JP5712077B2 - Mold for molding and urethane foam molding method - Google Patents

Description

  The present invention relates to a molding die for molding a urethane foam, and a urethane foam molding method for molding a urethane foam using the molding die.

  Urethane foam is formed by foaming the raw material by foaming reaction and curing the foamed raw material by resination reaction. The urethane foam is molded inside the mold, that is, molded urethane foam. At the time of molding, usually, in order to stabilize the foaming reaction, there are a step of heating the mold before pouring the raw material and a step for promoting resinification in the heated mold. Has been done. Specifically, for example, as described in Patent Document 1 below, a heater for heating the inner surface of the cavity is provided in the mold, and the mold before raw material injection is heated by the heater. In addition, after the raw material is injected, a process for promoting resinification is performed by heating the cavity inner surface to a temperature higher than the heated temperature.

JP-A-2-174893

  In the mold described in Patent Document 1, the specific part of the cavity inner surface before the raw material injection is heated so that the temperature is lower than the part other than the specific part. By lowering the foaming reactivity, it is possible to lower the foamability of the specific part and increase the hardness. After the raw material is injected into the cavity, the specific part and the part other than the specific part are heated to the resinization promotion temperature (125 ° C.) which is a temperature suitable for promoting resinization. The resin is formed at that temperature by a so-called hot cure method. As described above, in the mold described in Patent Document 1, by dividing the cavity inner surface before raw material injection into a low temperature region to some extent and a high temperature region to some extent, the degree of foaming reaction is made different between these two regions. It is possible to mold urethane foams having different hardnesses. However, after the foaming reaction is performed in these two regions, the two regions are heated to the resinization promotion temperature, so it takes time for the two regions to rise to a resinization promotion temperature of 100 ° C. or higher. Takes a long time.

  Moreover, although there is a cold cure method as a general method, a highly active polyol, specifically, an EO-added polyether polyol in which ethylene oxide (EO) is addition-polymerized to a terminal hydroxyl group is used at 40 to 70 ° C. Formed in a mold heated to a constant temperature. The EO-added polyether polyol contains a large amount of primary hydroxyl groups and is very reactive. For this reason, it is possible to cure the urethane foam while maintaining the temperature of the mold heated before the raw material injection. Therefore, according to the cold cure method, it is possible to eliminate or reduce the disadvantages of the hot cure method described above. However, since the temperature of the mold is lower in the cold cure method than in the hot cure method, the reaction heat is lost to the mold at the burr generated at the interface between the upper mold and the lower mold. The reactivity is lowered, the curing property is deteriorated, and it is necessary to take a longer demolding time.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the metal mold | die for molding which can aim at shortening of shaping | molding time, and a urethane foam shaping | molding method.

In order to solve the above-mentioned problems, a molding die according to the present invention is formed to mold a urethane foam by injecting a urethane foam raw material containing a polyol, a polyisocyanate, a foaming agent, a foam stabilizer, and a catalyst into the cavity. In the mold for molding, the molding mold includes a lower mold in which a recess is formed, and an upper mold that forms the cavity by clamping the lower mold so as to cover the recess. A lower mold bottom heater that heats the bottom surface of the recess, a lower mold upper heater that heats a portion of the lower mold that contacts the upper mold, and an inner surface that faces the cavity of the upper mold. A mold heater, and before the urethane foam raw material is injected into the cavity, the bottom surface of the recess is heated by the lower mold bottom heater to a predetermined temperature in the range of 40 to 70 ° C. Lower mold Each of the portion in contact with the upper mold and the inner surface of the upper mold facing the cavity is at a temperature higher by 5 ° C. or more than the predetermined temperature by each of the lower mold upper heater and the upper mold heater, and It is comprised so that it may heat to the resinification promotion temperature which is the range of 65-85 degreeC.

  Moreover, in order to solve the said subject, the urethane foam shaping | molding method of this invention is mixed by the mixing process of mixing the urethane foam raw material containing a polyol, polyisocyanate, a foaming agent, a foam stabilizer, and a catalyst, and the mixing process. An injection step of injecting the urethane foam raw material into a cavity of the molding die, and in the method of molding the urethane foam in the cavity, the molding die includes a lower mold in which a recess is formed, The upper die that forms the cavity and the cavity, the lower die bottom heater that heats the bottom surface of the recess, and the upper of the lower die are clamped to the lower die so as to cover the recess. A lower mold upper heater that heats a portion in contact with the mold, and an upper mold heater that heats an inner surface facing the cavity of the upper mold, and the urethane foam molding method includes: Furthermore, before the urethane foam raw material is injected, the bottom surface of the recess is heated to a predetermined temperature in a range of 40 to 70 ° C. by the lower mold bottom heater, and the upper mold of the lower mold is heated. Each of a portion in contact with the upper die and an inner surface facing the cavity of the upper die at a temperature higher than the predetermined temperature by 5 ° C. or more and 65 to 85 by the lower die upper heater and the upper die heater, respectively. A pre-injection heating step for heating to a resinization promotion temperature in the range of ° C., a portion in contact with the upper mold of the lower mold heated to the resinization promotion temperature, and the cavity of the upper mold And a resinization promoting step for promoting resinification of the urethane foam raw material injected in the injection step.

  In the molding die and the urethane foam molding method of the present invention, the bottom surface of the concave portion of the lower mold before raw material injection is heated to a predetermined temperature. Thereby, the foaming reaction of the injected raw material can be stably performed on the bottom surface of the lower mold recess. The lower mold upper part in contact with the upper mold of the lower mold before the raw material injection and the inner surface facing the cavity of the upper mold before the raw material injection are heated to a temperature suitable for promoting resinification. As a result, the material foamed in the cavity expands toward the upper part of the cavity and promotes the resinification reaction by contacting the upper part of the lower mold and the inner surface of the upper mold heated to a temperature suitable for resinization. Is possible. That is, according to the molding die and the urethane foam molding method of the present invention, it is possible to perform the resinification reaction with good response continuously to the foaming reaction, and to shorten the molding time. Is possible.

It is a table | surface which shows the physical property evaluation of the compounding quantity of the urethane foam raw material for shape | molding a urethane foam molded object, and the urethane foam molded object of each compounding quantity. It is a table | surface which shows the physical property evaluation of the compounding quantity of the urethane foam raw material for shape | molding a urethane foam molded object, and the urethane foam molded object of each compounding quantity. It is a schematic sectional drawing of the metal mold | die used when shape | molding the urethane foam molded object of an Example and a comparative example. It is a table | surface which shows the physical condition evaluation of the temperature conditions of each site | part of the shaping | molding die at the time of shape | molding the urethane foam molded object of an Example, and the urethane foam molded object of an Example. It is a table | surface which shows the temperature conditions of each site | part of the metal mold | die at the time of shape | molding the urethane foam molded object of a modification, and the physical property evaluation of the urethane foam molded object of a modification. It is a table | surface which shows the temperature of each site | part of the molding die at the time of shape | molding the urethane foam molded object of Example 10 inside a molding die for every elapsed time. It is a table | surface which shows the temperature of each site | part of the shaping die at the time of shape | molding the urethane foam molded object of Example 11 inside a shaping die for every elapsed time. It is a table | surface which shows the temperature of each site | part of the molding die at the time of shape | molding the urethane foam molded object of Example 12 inside a molding die for every elapsed time.

  The “molding mold” described in the present invention can individually heat the bottom surface of the lower mold, the inner surface of the upper mold facing the cavity, and the upper part of the lower mold continuous to the inner surface of the upper mold. It is said that. Before the urethane foam raw material is injected into the cavity, the bottom surface of the lower mold is heated to a temperature in the range of 40 to 70 ° C., the inner surface of the upper mold facing the cavity, and the upper mold The upper part of the lower mold continuous to the inner surface of the steel plate is at a temperature that is 5 ° C. or more higher than that temperature, and is heated to a temperature in the range of 65 to 85 ° C. At this time, the inner surface of the upper mold and the upper part of the lower mold may be heated to the same temperature or may be heated to different temperatures. Specifically, the upper part of the lower mold may be heated to a temperature higher by 5 ° C. than the temperature of the bottom surface of the lower mold, and the inner surface of the upper mold may be heated at a temperature higher than that temperature. By doing in this way, as the raw material expands and expands, the foamed raw material comes into contact with the hot cavity surface, and the balance between the foaming reaction and the resinification reaction can be suitably adjusted.

  The lower die or the upper die constituting the molding die may be a single member or a combination of a plurality of members. Specifically, when a core, an insert or the like is used at the time of molding, the one including the core, the insert or the like corresponds to the upper mold.

  In addition, the bottom surface of the lower mold is heated from the predetermined temperature to the resinization promoting temperature after a predetermined time has elapsed since the raw material was injected. Thus, by further heating the bottom surface of the lower mold after the raw material is injected, the resinification reaction can be further promoted, and the molding time can be further shortened. Incidentally, switching from the predetermined temperature to the resinification promotion temperature may be performed by a control device that controls the operation of a switching device that switches the temperature, or may be performed manually.

  The “predetermined time” for heating the bottom surface of the lower mold after the raw material injection can be arbitrarily set, but the bottom surface of the lower mold is heated after a stable foaming reaction is performed. Therefore, it is preferable that the time is assumed that the injected urethane foam raw material is foamed by the foaming reaction and is in contact with the inner surface of the upper mold. This estimated time may be an empirically found time or an actually measured time. For example, the raw material may be foamed in an open state as the temperature of the bottom surface of the lower mold, and the foam volume may be measured every fixed time, so that the foam volume reaches the cavity volume. Alternatively, the raw material may be foamed in the open state as the temperature of the bottom surface of the lower mold, and the rise time at which volume expansion substantially ends may be used.

In addition, urethane foam raw materials containing polyol, polyisocyanate, foaming agent, foam stabilizer, and catalyst are mixed in the urethane foam molded body, and the raw material is foamed by foaming reaction inside the molding die. There is a molded urethane foam formed by curing a foamed raw material by a resinification reaction. As the foaming agent of the molded urethane foam material molded by the “molding die” of the present invention, water is preferably employed, and the amount of water as the foaming agent is the polyol in the urethane foam material. When the total amount is 100 parts by weight, it is preferably 4.6 to 7 parts by weight. This blending amount is larger than the blending amount of water in a normal urethane foam raw material. For this reason, the foaming reactivity becomes high, and it is possible to reduce the density of the urethane foam molded body. Incidentally, the density of the urethane foam molded body, specifically, the apparent core density is preferably 16 to 35 kg / m ³ . Furthermore, the lower limit is preferably 18 kg / m ³ or more, and particularly preferably 20 kg / m ³ . Further, the upper limit is preferably 29 kg / m ³ or less, and particularly preferably 28 kg / m ³ or less.

  Furthermore, it is preferable to accelerate the resinification reaction in order to balance the foaming reaction with increased reactivity. Specifically, as the “polyol”, it is preferable to employ a PO-added polyether polyol (hereinafter abbreviated as “PO-added polyol”) obtained by addition-polymerizing propylene oxide to a polyhydric alcohol. By making the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of this PO-added polyol to the number of all terminal hydroxyl groups of the polyol 35% or more, a resin reaction with a relatively large number of primary hydroxyl groups Can be promoted.

  Conventionally, in order to promote the resinification reaction, an EO addition polyol in which ethylene oxide (EO) is addition-polymerized to the terminal hydroxyl group is often used. However, the primary hydroxyl group of the EO addition polyol is water and There was a problem that the foaming reaction proceeded rapidly because of the very high affinity. On the other hand, since the primary hydroxyl group of the PO-added polyol has a lower affinity with water than the primary hydroxyl group of the EO-added polyol, it is possible to suppress the foaming reaction. In other words, when the blending amount of water as a blowing agent is increased, the use of PO-added polyol makes it possible to perform foaming reaction and resin conversion without using a highly hydrolyzable catalyst such as an organotin catalyst. While maintaining a balance with the reaction, it is possible to mold a low-density urethane foam. In addition, since there is no need to use an organotin compound as a catalyst, there is no need to separately mix an organotin compound and water, and a catalyst, a foaming agent (water), and a foam stabilizer are mixed (premixed) in a polyol. It is possible to keep. This makes it possible to use a high-pressure injector instead of a low-pressure injector that tends to cause dripping of raw materials during injection.

  Incidentally, the ratio of the number of primary hydroxyl groups of the PO-added polyol to the number of all terminal hydroxyl groups of the polyol is preferably 35% or more, and more preferably 40% or more. In order to increase the ratio of the number of primary hydroxyl groups of the PO-added polyol to the number of terminal hydroxyl groups of the polyol, it is preferable to employ a PO-added polyol having a high primary hydroxyl group ratio. Specifically, the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl group to the number of terminal hydroxyl groups in the PO-added polyol is preferably greater than 50%. Furthermore, it is preferably 60% or more, and particularly preferably 65% or more. The number average molecular weight of the PO-added polyol is preferably 2500 to 7000, and more preferably 3000 to 5000.

  Further, the “polyol” of the present invention may be composed of only the above PO-added polyol, or may be composed of the above-mentioned PO-added polyol and one or more other polyols. . However, in the “polyol” of the present invention, in order to promote the resinification reaction, the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups to the number of terminal hydroxyl groups of all polyols in the urethane foam raw material is 65. % Or more is preferable. Furthermore, it is preferably 68% or more. As the polyol other than the PO-added polyol, any polyol that is usually employed as a urethane foam raw material may be used. However, in view of the high reactivity, it can be obtained by addition polymerization of ethylene oxide to a polyhydric alcohol. It is preferable that it is an EO addition polyol.

  The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl group to the number of terminal hydroxyl groups in the EO-added polyol is preferably greater than 60% in order to promote the resinification reaction. The above is preferable. However, since the primary hydroxyl group of the EO-added polyol has a very high affinity with water as described above, the first hydroxyl group contained in the terminal hydroxyl group of the EO-added polyol is considered in consideration of the balance with the foaming reaction. The ratio of the number of primary hydroxyl groups to the number of primary hydroxyl groups contained in the terminal hydroxyl group of the PO-added polyol is preferably 100% or less. Furthermore, it is desirable that it be 90% or less, particularly 80% or less.

  In addition, the “polyisocyanate” of the present invention is not limited as long as it is normally used as a raw material for urethane foam, but a highly reactive polyisocyanate is used because a highly reactive polyol is used. The need to do is low. For this reason, it is preferable to adopt the one in which the weight ratio of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is 80:20 in consideration of flowability and price. In addition, it is preferable that an isocyanate index is 85-105 in consideration of foamability etc. Furthermore, it is preferably 90-100.

  As described above, since the highly reactive polyol is employed in the raw material of the molded urethane foam molded by the “molding mold” of the present invention, the mold is heated to promote resinification. It is possible to lower the temperature during the process to some extent. In other words, in the “molding mold” of the present invention, the inner surface of the upper mold facing the cavity and the upper part of the lower mold continuous to the inner surface of the upper mold are heated to a temperature somewhat higher than the bottom surface of the lower mold. Therefore, it is possible to mold a urethane foam excellent in low density. Therefore, in the “molding mold” of the present invention, the bottom surface of the lower mold is heated to 40 to 70 ° C., and the inner surface of the upper mold and the upper part of the lower mold continuous to the inner surface of the upper mold are 65. Heating to ~ 85 ° C is preferred. Furthermore, it is preferable that the bottom surface of the lower mold is heated to 45 to 65 ° C., and the inner surface of the upper mold and the upper portion of the lower mold are heated to 70 to 80 ° C.

  As described above, the “molding mold” of the present invention can mold urethane foam in a relatively low temperature range as compared with the hot cure method, and can efficiently suppress energy. It is possible. In addition, when continuously molding urethane foam, it is necessary to cool the heated mold. In the “molding mold” of the present invention, the difference between the maximum temperature and the minimum temperature of the mold is required. It becomes possible to reduce the waste of energy due to heating and cooling. Furthermore, the time required for heating and cooling can be shortened, and the productivity of urethane foam can be improved. In addition, when the urethane foam raw material is injected into the cavity, the burrs formed at the interface between the upper mold and the lower mold are set at 5 ° C. higher than the bottom surface of the lower mold at the upper portion of the lower mold in contact with the upper mold. The cure time can be accelerated and the demolding time can be shortened. Also, by setting the mold temperature at the time of molding to a relatively low temperature (85 ° C or lower), it becomes possible to provide a resin seal between the upper mold and the lower mold, and control the generation of burrs. It becomes. As a result, it is possible to facilitate the burr removal process. Furthermore, by applying the resin seal, it is easy to adjust and remove the gas generated in the mold, and it is possible to suitably adjust the foaming pressure in the mold. Thereby, generation | occurrence | production of a crack etc. can be suppressed. In addition, it becomes easy to use a release agent having a non-volatile component having a melting point higher than the mold temperature, and when such a release agent is used, it is difficult for the molten release agent to adhere to the urethane foam surface. be able to. Furthermore, the surface skin layer becomes porous, and air permeability is high and a highly flexible urethane foam can be obtained.

  The following examples illustrate the present invention more specifically. However, the present invention is not limited to this embodiment, and can be implemented in various modes with various modifications and improvements based on the knowledge of those skilled in the art.

Urethane foam moldings according to various prescriptions were molded from a urethane foam raw material having the composition shown in FIGS. 1 and 2 by a molding method. Details of the urethane foam raw materials in FIGS. 1 and 2 are shown below.
Polyol 1A: Polypropylene glycol (PO-added PPG) obtained by addition polymerization of propylene oxide to polyhydric alcohol, primary hydroxyl group ratio (the first hydroxyl group contained in the terminal hydroxyl group relative to the number of terminal hydroxyl groups of PO-added PPG) Ratio of the number of secondary hydroxyl groups) = 68%, number average molecular weight 3000
Polyol 1B: PO-added PPG, primary hydroxyl group ratio = 60%, number average molecular weight 3000
Polyol 1C: PO-added PPG, primary hydroxyl group ratio = 75%, number average molecular weight 3000
Polyol 1D: PO-added PPG, primary hydroxyl group ratio = 50%, number average molecular weight 3000
Polyol 2A: polyether polyol obtained by addition polymerization of ethylene oxide to polyhydric alcohol (EO addition polyol), primary hydroxyl group ratio (the number of terminal hydroxyl groups contained in the terminal hydroxyl group relative to the number of terminal hydroxyl groups of the EO addition polyol) Number ratio of primary hydroxyl groups) = 70%, number average molecular weight 5000
Polyol 2B: EO addition polyol, primary hydroxyl group ratio = 65%, number average molecular weight 5000
Polyol 2C: EO addition polyol, primary hydroxyl group ratio = 75%, number average molecular weight 5000
Polyol 2D: EO addition polyol, primary hydroxyl group ratio = 60%, number average molecular weight 5000
Polyol 2E: EO addition polyol, primary hydroxyl group ratio = 80%, number average molecular weight 5000
・ Blowing agent; water, catalyst; mixture of triethylenediamine and dipropylene glycol in a mass ratio of 1: 2 (trade name “DABCO33LV” manufactured by Sankyo Air Products Japan)
・ Foam stabilizer: Dimethylsiloxane foam stabilizer (trade name “SZ-1142”, manufactured by Nihon Unicar)
Polyisocyanate; 2,4-TDI: 2,6-TDI = 80: 20

  Incidentally, the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the PO-added PPG to the number of all terminal hydroxyl groups of the polyol is shown in the “PO primary hydroxyl group ratio” column of FIG. 1 and FIG. The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the EO-added polyol to the number of all terminal hydroxyl groups of the polyol is shown in the column “EO primary hydroxyl group ratio” in FIGS. 1 and 2. Further, the combined ratio of the PO primary hydroxyl group and the EO primary hydroxyl group, that is, the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl group to the number of all terminal hydroxyl groups of the polyol, It is shown in the column of “total primary hydroxyl group ratio” in FIG. 1 and FIG. Furthermore, the ratio of the EO primary hydroxyl group ratio to the PO primary hydroxyl group ratio, that is, the number of primary hydroxyl groups contained in the terminal hydroxyl group of the EO-added polyol, the primary hydroxyl group contained in the terminal hydroxyl group of the PO-added PPG. The ratio to the number is shown in the column “EO1 class / PO1 class” in FIGS.

  FIG. 3 shows a molding die 10 for molding the urethane foam molded body of each of the above formulations. The molding die 10 includes a lower mold 14 in which a recess 12 is formed, and an upper mold 16 that is clamped to the lower mold 14 so as to cover the recess 12. The lower mold 14, the upper mold 16, Thus, the cavity 18 is formed. By injecting the mixed urethane foam raw material into the cavity 18, the raw material is foamed by the foaming reaction in the cavity 18, and the foamed raw material is cured by the resinification reaction to form the urethane foam. Is done.

  The molding die 10 is further provided with a heater for heating the inner surface of the cavity 18. Specifically, a first lower mold pipe 20 is embedded inside the bottom surface of the recess 12 of the lower mold 14, and the first lower mold pipe 20 extends to the outside of the lower mold 14. A hot water circulator 22 for circulating hot water having a relatively high temperature and a cold water circulator 24 for circulating hot water having a temperature lower than that circulated by the hot water circulator 22 are provided outside the mold. The first lower mold pipe 20 extending to the outside of the lower mold 14 is connected to the high temperature water pipe 26 of the high temperature water circulator 22 and the low temperature water pipe 28 of the low temperature water circulator 24 via the switching valve 30. It is connected. Thereby, the recessed part bottom face of the lower mold | type 14 is selectively heated by either high temperature water or low temperature water. Incidentally, what is constituted by the first lower mold pipe 20, the high temperature water circulator 22, the high temperature water pipe 26, the low temperature water circulator 24, the low temperature water pipe 28, and the switching valve 30 is an example of the lower mold bottom heater.

  A second lower mold pipe 32 is embedded in a portion of the lower mold 14 that is in contact with the upper mold 16, that is, inside the inner surface of the lower mold 14 that is continuous with the upper mold 16. Is extended to the outside of the lower mold 14 and connected to the high temperature water pipe 26 of the high temperature water circulator 22. Further, an upper mold pipe 34 is embedded inside the inner surface of the upper mold 16 facing the cavity 18, and the upper mold pipe 34 extends to the outside of the upper mold 16 and the high temperature water circulator 22 has a high temperature. It is connected to the water pipe 26. As a result, the inner surface of the lower die 14 that is continuous with the upper die 16, the inner surface of the upper die 16, that is, a part of the inner surface of the cavity 18 that defines the parting line of the urethane foam molded body, and the upper die 16 are defined. The inner surface of the cavity 18 is heated by hot water. By the way, the one constituted by the second lower mold pipe 32, the high temperature water circulator 22 and the high temperature water pipe 26 is an example of the lower mold upper heater, and is constituted by the upper mold pipe 34, the high temperature water circulator 22 and the high temperature water pipe 26. What is configured is an example of an upper heater.

  Using the molding die 10 having the above structure, a urethane foam molded body having the above-mentioned prescriptions is molded. Specifically, first, before the raw material is injected into the mold, the switching valve 30 is adjusted so that the low-temperature water flows through the first lower mold pipe 20 in order to heat the mold, and the second lower mold High-temperature water is allowed to flow through the mold pipe 32 and the upper mold pipe 34. The temperature of the high temperature water at this time is 80 ° C., and the temperature of the low temperature water is 50 ° C. Then, a solvent-based mold release agent having a melting point higher than the maximum mold temperature (85 ° C.) is applied to the inside of the molding die 10. As non-volatile components, paraffin hydrocarbons, ester waxes, polyhydric alcohol esters, silicones, fluorine-containing mold release agents, etc. can be used, but there is little adhesion to urethane foam moldings, and cells of urethane foam moldings Paraffinic hydrocarbons are preferred because they are less susceptible to roughening. Incidentally, this process is an example of a pre-injection heating process.

  Next, the polyol, foaming agent, catalyst, and foam stabilizer in the blending amounts shown in FIG. 1 or FIG. 2 are mixed (premixed) in a stirring vessel. Then, immediately before pouring into the mold, the mixed raw material and an amount of polyisocyanate corresponding to the isocyanate index shown in FIG. 1 or 2 are mixed. This process is an example of the mixing process. All the mixed raw materials are injected into the cavity 18 heated by a high-pressure injector. This process is an example of an implantation process.

  The raw material injected into the cavity 18 is foamed by the foaming reaction at the bottom surface of the recess of the lower mold 14 and expands in the cavity 18. The switching valve 30 is adjusted so that the high-temperature water flows through the first lower mold pipe 20 in anticipation of the expanded raw material coming into contact with the inner surface of the upper mold 16. Specifically, the switching valve 30 is adjusted after two minutes have elapsed since the urethane foam raw material was injected into the mold. This step is an example of a post-injection heating step. Further, the second lower mold pipe 32 and the upper mold pipe 34 in which high-temperature water has been flowed in advance accelerates the resinification reaction in the parting line portion of the urethane foam molded body and the portion above it. Further, the resin lowering reaction is promoted in the lower part of the urethane foam molded body by the first lower mold pipe 20 in which high-temperature water is poured in the heating process after injection. This process is an example of a resinification promotion process. And after leaving for 6 minutes in a resinification promotion process, a urethane foam molded object is demolded from a metal mold | die. The physical properties of the demolded urethane foam molded body were evaluated by the following methods.

In order to evaluate the degree of foaming of the urethane foam molded article, the apparent core density (kg / m ³ ) of the urethane foam molded article was measured in accordance with a method based on JIS K 7222: 2005. The apparent core density (kg / m ³ ) indicates that the smaller the value, the more suitable foaming is caused by the activated foaming reaction, and the urethane foam molded body is excellent in reducing the density. It is shown that. The values are shown in the “density” column of FIGS. 1 and 2.

    Moreover, in order to evaluate the restoration rate of a urethane foam molded object, the compression residual strain (%) was measured based on the method based on JISK6400-4: 2004A method. Specifically, the foamed part of the urethane foam molded body is cut out by 50 × 50 × 30 mm, and this is used as a test piece. The test piece is compressed to a thickness of 50%, sandwiched between parallel flat plates, and left at 70 ° C. for 22 hours. The test piece is taken out after being left for 22 hours, and its thickness is measured after another 30 minutes. Then, the ratio of the difference between the thickness value before the test and the measured value to the thickness value before the test is calculated, and the calculated value is set as the compression residual strain. Moreover, it changed into the predetermined conditions in JISK6400-4: 2004, and measured wet heat compression residual distortion (%). The test piece is compressed to a thickness of 50%, sandwiched between parallel plane plates, and left under conditions of 50 ° C. and 95% RH for 22 hours. After leaving for 22 hours, the test piece is taken out, and after 30 minutes, the thickness is measured, and the strain rate is calculated in the same manner as the compression residual strain. This calculated value is defined as wet heat compression residual strain. Each compression residual strain indicates that the smaller the value is, the higher the restoration rate of the urethane foam molded body is, and the less the polyurethane foam molded body is sag. In addition, each value is shown in the column of "compression residual strain" and "wet heat compression residual strain" of FIG. 1 and FIG.

  Moreover, the impact resilience (%) was measured based on the method based on JIS K 6400-3: 2011. Specifically, a steel ball having a diameter of 16 mm and a mass of 16 g is dropped from a height of 500 mm onto the upper surface of the urethane foam molded body, and the highest height bounced is measured. And the ratio of the measured value with respect to the height (500 mm) before dropping is calculated, and the calculated value is defined as rebound resilience. The rebound resilience indicates that the larger the value, the higher the resilience. The values are shown in the column of “Rebound resilience” in FIGS. 1 and 2.

  Furthermore, the molding result of the urethane foam molded body was visually evaluated. Specifically, the urethane foam molded body was divided, and the foamed portion of the urethane foam molded body on the divided surface was visually observed to confirm the presence or absence of cavities, cracks, and the like. In addition, it was confirmed whether or not the skin layer of the urethane foam molded body was stuck to the inside of the mold when the urethane foam molded body was removed from the mold. And when there was no cavity, a crack, etc. and the skin layer did not stick inside the mold at the time of demolding, it was evaluated as “◯”. On the other hand, if there are cavities, cracks, etc., but the skin layer does not stick inside the mold during demolding, it is evaluated as “△”, and there are cavities, cracks, etc., and the skin layer during demolding When there was also sticking to the inside of the mold, it was evaluated as “×”. This evaluation is shown in the “molding result” column of FIGS. 1 and 2.

From the above evaluation results, the urethane foam molded article excellent in reducing the density of 21 to 32 kg / m ³ by blending 4.6 to 7 parts by weight of water as a foaming agent with respect to 100 parts by weight of the polyol. It can be seen that it is possible to mold. However, the above prescription No. 7 and formulation no. As can be seen from FIG. 10, when the blending amount of water is 4.6 parts by weight, the density is within an allowable range but is relatively high. In addition, prescription No. In the case of 8, when the blending amount of water is 7 parts by weight, the density is relatively low and good, but it tends to crack during molding and the compression residual strain becomes large. For this reason, it is more preferable that the compounding quantity of water is 5-6.5 weight part with respect to 100 weight part of polyols.

  Moreover, since the foaming reaction tends to proceed faster as the amount of water increases, it is preferable to employ PO-added PPG as a polyol in order to suppress the foaming reaction to some extent and promote the resinification reaction. However, if the PO primary hydroxyl group ratio of this PO-added PPG is too low, the formulation No. 11-No. Since a problem arises in the molding result as shown in FIG. 13, the PO primary hydroxyl group ratio is preferably 35% or more, and more preferably 40% or more.

  Furthermore, in the urethane foam molded body of each of the above prescriptions, there is one in which an EO addition polyol is blended as a polyol in order to promote resinification, but the number of primary hydroxyl groups contained in the terminal hydroxyl group of the EO addition polyol. When the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of PO-added PPG (EO1 grade / PO1 grade) is increased, the resinification reaction proceeds excessively and a good urethane foam cannot be molded. As can be seen from FIG. 11-No. It is also clear from the fact that 13 EO1 class / PO1 class exceeds 100%. For this reason, it is preferable that EO1 class / PO1 class is 100% or less, more specifically 90% or less, and particularly preferably 80% or less.

  Furthermore, prescription No. In No. 9, only a PO-added polyol having a primary hydroxyl group ratio of 68% is used as the polyol in order to promote resinification. Since the primary hydroxyl group of the EO-added polyol is not included, the initial reaction is slow, the skin layer tends to be peeled off, and the demolding time tends to be required, so adjustment of the catalyst amount and the like is necessary. Therefore, the ratio of the number of primary hydroxyl groups contained in the polyol to the number of primary hydroxyl groups contained in the terminal hydroxyl group of the PO-added PPG (EO primary / PO primary) is preferably 10% or more, more preferably 20% or more. .

  Further, in order to optimize the mold temperature at the time of molding, the temperature of circulating water by each of the high-temperature water circulator 22 and the low-temperature water circulator 24, the switching timing between the high-temperature water and the low-temperature water by the switching valve 30, etc. The urethane foam molded bodies of Examples and Comparative Examples were molded by changing various conditions. Specifically, the above-mentioned prescription No. A urethane foam molded body having a blending amount of 1 was molded in accordance with the mold temperature conditions shown in FIGS. 4 and 5.

  The mold temperature shown in the figure is the temperature at the actual cavity surface of the molding die 10, and the cavity surface heated by the circulating water of the low-temperature water circulator 24, that is, the bottom surface of the lower mold is Although the temperature is the same as that of the circulating water, the cavity surface heated by the circulating water of the high-temperature water circulator 22, that is, the inner surface of the upper mold and the upper part of the lower mold is 5 ° C. lower than the temperature of the circulating water. It has become.

  Specifically, at the time of urethane foam molding of Example 1, as shown in FIG. 6, the upper parts of the upper mold and the lower mold are heated by circulating water at 80 ° C. More specifically, 80 ° C. circulating water is flowed by the high-temperature water circulator 22 before the urethane foam raw material is injected into the mold into the upper die pipe 34 and the second lower die pipe 32, and the 80 ° C. With the circulating water, the cavity surface continuous with the upper mold cavity surface and the lower mold upper mold is heated to 75 ° C. Incidentally, the elapsed time in the figure is the elapsed time after the urethane foam raw material is injected into the mold, and the upper cavity surface of the upper mold and the lower mold is 75 ° C. at the time of the raw material injection. I understand.

  The bottom surface of the lower mold is heated by circulating water at 50 ° C. before the raw material is injected, and is heated by circulating water at 80 ° C. after a predetermined time has elapsed. Specifically, before the raw material injection, circulating water at 50 ° C. is caused to flow through the first lower mold pipe 20 by the low-temperature water circulator 24, and the bottom surface of the lower mold becomes 50 ° C. by the circulating water at 50 ° C. It has been heated. Then, when two minutes have passed since the raw material was injected, the switching valve 30 is adjusted, and 80 ° C. circulating water is caused to flow through the first lower mold pipe 20 by the high-temperature water circulator 24. With the circulating water at 80 ° C., the bottom surface of the lower mold gradually rises from 50 ° C. after 2 minutes and reaches 75 ° C. after 4 minutes. Moreover, although the pipe is not embedded in the side part of the lower mold, the cavity surface of the lower mold side part is also heated by heat conduction from the first lower mold pipe 20 and the second lower mold pipe 32. The measured temperature is shown in the column of “lower mold side” in the figure.

  Incidentally, the predetermined time “2 minutes after the injection of the raw material” when the switching valve 30 is adjusted is a time corresponding to a so-called rise time (RT), a time when foaming is completed by the foaming reaction. That is, the switching timing of the high temperature water and the low temperature water by the switching valve 30 is the end of the rise time (RT), and the switching timing of the tenth embodiment in FIG. In the column, “RT end” is indicated.

  Moreover, the column of the molding status in FIG. 6 shows a remarkable reaction during the molding of the urethane foam, and shows the demolding timing at the end of molding. As can be seen from the figure, the foaming reaction actively progresses immediately after 2 minutes from immediately after the raw material injection, and the resinification reaction progresses actively after 2 minutes. Then, after 8 minutes, the urethane foam molded body is removed from the mold. That is, the molding time in the mold of the urethane foam molded body of Example 1 is 8 minutes, and the time is shown in the column of molding time of Example 1 in FIG.

  Next, the mold temperature of the urethane foam molded body of Example 2 will be described. The conditions regarding the mold temperature of the urethane foam molded body of Example 2 are the same as the conditions of Example 1 described above, except for the switching time between the high temperature water and the low temperature water by the switching valve 30 as shown in FIG. Therefore, only this switching time will be described. In the second embodiment, the switching valve 30 is adjusted after a time corresponding to 1/2 of the rise time from the injection of the raw material, that is, after 1 minute, and the high temperature water circulator 24 is connected to the first lower mold pipe 20. Circulates 80 ° C. circulating water. Accordingly, as shown in FIG. 7, the bottom water of the lower mold gradually rises from 50 ° C. after 1 minute by the 80 ° C. circulating water, and reaches 75 ° C. after 4 minutes. Note that “RT. T1 / 2” is shown in the column of the switching timing of the second embodiment in FIG. 4 as the switching timing by the switching valve 30 in the second embodiment.

  Next, the conditions relating to the mold temperature of the urethane foam molded body of Example 3 are the same as the conditions before the raw material injection of Examples 1 and 2 described above, as shown in FIG. Is not done. That is, in Example 3, as shown in FIG. 8, circulating water at 80 ° C. is passed through the upper mold pipe 34 and the second lower mold pipe 32, so that the upper mold cavity surface and the lower mold upper mold The continuous cavity surface is 75 ° C. On the other hand, circulating water at 50 ° C. is passed through the first lower mold pipe 20, and the bottom surface of the lower mold is 50 ° C. And since switching with the high temperature water and low temperature water by the switching valve 30 is not performed, the bottom face of the lower mold | type is maintained at 50 degreeC. For this reason, resinization at the bottom of the lower mold is not effectively promoted, and the molding time is slightly longer.

  In addition, about Examples 4-6 and Comparative Examples 1-6, although description is abbreviate | omitted in order to avoid that a specification becomes redundant, the temperature of the circulating water by the high temperature water circulator 22 in each Example and a comparative example Is a temperature 5 ° C. higher than the temperatures shown in the upper and lower mold columns in FIGS. 4 and 5. In addition, the temperature of the circulating water by the low-temperature water circulator 24 in each of the examples and the comparative examples is shown in the column of the lower mold bottom in FIGS. 4 and 5 when the switching by the switching valve 30 is not performed. When the switching by the switching valve 30 is performed, the initial temperature shown in the column of the bottom surface of the lower mold in FIGS. 4 and 5 is used.

In order to evaluate the degree of foaming of the urethane foam molded body of the example molded under the above conditions, the apparent core density (kg / m ³ ) of the urethane foam molded body was measured in accordance with a method based on JIS K 7222: 2005. did. The apparent core density (kg / m ³ ) indicates that the smaller the value, the more suitable foaming is caused by the activated foaming reaction, and the urethane foam molded body is excellent in reducing the density. It is shown that. The value is shown in the “density” column of FIG.

  Moreover, the evaluation regarding a shape and the evaluation regarding molding time were performed with respect to the urethane foam molded object of an Example and a comparative example. In the evaluation regarding the shape, the appearance of the urethane foam molded body was visually observed, and surface roughness, sticking of the skin layer to the mold, etc. were confirmed. Furthermore, the urethane foam molded body was divided, and the foamed portion on the divided surface was visually observed to check for the presence of cavities, cracks, and the like. Further, in the evaluation relating to the molding time, it was evaluated whether the molding time in the mold did not require a long time. In the urethane foam molded body of the example, the evaluation regarding the shape is good, and the molding time is relatively short. On the other hand, some urethane foam molded articles of comparative examples have poor evaluations regarding the shape, and some require a relatively long time for molding.

  Specifically, in the urethane foam molded bodies of Comparative Example 1 and Comparative Example 6, it was confirmed that the skin layer was stuck to the mold. Thereby, when the temperature of the bottom face of the lower mold at the time of foaming is too low (35 ° C.), it is estimated that a good skin layer is not formed. Further, in the urethane foam molded body of Comparative Example 2, the contact surface to the upper mold is rough. Thereby, when the temperature of the upper mold and the upper part of the lower mold continuous to the upper mold is too high (90 ° C.), it is presumed that the resinification proceeds too quickly and the surface becomes rough. In the urethane foam molded article of Comparative Example 4, the upper mold and the upper part of the lower mold continuous with the upper mold have a high temperature (90 ° C.) and the lower mold bottom has a high temperature (70 ° C. → 90 ° C.). For this reason, the entire surface of the urethane foam molded body of Comparative Example 4 is roughened. Furthermore, the inside of the urethane foam molded body of Comparative Example 4 is cracked. This is presumed that the foaming reaction has progressed too much because the temperature of the bottom surface of the lower mold during foaming is too high (70 ° C.). And the molding time in the urethane foam molded object of the comparative example 3 and the comparative example 5 is 1.5 times or more compared with the thing of an Example. Thereby, when the temperature of the upper mold and the upper part of the lower mold continuous to the upper mold is not so high (60 to 65 ° C.), it is presumed that the resinification is not promoted and the molding time is prolonged. .

  From the above results, in order to form a good skin layer and to promote the foaming reaction stably, the temperature of the bottom surface of the lower mold at the time of foaming, that is, the temperature heated by the circulating water of the low-temperature water circulator 24 is reduced. The temperature of the bottom surface of the mold is preferably 40 to 70 ° C, and more preferably 45 to 65 ° C. In addition, to accelerate the resinization and shorten the molding time, to suppress the surface roughness due to the excessive progress of resinization, the temperature of the cavity surface to promote the resinization of urethane foam after foaming, that is, The temperature of the cavity surface heated by the circulating water of the high-temperature water circulator 22 is preferably 65 to 85 ° C, and more preferably 70 to 80 ° C. Furthermore, it is possible to further shorten the molding time by increasing the temperature of the bottom surface of the lower mold after a predetermined time has elapsed since the raw material injection within the above conditions.

  Hereinafter, various aspects of the present invention will be listed.

(1) In a forming mold for forming a urethane foam by injecting a urethane foam raw material containing a polyol, a polyisocyanate, a foaming agent, a foam stabilizer, and a catalyst into the cavity,
The mold for molding is
A lower mold with a recess,
An upper mold that forms the cavity with the lower mold by being clamped to the lower mold so as to cover the recess,
A lower mold bottom heater for heating the bottom surface of the recess;
A lower die upper heater for heating a portion of the lower die that contacts the upper die;
An upper heater for heating the inner surface of the upper mold facing the cavity,
Before the urethane foam raw material is injected into the cavity, the bottom surface of the recess is heated to a predetermined temperature by the lower mold bottom surface heater, and the portion of the lower mold in contact with the upper mold and the upper mold Each of the inner surface facing the cavity is heated to a resinization promoting temperature which is higher by 5 ° C. or more than the predetermined temperature by each of the lower mold upper heater and the upper mold heater. Constructed mold for molding.

  (2) After the urethane foam raw material is injected into the cavity and a predetermined time elapses, the bottom surface of the recess is heated from the predetermined temperature to the resinization promoting temperature by the lower mold bottom heater. The molding die according to item (1) configured as described above.

(3) The predetermined time is
The molding gold as set forth in (2), wherein the urethane foam raw material injected in the injection step is assumed to be in contact with the inner surface of the upper mold by foaming by a foaming reaction. Type.

(4) The predetermined temperature is 40-70 ° C.
The molding die according to any one of items (1) to (3), wherein the resinification promotion temperature is 65 to 85 ° C.

(5) The molding die is
A first hot water circulator for circulating hot water;
A second hot water circulator for circulating hot water that is 5 ° C. higher than the hot water circulated by the first hot water circulator;
A first lower mold pipe that is embedded in the lower mold and heats the bottom surface of the recess by selectively circulating hot water by either the first hot water circulator or the second hot water circulator. When,
A second lower mold pipe which is embedded in the lower mold and heats a portion of the lower mold in contact with the upper mold by circulating hot water using the second hot water circulator;
Embedded in the upper mold and provided with an upper mold pipe for heating the inner surface of the upper mold facing the cavity by circulating hot water using the second hot water circulator,
The first hot water circulator, the second hot water circulator, and the first lower mold pipe are the lower mold bottom heater, and the second hot water circulator and the second lower mold pipe are the lower mold upper part. The molding die according to any one of items (1) to (4), wherein the second hot water circulator and the upper die pipe function as the heater as the heater.

(6) a mixing step of mixing a urethane foam raw material containing a polyol, a polyisocyanate, a foaming agent, a foam stabilizer, and a catalyst;
An injection step of injecting the urethane foam raw material mixed in the mixing step into a cavity of a molding die, and a method of molding urethane foam in the cavity,
The mold for molding is
A lower mold with a recess,
An upper mold that forms the cavity with the lower mold by being clamped to the lower mold so as to cover the recess,
A lower mold bottom heater for heating the bottom surface of the recess;
A lower die upper heater for heating a portion of the lower die that contacts the upper die;
An upper heater for heating the inner surface of the upper mold facing the cavity,
The urethane foam molding method further includes:
Before the urethane foam raw material is injected, the bottom surface of the recess is heated to a predetermined temperature by the lower mold bottom heater, and the portion of the lower mold in contact with the upper mold and the cavity of the upper mold A pre-injection heating step in which each of the facing inner surfaces is heated by each of the lower mold upper heater and the upper mold heater to a resinization acceleration temperature that is 5 ° C. or more higher than the predetermined temperature;
Promoting resinization of the urethane foam raw material injected in the injection step by a portion of the lower mold that is heated up to the resinization acceleration temperature and in contact with the upper mold and an inner surface facing the cavity of the upper mold A method for molding urethane foam, comprising the step of promoting resinification.

(7) The urethane foam molding method further includes:
After injection of the urethane foam raw material in the injection step, after the injection, the bottom surface of the recess is heated from the predetermined temperature to the resinization promotion temperature by the lower mold bottom heater. Including steps,
(6) The resin foaming of the urethane foam raw material injected in the injection step is also promoted by the bottom surface of the recess heated to the resinization acceleration temperature in the post-injection heating step. The urethane foam molding method described in 1.

(8) The predetermined time is
The urethane foam molding according to (7), wherein the urethane foam raw material injected in the injection step is assumed to be in contact with the inner surface of the upper mold by foaming by a foaming reaction. Method.

(9) The predetermined temperature is 40 to 70 ° C,
The urethane foam molding method according to any one of items (6) to (8), wherein the resinification promotion temperature is 65 to 85 ° C.

(10) The blowing agent mixed in the mixing step includes water, and the amount of the water is 4.6 to 7 parts by weight with respect to 100 parts by weight of the polyol.
The polyol mixed in the mixing step is
Including PO-added polyether polyol obtained by addition polymerization of propylene oxide to polyhydric alcohol,
Item (6) to (9), wherein the ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the PO-added polyether polyol to the number of all terminal hydroxyl groups of the polyol is 35% or more. ) The urethane foam molding method according to any one of the items.

  (11) The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl group to the number of terminal hydroxyl groups in the PO-added polyether polyol mixed in the mixing step is greater than 50% (10 ) The urethane foam molding method described in the item.

  (12) The urethane foam molding method as described in (10) or (11), wherein the PO-added polyether polyol mixed in the mixing step has a number average molecular weight of 2500 to 7000.

(13) The polyol mixed in the mixing step is
EO addition polyether polyol obtained by addition polymerization of ethylene oxide to polyhydric alcohol,
The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the EO-added polyether polyol to the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the PO-added polyether polyol is 100% or less. The urethane foam molding method according to any one of items (10) to (12).

  (14) The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups to the number of terminal hydroxyl groups in the EO-added polyether polyol mixed in the mixing step is greater than 60% (13). ) The urethane foam molding method described in the item.

  (15) The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups to the number of all terminal hydroxyl groups of the polyol mixed in the mixing step is 65% or more (6) Item 15. The method for molding urethane foam according to any one of Items 14 to 14.

(16) The polyisocyanate mixed in the mixing step is
2,4-toluene diisocyanate and 2,6-toluene diisocyanate,
The urethane foam molding method according to any one of items (6) to (15), wherein the mass ratio of 2,4-toluene diisocyanate to 2,6-toluene diisocyanate is 80:20 .

10: Mold for molding 14: Lower mold 16: Upper mold 20: First lower mold pipe (lower mold bottom heater)
22: High-temperature water circulator (lower die bottom heater) (lower die upper heater) (upper heater)
24: Low-temperature water circulator (lower mold bottom heater)
30: Switching valve (lower mold bottom heater)
32: Second lower mold pipe (lower upper heater)
34: Upper pipe (upper heater)

Claims (9)

In a forming mold for forming a urethane foam by injecting a urethane foam raw material containing a polyol, a polyisocyanate, a foaming agent, and a foam stabilizer into a cavity,
The mold for molding is
A lower mold with a recess,
An upper mold that forms the cavity with the lower mold by being clamped to the lower mold so as to cover the recess,
A lower mold bottom heater for heating the bottom surface of the recess;
A lower die upper heater for heating a portion of the lower die that contacts the upper die;
An upper heater for heating the inner surface of the upper mold facing the cavity,
Before the urethane foam raw material is injected into the cavity, the bottom surface of the recess is heated to a predetermined temperature in a range of 40 to 70 ° C. by the lower mold bottom heater, and the upper portion of the lower mold is heated. Each of the portion in contact with the mold and the inner surface of the upper mold facing the cavity is at a temperature higher than the predetermined temperature by 5 ° C. or more by each of the lower mold upper heater and the upper mold heater, and 65 to 65 ° C. A molding die configured to be heated up to a resinification promotion temperature in the range of 85 ° C.   After the urethane foam raw material is injected into the cavity and a predetermined time elapses, the bottom surface of the recess is heated from the predetermined temperature to the resinization promoting temperature by the lower mold bottom heater. The molding die according to claim 1. The predetermined time is
3. The molding die according to claim 2, wherein the time is assumed that the urethane foam raw material injected in the injection step is foamed by a foaming reaction and is in contact with the inner surface of the upper mold. . The molding die is
A first hot water circulator for circulating hot water;
A second hot water circulator for circulating hot water that is 5 ° C. higher than the hot water circulated by the first hot water circulator;
A first lower mold pipe that is embedded in the lower mold and heats the bottom surface of the recess by selectively circulating hot water by either the first hot water circulator or the second hot water circulator. When,
A second lower mold pipe which is embedded in the lower mold and heats a portion of the lower mold in contact with the upper mold by circulating hot water using the second hot water circulator;
Embedded in the upper mold and provided with an upper mold pipe for heating the inner surface of the upper mold facing the cavity by circulating hot water using the second hot water circulator,
The first hot water circulator, the second hot water circulator, and the first lower mold pipe are the lower mold bottom heater, and the second hot water circulator and the second lower mold pipe are the lower mold upper part. The molding die according to any one of claims 1 to 3, wherein the second hot water circulator and the upper mold pipe function as the heater as the heater. A mixing step of mixing a urethane foam raw material including a polyol, a polyisocyanate, a foaming agent, a foam stabilizer, and a catalyst;
An injection step of injecting the urethane foam raw material mixed in the mixing step into a cavity of a molding die, and a method of molding urethane foam in the cavity,
The mold for molding is
A lower mold with a recess,
An upper mold that forms the cavity with the lower mold by being clamped to the lower mold so as to cover the recess,
A lower mold bottom heater for heating the bottom surface of the recess;
A lower die upper heater for heating a portion of the lower die that contacts the upper die;
An upper heater for heating the inner surface of the upper mold facing the cavity,
The urethane foam molding method further includes:
Before the urethane foam raw material is injected, the bottom surface of the recess is heated by the lower mold bottom heater to a predetermined temperature in the range of 40 to 70 ° C., and the lower mold is in contact with the upper mold And the inner surface of the upper mold facing the cavity, each of the lower mold upper heater and the upper mold heater at a temperature higher than the predetermined temperature by 5 ° C. and in a range of 65 to 85 ° C. A pre-injection heating step for heating to a resinization acceleration temperature,
Promoting resinization of the urethane foam raw material injected in the injection step by a portion of the lower mold that is heated up to the resinization acceleration temperature and in contact with the upper mold and an inner surface facing the cavity of the upper mold A method for molding urethane foam, comprising the step of promoting resinification. The urethane foam molding method further includes:
After injection of the urethane foam raw material in the injection step, after the injection, the bottom surface of the recess is heated from the predetermined temperature to the resinization promotion temperature by the lower mold bottom heater. Including steps,
6. The resinization of the urethane foam raw material injected in the injection step is also promoted by the bottom surface of the recess heated to the resinification promotion temperature in the post-injection heating step. The urethane foam molding method as described. The predetermined time is
The urethane foam molding method according to claim 6, wherein the urethane foam raw material injected in the injection step is assumed to be in contact with the inner surface of the upper mold by foaming by a foaming reaction. . The blowing agent mixed in the mixing step includes water, and the amount of the water is 4.6 to 7 parts by weight with respect to 100 parts by weight of the polyol,
The polyol mixed in the mixing step is
Including PO-added polyether polyol obtained by addition polymerization of propylene oxide to polyhydric alcohol,
8. The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the PO-added polyether polyol to the number of all terminal hydroxyl groups of the polyol is 35% or more. The urethane foam molding method according to any one of the above. The polyol mixed in the mixing step is
EO addition polyether polyol obtained by addition polymerization of ethylene oxide to polyhydric alcohol,
The ratio of the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the EO-added polyether polyol to the number of primary hydroxyl groups contained in the terminal hydroxyl groups of the PO-added polyether polyol is 100% or less. The urethane foam molding method according to claim 8.

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