GB2244954A

GB2244954A - Vibration damping sheet

Info

Publication number: GB2244954A
Application number: GB9013353A
Authority: GB
Inventors: Masami Kita
Original assignee: Daicel Huels Ltd
Current assignee: Daicel Evonik Ltd
Priority date: 1988-12-28
Filing date: 1990-06-14
Publication date: 1991-12-18
Anticipated expiration: 2010-06-14
Also published as: GB9013353D0; JP2666079B2; DE4020512A1; JPH02178040A; GB2244954B

Abstract

A vibration damping sheet comprises two sheets of metal and an intermediate layer, inserted between the two sheets of metal, characterised in that the intermediate layer comprises a rubber composition comprising a butyl rubber, polyoctenylene and a copolymer of an olefin and an epoxy-containing acrylic ester. The intermediate layer may also comprise a copolymer of an olefin and an acrylic ester. The intermediate layer may itself be multilayered e.g. a layer comprising a butyl rubber, polyoctenylene and optionally a copolymer of an olefin and an acrylic ester sandwiched between two layers comprising a copolymer of an olefin and an epoxy containing acrylic ester.

Description

-I-

DESCRIPTION

VIBF,ATION DAMFING SHEET The present invention relates to a vibration damping composite metallic sheet, which comprises two sheets of metal and an intermediate layer, Inserted between the two sheets of metale comprising a rubber-based resin composition in film or sheet form, said rubber-based resin composition comprising a rubber composition comprising a butyl rubber, a copolymer of an olefin and an acrylic ester and a polyoctenylene resin and blended therewith a copolymer of an olefin and an epoxy-containing acrylic ester, and which has a vibration damping capability over a wide temperature range.

P RIOR ART In recent years, with an increasing tightening of noise regulations of housing, automobiles, etc., various methods have been studied as a countermeasure. An ever-increasing tendency is mainly the use of a vibration damping material in sound sources or parts which sound accompanying the vibration of the sound sources, and various vibration danpinS composite metallic sheets have hitherto been proposed in the art.

For example, Japanese Patent Publication No.

-212451/1964 discloses a vibration damping metallic sheet wherein a copolymer of vinyl acetate and a maleic diester, a copolyrier of vinyl chloride and ethylhexyl acrylate or the like is used as an intermediate layer. This invention utilizes a known fact that a vibrational energy is absorbed as a thermal energy through the utilization of a resin having viscoelasticity. in the resin having viscoelasticity, the viscoelasticity sensitively changes with a change In the temperature, so that it is anticipated that the vibration damping capability will disappear in a service temperature range.

In general, the vibration absorbing capability can be expressed in terms of a physical quantity called a loss factor, and it is a common knowledge in the art that the material exhibits a vibration absorbing capability when the loss factor is 0.055 or more. Viscoelastic substances, such as rubbers, copolymer resins and asphalt, have been thougl.t. to be effective when used as the above-described material. They are atisfactory in the vibration damping capability but poor in the adhesion to the metallic sheets or the processability for insertion between two sheets of metal, so that no thoroughly satisfiable material has been proposed in the art as yet.

Butyl rubber is very excellent in the vibration damping capability by virtue of its high hysteresis and best suited for improving the impact strength at a low temperature of other materials. However, it has drawbacks in respect of moldability, compatibility and adheslon.

Japanese Patent Laid-Open No. 291930/1989 discloses; (1) a vibration damping composite metallic sheet, characterized by comprising two sheets of metal and an intermediate layer, bonded therebetween, comprising a rubber resin composition comp-rising a butyl rubber and a polyoctenylene resin and blended therewith a copolymer of an olefin and acrylic acid copolymer, and having a vibration damping capability over a wide temperature range; and (2) a vibration damping composite metallic sheet, characterized by comprising two sheets of metal and an intermediate layer, bonded therebetween, comprising a multilayered film or sheet comprising a resin layer comprising a butyl rubber and a polyoctenylene resin and a resin layer comprising a copolymer of an olefin and acrylic acid, and having a vibration damping capability over a wide temperature range.

0 In view of the above, the present inventors hive made extensive and intensive studies with a view to developing a vibration damping composite metallic sheet having a high vibration damping capability through insertion, between metallic sheets, of a resin composition wherein the above-described various drawbacks of the viscoelastic substances have been eliminated.

SUMMARY OF THE INVENTION in the present invention a vibrition damping sh.eet comprises two sheets of metal and an intermediate layer, inserted, between the two sh,eets of metal, comprising a rubber cc-,,.,position compr-Jsing a buty', rubber, polyoctenylene and a copolymer of an olefin and an epoxy-cci-,taining acrylic ester. ther comprise a The rubber composition may furt copolymer of an olefin and an acr51ic ester.

tal Ise the two sheets of met he sheet may comprand three intermediate layers, the two outer layers of the three intermediate layers comprising a copolper of an olefin and an epoxy-contalining acrylic ester, the other, inserted between the two outer layers, compris4-ng a butyl rubber and polyoctenylene, The sheet may comprise the two sheets off metal i i i -5and three intermediate layers, the two outer layers of the three intermediate layers comprising a copolymer of an olefin and an epoxycontaining acrylic ester, the other, inserted between the two outer layers, comprising a butyl rubber, polyoctenylene and a copolymer of an olefin and an acrylic ester.

The copolymer o: an olefin and an e-Poxy-containing acrylate used in the present invention comprises an olefin copolymerized or grafted with an epoxycontaining acrylate by a known method commonly used in the art, and the content of the epoxy-containing acrylate is preferably 0.1 to 45%, still preferably I to 25%. When the content is less than 0.1t, no sufficient adhesion --:.n be attained. on the other hand, when the content exceeds 45%, the compatibility with the butyl rubber, copolymer of an olefin and an acrylic ester and polyoctenylene resin becomes poor, so that no sufficient mechanical strengths can be attained.

The butyl rubber used in the present invention is a chemically stable rubber prepared by blending a isobutylene monomer with a small arount of an isoprene monomer and subjecting the blend to cationic copolymerization. The butyl rubber also includes a chlorinated and a brominated butyl rubber.

The copolymer of an olefin and an acrylic ester used in the present invention is one prepared by blending an olefin monomer, such as ethylene, propylene or butylene, with a snall amount of an acrylic ester or a methacrylic ester and subjecting the blend to copolymerization by a known method, and the acrylic or methacrylic ester content is preferably 1 to 50%, still preferably 3 to 30%. When the content is less than 1%, no sufficient strengths can be attained. On the other hand, when the content (xceeds 50%, the -ibility w-h the butyl rubber or polyoctenylene c ompa t resin is poor, so that no Slafficient -.echanicai strengths can be attained, The polyoctenylene resin used ir. the present -ion is prepared by polymerizing cyclooctene and invent should have one double bond per eight carbon atoms and a molecular weight of 10,000 or more. The trans isomer content is 50% or more, preferably 60% or more, and the degree of crystallinity is preferaZly 10% or more. The polyoctenylene resin has a melting point c5f usually 400C or above, preferably 50 to 60'C and a glass transition point of -75 to -300C.

The cyclooctene as a base material con5tituting the polyoctenylene may be synthesized by various ting methods, e.g., by dimerizing buta-d-lene hydrogenat 1 one of the two remaining double bonds.

if necessary, dyes and pigments, various stabilizers, fillers, plasticizers, antioxidants, ultraviolet absorbers, nucleating agents, antistatic agents and glame retardants may be added to the rubbery resin composition as the intermediate layer of the vibration damping composite metallic sheet according to the present invention. The abovedescribed additives include those known as vulcanizing agents, vulcanization accelerators and various additives, such as peroxidles, sulfur com.pounds, phenolic resins, process oils and alicyClilc epoxy resins for use with the butyl rubber, copolymer of an olefin and an acrylic ester and. polyoctenylene resin.

The resin composition of the present invention may be prepared by meltmixing the ingredients according to various methods, such as roll milling or extrusion. For example, first the copolymer of an olefin and an epoxycontaining acrylate is melted, and the 'remaining ingredients, I.e., the butyl rubber, copolymer of an olefin and an acrylic ester and polyoctenylene resin may then be added thereto. Alternatively, the abovedescribed three ingredients may be simultaneously mixed together. lú necessary, -8it is also possible to add in any stage the abovedescribed additives, e. g., fillers, plasticizers and antioxidants. Alternatively, the three ingredients may be solution-mixed through dissolution in a suitable solvent.

The rubbery resin of the present Invention comprising a coplymer of an olefin and an epoxycontaining acrylate, a butyl rubber, a copolymer of an olefin and an acrylic ester, and a polyoctenylene resin is molded into a film or sheet,by making use of the conventionally known T-die film production apparatus or Inflation film productlon apparatus and then sandwiched between two sheets of netal and laminated under pressure. Alternatively, a cast film may be directly formed or. a metallic sheet by casting. In this case, the thickness of the film or sheet is preferably 10,ri to 1 mm, particularly preferably 20 to 150 pr..

The rubbery resin as an intermediate layer comprising a copolymer of an olefin and an epoxycontaining acrylate, a butyl rubber, a copolymer of an olefin and an acrylic ester, and a polyoctenylene resin may be prepared by a method which comprises melt-mixing the ingredients by various methods and molding the mixture into a film, or sl,,.eet. A-^-.ernativeiy, -9the ingredients may be directly molded into a twoor multilayered film by making use of a coextruding machine. In this case, when an adhesive layer comprising a copolymer of an olefin and an epoxycontaining acrylate is inserted between the metallic sheet and the rubbery resin film comprising a butyl rubber, a copolymer of an olefin and an acrylic ester and a polyoctenylene resin, the multilayered film causes no blocking between the film surfaces themselves while maintaining good adhesion to the metallic sheet, which favorably facilitates lamination with a metallic sheet.

Examples of the metallic sheet used in the present invention include those made of iron, nickel, titanium, aluminum, magnesium, copper, zinc and tin, various alloy sheets composed mainly of the above-described metallic sheets, e.g., sttainle5s steel sheets. There is no particular limitation on the thickness of the above-described metallic sheets as far as fabrication such as bending or drawing of the resultant vibration damping composite metallic sheet is possible. In general, the thickness may be 0.01 to 5 mm. The above-described r,,etallic sheets are commercially available. However, since they generally have fat or oil deposited thereon, it is preferred to use them 0 -10after degreasing. The degreasing may be conducted by any known method.

BRIEF DESCRIPTION OF THE DRAWIMGIS

Fig. 1 is a diagram showing a process of continuously producing a vibration damping composite metallic sheet; Fig. 2 is a diagram showing a step of continuously degreasing a metallic sheet; and Figs. 3 and 4 are graphs showing the temperature dependency of the loss factors of the materials used in Examples 1 to 6 and Comparative Examples 1 to 4.

In Fig. 1, each of numerals 1 and 1' designates a metallic sheet, each of numerals 2, 21, 3 and 3' a roll, each of numerals 4, 4' and 8 a leveller, each of numerals 5 and 5' a step of preheating, each of numerals 6 and 61 a roll, numeral 9 a step of reheating, numeral 10 a step of first cooling, numeral 11 a step of second cooling, each of nu.merals 12 and 13 a slitter, numeral 7 a rubbery resin film, and numeral 14 a vibration damping composite metallic sheet as a product. In Fig. 2, numeral 15 desldgnates a roll, each of numerals 16 and 18 an eiectrolyte cell, numeral 17 an anode plate, nurn.eral 19 a cathode plate, numeral 2^. a power supply, nL,-era-l 21 a step, of wathing with water, numeral 22 a step of drying, 1 - 1 1 numeral 23 a metallic sheet before degreasing, and a numeral 24 a metallic sheet after degreasing.

The vibration damping composite metallic sheet of the present invention is preferably produced by inserting a film or sheet of a rubbery resin comprising a copolymer.of an olefin and an-epoxy-containing acrylate, a butyl rubber, a copolymer of an olefin and an acrylic ester, and a polyoctenylene resin between two sheets of metal of the same or different kind and thermally pressing the resultant assembly by making use of a compression molding machine or rolls. In this case, various methods, such as laminating after cutting of the rretallic sheets and rubbery resin each into a size and a shape suitable for the subsequent fabrication and a continuous production method shown in rig.!., may be adopted. When the vibration damping composite metallic sheet is produced by the continuous production method shown In Fig. 1, preliminary degreasing of the metallic sheets In a step as shown in rig. 2 Is preferred because good adhesion can be attained thereby.

The vibration damping composite metallic sheet provided by the present invention not only exhibits a good vibration damping capability over a wide temperature range but also is very easy to conduct -12fabrication for preparing a composite because the rubbery resin as an intermediate layer comprising a copolymer of an olefin and an epoxy- containing acrylate, a butyl rubber, a copolymer of an olefin and an acrylic ester and a polyoctenylene resin may easily be molded into a film or-sheet and further exhibits a good adhesive property. <Examples> The present invention will now be described in more detail by way of the following txamples. The adhesion between the resin and the metal was evaluated in terms of an adhesive strength, and the T-peel strength and the tensile shear strength were mieasured dCcording to the methods as stipulated by JIS K 6854 and JIS K 6850, respectively, Example I

A copolymer resin of an olefin and an epoxycontaining acrylate (Rdxpearl; a product of N."i1pplon Petrochemicals Co., Ltd.), a butyl rubber (Butyl; a product of Exxon), a copolymer of an olefin and an acrylic ester (RexIon; a product of Nippon Petroch;m-icals Co., Ltd.) and a polyoctenylene resin (vestenamerBO12; a product of HUls) were blended together in prop portions specified in Table 1, and the blend was melted and kneaded in an ordinary i -13Banbury mixer and then pelletized. The pellets were molded into a 60 wm-thick film by making use of an ordinary T-die extruder. For the evaluation of the adhesive property, this film was sandwiched between two sheets of iron at 2001C to form a laminate by making use of an ordinary pres molding machine. The test pieces thus formed were allowed to stand in an air-conditioned room kept at a temperature of 230C and a relative humi6ity of 50% for 3 days to measure the T-peel strength, tensile shear strength and loss factor thereof. The results are given in Table I and Fig. 1.

Example 2 A butyl rubber (Butyl; a product of Exxon), a 6 an olef.in and an acrylic ester (Rex1on; copolymer o-.,L a product of Nippon Petrochemicals Co., Ltd.) and a polyoctenylene resin (VestenairerBO12; a product of HUls) were blended together in proportions specified in Table 1, and the blend was kneaded by rneans of rolls and then pelletized with an ordinary rubber shredder. A 60 wm-thick multilayered film comprising three I'ayers, i.e., a 15 =- thick layer of a copolymer of an olefin and an epoxy-containing acrylate, a 30 m-thick layer of a rubbery resin comprising a butyl rubber, a copolymer of an olefin and an acrylic -14ester and a polyoctenylene resin and a 15 1.m-thick layer of a copolymer of an olefin and an epoxycontaining acrylate, wherein said copolymer layers constitute the outer layers, was prepared from the above pellets and a copolymer resin of an olefin and an epoxy-containing acrylate (Rexpearl; a product of Nippor'Peo'trochemicals Co., Ltd.) by means of an ordinary inflation extruder for multilayered film. The formed multilayered film was then sandwiched between two sheets of iron at 2001C to form a laminate by means of a press molding machine. The test pieces thus formed were allowed to stand in an air-conditioned room, kept at a temperature off 231C and a relative humidity of 50% for 3 days to -,, easure the T-peel strength, tensile shear strength and loss factor thereoff. The results are given in Table 1 and Fig. 3.

Comparative Example 1 The.T-peel strength, tensile shear strength and loss factor of co. mparative test pieces were measured in the same manner as that of Example 1, except that the polyoctenylene resin was omitted. The results are given In Table 1 and Fig. 3. As is apparent from the results, the r.iol%- Aability was very poor.

Comparative Example 2 The T-peel strength, tensile shear strength and 1 -15loss factor of comparative test pieces were measured in the same manner as that of Example 2, except that the copolymer resin of an olefin and an epoxycontaining acrylate was omitted. The results are given in Table I and Fig. 3.

Example 3

The T-peel strength, tensile shear strength and loss factor of test pieces were measured in the same manner as that of Example 2, except that in molding the copolymer of an olefin and an ep6xy-containing acrylate into a multilayered film together with the butyl rubber, copolymer of an olefin and an acrylic ester and polyoctenylene resin, the copolymer of an olefin and an epoxy-containing acrylate was previously molded into two 10 =-thick films by means of an ordinary T-die extruder and a 30;jm-thick film comprising a butyl rubber, a copolymer of an olefin and an acrylic ester and a polyoctenylene resin was sandwiched therebetween for lamination, thereby forming a multilayered film. The results are given in Table 1 and Fig. 1, Tab le 1 Butyl T-peel Tensile rubber Vestenamer Rexlon Rcxpearl strength shear (Pts. wt.) (Pts. wt.) (Pts. wt.) (Pts. wt.) (kg/2.5 cmI S trength 2) (kg/cm Ex. 1 25 15 10 50 21 38 Ex. 2 40 10 10 1 40 24 104 L_ - i 40 10 10 40 32 99 Ex. 3 Comp - 29.4 - 11.8 58.8 6 23 Ex. I COMP. 66.6 16.7 16.7 8 26 Ex. 2 Note: three-layered film M 1 al 1 Example 4

A copolymer resin of an olefin and an epoxycontaining acrylate (Rexpearl; a product of Nippon Petrochemicals Co., Ltd.), a butyl rubber (Butyl; a product of Exxon) and a polyoctenylene resin (VestenamerBO12; a product of HCls) were blended together in proportions specified in Table 2, and the blend was nelted and kneaded in an ordinary Banbury mixer and then pelletized. The pellets were molded into a 60 pm-thick film by making use of an ordinary T-die extruder. For the evaluation of the -ween adhesive property, this film was sandwiched bet two sheets of iron at 2000C to form a laminate by t making use of an ordinary press molding machine. The test pieces thus formed were allowed to stand in an air-conditioned room kept at a temperature of 23'C and a relative humidity of 50% for 3 days to neasure the T-peel strength, tensile shear strength and loss factor thereof. The results are given in Table 2 and Fig. 4.

Ex&mple 5 A butyl rubber (Butyl; a product of Exxon) and a polyoctenylene resin (VestenamerBO12; a product of HUls) were blended together in proportions specified in Table 2, and the blend was kenaded by means of It -18rolls and then pelletized-with an ordinary rubber shredder. A 60 vmthick multilayered film comprising three layers, i.e., a 15 =-thick layer of a copolymer of an olefin and an epoxy-containing acrylate, a 30 umthick layer of a rubbery resin comprising a butyl rubber and a polyoctenylene resin and a 15 Pmthick layer of a copolymer of an clefin and an epoxycontaining acrylate, wherein said copolymer layers constitute the outer layers, was prepared from the above pellets and a copolymers resin'of an olefin and an epoxy-contain-,:.q acrylate (Rexpearl; a product of Nippon Petrochemicals Co., Ltd.) by means of an ordinary inflation extruder for multilayered film. The formed multilayered film was then sandwiched between two sheets bf iron at 200C to form a laminate by means of a press molding machine. The test pieces thus formed were allowed to stand in an air-conditioned room kept at a temperature of 230C and a relative humidity of 50% for 3 days to measure the T-peel strength, tensile shear strength and loss factor thereof. The results are given in Table 2 and Fig. 4.

Comparative Example 3 The T-peel strength, tensile shear strength and loss faQtor of corparative test pieces were measured in the same manner as that of Example 4, except that -19the polyoctenylene resin was omitted. The results are given in Table 2 and rig, 4. As is apparent from the results, the moldability was very poor.

Comparative Example 4 The T-peel strength, tensile shear strength and loss factor of compar- etive test-pieces were measured in the same manner as that of Example 5, except that the copolymer resin of an olefin and an epoxy-containing acrylate was onitted, The results are given in Table 2 and Fig. 4.

Example 6

The T-peel strength, tensile shear strength and loss factor of test pieces were measured in the same manner as that of Example 5, except that in molding the copolymer of an olefin and an.apoxy-containing acrylate Into a multilayered film together with the butyl rubber and polyoctenylene resin, the copoly-ner of an olefin and an epoxy-containing acrylate was previously molded into two 10 Lm-thick films by means of an ordinary T-die extruder and a 30.im-thick film comprising a butyl ruober and a polyoctenylene resin was sandwiched therebetween for lamination, thereby forming a multilayered film. The results are given in Table 2 and rig. 4.

Tabl.e 2 Butyl T-peel Tensile I rubber Vestenamer Rexpearl strength shear (pts- wt.) (Pts. wt.) (Pts. Wt.) (kq/2.5 cm) s trength (kcj/CM2) Ex. 4 25 25 50 14 85 Ex- 5 11 40 1 10 50 15 91 Ex. 6 45 15 40 25 88 COMP - 5 C, - 50 4 21 Ex. 3 Comp. 80 20 - 6 27 Ex. 4 Note: three-layered film 1 K) CD 1 1

Claims

1. A vibration damping sheet comprising two sheets of metal and an intermediate layer, inserted between the two sheets of metal, characterised in that the intermediate layer comprises a rubber composition comprising a butyl rubber, polyoctenylene and a copolymer of an olefin and an epoxy-containing acrylic ester.

2. The sheet as claimed in claim 1, characterised in that the rubber composition further comprises a copolymer of an olefin and an acrylic ester.

3. The sheet as claimed in claim 1 or 2, characterised in that the intermediate layer comprises three layers, the two outer layers of the three layers comprising a copolymer of an olefin and an epoxycontaining acrylic ester, the other, inserted between the two outer layers, comprising a butyl rubber and polyoctenylene.

4. The sheet as claimed in claim 3, characterised in that the other layer inserted between the two outer layers, comprises a butyl rubber, polyoctenylene and a copolymer of an olefin and an acrylic ester.

Published 1991 at The Patent Office. Concept House, Cardiff Road. Newport, Gwent NP9 I RI-i. Further copies may be obtained from Sales Branch, Unit 6. Nine Mile Point, Cwnifelinfach, Cross Keys, Newport, NPI. 7HZ. Printed by Multiplex techniques ltd, St Mary Cr-ay. Kent.