JP2013176886A - In-mold foam molding method - Google Patents

Abstract

An object of the present invention is to provide a method that can reduce the amount of steam used in foam molding in a mold compared to the prior art and that can produce a thermoplastic resin foam molded article having equivalent quality at low cost.
A first mold 2 and a second mold 3 through which steam can flow are combined, a cavity 9 having a desired shape is provided between the molds, and steam valves 12 and 17 are opened in the respective molds. In the cavity 9 of the mold provided with a steam supply line through which steam is supplied to the mold and a drain line for discharging fluid from the mold when the drain valves 13 and 18 are opened. After filling the plastic resin pre-expanded particles, when performing a mold heating step, one heating step, reverse one heating step, double-side heating step, heat retention step in order to obtain a foamed resin molded body, the reverse one heating step, An in-mold foam molding method, which is performed in a state where the drain valves 13 and 18 on both the first mold side and the second mold side are closed.
[Selection] Figure 1

Description

  The present invention relates to an in-mold foam molding method for producing a thermoplastic resin foam molded body such as a polystyrene-based resin foam molded body by in-mold foam molding, and in particular, reduces the amount of steam used as a heating medium compared to conventional methods. The present invention relates to a possible in-mold foam molding method.

  Conventionally, as an in-mold foam molding method for producing a thermoplastic resin foam molded article such as a polystyrene-based resin foam molded article by in-mold foam molding, for example, techniques disclosed in Patent Documents 1 to 3 have been proposed.

In Patent Document 1, pre-foamed particles of foamed resin are filled in a cavity formed between a closed moving mold and a stationary mold, and high temperature steam is passed through each of the moving mold and the stationary mold. After the mold heating is completed, the mold is heated from one mold to the other at a vapor pressure of 0.8 to 1.0 kg / cm ² so that high-temperature steam flows at high pressure between the pre-foamed grains in the cavity. High-temperature steam is passed through the molds for a predetermined time to carry out flow heating for rapidly foaming the pre-foamed grains, and then the steam outlets of both molds are closed, and 0.4-0 A foamed resin foam molding method is disclosed in which double-sided heating is performed to bake the surface of the foam molded body in the cavity at a vapor pressure of 0.5 kg / cm ² .

  In Patent Document 2, after filling foamable synthetic resin particles into a cavity in a molding die, steam is supplied from the mold vapor chamber into the cavity to foam the resin particles. A method of obtaining a foamed molded product by fusing, and the heating process is controlled by a control valve provided in a steam supply system to the mold steam chamber, and at least the mold heating process, the resin particles in the cavity In the molding method divided into one heating process that replaces the air present in between with steam and a double-sided heating process that foams and fuses resin particles in the cavity, when the one-side heating is performed, the set value of the vapor pressure is heated on both sides. The opening of the control valve is controlled by using a value proportional to the deviation between the set value and the pressure detection value in the molding die as the manipulated variable. Methods are disclosed.

In Patent Document 3, a first mold and a second mold through which steam can flow are combined, each has a cavity having a desired shape, and the mold is opened when a steam valve is opened in each mold. Thermoplastic resin pre-expanded particles were filled into the cavity of the mold provided with a steam supply line through which steam is supplied and a drain line for discharging fluid from the mold when the drain valve is opened. Thereafter, the following heating steps (a) to (e),
(A) a mold heating step of opening the steam valve and the drain valve of the first mold and the second mold and causing the steam to flow into the mold;
(B) Next, the first-type steam valve and the second-type drain valve are opened, the first-type drain valve and the second-type steam valve are closed, and the first-type steam valve is closed from the first-type side. Heating process while flowing steam to the mold side of 2,
(C) Next, the second-type steam valve and the first-type drain valve are opened, the second-type drain valve and the first-type steam valve are closed, and the second-type steam valve is closed from the second-type side. A reverse one-side heating process in which steam flows to the mold side of 1;
(D) Next, a double-sided heating step in which the steam valves of the first mold and the second mold are opened, the drain valves of the first mold and the second mold are closed, and the mold is heated.
(E) Next, the steam and drain valve of each of the first mold and the second mold are closed, and a heat retention process is performed in which the inside of the mold is kept with the retained steam, and then the mold is cooled and foamed. In the in-mold foam molding method for removing the resin molded body from the mold,
(B) One heating step is 7 seconds or more, (b) Pressure in the mold at the end of one heating step is 0.03 MPa or more, and (e) Heat retention step time / (b) One heating An in-mold foam molding method is disclosed in which the process time ratio is in the range of 0.8 to 1.2.

JP-A-5-104649 JP-A-8-300385 JP 2007-237468 A

  In the in-mold foam molding method for producing a thermoplastic resin foam molded article such as a polystyrene-based resin foam molded article by in-mold foam molding, a heating medium used in the in-mold foam molding (in order to save energy and reduce manufacturing costs) There is a need to provide a method that can reduce the amount of steam used.

  In the prior art of the in-mold foam molding method disclosed in Patent Documents 1 to 3 described above, the amount of steam used can be reduced to a certain extent. It has been demanded.

  The present invention has been made in view of the above circumstances, and provides a method capable of reducing the amount of steam used in foam molding in a mold as compared with the prior art and capable of producing a thermoplastic resin foam molded article having equivalent quality at low cost. Is an issue.

In order to achieve the above object, the present invention combines a first mold and a second mold through which steam can flow, has a cavity of a desired shape between the molds, and has a steam valve in each mold. In the cavity of the molding die provided with a steam supply line through which steam is supplied to the mold when opened and a drain line for discharging fluid from the mold when the drain valve is opened, After filling the expanded particles, the following heating steps (a) to (e),
(A) a mold heating step in which steam flows through the mold;
(B) Next, a heating step while flowing steam from the first mold side to the second mold side,
(C) Next, a reverse one-side heating step in which steam flows from the second mold side to the first mold side,
(D) Next, a double-sided heating step in which steam is passed through both molds to heat the mold,
(E) Next, in the in-mold foam molding method of performing a heat retaining step of retaining the inside of the mold with the retained steam, then cooling the mold and taking out the foamed resin molded body from the mold.
There is provided an in-mold foam molding method characterized in that the reverse heating step (c) is performed in a state in which both drain valves on the first mold side and the second mold side are closed.

  In the in-mold foam molding method of the present invention, it is preferable to heat the heating direction in the (b) one heating step from the smaller steam chamber volume to the larger one.

  In the in-mold foam molding method of the present invention, the (a) mold heating step may be performed so that the temperature of the surface facing the cavity of the mold reaches 100 ° C. or more.

  In the in-mold foam molding method of the present invention, the (b) one heating step may be performed by introducing steam into the mold from a bypass line to which steam having a pressure higher than that of the steam supply line is supplied. Good.

  The in-mold foam molding method of the present invention is the in-mold foam molding method including the heating steps (a) to (e), wherein (c) the reverse one heating step is performed by the first mold side and the second mold. By performing both the drain valves on the side closed, the amount of steam used can be reduced, and a high-quality thermoplastic resin foam molded article can be produced at low cost.

It is a block diagram which shows an example of a suitable shaping | molding apparatus in order to implement the in-mold foam molding method of this invention. It is a block diagram which illustrates the steam supply pipe line of the said shaping | molding apparatus.

Hereinafter, an embodiment of an in-mold foam molding method of the present invention will be described with reference to the drawings.
1 and 2 are views showing an example of a molding apparatus suitable for carrying out the in-mold foam molding method of the present invention. FIG. 1 is a configuration diagram of the molding apparatus, and FIG. 2 is a steam supply of the molding apparatus. It is a block diagram which illustrates a pipe line.

  The molding apparatus 1 includes a concave mold 2 that is a first mold and a convex mold 3 that is a second mold, and a mold 4 that can be closed and opened when these molds approach and separate from each other. have. The concave mold 2 includes a concave main body 5 provided with a large number of vapor holes and a frame 6 supporting the concave mold body 2. The convex mold 3 also supports the convex main body 7 provided with a large number of vapor holes and the same. The frame 8 is provided. In the mold closed state shown in FIG. 1, a cavity 9 is formed between the concave mold body 5 and the convex mold body 7 that matches the outer diameter of the foamed molded product to be manufactured, such as a fish box. A steam chamber 10 is provided between the concave body 5 and the frame 6, and a steam chamber 11 is also provided between the convex body 7 and the frame 8. The volume of the steam chamber 10 on the concave mold 2 side is the volume of the space surrounded by the concave mold body 5 and the frame 6. The volume of the steam chamber 11 on the convex mold 3 side is the volume of the space surrounded by the convex main body 7 and the frame 8.

  A steam supply line is connected to the steam chamber 10 on the concave side 2 via a concave side pressure regulating steam valve 12, and a drain line is connected to the opposite position via a concave side drain valve 13. A vacuum exhaust pipe line is connected to the pipe line via a vacuum valve 14. Further, a cooling water supply pipe line is inserted into the steam chamber 10 on the concave mold 2 side via a cooling water valve 15, and a pressure gauge 16 is connected to an appropriate place.

  Similarly, a steam supply conduit is connected to the steam chamber 11 on the convex 3 side via a convex pressure regulating steam valve 17, and a drain conduit is connected to the opposite position via a convex drain valve 18. And a vacuum exhaust line is connected to the drain line via a vacuum valve 19. In addition, a cooling water supply pipe line is inserted into the steam chamber 11 on the convex mold 3 side via a cooling water valve 20, and a pressure gauge 21 is connected to an appropriate place. Although not shown, a pre-expanded particle supply port connected to a supply line for filling the pre-expanded particles in the cavity 9 is provided at an appropriate position of the mold 4.

  As shown in FIG. 2, a steam supply line 22 for supplying steam to each of the steam chambers 10 and 11 is connected to a steam main pipe 23 through which high-pressure steam passes. 24 and an orifice type steam flow meter 25 are provided. The steam pressure reducing valve 24 normally has a supply steam pressure set to about 0.20 to 0.55 MPa. The orifice type steam flow meter 25 can display the flow rate of steam supplied through the steam supply line 22 by a display unit 26 connected to the flow meter.

Further, on the downstream side of the steam pressure reducing valve 24 of the steam supply line 22 and on the upstream side of the concave mold 2 and the convex mold 3, the concave pressure regulating steam valve 12 and the convex pressure regulating steam valve 17 are respectively provided. And are provided. The concave side pressure regulating steam valve 12 and the convex side pressure regulating steam valve 17 further depressurize the high-pressure steam from the steam pressure reducing valve 24. The supply steam pressure is usually set to about 0.03 to 0.18 MPa. ing. Then, steam is supplied from the concave-side pressure regulating steam valve 12 to the concave mold 2 and from the convex-side pressure regulating steam valve 17 to the convex mold 3.
Further, a concave type that is capable of supplying high-pressure steam to the concave mold 2 without the concave-side pressure regulating steam valve 12 on the downstream side of the steam pressure reducing valve 24 of the steam supply line 22 and upstream of the concave mold 2. A side bypass line 27 is provided. The bypass pipe 27 is provided with a concave-side bypass steam valve 29, and high-pressure steam can be supplied to the concave mold 2 by opening the bypass steam valve 29.
Further, on the downstream side of the steam pressure reducing valve 24 in the steam supply line 22 and upstream of the convex mold 3, high-pressure steam is supplied to the convex mold 3 without using the convex pressure regulating steam valve 17. A convex side bypass pipe 28 that can be supplied is provided. The bypass pipe 28 is provided with a convex bypass steam valve 30, and high-pressure steam can be supplied to the convex mold 3 by opening the bypass steam valve 30.

  In order to produce a thermoplastic resin foam molded article such as a polystyrene-based resin foam molded article using the molding apparatus configured as described above, the concave mold 2 and the convex mold 3 are brought close to each other and the mold 4 is closed. The pre-expanded particles are filled in the cavity 9, and then the pre-expanded particles are fused together while being foamed by steam heating of the mold 4, then the in-mold foam molding is performed, and then the mold 4 is cooled, and then the mold 4 Is performed, and the foamed molded product is released from the mold.

  The pre-foamed particles used in the in-mold foam molding method of the present invention are obtained by pre-foaming synthetic resin particles containing a foaming agent, and the synthetic resins constituting the synthetic resin particles are conventionally foamed. Can be appropriately selected from resin materials used for the production of resin molded products, and is not particularly limited. For example, polystyrene, high impact polystyrene, styrene-maleic anhydride copolymer, styrene-acrylonitrile Polystyrene resins such as copolymers, polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, polyester resins such as polyethylene terephthalate, etc., and polystyrene resins because of their strength and moldability Is preferred.

  Further, as the foaming agent, organic compounds that have a boiling point below the softening point of the synthetic resin and are gaseous or liquid at normal pressure are suitable. For example, propane, butane, pentane, cyclopentane, cyclopentadiene, hexane Further, hydrocarbons such as petroleum ether, low boiling point ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether, inorganic gases such as carbon dioxide and nitrogen, and the like are used. These foaming agents may use only 1 type and may use 2 or more types together. As a content rate of a foaming agent, it is 1-20 mass% with respect to the synthetic resin particle mass, Preferably it is 2-10 mass%. When the content of the foaming agent is less than the above range, the foaming ratio of the foamed molded product is insufficient and a lightweight foam cannot be obtained. On the other hand, even if the content of the foaming agent exceeds the above range, a further increase in the expansion ratio cannot be substantially expected, and foaming becomes unstable, which is not preferable.

(First embodiment)
In the in-mold foam molding method of the present invention, after filling the pre-expanded particles in the cavity 9 of the mold 4, the following heating steps (a) to (e),
(A) a molding die heating step of opening the concave side pressure regulating steam valve 12, the convex side pressure regulating steam valve 17, the concave side drain valve 13 and the convex side drain valve 18 and flowing steam to the molding die 4;
(B) Next, the concave side pressure regulating steam valve 12 and the convex side drain valve 18 are opened, and the convex side pressure regulating steam valve 17 and the concave side drain valve 13 are closed and the concave mold 2 side is shifted to the convex mold 3 side, or Opening the convex pressure regulating steam valve 17 and the concave drain valve 13, closing the concave pressure regulating steam valve 12 and the convex drain valve 18, and allowing the steam to flow from the convex 3 side to the concave 2 side while heating,
(C) Next, the convex side pressure regulating steam valve 17 is opened, the concave side pressure regulating steam valve 12 is closed, and the convex side is opened from the convex mold 3 side, or the concave side pressure regulating steam valve 12 is opened. A reverse heating process in which the pressure regulating steam valve 17 is closed and the steam flows from the concave mold 2 side to the convex mold 3 side;
(D) Next, a double-sided heating step in which the concave side pressure regulating steam valve 12 and the convex side pressure regulating steam valve 17 are opened, the concave side drain valve 13 and the convex side drain valve 18 are closed, and the mold 4 is heated.
(E) Next, the concave-side pressure regulating steam valve 12, the convex-side pressure regulating steam valve 17, the concave-side drain valve 13 and the convex-side drain valve 18 are closed, and the inside of the mold 4 is kept warm with the retained steam. Heat insulation process,
And do.
The in-mold foam molding method of the present invention is characterized in that the (c) reverse one-side heating step is performed in a state where the concave side drain valve 13 and the convex side drain valve 18 are closed.

  In each of the heating processes (a) to (d), when the pressure of the steam supplied to the concave mold 2 and the convex mold 3 is 0.03 to 0.18 MPa, the (a) mold heating process is 1 It is preferable to be about 3 seconds. (B) On the other hand, the heating step is preferably about 6 to 15 seconds. (C) The reverse one heating step is preferably about 2 to 5 seconds. (D) The double-sided heating step is preferably about 5 to 10 seconds. Moreover, it is preferable that (e) heat retention process be about 5 to 7 seconds.

(E) After completion of the heat retention step, the cooling water valves 15 and 20 are opened to introduce the cooling water into the molding apparatus 1 and flow toward the concave mold 2 and the convex mold 3 to cool the mold. . This water cooling step is preferably about 1 to 5 seconds.
After the water cooling step, the concave side drain valve 13, the convex side drain valve 18, the cooling water valves 15 and 20 are closed, and the vacuum valves 14 and 19 are opened to evacuate the inside of the molding die 4 so that the concave die 2 and the convex die are provided. 3 is allowed to cool (cooling step). This cooling is preferably about 20 to 100 seconds.

After standing to cool, the concave mold 2 and the convex mold 3 are moved away from each other to open the mold, and the foam molded body obtained by in-mold foam molding is taken out.
Thereafter, the mold is closed again, pre-expanded particles are filled into the cavity 9, and the above steps are repeated.

  In the present embodiment, the (c) reverse one-side heating step is performed with the concave-side drain valve 13 and the convex-side drain valve 18 closed, thereby reducing the steam flow rate used in the (c) reverse one-side heating step. Therefore, a high-quality thermoplastic resin foam molded article can be produced at a low cost.

(Second Embodiment)
In the in-mold foam molding method of the present invention, it is preferable to heat the heating direction in the (b) one heating step from a smaller steam chamber volume to a larger one.
When the volume of the concave chamber 2 and the volume of the convex chamber 3 has a relationship of concave> convex, the (b) one heating step includes the convex side pressure regulating steam valve 17 and the concave mold. The side drain valve 13 is opened, the convex side drain valve 18 and the concave side pressure regulating steam valve 12 are closed, and steam is flowed from the convex 3 side toward the concave 2 side.
In this case, (c) the reverse one-side heating step is performed with the concave side pressure regulating steam valve 12 opened, the convex side pressure regulating steam valve 17, the concave side drain valve 13 and the convex side drain valve 18 closed. This is done by flowing steam from the 2 side to the convex 3 side.
When the volume of the steam chamber 10 of the concave mold 2 and the volume of the steam chamber 11 of the convex mold 3 are in the relationship of concave <convex, the (b) one heating step is performed by using the concave side pressure regulating steam valve 12 and the convex The side drain valve 18 is opened, the concave side drain valve 13 and the convex side pressure regulating steam valve 17 are closed, and steam is flowed from the concave 2 side toward the convex 3 side.
In this case, (c) the reverse one-side heating step is performed with the convex side pressure regulating steam valve 17 opened and the concave side pressure regulating steam valve 12, the concave side drain valve 13 and the convex side drain valve 18 closed. It is performed by flowing steam from the mold 3 side to the concave mold 2 side.

  In this embodiment, (b) by heating the heating direction in the one heating step from the smaller one of the steam chamber volumes to the larger one, the time required for the one heating step can be shortened and the amount of steam used can be reduced.

(Third embodiment)
In the in-mold foam molding method of the present invention, the (a) mold heating step is preferably performed so that the temperature of the surface of the mold 4 facing the cavity 9 reaches 100 ° C. or more.
(A) In order to set the temperature of the surface of the mold 4 facing the cavity 9 in the mold heating process to 100 ° C. or higher, the (a) mold heating process should be about 1.5 to 3 seconds. preferable.

  In this embodiment, (a) the mold heating step is performed so that the temperature of the surface of the mold 4 facing the cavity 9 reaches 100 ° C. or higher, thereby reducing the heating time of the next (b) one heating step. The amount of steam used as a total of the molding cycle can be reduced.

(Fourth embodiment)
In the in-mold foam molding method of the present invention, (b) the one heating step is supplied with higher pressure steam than the low pressure steam supplied from the concave side pressure regulating steam valve 12 or the convex side pressure regulating steam valve 17. Preferably, steam is introduced into the mold 4 from the concave side bypass conduit 27 or the convex side bypass conduit 28. In this (b) one heating step, high pressure steam that is not decompressed is introduced into the mold 4 by opening the concave side bypass steam valve 29 or the convex side bypass steam valve 30.
In this (b) one-side heating step, by introducing high-pressure steam having a vapor pressure of about 0.20 to 0.55 MPa, the time required for the (b) one-side heating step is shortened to about 6 to 9 seconds.
In this (b) one heating step, the concave-side pressure regulating steam valve 12 or the convex-side pressure regulating steam valve 17 is closed, and only high-pressure steam from the concave-side bypass conduit 27 or the convex-side bypass conduit 28 is discharged. It can be introduced into the mold 4. Further, the concave side pressure regulating steam valve 12 or the convex side pressure regulating steam valve 17 is opened, and the high pressure steam from the concave side bypass pipe 27 or the convex side bypass pipe 28 is fed into the molding die 4 together with the low pressure steam. Can be introduced. Introducing high-pressure steam into the mold 4 together with low-pressure steam is a more preferable aspect because the pressure fluctuation of the steam is small and the steam can be supplied stably.

  In the present embodiment, (b) the one-side heating step is a concave-side bypass pipe that is supplied with higher-pressure steam than low-pressure steam supplied from the concave-side pressure-regulating steam valve 12 or the convex-side pressure-regulating steam valve 17. 27 or by introducing steam into the mold 4 from the convex side bypass conduit 28 (b) On the other hand, the time required for the heating process can be reduced, and the total amount of steam used in the molding cycle can be reduced. Can do.

[Comparative example]
In the comparative example, a polystyrene resin foam molded article was produced under conventional molding conditions.
As the molding apparatus, AD1313 manufactured by Kasahara Kogyo Co., Ltd. was used. A concave mold and a convex mold capable of molding a square box-shaped fish box having an outer dimension of 480 mm × 310 mm × 120 mm) and an inner dimension of 435 mm × 265 mm × 100 mm) were attached to this molding apparatus.
After closing the mold, polystyrene resin pre-expanded particles were filled in the cavity. As the pre-expanded particles, HDMF (bulk expansion ratio 60 times) manufactured by Sekisui Plastics Co., Ltd. was used.
Next, 0.065 MPa of steam was introduced into the molding die 4 from the concave side pressure regulating steam valve 12 and the convex side pressure regulating steam valve 17, and the respective heating steps (a) to (e) were continuously performed. . The concave side bypass steam valve 29 and the convex side bypass steam valve 30 were closed.

(A) Opening the concave side pressure regulating steam valve 12, the convex side pressure regulating steam valve 17, the concave mold side drain valve 13 and the convex mold side drain valve 18, and a mold heating process (1.0 Seconds),
(B) Next, the concave side pressure regulating steam valve 12 and the convex side drain valve 18 are opened, the concave side drain valve 13 and the convex side pressure regulating steam valve 17 are closed, and the steam is transferred from the concave mold 2 side to the convex mold 3 side. Heating step (13.2 seconds) [Step pressure of the one heating step (pressure in the cavity 9) is set to 0.020 MPa, and when the pressure reaches 0.020 MPa, the one heating step is terminated and the next reverse On the other hand, it was set to move to the heating process)
(C) Next, the convex side pressure regulating steam valve 17 and the concave side drain valve 13 are opened, the concave side pressure regulating steam valve 12 and the convex side drain valve 18 are closed, and the steam is transferred from the convex type 3 side to the concave type 2 side. Reverse heating process (3.0 seconds),
(D) Next, a double-side heating step (5) in which the concave side pressure regulating steam valve 12 and the convex side pressure regulating steam valve 17 are opened, the concave side drain valve 13 and the convex side drain valve 18 are closed, and the molding die 4 is heated. .0 seconds),
(E) Next, the concave-side pressure regulating steam valve 12, the convex-side pressure regulating steam valve 17, the concave-side drain valve 13 and the convex-side drain valve 18 are closed, and the inside of the mold 4 is kept warm with the retained steam. Thermal insulation process (5.0 seconds).

Next, the mold was cooled (cooling water cooling (3.0 seconds) and evacuation (55.0 seconds)), and then the mold was opened to obtain a fish box. The total amount of steam flow used was 6.6 kg / shot.
About the fish box obtained in this comparative example, as a result of investigating the quality as a foam-molded product by appearance inspection and internal fusion inspection, the quality was good (◯).
The total amount of steam flow used in this comparative example is shown in Table 1.

[Example 1]
(C) In the reverse one-side heating step, a fish box was manufactured under the same conditions as in the comparative example, except that the concave-side drain valve 13 and the convex-type drain valve 18 were closed and reverse one-side heating was performed.
The time of the one heating process until reaching the stepping pressure was 13.2 seconds, which was the same as the comparative example, but the total amount of steam flow was reduced to 6.2 kg / shot.
The quality of the fish box obtained in Example 1 was good (◯).
The total amount of steam flow used in Example 1 is shown in Table 1.

[Example 2]
The vapor chamber volumes of the concave mold 2 and the convex mold 3 were in the relationship of concave> convex. Therefore, (b) the heating direction (concave to convex in the comparative example) is changed from a convex shape to a concave shape in the one heating step, and (c) the heating direction is changed from a concave shape to a convex shape in the reverse one heating step. In-mold foam molding was performed under the same conditions as in Example 1.
(B) On the other hand, in the heating step, the convex side pressure regulating steam valve 17 and the concave side drain valve 13 are opened, the convex side drain valve 18 and the concave side pressure regulating steam valve 12 are closed, and the convex shape 3 side to the concave shape 2 The steam flowed to the side (11.8 seconds).
(C) In the reverse one-side heating step, the concave side pressure regulating steam valve 12 is opened and the convex side pressure regulating steam valve 17, the concave side drain valve 13 and the convex side drain valve 18 are closed, and the concave side pressure regulating valve 12 is closed. This was carried out by flowing steam on the convex mold 3 side (3.0 seconds).
By blowing steam from a convex mold having a small steam chamber volume, the one heating process time until reaching the stepping pressure was shortened to 11.8 seconds, and the total amount of steam flow was reduced to 6.0 kg / shot.
The quality of the fish box obtained in Example 2 was good (◯).
The total amount of steam flow used in Example 2 is shown in Table 1.

[Example 3]
(A) In-mold foam molding was performed under the same conditions as in Example 2 except that the time of the mold heating step was changed from 1.0 second to 2.0 seconds. (A) In the comparative example in which the time of the mold heating step was 1.0 second, the temperature of the surface facing the cavity of the mold was 97 ° C., but the time of the (a) mold heating step was 2. In the case of 0 seconds, the temperature of the surface facing the mold cavity reached 103 ° C.
The time of the one heating process until reaching the stepping pressure was shortened to 11.4 seconds, and the total amount of steam flow was reduced to 5.8 kg / shot.
The quality of the fish box obtained in Example 3 was good (◯).
The total amount of steam flow used in Example 3 is shown in Table 1.

[Example 4]
(B) On the other hand, in the heating step, together with the steam (0.065 MPa) from the convex-side pressure regulating steam valve 17, the convex-side bypass steam valve 30 provided in the convex-side bypass conduit 28 is opened and the high-pressure steam is opened. In-mold foam molding was performed under the same conditions as in Example 3 except that (0.30 MPa) was introduced into the mold.
The time of the one heating process until reaching the stepping pressure was shortened to 8.5 seconds, and the total amount of steam flow was reduced to 5.2 kg / shot.
The quality of the fish box obtained in Example 4 was good (◯).
The total amount of steam flow used in Example 4 is shown in Table 1.

From the results of Table 1, (c) in the reverse one-side heating step, Example 1 in which the concave-side drain valve 13 and the convex-side drain valve 18 are closed and reverse one-side heating is performed prevents the steam from being discharged from the drain valve. As a result, the steam flow rate was reduced compared to the comparative example.
In Example 2, the heating direction was changed from convex to concave under the heating conditions of Example 1, and steam was blown from a convex mold having a small steam chamber volume. It was shortened to 8 seconds, and the steam flow rate could be further reduced as compared with Example 1.
In Example 3, the heating time of the mold was changed from 1.0 seconds to 2.0 seconds under the heating conditions of Example 2, while the heating time was changed from 11.8 seconds to 11.4 seconds. As a result, the steam flow rate could be further reduced as compared with Example 2.
In Example 4, by introducing high-pressure steam into the mold in one heating step under the heating conditions of Example 3, the time of one heating step was shortened from 11.4 seconds to 8.5 seconds. The steam flow rate could be further reduced than 3.

  The present invention relates to an in-mold foam molding method for producing a thermoplastic resin foam molded body such as a polystyrene-based resin foam molded body by in-mold foam molding, and in particular, reduces the amount of steam used as a heating medium compared to conventional methods. The present invention relates to a possible in-mold foam molding method.

  DESCRIPTION OF SYMBOLS 1 ... Molding apparatus, 2 ... Concave mold, 3 ... Convex mold, 4 ... Mold, 5 ... Concave body, 6 ... Frame, 7 ... Convex mold body, 8 ... Frame, 9 ... Cavity, 10, 11 ... Steam chamber, 12 ... concave side pressure regulating steam valve, 13 ... concave side drain valve, 14, 19 ... vacuum valve, 15, 20 ... cooling water valve, 16, 21 ... pressure gauge, 17 ... convex side pressure regulating steam valve, 18 ... convex Die side drain valve, 22 ... Steam supply pipe, 23 ... Steam main pipe, 24 ... Steam pressure reducing valve, 25 ... Orifice type steam flow meter, 26 ... Display section, 27 ... Concave side bypass pipe, 28 ... Convex side bypass Pipe line, 29 ... concave side bypass steam valve, 30 ... convex side bypass steam valve.

Claims (4)

The first mold and the second mold through which steam can flow are combined, each has a cavity of a desired shape, and steam is supplied to each mold when the steam valve is opened. After filling the cavity of the mold provided with a steam supply line and a drain line for discharging a fluid from the mold when the drain valve is opened, each of the following heating Steps (a) to (e),
(A) a mold heating step in which steam flows through the mold;
(B) Next, a heating step while flowing steam from the first mold side to the second mold side,
(C) Next, a reverse one-side heating step in which steam flows from the second mold side to the first mold side,
(D) Next, a double-sided heating step in which steam is passed through both molds to heat the mold,
(E) Next, in the in-mold foam molding method of performing a heat retaining step of retaining the inside of the mold with the retained steam, then cooling the mold and taking out the foamed resin molded body from the mold.
(C) The reverse one-side heating step is performed in a state in which the drain valves on both the first mold side and the second mold side are closed.   2. The in-mold foam molding method according to claim 1, wherein the heating direction in the (b) one heating step is performed from a smaller steam chamber volume to a larger steam chamber volume.   The in-mold foam molding method according to claim 1 or 2, wherein (a) the mold heating step is performed such that the temperature of the surface facing the cavity of the mold reaches 100 ° C or higher.   The said (b) one-side heating process is performed by introduce | transducing a vapor | steam in the said shaping | molding die from the bypass line to which a high voltage | pressure vapor | steam is supplied rather than the said vapor | steam supply line. The in-mold foam molding method according to claim 1.

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