CN111703049B

CN111703049B - Dipping and blowing forming method and device thereof

Info

Publication number: CN111703049B
Application number: CN202010595184.6A
Authority: CN
Inventors: 陈志光; 段庆生
Original assignee: Xiamen Shidi Medical Technology Co ltd
Current assignee: Xiamen Shidi Medical Technology Co ltd
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2022-02-11
Anticipated expiration: 2040-06-22
Also published as: CN111703049A

Abstract

The invention provides a dip-blow molding method and equipment thereof. The dip-blow molding method is used for manufacturing a parison by blow molding by a dip-molding method. The method comprises the following steps: adding liquid raw materials into the plastic dipping mold cavity; immersing a mold core into the liquid raw material to enable the liquid raw material to be attached to the surface of the mold core to obtain a parison coated on the surface of the mold core, wherein a gas channel is arranged in the mold core, and a gas valve communicated with the gas channel is arranged on the side wall of the mold core; and transferring the mold core with the parison attached to the surface into a blow mold cavity of a blow mold, and carrying out blow molding to obtain the dip-blow molded product. The invention can solve the problems that the prior blow molding process has complex flow, the side wall and the closed end of a product have injection ports or joint seams, the defect rate of the product is high, the raw materials cannot be accurately metered, and the like.

Description

Dipping and blowing forming method and device thereof

Technical Field

The invention relates to the field of material forming, in particular to a dip-blow forming method and equipment thereof.

Background

Blow molding is a common plastic molding method, and is commonly used for manufacturing hollow plastic parts such as bottles, barrels, cans and the like. The process flow is roughly as follows: firstly, making raw materials into a parison by processes of extrusion molding, injection molding and the like, then placing the parison into a blow molding die, injecting compressed air into the parison to enable the parison to be blown to be tightly attached to the cavity wall of the blow molding die, and keeping the blowing pressure until a plastic part is cooled and shaped to obtain a blow molding product. Because the traditional blow molding process firstly finishes the melting and plasticizing of materials through an extruder or an injection molding machine, and then transfers the parison to a blow mold for blow molding, the process flow is complex, and the defects of welding marks, stripes, injection ports and the like are easily generated in the parison in the extrusion molding or injection molding process. In addition, the injection molding process is limited by the injection pressure, and thus it is difficult to process long products, while the extrusion molding process can process long products, but the parison is formed by a tube blank with openings at both ends, and when a hollow product with one closed end is formed, a joint seam or joint point is generated at one end in the subsequent blow molding process. Furthermore, the conventional blow molding process usually only uses solid materials such as granules or powder as raw materials, and cannot process liquid materials, so that it is difficult to accurately measure the raw materials, and thus the amount of the raw materials used for each product is slightly different.

Disclosure of Invention

The invention aims to provide an infusion molding method and infusion molding equipment, which are used for solving the problems that the existing blow molding process is complex in flow, a filling port or a joint seam is formed in the side wall and the closed end of a product, the defect rate of the product is high, raw materials cannot be accurately metered, and the like.

An aspect of the present invention provides an immersion blow molding method in which a parison for blow molding is made by an immersion molding method.

Further, the dip-blow molding method comprises the following steps: (1) adding liquid raw materials into the plastic dipping mold cavity; (2) immersing the mold core into the liquid raw material to make the liquid raw material attached to the surface of the mold core to obtain a parison coated on the surface of the mold core, wherein a gas channel is arranged inside the mold core, and a gas valve communicated with the gas channel is arranged on the side wall of the mold core; (3) and transferring the mold core with the parison attached to the surface into a blow mold cavity of a blow mold, and carrying out blow molding to obtain the dip-blow molded product.

Further, in the step (1), the liquid raw material is precisely metered.

Further, step (2) also includes heating the mold core.

Further, the step (2) also comprises the step of carrying out a leveling operation on the liquid raw material attached to the surface of the mold core.

Further, in step (3), after the core is moved to the blow mold cavity, the gas valve of the core is opened, gas is continuously introduced into the parison through the gas valve, the continuously introduced gas blows the parison attached to the surface of the core away from the surface of the core, and the parison is blow molded into an article having a shape corresponding to the inner wall of the blow mold cavity.

Further, the dip blow molding method is used for molding thermoplastic or elastic liquid polymer materials, and at least comprises one of PVC, PU, TPE, LSR, liquid rubber and latex.

Another aspect of the present invention provides an inflation molding apparatus for implementing the inflation molding method according to the present invention, the inflation molding apparatus including: a plastic-impregnated mold cavity capable of containing a liquid raw material; the mold core can be partially placed in the cavity of the dip mold, the mold core comprises a gas channel arranged in the mold core, a gas valve arranged on the side wall of the mold core and communicated with the gas channel, and a mold closing assembly arranged at the top of the mold core, and the gas channel is connected to an external gas pipeline; a blow mold cavity capable of receiving a portion of the mold core and having an inner wall forming a predetermined hollow shape.

Further, the inflation molding apparatus further includes a metering assembly for precisely metering the amount of the liquid material.

Further, the air valve is an annular air valve and is arranged into one or more.

Compared with the prior art, the invention has the following beneficial technical effects:

1. the dipping plastic process is used for replacing the traditional extrusion molding process or injection molding process to provide the parison in the blow molding process, so that the whole process flow is simplified;

2. the plastic dipping process can provide a long parison with one closed end, and a long product with one closed end and strict performance requirements on the closed end can be prepared;

3. the product with uniform thickness, smooth surface and no joint seam or joint point can be formed;

4. the raw materials can be accurately metered, and the consistency of the raw material dosage of each product is ensured;

5. no leftover material is generated in the whole forming process, so that the raw material is saved;

6. the molding die matched with the existing blow molding equipment can completely meet the functional requirements of the invention on the dipping and blowing die cavity and the production requirements.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any inventive exercise.

Fig. 1 is an overall schematic view of an infusion-blow molding apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic view of a mold core according to an embodiment of the present invention positioned in a mold cavity of a plastic infusion mold;

FIG. 3 is a schematic view of a mold core according to an embodiment of the present invention positioned in a blow mold cavity;

FIG. 4 is a schematic illustration of a blow molding operation being performed according to an embodiment of the present invention;

fig. 5 is a schematic view of a dip-blown molded article according to an embodiment of the invention.

Detailed Description

The inventive concept will be described in detail below with reference to specific embodiments, however, the following exemplary embodiments are only intended to fully convey the inventive concept to those skilled in the art, and do not limit the scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Various exemplary embodiments are described herein with reference to cross-sectional and/or exploded illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments disclosed herein should not necessarily be construed as limited to the specifically illustrated shapes of regions but are to include variations in shapes or differences in sizes that result, for example, from manufacturing. In this manner, the regions illustrated in the figures may be schematic in nature and the shapes of the regions may not reflect the actual shape of a region of a device and, as such, are not intended to be limiting.

In a conventional blow molding process, a parison is first prepared by an injection molding or extrusion molding process, then the parison is transferred to a cavity of a blow mold, the parison is blown up to be closely attached to the inner wall of the blow mold cavity by introducing compressed air thereto in a state where the parison is softened, and after cooling, the mold cavity is opened to obtain a hollow article having a predetermined shape. The articles of the conventional blow molding process tend to have flash due to the tendency to have weld marks, streaks, etc. in the parison during the injection and extrusion processes. In addition, the injection molding process is limited by the injection pressure, and thus it is difficult to process long products, while the extrusion molding process can process long products, but the parison is formed by a tube blank with openings at both ends, so that when a hollow product with one closed end is formed, a joint seam or joint point is generated at one end in the subsequent blow molding process. Furthermore, conventional blow molding processes usually only use solids such as granules or powders as raw materials, and cannot process liquid raw materials, so that it is difficult to accurately meter raw materials, resulting in a slight difference between the amounts of raw materials used for each product. Therefore, it is desirable to provide a process for preparing hollow plastic articles that overcomes the above technical problems.

The invention provides a dip-blow molding method and equipment thereof by replacing an extrusion molding process or an injection molding process in the traditional blow molding process by using a dip-blow molding process, so that a long hollow product with one closed end can be prepared by a relatively simplified process, the surface of the product is flat, and no joint seam or leftover material exists.

An infusion blow molding method provided according to the inventive concept will be described in detail below with reference to exemplary embodiments.

In the dip blow molding method according to the present invention, the parison for blow molding is made by a dip molding method. Referring to fig. 1 to 5, an infusion blow molding method according to the inventive concept may include: adding liquid raw material RM into the plastic dipping die cavity 200; immersing the mold core 300 provided with the air valve 330 into the liquid raw material RM, so that the liquid raw material RM is attached to the surface of the mold core 300 to obtain a parison PPR coated on the surface of the mold core 300; and transferring the mold core 300 with the parison PPR attached to the surface thereof into a blow mold cavity 400 of a blow mold, and performing blow molding to obtain a dip blow molded product PR.

The liquid feedstock RM, accurately metered by the metering assembly 100, is first introduced into the dip mold cavity 200. The liquid material RM may be a plastic dipping solution commonly used in the field of plastic dipping molding, such as PVC plastic dipping solution, LSR (liquid silicone rubber) slurry, etc., or may be liquid PU, liquid TPE, liquid rubber, liquid latex, etc. Although fig. 2 shows that the liquid raw material RM is precisely metered by installing a mass flow meter or a volume flow meter on the liquid raw material RM transfer line, the present invention is not limited thereto, and the liquid raw material RM may be precisely metered by a weight sensor, a liquid level sensor (not shown), or the like in the dipping mold cavity 200 as long as any apparatus or method capable of precisely metering the amount of the liquid raw material RM is used. The liquid raw material RM, which is more easily and precisely metered, is used as the raw material in the dip-blow molding method of the present invention, so that the amount of the raw material used per final product can be kept uniform, which helps ensure that the thickness between the final products is kept uniform.

And then, preheating the die core 300 at 50-300 ℃. The mold core 300 may be preheated by the heating assembly 310 within the mold core 300, although the invention is not limited thereto. For example, in another embodiment, the mold core 300 does not include the heating assembly 310, in which case the mold core 300 may be preheated by a heating device (not shown) capable of reaching a predetermined temperature. Alternatively, the mold core 300 may not be preheated.

Thereafter, the preheated (or not preheated) mold core 300 is transferred into the plastic dipping mold cavity 200, and the dipping liquid is attached to a surface of a portion of the mold core 300, and at the same time, the mold core 300 can be maintained at a predetermined temperature by a heating means in the mold core 300. If the mold core 300 is not preheated in the previous step, the mold core 300 may be heated to a predetermined temperature.

And then, the mold core 300 attached with the plastic dipping liquid is moved out of the plastic dipping mold cavity 200, and the plastic dipping liquid on the surface of the mold core 300 is leveled, so that a plastic dipping film with uniform thickness is formed on the surface of the mold core 300 by the plastic dipping liquid. A leveling method commonly used in the art may be employed, for example, by attaching the core 300 to a centrifuge, which rotates the core 300 while providing air flow in a direction parallel to the axial direction of the core 300. Of course, in another embodiment, the leveling operation may also be omitted.

Then, the mold core 300 with the parison PPR attached to the surface thereof is transferred to the blow mold cavity 400, and the mold core 300 and the blow mold cavity 400 are tightly closed by the mold clamping assembly 340. The core 300 is heated again by the heating unit 310 inside the core 300, so that the parison PPR on the surface thereof is softened. Optionally, a second heating assembly (not shown) may also be disposed within the blow mold cavity 400, and in another embodiment, the temperature of the enclosed space between the blow mold cavity 400 and the mold core 300 may be increased by the second heating assembly within the blow mold cavity 400, thereby softening the parison PPR. After the parison PPR is softened, gas (such as compressed air) is introduced into a gas passage 320 in the mold core 300 through an external gas pipe, and at the same time, a gas valve 330 on the sidewall of the mold core 300 is opened, and the softened parison PPR attached to the surface of the mold core 300 is inflated by the gas until the parison PPR is closely attached to the inner wall of the blow mold cavity 400. During this process, the core 300 may spin at a speed such that the gas is able to blow the parison PPR more uniformly. In some embodiments, the gas may be a heated gas, which is capable of promoting the softening of the parison PPR; in other embodiments, the gas may be a cooled gas, which may facilitate subsequent cooling set.

Thereafter, the dip blow molded article PR adhering to the inner wall of the blow mold cavity 400 is cooled. The dip-blow molded article PR may be cooled by introducing a low-temperature gas into the gas passage 320 of the mold core 300, but the present invention is not limited thereto, and for example, in another embodiment, the dip-blow molded article PR may be cooled by a cooling member (such as a cooling circulation passage) in the blow mold cavity 400. After the cooling operation is completed, the blow mold cavity 400 is opened to obtain the dip blow molded article PR.

An advantage of the present invention is that the blow mold cavity 400 can also be fully utilized with existing blow molding equipment, i.e., the blow mold cavity 400 shown in fig. 1 can be existing blow molding equipment. The forming mold matched with the existing blow molding equipment can completely meet the functional requirements of the invention on the dip-blow molding cavity 400 and the production requirements. The blow mold cavity 400 may be one of a single-station hollow molding structure, a multi-station hollow molding structure, a hollow molding structure with stretching, or a rotary hollow molding structure.

Another aspect of the present invention provides an infusion molding apparatus, which, in one embodiment and referring to fig. 1 to 5, includes: a metering assembly 100 for precisely metering the amount of liquid feedstock RM; a plastic dip mold cavity 200 capable of containing a liquid feedstock RM; the mold core 300 can be partially placed in the dip molding cavity 200, the mold core 300 comprises a heating component 310 and a gas channel 320 which are arranged inside the mold core, a gas valve 330 arranged on the side wall of the mold core, and a mold closing component 340 arranged on the top of the mold core, and the gas channel 320 is connected to an external gas pipeline; a blow mold cavity 400 capable of receiving a portion of the mold core 300 and having an inner wall forming a predetermined hollow shape. The blow mold cavity 400 can be a molding tool for an existing blow molding apparatus.

Specifically, the metering assembly 100 may be a mass flow meter, a volume flow meter installed on the liquid material RM delivery line, but the present invention is not limited thereto. The metering assembly 100 may also be an interlocking device consisting of a weight sensor or a liquid level sensor in the plastic dipping mold cavity 200 and a solenoid valve on a liquid raw material RM conveying pipeline, when the amount of the liquid raw material RM in the plastic dipping mold cavity 200 reaches a predetermined amount, the sensor transmits a signal to the interlocking device so that the solenoid valve is closed, and then the raw material feeding into the plastic dipping mold cavity 200 is stopped. Any apparatus or method can be used in the present invention as long as it can precisely meter the amount of the liquid raw material RM.

The cavity 200 is provided with a space capable of accommodating the liquid material RM and the mold core 300, and at least a portion of the mold core 300 can be inserted into the space. The number of the dip mold cavities 200 may be plural according to the molding cycle of the article.

The mold core 300 includes a mold clamping assembly 340 disposed at the top thereof and a mold core 300 body having a bar shape in appearance, and a gas channel 320 connected to an external gas line is provided in the mold core 300 body. In an embodiment, referring to fig. 2 to 5, a heating component 310 capable of heating the mold core 300 may be further disposed in the main body of the mold core 300, and the heating component 310 may be disposed in plurality. The gas line is provided in the center of the mold core 300 in the axial direction of the rod-shaped mold core 300, the gas line branches off at least one branch in the horizontal direction, and the end of the branch (i.e., the side surface of the mold core 300) is provided with a gas valve 330, and the gas valve 330 can be connected to and controlled to be opened or closed by an external circuit. When the air valve 330 is closed, the mold core 300 may have a smooth side surface. Alternatively, in an embodiment, referring to fig. 1 to 4, the gas line may have an annular passage in a horizontal direction, in which case the gas valve 330 is disposed around the side surface of the mold core 300, and the annular passage and the gas valve 330 may be provided in plurality. In another embodiment, the gas valve 330 may be a multi-point gas valve. The clamp assembly 340 at the top of the mold core 300 enables the mold core 300 to be tightly closed with the dip mold cavity 200 and the blow mold cavity 400 described below.

The blow mold cavity 400 is hollow and has an inner surface corresponding to the shape of the dip-blow molded article PR, in which the main body of the mold core 300 can be placed.

The dip blow molding method according to the present invention is specifically exemplified below.

Example one

The method comprises the steps of accurately metering PVC plastic dipping liquid through a mass flow meter, adding the measured PVC plastic dipping liquid into a plastic dipping die cavity 200, preheating a die core 300 to 80 ℃ through a heating component 310 in the die core 300, transferring the die core 300 into the plastic dipping die cavity 200, transferring the die core 300 out of the plastic dipping die cavity 200 after 3 minutes, connecting the die core 300 to a centrifugal machine, enabling the die core 300 to rotate at a rotating speed of 120rpm/min, simultaneously providing airflow along the axial direction of the die core 300 at a speed of 8m/s, transferring the die core 300 with a parison PPR attached to the surface into a blow molding die cavity 400 after 2 minutes, enabling the die core 300 and the blow molding die cavity 400 to be tightly closed through a die assembly 340 at the top of the die core 300, heating the die core 300 to 140 ℃, introducing 0.5MPa compressed air into a gas channel 320 in the die core 300, simultaneously enabling the die core 300 to rotate at a speed of 60rpm/min, stopping introducing the compressed air and stopping the rotation of the die core 300 after 1min, and (3) introducing air with the temperature of 10 ℃ and the normal pressure into the air channel 320 in the mold core 300, and opening the blow molding mold cavity 400 after 2min to obtain a hollow soaking and blowing molded product PR with one closed end and no flash.

Claims

1. A dip blow molding process, wherein a parison for blow molding is produced by a dip molding process, comprising the steps of: (1) adding liquid raw materials into the plastic dipping mold cavity; (2) immersing a mold core into the liquid raw material to enable the liquid raw material to be attached to the surface of the mold core to obtain a parison coated on the surface of the mold core, wherein a gas channel is arranged in the mold core, and a gas valve communicated with the gas channel is arranged on the side wall of the mold core; (3) and transferring the mold core with the parison attached to the surface into a blow mold cavity of a blow mold, and carrying out blow molding to obtain the dip-blow molded product.

2. The dip blow molding method according to claim 1, wherein in step (1), the liquid raw material is precisely metered.

3. The dip-blow molding method according to claim 1, wherein step (2) further comprises heating the core.

4. The dip-blow molding method according to claim 1, wherein the step (2) further comprises leveling the liquid material adhering to the surface of the core.

5. The dip-blow molding method according to claim 1, wherein in step (3), after the core is moved to the blow mold cavity, the gas valve of the core is opened, gas is continuously introduced into the parison via the gas valve, the continuously introduced gas blows the parison attached to the core surface off the core surface, and the parison is blow-molded into an article having a shape corresponding to the inner wall of the blow mold cavity.

6. The dip-blow molding process of claim 1, wherein the dip-blow molding process is used for molding thermoplastic or elastic liquid polymer materials, and comprises at least one of PVC, PU, TPE, LSR, liquid rubber, and latex.

7. An inflation molding apparatus for carrying out the inflation molding method according to any one of claims 1 to 6, characterized by comprising: a plastic-impregnated mold cavity capable of containing a liquid raw material; the mold core can be partially placed in the cavity of the dip mold, the mold core comprises a gas channel arranged in the mold core, a gas valve arranged on the side wall of the mold core and communicated with the gas channel, and a mold closing assembly arranged at the top of the mold core, and the gas channel is connected to an external gas pipeline; a blow mold cavity capable of receiving a portion of the mold core and having an inner wall forming a predetermined hollow shape.

8. The inflation molding apparatus according to claim 7, further comprising a metering assembly for precisely metering the amount of the liquid material.

9. The inflation molding apparatus according to claim 7, wherein the gas valve is an annular gas valve and is provided in one or more.