GB2112399A

GB2112399A - Particulate mixtures of rubbers and hardened petroleum extracts

Info

Publication number: GB2112399A
Application number: GB08235186A
Authority: GB
Inventors: John Groves Dolden
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1981-12-10
Filing date: 1982-12-09
Publication date: 1983-07-20
Also published as: GB2112399B; FR2518103B1; FR2518103A1; DE3245648A1

Abstract

Particulate mixtures which may be mixed with fillers at elevated temperature, e.g. above 120 DEG C, to form vibration and sound damping compositions comprise, as essential components, (1) a hardened extract, (2) particles of a non-cross-linked rubber, (3) particles of a cross-linked, non-thermoplastic rubber, and (4) a hydrocarbon oil which oil acts as an extender for the non-cross-linked rubber and is compatible with the hardened extract. The amount of filler mixed with the particulate mixture may be from 50 to 90, preferably 60 to 80% by weight of the total weight of the composition.

Description

SPECIFICATION Particulate mixture This invention relates to a particulate mixture suitable for use in forming vibration and sound damping compositions and to vibration and sound damping compositions formed using the particulate mixture.

It is known that flexible shaped materials having vibration and sound damping properties can be formed from compositions comprising bitumen, rubber and a relatively high proportion of filler. For example, published UK Patent Application No. 2041951A discloses bitumionous compositions suitable for forming flexible shaped materials e.g. sheets or mouldings having vibration and sound dampinq properties which compositions contain as essential components bitumen, hardened extract, a thermoplastic rubber, finely divided particles of a non-thermoplastic rubber and at least 50 per cent by weight of a filler in relation to the total weight of the essential components. The components of the bituminous compositions are mixed prior to forming vibration or sound damping materials in order to solubilise the thermoplastic rubber and disperse the filler and non-thermoplastic rubber.This mixing process is difficult to control because of the need to soften the bitumen in order to obtain a homogeneous mixture. The thermoplastic rubber dissolves in the softened bitumen to form a very viscous solution which is difficult to handle.

The applicants have discovered that a particulate mixture containing no bitumen may be mixed with a filler at elevated temperature to produce a composition which may be formed into flexible shaped materials having vibration and sound damping properties. The use of the particulate mixture overcomes or at least mitigates the problems associated with the use of bitumen since the particulate mixture and the filler can be measured and transported using solids handling equipment.

According to the present invention a particulate mixture suitable for use in forming vibration and sound damping compositions comprises as essential components, a hardened extract, particles of a non-cross-linked rubber, particles of a cross-linked, non-thermoplastic rubber and a hydrocarbon oil which acts as an extender for the non-crosslinked rubber and is compatible with the hardened extract.

Suitable proportions by weight of the essential components may be in the following ranges: % by weight Hardened Extract 25-35 Hydrocarbon oil 15-25 Non-cross-linked rubber 10-30 Cross-linked, non-thermoplastic rubber 1 5-40 The present invention includes a composition suitable for forming flexible vibration and sound damping materials formed by mixing together at an elevated temperature a particulate mixture as hereinabove defined and a filler, the amount of filler being present in a proportion by weight in relation to the total weight of the composition in the range 50 to 90 and preferably 60 to 80 per cent.

The hardened extract may be produced by blowing a petroleum extract with a gas containing free oxygen, preferably air, at 200-3500C either in the absence or presence of a catalyst e.g. a Friedel Crafts metal halide such as ferric chloride. The petroleum extract may be obtained by the solvent extraction of distillate petroleum fractions boiling in the lubricating oil range i.e. 350-6000C and containing a major proportion of aromatic hydrocarbons. Particular examples of petroleum extracts suitable for blowing with air to form hardened extract are materials sold by BP Oil International Limited under the trade names Enerflex 65 and Enerflex 96 process oils.

The blowing of the extract with an oxygen containing gas is believed to cause condensation of the aromatics giving a hardened product with a high proportion of asphaltenes, cyclics and toluene insolubles and a relatively low proportion of saturates. The hardened extract may have a penetration of from 0.1 to 6 at 250C as determined by the standard test method ASTM D5/73 and a softening point (Ring and Ball) of from 60 to 1 700C.

Preferably the hardened extract is added to the mixture in the form of particles which pass a 12.5 mm screen. The hardened extract is brittle and during mixing the particles may be broken up to form a fine powder.

The hydrocarbon oil must be capable of extending the non-cross-linked rubber and must be compatible with the hardened extract. Some naphthenic or paraffinic oils may be suitable but the hydrocarbon oil is preferably an aromatic oil containing at least 50% by weight of aromatics as determined by the Molecular Type Analysis (Clay-Gel) test ASTM D2007. Suitable aromatic oils are aromatic extracts having a aromatic content of from 50 to 90% by weight as determined by ASTM D2007.

An aromatic extract is an unblown petroleum extract which may be obtained by the solvent extraction of distillate petroleum fractions boiling in the lubricating oil range in the same manner as the extract precursor for the hardened extract. Therefore, the same extract as used in the production of the hardened extract e.g. Enerflex 65 and Enerflex 96 may be used in their unblown state as the hydrocarbon oil in the present invention. A particularly suitable aromatic extract in the range of processing oils sold by BP Oil International Limited under the Trade Name Enerflex is Enerflex 72.

This preferred extract has 84.5% by weight aromatics, 10% by weight saturates and 5.5% by weight polars as determined by ASTM D2007. Preferably the viscosity of the oil is low e.g. less than 20 Poise (2 Nsm-2) at 21 OC. The preferred aromatic extract Enerflex 72 has a viscosity of 8 to 10 Poise (0.8 to 1.0 Nsm-2) at 21 0C.

The non-cross-linked rubber may be any natural or synthetic rubber which has not been cross linked and which can be in the form of particles at ambient temperatures. Suitable rubbers include EPDM rubbers, polynorbornene rubbers, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, methacrylate grafted natural rubber and chlorinated polyethylene. The rubber may be added to the mixture in a powdered or pellet form and is preferably added to the mixture in the form of particles having a major dimension of less than 10 mm and more preferably less than 5 mm.

The particles of cross-linked, non-thermoplastic rubber are preferably finely divided particles and may, for example, be finer than 20 mesh BSS. The rubber will normally be vulcanised and may be, for example, a synthetic rubber, such as SBR or polybutadiene, or natural rubber. It may be oil extended and/or filled and may be tyre crumb, a material reclaimed from scrap tyres.

The particulate mixture according to the present invention may be produced by mixing together the essential components in a high speed powder mixer for from 2 to 10 minutes. The components may be charged into the mixer at ambient temperature. It has been found that the presence of a small amount of finely divided filler, e.g. talc, during this mixing stage facilitates the mixing process itself and also the subsequent handling of the mixture. Therefore from 1 to 10% of talc, by weight of the essential components, may be added prior to or during the mixing stage. The particulate mixture produced is nontacky, free-flowing and can be easily handled by conventional solids handling equipment.

The particulate mixture is an intimate mixture of particles. The hydrocarbon oil is adsorbed by the non-cross-linked rubber and hardened extract. If the non-cross-linked rubber is used in the form of pellets, e.g. having a major dimension of about 5 mm, then the rubber pellets are not significantly broken up but are coated by an oil extended layer of hardened extract and finely divided particles of cross-linked non-thermoplastic rubber.

As stated above, compositions suitable for forming materials having vibration and sound damping properties can be produced from the particulate mixture and a filler. The fillers are preferably powders having particles which are less than 1 20 mesh BSS.

Examples of suitable fillers are; ferric oxide, powdered limestone, silica, alumina, Portland cement, barytes, pulverised fuel ash, talc. Preferred fillers are barium sulphate (e.g. barytes) caicium carbonate (e.g. limestone) and ferric oxide or mixtures thereof.

The particulate mixture and filler may be mixed together in, for example, a Banbury internal rubber mixer for from 10 to 30 minutes at a temperature which is sufficiently high to soften the particulate mixture. Preferably the Banbury mixer is pre-heated to a temperature in the range 120 to 1 700C. The temperature inside the mixing chamber rises during the mixing and is allowed to reach 1 60 to 1 9O0C before water cooling is used to maintain the temperature in the preferred range of from 140 to 1 600C.

Flow aids known in the rubber industry may be included in the compositions according to the present invention. A suitable flow aid is sold by Anchor Chemicals under the trade name Interlube which comprises a blend of zinc fatty acids and lubricants on an inert carrier. The flow aid may be added to the particulate mixture during the first mixing stage or to the particulate mixture and filler during the second mixing stage and may be used in an amount of up to 10% by weight based on the weight of the essential components.

The composition produced by this mixing process can be formed into shaped materials by the conventional moulding and sheet forming 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 may be added to the composition in an amount from 0.1 to 2% by weight of the total weight of the composition to reduce the tendency for the composition to stick to the roilers during calendering. The anti-tack agent may be added to the particulate mixture during the first mixing stage or to the particulate mixture and filler during the second stage mixing stage.

The materials e.g. sheets or moulded articles formed from the compositions comprising the particulate mixture and a filler are particularly suitable for use in vibration and sound damping applications e.g. as sound insulation materials. The materials can be in the form of rolled sheets which can be stuck onto metal panels, e.g. by means of a suitable adhesive, or sheets can be supplied with a self adhesive backing. Heavily filled compositions, especially those filled with ferric oxide, calcium carbonate 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 The following components were charged into a one litre Papermeir high speed powder mixer and blended for 5 minutes at 2000 rpm, (1) 225 g hardened extract having a Ring and Ball softening point of 1 400C and a penetration value of less than 1.0 as determined by ASTM D5/73. The hardened extract was in the form of particles which passed a 12.5 mm screen and the composition of the hardened extract was as follows:- 38.6% by weight Cyclics 20.7% by weight Asphaltenes 20.6% by weight Heptane/toluene insolubles 1 5.2% by weight Resins 4.9% by weight Saturates The hardened extract had a conradson Carbon No. of 37.

(2) 1 50 g Enerflex 72, an aromatic extract supplied by BP Oil International Limited having the following composition as determined by ASTM D2007.

% by weight Saturates 10 Aromatic 84.5 Polars 5.5 The specific gravity of the oil was 0.995 at 1 50C and the kinematic viscosity at 60 C was 8x10-4m2/s (3) 250 g Cross-linked non-thermoplastic rubber which was 40 mesh BSS tyre crumb particles.

(4) 131 g Norsorex N, a finely powdered polynorbornene rubber sold by Societe Chimique de Charbonages. The particles being less than 500 Mm.

(5) 50 g Octadecylamine.

The product which was a non-tacky free flowing particulate mixture was charged together with 1,750 g of barium sulphate, having particles less than 120 mesh BSS, into a Banbury internal rubber mixer having a 2 litre mixing chamber. The Banbury mixing chamber and rotor were preheated with steam to 1 500C. The total mixing time in the Banbury was 18 minutes. The temperature rose to 1 9O0C in 10 minutes and water cooling was used to control the temperature so that it fell from 1 900C to 1 500C over the remaining 8 minutes of the mixing process. The product was discharged at a temperature of 1 500C and milled for 5 minutes on a Bridges 2 roll mill with 12't (305 mm) rollers to form a coherent hide approximately 4 mm thick.

A moulded sheet was formed from the hide by pressing approximately 900 g of the composition in a mould measuring 330 x 330 x 3 mm. The moulding process was carried out in a steam heated press at 1 500C for 5 minutes and the mould cooled to ambient temperature by passing cooling water through the plattens of the press.

The moulded sheet was flexible and resistant to impact at ambient temperatures. It had a density of 2.15 g/cm3 as determined by weighing a measured volume of the product and had an IHRD rubber hardness of 59. The low temperature properties of the product were assessed by cooling specimens of the sheet to -1 0CC and subjecting them to the following tests:- (a) Mandrel Test The specimen at -100C was bent around a 3 cm diameter mandrel as quickly as possible after removal from the cold bath and then allowed to straighten out again. The specimen was examined for cracks, splits or other faults and since no faults were visible it was said to have passed the test.

(b) Impact Test A steel ball was allowed to drop onto the surface of a specimen at -1 O0C. The weight of the ball and the height through which it was dropped were selected to give an impact of 5J on the specimen.

The specimen was examined for visible faults such as cracks or fractures. There were no such visible faults and so the material was said to have passed the test.

The ability of the product to be vacuum moulded was assessed by moulding 1 52 x 152 mm specimens using a 30 mm and a 60 mm deep truncated cone-shaped mould. Well formed and stable mouldings were obtained.

EXAMPLES 2 to 8 Moulded sheets were prepared as described in Example 1 using the formulations given in Table 1.

The hardened extract, aromatic extract and the finely divided particles of the cross-linked non-thermoplastic rubber were the same as for Example 1. EPDM rubber, Norsorex rubber and chlorinated polyethylene were used as the non-cross-linked rubbers. The Norsorex rubber was the same as that used in Example 1. The EPDM rubber was in the form of particles having a major dimension less than 10 mm. The fillers were powders having particles of less than 120 mesh BSS.

The density and IHRD hardness of each of the moulded sheets is also given in Table 1.

Formulations 2 to 7 passed the mandrel test and 5 Joule impact test described in Example 1 at --100C and formulation 8 passed these tests at 5cC. Acceptable vacuum mouldings could be prepared using a 30 mm deep truncated cone-shaped mould for all of the formulations and formulation 8 also produced acceptable mouldings using a 60 mm deep mould.

TABLE 1 COMPONENTS OF MOULDED SHEETS

g Formulation (grams) Component 2 3 4 5 6 7 8 PARTICULATE MIXTURE Hardened extract 192 156 169 203 156 225 225 Enerflex 72 128 104 113 135 104 150 150 Tyre Crumb 200 169 175 210 169 250 250 EPDM rubber 142 150 63 75 150 Norsorex rubber 63 75 65 Chlorinated polyethylene 131 65 Octadecylamine 7 6 6 8 6 25 38 Talc 43 36 37 45 36 50 25 FILLER Barium Sulphate 1875 1875 1825 1750 1125 1464 1607 Calcium Carbonate 700 236 118 PROPERTIES lRHD hardness 69 79 74 49 51 Density (gcm3) 2.4 2,6 2.5 2.1 23 2.2 2.2

Claims

1. A particulate mixture comprising as essential components, a hardened extract, particles of a non-cross-linked rubber, particles of a cross-linked, non-thermoplastic rubber and a hydrocarbon oil which oil acts as an extender for the non-cross-linked rubber and is compatible with the hardened extract.

2. A particulate mixture as claimed in claim 1 in which the proportions by weight of the essential components are in the following ranges % by weight Hardened Extract 25-35 Hydrocarbon oil 15-25 Non-cross-linked rubber 10-30 Cross-linked, non-thermoplastic rubber 1 5-40

3. A particulate mixture as claimed in either claim 1 or claim 2 in which the hydrocarbon oil is an aromatic oil comprising at least 50% by weight of aromatics as determined by ASTM D2007.

4. A particulate mixture as claimed in any of claims 1 to 3 in which the non-cross-linked rubber is EPDM rubber, polynorbornene rubber, nitrile rubber, styrene butadiene rubber, natural rubber, methacrylate grafted natural rubber or chlorinated polyethylene.

5. A particulate mixture as claimed in any of claims 1 to 4 in which the non-cross-linked rubber is added to the mixture in the form of particles having a major dimension of less than 10 mm.

6. A particulate mixture as claimed in any of claims 1 to 5 in which the cross-linked, nonthermoplastic rubber particles are finer than 20 mesh BSS.

7. A particulate mixture as claimed in any of claims 1 to 6 in which the cross-linked, non thermoplastic rubber is tyre crumb.

8. A particulate mixture as claimed in any of claims 1 to 7 in which the hardened extract is obtained by blowing a petroleum extract with a gas containing free oxygen.

9. A particulate mixture as claimed in any of claims 1 to 8 in which the hardened extract has a penetration of from 0.1 to 6 at 250C as determined by ASTM D5/73 and a softening point (Ring and Ball) of from 60 to 1700C.

10. A particulate mixture as claimed in any of claims 1 to 9 in which the hardened extract is added to the mixture in the form of particles which pass a 12.5 mm screen.

11. A composition suitable for forming flexible vibration and sound damping materials formed by mixing together at an elevated temperature, a particulate mixture as claimed in any of claims 1 to 10 and a filler, the amount of filler being present in a proportion by weight in relation to the total weight of the composition in the range 50 to 90%.

12. A composition as claimed in claim 11 in which the amount of filler by weight of the total weight of the composition is in the range 60 to 80%.

13. A composition as claimed in claim 11 or claim 12 in which the filler is added to the mixture in the form of particles of less than 120 mesh BSS.

14. A composition as claimed in any of claims 1 3 to 1 6 in which the temperature at which the filler and particulate mixture are mixed together is in excess of 12O0C.

1 5. A particulate mixture as claimed in claim 1 as described with reference to the Examples.

1 6. A composition as claimed in claim 11 as described with reference to the Examples.