AU621618B2 - Sound deadening sheet for heat fusion to fibrous substrates - Google Patents

Description

i I- i i ~ej=~n-sh1 P/00/011 Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Cc r c C c e4 0 TO BE COMPLETED BY APPLICANT Name of Applicant: TRI-TEX AUSTRALIA PTY LTD c :c ,'Actual Inventor(s): GRAEME MATTHEW BALL and DAVID MORRIS CAITHNESS :":Address for Service: CALLINAN LAWRIE, 278 High Street, Kew, 3101, Victoria, Australia t Invention Title: "SOUND DEADENING SHEET FOR HEAT FUSION TO FIBROUS

SUBSTRATES"

The following statement is a full description of this invention, including the best method of performing it known to me:performing it known to me:- -2- This invention relates to sound deadening materials. More specifically it relates to sound deadening formulations for use in combination with carpet, felt or other woven or non-woven fibrous substrates, the combinations themselves, as well as to methods for preparing such combinations.

Sound deadening formulations of the bituminous-rubber-filler type have been known for many years and an improvement in such formulations is the subject of International Patent Application No. PCT/AU87/00184.

|I Such bitumen-containing formulations may be adhered to a fibrous substrate but are specifically formulated to adhere to steel (see Australian Patent No. 498074) and have too little flex cracking resistance (when not adhered to steel) I C to withstand the flexing such as a carpet receives in an automobile. Additionally, I the necessary black colour of a bitumen-containing formulation may not always be C s aesthetically acceptable for such an application, nor does it permit the colour coding of such items where this is desirable.

S' Carpets shaped to fit the contours of the floor of a car have been employed for some years and indeed Australia is very advanced in this. In a known method of manufacture, low density polyethylene is applied in powder form to the back of the carpet and is heated in order for sufficient flow to occur to bind the 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 heating process, in the carpet making factory. The carpet usually lies on top of bituminous rubber sound deadening formulations which have previously been adhered to the steel floor panels. In some luxury model cars there may also be adhesively bonded felt underneath the carpet. It is also a requirement of some car manufacturers that the -i i I I I -3sound deadening formulation does not bleed any of its colour into the carpet thus staining it.

It is desired by some car manufacturers to combine the sound deadening formulation and the carpet into one product, thus eliminating the separate application of bitumen-containing sound deadening formulation and the necessary concomitant heating step. In many instances, however, car manufacturers may wish to attain a higher level of sound attenuation than is achievable by the application of bitumen-rubber-filler sound deadening formulation only, particularly for luxury model cars. In such cases, it is anticipated that formulations according to the present invention may be capable of forming the backing for the carpet or I !OO: may be used as a sandwich layer between carpet and felt and thus combine the 0 0 sound deadening properties of such formulations with the sound absorbing 0 0 0 0 0 properties of fibrous substrates, together with the wear properties and aesthetic 00 0 virtues of the carpet. Formulations according to the present invention are able to Sbe relatively readily heat-formed to suit the contours of the car, in fact more 0060 o readily heat-formed than the polyethylene backed carpets currently used. The 9 00 0o latter require a heat-forming temperature of from 135 C to 150 C, a temperature :*00 which is very close to the relaxation temperature of the polypropylene carpet. The a o0 relatively high specific gravity of sound deadening formulations according to the present invention and their good flexibility are believed to also help the carpet to drape better over the contours of the floor panels.

A U.S. method for improving the sound deadening qualities of carpet for automobiles basically consists of extruding a sheet of filled thermoplastic material by the commonly known methods and applying an acrylic adhesive to -,111 -4that sheet, or the carpet backing, or both, and pressing the two together. Such a process is messy because of the use )f adhesive. If adhesive is of the organic solvent type, the process presents environmental problems that are relatively expensive to overcome. If waterborne adhesives are employed considerable energy may be consumed in drying the adhesive. Another method of adhesive application is to employ hot melt adhesives. This requires the use of an extrusion device and the control of the rate of application of the adhesive which is obviously more difficult and more expensive than a process that does not require any adhesive.

An object of this invention is to provide a sound deadening formulation e in sheet form adapted for adhesion to carpet, felt or other woven or non-woven 0 0 fibrous substrate. The formulation of the sound deadening compound may be in 0 0 0 granular or pellet form for subsequent manufacture into sheet form but preferably 00 0 0 g ra 0 the formulation is already manufactured into sheet form from the ingredients. In either case, the purpose of this sheet is to be self-adhered by heat and pressure, to a carpet and/or felt of natural or synthetic fibre, of the woven or non-woven 0 0 0 0:'000 type. Where desired, the sheet can be adhered to a substrate with a suitable 0000 adhesive. In a preferred form woven carpet would be the substrate employed and the preferred type of carpet is that which may be shaped by heat and is presently used in the interior of cars as a sound absorbing material and for aesthetic purposes. In another preferred form the sound deadening formulation is sandwiched between carpet and felt.

In yet another preferred form it is adhered to felt and is the means by which the felt is given integrity and the sound attenuation of the felt is enhanced I Ir

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for use, behind a car dashboard or in the wheel arch area of a car to lower the noise of stone impingement. A further possible use of the formulation when adhered to felt, is to absorb noise in the interior of a motor vehicle. The sound deadening formulation acts as a "dead" barrier and a bouncing board for sound waves travelling through the fibres, having many collisions with those fibres and thus converting their energy to heat.

Such carpet, felt or other fibrous substrate may be manufactured by other organizations and part of the object of this invention is to enable the provision of a superior sound deadening formulation to a fibrous substrate manufacturer to make into sheet, which is adhered preferably by heat to the substrate, or for such a manufacturer to supply the substrate to us for application

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of the sheet in a similar manner, or to enable the provision of sound deadening SC formulation in continuous or discontinuous sheet form for application to a substrate as aforesaid.

1'5 According to one aspect of the present invention there are provided sound deadening formulations including the following:atactic polypropylene 3-10% t ethylene vinyl acetate copolymer 12-50% ethylene propylene rubber 3-10% antioxidant 0.05-0.4% barytes 0-80% calcium carbonate 0-80% alumina trihydrate 0-50% stearic acid (or metal stearates 2

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Me fIT4'~ -6being selected from one or more of calcium stearate, zinc stearate and aluminium stearate), 0.5-2.5% all the aforegoing percentages being weight percent.

Colorants or pigments of the usual types may be added as required.

This can enable colour coding of articles incorporating the formulations.

We have discovered that the strength of the adhesive bond to the substrate is enhanced by the use of atactic polypropylene. Additionally, the sound attenuation properties of the formulations are improved by the use of higher i* volume fractions of fillers in relation to polymeric materials. The use of atactic polypropylene especially in combination with stearic acid, greatly facilitates the 0 j incorporation of such higher filler loadings yet still enables ready processability in I the production of sheet. Furthermore, it has been found that the atactic polypropylene acts as a solid polymeric plasticiser for the other polymeric materials thus giving greater flexibility and a better "hand" to the sheet, without suffering o from the potential plasticiser migration problems associated with the use of conventional plasticiser or extender oils. Such plasticiser and/or oil migration has been known to cause staining and/or degradation of the material or substrate into which the plasticiser and/or oil migrates. In common with other plasticisers, atactic polypropylene lowers the heat softening point of the compound into which it is incorporated. This is advantageous when employing the formulations in sheet form for heat-adhesion to a fibrous substrate having a relatively low heat resistance

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such as some synthetic fibres employed in carpets and felt. The influence on Ir. 4 4 *f 4 44 54 4 4O 44 S S 444 4 44 54I It 4 0( -7softening point must be borne in mind when formulating a sound deadening formulation for a specific application and the level of atactic polypropylene may be adjusted accordingly, with preferred levels being between 3 and 10% by weight of the total formulation.

Atactic polypropylene is made 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 polymerization, through the solubility of the atactic polypropylene compared with that of isotactic polypropylene. It is generally desirable to separate out the atactic polypropylene because of its softening effect on isotactic polypropylene and hence a diminishing Sof desired mechanical properties. Atactic polypropylene varies in consistency from an oily material through to a waxy solid depending upon its molecular weight and its manufacturing feedstock. For example, atactic polypropylene from the S manufacturer of copolymer polypropylene is a sticky, waxy material. A known use 1'5 for atactic polypropylene is as an oil additive to improve lubrication properties.

ee Its previous use in such an application as the present invention is unknown to us.

The major polymeric binder employed in the sound deadening material Co o° formulations is ethylene vinyl acetate (EVA). Whilst almost any ethylene vinyl oo acetate can be used, it is advantageous to use a high vinyl acetate (VA) content copolymer as that increases the elastomeric properties of the resultant sheet i.e. its i ug 4e v1 coYn mar ke hefween by W "rubberiness". We prefer an EVA having a VA content of 28%. AFurthermore we prefer a reasonably high molecular weight EVA i.e. one having a lower melt index, because this enhances the resistance to cracking on cold flexing. For example, for Sa given formulation and same VA content, EVA having a VA content of 28% and .1 X-t y B l -8a melt index of 400 exhibits cracking on doubling 3mm sheet at 4 C. EVA having a VA content of 28% and a melt index of 40 shows no cracking under the same condition at -14 C. The preferred melt index is 40. However, EVA having a melt index between 20 and 400 can be employed in the invention. The preferred level of this 28/40 EVA in formulations according to the present invention is from 12 to by weight of total formulation.

"Ethylene propylene rubber" is employed to provide greater flexibility to the resultant sheet and to be part of the binder system. In preferred formulations ethylene propylene rubber, usually containing the form known as EPDM, is used at between 3 and 10% by weight of total formulation.

Fillers are employed to make the sound deadening formulation more 0 i00 0 dense, which assists both the vibration damping and the airborne sound absorbing 0 0 o o properties of the resultant sheet. The fillers used are those commonly employed S° in the rubber industry, namely barytes, calcium carbonate, clays and where flame °I retardancy is required, alumina trihydrate. Preferred fillers are calcium carbonate t and/or barytes at a weight percentage of from 65 to 80% of total formulation.

0o 9 0: Mixtures of the two may be anywhere in between these two weight percentage 6000 0: 0 S limits. When alumina trihydrate is employed it may generally replace approximately 20 to 100% of the other abovementioned fillers depending upon the degree of flame retardancy required. It is preferred that alumina trihydrate comprise from 20 to 50% by weight of the total amount of calcium carbonate, barytes and alumina trihydrate present.

Stearic acid or metal stearates are employed to give greater compatibility n^-IN between the fillers and the polymeric materials, to assist in wetting out the 1.

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f i -rfai^ -9fillers. Stearic acid has been found to be particularly effective when combined with atactic polypropylene at a preferred level of from 0.5 to 2.5% by weight of total formulation. The preferred metal stearates are calcium stearate, zinc stearate and aluminium stearate.

An antioxidant is employed. This is most often a hindered phenol type, but any known thermoplastics heat stabilizer may be employed whose function is to prevent breakdown of the atactic polypropylene, the EVA and the ethylene propylene rubber during processing and usage. A suitable material is Irganox 1076 from Ciba Geigy. In preferred formulations a level of from 0.05 to 0.4% by weight of total formulation is employed.

The formulations are prepared by combining the ingredients in an intensive mixer or other type of mixing machine and then extruding as sheet form or into granular or pellet form as desired.

A non-limiting example of a sound deadening formulation according to the invention comprises by weight percent:atactic polypropylene ethylene vinyl acetate copolymer 18.8% ethylene propylene rubber Irganox 1076 0.1% calcium carbonate 42.2% alumina trihydrate 30.12% stearic acid pigment 0.25% Other examples of formulations according to the invention are:

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Formulation Formulation No 1, No 2.

by weight by weight Calcium carbonate 41 0 Alumina trihydrate 31 41 EVA 28/40 19 47 Atactic polypropylene 3.6 4.7 EPDM (Vistalon 7000) 4 Black masterbatch (colorants) 0.4 0.7 LO Stearic acid 1 0.4 Antioxidant (Irganox 1076) 0.1 0.1 c The weight percent figures have been rounded off to the first decimal

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Formulation No. 1 has the following properties when converted to sheet of 3mm thickness.

Specific gravity 1.62 gms/cc Ash 63% by weight Hardness, Shore A 86 Bend Test Does not break when bent over a 12.5 mm Flammability diameter mandrel at -14 "C.

VO rating under US Underwriters Laboratory Specification 94 Under US FMVSS 302-1975 'FLAMMABILITY OF INTERIOR MATERIALS cc- L_ 11 Burn Rate (mm/min) Specification 1 SE/NBR 0.0 Specification 2 SE/NBR 0.0 Specification 3 SE 0.0 SE/NBR Self Extinguishing/No Burn rate SE Self Extinguishing Thus it can be seen that Formulation No. 1 exhibits desirable flammability properties.

Formulation No. 2 is considerably more flexible, yet still retains the VO rating under UL 94.

By removing or lowering the alumina trihydrate and substituting e.g., calcium carbonate in the formulations, the flammability may be worsened but the i product will become cheaper.

We have found, that by employing the abovementioned sound deadening formulations to make a suitable sound deadening sheet, it is possible Sto heat adhere a fibrous substrate to such a sound deadening sheet, preferably by making use of the residual heat in the sheet from the hot extrusion process and 4000 0 0 S pressing the fibrous substrate onto that sheet in a continuous manner with squeeze I 0 f rollers. Likewise a sandwich construction can be made. If desired, a sound deadening sheet 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, a method we have employed is to place a cut sheet of sound deadening formulation according to this invention on top of felt and, with radiant heaters above the sheet, it is heated for 30 to 90 seconds (depending upon /vtv y.i /Vti U^/ i ~__p4lrrauYllr~.rr~Dv"--1=-~ 12 intensity of radiation and thickness of sheet). Subsequently the laminate is passed between cooled pressure roll 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 construction. The combined product is not exposed to undesirably higher temperatures for very long and is thus not adversely affected.

Thus according to other aspects of the invention there are provided methods for combining sound deadening formulations with suitable substrates.

It is to be understood that various additions, alterations and modifications may be introduced into the foregoing without departing from the ambit of the invention as defined in the following claims.

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Claims (4)

1. A sound deadening formulation including the following components: atactic polypropylene 3-10% by weight; ethylene vinyl acetate copolymer 12-50% by weight; ethylene propylene rubber 3-10% by weight; antioxidant 0.05-0.4% by weight; barytes 0-80% by weight; calcium carbonate 0-80% by weight; alumina trihydrate 0-50% by weight; stearic acid or metal stearates (being selected from one or more of calcium stearate, zinc stearate, t C and aluminium stearate) by weight.

2. A sound deadening formulation as claimed in Claim 1 wherein the ethylene vinyl acetate copolymer has a vinyl acetate content of between 14% and cCc S 40% by weight. S 3. A sound deadening formulation as claimed in either Claim 1 or Claim 2 wherein the ethylene vinyl acetate copolymer has a vinyl acetate content of 28% I c by weight.

4. A sound deadening formulation as claimed in any one of Claims 1 to 3 wherein the ethylene vinyl acetate copolymer has a melt index of between 20 and

400. A sound deadening formulation as claimed in any one of Claims 1 to 4 "3 wherein the ethylene vinyl acetate copolymer has a melt index of i I-I I- l l--i'Il-r- -iuiu~ ~xur;r~rer~ B a C C Se e c o C c e 9*9000 o 9 00 OI 00 00 9 C 9 CCCo C eC CI Ca c S a o Qo 0 a t4a c c c -14- 6. A sound deadening formulations as claimed in any one of Claims 1 to wherein the total amount of calcium carbonate and/or barytes in the formulation is between 65 and 80% by weight. 7. A sound deadening formulation as claimed in any one of Claims 1 to 6 wherein alumina trihydrate comprises from 20 to 50% by weight of the total amount of calcium carbonate, barytes and alumina trihydrate present. 8. A sound deadening formulation as claimed in any one of Claims 1 to 7 wherein the antioxidant is a known thermoplastic heat stabilizer. 9. A sound deadening formulation as claimed in any one of Claims 1 to 8 wherein the antioxidant is of the hindered phenol type. 10. A sound deadening formulation as claimed in any one of Claims 1 to 9 wherein the antioxidant is that known as Irganox 1076. 11. A sound deadening formulation as claimed in any one of Claims 1 to wherein colorants and/or pigments are also present. 12. A sound deadening formulation having the following composition: atactic polypropylene 3.5% by weight; ethylene vinyl acetate copolymer 18.8% by weight; ethylene propylene rubber 4.0% by weight; Irganox 1076 0.1% by weight; calcium carbonate 42.2% by weight; alumina trihydrate 30.12% by weight; stearic acid 1.0% by weight; pigment 0.25% by weight. 13. A method of preparation of a sound deadening formulation as claimed iT O'U in any one of Claims 1 to 12, wherein the components are combined in an intensive mixer or other type of mixing machine and then extruded as either sheet form or into granular or pellet form. 14. A process of manufacturing a sound deadening material wherein a fibrous substrate is adhered to a heated or hot sound deadening formulation as claimed in any one of Claims 1 to 12 in sheet form by placing the fibrous substrate on one side of the sheet and then pressing the fibrous substrate onto the sheet with squeeze rollers, cooled pressure rollers or a press. A process of manufacturing a sound deadening material wherein fibrous o' substrates are adhered to both sides of a heated or hot sound deadening formulation as claimed in any one of Claims 1 to 12 in sheet form by placing the fibrous substrates on either side of the sheet and by then pressing the fibrous substrates onto the sheet with squeeze rollers, cooled pressure rollers or a press. 16. A process as claimed in either Claim 14 or Claim 15 wherein the fibrous V 0. 1 oooo° substrate/s is/are selected from one or more of carpet or felt of natural or synthetic fibre, being either woven or non-woven. So 17. A sound deadening material as manufactured in accordance with any one of Claims 14 to 16. 18. A sound deadening material comprising a sound deadening formulation as claimed in any one of Claims 1 to 12 in sheet form and one or more fibrous substrates selected from the group comprising woven or non-woven carpet or felt of natural or synthetic fibre. 19. A sound deadening formulation as claimed in any one of claims 1 to 12, i substantially as hereinbefore described, with reference to either the Example or 16 Formulation Number 1 or Formulation Number 2. DATED this 16th day of January, 1992. TRI-TEX AUSTRALIA PTY LTD By its Patent Trade Mark Attorneys: CALLINAN LAWRIE /-TO 09 0 0 0 0 00 0 0 0 0 00 00 c 0C