outer diameter of the inner die is 87.4 rtm or less, there is almost no frictional resistance, the extrusion pressure decreases rapidly, weld marks are generated, and the physical properties are also deteriorated due to lack of mixing. Also, 88.9
If it is more than a, the extrusion pressure will rise rapidly and it will be necessary to stop production.

In addition, in the case of 87.4+mm to 88.91m, the flow of the resin becomes smooth and the residual stress is small, so the tensile strength in the direction perpendicular to the flow is 50 mm compared to that in the flow direction.
% to 70% has improved to 85% to 90%.

In addition, it is possible to produce products with an accuracy of less than 1% for the target product dimensions, and the surface of conventional guibs has been known to be shark-skinned, scaly, or wavy in the direction of flow. However, by using Chi Gudai in this range, it was possible to produce a product with a surface skin that could be sold commercially.

; Example 1 of J Seripropylene Polyzorobire/A material exhibiting a specific volume change as shown in FIG. 3 was used.

The resin temperature at the artificial part of the annular die is 170°C, the specific volume is 1.272 cm3/ff, the inner diameter of the outer die is 100°, the outer diameter of the inner die is 90°, and the resin surface temperature at the outlet is 80°. ℃, the specific volume at that time is 1,148
cm3/y-, the inner diameter of the outer die is 97.8 rt
an ~100.0 city, the outer diameter of the inner die is 87. fan~
8B, 0ran.

When a tapered die in the above range is used, the tensile strength in the direction perpendicular to the flow is improved from 60% of that in the flow direction to 75% to 85%, and as with polyethylene, the error is 1 It becomes possible to produce with an accuracy within %,
・ξ Eve's surface skin also improved.

[Brief explanation of drawings]

FIG. 1 is a crystalline resin solid phase/molten phase specific volume-temperature diagram. ■、～■4 ...... Each specific volume T1 ...... Resin temperature at die inlet T2 ......... Resin temperature at die exit Tsukubu surface temperature T3 ・・・・・・・・・・・・Softening temperature or melting temperature Figure 2 shows the solid phase/molten phase specific volume-temperature diagram of polyethylene, and Figure 3 shows the solid phase/molten phase specific volume-temperature diagram of polypropylene. show. FIG. 4 is a side sectional view showing an example of the molding die of the present invention. l・・・・・・・・・・・・Inner die 2・・・・・・・・・Outer die 3・・・・・・・・・・・・Nonondo heater patent applicant Asahi Kasei Corporation Figure 1 Temperature (0C) Figure 2 - 4004080120160200 Temperature (0C) Figure 3 - 4004080120160200 Temperature (0C) Figure 4

Claims (1)

[Claims] A method for continuously molding a resin using an annular die fixed to an extruder, such that the surface temperature of the resin at the die exit is below the softening temperature or melting temperature of the resin, The outer diameter of the inner die and the inner diameter of the outer die of the annular die are as follows (
1) A die for molding a crystalline resin pipe characterized by being determined by the three equations (2) and (3). The ratio of the outer diameter of the inner die of the annular die is within the range of formula (1). (2) The ratio of the inner diameter of the outer die at the resin inlet part of the annular die to the inner diameter of the outer die at the resin outlet part is given by formula (2). (3) The ratio of the outer diameter of the inner die at the resin inlet of the annular die to the outer diameter of the inner die at the resin outlet, and the ratio of the inner diameter of the outer die at the resin inlet to the outer diameter at the resin outlet. The ratio of the inner diameter is d2//dI /i, which is in the relationship shown in equation (3). - Curved axis... (3)
The inner diameter of the outer die and the outer diameter of the inner die at the resin inlet are Dl and dl, and the inner diameter of the outer die and the outer diameter of the inner die at the resin outlet are D2 and d2. A crystalline resin whose specific volume changes significantly at or near the melting temperature, where vl is the specific volume of the molten phase M at the softening temperature or melting temperature, and v2 is the ratio of the molten phase M! The specific volume of the product curve extended to the surface temperature at the die exit, v3
is the specific volume in the solid phase S at the softening temperature or melting temperature T3, and is the specific volume in the solid phase S at the resin surface temperature at the exit of the V4Fi die.