EP0084048A1

EP0084048A1 - Flame retardant compositions, method of preparation and wire and cable products thereof

Info

Publication number: EP0084048A1
Application number: EP82902492A
Authority: EP
Inventors: Alexander F. Wu
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1981-07-29
Filing date: 1982-07-06
Publication date: 1983-07-27
Also published as: JPS58501235A; WO1983000488A1; EP0084048A4; NL8220273A; IT8222381A0; IT1195936B

Abstract

Nouveau matériau d'isolation à retardement de flamme, pouvant servir de revêtement d'isolation pour une variété de produits de fils à retardement de flamme, dans des applications allant du fil électronique d'une épaisseur de 5 mils ou plus jusqu'au câble de haute tension de 35 kilovolts ou plus, ainsi que pour des applications nucléaires. Le nouveau matériau d'isolation est constitué d'un polymère à base de polyoléfine et contient un agent de retardement de flamme, une argile traitée, un fluide de silicone avec d'autres ingrédients. La composition peut contenir un agent chimique de réticulation tel qu'un péroxyde ou peut être réticulée par radiation de haute énergie.A new flame-retardant insulation material that can be used as an insulation coating for a variety of flame-retardant wire products, in applications ranging from electronic wire with a thickness of 5 mils or more to cable high voltage of 35 kilovolts or more, as well as for nuclear applications. The new insulation material is made of a polyolefin-based polymer and contains a flame retardant, treated clay, silicone fluid with other ingredients. The composition may contain a chemical crosslinking agent such as a peroxide or may be crosslinked by high energy radiation.

Description

FLAME RETARDANT COMPOSITIONS, METHOD OF PREPARATION AND WIRE AND CABLE PRODUCTS THEREOF

BACKGROUND OF THE INVENTION A number of compositions have been prepared pursuant to prior patented technology which have very superior properties. One such composition is covered by the Pat ents Nos. 4,125,586 and 4,247,446. The composition has excellent properties but does have a relatively high cost, both in material content and in the processing of the material as well as in the final product as applied as an insulation on wire. One of the cost factors involved in the high, quality material of the 4,123,586 and 4,247,446 patents composition is that the processing costs are relatively high, because of the unique combination of ingredients which are employed to achieve the superior properties and the unique manner in which such ingredients must be combined to achieve the unique set of properties as set forth, in the patents.

Accordingly, it has been an object of the industry to achieve a desirable combination of superior properties but to do so at a lower cost both in the ingredients or materials employed and in the processing technology as the ease of processing of a material can substantially affect the cost of the final product. For example, as has been pointed out in the 4 123 586 patent there is a requirement, deemed essential heretofore, for separate processing and preparation of the flame retardant ingredient by a method described in the U.S. Patent 4,209,566 The processing of the higher specification material of the 4,123,586 and 4,247,446 patents, including the separate processing of the flame retardant ingredient of the 4,209,566 patent, leads to a lower rate of production of the compound for a given set of manpower and equipment and, accordingly, to a higher cost. This production rate is effectively a half of the rate of production according to this invention, but is for the relatively higher cost and higher specification materials of the patents 4,123,586 and 4,247,446 and its related processing by U.S. Patent 4,209,566. A further concern of the industry is to find a composition which not only has a lower cost and which is easier to process to a final insulation layer on a wire or cable, but which also meets a very substantial number of industry requirements as, for example, the standard requirements established by various testing agencies such as Underwriters Laboratory including, for example, the VW-1 test.

The patents 4,123,586, 4,247,446 and 4,209,566 are assigned to the same assignee as the subject application.

OBJECTS OF THE INVENTION It is accordingly one object of the present invention to provide an insulating composition which has superior flame retardance combined with superior wire insulation properties at a relatively low cost and methods of forming. Another object of the present invention is to provide a composition as described in the first object above which is relatively easy to process and to form into the pellet and into the wire insulation directly on a wire. Another object is to provide a composition at relatively low cost which not only has exceptional flame retardant properties and good physical prioerties for inclu sion in wire but, in addition, has very desirable electrical properties for use as a wire insulation. A further object of the present invention is to pro vide a composition which has high, flame retardancy and which has properties suitable for use as a power cable at voltages up to 35 kilovolts and above at suitable wall thicknesses and novel cable products insulated therewith. Another object of the invention is to provide a novel insulating composition suitable for use in wet environments and damp environments, and which at the same time has good flame retardant properties and which has a relatively low cost. Another object is to provide a wire insulation composition which is qualified for use in nuclear applications and, specifically, which will pass the tests specified in IEEE-323 and IEEE-383.

The foregoing object includes the subsidiary object of providing a composition at relatively low cost which passes the LOCA test, which is the worst type of accident which occurs in a nuclear facility and is an accident resulting in or associated with the loss of coolant in the reactor. Another object of the present invention is to provide a composition which is useable under UL specifications in applications at up to 105°C and higher in environments where, the cable is exposed to petroleum products such as in oil well applications or in locomotive applications.

Another object is to provide a composition which performs well at relatively thin wall thicknesses of the order of 5 or 10 mils and which is accordingly suitable for use in electronic wire type applications and wire products formed therewith.

It is a further object of the present invention to provide an insulating composition having high, dielectric strength, of the order of 1300 volts per mil. Another object is to provide an insulating composition which, passes Both, the UL VW -1 test and passes a 100-hour U-bend test as specified in the UL-1072 testing procedure on an unshielded power cable construction. Other objects will be in part apparent and in part pointed out in the description which follows.

BRIEF DESCRIPTION OF THE DRAWING The drawing comprises a perspective view of an insulated conductor comprising a metallic element having a flexible polyolefin insulation thereabout.

SUMMARY OF THE INVENTION Objects of this invention are achieved by preparing an insulating composition by first combining polyolefin polymer with a substantial proportion of an organic brominated flame retardant; a substantial proportion of mineral flame retardant, such as antimony oxide; and a substantial proportion of a silicone- treated clay material, and by combining these ingredients with a relatively smaller proportion of lead stabilizer compound and antioxidant compositions.

After the aforementioned ingredients are first combined, there is then added to this first combination, but at a lower temperature, a second combination of silicone fluid and organic peroxide. Following the second addition, the material is formed into the desired, configuration as insluation on a wire and the composition is heated under pressure to decompose the peroxide and to cause a chemical crosslinking of the material. Optionally, the peroxide component can be omitted and the composition can be crosslinked by radiation as with high voltage electrons.

DESCRIPTION OF A PREFERRED EMBODIMENT Polyolefin as used herein refers to polyethylene as a preferred component, but the polyolefin may also be copolymers of ethylene, including but not limited to ethylene ethyl acrylate, ethylene vinyl acetate copolymers, ethylene-propylene copolymers, terpolymers and quatrepoly mers such as EPDM. Also, the polyolefin may be either of the high density or the low density polyethylene or may be polyallomer. The organic halogenated flame retardant may preferably be the decabromodiphenyl oxide or decabromodiphenyl ether, but may also be ethylene bis (tetrabromophthalimide) sold commercially under the designation BT-93 by Saytech Corporation, or a brominated diphenyl oxide of a lover degree of bromination. In a more general sense, the stable organic halogenated flame retardant, such as the chlorinated flame retardant available commercially under the trade name Dechlorane of Hooker Chemical Corporation, may be employed. The antimony oxide flame retardant used in the present invention is the conventional or standard powdered compound The silicone-treated clay may be a commercially available composition sold under the designation Translink 37 Clay by the Freeport Kaolin Company. Alternatively, it may be a similar clay composition as taught in column 2 of U.S. Patent 3,148,169 assigned to the same assignee as the subject application.

Dibasic lead phthalate composition or ingredient may optionally be used in the composition of this invention and may be any organic lead compound in which the lead pro portion is roughly equivalent to that of the dibasic lead phthalate or greater. For example, other .organic compounds which have low volatility and which result in suitable stabilization properties may be employed but the dibasic lead phthalate is the preferred compound for this in gredient. By stabilization is meant that the lead compound can scavenge free halogen from the composition.

An antioxidant ingredient preferably includes the lower cost antioxidants such as commercially available Flectol H, commercially available Santowhite Crystals, or the combination as brought out in the specific example of Table I below where the composition cost is desirably kept at relatively low levels and where the temperature of performance of the composition is also at a relatively low level of about 105°C. However, where higher temperature performance is desirable, it is possible to achieve such higher temperature performance by inclusion of antioxidants as described with reference to Table V.

Considering next the silicone fluid ingredient, the silicone fluid is a reactive silicone such, as is described and set forth in the U.S. Patent 4,209,566,

The peroxide curing agent as indicated above may be an organic peroxide which decomposes, i.e., generates free radicals, at the elevated temperatures above the basic mixing temperatures and may be, as in the examples given, dicumyl peroxide. Alternatively, materials sold under the commercial designation Vul-Cup R may be employ although the cost is higher than that of the dicumyl peroxide. Such organic peroxides are known in the art an in the patent literature directed to this art and are described in part in the patents referenced above which patents are incorporated herein by reference,

Silicone gum can be used as an optional ingredient and is accordingly included as such, in Example 1 below, as is the dibasic lead phthalate above. The silicone gum useful in the novel composition of this invention is described in copending application Serial No. 196,989 filed October 14, 1980 and assigned to the same assignee as the subject application, The copending application 196,989 is incorporated herein by reference as is copending application. Serial No. (attorney Docket 41WC-2135) filed July 21, 1981. The benefits pointed out in the copending application will be obtained in reference to the composition of the present invention.

EXAMPLE 1

Referring to Table I, a set of ingredients and proportions of these ingredients is set forth for both a preferred concentration range of ingredients (given in proportions of parts by weight) and also for an operable range of concentrations.

The first seven ingredients as described in the Table I are thoroughly mixed in a Banbury mixing apparatus as follows: The seven ingredients are first introduced into a high intensity mixer, such as a Banbury, which has an initial temperature of about 150°F. The mixing action of the high intensity mixer generates heat in the composition and the composition temperature is measured during the mixing. The composition is dropped from the high intensity mixer when the chart or apparatus temperature reaches about 270°F. The heat which it has received is heat of mixing and no external heat need be applied for this temperature increase. The batch, of material, which has a probe temperature of about 280 to 290°F, is milled on a plastic mill after removal from the high intensity mixer. The material on the plastic mill is banded and taken off as sheets.

The sheet product is later blended with a mixture of liquid silicone fluid and a peroxide crosslinking agent, specifically, dicumyl peroxide. This blending is at a lower temperature, below the decomposition temperature of the peroxide crosslinking agent. The composition is blended in the high intensity mixer at a temperature of approximately 220 to 240°F maximum.

Following the introduction of the silicone fluid and the peroxide crosslinking agent to the compound, it is again rolled on a plastic mill into sheet form from which it can be cut into strip and pelletized for later use in an extruder.

* Prepared according to teaching of column 2 of U.S. Patent 3,148,169 or similar method,

** Flectol H is a commercial designation for polymerized

1,2-dihydro-2,2,4-trimethyl quinoline. *** Santowhite Crystals is a commercial designation for 4,4' -thiobis-(6 tert-butyl-m-cresol) ****Silicone fluid as described in U.S. Patents 4,123,586 4,247,446 or similar composition.

EXAMPLE 2

A composition prepared in this manner was extruded onto a #14 AWG wire as a 30 mil insulating sheath. It was crosslinked by subjecting the wire insulation to heating under pressure.

The crosslinked composition was demonstrated to have exceptionally good physical properties for use as a wire insulation including a high tensile value of over 2100 psi, and a high elongation percentage value of over 400%.

A table of data, Table II, is provided here giving the test results of a series of standard tests performed on the wire insulation formed in accordance with the method of the present invention as set forth above.

* Stretched to 100% of original length at 150º C and tensile strength in PSI measured. ** %RT/%RE = Percent of original tensile retained and percent original elongation retained. With reference to the experimental results reported in Table II above, a number of important observations can be made with respect to the efficacy of the crosslinked composition as a wire and cable insulation. One such observation is that, to the knowledge of the applicant, no prior composition which displays VW-1 properties (passes the VW-1 test), also has the capability of passing the U-bend test when employed as an insula tion on an unshielded cable. Prior cables having an insu lation layer which passed the VW-1 test required a shielding jacket to pass the U-bend test. Accordingly, the insulation composition and the cable formed with this composition is quite novel and unique.

In addition to the unique combination of an unshielde cable which passes both the U-bend and VW-1 tests, the

Table II of test results indicates that the novel composition of this invention has an oxygen index of 29.5, a value which is quite high for a composition having the other combination of properties. Another observation regarding the data of Table II is that the dielectric strength is quite high for a flame resistant material, particularly for a VW-1 grade material and more particularly for one with an oxygen index of 29.5 Such a combination of properties makes the novel composition of this invention uniquely suitable for use in power cable. Use in power cable is particularly suitable because of the relatively low cost of the novel composition and the power cable insulated with this novel composition, In part, the low cost of the novel composition is the result of the simpler processing of this composition. For example, standard equipment and standard processing steps may be employed even though the compound produced is quite unique and novel. In Table II, it will be observed that the tests of heat aging at 113°C gave results which establish that the loss of physical properties and, particularly, tensile and elongation properties, as a function of time is unusually slow. The UL test of heat aging to qualify a composition for use at 105°C is the heat aging at 113°C for 30, 60 and 90 days without a major loss of the tested properties. The Table II results evidence that the novel composition of this invention easily passes the UL test but also exceeds it in that the Table II data shows only minor loss of properties beyond 90 days and, in fact, for 120 and 150 days.

From Table II, it is also evident that the high dielectric strength can make possible a thin wall insulation of 10 mils or even of 5 mils so that products formed with the insulation of this invention can be used in electronic applications. Noreover, the ease of processing compositions of this invention makes fabrication of such electronic wire feasible,

EXAMPLE 3

A seven conductor control cable was fabricated usin seven strands of the #14 AWG conductor insulated with the 30 mil insulation coating. The individual insulated conductors were the same as that used above in carrying out the tests reported in Table I above. The control cable was then subjected to a burn test and the following data was obtained.

TABLE III 7 conductor control cable construction subjected to 210,000 BTU IEEE vertical flame test PASS

EXAMPLE 4

The composition prepared as descirbed with reference to the Table I above was employed in preparing a cable article. The cable was formed with a #2 AWG copper con ductor. An insulating layer having a thickness of 205 mils was formed by compounding and extruding the preferred composition in Table I above, onto the conductor followed by heating the compound at a temperature above the activation temperature of the peroxide and subjecting the cable to pressure in a manner known in the art.

The cable product prepared as described here was then subjected to a number of tests and the test results are reported in Table IV below:

*The U-bend test is specified as the UL-1072 testing procedure for an unshielded power cable construction. The foregoing results, particularly those reported with reference to Table II, are reported for an insulating composition which is used and useable at a basic operating temperature of about 105°C, The actual opera ting temperature of the composition can be above the

105°C, but reference is made to 105°C because it is the basis of a UL standard which is recognized in the industry. The composition of the present invention as described above meets the standards of the industry and does function as a 105°C insulating composition.

However, the composition is also inherently capable of functioning at higher temperatures and at higher temperature ratings. For example, the composition of the present invention will function at a temperature of 125°C and above and this 125°C temperature is again a standard UL temperature grade for an insulating composition. The manner in which the composition as described above is made to serve as a 125°C composition is by incorporating in the composition a combination of antioxidants as follows.

* Zinc salt of a mercapto imidazole

**Sterically hindered di-tertiary butyl phenol

Ingredients marked with * and ** are as set forth in Patent 4,260,661 which is incorporated herein by referenc All other ingredients are as set forth in Table I above.

Where higher temperature insulating compositions are desired, or, in other words, where it is desired to employ an insulating composition at a higher use temperatur generally a larger amount of the antioxidant components listed in Table V should be employed in the combination of Table IV for a higher projected use temperature.

To illustrate, if a use temperature of 125°C is sought, then the ratio or proportion of the ZMB-2 ingredient and also the proportion of Irganox ingredient sub- stantially as set forth in the lower ranges of values included in Table V should be employed. For still higher temperatures of use of the insulating compound prepare pursuant to this invention, employing the ingredients of Table V in some of still higher conventration ranges set forth for the ZMB and the Irgonox antioxidants will permit such higher use temperatures to be achieved.

As noted above, the peroxide ingredient of the com- position may be omitted and high energy radiation, such as high energy electrons, can be employed to cause crosslinking and curing of the coating composition also by methods well known in the art.

In the figure, there is illustrated a central con- ductor 12 about which has been formed an insulating layer 14 prepared pursuant to the present invention. The insulating layer 14 may be in the curable state or may be in the cured state. Also, the cured insulation may be chemically cured or cured by high energy radiation. The product illustrated is an insulated conductor 10, the conductor of which may be solid as illustrated or stranded.

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications are possible and it is desired to cover all modifications falling, within the spirit and scope of this invention.

Claims

What I claim as new and desire to secure by Letters Patent of the United States is:CLAIMS

1. A crosslinkable composition having apt properties as an insulation material comprising the following ingredients:

INGREDIENTS RANGE Polyethylene 100

Decabromodiphenyl oxide 10-50 Anitmony oxide 3-30

Silicone-treated clay 5-50

Dibasic lead phthalate 0-20 Silicone gum 0-20

Flectol H 0-10

Santowhite Crystals 0-5

Silicone fluid 1-5

2. The crosslinked composition of claim 1.

3. A cable coated with the composition of claim 1.

4. A cable insulated with the composition of claim 2.

5. A crosslinkable composition having apt insulation properties comprising:

INGREDIENTS RANGE

Polyethylene 100 Decabromodiphenyl oxide 10-50

Antimony oxide 3-30

Silicone-treated clay 5-50

Dibasic lead phthalate 0-20

Silicone gum 0-20 INGREDIENTS (Con't) RANGE(Con't)

Flectol H 0-10

Santowhite Crystals 0-5

Silicone fluid 1-5

Peroxide crosslinking agent

(Dicumyl peroxide) 1-5

6. The cured composition of claim 5,

7. An electrical product having a layer of the composition of claim 5 thereon.

8. A cable product having a coating of the composition of claim 5 thereabout.

9. Ab electrical product insulated with the composition of claim 6.

10. An electronic wire insulated with the composition of claim 2 to a thickness of 5 mils or more.

11. A high voltage cable insulated with, the composition of claim 2 to a thickness of over 30 mils.

12. A crosslinkable composition having apt properties as an insulation material comprising the following:

INGREDIENTS RANGE

Polyethylene 100

Decabromodiphenyl oxide 20-40

Antimony oxide 10-20

Silicone-treated clay 10-30

Dibasic lead phthalate 5-10

Silicone gum 0-10 INGREDIENTS(Con't) RANGE(Con't) Flectol H 1-5

Santowhite Crystals 0-3 Silicone fluid 1-3

13. The crosslinked composition of claim 12.

14. A cable coated with, the composition of claim 12

15. A cable insulated with the composition of claim 13.

16. A crosslinkable composition having apt insulation properties comprising:

INGREDIENTS RANGE

Polyethylene 100

Decabromodiphenyl oxide 20-40

Antimony oxide 10-20

Silicone-treated clay 10-30

Dibasic lead phthalate 5-10

Silicone gum 0-10

Flectol H 1-5

Santowhite Crystals 0-3

Silicone fluid 1-3

Peroxide crosslinking agent

(Dicumyl peroxide) 2-5

17. The cured composition of claim 16.

18. An electrical product having a Mayer of the composition of claim 17 thereon.

19. A cable product having a coating of the composition of claim 18 thereabout

20. An electrical product insulated with the composition of claim 19,

21. An electronic wire insulated with the composition of claim 13 to a thickness of 5 mils or more.

22. A high voltage cable insulated with the composition of claim 13 to a thickness of over 30 mils.

23. A curable polyolefin polymer compound of apt insulating properties comprising:

INGREDIENT RANGE Polyolefin 100 Brominated aromatic compound 10-50

Antimony oxide 3-30

Silicone-treated clay 5-50

Dibasic lead phthalate 0-20

Silicone gum 0-20 Zinc salt of a mercapto imidazole 1-10 Sterically hindered di-tertiary butyl phenol 1-5

Silicone fluid 1-5

24. The cossslinked composition of claim 23,

25. A conductive article insulated with the composition of claim 24.

26. A curable polyolefin polymer compound of apt insulating properties comprising:

INGREDIENT RANGE

Polyolefin 100 Brominated aromatic compound 10-50

Antimony oxide 3-30

Silicone-treated clay 5-50

Dibasic lead phthalate 0-20

Silicone fluid 1-5 Peroxide crosslinking agent Dicumyl peroxide 1-5

27. The crosslinked composition of claim 26,

28. A cable insulated with the composition of claim 26.

29. A curable polyolefin polymer compound of apt i sulating properties comprising:

INGREDIENT RANGE

Polyethylene 100 Brominated aromatic compound 20-40

Antimony oxide 10-20

Silicone-treated clay 10-30

Dibasic lead phthalate 5-10

Silicone gum 0-10 ZMB-2 1-5

Irgonox 1011 0-3

Silicone fluid 1-3

30 The crosslinked composition of claim 29

31. A cable insulated with the composition of claim 29.

32. A. curable ethylene base polymer compound of ap insulating properties comprising:

INGREDIENT RANGE

Polyethylene 100 Brominated aromatic compound 20-40

Antimony oxide 10-20

Silicone-treated clay 10-30

Dibasic lead phthalate 5-10

Silicone gum 0-10 Zinc salt of a mercapto imidazole 1-5 Sterically hindered di-tertiary butyl phenol 0-3

Silicone fluid 1-3 Peroxide crosslinking agnet Dicumyl peroxide 2-5

33. The crosslinked composition of claim 32.

34. A cable insulated with the composition of claim 32.