JP4806553B2 - Method for producing polyurethane foam for hot press molding - Google Patents

Description

The present invention relates to a method for producing a polyurethane foam for hot press molding .

  2. Description of the Related Art Conventionally, some polyurethane foams for hot press molding that are shaped by hot pressing contain a blocked isocyanate.

  The polyurethane foam for hot press molding containing the above-mentioned blocked isocyanate is produced by dissociating the blocking agent of the blocked isocyanate by heating at the time of hot press molding to generate an active isocyanate group, and the active isocyanate group is in the polyurethane foam for hot press molding. By undergoing a crosslinking reaction with excess hydroxyl groups, etc., it is shaped in a hot press state and the shape is fixed.

  However, since the polyurethane foam for hot press molding containing the blocked isocyanate generates heat due to the foaming reaction during production and becomes high temperature, the block agent of the blocked isocyanate is dissociated by the heat generation to generate an active isocyanate group. As a result, the isocyanate component becomes excessive and a good foam may not be obtained. Also, at the time of hot press molding, the undissociated blocked isocyanate contained in the polyurethane foam for hot press molding is insufficient and the shape cannot be fixed sufficiently, or the hardness of the resulting hot press molded product is insufficient. Is also likely to occur.

JP-A-5-329950

The present invention has been made in view of the above, by hot press can be performed satisfactorily shaping and form-locking, yet polyurethane foam heat press molding which can be obtained high hardness hot press molded product A method for producing a body is provided.

The invention according to claim 1 is a method for producing a polyurethane foam for hot press molding in which a polyol and a polyisocyanate are reacted and foamed in the presence of a foaming agent and an additive, and the additive includes a maximum exothermic temperature during the foaming. seen containing a blocked isocyanate having a higher and a lower dissociation temperature than the decomposition temperature of the urethane bond in the heat press molding polyurethane foam, and a reduction thermal agent to lower the maximum heating temperature during the foaming, as the blowing agent Water is 3 to 5 parts by weight with respect to 100 parts by weight of the polyol, the blocked isocyanate is 5 to 20 parts by weight with respect to 100 parts by weight of the polyol, and the source heat agent is 5 to 30 parts with respect to 100 parts by weight of the polyol. It is a weight part .

The invention of claim 2 is characterized in that, in claim 1 , the isocyanate index is 80 or more and less than 120.

The invention of claim 3 is characterized in that, in claim 1 or 2 , the heat reducing agent comprises an inorganic hydrate.

According to the method for producing a polyurethane foam for hot press molding in the invention of claims 1 to 3 , the additive is higher than a maximum exothermic temperature at the time of foaming of the polyurethane foam for hot press molding, and the polyurethane for hot press molding When the polyurethane foam for hot press molding is foamed, it comprises a blocked isocyanate having a dissociation temperature lower than the decomposition temperature of the urethane bond in the foam and a heat reducing agent that lowers the maximum exothermic temperature at the time of foaming. The maximum temperature can be lowered by a heat-reducing agent, and the blocking agent of the blocked isocyanate can be prevented from dissociating by the heat during foaming of the polyurethane foam for hot press molding, and the heat containing sufficient undissociated blocked isocyanate A polyurethane foam for press molding can be obtained. In addition, the obtained polyurethane foam for hot press molding is a polyurethane for hot press molding in which the blocked isocyanate of the blocked isocyanate is surely dissociated by heating during hot press molding to generate an active isocyanate group. A cross-linking reaction with surplus hydroxyl groups and the like in the foam can be carried out and shaped into a hot press state, whereby the shape of the hot press molded product can be fixed and the hardness of the hot press molded product can be increased.

  Hereinafter, embodiments of the present invention will be described in detail. The polyurethane foam for hot press molding of the present invention is obtained by a reaction between a polyol and a polyisocyanate, and is higher than the maximum exothermic temperature at the time of foaming of the polyurethane foam for hot press molding, and for the hot press molding. A blocked isocyanate having a dissociation temperature lower than the decomposition temperature of the urethane bond in the polyurethane foam is included.

  In the method for producing a polyurethane foam for hot press molding according to the present invention, a polyol and a polyisocyanate are reacted and foamed in the presence of a foaming agent and an additive. It contains a blocked isocyanate having a dissociation temperature higher than the maximum exothermic temperature and lower than the decomposition temperature of the urethane bond in the polyurethane foam for hot press molding, and a heat reducing agent that lowers the maximum exothermic temperature at the time of foaming.

  As the polyol used in the present invention, any one or both of known ether polyols and ester polyols used for the production of polyurethane foams are used.

  Examples of ether polyols include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose, or polyhydric alcohols thereof. The polyether polyol which added alkylene oxides, such as ethylene oxide and a propylene oxide, can be mentioned. As ester polyols, polycondensation of aliphatic carboxylic acids such as malonic acid, succinic acid and adipic acid and aromatic carboxylic acids such as phthalic acid and aliphatic glycols such as ethylene glycol, diethylene glycol and propylene glycol. The polyester polyol obtained in this way can be mentioned.

  The polyisocyanate may be aromatic, alicyclic or aliphatic, and may be a bifunctional isocyanate having two isocyanate groups in one molecule, or three in one molecule. Trifunctional or higher isocyanates having the above isocyanate groups may be used, and these may be used alone or in combination.

  For example, as the bifunctional isocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-phenylmethane diisocyanate, 2,4 ′ -Diphenylmethane diate, 2,2'-diphenylmethane diisocyanate, xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisonate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, etc. Aromatic ones such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, methylcyclohexane diisocyanate, butane-1,4-diisocyanate DOO, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, there may be mentioned aliphatic, such as lysine isocyanate.

  Examples of the tri- or higher functional isocyanate include 1-methylbenzole-2,4,6-triisocyanate, 1,3,5-trimethylbenzole-2,4,6-triisocyanate, biphenyl-2,4,4 ′. -Triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2 ', 5,5' tetraisocyanate, triisocyanate Examples thereof include phenylmethane-4,4 ′, 4 ″ -triisocyanate, polymeric MDI, etc. In addition, urethane prepolymers can also be used. Further, the polyisocyanate used in combination is limited to one kind each. However, it may be one or more, for example, aliphatic isocyanates It may be used in combination of two of one type and an aromatic isocyanate.

  Water is used as the foaming agent. The amount of water added is preferably about 3 to 5 parts by weight per 100 parts by weight of polyol.

  As the additive, at least a blocked isocyanate and a heat reducing agent are used. As the blocked isocyanate, those having a dissociation temperature higher than the maximum exothermic temperature at the time of foaming of the polyurethane foam for hot press molding and lower than the decomposition temperature of the urethane bond in the polyurethane foam for hot press molding are used. The maximum heat generation temperature of the polyurethane foam for hot press molding can be obtained by inserting a thermocouple into the foaming foam and measuring the temperature change over time. In addition, the decomposition temperature of the urethane bond in the polyurethane foam for hot press molding is foamed and cured by injecting a required amount of the reaction mixture into a 170 × 170 × 170 × mm foaming box opened at the top, It can be measured by installing a thermocouple in the center of the bottom of the foam box and measuring the temperature change during foaming and curing. This decomposition temperature can be measured by a known differential calorimetric analysis and is generally shown to be 165 to 190 ° C.

  As said block isocyanate, what has dissociation temperature in the range of 150 to 120 degreeC is more preferable. When the dissociation temperature of the blocked isocyanate is less than 120 ° C., even if a heat reducing agent is used, the blocked exothermic temperature is higher than the maximum exothermic temperature (temperature when using the heat reducing agent) of the polyurethane foam for hot press molding. The dissociation temperature of the polyurethane foam for hot press molding is lowered, so that the blocked isocyanate is dissociated at the time of foaming, and the undissociated unblocked blocked isocyanate remaining in the polyurethane foam for hot press molding is reduced. On the other hand, when the dissociation temperature of the block isocyanate exceeds 150 ° C., the dissociation temperature of the block isocyanate is higher than the decomposition temperature of the urethane bond in the polyurethane foam for hot press molding, and before the block isocyanate dissociates during the hot press molding. The urethane bond of the polyurethane foam for hot press molding is thermally decomposed, making it impossible to shape and increase the hardness of the hot press molded product.

  The blocked isocyanate is randomly blocked by at least two of polyisocyanate blocked with nonylphenol, polyisocyanate blocked with alkylphenol and ε-caprolactam, and combinations thereof, or alkylphenol, ε-caprolactam and nonylphenol. Converted polyisocyanates may be used, and further these may be used in combination.

  The polyisocyanate used for the blocked isocyanate can be used without limitation as long as it reacts with the blocking agent. For example, aliphatic diisocyanates such as hexamethylene diisocyanate and lysine diisocyanate, alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, and xylene diisocyanate. Including diisocyanate monomers, various diisocyanate monomers, urethane prepolymers and adducts having terminal isocyanate groups obtained by reaction of these diisocyanate monomers and polyols, and isocyanurate rings obtained by polymerizing diisocyanate monomers Mention may be made of polyisocyanate polymers.

  The amount of the blocked isocyanate with respect to 100 parts by weight of the polyol is an appropriate amount, but 5 to 20 parts by weight is particularly preferable. If it is less than 5 parts by weight, it is difficult to obtain the effect of the blocked isocyanate, while if it exceeds 20 parts by weight, a good polyurethane foam cannot be obtained.

  The heat reducing agent refers to a compound that releases water when a predetermined temperature is reached, and can suppress the heat of reaction of the polyurethane foam for hot press molding by the latent heat of vaporization of water to lower the maximum exothermic temperature. The maximum exothermic temperature of the polyurethane foam for hot press molding when no heat reducing agent is added is usually 140 ° C. to 150 ° C., and the maximum exothermic temperature is lowered to 110 ° C. to 130 ° C. by adding a heat reducing agent. be able to. Specific examples of the heat reducing agent include MW powder (registered trademark, manufactured by Shiraishi Calcium Co., Ltd.) containing water in the bubbles of the thermoplastic resin foam composed of granular closed cells and inorganic hydrate. . Examples of the inorganic hydrate include at least one selected from the group of dihydrate gypsum, magnesium sulfate hydrate, and magnesium phosphate hydrate. The amount of the heat reducing agent is an appropriate amount, but is generally about 5 to 30 parts by weight with respect to 100 parts by weight of the polyol.

  Examples of other additives include foam stabilizers and pigments. Any foam stabilizer may be used as long as it is used for polyurethane foams, and examples thereof include silicone foam stabilizers, fluorine-containing compound foam stabilizers, and known surfactants. As the pigment, those according to the required color are used.

  In addition, a catalyst for the reaction between the polyol and the polyisocyanate is used. As the catalyst, those known for polyurethane foams can be used. For example, amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, tetramethylguanidine, tin catalysts such as stannous octoate and dibutyltin dilaurate, phenylmercurypropionate or lead octenoate And metal catalysts (also referred to as organometallic catalysts). The general amount of the catalyst is about 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the polyol.

  Furthermore, in the present invention, the isocyanate index is preferably 80 or more and less than 120. If it is less than 80, since the isocyanate content is small, it becomes a polyurethane foam for hot press molding that is inferior in physical strength, and is also inferior in hot press moldability. On the other hand, when it is set to 120 or more, the amount of excess hydroxyl group contained in the polyurethane foam for hot press molding is insufficient, and the active isocyanate group and the hot press are generated by dissociating the blocking agent of the blocked isocyanate during hot press molding. It becomes difficult to obtain a crosslinking reaction with surplus hydroxyl groups in the polyurethane foam for molding, and it becomes difficult not only to form and fix the foam in a hot press state, but also to increase the hardness of the hot press molded product. In addition, when an isocyanate index exceeds 100, there exists the following effect | action. First, even if the hydroxyl end of the unreacted polyol reacts and the isocyanate index is high and it is theoretically considered that there is no hydroxyl group, the hardness will increase. Secondly, since the alphanate bond and biuret bond generated in association with the urethane reaction dissociate at about 120 ° C., a hydroxyl value is generated by heat at the time of hot press molding, and is bonded to an isocyanate group again. Hardness will increase. In addition, the isocyanate index in this invention shows 100 fraction of the number of moles of the isocyanate group in polyisocyanate (it does not contain block isocyanate) with respect to the total mole number of the hydroxyl group in water and polyols as a foaming agent. . Therefore, in the case of the isocyanate index 100, the water as a foaming agent, the hydroxyl group of polyols, and the isocyanate group of polyisocyanate are in an equivalent state.

  The polyurethane foam for hot press molding can be prepared by a one-shot method in which a polyol and a polyisocyanate are directly reacted in the presence of a catalyst, a foaming agent, a heat reducing agent and other appropriate additives, or a polyol and a polyisocyanate are preliminarily reacted. To obtain a prepolymer having an isocyanate group at the terminal, and reacting a polyol with this prepolymer in the presence of a catalyst, a foaming agent, a heat reducing agent, and other appropriate additives. Can also be done. In addition, slabs that are continuously produced by discharging the mixed and stirred raw material (reaction mixed raw material) onto a belt conveyor and naturally foaming and curing the raw material at room temperature and atmospheric pressure while the belt conveyor moves. Either a molding method or a molding method in which raw materials that have been mixed and stirred (reaction mixed raw materials) are filled in a mold and produced in batches may be used. Among them, the slab molding method that can be molded with a large product size is preferable for controlling the maximum exothermic temperature and controlling the dissociation of the blocked isocyanate.

  On the other hand, the manufacturing method of the hot press-molded product in the present invention is performed by hot press molding the polyurethane foam for hot press molding of the present invention at a temperature equal to or higher than the dissociation temperature of the blocked isocyanate. A preferable hot press temperature is a temperature lower than the decomposition temperature of the urethane bond in the polyurethane foam for hot press molding and higher than the dissociation temperature of the blocked isocyanate. Specifically, a hot press temperature of 130 to 150 ° C. is preferable.

  Examples of the present invention will be specifically described below together with comparative examples. Each component shown in Table 1 and Table 2 was used in accordance with the blending ratio in the same table and foamed by the slab method to obtain a polyurethane foam for hot press molding. The polyols in Tables 1 and 2 are polyether polyols (product number: A067, functional group number f = 3, OH number = 33, Mw = 3000), heat reducing agent 1 is dihydrate gypsum, and heat reducing agent 2 is magnesium phosphate 8 Hydrate, amine catalyst is N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine (product number: Cao Raiser No3, manufactured by Kao Corporation), metal catalyst is stannous octylate (product number MRH110, Johoku Chemical) Manufactured by Kogyo Co., Ltd.), the foam stabilizer is a silicone foam stabilizer (Part No .: BF2370, manufactured by Goldschmidt), the block isocyanate is a dissociation temperature of 140 ° C. (Part No .: Coronate 2512, MDI, manufactured by Nippon Polyurethane Industry Co., Ltd.), The polyisocyanate is tolylene diisocyanate (product number: T-80, manufactured by Nippon Polyurethane Industry Co., Ltd.). In addition, although it foamed favorably about Example and Comparative Example 1, about Comparative Examples 2-6, bursting (puncture), a down, etc. generate | occur | produced in the middle of foaming, or discoloration (scorch) was obtained to the obtained foam. Or a good foam could not be obtained. For this reason, some comparative examples cannot measure the following maximum exothermic temperature and 25% compression hardness.

In the said Example and comparative example, the thermocouple was inserted in the polyurethane foam for hot press molding in foaming, and the highest heat_generation | fever temperature was measured with the electronic measuring device (product number: NR-1000, Keyence Corporation make). Furthermore, for the polyurethane foams for hot press molding of the examples and comparative examples, the density (kg / m ³ ) conforms to JIS K7222-2004, and the 25% compression hardness (KPa / mm ² ) represents JIS K6400-. 2: Measured according to the 2004 D method. The 25% compression hardness is indicated by a compressive stress when the sample size is 100 × 100 × 20 mm and the sample is completely compressed to 25%. Each measured value is shown in the lower column of Tables 1 and 2.

Next, what was cut into 100 × 100 × 20 mm of the polyurethane foam for hot press molding of Examples and Comparative Examples 1 and 2 was thermoformed by being accommodated in an oven at 140 ° C. for 30 minutes and heated, The 25% compression hardness of the obtained thermoformed product was measured in the same manner as described above. Further, the rate of increase in hardness due to thermoforming was calculated by the formula [25% compression hardness after thermoforming / 25% compression hardness before thermoforming × 100]. The measurement results and calculation results are shown in the lower columns of Tables 1 and 2. As understood from the measurement results and calculation results in Tables 1 and 2, the hardness of the thermoformed product was higher in the example than in Comparative Example 1. From this, it is understood that the hardness of the example product is increased by heating, and it is understood that the hardness is increased even when hot press molding is performed.

Claims (3)

  In the method for producing a polyurethane foam for hot press molding, in which polyol and polyisocyanate are reacted and foamed in the presence of a foaming agent and an additive,
  The additive includes a blocked isocyanate having a dissociation temperature higher than the maximum exothermic temperature at the time of foaming and lower than the decomposition temperature of urethane bonds in the polyurethane foam for hot press molding, and the maximum exothermic temperature at the time of foaming. A heat reducing agent that lowers,
  3 to 5 parts by weight of water as the blowing agent with respect to 100 parts by weight of the polyol,
  5 to 20 parts by weight of the blocked isocyanate with respect to 100 parts by weight of the polyol,
  The method for producing a polyurethane foam for hot press molding, wherein the source heat agent is 5 to 30 parts by weight with respect to 100 parts by weight of the polyol.   The method for producing a polyurethane foam for hot press molding according to claim 1, wherein the isocyanate index is 80 or more and less than 120.   The method for producing a polyurethane foam for hot press molding according to claim 1 or 2, wherein the heat reducing agent comprises an inorganic hydrate.