CONFORMABLE ISOLATION TAPE

Abstract: A method of noise control in which a conformable sheet material formed from an extensible web and an adhesive is inserted between components to prevent, reduce, or eliminate noise produced by the components is provided. A conformable sheet material suitable for use in this method is also provided.

Description: CONFORMABLE ISOLATION TAPE FIELD OF THE INVENTION This invention relates to a pressure sensitive adhesive tape for cushioning adjacent components to reduce the noise caused by the surfaces of the components rubbing together. BACKGROUND OF THE INVENTION There are many industrial and automotive applications where components are assembled in close proximity to each other such that when the components are subjected to vibrations, they create annoying noises such as rattles and squeaks as the components rub against each other. Products that are currently available on the market to reduce or suppress these noises include felt, flocked cloth, velvet, and velour which may have a layer of a pressure sensitive adhesive. These materials find limited use in that all of these materials are relatively thick and do not conform to irregularly shaped surfaces because the materials are not extensible enough. There remains a need for a conformable tape which can be applied between components to suppress noises caused by vibration of the components. SUMMARY OF THE INVENTION The present invention provides a method of noise control comprising inserting between components a conformable sheet material comprising an extensible web and an adhesive on at least one face of said web so that noise produced by the components is prevented, reduced, or eliminated. The adhesive comprises the polymerization reaction product of starting materials comprising: (a) a polymerizable component comprising at least one acrylic acid ester of a nontertiary alcohol, wherein the alkyl group of said alcohol contains from 1 to about 14 carbon atoms and (b) a reinforcing comonomer. The present invention also provides a conformable sheet material comprising a nonwoven web and an adhesive on at least one face of said web. The adhesive comprises the polymerization reaction product of starting materials comprising a polymerizable component comprising: (a) at least one acrylic acid ester of a nontertiary alcohol, wherein the alkyl group of said alcohol contains from about 4 to about 14 carbon atoms, (b) acrylic acid, (c) at least one free radical initiator, and (d) a crosslinking agent. The weight ratio of acrylic acid ester to acrylic acid is from 91:9 to 96:4. The nonwoven web comprises thermoplastic elastomeric melt blown small diameter fibers having a diameter of less than about 50 microns, the thermoplastic elastomeric small diameter fibers being selected from elastomeric polyurethanes, elastomeric polyesters, elastomeric polyamides, elastomeric copolymers of ethylene and at least one vinyl monomer, elastomeric copolymers of ethylene and at least one urethane, or elastomeric A-B-A' block copolymers, wherein A and A' are the same or different thermoplastic polymer and wherein B is an elastomeric polymer block. The sheet material prevents, reduces, or eliminates noise when placed between components. DETAILED DESCRIPTION In a preferred embodiment of the invention, a conformable sheet material, having sufficient extensibility of the sheet to follow the contours of the surface and sufficient adhesive force to keep the sheet adhered tightly to the surface and resist any debonding that may occur as recovery of the sheet occurs, is applied over a curved or irregularly shaped surface of a first component. A second component is then assembled adjacent to the first component such that the sheet material prevents the surface of the first component from contacting the surface of the second component when the components are subjected to vibration, and any noises that would be caused from rubbing of the first component on the second component are prevented, eliminated, or reduced. As used herein, conformable refers to a sheet material which can be stretched or extended so that the sheet closely follows the contours of a curved or an irregularly shaped surface. The sheet material useful in the practice of the invention includes an extensible web having a pressure sensitive adhesive on at least one major surface of the web. The term extensible, as used herein, is synonymous with stretchable, and refers to a web which can be stretched or elongated at least 5% under a force of about 1.2 Newtons/100 mm, e.g., a 10.0 cm long sheet can be stretched to at least 10.5 cm. The amount of stretch that is useful depends upon the shape of the surface to be covered. A surface with large smooth curves will require less stretch for a sheet material to conform well, e.g. , about 5% to 10% stretch. For surfaces having small irregularities and intricate contours, the web can be stretched to at least 30%, and preferably, to greater than 100%, and more preferably greater than 200%. The preferred sheet material is also elastic. As used herein, elastic refers to the ability of a material to be stretched or extended, and to recover to a length less than the stretched length when the force to stretch the material is released. A preferred elastic material will have a percent recovery of at least 10%, e.g., when a 10.0 cm long web is stretched 50% to a length of 15 cm and released, the web will recover to a length less than 14.5 cm. More preferably, the material will have a percent recovery of at least 25%, and most preferably, at least 80%. Webs useful in the practice of the invention include extensible woven fabrics, elastic woven fabrics such as those sold under the tradenames of Lycra and Spandex, extensible nonwoven fabrics, elastic nonwoven fabrics, extensible films, elastic films such as polyurethane films, and the like. In the practice of the invention, the elastic web is preferably a nonwoven web having a basis weight of about 80 to 150 grams per square meter and an elongation at break of at least 250%, and more preferably, more than 300%. It is also desirable to have a tensile strength sufficient to allow the sheet material to be unwound from a roll and applied to the surface without breaking. The nonwoven web is formed from elastomeric thermoplastic materials that can be formed into elastomeric microfibers having a fiber diameter greater than 1 micron and less than about 50 microns. Preferably, the fiber diameters range from about 2 to 30 microns, and most preferably, from about 3 to 15 microns. Elastomeric thermoplastic materials that are suitable in forming the fibers of the nonwoven of the invention include elastomeric polyurethanes, elastomeric polyesters, elastomeric polyamides, elastomeric copolymers of ethylene and at least one vinyl monomer, elastomeric copolymers of ethylene and at least one urethane monomer, and elastomeric A-B-A' block copolymers wherein A and A' are the same or different thermoplastic polymer blocks and B is an elastomeric polymer block. Typically, A and A' are styrenic moieties, and B can be polyisoprene, polybutadiene, and the like. The elastomeric polyesters and elastomeric polyamides include co- polyesters (such as polyetherester) and co-polyamides. The nonwoven web may include non-elaεtomeric fibers made from materials including polyethylene, polyester, or polypropylene. The non-elastomeric material may also be co-extruded with an elastomeric material to form a bi-component or layered fiber. A bi-component fiber may include from 0 to about 70 percent, and preferably about 50 to 70 percent, non- elastomeric material. The fibers of the nonwoven web may further include fillers, dyes, pigments, and the like, in suitable amounts as long as they do not deleteriously affect the desired properties of the nonwoven web. Suitable methods of making the nonwoven webs by a melt blown process are described by Wente, Van A., "Superfine Thermoplastic Fibers" in Industrial Engineering Chemistry, Vol. 48, pages 1342 et seq (1956) , or in Report No. 4364 of the Naval Research Laboratories, published May 25, 1954, entitled "Manufacture of Superfine Organic Fibers" by Wente, Van A., Boone, CD., and Fluharty, E.L., except that a drilled die is preferably used. The thermoplastic elastomeric materials are extruded through the die into a high velocity stream of heated air which draws out and attenuates the fibers prior to their solidification and collection. The fibers are collected in random fashion, such as on a perforated screen cylinder, prior to complete fiber solidification so that the fibers are able to bond to one another to form a coherent web without the use of additional binders. The fibers may be blown directly onto an adhesive film on a carrier web to form the sheet. Nonwoven webs may also be formed by processes known in the art including air laying, spunbonding, spunlace, stitchbonding, and needle punching. The nonwoven webs may be coated with adhesive by any known process including laminating to a transfer tape, roll coating or knife coating the adhesive onto the nonwoven, and spraying the adhesive onto the nonwoven. The preferred adhesives in the practice of the invention include tackified cross-linked acrylate adhesives. Such acrylate adhesives are the polymerization reaction products of one or more monofunctional methacrylic or acrylic acid esters of non-tertiary alcohols having from 1 to 14 carbon atoms and a reinforcing comonomer. Preferably, the esters have from 4 to 14 carbon atoms. Examples of suitable acrylic acid esters include 2-ethylhexyl acrylate, n- butyl acrylate, isooctyl acrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, hexyl acrylate, and mixtures thereof. Preferred acrylates include isooctyl acrylate. The reinforcing comonomer is a monomer having a higher homopolymer glass transition temperature than the acrylate homopolymer. Suitable monomers include acrylic acid. The ratio of acrylate monomers to comonomers can range from about 60 to 99 parts by weight acrylate per one hundred parts of polymer and the comonomers can range from about 40 to 1 parts. When acrylic acid is used as the comonomer, the ratio of acrylate monomers to comonomers is preferably in the range of 88 to 99 parts acrylate and 12 to 1 parts comonomer. In a highly preferred embodiment, the acrylate is used in an amount from greater than 90 to less than 97 parts by weight per one hundred parts of acrylate and comonomer and the comonomer is used in an amount of from less than 10 to greater than 3 parts by weight per one hundred parts of acrylate and comonomer. The pressure sensitive adhesive is also preferably tackified with a suitable tackifier, i.e., one which is soluble in the monomers, and remains compatible with the polymers in the adhesive. The suitable tackifiers should exhibit no gross phase separation as evidenced by clouding of the monomers or syrup upon addition of the tackifier, or by blooming of the tackifier in the adhesive. A suitable tackifier is a glycerine rosin ester sold by Hercules, Inc., under the tradename of Foral™85. The tackifier is preferably used in amounts less than about 25 parts of tackifier per one hundred parts total of acrylate and comonomer, and more preferably, less than 15 parts. Cross-linking agents are also preferably included in the pressure sensitive adhesive to improve the cohesive strength of the adhesive. Useful cross- linking agents are generally known in the art and include multi-functional acrylates such as 1,6- hexanedioldiacrylate and tri ethylolpropane triacrylate, substituted triazines such as 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-s- triazine, metal acetyl acetonates, ortho alkyl titanates, peroxides, amide resins, melamine resins, and the like. The acrylate adhesives may be prepared by methods known in the adhesive industry such as solvent polymerization, radiation polymerization, and the like using a suitable initiator. Useful initiators include 2,2'-azobis(isobutyronitrile) and photoinitiators available from Ciba-Geigy under the Igracure tradename. In a preferred embodiment, the adhesive is the reaction product of monomers polymerized by ultraviolet radiation. For certain interior applications, such as in car interiors, the pressure sensitive adhesive is selected such that it has a very low amount of volatile material and passes the Fogging Test described below. The invention is further illustrated in the following non-limiting examples. TEST METHODS STRESS PANEL TEST (TEST METHOD A) This test is a measure of performance of the sheet material when it is stretched 5%, 10%, 15%, and 25% when aged at the elevated temperature cycling test described herein. The test panel is prepared by making rounded depressions across a 10 cm by 30.5 cm metal panel by laying a cylinder across the panel and pressing the panel against the cylinder in four different areas to obtain rounded depressions having dimensions of 0.15 cm deep by 1.5 cm wide gap above the depression (5%), 0.4 cm deep by 2.0 cm wide gap (10%), 0.5 cm deep by 2.2 cm wide gap (15%), and 0.7 cm deep by 2.4 cm wide gap (25%). The dimensions of the depressions are such that when a sheet is laid across the depression and stretched into the depression, the sheet is stretched to the percentage indicated above, i.e., 5%, 10%, etc. The panel is then coated with White High Solids Enamel WAEM 3967 available from PPG Industries and cured at 121°C for 35 minutes. The painted panel is then cleaned by wiping with a solution of 50% isopropanol and 50% water and wiping dry with a lint free cloth. A strip of tape measuring 2.54 cm by 25.4 cm is placed across the length of the panel over the depressions and smoothed down in the bridge areas of the panel with a PA-1 plastic applicator (available from Minnesota Mining & Manufacturing Co.) The panel is then placed in an oven at 70°C for one minute. While the panel is still in the oven, the tape is pressed into each depression on the panel with thumb pressure. The panel is then removed from the oven and the applicator is run across the tape in the depressions. The prepared panel is then conditioned at 21°C for 72 hours before testing the panel in an environmental cycling test. The test used in the environmental cycling test is General Motors Engineering Standards Test Number GM9505P (July, 1987) , incorporated herein by reference, Cycle D, except Cycle 6 is as shown below. The cycles consist of (1) 24 hours in humidity at 38°C; (2) 4 hours at 85°C, then cooled to room temperature; (3) 17 hours at 85°C; (4) 7 days at 70°C; (5) 4 hours at - 30°C; (6) 100 hours at 70°C. The panel is then examined for delamination of the tape from each of the depressions on the panel. Pass (P) indicates that the tape remained adhered to the depression in the panel after aging and Fail (F) indicates that the tape popped off of the depression in the panel. It is preferred that the tape of the invention passes at least the 15% depression after environmental cycling. FOGGING TEST (TEST METHOD B) This test is a measure of the tendency of the sheet material to produce a light scattering film (or fogging) on a glass surface. The procedure used is General Motors Engineering Standard Test Number GM9305P (January, 1992) Type A, incorporated herein by reference, in which a clean glass plate is placed in a beaker with the test material, sealed, and heated at 85°C. Any volatile materials will condense on the surface of the plate and fog the plate. The reflectance of the fogged plate is expressed as a percentage of the clean plate and is reported as the fogging number. The fogging number is preferably greater than 80%. TENSILE STRENGTH The tensile strength is determined according to ASTM D1682-64 using a sample width of 2.5 cm, a gauge length of 2.5 cm, and a crosshead speed of 25 cm/min. Results are shown in kiloPascals. ELONGATION AT BREAK The percentage elongation at break is determined according to ASTM D1682-64 using a sample width of 2.5 cm, a gauge length of 2.5 cm, and a crosshead speed of 25 cm/min. PERCENTAGE RECOVERY The percentage recovery is conducted at room temperature. A 2.54 cm by 10 cm long strip of sheet material is stretched to 15 cm (50% elongation) , held for 1 minute, and then the ends of the strip are released. After 10 minutes, the length of the strip is measured and the % recovery is calculated by the following formula: (Y - X) - ( Z - X) x 100 = % RECOVERY Y - X wherein X = initial length Y = length stretched to 50% elongation Z = length after ten minutes PEEL ADHESION This test measures the 90° peel adhesion of the adhesive on glass, acrylonitrile butadiene styrene (ABS) , and polypropylene panels. An adhesive tape is prepared by coating or laminating the adhesive to a 0.038 mm thick polyester film. The adhesive tape is cut into a strip measuring 1.27 cm by 15.2 cm and adhered to the test panel and rolled down with one pass of a 2.0 kilogram roller at a speed of about 30.5 cm per minute. The sample is conditioned at 21°C for 24 hours before testing. The panel is then mounted in a tensile tester so that the tape is removed at a 90° angle at a speed of 0.1016 cm per minute, and the test results are recorded in Newtons/decimeter (N/dm) . Prior to application of the adhesive tape, the glass and polypropylene panels are cleaned by washing with diacetone alcohol, wiping dry with a Kleenex™ brand tissue, washing 3 times with methyl ethyl ketone and drying with a tissue. The ABS panels are cleaned in a similar manner with diacetone alcohol, but washing 3 times with heptane. The ABS panels are White Smooth Finish ABS (Number 167150, from Cadillac Plastics). Example l An acrylate syrup was prepared by mixing 93.5 parts IOA (isooctyl acrylate), 6.5 parts AA (acrylic acid), and 0.04 parts photoinitiator (Irgacure™l84 available from Ciba Geigy) , and exposing the mixture to fluorescent black lights in a nitrogen atmosphere to form a syrup having a viscosity of about 3000 centipoise. A pressure sensitive adhesive composition was prepared by adding to 100 parts of syrup an additional 0.35 parts Irgacure™184, 0.15 parts cross- linker (2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-s- triazine) , 10 parts of a glycerine rosin ester tackifier (Foral™85 available from Hercules, Inc.). The composition was knife-coated to a thickness of 0.127 mm onto a release treated Kraft paper and cured in a nitrogen atmosphere with fluorescent black lamps having 90% of the emission spectra between 300 and 400 nm (nanometers) and a maximum at 351 nm and an intensity of about 0.7 milliwatts/square centimeter to form a pressure sensitive adhesive transfer tape. The total energy used to make the adhesive tape was 357 milliJoules/square centimeter as measured with a UV Integrating Radiometer, Model UR365CHI from E.I.T. A nonwoven tape construction was prepared by using a thermoplastic polyurethane (Morthane PS440-200, available from Morton International of Seabrook, NH) with 2 percent by weight black colorant (BASF Euthelyn Black 00-6005 C-4, available from BASF) and a process similar to that described in Wente, Van A. , "Superfine Thermoplastic Fibers" in Industrial Engineering Chemistry, Vol. 48, pages 1342 et seq (1956), or in Report No. 4364 of the Naval Research Laboratories, published May 25, 1954, entitled "Manufacture of Superfine Organic Fibers" by Wente, Van A., Boone, CD., and Fluharty, E.L., except that the melt blowing die had smooth surfaced orifices (10/cm) with a 5:1 length to diameter ratio. The die temperature was maintained between 235°C and 239°C, and the polymer throughput was 179 gm/hr/cm die width, and the fibers were deposited onto the pressure sensitive adhesive transfer tape. The thermoplastic material was extruded through the die into a high velocity stream of heated air (temperature was about 230°C and the air pressure was 150 kPa) which drew out and attenuated the fibers prior to complete solidification so that the fibers were bonded to each other to form a coherent nonwoven web with a basis weight of 125.9 grams/square meter. The tape had a tensile strength of 5,964 kiloPascals, an elongation at break of 400%, and a percentage recovery of 92%. Two samples of the tape was tested in the stress panel test with environmental aging. Both samples passed the 15% depression, and one of the samples passed the 25% depression, with only slight lifting on the edges of the other 25% sample. The average fogging number for the tape was 93.

Claims: WE CLAIM : 1. A method of noise control comprising inserting between components a conformable sheet material comprising an extensible web and an adhesive on at least one face of said web; wherein said adhesive comprises the polymerization reaction product of starting materials comprising: (a) a polymerizable component comprising at least one acrylic acid ester of a nontertiary alcohol, wherein the alkyl group of said alcohol contains from 1 to about 14 carbon atoms; and (b) a reinforcing comonomer; so that noise produced by said components is prevented, reduced, or eliminated. 2. A method of claim 1, wherein said extensible web is a nonwoven web. 3. A method of claim 1, wherein said adhesive is a pressure sensitive adhesive. 4. A method of claim 1, wherein said sheet material remains adhered to an ABS substrate after being elongated 15 percent and applied to said substrate. 5. A method of claim 1, wherein said sheet material remains adhered to a polypropylene substrate after being elongated 15 percent and applied to said substrate. 6. A method of claim 1, wherein said sheet material remains adhered to a substrate panel with a high solids automotive enamel paint described in Test Method A thereon, after being elongated 15 percent and applied to said substrate, and remains adhered after aging according to Test Method A. 7. A method of claim l, wherein said alkyl group of said alcohol contains from about 4 to about 14 carbon atoms, and said reinforcing comonomer is acrylic acid. 8. A method of claim l, wherein said starting materials further comprise an effective amount of a free radical photoinitiator, and said starting materials are polymerized by ultraviolet radiation. 9. A method of claim 2, wherein said nonwoven web comprises thermoplastic elastomeric melt blown small diameter fibers having a diameter of less than about 50 microns, the thermoplastic elastomeric small diameter fibers being selected from elastomeric polyurethanes, elastomeric polyesters, elastomeric polyamides, elastomeric copolymers of ethylene and at least one vinyl monomer, elastomeric copolymers of ethylene and at least one urethane, or elastomeric A-B- A' block copolymers, wherein A and A' are the same or different thermoplastic polymer and wherein B is an elastomeric polymer block. 10. A method of claim 9, wherein said nonwoven web comprises elastomeric polyurethane or an elastomeric polyurethane/polyolefin copolymer. 11. A method of claim 1, wherein said sheet material passes the fogging test set forth in Test Method B. 12. A conformable sheet material comprising a nonwoven web and an adhesive on at least one face of said web; wherein said adhesive comprises the polymerization reaction product of starting materials comprising a polymerizable component comprising: (a) at least one acrylic acid ester of a nontertiary alcohol, wherein the alkyl group of said alcohol contains from about 4 to about 14 carbon atoms, (b) acrylic acid, (c) at least one free radical initiator, and (d) a crosslinking agent; wherein the weight ratio of acrylic acid ester to acrylic acid is from 91:9 to 96:4; wherein said nonwoven web comprises thermoplastic elastomeric melt blown small diameter fibers having a diameter of less than about 50 microns, the thermoplastic elastomeric small diameter fibers being selected from elastomeric polyurethanes, elastomeric polyesters, elastomeric polyamides, elastomeric copolymers of ethylene and at least one vinyl monomer, elastomeric copolymers of ethylene and at least one urethane, or elastomeric A-B-A' block copolymers, wherein A and A' are the same or different thermoplastic polymer and wherein B is an elastomeric polymer block; and wherein said sheet material prevents, reduces, or eliminates noise when placed between components.

Inventors: BLAIR INGRID E, DOLNEY DAVID A, RAUSCHENBERG NANCY C, REED JOHN F, SCHROEDER KRISTIN M, TODDY JOHN N, BLAIR, INGRID, E., DOLNEY, DAVID, A., RAUSCHENBERG, NANCY, C., REED, JOHN, F., SCHROEDER, KRISTIN, M., TODDY, JOHN, N.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1995
Main classification: C09J7
IPC codes: B32B27, B65D81, C09J7, C09J133, D06N3, F16F15