US 5,423,607 AGranted

Method for blending diverse blowing agents

AssigneeDolco Packaging Corporation

InventorsClifford Jones, John L. Baker

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Abstract

A blending apparatus for continuously and accurately blending a plurality of diverse, normally gaseous or volatile liquid components, preferably two or three, at low pressures. In a preferred embodiment, the apparatus blends a first stream of volatile liquid component, preferably carbon dioxide with a liquid stream of any suitable hydrocarbon (including halogenated hydrocarbons) blowing agent in accordance with any predetermined ratio desired by those skilled in the art before introducing the blend into a suitable extrusion process for preparation of polymeric foams and the like. The apparatus combines the liquid components at a pressure substantially lower than the elevated pressure required during the extrusion process. In an alternative embodiment, the blending apparatus blends a liquid stream of volatile liquid component, preferably carbon dioxide with a liquid stream of a first hydrocarbon blowing agent in accordance with any predetermined ratio and subsequently blends a second hydrocarbon blowing agent with the blend of the liquid carbon dioxide and the first hydrocarbon blowing agent.

Claims12

Dependent claims

A method for blending diverse blowing agents for delivery of the agents to an extruder which contains molten thermoplastic resin at a pressure of at least 3500 p.s.i.g. for mixture therein with said thermoplastic molten resin to form a foamed thermoplastic extrusion mass, said method comprising:

providing a refrigerated supply of liquid carbon dioxide, maintaining said supply of carbon dioxide in said liquid state at a predetermined pressure of less than 500 p.s.i.g. and at a temperature sufficient to prevent flashing thereof at said predetermined pressure, and providing a stream thereof;
providing a supply of first volatile liquid blowing agent for said molten thermoplastic, storing said supply of blowing agent, and providing a stream thereof;
measuring the flow rate of said stream of carbon dioxide and providing a first signal proportional thereto;
measuring the flow rate of said stream of first blowing agent and providing a second signal proportional thereto;
controlling the flow rate of said stream of first blowing agent responsive to said first and second signals whereby to provide a predetermined ratio of blowing agent and carbon dioxide;
mixing said streams of carbon dioxide and first blowing agent at pressure of less than 500 p.s.i.g. to form a blend thereof;
and
pumping said blend into said extruder whereby to form a foamed thermoplastic mass.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/188,344Filed 27 Jan 1994 · division
Priority: 3 May 1991
Granted: 13 Jun 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

B01F 35/2211
Of operational parameters, e.g. level of material in the mixer, temperature or pressure: amount of delivered fluid during a period
B01F 23/19
Mixing gases with gases: mixing systems, i.e. flow charts or diagrams; Arrangements, e.g. comprising controlling means
B01F 35/2111
Of the operational parameters: flow rate
B01F 35/831
By controlling the ratio of two or more flows, e.g. using flow sensing or flow controlling devices: using one or more pump or other dispensing…