KR101771653B1

KR101771653B1 - Method for foaming of solid type material by variable pressure

Info

Publication number: KR101771653B1
Application number: KR1020150162652A
Authority: KR
Inventors: 김동건; 김효준; 박건욱; 유재근
Original assignee: 한국신발피혁연구원
Priority date: 2015-11-19
Filing date: 2015-11-19
Publication date: 2017-08-25
Also published as: KR20170058711A

Abstract

The present invention provides a variable-pressure foaming molding method of a solid molding material. The method of variable-pressure foaming molding of a solid molding material according to the present invention is a method of molding a mold-molding material in a mold-in-foaming (MIF) method having the same shape and dimensions as the cavity of a mold after completion of foaming in the mold. normal pressure) foam molding is performed through the pneumatic pressure after the pressurization of the molding material by the compression gas, thereby leading to the filling of the cavity of 100% of the molding material, thereby improving the foaming efficiency and improving the moldability.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of foaming a solid-

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a variable-pressure foaming molding method of a solid molding material, and more particularly, to a method of molding a mold of a mold in a molding in foaming (MIF) The molding material normal pressure foam molding is performed through the pneumatic pressure after pressurization of the molding material by the compression gas, whereby the filling of the cavity of the molding material induces 100% of the cavity, and the variable moldability of the solid molding material The present invention relates to a method for molding a compact.

The general expansion molding is carried out by an inflating foaming method as known in Patent Literatures 1 to 3. The inflating foaming method is a method in which a cavity for a foaming agent is filled in a cavity in a mold without any gap and then crosslinked for a predetermined time at high temperature and high pressure, The mold is instantaneously opened to expand and foam by the pressure difference between the inside and the outside of the mold. However, in the case of such a foamed foaming method, there is a disadvantage that the degree of expansion is different for each product, the shape is deformed at the time of expansion, and shrinkage is severe at reheating.

On the contrary, a molded in foaming (MIF) method in which foaming is completed in a cavity of a mold to mold a foam having the same shape and dimensions as the cavity of the mold is attracting attention. However, such a MIF method is a principle in which the molding material is not filled 100% in the cavity of the mold, but is injected only into the 10-70% space of the cavity and then filled in the cavity by foaming. Therefore, Successful molding of the foam with the same shape and dimensions as the cavity of the mold was determined.

However, in the case of most foamed compounds, in the conventional MIF process, the flowability of the molding material is considerably lowered when the molding material is foamed, so that the cavity of the mold is not 100% filled. There was a problem of poor sex.

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Korean Registered Patent Publication No. 10-1293923 entitled " Foam injection molding method for automobile interior material, foam injection molding die and its gas backpressure control device " Korean Patent Laid-Open Publication No. 10-2012-0001534 "Method of manufacturing integral foamed shoes" Korean Patent Laid-Open Publication No. 10-2002-0061658 entitled "Pressure Control Mold for Improving Surface Quality of Foamed Parts"

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to solve the problems of the related art, and it is an object of the present invention to provide a method of manufacturing a solid molding material by injecting a solid molding material into a cavity of a mold, injecting a compression gas, And 100% filling of the cavity of the molding material is induced by performing the foaming molding by operating the normal pressure again so that the foaming efficiency is increased and the foam is molded precisely and accurately in the same shape as the mold, Pressure foaming molding method of a new type of solid molding material in which the moldability is improved.

According to an aspect of the present invention for achieving the above object, the present invention provides a solid molded material injection apparatus comprising: a solid molded material injector supplying step in which a solid molded material (1), which is an EVA foam formulation, is supplied and accommodated in an injector (10); A solid molding material mold injection step in which the solid molding material 1 of the injector 10 is injected into the cavity 21 in the mold 20 at a set volume ratio of 25% to 75% with respect to the total volume of the cavity 21 ; A compression gas mold injection step in which a compression gas is injected into the cavity 21 of the mold 20 so that the solid molding material 1 of the cavity 21 is pressed with a set pressing force larger than normal pressure; A pressing force holding step in the mold for causing the set pressing force acting on the solid molding material (1) of the cavity (21) to be maintained for a set holding time; A step of discharging the compressed gas from the cavity 21 of the mold 20 so that normal pressure acts on the solid molding material 1 of the cavity 21; A solid-mold-material pressure holding step in the mold in which an atmospheric pressure acting on the solid-molding material (1) of the cavity (21) is maintained for a set holding time; And a foam releasing step of releasing the foam (2) foamed in the shape of the cavity (21) by opening the mold (20).

In the method of the present invention, the step of supplying the solid-molded material to the injection molding machine may be such that the solid molding material 1 is processed into a pellet 1a and supplied to the injection machine 10 have.

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In the same set pressing force of the ² ~ 100kgf / cm 2 solid molding material (1) of the cavity 21 in the injection of the compressed gas mold injection phase the compressed gas from the variable-pressure foam molding method of the solid-forming material according to the invention And the pressing force of the solid molding material in the mold is maintained for a set holding time of 2 to 100 kgf / cm < ² > for a set holding time of 1 to 50 minutes, wherein the compressed gas is atmospheric air, nitrogen gas, carbon dioxide gas, argon Gas, and helium gas.

In the above-described method of variable-pressure foaming molding of a solid molding material according to the present invention, the pressure-maintaining step of the solid molding material in the mold can maintain the atmospheric pressure for a set holding time of 1 to 50 minutes.

In the method of the present invention, the mold 20 is combined with the lower mold 20b and the lower mold 20b in which the cavity 21 of the predetermined shape is formed, And an O-ring 27 disposed in close contact with the upper surface of the lower mold 20b surrounding the cavity 21 and the lower surface of the upper mold 20a. The lower mold 20b includes a cavity 20a, (22) formed of a clearance space communicating with one end portion of the flow passage (21); A gas inflow channel 23 having a vertical cross-sectional shape into which a compressed gas flows and whose end is communicated with the backflow preventing space 22; And a gas discharge channel 24, which is disposed at a position spaced from the gas inlet channel 23 and has a vertical cross-sectional shape, in which the compressed gas is discharged and the end portion is communicated with the backflow preventing space 22 .

According to the variable-pressure foaming molding method of a solid molding material according to the present invention, the pressing force by the injection of the compressed gas is applied to the solid molding material injected into the cavity of the mold for a certain period of time, Since the foam molding is carried out, 100% filling of the cavity of the molding material is induced, whereby the foaming efficiency is increased and the moldability is improved.

1 is a conceptual view of a variable-pressure foaming and molding method of a solid molding material according to the present invention;
FIG. 2 is a block diagram showing a variable-pressure foaming molding method of a solid molding material according to an embodiment of the present invention; FIG.
FIG. 3 is a process conceptual diagram of each step of a method of forming a foamed material by a variable-pressure foaming according to an embodiment of the present invention; FIG.
4 and 5 are views showing a structure of a mold used in a variable-pressure foaming molding method of a solid molding material according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings 1 to 5. In the drawings and the detailed description, the construction and operation which can be easily understood by those skilled in the art from general foam molding, injection molding machine, pellet, mold, gas compressor and the like are simplified or omitted. In the drawings and specification, there are shown in the drawings and will not be described in detail, and only the technical features related to the present invention are shown or described only briefly. Respectively.

1, the solid molding material 1 injected into a space of the cavity 21 of the mold 20 is pressed by a pressurizing force to a set pressing force (high-pressure condition) The expansion of the solid molding material 1 in the variable pressure process from the high pressure to the atmospheric pressure is performed at the same time as the pouring of the solid molding material 1 is performed simultaneously with the pneumatic pressure (normal pressure condition) And the foamed solid molding material 1 is filled 100% in the entire space of the cavity 21 of the mold 20, so that the foam 2 is manufactured in a fine shape.

For this purpose, the variable-pressure foaming molding method of a solid molding material according to an embodiment of the present invention is a method of molding a mold of a solid-molded material injection machine, a step of injecting a solid molding material mold, a step of injecting a compressed- The pressurizing force holding step of the molding material, the compression gas discharging step in the mold, the pressure holding step of the solid molding material in the mold, and the foam releasing step.

The solid molding material injector supplying step is a step in which the solid molding material 1 is supplied to and accommodated in the injector 10. Here, the step of supplying the solid molding material injector according to the embodiment of the present invention allows the solid molding material 1 to be processed into the pellet 1a and supplied to the injector 10. [ The solid molding material 1 according to the embodiment of the present invention is obtained by mixing the EVA foam formulation with a kneader, a roll or the like according to a formulation table as shown in the following Table 1, ), But the solid molding material (1) according to the present invention is not limited thereto.

Material Content (part) EVA250 100 DCP 4 TAC 2 AC1000 12.5 ZnO 7.5 TiO ₂ 0.8 St / a 0.6 CaCO ₃ 5 Sum 132.4

The step of injecting the solid molding material mold is a step in which the solid molding material 1 of the injector 10 is injected into the cavity 21 inside the mold 20. The solid molding material 1 may be introduced at a set volume ratio of 80% or less with respect to the total volume of the cavity 21, wherein the step of injecting the solid molding material mold according to the embodiment of the present invention comprises So that the solid molding material 1 is introduced at a setting volume ratio of 25% to 75%.

Here, the step of injecting the solid molding material mold according to the embodiment of the present invention is performed such that the temperature of the mold 20 is set to 160 to 180 DEG C, the barrel temperature of the injector 10 is 90 to 110 DEG C, the injection speed is 140 to 160 mm / sec, and the injection pressure is set to 40 to 60 MPa.

The pressurized gas mold injection step is a step in which a compressed gas is injected into the cavity 21 of the mold 20 so that the solid molding material 1 of the cavity 21 is pressed with a set pressing force larger than normal pressure. The compressed gas may be supplied from a gas compressor 30 connected to the mold 20 and injected into the cavity 21 through the gas inlet channel 23 formed in the mold 20. [ In the step of injecting the compressed gas according to the embodiment of the present invention, the solid molding material 1 of the cavity 21 is pressed with a set pressing force of 2 to 100 kgf / cm ² by injection of the compressed gas. As the compressor body, general air, nitrogen gas, carbon dioxide gas, argon gas, helium gas and the like can be used.

In the step of holding the solid molding material pressing force in the mold, the step of holding the solid molding material pressing force in the mold is such that the setting pressing force acting on the solid molding material 1 of the cavity 21 is maintained for the setting holding time. In the step of holding the pressing force of the solid molding material in the mold according to the embodiment of the present invention, the set pressing force of 2 to 100 kgf / cm ² is maintained for a set holding time of 1 to 50 minutes.

Here, the temperature of the mold 20 is maintained at 160 to 180 DEG C even in the step of injecting the pressurized gas into the mold and the step of holding the pressing force of the solid molding material in the mold according to the embodiment of the present invention.

The step of discharging the compressed gas in the mold is a step of discharging the compressed gas from the cavity 21 of the mold 20 so that normal pressure acts on the solid molding material 1 of the cavity 21. [ The step of discharging the compressed gas in the mold allows the compressed gas to be quickly discharged at the time of foaming in the cavity 21 of the mold 20. [ The discharge of the compressed gas can be performed through the opening of the gas discharge channel 24 formed in the mold 20.

The step of retaining the solid molding material in the mold is a step of maintaining the atmospheric pressure acting on the solid molding material 1 of the cavity 21 for the set holding time. The step of maintaining the pressure of the solid molding material in the mold according to the embodiment of the present invention allows the atmospheric pressure to be maintained for a set holding time of 1 to 50 minutes. In such a step of maintaining the solid molding material at normal pressure in the mold, the foaming of the solid molding material 1 proceeds and the foam 2 is molded. The foam 2 is formed in a fine shape by filling the entire space of the cavity 21 of the mold 20 with 100%.

The foaming demolding step is a step of demolding the foamed product 2 in the shape of the cavity 21 by opening the mold 20 when the foamed body 2 is formed by the completion of the foaming molding.

4, the lower mold 20b, the upper mold 20a, and the lower mold 20a are formed by the same method as the mold 20 of the present invention, And an O-ring 27. The O-

As shown in Fig. 5, the lower mold 20b according to the embodiment of the present invention is provided with a backflow preventing space 22, a gas inflow channel 23, A gate electrode 24, and a gate 25 are formed.

The backflow prevention space 22 is formed by a fine space which communicates with one end of the cavity 21. The gas inflow channel 23 and the gas discharge channel 24 are connected to each other. The formation of such a backflow prevention space 22 prevents the gas inflow channel 23 and the gas exhaust channel 24 from being clogged by the back flow of the material in the foaming of the solid molding material 1 inside the cavity 21 .

The gas inflow channel 23 is a passage through which a compressed gas supply cable or pipe connected to the gas compressor 30 is connected and into which the compressed gas flows. The gas inflow channel 23 has a " . The gas discharge channel 24 is disposed at a position spaced apart from the gas inlet channel 23 and is a passage through which the compressed gas is discharged and has a vertical cross-sectional shape of 'b' 'in which the end portion is communicated with the backflow prevention space 22 .

An opening / closing valve is provided in the gas inlet channel 23 and the gas outlet channel 24 to allow the gas inlet channel 23 and the gas outlet channel 24 to open and close.

The gate 25 is a passage for transmitting the solid molding material 1 supplied from the injector 10 to the cavity 21 of the mold 20.

The upper mold 20a is engaged with the lower mold 20b to seal the cavity 21. [ The O-ring fixing groove 26, to which the O-ring 27 is fixed, may be formed in a circular shape on the lower surface of the upper mold 20a.

The O-ring 27 is disposed in close contact with the upper surface of the lower mold 20b surrounding the cavity 21 and the lower surface of the upper mold 20a. In the pressurized gas mold injection step and the solid- So that the set pressing force acting on the solid molding material 1 can be kept constant by preventing the compressed gas injected into the cavity 21 of the solid molding material 1 from leaking. For this purpose, the O-ring 27 may be made of a highly durable silicone material or a fluoro rubber material.

In order to verify the effect of the variable-pressure foaming molding method of the solid molding material according to the embodiment of the present invention, foam molding is performed under various processing conditions according to the processing condition table as shown in the following [Table 2] And then the dimensions of the foam (2) immediately after demoulding and the dimensions when it was cooled to room temperature were respectively measured and the shrinkage ratio was calculated. The produced foamed article 2 was evaluated in terms of the degree of molding compared with the shape of the cavity 21 of the metal mold 20. Table 3 below shows the correspondence and the shape similarity with the dimensions of the cavity 21 of the foam 2 and the mold 20, and the shrinkage ratio when cooled.

Processing condition item A B C D Ref. Material input amount
(Volume ratio of injection molding material to mold cavity volume,%) 40 40 40 40 100 pressure
change Pressure Pressure (kgf / cm ² ) 7 7 7 7 - Holding time (min) 0 2 4 10 - Atmospheric pressure Holding time (min) 10 8 6 0 - Characteristic Variable-pressure foaming existing
firing

Cavity size A B C D Ref.
size
horizontal 150 123 148 151 133 323 Vertical 120 95 118 120 108 250 thickness 10 8 9.5 10 9 21 Size relative to cavity (%) 82.0 98.7 100.7 88.7 215.3 Contrast of mold cavity
Foam shape Unformed Cavity and
Similarity Cavity and
Similarity Unformed Good One One 2 One 15

Based on the above-mentioned [Table 3], evaluation of the foam according to the processing conditions is as follows.

First, 30% of the molding material is charged into the cavity 21 of the mold 20, and then the pressing force is maintained for 4 minutes (min) at a pressure of 7 kgf / cm2. Then, The foamed foamed "C" specimen showed the most similar dimensional correspondence with a dimension of 100.7% of the cavity 21 of the mold 20. The shape was similar to the cavity 21 of the mold and the shrinkage rate was 2 %, Indicating excellent foam characteristics.

On the contrary, "Ref." Foam foamed by the conventional foaming process. The specimen had a large deviation of the foam size from 205% to 230% of the cavity (21) of the mold (20), and the foam size shrank by more than 15% after cooling to room temperature rather than immediately after the mold removal.

Next, comparative evaluation of the physical properties of the foam shows that the foam "C" measured by the variable pressure foaming process as shown in the following Table 4 has properties similar to those of the specimen "Ref." Prepared by the conventional foaming process , And specimens "A", "B", and "D" showed deterioration of physical properties.

Properties A B C D E Hardness 45 39 40 43 38 importance 0.35 0.21 0.25 0.32 0.2 The tensile strength 26.3 20.6 23.6 25.3 22.4 Elongation rate 150 210 270 130 260 CS 54 51 38 59 35

In the variable-pressure foaming molding method of a solid molding material according to the embodiment of the present invention configured as described above, after the solid molding material 1 is injected into the cavity 21 of the mold 20, compressed air is injected into the solid molding material (1) is subjected to a certain amount of pressing force for a certain period of time, and after the compressed air is discharged, normal pressure is applied again to perform foaming molding, so that 100% filling of the cavity of the solid molding material So that the foaming efficiency can be increased and the foam 2 can be precisely and precisely molded in the same shape as the mold 20 to improve moldability.

Although the above-described method for forming a variable-pressure foam of a solid molding material according to an embodiment of the present invention has been described with reference to the above description and drawings, it should be understood that the present invention is merely illustrative and not limitative of the present invention. It will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

1: Solid molding material
1a: pellet
2: foam
10: Injection machine
20: Mold
20a: HYPER
20b: Lower mold
21: Cavity
22: Backflow prevention space
23: gas inflow channel
24: gas discharge channel
25: Gate
26: O-ring fixing groove
27: O ring
30: gas compressor

Claims

A solid molding material injector supplying step in which a solid molding material 1 which is an EVA foam formulation is processed into a pellet 1a and supplied to and received by an injector 10;
A solid molding material mold injection step in which the solid molding material 1 of the injector 10 is injected into the cavity 21 in the mold 20 at a set volume ratio of 25% to 75% with respect to the total volume of the cavity 21 ;
Mold compressed gas mold to solid molding material (1) of 20 the compressed gas to the cavity 21 is injected into the cavity 21 of the to be pressed to set the pressing force of the atmospheric pressure (normal pressure) great ² ~ 100kgf / cm 2 than An injection step;
A pressing force holding step in the mold in which a set pressing force of 2 to 100 kgf / cm ² acting on the solid molding material 1 of the cavity 21 is maintained for a set holding time of 1 to 50 minutes;
A step of discharging the compressed gas from the cavity 21 of the mold 20 so that normal pressure acts on the solid molding material 1 of the cavity 21;
A step of maintaining a normal pressure acting on the solid molding material (1) of the cavity (21) for a set holding time of 1 to 50 minutes;
And a foam releasing step for releasing the foam (2) foamed in the shape of the cavity (21) by opening the mold (20)
In the step of injecting the solid molding material mold, the temperature of the mold 20 is set to 160 to 180 DEG C, the injection temperature of the injection machine 10 is 90 to 110 DEG C, the injection speed is 140 to 160 mm / sec, To 60 MPa,
Wherein the compressed gas comprises any one selected from the group consisting of general air, nitrogen gas, carbon dioxide gas, argon gas, and helium gas.

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The method according to claim 1,
The mold 20 has a lower mold 20b in which a cavity 21 of a predetermined shape is formed, an upper mold 20a which is coupled with the lower mold 20b to seal the cavity 21 and a lower mold 20b which surrounds the cavity 21, And an O-ring 27 disposed in close contact with the upper surface of the upper mold 20a and the lower surface of the upper mold 20a,
The lower mold 20b includes a backflow preventing space 22 formed of a clearance space communicating with one end of the cavity 21; A gas inflow channel 23 having a vertical cross-sectional shape into which a compressed gas flows and whose end is communicated with the backflow preventing space 22; A gas discharge channel 24 is disposed at a position spaced from the gas inlet channel 23 and has a vertical cross-sectional shape in which the compressed gas is discharged and the end portion is communicated with the backflow preventing space 22 Wherein said method comprises the steps of: