CA1086152A - Articles having a pressure-sensitive layer - Google Patents

Abstract

A B S T R A C T
An article having a pressure-sensitive layer, which layer consists of a bituminous composition comprising (a) from 50 to 97 %w of a bituminous component, (b) from 3 to 50.%w of one or more thermoplastic polymers, and (c) from 5 to 50 %w of a carbon black having an oil absorptivity of above 80 ml/100 gg all percentages being based on the weight of (a)+(b).

Description

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The invention r-elates to art.icles ha.vin@ a,~ressure-sensi.ti.ve layer, which layer consists of a mixture compris.ing a bituminous component, a thermoplastic polymer and a carbon black Pressure-sensiti.ve adhesives differ from o~her adheslves in that they function immediate].y upon appllcation without any physical or chemical change in the adhesive layer being involvedi they must provide instantaneous adhesion when applied under light pres~ure (see, e.g., Kirk-Othmer, Encyclopedia of chemical Technolo~y, 2nd editlon, volume 1, pa~e 382).
Articles havin~ pressure-æensitive layers consisting of a bituminous component and a thermopla.stic polymer are known e.g. from U.K. 1,329,298. Such articles usually have good low temperature flexi.bility, tack and adhesive strength.
However, there is now an increasing demand that such articles should also have a high flow resistance at hi~h tempera-tures e.g. at 90C and known articles are .sometimes unsatisfactory in this respect.
The Applicants have now discovered that if the pressure-sensitive layer comprises a carbon black, in addition to the bituminous component and the thermoplastic polymer, the artlcles have improved flow resistance at these high temperatures.
Accordingly, the present invention i.s- concerned with an article having a pressure-sentitive layer, wh.ich layer consists of a bituminous composi.tion comprisin~
(a) from 50 to 97 %w of a bituminous component, (b) from 3 to 50 %w of one or more thermoplastic polymers~
and ~ .

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(c) from 5 to 50 %w of a carbon black havin~ an oil absorptivity of above 80 ml/1~0 ~, all percentages being based on the wei~ht Or (a)~(b).
The oil absorptivity, also ~nown as the dibutyl phthalate absorption humber, is determined according to ASTM D2414-75.
The bituminous component of the pressure-sensitive layer may be a naturally occurring bitumen or derived from a mineral oil. Examples of suitable components include distillatlon or "strai~ht-run bitumens", precipitation bitumens e.g. propane bitumens, blown hitumens and mixtures thereof. Other suitable hituminous components include mixtures of one or more of these bitumens with extenders such as petroleum extracts e.g. aromatic extracts, distillates or residues. Particularly suitable are mixtures of a precipitation bitumen e.g. a propane bitumen and an aromatic petroleum extract, e.g. an aromatic extract of a heavy lubricating oil. Suitable bituminous components are those having a penetration of from 130 to 2,000 (0.1 mm) at 25C. Preferably the amount of the bitumen component is from 75 to 95 %w. ~ ~
Any thermoplastic polymer may be used as a component ~ ~;
of the pressure-sensitive layer. Suitable polymers are those prepared by the polymerization of olefinically ~ -unsaturated monomers. These polymers may be either homopolymers or copolymers and may ~e hydro~en~ted or unhydrogenate~.
The polymers ~ay be prerare~ from mono~ers which contain exclusively carbon and hydro~en. F.xamples Or such polymers are polyisobutylene3 polyisoprene, polybutadiene, ethylene-propylene copolymers and styrene-butadiene copolymers. The polymers may also be prepared from monomers which~ in addition to containing carbon and hydrogen, ~t least in part contain one or more other elements, such as oxygen. ~xamples of such polymers are ethylene-vinyl acetate copolymers, ethylene-ethy]. acrylate copolymers and ethylene-n-bu-tyl acrylate copolymers. Suitable polymers have molecular weights of at least 10,000, preferably ahove 50,000 and below 1,200,000. Some commercial thermoplastic polymers may be in admixture with various extender oils and these compositions may also be used as a component of the pressure-sensitive layer. Any extender oil present is re~arded as a part of the bituminous component insofar as the %w of the components of the present invention are concerned.
The preferred amount of polymer present in the pressure-sensitive layers is from 5 to 25 %w.
The preferred thermoplaætic polymers for use as a component of the pressure-sensitive layer are block copolymers having the general configuration:-A - B - (- B - A)n wherein each A is a thermoplastic polymer block of a monovinyl aromatic hydrocarbon or a 1-alkene, B is an .

elastomeric polymer block of a con,iugated diene or more than 1-alkene and n is an integer, suitably from 1 to 5, or a hydro~enated derlvative Or the block copolymer, The polymer blocks A preferably have a nu~ber average molecular weight~ in the ran~e o~ from 2,000 to 100~000, particularly from 7,500 to 50,000, The poly~er block B preferably has an average mclecular wei~ht in the range of from 25, ono to 1,000,000, oarticularly from 35,000 to 150,000, Whenever according to the brancheA
configuration two or more blocks B are immediately acljacent to each other they are treated as a single block for purposes of molecular weight, The amount of polymer blocks A in the block copolymers preferably ranges from 10 to 7~ %w, particularly from 20 to 50 %w. As examplefi of monovinyl aromatics suitable for the preparation of the polymer blocks in the present block copolymers may be mentioned styrene and alpha~methyl styrene, As conjugated ~ ;~
dienes suitable for the preparation of the polymer blocks B in the present block copolymers, preferably dienes with ~rom 4 to 8 carbon atoms per molecule are chosen, particularly butadiene and isoprene, Polymer hlocks B
may also be derived by the copolymerization of one or more conjugated dienes with one or more monovinyl aromatic compounds. The 1-alkenes useful for the preparation of ~5 either the thermoplastic blocks A or the ela.stomeric blocks B incluAe 1-alkenes havin~ from 2 to 12 carbon ~

6~2 atoms per molecule 5UC~. as ethylene~ pro~ylene, hutene-1, hexene-1 and octene-1.
Suitable examples of the block co~oly~ers considered herein are as follo~ls: polystyrene-polyisoprene-poly-styrene, ~olystyrene-polybutadiene-~olystyrene, poly-ethylene-(ethylene-pr~pylene copolymer)-polyethylene, polypropylene-(ethylene-propylene copolymer)-polypropylene, and their hydrogenated counterparts 9 particularly of the block copolymers containing diene homopolymer blocks.
The block copolymers may be formed by a number of different types Or processes includin~ the followin~:
A vinyl-arene such as styrene may be polymerized in an essentially inert hydrocarbon medium in the presence of mono-functional alkali metal hydrocarbyl initiator such as a lithium alkyl to form a polyvinyl arene block A terminated with a lithium ion. Immediately then, and without further treatment, a conjugated diene such as butadiene is introduced and block copolymerization is effected to produce the intermediate block copolymer A-B associated with the lithium ion. ~inally, a vinyl arene such as styrene i5 introduced and the polymerization continued to form khe desired linear polymer A - B - A.
Linear polymers may also be formed by a couplin~
process wherein ~he f1rst stage is as described above to form the initial polymer block A terminated with littlium~ followed by in-troduction of the conjugated diene to t`orm a polymer block having a mo:Lecular weight only half of final molecular weight of the conjugated diene polymer block in the ultimate produc-t. At this time~ a difunctional copling agent such as dibromo methane is added to form the desired three block pol-ymer A-B-(-B-A) , where n is 1, in other words A-B-A, which may contain an in~ignif-icant coupling residue in the center block B. This coupling residue is ignored in the description of the block copolymers in this speciEication.
Non-linear~ i.e.~ branched block copolymers are readily formed em-ploying multifunctional coupling agents such as~ e.gO, trichlorobenzene and ,~
tetrachloroethane. ~
The block copolymers may be hydrogenated if desired by any suitable ;
technique. The hydrogenation may be complete or partial. It is also possible to selectively hydrogenate just the centre block so as to convert eOg. a polyisoprene block to an ethylene propylene rubber (EPR) block.
t ; Mixtures of one or more thermoplastic polymers may also be used~
Suitable mixtures are referred to in Canadian Patents NosO 1,043,483 and 818,611.
As stated hereinbefore the carbon black used as a component of the pressure-sensitive layer should have an oil absorptivity of at least 80 ml/100 g. Preferred carbon b1acks are those which ha~e an oil absorptivity '~.

' ~ -7-z of at least 1~0 ml/100 ~ U; tah]y of from 100~1~5 ml/100 ~.
The average ~rtic]e diameter Or the carbon ~l~ck m~y vary between wlde llmits e.~. frcm 90 to 1,nO0 A but those having an average particle d:iameter o~ below 500 A are preferred. Preferred amounts of carbon black are from 15 to 35 %w, b~sed on wei~ht of bituminolls component and thermoplastic polymer.
Examples of suita~le carbon hlacks include channel process ~as blacks e.~. hig~ colour channel, medlum colour chanel, regular colour channel, easy processin~ channel, medium processing channel, medium flow channel and lon~
flow channel carbon blacks; furnace process gas blacks ~ e.g. fine furnace gas black; and furnace process oll ; blacks e.g. super-a~rasion furnace, intermediate super-abrasion furnace, intermediate super-ahrasion furnace (lo~ structure), intermediate super-abrasion furnace (high structure), high-abrasion furnace, high-abrasjon furnace (low structure) ~ -~
hîgh abbrasion furnace (hi~h structure) fast extruding furnace~ general purpose furnace and conductive furnace oil blacks.
Articles having a pressure-sensitive layer are, for example, sheets of roofing materials, in ~articular of synthetic roofing material e.g. butyl rubher, ethene-propene rubber sheets, pressure-sensitive labels or pressure-sensitive foils e.g. aluminhlm, insulating tapes ~or electrical devices, medical adhesive tapes, sound-deadening materials .

,, etc. Also considered as art;cles havirg a pre.sæure-sensit;ve layer are roors having a cold layer of the pressure-sensi.ti.ve :
layer. This method of a.~lication oF pressure-sensitive adhesives is of special utillty for materia.ls havin~
a low heat distortion temperature such as formed polystyrene sheets which may be col~-stuck on roofs or a~ainst walls ~.~
in this way. .
The article usually consists of a sheet which may be in the form of a roll to simpli~y transport and handleability thereof. The pressure-sensiti.ve layer may be protected ; :~
by cover sheets or cover tapes which have a.n adhesive-repellant surface~ e.~. due the impre~nation with wax or adhesi.ve repellant organo-polysi.loxanes. It is also ~ossible to cover the back of the sheet with organo-polysiloxanes . 15 or other adheæive-repellant compounds and thereafter to roll the sheets up. Articles such aæ sheets or tapes ~-can also have on two sides a pressure-æensitive layer so that other materia1s can adhere to both æides. ~hese . two layers are usually protected by covering layers wi.th an adhesive-repellant sur.face. An article can alæo consist of a cover foil with an adhesive-repellant surface and a layer consistin~ of the self-adhesive mixture, a second cover foil being a~plied to the self adherin~ layer so that after removal of the two cover la.yers only the layer consistin~ of the æelf-adhesive mixture iæ left e.g.
between two articles required to adhere to each other. ~ -- , . .

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The viscosity of the adhesive layer ~t the surf`ace temper~-ture of use o~ the articles, e.~. 25C, ls preferably more than 5,000 poises in order to provide su~ficient peel stren~th and preferably less than 500,000 po;ses in order to retain sufficient tackiness.
The pressure-sensitive layer may contain other components such as pigments, compounds inflvencin~ the rheological properties of the mixture like ~lass and asbestos fibres, and inor~anic and/or or~anic fillers such as challc, unbaked powdered gypsum, diatomaceous earth and quartz flour.
The pres~ure-sensitive layer may also contain other customery additives such as oxidation inhibitors.
The invention will now be illustrated with reference to the following examples.
r~ArlL~6 1 ~o l~l Pressure-sensitive compositions were prepared by mixin~
(a) 74.5 %w of a bituminous component comprisin~ 64 pbw of a propane bitumen and 36 pbw of an aromatic extract;
the component had a penetration of 400 (0.1 mm) at 25~C (ASTM D5);
(b) 10 %w of a block copolymer having the ~eneral configurfltion polystyrene-polyisoprene-polystyrene (9,500-140,000-9,500);
~c) 15.5 %w of a block copolymer mixture comprising 10 pbw of a block copolymer having the general configuration polystyrene-polybutadiene-polystyrene (20,000-409000-20,000) ~8~5~:

and 5.5 pbw of an extender oil, and ~:
(d) 25 %w of various carbon black~, (furnace carbon blacks), The %w are based on the wei~ht of (a)+(b)+(c). The average particle di.ameter and oil-absorptivities (ASTM D2414-75) `.. 5 of the carbon blacks u~ed are given in Table I.
Articles according to the i.nvention were prepared by coating aluminium ~oil (5 cm x 5 cm; 140-220 g/m2) with a 1.5 mm thick layer of the pressure-sen.sitive compo~i.tions.
The resistance to flow of such articles was determined b~ adhering these articles on an aluminium substrate which is then placed vertically in an oven having a temperature of 90C. The movement of the article over a number of days (maximum 14) is an indication of the resistance to flow of the article at hi.gh temperatures.
I 15 The results are given in Table I.

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~xam~le Carbon black propert,le.s ~low (mm) ~ y ~ ) oil-absorpt.ivity dia~eter (ml/100 g) (A) _______ _____ ___ ____ __ _ ______ ____________ a - > 130 ~r 115 . 210 0 : VI 115 95 2.5 : VII 110 230 0 VIII g5 510 1. 0 76 310 7. 5 c 71 750 49 . d 67 575 > 130*
:' e 65 600 77 :
f 62 240 10.5 _========_=_===== _=====_===_===_=====_===========_=
. * article complete s1ides off aluminium sheet. ~

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An article having a pressure-sensitive layer, which layer consists of a bituminous composition comprising (a) from 50 to 97 % w of a bituminous component, (b) from 3 to 50 % w of one or more thermoplastic polymers, and (c) from 5 to 50 % w of a carbon black having an oil absorptivity of above 80 ml/100 g, all percentages being based on the weight of (a)+(b).

2. An article as claimed in claim 1, wherein the bituminous component has a penetration of from 130 to 2,000 (0.1 mm) at 25°C.

3. An article as claimed in claim 1, wherein the bituminous component is a mixture of a precipitation bitumen and an extender oil.

4. An article as claimed in claims 1, 2 or 3, wherein the amount of bituminous component is from 75 to 95 % w.

5. An article as claimed in claims 1, 2 or 3, wherein the thermoplastic polymer is one or more block copolymers having the general configuration:-A - B - (- B - A)n wherein each A is a thermoplastic polymer block of a monovinyl aromatic hydro-carbon or a 1-alkene, B is an elastomeric polymer block of a conjugated diene or more than 1-alkene and n is an integer, suitably of from 1 to 5, or a hydrogenated derivative of the block copolymer.

6. An article as claimed in claims 1, 2 or 3, wherein the thermoplastic polymer is one or more block copolymers having the general configuration:-A - B - (- B - A)n wherein each A is a thermoplastic polymer block of a monovinyl aromatic hydra-carbon or a 1-alkene, B is an elastomeric polymer block of a conjugated diene or more than 1-alkene and n is an integer, suitably of from 1 to 5, or a hydrogenated derivative of the block copolymer wherein the amount of thermo-plastic polymer is from 5 to 25 % w.

7. An article as claimed in claims 1, 2 or 3, wherein the carbon black has an oil absorptivity of from 100 to 185 ml/100 g.

8. An article as claimed in claims 1, 2 or 3, wherein the carbon black has an average particle diameter of below 500 .ANG..

9. An article as claimed in claims 1, 2 or 3, wherein the amount of carbon black is from 15 to 35 % w.