REACTION INJECTION MOLDING SYSTEM AND PROCESSES FOR PRODUCING POLYURETHANE ARTICLES
An externally heated reaction injection molding (“RIM”) system and processes for producing polyurethane articles. The system comprises a mixing chamber for combining a prepolymer and a chain extender and one or more heating systems for heating at least one of the prepolymer and the chain extender upstream of the mixing chamber. In one embodiment, the process comprises injecting a heated prepolymer and/or a heated chain extender into a mixing chamber and initiating a curing of the prepolymer in a mixing chamber. By employing heat to decrease the viscosity of the prepolymer and/or the chain extender, prepolymers and/or chain extenders that have high room temperature viscosities or are in the solid state at room temperature, may be utilized in the RIM system.
1 . An externally heated reaction injection molding system in communication with a prepolymer storage vessel and a chain extender storage vessel.
2 . The system of claim 1 , wherein the system comprises:
a mixing chamber for combining a prepolymer and a chain extender; and
a heating system for heating at least one of the prepolymer and the chain extender upstream of the mixing chamber and downstream of the storage vessels.
3 . The system of claim 2 , wherein the heating system heats one or more conduits between the mixing chamber and at least one of the prepolymer storage vessel or the chain extender storage vessel.
4 . The system of claim 3 , wherein at least one of the prepolymer storage vessel or the chain extender storage vessel are heated.
5 . The system of claim 2 , wherein the system is capable of heating at least one of the prepolymer and the chain extender to a temperature greater than 70° C.
6 . The system of claim 2 , wherein the system is capable of heating at least one of the prepolymer and the chain extender to a temperature greater than 100° C.
7 . The system of claim 2 , wherein the system is capable of employing at least one of a prepolymer and a chain extender having a room temperature viscosity greater than 3000 centipoise.
8 . The system of claim 2 , wherein the system is capable of employing at least one of a prepolymer or a chain extender that is a solid at room temperature.
9 . The system of claim 2 , wherein the system is capable of employing at least one of a prepolymer or a chain extender having a melting point in the range of 40° C.-140° C.
10 . The system of claim 2 , further comprising:
a first conduit in fluid communication with the prepolymer storage vessel;
a first pump in fluid communication with the prepolymer storage vessel for pumping prepolymer through the first conduit to the mixing chamber;
a second conduit in fluid communication with the chain extender storage vessel; and
a second pump in fluid communication with the chain extender storage vessel for pumping chain extender through the second conduit to the mixing chamber.
11 . The system of claim 10 , further comprising a first heating system for independently heating the prepolymer and a second heating system for independently heating the chain extender.
12 . The system of claim 11 , wherein the first heating system comprises a first heated fluid that circulates around at least a portion of the prepolymer storage vessel, and wherein the second heating system comprises a second heated fluid that circulates around at least a portion of the chain extender storage vessel.
13 . The system of claim 2 , wherein the mixing chamber comprises an L head for mixing the prepolymer and the chain extender.
14 . The system of claim 2 , wherein the system is capable of combining the prepolymer and the chain extender at a weight ratio of from 3:1 to 10:1.
15 . The system of claim 2 , wherein the system is capable of combining the prepolymer and the chain extender at a weight ratio greater than 5:1.
16 . A process for producing an article in a reaction injection molding system, the process comprising the steps of:
(a) injecting a prepolymer and a chain extender into a mixing chamber, wherein at least one of the prepolymer and the chain extender is heated; and
(b) initiating a curing of the prepolymer in the mixing chamber, wherein the prepolymer and the chain extender have a gel time greater than 2 seconds.
17 . The process of claim 16 , wherein the gel time is greater than 4 seconds.
18 . The process of claim 16 , wherein the at least one of the prepolymer and the chain extender that is heated has a viscosity at 25° C. that is greater than 3000 centipoise.
19 . The process of claim 16 , wherein the at least one of the prepolymer and the chain extender that is heated has a viscosity at 25° C. that is greater than 5000 centipoise.
20 . The process of claim 16 , wherein the viscosity of the at least one of the prepolymer and the chain extender that is heated is reduced by at least 2000 centipoise.
21 . The process of claim 16 , wherein the viscosity of the at least one of the prepolymer and the chain extender that is heated is reduced by at least 4000 centipoise.
22 . The process of claim 16 , wherein the chain extender is in solid form at room temperature.
23 . The process of claim 16 , wherein the prepolymer is in solid form at room temperature.
24 . The process of claim 16 , wherein at least one of the prepolymer and the chain extender is heated to a temperature above 70° C.
25 . The process of claim 16 , wherein at least one of the prepolymer and the chain extender is heated to a temperature above 100° C.
26 . The process of claim 16 , further comprising the step of:
heating the mixing chamber.
27 . The process of claim 16 , further comprising the step of:
independently heating at least one of the prepolymer and the chain extender.
28 . The process of claim 16 , wherein the chain extender has a melting point in the range of 40° C.-140° C.
29 . The process of claim 16 , wherein the chain extender has a melting point greater than 60° C.
30 . The process of claim 16 , wherein the prepolymer has a melting point in the range of 60° C.-120° C.
31 . The process of claim 16 , wherein the prepolymer has a melting point greater than 60° C.
32 . The process of claim 16 , wherein the prepolymer has a NCO content of 2 to 12%.
33 . The process of claim 16 , wherein the prepolymer has a NCO content of less than 15%.
34 . The process of claim 16 , wherein at least one of the prepolymer and the chain extender has a melting point below 50° C.
35 . The process of claim 16 , wherein the chain extender is a halogenated aromatic diamine.
36 . The process of claim 16 , wherein the chain extender is a halogenated diaromatic diamine.
37 . The process of claim 16 , wherein the chain extender is selected from the group consisting of methylene bis orthochloroaniline (MOCA), methylene bis diethylanaline (MDEA), methylene bis chlorodiethylanaline (MCDEA), and hydroquinone-bis-hydroxyethyl ether (HQEE).
38 . The process of claim 16 , wherein the prepolymer is a toluene diisocyanate(“TDI”)-based prepolymer.
39 . The process of claim 16 , wherein the prepolymer is a diphenylmethane diisocyanate (“MDI”)-based prepolymers.
40 . The process of claim 16 , wherein the prepolymer is MDI-based and the chain extender is DMTDA.
41 . The process of claim 16 , wherein the prepolymer is TDI-based and the chain extender is selected from the group consisting of MDEA and MCDEA.
42 . The process of claim 16 , wherein the prepolymer is TDI-based and the chain extender is DETDA.
43 . The process of claim 16 , wherein the prepolymer is MDI-based and the chain extender is selected from the group consisting of MOCA and MCDEA.
44 . The process of claim 43 , wherein the article has a hardness of 45 to 85 Shore D.
45 . The process of claim 43 , wherein the article softens by less than 30 Shore D units when heated to 150° C.
46 . The process of claim 16 , wherein the prepolymer is the reaction product of a polyol and an aromatic diisocyanate and the chain extender is a diaromatic diamine.
47 . A process for producing an article in a reaction injection molding system, the process comprising the steps of:
(a) injecting a prepolymer and a chain extender into a mixing chamber to form a reaction mixture, wherein at least one of the prepolymer or chain extender is heated to reduce its viscosity by at least 2000 centipoise relative to room temperature;
(b) directing the reaction mixture into a mold; and
(c) curing the reaction mixture to form the article.
48 . The process of claim 47 , wherein the prepolymer and the chain extender have a gel time greater than 2 seconds.
49 . The process of claim 47 , wherein the prepolymer and the chain extender have a gel time greater than 4 seconds.
50 . The process of claim 47 , wherein the prepolymer is heated.
51 . The process of claim 47 , wherein the chain extender is heated.
52 . The process of claim 47 , wherein both the prepolymer and the chain extender are heated.
53 . The process of claim 47 , wherein the viscosity is reduced by at least 2000 centipoise.
54 . The process of claim 47 , wherein the viscosity is reduced by at least 4000 centipoise.