JPS59102930A - Molding process - Google Patents

Abstract

PURPOSE:To mold a polyolefin resin with preventing occurrence of defects and crosslinking in the inside of a molding machine, by introducing a nitrogen gas to a feed opening for a material of the molding machine and blowing it to an outlet of an outer die. CONSTITUTION:A polyolefin grafted with a silane is blended with a silanol condensation catalyst, fed to a hopper, and molded with blowing a nitrogen gas to a feed opening for a material of a molding machine and/or to an outlet of an outer die. EFFECT:A molded article having improved appearance of the surface and low variability of physical properties can be obtained even by an injecting molding machine.

Description

[Detailed description of the invention] Concerning a method for manufacturing shaped articles.

Recently, silane-grafted polyolefins can be easily crosslinked in the presence of moisture and a silanol condensation catalyst after molding. I
Due to its excellent heat resistance and stress resistance, it is being used in a wide range of applications such as pipes, pipes, and films.

The manufacturing method involves adding a silane canopring agent and a free radical generator to a polyolefin resin, and kneading the mixture in an extruder at a high temperature higher than the decomposition temperature of the free radical generator to produce a silane-grafted polyolefin. A master patch containing a silanol condensation catalyst is produced. A masterbatch containing this silane-grafted polyolefin and a silanol condensation catalyst is mixed at a predetermined ratio and charged into a molding machine to produce a molded article, which is then crosslinked in the presence of moisture. However, when making molded articles from a mixture of a silane-grafted polyolefin and a silanol condensation catalyst, the major problems are the formation of lumps due to the crosslinking phenomenon within the cylinder and the generation of large amounts of eye oil. ! In the case of insulating layer coating for power cables, pipe extrusion, and extrusion molding of sheets and films, it is necessary to eliminate eye grease that adheres to the in-die tip and end, improving continuous productivity, yield, etc.
Furthermore, it has a great influence on the performance of molded products, making production difficult in some cases, and is currently a major obstacle to the use of 7-run crosslinked polyolefins.

As a result of intensive study to overcome this situation, the inventor found that
We have discovered that the use of nitrogen gas has a surprising effect on preventing eye oil and crosslinking within the cylinder, and have completed the present invention.

That is, in the present invention, when a silanol condensation catalyst is added to a silane-grafted polyolefin and molded, nitrogen gas is blown into the old material supply port of the molding machine and/or nitrogen gas is blown into the out-die outlet. , to prevent the formation of eye oil and crosslinking inside the molding machine? The present invention provides a molding method with a characteristic feature. More specifically, in the present invention, when a molded article is made from a mixture of a silane-grafted polyolefin and a silanol condensation catalyst, or when a single silane-grafted polyolefin is molded, nitrogen gas is blown into the popper to cover the insulating layer of the electrical cable. By preventing oil from forming on the tip of the in-die during pipe molding and by preventing crosslinking within the cylinder, it prevents the occurrence of lumps during long-term continuous production. Furthermore, even in injection molding, which is difficult with disilane cross-linked polyolefin due to the prevention of cross-linking in the cylinder, it is possible to obtain molded products with a good surface appearance and less variation in physical properties, making it possible to virtually eliminate injection molding. It can now be applied to other fields as well. Furthermore, in extrusion molding, eye oil that adheres to the tip of the out die is a big problem, and the cause of this eye oil generation was thought to be a phenomenon on the inner surface of the cylinder, die, etc. By spraying crab gas from the beginning of extrusion molding on the areas where eye oil is generated, no eye oil will be generated at all.
I discovered a serious fact. Based on this fact, it is estimated that oxygen and moisture in the air that comes into contact with the moment the molten resin is discharged have a major influence on the cause of the above-mentioned in-dye eye discharge and out-die discharge. Furthermore, this cause estimation is applied not only to silane-grafted polyolefins but also to general polyolefin resins and other resins.

In addition, although nitrogen gas is used in the present invention, this is because it is believed that it is possible to use only nitrogen gas from an economic point of view in actual production, and other inert gases may also have the same effect. Needless to say, you can see it.

As described above, the present invention uses nitrogen gas to add a silanol condensation catalyst to a silane-grafted polyolefin to prevent the generation of eye oil when molding or when molding a silane-grafted polyolefin alone. prevent,
Moreover, the ability to prevent cross-linking within the cylinder 17 greatly expands the scope of application of silane-grafted polyolefins, and has great industrial significance.

The present invention will be specifically explained below using Examples.

Example Low density polyethylene (MI: 2. O11 parts: 0.
922) Base silane-crafted polyethylene grafted with vinyltrimethoxysilane 95 heavy parts to dibutyl SIS dilauray) (DBTDL) 1 heavy part added L 7' low density ho IJ ethylene paste masterbatch 5 M f 4 parts When mixing and putting into the hopper of a 65mmΦ extruder and extruding it into a steel core with a diameter of 1.2Φ with a thickness of 0.5mm using the wire lamination method, there were It's blowing when you can feel the airflow of cogas on your skin (secondary cylinder pressure, 0.5 kdJ or less).

As a comparative example, the same electron π9 coating extrusion was carried out without using Crab X gas at all, and the results of the T system were excellent.

Example 2 High-density polyethylene (ΔlI: 1.o, density 1jp (1
955) Mix 4 parts of silane-grafted polyethylene 95-based fall with vinyltrimethoxysilane grafted with 4 parts of a high-density polyethylene paste master patch 5 parts to which 1 part by weight of TDL has been added, and further i
After mixing 5 layers of carbon masterbatch with n+ tight anti-polyethylene paste, the mixture was charged into the hopper of a 90-port Φ extruder. At that time, a 71Φ hole was made at the top of the connection between the hopper and the extruder body, and a thin nail pipe was inserted into the hole, and nitrogen gas was blown into the material supply port of the cylinder.

Furthermore, nitrogen gas was blown onto the extruder tip out-die outlet from four directions: top, bottom, left and right, and the outer diameter was 341Φ and the wall thickness was 2.
, I pushed out the vibe of the 5th victory.

Comparative Example 2 Pipe extrusion with the same dimensions as in Example 2 was performed without using nitrogen gas for a period of time.

Example 3 Silane-grafted polyolefin 95h1 grafted with vinyltriethoxysilane based on low density polyxfv (Ml: 5.O1 density 0.922)
A cylindrical container made by injection molding of 3502 (outer diameter 10 gates Φ wall thickness 2 mm ), nitrogen gas was blown from the hopper in the same manner as in Example (2).

Regarding the molded products, the iT value was determined based on the appearance and tensile test Ei>.

Comparative Example 3 The same molding as in Example 3 was performed without using nitrogen gas.

Patent applicant Sumitomo Bakelite Co., Ltd.-21!

Claims (1)

[Claims] When adding a silanol condensation catalyst to a silane-grafted polyolefin and molding it, blowing nitrogen gas into the material supply port of the molding machine and/or blowing nitrogen gas into the out-die outlet can prevent the generation of eye oil and Molding method characterized by preventing crosslinking inside the molding machine