Method for entraining gas in a liquid chemical precursor for reaction injection molding

• US 4,157,427 A
• Filed: 10/11/1977
• Issued: 06/05/1979
• Est. Priority Date: 10/11/1977
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Ferber, George
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US05/840,904
• Time in Patent Office: 602 Days
• Field of Search: 260/2.5 BC, 260/2.5 BD, 521/917, 521/133
• US Class Current: 521/133
• CPC Class Codes: B29B 7/7414 with rotatable stirrer, e.g. using an intermeshing rotor-stator system B29B7/7423 takes precedence
• CPC Class Codes: B29B 7/7433 Plants
• CPC Class Codes: B29C 67/246 Moulding high reactive monomers or prepolymers, e.g. by reaction injection moulding [RIM], liquid injection moulding [LIM] casting monomers B29C39/006, mixing construction B29B7/74
• CPC Class Codes: Y10S 261/26 Foam
• CPC Class Codes: Y10S 264/83 Injection molding of polyolefin-type foam
• CPC Class Codes: Y10S 521/917 Specialized mixing apparatus utilized in cell forming process

Abstract

In a preferred embodiment, minute bubbles of a suitable gas are rapidly entrained in a liquid chemical constituent of a reaction injection molding system (e.g., polyurethane) to reduce the viscosity of the constituent and the density of parts molded therefrom. A small portion of the constituent is continuously withdrawn from and returned to a main holding tank via a recirculation line wherein minute gas bubbles are dispersed from a microporous stone into the flowing portion of the constituent. The recirculating and gas entraining processes are continued until a predetermined quantity of the gas is dispersed in the molding constituent.

Claims

1. A method of rapidly entraining a predetermined quantity of a gas into a liquid constituent which is intended subsequently to be mixed with a second constituent reactive therewith to form a cellular polyurethane body, said method comprising the steps of

containing said liquid constituent in a stirred vessel, said vessel being equipped with a recirculation line leading away from and returning to said vessel,

withdrawing a relatively small portion of said liquid constituent from said vessel through said line,

entraining minute bubbles of a gas in said portion of said liquid constituent, said bubbles emanating from a rigid microporous structure positioned in the line and in the path of the flowing constituent,

returning said portion of said liquid constituent containing the entrained bubbles through said line to said stirred vessel,

repeating said withdrawing, entraining and returning steps until a desired amount of said gas is entrained in the liquid constituent.

2. In the practice of dispersing a predetermined quantity of a gaseous agent in a known quantity of liquid precursor material contained in a stirred vessel preparatory to said precursor material being mixed with another precursor material and the mixture then being injected into a mold wherein it reacts to form an injection molded cellular polyurethane article, the improved method comprising

continuously withdrawing from the vessel a relatively small portion of said liquid material in a continuous flowing stream.

introducing a said gas into said portion of said liquid material in the form of minute entrained bubbles, and

returning the gas containing liquid portion to the main body of the liquid in the stirred vessel, the introduction of said gas into said flowing stream being continued until the quantity of gas in the liquid in said vessel reaches a desired predetermined quantity suitable for the production of said articles.

3. A method of rapidly entraining a predetermined quantity of a gaseous blowing agent in a liquid constituent which is intended subsequently to be mixed with a second constituent reactive therewith to form a cellular polyurethane body, said method comprising the steps of

containing said liquid constituent in a stirred vessel, said vessel being equipped with a recirculation line leading away from and returning to said vessel,

withdrawing a relatively small portion of said liquid constituent from said vessel through said line,

entraining minute bubbles of a gas in said portion of said liquid constituent, said bubbles emanating from a rigid microporous structure positioned in the line to contact the liquid constituent flowing therethrough,

dividing the bubbles entrained in the liquid constituent into smaller bubbles,

returning said portion of said liquid constituent containing the entrained bubbles through said line to said stirred vessel,

repeating said withdrawing, entraining, dividing, and returning steps until a desired amount of said gas is entrained in the constituent.

4. In the practice of dispersing a gaseous blowing agent in a quantity of liquid precursor material contained in a stirred vessel preparatory to said liquid precursor material being employed in the production of reaction injection molded polyurethane articles, the improved method comprising

continuously withdrawing from the vessel a relatively small portion of said liquid material in a continuous flowing stream,

introducing a said gaseous agent into said portion of said liquid material in the form of minute uniformly dispersed bubbles,

returning the gas containing portion to the main body of the liquid material in the stirred vessel, and

measuring the specific gravity of the gas containing liquid in the stirred vessel and continuing the introduction of the gas into said flowing stream until a desired specific gravity corresponding to a predetermined concentration of gaseous blowing agent entrained in the liquid constituent is reached.