JPH02140216A - Production of water absorbing polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain the subject foam, having elasticity, excellent in absorbing and holding performance for aqueous liquids and useful as disposable diapers, etc., by blending a polyether polyol with polyethylene glycol in a specific proportion. CONSTITUTION:(A) A polyether polyol having an average molecular weight within the range of 1500-15000 and 40-90wt.% content of polyoxyethylene units and (B) a polyol, consisting of polyethylene glycol having an average molecular weight within the range of 300-12000 at a weight ratio of the components (A) to (B) within the range of (85:15)-(15:85) are used as a polyol to provide the objective foam by a one-shot method. Furthermore, a bifunctional polyether polyol is preferably used as the component (A).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing water-absorbing polyurethane foam, and more specifically, to a foam that has elasticity and has an ability to absorb and retain water-based liquids. The present invention relates to a method for producing water-absorbing polyurethane foam with excellent properties.

[Problems to be solved by conventional techniques and inventions] Conventionally,
Proposed methods for producing hydrophilic polyurethane foams that have water absorption and water retention properties include adding a water-absorbing resin to flexible polyurethane foam, and using polyols with specific hydrophilic groups. However, these methods have the following problems. For example, the method of adding a water-absorbing resin has the disadvantage that since the water-absorbing resin is a solid, it is difficult to uniformly disperse it in the foam, resulting in a lack of uniformity and the formation of parts with poor hydrophilicity. Ta. Furthermore, it has the disadvantage that the added water-absorbing resin is detached during water absorption and swelling.

Next, as a method using the prepolymer method, JP-A-49-6
The method disclosed in Publication No. 9794 uses a prepolymer made by reacting a bifunctional or higher-functional polyoxyethylene polyol with an organic polyisocyanate, but since a large amount of water is used, many urea bonds are formed, resulting in hydrophilicity. Hydrophilic polyurethane foam with high absorption capacity could not be obtained because the properties were inhibited. Furthermore, the prepolymer method requires complicated steps and is disadvantageous from an economic standpoint.

Furthermore, regarding the one-shot method, see Japanese Patent Publication No. 516316, Japanese Patent Application Laid-open No. 56-43247, and Japanese Patent Application Laid-open No. 59646.
All of them are excellent as hydrophilic polyurethane foams and have some moisture absorption performance, but their liquid absorption performance is low and they are insufficient as water-absorbing polyurethane foams. Met.

Furthermore, if the ethylene oxide content of the polyol component is increased to 50% by weight or more for the purpose of increasing absorption, the foaming ratio will also increase to 1.
0 times, and the polyurethane foam obtained using this shrinks in size by about 15% or more over time, so the use of special foam stabilizers, foam stabilizers, and foam shrinkage inhibitors is essential. It had become.

[Means to solve the problem]

In order to solve these problems in the conventional technology, the present inventors have made extensive studies and found that a film with uniformity and good dimensional stability can be produced without using special foam stabilizers, foam stabilizers, foam shrinkage inhibitors, etc. Polyurethane foam was obtained, and the present invention was completed by discovering a method for providing water-absorbing polyurethane foam that has elasticity and extremely high water-absorbing performance.

That is, in producing polyurethane foam using polyol and organic polyisocyanate as essential components, the present invention provides polyurethane foam having an average molecular weight of 1,500 as the polyol.
Consisting of polyether polyol (I) having a polyoxyethylene unit content of 40 to 90% by weight in the range of 15,000 to 15,000, and polyethylene glycol (II) having an average molecular weight of 300 to 12,000, and the weight ratio of polyether polyol (I) to polyethylene glycol (II) is 85:15 to 15:
The present invention provides a method for producing water-absorbing polyurethane foam, characterized in that it is produced by a one-shot method using a polyol in the range of 85%.

The polyether polyol (I) used in the present invention is:
It can be obtained by reacting ethylene oxide and other epoxides with various polyols as an initiator.
Examples of initiators include diols such as evapoethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and hexylene glycol, glycerin, trimethylolpropane,
Triols such as trimethylolethane and hexanetriol are mentioned.

The initiator may be, for example, a mixed initiator of diols and triols, or a single initiator. In particular, it is preferable to use only diols that provide a bifunctional polyether polyol because the water absorption performance is excellent.

Other epoxides used in combination with ethylene oxide include propylene oxide, butylene oxide, and the like. Furthermore, the polymerization of ethylene oxide and other epoxides may be either random copolymerization or block copolymerization.

In the present invention, polyether polyols (I) having an average molecular weight of 1,500 to 15,000 can be used. More preferably 4,000 to 12,000
is within the range of If a foam with an average molecular weight of less than 1,500 is used, the resulting foam will have poor absorption performance and is not suitable for the purpose of the present invention.

Furthermore, when using a polyol with an average molecular weight exceeding 15,000, it is not only difficult to handle due to its high viscosity when melted, but also has poor foaming stability and low mechanical strength of the finished foam, making it impractical. It becomes something lacking.

In the present invention, the content of polyoxyethylene units in polyether polyol (I) is 40 to 90% by weight, more preferably 50 to 80% by weight. 40
If the amount is less than % by weight, the resulting foam will have poor foaming stability and poor absorption performance. If the content of polyoxyethylene units exceeds 90% by weight, the foaming stability will be poor and the mechanical strength during absorption and swelling will be extremely low.

The polyethylene glycol (n) used in the present invention is
Those having an average molecular weight in the range of 300 to 12,000 can be used, and more preferably in the range of 400 to 9,000. When the average molecular weight is less than 300, the foaming stability is poor and the absorption performance is also poor, while when the average molecular weight is over 12,000, the viscosity when melted is high and it becomes easy to solidify, making it difficult to handle. Otherwise, the foaming stability is poor and the mechanical strength of the foam is low, making it impractical.

The present invention uses polyether polyol (I) and polyethylene glycol (II) together as polyol components, and the weight ratio of polyether polyol (I) to polyethylene glycol (II) is 85:
15 to 15:85, preferably 8
It is used in the range of 0:20 to 20:80.

If the polyether polyol (I) is less than 15 parts, the mechanical strength after absorption and swelling is low, and if the polyether polyol (I) is more than 85 parts, the foaming stability is poor, resulting in poor foam uniformity. It is undesirable because it lacks properties and shrinks.

In the present invention, the above-mentioned polyol component and organic polyisocyanate 1- are essential components, but in addition, crosslinking agents, foam stabilizers, antifoaming agents, catalysts, blowing agents, etc. are generally used in the production of flexible polyurethane foam. You can use as appropriate.

Examples of the organic polyisocyanate include 2,4-isomer and 2,6-isomer of toluene diisocyanate-1- or a mixture thereof, diphenylmethane diisocyanate-1, xylylene diisocyanate, knuck diisocyanate,
Hexamethylene diisocyanes 1 to 1 are used.

The crosslinking agent is preferably polyfunctional and reacts with isocyanate groups, and is added as necessary. For example, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, glycerin, trimethylolpropane, ethylene oxide adduct of trimethylolpropane, 2,4,6-1-lyaminotoluene, ethylenediamine, trimethylenediamine, tetra methylene diamine, pentamethylene diamine,
ethanolamine, jetanolamine, hydrazine,
Triethanolamine etc. are used.

As the foam stabilizer, silicone foam stabilizers such as polyoxyalkylene siloxane copolymers, or surfactants such as sulfonated products of ethylene oxide and/or propylene oxide adducts of various fatty acids are used.

As the antifoaming agent, silicone antifoaming agents, surfactants, and the like are used.

As the catalyst, an amine catalyst, an organic metal catalyst, an alkali catalyst, etc. are used.

As the blowing agent, water or a low-boiling halogenated hydrocarbon can be used alone or in combination.

Furthermore, inorganic/organic fillers, coloring agents such as pigments, preservatives, fragrances, and other auxiliary agents can be added as necessary.

In addition, various surfactants and inorganic substances such as sodium silicate, calcium carbonate, and tricalcium phosphate are added to increase the wettability of the obtained water-absorbing polyurethane foam with the absorbed liquid and to improve the initial absorption rate. The addition of is also effective.

In the present invention, the foaming stability is good by using the above-mentioned raw materials and manufacturing by the one-shot method.
A water-absorbing polyurethane foam with high absorbency and retention performance is obtained.

In addition, there is no change in mechanical strength during absorption and swelling, and there is no change in collapse or the like even when immersed in water for a long time.

Although it is also possible to produce polyurethane foam by a prepolymer method using the polyol component of the present invention, it is not preferred because it has disadvantages such as complicated steps.

Even after absorbing water and swelling, the water-absorbing polyurethane foam obtained by the production method of the present invention returns to its original state by drying and can be reused. Moreover, in the present invention,
Furthermore, polyacrylate-based, polyethylene oxide-based,
Conventionally known water-absorbing resins such as polyvinyl alcohol type and carboxymethyl cellulose type can also be combined.

〔Effect of the invention〕

The elastic water-absorbing polyurethane foam according to the present invention can be used in toys, as well as in conventional hydrophilic polyurethane foams.
In addition to being used for cosmetic tools, cleaning tools, etc., sanitary and medical supplies such as sanitary napkins and disposable diapers, which require higher absorption performance, as well as freshness-preserving agents, water-retaining agents, and moisturizing agents for vegetables, etc. It can be suitably used in applications where absorption of liquid and retention of the absorbed liquid is required, such as in the agricultural and forestry field such as components, in the food packaging field such as drip-absorbing sheets, and household goods such as wipers.

〔Example〕

Hereinafter, the manufacturing method of the present invention will be specifically explained using Examples. The amount of each component used in the reaction mixture is expressed in parts by weight, with the polyol component being 100.

Examples 1-27. Comparative Examples 1 to 9 The following crosslinking agents, catalysts, blowing agents, antifoaming agents, foam stabilizers, surfactants, fillers, etc. as shown in Tables 1 to 7 were added to the various polyols shown below. In addition, 1
Stir at high speed for 5 seconds.

After that, organic polyisocyanate (TDI, Sumidur T-80 manufactured by Sumitomo Bayer Urethane) was prepared from Table 1.
After adding the amount shown in 7 and stirring/mixing: When left to stand,
It foamed and gelled in a few minutes. After gelation, the reaction was completed by leaving the mixture in a 50°C warmer for 20 minutes.

For the polyurethane foam obtained by such a one-shot method, foaming stability, foam density, absorption amount, absorption retention amount, absorption rate, volumetric swelling rate, and water absorption time were measured using the following evaluation methods.

The results are shown in Tables 1-7.

In Tables 1 to 7, IJCQ 1ndex indicates the ratio (%) of polyisocyanate actually used with respect to the theoretical amount of polyisocyanate required for reaction with the active hydrogen compound in the reaction mixture.

<Polyol used> Note) *1 Ethylene oxide/propylene oxide block polymer *2 Random-L-2, -3: Using ethylene glycol as an initiator, ethylene oxide (EO
) and propylene oxide (PO) in a predetermined amount.

<Crosslinking agent used> DEA Nitriethanolamine, Wako Pure Chemical Industries Ltd. TE8 Nitriethanolamine, Wako Pure Chemical Industries Ltd. Glycerin: Wako Pure Chemical Industries Ltd. TMP-30: ) Limethylolpropane E0 30 mole adduct Catalyst used> Kaolizer No. 1: manufactured by Kao ■, tetramethylhexamethylenediaminesufnus octoate: manufactured by Wako Pure Chemical Industries ■Triethylenediamine: manufactured by Wako Pure Chemical Industries ■<Defoamer used> SH200: Viscosity 100cs (25°C) Dimethylpolysiloxane, made by Toray Silicone■ <Foam stabilizer used><Surfactantused> Active agent A: Methyl capped product of 6 mole adduct of nilauryl alcohol EO Active agent B: Sorbicun fatty acid ester EO Adduct (filler used): Calcium carbonate manufactured by Nikatayama Chemical Industry ■, average particle size 10μ Calcium silicate: manufactured by Katayama Chemical Industry ■, average particle size 3μ Form evaluation method> 8. Absorption amount Dry 5mm thick After accurately weighing 1 g of the test piece, 10
Cut into 10mm square pieces and place in a 300ml beaker. 100 m of physiological saline was added, and the foam was forcibly immersed with a wire mesh to prevent it from floating, and left for 30 minutes. After that, 8
The foam was left on a 0-mesh wire net for 5 hours to drain the water, and the weight of the foam was measured. The amount of absorption was determined using the formula shown below.

W.

-0: Weight of the polyurethane foam when dry (g) W,: Weight of the polyurethane foam after absorption (g) B, Absorption/retention amount The polyurethane foam after absorption used for evaluation of absorption amount was centrifuged 1, Dehydrate at 500 rpm for 5 minutes,
The foam weight after dehydration was measured. The amount of absorption and retention was calculated using the formula shown below.

weak. : Weight of polyurethane foam when dry (g) -2: Weight of polyurethane foam after dehydration (g) C0 absorption rate The absorption rate of physiological saline is measured using the apparatus shown in FIG.

Set the measuring table 2 at the same level as the liquid level of the physiological saline 7 in the buret 1, place the filter paper 4 (No. 2) on the glass filter 3 (No. 1) with a diameter of 70 mm in the measuring table 2, and test. Piece 5 (5 mm thick, 0.6 g, circular) was placed on it, load 6 (385 g) was placed on it immediately, and then it was left for 10 minutes. The amount of physiological saline absorbed during this period was expressed as absorption rate.

D. Volumetric swelling rate A dried 30x30x5mm test piece was placed in physiological saline for 3 minutes.
After immersion for 0 minutes, the volume was measured and the ratio to the volume of the original test piece was expressed as a magnification.

E. Water absorption time: Place the dried 30 x 30 x 5 mm test piece horizontally.
-Drop physiological saline onto the foam surface. The time required for complete absorption of saline on the foam surface is expressed in seconds.

F. Foaming stability O: After the reaction is completed under the one-shot manufacturing conditions, almost no shrinkage is observed even if the product is left at room temperature.

Δ: Shrinkage rate is 5 to 30%.

×: Shrinkage rate is 30% or more.

As is clear from Tables 1 to 7, the polyurethane foams obtained in the examples of the present invention had elasticity and excellent absorption and retention properties.

On the other hand, the foam obtained in the comparative example had poor foaming stability, poor elasticity, and poor absorption performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an absorption rate measuring device. 1 Buret 2 Measurement stand 3 Glass filter 4 Filter paper 5 Test piece 6 Load 7 Physiological saline Applicant's agent Kaoru Furutani

Claims (1)

[Claims] 1. In producing polyurethane foam using polyol and organic polyisocyanate as essential components, the polyol has an average molecular weight of 1,500 to 15,00.
a polyether polyol (I) having a polyoxyethylene unit content of 40 to 90% by weight in the range of 0;
A polyol consisting of polyethylene glycol (II) having an average molecular weight in the range of 300 to 12,000, and in which the weight ratio of polyether polyol (I) to polyethylene glycol (II) is in the range of 85:15 to 15:85. A method for producing water-absorbing polyurethane foam, characterized in that it is produced by a one-shot method. 2. The method for producing a water-absorbing polyurethane foam according to claim 1, wherein the polyether polyol (I) is a bifunctional polyether polyol.