CA1296822C

CA1296822C - Adhering process

Info

Publication number: CA1296822C
Application number: CA000515730A
Authority: CA
Inventors: Eric George Kent
Original assignee: Polysar Ltd
Current assignee: MULTIPLES OF FIVE HOLDINGS Inc
Priority date: 1985-08-21
Filing date: 1986-08-11
Publication date: 1992-03-03
Anticipated expiration: 2009-03-03
Also published as: GB2179359B; GB8620186D0; FR2586420B1; NL8602118A; FR2586420A1; DE3628053A1; GB2179359A; BE905298A

Abstract

ADHERING PROCESS
Abstract of the Disclosure 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

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~ield of t~e Invention This invention relates to 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 to the substrate is obtained as well as self-bonding or fusion of overlapping layers.
Back ~ound of the Invention 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 ~or 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 or tape. In the application of such coatings in the ~orm of sheet or tape, a separate adhesive layer is generally used to achieve adhesion of the sheet to the substrate and o~ overlapping layers of the sheet to each other. In commercial wrapping operations, such as pîpe wrapping, it is normal practice to use a sheet carrying such an adhesive layer, and to stretch the sheet slightly, up to about 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 ~lexible material is stretched, and wrapped, usually spirally around an electrical c~ble. 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 tackifîer resin and requires that the proportion of butyl rubber be below 25 percent, and a tackifier is required to produce a composi~ion w'nich seals readily. U.S. Patent No. 3,298,992 issued to H. M. Bond et al discloses tape composi~ions containing specific proportions of butyl rubber, polyisobutylene, a chlorinated hydrocarbon resin and a high styrene copolymer of butadiene and styrene. Generally these materials when formed into a roll without a liner adhere together or fuse so that after a short period of time it is impossible to unwind them. To avoid this problem, self-adhering tapes have been provided with a removable liner between overlapping layers. Removal of the liner is time consuming and may be difficult when it becomes tightly adhered to the tape.
DISCLOSURE AND PRACTICE OF Il~VENTION
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The present invention is based on the discovery of certain compositions in sheet or tape 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 s~retching elongation of at least about 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 about 50 percent by weight is an isobutylene-isoprene polymer, the balance being polyisobutylene, an ethylene propylene polymer or natural rubber. They are s~rong but can be readily stretched without breaking. They have good ozone resistance and are readily handleable over a wide temperature range. The a -olefin polymers may be isotactic polypropylene or those polyethylenes which are generally referred to as low pressure polyethylene.

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A further aspect of the invention is the surprising discovery that the presence of filler or pigment in the tape increases the rate of fusion of overlapping layers of the stretched, wrapped tape.
According to my discovery, there is provided the proce,ss 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 oE (all parts being parts by weigh~) (a) a mixture of from about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of elas~omeric polymer9 and (b) a mixture of from about 15 ~o about 25 parts of isotactic polypropylene and from abou~ 75 to about 85 parts of elastomeric polymer, said elastomeric polymer consisting of from about 50 to 100 par~s by weight of an isobutylene-isoprene polymer and from 0 to about 50 parts by weight of one or more polymers selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecular weight from abou~ 50,000 to about 100,000 and ~iii) a polymer o~ ethylene and propylene containing rom about 50 to about 65 percent by weight ethylene, wherein said flexible layer is subjected to a stretching elongation of at least about 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.
Further according to my discovery, there is provided the proces,s of afixing to a substrate a flexible layer having insufficient tack to self-bond in the relaxed state9 said layer comprising a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) a mixture of from about 15 to about 30 parts of linear low density polyethylene and from about : ~ - 4 -,~i ,~:,,,., . . ~, .

70 to about 85 parts of elastomeric polymer, and (b) a mixture of from about 15 to about 20 parts of isotactic polypropylene and from about 80 to about ~5 parts of elastomeric polymer, said raw polymer mixtures (a) and (b) also containing from about 0.5 to about 20 parts by weight, per 100 parts of total polymer, of one or more filler or pigment, said elastomeric polymer consisting of from about 50 to 100 parts by weignt of an isobutylene-isoprene polymer and from 0 to about 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 about 50,000 to about 100,000, wherein said flexible layer is subjected to a stretching elongation of at least about 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 about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene or from a polymer containing from about 0.5 to about 1.5 weight percent of chlorine or from about 1.5 to about 2.5 weight percent of bromine and from about 95 to about 99 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene.
Such polymers are commercially available and have a molecular weight, expressed as the Mooney viscosity, of from about 30 to about 80 (~L 1+8 at 100C).
Polyisobutylene elastomer is available commercially as various molecular weight products. It is prepared using Friedel-Crafts catalysts at low temperature and its manufac~ure is well known in the art.
Polyisobutylene preferred in the raw polymer mixture has a ~296~2 Staudinger molecular weigi~t of from about 50,000 to about 100,000, and especially from about 60,000 to about 80,000. Grades having higher molecular weights, for example about 120,000 to about 135,000, result in very strong tapes which are difficult to stretch and which do not fuse satisfactorily at room temperature when stretched and wrapped. On the other hand, very low molecular weignt grades result in tapes which are tacky and difficult to handle.
Elastomeric copolymers of ethylene and propylene are well known to those skilled in the art and a variety are available commercially. Suitable such copolymers include EYR (ethylene-propylene rubber) and EPDM
(ethylene-propylene-terpolymer) containing by weight ~rom about 50 percent to about 65 percent ethylene. The third monomer which is used in a small amount in the production o EPDM is a copolymerizable polyene. Those polyenes which are generally used commercially are non-conjugated dienes including 5-ethylidene-2-norbornene, 1,4 hexadiene and cyclic dienes such as dic~clopentadiene.
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 conventional grades are produced by a high pressure process which operates at a pressure of from about 15,000 to 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 about 0.91 to 0.94 gm/cm3. In the newer or low pressure processes the polymer is produced either in gas phase 1uidized bed reactors at pressures of abvut 100 to 300 p5 i or in liquid phase reactors. In ~hese low pressure processes, the ethylene units polymerize in a linear fashion and randomly 61~2Z

spaced short branches or side chains are incorporated by copolymerizing small amounts, up to about 20 percent by weight, of ~ -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 is to be understood to mean the low pressure produced copolymers having a density in the range from ~.9l to 0.94 gm/cm3. They generally range in 10 molecular weight from about lO0,000 to 500,000 wi~h those in the range from about lO0,000 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 ~o self-bond in the relaxed state. LLDPE is available commercially in gradPs 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 about 0.2 to about 5 according to ASTM-D-1238.
The polypropylene which can be used in ~he practice of the present invention is preferably hi~hly crystalline in which propylene is polymerized predominantly in the isotactic configuration. It may also contain a small proportion, up to about 15 percent by weight, of the atactic configuration or of ano~her copolymerized ~-olefin such 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 number of grades of polypropylene are available commercially covering a wide range of melt flow index. The grades having a melt flow index according to ASTM-D-1238 of from about 2 to about 12 are preferred.

~Z9~ 2 The relative proportions of thermoplastic polymer and elastomeric polymer used in the present invention fall within a narrow range. ~xpressed in parts per 100 of total polymer in the compositions, the proportion of linear low density polyethylene is rom about 15 to about 30 parts, preferably from about lS to about 25 parts. The proportion of polypropylene is from about lS to about 25 parts, preferably from about lS to about 20 parts.
Proportions below the lower limits of the above ranges result in sheets or tapes 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 about 20 parts by weight, based on 100 parts of total polymer. They may be selected from those generally used in rubber compounds, exeL~plified by carbon blac~, calcium carbonate, talc, aluminum powder, titanium oxide and zinc oxide. The amount of a particular filler or pigment which can be used without adversely afecting the tensile and/or fusion properties of the flexible layer can be readily determined by those skilled in the art. It has surprisingly been found tha~ carbon black and pigments, when present in the range from 5 to about 20 parts by weight, actually appear to 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 desirable to include carbon black or pigment in the compositions. To achieve this effect it is preferred to use ti~anium oxide or carbon black, the preferred carbon black being a high abrasion or super , ~, 3LZ~68~2Z

abrasion furnace black. For electrical applications in which conductivity is desired, it is desirable to also use from about 10 to about 30 parts by weight per 100 parts of total 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 10 retardants. The use of a separate tackifier 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-heated to a suitable temperature generally in the range of about 150 to about 170C and mixed until it fluxes and forms a band on the mill rolls, which usually takes about two minutes. The elastomeric polymer(s) and any additives are then added to the mill and the mixing continued until a uniform blend is obtained, which usually takes a further five 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 polymers in any order to a preheated mixer and mixing until a uniform compound is obtained, usually about 5 minutes. Sheets of the flexible layer may be prepared such as by passing the compound ~hrough a calendar or an extruder equipped with a sheet die. The thickness of the sheets is not critical but generally is from about 0.1 to about 5 mm. For most applications it is preferred to use sheets having a thickness of from about 0.3 to about 3 mm. The fle~ible layer may be used in sheet for~ although ~96l~;~2 for a variety of applications it is desirably in tlle form of a tape prod.lced by cutting the sheet to form tapes l~aving 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 about 50 percent and in the elongated state applying it to the substrate, as for example in a wrapping action. Such stretching results in the sheets or ~apes 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 witnin a few hours of application. In order to develop the self-bonding properties required, the flexible layer is elongated by at least about 50 percen~. The upper limit of elongation depends on the composition of tne particular sheet or tape and must be below the level which would cause rupture.
Preferably, I have found that an elongation of from about 75 percent to about 150 percent provides an optimum balance between developing self-bonding properties and avoiding rupture.
The process of my invention 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 made to 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, particularl~ in the form of tapes, in the electrical trade for splicing cables, and for .~

~29~2 repairing splices and damaged insulation especially in cold weather environments.
The following examples illustrate the scope o~ my 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 Limîted and contained about 98.4 weight percent of isobu~ylene and about 1.6 weight percent of isoprene and had a Mooney viscosity (ML 1+12 at 125C) of about 55. The polyethylene was DOWLEX~ 2045 supplied by Dow Chemical having a Melt Index of 1.0 gm/10 min as determined by ASTM
Method D-1236 and a density of 0.92 as determined by ASTM
Method D-792. The internal mixer was preheated to about 160C and the polymers added and mixed for about 5 minutes. The compounds were sheeted out on a rubber mill to a thickness of about 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 the tapes, pressing overlapping layers together, and observing the degree of self-adhesion 8S the ease with which the layers could be hand separated. ~ tape 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 tempera~ure. The results are shown in Table I.
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~2~6~2 TARLE I
Compound/Ta~e No. l 2 3 4 Butyl rubber 90 80 75 70 Polyethylene lO 20 25 30 Carbon black 3 3 3 3 Antioxidant 9.05 0~05 0.05 0-05 Unstretc'ned tack ** * * Nil Degree of Fusion High High High Partial (Gvernight at R.T.) * slight ~ layers separate under very light force 0 ** moderate - layers separated without tearing but under a firm force.
Notes:
Carbon Black - IRB #4 ~
Antioxidant - IRGANOX lOlO
ample 2 Using the procedure of Example 1, the compounds shown in Table II were prepared and evaluated. The butyl rubber and polyethylene were the same as used in Example l. In comparing the properties o Tape No. 5 with Tape No. 4 of Table I, it is seen that the presence of lO parts of carbon black per lOO parts of total polymer results in a higher level of fusion. Tape No. 7, which is outside the scope of the invention, shows that for rep].acement of part of the butyl rubber with EPD~, the addition of carbon black essentially eliminates the fusion. Tapes No. 8 and ~, which are outside the scope of the invention, shows that above the critical level of polyethylene the tape will not fuse.

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TABLE_II
Com~ound/Ta~e No. 5 6 7 8 9 Butyl rubber 70 80 40 65 65 EPDM 585 ~ 40 -- -Polyethylene 30 20 20 35 35 Carbon black lO l0 l0 lO 20 Unstretched Tack Nil Nil Nil Nil Nil Degree of Fusion (overnight at R.T.) High High Very low I~one None Notes:
10 EPDM 585 - A copolymer of ethylene 9 propylene and ethylene norbornene, containing about 62 percent ethylene, supplied by Polysar Limited.
Carbon black - N-330 type Example 3 Using ~he procedure of Example l, 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 l0l0 antioxldant were prepared and evaluated~
The first compound contained no additional material, the second also contained 20 par~s of N~330 type carbon black and the third contained 21.3 parts of TITANOX ALO titanium oxide (parts being by weigh~ per l00 parts of total polymer).
None of the tapes possessed unstretched tack.
After stretching and applying, on standing overnight the inner layers of ~he wrapped tape from the first compound had fused although a portion of the outer layer could ~e unwrapped without tearing. The tapes from the second and third compounds had fused so that the layers could not be separated .. , ~29~ 2 F~am2~e 4 A compound containing 48 grams of butyl rubber and 12 grams of isotactic polypropylene was prepared and evaluated using ~he procedure of Example 1. The butyl rubber, Butyl 111, was supplied by Polysar Limited and contained about 99.3 weight percent isobutylene and about 0.7 weight percent of isoprene and had a Mooney viscosity ~ML 1+8 at 100C) of about 70~ The polypropylene, PROFAX~
6524 was supplied by Hercules. Tapes prepared from the compound had slight surface tack but wnen overlapped on each other and pressed together did not bond and could be readily separated. A strip was elongated by about 100 percent and wrapped around a metal rod. It clung tigntly to the rod and overlapping layers adhered strongly to each other and after 24 hours the overlapping layer had fused.
ample 5 Example 4 was repeated except that 15 grams of the polypropylene and 45 grams of t~e butyl rubber were used in preparing the compound. The unstretched tape had negligible tack, whereas overlapping layers of the elongated, wrapped tape self-bonded strongly. They could be unwound aEter 24 hours but required the application of significant force to do so.
ample_6 Example 4 was repeated except that instead of butyl rubber, brominated butyl rubber was used containing about 96.1 weight percent of isobutylene, about 1.8 weight percent of isoprene and about 2.1 weight percent of bromine and having a Mooney viscosity (ML 1+4 at 125C) of about 52. The uns~retched t~pe had no significant tack ` wherea~ the overlapping layers of the elongated, wrapped tape adhered fairly strongly to each other.

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Example_7 Using the procedure of Example 1, the compounds shown in ~able III were prepared and evaluated. The butyl rubber was POLYSAR Butyl 301 as used in E~ample 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 III
Compound/Tape No. 10 11 12 13 Bu~yl rubber 80 75 75 70 Polypropylene 20 25 25 30 Carbon black -- 0 20 0 Unstretched tack v. slight nil nil nil Degree of Fusion high low none none ample 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 of the 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
Compound/T~e No. 14 15 16 17 Butyl rubber 85 85 90 90 Shell RMT6100 15 -- 10 --30 Esso PP00400 -- 15 -- 10 Carbon black 3 3 3 3 Antioxidant ~ 0.5 0.5 0.5 0.5 Un.stretched tack slight slight tacky tacky , ..

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Notes:
_ _ Shell RMT6100 a~d Esso PP00400 - isotactic polypropylene supplied by Shell Chemical and Esso Chemical, respectively.
Carbon black - N-330 type Antioxidant - IRGANOX 1010 Butyl rubber - as used in Example 1 ample 9 Using th~ 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.
TABLE V
Compound/Tape_No. 18 19 20 21 __ Butyl rubber 40 40 42.5 40 Polyisobutylene 40 20 Natural rubber -- 40 -- --EPDM 585 -- -- 42.5 --Polypropylene 20 20 15 20 Carbon black -- -- 3.0 --Antioxidant -- - 0.05 --Unstretched tacknil slight slight nil Notes:
__ EPDM 585 - As used in Example 2.
EPDM 346 - A copolymer of ethylene, propylene and ethylidene norbornene containing about 62 percent by weight ethylene, and supplied by Polysar Limited.
Carbon black - N-330 type Antioxidant - IRGANOX lOlO

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Claims

1. 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 about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of elastomeric polymer, and (b) a mixture of from about 15 to about 25 parts of isotactic polypropylene and from about 75 to about 85 parts of elastomeric polymer, said elastomeric polymer consisting of from about 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to about 50 parts by weight of one or more polymer selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecular weight from about 50,000 to about 100,000 and (iii) a polymer of ethylene and propylene containing from about 50 to about 65 percent by weight ethylene, wherein said flexible layer is subjected to a stretching elongation of at least about 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.

2. The process of Claim 1 wherein said isobutylene-isoprene polymer is a copolymer containing from about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene.

3. A process of Claim 1 wherein said isobutylene-isoprene polymer contains from about 95 to about 99 weight percent of isobutylene, from about 0.5 to about 3 weight percent of isoprene and from about 0.5 to about 1.5 weight percent of chlorine or from about 1.5 to about 2.5 weight percent of bromine.

4. A process of Claims 1, 2 or 3 wherein said homopolymer of isobutylene has a molecular weight from about 60,000 to about 80,000.

5. The process of Claims 1, 2 or 3 wherein said polymer of ethylene and propylene is a copolymer of ethylene, propylene and ethylidene norbornene.

6. The process of Claims 1, 2 or 3 wherein said isobutylene-isoprene polymer has a Mooney viscosity (ML
1+8 at 100°C) of from about 30 to about 80.

7. The process of Claims 1, 2 or 3 wherein said stretching elongation is from about 75 percent to about 150 percent.

8. The process of affixing to a substrate a flexible layer having insufficient tack to self-bond in the relaxed state, said layer consisting of a raw polymer mixture selected from the group consisting of (all parts being parts by weight) (a) from about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of isobutylene-isoprene polymer, and (b) from about 15 to about 20 parts of isotactic polypropylene with from about 80 to about 85 parts of isobutylene-isoprene polymer, said raw polymer mixture also containing from about 0.5 to about 20 parts by weight, per 100 parts of total polymer, of one or more filler or pigment, wherein said flexible layer is subjected to a stretching elongation of at least about 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.

9. The process of Claim 8 wherein said isobutylene-isoprene polymer is a copolymer containing from about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene.

10. The process of Claim 8 wherein said filler or pigment is selected from carbon black and titanium oxide.

11. 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 about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of elastomeric polymer, and (b) a mixture of from about 15 to about 20 parts of isotactic polypropylene and from about 80 to about 85 parts of elastomeric polymer, said raw polymer mixtures also containing from about 0.5 to about 20 parts by weight, per 100 parts of total polymer, of one or more filler or pigment, said elastomeric polymer consisting of from about 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to about 50 parts by weight of one or more polymer selected from (i) natural rubber and (ii) a homopolymer of isobutylene having a molecular weight from about 50,000 to about 100,000, wherein said flexible layer is subjected to a stretching elongation of at least about 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.

12. The process of Claim 11 wherein said isobutylene-isoprene polymer is selected from (a) a copolymer containing from about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene and (b) a copolymer containing from about 95 to about 99 weight percent of isobutylene, from about 0.5 to about 3 weight percent of isoprene and from about 0.5 to about 1.5 weight percent of chlorine or from about 1.5 to about 2.5 weight percent of bromine.

13. The process of Claim 12 wherein said stretching elongation is from about 85 percent to about 150 percent.

14. The process of Claims 11, 12 or 13 wherein said filler or pigment is selected from carbon black and titanium dioxide and is present in an amount from about 5 to about 20 parts by weight based on total polymer.

15. A tape having insufficient tack to self-bond in the relaxed state and being capable of fusing into a homogeneous mass when elongated by at least about 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 about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of elastomeric polymer, and (b) a mixture of from about 15 to about 25 parts of isotactic polypropylene and from about 75 to about 85 parts of elastomeric polymer, said elastomeric polymer consisting of from about 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to about 50 parts by weight of one or more polymer selected from (i) natural rubber, (ii) a homopolymer of isobutylene having a molecular weight from about 50,000 to about 100,000 and (iii) a polymer of ethylene and propylene containing from about 50 to about 65 percent by weight ethylene.

16. The tape of Claim 15 wherein said isobutylene-isoprene polymer is a copolymer containing from about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene.

17. The tape of Claim 15 wherein said isobutylene-isoprene polymer contains from about 95 to about 99 weight percent of isobutylene, from about 0.5 to about 3 weight percent of isoprene and from about 0.5 to about 1.5 weight percent of chlorine or from about 1.5 to about 2.5 weight percent of bromine.

18. The tape of Claims 15, 16 or 17 wherein said homopolymer of isobutylene has a molecular weight from about 60,000 to about 80,000.

19. The tape of Claims 15, 16 or 17 wherein said polymer of ethylene and propylene is a copolymer of ethylene, propylene and ethylidene norbornene.

20. A tape having insufficient tack to self-bond in the relaxed state and being capable of using into a homogeneous mass when elongated by at least about 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 about 15 to about 30 parts of linear low density polyethylene and from about 70 to about 85 parts of elastomeric polymer, and (b) a mixture of from about 15 to about 20 parts of isotactic polypropylene and from about 80 to about 85 parts of elastomeric polymer, said raw polymer containing from about 5 to about 20 parts by weight, per 100 parts of total polymer of one or more filler or pigment, and elastomeric polymer consisting of from about 50 to 100 parts by weight of an isobutylene-isoprene polymer and from 0 to about 50 parts by weight

21 of one or more polymer selected from (i) natural rubber and (ii) a homopolymer of isobutylene having a molecular weight from about 50,000 to about 100,000.
21. The tape of Claim 20 wherein the amount of said filler or pigment is from about 5 to about 20 parts by weight.

22. The tape of Claims 20 or 21 wherein said filler or pigment is carbon black.

23. The tape of Claims 20 or 21 wherein said filler or pigment is titanium oxide.

24. The tape of Claims 20 or 21 wherein said isobutylene-isoprene polymer is a copolymer containing from about 97 to about 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene.

25. The tape of Claims 20 or 21 wherein said isobutylene-isoprene polymer contains from about 95 to about 99 weight percent of isobutylene, from about 0.5 to about 3 weight percent of isoprene and from about 0.5 to about 1.5 weight percent of chlorine or from about 1.5 to about 2.5 weight percent of bromine.

26. The tape of Claims 20 or 21 wherein said homopolymer of isobutylene has a molecular weight from about 60,000 to about 80,000.