WO2012178145A2

WO2012178145A2 - Injection molding apparatus and method for downstream injection of fluid into material flow

Info

Publication number: WO2012178145A2
Application number: PCT/US2012/043944
Authority: WO
Inventors: Mark D. Moss; Vito Galati
Original assignee: Synventive Molding Solutions, Inc.
Priority date: 2011-06-23
Filing date: 2012-06-25
Publication date: 2012-12-27
Also published as: WO2012178145A3

Abstract

An apparatus for expanding the matrix of a polymer material injected under pressure into the cavity (60c) of a mold (60), the apparatus comprising: an injection machine having a barrel (70) into which a selected polymer material is delivered, the barrel (70) comprising an elongated tubular passage terminating at a downstream end in a barrel exit port (74), the polymer material being converted within the barrel (70) to a fluid that travels as a flow under pressure; a manifold (50), one or more nozzles (64) each having a downstream exit port sealably communicating with a corresponding gate in the cavity (60c) of the mold (60); and, an injecting system (30, 30h, 30n) having an exit or outlet port (X) sealably communicating with an inlet (40) to the manifold (50) or with a channel to the manifold or with one or more of the nozzles, the injecting system injecting a selected inert fluid into the pressurized fluid polymer material.

Description

INJECTION MOLDING APPARATUS AND METHOD FOR DOWNSTREAM INJECTION OF FLUID INTO MATERIAL FLOW

RELATED APPLICATIONS

[01] The disclosures of all of the following are incorporated by reference in their entirety as if fully set forth herein: U.S. Patent No. 5,894,025, U.S. Patent No. 6,062,840, U.S. Patent No. 6,294,122, U.S. Patent No. 6,309,208, U.S. Patent No. 6,287,107, U.S. Patent No. 6,343,921 , U.S. Patent No. 6,343,922, U.S. Patent No. 6,254,377, U.S. Patent No. 6,261 ,075, U.S. Patent No. 6,361 ,300 (7006), U.S.

Patent No. 6,419,870, U.S. Patent No. 6,464,909 (7031), U.S. Patent No. 6,599,116, U.S. Patent No. 6,824,379, U.S. Patent No. 7,234,929 (7075US1), U.S. Patent No. 7,419,625 (7075US2), U.S. Patent No. 7,569,169 (7075US3), U.S. Patent

Application Serial No. 10/214,118, filed August 8, 2002 (7006), U.S. Patent No.

7,029,268 (7077US1), U.S. Patent No. 7,270,537 (7077US2), U.S. Patent No.

7,597,828 (7077US3), U.S. Patent Application Serial No. 09/699,856 filed October 30, 2000 (7056), U.S. Patent No. 6,005,013, U.S. Patent No. 6,051 ,174, U.S. Patent application publication no. 20020147244, U.S. Patent Application Serial No.

10/269,927 filed October 11 , 2002 (7031), U.S. Application Serial No. 09/503,832 filed February, 15, 2000 (7053), U.S. Application Serial No. 09/656,846 filed

September 7, 2000 (7060), U.S. Application Serial No. 10/006,504 filed December 3, 2001 , (7068) and U.S. Application Serial No. 10/101 ,278 filed March, 19, 2002 (7070).

BACKGROUND OF THE INVENTION

Extrusion systems have been developed having devices that inject inert gases that have been converted to liquid into the barrel of extruder under very high pressure. Such systems attempt to mix the liquefied high pressure gases together with a polymer material that has been melted within the barrel and inject such mixed inert liquid-polymer fluid into a die at the exit of the barrel of the extruder whereby the polymer material is formed into a cooled body of foamed polymer material that contains cells created by expansion of the inert liquid within the body of polymer material.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided an apparatus for expanding the matrix of a polymer material injected under pressure into the cavity of a mold, the apparatus comprising:

an injection machine having a barrel into which a selected polymer material is delivered, the barrel comprising an elongated tubular passage terminating at a downstream end in a barrel exit port, the polymer material being converted within the barrel to a fluid that travels as a flow under pressure;

a manifold having one or more downstream fluid delivery passages into which the flow of fluid polymer material is received from the exit port of the barrel, the fluid delivery passages of the manifold receiving and distributing the flow of fluid polymer material;

one or more nozzles communicating downstream with the one or more fluid delivery passages of the manifold to receive the flow of polymer fluid material, each nozzle having a downstream exit port sealably communicating with a corresponding gate in the cavity of the mold;

an injecting system having an exit port sealably communicating with an inlet to the manifold or with the manifold or with one or more of the nozzles, the injecting system injecting a selected inert fluid into the pressurized fluid polymer material under a pressure selected to cause the inert fluid to mix into the flow of the fluid polymer material.

The injecting system typically injects the inert fluid into the inlet to the manifold, the inlet comprising a body that is mountable between the exit port of the barrel and a master receiving inlet passage of the manifold such that fluid exiting the barrel is sealably delivered from the barrel through the inlet, through the master receiving passage and into the one or more fluid delivery passages of the manifold. The body of the inlet has a central passage that receives and through which the fluid polymer material flows downstream into the manifold. The inlet preferably includes a mechanically driven mixing device disposed within the central passage of the passage.

The injecting system typically injects the inert fluid into the central passage of the inlet at a position disposed upstream of the mixing device.

The barrel typically has a screw that is mechanically driven to convert the polymer material into a fluid and force the fluid polymer material to travel from an upstream end of the barrel through the elongated tubular passage under pressure to the exit port of the barrel.

The injecting system preferably injects the inert fluid into the flow of fluid polymer material downstream of the exit port of the barrel.

In another aspect of the invention there is provided a method of molding a part from a solid polymer material, the method comprising:

delivering a selected solid polymer material into a bore of a barrel having a screw and mechanically turning the screw to liquify the polymer and drive the liquefied polymer downstream through an exit of the barrel into an entry of an inlet mechanism sealably communicating with a distribution manifold;

further driving the liquified polymer material with the screw under pressure as a pressurized flow through a channel through the inlet into an entry of a flow channel in the manifold;

further driving the flow of liquefied polymer through the channel in the manifold into and through the entry of a nozzle and further through a flow bore in the nozzle and further to and through an exit port of the nozzle that is sealably mated with a gate of a mold;

injecting a selected inert fluid into the flow of the liquified polymer at a position downstream of the exit of the barrel, the inert fluid being injected under pressure and at a temperature sufficient to effect a substantially homogenous mixture of the selected inert fluid with the liquified polymer material; driving the liquified polymer material and selected inert fluid mixture as a combined flow of fluids through the exit port of the nozzle and the gate of the mold into a cavity of the mold.

The selected inert fluid is typically injected into the flow of liquefied polymer material within the channel of the inlet mechanism downstream of the bore of the barrel.

The selected inert fluid is preferably mechanically mixed with the liquefied polymer material within one of the channels of the inlet or the manifold or within the bore of the nozzle.

In another aspect of the invention there is provided an apparatus for expanding the matrix of a polymer material injected under pressure into the cavity of a mold, the apparatus comprising:

an injecting system having an exit port sealably communicating downstream of the exit port of the mold with an inlet to the manifold or with the manifold or with one or more of the nozzles, the injecting system injecting a selected inert fluid into the pressurized fluid polymer material under a pressure selected to cause the inert fluid to mix into the flow of the fluid polymer material. There is also provided in accordance with the invention, a method for expanding the matrix of a polymer material injected under pressure into a cavity of a mold, the method comprising:

delivering a selected polymer material into the barrel of an injection machine, the barrel comprising an elongated tubular passage terminating at a downstream end in a barrel exit port,

converting the polymer material within the barrel to a fluid that travels as a flow under pressure;

delivering the polymer material from the exit port of the barrel to a manifold having one or more downstream fluid delivery passages, the fluid delivery passages of the manifold receiving and distributing the flow of fluid polymer material;

delivering the polymer material from the one or more fluid delivery passages of the manifold to one or more nozzles each having a downstream exit port sealably communicating with a corresponding gate in the cavity of the mold;

injecting a selected inert fluid into the pressurized fluid polymer material downstream of the exit port of the barrel under a pressure selected to cause the inert fluid to mix into the flow of the fluid polymer material.

In such a method the inert fluid is typically injected into the flow of fluid polymer material via injection into an inlet that communicates the flow of fluid polymer material between the exit port of the barrel and an inlet port to the manifold.

Alternatively in such a method, the inert fluid can be injected into the flow of fluid polymer material via injection into a fluid passage disposed in the manifold or via injection into a passage disposed in a nozzle.

Brief Description of the Drawings

[02] The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the

accompanying drawings in which:

[03] Fig. 1 is a top view of an apparatus according to the invention showing a manifold and mold and injector and an interface plate mounted in the center of the manifold with an inlet body mounted in the center of the interface plate for interfacing between the barrel of an extruder or injection machine and the manifold;

[04] Fig. 2 is a sectional view taken along lines 2-2 of Fig. 1 of one embodiment of the invention where the inlet has simple unobstructed passage between the exit of the barrel and the inlet to the master passage of the hotrunner or manifold;

[05] Fig. 3 is a sectional view taken along lines 2-2 of Fig. 1 of another embodiment of the invention showing the inlet body having a mechanical mixing device disposed within the passage of the inlet body;

[06] Fig. 4 is an isometric phantom view of the Figs. 1-3 apparatuses.

DETAILED DESCRIPTION

[07] Polymer material 80, Figs. 2, 3, is deposited in solid form into the interior bore of the barrel 70 of an extruder or injection machine. Once deposited, the polymer material 80 is engaged by a screw 72 that is mechanically driven to cause the polymer to melt under shear force and applied heat into a fluid capable of flowing under the force of pressure exerted by the screw 72. The fluidized polymer material within the bore of the barrel 70 is forced under pressure through a downstream exit port 74 of the barrel or with which the bore of the barrel

communicates. The exit port 74 of the barrel 70 is sealably interconnected to the upstream entrance Z of the inlet body 40. The fluidized polymer material is further forcibly delivered under pressure in a downstream direction through the channel 42 and into the upstream entry port 52e of a master or central hotrunner channel 52. The master hotrunner channel 52 branches into one or more distribution channels 55. The distribution channels 55 are sealably interconnected to the entry ports 66 of the bores of one or more nozzles 64, the exit ports 76 of which in turn are sealably interconnected to associated gates 62 that lead into the cavity 60c of a mold 60. The fluidized polymer material is typically maintained under high pressure during the course of its travel from the exit 74 of the barrel 70 up to the gates 62.

[08] FIG. 1 shows a portion of an injection molding system comprising the manifold 50, a top clamp plate 5 and a cylindrical positioning plate 20 mounted on the upstream surface of the top clamp plate 5 and an inlet 40 mounted in a receiving recess in the upstream surface of the manifold 50. In the embodiment shown in Figs. 1-4, a super critical fluid injector system 30 is mounted on the upstream side of the manifold 50 adjacent the inlet body 40. The injector system 30 has an outlet port X that communicates and injects a selected inert fluid such as C0₂. nitrogen, inert volatile hydrocarbons (preferably low molecular weight hydrocarbons), inert volatile chlorofluorocarbons, HFCs, HCFCs, helium and mixtures of two or more such inert fluids under high pressure into the central flow channel or passage 42 of the inlet body. The injected super critical fluid mixes into the flow of the polymer material flowing through the channel 42. As shown, the channel 42 is disposed downstream of the exit port 74 of the barrel 70 and barrel screw 72, the inlet body 40 being a body that is independent of the body of the barrel 70 and any other extensions of the bore 73 .of the barrel 70. In an alternative embodiment, the fluid injector system can be arranged and adapted to inject the supercritical fluid directly into a channel 52 of the hotrunner or manifold 50, such an injector shown in Fig. 2 as injector 30h.

Alternatively, the injector system can be arranged and adapted to inject the supercritical fluid directly into the flow channel or bore 67 of a nozzle 64, such an injector shown in Fig. 2 as injector 30n. In each embodiment, the injector 30, 30h, 30n, injects the supercritical fluid into the polymer flow at a point or location disposed downstream of the exit 74 of the barrel 70.

[09] The supercritical fluid that is injected by the injector 30 is injected into the flow of fluidized polymer material at a position downstream of the bore 73 of the barrel 70 and any extensions thereof. The supercritical fluid could alternatively be injected into one of the channels 52, 55 of the manifold or into the bore of a nozzle 70. Typically the pressure of the supercritical fluid is adjusted to a pressure selected to maximize mixing of the supercritical fluid with the polymer fluid within the channels 42 or 52, 55 or the bore of the nozzles 64. The selected fluid can be injected in a supercritical fluid state or in a non-supercritical fluid state and converted into a supercritical fluid state after being injected. The conditions of the supercritical fluid and methods for rendering the fluid in a supercritical fluid condition or state are disclosed for example in U.S. patent no. 5,158,986 the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein. The condition and amount or volume of supercritical fluid is selected and injected such that the part formed in the mold from the polymeric material contains groups or aggregates or regions of closed microcells that are of average size of less than about 100.0 urn (micrometers) in diameter, preferably less than about 10.0 urn and most preferably less than about 1.0 um. And, most preferably the condition and amount or volume of the supercritical fluid is selected and injected such that the part formed contains aggregates or regions of closed microcell density of equal to or greater than about 10² cells/cubic centimeter or cc.

[10] As shown, a mixing mechanism 90 is provided to effect mixing within the channel 42 of the inlet 40. A mixing mechanism 100, 75 can also be provided to effect mixing within the channels 52, 55 and/or the bore of the nozzles 64. The mixing mechanism can comprise a mechanical device, a stream of fluid or the like.

[11] The exact type of supercritical fluid selected for injection via the injector 30 is preferably a gas or liquid that is miscible with the polymer fluid and does not chemically react with or otherwise chemically alter the molecular nature of the polymer material. The temperature and pressure that is selected for injection of the supercritical fluid can be varied as desired in order to effect the desired amount of mixing with and pressurization within the flow of the fluidized polymer material. The degree to which the supercritical fluid is pressurized and heated depends on and is selected depending on the nature of the polymer material (such as PET versus polypropylene versus EVOH versus another selected polymer or mixture of polymers) and the temperature and pressure of the fluidized polymer material. The types of supercritical fluid and the pressure and temperature conditions thereof are described in for example U.S. Patent No. 6,005,013, U.S. Patent No. 6,051 ,174, U.S. Patent application publication no. 20020147244, the disclosures of all of which are incorporated herein by reference as if fully set forth herein.

[12] Once the supercritical fluid is injected into the flow of the polymer fluid the supercritical fluid is maintained under very high pressure within the polymer- supercritical fluid flow up until the mixed fluid stream exits the nozzle 70 at the exit port 76 through the gate 62 into the cavity of the mold 60 at which point the dissolved or otherwise intermixed supercritical fluid expands rapidly within the matrix of the polymer material to form microcells and essentially cause the polymer matrix to form a foamed matrix. The foamed polymer matrix is rapidly cooled within the cavity of the mold to a solid form that assumes the shape of the cavity into which it is injected and within which it is cooled.

Claims

1. Apparatus for expanding the matrix of a polymer material injected under pressure into the cavity of a mold, the apparatus comprising:

an injecting system having an exit port sealably communicating with an inlet to the manifold or with a flow channel of the manifold or with a flow bore of one or more of the nozzles, the injecting system injecting a selected inert fluid into the pressurized fluid polymer material under a pressure selected to cause the inert fluid to mix into the flow of the fluid polymer material.

2. The apparatus of claim 1 wherein the injecting system injects the inert fluid into the inlet to the manifold, the inlet comprising a body that is mountable between the exit port of the barrel and a master receiving inlet passage of the manifold such that fluid exiting the barrel is sealably delivered from the barrel through the inlet, through the master receiving inlet passage and into the one or more fluid delivery passages of the manifold.

3 The apparatus of claim 1 wherein the body of the inlet has a central passage that receives and through which the fluid polymer material flows

downstream into the manifold.

4. The apparatus of claim 3 wherein the inlet includes a mechanically driven mixing device disposed within the central passage of the passage.

5. The apparatus of claim 4 wherein the injecting system injects the inert fluid into the central passage of the inlet at a position disposed upstream of the mixing device.

6. The apparatus of claim 1 wherein the barrel has a screw that is mechanically driven to convert the polymer material into a fluid and force the fluid polymer material to travel from an upstream end of the barrel through the elongated tubular passage under pressure to the exit port of the barrel.

7. The apparatus of claim 1 wherein the injecting system injects the inert fluid into the flow of fluid polymer material downstream of the exit port of the barrel.

8. A method of molding a part from a solid polymer material, the method comprising:

further driving the flow of liquefied polymer through the channel in the manifold into and through the entry of a nozzle and further through a flow bore in the nozzle and further to and through an exit port of the nozzle that is sealably mated with a gate of a mold; injecting a selected inert fluid into the flow of the liquified polymer at a position downstream of the exit of the barrel, the inert fluid being injected under pressure and at a temperature sufficient to effect a substantially homogenous mixture of the selected inert fluid with the liquified polymer material;

driving the liquified polymer material and selected inert fluid mixture as a combined flow of fluids through the exit port of the nozzle and the gate of the mold into a cavity of the mold.

9. The method of claim 8 wherein the selected inert fluid is injected into the flow of liquefied polymer material within the channel of the inlet mechanism downstream of the bore of the barrel.

10. The method of claim 8 wherein the selected inert fluid is mechanically mixed with the liquefied polymer material within one of the channels of the inlet or the manifold or within the bore of the nozzle.

11. Apparatus for expanding the matrix of a polymer material injected under pressure into the cavity of a mold, the apparatus comprising:

one or more nozzles communicating downstream with the one or more fluid delivery passages of the manifold to receive the flow of polymer fluid material, each nozzle having a downstream exit port sealably communicating with a corresponding gate in the cavity of the mold; an injecting system having an exit port sealably communicating

downstream of the exit port of the moid with an inlet to the manifold or with the manifold or with one or more of the nozzles, the injecting system injecting a selected inert fluid into the pressurized fluid polymer material under a pressure selected to cause the inert fluid to mix into the flow of the fluid polymer material.

12. Method for expanding the matrix of a polymer material injected under pressure into a cavity of a mold, the method comprising:

13. Method of claim 12 wherein the inert fluid is injected into the flow of fluid polymer material via injection into an inlet that communicates the flow of fluid polymer material between the exit port of the barrel and an inlet port to the manifold.

14. Method of claim 12 wherein the inert fluid is injected into the flow of fluid polymer material via injection into a fluid passage disposed in the manifold or via injection into a passage disposed in a nozzle.