US3641216A - Thermoplastic compositions for the preparation of inherently flexible dimensionally-stabl esolvent-weldable sheet materials - Google Patents

Abstract

THIS INVENTION RELATES TO SPECIFIED THERMOPLASTIC COMPOSITIONS BASED ON INTIMATE FUSION BLENDS OF CERTAIN CHLORINATED OLEFIN POLYMERS WITH MINOR AMOUNTS OF ESSENTIALLY LINEAR, NON-CHLORINATED OLEFIN POLYMERS. THESE COMPOSITIONS ARE PARTICULARLY USEFUL FOR THE PREPARATION OF SHEET MATERIAL FOR USE AS FLASHING OR MEMBRANE IN VARIOUS CONSTRUCTION ASSEMBLIES SUCH MATERIAL HAVING UNEXPECTEDLY ENHANCED DIMENSIONAL STABILITY WHILE RETAINING A NECESSARY LEVEL OF INHERENT FLEXIBILITY AND THE ABILITY TO BE EASILY SOLVENT WELDED INTO UNITARY STRUCTURES.

Description

United States Patent THERMOPLASTIC COMPOSITIONS FOR THE PREP- ARATION 0F INHERENTLY FLEXIBLE, DI- MENSIONALLY-STABLE, SOLVENT-WELDABLE SHEET MATERIALS David F. Schnebelen, Plaquemine, and Robert B. Cramer, Baton Rouge, La., assignors to The Dow Chemical Company, Midland, Mich.

No Drawing. Continuation-impart of abandoned application Ser. No. 659,555, July 24, 1967. This application Apr. 23, 1969, Ser. No. 818,810

Int. Cl. C08f 29/12 US. Cl. 260-897 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to specified thermoplastic compositions based on intimate fusion blends of certain chlorinated olefin polymers with minor amounts of essentially linear, non-chlorinated olefin polymers. These compositions are particularly useful for the preparation of sheet material for use as flashing or membrane in various construction assemblies such material having unexpectedly enhanced dimensional stability while retaining a necessary level of inherent flexibility and the ability to be easily solvent welded into unitary structures.

This application is a continuation-in-part of copending application Ser. No. 659,555, filed July 24, 1967, now abandoned.

It is standard construction practice to overcome leakage problems by using flashing in valleys between intersecting roof surfaces, over fascia boards, at joints such as those involving masonry, metal or wood (as where chimneys or vent pipes intersect a roof or where masonry parapet walls abut a roof) or 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, aluminum or a tar-impregnated roofing paper. Recently, in quality installation, particular types of resilient plastic sheet materials have been used for the purpose.

Each of the conventional flashings has some serious recognized shortcomings. Thus, the sheet metal flashings are difficult to seal tightly, especially at joints involving wooden structural supports. Nails driven through such flashings to hold them in place establish potential leaks. These, of course, tend to become progressively worse if 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 or soldering. Such operations are slow and consequently 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. They are, in addition, combustible.

In attempting to overcome some of the defects of prior flashing materials, some use has been made of natural rubber sheeting. While having a reasonable level of flexibility it is not long-lived, as it oxidizes and becomes brittle and weak in the course of a very few years. In addi- 3,641,216 Patented Feb. 8, 1972 tion, use has been made of sheeting prepared from synthetic rubber, e.g., butyl rubber sheeting. This type of sheeting, however, requires vulcanization for fabrication, is generally incapable of being joined into larger sheets in the absence of adhesives and is difficultly formulated to provide flame-resistant materials.

Particular types of plasticized, resilient, synthetic thermoplastic sheets formed from vinylidene chloride interpolymers have, despite their comparatively recent origin, been used as flashing with success. Although these prior types of flashing made from synthetic resins give very good service when installed in fairly mild climates, a tendency to stiffen is frequently encountered when such materials are installed in areas where extremes in temperature and/or humidity exist. This loss of flexibility is due at least in part to a gradual volatilization or release of the plasticizing component from the flashing composition. Similar problems are also encountered when using flashing based on plasticized polyvinyl chloride resins. Further, prior known thermoplastic sheeting suffers from a lack of dimensional stability resulting in excessive shrinkage when exposed to elevated temperatures, as encountered during exposure to the sun, for extended periods of time, as well as a loss in tensile properties when exposed to conditions of fabrication and/or use.

Many of these same disadvantages of prior known sheeting are apparent when such materials are used as membranes to cover entire roofs, or to act as water and water vapor barriers under concrete slabs and/or when placed adjacent to sub-surface Walls, etc.

Accordingly, it is the principal object of this invention to provide a long-lived, inherently resilient, dimensionally stable and non-combustible flashing or membrane for use in construction, which material additionally is: corrosion resistant; easily sealed to other sheets of like materials by conventional solvent welding and/0r dielectric, ultrasonic, or resistance welding techniques; capable of forming a tight seal around nails or other fastening devices driven through it; is not damaged or significantly deformed when subjected to temporary localized stress; is compatible with conventional roofing materials such as pitch and asphalt; it essentially impermeable to moisture and solvents; and which retains substantially its original flexibility and dimensional stability under a wide variation of climatic and environmental conditions over extended periods of time.

A related object is the provision of improved structures comprising the new flashing and membrane material.

The above and related objects are attained by preparing compositions comprising essentially an intimate fusion blend of:

(1) From 65 to 98 percent by weight of a chlorinated olefin polymer having a molecular weight of from about 20,000 and 300,000 and containing from about 25 to 50 percent by weight of chemically combined chlorine and having a crystallinity of less than about 10 percent when containing about 34 or more weight percent chlorine;

(2) From 0 to 20 percent by Weight of a polymer of vinyl chloride, containing at least about mole percent of vinyl chloride in the polymer molecule, and;

(3) From 2 to 15 percent by weight of an essentially linear polymer of ethylene, containing at least about 90 mole percent of ethylene in the polymer molecule; wherein said compositions have a 100 percent modulus of less than 500 p.s.i.

The chlorinated polyolefins used in the present invention are obtained by practice of a chlorination procedure which comprehends the suspension chlorination in an inert medium of finely divided essentially linear polyethylene and interpolymers containing at least about 90 mole percent ethylene with the remainder being one or more ethylenically unsaturated comonomers, to a desired total of combined chlorine content, wherein such polymer is first chlorinated at a temperature below its agglomeration temperature for a period suflicient to provide a chlorine content of from about 2 to 23 percent chlorine, based on the total weight of the polymer; followed by the sequential suspension chlorination of such polymer, in a particulate form, at a temperature above its agglomeration temperature but at least about 2 C. below its crystalline melting point for a period suflicient to provide a combined chlorine content of up to about 50 weight percent based on the total weight of the polymer and wherein at least about 2 percent chlorine is added during the sequential chlorination step.

Preferably, the polyolefinic materials to be chlorinated are those distinct species and varieties of essentially linear and unbranched highly porous polymers containing at least about 90 mole percent ethylene in the polymer molecule with a remainder being one or more ethylenically unsaturated comonomers, such polymers being prepared under the influence of catalyst systems comprising admixtures of strong reducing agents such as triethyl aluminum and compounds of Groups IV-B, V-B and VI-B metals of the Periodic System, such as titanium tetrachloride, and the like and having a molecular weight less than about 1,000,000 and preferably between about 20,000 and 300,000.

Exemplary of useful ethylenically unsaturated comonomers are the non-aromatic hydrocarbon olefins having 3 or more carbon atoms such as propylene, butene-l and 1,7-octadiene and the like; cycloaliphatic olefins such as cyclopentene and 1,5-cyclooctadiene and the like; substituted olefins such as acrylic acid and its esters; conjugated diolefins such as butadiene and the like; and the alkenyl aromatic compounds such as styrene and its derivatives, among many other polymerizable materials known to the art.

It has also been found to be of special advantage to carry out the chlorination in the presence of inert substances of inorganic or organic chemical nature which are such that they have an affinity for adsorption onto the surfaces of the polyolefin during chlorination so that they may function as barriers to inhibit particle agglomeration. Exemplary of useful inert materials are: carbon black and titanium dioxide and the like. Such materials may be employed for the desired purpose without significantly detracting from the highly desirable elastomeric properties of the polymer.

Stabilizers may also be included in the compositions to protect the chlorinated olefin polymer against possible decomposition by the heat of processing or by subsequent exposure of fabricated sheet material to climatic and environmental conditions of use. Suitable stabilizers include those materials conventionally employed in the preparation of vinyl polymer and copolymer sheet compositions, e.g. organic complexes and/or salts of lead, tin, barium, cadium, zinc, sodium, etc., and particularly the sulfur containing organo tin compounds including the alkyl tin mercaptides as well as dibutyl tin laurate and dibutyl tin maleate and various epoxide compounds such as the epoxidized fatty acids and oils, among others. Stabilizers are preferably used in amounts sufficient to provide between about 1 and parts by weight per 100 parts of the chlorinated olefin polymer constituent. Other conventional additives, such as non-epoxidized fatty acids and oils, and low molecular weight polymers and waxes may also be employed, if desired.

Although the chlorinated olefin polymers employed for the purposes of the present invention are inherently resistant to burning, it may in some instances be advantageous to incorporate minor amounts, i.e. from between about 1 and 10 parts per 100 parts of chlorinated olefin polymer, of one or more flame-retarding agents, e.g. oxides of antimony and/or various halogenated materials such as tetrabromophthalic anhydride, perchloropentacyclodecane, tris (2,3-dibromopropyl) phosphate, tetrabromo bisphenol-A, among many others.

The polymers of vinyl chloride which may optionally be used in the designated amounts include homopolymers of vinyl chloride and interpolymers of vinyl chloride wherin there is present at least about 95 mole percent of vinyl chloride in the polymer molecule. As copolymerization components there can be used vinyl esters such as vinyl acetate, vinyl propionate or vinyl butyrate, vinyl stearate, vinylidene chloride, esters of aliphatic, unsaturated alcohols containing from about 1 to 10 carbon atoms with acrylic acid, methacrylic acid, maleic acid or fu-maric acid. Such polymers may be used as a filler if desired, without adversely affecting the inherent flexibility, dimensional stability and solvent-weldability of the described com positions and articles formed therefrom.

The essentially linear polymers of ethylene which are utilized for the purpose of the present invention are those polymers containing at least about 90 mole percent of ethylene in the polymer molecule. Distinct species and varieties of polyethylene and its interpolymers with one or more ethylenically unsautrated comonomers such as propylene, butene-l and the like are known which have essentially linear and unbranched molecular structures that are relatively free from extensive side-chain .networks and which have molecular weights in excess of 5,000 and, more advantageously,.from at least 20,000 to as much as 5,000,000 and greater.

Utilization of such material, in the required amounts, is necessary in the present invention to provide necessary dimensional stability and tensile strength retention during fabrication and/or utilization of sheeting prepared from the compositions described herein as flashing or as continuous membrane in various construction assemblies. More particularly it has been discovered, which discovery represents a portion of the present invention that the use of such essentially linear ethylene polymers unexpectedly permits the preparation of sheeting which is resistant to shrinking and/or undesirable distortion even when such sheet is subjected to localized stress and/or to elevated temperatures for extended periods of time, without resort to costly lamination of such sheeting to conventionally used reinforcement materials such as nylon or polyester fiber mats and the like. Further, utilization of such essentially linear ethylene polymers within the amounts prescribed, and wherein the resulting compositions have a 100 percent modulus of less than 500 psi, as provided by the herein prescribed combinations of specified materials, does not adversely affect the required inherent flexibility and solvent-weldability of such sheeting.

Sheet materials may be prepared from the intimate fusion blend of the present invention by conventional techniques such as by extrusion through a single sheet die to form a sheet of desired thickness.

The following example, wherein all parts and percentages are to be taken by weight, illustrates the present invention but is not to be construed as limiting its scope.

EXAMPLE To 4,000 grams of deionized water was added, with stirring, 200 grams of a polyethylene having an essentially linear and unbranched structure (containing less than about 1 methyl group per 100 methylene units), and having a melt index of about 1 and a molecular weight of about 60,000. Such polyethylene had been previously prepared by a process using a catalyst composed of triisobutyl aluminum and titanium tetrachloride. The resulting admixture was then charged to a 1 /2 gallon autoclave with 8 grams of calcium chloride; about 0.5 cc. of a percent solution of ditertiary bntyl peroxide in butanol; and about 10 drops of a commercially available wetting agent.

The charge was then chlorinated, in a first chlorination step, under about 30 p.s.i. (gauge) of chlorine pressure at a temperature of about C. until a chlorine content of about 20 percent was obtained. The charge was then chlorinated in a second suspension chlorination step, at a temperature of about 126 C. until a total chlorine content of about 42 percent was obtained. The chlorination product was then isolated from the dispersion by filtration, washed free of residual hydrochloric acid and dried.

The dried material was then used to prepare the following formulations by dry-blending of the designated mate rials in a ribbon blender.

TABLE I Sample identification Parts/100 parts Material Chlorinated polyethylene Linear, polyethylene (density of at 0.95) Polyvinyl chloride (K value of 61434.5) Heat stabilizer Phosphite stabilizer Epoxidized oil Self-extinguishing agen Stearic acid Talc Black pigment (0.3 part carbon black per 0.75

part high-pressure essentially non-linear polyethylene) 1 T102 pigment 2 l The invention.

2 For comparison.

The above blends were individually run through a continuous farrel mixer at a temperature between about 320 and 380 F. until individual intimate fusion blends were obtained. The fusion blends were then each separately extruded through a single sheet die to form individual 2.0 mil-thick sheet materials.

The following Table II summarizes the physical properties of each of the described sheet materials. The column headings of Table II have the following meanings:

TABLE II Physical property 1 1 2 2 3 2 Percent shrinkage 6 25 25 Percent relative crystallinity 2 100% modulus, p.s.i 460 450 250 Percent elongation 500 550 650 Ultimate tensile, p.s.i. l, 600 1, 700 1,350 Solvent-weldability. Excellent Excellent Excellent 1 The invention. 2 For comparison.

It is apparent from the data presented in Table II that the presence of linear polyethylene (Run No. 1) in the amounts prescribed greatly reduces the percent shrinkage while retaining necessary flexibility and solvent weldability of such sheet. That this improvement is unexpected and cannot be attributed to, or predicted from, a significant increase in the crystallinity of the sheet is believed to be apparent from a comparison of Runs 1 and 2, wherein a crystallinity difference of only 3 percent is present. Further, a comparison of Run 3 with Run 1 illustrates that the utilization of 7.5 parts of a high pressure, essentially non-linear polyethylene (in the form of a master-batch comprised of 0.3 part carbon black and 0.75 part high pressure polyethylene); does not provide such dimensional stability in otherwise equivalent formulations.

Further, by way of comparison, it has been found that compositions, as essentially described in Run No. l but having linear polyethylene present in amounts exceeding 15 percent by weight, are characterized by a 100 percent modulus of greater than 500 p.s.i. and form individual sheets which are incapable of being easily solvent weldable as required for use as flashing materials. Similarly, it has been found that individual sheets prepared from any composition as essentially contemplated by the present invention but having a 100 percent modulus of 500 p.s.i. and above are insufficiently solvent-weldable for industrial use as flashing material.

Still further, by way of comparison, it has been found that utilization of chlorinated olefin polymers having molecular weights exceeding 1 million are generally incapable of being fabricated into sheet-like structure without the addition of significant amounts of plasticizers or other processing aids. By way of illustration, it has been found that the non-plasticized chlorinated polyolefin as described in Example I above can be extruded through a standard Instron rheometer orifice, using a 190 C. barrel temperature, at a 150 sec. shear rate with a resultant shear stress of from 25 p.s.i., whereas under the same conditions chlorinated polyethylene having a molecular weight of from 1 million to 5 million are characterized by a shear stress of greater than about p.s.i. and often cannot be made to pass through the orifice of the rheometer.

It has also been found that utilization of chlorinated polyolefins as herein described, but having a chlorine content of greater than about 50 weight percent provides sheet material having reduced resistance to heat. Also, chlorinated polyolefins, as herein described, but having a chlorine content of less than about 25 weight percent are less resistant to burning, and utilization of chlorinated olefin polymers having in excess of about 10 percent relative crystallinity, results in sheet materials characterized by reduced ability to be solvent welded.

What is claimed is:

1. In the process of preparing sheet material from blends consisting essentially of chlorinated polyethylene and linear polymers of ethylene the improvement consisting of forming said sheet material from fusion blends of (1) from about 65 to 98 percent by weight of a chlorinated olefin polymer having a molecular weight of from about 20,000 to 300,000 and containing from about 25 to 50 percent by weight of chemically combined chlorine and having a crystallinity of less than 10 percent wherein said chlorinated olefin polymer is prepared by the chlorination in aqueous suspenslon of an olefin polymer selected from the group consisting of essentially linear homopolymers of ethylene and interpolymers containing at least about mole percent of ethylene in the polymer molecule with the remainder being at least one ethylenically unsaturated comonomer, and wherein said olefin polymer is first chlorinated at a temperature below its agglomeration temperature up to a chlorine content of between about 2 to 23 percent based on the weight of olefin polymer, and then chlorinated in a second stage at a temperature above the agglomeration temperature but below the crystalline melting point of said olefin polymer and wherein at least about 2 percent chlorine is added during the second stage; and

(2) from about 2 to 15 percent by weight of an essen- References Cited tially linear polymer of ethylene containing at least UNITED A S A NTS about 90 percent of ethylene in the polymer m l 3 086 957 4/1963 Carter 260 45.5 cule; 5 2,592,763 4/1952 Taylor 260-94.9 wherein said sheet material has a 100 percent modulus 2,4 7,550 4 1949 Fl h et 1, 260 23 of less than 500 p.s.i.

2. The process of claim 1 wherein said chlorinated MURRAY TILLMAN, Primary Examiner olefin polymer is chlorinated polyethylene and said C J SECCURO, Assistant E i polymer of ethylene is polyethylene. 10

3. The process of claim 2 wherein said chlorinated polyethylene contains about 42 percent by weight chlorine. 260 23 XA, 23 EP, 41 B, 41 R, 45.75, 45.85, 45.95