LOWER DENSITY, THERMOFORMABLE, SOUND ABSORBING POLYURETHANE FOAMS
Polyurethane foams formed under vacuum (below atmospheric pressure) conditions using primarily graft polyether polyols reacted with primarily toluene diisocyanate have lower densities (up to 1.3 lb/ft 3 ), lower hardness (IFD 25 up to 50 lbs), and exhibit superb thermoformability and fire retardance while retaining good sound insulating characteristics. The foam-forming ingredients are mixed together and foamed under controlled pressures in the range 0.5 to 0.95 bar (absolute). Such foams taken alone, or in combination with a barrier layer to form a laminate, are thermoformed to create a sound insulator for a motor vehicle instrument panel.
1 . A process for producing a thermoformable polyurethane foam-containing sound insulative laminate, comprising:
(1) preparing a foam-forming composition from: (a) from 0 to 100% by weight of total polyol of a graft polyol having a functionality in the range from about 2.5 to 3.5 and a hydroxyl number in the range from about 20 to 70; (b) from 0 to 20% by weight of total polyol of a polyether polyol; (c) a polyisocyanate containing at least 80% by weight toluene diisocyanate and up to 20% by weight methylene diisocyanate; and (d) one or more blowing agents,
(2) forming the polyurethane foam from the foam-forming composition under controlled pressure conditions from about 0.50 to about 0.95 bar (absolute), wherein the density of the resulting polyurethane foam is 1.3 lb/ft 3 or less; and
(3) thermoforming a layer of the polyurethane foam to a barrier layer to join said layers together to form the sound insulative laminate, wherein the barrier layer is a material selected from the group consisting of filled asphalt, filled EVA, filled EPDM, filled rubber, filled PVC, and bitumen board.
2 . The process of claim 1 , wherein the polyurethane foam has an IFD 25 of 50 lbs or below.
3 . The process of claim 1 , wherein the foam-forming composition includes (e) from 0 to 20% by weight of total polyol of a polyester polyol.
4 . The process of claim 1 , wherein the foam-forming composition includes (e) one or more additives selected from the group consisting of: stabilizers, antimicrobial compounds, extender oils, dyes, pigments, and antistatic agents.
5 . The process of claim 1 , wherein the blowing agent is water.
6 . The process of claim 1 , wherein the polyurethane foam retains a 70% compression set after thermoforming the laminate.
7 . The process of claim 1 , wherein the polyurethane foam is not pre-treated with a thermoforming agent prior to thermoforming the laminate.
8 . A thermoformed article formed from the laminate of claim 1 .
9 . A sound insulator for an instrument panel, comprising:
a flame retardant, thermoformable, flexible, open celled polyurethane foam having a density of 1.0 lb/ft 3 or less and an IFD 25 of 50 lbs. or less, wherein the foam is in the form of a sheet or slab, and
a reinforcement, backing or decorative covering applied to at least one surface of the foam sheet or slab to form a laminate.
10 . The sound insulator of claim 9 , wherein the reinforcement, backing or decorative covering is applied to a surface of the foam sheet or slab as the foam by thermoforming.
11 . The sound insulator of claim 10 , wherein the foam is thermoformed under compression at a temperature in the range of about 300° F. to about 400° F. to form the sound insulator.
12 . The sound insulator of claim 11 , wherein the thermoformed foam retains a 70% compression set.
13 . The sound insulator of claim 10 , wherein the foam is in the form of a sheet or slab that has a thickness of from about 0.3 to 2.0 inches before it is thermoformed.
14 . The sound insulator of claim 10 , wherein the foam is not pre-treated with a thermoforming agent prior to thermoforming.
15 . The sound insulator of claim 9 , wherein the reinforcement, backing or covering is formed of a material selected from the group consisting of: filled asphalt, filled EVA, filled EPDM, filled rubber, filled PVC, and bitumen board.
16 . The sound insulator of claim 9 , wherein the reinforcement, backing or covering is adhered to the foam with an adhesive prior to thermoforming.