Attached, High Reactivity Rigid Polyurethane Foams

Abstract

Polyurethane foams are made and attached to a substrate having an open cavity, but reacting prepolymer and polyol components in the presence of certain carbamate blowing agents. This process allows for very fast curing, good quality, adherent foamy to be produced on, for example, vehicle parts and assemblies, for acoustical or vibration dampening and for structural reinforcement.

Description

EXAMPLE 1

Prepolymer Component A is made by mixing the following components together under a nitrogen atmosphere and heating at 71° C. until a constant NCO content is obtained:

		Equivalent
Component	Parts by Weight	Weight	Functionality
Hydroxyethyl	4.7	131	1
methacrylate
400 MW Poly(propylene	1.88	200	2
oxide) diol
Polymeric MDI	68.37	141	3.2
Plasticizer (Jayflex ™ L9P)	25.0	—	0
Benzoyl Chloride	0.025	—	Stabilizer

The resulting plasticized Prepolymer Component A has a % NCO of ˜12% weight percent. The free MDI content of Prepolymer Component A is ˜19% by weight.

Polyol Component A is made by mixing the following ingredients:

		Equivalent
Ingredient	Parts by Weight	Weight	Functionality
Amine-initiated polyol	80	143.5	4
(Voranol 391, Dow
Chemical)
Polyether polyol 1 (PG 76-	5.00	93.5	3
600, Arch Chemicals)
Polyether polyol 2 (PG 76-	67.750	467.5	3
120, Arch Chemicals)
Primary amine-	2.5	156	3
terminated polyether
(Jeffamine ® T403 from
Huntsman Chemicals)
Carbamate/ethylene	1.5	—	—
glycol mixture1 (Specflex
NR 566, from Dow
Chemical)
Organotin Catalyst (UL-1	0.25	—	—
from Air Products and
Chemicals)
Organosilicone Surfactant	1	—	—
(Tegostab B-8404,
Goldschmidt)
1Contains approximately 45% ethylene glycol by weight.

Foam is prepared by mixing Prepolymer Component A and Polyol Component A at a 1:1 volume ratio at the mixing head of a Gusmer H7 foaming machine at a dispensing pressure of 500-1200 psi (3447-8274 kPa), dispensing the mixture into a 1-quart cup, and allowing it to cure at room temperature. Both components are preheated to 160° F. (71° C.) to reduce the viscosity and obtain better mixing. Cream time for this formulation is less than one second. A stable foam having excellent cell structure and a density of about 12 pounds per cubic foot (192 kg/m³) is obtained.

EXAMPLE 2

Prepolymer Component B is made by reacting 44.377 parts of Papi® 20 polymeric MDI (29.5% NCO, 3.2-functional), from Dow Chemical with 10.706 parts of a 216 equivalent weight polypropylene oxide) diol (Voranol® 220-260 polyol from Dow Chemical), 2.567 parts n-butanol, 42 parts of a non-reactive plasticizer (Platinol 711P from BASF), and 0.35 parts of an organosilicone surfactant (DC198 from Air Products).

The resulting plasticized Prepolymer Component A has a % NCO of 9.7 weight percent, an equivalent weight of 429, a M_n of 1000 (exclusive of plasticizer) and an average functionality of 2.52 isocyanate groups/molecule (exclusive of plasticizer). The free MDI content of Prepolymer Component A is <5%.

Polyol Component B is made by mixing the following ingredients:

	Parts by	Equivalent
Ingredient	Weight	Weight	Functionality
Carbamate/ethylene glycol	11.8	43.9	2
mixture1 (Specflex NR 566, from
Dow Chemical)
Amine-initiated polyol (Voranol ®	26	70	4
800 polyol from Dow Chemical)
Poly(propylene oxide) polyol	49.45	143.5	4
(Voranol ® 391 polyol from Dow
Chemical)
Primary amine-terminated	1.5	—	3
polyether (Jeffamine ® T403 from
Huntsman Chemicals)
Amine curing agent (D.E.H 39,	2.75	64.5	3
from Dow Chemical)
Tertiary amine catalyst (SPI 847,	2.5	—	—
from Specialty Products
International)
Silicone Surfactant (Tegostab ®	5	—	—
8450, from Th. Goldschmidt)
Water	1	9	2

Foam Example 2 is prepared by mixing Prepolymer Component B and Polyol Component B in the general manner described in Example 1, except the component weight ratio is 4:1. The resulting foam has a cream time of less than 2 seconds and a tack free time of less than 15 seconds. Its free rise density is 12-14 pounds/cubic foot (192-224 kg/m³). The compressive modulus of a 2″×2″×1″ (5×5×2.5 cm) skinless section of the resulting foam is measured according to ASTM after preconditioning the foam at 50° C. for one hour. The compression modulus is ˜9000 psi (˜62,000 kPa).

EXAMPLE 3

Polyol Component C is made by mixing the following ingredients:

	Parts
	by	Equivalent
Ingredient	Weight	Weight	Functionality
Carbamate/ethylene glycol mixture1	8	43.9	2
(Specflex NR 566, from Dow
Chemical)
Amine-initiated polyol (Voranol ®	27	70	4
800 polyol from Dow Chemical)
Poly(propylene oxide) polyol	58.6	143.5	4
(Voranol ® 391 polyol from Dow
Chemical)
Primary amine-terminated polyether	1.5	—	3
(Jeffamine ® T403 from Huntsman
Chemicals)
Amine curing agent (D.E.H 39, from	3.5	64.5	3
Dow Chemical)
Amine Catalyst (Dabco WT catalyst	1.25	—	—
from Air Products)
Odor Modifier (10125WS from Odor	0.15	—	—
Control Co.)

Foam Example 3 is prepared by mixing Prepolymer Component B and Polyol Component D in the general manner described in Example 2. The resulting foam has a cream time of less than 2 seconds and a tack free time of less than 20 seconds. Its free rise density is 22-24 pounds/cubic foot (352-384 kg/m³). Compression modulus measured as in Example 2 is 28,000 psi (193,000 kPa).

EXAMPLE 4

A polyisocyanate composition is prepared by mixing 65 parts by weight of a 3.2-functional, 141 equivalent weight polymeric MDI (Papi® 20, from Dow Chemical) with 35 parts of a hydrocarbon oil. Foam Example 4 is prepared by reacting it with Polyol Component C, in the same general manner as described in Example 1, except the volume ratio is 2:1 and the isocyanate index is 1.34. The cream time is less than one second and tack free time is less than 20 seconds. Polyol Composition D is made by blending the following components:

	Parts by	Equivalent
Ingredient	Weight	Weight	Functionality
Carbamate/ethylene glycol	8.2	43.9	2
mixture1 (Specflex NR 566, from
Dow Chemical)
Polyether polyol (Voranol ® 280	23.36	200	7
polyol from Dow Chemical)
Polyether polyol (Voranol ® 391	51.4	143.5	4
polyol from Dow Chemical)
Primary amine-terminated	8.6	156	3
polyether (Jeffamine ® T403 from
Huntsman Chemicals)
Tertiary amine catalyst (SPI 847,	1.6	—	—
from Specialty Products
International)
Reactive amine catalyst (Debco	4.54	210	1
NE-200, from Air Products)
Silicone Surfactant (Tegostab ®	2.3	—	—
8404, from Th. Goldschmidt)

Claims

1. A method of forming a rigid polyurethane foam attached to a substrate having an open cavity, comprising mixing a polyisocyanate component with a polyol component in the presence of at least one catalyst for the reaction of a polyol with a polyisocyanate and a blowing agent, dispensing the resulting mixture onto a substrate defining an open cavity and subjecting the mixture to conditions sufficient to cause the mixture to cure to form a foam having a bulk density of 3 to 40 pounds per cubic foot (48-640 kg/m3) that is adherent to the substrate, wherein (a) the polyisocyanate component contains at least one compound having a plurality of free isocyanate groups,(b) the polyol component contains isocyanate-reactive materials that have an average functionality of at least about 2.3 and includes at least one polyol and,(c) the volume ratio of the polyisocyanate component to the polyol component is no greater than 5:1 and no less than 1:5,(d) the ratio of isocyanate groups in the polyisocyanate component to the number of isocyanate-reactive groups in the polyol component is from about 0.7:1 to about 1.5:1;(e) the blowing agent is a carbamate of an alkanolamine; and(f) the cream time of the mixture is less than 2 seconds.

2. The method of claim 1 wherein the carbamate is contained in a non-aqueous medium.

3. The method of claim 2 wherein the carbamate is a reaction product of carbon dioxide and N-methyl-2-aminoethanol, N-ethyl-2-aminoethanol, 2-(2-N-methyl-aminoethyl)-1,2-ethanediol, N,N′-bis-(β-hydroxyethyl)-ethylene diamine, N,N′-bis-(β-hydroxypropyl)ethylene diamine, N,N′-bis-(β-hydroxyethyl)-1,2-propylene diamine, N,N′-bis-(β-hydroxypropyl)-1,3-propane diamine, N,N′-bis-(β-hydroxyethyl)-1-methyl-2,4-diaminocyclohexane N,N′-bis-(β-hydroxyethyl)-1-methyl-2,6-diaminocyclohexane, N,N′-bis-(β-hydroxypropyl)-p-xylylene diamine, N-(β-hydroxyethyl-N′-(β-hydroxypropyl) ethylene diamine or tris-(β-hydroxyethyl)-1,6,11 triaminoundecane

4. The method of claim 2 wherein the carbamate is the reaction product of carbon dioxide and an alkanolamine having the structure HzN—[(CHR′—CHR″—O—)a—(CH2)x—OH]y

5. The method of claim 4 wherein the alkanolamine is 2-(2-aminoethoxy)ethanol or 2-(2-(2-aminoethoxy)ethoxy)ethanol.

6. The method of claim 1 wherein the isocyanate-terminated prepolymer component is a reaction product of an organic polyisocyanate and at least one polyol.

7. The method of claim 1 wherein the isocyanate-terminated prepolymer is a reaction product of an organic polyisocyanate, at least one polyol and a hydroxyl-functional acrylate or methacrylate.

8. The method of claim 6 wherein the polyisocyanate component includes at least one plasticizer.

9. The method of claim 1 wherein at least one polyol in the polyol component contains a tertiary amine group.

10. The method of claim 1 wherein the polyol component contains at least one amine-terminated polyether.

11. The method of claim 1 wherein the blowing agent is blended into the polyol component before the polyol component and polyisocyanate component are mixed.

12. The method of claim 1 wherein the catalyst is blended into the polyol component before the polyol component and polyisocyanate component are mixed.

13. The method of claim 1 wherein the cream time is less than 1 second.

14. The method of claim 1 wherein the substrate having an open cavity is an automotive part.

15. The method of claim 14 wherein the automotive part is assembled onto a vehicle or vehicle frame when the foam formulation is applied and foamed.

16. The method of claim 15 wherein the automotive part is a pillar, rocker, sill, sail, cowl, plenum, seam, frame rail, vehicle sub assembly, hydro-formed part, cross car beam or engine cradle.