JPH04234621A - Manufacture method for extrusion molding - Google Patents

Abstract

PURPOSE: To provide a method for manufacturing a molding made of a polymer entirely or partly of a product or particularly a power cable, a pipe or the like by an extruding method. CONSTITUTION: In the method for manufacturing an extrusion molding molded to constitute different parts of the molding formed by extruding a modified polymer and a non-modified polymer via an extrusion head comprising the steps of plasticizing the polymer in an extruder, separating it to a main part and a sub-part, modifying one of both the parts, and then passing both the parts via the head; the plasticized polymer is modified by a chemical reaction. The molding having a performance multilayer structure can be easily, simply manufactured by a single extruder.

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 molded articles, in particular power cables, pipes, etc., which consist wholly or partly of polymers, by extrusion.

0002

BACKGROUND OF THE INVENTION Techniques for compounding polymers to provide desired properties have long been developed, but special formulation designs often involve compromises between the properties required for different parts of an extrudate. For example, abrasion resistance (required only on external surfaces) is often obtained at the expense of reduced flexibility.

Compromises of this type can be avoided by using two (or more) different polymer compositions, but necessarily involve the use of separate extruders for each composition, or When an extruder is used, there is a problem in that at least two or more operations are required, and the cost increases in both cases.

Furthermore, in the method of feeding two extruders to a common extrusion head (which is a satisfactory method of achieving good adhesion between the materials), the screw axes of each extruder are placed at a considerable angle to each other. (e.g. at right angles) and in this case, among many single extrusion lines, if the production line is to be located within a standard rectangular building, an efficient floor layout may be required. make it difficult

Pigmentation is achieved by extracting a secondary portion of the extruder output, mixing it with a suitable pigment, and feeding it back into the extrusion head, where this portion forms the outer layer of the extrudate. It is already known that extruded articles with a distinct surface layer of the article can be obtained at relatively low cost and production equipment for this is available commercially (for example from Fra
ncisShaw Ltd. from).

However, heretofore it has not been recognized that techniques can be adapted to obtain different surface layers and other parts beyond the scope of simple mixing of types and amounts of added mixture components.

[0007]

[Problems to be Solved by the Invention] The present invention improves the drawbacks of the prior art as described above, and makes it possible to easily and conveniently produce an excellent molded product having a high-performance multilayer structure using a single extruder. The purpose is to provide a method to do so.

[0008]

SUMMARY OF THE INVENTION The present invention involves plasticizing a polymer in an extruder, separating it into a major part and a minor part, modifying one of these parts, and then dividing both parts. This is a method for producing an extrusion molded product, which includes steps for passing both a modified polymer and a non-modified polymer through an extrusion head to constitute different parts of a molded product formed by extrusion.

Furthermore, the present invention is characterized in that the plasticized polymer described above is modified by a chemical reaction. Preferably, the above chemical reactions involve grafting side chains or introducing reactive sites for subsequent crosslinking to modify the chemical, physical, and rheological properties of the polymer, among other things. Contains operations.

[0010] Further, as the above-mentioned sub-portion, suitable compounding components may be mixed in advance before fractionating a part of the polymer, or alternatively, by appropriately designing the extruder, the sub-portion may be After the is fractionated, the formulation ingredients may be added to the main portion.

[0011] Although the fractionation of a portion of the polymer from the main portion can be controlled by a gear pump, in many cases the introduction of various chemical reagents into the appropriate portions of the polymer is a pretreatment for useful chemical reactions. Become. In the case of small portions, it is advantageous to preferably inject them in liquid form into a cavity transfer mixer.

[0012] The chemical reaction takes place in the mixer, extrusion head, and/or connecting conduit, optionally heated if necessary. Also, in the case of the main part,
Mixing and chemical reactions can occur downstream from the branch point within the extruder.

[0013]

EXAMPLES The following examples are provided for the purpose of merely illustrating the present invention.

(Example 1) Glass fiber immediately after new molding has high tensile strength, but after a certain period of time after the glass surface is exposed to air, the strength decreases significantly. A special polymer coating, or matrix, is usually used to protect the material.

Although polyethylene is inexpensive and easily available, and its properties meet most requirements, its adhesive strength to glass surfaces is extremely low. Ethylene/acrylic acid copolymers adhere strongly to glass, but are very expensive and have lower softening points than polyethylene.

According to the present invention, the degree of melt flow (melt
Low density polyethylene (as delivered, without additives) with a flow rate of 2 is plasticized in a 90 mm 26D extruder with a polyethylene type screw. 1 of the materials plasticized by the attached gear pump
0% was extracted and modified by injecting 2% (volume %) of acrylic acid in which 0.2% by weight of dicumyl peroxide was dissolved into the extracted material to obtain Fr.
Ancis Show type cavity transfer mixer (operated independently from the extruder) is used to mix and heat to a temperature of about 190° C. for about 1 minute to graft acrylic side chains onto the polyethylene.

This grafted branch stream (minor portion) is recombined with the unmodified main stream (main portion) in an extrusion crosshead that combines a thin inner layer of modified polymer with an unmodified main stream. The reinforced glass fibers are designed to be covered with a thicker outer layer of polyethylene.

In this example, since high-density ethylene/acrylic acid copolymer is not commercially available, in order to reach a result that cannot be easily obtained using two extruders, It can be modified to use high density polyethylene.

(Example 2) Plasticized polyvinyl chloride (P
VC) is widely used as insulation/sheathing material for low voltage power cables with many attractive properties, but low melting point and low abrasion resistance. Although these weaknesses are significantly improved by crosslinking, a significant amount (5-10%) of
It requires the use of expensive additives which reduce the flame resistance, and in most cases irradiation techniques must be used which are also expensive and result in limitations on the dimensions of the molded parts.

According to the invention, a conventional PVC formulation is plasticized using the same equipment used in Example 1. A gear pump separates 10% of the extrudate from the extruder and contains 5% by weight of (3,4-diamino-n-butyl)trimethoxysilane and a trace amount (approximately 0.02%) of dibutyltin dilaurate. Add. This mixture is approx.
The silane is grafted by heating at 200°C for 1 minute, and the mixture is then recombined with the main polymer stream in a double wire coating crosshead to cover the skin portion of the wire coating with the modified polymer. Form.

After 24 hours of exposure to water at 85° C., the outer layer portion is effectively crosslinked and the wire becomes resistant to the abrasion encountered when it is drawn into the guide conduit, and also to the soldering iron. It is also suitable for connecting various devices that may come in contact with each other for a short period of time, and is also suitable for use in high-temperature environments such as wiring under the hood of a vehicle.

An example of this is British Patent No. 1,485,26.
Modifications can be made to use other aminosilanes or iminosilanes such as those described in Publication No. 3.

(Example 3) In this example, the two-layer extruder is very large, and a thin metal foil moisture barrier material (aluminum,
Example 1 is similar to Example 1, except that it is applied as a cable sheath material over lead or copper. The acrylic acid grafted polyethylene promotes adhesion and eliminates the use of preformed metal/plastic laminates.

Example 4 This example shows that polyethylene grafted with acrylic acid forms the outer part of a two-layer extrusion;
Same as Example 3 except that this extruded product is applied as a dielectric material of a television antenna lead-in wire,
A copper tape with a longitudinal butt joint (butt joint) is applied in the longitudinal direction of the still soft extrudate, ensuring a proper bond without loss, based on the strong adhesive bond between the graft polymer and the copper tape. Make it.

(Example 5) The heat resistance of polyethylene packaging films can be dramatically improved by crosslinking, but on the other hand it can be difficult, if not completely impossible, to form a heat seal. Accompany.

In accordance with the present invention, low density polyethylene with a melt flow degree of 2 containing approximately 0.05% dibutyltin dilaurate is plasticized in the first compartment of a 30D extruder with a specially designed barrier mixing screw. . The machine is degassed at 10D from the inlet, at which point 10% of the plasticized material is withdrawn as in the previous examples, but in this case a minor portion of the material is removed by means of a gear pump. is fed directly to the extruder head, and the main stream or major portion of the polymer left in the extruder is modified.

A solution of 0.265% dicumyl peroxide in 2.5% vinyltrimethoxysilane (
% by weight of polymer) and after the mixture has been homogeneously mixed by the homogenizing mixing zone of the extrusion screw, the temperature is increased to about 230° C. to graft the silane onto the polymer.

Next, this main flow (main part) and the extraction flow (
(sub-portions) are recombined in a blow coating crosshead such that at least one surface of the film formed is comprised of unmodified drawstream material. After being left in a humid atmosphere for about a week, the modified polymer is crosslinked by a silanol condensation reaction, but the surface formed of the non-crosslinked polymer remains completely heat-sealable. .

Example 6 A polypropylene masterbatch colored orange with a commercially available colorant is plasticized in a single screw extruder at 180°C. Approximately 28% of this is extracted from near the end of the extrusion barrel using a gear pump as in the previous embodiments and is supplied to an independently driven cavity transfer mixer.

10 parts by weight of trimethylolpropane trimethacrylate, 1 part by weight of 4'-benzoyl-3'
A liquid mixture of -hydroxy-2-phenoxyethyl acrylate (BHPEA) and 0.02 parts by weight of dicumyl peroxide was added using a metering pump and a force injector at 1.2 parts of mixture per 100 parts of polymer.
part (by weight) into the cavity transfer mixer, and the residence time in the cavity transfer mixer was 2 minutes.

The effluent from this cavity transfer mixer and the remainder of the extruder effluent were fed through separate passages to a common crosshead and applied in concentric layers onto a 1 mm diameter copper wire. A brightly colored factory wiring cable was produced by molding unmodified polypropylene to form the inner layer (for insulation) and modified polypropylene from the transfer mixer to form the outer overall seed layer.

Total radial thickness of polypropylene approximately 1 mm
Approximately 0.02 mm of the cable was modified to be resistant to ultraviolet light so that the cable could be used outdoors. A sample scraped from the outer layer and extracted with dichloromethane was analyzed by ultraviolet spectroscopy and revealed that about 0.73% of BHPEA could not be extracted. This means that this part was grafted onto the polymer, which is about 3/4 of the BHPEA used.
It was equivalent to

[0033]

Effects of the Invention According to the present invention, a polymer can be easily and conveniently plasticized in an extruder, separated into a main part and a subsidiary part, and after modifying one of these parts, both parts can be plasticized. are passed through an extrusion head, and the modified polymer and non-modified polymer are extruded into a molded article.
A method for producing an extruded product that can be molded to form mutually different parts is provided, and furthermore, an excellent molded product having a high-performance multilayer structure can be produced using a single extruder. be.

Claims (4)

[Claims] Claim 1: Plasticizing a polymer in an extruder, separating it into a main part and a subsidiary part, modifying only one of the parts, and then extruding both parts together to produce a molded product. 1. A method for producing an extruded article, characterized in that a polymer and an unmodified polymer are extruded to form different parts of the extruded article, and the plasticized polymer is modified by a chemical reaction. 2. The method of claim 1, wherein the chemical reaction grafts side chains onto the polymer. 3. The method according to claim 2, wherein the side chain introduces an active site for crosslinking of the polymer. 4. An extrusion molded product produced by the method according to any one of claims 1 to 3.