JP2008266442A - Process for producing hydrophilic flexible polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrophilic flexible polyurethane foam which remarkably excels in water absorption performance such as a rate of absorbing water, an amount of water absorbed, and a retention of water absorbed and can be easily produced. <P>SOLUTION: The hydrophilic flexible polyurethane foam is obtained by subjecting a flexible polyurethane foam obtainable by foaming a foam raw material containing a polyol and a polyisocyanate to press processing immediately after foaming. The shape of the cells of the foam is intentionally changed by the press processing immediately after foaming. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a hydrophilic flexible polyurethane foam.

  Hydrophilic flexible polyurethane foam has excellent elasticity, water absorption due to being a porous body, water retention, glass cleaning for liquid crystal glass and building glass, etc., wiping material for moisture in clean rooms in the field of OA equipment, It is used in a wide range of applications such as wipers, hard disk cleaning, ink absorbers for printers, water absorption rolls, fields that require sweat absorption and moisture retention, materials for hydroponics, and materials for wiping moisture after washing a car.

Conventionally, the following methods (1) to (5) are known as methods for imparting hydrophilicity to a flexible polyurethane foam.
(1) A method in which a specific hydrophilic polyol is used as a raw material polyol and the reaction is performed with a low isocyanate index (Japanese Patent Laid-Open No. 2002-105164)
(2) A method of foaming a specific hydrophilic polyol with an excessive amount of water (Japanese Patent Laid-Open No. 61-78819)
(3) Method of adding a water-absorbing substance such as a water-absorbing resin when foaming the foam raw material
(4) Method of impregnating flexible polyurethane foam with additives such as water-absorbent resin and inorganic hydrophilic filler
(5) Method of hydrophilizing the foam surface by plasma treatment of flexible polyurethane foam
(6) Method of heat-pressing flexible polyurethane foam (paragraph 0032 of JP-A-2006-89507, claims 17-22 of JP-T-2002-511114)
JP 2002-105164 A JP-A-61-78819 JP 2006-89507 A Special table 2002-511114

  However, among the conventional techniques described above, in the methods (1) and (2), the obtained flexible polyurethane foam is slightly inferior in terms of water absorption rate. There is a risk of foaming inhibition. In the method (4), there is a problem of dropping off the impregnated additive. The method (5) has disadvantages that the processing cost is high and it is difficult to make the foam inner surface hydrophilic. In the method (6), the amount of elution when the flexible polyurethane foam comes into contact with water, hot water or a solvent is large.

  An object of the present invention is to solve the above-mentioned conventional problems and to provide a hydrophilic flexible polyurethane foam that is remarkably excellent in water absorption performance such as a water absorption speed, a water absorption amount, and a water absorption retention amount and that has a small elution amount.

  The method for producing a hydrophilic flexible polyurethane foam of the present invention (invention 1) is characterized by foaming a foam raw material containing a polyol and a polyisocyanate and pressing the flexible polyurethane foam immediately after foaming.

  The method for producing a hydrophilic flexible polyurethane foam according to claim 2 is characterized in that, in claim 1, pressing is performed so that the thickness of the foam is 10 to 50% of the original thickness.

  The method for producing a hydrophilic flexible polyurethane foam according to claim 3 is characterized in that, in claim 1 or 2, the press is started within 1 to 5 minutes after the generation of health foam.

  The method for producing a hydrophilic flexible polyurethane foam according to claim 4 is characterized in that pressing is performed for 5 to 30 minutes in any one of claims 1 to 3.

  The method for producing a hydrophilic flexible polyurethane foam according to claim 5 is characterized in that, in any one of claims 1 to 4, an isocyanate index of the foam raw material is 60 to 95.

  According to the present invention, by pressing the flexible polyurethane foam immediately after foaming and intentionally changing the shape of the cell, it is possible to make the capillary phenomenon remarkable and improve the water absorption performance such as the water absorption speed, the water absorption amount, the water absorption retention amount, etc. it can.

  This press treatment is preferably a treatment for pressing the flexible polyurethane foam so that its thickness is 10 to 50% of the original thickness.

  Moreover, in this invention, the hydrophilic flexible polyurethane foam which was further excellent in water absorption performance can be obtained by starting a press within 1 to 5 minutes after generation | occurrence | production of health foam, and performing for 5 to 30 minutes.

  In addition, by setting the isocyanate index of the foam raw material as slightly low as 60 to 95, the OH group of the polyol that does not contribute to the urethane reaction is left in the foam in a free state, and high water absorption is obtained by this OH group. Can do.

  In the present invention, the press treatment may be performed a plurality of times or stepwise.

  Below, the manufacturing method of the hydrophilic flexible polyurethane foam of this invention is demonstrated in detail.

  The manufacturing method of the hydrophilic flexible polyurethane foam of this invention presses the flexible polyurethane foam obtained by foaming the foam raw material containing a polyol and polyisocyanate immediately after foaming.

  There is no restriction | limiting in particular as a polyol used by this invention, The polyester-type polyol used for manufacture of a normal flexible polyurethane foam, a polyether-type polyol, Preferably a polyether-type polyol is mentioned. Polyether-based polyols include poly (oxy) in which propylene oxide or ethylene oxide is added alone to one or more compounds containing two or more active hydrogens, such as glycerin, trimethylolpropane, pentaerythritol, sorbitol or amines. Propylene) polyol or poly (oxypropylene) poly (oxyethylene) polyol in which both are blocked and randomly added. The polyol used in the present invention preferably has a molecular weight of 400 to 12,000 and an average functional group number of 2 or more.

  As the polyisocyanate, any of those used in the production of ordinary flexible polyurethane foams can be used. For example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, dicyclohexyl. Examples include methane diisocyanate, xylylene diisocyanate, polymethyl polyphenyl isocyanate, crude TDI, crude MDI, and modified MDI.

  The blending amount of the isocyanate is usually an amount in which the isocyanate index of the foam raw material is in the range of 80 to 120. As described later, the water absorption of the hydrophilic flexible polyurethane foam obtained by setting this isocyanate index to a low value. Performance can also be improved.

  Water as a foaming agent is blended in the foam raw material, and preferably a catalyst, a crosslinking agent, a foam stabilizer and the like are further blended.

  The amount of water is usually 0.5 to 4.0 parts by weight, particularly 0.5 to 2.5 parts by weight, based on 100 parts by weight of the total polyol, but as described later, water is used in a large excess amount. Thus, the water absorption performance of the obtained hydrophilic flexible polyurethane foam can be enhanced.

  Catalysts include tetramethylhexamethylenediamine, pentamethyldiethylenetriamine, dimethylcyclohexylamine, bis- (dimethylaminoethyl) ether, tetramethylpropylenediamine, trimethylaminoethylpiperazine, tetramethylethylenediamine, dimethylbenzylamine, methylmorpholine, ethylmorpholine. Ordinary amine catalysts used for the production of flexible polyurethane foams such as triethylenediamine can be used. The amount of the catalyst used is preferably 0.001 to 6 parts by weight, particularly 0.1 to 4 parts by weight, based on 100 parts by weight of the total polyol.

  Moreover, as a crosslinking agent mix | blended when the thing of high hardness is desired by a use, trimethylol propane, diethylene glycol, 1, 4- butanediol, dipropylene glycol, etc., or propylene oxide or ethylene oxide was added to these. The compounding amount is preferably 0 to 10 parts by weight with respect to 100 parts by weight of the total polyol.

  Further, as the foam stabilizer, a foam stabilizer such as a silicone surfactant usually used for foaming flexible polyurethane foam is used, and the blending amount thereof is 0.1 to 7 weights with respect to 100 parts by weight of the total polyol. Parts, especially 0.5 to 5 parts by weight.

  Furthermore, you may mix | blend colorants, such as a pigment, with a foam raw material as needed.

  In the present invention, it is preferred that the rise time be 60 to 120 seconds, particularly 80 to 100 seconds.

  The conditions for foaming and producing the flexible polyurethane foam from the blended blend of the above components may be normal conditions, but the foaming temperature is preferably 20-30 ° C. The foam raw material foaming method may be either a prepolymer method or a one-shot method.

  In the present invention, the polyurethane foam thus foamed is pressed immediately after foaming. 1 and 2 are a perspective view and a sectional view for explaining an example of this pressing method.

  As shown in FIG. 1, a mold for performing foam molding is composed of a lower mold 1 and an upper mold 2. The lower mold 1 has a container shape with the upper part opened, and the upper mold 2 has a size that can be fitted into the lower mold 1 from above. Both the lower mold 1 and the upper mold 2 are made of punching plates.

  In order to perform foam molding using this mold, the nonwoven fabrics 3 and 4 are attached to the inner surface of the lower mold 1 and the lower surface of the upper mold 2 as shown in FIGS. 2 (a) and 2 (d).

  In foam molding, the foam raw material is supplied into the lower mold 1 as shown in FIG. 2 (b), and foamed as shown in FIG. 2 (c). The foam F in which health bubbles are generated is pressed with the upper mold 2 and compressed to a certain thickness as shown in FIG.

  The pressing is preferably performed within 5 minutes, particularly within 1 minute after the foamed foam F reaches the rise time.

This pressing is preferably performed such that the percentage t ₂ / t ₁ × 100% of the thickness t ₂ at the time of pressing with respect to the original thickness t ₁ of the foam F is 10 to 50%.

  Thus, the flexible polyurethane foam obtained by pressing the foamed foam F immediately after the rise is such that the cells are made fine by pressing, and is excellent in hydrophilicity. Further, when the pressing is performed immediately after the rise, the amount of elution by the solvent of the water and hot water of the flexible polyurethane foam 12 becomes a sufficiently low value. For this reason, when hot pressing is performed after a long time has elapsed after the rise, thermal decomposition occurs due to the hot press, which results in a flexible polyurethane foam with a large amount of elution, whereas pressing was performed immediately after the rise time. In this case, since the thermal decomposition does not occur, the elution amount becomes a low value.

  The flexible polyurethane foam F is appropriately cut into a slab of flexible polyurethane foam.

  In the present invention, it is preferable to use a hydrophilic polyol as the polyol. The hydrophilic polyol is preferably a polyether polyol having an EO content of 20 to 80% by weight, particularly 50 to 80% by weight. In this case, the ratio of the hydrophilic polyol in the total polyol is preferably 50 to 70% by weight.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

The raw materials used in the following examples and comparative examples are as follows.
[Raw materials]
Hydrophilic polyol: Polyether polyol Trade name “700W”
(Average molecular weight 7000)
General-purpose polyol: Polyether polyol Product name “EXENOL82” manufactured by Asahi Glass Co., Ltd.
8 "(average molecular weight 5000, hydroxyl value 34, EO content 15% by weight)
Crosslinking agent: 1,4-butanediol Polyisocyanate: Pure MDI (EX-190 manufactured by Mitsui Takeda Chemical Co., Ltd.) / Crew
De DI (44V20 made by Sumika Bayer Urethane) = 80/20 (weight
Ratio) Foaming agent: Water Amine-based catalyst: Triethylenediamine Made by Toyo Soda Co., Ltd. Trade name “TOYOCATTF”
Amine-based catalyst: Triethylenediamine, manufactured by Tosoh Corporation, trade name “A133”
Foam stabilizer: Toray Dow Corning Silicone product name “SF2936”

Moreover, the physical property test method of the obtained flexible polyurethane foam is as follows.
[Physical property test]
Density: Determined by dividing the weight of the test piece 200 × 200 × 10 mm by the volume (JIS K 6
401).
Water absorption speed: Move 0.5ml water droplets by contacting them with the sample surface.
The time until complete absorption was measured. The water absorption speed on the surface in the direction perpendicular to the press direction of the sample was defined as the water absorption speed in the vertical direction, and the water absorption speed on the surface in the same direction as the press direction was determined as the water absorption speed in the horizontal direction.
Elution amount: The elution amount was determined by acetone extraction for 8 hours.

Example 1
General-purpose polyol 20 parts by weight Hydrophilic polyol 70 parts by weight 1,4-butanediol 10 parts by weight Polyisocyanate 12 parts by weight
(0.25 equivalent)
Were mixed uniformly to obtain a prepolymer.
100 parts by weight of the prepolymer Water 2 parts by weight Amine-based catalyst (TOYOCATTF) 0.3 part by weight Amine-based catalyst (A133) 0.5 part by weight Foam stabilizer 2.5 part by weight Polyisocyanate 64 parts by weight (isocyanate index 90)
And foamed in a 200 × 200 mm rectangular container mold. The rise time was about 90 seconds on average. Immediately after the rise is stopped (ie, within 1 to 5 minutes), the foam is taken out of the mold and pressed from above with an aluminum plate with release paper, and the thickness is reduced to half (50%). By maintaining for a minute, a flexible polyurethane foam having fine cells was obtained.

Comparative Example 1
The same physical properties were measured using the flexible polyurethane foam before pressing of Example 1 as a sample.

  From Table 1, it can be seen that according to the present invention, a hydrophilic flexible polyurethane foam excellent in water absorption performance and having a small amount of elution is provided.

It is a perspective view of the metal mold | die used for a press. It is sectional drawing which shows the press method.

Explanation of symbols

1 Lower mold 2 Upper mold 3, 4 Nonwoven fabric

Claims (5)

  A method for producing a hydrophilic flexible polyurethane foam, comprising foaming a foam raw material containing a polyol and a polyisocyanate and pressing the flexible polyurethane foam immediately after foaming.   2. The method for producing a hydrophilic flexible polyurethane foam according to claim 1, wherein pressing is performed so that the thickness of the foam is 10 to 50% of the original thickness.   The method for producing a hydrophilic flexible polyurethane foam according to claim 1 or 2, wherein the pressing is started within 1 to 5 minutes after the generation of the healthy foam.   The method for producing a hydrophilic flexible polyurethane foam according to any one of claims 1 to 3, wherein pressing is performed for 5 to 30 minutes.   The method for producing a hydrophilic flexible polyurethane foam according to any one of claims 1 to 4, wherein an isocyanate index of the foam raw material is 60 to 95.

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