GB2324303A

GB2324303A - Bituminous composition

Info

Publication number: GB2324303A
Application number: GB9807060A
Authority: GB
Inventors: Martine Jeanne Dupont; Gerardus Wilhelmus J Heimerikx; Erik Adrianus Theuni Trommelen
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1997-04-03
Filing date: 1998-04-01
Publication date: 1998-10-21
Also published as: GB9807060D0

Abstract

The invention provides a bituminous composition comprising a bitumen component, an elastomer in an amount of less than 20 %wt, based on total bituminous composition, and a photoinitiator; a process for preparing such bituminous composition; a bituminous felt membrane comprising a carrier and such bituminous composition; and a process for welding the joints of such bituminous felt membranes onto each other. The elastomer may be a thermoplastic rubber, e.g. a styrene-butadiene block copolymer.

Description

BITUMINOUS COMPOSITION The present invention relates to a bituminous composition which is suitable for use in bituminous felt membranes, especially roofing felts.

Of the various known methods to fix roofing felts on a roof, the torching method is the most widely applied. In this method the roofing felt is fixed to the roof by the application of heat from a propane torch whilst the felt is being rolled into position.

This method has, however, the risk of burn-through if the felt is heated too strongly, and the high risk of fire during construction due to employing naked flames.

In addition, increasing environmental awareness, makes it necessary within the roofing industry to develop new methods which can be applied at lower temperatures.

Surprisingly, it has now been found that roofing felts can attractively be fixed at roofs at a much lower temperature whilst the above-mentioned risks are avoided, when the roofing felts comprise a particular bituminous composition and use is made of UV radiation.

Accordingly, the present invention provides a bituminous composition comprising a bitumen component, an elastomer in an amount of less than 20 %wt, based on total bituminous composition, and a photoinitiator.

Suitably, the photoinitiator is present in an amount of less than 20 %wt, based on total bituminous composition. Preferably, the photoinitiator is present in an amount in the range of from 5 to 15 %wt, based on total bituminous composition.

Preferably, the elastomer is present in an amount of less than 15 %wt, based on total bituminous composition. More preferably, the elastomer is present in an amount in the range of from 10 to 15 %wt, most preferably in an amount in the range of from 10 to 13 %wt, based on total bituminous composition.

The bituminous composition according to the present invention comprises an elastomer. Elastomers are generally associated with polymer compositions of conjugated dienes, such as butadiene or isoprene, or with copolymer compositions of conjugated dienes with a monovinylaromatic hydrocarbon, such as styrene. It is emphasized that the elastomer used in the bituminous composition according to the invention is not restricted to such polymer compositions or copolymer compositions. Suitable elastomers include polyesters, polyacrylates, polysulphides, polysilicones and polyesteramides, provided they show an elastomer behaviour and contain unsaturations in the molecular backbone.

Although, the present bituminous composition preferably comprises one type of elastomer, it should be noted that in the context of the present invention also use can be made of a mixture of two or more different types of elastomers defined hereinbefore. In that case, the total amount of elastomer present does not exceed the amounts specified hereinbefore. The bituminous composition may in addition contain one or more of the resins taught in the art.

Preferably, the elastomer used is a thermoplastic rubber. Although a wide range of thermoplstic rubbers can be used in accordance with the present invention, the preferred thermoplastic rubber comprises a block copolymer composition comprising at least one block of conjugated diene and at least one block of a monovinylaromatic hydrocarbon. Preferably, the thermoplastic rubber comprises a block copolymer composition comprising at least one block of conjugated diene and at least one block of monovinylaromatic hydrocarbon, wherein the block copolymer composition has a vinyl content of at least 25% by weight based on the total diene content. Preferably, the block copolymer composition has a diblock content of 25 wt% or less, and any diblock copolymer present has an apparent molecular weight which is in the range of from 40,000 to 170,000.

With the term "apparent molecular weight" as used throughout the specification is meant the molecular weight of a polymer, as measured with gel permeation chromatography (GPC) using poly(styrene) calibration standards (according to ASTM D 3536).

By "diblock content", there should be understood the amount of non-coupled diblock copolymer that is finally present in the prepared block copolymer composition. Where the block copolymer is prepared via the full sequential preparation method, essentially only triblock copolymers are formed having an apparent molecular weight in the range from 120,000 to 340,000.

The diblock content is preferably less than 20 %wt, more preferably 15 wt or less.

The block copolymer composition constituents may be either linear or radial; good results have been given by both copolymer types. The block copolymer composition constituents include linear triblock copolymers (ABA), multi-armed block copolymers ((AB)nX), and (AB)nX(B)m, and diblock copolymers (AB), with A representing a monovinyl aromatic hydrocarbon polymer block, B representing a conjugated diene polymer block, n being an integer of 2 or higher, preferably between 2 and 6; m being an integer of 1 or higher, preferably 1 to 4; n + m preferably being 3 6, and X representing the residue of a coupling agent.

The coupling agent may be any di- or polyfunctional coupling agent known in the art, for example, dibromoethane, silicon tetrachloride, diethyl adipate, divinylbenzene, dimethyldichlorosilane, methyl dichlorosilane. Particularly preferred in such a preparation route is the use of non-halogen containing coupling agents, for example gamma-glycidoxypropyltrimethoxysilane (Epon 825), and diglycidylether of bisphenol A.

The block copolymers, which are useful as modifiers in the bituminous compositions according to the present invention, may be prepared by any method known in the art including the well known full sequential polymerisation method, optionally in combination with reinitiation, and the coupling method, as illustrated in e.g. U.S. Patents Nos. 3,231,635; 3,251,905; 3,390,207; 3,598,887 and 4,219,627 and EP 0413294 A2, 0387671 B1, 0636654 Al, WO 04/22931.

The block copolymer may therefore, for example, be prepared by coupling at least two diblock copolymer molecules AB together.

Techniques to enhance the vinyl content of the conjugated diene portion are well known and may involve the use of polar compounds such as ethers, amines and other Lewis bases and more in particular those selected from the group consisting of dialkylethers of glycols.

Most preferred modifiers are selected from dialkyl ether of ethylene glycol containing the same or different terminal alkoxy groups and optionally bearing an alkyl substituent on the ethylene radical, such as monoglyme, diglyme, diethoxyethane, 1,2-diethoxypropane, 1-ethoxy-2,2-tert-butoxyethane, of which 1,2diethoxypropane is most preferred.

The apparent molecular weight of diblock copolymer (AB) is in the range of from 40,000 to 170,000.

Preferably, said diblock copolymer apparent molecular weight is in the range of from 60,000 to 130,000, more preferably from 70,000 to 120,000.

The content of monovinyl aromatic hydrocarbon of the final block copolymer is suitably in the range of from 10 to 55% by weight, preferably in the range of from 15 to 45% by weight, and more preferably 25 to 40% by weight, based on the total block copolymer.

Suitable monovinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tertbutylstyrene, 2,4-dimethylstyrene, a-methylstyrene, vinylnaphthalene, vinyltoluene and vinylxylene, or mixtures thereof of which styrene being the most preferred.

The total vinyl content of the block copolymer is at least 25% by weight. Suitably the vinyl content is in the range of from 30 to 80 % by weight, preferably from 35 to 65% by weight, and more preferably from 45 to 55% by weight.

Suitable conjugated dienes include those having from 4 to 8 carbon atoms, for example 1,3-butadiene, 2methyl-1,3-butadiene (isoprene) , 2,3-dimethyl-1,3butadiene, 1,3-pentadiene and 1,3-hexadiene. Mixture of such dienes may also be used. Preferred conjugated dienes are 1,3-butadiene and isoprene, with 1,3butadiene being the most preferred.

It will be appreciated that with the term "vinyl content" actually is meant that a conjugated diene is polymerised via 1,2-addition. Although a pure "vinyl" group is formed only in the case of 1,2 addition polymerisation of 1,3 butadiene, the effects of 1,2 addition polymerisation of other conjugated dienes on the found final properties of the block copolymer and the blends of it with bitumen will be the same.

When exposed to UV radiation the photoinitiator to be used in accordance with the present invention forms radicals which establish the formation of cross-links between unsaturated moieties present in the bituminous composition. In this way an excellent adhesion can be established between the joints of the roofing felt which are to be welded together, ensuring a good watertight bond over a long period of time. It will be understood that the intensity of the UV radiation should, of course, be sufficient to melt at least part of the bitumen component present in the joints and to generate formation of radicals originating from the photoinitiator.

Therefore, the present invention also provides a process for welding joints of bituminous felt membranes together which comprise a bituminous composition as defined hereinbefore, comprising melting at least part of the bitumen component present in the joints by means of UV radiation under formation of radicals originating from the photoinitiator, and subsequently contacting the radiated joints of the bituminous felt membranes so obtained.

The welding process can advantageously be carried out at a temperature of below 150 "C. Preferably, the welding process in accordance with the present invention is carried out at a temperature in the range of from 40 to 100 "C.

It will understood that any photoinitiator taught in the art can be used provided that the radiation output of the UV source to be used includes one or more wavelengths of UV radiation which are absorbed by the photoinitiator (i.e. one or more wavelengths corresponding to one or more wavelengths in the UV absorbance spectrum of the photoinitiator). Preferably, the radiation output of the UV source to be used include more than 50 % of the wavelengths of UV radiation which are absorbed by the photoinitiator.

More preferably, the radiation output of the UV source to be used include all wavelengths of UV radiation which are absorbed by the photoinitiator.

Suitable photoinitiators include benzoin ethers, benzyl ketals, acetophenones, phosphine oxides, benzophenone and related compounds with amines, and thioxanthones. Suitably, a mixture of two or more of these photoinitiators can be used in accordance with the present invention, e.g. a mixture of a benxyl ketal and a thioxanthone.

Preferably, the photoinitiator is thermally stable up to a temperature of 200 "C.

The present invention also provides a bituminous felt membrane comprising a carrier and a coating which comprises a bituminous composition as defined hereinbefore. Preferably, the bituminous felt membrane is a roofing felt. The carrier of the bituminous felt membrane may be any of those taught in the art.

According to the type of roofing felt, the carrier may comprise one of a number of different types of fibrous materials and fabrics such as vegetable fibres, animal fibres, mineral fibres, synthetic fibre fabrics and combinations of these materials. The bituminous felt membrane may further comprise any other material taught in the art such as fillers, or decorative mineral particles applied to the upper surface of the membrane.

Preferably, the bituminous composition comprises a filler.

The membrane may either consist of one layer or a multiple layer system.

The bituminous composition according to the present invention can also be applied as an adhesive compound which can be applied to parts (joints) of bituminous felt membranes which are to be welded together. Thus, a thin photoinitiator-containing bituminous composition according to the present invention can be added/sprayed onto a conventional bituminous felt membrane for its use in UV curing.

The present invention still further provides a process for preparing a bituminous composition as defined hereinbefore comprising mixing the bitumen component, the elastomer and the photoinitiator at a temperature in the range of from 140 to 200 OC, preferably at a temperature in the range of from 160 to 180 "C. Suitably, the bitumen component and the thermoplastic rubber are mixed before the photoinitiator is added the mixture so obtained. The photoinitiator is suitably added to such mixture at a temperature in the range of from 140 to 200 OC, preferably in the range from 160 to 1800C.

The bitumen component may be a naturally occurring bitumen or derived from a mineral oil. Also petroleum pitches obtained by a cracking process and coal tar can be used as the bitumen component as well as blends of various bituminous materials. Examples of suitable bitumen components include distillation or "straightrun bitumens1,, precipitation bitumens, e.g. propane bitumens, blown bitumens, e.g. catalytically blown bitumen, and mixtures thereof. Other suitable bituminous components include mixtures of one or more of these bitumens with extenders (fluxes) such as petroleum extracts, e.g. aromatic extracts, distillates or residues, or with oils. Suitable bitumen components (either "straight-run bitumens" or "fluxed bitumens") are those having a penetration in the range of from 100 to 300 dmm, preferably, in the range of from 130 to 250 dmm, and of softening point in the range of from 25 to 50 OC, preferably in the range of from 30 to 45 "C (as measured by ASTM D 36)(as measured by ASTM D 5) at 25"C.

In accordance with the present invention a welding process is provided which can advantageously be carried out at a much lower temperature when compared with the conventional torch method, whilst a similar or even higher adhesion strength between the joints can be obtained.

Example Bituminous compositions in accordance with the invention were prepared by blending elastomer with bitumen at 1600C in a Silverson L2R high shear mixer.

During elastomer addition the temperature increased to 1800C, which is caused by the energy input of the mixer.

At 1800C the temperature was kept constant by on/off switching of the mixer. Blending was continued until a homogeneous blend was obtained which was monitored by fluorescence microscopy. After blending, the filler (Wigro=limestone) was incorporated under low shear stirring at 1800C, followed by the addition of Irgacure 369 photoinitiator at a temperature of 1400C.

Irgacure 369 (Irg 369) is a photoinitiator commercially available from Ciba-Geigy which is reported to be 2-benzyl-2-dimethylamino-1- (4- morpholinophenyl) -butanone-1.

The composition of the blends is reported in Table I.

Table I

Blend Polymer PX-2000 B-180 Wigro Irg.369 No. Type (g) PBl)(g) BFE2)(g) (g) (g) (g) 1 KX-219 59 300 135 212 2 KX-222 j 59 435 212 71 1) PB: Propane Bitumen 2) BFE: Bright Furfural extract PX-200 and B-180 are known bitumens, where the number corresponds with the PEN-value at 250C. The PX-200 bitumen used (asphaltene content 7%) is more compatible with the elastomers than B-180 bitumen (asphaltene content 13%).

KRATON-D-KX-219 is commercially available from Shell Chemical Companies and is a radial styrenebutadiene (SB)4 block copolymer with 8% by weight diblock. The 1,2 vinyl content is about 50% and the polystyrene content is 30%wt.

Kraton-D-KX222 is commercially available from Shell Chemical Companies and is a radial-styrene-butadiene block copolymer of approximate structure (SB)2B2. The polystyrene content is 18% by weight. The 1,2 vinyl content is about 49%.

Preparation of membranes for adhesion testing The sheets for the adhesion testing were prepared by pouring a certain quantity of Bituminous composition, heated to 1400C, in a spacer with defined dimensions and placed on a carrier. Covered with silicon paper the sample is placed in a Pasadena hydraulic press and pressed for 5 minutes with a load of 15000 Pounds at 1400C. After cooling down period of 10 minutes a spacer is placed on the other side of the carrier and the procedure as described above is repeated.

A polyester carrier (T679/26391 from AKZO Nobel Fibers B.V.) was used for T-peel testing. The membranes were obtained by cutting the sheet in pieces of 200x25 mm.

W radiation heating The heating of the membranes was done with a laboratory UV cure conveyorized system providing intense ultraviolet energy ex-UVPS Process Supply, Inc.

The apparatus was equipped with a tri-power switch in order to supply 300, 200 or 125 Watt per inch (WPI).

The conveyor system was constructed with a Teflon coated fibreglass belt. Th 0-250 feet per minute (FPM) variable speed control was used to vary the radiation time and consequently the heating of the membranes.

The UV radiation was produced by a 'H' Bulb mercury lamp. The output spectra of the lamp coincide with the absorption spectrum of the photoinitiator Irgacure 369 which is between 300nm and 350nm.

The heating of the membranes was performed by placing two membranes of equal composition on the conveyor belt, with which they were transported with a certain speed under the UV lamp; this is referred to as an UV-cycle.

The conditions of the experiments carried out are given in table 2.

welding of the membranes Immediately after heating, the temperature of the membranes was measured with a thermocouple (type K).

The measurements were carried out at one end of the specimen pressing the thermocouple into the top-layer of one of the bituminous felts immediately followed by placing the other membrane on top of it. The accuracy of the temperature measurements carried out is + 1.40C.

Adhesion was prevented over a length of 50 mm by covering the ends of the membranes with silicon paper; these free ends are used for placing the samples in the clamps of the tensile tester. The welding was established by rolling a weight of 1.0 kg for a total of 20 times over the membranes. The welded specimen was allowed to cool down to ambient temperature before peel testing.

Table 2 Welding Conditions 1 1 UV cycle 15-20 sec 300 WPI 2 no UV light - room temperature 3 no UV light - hot air = reference 4 1 UV cycle 15-20 sec 125 WPI 5 hot air + 1 UV cycle 15-20 sec 125 WPI Adhesive strength; T-peel testing The adhesive strength between membranes was tested according to a T-peel test with an Instron (4501) tensile tester. The ends of a specimen (50mm each) were clamped in the grips and the sample was stretched a constant rate of displacement of 254 mm (10 in.)/min according to ASTM D1876-93. The peel tests were performed at ambient temperature (20 - 21"C). The accuracy of the loadcell is equal to or better than 0.25% of the indicated load. The peeling load reported is the average load measured over a certain displacement.

The results, for the five welding conditions of table 2, are reported in table 3.

Table 3

Bituminous composition Welding Condition 1 2 Temp OC Load, N Temp C Load, N 1 44 80 33 178 2 51 93 56 156 3 23 54 23 91 4 55 56 50 80 5 29 58 30 107

Claims

CLAIMS 1. Bituminous composition comprising a bitumen component, an elastomer in an amount of less than 20 %wt, based on total bituminous composition, and a photoinitiator.
2. Bituminous composition according to claim 1, wherein the photoinitiator is present in an amount of less than 20 %wt, based on total bituminous composition.
3. Bituminous composition according to claim 1 or 2, wherein the thermoplastic rubber is present in an amount in the range of from 10 to 15 %wt, based on total bituminous composition.
4. Bituminous composition according to any one of claims 1 to 3, wherein the photoinitiator is present in an amount in the range of from 5 to 15 %wt, based on total bituminous composition.
5. Bituminous composition according to any one of claims 1 to 4, wherein the elastomer is a thermoplastic rubber.
6. Bituminous composition according to claim 5, wherein the thermoplastic rubber comprises a block copolymer composition comprising at least one block of conjugated diene and at least one block of conjugated, wherein the block copolymer composition has a vinyl content of at least 25% by weight based on the total diene content.
7. Bituminous composition according to any one of claims 1 to 6, wherein the bitumen component is a bitumen having a penetration in the range of from 100 to 300 dmm (as measured by ASTM D 5 at 250C) and a softening point in the range of from 25 to 50 "C (as measured by ASTM D 36).
8. Bituminous felt membrane comprising a carrier and a coating which comprises a bituminous composition as defined in any one of claims 1 to 7.
9. Process for preparing a bituminous composition as defined in any one of claims 1 to 7 comprising mixing the bitumen component, the elastomer and the photoinitiator at a temperature in the range of from 140 to 200 OC.
10. Process for welding joints of bituminous felt membranes together which comprise a bituminous composition as defined in any one of claims 1 to 7, comprising melting at least part of the bitumen component present in the joints by means of UV radiation under formation of radicals originating from the photoinitiator, and subsequently contacting the radiated joints of the bituminous felt membranes so obtained.