Vibration damper having extended temperature range and low temperature shock resistance

• US 5,118,562 A
• Filed: 09/24/1990
• Issued: 06/02/1992
• Est. Priority Date: 09/24/1990
• Status: Expired due to Fees

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Johnson, Roger W., Wright, Charles D., Sell, William D.
• Primary Examiner(s): Cashion, Jr., Merrell C.
• Assistant Examiner(s): NAKARANI, DHIRAJLAL S
• Application Number:
  US07/587,087
• Time in Patent Office: 617 Days
• Field of Search: 428/327, 428/461, 428/463, 428/483, 428/520, 428/522
• US Class Current: 428/327
• CPC Class Codes: B32B 2250/24 All layers being polymeric
• CPC Class Codes: B32B 2307/558 Impact strength, toughness
• CPC Class Codes: B32B 2307/56 Damping, energy absorption
• CPC Class Codes: B32B 25/08 of synthetic resin
• CPC Class Codes: B32B 27/06 as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a layer of a particular substance B32B9/045; next to a bituminous or tarry layer B32B11/046; next to a water setting substance layer B32B13/12; next to a metal layer B32B15/08; next to a glass layer B32B17/10; next to a layer formed of natural mineral fibres or particles B32B19/045; next to a wood layer B32B21/08; next to a cellulosic plastic layer B32B23/08; next to a natural or synthetic rubber layer B32B25/08
• CPC Class Codes: C08L 2205/18 Spheres
• CPC Class Codes: C08L 2666/24 Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
• CPC Class Codes: C08L 33/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C08L 51/04 grafted on to rubbers
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/31692 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31699 Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31797 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31928 Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

Constrained layer damping structures are often based on viscoelastic layers of iso-octyl acrylate:acrylic acid or analogous copolymers. As the acrylic acid content is increased, the peak damping temperature also increases; unfortunately, however, the copolymer becomes more brittle and susceptible to shock, especially at low temperatures. Incorporating small amounts of rubbery polymer particles (especially core-shell polymers) in the viscoelastic copolymer alleviates this problem.

Claims

1. A damping structure comprising in combination a stiff constraining sheet, to one surface of which is firmly adherently bonded a layer of viscoelastic material that comprises

(a) a matrix consisting essentially of a brittle copolymer of monomers consisting essentially of

(1) at least one alkyl acrylate ester of non-tertiary alcohol having 1-14 carbon atoms and

(2) at least one copolymerizable polar monomer, and

(b) dispersed throughout said viscoelastic material, a multiplicity of rubbery particles, the rubbery particles consisting essentially of a rubbery core surrounded by a thin shell of polymeric material that is compatible with the copolymer matrix.

2. The damping structure of claim 1 wherein the copolymer is an iso-octyl acrylate:

acrylic acid copolymer.

3. The damping structure of claim 2 wherein the copolymer contains at least 20% acrylic acid.

4. The damping structure of claim 2 wherein the copolymer contains at least 25% acrylic acid.

5. The damping structure of claim 2 wherein the copolymer contains at least 30% acrylic acid.

6. The damping structure of claim 1 wherein the viscoelastic material contains 1-15% core-shell polymer.

7. The damping structure of claim 1 wherein the viscoelastic material contains 5-10% core-shell polymer.

8. The damping structure of claim 1 wherein the core-shell polymer has a core of butyl acrylate and a shell of methyl methacrylate.

9. The damping structure of claim 1 wherein the rubbery particles are styrene:

butadiene rubber.

10. The damping structure of claim 1 wherein the core-shell polymer has a core of styrene:

butadiene rubber and a shell of methyl methacrylate.

12. The damping structure of claim 2 wherein the viscoelastic layer comprises a matrix of a brittle copolymer of 20-30 parts acrylic acid and correspondingly 80-70 parts isooctyl acrylate and, dispersed throughout said matrix of brittle copolymer 5-10 parts of compatible core-shell polymer.

13. A damped laminate comprising the damping structure of claim 1 adhered to a substrate.

11. In a damping structure incorporating a layer of brittle viscoelastic material, the improvement comprising incorporating in said layer a sufficient amount of rubbery polymer particles to render said viscoelastic layer less susceptible to shock at room temperature or below and further wherein the rubber particles comprise a rubbery core surrounded by a thin shell of a polymeric material that is compatible with the viscoelastic material.