JPS63222819A - Manufacture of polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain the polyurethane foam slab of super low density with flat top surface by lifting, with the foaming rise, the cylindrical pulling-up jig capable of rising and lowering along the side wall of a foaming tank, when the foaming is carried out under reduced pressure-atmosphere by reducing the pressure in a pressure reduction chamber. CONSTITUTION:Foaming stock solution is expanded by its foaming action, and is brought in contact with the inner surface of a pulling-up jig 12. The pressure in a pressure reduction chamber is reduced to a prescribed degree, and the pulling-up jig 12 is drawn up at the same speed as the rise speed from the time when said solution is brought in contact with the inner surface of the pulling-up jig 12. Consequently, even if the liquid surface of the foaming stock solution rises by its expansion, the portion being in contact with the pulling-up jig 12 with rectangular cylindrical shape at the vicinity of the rising point does not receive any frictional resistance. Accordingly, the height of a slab is not shortened by obstruction of foaming at the peripheral edge of the slab, and the polyurethane foam slab with flat top surface is obtained. Consequently, the polyurethane foam slab of super low density with flat top surface may be obtained, can then there is no risk of the occurrence of scorch phenomenon or a fire and its yield is heightened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyurethane foam, and particularly to a method for producing polyurethane foam with a flat top surface and an ultra-low density.

[Prior Art and Problem 1] As is well known, polyurethane foams are used in a wide range of applications and are manufactured in a variety of products ranging from low-density to high-density quantities depending on the intended use.

The conventional method for adjusting the density of a product when manufacturing polyurethane foam is to increase or decrease the amount of blowing agents (mainly water) and blowing aids (low boiling point solvents such as trichloromonofluoromethane and methylene chloride). It is being done.

Therefore, when manufacturing low-density polyurethane foam, foaming is performed using a large amount of water to increase the foaming ratio.

By the way, the foaming effect in the production of polyurethane foam is due to carbon dioxide gas generated by the reaction between organic isocyanate and water, so in conventional production methods, the raw material urethane foam is produced according to the density of the desired product. However, it was necessary to add a large amount of water as a blowing agent, which caused the following problems.

(2) Since most of the water and isocyanate are reacted, the internal temperature of the foam becomes extremely high due to the heat of reaction, which tends to cause so-called scorch (discoloration due to burning). Therefore, scorch inhibitors must be added.

■Addition ratio of water is 6 to 100 parts of polyol.
The upper limit is 711 parts, but such low-density foams significantly exacerbate the above-mentioned problems and pose a risk of fire.

■As the amount of organic isocyanate, trichloromonofluoromethane, etc. used increases, gas loss increases and participation decreases.

Furthermore, as shown in FIG. 4, for example, the polyurethane foam slab 2 is manufactured by pouring a polyurethane foaming stock solution into a large container (foaming tank) 1, foaming it, and curing it. .

In this case, the foaming operation is usually performed with the inner surface of the foaming tank 1 covered with release paper (not shown). This batch-type manufacturing method has the feature that it can be carried out even in a relatively narrow space. Furthermore, this method has the advantage that by changing the shape of the foaming tank 1, slabs of arbitrary shapes can be manufactured.

However, according to the conventional batch-type manufacturing method, when the polyurethane foaming stock solution is stirred and poured into the foaming tank 1, the foaming reaction proceeds and the liquid level gradually rises. At this time, as the foaming reaction progresses, the viscosity of the rising stock solution also increases, so foaming is inhibited near the area where it contacts the foaming tank 1 due to frictional resistance with the inner surface of the foaming tank.

For this reason, the polyurethane foam slab 2 after foaming is completed.
As shown in FIG. 5, the slab has a shape that is high at the center and low at the periphery, making it impossible to obtain a flat top surface.

As a result, as shown by the two-dot chain line in FIG. 5, the convex top of the obtained slab 2 must be cut off to a predetermined size, resulting in waste parts and an increase in the number of steps. There was a problem.

The present invention has been made in view of the above circumstances, and is a polyurethane foam that can obtain a polyurethane foam slab with a flat top and ultra-low density by using a cylindrical pulling jig in a foaming tank in a reduced pressure atmosphere during foaming. The purpose is to provide a manufacturing method for.

[Means for Solving the Problems] The present invention includes storing a foaming tank in advance in a vacuum chamber, stirring and mixing and injecting a polyurethane foam foam stock solution into the foaming tank, and then reducing the pressure in the vacuum chamber. When foaming is carried out under a reduced pressure atmosphere, a cylindrical lifting jig whose both ends are open and whose wall surface can be raised and lowered along the side wall surface of the foaming tank is raised in accordance with the rise of foaming.

The specific shape of the foaming tank in the present invention is not limited as long as it has a cylindrical shape with a flat bottom, side walls perpendicular to the bottom, and an open top. That is, it may be prismatic or cylindrical. On the other hand, the cylindrical lifting jig in the present invention is a cylindrical body corresponding to the cross-sectional shape of the cylindrical foam container.

In the present invention, the polyurethane foam foaming stock solution includes polyols such as polyether polyols and polyester polyols, organic isocyanates such as tolylene diisocyanate, amine catalysts, tin catalysts, blowing agents (water), foam stabilizers (silicone oil), and others. Pigments, fillers, etc. are used in appropriate combinations depending on the required properties.

In the present invention, the form of obtaining a predetermined reduced pressure atmosphere is as follows:
For example, a foaming tank may be accommodated in a vacuum chamber prepared separately for foaming. However, batch-type processes are easier to apply.

In the present invention, the amount of pressure reduction from normal pressure and the timing of pressure reduction vary depending on the formulation, ie, the desired density, physical properties, etc. However,
The amount of pressure reduction is preferably in the range of 100 to 500 grams per day. Moreover, the timing of depressurization may be started at the same time as the start of rice, or may be started in the middle of rice.

[Function] According to the present invention, during foaming, a cylindrical lifting jig whose both ends are open and whose wall surface can be raised and lowered along the side wall surface of the foaming tank is raised in accordance with the rise of foaming, thereby increasing the contact surface. The generation of frictional resistance is avoided. Therefore, inhibition of foaming in the contact area is prevented, and a flat polyurethane foam slab is obtained.

At that time, the cylindrical lifting jig may be lowered in advance before the foaming stock solution starts to rise, and then manually or automatically pulled up from the rice starting point in line with the rice, or it may be raised a little after the rice starts. It may also be raised together.

Further, in the present invention, since the foaming action is performed under reduced pressure, the foaming action is enhanced. That is, the formation of bubbles depends on the escape power of the carbon dioxide gas generated in the foaming stock solution, and this escape force is determined by the relative magnitude of the vapor pressure of the generated carbon dioxide gas with respect to the atmospheric pressure.

Therefore, even if all the tanks of generated carbon dioxide gas are the same and their partial pressures are the same, if the atmospheric pressure is low, the escape force will be large. Moreover, since the generated carbon dioxide gas is easily vaporized, the ratio of effective foaming is improved even if the amount of carbon dioxide gas generated is the same.

In this way, even when a foaming stock solution with the same formulation is used, the foaming ratio is increased by improving the vaporization efficiency of the generated carbon dioxide gas and reinforcing its foaming action, and the foaming ratio is increased with ultra-low density, e.g.
A polyurethane foam of ~10 Ka/m3 is obtained.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3. Here, FIG. 1 is an explanatory diagram of a polyurethane foam manufacturing apparatus according to the present invention, FIG. 2 is a perspective view of a foaming tank according to the same apparatus, and FIGS. 3 (A) to (D) show the operation of the same apparatus. FIG.

11 in the figure is a large foaming tank with a flat bottom and an open top. The foaming tank 11 is square as shown, and has a foaming space with a rectangular cross section. Inside the foaming tank 11, a rectangular cylindrical lifting jig 12 with both ends open is provided so as to be slidable along the inner surface of the IIl wall of the foaming tank 11. The rectangular cylindrical pulling jig 12 may be made of a steel plate such as stainless steel, iron, or tin, a plastic plate such as polyester, polycarbonate, or melamine, or a wooden board. It is preferable to use it by coating or pasting a releasable film.

A reinforcing bar 13 is provided at the upper end opening of the lifting jig 12 and extends approximately across the center thereof. In addition, the jig 12
A pulling wire 14... is connected to the wire 14.
The other end is a pulling rotation shaft 15a, 15b arranged above.
It is connected to a winding roll 16 provided at. The pulling rotation shaft 15a.

Sprockets 17 and 17 are pivotally attached to each of the sprockets 15b, and a sprocket chain 18 is wound and tensioned between both sprockets. Further, a drive motor 19 is connected to one of the pulling rotation shafts 15a to rotationally drive the rotation shaft 15a. By driving the motor 19, one of the pulling rotation shafts 15
When rotating a, the other pulling rotation shaft 15t) is also rotated at the same speed via the sprocket mechanism. Therefore, the wires 14 are tied up or wound around the rolls 16 at a constant speed, and the cylindrical pulling jig 12 can be freely raised and lowered.
It looks like this. A foaming stock solution inlet 20 is opened in the side wall of the foaming tank 11, and a door 21 that can be opened and closed is provided in the inlet 20. In addition, the pulling rotation shaft 15a,
15b is supported by a bearing (not shown), and the bearing is connected to the foaming tank 1.
It is fixed to the outer wall of 1. Further, the foaming tank 11 is placed on a roller 22.

The foaming tank 11 is housed in a reduced pressure chamber 23. An air supply pipe 25 having an N magnetic valve 24 interposed therein is connected to the upper part of the decompression chamber 23 . Further, an intake pipe 27 having a solenoid valve 26 interposed therein is connected to the lower part of the decompression chamber 23.
7 is connected to a vacuum pump (not shown). A foaming stock solution inlet 28 is opened on the side of the reduced pressure v21 at a position corresponding to the foaming stock solution introduction port 20, and the foaming stock solution inlet 28 is opened at a position corresponding to the foaming stock solution introduction port 20.
is provided with a door 29 that can be opened and closed. Furthermore, a side wall opening m30 for entering and exiting the foaming tank 11 is provided on the side wall of the decompression chamber 21. In addition, 31 in the figure is a conveyor for conveying the foaming tank 11, and 32 is a decompression chamber 2.
This is a gauge attached to 1.

A rail 41 is attached near the decompression chamber 21. A cart 43 having wheels 42 on its legs is placed on this rail 41, and can approach or retreat from the foaming tank 11 by expanding and contracting the extrusion cylinder 44. A rotating shaft 45 is stretched horizontally on the cart 43, and a cylindrical mixing and stirring tank 46 is pivotally fixed to the rotating shaft 45. The rotation shaft 45 is rotatably driven by a motor and an irregular gear (not shown), so that the mixing and stirring tank 46 is rotatably tilted in the direction indicated by the arrow in the figure. A stirring blade 47 is provided inside the mixing and stirring tank 46 in the axial direction thereof, and this stirring blade 47 is rotationally driven by a motor 48 attached below the mixing and stirring tank 46 . In addition, the mixing stirring tank 4
At the lower end of the side of 6, there is a foaming liquid discharge i! 49 extends diagonally downward. This R foam stock solution discharge pipe 49 and the mixing stirring tank 46 are communicated with each other via an 'R magnetic valve 50 provided at the boundary between the two. Furthermore, a mixing stirring tank 46
A metering tank 51 for the organic isocyanate component is disposed in the upper part of the container, and the metering tank 51 is connected to an organic isocyanate supply source via a pipe 52. A raw material supply pipe 53 is provided at the lower end of the measuring tank 51, and an i valve 54 is provided between the raw material supply pipe 53 and the measuring tank 51. Further, the raw material supply pipe 53 is connected to a polyurethane foam raw material supply pipe 55 for materials other than isocyanate components, such as polyols and catalysts.

A cleaning solvent supply pipe 56 for polyurethane foam raw materials is attached to the organic isocyanate component measuring tank 51,
This supply pipe 56 is connected to a cleaning solvent tank 57. Further, a cleaning solvent waste liquid receiver 58 is installed, and this waste liquid receiver 58 is connected to the cleaning solvent tank 57 via a pump 59.

Next, the operation of the manufacturing apparatus having the above structure will be explained.

First, as shown in FIG. 3(A), with the lifting jig 12 lowered to a predetermined position, the inner surface of the foaming tank 11 is lined with release paper, and the inner surface of the rectangular cylindrical lifting jig 12 is covered with release paper. Also, attach release paper or apply a release agent. Next, the foaming tank 11
After being accommodated in the decompression chamber 21 as shown in Fig. 1 (M!!
With the valves 24 and 26 closed), the extrusion cylinder 44 is expanded and contracted, and the mixing stirring tank 46 is retreated from the foaming tank 11, and the polyurethane foam foaming stock solution is adjusted. That is,
After the organic isocyanate component is supplied into the measuring tank 51 from the piping 52 and measured, the electromagnetic valve 54 is opened to introduce a predetermined amount of the isocyanate component into the mixing tank 46 from the raw material supply pipe 53. At the same time, other raw materials such as the polyol component and catalyst are mixed from the pipe 55 into the stirring tank 46.
Put it inside. Subsequently, the stirring blade 47 is rotated to mix uniformly.

Next, the mixing and stirring tank 46 is advanced to the illustrated position by driving the extrusion cylinder 54 to extend, and the tip of the foaming stock solution discharge pipe 49 is inserted into the foaming tank 11 from the foaming stock solution inlet 28,20. At that time, 1129.21 is pushed by the foaming stock solution discharge pipe 49 so that it can be easily opened.

Continuing! By opening the magnetic valve 50, the mixing tank 4
The foaming stock solution adjusted in the foaming tank 6 is injected into the foaming tank 11 through the discharge pipe 49. At this time, the rotating shaft 45 is rotated as necessary to tilt the mixing and stirring tank 46 forward to promote outflow of the foaming stock solution.

Thereafter, the extrusion cylinder 44 is driven to contract, thereby causing the mixing and stirring tank 46 to move backward, thereby allowing m528°20. Next, the foaming stock solution expands and rises due to the foaming action, and comes into contact with the inner surface of the lifting jig 12, as shown in FIG. 3(B). Here, after the rise starts, the intake pipe 27
of? ! The magnetic valve 26 was opened, the pressure reduction chamber 21 was connected to a vacuum pump, and the pressure inside the vacuum chamber was reduced by a predetermined amount. Next, as described above (from the point of contact with the inner surface of the pulling jig 12, the pulling jig 12 is pulled upward at the same speed as the rice speed. As a result, even if the liquid level rises due to expansion of the foaming stock solution, ,
The portion in contact with the rectangular cylindrical lifting jig 12 near the prologue is not subjected to any frictional resistance.

Therefore, unlike when foaming in a conventional foaming tank, foaming is inhibited at the peripheral edge of the slab and the height is not reduced, a polyurethane foam slab with a flat top surface can be obtained.

On the other hand, while the polytan foam slab is being foam-molded in the foaming tank 11 as described above, in the mixing stirring tank 46 and the isocyanate component measuring tank 51, which have retreated from the foaming W 111, the inner surface is formed as follows. The adhered polyurethane foaming solution is washed away. That is, pump 5
9 is driven, the cleaning solvent is supplied into the cleaning solvent tank 57, and the mixing tank 46 is further filled with the cleaning solvent. Next, by rotating the stirring blade 47, the mixing stirring tank 46
After dissolving the foaming stock solution adhering to the inner wall of the solenoid valve 5,
0 to drain the cleaning solvent. When the cleaning solvent is discharged, the foaming stock solution adhering to the inner wall of the discharge pipe 49 is also dissolved. The cleaning solvent discharged in this manner is stored in a waste liquid receiver 58 and then sent to a cleaning solvent tank 57 by a pump 59 to be reused.

When the cleaning is completed, the next foaming material is prepared in the same manner as described. After returning the inside of the decompression chamber 23 to its initial state, the side door 30 of the decompression chamber 23 is opened, the foaming tank 11 is taken out using the rollers 18, and another foaming tank is placed in its place at the position shown in the figure. will be installed in In this way, polyurethane foam slabs can be continuously manufactured by repeating the same operations as above.

According to the present invention, after the polyurethane foam stock solution is poured into the foaming tank 11 using a stirring table, the pressure is reduced!
When foaming is performed by reducing the pressure inside the foam to a predetermined pressure, the cylindrical lifting jig 12 having the above-described structure is raised in accordance with the rise of foaming, so that by using the jig 12, a polyurethane foam slab with a flat top surface can be obtained. Moreover, by foaming under a predetermined reduced pressure, the vaporization efficiency of carbon dioxide gas is increased and the foaming action is enhanced, and this slab is made into an ultra-low density, e.g.
Can be made to 0KO/m3. In addition, polyurethane foam slabs of various densities can be obtained using the same stock solution with no scorch phenomenon or fire hazard.

Note that the structure of the polyurethane foam manufacturing apparatus described in the above embodiments is of course not limited to the structure described above.

Furthermore, in the above embodiment, the solenoid valve of the intake pipe was opened and suction was carried out by a vacuum pump as a means for reducing the pressure inside the decompression chamber, but the invention is not limited to this. The pressure may be reduced.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to obtain a polyurethane foam slab with a flat top surface and an ultra-low density compared to the conventional one, and also to achieve a high yield without scorch phenomenon and no risk of fire outbreak. A method for producing high quality polyurethane foam can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the manufacturing process of the present invention's retin foam, Fig. 2 is a perspective view of a foaming tank related to the device, Fig. 3 is an explanatory diagram of the operation of the device, and Fig. 4 is An explanatory diagram of a conventional batch-type manufacturing method, FIG. 5 is a perspective view of a polyurethane foam slab produced by conventional method 6. 11... Foaming tank, 12... Cylindrical pulling jig, 13.
... Par, 14... Pulling wire, 15a. 15b... Pulling rotation shaft, 16... Winding roll,
17... Sprocket, 18... Sprocket chain, 19.48... Motor, 20.28... Foaming stock solution inlet, 21.29... Vinegar, 24.26.50°54... Solenoid valve, 30... Side opening door, 41... Rail, 42... Wheel, 43... Dolly, 44... Extrusion cylinder, 45... Rotating shaft, 46... Mixing stirring Tank, 47... Stirring blade, 49... Foaming stock solution discharge pipe,
51...Measuring tank, 52...Piping, 53...Raw material supply pipe, 55...Raw material supply pipe, 56...Cleaning solvent supply pipe, 57...Cleaning solvent tank, 58... Cleaning solvent waste liquid receiver, 59...pump.

Claims (1)

[Claims] A foaming tank is stored in a vacuum chamber in advance, and after agitating and mixing a polyurethane foam stock solution into the foaming tank and injecting the foaming solution into the foaming tank, the interior of the vacuum chamber is depressurized and foaming is performed under a reduced pressure atmosphere. A method for producing polyurethane foam, characterized in that a cylindrical lifting jig that can be raised and lowered along the side wall surface of the foaming tank is raised in accordance with the rise of foaming.