GB2463858A

GB2463858A - Foamed insulation

Info

Publication number: GB2463858A
Application number: GB0815180A
Authority: GB
Inventors: Didier Trau
Original assignee: Zephyros Inc
Current assignee: Zephyros Inc
Priority date: 2008-08-20
Filing date: 2008-08-20
Publication date: 2010-03-31
Also published as: GB0815180D0

Abstract

Foamed insulation is provided in cavities by providing foamable material on a carrier 1 in the cavity and foaming the material within the cavity. In order to improve the uniformity of the foam and reduce the time required for foaming the carrier 1 is provided with ribs 4, 5, 6, 7 which protrude into the cavity to ensure that foamable material is provided on at least some parts of the ribs 4, 5, 6, 7 deep into the cavity. The foamable material is heat activated. The present invention is particularly useful in the provision of sound insulation in vehicles. The foamable material foams at temperatures employed in the vehicle assembly such as the paint bake or e-coat bake ovens. The carrier may be of steel or aluminium or formed from a thermoplastics material such as by blow, extrusion or injection moulding. There may be two types of foamable materials, one 8 on the ribs and the other 24 on the carrier 1.

Description

IMPROVEMENTS IN OR RELATING TO INSULATION

The present invention relates to improvements in or relating to the provision of insulation; including both sound and heat insulation. The invention is particularly useful in the provision of insulation in transportation vehicles such as automobiles, trucks, busses, railroad vehicles and aircraft although it may have use in other industries such as the furniture and construction industries.

It is known that insulation such as sound insulation may be provided in cavities in vehicles by the provision of foamable material within the cavities which can be foamed during the vehicle assembly process such as during the paint bake process or the baking of the anticorrosion coating applied to the body in white often known as the se-coat' process. The nature of the foamable material and the degree of expansion of the foam may be selected according to the size and shape of the cavity within which the insulation is to be provided and according to the nature of the insulation that is to be provided. For example where sound insulation is to be provided an open cell foam may be desirable to ensure capture of the sound waves.

If thermal insulation is to be provided a closed cell foam may be employed. Similarly if it is desired that the foam provide a degree of reinforcement a denser foam based on a lower degree of expansion may be required.

It has been proposed that the foamable material may be provided in the cavity by * ** direct attachment to the walls of the cavity or alternatively it may be provided on a carrier which can be attached to the internal walls of the cavity. S... * . *..

One difficulty that arises however is that when it is required to fill large cavities or cavities of intricate shape it can be difficult not only to fill the cavity but to provide a uniform foam structure throughout the cavity. The present invention therefore provides a system whereby the uniformity of the foam is improved. Another problem associated with the provision of foam in large cavities is that it is necessary to provide a relatively thick layer of foamable material in order to fill the cavity and provide adequate insulation. The thicker the layer of the foamable material the longer the time required to generate the foam which can require special steps in vehicle production as opposed to the preferred use of the duration of the component containing the cavity in the paint bake or e-coat bake oven to develop the foam.

The quantity and/or uniformity of the foam is improved by providing the foamable material on a carrier and providing ribs on the carrier at least some parts of which carry the foamable material and which when the carrier is assembled in the area where the insulation is required, extend into the cavity. In this way at least some of the foamable material protrudes into the area to be insulated beyond the body of the carrier At least some of the foam is thus produced within the cavity. In certain embodiments upon expansion of the foamable material the foam can fill the spaces between the ribs although the degree of expansion can be controlled to provide an acoustic gap.

The foamable material is usually a heat activated material and when the foam is required to produce insulation in vehicles the foamable material may be formulated so that it will foam at temperatures employed in vehicle assembly such as in the paint bake or e-coat bake ovens. The conductivity of the ribs on the carrier can help to ensure a more uniform heating of the foamable material resulting in a more uniform foam structure. The use of the ribbed carrier structure may also be useful in that it allows the foam that needs to be produced to provide the insulation to be provided from a thinner layer of formable material. This can have economic benefits in that the foamable material tends to be more expensive than the material from which the carrier is made. The foam may also fill gaps between the ribs.

The carrier may be made of any suitable material that can be shaped to provide the desired ribbed structure. Where the foamable material is heat activated it is preferred that the carrier have a high thermal conductivity to enhance the uniformity *. 25 of the heating of the foamable material. The carrier may be made from metal s * stampings or it may be assembled from various components for example the ribs may be produced separately and welded together to form the carrier possibly with : intervening sections. The carrier may be of steel or aluminium is particularly preferred to minimise the weight contributed by the insulation system. Alternatively the carrier may be formed from a thermoplastic material such as by blow moulding, *..* * . extrusion or injection moulding which has the benefits that the ribs can be integrally formed with the carrier.

The foamable material can be of any suitable material depending upon the nature of the insulation to be provided. The foamable material is preferably heat activated and is preferably a material that will flow and expand when heated. In certain instances it may also contain materials that will cross-link (or cure) at the foaming temperature to provide some rigidity to the foam if this is required. The degree of expansion of the foam is usually above 100% and is preferred to be in the range 200% to 3000% more preferably 200% to 2500%.

Examples of materials that may be included in the foamable material are given below.

Polymer or Copolymer Depending upon the properties required of the foam the foamable material may include one or more additional polymers or copolymers, which can include a variety of different polymers, such as thermoplastics, elastomers, plastomers and combinations thereof or the like. For example, and without limitation, polymers that might be appropriately incorporated into the structural adhesive include halogenated polymers, polycarbonates, polyketones, urethanes, polyesters, silanes, sulfones, allyls, olefins, styrenes, acrylates, methacrylates, epoxies, silicones, phenolics, rubbers, polyphenylene oxides, terphthalates, acetates (e.g., EVA), acrylates, methacrylates (e.g., ethylene methyl acrylate polymer) or mixtures thereof. Other potential polymeric materials may be or may include, without limitation, polyolefin (e.g., polyethylene, polypropylene) polystyrene, polyacrylate, poly(ethylene oxide), poly(ethyleneimine), polyester, polyurethane, polysiloxane, polyether, polyphosphazine, polyamide, polyimide, polyisobutylene, polyacrylonitrile, poly(vinyl chloride), poly(methyl methacrylate), poly(vinyl acetate), poly(vinylidene chloride), polytetrafluoroethylene, polyisoprene, polyacrylamide, polyacrylic acid, polymethacrylate. * ** * * * I.

When used, these polymers can comprise a small portion or a more substantial portion of the material. When used, the polymers preferably comprises about 0.1% I..

to about 50%, 80% more preferably about 20% to 70% by weight of the foamable material.

S. **I * In certain embodiments, it may be desirable to include one or more thermoplastic polyethers and/or thermoplastic epoxy resins in the foamable material. When included, the one or more thermoplastic polyethers preferably comprise between about 1% and about 90% by weight of the foamable material, more preferably between about 3% and about 60% by weight of the foamable material and even more preferably between about 4% and about 25% by weight of the foamable material. As with the other materials, however, more or less thermoplastic polyether may be employed depending upon the intended use of the foamable material.

Thermoplastic polyethers may also be included. The thermoplastic polyethers may also include aromatic ether/amine repeating units in their backbones. The thermoplastic polyethers preferably have a melt index between about 5 and about 100, more preferably between about 25 and about 75 and even more preferably between about 40 and about 60 grams per 10 minutes for samples weighing 2.16 Kg at a temperature of about 190°C. Of course, the thermoplastic polyethers may have higher or lower melt indices depending upon their intended application. Preferred thermoplastic polyethers include, without limitation, polyetheramines, poly(amino ethers), copolymers of monoethanolamine and diglycidyl ether, combinations thereof or the like.

Preferably, the thermoplastic polyethers are formed by reacting an amine with an average functionality of 2 or less (e.g., a difunctional amine) with a glycidyl ether (e.g., a diglycidyl ether). As used herein, the term difunctional amine refers to an amine with an average of two reactive groups (e.g., reactive hydrogens).

According to one embodiment, the thermoplastic polyether is formed by reacting a primary amine, a bis(secondary) diamine, a cyclic diamine, a combination thereof or the like (e.g., monoethanolamine) with a diglycidyl ether or by reacting an amine with an epoxy-functionalized poly(alkylene oxide) to form a poly(amino ether). According * to another embodiment, the thermoplastic polyether is prepared by reacting a difunctional amine with a diglycidyl ether or diepoxy-functionalized poly(alkylene ** S oxide) under conditions sufficient to cause the amine moieties to react with the epoxy moieties to form a polymer backbone having amine linkages, ether linkages and pendant hydroxyl moieties. Optionally, the polymer may be treated with a monofunctional nucleophile which may or may not be a primary or secondary amine.

*S55*5 * Additionally, it is contemplated that amines (e.g., cyclic amines) with one reactive group (e.g., one reactive hydrogen) may be employed for forming the thermoplastic polyether. Advantageously, such amines may assist in controlling the molecular weight of the thermoplastic ether formed.

Examples of preferred thermoplastic polyethers and their methods of formation are disclosed in United States Patents Nos. 5,275,653; 5,464924 and 5,962,093.

Advantageously, the thermoplastic polyethers can provide the foamable material with various desirable characteristics such as desirable physical and chemical properties for a wide variety of applications as is further described herein.

Although not required, the foamable material may include one or more ethylene polymers or copolymers such as ethylene acrylates, ethylene acetates or the like.

Ethylene methacrylate and ethylene vinyl acetate are two preferred ethylene copolymers.

It may also be desirable to include a reactive polyethylene resin that is modified with one or more reactive groups such as glycidyl methacrylate or maleic anhydride.

Examples of such polyethylene resins are sold under the tradename LOTADER� (e.g., LOTADER AX 8900) and are commercially available from Arkema Group.

Blowing Agent One or more blowing agents are included in the foamable material for producing inert gasses that form, as desired, an open and/or closed cellular structure within the foam.

The blowing agent may include one or more nitrogen containing groups such as amides, amines and the like. Examples of suitable blowing agents include azodicarbonamide, dinitrosopentamethylenetetramine, azodicarbonamide, dinitrosopentamethylenetetramine, 4,4-oxy-bis-(benzenesulphonylhydrazide), trihydrazinotriazine and N, N1-dimethyl-N, N*-dinitrosoterephthalamide. An accelerator * *. 25 for the blowing agents may also be provided in the foamable material. Various S*.

accelerators may be used to increase the rate at which the blowing agents form inert gasses. One preferred blowing agent accelerator is a metal salt, or is an oxide, e.g. * a metal oxide, such as zinc oxide. Other preferred accelerators include modified and unmodified thiazoles or imidazoles. * 30

** * ..� * The amounts of blowing agents and blowing agent accelerators that should be used can vary widely depending upon the type of cellular structure desired, the desired amount of expansion of the foamable material, the desired rate of expansion and the like. Exemplary ranges for the amounts of blowing agents and blowing agent accelerators in the foamable material range from about 0.001% by weight to about 5% by weight and are preferably in the foamable material.

Filler The foamable material may also include one or more fillers, including but not limited to particulate materials (e.g., powder), beads, microspheres such as Zeospheres available from Zeelan Industries, or the like. Preferably the filler includes a material that is generally non-reactive with the other components present in the activatable material. While the fillers may generally be present within the foamable material to take up space at a relatively low weight, it is contemplated that the fillers may also impart properties such as strength and impact resistance to the foarnable material.

Examples of fillers that may be used include silica, diatomaceous earth, glass, clay (e.g., including nanoclay), talc, pigments, colorants, glass beads or bubbles, glass, carbon or ceramic fibers, nylon or polyamide fibers (e.g., Kevlar), antioxidants, and the like. Such fillers, particularly clays, can assist the foamable material in leveling itself during flow of the material. The clays that may be used as fillers may include clays from the kaolinite, illite, chloritem, smecitite or sepiolite groups, which may be calcined. Examples of suitable fillers include, without limitation, talc, vermiculite, pyrophyllite, sauconite, saponite, nontronite, montmorillonite or mixtures thereof. The clays may also include minor amounts of other ingredients such as carbonates, feldspars, micas and quartz. The fillers may also include ammonium chlorides such as dimethyl ammonium chloride and dimethyl benzyl ammonium chloride. Titanium dioxide might also be employed.

In one preferred embodiment, one or more mineral or stone type fillers such as calcium carbonate, sodium carbonate or the like may be used as fillers. In another *... 25 preferred embodiment, silicate minerals such as mica may be used as fillers. * a *a�.

When employed, the fillers in the foamable material can range from 10 % or less to % or greater by weight of the foamable material, but more typical from about 20 to % by weight of the foamable material. According to some embodiments, the foamable material may include from about 0 % to about 3 % by weight, and more *S**** * preferably slightly less that I % by weight clays or similar fillers. Powdered (e.g. about 0.01 to about 50, and more preferably about I to 25 micron mean particle diameter) mineral type filler can comprise between about 5 % and 70 % by weight, more preferably about 10 % to about 50% by weight.

Other Components and Additives It is contemplated that most nearly any additional chemicals, materials or otherwise may be added to the foamable material assuming they are suitable for the foamable material and suitable for a chosen application of the foamable material.

Other additives, agents or performance modifiers may also be included in the foamable material as desired, including but not limited to an antioxidant, a UV resistant agent, a flame retardant, an impact modifier, a heat stabilizer, a colorant, a processing aid, a lubricant, a reinforcement (e.g., chopped or continuous glass, ceramic, aramid, or carbon fiber, particulates or the like). Liquid polysufides may be used to improve the environmental exposure of the adhesive such as exposure to humidity and salt water.

When determining appropriate components for the foamable material, it may be important to form the material such that it will only foam at appropriate times or temperatures. For instance, in some applications, it is undesirable for the material to be reactive at room temperature or otherwise at the ambient temperature in a production environment. More typically, the foamable material becomes activated to flow at higher processing temperatures. As an example, temperatures such as those encountered in an automobile assembly plant may be appropriate, especially when the foamable material is processed along with the other components at elevated temperatures or at higher applied energy levels, e.g., during painting preparétion steps. Temperatures encountered in many coating operations (e.g., in a paint and/or e-coat curing oven), for instance, range up to about 250°C or higher. It may be * desirable that the material will also flow and cure at the foaming temperature and the *. 25 foamable material can be formulated accordingly. * * S...

Other materials that may be included depending on the function the foam is to perform are: 5.

An epoxy elastomer adduct S.....

* The epoxy elastomer adduct imports flexibility to the foam and the ability to initiate plastic deformation. Various epoxy/elastomer adducts may be employed in the present invention. The epoxy/elastomer hybrid or adduct may be included in an amount of up to about 50% by weight of the foamable material. The epoxy elastomer adduct is approximately at least 5%, more typically at least 7% and even more typically at least 10% by weight of the foamable material and more preferably about 5% to 20% by weight of the adduct based on the foamable material. The elastomer-containing adduct may be a combination of two or more particular adducts and the adducts may be solid adducts, liquid adducts or semi-solids at a temperature of 23°C or may also be combinations thereof. In one preferred embodiment, the adduct is composed of substantially entirely (i.e., at least 70%, 80%, 90% or more) of one or more adducts that are solid at a temperature of 23°C.

The adduct itself generally includes about 1:5 to 5:1 parts of epoxy to elastomer, and more preferably about 1:3 to 3:1 parts of epoxy to elastomer. More typically, the adduct includes at least about 10%, more typically at least about 20% and even more typically at least about 40% elastomer and also typically includes not greater than about 60%, although higher or lower percentages are possible. The elastomer compound suitable for the adduct may be a thermosetting elastomer, although not required. Exemplary elastomers include, without limitation, natural rubber, styrene-butadiene rubber, polyisoprene, polyisobutylene, polybutadiene, isoprene-butadiene copolymer, neoprene, nitrile rubber (e.g., a butyl nitrile, such as carboxy-terminated butyl nitrite), butyl rubber, polysulfide elastomer, acrylic elastomer, acrylonitrile elastomers, silicone rubber, polysiloxanes, polyester rubber, diisocyanate-linked condensation elastomer, EPDM (ethylene-propylene diene rubbers), chlorosulphonated polyethylene, fluorinated hydrocarbons and the like. In one embodiment, recycled tire rubber is employed. Examples of additional or alternative epoxy/elastomer or other adducts suitable for use in the present invention are disclosed in United States Patent Publication 2004/0204551.

* The elastomer-containing adduct is included to modify structural properties of the ** 25 foamable material such as strength, toughness, stiffness, flexural modulus, or the *S* S like. Additionally, the elastomer-containing adduct may be selected to render the activatable material more compatible with coatings such as water-borne paint or : primer system or other conventional coatings. S..

S

Core/shell polymers *1 5.15 * * As used herein, the term core/shell polymer denotes a polymeric material wherein a substantial portion (e.g., greater than 30%, 50%, 70% or more by weight) thereof is comprised of a first polymeric material (i.e., the first or core material) that is substantially entirely encapsu'ated by a second polymeric material (i.e., the second or shell material). The first and second polymeric materials, as used herein, can be comprised of one, two, three or more polymers that are combined and/or reacted together (e.g., sequentially polymerized) or may be part of separate or same core/shell systems. When used the core/shell polymer should be compatible with the formulation and preferably has a ductile core and a rigid shell which is compatible with the other components of the foamable material.

The first and second polymeric materials of the core/shell polymer can include elastomers, polymers, thermoplastics, copolymers, other components, combinations thereof or the like. In preferred embodiments, the first polymeric material, the second polymeric material or both include or are substantially entirely composed of (e.g., at least 70%, 80%, 90% or more by weight) one or more thermoplastics. Exemplary thermoplastics include, without limitation, styrenics, acrylonitriles, acrylates, acetates, polyamides, polyethylenes or the like.

Preferred core/shell polymers are formed by emulsion polymerization followed by coagulation or spray drying. It is also preferred for the core/shell polymer to be formed of or at least include a core-shell graft co-polymer. The first or core polymeric material of the graft copolymer preferably has a glass transition temperature substantially below (i.e., at least 10, 20, 40 or more degrees centigrade) the glass transition temperature of the second or shell polymeric material. Moreover, it may be desirable for the glass transition temperature of the first or core polymeric material to be below 23°C while the glass temperature of the second or shell polymeric material to be above 23°C, although not required.

Examples of useful core-shell graft copolymers are those where hard containing * compounds, such as styrene, acrylonitrile or methyl methacrylate, are grafted onto a *** 25 core made from polymers of soft or elastomeric compounds such as butadiene or S...

butyl acrylate. Untied States Patent No. 3,985,703, describes useful core-shell polymers, the cores of which are made from butyl acrylate but can be based on ethyl isobutyl, 2-ethylhexyl or other alkyl acrylates or mixtures thereof. The core polymer, *.* may also include other copolymerizable containing compounds, such as styrene, vinyl acetate, methyl methacrylate, butadiene, isoprene, or the like. The core polymer material may also include a cross linking monomer having two or more nonconjugated double bonds of approximately equal reactivity such as ethylene glycol diacrylate, butylene glycol dimethacrylate, and the like. The core polymer material may also include a graft linking monomer having two or more nonconjugated double bonds of unequal reactivity such as, for example, diallyl maleate and allyl methacrylate.

The shell portion is preferably polymerized from methyl acrylates such as methyl methacrylate and optionally other alkyl acrylates and methacrylates, such as ethyl, butyl, or mixtures thereof acrylates or methacrylates as these materials are compatible with the phenoxy resin and any epoxy resins that are used in the formulation. Up to 40 percent by weight or more of the shell monomers may be styrene, vinyl acetate, vinyl chloride, and the like. Additional core-shell graft copolymers useful in embodiments of the present invention are described in United States Patent Nos. 3984,497; 4,096,202; 4,034,013; 3,944,631; 4306,040; 4,495,324; 4,304,709; and 4,536,436. Examples of core-shell graft copolymers include, but are not limited to, "MBS" (methacrylate-butadiene-styrene) polymers, which are made by polymerizing methyl methacrylate in the presence of polybutadiene or a polybutadiene copolymer rubber. The MBS graft copolymer resin generally has a styrene butadiene rubber core and a shell of acrylic polymer or copolymer. Examples of other useful core-shell graft copolymer resins include, ABS (acrylonitrile-butadiene-styrene), MABS (methacrylate-acrylonitrile-butadiene- styrene), ASA (acrylate-styrene-acrylonitrile), all acrylics, SA EPDM (styrene-acrylonitrile grafted onto elastomeric backbones of ethylene-propylene diene monomer), MAS (methacrylic-acrylic rubber styrene), and the like and mixtures thereof.

Examples of useful core/shell polymers include, but are not limited to those sold under the tradename, PARALOID, commercially available from Rohm & Haas Co. One particularly preferred grade of PARALOID impact modifier has a polymethyl * ** methacrylate shell and an MBS core modifier and is sold under the designation EXL- 2650; the product E-950 solid by Akema may also be used with equal effectiveness. *.

*.*. When a core/shell polymer is used we prefer to use from 5% to 30% of the core shell polymer particularly when the foamable formulation is to be applied as a paste as higher amounts can lead to an undesirably high viscosity. S..

Curing Agent Depending upon the nature of the foam and its desired function one or more curing agents may be included in the foamable material used in this invention. Optionally curing agent accelerators may also be included. The amounts of curing agents and curing agent accelerators used can vary widely depending upon the type of foam desired, the desired structural properties of the foam and the like and the desired amount of expansion of the foamable material and the desired rate of expansion.

Exemplary ranges for the curing agents or curing agent accelerators present in the activatable material range from about 0.001% by weight to about 7% by weight.

Preferably, the curing agents assist the foamable material in curing by crosslinking of the polymers, particularly any phenoxy epoxy resins or both and any epoxy resin that may be present. It is also preferable for the curing agents to assist in thermosetting the foamable material. Useful classes of curing agents are materials selected from aliphatic or aromatic amines or their respective adducts, amidoamines, polyamides, cycloaliphatic amines, anhydrides, polycarboxylic polyesters, isocyanates, phenol-based resins (e.g., phenol or cresol novolak resins, copolymers such as those of phenol terpene, polyvinyl phenol, or bisphenol-A formaldehyde copolymers, bishydroxyphenyl alkanes or the like), or mixtures thereof. Particular preferred curing agents include modified and unmodified polyamines or polyamides such as triethylenetetramine, diethylenetriamine tetraethylenepentamine, cyanoguanidine, dicyandiamides and the like. If an accelerator for the curing agent is used examples of materials includes a modified or unmodified urea such as methylene diphenyl bis urea, an imidazole or a combination thereof.

Epoxy Resin The formulations of the present invention may include epoxy resins. Epoxy resin is used herein to mean any of the conventional dimeric, oligomeric or polymeric epoxy materials containing at least one epoxy functional group. It is preferred that the epoxy resin has an epoxy content of more than 40%. Moreover, the term epoxy resin * * can be used to denote one epoxy resin or a combination of multiple epoxy resins.

The polymer-based materials may be epoxy-containing materials having one or more **** oxirane rings polymerizable by a ring opening reaction. In preferred embodiments, the foamable material includes between about 2% and 75% by weight epoxy resin, more preferably between about 4% and 60% by weight epoxy resin and even more S..

preferably between about 25% and 50% by weight epoxy resin. Of course, amounts of epoxy resin may be greater or lower depending upon the intended application of the foamable material.

The epoxy may be aliphatic, cycloaliphatic, aromatic or the like. The epoxy may be supplied as a solid (e.g., as pellets, chunks, pieces or the like) or a liquid (e.g., an epoxy resin) although liquid resins are preferred to enhance processability of the adhesive formulation. As used herein, unless otherwise stated, a resin is a solid resin if it is solid at a temperature of 23°C and is a liquid resin if it is a liquid at 23°C.

The epoxy may include an ethylene copolymer or terpolymer.

An epoxy resin may be added to the foamable material to increase the adhesion, flow properties or both of the material. One exemplary epoxy resin may be a phenolic resin, which may be a novolac type or other type resin. Other preferred epoxy containing materials may include a bisphenol-A epichlorohydrin ether polymer, or a bisphenol-A epoxy resin which may be modified with butadiene or another polymeric additive or bisphenol-F-type epoxy resins. Moreover, various mixtures of several different epoxy resins may be employed as well. Examples of suitable epoxy resins are sold under the tradename Araldite GY 282, GY 281 and GY 285 supplied by 1-funtsman.

The invention is however particularly useful in the provision of foam to provide acoustic insulation. In this application high expansion soft foam is generally used and typically will not include epoxy resins and curing agents. The invention allows the formation of a large volume of foam and also to create an acoustic gap between the foam and component.

The optimum rib structure of the insulation device of the present invention will depend upon the size and the shape of the location where the insulation is to be provided. We prefer however that the rib structure is such that foamable material is provided at least 50% of the distance into the cavity and preferably at least 60% of the distance more preferably at least 75% of the distance into the cavity. The length 25 of the ribs allows one to optimize the size and structure of the foam and also of any S...

acoustic gap that may be required to be provided. *aS*

The present invention is particularly useful in the provision of sound insulation in vehicles and may be used to provide selective insulation which can absorb the high frequency sounds such as those generated by an engine without disruption the low frequency sounds such as those emitted by a radio or CD loudspeaker. Thus providing a simple way of filtering out undesirable noises. In a further embodiment the invention may be used to provide structures comprising two types of foam. For example a closed cell foam may be formed around the part to prevent water ingress and an open cell foam may be formed inside to absorb sound. Alternatively insulating foam may be formed around reinforcing foam and in this instance the ribs themselves may be of a foamable material such as an epoxy based material.

The invention is illustrated by reference to the accompanying drawings in which Figure 1 shows a carrier for a foamable material that can be used to provide sound insulation in a vehicle.

Figure 2 is a view through cross section A-A of Figure 1 and showing how the foamable material is provided on the ribs of the carrier of Figure 1.

Figure 3 is a further illustration of how foamable material may be carried on the ribs of a carrier.

Figure 4 shows the structure of Figure 3 after the foamable material has been foamed.

Figure 5 shows the ribbed structures of Figure 3 provided with foamable material at different locations.

Figure 6 shows the structure of Figure 5 after the foamable material has been foamed.

Figure 7 shows the carrier similar to that illustrated in Figures 1 and 2 after the foamable material has been foamed. * **

Figure 8 shows how two different types of foamable material may be provided and S.. S * S **S.

*:::: Figure 9 shows how two foams may be provided from the structure of Figure 8. *S.

Figure 1 shows an oval carrier (1) having a hollow section (2), a surround (3) and provided with ribs (4), (5), (6) and (7).

Figure 2 is a cross section through A-A of Figure 1 showing how foamable material (8) can be provided on the ribs and also on projections (9) and (10) provided on the side of the carrier.

Figure 3 further illustrates how foamable material (8) can be provided on both a carrier (11) and ribs (12), (13) and (14) extending from the carrier. Figure 4 shows the structure illustrated in Figure 3 after the foamable material (8) has been foamed to produce foam (15).

Figure 5 shows an alternative method of providing foamable material (8) on the ribbed carrier of Figure 3 and Figure 6 illustrates how the use of the ribs allows the position of the foam (15) to be controlled and to provide acoustic cavities (16) and (17).

Figure 7 shows a carrier covered with foam (18) and provided with ribs (19), (20), (21, (22) and (23) also provided with foam (18).

Figure 8 shows a ribbed carrier similar to that shown in Figure 3 provided with two types of foamable material, one (8) on the ribs and the other (24) on the carrier.

Figure 9 shows how the foamable materials of Figure 8 can be foamed to provide two different foams (18) and (25).

The invention is particularly useful for the provision of sound insulation in transport vehicles particularly for the provision of insulation in large cavities in automobiles, busses, trucks, trains and aircraft. It is however envisaged that the invention will find use in other industries such as the construction and furniture industries. * S. * . . * ** S... * * S... *0** * * S S. S

S S..

S

*.SSSS * S

Claims

CLAIMS1. A system for the provision of foam structures within a cavity comprising a foamable material on a carrier provided with ribs wherein at least some parts of the ribs carry the foamable material the ribs being adapted so that when the carrier is assembled in the cavity they extend into the cavity.
2. A system according to claim I in which the foamable material is a heat activated material.
3. A system according to claim 1 or claim 2 in which the foamable material is formulated so that it will foam at temperatures employed in vehicle assembly such as in the paint bake or e-coat bake ovens.
4. A system according to any of the preceding claims in which the carrier is of material that has a high thermal conductivity.
5. A system according to claim 4 in which the carrier is made from metal.
6. A system according to any of claims 1 to 4 in which the carrier is formed from thermoplastic material by blow moulding, extrusion or injection moulding.
7. A system according to any of the preceding claims in which the degree of * ** expansion of the foamable material is in the range 200% to 3000%. * * I I.
8. A system according to claim 7 in which the degree of expansion is in the range 200% to 2500%.I S..
9. The use of a system according to any of the preceding claims for the provision of foam to provide acoustic insulation.
10. The use according to claim 9 in which the foam is a high expansion soft foam.