GB2041951A - Bituminous compositions - Google Patents

Abstract

Bituminous compositions contain as essential components bitumen, hardened extract, a thermoplastic and a non-thermoplastic rubber and at least 50 percent by weight of a filler in relation to the total weight of the essential components. The compositions can be formed into flexible shaped materials, e.g. sheets or mouldings having vibration and sound damping properties which can be used in the building and automotive industries.

Description

SPECIFICATION Bituminous compositions This invention relates to bituminous compositions which contain bitumen, hardened extract, rubber and filler and to flexible shaped materials having vibration damping properties formed from the compositions. The shaped materials can be used in the building and automotive industries where vibration and sound damping is required, e.g. for sound insulation.

The bituminous compositions according to the present invention comprise, as essential components, a bitumen, a hardened extract, a thermoplastic rubber, finely divided particles of a nonthermoplastic rubber and a filler, the filler being present in a proportion by weight in relation to the total weight of the essential components in the range 50 to 90 percent and preferably in the range 60 to 80 percent.

Most suitably the proportions by weight of the essential components based on 1 00 parts of bitumen and hardened extract can be selected from the following: Bitumen and hardened extract 100 parts (of which the bitumen is 70 to 50 parts and the hardened extract is 30 to 50 parts) Filler 200 to 1800 and preferably more than 300 parts Thermoplastic rubber 5 to 40 parts and preferably more than 20 parts Non-thermoplastic rubber 50 to 120 parts and preferably more than 60 parts The compositions can and usually do contain an anti-oxidant and/or a thermal stabiliser to minimise oxidation and thermal degradation during mixing and processing. Anti-oxidants and thermal stabilisers are compounds which are well known in the rubber industry and any of these compounds can be used in the present compositions.These compounds can be present in the compositions in amounts in the range 1 to 5 parts by weight. Some examples are octylated diphenylamine (e.g. Nonox OD sold by ICI Ltd.), Polymerised 2,2,4-trimethyl-1-2-dihydroquinoline (e.g. Flectol H sold by Monsanto Ltd.) and alkylated aryl phosphites (e.g. Polygard HR sold by The Rubber Regenerating Company Ltd.).

The compositions can be formed into flexible shaped materials by techniques which are well known in the rubber industry. The shaped materials can be in the form of sheets, rolls or moulded articles. Moulded articles can be formed which retain their shape on exposure to temperatures of up to 1 00C for periods of up to 5 hours. The materials have good vibration and sound damping properties and retain their flexibility over a relatively wide temperature range.

The quantity of thermoplastic rubber present is an important factor in determining the low temperature flexibility and impact resistance of the material. The rubber is soluble in the bitumen. The flexibility and impact resistance of the material are largely dependent on the blend of the thermoplastic rubber, bitumen and hardened extract present.

The presence of the hardened extract facilitates dissolution of the thermoplastic rubber in the bitumen, thus enabling the mixing temperatures to be reduced sufficiently to prevent any substantial thermal degradation of the thermoplastic rubber. There appears to be an optimum ratio of hardened extract to bitumen present which gives the highest solubility and maximum rate of dissolution of thermoplastic rubber in the bitumen/hardened extract blend and which imparts the maximum beneficial effect in the materials formed from the compositions. In addition the hardened extract decreases the tackiness of and imparts hardness to the compositions. Most suitably sufficient hardened extract should be present to give in the compositions a hardness value when measured on the International Rubber Hardness Degree Scale of at least 60 when it is the intention to calender compositions.The hardness is also significantly affected by the quality of filler. For example, when the quantity of filler is at a maximum, a minimum of 30 parts of hardened extract to 70 parts of bitumen is usually sufficient to ensure an initial RHD hardness of 60 and when the quantity of filler is at a minimum the quantity of hardened extract shouid be increased to 50 parts to 50 parts of bitumen.

The quantity of non-thermoplastic rubber present is an important factor in determining the stretch elongation characteristics of the material. An upper limit of 1 5 percent by weight in relation to the total weight of the essential components appears to be suitable for most purposes. The presence of amounts which are much in excess of 1 5 percent can give rise to difficulty in calendering when forming the compositions into good quality sheets.

The bitumen may be derived from petroleum, e.g. the residues from the vacuum distillation of crude oils and may be a straight run bitumen, an oxidised bitumen obtained by air blowing an atmospheric or vacuum residue to a suitable penetration, or an asphalt obtained from an atmospheric or vacuum residue by precipitation with a low boiling paraffin hydrocarbon, e.g. propane. The bitumen may have a penetration of from 10 to 450 at 252C and a softening point (Ring and Ball) of from 25 to 1500C.

The hardened extract may be produced by blowing a petroleum extract with an oxygen containing gas, preferably air, at 250-3500C either in the absence or presence of a catalyst, e.g. a Friedel-Crafts metal halide such as ferric chloride. Petroleum extracts are obtained by the solvent extraction of distillate petroleum fractions boiling in the lubricating oil range, i.e. 350-6002C and contain a major proportion of aromatic hydrocarbons. The blowing of the extract is believed to cause condensation of the aromatics giving a hardened product with a high proportion of asphaltenes, cyclic and insoluble compounds and a relatively low proportion of saturates. The hardened extract may have a penetration of from 0.1 to 6 at 250C and softening points (Ring and Ball) of from 60 to 1 700C.

Thermoplastic rubbers are known and any of the known rubbers may be used. They are normally synthetic polymers produced by the block co-polymerisation of a diene, e.g. butadiene, and another unsaturated monomer, e.g. styrene. Examples of suitable thermoplastic rubbers are those sold by Phillips Petroleum Company under the Registered Trade Mark "Solprene" and by Shell Chemical Company under the Registered Trade Mark "Cariflex". Bitumen and thermoplastic rubbers are compatible and form a homogenous blend when mixed at an elevated temperature of, e.g.

1 80-2200C. The thermoplastic rubber may be used in any form but is preferably used as powder or crumb to reduce the time of dissolution in the bitumen.

The non-thermoplastic rubber is used in the form of finely divided particles which,for example, may be finer than 20 mesh BSS. The rubber will normally be vulcanised and may be, for example, a synthetic rubber, e.g. SBR or polybutadiene or natural rubber. It may be oil extended and/or filled and is usually reclaimed from scrap tyres. The non-thermoplastic rubber is not believed to blend with the bitumen but to remain as discrete particles which act to stiffen the bitumen but which, at the same time, give resilience to the composition. The non-thermoplastic rubber particles may be mixed with the bitumen at the same time as the thermoplastic rubber or subsequently.

Any of the normal fillers for bitumen is suitable as a component of the present compositions. They may be powdered or fibrous but are preferably the former. Examples of suitable fillers are powdered limestone, silica, alumina, Portland cement, barytes, pulverised fuel ash, talc, asbestos fibres and glass fibres. In particular, compositions forming materials which have useful sound damping properties can be prepared by employing heavy fillers such as finely divided calcium carbonate (e.g. limestone), barium sulphate (e.g. barytes) or mixtures thereof, alumina or light fillers such as pulverised fuel ash, either alone or in mixtures. The preferred fillers are limestone, barium sulphate and ferric oxide.

The presence of a small amount of talc during the mixing stage has been found to facilitate subsequent handling of the composition, and the filler content may include 0.52% wt by weight of the composition of talc, added to the mixing stage.

It is a characteristic of the present compositions that a relatively large quantity of filler can be present without any appreciable loss in processing characteristics of the compositions and without imparting brittleness in the materials formed therefrom. The quantity and type of the filler present are the principal factors in determining the vibration and sound damping properties of the materials formed from the compositions.

The composition must be mixed prior to forming materials therefrom. The object of mixing is to solubilise the thermoplastic rubber and disperse the filler and non-thermoplastic rubber. To ensure complete homogeneity of the components and to develop optimum physical properties the compositions may be mixed in, e.g. a Z-blade mixer at temperatures in the range 120 to 1 300C for 1 to 2 hours followed by milling to a thick hide.

The mixed compositions can be formed into shaped materials by the conventional moulding and sheeting techniques used in the rubber industry. For example, the compositions can be fabricated into sheets by milling and calendering. An anti-tack-agent, e.g. a long chain hydrocarbyl amine such as octadecylamine can be added to the compositions in an amount of from 0.1 to 1% by weight of total composition to prevent them from sticking to the rollers during calendering. Most suitably the temperature during calendering can be in the range 50 to 1 000C.

The materials of the present invention, e.g. sheets or moulded articles formed from the compositions of the invention, are particularly suitable for use in vibration and sound damping applications, e.g. as sound insulation materials. The materials can be in the forms of rolled sheets which can be stuck onto metal panels, e.g. by means of a bitumastic adhesive, or sheets can be supplied with a self adhesive backing. Heaviiy filled compositions, especially those filled with ferric oxide or barium sulphate, have a very high mass and the materials formed therefrom are particularly suitable for sound insulation. For example, when the material is in the form of sheets it can be used as a sound insulating curtain which can be draped round noisy machinery. Alternatively, the material can be in the form of shaped moulded articles which are, for example, suitable for use in insulating the floor pans of automobiles. The materials are also suitable for use as carpet underlays to reduce vibration through floors.

The invention is illustrated by the following Examples.

EXAMPLE 1 Five bituminous compositions, the formulations of which are given in Table 1, were prepared in the following manner. The roller mixing head, type 50 of a Brabender Plastograph type 100, was charged with the components of the composition. Each composition was mixed for one hour at a temperature in the range 1 50-1 800C and at a speed of 60 rpm. Two samples of each composition were then formed into two sheets using the following techniques.

One sample was pressed into a mould between the heated plattens of a hydraulically operated press in which it was subjected to a temperature of 1 600C for 3 minutes at zero pressure and then at a pressure of 20 tonnes for 3 minutes. The sheet thus formed measured 5.5 x 4.5 x 0.6 cm. The IRHD hardness of the sheet was then measured.

The other sample of each composition was moulded in a similar manner at a temperature of 1 600C for 3 minutes at zero pressure and then at a pressure of 20 tonnes for 3 minutes to form a sheet measuring 10 x 10 x 0.2 cm. The sheet was cooled to a temperature of -250C by placing it for one hour in a bath containing a mixture of glycol and water at a temperature of -250C. The impact resistance of the cold sheet was then measured by dropping a T inch diameter steel bali onto it from a series of heights until the sheet was damaged. The temperature of the sheet was maintained throughout the tests at -250C by returning it to the bath for 30 minutes between impacts.The impact resistance quoted is in terms of the energy in Joules corresponding to the maximum height through which the ball was dropped without damaging the sheet.

The flexibility of the sheets was assessed by bending each sheet round a mandrel having a diameter of 3 cm. The sheets were first cooled to a temperature of -250C by placing them in a bath containing a glycol/water mixture at a temperature of -250C.

The sound damping capacity of the 0.2 cm thick sheets was calculated from a measurement of the Q value (a damping factor) using the expression 1 Q=# tan 6 where a is the loss angle of the material.

The test was carried out by bonding a piece of the sheet to a vibrating reed one end of which was firmly clamped in a vertical position in a heavy rigid structure isolated from background vibrations. The reed was set in oscillation by a magnetic transducer driven by a sweep oscillator. Measurements were taken over the 0 to 2Q00 Hz region at ambient temperature.

The data obtained from these tests is given in Table 2.

By way of comparison, similar tests were carried out on sheets made from a known bitumen/filler composition containing 60 percent by weight of filler and a known filled ethylene vinyl acetate polymer composition. The data obtained from the tests is given in Table 2.

The data illustrates the superior flexibility and impact resistance at low temperatures of the sheets according to the present invention in comparison with sheets formed from known bitumen/filler and filled ethylene vinyl acetate poiymer compositions.

The data also illustrates the satisfactory vibration damping properties of the sheets of the present invention in comparison with control sheets. In addition, the data shows that sheets according to the present invention can have a higher density than that of the control sheets and thus are particularly suitable for airborne noise insulation.

EXAMPLE 2 A 5 litre capacity Winkworth Z-blade mixer was charged with the following components: bitumen (200 penetration) 480 g; hardened extract (softening point 1400 C) 320 g; thermoplastic rubber (Solprene 411 P) 300 g; filler (Snowcal 7 ML limestone filler ex Cement Marketing Board) 2400 g; non-thermoplastic rubber (tyre crumb) 500 g; thermal stabiliser (Polygard HR) 20 g; lubricant (octadecylamine) 40 g. The components were mixed for 90 minutes at a temperature of 1 300C under a blanket of nitrogen.

About 1 kilogram of the mixed composition was then milled in a 12 inch Bridges two roll mill fitted with a steam heated roller to form a hide. When the hide had reached a temperature of 800C it was passed through the 1.75 mm nip of a two roll calender pre-heated to 700C to give a smooth glossy sheet. The sheet had an impact resistance of > 5 Joules at -250C and an IRHD hardness of 44. The sheet at a temperature of -250C withstood flexing through 1 800 when wrapped around a 3 cm mandrel.

EXAMPLE 3 A 1 litre capacity Winkworth Z-blade mixer was charged with the following components: bitumen (200 penetration) 40.6 g; hardened extract (softening point 1 400C) 20.3 g; thermoplastic rubber (Solprene 411 P1 12.9 g; filler (Snowcal 7 ML limestone filler ex Cement Marketing Board, 280 g; non-thermoplastic rubber (tyre crumb) 52.5 g: thermal stabiliser (Polygard HR) 2 g; lubricant (octadecylamine) 4 g. The charge was mixed under a blanket of nitrogen for 90 minutes at a temperature of 1 300C to give a crumb having an impact resistance in the range 2 to 5 Joules at -250C.

The crumb was then passed through a heated 12 inch Bridges two roll mill for 10 to 1 5 minutes to give a hide. The hide having a temperature of 552C was immediately passed through about a 1.5 mm nip 12 inch calender, the rolls of which were pre-heated to a temperature of 700 C. A good quality calendered sheet was obtained. The sheet had an IRHD hardness of 72 and an impact resistance of > 2 Joules at -250C. The sheet at a temperature of-250C withstood flexing at 1800 when wrapped around a 3 cm diameter mandrel.

EXAMPLE 4 Six batches, each of approximately 50 kg of the following composition were prepared in a Winkworth Z-blade mixer under a nitrogen blanket: %wt Bitumen (200 penetration) 8.9 Hardened extract (softening point 1400C) 5.9 Thermoplastic rubber (Solprene 411 P) 5.5 Non-thermoplastic rubber (40 mesh tyre crumb) 9.3 Lubricant (octadecylamine) 0.5 Thermal stabiliser(P0lygard HR) 0.5 Filler (Snowcal 7ML limestone filler, ex Cement Marketing Board) 69.4 Each batch was mixed for a period of 3 hours at a temperature in the range 130--1500C.

All 300 kg of the material so prepared were charged to a Banbury internal mixer, heated by friction to a temperature of 1 050C, and then discharged to a one metre wide, two roll mill and milled to a thick hide. The hide having a temperature of 700C was passed through the nip of a two bowl calender to produce a sheet one mitre wide and 3.5 mm thick, with a surface mass of 6.2 kg/m2.

Test method iSO/R 140 1 960 was used to measure the sound insulation properties of the calendered sheet.

Three specimens were used in the test:- Specimen 1 An 18 SWG steel panel damped by a rigid rectangular frame over an aperture of 2.4 m2 between two reverberant rooms.

Specimen 2 An 18 SWG steel panel with the 3.5 mm thick calendered sheeet bonded to one side and mounted as above.

Specimen 3 An 1 8 SWG steel panel with a layer of 12 mm chip foam and the 3.5 mm thick calendered sheet bonded to one side to form a space layer system and mounted as above.

The results, which are given in Table 3 below, are expressed in terms of the Sound Reduction Index (R) which is defined as the number of decibels by which sound energy is reduced in transmitting through the test sample.

The measurements were made at one third octave band widths over the frequency range 1008,000 Hz, and the arithmetic mean value of R over this range for each specimen was:- Specimen 1 - the steel sheet 30 dB Specimen 2 - the steel sheet + single layer of bitumen sheet 34.5 dB Specimen 3 - the steel sheet + space layer system 38.5 dB The results are considered very satisfactory for a material weighing 6.2 kg/m2.

Table 1

Components of the test compositions in grammes Sheet No. Bitumen 200 Hardened Thermoplastic Non-thermo- Filler penetration extract rubber plastic rubber softening Solprene 411P tyre crumb point 140 C C Calcium Barium Ferric carbonate sulphate oxide 1 6 4 3.76 6.25 - 80 2 12.6 6.2 4.7 17.5 60 - 3 9.5 4.7 3.5 13.1 70 - 4 12.6 8.5 2.3 23.2 - - 53.5 5 11 5.5 3.5 12.5 - - 67.5 Control A Bitumen/Filler Composition Control B Filled - ethylene vinyl acetate polymer Composition All compositions contained 0.5 percent by weight of the thermal stabiliser Polygard HR.

Table 2

Low tempera Sheet Density I.R.H.D.

ture impact No. gramsycc hardnese Vibration Flexibility resistance damping factor at -25 C Joules/Temp C Q value at 500 MS 1 2.58 90 > 5 J at -25 C 10.2 Passed 2 1.62 65 < 5 J at -25 C 14.4 Passed 3 1.79 84 # 5 J at -25 C 9.8 Passed 4 1.80 56 > 5 J at -25 C 15.5 Passed 5 2.20 87 > 5 J at -25 C 13.5 Passed Control A 1.65 not tested 1 J at 17 C 9.8 Falled (at +7 C) Control B 2.25 90 < 2 J at -25 C 15 Falled (at -25 C) Table 3 Third Octave Band Sound Reduction Index (R) dB

Centre Frequency Hz 1 2 3 Centre Frequency Hz 1 2 3 100 15.5 19.5 18.5 1000 31 34.5 45.5 125 47 21.5 18.5 1250 33 38 48.5 160 20 24 20 1600 35 38.5 48.5 200 18.5 20.5 20.5 2000 36 39 46.5 250 21.5 28.5 21 2500 36 40 48 315 23 28 23.5 3150 39.5 43 50.5 400 24.5 29 29 4000 40.5 45 52 500 26 31.5 33.5 5000 41 48 52 630 28 33 39 6300 43.5 49 53.5 800 29 34 41 8000 43.5 51.5 57

Claims (10)

CLAIMS:

1. A bituminous composition comprising, as essential components, a bitumen, a hardened extract, a thermoplastic rubber, finely divided particles of a non-thermoplastic rubber and a filler, the filler being present in a proportion by weight in relation to the total weight of the essential components in the range 50 to 90 percent.

2. A bituminous composition according to claim 1 in which the proportion of filler is in the range 60 to 80 percent by weight of the total weight of the essential components.

3. A bituminous composition as claimed in claims 1 or 2 having the following components in parts by weight: Bitumen and hardened extract: 100 parts (of which bitumen is 70 to 50 parts and the hardened extract is 30 to 50 parts) Filler: 200 to 1800 parts Thermoplastic rubber: 5 to 40 parts Non-thermoplastic rubber: 50 to 120 parts

4. A bituminous composition according to claim 3 in which the amount of filler is in the range 300 to 1800 parts by weight.

5. A bituminous composition according to claims 3 or 4 in which the amount of thermoplastic rubber is in the range 20 to 40 parts by weight.

6. A bituminous composition according to claims 3, 4 or 5 in which the amount of nonthermoplastic rubber is in the range 60 to 120 parts by weight.

7. A bituminous composition as claimed in any one of claims 3 to 6 which also contains from 1 to 5 parts by weight of an anti-oxidant and/or a thermal stabiliser.

8. A bituminous composition as claimed in any one of claims 1 to 7 in which the filler is limestone, barium sulphate or ferric oxide.

9. A composition as claimed in any of the previous claims in which the non-thermoplastic rubber is tyre crumb.

10. A bituminous composition as hereinbefore described with reference to any of the Examples 1 to4.