WO1995017469A1

WO1995017469A1 - Improvements in or relating to sound deadening materials

Info

Publication number: WO1995017469A1
Application number: PCT/AU1994/000785
Authority: WO
Inventors: Graeme Matthew Ball
Original assignee: Tri-Tex Australia Pty. Ltd.
Priority date: 1993-12-21
Filing date: 1994-12-21
Publication date: 1995-06-29
Also published as: SG45333A1

Abstract

A sound deadening material comprising at least one component selected from each of the following component groups: (i) an elastomeric component, a polymeric component or both an elastomeric and a polymeric component; (ii) a filler; (iii) a melt viscosity modifier comprising tall oil pitch.

Description

TITLE: IMPROVEMENTS IN OR RELATING TO SOUND DEADENING MATERIALS Background of the Invention

The present invention relates to improvements in or relating to sound deadening materials. Sound deadening materials of the heat fusible type are well known and used in large quantities in automobiles, household dishwashing machines and other applications where it is desired to reduce the noise arising from resonant vibrations of the sheet metal panels. Other possible areas of application are air conditioning ductwork, machine surrounds and metal roofing (to lower the noise from the "drumming" of rain). The use of relatively thin steel panels in automobiles, dishwashers, etc. leads to an unacceptable level of noise without the use of a sound deadening material. In the automotive industry weight is a very important factor affecting, amongst other things, fuel consumption. Hence a heat fusible sound deadening material which has greater efficiency is clearly beneficial. Well known heat fusible sound deadening materials are those based on bitumen and are hence necessarily black in colour. Bituminous materials of this type are disclosed in Australian Patent Specification Nos. 34339/68, 405091, 498,074 and 606877.

Our earlier PCT Application No. PCT/AU92/00375 discloses formulations and methods which lead to superior sound deadening performance as measured, for example, by the Geiger Thick Plate Method. In that specification there is disclosed the use of a compatibilising agent, preferably ricinoleic acid LAV as a material which enables the use of high volume fractions of fillers whilst still retaining the ability to suitably process such materials with their very high filler loadings. It is also disclosed that such compatibilising agents enable improved hot slump, impact strength and cold bend resistance, compared with formulations without such a compatibilising agent.

Sound deadening materials, particularly for vibration damping, in sheet or pad form, are most often adhered to metal panels by simply laying a sheet or pad of sound deadening material onto a metal panel and heating the two together. In automobile manufacturing the sound deadening material may conveniently be applied as the panels travel along a conveyor belt towards an oven. The self adhesive properties of a sound deadening material at elevated temperatures may create a bond of one with the other. Alternatively, an adhesive may be applied to either or both surfaces to enable a bond to be made at room temperature. In either case the bond needs to have high tenacity in order to meet the conditions of application in automobile manufacturing and subsequent to that, e.g. up to 180°C in the oven and later possible extreme cold in usage. There also exists a need to obviate the possibility of the sound deadening material breaking away with time and vibration. Thus a frequent requirement of such a sound deadening material is that it have excellent adhesion properties. It is an additional requirement by some automobile manufacturers that the sheet material is able to withstand bending around a 51mm mandrel at - 4°C. It has been suggested that the temperature at which this test is carried out will become even lower in the future.

Sound deadening materials of the bituminous, rubber, filler type have been known for many years and have achieved wide acceptance in the marketplace as vibration damping materials. Such bituminous materials have also been adhered to fibrous substrates such as felt and carpet but generally have too little flex cracking resistance to withstand the flexing that a carpet would typically receive in an automotive application. Additionally the necessarily black colour of a bituminous material may not always be acceptable for such an application.

Carpets moulded and shaped to fit the contours of the floor pan of a car have been employed for many years. In a known method of manufacture, low density polyethylene is applied in powder form to the back of carpet and is heated in order for sufficient flow to occur to bind the polyethylene particles to each other and to the weave and its carpet backing. Such a coating enables the carpet to be formed to shape, usually by a heat process, in the carpet making factory. Such carpet usually lies on top of a vibration damping material which has previously been adhered to the steel floor pan of an automobile. In an increasing number of cars there is also a layer of flexible sound barrier material heat bonded to felt and other non-woven substrates, which is laid underneath the carpet. In Australian made cars this may be, for example, material made in accordance with Australian Patent Specification 35253/89. Such a combination of materials has the ability to lower the level of road noise and other external noise experienced in the interior of the car. With the advent of superior music reproduction systems in cars, this is a highly desired feature. However, there exists a need for materials having the further improved sound barrier performance which can be achieved by the inclusion of even higher levels of filler than is possible in the aforementioned known prior art.

Plasticisers and processing oils are known to facilitate the use of higher volume fractions of fillers and have frequently been used for such a purpose. These materials form part of many formulations for similar products in the Patent literature. However, these substances can often lead to "window fogging" in cars and/or migration to other surfaces which can lead to part failure. Car manufacturers generally have a test for window fogging on materials such as those which are the subject of this specification, because of the known propensity to such problems arising from the use of liquid substances to plasticise or extend the polymeric materials. It is accordingly desirable that any new material contains very high levels of filler so as to exhibit improved sound barrier properties while being substantially free of plasticisers and/or processing oils in a liquid form. Summary of the Invention The present invention accordingly provides, in one embodiment, a sound deadening material comprising at least one of each of the following component groups:

(i) an elastomeric component, a polymeric component or both an elastomeric and a polymeric component;

(ii) a filler; and (iii) a melt viscosity modifier comprising tall oil pitch.

A sound deadening material according to the present invention may optionally also include one or more of each of the following optional components:

- a compatibilising agent;

- a flame retardant; - an appropriate stabiliser;

- an anti-oxidant;

- a tackifier;

- a softening agent preferably comprising atactic polypropylene;

- a polar additive; - a liquid plasticiser;

- a lubricant.

The present invention also provides, in another embodiment, a method for forming a sound deadening material in sheet or pad form comprising the steps of:

(a) compatibilising a filler or fillers by treatment with a compatibilising agent to form a pre-blend;

(b) mixing the pre-blend with other ingredients including:

(1) an elastomeric component, a polymeric component or both an elastomeric and a polymeric component; and (ii) a melt viscosity modifier comprising tall oil pitch; and (c) forming a sheet or pad from said mix.

The present invention also provides, in yet another embodiment, a method for applying a sound deadening material to a metal panel comprising the steps of:

(d) forming a sheet or pad of sound deadening material as described herein;

(e) laying said sheet or pad on a metal panel; and (f) heating said metal panel and said sheet or pad whereby to bond said sheet or pad to said metal panel. Formulations according to the present invention are preferably substantially free of bitumen or asphalt. A sound deadening material according to the present invention is conveniently provided in sheet or pad form.

Ricinoleic acid is the compatibilising agent preferred for use according to the invention. Ricinoleic acid of low acid value (LAV) namely 130 - 145, has been found to be particularly preferred for use as a compatibilising agent according to the present invention.

Ricinoleic acid may be made with different levels of acid value with a common form having an acid value in the range of 170 - 186. For purposes of clarity the higher acid value is designated herein as 'HAV, whilst the lower acid value form is designated herein as 'LAV. We have found the LAV form to be more efficacious, and hence this form is presently preferred in formulations according to the present invention.

The particularly preferred ricinoleic acid LAV has the following typical analysis: Appearance Pale amber liquid, cloudy when cold, which deposits a small amount of related fatty acid on aging.

Colour (Gardner) 7 max.

Acid value 130 - 145

Water content % 1.5 max

Hydroxy 1 value 145 - 160 Iodine value 80 - 90

Saponification value 180 - 195

A synthetic rubber or natural rubber may be employed as an elastomeric component according to the present invention. An elastomer provides greater flexibility of the sheet and forms part of the binder system. Whilst any synthetic rubber or mixture thereof may be used in accordance with the invention acrylonitrile butadiene rubber (NBR) and butyl rubber have shown good efficiency and are considered particularly suitable for use in accordance with the invention.

Butyl rubber either straight, chlorinated or brominated, ethylene propylene rubber, polychloroprene or acrylonitrile butadiene rubber have shown the best sound deadening efficiency. The preferred rubber is acrylonitrile butadiene rubber (NBR) containing 25 to 50% by weight acrylonitrile and having a Mooney viscosity of 20 to 80. NBR may be employed in the range of 0 to 15% by weight, and in the preferred formulations is used in the range of 2 to 10% by weight.

Any low K-value PVC can be employed as a polymeric component in accordance with the present invention. The PVC is preferably co-polymerised with vinyl acetate to give a degree of internal plasticisation, increased capacity for high filler loading and greater heat stability. The preferred grade of PVC is Lacovyl SA 6001 (trade mark) manufactured by Atochem France, which has a K-value of 45 and a vinyl acetate content of 14%. PVC, when used, is preferably present in formulations according to the present invention in the range of 0 to 15% by weight. In the preferred formulations PVC, when present, is used in the range of 3 to 12% by weight.

An appropriate stabiliser for PVC is used when PVC is present in formulations according to the present invention. Any of the known heat stabilisers for PVC is suitable. The most efficient stabiliser and the preferred type is based on basic lead sulphate in a non- dusting extruded form. Heat stabilisers for PVC may be employed in formulations according to the present invention in the range of 0.5 to 1.5% by weight, when PVC is present in the formulation.

Other polymers, including chlorinated polyethylene (although not as cost effective as other copolymers such as PVC copolymer), or high vinyl acetate content (i.e. 28% or greater VA content) ethylene vinyl acetate, may also be used as a polymeric component in accordance with the present invention. In general it has been found that sound deadening efficiency with such polymers is inferior to formulations containing PVC. However, such formulations have generally been found to still be superior to the sound deadening efficiency of the bituminous materials previously used for vibration damping applications.

In one preferred embodiment suitable for use in sound barrier applications the polymeric component employed in sound deadening formulations according to the present invention preferably comprises ethylene vinyl acetate (EVA). Whilst any vinyl acetate content EVA can be used in this preferred arrangement, it is particularly advantageous to use a high vinyl acetate content copolymer as that increases the elastomeric properties, or the "rubberiness" of the sheet. We prefer to use an EVA having a vinyl acetate content of not less then 20% and preferably about 28% in formulations according to the present invention.

Furthermore, we prefer a reasonably high molecular weight EVA, ie, an EVA having lower melt index, because this enhances the resistance to cracking on cold flexing. Polymeric components suitable for use in accordance with the present invention may comprise more than one type of polymeric material. The melt viscosity modifier used in accordance with the present invention comprises tall oil pitch.

It is believed that the tall oil pitch modifies the melt viscosity through an ability to assist in compatibilising the components of sound deadening formulations. Tall oil pitch is that material which remains undistilled after the distillation of a batch of tall oil is completed and generally comprises 15 to 20% of crude tall oil (CTO). It is frequently used as boiler fuel because of having low industrial usage compared with that of the other fractions obtained from the distillation of CTO namely, tall oil acids, tall oil rosins, distilled tall oil and tall oil heads.

Tall oil pitch has the following typical analysis:

Color Dark

Form Resinous, tacky, thermoplastic

Softening Point, °C 40

Specific Gravity at 25°/25°C 1.025

Weight per gal., lb. 8.6

Saponification Number 80-120

Unsaponifiables, % 30-45.

Rosin acids 5-15

Fatty Acids, % 2-8

Sterols, % 8-12

Acid number 15-20

Ash, % 0.3-1.0

Tall oil pitch is a by-product obtained in the production of tall oil rosin and tall oil fatty acids. In the U.S.A. for example, generally from 15% to 25% of crude tall oil (CTO) ends up as tall oil pitch. With lower-grade Northern U.S. and Scandinavian crude tall oil, the yields may run as high as 30%.

As will be appreciated by the skilled reader, tall oil pitch does not have a single composition. The composition of a tall oil pitch may vary for example with the type of trees and location. The term tall oil pitch as used herein may accordingly refer to that range of materials commonly described as "tall oil pitch".

One particularly preferred tall oil pitch for use in formulations according to the present invention is marketed under the trade mark PINECHEM 450 by Eka Nobel.

The filler employed in formulations according to the present invention makes the sound deadening material more dense. Increased density particularly assists the sound barrier properties of a sound deadening material as sound barrier performance is mass related. The fillers used in formulations according to the present invention are preferably powder form fillers and may be those commonly employed in the rubber industry. Such fillers include barytes, calcium carbonate, dolomite, micaceous ^'fillers, clays, magnesium carbonate, silica, alumina trihydrate and mixtures thereof. Alumina trihydrate is particularly suitable for use in formulations where additional flame retardancy is desired. The filler used in accordance with the invention may comprise a mixture of fillers. The total filler content of formulations according to the present invention is preferably not less than 70% more preferably between 70 and 95% by weight.

The preferred fillers are calcium carbonate (whiting, limestone, chalk) and/or barytes at a combined weight percentage of 70 to 95%. Mixtures of the two may be anywhere in between these two weight percentages. When alumina trihydrate is employed it preferably replaces approximately 20 to 50% by weight of the other above mentioned fillers depending upon the degree of flame retardancy required.

For some applications, very high mass together with high flexibility is required in a flexible sound barrier material in sheet form. In these instances high Specific Gravity is advantageous as the sheet may be thinner and thus less stiff than a thicker sheet of equivalent mass. This area has been occupied by mainly leaded vinyl sheet, however there are considerable toxicity concerns in the manufacture of such products and in the ultimate recycling of them. Flexible sound barrier material in sheet form made in accordance with the present invention, containing very high loadings of barium sulphate or heavy metal oxides such as the iron oxides could be substituted for previously used leaded vinyl.

The use of higher volume fractions of filler leads to better sound deadening efficiency for a given system. Without the use of a melt viscosity modifier, formulations provided by the present invention with their high volume fraction of fillers would be stiff, brittle and difficult to manufacture by the known methods and would show inferior hot bonding to substrates.

The use of ricinoleic acid LAV as the coupling or compatibilising agent, together with tall oil pitch as the melt viscosity modifier in sound deadening material formulations according to the present invention has surprisingly been found to enhance sound deadening properties. In addition, formulations according to the present invention have been found to exhibit improved resistance to cold bending of the sheet product. Furthermore, formulations according to the present invention are more readily "workable" in the manufacture of sheet both through a "plasticising" effect and higher melt strength, each being important factors when manufacturing sheet with very high filler loading. We have found that the presence of tall oil pitch assists in lowering the temperature at which peak performance of sound deadening occurs, as measured by the Geiger Thick Plate method (see below), when used in a system where the filler has been pre-treated with ricinoleic acid. Furthermore, the peak level of sound deadening performance as measured by the Geiger Thick Plate method, has not been found to be lowered by the addition of tall oil pitch at the levels preferred for use in accordance with the present invention. This would normally have been predicted for an ingredient that has the effect of making the sound deadening sheet less stiff, however, in formulations according to the present invention the sound deadening performance as measured by the Geiger Thick Plate method has generally been found to be enhanced. Formulations made according to the present invention have also been found to show improved sound deadening efficiency at lower temperatures through the peak of that sound deadening occurring at a lower temperature compared with the same formulations without tall oil pitch. This is an important characteristic, particularly for those countries with much colder winter temperatures than those of Australia. We have found that formulations according to the invention may additionally include optional components. Such optional components may be incorporated to tailor the formulation for a particular application. It is to be appreciated that any optional component which is used may be present in the form of a plurality or mixture of components which together form that component. For example, an optional flame retardant component used in a formulation according to the present invention may comprise a single flame retardant compound or a group or mixture of flame retardant compounds.

Flame retardant properties may be imparted to formulations of the present invention by the use of a flame retardant. Alumina tri-hydrate has been found particularly suitable for use as a flame retardant in accordance with the present invention. When desired, up to 50% by weight of the filler may be replaced with alumina tri-hydrate. If there is no PVC present in the formulation to otherwise confer a degree of flame retardancy to the formulation, alumina tri-hydrate is preferably used when flame retardancy is required.

An anti-oxidant may also be used in accordance with the present invention. The presence of an anti-oxidant tends to lessen the hardening caused by oxidation during processing and ageing, which could otherwise lead to embrittlement. Its presence in formulations of the present invention has been found to generally improve long term properties of the material. The antioxidant may be of the hindered phenol type. However, any known thermoplastics heat stabiliser which functions to resist breakdown of the formulation during processing and usage may be used in accordance with the present invention. Preferred anti-oxidants are Ciba Geigy's Irganox 565 and Irganox B215 (trade marks). When present, the anti-oxidant is employed in the range of 0.05 to 0.5% by weight of the total formulation.

One or more tackifiers may also be employed in formulations according to the present invention. Tackifier components are primarily used to increase the bond to metal or to other substrates at the elevated temperatures employed for adhering heat fusible sound deadening materials. Preferably they are not tacky at room temperature. Some tackifiers also have the effect of extending the rubber component due to their compatibility with rubber, thus increasing the rubber like properties. The tackifier component preferred for use in accordance with the present invention is of the pine rosin type also variously known as tall oil rosins, pine oleoresins and their esters. A polar additive may also be employed in formulations suitable for vibration damping according to the present invention. Preferred polar additives are carboxylic acids, such as oxalic acid. Oxalic acid has been found to assist in attaining sound deadening efficiency, particularly when PVC is not present in the formulation. Oxalic acid has also been found suitable for use due to its polarity when liquid plasticisers are employed. Oxalic acid assists in the conversion of sound energy to heat energy. Similar effects can be obtained from other polar substances such as phthalic anhydride.

Liquid plasticisers may be employed in formulations according to the present invention. Plasticisers are present in order to increase the softness of the formulations. Care needs to be taken in their selection to avoid their leaching out, migrating to other materials in contact or volatilising to cause window fogging in cars.

Where it is desired to further soften a formulation without reducing the filler content, this may be achieved by the addition of a softening agent, preferably a solid material such as atactic polypropylene. Atactic polypropylene acts like a plasticiser for the other polymeric materials in the formulation and gives a better "hand" to the sheet, without suffering from the potential plasticiser migration problems associated with the use of conventional plasticiser or extender oils. In common with other substances which show a plasticising ability, atactic polypropylene lowers the heat softening point of the compound into which it is incorporated. This can be advantageous when employing the sound barrier material for heat adhering to a fibrous substrate having a relatively low heat resistance as do some synthetic fibres employed in carpet and felt. The influence on softening point must be borne in mind when formulating for a specific application and the level of atactic polypropylene adjusted accordingly, with levels varying between 0 and 7.5% by weight of the total formulation.

Atactic polypropylene occurs as a by-product during the manufacture of isotactic polypropylene (normally called simply, polypropylene) and the former is separated from the latter in the solvent used in Ziegler-Natta polymerisation, through the solubility of the atactic polypropylene compared with that of isotactic polypropylene. It is generally considered desirable to separate out the atactic polypropylene because of its softening effect on isotactic polypropylene and hence a lowering of some mechanical properties. Lubricants may be used to improve the hot slump and to generally improve the processing of a sound deadening material. Waxes, stearic acid (used as part of the main mix as opposed to the compatibilising agent which is pre-mixed with the filler) and calcium stearate as well as other well known fatty acid ester lubricants may be employed, but are not essential. Detailed Description of the Preferred Embodiments

One preferred formulation for a sound deadening material according to the present invention having sound barrier properties consists of the following: ethylene vinyl acetate copolymer 5-15% by weight melt viscosity modifier (TOP) 0.5-3% by weight synthetic rubber 1-15% by weight barytes 0-95% by weight calcium carbonate 0-90% by weight iron oxide 0-95% by weight alumina trihydrate 0-50% by weight atactic polypropylene 0-7.5% by weight pine rosin 0-5% by weight antioxidant 0-0.4% by weight

The total amount of filler (barytes, calcium carbonate, iron oxide and/or alumina trihydrate) present in the preferred formulation is preferably in the range of 70-95% by weight of the total formulation.

The sound deadening material provided by the present invention may be in granular form for subsequent manufacture into sheet or may be manufactured from the ingredients directly as sheet material.

The most common usage of this sheet is to be self adhered by heat and pressure, to carpet, felt of natural or synthetic fibre, and carpet of the woven or non-woven type or to be heat adhered to some other substrate. Where self adhesion by heat is not appropriate, the sheet can be adhered to a substrate using a suitable adhesive.

An area of common usage for sound deadening materials is that of Mass Backed Carpet which refers to woven carpet which generally is shaped by heat and is used in the interior of cars as a sound absorbing and sound barrier material as well as for aesthetic purposes. In another form sound deadening sheet may be sandwiched between carpet and felt or other non-woven fibrous substrate. In yet another form it is adhered to felt or other non- woven fibrous substrate and is the means by which the felt is given integrity and its sound attenuation ability is enhanced for use behind a car dashboard or in the wheel arch area of a car to lower the noise of stone impingement. Another area of potential usage for sound deadening materials according to the present invention is in metal house siding and roof decking, in an expanded or non-expanded form, as a means of obtaining reduced noise transmission as well as improved heat insulation. The manufacture of such carpet, felt or other fibrous substrates is well known and the present invention makes available a superior flexible sound barrier material in sheet form, which may be adhered preferably by heat, to such substrates. Formulations made according to the invention are suitable for extrusion directly onto the back of carpet if desired.

In some instances it is desirable for the material provided by the present invention to form the backing for the carpet but in other instances it may be used as the sandwich layer between carpet and felt and thus combine the sound deadening properties of such a sheet with the sound absorbing properties of fibrous substrates, together with the wear properties and aesthetic virtues of carpet. Such products as these are able to be readily heat formed to suit the contours of the floor pan etc of a car, in fact more readily heat formed than the polyethylene backed carpets currently used which typically require 135 to 150°C forming temperature, which is of the order of the relaxation temperature of the polypropylene carpet fibre frequently employed in cars. The relatively high specific gravity of the flexible sound barrier material provided by the present invention also helps the carpet to better drape over the contours of the floor panels. We have found that by employing formulations of flexible sound barrier material according to the present invention to make a suitable sheet, it is possible to heat adhere a fibrous substrate to such a sound deadening sheet, preferably by making use of the residual heat in the sheet from the extrusion process and pressing the fibrous substrate onto that sheet in a continuous manner with squeeze roll. Likewise a sandwich construction can be made. if desired flexible sound barrier material in either continuous form or cut to shape can be adhered to a fibrous substrate by heating the sheet preferably with infra red radiation. By way of example one method we have employed is to place a cut sheet of material according to this invention on top of felt and with radiant heaters above the product it is heated for 30 to 90 seconds (depending upon intensity of radiation and thickness of sheet). Subsequently the laminate is passed between cooled pressure rolls or is pressed in a press to strongly adhere the sheet to the substrate. Likewise a further substrate may be added at the pressing stage to form a sandwich.

An adhesive film may be employed in the present invention particularly for vibration damping applications when it is required that the sheet material is to be heat fused to a metallic substrate that is to be subjected to vibration over a long period of time, or when it is otherwise appropriate. Our earlier PCT Application No. PCT/AU92/00375 discloses that when extremely high bond strength or resistance to cold shock is required, an adhesive laminate (of a different nature to that in Australian Patent Specification No. 34339/68, but for the same purpose) may also be employed. Such a laminate may be similariy employed in accordance with the present invention. Such a laminate or ply may be applied to the heat fusible sound deadening material at the time of manufacture and on the side of the sheet that is subsequently in contact with the metal. The laminate may conveniently be applied in film form or by the known extrusion methods or by other known coating methods. Suitable polymers for laminating are of the ethylene acrylic acid copolymer type. By applying such a laminate the strength of an otherwise good bond between metal and sound deadening material may be increased to the point where repeated blows at - 14°C will not dislodge the heat fusible sound deadening material from the steel substrate. Such a laminate is not sticky at room temperature and also serves as a useful means of preventing blocking of sheets of heat fusible sound deadening material, when stacked together under high loading at 45°C. In another particularly preferred form the present invention provides a sound deadening material which avoids the need for the inclusion of bitumen or asphalt. According to this embodiment the invention provides a heat fusible sound deadening material suitable for vibration damping applications comprising:

% by weight an elastomeric component 0 to 15%

(optionally acrylonitrile butadiene rubber) a polymeric component (optionally PVC) 0 to 15% a compatibilising agent

(optionally ricinoleic acid LAV) 0.1 to 5% a filler (optionally calcium carbonate) 70 to 90% tackifier (optionally pine rosin) 0 to 10% tall oil pitch 1 to 10% anti-oxidant

(optionally Irganox 565 or B215) 0.05 to 1% a heat stabiliser for PVC (if present) 0.3 to 1.5% a lubricant 0 to 4%

Other ingredients which are optionally employed include alumina tri-hydrate in the range of 0 to 50% by weight, and oxalic acid in the range of 0 to 1% by weight. It is to be understood that the minimum proportion of any elastomeric component, plus any polymeric component is together 5% by weight of the total weight of the formulation. Sound deadening materials according to formulations provided by the present invention may be prepared by pre-blending the filler and compatibilising agent, preferably ricinoleic acid LAV, and subsequently mixing the blend with the other ingredients in an intensive mixer where the ingredients are mixed, melted and homogenised. This may be followed by extrusion and calandering to convert the melt into sheet form. Other methods of forming sheets of sound deadening material according to the present invention include direct extrusion or calandering of sheet.

In a preferred embodiment, ricinoleic acid is applied to the filler(s) in a suitable mixer, to form a pre-blend. The mixer is preferably of a type which elevates the temperature of the blend to between 40°C and 110°C. so as to shorten the reaction time of the two ingredients. It is preferable if the pre-blend is made with only the ricinoleic acid and filler(s) being present. The pre-blend is later employed with the remaining ingredients which include a proportion of tall oil pitch. It is presently preferred that the tall oil pitch is added cold with the remaining ingredients of the formulation. For example, in one preferred arrangement according to the present invention the pre-blend is batch weighed together with each other ingredient without further mixing ready for loading into a Banbury Mixer.

The Geiger Thick Plate Test is a method of assessment of sound deadening accepted and specified by motor vehicle manufacturers in Australia. In this test, a sheet of sound deadening material is adhered to a steel plate. The plate is caused to ring at a particular frequency (around 160Hz) and the decibel level is recorded. When the source of vibration is stopped, the time for the decibel level to decay by a given amount is recorded. This procedure is repeated for a number of temperatures. Many vehicle manufacturers specify a Geiger Plate minimum decibel decay value (measured in decibels per second, or dB/s) at 21 °C, possibly because this temperature is a generally desirable temperature for vehicle operation. Heat fusible sound deadening material of the bituminous type made to Australian

Patent Specification No. 606877 (in the name of Sound Deadeners Australia Pty Ltd.), has a sound decay rate measured by the Geiger Thick Plate Method, under Australian Standard K 154.10, of at least 27 dB/s at 21°C, for a 2.5 mm thickness. Australian Patent Specification No. 14241/76 cites a sound decay rate of 9 dB/s for bituminous material made in accordance with that Specification. Some Australian automobile manufacturers have a requirement of a minimum decay rate of 9 dB/s at 21 °C and a minimum of 4 decibels per second at all temperatures from - 18°Cto + 43°Cfor heat fusible sound deadening material of 1.75 to 2.25 mm thickness. Heat fusible sound deadening materials made in accordance with the present invention have been found to exceed those values. Furthermore, formulations according to the invention enable considerably enhanced sound deadening efficiency at temperatures below

21 °C. Whilst not fully understood, it appears that the presence of tall oil pitch in formulations according to the present invention has the effect of shifting downwards the peak performance of sound deadening to a lower temperature without lowering that peak performance. It is thought that tall oil pitch has a softening or plasticising effect on the elastomeric components of formulations according to the invention.

General Motors Holden Ltd., in their Material Specification HN 1260, require a minimum decay rate of 15 decibels per second (dB/s) at 21 °C, with the weight of deadener

2 calculated back to 2.4 kg/m . Heat fusible sound deadening material can more realistically be assessed on the basis of sound decay rate in decibels per second on a standardised mass per area, using the same Geiger Thick Plate Method of test. Mass is an important consideration in automobiles and this method takes into account the efficiency of the heat fusible sound deadening material with respect to mass.

Formulations produced according to the present invention have been found to have a rating of beyond three times the above requirement. Furthermore, formulations made according to the invention have been found to have greater sound deadening efficiency for the whole temperature range of 0°C to 43 ^βG, than the prior art bituminous materials at 21 °C. Additionally, non-bituminous formulations according to the present invention may be produced in various colours with suitable pigmentation, thus e.g. enabling colour coding.

A further requirement for a heat fusible sound deadening material for the automotive industry is to have sufficient impact strength and resistance to cold bending in the non-adhered state, such that on a cold day breakage will not occur when the sheet material is handled at temperatures below 0°C.

We have found in comparative tests that in preferred formulations for the production of heat fusible sound deadening sheet, if ricinoleic acid LAV is merely substituted with tall oil pitch, the resultant sheet product, in general, fails the bend test around a 51mm diameter mandrel at both 12°C and - 6°C. This test consists of conditioning a 50 mm wide strip of sound deadening material at the relevant temperature, (together with the 51mm mandrel) for a minimum of eight hours. Following this the strip is bent 180° around the mandrel and it is observed if cracking or breakage occurs. The test is carried out at 23°C, 12°C and - 6°C. Furthermore, the peak sound deadening performance as measured on the Geiger Plate, is lower than that for the same formulation treated with ricinoleic acid LAV. We have also discovered that for formulations of the type applicable to the present invention, it is less effective to apply the tall oil pitch to the filler in the pre-blending step, either together with the ricinoleic acid LAV or as a separate but later mixing step to that of reacting the ricinoleic acid LAV with the filler. This applies regardless of whether the pre- treated filler is still at an elevated temperature when the tall oil pitch is applied. For example, a formulation without tall oil pitch which passed the bend test at 12°C, failed that same test when the filler is dual pre-treated with ricinoleic acid and tall oil pitch. The same formulation, but using calcium carbonate treated with ricinoleic acid and with the same quantity of tall oil pitch added cold, but together with the remainder of the formulation, when manufactured into sheet, has been found to pass the 12°C bend test and even the test at - 6°C.

It is convenient to further describe the invention in relation to the following examples showing various embodiments of the present invention suitable for vibration damping applications.

Example 1 Weight Percentage

TOP and

Ingredient Range No TOP No Ricinoleic Ricinoleic Calcium carbonate 70-90 79.4 79.4 79.0 Ricinoleic acid 0.1-5 1.6 0.0 1.5 PVC 0-15 6.3 6.3 6.2

PVC stabiliser 0-1.5 1.1 1.1 1.0 Nitrile rubber 0-15 4.2 4.2 4.1 Pine rosin 0-10 6.9 5.8 5.2 Antioxidant 0-0.5 0.2 0.2 0.2 Oxalic acid 0-1 0.5 0.5 0.5 Tall oil pitch 0-10 0.0 2.7 2.5

The "No TOP" example has a peak sound deadening decay of greater than 45 dB/s

2 when calculated back to 2.4 kg/m at a temperature of approximately 20°C and passes the

12°C bend test, but fails at - 6°C. By contrast, when the ricinoleic acid treatment is substituted with tall oil pitch in the "No Ricinoleic" example, the result is a peak sound

2 deadening decay of approximately 37 dB/s when calculated back to 2.4 kg/m at a temperature of approximately 37°Cand still passes the 12°Cbend test, but fails at - 6°C. When double the amount of tall oil pitch is used, the result is very similar. When both ricinoleic acid and tall oil pitch are used (the tall oil pitch being added as part of the remaining formulation i.e. the tall oil pitch is not part of the premix) the peak sound deadening decay increases to greater

2 than 50 dB/s when calculated back to 2.4 kg/m at a temperature of approximately 15°Cand passes both the 12°C bend test and that at - 6°C. Example 2 Weight Percentage

Ingredient Range No TOP With TOP

Calcium carbonate 70-90 89.3 88.2

Ricinoleic acid 0.1-5 1.2 1.1

Nitrile rubber 0-15 5.3 5.2

Pine rosin 0-10 4.3 4.2

Antioxidant 0-0.5 0.2 0.2

Tall oil pitch 0-10 0 1.2

The formulation "No TOP" has a peak sound deadening decay rate of approximately 35

2 dB/s when calculated back to 2.4 kg/m at a temperature of approximately 30°C and passes the

12°Cbend test, but fails at - 6°C. The formulation "With TOP" has a peak sound deadening decay rate which is similar but a little greater, however the peak is at a temperature of approximately 22°C. This formulation passes the 12°C bend test and the -6°C test. Both formulations are very economical with their high loading of filler and small quantity of elastomeric materials.

Example 3

Weight Percentage

Ingredient Range No TOP With TOP

Calcium carbonate 70-90 88.0 88.0

Ricinoleic acid 0.1-5 1.3 1.3

Nitrile rubber 0-15 5.9 5.9

Pine rosin 0-10 4.2 1.9

Oxalic acid 0-1 0.6 0.6

Antioxidant 0-0.5 0.2 0.2

Tall oil pitch 0-10 0.0 2.4

The formulation "No TOP" has a peak sound deadening decay rate of approximately 32 dB/s when calculated back to 2.4 kg/m 2 at a temperature of approximately 20°Cand passes the

12°Cbend test, but fails at -6°C. The formulation "With TOP" has a peak sound deadening decay rate which is similar, however the peak is at a temperature of approximately 12°C. This formulation passes the 12°Cbend test and the -6°Ctest. Oxalic acid was shown in PCT/AU92/

00375 to depress the temperature at which peak sound deadening occurs and this temperature is further depressed through the addition of tall oil pitch in accordance with the present example compared with a formulation containing oxalic acid. Both formulations show good economy with their high loading of filler and no PVC. Example 3

Weight Percentage

Ingredient Ranee Calcium carbonate 70-90 78.6 76.7 76.0 EVA 5-16 11.8 15.4 15.2

Nitrile rubber 1-15 3.9 5.1 5.1 Atactic polypropylene 0-7.5 3.1 1.3 1.3 Tall oil pitch 0.5-3 2.6 1.5 1.5 Antioxidant 0-0.4 0.1 0.1 PPiinnee rroossiinn 0-5 0 0 1.0

Each of the above formulations showed good sound barrier properties.

Example 4 Weight Percentage

Ingredient Range B Baarryytteess 0-95 85.6 90.0 0

Iron Oxide 0-95 0 0 90.1

EVA 5-15 8.6 5.8 5.8

Nitrile rubber 1-15 2.9 1.9 1.9

Atactic polypropylene 0-7.5 0.7 0 0 T Taallll ooiill ppiittcchh 0.5-3 1.7 1.2 1.2

Antioxidant 0-0.4 0 0 0.1

Pine rosin 0-5 0.6 1.2 1.2

The higher filler loadings showed superior sound barrier properties. The barytes formulations exhibited illustrated easier sheeting capabilities. While it has been convenient to describe the invention herein in relation to particularly preferred embodiments and examples, it is to be appreciated that various modifications, alterations and/or additions to the embodiments and examples described herein may be made within the scope and ambit of the present invention.

Claims

1. A sound deadening material comprising at least one component selected from each of the following component groups:

(ii) a filler; (iii) a melt viscosity modifier comprising tall oil pitch.

2. A sound deadening material according to claim 1 which includes

(i) a synthetic rubber elastomeric component and an ethylene vinyl acetate polymeric component;

(ii) a filler; and (iii) a melt viscosity modifier comprising tall oil pitch.

3. A material according to claim 2 wherein the filler is selected from the group consisting of barytes, calcium carbonate, dolomite, micaceous fillers, clays, alumina trihydrate and mixtures thereof.

4. A material according to claim 3 which further includes one or more of the following components:

(i) a softening agent;

(ii) a tackifier; (iii) an a i oxidant.

5. A material according to claim 4 wherein the softening agent comprises ataαic polypropylene.

6. A material according to claim 4 wherein the tackifier comprises a pine rosin or a tall oil ester.

7. A material according to claim 3 wherein the ethylene vinyl acetate polymeric component has a vinyl acetate content of not less than 20wt%.

8. A material according to claim 7 wherein the vinyl acetate content of the ethylene vinyl acetate polymeric component is about 28wt%.

9. A material according to claim 7 wherein the elastomeric component is selected from the group consisting of acrylonitrile butadiene rubber, butyl rubber, and mixtures thereof.

10. A material according to claim 7 wherein the filler comprises from 70wt% to 95wt% of the total weight of the material.

11. A material according to claim 7 wherein alumina trihydrate comprises from 20wt% to 50wt% of the total weight of the filler.

12. A flexible sound deadening material comprising: ethylene vinyl acetate copolymer 5-15% by weight melt viscosity modifier comprising tall oil pitch 0.5-3% by weight synthetic rubber 1-15% by weight barytes 0-95% by weight calcium carbonate 0-90% by weight iron oxide 0-95% by weight alumina trihydrate 0-50% by weight atactic polypropylene 0-7.5% by weight pine rosin 0-5% by weight antioxidant 0-0.4% by weight wherein the total amount of filler comprising barytes, calcium carbonate, iron oxide and alumina trihydrate is in the range of 70-95 wt% of the total weight of the material.

13. A soimd deadening material comprising at least one compound selected from each of the following groups:

(i) εn elastomeric component, a polymeric component or both an elastomeric and a polymeric component;

(ii) a filler; (iii) a melt viscosity modifier comprising tall oil pitch;

(iv) a compatibilising agent.

14. A material according to claim 13 wherein the elastomeric component is selected from the group consisting of synthetic rubbers and natural rubber and wherein the polymeric component is selected from the group consisting of polyvinylchloride, a polyvinylchloride/vinyl acetate copolymer, chlorinated polyethylene and ethylene vinyl acetate.

15. A material according to claim 14 wherein the compatibilising agent comprises ricinoleic acid.

16. A material according to claim 15 wherein the ricinoleic acid has an acid value in the range of 130-145.

17. A material according to claim 15 wherein the filler is a power form filler selected from the group consisting of barytes, calcium carbonate, micaceous fillers, clays, magnesium carbonate, silica and mixtures thereof.

18. A material according to claim 17 wherein the filler comprises from 70wt% to 90wt% of the total weight of the material.

19. A material according to claim 17 in sheet or pad form.

20. A material according to claim 15 which further includes one or more of the following components:

(i) atactic polypropylene;

(ii) a tackifer; (iii) an antioxidant;

(iv) a flame retardant;

(v) a stabiliser;

(vi) a polar additive;

(vii) a liquid platiciser; (viii) a lubricant.

21. A material according to claim 20 wherein the tackifier comprises a pine rosin or a tall oil ester.

22. A material according to claim 20 wherein the polar additive comprises oxalic acid or phthalic anhydride.

23. A heat fusible sound deadening material in sheet or pad form having the following composition: an elastomeric component 0 to 15% by weight a polymeric component 0 to 15% by weight a compatibilising agent 0.1 to 5% by weight a filler 70 to 90% by weight tackifier 0 to 10% by weight tall oil pitch 1 to 10% by weight anti-oxidant 0.05 to 1% by weight a lubricant 0 to 4% by weight oxalic acid 0 to 1% by weight alumina trihydrate 0 to 30% by weight wherein when the polymeric component comprises polyvinylchloride a heat stabiliser is also present in the range of 0.3 to 1.5% by weight and wherein the elastomeric and the polymeric component together comprise at least 5wt% of the total weight of the material.

24. A sound deadening material according to claim 23 wherein the elastomeric component comprises acrylonitrile butadiene rubber, the polymeric component comprises PVC, the compatibilising agent comprises ricinoleic acid LAV, the filler comprises calcium carbonate and the tackifier comprises pine rosin.

25. A sound deadening material according to claim 24 wherein the elastomeric component is present in the range of 2 to 10% by weight of the total weight of the material and the PVC if present comprises 3 to 12% by weight of the total weight of the formulation.

26. A method for forming a sound deadening material in sheet or pad form comprising the steps of:

(a) compatibilising a filler or fillers by treatment with a compatibilising agent to form a pre-blend, (b) mixing the pre-blend with other ingredients including:

(i) an elastomeric component, a polymeric component or both an elastomeric and a polymeric component; and (ii) a melt viscosity modifier comprising tall oil pitch; and

(c) forming a sheet or pad from said mix.

27. A method according to claim 26 wherein the temperature of the pre-blend is raised by between 40°C and 110°C during the compatibilising step.

28. A method according to claim 26 wherein the filler is a powder form filler selected from the group consisting of barytes, calcium carbonate, micaceous fillers, clays, magnesium carbonate, silica, and mixtures thereof.

29. A method according to claim 28 wherein the compatibilising agent comprises ricinoleic acid having an acid value in the range of 130-145.

30. A method according to claim 29 wherein the elastomeric component is selected from the group consisting of synthetic rubbers and natural rubber and wherein the polymeric component is selected from the group consisting of polyvinylchloride, a polyvinylchloride/vinyl acetate copolymer, chlorinated polyethylene and ethylene vinyl acetate.

31. A method for applying a sound deadening material to a metal panel comprising the steps of:

(d) forming a sheet or pad of sound deadening material according to claim 23;

(e) laying said sheet or pad on a metal panel; and

(f) heating said metal panel and said sheet or pad whereby to bond said sheet or pad to said metal panel.