APPLICATION OF ADHESIVES

Abstract

Applying heat activatable adhesive to a substrate, the adhesive is solid at ambient temperature and can be melted at a temperature below its heat activation temperature wherein the adhesive formulation is supplied to a hot melt applicator where it is heated to above its melting point and below its activation temperature and the melt viscosity of the molten adhesive is controlled so that it can be ejected from the hot melt applicator onto a substrate to provide a coherent bead that adheres to the substrate and is dry to the touch on cooling and upon activation the adhesive is capable of expanding with a volume expansion greater than about 250%.

Claims

1. A process for the application of a heat activatable adhesive to a substrate, wherein the heat activatable adhesive is solid at ambient temperature and can be melted at a temperature below its heat activation temperature, wherein a particulate heat activatable adhesive formulation is supplied to a hot melt applicator, wherein the heat activatable adhesive is heated to above its melting point and below its activation temperature, wherein the melt viscosity of the molten adhesive is controlled whereby the molten adhesive is ejected from the hot melt applicator onto a substrate to provide a coherent bead that adheres to the substrate and is dry to the touch on cooling and wherein upon activation the adhesive is capable of expansion when heated with a volume expansion greater than about 250%.

2. The process according to claim 2, wherein the hot melt applicator is a hand held hot melt gun.

3. The process according to claim 1 or 2, wherein the hot melt applicator is equipped with a nozzle having a diameter of about 2 mm to about 8 mm.

4. The process according to claim 1, wherein the heat activatable adhesive is heated to a temperature within the range of about 90 C. to about 115 C.

5-9. (canceled)

10. The process according to claim 1, wherein the molten adhesive is applied to the substrate at an angle of application within the range of about 45 to about 90.

11. The process according to claim 4, wherein the adhesive is thermohardenable and hardening is caused by the activation of a heat activatable curing agent within the adhesive formulation.

12. The process according to claim 1 for the provisions of a pattern or array or a continuous bead of a thermoactivatable material on a substrate for subsequent activation.

13. The process according to claim 4, wherein the coherent bead that adheres to the substrate is subsequently activated at a temperature in the range of about 80 C. to about 150 C. thereby expanding the heated adhesive with a volume expansion greater than about 250%.

14. The process according to claim 4, wherein the coherent bead that adheres to the substrate is subsequently activated at a temperature in the range of about 150 C. to about 220 C. thereby expanding the heated adhesive with a volume expansion greater than about 250%.

15. The process according to claim 1, wherein the adhesive formulation is in the form of a powder with an average particle size of from about 20 .Math. to about 250 .Math..

16. The process according to claim 4, wherein the adhesive formulation is in the form of micro-pellets with an average particle size of from about 250 .Math. to about 1000 .Math..

17. The process according to claim 4, wherein the adhesive formulation is in the form of pellets with an average particle size of from about 1000 .Math. to about 6000 .Math..

18-19. (canceled)

20. The process according to claim 1, wherein the adhesive formulation contains a blowing agent selected from chemical blowing agents and physical blowing agents.

21-24. (canceled)

25. The process according to claim 1 in which the hot melt applicator comprises a barrel that is set at a temperature in the range of about 85 C. to about 115 C. and a pressure of from about 2 bars to about 8 bars, preferably about 5 bars to about 7 bars, such that the molten adhesive is delivered from the hot melt applicator onto a substrate.

26. The process according to claim 1, wherein the adhesive formulation has a viscosity at 100 C. with a shear rate of 100 s.sup.1 in the range of about 50 Pa-s to about 500 Pa-s and with a shear rate of 0.1 s.sup.1 in the range of about 1000 Pa-s to about 10,000 Pa-s.

27. The process according to claim 1, wherein the adhesive formulation contains a base resin with a narrow molecular weight distribution such that 70% of the polymers in the base resin are within 10,000 atomic mass units (amu) of each other.

28. The process according to claim 1, wherein the melt viscosity of the adhesive formulation is controlled by the use of polymers together with one or more cross linking agents which are activated at temperatures within the hot melt applicator to control the melt viscosity.

29-30. (canceled)

31. A particulate heat activatable adhesive formulation, which is solid at ambient temperature and can be melted at a temperature below its heat activation temperature, for providing a coherent bead of the adhesive onto a substrate by means of a hot melt applicator, wherein the coherent bead adheres to the substrate and is dry to the touch on cooling and wherein upon activation the adhesive is capable of expansion when heated with a volume expansion greater than about 250%, wherein the particulate heat activatable adhesive formulation comprises (i) one or more copolymer of ethylene and butyl acrylate, wherein the relative content of butyl acrylate is preferably within the range of from about 20 wt % to about 50 wt %; (ii) one or more copolymer of ethylene and vinyl acetate, wherein the relative content of vinyl acetate is preferably within the range of from about 15 wt % to about 45 wt %; and (iii) one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate; and (iv) optionally, one or more reactive hydroxylated polyester resin.

32. The adhesive formulation according to claim 31, wherein (i) the overall content of said one or more copolymer of ethylene and butyl acrylate is within the range of from about 20 wt % to about 60 wt %, relative to the total weight of the adhesive formulation; and/or (ii) the overall content of said copolymer of ethylene and vinyl acetate is within the range of from about 2.0 wt % to about 20 wt %, relative to the total weight of the adhesive formulation; and/or (iii) the overall content of said one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate is within the range of from about 1.0 wt % to about 10 wt %; and/or (iv) the overall content of said optionally present one or more reactive hydroxylated polyester resin is within the range of from about 2.0 wt % to about 20 wt %, relative to the total weight of the adhesive formulation.

33. The adhesive formulation according to claim 31, which is in the form of a powder with an average particle size of from about 20 .Math. to about 6000 .Math..

34-45. (canceled)

Description

[0033] We have found that the inclusion of a base resin with a narrow molecular weight distribution is preferably included in the formulation for achieving these desired viscometrics. The molecular weight distribution is preferably such that about 70% of the polymers in the base resin are within about 10,000 atomic mass units (amu) of each other, more preferably about 80% of the polymers in the base resin are within about 5000 amu of each other and even more preferably about 90% of the polymers are within about 1000 amu of each other. Preferably, the base resin comprises about 50 wt % to about 100 wt % of the material or of the polymeric constituents of the material, and more preferably about 60 wt % to about 90 wt % of the material or of the polymeric constituents of the material, relative to the total weight of the base resin.

[0034] In a preferred adhesive formulation for use in this invention to produce foamed seals and sound insulating baffles the desired melt viscosity of the formulation is achieved by the use of polymers together with cross linking agents which are activated at temperatures within the gun to control the melt viscosity. In particular we prefer to use ethylene copolymers with polar comonomers such as ethylene vinyl acetate copolymers or ethylene acrylate copolymers such as ethylene butyl acrylate copolymers.

[0035] We prefer to use copolymers with a high content of ester comonomer such as copolymers containing from about 25 wt % to about 50 wt % comonomer, more preferably from about 30 wt % to about 46 wt % comonomer and also which melt at a temperature in the range of about 60 C. to about 85 C., preferably about 60 C. to about 75 C.

[0036] In a preferred embodiment, the adhesive formulation according to the invention comprises a reactive elastomeric terpolymer of ethylene with a first comonomer selected from alkyl acrylates and alkyl methacrylates, and with a second comonomer selected from glycidyl acrylate and glycidyl methacrylate. Preferably, the content of said reactive elastomeric ethylene terpolymer is within the range of from about 1.0 wt % to about 10 wt %, more preferably about 2.0 wt % to about 8.0 wt %, and most preferably about 3.0 wt % to about 6.0 wt %, relative to the total weight of the adhesive formulation.

[0037] In a particularly preferred embodiment, the adhesive formulation according to the invention comprises a terpolymer of ethylene/butyl acrylate/glycidyl methacrylate (reactive elastomeric ethylene terpolymer).

[0038] In preferred embodiments, the adhesive formulation that is delivered according to the invention comprises [0039] (i) one or more copolymer of ethylene and butyl acrylate, wherein the relative content of butyl acrylate is preferably within the range of from about 20 wt % to about 50 wt %, more preferably about 25 wt % to about 45 wt %, still more preferably about 30 wt % to about 40 wt %, relative to the total weight of the copolymer of ethylene and butyl acrylate; and wherein the overall content of said one or more copolymer of ethylene and butyl acrylate is preferably within the range of from about 20 wt % to about 60 wt %, more preferably about 25 wt % to about 55 wt %, and most preferably about 28 wt % to about 50 wt %, relative to the total weight of the adhesive formulation; and/or [0040] (ii) one or more copolymer of ethylene and vinyl acetate, wherein the relative content of vinyl acetate is preferably within the range of from about 15 wt % to about 45 wt %, more preferably about 20 wt % to about 40 wt %, still more preferably about 25 wt % to about 35 wt %, relative to the total weight of the copolymer of ethylene and vinyl acetate; and wherein the overall content of said one or more copolymer of ethylene and vinyl acetate is preferably within the range of from about 2.0 wt % to about 20 wt %, more preferably about 5.0 wt % to about 15 wt %, and most preferably about 8.0 wt % to about 13 wt %, relative to the total weight of the adhesive formulation; and/or [0041] (iii) one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate, wherein the overall content of said one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate is preferably within the range of from about 1.0 wt % to about 10 wt %, more preferably about 2.0 wt % to about 8.0 wt %, and most preferably about 3.0 wt % to about 6.0 wt %, relative to the total weight of the adhesive formulation; and/or [0042] (iv) one or more reactive hydroxylated polyester resin; wherein the overall content of said one or more reactive hydroxylated polyester resin is preferably within the range of from about 2.0 wt % to about 20 wt %, more preferably about 5.0 wt % to about 12 wt %, and most preferably about 6.0 wt % to about 11 wt %, relative to the total weight of the adhesive formulation.

[0043] Cross linking agents such as peroxides are also included to control melt viscosity and the sagging (undesirable melt flow) of the polymers as they are applied to the substrate in the melt. We prefer to include from about 1 wt % to about 5 wt % of peroxide cross linking agent based on the weight of ethylene copolymers in the formulation.

[0044] In a preferred embodiment, the adhesive formulation according to the invention neither contains ehylene/acrylic acid copolymers nor divinylbenzene/butadiene copolymers.

[0045] In one embodiment, the formulation includes one or more solubilizing agents, which assist the delivered molten material in solubilizing contaminants on a substrate surface. Examples of such solubilizing agents include hydrocarbons (e.g., hydrocarbon process oils), phthalate plasticizers, liquid polyolefins or the like. Preferably, when used, such solubilizing agents are between about 1 wt % and about 30 wt % of the flowable material, more preferably between about 5 wt % and about 20 wt % of the flowable material.

[0046] In another embodiment, the formulation may include one or more polar components, which can aid in adhesion of the material to the substrate. Preferably, such components have relatively low melting points (e.g., between about 50 C. and about 100 C.). Examples of such components include oxidized or otherwise functionalized waxes, petroleum resins, resin esters or combinations thereof. Preferably, when used, such polar components are between about 1 wt % and about 30 wt % of the formulation, more preferably between about 2 wt % and about 15 wt % of the formulation.

[0047] In still another embodiment, the formulation includes one or more components such as waxes that are modified with an adhesion promoter such as an acid anhydride group. Preferably, when used, such modified components are about 1 wt % and about 30 wt % of the flowable material, more preferably between about 5 wt % and about 20 wt % of the flowable material.

[0048] All the adhesive formulations to which this invention is applicable may also include one or more fillers, including but not limited to particulated materials (e.g., powder), beads, microspheres, or the like. The precursor layer may also be substantially free of any filler material. Fillers can be useful to reduce any blocking tendency of the unfoamed adhesive powder, reduce cost, and reduce the coefficient of thermal expansion of the activated material. The precursor layer may include a filler that comprises less than about 25 wt % of the precursor material. Ideally, the filler may comprise less than about 2.5 wt % of the precursor layer. Any filler present may include a material that is generally non-reactive with the other components present in the precursor layer. Certain fillers can also reduce the tendency of the particles to agglomerate as well as reducing the blocking tendency.

[0049] Examples of suitable fillers include silica, diatomaceous earth, glass, clay (e.g., including nanoclay), talc, pigments, colorants, glass beads or bubbles, glass, carbon or ceramic fibers, nylon aramid or polyamide fibers (e.g., Kevlar), antioxidants, and the like. Such fillers, particularly clays, can assist the activatable 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.

[0050] In one embodiment it is preferred to include a thixotropic filler such as aramid fibre or certain clays in the adhesive formulation used in this invention. The inclusion of such a thixotropic filler can reduce the tendency of the adhesive formulation to flow and sag when it is a fluid state or when it is heated to the activation temperature.

[0051] The adhesive formulations that are delivered according to the present invention may be foamable and they may contain a heat activatable blowing agent for example one that decomposes to produce gas at temperatures above the melt application temperature such as temperatures experienced in the automotive anticorrosion coating bake oven. Typically temperatures are in the range of about 150 C. to about 220 C. (typical bodyshop bakes) or in the range of about 80 C. to about 150 C. (typical paintshop bakes). The blowing agent is compatible with the other components and capable of expanding or decomposing on heating, such as when the formulation is activated, in order to lower the density of the final material. A blowing agent accelerator which reduces the temperature at which gas is liberated by the blowing agent may also be included. Zinc oxide is an example of a suitable blowing agent accelerator.

[0052] Examples of suitable blowing agents include chemical blowing agents (e.g., those agents that provide for material expansion via a chemical reaction) comprising but not limited to azo compounds, such as azodicarbonamide, azodiisobutyro-nitrile, barium azodicarboxylate; nitroso compounds such as N,N-dimethyl-N,N-dinitrosoterephthalamide, dinitrosopentamethylenetetramine; hydrazides such as benzenesulfonhydrazide, p,p-oxybis (benzenesulfonylhydrazide), trihydrazinotriazine; carbazides, such as 4,4-oxybenzene sulfonyl semicarbazide, p-toluene sulfonyl semicarbazide; triazines such as trihydrazino triazine; and reactive couples such as mixtures of citric acid and sodium bicarbonate. Such materials may be used singly or in combinations of two or more thereof. Suitable commercially available blowing agents include products sold under the names HYDROCEROL (from Boehringer Ingelheim), CELOGEN OT, AZ, AZNP, and RA (from Crompton), FICEL, GENITRON and PLANAGEN (from Bayer), and SAFOAM FP, RPC and RIC FP (from Reed International Corporation). Preferred blowing agents are p,p-oxybis(benzenesulfonylhydrazide) (for example, CELOGEN OT) and azodicarbonamide (for example, CELOGEN AZ).

[0053] The blowing agent may also be a physical blowing agent, such that material expansion occurs via a phase change mechanism. Physical blowing agents can comprise a volatile gas trapped in a thermoplastic shell which softens and lets the gas expand at the foaming temperature. An example of such a blowing agent in sold under the trade name Expancel, sold by Akzo Nobel, Sundsvall, Sweden.

[0054] When a cross linking agent is included to cross link the foam the blowing agent may be selected to generate gases for foaming at around the activation temperature of the cross linking agent. It is preferred that the crosslinking agent will cure the adhesive during foam formation so that the molten formulation is sufficiently viscous to entrap the gas produced by the decomposition of the blowing agent. When the formulations to produce soft foams useful for seals and sound transmission barriers they should contain sufficient blowing agent to cause the desired degree of expansion (greater than about 250%) in the time and at the temperature to which the material is exposed, for example in the automotive anticorrosion coating bake oven.

[0055] The hand held melt applicator used in this invention may be any well known hand held devices such as a pump action or pressure applicator in which the adhesive formulation is converted into a flowable state within the applicator and expelled from the applicator onto the substrate to deliver an adhesive layer on the substrate. The adhesive layer may be continuous or discontinuous and may be in a predetermined pattern. We have found that the invention allows the heat activatable adhesive to be readily applied by hand to provide an accurate deposit, such as a continuous or discontinuous bead of a heat activatable adhesive on the substrate which may be subsequently activated at elevated temperature and is not tacky to the touch at ambient temperature upon cooling after delivery.

[0056] The present invention is particularly useful in providing adhesives in the automobile, aircraft and furniture industries particularly in automotive body repair shops and in low volume assembly lines such as in the manufacture of trucks and busses.

[0057] If necessary the substrate may be cooled when the adhesive is being applied. Cooling may enhance the bond between the adhesive and the substrate and it may also reduce the likelihood of premature activation of the adhesive. Although we have found that generally this is not necessary. Alternatively, the substrate may be heated.

[0058] In a preferred embodiment, the surface of the substrate is pretreated prior to application of the adhesive formulation according to the invention. Pollution of the surface can be reduced when the material, e.g. the metal, is cold. Oily surfaces are preferably degreased chemically and/or physically. The surface may be equipped with primers or adhesion promoters, although less preferred.

[0059] In another preferred embodiment, the surface of the substrate is preheated and the adhesive formulation is applied without additional surface preparation. The preheating may be performed by means of conventional heating equipment including but not limited to IR lamps, hot air blow systems, heat resistance, plasma, and the like. After preheating of the surface of substrate, it may allow to cool down to ambient temperature or alternatively, the adhesive formulation may be applied to the surface of the substrate at elevated temperature of the surface of the substrate.

[0060] In a preferred embodiment, the substrate is a metal substrate or comprises metal. Preferably, the metal comprises steel, aluminum, and/or magnesium.

[0061] In a preferred embodiment, the substrate comprises a polymer and/or a composite material. Preferably, the polymer and/or composite material is selected from the group consisting of polyamides, fiber reinforced plastics (FRP), thermosets, bulk molding compounds (BMC), sheet molding compounds (SMC), and prepregs.

[0062] Preferably, the substrate has ambient temperature.

[0063] Preferably, the molten adhesive is applied to the substrate at an angle of application within the range of about 45 to about 90.

[0064] The adhesive formulation may be delivered in several stages so that the thickness of the activation layer adhesive is increased. The hand held delivery may be repeated in one or more specific areas of the substrate so that the thickness of the film of activatable adhesive is increased in the one or more specific areas. Alternatively, a second composition can be applied to the first composition. This could be of interest for example to tailor the adhesive for maximum performance should two different substrates be bonded. Additionally the adhesive can be applied to selected areas of the substrate. The adhesive formulation is preferably storage stable for at least six months, more preferably at least one year.

[0065] The present invention may be used to apply adhesives to any substrate and may be used for the bonding together of a range of substrates. For example the adhesive may be used to bond together metal substrates such as in vehicle manufacture. It may be used in the bonding of different substrates such as the bonding of metal to fiber reinforced composites.

[0066] Another aspect of the invention relates to a particulate heat activatable adhesive formulation according to the invention as described above, which is solid at ambient temperature and can be melted at a temperature below its heat activation temperature, for providing a coherent bead of the adhesive onto a substrate by means of a hot melt applicator, wherein the coherent bead adheres to the substrate and is dry to the touch on cooling, and preferably wherein upon activation the adhesive is capable of expansion when heated with a volume expansion greater than 250%, wherein the adhesive formulation according to the invention comprises [0067] (i) one or more copolymer of ethylene and butyl acrylate, wherein the relative content of butyl acrylate is within the range of from about 20 wt % to about 50 wt %, more preferably about 25 wt % to about 45 wt %, still more preferably about 30 wt % to about 40 wt %, relative to the total weight of the copolymer of ethylene and butyl acrylate; and wherein the overall content of said one or more copolymer of ethylene and butyl acrylate is preferably within the range of from about 20 wt % to about 60 wt %, more preferably about 25 wt % to about 55 wt %, and most preferably about 28 wt % to about 50 wt %, relative to the total weight of the adhesive formulation; [0068] (ii) one or more copolymer of ethylene and vinyl acetate, wherein the relative content of vinyl acetate is within the range of from about 15 wt % to about 45 wt %, more preferably about 20 wt % to about 40 wt %, still more preferably about 25 wt % to about 35 wt %, relative to the total weight of the copolymer of ethylene and vinyl acetate; and wherein the overall content of said one or more copolymer of ethylene and vinyl acetate is preferably within the range of from about 2.0 wt % to about 20 wt %, more preferably about 5.0 wt % to about 15 wt %, and most preferably about 8.0 wt % to about 13 wt %, relative to the total weight of the adhesive formulation; and [0069] (iii) one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate, wherein the overall content of said one or more terpolymer of ethylene/butyl acrylate/glycidyl methacrylate is preferably within the range of from about 1.0 wt % to about 10 wt %, more preferably about 2.0 wt % to about 8.0 wt %, and most preferably about 3.0 wt % to about 6.0 wt %, relative to the total weight of the adhesive formulation; and [0070] (iv) optionally, one or more reactive hydroxylated polyester resin; wherein the overall content of said one or more reactive hydroxylated polyester resin is preferably within the range of from about 2.0 wt % to about 20 wt %, more preferably about 5.0 wt % to about 12 wt %, and most preferably about 6.0 wt % to about 11 wt %, relative to the total weight of the adhesive formulation.

[0071] All preferred embodiments that have been described above in relation to the process according to the invention analogously apply to the adhesive formulation according to the invention and thus are not repeated hereinafter.

[0072] Another aspect of the invention relates to the use of the particulate heat activatable adhesive formulation according to the invention as described above, which is solid at ambient temperature and can be melted at a temperature below its heat activation temperature, for providing a coherent bead of the adhesive onto a substrate by means of a hot melt applicator, wherein the coherent bead adheres to the substrate and is dry to the touch on cooling, and preferably wherein upon activation the adhesive is capable of expansion when heated with a volume expansion greater than 250%. Preferably, the particulate heat activatable adhesive formulation according to the invention is used in the process according to the invention as described above.

[0073] All preferred embodiments that have been described above in relation to the particulate heat activatable adhesive formulation according to the invention and the process according to the invention, respectively, analogously apply to the use according to the invention and thus are not repeated hereinafter.

[0074] Another aspect of the invention relates to a cartridge for a hot melt applicator, preferably a hand held hot melt gun, which cartridge comprises the adhesive formulation according to the invention.

[0075] Another aspect of the invention relates to a substrate comprising at its surface a coherent bead of the adhesive formulation (melted and subsequently congealed adhesive material) that adheres to the substrate and is dry to the touch on cooling and wherein upon activation the adhesive is capable of expansion when heated with a volume expansion greater than about 250%.

[0076] Another aspect of the invention relates to a substrate comprising at its surface an expanded, i.e. heat activated adhesive material according to the invention.

[0077] All preferred embodiments that have been described above in relation to the process according to the invention, the particulate heat activatable adhesive formulation according to the invention, and its use according to the invention, analogously apply to the cartridge and the substrates according to the invention and thus are not repeated hereinafter.

[0078] The invention is illustrated by reference to the following Example.

[0079] A formulation suitable for the production of soft foam seals and sound barriers and comprising the following materials:

TABLE-US-00001 wt % random copolymer of ethylene and butyl acrylate (35 wt %) 20 to 35 random copolymer of ethylene and butyl acrylate (35 wt %) 8 to 15 copolymer of ethylene and vinyl acetate (28 wt %) 8 to 13 reactive elastomeric ethylene terpolymer 3 to 6 reactive hydroxylated polyester resin 6 to 11 hydrocarbon resin 7 to 10 filler 10 to 20 peroxide crosslinking agent 0.7 to 1.6 benzoyl peroxide 0.4 to 1 dipentaerythritol pentaacrylate (curing agent) 0.5 to 1.8 azodicarbonic acid diamide preparation (blowing agent) 3 to 5 blowing agent accelerator 1.5 to 3 100.00
was blended and pelletized. The pellets were fed to a hand held hot melt gun such as shown in FIG. 1. The melt temperature of the gun was set at 100 C.

[0080] The polymers have a high ester co monomers (vinyl acetate or butyl acrylate) content to provide polymers with a low melt temperature and good adhesion properties (high polarity).

[0081] The use of the peroxide cross linking agent controls the sagging behavior of the formulation (low viscosity and low T.sub.melt polymers), and also controls the crosslinking density and reactivity of the formulation.

[0082] The material (1) was fed to the barrel (2) of the hot melt gun provided with a handle (4). It was then delivered from the nozzle (3) of the hot melt gun (1) onto a surface (5) as a continuous bead (6) by applying pressure from the plunger (7) as is shown in FIG. 2. The bead was dry to the touch on cooling. The material could be foamed by as much as 1000% in the automobile e-coat oven where it is heated to about 150 C. for about 30 minutes.