JP4574278B2 - Method for producing flexible polyurethane foam - Google Patents

Description

  The present invention relates to the production of a flexible polyurethane foam in which a flexible polyurethane foam is formed from a flexible polyurethane foam raw material containing a volatile organic compound, and then the removal or content of the volatile organic compound in the flexible polyurethane foam is reduced by post-treatment. Regarding the method.

  Conventionally, when a flexible polyurethane foam material is produced by foaming a flexible polyurethane foam material, the flexible polyurethane foam material often contains a volatile organic compound. For example, 2,6-di-t-butyl P-cresol (hereinafter referred to as BHT), which is included as an antioxidant in the soft polyurethane foam raw material, is used for preventing deterioration of the raw material and preventing discoloration of the flexible polyurethane foam during foaming. ) Is a volatile organic compound.

  However, BHT has a high sublimation property, and the problem of BHT remaining in the flexible polyurethane foam after foaming has been pointed out. For example, when a soft polyurethane foam is used for a mattress, a cushion, or a pad material, there is a problem that BHT sublimated from the soft polyurethane foam adheres to the fabric covering the flexible polyurethane foam and causes discoloration of the fabric. In the use of automobile parts such as seat cushion pads, BHT is cited as a volatile organic compound (VOC) that affects air pollution.

  Under these circumstances, recently, as a countermeasure against BHT, it has been proposed to use a substitute having a lower volatility than BHT, or to apply a heat treatment after foaming when BHT is used.

  The method of using a substitute having a lower volatility than BHT is a very effective measure, but there are few substitutes having an antioxidant effect equivalent to that of BHT, and the cost of raw materials due to the substitute cannot be avoided. is there.

In addition, when heat treatment is performed after foaming, a very long time is required to sufficiently remove BHT. Further, when heat is applied for a long time, the foam is deteriorated, resulting in thermal discoloration and deterioration of physical properties. In addition, although the process by water vapor | steam is also proposed as heat processing, a drying process is needed and there exists a problem which costs increase in terms of equipment.
JP 2000-95838 A

  The present invention has been made in view of the above points, and is a flexible polyurethane foam capable of realizing removal of volatile organic compounds such as BHT or reduction of the content in a short time and without causing deterioration of the physical properties of the foam. A manufacturing method is provided.

The invention of claim 1 is to form a flexible polyurethane foam by foaming a flexible polyurethane foam raw material containing a volatile organic compound composed of 2,6-di-t-butyl P-cresol, and then superheat the flexible polyurethane foam. The present invention relates to a method for producing a flexible polyurethane foam characterized by applying steam.

  According to the present invention, a soft polyurethane foam raw material containing a volatile organic compound such as BHT is foamed to form a flexible polyurethane foam, and then superheated steam is applied to the flexible polyurethane foam. Volatile organic compounds can be removed or the content can be reduced. In addition, the superheated steam is a steam obtained by further heating a saturated steam at 100 ° C. as is known, and is in a gaseous state even when the temperature is lowered. Therefore, when the superheated steam is applied to the soft polyurethane foam, the soft polyurethane is used. It does not wet the foam and does not require a drying step after the superheated steam treatment. Furthermore, since superheated steam has a much larger heat capacity per unit volume than high-temperature air, the processing time for the flexible polyurethane foam can be shortened, so not only can the flexible polyurethane foam be produced efficiently, but also the foam generated by prolonged heating. Can prevent deterioration of physical properties.

In the method for producing a flexible polyurethane foam in the present invention, after forming a flexible polyurethane foam by foaming a flexible polyurethane foam raw material containing a volatile organic compound composed of 2,6-di-t-butyl P-cresol , It is characterized by applying superheated steam to the polyurethane foam.

  In the present invention, the flexible polyurethane foam raw material comprises a polyol, an antioxidant, a catalyst, a foaming agent, a foam stabilizer, an auxiliary agent added as appropriate, and a polyisocyanate.

  As the polyol, ether-based polyol or ester-based polyol known for use in flexible polyurethane foam can be 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 also be used. In addition, a polymer polyol obtained by polymerizing an ethylenically unsaturated compound in a polyether polyol or polyester polyol can also be used.

  As the antioxidant, BHT (2,6-di-t-butyl P-cresol) is preferable, but ascorbic acid, sodium ascorbate, formaldehyde, acetaldehyde (water-soluble aldehyde), sodium sulfite, formaldehyde sulfosilic acid Among the antioxidants such as sodium, isoascorbic acid, thioglycerol, thiosorbitol, thiourea, thioglycolic acid, cysteine hydrochloride, 1,4-diazobicyclo- (2,2,2) -octane, volatilization The effect of the present invention can also be obtained when a material having properties is used. BHT is a volatile organic compound, and a general amount is 0.01 to 0.6 parts by weight with respect to 100 parts by weight of polyol.

  As the catalyst, an amine catalyst such as triethylamine or tetramethylguanidine, a tin catalyst such as stannous octoate, or a metal catalyst such as phenylmercurypropionate or lead octenoate (also referred to as an organometallic catalyst) is used. Can do. A common amount of catalyst is 0.01 to 2.0 parts by weight per 100 parts by weight of polyol.

  As the blowing agent, water or hydrocarbons such as pentane can be used alone or in combination. In the case of water, carbon dioxide gas is generated during the reaction of the raw material composition, and foaming is performed by the carbon dioxide gas. The amount of the blowing agent is appropriately determined. In the case of water, about 0.5 to 7.0 parts by weight is preferable with respect to 100 parts by weight of the polyol.

  Any foam stabilizer may be used as long as it is used in the production of flexible polyurethane foams. Examples thereof include silicone foam stabilizers, fluorine-containing compound foam stabilizers, and known surfactants. A common amount of foam stabilizer is 0.1 to 3.0 parts by weight per 100 parts by weight of polyol.

  Other auxiliary agents that can be added as appropriate include ultraviolet absorbers, flame retardants, fillers, colorants, and the like. A well-known thing is used as a ultraviolet absorber. Examples thereof include benzophenone-based, benzotriazole-based, and benzoxazinone-based compounds. Examples of benzophenone compounds include 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-. Examples thereof include tetrahydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and the like. The flame retardant is particularly suitable for urethane foam for clothing, and examples thereof include those made of an organic phosphate compound.

As the polyisocyanate, aliphatic or aromatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them can be used. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexamethane diisocyanate. Examples of the aromatic polyisocyanate include toluene diisocyanate (TDI), diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, Examples thereof include polymeric polyisocyanate (crude MDI). Other prepolymers can also be used.

  A flexible polyurethane foam is formed by a known foaming method in which the polyurethane foam raw material is mixed and reacted with a stirrer, and superheated steam treatment is performed by applying superheated steam to the foamed soft polyurethane foam. Removal of volatile organic compounds and content reduction are performed.

  As is well known, superheated steam is steam obtained by further heating a saturated steam at 100 ° C. The superheated steam is generated as follows. First, generate saturated steam with a steam generator (boiler for gas, petroleum, etc.), then depressurize the saturated steam with a pressure reducing valve, and introduce the resulting reduced-pressure saturated steam into the superheated steam generator to generate superheated steam. To do. The decompression valve is a device for controlling the discharge amount of superheated steam, and by reducing the pressure, excessive volume expansion in the superheated steam discharged under atmospheric pressure is prevented, and disasters such as explosions are avoided. As the superheated steam generator, a known device that can superheat saturated steam to form superheated steam can be used.

  The superheated steam treatment time for applying the superheated steam to the flexible polyurethane foam is appropriately selected, but is usually about several seconds to 3 minutes. If the superheated steam treatment time is too long, the flexible polyurethane foam is deteriorated and the physical properties are lowered. Therefore, the treatment time is preferably short. The superheated steam may be applied to one surface of the flexible polyurethane foam or may be applied to the entire surface. Since the flexible polyurethane foam has an open cell structure, the superheated steam applied to one surface reaches the entire inside of the flexible polyurethane foam, and can exert a removing action on the BHT in the flexible polyurethane foam. Further, since the superheated steam maintains a gaseous state even when the temperature falls upon the soft polyurethane foam, the soft polyurethane foam does not get wet by the superheated steam treatment, and subsequent drying treatment is unnecessary.

Examples of the present invention will be described below. A polyurethane foam raw material having the following composition was stirred and mixed at 20 ° C. according to a conventional method and foamed to form a flexible polyurethane foam.
Polyurethane foaming raw material ・ Polyol (Sanyo Chemical Industries, Sannix GP-3050): 100 parts by weight ・ Antioxidant (BHT): 0.10 parts by weight ・ Catalyst (Air Products Japan, DABCO33-LV): 0 .4 parts by weight ・ Foaming agent (water): 2.4 parts by weight ・ Foam stabilizer (Nihon Unicar Co., Ltd., SZ-1136): 1.5 parts by weight 35.1 parts by weight

  The apparent density, 25% hardness, impact resilience, tensile strength, elongation, and compressive residual strain were measured for the obtained flexible polyurethane foam according to JIS K 6400. The measurement result of each physical property value is shown in the column before superheated steam treatment in Table 1.

  Further, a required number of 200 × 200 × 10 mm test pieces are cut from the foamed flexible polyurethane foam, the test pieces are placed on a wire mesh, and the test piece is placed from the outlet of the pipe facing downward from above the test piece. Superheated steam treatment was performed by spraying and applying superheated steam. The wire mesh is rough enough to allow superheated steam to pass through and has a strength sufficient to hold the test piece. The superheated steam has a saturated steam pressure (primary pressure) of 0.6 MPa before decompression by the decompression valve, a pressure (secondary pressure) after decompression by the decompression valve of 0.04 MPa, and the temperature of the superheated gas at the outlet of the pipe. Is 190 ± 5 ° C., the pipe diameter is ½, and the distance between the test piece and the superheated steam pipe outlet is 50 mm. In addition, the processing time (spraying time) for applying the superheated steam to the test piece was 5 seconds, 10 seconds, 20 seconds, 30 seconds, 60 seconds, 3 minutes, and one test piece was assigned to each processing time. . The residual amount of BHT was measured with a gas chromatograph (Shimadzu Corporation, GC-17A) on the test piece before the superheated steam treatment (untreated product) and on the test piece after the superheated steam treatment. In addition, the measurement of BHT with respect to the test piece after a superheated steam process was performed with respect to the surface which applied the superheated steam. Moreover, about the test piece after a superheated steam process for 3 minutes, it measured also about each said physical-property value. The measured value of BHT is as shown in Table 2, and the measured value of the physical property value for the test piece after 3 minutes of superheated steam treatment is as shown in the column after superheated steam treatment in Table 1.

  For comparison, water vapor having a temperature of 60 ° C. and humidity of 60% was applied to the test piece for 2 hours, and then left to dry at room temperature for 1 hour, and water vapor having a temperature of 80 ° C. and humidity of 90% was applied to the test piece for 1 hour. After being applied, water vapor is applied to a sample that has been left to dry at room temperature for 1 hour, and water that has been heated to 120 ° C. and 100% humidity for 10 minutes and then left to dry at room temperature for 1 hour. The remaining amount of BHT was measured on the surface. Each measurement result is as shown in Table 2.

  As is apparent from Table 2, it can be seen that the residual BHT of the flexible polyurethane foam is reduced by performing the superheated steam treatment in the present invention. In particular, the amount of residual BHT can be reduced to 37 ppm even with a superheated steam treatment of only 30 seconds, and the amount of residual BHT can be reduced to 9 ppm with a superheated steam treatment of 60 seconds and 4 ppm with a superheated steam treatment of 3 minutes. . Moreover, as is apparent from Table 1, it can be seen that the physical property value hardly decreases even by the superheated steam treatment for 3 minutes. On the other hand, in the conventional water vapor treatment, 154 ppm when 60 ° C. × 60% water vapor is applied for 2 hours, 76 ppm, 120 ° C. × 100% water vapor when 80 ° C. × 90% water vapor is applied for 1 hour. When it is applied for 10 minutes, it becomes 41 ppm, and it is necessary to perform the steam treatment for a longer time than the superheated steam treatment in relation to the decrease in the remaining amount BHT. Moreover, in the case of steam treatment, the flexible polyurethane foam is wetted by the steam treatment, and therefore, a drying treatment must be performed after that. In the case of superheated steam treatment, it takes extra time for drying. Since the flexible polyurethane foam does not get wet by the superheated steam treatment, it is not necessary to perform the drying treatment, and it is possible to further reduce the time.

  In the above description, the case of BHT is mainly shown as the volatile organic compound, but the present invention also removes or contains other volatile organic compounds contained in the flexible polyurethane foam. Reduction effect can be expected.

Claims (1)

A soft polyurethane foam material is formed by foaming a flexible polyurethane foam material containing a volatile organic compound composed of 2,6-di-t-butyl P-cresol, and then superheated steam is applied to the flexible polyurethane foam. A method for producing a flexible polyurethane foam.