JP2006089507A - Hydrophilic flexible polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain hydrophilic flexible polyurethane foam that has remarkably excellent water absorption performances such as water absorption rate, water absorption amount and water retention amount and is readily and inexpensively produced. <P>SOLUTION: The hydrophilic flexible polyurethane foam is obtained by foaming a foam raw material comprising a polyol and a polyisocyanate to give flexible polyurethane foam and heat-treating the flexible polyurethane foam. A part of the resin surface of the foam is thermally decomposed and the surface is made into a state coated with its decomposition product. Since the main component of the decomposition product has a hydrophilic group and exhibits strong hydrophilicity, the flexible polyurethane foam after heat treatment becomes flexible polyurethane foam having excellent water absorption performances such as water absorption rate, water absorption amount and water retention amount. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrophilic flexible polyurethane foam, and more particularly to a hydrophilic flexible polyurethane foam excellent in water absorption performance such as a water absorption rate, a water absorption amount, and a water absorption retention amount.

  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
JP 2002-105164 A JP-A-61-78819

  However, among the above conventional techniques, in the methods (1) and (2), the obtained flexible polyurethane foam is slightly inferior in water absorption speed, and in the method (3), a water-absorbing substance is blended with the foam raw material. There is a risk of inhibiting foaming. In the method (4), there is a problem of dropping off the impregnated additive. Further, the method (5) has a drawback that the processing cost is high and it is difficult to make the foam inner surface hydrophilic.

  Accordingly, 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 can be easily and inexpensively manufactured. .

  The hydrophilic flexible polyurethane foam of the present invention (invention 1) is characterized by heat-treating a flexible polyurethane foam obtained by foaming a foam raw material containing a polyol and a polyisocyanate.

  The hydrophilic flexible polyurethane foam according to claim 2 is characterized in that, in claim 1, the heat treatment is a hot press treatment.

  The hydrophilic flexible polyurethane foam according to claim 3 is the treatment according to claim 2, wherein the hot press treatment is performed at 120 to 250 ° C., and the flexible polyurethane foam is pressed so that the thickness becomes 1/1 to 1/10. It is characterized by being.

  A hydrophilic flexible polyurethane foam according to a fourth aspect is characterized in that, in any one of the first to third aspects, the polyol contains a hydrophilic polyol.

  The hydrophilic flexible polyurethane foam of claim 5 is characterized in that, in claim 4, the hydrophilic polyol is a polyether polyol having an ethylene oxide content of 20% by weight or less.

  The hydrophilic flexible polyurethane foam according to claim 6 is the flexible polyurethane foam according to any one of claims 1 to 5, wherein the flexible polyurethane foam is obtained by modifying a polyol component and an isocyanate component by a prepolymer method, and the NCO of the obtained prepolymer. It is characterized by being foamed using water at an equivalent ratio of 3 times or more with respect to the group.

  The hydrophilic flexible polyurethane foam according to claim 7 is characterized in that, in any one of claims 1 to 6, the polyol contains a high molecular weight polyol having an average molecular weight of 3000 to 12000 and a low molecular weight polyol having an average molecular weight of 400 to 1000. Features.

  The hydrophilic flexible polyurethane foam according to an eighth aspect is characterized in that the isocyanate index of the foam raw material is 60 to 95 in any one of the first to seventh aspects.

  According to the present invention, by heat-treating the flexible polyurethane foam, a part of the resin surface of the foam can be thermally decomposed, and the surface can be coated with the decomposition product. Since the main component of this decomposition product contains a hydrophilic group and is strongly hydrophilic, the flexible polyurethane foam after heat treatment is a hydrophilic flexible polyurethane excellent in water absorption performance such as water absorption speed, water absorption amount, water absorption retention amount. It becomes a form.

  As this heat treatment, a hot press treatment is preferable. According to the hot press treatment, the entire foam can be hydrophilized, and a hydrophilic flexible polyurethane foam having further excellent water absorption performance can be obtained. This hot press treatment is preferably a treatment of pressing a flexible polyurethane foam at 120 to 250 ° C. so that the thickness thereof is 1/1 to 1/10. Furthermore, it is more preferable that it is a process of pressing so as to be 1/2 to 1/4. In the following, N when the flexible polyurethane foam is pressed so as to have a thickness of 1 / N is referred to as a press magnification.

Moreover, in this invention, the hydrophilic flexible polyurethane foam which was further excellent in water absorption performance can be obtained by employ | adopting the following conditions.
(1) A hydrophilic polyol is used as the polyol. The hydrophilic polyol is preferably a polyether polyol having an ethylene oxide (EO) content of 20% by weight or less.
(2) A polyol component and an isocyanate component are modified by a prepolymer method, and a hydrophilic polyurethane foam is obtained by foaming using water as a foaming agent in an equivalent ratio of 3 times or more with respect to the NCO group of the prepolymer. To manufacture. Thereby, since the resin of a raw material has hydrophilicity, the outstanding water absorption performance is obtained.
(3) When the prepolymer method is used, a high molecular weight polyol having an average molecular weight of 3000 to 12000 and a low molecular weight polyol having an average molecular weight of 400 to 1000 are used in combination as a polyol to form a foam having a fine cell structure. The water absorption is enhanced by the capillary effect of this fine cell.
(4) When carrying out by the one-shot method, by setting the isocyanate index of the foam raw material to a slightly low value of 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. High water absorption is obtained by the OH group.

  Hereinafter, embodiments of the hydrophilic flexible polyurethane foam of the present invention will be described in detail.

  The hydrophilic flexible polyurethane foam of the present invention is obtained by heat-treating a flexible polyurethane foam obtained by foaming a foam raw material containing a polyol and a polyisocyanate.

  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, particularly 0.5 to 5 parts by weight.

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

  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 flexible polyurethane foam according to the present invention is obtained by foaming such a foam raw material. There is no particular limitation on the foaming method, and either the prepolymer method or the one-shot method may be used. As described later, the prepolymer method is adopted to enhance the water absorption performance of the obtained hydrophilic flexible polyurethane foam. You can also.

  The hydrophilic flexible polyurethane foam of the present invention is provided with hydrophilicity by heat-treating such a flexible polyurethane foam. As the heat treatment method, any method that can thermally decompose a part of the cell skeleton surface of the foam may be used, and various methods such as microwave treatment and hot air treatment can be adopted.

  Although the thermal decomposition temperature at the time of heat treatment varies depending on the type of foam, it is usually about 120 to 250 ° C, particularly about 160 to 180 ° C, and particularly preferably around 170 ° C. This is because if the heat treatment temperature is lower than this range, sufficient hydrophilicity cannot be imparted, and if it is high, the resin is completely melted and the cell structure is destroyed.

  As described above, this heat treatment is preferably a hot press treatment from the viewpoint of uniformly treating the entire foam and imparting high water absorption performance. In this case, the hot pressing conditions are 120 to 250 ° C., preferably 150 to 200 ° C., 1 to 10 times, preferably 2 to 4 times, and particularly preferably about 2 times. This is because if the press magnification is too small, a sufficient water absorption effect cannot be obtained, and if it is too large, the space held by the cell structure of the foam becomes small, and the water absorption capacity becomes small.

In the present invention, in the production of the flexible polyurethane foam to be subjected to such heat treatment, the following conditions are adopted, so that the hydrophilic flexible polyurethane is further excellent in water absorption performance such as water absorption rate, water absorption amount, and water absorption retention amount. A form can be obtained.
(1) A hydrophilic polyol is used as the polyol. This hydrophilic polyol is preferably a polyether polyol having an EO content of 20% by weight or less, particularly 5 to 15% by weight. In this case, the ratio of the hydrophilic polyol in the total polyol is preferably 5 to 15% by weight. This is because if the ratio of the hydrophilic polyol is less than this range, a sufficient effect of improving the water absorption performance cannot be obtained, and if it is large, the reaction is greatly inhibited.
(2) When creating a foam by the prepolymer method, a hydrophilic flexible polyurethane foam is produced by using an excess of water in an equivalent ratio of 3 times or more, especially 3 to 10 times the NCO group of the modified prepolymer. To do. In this case, it is preferable to react the isocyanate component with the polyol component so that all of its OH groups are NCO-terminated to obtain a prepolymer, and to react and foam the foam raw material remaining in this prepolymer. In this case, it is more effective to use a hydrophilic polyol as the polyol to be reacted.
(3) When a foam is prepared by the prepolymer method, the foam has a fine cell structure by using a high molecular weight polyol having an average molecular weight of 3000 to 12000 and a low molecular weight polyol having an average molecular weight of 400 to 1000 as a polyol. The water absorption performance can be given by the capillary effect. In this case, the use ratio of the low molecular weight polyol in the polyol component is preferably 30% or more, particularly 40 to 50% by weight. Outside this range, it is difficult to obtain a fine cell structure.
(4) When the foam is prepared by the one-shot method, the isocyanate index of the foam raw material is set to 80 or less, particularly 60 to 95, slightly lower. This is because if the isocyanate index is larger than this range, a sufficient effect cannot be obtained, and if it is smaller, foam foaming becomes difficult. In this case, it is more effective to use a hydrophilic polyol as the polyol to be reacted.

  In particular, by using a polyol containing a hydrophilic polyol and subjecting a flexible polyurethane foam produced by the prepolymer method to hot press treatment in the presence of a large excess of water, water absorption performance such as water absorption speed, water absorption, water absorption retention Can be obtained.

  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]
Polyol 1: Polyether polyol Trade name “Sanix GS3” manufactured by Sanyo Kasei Co., Ltd.
000 "(average molecular weight 3000, hydroxyl value 56)
Polyol 2: Polypropylene polyol Trade name “Actco” manufactured by Mitsui Takeda Chemical Co., Ltd.
32-160 "(average molecular weight 1000, hydroxyl value 160)
Hydrophilic polyol: Polyether polyol Product name “EXENOL82” manufactured by Asahi Glass Co., Ltd.
8 "(average molecular weight 4800, hydroxyl value 34, EO content 15% by weight)
Polyisocyanate: Mixing of 2,4-TDI / 2,6-TDI = 80/20 (weight ratio)
Polyisocyanate Made by Mitsui Takeda Chemical Co., Ltd. Blowing agent: Water Amine-based catalyst: Triethylenediamine Made by Toyo Soda Co., Ltd. Trade name “TOYOCATTF”
Silicone-based surfactant: Product name “SZ1127” manufactured by Japan Unica Company

吸水保持量：上記の吸水させたサンプルをさらに４時間金網上で放置して水を切り、以
下に示す式により、吸水保持量を求めた。

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.
Water absorption: 1 g of sample is precisely weighed, then chopped into 10 mm squares and placed in a beaker. S
Add enough pure water to completely impregnate the sample and prevent the sample from floating
And impregnated for 1 hour. Then leave it on the wire mesh for 30 minutes
The absorption amount was determined by the following formula.

Water absorption retention amount: The above water-absorbed sample was left on the wire mesh for 4 hours to drain the water.
The water absorption retention amount was determined according to the formula shown below.

Examples 1-5, Comparative Examples 1-5
A flexible polyurethane foam was produced by the composition and foaming method shown in Table 1. In Examples 1 to 5, the obtained flexible polyurethane foam was heat-treated by the following method to obtain a sample. In Comparative Examples 1 to 5, the sample was used without any heat treatment.

[Heat treatment method]
The flexible polyurethane foam obtained by foaming with each formulation was cut to a thickness of 20 mm at 200 mm × 200 mm, and this was hot-pressed at 170 ° C. in the thickness direction at a press magnification of 2 times, and a thickness of 10 mm at 200 mm × 200 mm. A sample was obtained.
Among the foaming methods, in the one-shot method, isocyanate was further mixed and foamed in a blend in which raw materials other than polyisocyanate were mixed at a predetermined ratio. In the prepolymer method, a polyisocyanate was reacted with a polyol to modify the prepolymer, and the remaining raw materials were mixed with this prepolymer and foamed.

  From Table 1, it can be seen that according to the present invention, a hydrophilic flexible polyurethane foam excellent in water absorption performance is provided. In particular, in Example 4 in which an excess amount of water was blended by a prepolymer method using a hydrophilic polyol, a highly water-absorbing hydrophilic flexible polyurethane foam excellent in both water absorption and water absorption was obtained. It was.

Claims (8)

  A hydrophilic flexible polyurethane foam obtained by heat-treating a flexible polyurethane foam obtained by foaming a foam raw material containing a polyol and a polyisocyanate.   2. The hydrophilic flexible polyurethane foam according to claim 1, wherein the heat treatment is a hot press treatment.   3. The hydrophilic soft polyurethane according to claim 2, wherein the hot press treatment is a treatment of pressing the flexible polyurethane foam so as to have a thickness of 1/1 to 1/10 at 120 to 250 ° C. Form.   The hydrophilic flexible polyurethane foam according to any one of claims 1 to 3, wherein the polyol contains a hydrophilic polyol.   5. The hydrophilic flexible polyurethane foam according to claim 4, wherein the hydrophilic polyol is a polyether polyol having an ethylene oxide content of 20% by weight or less.   The flexible polyurethane foam according to any one of claims 1 to 5, wherein the flexible polyurethane foam is obtained by modifying a polyol component and an isocyanate component by a prepolymer method, and having an equivalent ratio of 3 times or more with respect to the NCO group of the obtained prepolymer. A hydrophilic flexible polyurethane foam characterized by being foamed with water.   The hydrophilic flexible polyurethane foam according to any one of claims 1 to 6, wherein the polyol contains a high molecular weight polyol having an average molecular weight of 3000 to 12000 and a low molecular weight polyol having an average molecular weight of 400 to 1000.   The hydrophilic flexible polyurethane foam according to any one of claims 1 to 7, wherein an isocyanate index of the foam raw material is 60 to 95.