JPH09262852A - Manufacture of crosslinked polyolefin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recycle a waste material and realize the manufacturing of a molded body having high value added by a method wherein, after being shaped in a predetermined shape, the powdered material of a crosslinled polyoledfin is formed by being heated at a temperature higher than the melting point and under pressure and, in succession, cooled down under pressure. SOLUTION: The specimens 4 of crosslinked polyethylene (XLPE) in a fine powder picked from a crosslinked polyethylene insulated cable are prepared and then formed into a sheet with a pressing machine. First of all, a stainless steel plate 2 having a smooth surface is placed on a reinforcing plate 1. Then, a stainless steel form 3, which has a predetermined thickness and at the central part of which a four-cornered space part 3a is provided, is placed on the stainless steel plate 2. After that, specimens 4 are fed in the space part 3a to overflowing. Next, the stainless steel plate 2 and the reinforcing plate 1 are placed on the firm 5 in the order named. After being pre-heated by being pinched between hot platens 7, in which the heaters 6 of the pressing machine 6 are built, the whole assembly is heated under pressure up to the melting point of the XLPE and finally cooled down under pressure in order to obtain a sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crosslinked polyolefin molded body, and particularly to a powder obtained by recovering a crosslinked polyolefin waste material such as crosslinked polyethylene and mechanically crushing or crushing the waste material. It relates to a method for producing a shaped body from granules (powder or granular pieces).

[0002]

2. Description of the Related Art Generally, crosslinked polyethylene (XLPE), which is a typical crosslinked polyolefin, has been widely used for several decades as an insulating material for electric wires and cables. And in such cross-linked polyethylene,
In order to effectively utilize the waste (waste) generated during manufacturing and the insulator of the removed CV cable (cross-linked polyethylene insulation cable), as a recycling system, oil fuel technology and pulverized fuel equivalent to pulverized coal are produced. Research on the practical application of technology has been carried out for a long time, and it is considered to be used as a molding material having a higher added value in addition to fuel.

[0003]

However, it has hitherto been impossible to obtain a molded product by molding a fine powder material of crosslinked polyolefin. That is, in a cross-linked polyolefin such as cross-linked polyethylene (XLPE), the polyolefin polymers are bonded to each other in a mesh shape, so that simply heating above the melting point does not melt and soften like uncross-linked polyolefin, but they are dispersed. It became a small piece, and a molded body could not be obtained.

The present invention has been made in view of the above circumstances, and provides a method for producing a molded article having a high added value such as a sheet by recycling a waste material of a crosslinked polyolefin such as crosslinked polyethylene. The purpose is to

[0005]

Means for Solving the Problems The method for producing a crosslinked polyolefin molded article of the present invention is a method in which a powdered particle of a crosslinked polyolefin is shaped into a predetermined shape and then pressure-molded while being heated to a temperature above the melting point of the crosslinked polyolefin. And then cooling with pressurization.

Typical examples of the crosslinked polyolefin used in the present invention include crosslinked polyethylene (XLPE), but crosslinked polypropylene (PP), ethylene-vinyl acetate copolymer (EVA) and ethylene-ethyl acrylate copolymer. Examples thereof include a cross-linked body of a combination (EEA), and not only these simple substances but also a blended body can be used. As the crosslinked polyethylene, not only a crosslinked body of low density polyethylene (LDPE) but also a crosslinked body of high density polyethylene (HDPE), LLDPE, VLDPE or the like can be used. Further, the cross-linking method is not limited, and cross-linking is performed by a method such as chemical cross-linking, electron beam cross-linking, or silane graft water cross-linking (silane cross-linking) in which an organic silane compound is mixed and water is permeated in the presence of a catalyst to cross-link. Polyolefins can also be used.

In the present invention, a molded article made of a crosslinked polyolefin such as an insulator of a CV cable is used.
It is mechanically crushed or crushed before use. The size of the powder or granular material (powder or granular particles) is preferably in the range of several μm to 10 mm in diameter (powder diameter or particle size), more preferably several μm to several 100 μm. In particular, a transparent molded body can be obtained from a fine powder cross-linked polyolefin material having a diameter of several μm. Further, it is not preferable to use a cross-linked polyolefin material having a particle size of more than 10 mm, because the resulting molded product has poor mechanical properties, especially elongation.

The heating temperature at the time of molding such a crosslinked polyolefin powder is set to a temperature equal to or higher than the melting point of the crosslinked polyolefin. It is possible to heat up to a temperature about 200 ° C higher than the melting point, but if the heating temperature during molding is too high, discoloration (yellowing) due to oxidative deterioration of the polyolefin will occur at the end of the molded body, etc. Absent.

The pressure applied at the time of pressurization / heat molding is
Cool to 10kgf / cm ² or more and continue applying such pressure. The slower the cooling rate, the more excellent the transparency and the mechanical strength of the molded product. In the present invention, 10 ° C / min
It is desirable to gradually cool at the following cooling rate. Furthermore, it is preferable to release the pressure after cooling to a temperature equal to or lower than the melting point of the crosslinked polyolefin.

Further, in the present invention, the above-mentioned crosslinked polyolefin powder and granules are filled in a mold while decompressing and bleeding, shaped into a predetermined shape (shape inside the mold), and then pressed. -A molded product having a predetermined shape such as a thick plate or a column can be obtained by heating and molding, and then cooling while pressing in a mold. In particular, a sheet formed by press molding as shown below. The shaped body can be suitably manufactured.

That is, the crosslinked polyolefin powder is
After filling and shaping in a mold having a predetermined thickness, it is sandwiched between a pair of heating plates and heated under pressure, and then cooled while being pressurized, thereby forming a film with good characteristics or A sheet-shaped molded body can be easily manufactured.

The molded product obtained by the method of the present invention has a low raw material cost and sufficiently good mechanical properties, so that it can be widely used as a stationery such as an underlay or a household item. In addition, since the obtained molded product does not contain a plasticizer unlike a polyvinyl chloride product, it does not transfer the plasticizer and is unlikely to become dirty. Furthermore, since it does not contain halogen-based elements, there is no risk of polluting the environment when it is recycled and finally discarded.

[0013]

Embodiments of the present invention will be described below.

Examples 1 to 6 Insulators taken from CV cables and insulators with a semiconductive layer (insulator + inner semiconductive layer + outer semiconductive layer) were crushed into fine powders (powder diameter: several μm). The XLPE sample and the semi-conductive XLPE sample in the form of fine powder were prepared.

Next, these samples were sandwiched between two stainless steel plates each having a mirror-finished surface by an appropriate amount, and these were sandwiched between the hot plates of a press machine (pressurizing / heating device) together with the reinforcing plates arranged above and below. After preheating for 10 minutes, 10kgf / cm while heating to a temperature above the melting point of XLPE shown in Table 1.
Pressurized at a pressure of ² or more for 10 minutes. After that, it was gradually cooled while being pressurized. Also, as Comparative Example 1, the same finely powdered XLPE sample as in Example 1 was pressed while being heated to a temperature (180 ° C.) higher than the melting point of XLPE, and then the hot platen was opened to release the pressure. After cooling. Further, as Comparative Example 2, a finely powdered XLPE sample was subjected to a temperature (1
After pressurizing while heating to (00 ° C.), it was gradually cooled while being pressurized.

Thus, a film (thin film) shaped molded body was obtained except for Comparative Example 1. Table 1 shows the results of observing the film thickness and the state of the obtained molded body with the naked eye.

[0017]

[Table 1] From the results in Table 1, in Examples 1 to 5, fine powder XLPE was used.
Since the sample is pressurized while being heated to a temperature above the melting point of XLPE (approximately 120 ° C or higher), and then gradually cooled while being pressurized, it is possible to obtain a transparent film with a film thickness of 0.125 to 0.305 mm. it can. In addition, fine powdery semi-conductive XLPE
In Example 6 in which the sample was used and similarly formed, a uniform black film having a film thickness of 0.290 to 0.330 mm was obtained.

On the other hand, in Comparative Example 1, after pressing and heating by sandwiching between the heating plates, the film was taken out from the press machine and the pressurization was released for cooling, so that the film could not be formed. . Further, in Comparative Example 2, since pressure molding is performed while heating at a temperature equal to or lower than the melting point of XLPE, an unmelted portion (a powder boundary portion due to unmelting) was observed at the end portion and part of the film.

Examples 7 to 15 Insulators collected from CV cables were crushed or crushed,
A finely powdered XLPE sample having a particle diameter of several μm, a coarse granular XLPE sample A having a particle diameter of 2 to 10 mm, and a granular XLPE sample B having a particle diameter of 2 to 3 mm were prepared. Also, CV
The insulator with the semiconductive layer of the cable was crushed to prepare a fine powdery semiconductive XLPE sample.

Next, these samples were molded into a sheet by using a press machine (pressurizing / heating apparatus) as shown below. That is, as shown in FIG. 1A, first, a stainless plate 2 having a smooth surface is placed on a reinforcing plate 1, and a thickness (1 mm, 2 mm, 3 mm) corresponding to a sheet to be molded is placed on the stainless plate 2.
mm) and a square-shaped space 3a provided in the central portion of the stainless steel mold 3 is arranged.
The fine powdery or granular sample 4 was supplied in a heap into the space 3a. In addition, the mold 3 is provided with a groove 3b that communicates the central space 3a with the outside, and the air contained between the powder and granular material of the sample 4 presses this groove 3b when pressurizing. It is designed to be pulled out to the outside.

Next, as shown in FIG. 1B, the form 3
After the stainless steel plate 2 and the reinforcing plate 1 were placed in this order on the above, the whole of them was sandwiched between the heating plates 7 including the heater 6 of the press machine 5, as shown in FIG. Then, after preheating for 10 minutes or 20 minutes, while heating to a temperature above the melting point of XLPE shown in Table 2, at a pressure of 10 kgf / cm ² or more.
Pressurized for 20 minutes. After that, the material was cooled gradually or rapidly with the pressure applied. Thus, a transparent or translucent sheet having a thickness of 1 mm was obtained.

Then, a tensile test was conducted on the obtained sheet to measure the tensile strength and the elongation, respectively. The appearance (color or transparent or translucent) of the obtained sheet and the result of the tensile test are shown in Table 2.

[0023]

[Table 2] From the results of Table 1, it was found that in Examples 7 to 15, sheets having the same tensile strength as the polyethylene press sheet and a sufficiently satisfactory elongation for practical use were obtained. Particularly, in Examples 7 to 12 in which molding was performed using a finely powdered XLPE sample, granular XLP or the like was used.
As compared with Examples 13 to 15 in which molding was performed using the E sample, a large elongation and a transparent sheet was obtained. This is considered for the following reason. That is,
By pressurization and heating of XLPE, the cross-linked portion does not melt and does not mix, but the non-cross-linked portion melts and this bonds the cross-linked portion as a binder. Further, in the finely powdered XLPE sample, since the surface area of the powdery particles is large, the degree to which the powder particles are fused and adhered (fused) to each other is large, and it is considered that the sample is transparent and exhibits a relatively large elongation. .

[0024]

As described above, according to the production method of the present invention, a waste material of crosslinked polyolefin such as crosslinked polyethylene (XLPE) is recycled and used, and it has sufficient mechanical strength and is of practical value. It is possible to obtain a molded product having a high sheet shape.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a method of molding a sample of XLPE into a sheet in an example of the present invention.

[Explanation of symbols]

 2 ………… Stainless steel plate 3 ………… Formwork 4 ………… Fine powder or granular sample 5 ………… Press machine 7 ………… Hot platen

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 105: 26

Claims (5)

[Claims] 1. A crosslinked polyolefin molding, which comprises shaping a powdered particle of a crosslinked polyolefin into a predetermined shape, pressurizing while heating to a temperature equal to or higher than a melting point of the crosslinked polyolefin, and then cooling while pressurizing. Body manufacturing method. 2. The crosslinked polyolefin powder or granular material is filled in a mold having a predetermined thickness, and the mold is sandwiched between a pair of heating plates together with the mold to apply pressure while heating and then cool while applying pressure. The method for producing a crosslinked polyolefin molded body according to claim 1, wherein 3. The method for producing a crosslinked polyolefin molded product according to claim 1, wherein the diameter of the powdered particles of the crosslinked polyolefin is in the range of several μm to 10 mm. 4. The method for producing a crosslinked polyolefin molded product according to claim 1, wherein the pressurizing during the cooling is carried out at a pressure of 10 kgf / cm ² or more. 5. The method for producing a crosslinked polyolefin molded article according to claim 1, wherein the cooling is performed by gradually cooling at a cooling rate of 10 ° C./min or less.