JPS6135928A - Manufacture of thermoplastic resin pipe - Google Patents

Abstract

PURPOSE:To obtain an expected smooth pipe with high roundness by a method wherein thermoplastic resin pipe, which is extruded from a die and is in molten state, is led to a refrigerant tank so as to heighten its melt viscosity up to a degree not so higher as the viscosity in perfectly solidified state and, after that, sized under reduced pressure at a vacuum chamber. CONSTITUTION:A sizing device 4 consisting of an extruder 1 equipped with a pipe die 3, the temperature of the mandrel of which is adjustable, and a vacuum chamber 6, which is located in a refrigerant tank 5 and equipped with sizers 8 and 8', is provided. The molten thermoplastic resin pipe extruded from the die 3 is rapidly led to the refrigerant tank 5 in order to heighten the melt viscosity of the pipe up to a degree not so higher as the viscosity in perfectly solidified state. After that, the pipe is introduced in the vacuum chamber 6 and sized under reduced pressure by means of the sizers 8 and 8' in order to obtain an desired pipe. Due to the method as mentioned above, the desired thermoplastic resin pipe excellent in transparency, roundness and surface smoothness on inner and outer surfaces can be manufactured.

Description

[Detailed Description of the Invention] Chapter R: Industrial Application Fields The present invention is a thermoplastic resin with excellent transparency, smoothness of inner and outer surfaces, and roundness, which is highly useful as a medical tape and food hose. It concerns a method of manufacturing porcelain resin pipes, especially soft vinyl chloride resin pipes.

``Prior art'' In order to continuously manufacture a pipe made of thermoplastic resin, for example, a pipe made of vinyl chloride resin, it is necessary to combine both soft and hard pipes with die rings and mandrels. When extrusion molding is performed using a die, the pipe will not lose its shape due to the pressure difference between the inside and the outside air.

Generally, air holes are provided in the mandrel and molding is carried out while supplying weakly pressurized air. On the other hand, the main difference between the manufacturing methods of soft pipes and hard pipes is largely due to the difference in melt viscosity of the thermoplastic resin, and the difference is whether or not a cisizer is used. For example, hard vinyl chloride resin pipes are mainly molded using a sizer, whereas soft vinyl chloride resin pipes are molded using a sizer.

In other words, soft vinyl chloride resin has a low melt viscosity;
Even if weak compressed air is sent during molding, the pipe expands and comes into contact with the sizer, resulting in deformation or elongation.
Use of sizers is inappropriate and rare. The use of sizers in the molding of soft vinyl chloride resins is limited to a very small range, such as coextrusion molding with hard resins.

In the molding method of soft PVC resin pipes that does not use a sizer, increasing the temperature is advantageous in terms of the transparency and smoothness of the resulting pipe, but it decreases the melt viscosity and causes problems due to its own weight. The drawback was that it was difficult to hold the pipe in a circular shape (To3), and it was extremely difficult to set appropriate molding temperature conditions. If a pipe is formed under extreme temperature conditions such as transparency and external surface smoothness,
Due to poor roundness and a temperature difference between the die ring and the mandrel, the inner surface of the pipe is less smooth than the outer surface of the pipe, making it impossible to use it as a medical tube. There wasn't.

"Problems to be Solved by the Invention" Having fully grasped the shortcomings of the prior art, the inventor of the present invention has conducted extensive studies on a method for obtaining a soft thermoplastic resin pipe with high transparency, smooth inner and outer surfaces, and high roundness. As a result, even if the thermoplastic resin has a low melt viscosity, the die ring of the pipe die and the mandrel are kept at the same temperature, and even if the shape of the extruded molten resin pipe is slightly distorted due to its own weight, It was discovered that by increasing the melt viscosity to the extent that it does not completely solidify and then reducing the pressure on the outside of the pipe, it is possible to produce a thermoplastic resin pipe that is transparent, has smooth inner and outer surfaces, and has a high degree of roundness. The present invention has now been completed.

That is, one object of the present invention is to provide a method for manufacturing a thermoplastic resin pipe that has excellent transparency, smoothness of inner and outer surfaces, and high roundness.

``Structure of the Invention'' The gist of the present invention is to provide a method for manufacturing thermoplastic resin pipes by continuous extrusion, and an extruder equipped with a pipe die that allows mandrel ovih* adjustment. Using a sizing device that does not involve a refrigerant tank that stores liquid refrigerant and a vacuum chamber located within the refrigerant tank and equipped with a sizer, the molten thermoplastic resin pipe extruded from the pipe die is quickly transferred to the refrigerant tank. The method of manufacturing a thermoplastic resin pipe is characterized in that the melt viscosity of the pipe is increased to such an extent that the pipe is not completely solidified, and then the pipe is introduced into a vacuum chamber and sized under reduced pressure at the same time.

The method of the present invention will be explained in detail according to the drawings.

Fig. 5 shows an example of a thermoplastic resin pipe manufacturing apparatus used in the method of the present invention, and is a schematic longitudinal sectional front view thereof, and Fig. 9.2 shows another example of a sizing apparatus, a schematic longitudinal sectional front view thereof.
Figures (A), (B), and (C) are longitudinal sectional front views of pipe dies, respectively; (A) and (CI) are straight dies;
c) shows the rad die to the cross.

In the figure, l is the extruder %- is the hopper, 3 is the pipe die,
Hiro, Kosan is a sizing device, j%ko! is the refrigerant tank, 6, kot is the decompression chamber, 7, the core is the refrigerant, r, r', kot, kol'
is the sizer, Ri, Ri', Kota, Kode' is the throttle, IQ, Ko0 is the pressure reducing pump, //, Kol is the refrigerant transfer pump, lλ,
Co2 is CoC1, IJ, JJ is the refrigerant liquid shielding plate, /F is the refrigerant storage chamber, is is the refrigerant discharge pipe, /4 is the take-up device, JD, I
AI is straight die, 50 is crosshead die, 31
1 Kohachi 21 is die ring, JJ, $ko, jko is mandrel, 33, Kohachi 3, j3 is rod heater, 34c1 dahiro%
! Hiro is an air hole, 31.11 is a spider, 36%416.
16 is a lead wire, and a and b are thermoplastic resin pipes, respectively. The ti arrow indicates the moving direction of the pipe or the flowing direction of the molten resin.

In the method of the present invention, a thermoplastic resin is charged into a pumper 2 in an extrusion mode 1, melted by the extruder 1, and then a molten pipe is extruded from a pipe die 3.

The pipe die 3 is a straight die 30. as shown in FIGS. Raddai 50 etc. are used for 〇 and cross, and Daidai Ring 3 is used for armpit die.
1. g/, j and 3 mandrels.

Goo! λ > 1), Dairing J/%ll.

J/ is usually heated during molding so that it reaches the optimum temperature of the thermosetting resin. On the other hand, for example, rod-shaped heaters 33, μ3, and I3 are inserted to prevent the occurrence of the melting of the mandrel itself. lK6
Heat it to a temperature higher than that of the thermoplastic resin pipe. The heater is Spider 3! , Hiro! A lead wire 36 connected to the space or cross through the space Jj of the RAD die,
Hiro 6! The structure is such that heating and heating can be adjusted by changing the voltage of B. In addition, the pipe die has air holes 3hiro, l-, and maquidrel that lead to the space of the spider. - Air hole to buy through! μ is bored, so that when the thermoplastic resin pipe is molded, the air pressure inside and outside the pipe is the same. In the method of the present invention, it is preferable to use the straight die shown in FIG. 3 (=) which has a short land portion. All arrows in FIG. 3 indicate the direction in which the resin flows.

The method of the invention quickly leads the molten pipe extruded from the extruder 5 to the sizing equipment. The sizing device 1 is provided within a range of 500 meters, preferably within a range of 50 meters, from the extruder 1 in order to keep the deformation of the molten pipe extruded from the extruder 1 to as small a range as possible. The sizing device is water.

A refrigerant tank that stores liquid refrigerant 7 such as silicone oil! and a depressurization chamber 6 located within the refrigerant tank j and capable of reducing the pressure (negative pressure) when the refrigerant is stored, expanding both the shim refrigerant tank and the decompression chamber,
Usually, it is fixed so that it does not move during the manufacture of thermoplastic resin pipes. And the refrigerant tank! A through hole is drilled at a position below the refrigerant liquid level so that the extruded thermoplastic resin pipe a passes through the decompression chamber 6 line.

When the pressure in the decompression chamber becomes negative, the refrigerant 7 enters the refrigerant tank from the through hole.
The structure is such that the decompressed air flows into the vehicle. The pressure in the decompression chamber is not particularly limited, but is between 750 and 7 hiO.
(2) It is preferable to maintain a constant pressure in the range of Hg (vacuum IO-10 wig).

The through hole of the refrigerant tank j is equipped with a restrictor (9') that can open and close the through hole.
The refrigerant is squeezed to match the thickness of the pipe a, and a flexible material such as absorbent cotton is used to store the refrigerant between the pipe a and the restrictor to prevent the refrigerant 7 from leaking out of the refrigerant tank. Easily absorbed - preferably provided with a drainage hole. To reduce the pressure in the vehicle, a means for reducing the pressure in the cough room, such as a vacuum pump 50. An air exhaust pipe leading to a steam ejector, an aspirator, etc. is opened, and a refrigerant exhaust pipe /j is opened in the decompression chamber aWJ in order to automatically maintain the refrigerant 7 in the decompression chamber 6 at a constant depth. Open it. The refrigerant 7 discharged from the refrigerant discharge pipe/J is stored in the refrigerant storage 1 in which the space has the same pressure as the depressurization blockage section! /4'
The refrigerant 7 is stored in the refrigerant and is circulated and used by the refrigerant transfer pump, and when the refrigerant becomes excessive, it is discharged from the system.

Thus, sizers t and r' are provided in the through hole of the decompression chamber t to match the thickness of the thermoplastic resin pipe a. The sizers r and r' are.

Generally, the sizer may be made of metal such as stainless steel or aluminum, preferably a sizer made of metal coated with fluorocarbon resin or a sizer itself made of fluororesin. r,
The diameter of the pipe a is slightly larger than the dimension (diameter) of the pipe a, preferably larger than the dimension (diameter) of the pipe a.
When the refrigerant 7 is introduced into or discharged from the decompression chamber 6, a gap is created that allows the refrigerant 7 to be sucked together.

That is, it is cooled by the refrigerant 7 after passing through the constrictor.

When the melt viscosity of the thermobreathable resin is increased to such an extent that it is not completely solidified and the pipe passes through the sizer T, the refrigerant tank J
The refrigerant 7 is injected into the reduced pressure vehicle weight while sealing the reduced pressure chamber, and at this time the pipe is expanded in diameter. At this time, the refrigerant 7 acts as a lubricant. When the pipe that has been completely solidified in the vacuum chamber is taken out from the vacuum chamber, the refrigerant is sucked from the sizer r' and acts as a lubricant, and the pipe a is taken out by the take-off device/A through the throttle filter'. It will be done. The distance between the diaphragm and the sizer R varies depending on the melt viscosity of the heat-circulating resin, the wall thickness of the pipe, the temperature of the refrigerant, etc., but it should be within the range where the heat-circulating resin pipe is sufficiently soft and sizing is possible. It is desirable to squeeze the sizer T close to the router, and it is 150
It is preferable to keep it within 0vx, especially around JOwm. In addition, if the difference between the diameters of sizers r and r' and pipe a is too large, the amount of refrigerant sucked into the decompression chamber at once will increase, and the refrigerant in the decompression guide will vibrate violently, which will adversely affect pipe forming. If the difference is too small, the sizers r and r' will easily adhere to the pipe a, causing scratches, elongation, etc. It is preferable to install a flow 12 in contact with the thermoplastic resin pipe a on the line of the communicating through-hole through a core. Of course, the roller shielding plate 13 may be provided perpendicularly to the refrigerant liquid surface or into the liquid.

Furthermore, the sizing device used in the method of the present invention is as follows.

It is not limited to the sizing device shown in Figure 1.
For example, the sizing device shown in FIG. 1 may be used. The sizing device λμ has a refrigerant discharge pipe connected to the refrigerant transfer bombco I opened at the bottom of the decompression chamber 26 in order to adjust the refrigerant core in the decompression gxg to an arbitrary depth. If the vacuum chamber is opaque, it is desirable to provide a viewing window through which the interior of the vacuum chamber can be seen.

The thermoplastic resin used in the method of the present invention is not particularly limited, but includes, for example, vinyl chloride resin, polystyrene resin, MuB8 resin, acrylic resin, polyethylene,
Polypyrene, polyamide resin, boria heptatar resin, etc. are used, and one or a mixture of two or more of these may be used. In order to manufacture medical tubes, food hoses used for transporting foods, beverages, etc., vinyl chloride resins or mixtures of vinyl chloride resins and acrylic resins are particularly useful. As the vinyl chloride resin, vinyl chloride or a mixture of vinyl chloride and a comonomer copolymerizable with it can be used by suspension polymerization or bulk polymerization.

Any material produced by a conventional method such as a fine suspension polymerization method or an emulsion method can be used.

The acrylic resin has the general formula (1) % formula % [wherein R represents a hydrogen atom or a lower alkyl group, and R1 represents a hydrogen atom or an alkyl group having a carbon atom number of /-/f. ) Acrylic W1. Polymers or copolymers whose main component is acrylic acid ester or acrylic acid ester are used.

Typical examples include polymethyl acrylate, polymethyl methacrylate, and methacrylic methyl-butadiene-styrene copolymer (Mn2). The molecular weight of these acrylic resins is generally in the range of JO-2JO, and the particle size is preferably 500 μm or less. The blending ratio of acrylic resin to vinyl chloride resin is 50 parts by weight of vinyl chloride resin.
It is less than 7 parts by weight, preferably ij O,j -7 parts by weight, especially in the range of 3 to 3 parts by weight.

The dusting agent for reconstituting vinyl chloride resins is not particularly limited as long as it is a layering agent that is normally used for layering vinyl chloride resins1. 7-talic acid ester-based lubricating agents, trimellitic acid ester-based coating agents represented by tri-ethylhexyl trimellitate, fatty acid ester plasticizers represented by dico-ethylhexyl adipate, and phosphorus-sensitive tricresyl. There are various types of coating agents such as phosphoric acid ester coating agents typified by , and polyester coating agents typified by polycondensates of adipic acid and ethylene glycol. The blending ratio of plasticizer to vinyl chloride resin is 30% of the composition.
-HiroOθ parts by weight, preferably in the range of j0 to aOO parts by weight. For example, polyvinyl chloride (degree of polymerization t3oo)
i o o parts by weight of di-2-ethylhexyl phthalate 5
By uniformly mixing 0 parts by weight, the Jx day hardness is approximately 7.
0 soft vinyl chloride resin composition is obtained. Furthermore, to give the pipe even better surface smoothness.

It is preferred to add a small amount of a lubricant such as stearic acid or a metal salt of stearic acid to the composition.

"Effects of the Invention" According to the method of the present invention, the thermoplastic resin pipe is extruded in a completely molten state, and there is no temperature difference between the inside and outside when it is extruded, and it is further rapidly cooled in a refrigerant tank. The obtained thermoplastic resin pipe has excellent transparency, and since it is extruded with a low melt viscosity, that is, with improved fluidity, the liquid refrigerant is lubricated during ising to further reduce the pressure. Because it acts as a lubricant, the proportion of the pipe that comes into direct contact with the sizer is small, resulting in excellent smoothness, and the effect of lubricant is even more effective when a lubricant is mixed in the thermoplastic resin. In addition, in the method of the present invention, the resin pipe is sized under reduced pressure after its melt viscosity has solidified and increased to a high degree, so that the resin pipe does not lose its shape due to its own weight, such as sagging, and has extremely excellent roundness. Can be used to form pipes. In particular, pipes manufactured from a vinyl chloride resin composition in which acrylic resin is blended with soft vinyl chloride resin have improved transparency, and the melt viscosity of the resin pipe is higher than that of 4DK, which does not contain acrylic resin. No deformation such as curling is observed, and the roundness is further improved and the elastic modulus is high. Pipes made of vinyl chloride resin are suitably used for medical tubes such as dialysis tubes, cardiopulmonary tubes, and blood transfusion tubes, and food pipes used for transporting foods, beverages, and the like.

"Examples" Next, the method of the present invention will be described in detail in Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1. Ratio Example 1 Polyvinyl chloride (degree of polymerization t3oo) 0 parts by weight, IJJ (phthalic di-2-ethylhexyl) 502
7 parts by weight of epoxidized aluminum oil, 1.2 parts by weight of calcium-zinc stabilizer, 9.1 parts by weight of stearic acid and 0.1 part by weight of barium stearate were uniformly kneaded, and vinyl chloride was mixed. Pellets of the resin composition were produced. The pellets were transferred to the pipe manufacturing equipment shown in Fig. 1, which was connected to an extruder with a diameter of 4LOwsφ and WD = 22 equipped with a straight pipe die shown in Fig. 3 (A), and pipes were continuously formed under the following forming conditions. It was pushed out. Pipe dimensions are outer diameter/jsmg
1, and the inner diameter is 50 wm.

Temperature setting> Unit: 2℃ Cylinder, die head.

On (40s O, H 1 Hiroj 111 /6! /'l!
/60 Die Link, Mantosil, resin temperature.

DI D2 170 +2DD 200 /9
1. Sizing device> Refrigerant tank length, decompression chamber length, degree of decompression.

200m 500exa -rmHg sizer diameter, sizer material 1! Check the transparency and roundness of fluororesin molded pipes with the naked eye.

Observation of internal and external smoothness using an electron microscope.

All showed good results.

For comparison, sizer diameter/j, js is used as a sizing device.
J21, using a CODOcxs refrigerant tank equipped with a fluororesin sizer material, we observed the transparency, roundness, and smoothness of the inner and outer surfaces without vacuum sizing. 1 was in good condition, but the roundness was extremely poor due to curling due to its own weight, making it difficult to put it to practical use.

Example λ, J Vinyl chloride resin (polymerization [1300) / 00 parts by weight,
phthalate, Gikoethylhexyl refi, 7 parts by weight of Epocyanseed oil, 1.1 parts of calcium-zinc stabilizer.
Part by weight, polymethacrylic methyl (molecular weight approximately 600,000) 1
Part by weight, 17797150.1 part by weight and 0.1 part by weight of barium stearate were mixed and kneaded to produce a pellet-like composition. Using the pipe manufacturing apparatus used in Example 1, a pipe was manufactured using the composition under the following set temperature conditions (unit: °C).

cylinder die head,
Dairing ol ox as 04
HDI D Hit/JOIJO/50
/70 /70 /77 /O A mandrel heated to 190° C. (resin temperature iro° C.) was used as Example 1, and a material that was not heated was used as Example 3 (mandrel temperature: at most up to the resin temperature).

The transparency, roundness, and smoothness of the inner and outer surfaces of the manufactured pipe were examined, and all results were good except for the inner smoothness of Example 3. Although the inner surface smoothness of Example J was good, slightly small ridges were observed.

Examples, Comparative Examples L/D = here, compression roux paste 0 φ extruder equipped with straight die device (H) in Figure 3, sizing device shown in Figure 2 A pipe was extruded from low-density polyethylene at the following temperature range (unit: -°C) using a thermoplastic resin pipe manufacturing equipment combining:

Cylinder, die head, die ring, mandrel a, at as iao tto ttz ito
iro ir.

For comparison, a pipe was formed using the sizing device used in Comparative Example 1 at the above-mentioned temperature.

The obtained pipes were observed for roundness and internal smoothness, and the results are summarized in the table below.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal sectional front view showing an example of a thermoplastic resin pipe manufacturing device, Fig. 2 is a schematic longitudinal sectional front view showing another example of a sizing device, and Figs. 3 (a), (b), and ( c) is a longitudinal sectional front view showing an example of a pipe die. In the figure, l is extrusion type, g, 2 hiro is sizing equipment,! , koj is the refrigerant tank, t, kot is the decompression chamber, r, r'5.2r, 2
r' is sizer, 3, Hiroko, j is mandrel, 33
,v3,! 3 indicates a heater. Patent applicant: Mitsubishi Monnant Plastic Vinyl Co., Ltd. Agent: Patent attorney: For Hase - Atsushi Otani 1 Illustration 2 (2) On page 77, line 1O and page 19, line S, stearic acid Correct the words "barium" to "butyl stearate."that's all

Claims (3)

[Claims] (1) In a method of manufacturing thermoplastic resin pipes by continuous extrusion, an extruder is equipped with a pipe die that allows temperature control of the mandrel, and a refrigerant tank is used to store liquid refrigerant. The molten thermoplastic resin pipe extruded from the pipe die is quickly guided to a refrigerant tank to completely solidify the molten viscosity of the pipe using a sizing device consisting of a decompression chamber located at the same location and equipped with a sizer. 1. A method for producing a thermoplastic resin pipe, the method comprising: increasing the pressure to a level where the pipe does not swell, and then sizing the thermoplastic resin pipe at reduced pressure at the same time as introducing it into a reduced pressure chamber. (2) The method for manufacturing a thermoplastic resin pipe according to claim 1, in which the temperature of the mandrel device is set to be higher than the temperature of the thermoplastic resin pipe in a molten state. (3) The degree of vacuum in the vacuum chamber during vacuum sizing is between 50 and 20.
The method for manufacturing a thermoplastic resin pipe according to claim 1, wherein the temperature is within the range of mmHg.