US3219617A - Elastic non-vulcanized flashing compositions of vinylidene chloride-acrylonitrile copolymers containing modifying amounts of a linear chlorinated polyolefin and a rubbery copolymer of an aliphatic conjugated diolefin and acrylonitrile - Google Patents

Description

United States Patent Arnoid t). Mack and Charles D. Batclse, Midland, Mich,

assignors to The Dow Chemical Company, Midland,

Mich a corporation of Delaware No Drawing. Filed May 6, 1963, Ser. No. 278,336 11 Qlaims. ((Jl. 26tl-3l.4)

This invention relates to improvements in compositions that are especially well suited to prepare resilient sheet material of the type particularly adapted to be employed as ilashin in, and for, various construction assemblies.

It is standard construction practice to use flashing in exposed angles between roof and gutter, or in valleys between intersecting roof surfaces, over fascia boards, at joints between masonry or metal and wood (as where chimneys or vent pipes intersects a roof and where masonry parapet walls abut a wooden roof) and between wooden and masonry members of sill structures at floors or windows, as well as in many other places where similar problems exist. The nature of the flashing employed generally varies according to the type and intended permanence of the structure. The more durable flashings heretofore employed have been sheet copper or sheet lead. Less permanent flashings can be made of galvanized iron or of a tar-impregnated rooflng paper. Recently, in quality installations, sheet materials containing polymers of vinylidene chloride have been used for this purpose.

Each of the conventional prior known fiashings has some serious recognized shortcomings. Thus, the sheet metal flashings are difiicult to seal tightly, especially at joints involving wooden structural supports, and nails driven through such flashing to hold it in place establish potential leaks. These, of course, tend to become progressively worse as electrolysis occurs at the point of contact between the nail and the flashing.

There are atmospheric conditions, especially in factory districts or in coal-burning communities, which exert an accelerated corrosive effect on metal flashings. Joints in metal flashing must be made by welding (as in the case of lead) or soldering. Such operations are slow and expensive, and in addition, require considerable skill for proper results.

Flashings made of roofing paper are weak. As they age, they tend to develop leaks around nail holes. They also, particularly on aging, become brittle in cold weather and, in addition, are combustible.

Furthermore, none of the prior metal or tar impregnated paper flashings have been resilient enough to be safely walked on without permanent or damaging deformation.

In attempting to overcome some of the defects of prior flashing materials, some use has been made of rubber sheeting. While this has been relatively easier to apply, it also has pronounced and disadvantageous drawbacks. Thus, it is not long-lived, since it oxidizes and becomes brittle and weak in the course of a very few years.

As has been indicated, resilient, synthetic, thermoplastic sheeting containing polymers of vinylidene chloride have been used as flashing with considerable success, although such material suffers from a tendency to lose flexibility and other desirable properties with age, particularly when exposed to low temperatures for relatively long periods.

Accordingly, it is an object of this invention to provide a new, long-lived, resilient, self-extinguishing, unvulcan- "Ice izable, thermoplastic flashing material which is especially adapted to retain its flexibility and strength properties under a wide variation of climatic conditions over extended periods of time, and particularly when exposed to low temperatures.

Yet another object of the present invention is to provide an improved flashing material which does not deteriorate or spoliate the properties of wooden members to which it is bonded, sealed, or otherwise attached.

Still 'another object of the present invention is to pro vide an improved, unvulcanizable, thermoplastic, flashing material of corrosion resistant character for use in construction.

A still further object of the invention is to provide an improved thermoplastic flashing material which is easily sealed to other sheets of like material and which forms a tight seal around nails and other fastening devices that are driven through it.

An additional object of this invention is to provide an improved thermoplastic flashing material which is not damaged or permanently deformed when subjected to temporary localized stress.

Other and related objects and advantages will become evident from the following specification and claims.

The flashing material of the present invention is formed from a composition consisting essentially of a homogeneous admixture of (I) from about 50 to 90 percent by weight of a homogeneous copolymeric mixture of (1) from about to percent by weight of a copolymer of (A) about 82 to 88 percent vinylidene chloride and (B) complementarily, about 18 to 12 percent acrylonitrile; (2) from about 15 to 30 percent by weight of a rubberlike copolymer of (a) about 70 to percent by weight of at least one open chain aliphatic conjugated 'diolefin having from 4 to about 9 carbon atoms, and (b) complementarily, from about 5 to 30 percent acrylonitrile; (3) from about 20 to about 80 parts by weight for each parts by weight of said copolymeric mixture of a non-volatile plasticizer for said mixture; (4) from about 30 to about 100 parts by Weight of a soft-reinforcing carbon per 100 parts by weight of said mixture and; (II) complementarily, from about 50 to 10 percent by weight of a chlorinated polyolefin selected from the group consisting of polymerized non-aromatic hydrocarbon monoolefins of from 2 to 4 carbon atoms, said polyolefin having an essentially linear and unbranched molecular structure, a density of at least about 9.93 grams per cubic centimeter, and containing between about 25 and 50 percent of combined chlorine essentially uniformly distributed along the polymer molecule.

The flashing material of the present invention is in a non-cured or unvulcanized state when incorporated in the structure of which it forms a part and remains substantially unvulcanized, with the advantages to be described on aging.

The compositions and resulting flashings of the invention are notably improved against prolonged atmospheric deterioration which may tend to undesirably degrade other resilient, cured, thermoplastic, flashing materials, and are especially resistant to the deleterious effect of extended exposure to low temperatures. Additionally, the compositions of the present invention may advantageously be used in the form of sheets to provide a highly effective unitary roofing material.

The rubber-like copolymers useful for the purposes of the present invention are copolymers of (1) an open chain aliphatic conjugated diolefin having from 4 to about 9 carbon atoms, such as butadiene or isoprene, with (2) acrylonitrile. The contemplated copolymers are rubber-like elastorners having a Mooney viscosity at 212 F. of 11 to 146, and preferably in the range of 30. Such rubber-like copolymers are known and may be prepared by copolymerizing the monomers in aqueous emulsion, as for example, by the procedure as generally disclosed in US. Patent No. 2,462,354.

The improved compositions useful for flashing stock, according to the present invention, require the presence of plasticizers in the stated range of proportions if the product is to have the required workability in the raw or non-cured, thermoplastic state. Required toughness and resilience needed during the handling and installation of the flashing material is also ensured by the presence of plasticizers in the specified proportions.

The plasticizers useful in practice of the present invention are selected from certain of those known to be effective in vinyl resin plasticization. However, the plasticizers that are most suitable for utilization are not recognizable from ordinary practices and establishd criteria in the vinyl polymer art. For example, dioctyl phthalate, dioctyl sebacate, dioctyl adipate, and many other common plasticizers for standard vinyl polymers do not flux readily with the copolymer mixture that is utilized in practice of the present invention. Thus, they are not particularly desired for use in the present compositions.

Nonetheless, the sole plasticizers (or primary plasticizers in plastifying combination thereof) that are satisfactory for practice of the present invention may be selected from a wide variety of plasticizing materials. Besides flexibility, another essential requirement for the plasticizer is that it be substantially non-volatile.

The effectiveness of various compounds as plasticizers for the polymeric compositions of the present invention may be readily determined by conducting a volatility or weight loss test. In this test, the polymeric mixture to be used in practice of the invention is blended into a homogeneous admixture with the trial plasticizer in a ratio of about 40 parts of the plasticizing compound to about 100 parts of copolymer resin. About 40 parts of finely divided carbon black and about 1.0 part of stearic acid is included in the formulation. The blended ingredients are compression molded and trimmed, if necessary, in the form of 0.04 x 1 x 1 inch test specimens.

Volatility of the plasticizer is determined from the test specimens by measuring weight loss thereoef after a one Week exposure in a circulating oven at about 150 F. For purposes of this invention, the plasticizer employed should, in the test described, have a volatility or weight loss that does not exceed about 1.5 percent, based on original plasticified composition weight.

Representative of suitable primary plasticizers for use in the present flashing compositions are dicarbitol phthalate; ethoxy diglycol phthalate; n-butyl benzyl phthalate; and dibutyl phthalate. Still other plasticizers adapted for use in the present invention are, on the basis of requirements, therefore, apparent. Selection may be made in specific instances following routine and straightforward preliminary testing on the above-indicated basis.

The presence of an amount of soft filler or reinforcing compound in the stated range serves the purpose of strengthening the sheets made from the composition of the present invention. The reinforcing compound in the compositions for the flashing is usually carbon black of the kind widely used in the rubber art and known therein as a soft reinforcing carbon. Such a material has a specific gravity of about 1.80, a particle size of about 99.9 percent through a 200 mesh screen (US. Standard Sieve Series); and a moisture and ash content at 100-105 C. of about 0.5 weight percent, maximum.

The chlorinated polyolefin constituent useful for the purposes of the present invention is advantageously selected from those distinct species and varieties of polyethylene, polypropylene, polybutylene and their copolymers which have a density of at least about 0.93 gram per cubic centimeter and essentially linear and unbranched molecular structures that are relatively free from extensive sidechain networks, and which contain between about 25 and 50 percent of combined chlorine distributed uniformly along the polymer molecule.

Essentially linear and unbranched polyolefins may advantageously be prepared having apparent molecular weights (as would be indicated from observation of such of their intrinsic properties as melt viscosity and the like) in excess of 5,000 and, more advantageously, from at least 20,000 and usually from at least 40,000 to as much as 500,000 and 3,000,000 and greater. For example, as has been disclosed in Belgian Patent No. 533,- 362, such polymers may be prepared from ethylene and other olefins, according to a process first proposed by Dr.

Karl Ziegler and his associates in Germany, by conducting the polymerization under the influence of catalyst systems comprising admixtures of strong reducing agents, such as aluminum alkyls, and compounds of Group IV-B, V-B and VI-B metals of the Periodic System, especially titanium and zirconium. Relatively low pressures ranging from 1 to atmospheres may be employed with benefit when Ziegler catalyst systems are utilized for the polymerization of olefins. Other known processes for producing macromolecular polyolefins of such nature, particularly polyethylene, employ such materials for catalysts as chromium oxide on silicated alumina, hexavalent molybdenum compounds and charcoal supported nickel-cobalt. Belgian Patent No. 530,617 and Canadian Patent No. 502,597 are representative of other art that relates to the various macromolecular linear polyolefins, particularly polyethylene, that have recently become available.

The usual methods of chlorinating the conventional non-linear and branch structured, relatively low molecular weight polyolefins, particularly polyethylene, and its copolymers are generally not Well suited for adaptation to the chlorination of essentially linear and relatively high molecular Weight macromolecular polyolefins that are substantially devoid of extensive side-chain networks and which have many other distinctive and distinguishing characteristics.

It is known however that linear and unbranched polyolefins may be chlorinated by subjecting them to the action of a chlorinating agent in the presence of a freeradical catalyst while the polymer being chlorinated is dissolved in a solvent liquid which is substantially inert to the chlorinating agent. Such chlorination is generally conducted at a temperature which is at least about that required for the solvent to dissolve about 1 percent by weight of the polymer, and not in excess of a temperature that might induce substantial deleterious dehydrochlorination of the chlorinated polymer. The chlorinated polyolefins prepared in accordance with such solution chlorinating technique, particularly chlorinated polyethylenes, usually have a more uniform distribution of the substituent chlorine atoms along the polymer molecule than may otherwise be readily obtained. schematically, such structural arrangement in a solution chlorinated polyethylene having a relatively high combined chlorine content may be represented in the following manner:

It has further been found that chlorinated polyolefins having the above described structure and properties may be prepared by the carefully controlled suspension chlorination of the herein described essentially linear and unbranched polyolefins. For example, it has been found that the suspension chlorination of essentially linear and unbranched polymers of non-aromatic hydrocarbon monoolefins of from 2 to 4 carbon atoms, to a desired total of combined chlorine content in at least two steps, wherein not more than from about 20 to 25 percent by weight of chlorine is added, at a temperature below the melting point of such polyolefin, in the initial step with the remaining chlorine being added in a second step utilizing temperatures above that employed for the first step but less than about 150 C., will provide materials having the desirable properties and characteristics of the hereinbefore described solution chlorinated materials, and are advantageously used for the practice of the present invention.

Generally products prepared in accordance with solution chlorinating processes or the multiple stage suspension chlorination, as described herein, tend to have greater elongations and elasticities than may be obtained in products chlorinated by other methods and are preferred for the purposes of the present invention.

Additionally, known rubber pigments and fillers may be incorporated in the composition, if desired, in amounts insufficient to form stiff or rigid sheets. Such pigments and fillers may be employed to impart various colors to the flashing material in order to have it harmonize or contrast with the color of the placement surface. The composition may also include antioxidants, light stabilizers, and other additives known in the art which do not deleteriously affect the properties of the flashings formed from such composition.

The compositions can be prepared in various ways. One convenient manner is to miX together the required copolymer, carbon black, chlorinated polyolefin and any other dry powdered ingredients (if any be used). Then, after suitably warming the mixed ingredients at a temperature well below the fusion or softening temperature of the mixture, the plasticizer or combination of plasticizers is added. After this, the mixing of the formulation is continued until a uniform, homogeneous mass is obtained. It may be advantageous, at this stage, to add small amounts of stearic acid or other known roll-release agents. The resulting mixture is thoroughly blended in a ribbon blender or similar device and thereafter extruded into a continuous sheet. For use as flashing, the sheets are preferably made in thicknesses of from about 0.03 to about 0.12 inch. A convenient and generally useful thickness as has been indicated is about 0.06 inch. Of course thinner or thicker sheet material may be made and employed in various applications as may be desired or required in particular instances. Even in sheets thicker than about 0.12 inch however the flashing material of the present invention retains its many inherent beneficial attributes and properties.

The uncured sheets of the present invention make possible the formation of a permanent bond between overlapping areas of adjoining sheets or strips of the flashing, as well as the formation of a tight bond that conforms closely to metal or masonry surfaces. This is the case even when the surface being sealed is of irregular contour. Such bonds between adjoining sheets of the composition are made by moistening the touching surfaces of the lapped sheets with a solvent. Advantageously a ketone (such as acetone, methyl ethyl ketone, or methyl isobutyl ketone) is employed for the purpose. The solvent-wet surfaces are then pressed together to secure the desired moisture-proof joiner.

When there is no combustion hazard (as, for example, in the installation of flashing or waterproof sheathing or subgrade masonry foundations), joints between sheets of the flashing may be made by playing a flame (as from a blowtorch or heat from infrared lamps) on the overlapped sheets. Other available sources of heat may be employed to effect evaporation of the solvent from the moistened overlapping surfaces of the flashing and thus ensure the seal.

Bonds between the new flashing and metal or masonry surfaces are readily made by applying to one or both, of the intended contacting surfaces an adhesive comprising, as part of its solvent component, a ketone or a cyclic other (such as dioxane or tetrahydrofuran) which is capable of superficially softening the flashing. An especially useful adhesive comprises a ketone solution of an adhesive vinyl polymer or a ketone solution of an adhesive vinyl ester/synthetic rubber blend. Commonly, a dilute adhesive of this type is applied as a prime coat on the metal or masonry surface. This is allowed to dry to a tacky. state. After this, there is applied over the dried adhesive layer a more concentrated adhesive formulation of the same type. The flashing is pressed into place before the adhesive has finally dried. One useful commercial adhesive for the purpose is a product available commercially as Amercoat 20-Y Adhesive. This material is a composition of a vinyl ester polymer dissolved in a ketone. Another particularly useful adhesive for the instant purpose is a product available commercially as 3M Adhesive B01369. This adhesive is believed to be a polyvinyl ester/synthetic rubber blend dissolved in a ketone.

It may be desirable in some parts of a structure to secure the flashing to wooden members by means of an adhesive. In such case, the general type of adhesive described above is satisfactory. However, in many types of installation the flashing will be fastened to wooden members by nailing. In the latter case, especially when large headed roofing nails are used, no Washer or gasket is required about the nail. The flashing is not under such tension as to tear away from the nail, and there is no danger of embrittlement.

In order that those skilled in the art may better understand how compositions in accordance with the present invention may be prepared, the following example is given by way of illustration and not by way of limitation. All parts and percentages in the example are by weight.

Example Approximately equivalent proportions of the hereinafter specified ingredients were blended in a ribbon blender, and subsequently transferred to a two roll compounding mill operating at 100 C.

Parts 82 percent vinylidene chloride/ 18 percent acrylonitrile copolymer 100 Thermax (reinforcing carbon having an average particle size of about 450 millirnicrons in which at least 99.9 percent passed a 200 mesh screen (US.

To such mixture was then added 34 percent by weight, based on the total weight of the mixture of a chlorinated olefinic copolymer having a density of about 1.2 and being composed of about 99.3 percent by weight ethylene and about 0.7 percent by weight butene; said copolymer having an essentially linear and unbranched molecular structure containing less than about 3 methyl groups per 100 methylene units in its molecule, and having chlorine essentially uniformly attached thereto in amount of between about 35 and percent. The admixture was then formed into a continuous sheet having a thickness of about 0.060 of an inch. Such admixture was designated as Formulation I.

For purposes of comparison, a continuous sheet was prepared as described herein utilizing a composition from which both the chlorinated polyolefin and rubbery butadiene/acrylonitrile copolymer constituents were excluded. Such composition was designated as Formulation II.

In yet another comparison, a continuous sheet was prepared as described herein utilizing a composition from which only the chlorinated polyolefin constituent was excluded. Such composition was designated as Formulation III.

The following table summarizes the results of physical properties determined on the above-described sheet materials. The column headings of such table have the following meanings:

'7 Impact strengthNumber of ft./lb. at 18 C. to produce fracture by dropping a Vs inch diameter metal sphere on the surface of the article Hardness (Shore durometer)ASTM No. D676-55-T Tensile strengths and percent elongation were also de termined by the procedures as essentially described in the ASTM Test No. D-412l T.

From the above data it can be seen that incorporation of the designated amounts of the hereinbefore described rubber-like copolymers of butadiene-1,3/acrylonitrile, and the chlorinated olefinic copolymer, into the vinylidene chloride/acrylonitrile copolymer composition produces articles having greatly enhanced flexibility at low temperatures, while retaining the desirable physical characteristics of the vinylidene chloride polymer. Furthermore, the compositions of the present invention retain essentially all of their highly desirable properties when subjected to extended periods of weathering, such as, for example, during accelerated aging in an oven heated to about 150 C., and during direct weathering exposure in Arizona. In addition, the compositions of the present invention have little or no tendency to attack conventionally used backing materials, such as Wood.

Similar good results are obtained from any composition comprising (1) from about 50 to 90 percent by weight of a homogeneous copolymeric mixture of (1) from about 70 to 85 percent by weight of a copolymer of (A) about 82 to 88 percent vinylidene chloride and (B) complementarily, about 18 to 12 percent acrylonitrile; (2) from about 15 to 30 percent by weight of a rubberlike copolymer of (a) about 70 to 90 percent by weight of at least one open chain aliphatic conjugated diolefin having from 4 to about 9 carbon atoms, and (b) complementarily, from about 5 to 30 percent acrylonitrile; (3) from about 20 to about 80 parts by weight for each 100 parts by weight of said copolymeric mixture of a nonvolatile plasticizer for said mixture; (4) from about 30 to about 100 parts by weight of a soft-reinforcing carbon per 100 parts by weight of said mixture and; (II) complementarily, from about 50 to 10 percent by weight of a chlorinated polyolefin as hereinbefore described.

What is claimed is:

1. A composition consisting essenitally of a homogeneous admixture of (I) from about 50 to 90 percent by weight of a homogeneous copolymeric mixture of (1) from about 70 to 85 percent by weight of a copolymer of (A) about 82 to 88 percent vinylidene chloride and (B) complementarily, about 18 to 12 percent acrylonitrile; (2) from about 15 to 30 percent by weight of a rubberlike copolymer of (a) about 70 to 95 percent by weight of at least one open chain aliphatic conjugated diolefin having from 4 to about 9 carbon atoms, and (b) complementarily, from about 5 to 30 percent acrylonitrile; (3) from about to about 80 parts by weight for each 100 parts by weight of said copolymeric mixture of a non-volatile plasticizer for said mixture; (4) from about 30 to about 100 parts by weight of a soft-reinforcing carbon per 100 parts by weight of said mixture and;

(II) complementarily, from about 50 to 10 percent by weight of a chlorinated polyolefin selected from the group consisting of polymerized non-aromatic hydrocarbon monolefins of from 2 to 4 carbon atoms, said polyolefin having an essentially linear and unbranched molecular structure, a density of at least about 0.93 gram per cubic centimeter and containing between about 25 and 50 percent of combined chlorine essentially uniformly distributed along the polymer molecule.

2. The composition of claim 1, wherein said rubber-like copolymer is a copolymer of butadiene and acrylonitrile.

3. The composition of claim 1, wherein said plasticizer is dicarbitol phthalate.

4. The composition of claim 1, wherein substantially all the particles in said soft reinforcing carbon pass a 200 mesh screen of the US. Standard Sieve Series.

5. The composition of claim 1, wherein said chlorinated polyolefin is a copolymer of ethylene and butene.

6. The composition of claim 5, wherein said copolymer is composed of about 99.3 percent by weight ethylene and 0.7 percent by weight butene.

7. Non-vulcanizable, resilient, thermoplastic sheet for use as flashing consisting essentially of a homogeneous mixture of (I) from about 50 to percent by weight of a homogeneous copolymeric mixture of (1) from about 70 to 85 percent by weight of a copolymer of (A) about 82 to 88 percent vinylidene chloride and (B) complementarily, about 18 to 12 percent acrylonitrile; (2) from about 15 to 30 percent by weight of a rubber-like copolymer of (a) about 70 to percent by weight of at least one open chain aliphatic conjugated diolefin having from 4 to about 9 carbon atoms, and (b) complementarily from about 5 to 30 percent acrylonitrile; (3) from about 20 to about 80 parts by weight for each parts by weight of said copolymeric mixture of a non-volatile plasticizer for said mixture; (4) from about 30 to about 100 parts by weight of a soft-reinforcing carbon per 100 parts by weight of said mixture and;

(II) complementarily, from about 50 to 10 percent by weight of a chlorinated polyolefin selected from the group consisting of polymerized non-aromatic hydrocarbon monolefins of from 2 to 4 carbon atoms, said polyolefin having an essentially linear and un branched molecular structure, a density of at least about 0.93 gram per cubic centimeter and containing between about 25 and 50 percent of combined chlorine uniformly distributed along the polymer molecule.

8. The non-vulcanizable, resilient, thermoplastic sheet of claim 7, wherein said plasticizer is dicarbitol phthalate.

9. The non-vulcanizable, resilient, thermoplastic sheet of claim 7, wherein substantially all the particles in said soft-reinforcing carbon pass a 200 mesh screen of the US. Standard Sieve Series.

10. The non-vulcanizable, resilient, thermoplastic sheet of claim 7, wherein said chlorinated polyolefin is a copolymer of ethylene and butene.

11. The non-vulcanizable, resilient, thermoplastic sheet of claim 7, wherein said copolymer is composed of about 99.3 percent by weight ethylene and 0.7 percent by weight butene.

References fitted by the Examiner UNITED STATES PATENTS 2,456,454 12/1948 Signer 260-455 2,469,721 2/ 1949 Gidley 260-45.5 2,547,605 4/1951 Signer et al. 260-45.5 3,076,781 2/1963 Frey 26045.5

OTHER REFERENCES Buttrey, Plasticizers, CleaverHume Press Ltd., 1957, pages 24-25.

MORRIS LIEBMAN, Primary Examiner.

Claims (1)

1. A COMPOSITION CONSISTING ESSENTIALLY OF A HOMOGENEOUS ADMIXTURE OF (I) FROM ABOUT 50 TO 90 PERCENT BY WEIGHT OF A HOMOGENEOUS COPOLYMERIC MIXTURE OF (1) FROM ABOUT 70 TO 85 PERCENT BY WEIGHT OF A COPOLYMER OF (A) ABOUT 82 TO 88 PERCENT VINYLIDENE CHLORIDE AND (B) COMPLEMENTARILY, ABOUT 18 TO 12 PERCENT ACRYLONITRILE; (2) FROM ABOUT 15 TO 30 PERCENT BY WEIGHT OF A RUBBERLIKE COPOLYMER OF (A) ABOUT 70 TO 95 PERCENT BY WEIGHT OF AT LEAST ONE OPEN CHAIN ALIPHATIC CONJUGATED DIOLEFIN HAVING FROM 4 TO ABOUT 9 CARBON ATOMS, AND (B) COMPLEMENTARILY, FROM ABOUT 5 TO 30 PERCENT ACRYLONITRILE; (3) FROM ABOUT 20 TO ABOUT 80 PARTS BY WEIGHT FOR EACH 100 PARTS BY WEIGHT OF SAID COPOLYMERIC MIXTURE OF A NON-VOLATILE PLASTICIZER FOR SAID MIXTURE; (4) FROM ABOUT 30 TO ABOUT 100 PARTS BY WEIGHT OF A SOFT-REINFORCING CARBON PER 100 PARTS BY WEIGHT OF SAID MIXTURE AND; (II) COMPLEMENTARILY, FROM ABOUT 50 TO 10 PERCENT BY WEIGHT OF A CHLORINATED POLYOLEFIN SELECTED FROM THE GROUP CONSISTING OF POLYMERIZED NON-AROMATIC HYDROCARBON MONOLEFINS OF FROM 2 TO 4 CARBON ATOMS, SAID POLYOLEFIN HAVING AN ESSENTIALLY LINEAR AND UNBRANCHED MOLECULAR STRUCTURE, A DENISTY OF AT LEAST ABOUT 0.93 GRAM PER CUBIC CENTIMETER AND CONTAINING BETWEEN ABOUT 25 AND 50 PERCENT OF COMBINED CHLORINE ESSENTIALLY UNIFORMLY DISTRIBUTED ALONG THE POLYMER MOLECULE.