Low-Pressure Molding System

Abstract

The present invention relates to extrusion molding machines and methods of producing extrusion molded parts and, more particularly, to extrusion molding machines that adjust operating parameters of the extrusion molding machine during an extrusion molding run to account for changes in material properties and pressures of the extrusion material and methods of accounting for changes in extrusion molding material properties during an extrusion molding run and/or compounding of materials.

Claims

1. A method comprising: (a) filling a molten thermoplastic material into an at least one mold cavity of a molding apparatus, the molten thermoplastic material having a melt pressure that, upon entering into the at least one mold cavity, exceeds a pre-injection pressure of the molten thermoplastic material; and, (b) while filling the at least one mold cavity with the molten thermoplastic material, maintaining the melt pressure substantially constant at less than 6000 psi, wherein: the thermoplastic material has a melt flow index of about 0.1 g/10 min to about 500 g/10 min.

2. The method of claim 1, wherein the molding apparatus comprises a breaker plate in the manifold having heated runners in fluid communication with the at least one mold cavity, wherein the melt pressure of the molten thermoplastic material is maintained substantially constant while the molten thermoplastic material is transported from an entry point through the breaker plate to the heated runners.

3. The method of claim 1, wherein the filling of the molten thermoplastic material into the at last one mold cavity comprises applying a hydraulic pressure to the molten thermoplastic material, and wherein maintaining the constant melt pressure comprises monitoring the melt pressure of the molten thermoplastic material upon entering into the at least one mold cavity and the melt pressure of the molten thermoplastic material during filling of the at least one mold cavity, and adjusting the hydraulic pressure applied to the molten thermoplastic material entering into the at least one mold cavity.

4. The method of claim 1, wherein the molding apparatus comprises a pressure relief valve disposed between an breaker plate and the at least one mold cavity, the pressure relief valve having a predetermined set point at the substantially constant melt pressure and maintaining the substantially constant melt pressure on molten thermoplastic material through the pressure relief valve at a melt pressure higher than the predetermined set point, the pressure relief valve reducing the melt pressure of the thermoplastic material as it passes through the pressure relief valve and enter into the at least one mold cavity.

5. The method of claim 1, wherein the molding apparatus automatically adjusting an extrusion molding process to compensate for variations in the flowability and/or temperature variations of a molten plastic material, the method comprising: providing an extrusion molding machine with at least one mold cavity; providing an injection molding controller, which includes a pressure control output that is configured to generate a control signal, which, at least partially determines an extrusion molding pressure and/or temperature for the extrusion molding process of the extrusion molding machine; measuring a first control signal generated from the pressure control output and/or temperature output at a first time in an extrusion molding cycle; measuring a second control signal generated from the pressure control output and/or temperature output at a second time in the same extrusion molding cycle, subsequent to the first time; comparing the first control signal generated from the pressure control output and/or temperature output and the second control signal generated from the pressure control output and/or temperature output to obtain a comparison result; and determining a third control signal for the pressure control output and/or temperature output, based at least in part on the comparison result, at a third time that is subsequent to the second time.

6. The method of claim 5, wherein the determining includes determining the third control signal at a third time, which is within the same extrusion molding cycle as the second time.

7. The method of claim 5, wherein the third time is located in a subsequent molding cycle from the second time.

8. The method of claim 5, including: determining a time difference between the first time and the second time; and wherein the comparing includes comparing the first control signal and the second control signal, based, at least in part, on the time difference, to obtain the comparison result.

9. The method of claim 8, wherein the comparison result is a flow factor (FF) that is used as a soft sensor melt viscosity input to by the controller.

10. The method of claim 9, wherein the FF is determined by the formula:
FF=(CS1-CS2)/T; where CS1 is the first control signal; CS2 is the second control signal; and T is the time difference between CS1 and CS2.

11. The method of claim 10, wherein the third control signal is proportional to the flow factor.

12. The method of claim 10, wherein T is between 0.1 milliseconds and 10 milliseconds.

13. The method of claim 5, wherein the comparison result is used as a basis for a viscosity change index (VCI) that is used as a soft sensor melt viscosity input to by the controller.

14. The method of claim 13, wherein the VCI is determined by the following formula:
VCI=(CS1-CS2)/S where CS1 is a first control signal; CS2 is a second control signal; and S is the position difference for the melt moving machine component.

15. The method of claim 13, wherein the third control signal is proportional to the VCI.

16. The method of claim 13, wherein S is between 0.5 microns and 10 microns.

17. The method of claim 1, wherein the comparing of the first control signal and the second control signal includes comparing the first control signal and the second control signal to optimal control signals based on an optimal pressure curve.

18. The method of claim 5, wherein the providing of the extrusion molding machine includes providing a melt moving machine component; and further comprising: measuring a first position of the melt moving machine component at the first time; measuring a second position of the melt moving machine component at the second time; determining a position difference between the first position and the second position; and wherein the comparing includes comparing the first control signal and the second control signal, based, at least in part, on the position difference, to obtain the comparison result.

19. The method of claim 5, further comprising controlling the injection molding pressure by sending the third control signal to a melt pressure control device.

20. A controller configured to automatically adjust an extrusion molding process to compensate for variations in the flowability of a molten plastic material, the controller adapted to: measure a first control signal generated from a pressure control output of the controller at a first time in an extrusion molding cycle using a control signal measurement device; measure a second control signal generated from the pressure control output of the controller at a second time in the same extrusion molding cycle, subsequent to the first time using the control signal measurement device; compare the first control signal generated from the pressure control output of the controller and the second control signal generated from the pressure control output of the controller to obtain a comparison result; and determine a third control signal for the pressure control output, based at least in part on the comparison result, at a third time that is subsequent to the second time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0293] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims:

[0294] FIG. 1 illustrates a diagrammatic front view of a plastic extrusion machine according to one or more embodiments shown and described herein;

[0295] FIG. 2 is a illustration of a breaker plate for extrusion molding at low, substantially constant pressure in accordance with an embodiment of the disclosure;

[0296] FIG. 3 is a illustration of a blow molding machine for molding at low, substantially constant pressure in accordance with another embodiment of the disclosure;

[0297] FIG. 4 is a schematic illustration of a parison entering a blow mold;

[0298] FIG. 5 is a schematic illustration of a bottle blow mold process for molding at low, substantially constant pressure in accordance with another embodiment of the disclosure;

[0299] FIG. 6 illustrates a diagrammatic front view of a plastic injection molding machine according to one or more embodiments shown and described herein;

[0300] FIG. 7 illustrates a diagrammatic front view of a hot runner mold that could be improved by the method of injection molding at low, substantially constant pressure in accordance with an embodiment of the disclosure;

[0301] FIG. 8 illustrates a diagrammatic front view of a more detailed hot runner mold;

[0302] FIG. 9 illustrates a diagrammatic view of the iMFLUX low-pressure process molding thick-to-thin-to-thick in this PP demo part. This application requires automatic control software and sensors that provide absolutely constant filling pressure, with no hesitation enabling a 0.030 inch. Diameter runner having a 3-inch long “filament” portion before entering and filling the cavity of the part without freezing.

DETAILED DESCRIPTION

[0303] All pressures disclosed herein are gauge pressures, which are pressures relative to ambient pressure.

[0304] Disclosed herein is a method of injection molding at low, substantially constant melt pressures. Embodiments of the disclosed method now make possible a method of injection molding that is more energy—and cost—effective than conventional high-velocity injection molding process. Embodiment of the disclosed method surprisingly allow for the filling of a mold cavity at low melt pressure without undesirable premature hardening of the thermoplastic material in the mold cavity and without the need for maintaining a constant temperature or heated mold cavity. As described in detail below, one of ordinary skill in the art would not have expected that a constant pressure method could be performed at low pressure without such premature hardening of the thermoplastic material when using an unheated mold cavity or cooled mold cavity.

[0305] Embodiments of the disclosed method also allow for the formation of quality injection molded parts that do not experience undesirable sink or warp without the need to balance the pre-injection mold cavity pressure and the pre-injection pressure of the thermoplastic materials. Thus, embodiments of the disclosed method can be performed using atmospheric mold cavities pressures and eliminate the need for including pressurizing means in the mold cavity.

[0306] Embodiments of the method can also produce quality injection molded parts with significantly less sensitivity to variations in the temperature, viscosity, and other such properties of the thermoplastic material, as compared to conventional high-pressure injection molding process. In one embodiment, this can advantageously allow for use of thermoplastic materials formed from recycled plastics (e.g., post-consumer recycled plastics), which inherently have batch-to-batch variation of the material properties.

[0307] Additionally, the low melt pressures used in the disclosed method can allow for use of low hardness, high thermal conductive mold cavity materials that are more cost effective to manufacture and are more energy efficient. For example, the mold cavity can be formed of a material having a surface hardness of less than 30 Rockwell C (Rc) and a thermal conductivity of greater than 30 BTU/HR FT ° F. In one embodiment, the mold cavity can be formed of an aluminum alloys, such as, for example aluminum alloys 6061 Al and 7075 Al.

[0308] Embodiments of the disclosed method can further allow for the formation of high quality thin-walled parts. For example, a molded part having a length of molten thermoplastic flow to thickness (L/T) ratio of greater than 100 can be formed using embodiments of the method. It is contemplated the embodiments of the method can also form molded parts having an L/T ratio greater than 200, and in some cases greater than 250.

[0309] Molded parts are generally considered to be thin walled when a length of a flow channel L divided by a thickness of the flow channel T is greater than 100 (i.e., L/T>100).

[0310] A sensor may be located near the end of fill in the mold. This sensor may provide an indication of when the melt front is approaching the end of fill in the mold. The sensor may sense pressure, temperature, optically, or other means of identifying the presence of the polymer. When pressure is measured by the sensor, this measure can be used to communicate with the central control unit to provide a target “packing pressure” for the molded component. The signal generated by the sensor can be used to control the molding process, such that variations in material viscosity, mold temperatures, melt temperatures, and other variations influencing filling rate, can be adjusted for by the central control unit. These adjustments can be made immediately during the molding cycle, or corrections can be made in subsequent cycles. Furthermore, several readings can be averaged over a number of cycles then used to make adjustments to the molding process by the central control unit. In this way, the current injection cycle can be corrected based on measurements occurring during one or more cycles at an earlier point in time. In one embodiment, sensor readings can be averaged over many cycles so as to achieve process consistency.

[0311] Once the mold is completely filled, the melt pressure and the mold pressure, if necessary, are reduced to atmospheric pressure at time and the mold cavity can be opened. During this time if using an injection molding machine, the reciprocating screw stops traveling forward. Advantageously, the low, substantially constant pressure conditions allow the shot comprising molten thermoplastic material to cool rapidly inside the mold, which, in various embodiments, can occur substantially simultaneously with venting of the melt pressure and the mold cavity to atmospheric pressure. Thus, the injection molded part can be ejected from the mold quickly after filling of the mold cavity with the shot comprising molten thermoplastic material.

[0312] Melt Pressure

[0313] As used herein, the term “melt pressure” refers to a pressure of the molten thermoplastic material as it is introduced into and fills a mold cavity of a molding apparatus. During filling of substantially the entire mold cavity, the melt pressure of the shot comprising molten thermoplastic material is maintained substantially constant at less than 6000 psi. The melt pressure of the shot comprising molten thermoplastic material during filling of substantially the entire mold cavity is significantly less than the injection and filling melt pressures used in conventional injection molding processes and recommended by manufacturers of thermoplastic materials for use in injection molding process. Other suitable melt pressures include, for example, less than 5000 psi, less than 4500 psi, less than 4000 psi, and less than 3000 psi. For example, the melt pressure can be maintained at a substantially constant pressure within the range of about 1000 psi to less than 6000 psi, about 1500 psi to about 5500 psi, about 2000 psi to about 5000 psi, about 2500 psi to about 4500 psi, about 3000 psi to about 4000 psi, and about 3000 psi to less than 6000 psi.

[0314] As described above, a “substantially constant pressure” refers to a pressure that does not fluctuate upwardly or downwardly from the desired melt pressure more than 30% of the desired melt pressure during filling of substantially the entire mold cavity with the shot comprising molten thermoplastic material. For example, the substantially constant pressure can fluctuate (either as an increase or decrease) from the melt pressure about 0% to about 30%, about 2% to about 25%, about 4% to about 20%, about 6% to about 15%, and about 8% to about 10%. Other suitable fluctuation amounts include about 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, and 30%. The melt pressure during filling of substantially the entire mold cavity can increase or decrease, respectively, for example, at a constant rate, and be considered substantially constant so long as the maximum increase or decrease in the melt pressure during filling of substantially the entire mold cavity is no greater than the 30% of the desired melt pressure. In yet another embodiment, the melt pressure during filling of substantially the entire mold cavity can increase over a portion of time and then decrease over a remaining portion of time. This fluctuation will be considered a substantially constant pressure so long as the maximum increase or decrease in the melt pressure during filing is less than 30% of the desired melt pressure.

[0315] The melt pressure of the thermoplastic material filling into the mold cavity can be measured using, for example, a pressure transducer disposed at the filling point. The location in the molding apparatus where the molten thermoplastic material enters the mold cavity. For example, for a molding apparatus having a single mold cavity coupled to a nozzle, the filling point can be at or adjacent to the nozzle. Alternatively, for a molding apparatus having a plurality of mold cavities and a runner system for transporting the molten thermoplastic material from the nozzle to each of the mold cavities, the filling points can be the points of contact between the runner system and each of the individual mold cavities. The molten thermoplastic material is maintained at the substantially constant melt pressure as it is transported through the runner system. In general, the runner system is a heated runner system that maintains the melt temperature of the shot comprising molten thermoplastic material as it is transported to the mold cavities.

[0316] The melt pressure of the thermoplastic material during filling of substantially the entire mold cavity can be maintained, for example, by measuring the melt pressure using a pressure transducer disposed at the nozzle and maintaining a constant pressure at the nozzle. In another embodiment, the melt pressure of the shot comprising thermoplastic material during filing of substantially the entire mold cavity can be measured using a pressure transducer disposed in the mold cavity opposite the gate.

[0317] In another embodiment, once substantially the entire mold cavity is filled, the melt pressure can be increased to fill and pack the remaining portion of the mold cavity.

[0318] Maintaining Substantially Constant Pressure

[0319] A closed loop controller and/or another pressure regulating devices may be used instead of the closed loop controller. For example, a pressure regulating valve (not shown) or a pressure relief valve (not shown) may replace a controller to regulate the melt pressure of the molten thermoplastic material. More specifically, the pressure regulating valve and pressure relief valve can prevent over pressurization of the mold. Another alternative mechanism for preventing over pressurization of the mold is to activate an alarm when an over pressurization condition is detected.

[0320] Thus in another embodiment, the molding apparatus can include a pressure relief valve disposed between an breaker plate and the mold cavity. The pressure relief valve has a predetermined pressure set point, which is equal to desired melt pressure for the filling of the mold. The melt pressure during the filling of the mold cavity is maintained substantially constant by applying a pressure to the molten thermoplastic material to force the molten thermoplastic material through the pressure relief valve at a melt pressure higher than the predetermined set point. The pressure relief valve then reduces the melt pressure of the thermoplastic material as it passes through the pressure relief valve and is introduced into the mold cavity. The reduced melt pressure of the molten thermoplastic material corresponds to the desired melt pressure for filling of the mold cavity and is maintained substantially constant by the predetermined set point of the pressure release valve.

[0321] In one embodiment, the melt pressure is reduced by diverting a portion of thermoplastic material to an outlet of the pressure relief valve. The diverted portion of the thermoplastic material can be maintained in a molten state and can be reincorporated into the injection system, for example, through the heated barrel.

[0322] Mold Cavity Pressure

[0323] As used herein, the “mold cavity pressure” refers to the pressure within a closed mold cavity and/or an open extrusion mold, and/or blow molding mold. The mold cavity and/or an open extrusion mold, and/or blow molding mold. Pressure can be measured, for example, using a pressure transducer placed inside the mold cavity and/or an open extrusion mold, and/or blow molding mold. In embodiments of the method, prior to introducing molten thermoplastic material into the mold cavity and/or an open extrusion mold, and/or blow molding mold., the mold cavity pressure is different than the pressure of the molten thermoplastic material. For example, the mold cavity pressure can be less than the pressure of the molten thermoplastic material. In another embodiment, the mold cavity pressure can be greater than the pressure of the molten thermoplastic material. The mold cavity pressure can have a pressure greater than atmospheric pressure. In yet another embodiment, the mold cavity can be maintained at a vacuum prior to and/or during filling.

[0324] In various embodiments, the mold cavity and/or breaker plate pressure can be maintained substantially constant during filling of substantially the entire mold cavity with the shot comprising molten thermoplastic material. The term “substantially constant pressure” as used herein with respect to a melt pressure of a thermoplastic material, means that deviations from a baseline melt pressure do not produce meaningful changes in physical properties of the thermoplastic material. For example, “substantially constant pressure” includes, but is not limited to, pressure variations for which viscosity of the melted thermoplastic material do not meaningfully change. The term “substantially constant” in this respect includes deviations of up to approximately 30% from a baseline melt pressure. For example, the term “a substantially constant pressure of approximately 4600 psi” includes pressure fluctuations within the range of about 6000 psi (30% above 4600 psi) to about 3200 psi (30% below 4600 psi). A melt pressure is considered substantially constant as long as the melt pressure fluctuates no more than 30% from the recited pressure.

[0325] For example, the substantially constant pressure can fluctuate (either as an increase or decrease) from the melt pressure about 0% to about 30%, about 2% to about 25%, about 4% to about 20%, about 6% to about 15%, and about 8% to about 10%. Other suitable fluctuation amounts include about 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, and 30%. The mold cavity pressure can be maintained substantially constant at a pressure greater than atmospheric pressure.

[0326] The mold cavity can include, for example, one or more vents for maintaining the mold cavity pressure substantially constant. The vents can be controlled to open and close in order to maintain the substantially constant mold cavity pressure.

[0327] In one embodiment, a vacuum can be maintained in the filling of substantially the entire mold cavity with the molten thermoplastic. Maintaining a vacuum in the mold cavity during injection can advantageously reduce the amount of melt pressure required to fill the cavity, as there is no air to force from the mold cavity during filling. The lack of air resistance to the flow and the increased pressure drop between the melt pressure and the end of fill pressure can also result in a greater flow length of the shot comprising molten thermoplastic material.

[0328] Mold Temperature

[0329] In embodiments of the method, the mold cavity is maintained at room temperature or cooled prior to filling of the mold with the molten thermoplastic material. While the mold surfaces may increase in temperature upon contact with the molten thermoplastic material, an internal portion of the mold cavity spaced at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, at least 6 mm, at least 7 mm, at least 8 mm, at least 9 mm, or at least 10 mm from the most immediate surface of the mold cavity contacting the thermoplastic material is maintained at a lower temperature. Typically, this temperature is less than the no-flow temperature of the thermoplastic material. As used herein, the “no-flow temperature” refers to the temperature at which the viscosity of the thermoplastic material is so high that it effectively cannot be made to flow. In various embodiments, the internal portion of the mold can be maintained at a temperature of less than 100° C. For example, the internal portion can be maintained at a temperature of about 10° C. to about 99° C., about 20° C. to about 80° C., about 30° C. to about 70° C., about 40° C. to about 60° C., and about 20° C. to about 50° C. Other suitable temperatures include, about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99° C. In one embodiment, the internal portion is maintained at a temperature of less than 50° C.

[0330] Heretofore, when filling at low constant pressure, the filling rates were reduced relative to conventional filling methods. This means the polymer would be in contact with the cool molding surfaces for longer periods before the mold would completely fill. Thus, more heat would need to be removed before filling, and this would be expected to result in the material freezing off before the mold is filled. It has been unexpectedly discovered that the thermoplastic material will flow when subjected to low, substantially constant pressure conditions despite a portion of the mold cavity being below the no-flow temperature of the thermoplastic material. It would be generally expected by one of ordinary skill in the art that such conditions would cause the thermoplastic material to freeze and plug the mold cavity rather than continue to flow and fill the entire mold cavity. Without intending to be bound by theory, it is believed that the low, substantially constant pressure conditions of embodiments of the disclosed method allow for dynamic flow conditions (i.e., constantly moving melt front) throughout the entire mold cavity during filling. There is no hesitation in the flow of the molten thermoplastic material as it flows to fill the mold cavity and, thus, no opportunity for freeze-off of the flow despite at least a portion of the mold cavity being below the no-flow temperature of the thermoplastic material. Additionally, it is believed that as a result of the dynamic flow conditions, the molten thermoplastic material is able to maintain a temperature higher than the no-flow temperature, despite being subjected to such temperatures in the mold cavity, as a result of shear heating. It is further believed that the dynamic flow conditions interfere with the formation of crystal structures in the thermoplastic material as it begins the freezing process. Crystal structure formation increases the viscosity of the thermoplastic material, which can prevent suitable flow to fill the cavity. The reduction in crystal structure formation and/or crystal structure size can allow for a decrease in the thermoplastic material viscosity as it flows into the cavity and is subjected to the low temperature of the mold that is below the no-flow temperature of the material.

[0331] In various embodiments, the mold can include a cooling system that maintains the entire mold cavity at a temperature below the no-flow temperature. For example, even surfaces of the mold cavity which contact the molten thermoplastic material can be cooled to maintain a lower temperature. Any suitable cooling temperature can be used. For example, the mold can be maintained substantially at room temperature. Incorporation of such cooling systems can advantageously enhance the rate at which the as-formed plastic part leaves the mold.

[0332] Thermoplastic Material

[0333] A variety of thermoplastic materials can be used in the low, substantially constant pressure injection molding methods of the disclosure. In one embodiment, the molten thermoplastic material has a viscosity, as defined by the melt flow index of about 0.1 g/10 min to about 500 g/10 min, as measured by ASTM D1238 performed at a temperature of about 230 C and a weight of 2.16 kg. For example, for polypropylene the melt flow index can be in a range of about 0.5 g/10 min to about 200 g/10 min. Other suitable melt flow indexes include about 1 g/10 min to about 400 g/10 min, about 10 g/10 min to about 300 g/10 min, about 20 to about 200 g/10 min, about 30 g/10 min to about 100 g/10 min, about 50 g/10 min to about 75 g/10 min, about 0.1 g/10 min to about 1 g/10 min, or about 1 g/10 min to about 25 g/10 min. The MFI of the material is selected based on the application and use of the molded article. For examples, thermoplastic materials with an MFI of 0.1 g/10 min to about 5 g/10 min may be suitable for use as preforms for Injection Stretch Blow Molding (ISBM) applications. Thermoplastic materials with an MFI of 5 g/10 min to about 50 g/10 min may be suitable for use as caps and closures for packaging articles. Thermoplastic materials with an MFI of 50 g/10 min to about 150 g/10 min may be suitable for use in the manufacture of buckets or tubs. Thermoplastic materials with an MFI of 150 g/10 min to about 500 g/10 min may be suitable for molded articles that have extremely high L/T ratios such as a thin plate. Manufacturers of such thermoplastic materials generally teach that the materials should be injection molded using melt pressures in excess of 6000 psi, and often in great excess of 6000 psi. Contrary to conventional teachings regarding injection molding of such thermoplastic materials, embodiments of the low, constant injection molding method of the disclosure advantageously allow for forming quality injection molded parts using such thermoplastic materials and processing at melt pressures below 6000 psi, and possibly well below 6000 psi.

[0334] The thermoplastic material can be, for example, a polyolefin. Exemplary polyolefins include, but are not limited to, polypropylene, polyethylene, polymethylpentene, and polybutene-1. Any of the aforementioned polyolefins could be sourced from bio-based feedstocks, such as sugarcane or other agricultural products, to produce a bio-polypropylene or bio-polyethylene. Polyolefins advantageously demonstrate shear thinning when in a molten state. Shear thinning is a reduction in viscosity when the fluid is placed under compressive stress. Shear thinning can beneficially allow for the flow of the thermoplastic material to be maintained throughout the injection molding process. Without intending to be bound by theory, it is believed that the shear thinning properties of a thermoplastic material, and in particular polyolefins, results in less variation of the materials viscosity when the material is processed at low pressures. As a result, embodiments of the method of the disclosure can be less sensitive to variations in the thermoplastic material, for example, resulting from colorants and other additives as well as processing conditions. This decreased sensitivity to batch-to-batch variations of the properties thermoplastic material can also advantageously allow post-industrial and post-consumer recycled plastics to be processed using embodiments of the method of the disclosure. Postindustrial and post-consumer recycled plastics are derived from end products that have completed their life cycle and would otherwise have been disposed of as a solid waste product. Such recycled plastic, and blends of thermoplastic materials, inherently have significant batch-to-batch variation of their material properties.

[0335] The thermoplastic material can also be, for example, a polyester. Exemplary polyesters include, but are not limited to, polyethylene terphthalate (PET). The PET polymer could be sourced from bio-based feedstocks, such as sugarcane or other agricultural products, to produce a partially or fully bio-PET polymer. Other suitable thermoplastic materials include copolymers of polypropylene and polyethylene, and polymers and copolymers of thermoplastic elastomers, polyester, polystyrene, polycarbonate, poly(acrylonitrile-butadiene-styrene), poly(lactic acid), bio-based polyesters such as poly(ethylene furanate) polyhydroxyalkanoate, poly(ethylene furanoate), (considered to be an alternative to, or drop-in replacement for, PET), polyhydroxyalkanoate, polyamides, polyacetals, ethylene-alpha olefin rubbers, and styrene-butadiene-styrene block copolymers. The thermoplastic material can also be a blend of multiple polymeric and non-polymeric materials. The thermoplastic material can be, for example, a blend of high, medium, and low molecular polymers yielding a multi-modal or bi-modal blend. The multi-modal material can be designed in a way that results in a thermoplastic material that has superior flow properties yet has satisfactory chemo/physical properties. The thermoplastic material can also be a blend of a polymer with one or more small molecule additives. The small molecule could be, for example, a siloxane or other lubricating molecule that, when added to the thermoplastic material, improves the flowability of the polymeric material.

[0336] Other additives may include foaming agents and other expanding additives, inorganic fillers such calcium carbonate, calcium sulfate, talcs, clays (e.g., nanoclays), aluminum hydroxide, CaSiO3, glass formed into fibers or microspheres, crystalline silicas (e.g., quartz, novacite, crystallobite), magnesium hydroxide, mica, sodium sulfate, lithopone, magnesium carbonate, iron oxide; or, organic fillers such as rice husks, straw, hemp fiber, wood flour, or wood, bamboo or sugarcane fiber.

[0337] Other suitable thermoplastic materials include renewable polymers such as nonlimiting examples of polymers produced directly from organisms, such as polyhydroxyalkanoates (e.g., poly(beta-hydroxyalkanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate, NODAX (Registered Trademark)), and bacterial cellulose; polymers extracted from plants, agricultural and forest, and biomass, such as polysaccharides and derivatives thereof (e.g., gums, cellulose, cellulose esters, chitin, chitosan, starch, chemically modified starch, particles of cellulose acetate), proteins (e.g., zein, whey, gluten, collagen), lipids, lignins, and natural rubber; thermoplastic starch produced from starch or chemically starch and current polymers derived from naturally sourced monomers and derivatives, such as bio-polyethylene, bio-polypropylene, polytrimethylene terephthalate, polylactic acid, NYLON 11, alkyd resins, succinic acid-based polyesters, and bio-polyethylene terephthalate.

[0338] The suitable thermoplastic materials may include a blend or blends of different thermoplastic materials such in the examples cited above. As well the different materials may be a combination of materials derived from virgin bio-derived or petroleum-derived materials, or recycled materials of bio-derived or petroleum-derived materials. One or more of the thermoplastic materials in a blend may be biodegradable. And for non-blend thermoplastic materials that material may be biodegradable.

[0339] Exemplary thermoplastic resins together with their recommended operating pressure ranges are provided in the following chart:

[0340] Injection Pressure Material Material Full Name Range (PSI) Company Brand Name pp Polypropylene 10000-15000 RTP RTP

[0341] 100 Imagineering series Plastics Poly—propylene Nylon 10000-18000 RTP RTP

[0342] 200 Imagineering series Plastics Nylon ABS Acrylonitrile 8000-20000 Marplex Astalac Butadiene ABS Styrene PET Polyester 5800-14500 Asia AIE PET International 401F Acetal 7000-17000 API

[0343] Kolon Kocetal Copolymer PC Polycarbonate 10000-15000 RTP RTP

[0344] 300 Imagineering series Plastics Poly—carbonate PS Polystyrene 10000-15000 RTP RTP 400 Imagineering series Plastics SAN Styrene 10000-15000 RTP RTP 500 Acrylonitrile Imagineering series Plastics PE LDPE & 10000-15000 RTP RTP 700 HDPE Imagineering Series Plastics TPE Thermoplastic 10000-15000 RTP RTP 1500 Elastomer Imagineering series Plastics PVDF Polyvinylidene 10000-15000 RTP RTP 3300 Fluoride Imagineering series Plastics PTI Poly—10000-15000 RTP RTP

[0345] 4700 trimethylene Imagineering series Terephthalate Plastics PBT Polybutylene 10000-15000 RTP RTP 1000 Terephthalate Imagineering series Plastics PLA Polylactic Acid 8000-15000 RTP RTP 2099 Imagineering series Plastics

[0346] While the molten thermoplastic material maintaining the melt pressure of the molten thermoplastic material at a substantially constant pressure of less than 6000 psi, specific thermoplastic materials benefit from the invention at different constant pressures. Specifically: PP, nylon, PC, PS, SAN, PE, TPE, PVDF, PTI, PBT, and PLA at a substantially constant pressure of less than 10000 psi; ABS at a substantially constant pressure of less than 8000 psi; PET at a substantially constant pressure of less than 5800 psi; Acetal copolymer at a substantially constant pressure of less than 7000 psi; plus poly(ethylene furanate) polyhydroxyalkanoate, polyethylene furanoate (aka PEF) at substantially constant pressure of less than 10000 psi, or 8000 psi, or 7000 psi or 6000 psi, or 5800 psi.

[0347] As described above, a low and substantially constant pressure method can achieve one or more advantages over conventional molding processes e.g. being cost effective and having a efficient process that eliminates the need to balance the pre-injection pressures of the mold cavity and the thermoplastic materials, a process that allows for use of atmospheric mold cavity pressures and, thus, simplified mold structures that eliminate the necessity of pressurizing means, the ability to use lower hardness, high thermal conductivity mold cavity materials that are more cost effective and easier to machine, a more robust processing method that is less sensitive to variations in the temperature, viscosity, and other material properties of the thermoplastic material, and the ability to produce quality injection molded parts at low pressures without premature hardening of the thermoplastic material in the mold cavity and without the need to heat or maintain constant temperatures in the mold cavity.

[0348] Parts molded using a conventional, higher pressure process usually have a reduced number of oriented bands when compared to a part molded using a low constant pressure process.

[0349] Parts molded using a low constant pressure process may have less molded-in stress. In a conventional process, the velocity-controlled filling process combined with a higher transfer or switchover to pressure control may result in a part with high levels of undesirable molded-in stress. If the pack pressure is set too high in a conventional process, the part will often have an over-packed gate region.

[0350] Moreover, one skilled in the art will recognize the teachings disclosed herein may be used in the construction of stack molds, multiple material molds including rotational and core back molds, in combination with in-mold decoration, insert molding, in mold assembly, and the like.

[0351] While particular embodiments have been illustrated and/or described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

[0352] The method and/or machinery could also use constant low-pressure molding in an injection blow molding process, by controlling the filling process by actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills, the polymer is injection molded onto a core pin; then the core pin is rotated to a blow molding station to be inflated and cooled. The process is divided into three steps: injection, blowing and ejection.

[0353] The method and/or machinery could also use constant low-pressure molding in an extrusion blow molding process, by controlling the filling process by actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills, plastic is melted and extruded into a hollow tube (a parison). This parison is then captured by closing it into a cooled metal mold. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container, or part. After the plastic has cooled sufficiently, the mold is opened, and the part is ejected. Continuous and Intermittent are two variations of Extrusion Blow Molding. In continuous extrusion blow molding the parison is extruded continuously and the individual parts are cut off by a suitable knife. In Intermittent blow molding there are two processes: straight intermittent is similar to injection molding whereby the screw turns, then stops and pushes the melt out. With the accumulator method, an accumulator gathers melted plastic and when the previous mold has cooled and enough plastic has accumulated, a rod pushes the melted plastic and forms the parison. In this case the screw may turn continuously or intermittently. With continuous extrusion the weight of the parison drags the parison and makes calibrating the wall thickness difficult. The accumulator head or reciprocating screw methods use hydraulic systems to push the parison out quickly reducing the effect of the weight and allowing precise control over the wall thickness by adjusting the die gap with a parison programming device.

[0354] The method and/or machinery could also use constant low-pressure molding in extruders for 3D printingTypes of extruders (depending on the drive) by controlling the process by actual plastic pressure leaving the nozzle, e.g. having an adjustable nozzle and/or breaker plate/pressure valve enabling the nozzle to distribute its material at a low and constant plastic pressure, that eliminates flow hesitations. Within extruders for 3D printing there are two types depending on the type of drive: Direct and Bowden. In the direct extruder, as its name suggests, the filament runs directly from the cog of the extruder to the HotEnd. There are even systems in which these two parts are together.

[0355] The method and/or machinery could also have a constant low-pressure extrusion in an injection molding machine given the constant low-pressure molding by controlling the filling process by actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills using at least one breaker plate to build the necessary back pressure needed to keep a constant low pressure. The holes in the breaker plate would automatic create some friction heat and having a heat sensor on both sides of the breaker plate would enable a better control and uniformity of the plastic material passing through the breaker plate e.g. also having the breaker plate temperature controlled by cooling and/or heating measures

[0356] The method and/or machinery could also have a constant low-pressure extrusion in an injection molding machine where the breaker plate and/or pressure valve could be added to the injection unit and/or being built in to a manifold being bolted on to the mold in the machine and/or being part of such mold e.g. built in to a hot runner manifold. The apparatus holding the breaker plate and/or pressure valve could also be controlling shear heat and/or measuring the temperature of the material entering and/or leaving the obstacle/pass way creating the shear heat e.g. the breaker plate potentially having the possibility to control the passage size creating the shear heat. This could include the control of heat, cooling, pressure and flow speed to achieve the desired output

[0357] The method and/or machinery could also have a breaker plate in the injection unit of an injection molding machine given the constant low-pressure molding using at least one breaker plate to control the uniformity of the material composition including temperature. A breaker plate could also be placed in the hot runner manifold of the mold in the injection molding machine. Here having the benefit that the hot runner system already was set up for temperature control. And now it would also be possible to control friction heat e.g. if the holes in the breaker plate was matching the size of the gates into the cavity/cavities.

[0358] The method and/or machinery could also have a constant extrusion with at least on breaker plate having traps build in enabling separation of materials of different density, viscosity e.g. also with temperature deviations like having hot and cooler areas for the material to pass this made possible given the constant low pressure. Consistent low pressure protects the plastic material from degenerating and makes it much better to recycle both coming from virgin material as well as going through the recycling process. When different types of plastics are melted together, they tend to phase-separate, like oil and water, and set in these layers. The phase boundaries cause structural weakness and delamination in the resulting material, meaning that polymer blends are useful in only limited applications. The two most widely manufactured plastics, polypropylene and polyethylene, behave this way, which limits their utility for recycling. Each time plastic is recycled, additional virgin materials must be added to help improve the integrity of the material. So, even recycled plastic has almost always new plastic material added in. The same piece of plastic can only be recycled about 2-3 times before its quality decreases to the point where it can no longer be used. Consistent low pressure protect the plastic material from degenerating and makes it much better to recycle and when processed through an extruder under consistent low pressure it could e.g. be possible to direct dissimilar materials in a fixed direction enabling separation and/or centering of the unwanted and/or wanted material into the center core of a given extruded profile minimizing surface blemishes and delamination of the extruded product.

[0359] The method and/or machinery could also have a constant extrusion with at least on breaker plate having traps build in enabling enhanced mixing/compounding of materials of different density, viscosity e.g. also with temperature deviations like having hot and cooler areas for the material to flow through positioning e.g. additives like glass fiber or blowing agent in the center of the melt flow enabling enhanced surface on the finished parts, this made possible given the constant low pressure. Consistent low pressure also enabling a longer profile in the extrusion mold with extra cooling due to the no hesitation in the flow front enabling straighter and more homogenic extruded profiles leaving the extruder.

[0360] The method and/or machinery could also have a constant extrusion with at least on breaker plate having traps build in enabling separation of materials of different density, viscosity e.g. in a twin extruder e.g. with dissimilar screws e.g. also with temperature deviations like having hot and cooler areas/zones in the extruder for the material to pas through. This made possible given the constant low pressure that has proven an excellent success rate going thick to thin and back to thick without hesitation in uneven fill rates in cavities in injection molds. Consistent low pressure furthermore protects the plastic material from degenerating and makes it much better to recycle both coming from virgin material as well as going through the recycling process.

[0361] The method and/or machinery could also have a constant extrusion in an injection molding machine given the constant low pressure molding allowing a traditional injection unit to have much larger and more humogen plasticizing output extruding the plastic into the cavity/cavities than just injecting the plasticized material is in front of the screw tip, also needing a material cushion left in front of the screw for injection into the mold during the holding pressure phase.

[0362] The method and/or machinery could also have a constant extrusion in an injection molding machine given the constant low pressure molding using at least one breaker plate to build the necessary back pressure needed to keep a constant low pressure when using the extrusion feature on a injection unit on a traditional injection molding machine. This would also enable a given injection molding machine to have a much wider range of shot weight without the degeneration of the material in the injection unit.

[0363] The method and/or machinery could also have a constant extrusion in an injection molding machine given the constant low pressure molding using at least one breaker plate to build the necessary back pressure needed to keep a constant low pressure when using the extrusion feature on an injection unit on a traditional injection molding machine. E.g. combining the extrusion feature with injecting the plasticized material is in front of the screw tip thereby increasing the material that can be introduced into the cavity/cavities in the machine and e.g. applying a constant extrusion of the material using the space in front of the screw to hold a cushion while the mold open and closes and/or during the holding pressure phase of the molding process. These features could also be used in one of the three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding.

[0364] The method and/or machinery could also have a blow mold that has a cavity that fills (e.g. neck and thread on a bottle) due to the low constant fill without hesitation where the material packs as it fills where after filling neck and thread turns into extrusion e.g. by mechanically opening space for the extrusion, and/or injection of a parison by controlling the filling process during the actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills. The parison is then clamped into a mold and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

[0365] The method and/or machinery could also have a constant extrusion in an blow molding machine given the constant low pressure molding using at least one breaker plate and/or pressure valve to build the necessary back pressure needed to keep a constant low pressure enabling it to pack e.g. the entry area (the neck and thread portion) of a bottle blow mold as it fills, where after it acts as an extrusion mold for the rest of the parison. The parison is then clamped into a mold and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

[0366] The method and/or machinery could also have a constant extrusion in an blow molding machine given the constant low pressure molding using at least one breaker plate and/or pressure valve to build the necessary back pressure needed to keep a constant low pressure enabling it to pack e.g. the entry area (the neck and thread portion) of a bottle blow mold as it fills this packable portion of the blow mold e.g. having slides and/or core pulls being movable in respect to the rest of the blow mold.

[0367] The method and/or machinery could also have a constant low pressure extrusion in an blow molding machine given the constant low pressure molding using at least one breaker plate and/or pressure valve to build the necessary back pressure needed to keep a constant low pressure enabling and/or controlling the filling process by actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills it to pack material in part and/or in full using one of the three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding.

[0368] The method and/or machinery could also have a constant extrusion in an blow molding machine given the constant low pressure molding using at least one breaker plate and/or pressure valve to build the necessary back pressure needed to keep a constant low pressure enabling it to pack the material better and more consistent in parison and/or preform enabling a better blow molded product.

[0369] The method and/or machinery could also have a constant low pressure extrusion in an blow molding machine given the constant low pressure molding using at least one breaker plate to build the necessary back pressure needed to keep a constant low pressure enabling it to pack e.g. the entry area (the neck and thread portion) of a bottle blow mold as it fills.

[0370] The method and/or machinery controlling the filling process by actual plastic pressure filling and packing the extrusion mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills could also have a compression molding feature compressing the initial plastic profile as it comes out the extrusion tool from one or more angles/surfaces

[0371] The method and/or machinery could also have a compression molding feature having one or more compressing wheels with continues compressing cavities and/or cores shaping the initial plastic profile as it comes out the extrusion tool from one or more angles/surfaces

[0372] The method and/or machinery could also have a continues low pressure label applied to the plastic profile as it comes out the extrusion tool from one or more angles/surfaces

[0373] The method and/or machinery could also have a continues low barrier label applied to the plastic profile as it comes out the extrusion tool from one or more angles/surfaces

[0374] The method and/or machinery could also have a continues stamping/cutting and/or shaping of parts from the plastic profile as it comes out the extrusion tool from one or more angles/surfaces

[0375] The method and/or machinery could also have a continues stamping/cutting and/or shaping of parts from the plastic profile as it comes out the extrusion tool having the excess material from the plastic profile returned into the extruder for a continues re-use

[0376] The method and/or machinery could also have a continues stamping/cutting and/or shaping of pre-foamed preforms for e.g. shoe soles from the plastic profile as it comes out the extrusion tool from one or more angles/surfaces followed by the preform getting placed in a heated mold cavity for the final expansion and/or compression

[0377] The method and/or machinery could also have a continues stamping/cutting and/or shaping of parts from the plastic profile as it comes out the extrusion tool from one or more angles/surfaces where one of the operations is pressing a hinge function into the profile and bending the hinge stretching the plastic molecules into the opening direction enhancing the function and lifetime of the hinge

[0378] The method and/or machinery could also have a new innovative hot runner system due to the possibilities of the constant low-pressure technology controlling the filling process by actual plastic pressure filling and packing the mold and/or part of the mold using a low and constant plastic pressure, that eliminates flow hesitations, packs the part as it fills, and reduces pressure loss within the mold as it fills. Having proved that it enables filling of unbalanced and/or different size cavities. Therefore, the manifolds of this new hot runner system would need less height since it would not need the extra layers to balance the different hot runner drops. The new system could e.g. have small breaker plates of e.g. different configuration to e.g. accommodate a straight feed line to e.g. ten hot runner drops.

[0379] The method and/or machinery could also have a new innovative hot runner system due to the constant low-pressure technology that has proved that it enables filling of unbalanced and/or different size cavities. Therefore, the manifolds of this new hot runner system would need less height and could have more cavities feed by hot runner drops in a given mold plate due to the design freedom in having the need for a balanced feed system as current hot runner systems have for injection molding today.

[0380] The method and/or machinery could also have a new innovative hot runner system due to the constant low-pressure technology that has proved that it enables filling of unbalanced and/or different size cavities. Therefore, the manifolds of this new hot runner system could enable extrusion molding and the different forms of blow molding to benefit from these new hot runner systems that in standard injection molds with cold runners have shown how long thin cold runner lines can feed thick walled parts in cavities without any and/or very little hesitation in the fill pattern.

[0381] The method and/or machinery could also have a new innovative hot runner system based on the possibilities of the constant low-pressure technology enabling e.g. a 0.030 inch. Diameter runner Having a 3-inch long “filament” portion before entering and filling the cavity of the part without freezing diameter and length can vary depending on part size and choice of material. Having at least one cold runner portion that is reheated during every molding cycle before injection of the next portion molten plastic material making the thin filament molten again and given a relative thin diameter of the filament it can be reheated relative fast eliminating the use of expensive standard hot runner drops.

[0382] The method and/or machinery could also have a new innovative hot runner system based on the possibilities of the constant low-pressure technology enabling e.g. a 0.030 inch. Diameter runner Having a 3-inch long “filament” portion before entering and filling the cavity of the part without freezing diameter and length can vary depending on part size and choice of material. Having at least one cold runner portion that is reheated during every molding cycle before injection of the next portion molten plastic material making the thin filament molten again and given a relative thin diameter of the filament it can be reheated relative fast

[0383] For heating non-conductive materials such as plastics, induction can be used to heat an electrically conductive susceptor e.g., graphite, which then passes the heat to the non-conducting material. Induction produces an electromagnetic field in a coil to transfer energy to a work piece to be heated. The material used to make the work piece can be a metal such as copper, aluminum, steel, brass or aloeids and mixed materials created for strength and conductivity. It can also be a semiconductor such as graphite, carbon or silicon carbide. Induction heating finds applications in processes where temperatures are as low as 100° C. (212° F.) and as high as 3000° C. (5432° F.).

[0384] Other heating applications can be used to reheat the filament parts of the mold and in it might also be possible to use this new innovative hot runner system for high pressure injection molding application. The filament part could also be a more traditional form of gate design that resides in a mold part/component that can be reheated a predetermined time during each injection molding cycle.

[0385] The method and/or machinery could also have a new innovative hot runner system having conductive heating as heating source in whole or in part e.g. in combination with a traditional heated hot runner manifold. The conductive heating as heating source in whole or in part could also be used in combination with a three plate molds that are used when part of the cold runner system is on a different plane to the injection location. The runner system for a three-plate mold sits on a second parting plane parallel to the main parting plane. This second parting plane enables the runners and sprue to be ejected when the mold is opened.

[0386] The conductive heating as heating source in whole or in part could also be used in combination with insulated runners that normally are unheated, this type of runner requires extremely thick runner channels to stay molten during continuous cycling. These molds have extra-large passages formed in the mold plate. During the fabrication process, the size of the passages in conjunction with the heat applied with each shot results in an open molten flow path. This inexpensive system eliminates the added cost of the manifold and drops but provides flexible gates of a heated hot runner system. It allows for easy color changes.

[0387] The abovementioned suggestions are meant to be used in both as standalone and in combinations and in part combinations not limited to any of the described molding technologies in creation of new patent claims for current and/or dependent patent applications.