GB2179359A - Adhering process and self-bonding polymer tapes therefor - Google Patents

Abstract

A process is provided for affixing to a substrate a non-tacky, flexible layer consisting of a raw polymer mixture of a minor proportion of linear low density polyethylene or isotactic polypropylene and a major proportion of elastomeric polymer of which at least about 50 percent by weight is butyl rubber, by applying a stretching elongation to the flexible layer before application to the substrate. The process may be used in a wide variety of applications, for example, to cover metal parts, make repairs to cracked cover components and electrical wiring splicing and to repair leaks in pipes or hoses.

Description

SPECIFICATION Adhering process This invention relates two affixing a non-tacky, flexible layer in sheet or tape form to a substrate by applying a stretching elongation to the flexible layer before application to the substrate whereby adhesion tothe sub- strate is obtained as well as self-bonding our fusion of overlapping layers.

Many articles need to be coated for protection from the environment. For example, metal surfaces may be protected by covering with a coating layer, thereby preventing chemical, oxidative or other attack of the surface. The technology for the application of such coatings is well known and includes application from solution, by the application of a paint, or application as a thin sheet ortape. In the application of such coatings in the form of sheet or tape, a separate adhesive layer is generally used to achieve adhesion ofthe sheet to the substrate and of overlapping layers of the sheetto each other.In commercial wrapping operations, such as pipe wrapping, it is normal practice to use a sheet carrying such an adhesive layer, and to stretch the sheet slightly, up to 5 percent, to ensure that it is wrapped tightly around the pipe.

In electrical applications such as cable splices, a tape in the form of a strip of flexibie material is stretched, and wrapped, usually spirally around an electrical cable. The overlapping layers tend to fuse to one another so that they can no longer be separated readily. Earlier such tapes were based on natural rubber, whereas later tapes which are described in the literature are based on combinations of synthetic polymers. U.S. Patent No.2,569,541 issued to Harold E. Selby discloses such compositions containing polyethylene, butyl rubber, polyethylene and a tackifier resin and requires that the proportion of butyl rubber be below 25 percent, and a tackifieris required to produce a composition which seals readily. U.S. Patent No.3,298,992 issued to H. M.

Bond et al discloses tape compositions containing specific proportions of butyl rubber, polyisobutylene, a chlorinated hydrocarbon resin and a high styrene copolymer of butadiene and styrene. Generally these mat- erials when formed into a roll without a liner adhere together orfuse so that after a short period of time it is impossibleto unwind them. To avoid this problem, self-adhering tapes have been provided with a removable liner between overlapping layers. Removal ofthe liner istime consuming and may be difficultwhen it be- comes tightly adhered to the tape.

The present invention is based on the discovery of certain compositions in sheet ortape form, which are not tacky and therefore do not stick together when overwrapped in the relaxed state, but which fuse and produce a homogeneous body when subjected to a stretching elongation of at least 50 percent and wrapped around a substrate. The compositions comprise raw polymer mixtures consisting of certain a -olefin polymers mixed in specific proportions with an elastomeric polymer component of which at least 50 percent by weight is an isobutylene-isoprene polymer, the balance being polyisobutylene, an ethylene propylene polymer or natural rubber. They are strong but can be readily stretched without breaking. They have good ozone resistance and are readily handleable over a widetemperature range.The a -olefin polymers may be isotactic polypropylene or those polyethylenes which are generally referred to as low pressure polyethylene.

Afurtheraspectofthe invention is the surprising discovery that the presence of filier or pigment in the tape increases the rate of fusion of overlapping layers of the stretched, wrapped tape.

The present invention provides a process of affixing to a substrate a flexible layer having insufficient tackto self-bond in the relaxed state, said layer comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture offrom 15to30 parts of linear low density polyethylene and from 70 to 85 parts of elastomeric polymer, and (b) a mixture of from 15 to 25 parts of isotactic polypropylene and from 75 to 85 parts of elastomeric polymer, said elastomeric polymer consisting offrom 50to 100 parts by weight of an isobutylene-isopropene polymer and from Oto 50 parts by weight of one or more polymers selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecular weight from 50,000 to 100,000 and (iii) a polymer of ethylene and propylene containing from 50 to 65 percent byweight ethylene, wherein said flexible layer is subject two a stretching elongation of at least about 50 percentimmediately prior to contact with the substrate, applying the elongated layerto the substrate in a wrapping operation and allowing overlapping layers of said flexible layer to bond to and fuse with each other.

One embodiment ofthe process of the invention provides the process of affixing to a substrate a flexible layer having insufficient tack to self-bond in the relaxed state, said layer comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture of from 1 5 to 30 parts of linear low density polyethylene and from 70 to 85 parts of elastomeric polymer, and (b) a mixture of from 15to 20 parts of isotactic polypropylene and from 80to 85 parts of elastomeric polymer,said raw polymermixtures (a) and (b) also containing from 0.5to 20 parts by weight, per 100 parts oftotal polymer, of one or morefilleror pigment, said elastomeric polymer consisting of from 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to 50 parts by weight of one or more polymers selected from (i) natural rubber and (ii) a homopolymer of isobutylene having a molecular weight of from 50,000 to 100,000, wherein said flexible layer is subjected to a stretching elongation of at least 50 percent immediately prior to contact with the substrate, applying the elongated layer to the substrate in a wrapping operation and allowing overlapping layers of said flexible layer to bond to and fuse with each other.

The isobutylene-isoprene polymer may be selected from a polymer containing from 97 to 99.5weight percent of isobutylene and from 0.5 to 3 weight percent of isoprene orfrom a polymer containing from 0.5to 1.5 weight percent of chlorine or from 1.5 to 2.5 weight percent of bromine and from 95 to 99 weight percentof isobutylene, and from 0.5 to 3 weight percent of isoprene. Such polymers are commercially available and have a molecular weight, expressed as the Mooney viscosity, of from 30 to 80 (ML 1+8 at 100 C).

Poiyisobutylene elastomer is available commercially as various molecular weight products. It is prepared using Friedel-Crafts catalysts at lowtemperature and its manufacture is well known in the art. Polyisobutylene preferred in the raw polymer mixture has a Staudinger molecular weight offrom 50,000to 100,000, and especially from 60,000 to 80,000. Grades having higher molecularweights, for example 120,000 to 135,000, result in very strong tapes which are difficultto stretch and which do not fuse satisfactorily at room temperature when stretched and wrapped. On the other hand, very low molecular weight grades result in tapes which are tacky and difficultto handle.

Elastomeric copolymers of ethylene and propylene are well known to those skilled in the art and a variety are available commercially. Examples of copolymers are EPR (ethylene-propylene rubber) and EPDM (ethylene-propylene-terpolymer) containing by weight from 50 percent to 65 percent ethylene. The third monomer which is used in a small amount in the production of EPDM is a copolymerizable polyene. Those polyenes which are generally used commercially are non-conjugated dienes e.g. 5-ethylidene-2-norbornene, 1,4 hexadiene and cyclic dienes such as dicyclopentadiene.

The natural rubber is preferably selected from the commercially available SMR grades.

Polyethylene is a well-known article of commerce and a large number of grades are available. The old or conventionai grades are produced by a high pressure process which operates at a pressure of from 15,000to 50,000 psi. The polymers produced in this process contain a variety of short and long chain branches and have densities falling in the range from 0.91 to 0.94 gm/cm3. In the newer or low pressure processesthe polymer is produced either in gas phase fluidized bed reactors at pressures of 100 to 300 psi or in liquid phase reactors.In these low pressure processes, the ethylene units polymerize in a linear fashion and randomly spaced short branches or side chains are incorporated by copolymerizing small amounts, up to 20 percent by weight, of o-olefins such as propylene, butene, hexene and octene and the like. The frequency and length of the side chains controls the density of the polymer. The term linear low density polyethylene (LLDPE) is commonly used, and when used herein isto be understood to mean the low pressure produced copolymers having a density in the range from 0.91 to 0.94 gm/cm3.They generally range in molecularweightfrom 100,000 to 500,000 with those in the range from 100,000 to 300,000 being preferred. These polymers have been found to be useful in the practice of the invention, whereas the use of polyethylene produced at high pressure results in tapes which are weak and which tend to self-bond in the relaxed state. LLDPE is available commercially in grades covering a range of melt flow index, which is a measure of the viscosity under melt flow conditions. Those preferred in the practice of the present invention fall within the range from 0.2 to 5.0 according to ASTM-D-1238.

The polypropylene which can be used in the practice of the present invention is preferably highly crystalline in which propylene is polymerized predominantly in the isotactic configuration. It may also contain a small proportion, up to 15 percent by weight, of the atactic configuration or ofanother copolymerized a-olefinsuch as butene, pentene, hexene, octene and the like. The term polypropylene is used herein to include homopolymers of propylene as well as such copolymers. A large numberof grades of polypropylene are available commercially covering a wide range of meltflow index. The grades having a melt flow index according to ASTM-D-1 238 of from 2to 12 are preferred.

The relative proportions of thermoplastic polymer and elastomeric polymer used in the present invention fall within a narrow range. Expressed in parts per 100 oftotal polymer in the compositions, the proportion of linear low density polyethylene is from 15 to 30 parts, preferably from 15to 25 parts. The proportion of polypropylene is from 15to 25 parts, preferably from 15to 20 parts. Proportions below the lower limits ofthe above ranges result in sheets ortapes having a level of tack which causes self adhesion when overlapped in the relaxed or unstretched state, whereas proportions higher than the upper limits result in products in which overlapping layers do not fuse within a reasonable time at normal temperatures when stretched and wrapped.

Filler or pigment may be included in the flexible layer containing a linear low density polyethylene if desired in an amount up to 20 parts by weight, based on 100 parts of total polymer. They may be selected from those generally used in rubber compounds, exemplified by carbon black, calcium carbonate, talc, aluminum powder,titanium oxide and zinc oxide. The amount of a particularfiller or pigment which can be used without adversely affecting the tensile and/orfusion properties of the flexible layer can be readily determined by those skilled in the art. It has surprisingly been found that carbon black and pigments, when present in the range from 5 to 20 parts byweight, actually appearto increase the rate of fusion of overlapping layers of stretched wrapped sheets or tapes.Thus, when the higher levels of a-olefin polymer are used it is desirableto include carbon black or pigment in the compositions. To achieve this effect it is preferred to usetitanium oxide or carbon black, the preferred carbon black being a high abrasion or super abrasion furnace black. For electrical applications in which conductivity is desired, it is desirable to also use from 10 to 30 parts by weight per 100 parts oftotal polymers of an electrically conducting carbon black or metal powder, such as aluminum powder.

Other optional ingredients may be incorporated into the flexible layer to achieve various performance objectives. For example, there can be added antioxidants and stabilizers, processing aids, lubricants and fire retardants. The use of a separatetackifier is not required.

The flexible layer is prepared by mixing procedures well known in the art of processing of synthetic rubbers using either a two roll mill or an internal mixer. When using a two roll mill, the thermoplastic polymer is added to the mill which has been pre-heatedto a suitable temperature generally in the range of 150 to 1700C and mixed until itfluxesand forms a band on the mill rolls, which usually takes about two minutes. Theelastome ric polymer(s) and any addivitives are then added to the mill and the mixing continued until a uniform blend is obtained, which usually takes a furtherfive minutes. The mixture is taken off the mill as strips of compound.

Compound may also be produced in bulk form using an internal mixer by adding the polymer in any order to a preheated mixer and mixing until a uniform compounds obtained, usually about 5 minutes. Sheets of the flexible layer may be prepared such as by passing the compound through a calendar or an extruderequipped with a sheet die. The thickness of the sheets is not criticat but generally is from 0.1 to 5 mm. For mostapplications it is preferred to use sheets having a thickness of from 0.3 to 3 mm. The flexible layer may be used in sheet forum although for a variety of applications it is desirably in the form of a tape produced by cutting the sheet to form tapes having the desired width.

The flexible layer, in sheet or tape form, is applied to the substrate by subjecting it to a stretching elongation in one direction of at least 50 percent and in the elongated state applying itto the substrate, as for example in a wrapping action. Such stretching results in the sheets or tapes developing the ability to self-bond and the overlapping layers adhere strongly to each other. These layers have the appearance of a fused sheet on or covering the substrate within a few hours of application. In order to developthe self-bonding properties required, the flexible layer is elongated by at least 50 percent. The upper limit of elongation depends on the composition of the particular sheet or tape and must be below the level which would cause rupture.Preferably, an elongation of from 75 percent to 150 percent provides an optimum balance between developing self-bonding properties and avoiding rupture.

The inventive process may be used in a wide variety of applications such as splicing, encapsulation and connection. Metal parts can be readily covered with such a flexible layer for storage or environmental reasons; for example a metal pylon may be so covered to protect it when immersed in water. Minor repairs may be madeto existing covers of exposed parts, for example underneath cars, trucks or other like vehicles.

Damaged boots on tie rod ends or rack and pinion steering components may be readily repaired by covering with a flexible layer in accordance with this invention. The process may be used, particularly in the form of tapes, in the electrical trade for splicing cables, and for repairing splices and damaged insulation especially in cold weather environments.

The following examples illustrate the scope of the invention.

Example 1 Sixty grams of each of four compounds of butyl rubber and linear low density polyethylene were prepared in a laboratory sized internal mixer in the relative proportions (parts by weight) shown in Table 1. The butyl rubber was POLYSAR Butyl 301 supplied by Polysar Limited and contained 98.4 weight percent of isobutylene and 1.6 weight percent of isoprene and had a Mooney viscosity (ML 1 + 12 at 125 C) of about 55. The polyethylene was DOWLEX 2045 supplied by Dow Chemical having a Melt Index of 1.0 gm/1 0 min as determined by ASTM Method D-1 236 and a density of 0.92 as determined by ASTM Method D-792. The internal mixer was preheated to 160 C and the polymers added and mixed for 5 minutes.The compounds were sheeted out on a rubber mill to a thickness of 1.5 mm and tapes having a width of 0.6 centimeters cut from each sheet.

The degree of unstretched tack of the tapes was determined by folding thetapes, pressing overlapping layers together, and observing the degree of self-adhesion as the ease with which the layers could be hand separated. Atape from each compound was elongated by 75 to 100 percent and wrapped around a metal rod.

The wrapping was examined after standing overnight at room temperature. The results are shown in Table I.

TABLE I Compound/ Tape No. 1 2 3 4 Butyl rubber 90 80 75 70 Polyethylene 10 2Q 25 30 Carbon black 3 3 3 3 Antioxidant 0.05 0.05 0.05 0.05 Unstretchedtack ** * * Nil DegreeofFusion High High High Partial (Overnight at R.T.) * slight - layers separate undervery iightforce ** moderate -layers separated without tearing but under a firm force.

Notes: Carbon Black IRB #4 Antioxidant- IRGANOX1010 Example 2 Using the procedure of Example 1, the compounds shown in Table II were prepared and evaluated. The butyl rubberand polyethylene were the same as used in Example 1. In comparing the properties of Tape No.5 with Tape No.4 of Table I, it is seen that the presence of 10 parts of carbon black per 100 parts oftotal polymer results in a higher level of fusion.Tape No.7, which is outside the scope of the invention, shows thatfor replacement of part of the butyl rubber with EPDM, the addition of carbon black essentially eliminates the fusion Tapes No. 8 and 9, which are outside the scope of the invention, shows that above the critical level of polyethylene the tape wil I not fuse.

TABLE II Compoundi Tape No. 5 6 7 8 9 Butyl rubber 70 80 40 65 65 EPDM 585 -- -- 40 -- - Polyethylene 30 20 20 35 35 Carbon black 10 10 10 10 20 UnstretchedTack Nil Nil Nil Nil Nil Degree of Fusion (overnight at R.T.) High High Very low None None Notes: EPDM 585 -A copolymer of ethylene, prppylene and ethylene norbornene, containing about 62 percent ethylene, supplied by Polysar Limited.

Carbon black- N-330type Example3 Using the procedure of Example 1,three compounds containing 75 parts by weight of POLYSAR Butyl 301, 25 parts by weight of DOWLEX 2045 polyethylene and 0.05 parts of IRGANOX 1010 antioxidantwere prepared and evaluated. The first compound contained no additional material, the second also contained 20 parts of N-330 type carbon black and the third contained 21.3 partsofTITANOXALOtitanium oxide (parts being by weight per 100 parts oftotal polymer).

None of the tapes possessed unstretched tack. After stretching and applying, on standing overnightthe inner layers ofthe wrapped tape from the first compound had fused although a portion of the outer layer could be unwrapped without tearing. The tapes from the second and third compound had fused so thatthe layers could not be separated.

Example4 A compound containing 48 grams of butyl rubber and 12 grams of isotactic polypropylene was prepared and evaluated using the procedure of Example 1. The butyl rubber, Butyl 111, was supplied by Polysar Limited and contained 99.3 weight percent isobutylene and 0.7 weight percent of isoprene and had a Mooney viscosity (ML 1+8 at 1 OO"C) of 70. The polypropylene, PROFAX 6524 was supplied by Hercules. Tapes prepared from the compound had slightsurface tack but when overlapped on each other and pressed together did not bond and could be readily separated. A strip was elongated by 100 percent and wrapped around a metal rod.It clung tightly to the rod and overlapping layers adhered strongly to each other and after 24 hours the overlapping layer had fused.

Example5 Example 4was repeated exceptthat 15 grams ofthe polypropylene and 45 grans ofthe butyl rubberwere used in preparing the compound. The unstretched tape had negligibletack, whereas overlapping layers ofthe elongated, wrapped tale self-bonded strongly. They could be unwound after 24 hours but required the application ofsignificantforce to do so.

Example 6 Example 4was repeated exceptthat instead of butyl rubber, brominated butyl rubber was used containing 96.1 weight percent of isobutylene, 1.8 weight percent of isoprene and 2.1 weight percent of bromine and having a Mooney viscosity (ML 1+4 at 125"C) of 52. The unstretched tape had no significant tack whereas the overlapping layers of the elongated, wrapped tape adhered fairly strongly to each other.

Example 7 Using the procedure of Example 1, the compounds shown in Table Ill were prepared and evaluated. The butyl rubber was POLYSAR Butyl 301 as used in Example 1, and the polypropylene was the same as used in Example 3. The carbon black was N-330 type. These results show the criticality of the amount of polypropylene which may be used in the invention, tapes No. 12 and 13 being outside the scope of the invention.

TABLE Ill Compoundl Tape No. 10 11 12 13 Butyl rubber 80 75 75 70 Polypropylene 20 25 25 30 Carbon black -- 0 20 0 Unstretchedtack v. slight nil nil nil Degree of Fusion high low none none Example 8 Using the procedure of Example 1, the compounds shown in Table IV were prepared and evaluated. Tapes 14 and 15 had slight unstretched tack. On the other hand, Tapes 16 and 17 which are outside the scope ofthe invention were tacky and overlapping layers of unstretched tapes tore when an effort was made to separate them. In all cases, the stretched wrapped tapes had fused when examined after standing at room temperature overnight.

TABLE IV Compoundl Tape No. 14 15 16 17 Butyl rubber 85 85 90 90 Shell RMT6100 15 -- 10 - Esso PP00400 -- 15 -- 10 Carbon black 3 3 3 3 Antioxidant 0.5 0.5 0.5 0.5.

Unstretchedtack slight slight tacky tacky Notes: Shell RMT61 00 and Esso PP00400 - isotactic polypropylene supplied by Shell Chemical and Esso Chemical, respectively.

Carbon black- N-330type Antioxidant-IRGANOX 1010 Butyl rubber-as used in Example 1 Example 9 Using the procedure of Example 1, the compounds shown in Table V were prepared and evaluated. The butyl rubber was Butyl 301 and the polypropylene was PROFAX 6524, as used in previous examples. The elongated, wrapped tapes prepared from all compounds had fused when examined after standing overnight.

TABLEV Compoundl Tape No. 18 19 20 21 Butylrubber 40 40 42.5 40 Polyisobutylene 40 -- -- - Natural rubber -- 40 -- - EPDM 585 -- -- 42.5 - EPDM 346 -- -- -- 40 Polypropylene 20 20 15 20 Carbon black -- -- 3.0 - Antioxidant -- -- 0.05 - Unstretchedtack nil slight slight nil Notes: EPDM 585 - As used in Example 2.

EPDM 346 - A copolymer of ethylene, propylene and ethylidene-norbornene containing 62 percent by weight ethylene, and supplied by Polysar Limited.

Carbon black- N-330type Antioxidant - IRGANOX 1010 The present invention also includes a tape having insufficienttackto self-bond in the relaxed state, and being capable of fusing into a homogeneous mass when elongated byat least 50 percent and wrapped into overlapping layers, said tape comprising a raw polymer mixture selected from the group consisting of(all parts being parts byweight) (a) a mixture offrom 15 to 30 parts of linear low density polyethylene and from 70 to 85 parts of elastomeric polymer, and (b) a mixture of from 15 to 25 parts of isotactic polypropylene and from 75 to 85 parts of elastomeric polymer, said elastomeric polymer consisting of from 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to 50 parts by weight of one or more polymer selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecularweightfrom 50,000 to 100,000, and (iii) a polymer of ethylene and propylene containing from 50 to 65 percent by weight ethylene.

The present invention further includes a process for affixing to a substrate a non-tacky, flexible layercomprising a raw polymer mixture of a minor proportion of linear low density polytheylene or isotactic polypropylene and a major proportion of elastomeric polymer of which at least 50 percent by weight is butyl rubber, comprising applying a stretching elongation to the flexible layer before application to the substrate.

It should be noted that any numerical value given in this specification (description of claims) includes that value when qualified by "about" or "substantially".

Claims (20)

1. A process of affixing to a substrate a flexible layer having insufficient tack to self-bond in the relaxed state, said layer comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture offrom 15to 30 parts of linear low density polyethylene and from 70 to 85 parts ofelastomeric polymer, and (b) a mixture of from 15 to 25 parts of isotactic polypropylene and from 75 to 85 parts of elastomeric polymer, said elastomeric polymer consisting of from 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to 50 parts by weight of one or more polymer selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecularweightfrom 50,000 to 100,000 and (iii) a polymer of ethylene and propylene containing from 50to 65 percent byweight ethylene, wherein said flexible layer is subjected to a stretching elongation of at least 50 percent immediately priorto contact with the substrate, applying the elongated layer to the substrate in a wrapping operation and allowing overlapping layers of said flexible layerto bond to and fuse with each other.

2. The process of Claim 1 wherein said isobutylene-isoprene polymer is selected from (a) a copolymer containing from 97 to 99.5 weight percent of isobutylene and from 0.5 to 3 weight percent of isoprene and (b) a copolymer containing from 95to 99 weight percent of isobutylene, from 0.5to 2.0 weight percent ofiso- prene-and from 0.5 to 1.5 weight percent of chlorine orfrom 1.0 to 3.0 weight percent of bromine.

3. A process of Claims 1 or2 wherein said homopoiymer of isobutylene has a moiecularweightfrom 60,000 to 80,000.

4. The process of Claims 1 or 2 wherein said polymer of ethylene and propylene is a copolymerof ethylene, propylene and ethylidene norbornene.

5. The process of any preceding claim wherein said isobutyiene-isoprene polymer has a Mooneyviscosity (ML 1+8 at 1 OO"C) of from 30 to 80.

6. The process of Claims 1,2,3 or Swherein said raw polymer mixture is selected from the group consisting of (all parts being parts by weight) (a) from 15to 30 parts of linear low density polyethylene with from 70to 85 parts of elastomeric polymer, and (b) from 20 to 25 parts of isotactic polypropylene with from 80 to 85 parts of elastomeric polymer, said raw polymer mixture also containing from 0.5 to 20 parts by weight, per 100 parts oftotal polymer, of one or more filler or pigment, said elastomeric polymer consisting of from 50to 100 parts by weight of an isobutylene-isoprene polymer and from Oto 50 parts by weight of one or more polymers selected from (i) natural rubber and (ii) homopolymer of isobutylene having a molecular weight offrom 50,000 to 100,000.

7. The process of Claim 6 wherein said filler or pigment is selected from carbon black and titanium oxide.

8. The process of Claim 6 wherein said mixture contains from 5 to 20 parts by weight based on total polymer of carbon black ortitanium dioxide.

9. The process of Claims 6,7 or 8 wherein said isobutylene-isoprene polymer is copolymer containing from 97 to 99.5 weight percent of isobutylene and from 0.5to 3 weight percent ofisoprene.

10. Atape having insufficienttackto self-bond in the relaxed state, and being capable of fusing into a homogeneous mass when elongated byat least 50 percent and wrapped into overlapping layers, said tape comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture of from 15 to 30 parts of linear low density polyethylene and from 70 to 85 parts ofelastomeric polymer, and (b) a mixture offrom 15 to 25 parts of isotactic polypropylene and from 75 to 85 parts of elastomeric polymer, said elastomeric polymer consisting of from 50to 100 parts by weight of an isobutylene-isoprene polymer and from Oto 50 parts by weight of one or more polymer selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecular weightfrom 50,000 to 100,000, and (iii) a polymerofethylene and propylene containing from 50 to 65 percent by weight ethylene.

11. The tape of Claim 10 wherein said isobutylene-isoprene polymer is selected from (a) a copolymer containing from 97 to 99.5 weight percent of isobutylene and from 0.5to 3 weight percent of isoprene and (b) a copolymer containing from 95 to 99 weight percent of isobutylene, from 0.5 to 2.0 weight percent of iso prene and from 0.5 to 1.5 weight percent of chlorine orfrom 1 .Oto 3.0 weight percent of bromine.

12. The tape of Claim 10 wherein said homopolymer of isobutyiene has a molecularweight from 60,000 to 80,000.

13. The tape of Claim 10 wherein said polymer of ethylene and propylene is a copolymer of ethylene, propylene and ethylidene norbornene.

14. The tape of Claim 10 comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture of from 15 to 30 parts of linear low density polyethylene and from70 to 85 parts of elastomeric polymer, and (b) a mixture of from 20to 25 parts of isotactic polypropylene and from 80 to 85 parts of elastomeric polymer, said raw polymer also containing from 0.5 to 20 parts byweight, per 100 parts of total polymer of one or more filler or pigment, and elastomeric polymer consisting offrom 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to 50 parts by weight of one or more polymer selected from (i) natural rubber and (ii) a homopolymer of isobutylene having a molecularweight from 50,000 to 100,000.

15. The tape of Claim 14 wherein said filler or pigment is selected from carbon black and titanium dioxide present in an amount from 5 to 20 parts by weight based on total polymer.

16. The tape of Claims 14 or 15 wherein said isobutylene-isoprene polymer is selected from (a) a copolymer containing from 97 to 99,5 weight percent of isobutylene and from 0.5to 3 weight percent of isoprene and (b) a copolymer containing from 95 to 99 weight percent of isobutylene, from 0.5 to 2.0weight percent of isoprene and from 0.5to 1.5 weight percent of chlorine or from 1.0 to 3.0 weight percent of bromine.

17. A tape as claimed in claim 10 substantially as described with reference to any one of the Examples.

18. A process for affixing to a substrate a non-tacky, flexible layer comprising a raw polymer mixture of a minor proportion of linear low density polyethylene or isotactic polypropylene and a major proportion of elastomeric polymer of which at least 50 percent by weight is butyl rubber, comprising applying a stretching elongation to the flexible layer before application to the substrate.

19. A process as claimed in claim 18, substantially as described with reference to any one of the Examples.

20. A process as claimed in claim 1, substantially as described with reference to any one of the Examples.