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    • 专利摘要:
    "METHOD FOR SUBSTANTIALLY CONSTANT LOW PRESSURE INJECTION MOLDING" An injection molding method at substantially constant low melting pressures is presented here. The modalities of the presented method enable an injection molding method that is more energy efficient - and cost effective - than conventional high speed injection molding processes. The modalities of the presented method allow, surprisingly, the filling of a mold cavity at low melting pressure without undesirable premature hardening of the thermoplastic material in the mold cavity and without the need to maintain a constant temperature or the heated mold cavity. Until now, it was not expected that a constant pressure method could be performed at low pressure without premature hardening of the thermoplastic material with the use of an unheated mold cavity or cooled mold cavity.
    公开号:BR112013029835B1
    申请号:R112013029835-9
    申请日:2012-05-21
    公开日:2020-11-10
    发明作者:Ralph Edward Neufarth；Charles Jonh Berg Jr.；Gary Francis Schiller；Gene Michael Altonen；John Moncrief Layman；Rainer Scharrenberg
    申请人:Imflux Inc；
    IPC主号:
    专利说明:

    BACKGROUND OF THE INVENTION Description field
    [0001] The present description relates to methods for injection molding and, more particularly, to methods for injection molding at substantially constant low melting pressures. Brief description of related technology
    [0002] Injection molding is a technology commonly used for high-volume manufacturing of parts made from meltable materials, most commonly of parts made from plastic. During a repetitive injection molding process, a thermoplastic resin, most often in the form of small microspheres, is introduced into an injection molding machine that melts the resin microspheres under heat and pressure. The resin, now molten, is forcibly injected into a mold cavity that has a particular cavity shape. The injected plastic is kept under pressure in the mold cavity, cooled and then removed as a solidified part that has a shape that essentially replicates the shape of the mold cavity. The mold itself can have a single cavity or multiple cavities. Each cavity can be connected to a flow channel through a port, which directs the flow of the molten resin into the cavity. A molded part can have one or more doors. It is common for large parts to have two, three or more ports to reduce the flow distance the polymer needs to travel to fill the molded part. The one or multiple ports per cavity can be located anywhere in the geometry of the part and have a cross section in any shape, such as essentially circular or have a shape with an aspect ratio of 1.1 or more. Thus, a typical injection molding procedure comprises four basic operations: (1) heating the plastic in the injection molding machine to allow it to flow under pressure; (2) injecting the molten plastic into a defined mold cavity or cavities between two mold halves that have been closed; (3) allowing the plastic to cool and harden in the cavity or cavities while under pressure; and (4) opening the mold halves to cause the part to be ejected from the mold.
    [0003] The molten plastic resin is injected into the mold cavity and is forced, through the cavity, by the injection molding machine until the plastic resin reaches the location in the cavity furthest from the door. The resulting wall thickness and length of the part is a result of the shape of the mold cavity.
    [0004] Although it may be desired to reduce the wall thickness of the injected molded parts, in order to thereby reduce the plastic content, and thus, the cost of the final part, reduce the wall thickness with the use of a molding process by conventional injection it can be an expensive and not trivial task, specifically when projecting wall thicknesses smaller than 1.0 millimeter. As a liquid plastic resin is introduced into an injection mold in a conventional injection molding process, the material adjacent to the cavity walls immediately begins to "freeze" or solidify, or cure, due to the fact that the liquid plastic resin cools at a temperature below the temperature without material flow and the liquid plastic portions become stationary. As the material flows through the mold, a boundary layer of material is formed against the sides of the mold. As the mold continues to fill, the boundary layer continues to get thicker, and ultimately, it closes the material flow path and prevents additional material from flowing into the mold. The plastic resin that freezes on the mold walls is exacerbated when the molds are cooled, a technique used to reduce the cycle time of each part and increase the machine's performance.
    [0005] There may also be a desire to design a part and the corresponding mold so that the liquid plastic resin flows from areas that have the largest wall thickness towards areas that have the smallest (thinnest) wall thickness. Increasing the thickness in certain regions of the mold can ensure that sufficient material flows into areas where strength and thickness are required. This "thin to coarse" flow path requirement can contribute to the inefficient use of plastic and result in higher part cost for injection molded part manufacturers, due to the fact that additional material needs to be molded into parts in locations where that the material is unnecessary.
    [0006] A method to decrease the thickness of the wall of a piece is to increase the pressure of the liquid plastic resin as it is introduced into the mold. By increasing the pressure, the molding machine can continue to force the liquid material into the mold before the flow path closes. The increase in pressure, however, presents cost and performance disadvantages. As the pressure required to mold the component increases, the molding equipment must be strong enough to withstand the additional pressure, which, in general, is more expensive. A manufacturer may have to purchase new equipment to accommodate these increased pressures. In this way, a decrease in the wall thickness of a given part can result in significant capital expenditures for carrying out manufacturing using conventional injection molding techniques.
    [0007] Additionally, when the liquid plastic material flows into the injection mold and freezes, the polymer chains retain the high levels of stress that were present when the polymer was in liquid form. These "under molding" stresses can lead to parts that undesirably warp or sink after molding, have reduced mechanical properties and have reduced resistance to chemical exposure. The reduced mechanical properties are particularly important for controlling and / or minimizing injection molded parts such as thin-walled tubes, parts with live joints and closing systems. SUMMARY OF THE INVENTION
    [0008] According to one embodiment of the description, a method includes (a) filling a mold cavity of a molding apparatus, with a dose comprising a molten thermoplastic material, and (b) while substantially filling the entire cavity of molding mold with the dose comprising the molten thermoplastic material, keep the melt pressure substantially constant at less than 41.4 MPa (6000 psi). the thermoplastic material has a melt flow index of 0.1 g / 10 min to about 500 g / 10 min. BRIEF DESCRIPTION OF THE DRAWINGS
    [0009] The modalities presented in the drawings are illustrative and exemplary in nature and are not intended to limit the subject defined by the claims. The following detailed description of the illustrative modalities can be understood when read in conjunction with the following drawings, where similar structures are indicated with similar reference numbers and in which:
    [00010] Figure 1 illustrates a diagrammatic front view of a high speed injection molding machine, according to one or more modalities shown and described in this document;
    [00011] Figure 2 is a schematic illustration of a pressure profile for an injection molding method at substantially constant low pressure, according to an embodiment of the description;
    [00012] Figure 3 is a schematic illustration of a pressure profile for an injection molding method at substantially constant low pressure, according to another embodiment of the description; and
    [00013] Figure 4 is a schematic illustration of a pressure profile for an injection molding method at substantially constant low pressure, according to an embodiment of the description;
    [00014] Figure 5 is a schematic illustration of a pressure profile for an injection molding method at substantially constant low pressure, according to yet another embodiment of the description. DETAILED DESCRIPTION
    [00015] All pressures presented here are calibrated pressures, which are pressures relative to the ambient pressure.
    [00016] Here is presented an injection molding method at substantially constant low melting pressures. The modalities of the presented method enable an injection molding method that is more efficient, from an energy point of view - and cost -, than the conventional high speed injection molding process. The modality of the presented method allows, surprisingly, the filling of a mold cavity at low melting pressure without undesirable premature hardening of the thermoplastic material in the mold cavity and without the need to maintain a constant temperature or the heated mold cavity. As described in detail below, the person skilled in the art would not expect that a method with constant pressure could be performed at low pressure without such premature hardening of the thermoplastic material during the use of an unheated mold cavity or cooled mold cavity.
    [00017] The modalities of the presented method also allow the formation of quality injection molded parts that do not suffer undesirable warping or sinking, without the need to balance the pre-injection pressure of the mold cavity and the pre-injection pressure of the thermoplastic materials. In this way, the modalities of the described method can be performed using mold cavities at atmospheric pressures and eliminate the need to include pressurizing means in the mold cavity.
    [00018] The method modalities can also produce quality injection molded parts with significantly less sensitivity to variations in temperature, viscosity and other properties of the thermoplastic material, compared to the conventional high pressure injection molding process. In one embodiment, this can advantageously allow the use of thermoplastic materials formed from recycled plastics (for example, recycled plastics after consumption), which inherently vary material properties from batch to batch.
    [00019] Additionally, the low melting pressures used in the presented method may allow the use of highly heat-conducting mold cavity materials, with low hardness, which have a lower manufacturing cost and are more energy efficient. For example, the mold cavity can be formed of a material that has a surface hardness less than 30 Rockwell C (Rc) and a thermal conductivity greater than 30 BTU / HR FT ° F. In one embodiment, the mold cavity can be formed of an aluminum alloy, such as, for example, 6061 Al and 7075 Al aluminum alloys.
    [00020] The modalities of the presented method can additionally allow the formation of pieces with high quality thin wall. For example, a molded part that has a ratio between the length and the flow of molten thermoplastic (L / T) greater than 100, can be formed using the method modalities. It is contemplated that the method modalities can also form molded parts that have an L / T ratio greater than 200 and, in some cases, greater than 250.
    [00021] 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). For mold cavities that have a more complicated geometry, the L / T ratio can be calculated by integrating the dimension T along the length of the mold cavity 32 of a port 102 to the end of the mold cavity 32, and determining it if the longest flow length from port 102 to the end of the mold cavity 32. Then, the L / T ratio can be determined by dividing the longest flow length by the average part thickness. In the case where a mold cavity 32 has more than one port 30, the L / T ratio is determined by integrating L and T for the portion of the mold cavity 32 filled by each individual port and the general L / T ratio for a given mold cavity is the highest L / T ratio that is calculated for any of the doors.
    [00022] Figure 1 illustrates an example injection molding apparatus 10 for use with the presented process modalities. The injection molding apparatus 10 generally includes an injection system 12 and a pressing system 14. A thermoplastic material can be introduced into the injection system 12 in the form, for example, of pellets 16. Pellets 16 can be placed in a feeder tank 18, which feeds pellets 16 into a heated cylinder 20 of the injection system 12. Pellets 16, after being fed into heated cylinder 20, can be directed to the end of the heated cylinder 20 by a reciprocating screw 22. The heating of the heated cylinder 20 and the compression of the pellets 16 by the reciprocating screw 22 cause the pellets 16 to melt, forming a molten thermoplastic. The molten thermoplastic material is typically processed at a temperature of about 130 ° C to about 410 ° C.
    [00023] The reciprocating thread 22 forces the molten thermoplastic material towards a nozzle 26 to form a dose comprising molten thermoplastic material 24, which will be injected into the mold cavity 32 of a mold 28. The mold cavity 32 is formed between the first and second mold parts 25, 27 of the mold 28, and the first and second mold parts 25, 27 are held together under pressure by a press or press unit 34. The press or press unit 34 applies a pressing force that needs to be greater than the force exerted by the injection pressure that acts to separate the two halves of the mold during the molding process to hold the first and second parts of the mold 25, 27 together, while the thermoplastic material melts 24 is injected into the mold cavity 32. To withstand these pressing forces, the pressing system 14 may include a mold structure and a mold base, the mold structure and the mold base being formed in a manner material that has a surface hardness greater than about 165 BHN and, preferably, less than 260 BHN, although materials that have BHN surface hardness values greater than 260 can be used, provided the material is easily machined, as further discussed below.
    [00024] Since the dose comprising the molten thermoplastic material 24 is injected into the mold cavity 32, the reciprocating screw 22 stops the forward movement. The molten thermoplastic material 24 takes the form of the mold cavity 32 and the molten thermoplastic material 24 cools inside the mold 28 until the thermoplastic material 24 solidifies. When the thermoplastic material 24 has solidified, the press 34 releases the first and second mold parts 25, 27, the first and second mold parts 25, 27 being separated from each other, and the finished part can be ejected from the mold 28. The mold 28 can include a plurality of mold cavities 32 to increase total production rates. The cavity shapes of the plurality of mold cavities can be identical, similar or different from each other. (A set of dissimilar mold cavities can be considered a family of mold cavities).
    [00025] The method generally includes injecting the dosages, and which comprises molten thermoplastic material, into the mold cavity 32 to fill the mold cavity. Referring to Figure 2, at t1, which is before injection, the dose that comprises molten thermoplastic material has a pre-injection pressure. As used here, the pre-injection pressure of the dose comprising molten thermoplastic material refers to the pressure of the thermoplastic material after it has been heated in a molten state in the heated cylinder and prepared in the dose, and just before the injection of the dose, which comprises the thermoplastic material melted in the mold cavity or a sprue or feed system in fluid communication with the nozzle and the mold cavity. The pre-injection pressure of the dose comprising optionally molten thermoplastic material may not be equal to the pressure of the mold cavity prior to injection. In one embodiment, prior to injection, the mold cavity may be at atmospheric pressure, for example, as shown in Figures 2 and 4. In another embodiment, the mold cavity may have a slightly positive pressure, as shown in Figure 3. In yet another embodiment, a vacuum can be induced in the mold cavity.
    [00026] As illustrated in Figure 2, upon injection into the mold cavity during t2, the dose pressure comprising molten thermoplastic material increases to a melting pressure that is greater than the pre-injection pressure of the dose comprising molten thermoplastic material . Referring again to Figure 1, for example, the injection of the dose comprising molten thermoplastic material may include the translation of the reciprocating screw 22 in the direction of arrow A in Figure 1, in the direction of the nozzle 26, to force the dose comprising the molten thermoplastic material 24 through the nozzle 26 and into the mold cavity 32. In various embodiments, the dose comprising the molten thermoplastic material 24 can be injected into the mold cavity 32 of a mold 28 through a port 30, which directs the flow from the molten thermoplastic material 24 to the mold cavity 32. The mold cavity 32 can be formed, for example, between the first and second mold parts 25, 27 of the mold 28. The first and second mold parts 25, 27 of the mold 28 can be held together under pressure by a press 34.
    [00027] Referring again to Figure 2, substantially the entire mold cavity or the entire mold cavity is filled with the dose comprising thermoplastic material melted at time t3. The melting pressure is maintained at a substantially constant pressure of less than 41.4 MPa (6,000 psi) during substantial filling of the entire mold cavity. As used here, the term "substantially constant pressure" refers to a pressure that does not fluctuate, up or down, from the melt pressure, more than 30% of the desired melt pressure when filling substantially the entire mold cavity with the dose comprising the molten thermoplastic material. For example, the substantially constant pressure can fluctuate (as an increase or decrease) in the melting pressure from 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 amounts of oscillation include about 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30%. The oscillation is illustrated in Figure 2 as a ΔP of the desired melting pressure. Without sticking to the theory, it is believed that maintaining a substantially constant pressure as defined here can avoid hesitation of the melting front as the molten thermoplastic material flows into the mold cavity. Such dynamic flow conditions can advantageously allow the dose comprising molten thermoplastic material to maintain a uniform flow and compaction conditions until the last point of filling of the mold without freezing or another break in the molten material. As shown in Figures 3 and 4, the melting pressure during substantial filling of the entire mold cavity can increase or decrease, respectively, for example, at a constant rate, and can be considered substantially constant as long as the maximum increase or decrease the melting pressure during substantial filling of the entire mold cavity is not greater than 30% of the desired melting pressure. Again, this oscillation is illustrated in Figures 3 and 4 as an ΔP of the desired melting pressure.
    [00028] Referring to Figure 5 and discussed in detail below, since substantially the entire mold cavity is filled (at time t3), the melting pressure can be reduced to a compaction pressure to fill the remaining portion of the cavity mold (at time t3 '). The compaction pressure can be kept substantially constant until the entire mold cavity is filled.
    [00029] A sensor can be located near the filling end in the mold cavity. This sensor can provide an indication of when the mold front approaches the filling end in the cavity. The sensor can capture pressure, temperature, optically, or other means of identifying the presence of the polymer. When pressure is measured by the sensor, this measurement can be used to communicate with the central control unit to provide a target "compaction pressure" for the molded component. The signal generated by the sensor can be used to control the molding process, so that variations in material viscosity, mold temperatures, melting temperatures and other variations that influence the fill rate, can be adjusted by the central control. These adjustments can be made immediately during the molding cycle, or corrections can be made in subsequent cycles. In addition, it is possible to average several readings over several 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 that take place during one or more cycles at a point in the previous time. In one embodiment, you can average the sensing readings over many cycles in order to achieve process consistency.
    [00030] Once the mold cavity is completely filled, the melting pressure and the mold cavity pressure, if necessary, are reduced to atmospheric pressure at time t4 and the mold cavity can be opened. During that time, the reciprocating screw 22 interrupts the forward path. Advantageously, the conditions of substantially constant low pressure allow the dose comprising molten thermoplastic material to cool rapidly within the mold, which, in various embodiments, can occur substantially simultaneously with the venting of the melting pressure and the pressure mold cavity atmospheric. In this way, the injection molded part can be ejected from the mold quickly after filling the mold cavity with the dose comprising molten thermoplastic material. Fusion pressure
    [00031] As used herein, the term "melting pressure" refers to a pressure of a dose that comprises molten thermoplastic material as it is injected and fills a mold cavity of a molding apparatus. During substantial filling of the entire mold cavity, the melting pressure of the dose comprising molten thermoplastic material is kept substantially constant at least 41.4 MPa (6,000 psi). The melting pressure of the dose comprising molten thermoplastic material during substantial filling of the entire mold cavity is significantly less than the injection and filler melting pressures used in conventional injection molding processes and recommended by manufacturers of thermoplastic materials for use. in the injection molding process. Other suitable melting pressures include, for example, less than 34.5 MPa (5000 psi), less than 31.0 MPa (4500 psi), less than 27.6 MPa (4000 psi), and less than 20.7 kPa (3000 psi). For example, the melting pressure can be maintained at a substantially constant pressure within the range of about 6.9 MPa (1000 psi) less than 41.4 MPa (6000 psi), about 10.3 MPa (1500 psi) ) at about 37.9 MPa (5500 psi), about 13.8 MPa (2000 psi) at about 34.5 MPa (5000 psi), about 17.2 MPa (2500 psi) at about 31, 0 MPa (4500 psi), about 20.7 MPa (3000 psi) to about 27.6 MPa (4000 psi) and about 20.7 MPa (3000 psi) less than 41.4 MPa (6000 psi) .
    [00032] As described above, a "substantially constant pressure" refers to a pressure that does not oscillate above or below the desired melting pressure more than 30% of the desired melting pressure during substantial filling of the entire mold cavity with the dose comprising molten thermoplastic material. For example, the substantially constant pressure can fluctuate (as an increase or decrease) in the melting pressure from 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 amounts of oscillation include about 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30%. The oscillation is illustrated in Figure 2 as a ΔP of the desired melting pressure. Referring to Figures 3 and 4, the melting pressure during substantial filling of the entire mold cavity can increase or decrease, respectively, for example, at a constant rate, and can be considered substantially constant as long as the increase or decrease maximum melting pressure during substantial filling of the entire mold cavity is not greater than 30% of the desired melting pressure. Again, this oscillation is illustrated in Figures 3 and 4 as an ΔP of the desired melting pressure. In yet another embodiment, the melting pressure during substantial filling of the entire mold cavity may increase over a portion of time t3 and then decrease over a remaining portion of time t3. This oscillation will be considered a substantially constant pressure as long as the maximum increase or decrease in the melting pressure during filling is less than 30% of the desired melting pressure.
    [00033] The melting pressure of the dose comprising thermoplastic material upon injection into the mold cavity can be measured using, for example, a pressure transducer arranged at the injection point. As used herein, the "injection point" is the location in the molding apparatus where the dose comprising molten thermoplastic material enters the mold cavity. For example, for a molding apparatus that has a single mold cavity coupled to a nozzle, the injection point can be over or adjacent to the nozzle. Alternatively, for a molding apparatus that has a plurality of mold cavities and a sprue system for transporting the molten thermoplastic material from the nozzle to each of the mold cavities, the injection points can be the points of contact between the system sprue and each individual mold cavity. The dose comprising molten thermoplastic material is maintained at substantially constant melting pressure as it is transported through the sprue system. In general, the sprue system is a heated sprue system that maintains the melting temperature of the dose comprising molten thermoplastic material as it is transported to the mold cavities.
    [00034] The melting pressure of the dose comprising thermoplastic material during substantial filling of the entire mold cavity can be maintained, for example, by measuring the melting pressure using a pressure transducer arranged in the nozzle and maintaining constant pressure in the nozzle when injecting into the mold cavity. In another embodiment, the melting pressure of the dose comprising thermoplastic material during substantial filling of the entire mold cavity can be measured with the use of a pressure transducer disposed in the mold cavity as opposed to the port.
    [00035] Percent cavity filling is defined as the% of the cavity that is filled on a volumetric basis. Thus, if a cavity is 95% filled, then the total volume of the mold cavity that is filled is 95% of the total volumetric capacity of the mold cavity. Substantially the entire mold cavity is filled when at least 70%, at least 72%, at least 74%, at least 76, at least 78%, at least 80%, at least 82%, at least 84%, at least 86%, at least 88%, at least 90%, at least 92%, at least 94%, at least 96%, at least 98% or at least 99% of the mold cavity is filled with the molten thermoplastic material. For example, substantially the entire mold cavity is filled when about 70% to about 100%, about 75% to about 99%, about 80% to about 98% or about 90% to about 95 % of the mold cavity is filled with the molten thermoplastic material. The percentage of the mold cavity filled with the dose comprising molten thermoplastic material can be determined, for example, by placing a pressure transducer in the mold cavity at the end of the mold cavity filling point that corresponds to the desired percentage of filling . The pressure transducer alerts the operator when the dose comprising molten thermoplastic material has reached the desired fill percentage.
    [00036] Referring to Figure 5, in one embodiment, since substantially the entire mold cavity is filled (at the end of time t3), a reduced melting pressure can be used to fill and pack the remaining portion of the cavity mold (time t3 '). The melting pressure of the dose comprising molten thermoplastic material can be reduced to a compaction pressure less than the melting pressure since substantially the entire mold cavity is filled to provide an ideal pressure to fill the remaining portion of the mold cavity. and avoid overpressurizing or overcompressing the mold cavity. The remaining portion of the mold cavity can be filled while maintaining the melting pressure of the dose comprising molten thermoplastic material substantially constant at the compaction pressure. The compaction pressure can be, for example, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% of the melt pressure.
    [00037] In another embodiment, since substantially the entire mold cavity is filled, the melting pressure can be increased to fill and pack the remaining portion of the mold cavity. Keeping the pressure substantially constant
    [00038] In one embodiment, a hydraulic pressure is applied to the dose comprising the molten thermoplastic material 24 to inject the dose comprising the molten thermoplastic material 24 into the mold cavity at the melting temperature. Hydraulic pressure can be applied, for example, by moving the reciprocating screw 22 in the direction of arrow A in Figure 1, in the direction of the nozzle 26, to force the dose comprising the molten thermoplastic material 24 through the nozzle 26 and into the cavity mold pressure 32. The melting pressure is then kept substantially constant during filling of the dose comprising the molten thermoplastic material 24 in the mold cavity 32 by monitoring the melting pressure of the dose comprising the molten thermoplastic material 23 when injection into the mold cavity 32 and the melting pressure of the dose comprising the molten thermoplastic material 24 during filling of the mold cavity 32 and adjusting the hydraulic pressure applied to the dose comprising the molten thermoplastic material during injection into the mold cavity . The fusion pressure can be monitored using pressure transducers arranged at the injection point, for example, the nozzle 26 and the mold cavity 32.
    [00039] A controller 50 is communicatively connected to a sensor 52 and a screw control 36. Controller 50 may include a microprocessor, a memory and one or more communication links. Controller 50 can be connected to sensor 52 and screw control 36 via wired connections 54, 56, respectively. In other embodiments, controller 50 can be connected to sensor 52 and screw control 56 via a wireless connection, a mechanical connection, a hydraulic connection, a pneumatic connection or any other type of communication connection known to the person skilled in the art which will allow controller 50 to communicate with sensor 52 and screw control 36.
    [00040] In the mode of Figure 1, sensor 52 is a pressure sensor that measures (directly or indirectly) the melting pressure of the molten thermoplastic material 24 at the nozzle 26. The sensor 52 generates an electrical signal that is transmitted to the controller 50. Controller 50 then controls screw control 36 to advance screw 22 at a rate that maintains a substantially constant melting pressure of the molten thermoplastic material 24 at nozzle 26. While sensor 52 can directly measure melting pressure , the sensor 52 can measure other characteristics of the molten thermoplastic material 24, such as temperature, viscosity, flow rate, etc., which are indicative of melting pressure. Similarly, sensor 52 does not need to be located directly at nozzle 26, but instead, sensor 52 can be located anywhere within injection system 12 or mold 28 that is fluidly connected to nozzle 26 Sensor 52 does not need to be in direct contact with the injected fluid and may alternatively be in dynamic communication with the fluid and be able to capture fluid pressure and / or other fluid characteristics. If sensor 52 is not located inside nozzle 26, the appropriate correction factors can be applied to the measured characteristic in order to calculate the melting pressure at nozzle 26. In still other embodiments, sensor 52 does not need to be arranged which is fluidly connected to the nozzle. Instead, the sensor could measure the pressing force generated by the pressing system 14 on a mold dividing line between the first and second mold parts 25, 27. In one aspect, the controller 50 can maintain the pressure accordingly with sensor input 52.
    [00041] Although an active open loop controller 50 is illustrated in Figure 1, other pressure regulating devices can be used instead of closed loop controller 50. For example, a pressure regulating valve (not shown) or a pressure relief valve (not shown) can replace controller 50 in order to regulate the melting pressure of the molten thermoplastic material 24. More specifically, the pressure regulating valve and pressure relief valve can prevent pressurization in excess mold 28. Another alternative mechanism to prevent overpressurization of mold 28 is to activate an alarm when an overpressurization condition is detected.
    [00042] Thus, in another embodiment, the molding apparatus may include a pressure relief valve disposed between an injection point and the mold cavity. The pressure relief valve has a predetermined pressure set point, which is equal to the desired melting pressure for injection and filling of the mold cavity. The melting pressure during injection and filling of the mold cavity is kept substantially constant by applying pressure to the dose comprising molten thermoplastic material to force the dose comprising molten thermoplastic material through the pressure relief valve to a higher melting pressure than the predetermined set point. The pressure relief valve then reduces the melting pressure of the dose comprising the thermoplastic material it forms through the pressure relief valve and is injected into the mold cavity. The reduced melting pressure of the dose comprising molten thermoplastic material corresponds to the desired melting pressure for filling the mold cavity and is kept substantially constant by the predetermined set point of the pressure release valve.
    [00043] In one embodiment, the melting pressure is reduced by diverting a portion of the dose comprising thermoplastic material to an outlet of the pressure relief valve. The dose-diverted portion comprising thermoplastic material can be maintained in a molten state and can be reincorporated into the injection system, for example, through the heated cylinder. Mold cavity
    [00044] The molding apparatus includes a mold that has at least one mold cavity. The mold can include any suitable number of mold cavities. The method embodiments disclosed herein advantageously allow the use of molds having asymmetrically oriented mold cavities and / or mold cavities having different shapes. The use of substantially constant low filling pressures of method modalities can allow each mold cavity to be filled under balanced compaction conditions despite the asymmetry in the mold cavity arrangement. In this way, quality injection molded parts can be formed in each of the mold cavities of the mold despite the asymmetric orientation. The ability to asymmetrically arrange the mold cavities of a mold can advantageously allow the high density of mold cavity in a mold, thus allowing an increased number of injection molded parts to be formed by a single mold and / or allowing a reduction in the mold size. Mold cavity pressure
    [00045] As used herein, "mold cavity pressure" refers to the pressure within a closed mold cavity. The mold cavity pressure can be measured, for example, with the use of a pressure transducer placed inside the mold cavity. In method embodiments, prior to injection of the dose comprising molten thermoplastic material in the mold cavity, the pressure of the mold cavity is different from the pre-injection pressure of the dose comprising molten thermoplastic material. For example, the mold cavity pressure may be less than the pre-injection pressure of the dose comprising molten thermoplastic material. In another embodiment, the mold cavity pressure may be greater than the pre-injection pressure of the dose comprising molten thermoplastic material. For example, the mold cavity pressure before injection can be at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 40% or at least 50% different ( greater or less than) of the pre-injection pressure of the dose comprising molten thermoplastic material. In one embodiment, mold cavity pressure is at least 103.4 kPa (15 psi) different (greater or less than) from the injection pre-pressure of the dose comprising molten thermoplastic material. Referring to Figures 2 and 4, in various embodiments, the pressure of the mold cavity before injection can be atmospheric pressure. In other embodiments, for example, as shown in Figure 3, the mold cavity pressure may have a pressure greater than atmospheric pressure. In yet another embodiment, the mold cavity can be maintained in a vacuum before injection.
    [00046] In various embodiments, the mold cavity pressure can be kept substantially constant during substantial filling of the entire mold cavity with the dose comprising molten thermoplastic material. The term "substantially constant pressure" as used herein with respect to a melting pressure of a thermoplastic material, means that deviations from a baseline melting pressure do not produce significant changes in the physical properties of the thermoplastic material. For example, "substantially constant pressure" includes, but is not limited to, pressure variations by which the viscosity of the molten thermoplastic material does not change significantly. The term "substantially constant" in this respect includes deviations of up to approximately 30% from a baseline melting pressure. For example, the term "a substantially constant pressure of approximately 31.7 MPa (4,600 psi)" includes pressure fluctuations within the range of about 41.4 MPa (6,000 psi) (30% above 31.7 MPa (4,600 psi) psi)) at about 22.1 MPa (3,200 psi) (30% below 31.7 MPa (4,600 psi)). A melting pressure is considered to be substantially constant as long as the melting pressure does not oscillate more than 30% of the stated pressure.
    [00047] For example, the substantially constant pressure can fluctuate (like an increase or decrease) in the melting pressure from 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 amounts of suitable oscillation include about 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30%. Referring to Figure 2, for example, the mold cavity pressure can be maintained at substantially constant atmospheric pressure during substantial filling of the entire mold cavity with the dose comprising molten thermoplastic material. Referring to Figure 3, for example, the mold cavity pressure can be kept substantially constant at a pressure greater than atmospheric pressure which is equal to the pre-injection pressure of the mold cavity. In another embodiment, the mold cavity pressure can be maintained at a substantially constant pressure that is greater than the pre-injection pressure of the mold cavity. For example, mold cavity pressures suitable for filling the mold cavity include, for example, about 3447 kPa (50 psi) to about 3447.4 kPa (500 psi).
    [00048] The mold cavity may include, for example, one or more air outlets to maintain the mold cavity pressure substantially constant. The air outlets can be controlled to open and close in order to keep the mold cavity pressure substantially constant.
    [00049] In one embodiment, a vacuum can be maintained in the mold cavity during injection and substantial filling of the entire mold cavity with the dose comprising molten thermoplastic. Maintaining a vacuum in the mold cavity during injection can advantageously reduce the amount of melting pressure required to fill the cavity, as there is no air to force from the mold cavity during filling. The lack of resistance to air flow and the increased pressure drop between the melting pressure and the end of the filling pressure can also result in a longer flow length of the dose comprising molten thermoplastic material.
    [00050] Referring to Figure 5, in another embodiment, the mold cavity pressure can increase during substantial filling of the entire mold cavity with the dose comprising molten thermoplastic material. For example, the mold cavity pressure can increase in proportion to the displaced volume of the mold cavity during filling. The increase in mold cavity pressure can occur, for example, at a substantially constant rate. The mold cavity may include an air outlet to maintain the mold cavity pressure rising below a predetermined set point. The predetermined set point can be, for example, about the melting pressure of the dose comprising molten thermoplastic material. The predetermined set point can also be, for example, a pressure above which it could damage the mold cavity or adversely affect the quality of the injection molded part.
    [00051] When the mold cavity is completely filled with the dose comprising molten thermoplastic material and the material has cooled, the mold cavity pressure can be vented, if necessary, to atmospheric pressure and the mold can be opened for release injection molded part. Mold cavity temperature
    [00052] In method modalities, the mold cavity is kept at room temperature or cooled before injection and filling the mold cavity with the dose that comprises molten thermoplastic material. While the mold cavity surfaces may have their temperature increased by 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 in contact with the dose comprising thermoplastic material is kept at a lower temperature. Typically, this temperature is less than the no flow temperature of the thermoplastic material. As used here, "temperature without flow" refers to the temperature at which the viscosity of the thermoplastic material is so high that it cannot actually be made to flow. In various embodiments, the inner portion of the mold can be maintained at a temperature below about 100 ° C. For example, the inner 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 from 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 inner portion is maintained at a temperature below 50 ° C.
    [00053] So far, during filling at constant low pressure, filling rates have been reduced compared to conventional filling methods. This means that the polymer would be in contact with the molded surfaces cooled for longer periods before the mold was completely filled. Thus, it would be necessary for more heat to be removed before filling, and this is expected to result in the material freezing before the mold is filled. It has been unexpectedly found that the thermoplastic material will flow when subjected to substantially constant low pressure conditions regardless of whether a portion of the mold cavity is below the temperature without flow of the thermoplastic material. In general, it would be expected by the person skilled in the art that such conditions would cause the thermoplastic material to freeze and clog the mold cavity instead of continuing to flow and fill the entire mold cavity. Without sticking to the theory, it is believed that the substantially constant low pressure conditions of the revealed method modalities allow dynamic flow conditions (i.e., melting front in constant motion) 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, therefore, no opportunity to freeze the flow regardless of the fact that at least a portion of the mold cavity is below the temperature without material flow thermoplastic. Additionally, it is believed that, as a result of dynamic flow conditions, the molten thermoplastic material has the ability to maintain a temperature higher than the temperature without flow, despite being subjected to such temperatures in the mold cavity, as a result of heating by shear. It is also believed that dynamic flow conditions interfere with the formation of crystal structures in the thermoplastic material as the freezing process begins. The formation of a crystal structure increases the viscosity of the thermoplastic material, which can prevent the proper flow from filling the cavity. The reduction in the formation of the crystal structure and / or the size of the crystal structure can allow a decrease in the viscosity of the thermoplastic material as it flows in the cavity and is subjected to the low temperature of the mold which is below the temperature without material flow.
    [00054] In various embodiments, the mold may include a cooling system that maintains the entire mold cavity at a temperature below the temperature without flow. For example, even surfaces of the mold cavity that come into contact with the dose comprising molten thermoplastic material can be cooled to maintain a lower temperature. Any suitable cooling temperature can be used. For example, the mold can be kept substantially at room temperature. The incorporation of such cooling systems can advantageously enhance the rate at which the injection molded part thus formed is cooled and ready for ejection from the mold. Thermoplastic material
    [00055] A variety of thermoplastic materials can be used in the low pressure injection molding methods substantially contained in the description. 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 degrees Celsius and a weight of 2.16 kg. For example, for polypropylene, the melt flow index can be in the range of about 0.5 g / 10 min to about 200 g / 10 min. Other suitable melt flow rates 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 example, thermoplastic materials with an MFI of 0.1 g / 10 min at about 5 g / 10 min may be suitable for use as preforms for Injection Stretch Blow Molding (ISBM) applications Blow Molding). Thermoplastic materials with an MFI of 5 g / 10 min to about 50 g / 10 min can be suitable for use as lids and closure systems 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 tubes. Thermoplastic materials with an MFI of 150 g / 10min at about 500 g / 10 min can be suitable for molded articles that have extremely high L / T ratios like a thin plate. Manufacturers of such thermoplastic materials generally teach that materials should be injection molded using melting pressures above 41.4 MPa (6,000 psi) and often well above 41.4 MPa (6,000 psi) psi). Contrary to conventional teachings regarding the injection molding of such thermoplastic materials, the modalities of the low injection molding method contained in the description advantageously allow the formation of quality injection molded parts with the use of such thermoplastic materials and the processing a melting pressures below 41.4 MPa (6,000 psi) and possibly much below 41.4 MPa (6,000 psi).
    [00056] The thermoplastic material can be, for example, a polyolefin. Exemplary polyolefins include, but are not limited to, polypropylene, polyethylene, polymethyl pentene and polybutene-1. Any of the aforementioned polyolefins could give rise to biobased raw materials, such as sugar cane or other agricultural products, to produce biopolypropylene or biopolietylene. Polyolefins advantageously demonstrate thinning under shear when in a molten state. Thinning under shear is a reduction in viscosity when the fluid is placed under compressive stress. Thinning under shear can beneficially allow the flow of the thermoplastic material to be maintained throughout the injection molding process. Without sticking to the theory, it is believed that the shearing properties under shear of a thermoplastic material, and in particular polyolefins, result in less variation in the viscosity of materials when the material is processed at low pressures. As a result, the modalities of the description method may be less sensitive to variations in the thermoplastic material, for example, resulting from dyes and other additives as well as processing conditions. This decreased sensitivity to variations in the properties of thermoplastic material from batch to batch, can also advantageously allow post-industrial and post-consumer recycled plastics to be processed using the description method modalities. Post-industrial and post-consumer recycled plastics are derived from final products that have completed their life cycle and would otherwise have been discarded as a solid waste product. Such recycled plastic and blends of thermoplastic materials, inherently vary from lot to lot of their material properties.
    [00057] The thermoplastic material can also be, for example, a polyester. Exemplary polyesters include, but are not limited to, polyethylene teraftalate (PET). The PET polymer could give rise to biobased raw materials, such as sugar cane or other agricultural products, to produce a polymer of partially or completely PET. Other suitable thermoplastic materials include copolymers of polypropylene and polyethylene, and polymers and copolymers of thermoplastic elastomers, polyester, polystyrene, polycarbonate, poly (acrylonitrile-butadiene-styrene), polylactic acid, polyesters based on polyethylene polyhydroxyalkanoate furanate, polyethylene furanoate, (considered an alternative to, or compatible replacement, PET), polyhydroxyalkanoate, polyamides, polyacetals, rubbers of ethylene-alpha olefin, 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 weight polymers that produce a multimodal or bimodal blend. The multimodal material can be designed in a way that results in a thermoplastic material that has superior flow properties and has, in addition, satisfactory chemical-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 molecule or another lubricating molecule which, when added to the thermoplastic material, improves the fluidity of the polymeric material.
    [00058] Other additives may include inorganic fillers such as calcium carbonate, calcium sulfate, talc, clays (for example, nano-clay), aluminum hydroxide, CaSiO3, glass formed in fibers or microspheres, crystalline silicas (for example, 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 fiber, bamboo or sugar cane.
    [00059] Other suitable thermoplastic materials include renewable polymers as non-limiting examples of polymers produced directly from organisms, such as polyhydroxy alkanoates (eg, poly (beta-hydroxy alkanoate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate, NODAX (trademark)), and bacterial cellulose; polymers extracted from plants, agricultural and forestry, and biomass, such as polysaccharides and their derivatives (eg, gums, cellulose, cellulose esters, chitin, chitosan, starch, chemically modified starch, particles cellulose acetate), proteins (eg zein, whey, gluten, collagen), lipids, lignins and natural rubber; thermoplastic starch produced from starch or chemically modified starch and current polymers derived from naturally occurring monomers and derivatives, such as bio-polyethylene, bio-polypropylene, poly-trimethylene terephthalate, polylactic acid, Nylon 11, alkyd resins, succinic acid-based polyesters and terephthalate of biopolyethylene.
    [00060] Suitable thermoplastic materials can include a blend or blends of different thermoplastic materials as in the examples mentioned above. Likewise, different materials can be a combination of materials derived from virgin bio-derived materials or petroleum derivatives, or recycled materials from bioderivated materials or petroleum derivatives. One or more of the thermoplastic materials in a blend can be biodegradable. And, for thermoplastic materials other than blend, that material can be biodegradable.
    [00061] Exemplary thermoplastic resins are provided together with their recommended operating pressure ranges in the following chart:


    [00062] Although more than one of the modalities involves substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material while maintaining the melting pressure of the dose comprising the molten thermoplastic material at a substantially constant pressure less than about of 41.4 MPA (6,000 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 less than 68.9 MPa (10,000 psi); ABS at a substantially constant pressure less than 55.2 MPa (8,000 psi); PET at a substantially constant pressure less than 40.0 MPa (5,800 psi); Acetal copolymer at a substantially constant pressure less than 48.3 MPa (7,000 psi), plus poly (ethylene furanate) polyhydroxyalkanoate, polyethylene furanoate (also known as PEF) at a substantially constant pressure less than 68.9 MPa (10,000 psi) ), or 55.2 MPa (8,000 psi), or 48.3 MPa (7,000 psi) or 41.4 MPa (6,000 psi) or 40.0 MPa (5800 psi).
    [00063] As described in detail above, the substantially constant low pressure method disclosed can achieve one or more advantages over conventional high pressure injection molding processes, prior art constant high pressure injection molding processes and prior pressure lower injection molding process. For example, the modalities include a lower cost and efficient process that eliminates the need to balance pre-injection pressures from the mold cavity and thermoplastic materials, a process that allows the use of atmospheric mold cavity pressures and, thus, simplified mold structures that eliminate the need for pressurizing means, the ability to use lower hardness mold cavity materials with high thermal conductivity that are lower cost and easier to machine, a more robust processing method which is less sensitive to variations in temperature, viscosity, and other properties of thermoplastic material and the ability to produce quality injection molded parts at low pressures without premature quenching of the thermoplastic material in the mold cavity and without the need to heat or maintain constant temperatures in the mold cavity.
    [00064] In one example, the sample pieces were molded using a constant low pressure process below 41.4 MPa (6,000 psi) of injection pressure.
    [00065] The samples were isolated from the injection molded parts using a common laboratory microtome. At least four samples were taken from each injection molded part. The cross section of the samples was then prepared to expose the compositional layers (skin, core, etc.) of each sample.
    [00066] Synchrotron measurements were taken on the G3 Deutsches Elektronen Synchrotron (DESY) to DORIS III beam line with the MAXIM detector set, that is, the first measurements were taken by the scintillation counting device to calculate the point-to-point average to obtain sample diffraction overviews. The spatially separated diffraction images were then taken by the MAXIM position sensitive camera (a 2D Hamamatsu 4880 detector with multi-channel plate [MCP] in front of its CCD sensor).
    [00067] Synchrotron measurements revealed that injection molded parts that have a certain thickness, which were molded using a constant low pressure process show an extra distinct and discernible band or zone of oriented polypropylene crystallites (see red arrow in the Figure below) at the core of the part. This extra area of oriented material can be seen in molded parts using steel or aluminum molds. Parts molded using a larger conventional process usually have a reduced number of oriented bands when compared to a molded part using a substantially constant low pressure process.
    [00068] Parts molded using a constant low pressure process may have less stress under molding. In a conventional process, the controlled speed filling process combined with a major transfer or change to control pressure can result in a part with high levels of stress under undesirable molding. If the compaction pressure is set too high in a conventional process, the part will often have an overcompressed door region. Molding stress can be visually assessed by placing the parts on a transverse polarized light table. The birefringence observed in the molded parts can be used to observe the differences in stress under molding. This is typically seen as stress line patterns on the part. The increasing number of lines and / or the non-uniformity of the stress lines is typically undesirable.
    [00069] It should be noted that the terms "substantially", "about" and "approximately" unless otherwise specified, can be used in the present invention to represent the inherent degree of uncertainty that can be attributed to any comparison, value, measurement or other quantitative representation. These terms are also used in the present invention to represent the degree to which a quantitative representation can vary from a stated reference without resulting in a change in the basic function of the subject in question. Unless otherwise defined in the present invention, the terms "substantially," "about" and "approximately" mean that the comparison, value, measurement, or other quantitative representation may be within 5% of the stated reference.
    [00070] It should be evident that the various embodiments of the products illustrated and described herein can be produced by a substantially constant low pressure molding process. Although specific reference has been made in the present invention to products to contain consumer goods or to the goods products themselves, it should be apparent that the molding method discussed in the present invention may be suitable for use in conjunction with products for use in the goods industry consumer goods, food service industry, transportation industry, medical industry, toy industry and the like. Furthermore, the person skilled in the art will recognize that the teachings presented here can be used in the construction of stack molds, multi-material molds including rotational and core molds, in combination with in-mold decoration, insert molding, mold assembly and the like.
    [00071] All the documents cited in the Detailed Description of the Invention are, in their relevant part, incorporated herein by way of reference. The citation of any document should not be interpreted as an admission that it represents prior art with respect to the present invention. If any meaning or definition of a term in this written document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to the term in this written document will take precedence.
    [00072] Although particular modalities have been illustrated and described here, it must be understood that several other changes and modifications can be made without departing from the spirit and scope of the subject claimed. Furthermore, although several aspects of the subject matter have been described here, such aspects need not be used in combination. Therefore, it is intended that the attached claims cover all such changes and modifications that are within the scope of the claimed matter.
    权利要求:
    Claims (10)
    [0001]
    1. Method comprising: (a) providing a molding apparatus (10) with more than one mold cavity (28), the mold cavities (28) having different cavity shapes and / or mold cavities (28 ) asymmetrically oriented; (b) filling the mold cavities (28) with a dose, the dose comprising a molten thermoplastic material (24) that has a melting pressure (t2, t3) which, when injected into the mold cavities, exceeds a pre-injection pressure (t1) of the dose comprising the molten thermoplastic material; characterized by the fact that it further comprises: (c) while filling the mold cavities with the dose comprising the molten thermoplastic material, until 70 to 100% of the mold cavities are filled, maintain the melting pressure (t3) substantially constant within the range of 70 kgf / cm2 (1000 psi) to less than 422 kgf / cm2 (6000 psi); and (d) removing, from the mold cavities, parts that have a shape that essentially duplicates the particular shape of the cavity; (e) upon contact of a mold cavity surface with the molten thermoplastic material, keep an internal portion of said mold cavity spaced at least 2 mm from the most immediate surface of the mold cavity in contact with the dose comprising material thermoplastic at a temperature below 100 ° C, where: the thermoplastic material has a melt flow index of about 0.1 g / 10 min to about 500 g / 10 min.
    [0002]
    2. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure that is between 105 and 387 kgf / cm2 (1500 and 5500 psi).
    [0003]
    3. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure that is between 141 and 352 kgf / cm2 (2000 and 5000 psi).
    [0004]
    4. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure that is between 176 and 316 kgf / cm2 (2500 and 4500 psi).
    [0005]
    5. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure that is between 211 and 281 kgf / cm2 (3000 and 4000 psi).
    [0006]
    6. Method according to claim 1, characterized by the fact that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure that is between 211 and 422 kgf / cm2 (3000 6000 psi).
    [0007]
    Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure so that the substantially constant pressure varies from 2 to 25%.
    [0008]
    8. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure so that the substantially constant pressure varies from 4 to 20%.
    [0009]
    9. Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure so that the substantially constant pressure varies from 6-15%.
    [0010]
    Method according to claim 1, characterized in that it includes, while substantially filling the entire mold cavity with the dose comprising the molten thermoplastic material, maintaining the melting pressure in the nozzle of the molding apparatus in a substantially constant pressure so that the substantially constant pressure varies / fluctuates by about 0, 2, 4.6, 8, 10, 12, 14, 16, 18, 20, 22, or 24%.
    类似技术:
    公开号 | 公开日 | 专利标题
    BR112013029835B1|2020-11-10|substantially constant low pressure injection molding method
    BR112013029234B1|2021-07-06|method and apparatus for substantially constant pressure injection molding of thin-walled parts
    EP2709816B1|2019-09-11|Method for injection molding at low, substantially constant pressure
    JP6334699B2|2018-05-30|Injection molding machine and method considering changes in material properties during injection molding operation
    TWI535550B|2016-06-01|Method for injection molding at low, substantially constant pressure
    AU2016201460A1|2016-05-19|Method and apparatus for substantially constant pressure injection molding of thinwall parts
    同族专利:
    公开号 | 公开日
    AU2012258950B2|2016-04-07|
    US20120295050A1|2012-11-22|
    CN103561934A|2014-02-05|
    MX2013013595A|2014-01-08|
    KR20140006065A|2014-01-15|
    AU2012258950A1|2013-11-28|
    RU2583394C2|2016-05-10|
    JP5841245B2|2016-01-13|
    KR20160075823A|2016-06-29|
    US9707709B2|2017-07-18|
    EP2709814A1|2014-03-26|
    CA2834890C|2016-07-12|
    MX369888B|2019-11-25|
    BR112013029835A2|2016-12-06|
    CA2834890A1|2012-11-29|
    EP2709814B1|2019-07-03|
    RU2013149942A|2015-06-27|
    ZA201307911B|2015-11-25|
    JP2014515325A|2014-06-30|
    CN103561934B|2017-02-15|
    WO2012162227A1|2012-11-29|
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    法律状态:
    2018-04-03| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|
    2019-11-05| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|
    2020-03-10| B25A| Requested transfer of rights approved|Owner name: IMFLUX INC. (US) |
    2020-07-07| B09A| Decision: intention to grant|
    2020-11-10| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 21/05/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US201161488555P| true| 2011-05-20|2011-05-20|
    US61/488,555|2011-05-20|
    PCT/US2012/038806|WO2012162227A1|2011-05-20|2012-05-21|Method for injection molding at low, substantially constant pressure|
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