KR830000407B1 - Process for preparing filled and curable polymer materials - Google Patents

Abstract

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Description

Process for preparing filled and curable polymer materials

The present invention relates to a method for preparing a filler-containing polymer that can be cured by water action due to the silane compound graft-bonded onto the base molecule of the polymer.

In order to manufacture a synthetic resin product having high thermal stability and durability, it has been known for a long time to harden a polymer material with an organic peroxide. This curing process is performed under heat supply and high pressure.

In the meantime, however, other hardening methods have also emerged, in which the siloxane technique became known and realized.

Contrary to conventional peroxidative curing, here low molecular weight compounds are grafted onto the macromolecules of the base polymer and then the macromolecules are cured as a secondary reaction proceeds.

Particularly suitable for graft bonding on polyethylene molecules, for example, are some polyfunctional organosilanes, which optionally process unsaturated vinyl groups and alkoxy groups that can be readily hydrolyzed. In the graft bonded state, the polyethylene is still thermoplastic.

Now, when the minimum amount of water is supplied, the silicon atom in the silanol group contains an alkoxy group.

This curing method allows particularly reasonable provision of curable products, further improves thermal stability as compared to conventional peroxide curing methods, and is superior to commercially available VPE compounds in aging stability of cured materials.

However, when it is necessary to mix inexpensive inorganic fillers with such a curable raw material, for example to save a polymer raw material or for a product of a certain property, a problem arises as in the case of a material in which a normal peroxide curing agent is mixed.

This is because the moisture adsorbed on the filler is likely to cause precure during the ground bonding process.

The result is poor, uneven melt and unsightly extruded surfaces. It is an object of the present invention to find the possibility of obtaining a polymerized product without the risk of pre-curing when the inorganic filler is added in a material that depends on the curing mechanism acting on the basis of moisture.

A polymer, such as a homopolymer or copolymer of ethylene, is first mixed, stirred and granulated with the filler in the dry state, and the silane compound is diffused at room temperature or slightly higher in the material so prepared or already in such preparation. The above object is achieved by the present invention, wherein the curing agent-containing granules are mixed with an antioxidant and a curing catalyst-containing polymer batch, and finally the granules are subjected to an extrusion process and molded in the same process. This method ensures the production of good surface-shaped products and prevents precure.

Due to the much higher content of fillers compared to non-filled polymeric materials,

Particularly suitable fillers for the purposes of the present invention are moisture-free calcite fillers. This includes, for example, high whiteness natural acids known under the trade names Durcal 2 and Millicarb.

For example, in the production of insulators for electric cables or conductors, fillers, preferably up to 65 parts, in particular 45-55 parts, may be added to the base polymer in a single state.

However, in the practice of the present invention such fillers may be added in the state of polymer batches of high filler concentration.

In this case, for example, a batch consisting of 90 parts of filler such as lime carbonate and 30 parts of polyethylene (when polyethylene is a base material at the same time) is suitable.

In this case it is particularly advantageous to select a base material with a melt index between 0.2 and 4.0, in particular about 2.0. The extruded state and the dispersibility of the packing are then particularly good.

It may sometimes be advantageous to deviate from the process and mix polyethylene granules or copolymer granules already containing silane compounds with fillers such as batches containing lime carbonate.

After completion of the silane diffusion infiltration process, for example, an addition operation of lime carbonate is performed in a stirrer which operates rapidly or slowly, but this addition operation may be performed directly in the extruder, for example, by a conventional mixing device.

According to the method of the present invention, various products made of synthetic resin and curable can be made. The present invention can be suitably used when continuous production of long products is required due to a simple production technique that can be practiced without a large investment in commercial customary machinery. For example, it may be a synthetic resinous shape or a tubular material, or it may be a simple skin for the seam if it is necessary to protect the seam with a high heat-resistant skin.

However, a particularly advantageous use of the method of the invention lies in the manufacture of electrical cables, in particular the manufacture of electrical cables for low voltages.

Moisture hardening material acts as an insulator for wires. Since the insulation is only 2-3mm thick, the moisture supply for hardening can sometimes be completely omitted, resulting in a dramatic increase in cable manufacturing speed.

The filler used according to the invention, in addition to having a low water content, also plays a role in particle shape and particle size distribution. Particularly suitable are as follows.

Durcal 2 Millicarb

Particle Form Crystals / Rhombuses Crystals / Rhombuses

CaCO ₃ 99.0% 99.75%

Fe ₂ O ₃ 0.04% 0.02%

BET-Surface Area 4㎡ / g 2.5㎡ / g

Moisture <0.2% <0.2%

Average particle diameter-φ 3㎛ 3㎛

Finer than 2μ 40% 35%

As shown in the table, these two materials have extremely fine particle diameters and low hygroscopicity.

For example, to make a siloxane hardenable compound for insulators of low-voltage cable lines that must contain 45-55 parts of lime carbonate, the polyethylene granules of melt index 2.0, for example, are premixed in a dry state in a suitable mixer with 45-55 parts of lime carbonate. Let's do it. This premix is then stirred in a mixed extruder such as a so-called kneader and assembled without water, ie dry.

The lime carbonate packed granules thus treated are coated with a siloxane reagent in a low temperature mixing process, ie at a temperature of about 18-50 ° C. Due to the high content of lime carbonate, the silane solution penetrates into the granule surface relatively quickly, resulting in dry granules.

Granules containing the siloxane reagent are mixed with a PE batch containing an antioxidant and a curing catalyst in addition to lime carbonate in a ratio of 95: 5. Then surface bonding and molding takes place at about 200 ° C. in the same process in the same extruder.

The composition of the compounding agent as an example is as follows.

Formulation Example 1

Polyethylene 100 parts Filler 45-55

2.5 parts of silane and 0.2 parts of acid

0.07 parts catalyst

Formulation Example 2

Polymer Polymer Part 100 Refills Part 45-55

2.0 parts of silane and 0.2 parts of acid

0.07 parts catalyst

Claims (1)

In preparing a filler-containing polymer in which a silane compound is grafted onto a polymer molecule and can be cured by the action of water, a polymer such as a homopolymer or copolymer of ethylene is first premixed with the filler in a dry state, stirred, Granulate, disperse the silane compound at room temperature or slightly higher temperature in the material so prepared or already in such a preparation and mix the curing agent-containing granules with the antioxidant and curing catalyst-containing polymer batches. A method for producing a filled and curable polymer material, characterized in that the granules are graft bonded in an extrusion process and cured in the same process.