JPS58208336A - Polyethylene crosslinkable composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that polyethylene is ethylene,
A cross-linkable polyethylene composition, which is a partially cross-linked fin copolymer, in particular by irradiation, and in particular a cross-linkable polymer between the partially cross-linked polymer and an organic cross-linking agent. Regarding the composition. This composition can be used, for example, to coat wire.

Polyethylene is used in a wide variety of end uses, particularly in the form of packaging materials, pipes, and molded articles. # Polyethylene can be used to coat the wire.

Irradiation of polyethylene affects the properties of the polyethylene, in particular the processability of the polyethylene and of the products made therefrom, with favorable results for such addition. Although it is known in the art to irradiate polyethylene, such irradiation is primarily carried out on processed articles, such as films, fibers, sheets or molded articles used as packaging materials, and/or relatively High doses 1, eg, at least 2 doses are performed in rads.

Density 0.95-0.97g/cm', ASTM method D
-1238 (condition E) melting coefficient determined from 3 to 13
A method for improving the melt strength and melt extensibility of polyethylene in dg/min is disclosed in U.S. Patent No. 3,563 to L.H.
, No. 870. This method involves subjecting the polyethylene to high energy irradiation of 0.05 to 0.15 megarads.

Improved method of irradiating polyethylene, especially granular.

Homogeneous polymer of ethylene and ethylene and α-1/F>
The method of irradiating copolymers with
Gee on the date. White (G.H.), European Patent Application No. 0 047 171. In this method, polyethylene is exposed to low levels of electrons or gamma in an inert atmosphere, particularly an atmosphere of water vapor.
Irradiate with a line.

Polyethylene compositions containing crosslinkers are known. For example, Reece dated June 14, 1977.
U.S. Pat. No. 4,029,729 to U.S. Pat. It describes how to do this. Other crosslinkable compositions of polyethylene/peroxides are also known, eg F.M. ρracopio, August 28, 1962
Canadian Patent W4 647.433 describes compositions in which the peroxide is dicumyl peroxide.

Density 0.920-0.970g/cm9. Melting coefficient lO
A composition comprising ~35 dg/' of polyethylene, bis(t-fulkylperoxyalkyl)benzene, and an antioxidant is disclosed in Power Nata Patent Application No. 39 dated February 9, 1982.
It is known in the art to use crosslinkable compositions of polyethylene and stone peroxide as described in US Pat. No. 5,824, supra, for coating wire. However, the polyethylene of such compositions capable of 6f cross-linking is often low-density polyethylene produced by high-pressure polymerization. When other polyethylenes, especially linear low-density polyethylenes, are cross-linked using organic harsheners, the resulting cross-linked composition may have defects in the wire coating process or the resulting coated product may have defects in its properties. This makes the product unsatisfactory in end use.

In the prior art, it has been found that cross-linkable compositions, in particular compositions containing so-called linear low density polyethylene, can be used in many applications, including wire coating processes.

According to the invention, (a) 0,910~0,955
a partially cross-linked polymer having a density of g/Cm3 and obtained from a copolymer of ethylene and one or more higher alpha-olefins having 3 to 10 carbon atoms, with the proviso that the copolymer The coalescence is such that the gel content of the partially cross-linked polymer obtained therefrom is 0, . (b) an organic cross-linking agent; and (b) an organic cross-linking agent. be done.

In a preferred embodiment of the composition of the present invention, the copolymer (a) is particularly characterized in that 2.5 mm is less than rad [gamma
irradiated with radiation or electron beams.

In other embodiments, the copolymer of (a) is crosslinked with an organic crosslinker.

In other embodiments of the invention, the organic cross-linking agent is an acetylene diperoquine compound, a bis(thi-furkylperoxy)alkane, or a bis(t-furkylperoxyalkyl)benzene.

In yet another embodiment of the composition, the copolymer is a low-density ethylene/higher α-olefin copolymer produced by solution polymerization, particularly a higher α-olefin having 4 to 10 carbon atoms and ethylene. It is a linear low density polyethylene copolymer.

The copolymers that can be used in the compositions of the invention have a density of o, 95
5 g/cm" or less, especially 0.910~0,55 g/cm"
cm”, preferably 0.920-0, 930 g/
Cm3 ethylene/α-olefin copolymer. The density of the copolymer used depends in particular on the end use of the composition. Such copolymers are copolymers of ethylene and α-olefins having a carbon number of 3 to 1O1, especially 4 to 1O, such as ethylene and oligoacids such as butene-1, hexene-1,
and 7/or a copolymer with octene-1. Methods for making such copolymers are known in the art. This copolymer, before being partially cross-linked, has a melting coefficient of 10 to 35 g/min, in particular 15 to 25 dg/min.

In certain embodiments of the invention, the copolymer is so-called linear low density polyethylene. Such polymers are copolymers of ethylene and higher α-olefins and are well known in the art. Linear low-grade polyethylene is especially
It can be produced by a solution polymerization method or a gas phase polymerization method using a coordination catalyst.

A method for partially cross-linking the copolymer will be described later.

The compositions of the invention also include an organic peroxide crosslinker. Organic crosslinking agents are known in the art and are used to crosslink polyethylene. Examples of such cross-linking agents include dicumyl peroxide, commercially available from Hercules under the tradename o+-cup, acetylenodibeoxy compounds, such as LUPERSOL. ) under the trade name of Wallas and Tiana.
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,bis(t-alkylperoxo)alkane and bis(t-alkylperoxyalkyl) commercially available from d Tiernan). Benzene, such as bis(t-butylperoxypropyl)benzene, commercially available from Hercules under the trade name VULCUρ.

The uninvented composition relates to partially cross-linked song unions.
．． It contains from 3 to 7.5% by weight, especially from 0.3 to 3.0% by weight, of organic peroxide crosslinking agents. Suitable amounts of crosslinking agents depend, among other things, on the end use of the composition and the type of partially crosslinked conjugate used in the composition.

The copolymers used in the uninvented compositions are those in which the partially crosslinked polymer gel Venus obtained therefrom is crosslinked to an extent of less than 0.1% by weight.

In this specification, gel uses xylene as a solvent,
shall mean the material remaining after Soxhlet extraction of a partially cross-linked polymer using a 200 TYLER C mesh wire screen in the extractor. However, different definitions are sometimes used for product quality standards in the industry, as shown in the examples below.

One of the methods for partially cross-linking the dihandylene/higher α-olefin copolymer is to use a cross-linking agent. Examples of cross-linking agents are the organic cross-linking agents mentioned above, and other organic cross-linking agents such as α, α”-7 zobisisobutyronitrile, and silane cross-linking agents such as 1963-1
T R 9 Santeri (T, R, 5
U.S. Patent No. 3,075,948 to
and U.S. Pat. No. 3,646, issued February 29, 1972 (H.G.
, No. 155.

Many methods of crosslinking polyethylene are known in the art and can be used in the present invention to partially crosslink the copolymers. For example, the copolymer pellets 7) may be coated with a cross-linking agent used to partially cross-link the copolymer and/or
Or impregnate pellets. The pellets are then extruded through an extruder to partially cross-link the copolymer and pelletized again. Alternatively, pellets of copolymer may be fed into an extruder and the crosslinking agent may be incorporated immediately into the molten copolymer in the extruder for partial crosslinking, and then copolymer Repellent the polymer. The partially crosslinked polymer pellets thus obtained are then combined with an organic crosslinker to form the composition of the invention.

Another method for partially cross-linking a copolymer is to irradiate the copolymer with electron beams or gamma radiation, particularly at doses below 2.5 rad. The copolymer may be irradiated, for example, in granular form.

Irradiation is not carried out in the form of sheets, films or other embossed products. In particular, the granules can be pellets 7), powders or the like. It is this type of partially cross-linked aggregate that can be fed from the compositions of the invention to processing equipment, such as an extruder, used to process the product. Methods for irradiating polyethylene containing ethylene higher α-olefin copolymers in this manner are known and are described, for example, in the aforementioned European Patent No. 0 047 171 to G. White. In White's method, the polyethylene is first exposed to an atmosphere of water vapor at a temperature of at least 80° C. to facilitate the reduction of oxygen uptake in the particulates.

Next, the granules are irradiated with electron beams or gamma rays. It must be ensured that the particles do not come into contact with oxygen during the irradiation process.

Preferably, the irradiation is carried out in an inert, oxygen-free atmosphere, in particular in an aqueous atmosphere.

The dose of radiation depends, inter alia, on the end use of the composition of the invention and on the degree of desired change in the properties of the song aggregate.

Irradiation of multiple parts results in the formation of a gel, which is undesirable in some cases. Normally, irradiation does not produce a polygonal gel until the irradiation dose reaches a certain limit. This limit value is specific to the irradiation! Although it depends on the poly "1,000", if the limit value of -1=1 is exceeded, a gel will form rapidly. As mentioned above, the gel content of the partially cross-linked polymers of the present invention is less than 0.1% by weight.

Sources of electrons and gamma rays are well known and any convenient source can be used. The intensity of the irradiation can be varied within a wide range. The intensity is selected primarily by the availability of a suitable radiation source and the time required to deliver the required amount of radiation.

The irradiated granules of the copolymer contain free radicals that can react with oxygen, thus imparting a long-term tit on the properties of the polymer, and especially on the properties of the manufactured articles made therefrom. The G. White patent states that the irradiated particulates must be maintained in an inert atmosphere, such as an atmosphere of water vapor, for a period of time after irradiation is complete. The length of this period depends on whether electron or gamma radiation is used.

The Mi composition of the present invention contains antioxidants and other stabilizers.

It may contain fillers, pigments, etc. A preferred antioxidant is 4,4'-thiobis(6-tert-butyl-m-cresol),
R and Santowide Crystals
It is commercially available under the trade name te cryStalS).

However, since polarizing additives, especially stabilizers, are affected by irradiation or cross-linking, such stabilizing additives are necessary in order to contain the desired amount of effective additives in the partially cross-linked singlymer. It is often necessary to incorporate agents into the polymer.

Alternatively, stabilizers are added to the partially cross-linked polymer, especially after irradiation.

Methods of controlling the rate of cross-linking of polyethylene by organic cross-linking agents using additives are known.
H.R.IU-SE7 dated June 7, 966 (
H.R.LARSEN) Canadian Patent No. 736 039
listed in the number. In particular, such additives tend to suppress immature crosslinking in polyethylene. In a preferred embodiment of the present invention, additives are used to cross-link the ethylene/alpha-olefin copolymer, in particular the cross-linking of compositions comprising a partially cross-linked polymer and an organic cross-linker. Adjust the speed. Preferred additives are 2-mercaptobenzthiazole and 4,4°-thiobis(6
-4-butyl-m-crenol).

The compositions of the invention can be made by methods known in the art, for example by feeding the partially crosslinked polymer in granular form into an extruder, especially an extruder equipped with a suitable mixing screw. Additives, especially organic crosslinkers, are 197
HΦJ Kunku (H,
As described in Canadian Pat. The combined pellets are coated and/or impregnated. Alternatively, an organic cross-linking agent, such as peroxide, is used in the form of a powder supported on a clay carrier, which is shaken and blended with the partially cross-linked polymer in the powder, and then weighed at an appropriate location in the extruder. Extrusion can be performed by mixing it into the song coalesce. If desired, the compositions of the invention can be converted into a form suitable for end use by methods known in the art, such as pelletizing or milling.

The compositions of the invention can be used in the manufacture of a wide range of products, especially in the wire coating industry.

The invention is illustrated by the following examples.

Example l Ethylene/butene-1 copolymer with a density of 0.924 g/cm3, a narrow molecular weight distribution, a melting coefficient of 20 dg/min, and 50 ppm of a sterically hindered phenolic antioxidant. Then, 2 megahalides are irradiated with gamma rays in air to form a partially cross-linked polymer. This irradiated polyethylene 94.5 = i%, Gui φ cup dicumyl peroxide supported on clay 5% hair (active peroxide 2
A cross-linkable composition was prepared by mixing 0.5 weight 4% of Santono, Nx antioxidant IF agent.

A 14 gauge (0.17 cm diameter) copper wire was coated with this crosslinkable composition using a laboratory wire coater at a speed of approximately 111 m/min. The melting temperature of the composition was 166°C. The wire was coated to a thickness of approximately 1.2 mm. There were no problems with this process.

Ontario Hydro Standards (Ontari.

)1ydro 5standard 5specifica
tion) Gel content was measured by the method of M-4053M-78. In summary, this method uses 0.3 to 0.5
Wrap the material in g in 200 m of wire cloth, and add 500 m of xylene containing phenolic antioxidant 1F, which has a physical disability.
1 for 5 hours and placed in a vacuum dryer or air circulation dryer for at least 12 hours. The amount of insoluble polymer is the gel content.

The gel content after extrusion onto wire was 0%, but after vulcanization at 210° C. in steam it was more than 75%.

Example 2 Samples of the cross-linkable composition of Example 1 were tested using Ontario II/Idro Standard M-405SM for the following tests.
- Passed the required value of 78.

Tensile Strength and Elongation (ASTM D63B) Retention of Tensile Strength and Elongation After Aging (ASTM01870) Brittle Point Temperature (ATSM D748) Flexural Modulus (ASTM D790 Method B) 75°
Moisture absorption after 14 days in C (ASTMD 470) Patent applicant: DuPont Canada, Inc. Patent attorney: Mokichi Odashima

Claims (1)

[Claims] 1. (a) having a density of 0.910 to 0.955 g/Cm3, containing one ethylene and one or more carbon atoms of 3 to 3;
a partially cross-linked polymer obtained from a copolymer with a higher α-olefin of 10, provided that the gel content of the partially cross-linked polymer obtained therefrom is 0°1. 2. A composition capable of cross-linking, characterized in that it has been subjected to a pre-caulking cross-linking treatment to an extent of less than 1,000%, and (b) an organic cross-linking agent. #, the polymer is F!g in an inert atmosphere
2. A method as claimed in claim 1, in which the preswaged parts are partially cross-linked by injection. 3. The method according to claim 1, wherein in (, a), the symbiotic union is partially cross-linked by pre-caulking with a cross-linking agent. The organic cross-linking agents in a and (b) include dicumyl peroxide, acetylene oxide compound, bis(t
-furkylperoxy)alkanes and bis(t-furkylperoxyalkyl)benzenes, and the organic crosslinking agent is selected from the group consisting of % of the acid. 5. The method of claims 1 to 4, wherein the amount of organic crosslinking agent in (b) is 0.3 to 3.0% of the partially crosslinked polymer. 6. The density of the copolymer is 0.920 to 0.930 g/'
The method according to claims 1 to 5, wherein Cm3. 7. The copolymer consists of ethylene and a higher α having 4 to 10 carbon atoms.
7. The method according to claim 1, wherein the copolymer is a copolymer with -olefin, and the melting coefficient of the copolymer before being partially cross-linked is 10 to 35 dg/min. 8. Ci) Feeding the wire into the wire-coated die mold on the extruder, (ii) (a) 0,910~0,955g
/cm'', and j=1 of ethylene and one or more higher α-olefins having 3 to 10 carbon atoms.
The partially cross-linked polymer obtained from the coalescence, provided that the copolymer is such that the gel content of the partially cross-linked polymer obtained from the coalescence is less than 0.1%. and (b) coating the wire with a composition comprising 0.3 to 7.5 percent of the cross-linked cross-linking agent by an organic cross-linking agent. (ii+) A method for coating a wire, comprising the steps of subjecting the coated wire thus obtained to vulcanization conditions to cross-link the composition. 9. The copolymer is a copolymer of ethylene and a higher olefin having 4 to 10 carbon atoms, and the copolymer has a melting coefficient of 10 to 35 d g 1 min before being partially cross-linked. The method according to claim 8. 10. The method according to claims 8 to 9, wherein the content of the organic cross-linking agent is 0.3 to 3.0% by weight of the partially cross-linked copolymer. 11. The organic crosslinking agent in (b) is dicumyl peroxide, acetylene ciba-oxy compound, bisCt
-alkylperoxy)alkanes and bis(t-furkylperoxyalkyl)benzenes. 12. The density of the copolymer is 0.920 to 0.930 g/
cm'.