JP2006124579A - Polyurethane foam and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for readily producing a polyurethane foam having the thickness set at ≤10 mm and a high density obtained by regulating the density thereof to about 600-900 kg/m<SP>3</SP>with high mass productivity by adopting an RIM (reaction injection molding) method. <P>SOLUTION: The platy polyurethane foam is obtained from a main raw material composed of a polyol and an isocyanate and various kinds of auxiliary raw materials. The main raw material is mixed with the various kinds of auxiliary raw materials and a gas-dissolved raw material M prepared by dissolving a foam-forming gas therein under pressure is injected into a forming mold 30 under required pressure regulation. The pressure is then returned to atmospheric pressure just after completing the injection to produce the polyurethane foam. The thickness thereof is regulated to ≤10 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyurethane foam and a method for producing the same, and more specifically, by adopting reaction injection molding (hereinafter referred to as RIM molding), it is possible to cope with a thin plate shape or a complicated shape, and a high The present invention relates to a polyurethane foam capable of maintaining good moldability in density and a method for producing the same.

  Polyurethane foam, which has high weather resistance and workability, has many uses because of its elasticity derived from its structure. Product materials such as vibration damping materials, seal materials, cushion materials, heat insulating materials, polishing pads or cushion pads, etc. However, it is preferably employed. In the above-described product applications, there is a demand for moldability that is high in density, can withstand high load loads, and can be easily manufactured into a required shape, particularly a thin plate shape.

However, the slab foaming method, which is a general method for producing foams, is a method in which a foaming material is naturally foamed and cured at room temperature and atmospheric pressure, and is widely used because it is excellent in mass productivity and easy to manage. On the other hand, the density of mass-produced products has a low upper limit of about 200 kg / m ^3, and when a thin plate-like foam is to be produced, a block-like large foam obtained by natural foaming (hereinafter referred to as the raw material) In the so-called ski machining, the dimensional accuracy deteriorates due to the low density in the so-called ski machining, and it is difficult to produce a sheet-like foam of 10 mm or less, particularly 6 mm or less. It was. As another method, without adding a foaming agent, air is entrained by stirring a foam material having high viscosity, and before the air is united and defoamed in the material, it is heated and cured, In this method, it is possible to form a thin plate-like foam having a thickness of 10 mm or less. However, in the mechanical floss foaming method, a problem is pointed out that it is difficult to produce a high-density foam having 500 kg / m ³ or more due to the problem of moldability, particularly curing. If the increase in production cost due to deterioration of moldability or cure property at high density is allowed, desired foam production becomes possible, but on the other hand, high hardness due to high density makes skiing difficult, Post-processing such as primary cutting with a guillotine cutter or the like, and thickness adjustment such as sanding is essential, and additional manufacturing costs are required, which is not realistic.

  On the other hand, a RIM molding method is known as a molding method for providing a solid, non-foamed, so-called solid molded product using a molding die. This molding method can also be applied to thin plate shapes and complex shapes, and for this reason, it has conventionally been suitably applied to automotive bumpers, fenders, mudguards, etc., but is basically a solid body molding method. It was not used in the production of foams. Especially for the above-mentioned applications, the appearance requirements for the finished molded product are strict, and bubbles such as pinholes or voids generated on the surface of the molded body due to the gas remaining in the RIM molding raw material cause direct appearance defects, Since it is a cause of appearance defects such as armpits, orange peels or prestars in painting performed in the subsequent process, it is usually not considered to mix bubbles in the RIM molding raw material, and it has been required to eliminate them as much as possible. . For the purpose of exceptionally improving the fluidity of the RIM molding material and increasing the injection efficiency into the mold, so-called air (gas) loading, in which air such as dry air is mixed into the RIM molding material, is mixed. The technique to do was known. However, even in this case, after the RIM molding raw material is injected into the mold, it is controlled so that the mixed air is blown out of the mold so that the air is not foamed. Foam cannot be manufactured.

Also, as described in [Patent Document 1] below, the RIM molding method is adopted to produce an integral skin (polyurethane) foam (a foam in which only the surface layer is in a solid state and only the inside is in a foamed state). May be. However, in this method, it is only possible to produce a foam in which the two solid layers constituting the front and back of the molded product have a three-layer structure existing on both sides of the foam layer, and the foam state is uneven. Because of the structure in which the layers are stacked, it has been difficult to form a thin plate shape of 6 mm or less. Furthermore, since a foaming agent related to chemical foaming such as Freon, alternative Freon or water is used, it is difficult to control the gas generation, and it is difficult to control the density, cell diameter and distribution of the cell diameter. It was not suitable for the production of highly foamed materials.
JP-A-3-063422

In order to overcome the above-mentioned problems and achieve the intended purpose, the polyurethane foam according to the present invention is a plate-like polyurethane foam obtained from a main raw material consisting of polyol and isocyanate and various auxiliary raw materials,
The main raw material and various auxiliary raw materials are mixed, and a gas-dissolved raw material in which a foaming gas is dissolved under pressure is injected into the mold under the required pressure adjustment, and then returned to normal pressure immediately after the completion of the injection. The thickness is set to 10 mm or less.

In order to overcome the above-mentioned problems and achieve the intended object, a method for producing a polyurethane foam according to another invention of the present application is a method for producing a plate-like polyurethane foam obtained from a main raw material comprising polyol and isocyanate and various auxiliary raw materials. In the manufacturing method,
The main raw material and various auxiliary raw materials are mixed, and a gas-dissolved raw material in which a foaming gas is dissolved under pressure is injected into a mold under a required pressure regulation.
By returning the required amount of the gas-dissolved raw material to normal pressure immediately after injection into the mold,
A polyurethane foam having a thickness set to 10 mm or less is manufactured.

According to the polyurethane foam and the method for producing the same according to the present invention, a plate-like polyurethane foam whose thickness is set to 10 mm or less can be easily produced by employing the RIM molding method. Further, a high-density polyurethane foam having a density of about 600 to 900 kg / m ³ can be produced with high mass productivity. Further, the cell diameter can be arbitrarily controlled and the diameter can be homogenized.

  Next, a polyurethane foam according to a preferred embodiment of the present invention and a method for producing the same will be described below with reference to preferred embodiments. The inventor of the present application uses a reaction-injection molding method (hereinafter referred to as a RIM molding method) for a gas-dissolved raw material in which a foaming gas such as an inert gas is dissolved in a polyurethane-based raw material under pressure control such as predetermined pressure regulation. It has been found that a plate-like polyurethane foam having a thickness of 10 mm or less, preferably 6 mm or less can be produced easily and with high mass productivity. It is also possible to produce a polyurethane foam having a large number of fine cells having a cell diameter of 20 to 100 μm uniformly by making a dissolved amount of the foaming gas and selecting a polyol as a raw material of the polyurethane foam. I also found out.

  Prior to the description of the present invention, a reaction injection molding apparatus (hereinafter simply referred to as a manufacturing apparatus) that is preferably used in the present invention will be described in order to contribute to an understanding thereof. As a manufacturing apparatus, a foaming gas supply means for supplying a foaming gas while applying a predetermined pressure to a polyol storage means such as a tank in this apparatus is added based on a known reaction injection molding apparatus. It has become a form. Further, when the polyol is stored in the tank and the foaming gas is dissolved therein, it is preferable to have a polyol stirring means. In addition, there is no problem even if the supply position is any position as long as the foaming gas can be sufficiently dissolved in the polyol.

In addition, the gas-dissolved raw material, which is a reaction mixture obtained by collision-mixing polyol, foam-forming gas, isocyanate, etc. in the mixing head in the production equipment, has a cavity with an external contour shape that is immediately required (polyurethane foam to be obtained). Then, it is injected at a high pressure of, for example, 150 kg / cm ² into a reaction injection mold (hereinafter simply referred to as a mold) having a predetermined internal pressure. This mold is provided with a vent that discharges internal air that hinders the rapid injection of the reaction mixture, as in the known mold, but in the present invention, the internal air of the mold using this vent is provided. The discharge or the like is performed under control (described later [0020]).

  As shown in FIG. 1, the polyurethane foam manufacturing method according to the present embodiment includes a raw material preparation stage S1, a mixing / injection process S2, a molding process S3, and a final process S4. Here, the mixing / injection step S2 is a step in which polyol, isocyanate, and the like are collided and mixed under pressure to inject into the mold as a gas-dissolved raw material, and the final step S4 is a product molded in the mold. This is a process in which demolding, inspection, etc. are performed, and since it is the same as the conventional reaction injection molding method, the details are omitted. The gas-dissolved raw material injected into the mold in the mixing / injection step S2 is substantially the same in volume as the gas-dissolved raw material in a state where the foaming gas is vaporized under reduced pressure under normal pressure. In addition to this, it is injected after being weighed. In addition, in-mold injection determined by the type of polyol, isocyanate, or various auxiliary materials, etc., in order to ensure reliable injection into the mold. In consideration of the subsequent foaming / curing speed and liquid flowability, as well as the generation of voids derived from the entrainment of air existing in the path and mold, etc., gas dissolved raw materials that become excessive (overpack) are used. May be.

In the raw material preparation stage S1, adjustment of polyol, isocyanate and the like (hereinafter referred to as liquid raw material) is carried out. In the present invention, 10 to 2, The foaming gas in a range of 000 parts by volume, preferably 70 to 500 parts by volume, is mixed and dissolved. In order to dissolve a larger amount of foaming gas, a known foaming gas is filled and pressurized in the tank and dissolved, and supercritical or subcritical liquid gas is used as a raw material under pressure. It is preferable to mix. If the value of the foaming gas is less than 10 parts by volume, the amount of foaming gas dissolved is small, and in the normal pressure step S32 described later ([0021]), the foaming gas does not foam to a desired foaming ratio or is homogeneous. Is difficult to form, or a high-density body in which it is difficult to express the properties of the foam. On the other hand, if the volume exceeds 2,000 parts by volume, it is difficult to dissolve the foaming gas in the liquid raw material, and the excess foaming gas fills the molding die, leading to cell coalescence. A good foamed molded article cannot be produced. The amount of the foaming gas dissolved determines the density of the resulting polyurethane foam. For example, the average density of each raw material is about 1,000 kg / m ³ and the amount of foaming gas dissolved is 25 volumes. Part, the density of the polyurethane foam is 800 kg / m ³ . Since the density of a general solid polyurethane molded product is 1,000 to 1,200 kg / m ³ , the polyurethane according to the present invention can be prepared by simply adjusting the dissolved (gas loading) amount of the foaming gas. The density of the foam can be easily set in the range of 900 kg / m ³ . In addition, by setting the dissolved amount of the foaming gas to 70 parts by volume or more, the density can be set to a relatively low density of 600 to 700 kg / m ³ .

As the foam-forming gas used here, known substances that do not affect the reaction with polyol or isocyanate, such as CO _{2 having} a large diffusion coefficient, dry air (dryer) or nitrogen, can be employed. In addition, the amount dissolved in the polyol is determined by the type of foaming gas and the pressure in the tank. This relationship is confirmed by acquiring these calibration curves and the like in advance. Here, the foam-forming gas is mixed with a chemically stable polyol, but may be mixed with an isocyanate.

  Known compounds are used as the polyol and isocyanate which are the main raw materials of the polyurethane foam. The polyol is an active hydrogen-containing compound having at least two active hydrogens. For example, the active hydrogen-containing compound is a polycrystal having a molecular weight of usually 400 to 20,000, preferably 800 to 15,000. Examples include ether polyol, polymer polyol, polyester polyol, and polyether polyamine. Further, the isocyanate is a compound having at least two isocyanate groups. Examples of the isocyanate compound include polyisocyanate or a modified product of polyisocyanate. Examples of the polyisocyanate include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate, and aliphatic polyisocyanates such as hexamethylene diisocyanate. Examples of the modified polyisocyanate include urethane-modified polyisocyanate, carbodiimide-modified polyisocyanate, allophanate-modified polyisocyanate, urea-modified polyisocyanate, burette-modified polyisocyanate, uretonimine-modified polyisocyanate, and isocyanate prepolymer.

Furthermore, in addition to the above-mentioned main raw material, a crosslinking agent is added as an auxiliary raw material. A crosslinking agent is a chain extender blended as an additive to polyols, isocyanates, etc., and can be used at either the amine end or the hydroxyl end. In the present invention, good bubble formation due to gas dissolution when using CO ₂ in a supercritical state (critical temperature: 31.3 ° C., critical pressure: 7.38 MPa (72.9 atm)) and molding with elongation characteristics When obtaining a product, diethylene glycol is preferred. Specifically, polyalkylene glycol such as ethylene glycol, 1,3-propanediol, 1,4-butanediol or 1,5-pentanediol, polyoxyalkylene glycolicol such as diethylene glycol, dipropylene glycol or triethylene glycol , Alkanol oxide such as diethanolamine or triethanolamine, polyhydric alcohol such as trimethylolpropane or glycerin, ethylenediamine, aniline, glycerin, 2,4- / 2,6-tolylenediamine isomer mixture, etc. Examples thereof include a low molecular polyol added in an amount of 1 to 2 mol per group.

  Examples of the catalyst include triethylenediamine, N, N, N ′, N′-tetramethylhexane-1,6-diamine, N, N, N ′, N ″, N ″ -pentamethy, rudiethylenetriamine, N, N ′. -Bis (N ", N" -dimethyl-3-aminopropyl) N, N-dimethylethylenediamine, N-methyl-N "-(2-dimethylamino) ethylpiperazine, N-ethylmorpholine, 1-methylimidazole, Tertiary amine catalysts such as 1,2-dimethylimidazole, 3- (dimethylamino) propylimidazole or dimethylaminoethanol, and organometallic catalysts such as dibutyltin dilaurate or dimethyltin dilaurate are used alone or in combination. Furthermore, in reaction injection molding, internal mold release agents, foaming aids, flame retardants, antioxidants can be used as necessary. Auxiliaries such agents may be used as auxiliary material. As the internal mold release agents include, for example, amine solutions of fatty acid metal salt.

  The polyol and isocyanate, which are the main raw materials of the polyurethane foam described so far, and the crosslinking agent and catalyst in the auxiliary raw material have a great influence on the cell diameter of the polyurethane foam to be produced. By adopting highly reactive raw materials as each of these raw materials, the foaming / curing time of the gas-dissolved raw material injected into the mold is controlled, and the size of bubbles generated from the gas-dissolved raw material, that is, the cell diameter is controlled. An arbitrary size is set. By this method, it is possible to easily obtain a polyurethane foam having minute cells such as 20 to 100 μm, which has been difficult to produce.

  The molding step S3 is a step of injecting a metered required amount of the gas-dissolved raw material into the molding die and molding polyurethane foam according to the cavity shape of the molding die. It consists of S32 and resinification step S33. In the pressure-regulating injection step S31, as shown in FIG. 2, a predetermined amount of gas-dissolved raw material M is injected into the cavity 30a of the mold 30 (see FIG. 2A), and the injection is completed in the cavity 30a. It is a stage (see FIG. 2B and FIG. 2C), and is completed in a short time of about 1 second. In this pressure-regulated injection step S31, the pressure in the cavity 30a is regulated so that the foaming gas that is the source of the cell is not vaporized and separated from the gas-dissolved raw material M, specifically, in the polyol storage means ( The gas dissolved raw material M is kept substantially the same as the path to the mold). That is, the inside of the cavity 30a is adjusted to a predetermined pressure in advance, and when the gas-dissolved raw material M starts to be injected therein, the volume of the internal air (of the mold) corresponding to the injection amount is continuously discharged. The By doing so, the quick injection completion of the gas-dissolved raw material M in the cavity 30a and the escape to the outside of the mold and the generation of cells due to the vaporization of the foaming gas dissolved therein are prevented. Both are compatible. Note that the gas-dissolved raw material M at this stage is in a state in which the foaming gas is dissolved, so that the viscosity thereof is low and the injection into the cavity 30a is also efficiently performed.

  The vent 32 that can perform such continuous control includes a pressure-regulating valve having a structure that opens when the pressure exceeds a certain pressure, a pressure applied to the gas-dissolved raw material M, and a molding die. A control valve that has an aperture calculated from the injection speed with respect to 30 and the inner volume of the mold 30 and can be controlled to open and close from the moment when the gas-dissolved raw material M is injected until the complete injection is completed. Is adopted. Further, the number of vents 32 may be not limited to a single one but may be provided at several places so that partial pressure fluctuations in the cavity 30a can be suppressed. The vents 32 provided at the plurality of locations are controlled so as to be sequentially closed according to the degree of injection so that the gas-dissolved raw material M does not leak out. Basically, while the gas-dissolved raw material M is being injected into the mold 30, the vent 32 discharges the internal air in the mold 30 by the same volume as that of the gas-dissolved raw material M being injected. The foaming gas is prevented from escaping from the raw material M, so that the gas-dissolved raw material M containing a pre-calculated amount of foaming gas, which is the source of the cell, is injected into the mold 30. . More preferably, during the injection of the gas-dissolved raw material M, (counter) air or the like having a predetermined pressure is supplied from the vent 32 to the inside of the mold 30 so as to act as a counter, so that the counter pressure is applied. You may make it prevent escape from the gas-dissolved raw material M of the gas for foaming. In this case, the inside of the mold is kept at a predetermined pressure, and before the gas-dissolved raw material is completely injected into the mold, the foaming gas escapes from the gas-dissolved raw material, and the density of the polyurethane foam increases. It is preventing. Further, precise control is not necessary for the vent 32, and there is an advantage that the complexity in the manufacturing process can be reduced.

  Then, the normal pressure stage S32 is started from the point in time when the injection of the total amount of the gas dissolved raw material M thus measured into the cavity 30a is completed. That is, in the pressure-regulating injection step S31, the pressure of the gas-dissolved raw material M injected into the cavity 30a is exhausted in conjunction with the internal air of the mold 30 that substantially matches the amount of the gas-dissolved raw material M to be injected. In this normal pressure-generating step S32, the pressure applied to the gas-dissolved raw material M, for example, by fully opening the vent 32, has been suppressed. Is released instantly. By instantaneous release of the pressure, as shown in FIG. 3, the gas dissolved raw material M injected into the cavity 30a is instantly foamed to increase the volume, and the cavity 30a is almost completely filled as measured. In terms of time, it is completed immediately after the completion of the regulated pressure injection step S31.

  That is, at this moment, all the foaming gas dissolved in the gas-dissolved raw material M is vaporized to form the cell 20. This means that a large number of so-called nuclei that are the basis of the cell 20 are generated at substantially the same time (see FIG. 3A), and the size and cell diameter of the generated cell 20 are uniform. That is, the cell diameter is monodispersed (see FIG. 3B). This is because when the gas-dissolved raw material M in which the inert gas is dissolved is in the same equilibrium system as in the present embodiment, the inert gas is vaporized at the same probability regardless of the part, and the expansion rate of the vaporized gas This is because non-uniformity due to the site does not appear and vaporizes uniformly and randomly. Thus, the cell 20 of the polyurethane foam according to the present invention exhibits high monodispersity with a polydispersity of 0.95 to 1.05 at the average diameter. Moreover, in the same equilibrium system, it becomes a substantially spherical shape, and the effect that the pressing force of the foam is uniform is also expected.

  Then, by completing the pressure-regulating injection step S31 and the normal pressure step S32 described above, the gas-dissolved raw material M is injected almost completely with the fine and homogeneous cells 20 in the cavity 30a. The resinizing step S33 is performed before the cell 20 in the injected gas-dissolved raw material M becomes larger or deformed due to the passage of time, that is, under the regulated pressure injection step S31 and the normal pressure step S32. At the same time when the process is completed, the liquid raw material is completely reacted and cured to form a resin. In the present invention, by using polyols, isocyanates, cross-linking agents, etc. that exhibit normal reactivity, the resinification reaction is completely completed 15 seconds after the reaction injection, and the mold can be removed from the mold 30. . In addition, the increase in the viscosity due to the resinification reaction is started immediately after the collision mixing, and the resinization is actually started from the pressure-regulating injection step S31. In addition, when a highly reactive substance is selectively used as the polyol and isocyanate, which are the main raw materials of polyurethane foam, the resinification reaction is completely completed after about 5 seconds from the collision of both raw materials into the gas-dissolved raw material M. Complete.

  Further, in the normal pressure stage S32, not only the resinization reaction of the gas-dissolved raw material M proceeds, but also the foaming gas is vaporized from the gas-dissolved raw material M as the cell diameter increases. Since the viscosity is not lowered due to the dissolution of the foaming gas, the progress of the resinification reaction is accelerated as the cell diameter increases. That is, the cell diameter can be controlled by controlling the reactivity of the liquid raw material comprising polyol and isocyanate. It is empirically known that the time required for the reaction of the liquid raw material used in the normal reaction injection molding method is about 30 seconds, and in this case, the cell diameter exceeds 100 μm. By completing this reaction earlier, it is possible to produce a polyurethane foam in which cells having a cell diameter of 20 to 100 μm are uniformly dispersed. On the other hand, in the pressure-regulating injection step S31, since the foaming gas is dissolved in the gas-dissolved raw material M and the viscosity is lowered, the increase in the viscosity due to the progress of the resinification started after the collision mixing is offset and has an adverse effect. Will not come out.

  Through such a process, a polyurethane foam having the cavity 30a as an outer contour shape is formed. In general, a high-density layer of several μm called a skin layer is formed on the surface of the polyurethane foam obtained by reaction injection molding. This skin layer is very thin, so-called film-like and easy to remove. Therefore, it is easy to produce a polyurethane foam having cells 20 opened on the surface. In addition, since the present invention also has a feature that the reaction injection molding method is manifested, it is easy to produce, for example, a complex-shaped foam molded article at one time.

  The polyurethane foam according to the present invention can make use of characteristics such as thickness, hardness due to high density or high load resistance, such as vibration damping materials, seal materials, cushion materials, heat insulating materials, polishing pads or cushion pads. Can be suitably employed.

(Experimental example)
Next, experimental examples of the polyurethane foam and the production method according to the present invention will be shown. Using the following raw materials and equipment, prepare gas dissolved raw materials by dissolving the foaming gas in accordance with Table 1 (foaming gas type, dissolved amount and tank internal pressure (MPa)). Polyurethane foams according to Examples 1 to 9 and Comparative Examples 1 and 2 by being injected into a mold having a width of 1,000 mm × depth of 1500 mm × thickness of 2 to 6 mm according to the described conditions (overpack rate and counter pressure) Manufactured. For the polyurethane foams according to Examples and Comparative Examples, rise time (seconds), density (kg / m ³ ), average cell diameter (μm), and cell diameter variation (difference between maximum value and minimum value (polydispersity) Degree)).

(Raw material)
Polyol A: polyether polyol (trade name SC-229; manufactured by Sanyo Chemical)
・ Polyol B: Polyether polyol (trade name: M390; manufactured by Sumika Bayer Urethane)
・ Isocyanate A: MDI-modified polyisocyanate (trade name: Coronate 1057; made by Nippon Polyurethane)
・ Isocyanate B: MDI-modified polyisocyanate (trade name: M393; manufactured by Sumika Bayer Urethane)
・ Catalyst: Dibutinetine dilaurate, triethylamine ・ Crosslinking agent A: Glycol (trade name: Ethylene glycol; manufactured by Nisso Oil)
・ Crosslinking agent B: Urea (trade name diethyl toluenediamine; manufactured by Sumika Bayer Urethane)
(Used equipment)
・ Reaction injection (RIM) molding machine: Product name MC-240; Made by Polyurethane Engineering

(Conditions related to measurement, etc.)
-Dissolved amount of gas for foaming (gas loading amount (volume part)): flow meter (trade name ME-200; manufactured by Polyurethane Engineering)
Is attached to the gas-dissolved raw material flow path in the RIM molding machine and measured. This numerical value is for 100 parts by volume of polyol, not for all liquid raw materials.
-Overpack rate: Expresses the volume of the gas-dissolved raw material to be filled as a ratio when the volume of the mold is 1.
Counter pressure (MPa): A discharge pressure of counter air supplied into a mold into which a gas-dissolved raw material is injected.
-Rise time (seconds): A small amount of gas-dissolved raw material is discharged from the discharge nozzle of the RIM molding machine, and the foaming / curing process of polyurethane foam under normal temperature and atmospheric pressure is visually observed (after discharging, the foaming reaction is complete) And a certain period of time due to the curing reaction until the shape change stops).
Density (kg / m ³ ) and average cell diameter (μm): Measured according to JIS K 6400.
-Cell diameter variation: N = 30, calculated from the maximum value and the minimum value.

(results of the experiment)
The experimental results are also shown in Table 1 above. From Table 1, it was confirmed that by following the production method of the present invention, a polyurethane foam having a very thin thickness of 2 mm and a high density was produced in a short time. It was also confirmed that the average cell diameter was small and the variation was small (more uniform) than Comparative Examples 1 and 2 according to the prior art. In Examples 1 and 2, since a counter pressure was not applied in the mold, a high density closer to solid was achieved. In Example 3, since the amount of dissolved gas is increased by using carbon dioxide as the foaming gas, a polyurethane foam having a lower density is obtained. In Examples 4 and 5, carbon dioxide gas was dissolved in the liquid raw material in a supercritical state, the raw material system was made more reactive, and the gas was dissolved while facilitating the injection into the mold. By supplying counter air under pressure in order to efficiently prevent escape of the foaming gas dissolved in the raw material, a low density and a small average cell diameter are achieved. In Examples 6 to 9, the cavity height corresponding to the thickness in the mold was changed to 3 to 6 mm under the same conditions as in Example 1. Similar polyurethane foams could be produced.

It is process drawing which shows the manufacturing process of the polyurethane foam which concerns on the suitable Example of this invention. It is a state figure which shows the mode in pressure adjustment injection | pouring step S31. It is a state figure which shows the mode in normal pressure step S32.

Explanation of symbols

30 Mold M Gas dissolved material

Claims (6)

In a plate-like polyurethane foam obtained from a main raw material consisting of polyol and isocyanate and various auxiliary raw materials,
The main raw material and various auxiliary raw materials are mixed, and the gas-dissolved raw material (M), in which the foaming gas is dissolved under pressure, is injected into the mold (30) under the required pressure, and the injection is completed. A polyurethane foam produced immediately after returning to normal pressure and having a thickness set to 10 mm or less. The polyurethane foam according to claim 1, wherein the density is 900 kg / m ³ or less by adjusting the dissolved amount of the foaming gas. ^3. The polyurethane according to claim 1, wherein a density of the foaming gas is set in a range of 600 to 700 kg / m ³ by setting the dissolved amount of the foaming gas to 70 parts by volume or more with respect to 100 parts by volume of the polyol. Form. In a method for producing a plate-like polyurethane foam obtained from a main raw material consisting of polyol and isocyanate and various auxiliary raw materials,
The main raw material and various auxiliary raw materials are mixed, and a gas-dissolved raw material (M) in which a foaming gas is dissolved under pressure is injected into a mold (30) under a required pressure regulation.
By returning the required amount of the gas-dissolved raw material (M) to normal pressure immediately after the injection into the mold (30),
A method for producing a polyurethane foam, comprising producing a polyurethane foam having a thickness set to 10 mm or less.   Pressure adjustment to the gas-dissolved raw material (M) and recovery to normal pressure are performed in accordance with the injection of the gas-dissolved raw material (M) into the mold (30). The method for producing a polyurethane foam according to claim 4, wherein the polyurethane foam is supplied. The amount of the gas-dissolved raw material (M) injected into the molding die (30) is such that the inner volume of the molding die (30) is substantially equal to the volume of the gas-dissolved raw material (M) at normal pressure. The method for producing a polyurethane foam according to claim 4 or 5, wherein the polyurethane foam is produced.

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