JP2938371B2 - Extrusion molding machine and extrusion molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extruding a synthetic resin such as polyethylene, a method for producing electric wires and cables using the extrusion method, and an extruder used for the method.

[0002]

2. Description of the Related Art For example, the production of a cross-linked polyethylene insulated power cable, particularly the formation of an insulator made of the cross-linked polyethylene is performed as follows. An antioxidant such as a phenolic antioxidant is added to the low-density polyethylene pellets and kneaded with a pelletizing extruder to obtain an antioxidant-containing low-density polyethylene pellet. Next, a crosslinking agent composed of an organic peroxide such as dicumyl peroxide is added to the pellet, and the mixture is stirred with a stirrer such as a Henschel mixer or a super mixer to impregnate the pellet with the crosslinking agent and crosslink with the antioxidant. And pellets containing the agent.

[0003] Thereafter, the pellets are put into an extruder, melted and kneaded, and extruded and coated on a conductor from a crosshead die to form an uncrosslinked insulator. Then, this is sent to a cross-linking device such as a cross-linking cylinder and heated to cross-link the insulator.

In such a production method, the steps of adding an anti-aging agent, adding a cross-linking agent, and extruding a conductor are separately separated. There is a need for a transportation step or the like, and the work is extremely inefficient, and there is a risk that foreign matter, dust and the like may be mixed in each step.

For this reason, a method has been considered in which the addition of a crosslinking agent and the extrusion coating of a conductor are simultaneously performed to improve the working efficiency and reduce the contamination of foreign substances. In this method, a cross-linking agent press-in hole that penetrates a cylinder or screw of an extrusion molding machine for extrusion coating is formed, a liquid cross-linking agent is press-fitted from the cross-linking agent press-in hole, and an anti-aging agent in the cylinder is formed. And a crosslinking agent mixed in a low-density polyethylene in a molten state containing

However, in this method, when the cross-linking agent is press-fitted from the cross-linking agent press-in hole on the cylinder side, a resin slip phenomenon occurs in which the molten resin slips between the inner wall surface of the cylinder. Trouble occurs. Also, when press-fitted from the screw-side cross-linking agent press-in hole, the cross-linking agent is not sufficiently dispersed and permeated into the molten resin, and the remaining liquid cross-linking agent that has not penetrated remains in the groove from the base of the screw flight. The remaining cross-linking agent may cause inconvenience such as scorch (resin seizure).

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent a resin slip phenomenon or a scorch from occurring even when an additive such as a crosslinking agent is directly added to a synthetic resin in an extruder. It is another object of the present invention to make it possible to simultaneously perform addition of an additive and extrusion molding of a synthetic resin.

[0008]

SUMMARY OF THE INVENTION The above problem is a groove in the supply portion of the compression section side of the screw of the extruder, the groove
Is provided on the front side of the nozzle with an injection nozzle having an injection port formed of a porous plate and projecting from the bottom of the groove. The problem can be solved by mixing an additive into the resin in a mist state and melt-kneading the synthetic resin.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
1 and 2 show an example of an extruder according to the present invention. In the figures, reference numeral 1 denotes a cylinder of the extruder. A screw 2 is inserted into the cylinder 1, and a hopper 3 for charging synthetic resin pellets and powder into the cylinder 1 is attached to the rear side of the cylinder 1. The base of the screw 2 is connected to a rotation drive device 5 via a thrust bearing 4 so as to rotate. Further, heaters 6 are provided outside the cylinder 1 so that the synthetic resin inside can be heated. A crosshead die 7 is mounted at the tip of the cylinder 1.

[0010] The screw 2 has, from its base side,
As shown by the broken lines, three areas called a supply section A, a compression section B, and a measurement section C are formed. An injection nozzle 8 is attached to a position near the compression section B of the supply section A of the screw 2 as shown in FIG. The injection nozzle 8 is inserted into and fixed to a small hole formed through the hollow screw 2.
A cylindrical upper body 10 screwed to the main body 9 and having a tip protruding from the bottom of the groove; and a porous plate injection port 1 made of a sintered metal plate fixed to the tip of the upper body 10.
1, the main body 9 and the upper body 10
Are formed.

One end of the introduction hole 12 of the injection nozzle 8 opens to the injection port 11 as described above, and the other end is connected to one end of a supply pipe 13 made of a flexible metal. The other end of the supply pipe 13 passes through a hollow portion in the screw 2, reaches the outside of the screw 2, and is connected to a liquid additive supply device 14 via a rotary joint 13 a.

The liquid additive supply device 14 includes a melting tank 15,
The storage tank 16 and the pressure pump 17 are main components, and the additive solid at room temperature is heated and melted in the melting tank 15 and sent to the storage tank 16, and the additive liquid at room temperature is added to the storage tank 16. It is stored in. The liquid additive starts from pipe 1
8, a filter 19, a flow meter 20, and a pressure feed pump 17, where the pressure is increased to 5 to 50 kg / cm ² , and a pressure gauge 21 and a filter 22 are sent to the supply pipe 13. The mist is ejected from the ejection port 11 of the ejection nozzle 8 in the form of a mist.

As shown in FIG. 2, the injection nozzle 8 is provided in front of the groove of the screw 2, that is, at a position close to the flight 2a on the front side.
2, the injection port 11 of the injection nozzle 8 is always in contact with the unmelted synthetic resin N as shown in FIG. It can be sprayed on the molten synthetic resin N. The number of the injection nozzles 8 to be installed may be one for one screw 2,
It is not necessary to provide a large number of pieces, and at most a few pieces are sufficient.

Next, a method for forming an insulator of a crosslinked polyethylene insulated power cable will be described as an example of an extrusion method using such an extruder. First, the above-described extruder is started, and low-density polyethylene pellets to which an antioxidant has been added in advance are charged from the hopper 3. On the other hand, dicumyl peroxide as a cross-linking agent is charged into the melting tank 15 of the liquid additive supply device 14, and heated here.
It is melted and sent to the storage tank 16. Liquid dicumyl peroxide from the storage tank 16 is supplied to the pressure pump 17 via the pipe 18, the filter 19, and the meter 20.

The liquid dicumyl peroxide pressurized to a pressure of 5 to 50 kg / cm ^{2 by} the pressure feed pump 17 passes through the pressure gauge 21, the filter 22, the rotary joint 13a, the supply pipe 13 and the injection nozzle 8 Mouth 11
From the mist. At this time, since the position of the injection nozzle 8 is determined so as to be in contact with the unmelted low-density polyethylene pellets as shown in FIG. 2, the sprayed dicumyl peroxide is added to the unmelted pellet-shaped polyethylene. Sprayed under pressure, dicumyl peroxide uniformly adheres to the entire surface of the low-density polyethylene pellets. In this state, the pellets are sequentially fed forward, melted and kneaded, so that dicumyl peroxide is Permeation and dispersion into low-density polyethylene are performed uniformly.

As a result, dicumyl peroxide does not remain at the bottom of the groove of the screw 2 and there is no scorch due to this. In this way, the low-density polyethylene in the molten state, into which dicumyl peroxide is uniformly added and permeated, is sent to the tip side with the rotation of the screw 2, and is extruded onto the conductor from the crosshead die 7 and is not crosslinked. And insulator. At this time, if necessary, the inner semiconductive layer and the outer semiconductive layer can be simultaneously extrusion-coated by a three-layer coextrusion method. The cable on which the uncrosslinked insulator is formed is sent to the crosslinking device,
It is heated above the activation temperature of dicumyl peroxide and crosslinked to form a crosslinked insulator, thereby obtaining the desired crosslinked polyethylene insulated power cable.

According to such an extrusion molding method, the addition of dicumyl peroxide, which is a cross-linking agent, and the formation of an insulator can be efficiently performed in one step.
The risk of foreign matter being mixed in is also reduced. Further, since the injection and addition of dicumyl peroxide as a crosslinking agent is performed from the screw 2 side, there is no resin sliding phenomenon in the conventional method, and a stable extrusion operation can be performed. Furthermore, the installation position of the injection nozzle 8 is set in the groove in front of the supply portion A of the screw 2,
Since the atomized dicumyl peroxide is injected from the injection nozzle 8 at the front side of the groove, the dispersion and permeation of dicumyl peroxide to the low-density polyethylene are uniformly performed as described above. Thus, dicumyl peroxide does not remain at the bottom of the groove of the screw 2, and there is a possibility that scorch may occur. In addition, since dicumyl peroxide is uniformly added to the low-density polyethylene, the insulator is uniformly crosslinked.

In the extrusion molding method of the present invention, various additives other than the crosslinking agent represented by dicumyl peroxide, such as an antioxidant, a crosslinking assistant,
A stabilizer, an ultraviolet absorber, and a polymerizable silane compound such as vinylalkoxysilane for silane crosslinking can be used in the same manner. If necessary, two or more additives,
For example, a mixture of an organic peroxide and a polymerizable silane compound can be injected from the injection nozzle 8.

As the synthetic resin, not only various polyethylenes other than low-density polyethylene but also thermoplastic synthetic resins such as polypropylene, polystyrene, acrylic resin, polyamide, polycarbonate and vinyl chloride resin can be used. Furthermore, in addition to extrusion coating of insulators of electric wires and cables, not only extrusion coating of inner and outer semiconductive layers, sheaths and the like, but also various extrusion molding other than these extrusion coating, for example, molding of a plastic sheet by a T-die,
It goes without saying that the present invention can be applied to profile extrusion molding, extrusion lamination, inflation molding and the like.

Hereinafter, specific examples will be described. (Example 1) A crosslinked polyethylene insulated power cable was manufactured using the extruder shown in FIGS. A low-density polyethylene containing 0.2% by weight of a phenolic antioxidant is supplied to the above-mentioned extruder, and a molten liquid dicumyl peroxide at a temperature of 60 to 65 ° C. and a pressure of 20 to 25 kg / cm ² is supplied from an injection nozzle. Sprayed. The injection amount of dicumyl peroxide was adjusted so as to be 2 parts by weight with respect to 100 parts by weight of the low-density polyethylene. The obtained cable is sent to a crosslinking device, where it is heated,
Crosslinking was performed to obtain the desired crosslinked polyethylene insulated power cable. The thermal deformation rate of the crosslinked insulator of this power cable is 17
１８18%, the gel fraction was 80-84%, and it was found that dicumyl peroxide was uniformly dispersed and sufficiently crosslinked. No scorch was observed during extrusion molding.

Example 2 A crosslinked polyethylene insulated wire for outdoor use was manufactured using the extruder shown in FIGS. A low-density polyethylene containing 0.2% by weight of a phenolic antioxidant and 0.8% by weight of carbon black is supplied to the extruder, and a temperature of 60 to 6 is supplied from an injection nozzle.
Dicumyl peroxide in the form of a molten liquid at 5 ° C. and a pressure of 20 to 25 kg / cm ² was injected. Dicumyl peroxide was added in an amount of 2 parts by weight per 100 parts by weight of low-density polyethylene.
The injection amount was adjusted so as to be parts by weight. The obtained electric wire was sent to a cross-linking device, where it was heated and cross-linked to obtain a target outdoor cross-linked polyethylene insulated electric wire. The cross-linked insulator of this wire has a heating deformation rate of 15 to 18% and a gel fraction of 7
It was found to be 8 to 82%, indicating that dicumyl peroxide was uniformly dispersed and sufficiently crosslinked. No scorch was observed during extrusion molding.

Example 3 A silane cross-linked outdoor cross-linked polyethylene insulated wire was manufactured using the extruder shown in FIGS. A low-density polyethylene containing carbon black, dibutyltin silaurate (crosslinking catalyst), an antioxidant and a copper inhibitor is supplied to the above extruder, and a mixture of trimethoxyvinylsilane and dicumyl peroxide is injected from an injection nozzle. Temperature 50-55 ° C,
Injection was performed at a pressure of 20 to 25 kg / cm ² . The injection amount was adjusted so that the addition amount of this mixture was 2 parts by weight with respect to 100 parts by weight of the low-density polyethylene. 8
It was immersed in warm water of 0 ° C. for 24 hours to perform silane crosslinking. The insulator of this electric wire had a heating deformation rate of 8% and a gel fraction of 82%, and it was found that trimethoxysilane and dicumyl peroxide were uniformly dispersed and added, and were sufficiently crosslinked. did. No scorch was observed during extrusion molding.

[0023]

As described above, according to the present invention,
Since the addition of an additive such as a cross-linking agent and the extrusion molding of an insulator and the like can be performed at once, the production efficiency is improved, and the risk of dust and foreign matter being mixed is reduced. In addition, the additives are uniformly dispersed in the synthetic resin. Further, there is obtained an effect that a stable extrusion operation can be realized without occurrence of a resin sliding phenomenon or scorch.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an extrusion molding machine of the present invention.

FIG. 2 is an enlarged configuration diagram of a main part showing an example of a mounting state of an injection nozzle according to the present invention.

[Explanation of symbols]

2: Screw, A: supply unit, 8: injection nozzle, 14: liquid additive supply device, N: unmelted synthetic resin

Continuation of the front page (72) Inventor Koji Hosoya 1800 Kishioka-cho, Suzuka-shi, Mie Prefecture Fujikura Co., Ltd. Suzuka Factory (56) References JP-A-54-19191 (JP, A) JP-A-4-44826 (JP, A) JP-A-3-111433 (JP, A) JP-A-6-190898 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 47/36 B29C 47/02 B29C 47 / 10 B29K 23:00

Claims (4)

(57) [Claims] An injection nozzle for spraying a liquid additive in a mist state is provided in a groove of a supply portion of a screw of an extruder, and a pressure supply means for pressurizing and supplying the liquid additive to the injection nozzle is provided. An injection nozzle protrudes from the bottom of the groove and has an injection port made of a porous plate .
It is the groove of the supply part near the compression part of Clew,
An extrusion molding machine characterized by being on the front side . 2. A synthetic resin is charged into the extruder according to claim 1, and when the synthetic resin is melt-kneaded, a liquid additive is sprayed in a mist form from a spray nozzle, and the additive is added to the unmelted synthetic resin. An extrusion molding method characterized by incorporating a compound. 3. A synthetic resin is charged into the extruder according to claim 1, and when the synthetic resin is melt-kneaded, a liquid additive is sprayed in a mist form from a spray nozzle, and the additive is added to the unmelted synthetic resin. And melt-kneading the mixture, and extrusion-coating the mixture on a conductor. 4. Oite to claim 3, a polyethylene synthetic resin contains a anti-aging agent, wires additive is characterized in that an organic peroxide, preparation of the cable.