JP2003268064A - Method for producing hydrophilized open cell polyurethane foam and hydrophilized open cell polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrophilized open cell polyurethane foam suitable as a waste ink-absorbing material, an artificial culture medium for raising seedlings, and the like. <P>SOLUTION: This method for producing the polyurethane foam from a polyisocyanate compound, a hydroxy compound having a polyoxyethylene content of ≥20 wt.%, a foaming agent, a catalyst, and a polydimethylsiloxane- polyoxyalkylene copolymer as essential components, wherein a polydimethylsiloxane-polyoxyalkylene copolymer having a specific structure and a good foam-stabilizing property and a polydimethylsiloxane-polyoxyalkylene copolymer having a specific structure and not having a good foam-stabilizing property are used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to open-celled flexible and semi-rigid polyurethane foams. More specifically, it relates to a hydrophilized open-cell polyurethane foam having improved water absorption.

[0002]

2. Description of the Related Art Conventionally, two techniques have mainly been used for producing a hydrophilic polyurethane foam having open cells. The first technique is a technique in which a molecular structure having hydrophilicity is incorporated into the molecular structure forming the skeleton of polyurethane foam, and the second technique is a hydrophilization technique in which a hydrophilized product is added to the foam. The first technique is to increase the polyoxyalkylene content in the hydroxy compound to be used, or to set the NCO group / OH group index to 100 or less to leave residual OH groups in the molecular structure,
Alternatively, a method of introducing a hydrophilic amino group or a carboxylate group, a sulfonate group, or the like into the molecular structure, or a polydimethylalkylene-polyoxyalkylene copolymer in which the terminal of polyoxyalkylene is a methoxy group is used as a foam stabilizer. It is the technology to use. The second technique relates to a method of foaming by adding a general nonionic, anionic or cationic surfactant having or not reacting with isocyanate to a raw material system at the time of foam foaming. is there. As another method of the second technique, there is a method in which the foam is produced and then immersed in a solution of a surfactant to adhere the surfactant to the surface of cells. Also in this case, a surfactant having or without reactivity can be used as a matter of course. However, even if the above-mentioned first and second techniques and the combination thereof are carried out, a hydrophilic open-cell polyurethane foam capable of easily absorbing water when a water droplet is dropped on the foam surface cannot be obtained.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the rate of water absorption of polyurethane foam. Another purpose is to increase the absorption of water. Another purpose is to increase the ability to retain absorbed water. Another object is to provide a foam that can be used as a waste ink absorber for printers or an artificial medium for raising seedlings.

[0004]

According to the present invention, a polyurethane foam is made hydrophilic by adding a polydimethylsiloxane-polyoxyalkylene copolymer having no special foam-stabilizing property. In the present invention, when a polyurethane foam is produced using a polyisocyanate compound, a hydroxy compound, a foaming agent, a catalyst, and a polydimethylsiloxane-polyoxyalkylene copolymer as essential components, the following two types of polydimethylsiloxane-polyoxyalkylene copolymers are used. By using the combined use, it is possible to achieve the production of a hydrophilized open-cell polyurethane foam. (1) The polyoxyalkylene terminal of the polydimethylsiloxane-polyoxyalkylene copolymer has a C _{1 to} C ₄ alkoxy group and / or an aliphatic acyloxy group, and the polyoxyalkylene chain has a number average molecular weight of 900 or more. A polydimethylsiloxane-polyoxyalkylene copolymer having a foam-regulating property, wherein the polyoxyethylene content in the polyoxyalkylene is 50% by weight or more. (2) The polyoxyalkylene terminal of the polydimethylsiloxane-polyoxyalkylene copolymer has a C _{1 to} C ₄ alkoxy group and / or acetoxy group, and the polyoxyalkylene chain has a number average molecular weight of less than 800 and ethylene. Oxide content is 60 in total oxyalkylene
A polydimethylsiloxane-polyoxyalkylene copolymer having a foam control property of not less than wt%.

The silicone type foam stabilizer used in the polyurethane foam of the present invention has a polyoxyalkylene terminal having a C _{1 to} C ₄ alkyloxy group and / or an aliphatic acyloxy group, and the polyoxyalkylene chain has a number average molecular weight. Therefore, it is necessary to use a polydimethylsiloxane-polyoxyalkylene copolymer having a polyoxyethylene content of 900 or more and a polyoxyethylene content in the polyoxyalkylene of 50% by weight or more. In the case of a compound having a polyoxyalkylene terminal having other groups that react with isocyanates such as a hydroxyl group, an amino group and an epoxy group, for example, the polyoxyalkylene terminal of the polydimethylsiloxane-polyoxyalkylene copolymer is C _{1 to} C ₄ alkyloxy group and / or acetoxy group, polyoxyalkylene chain having a number average molecular weight of less than 800, and ethylene oxide content of 60% by weight or more based on the total oxyalkylene and having no foam-stabilizing property. Even if the dimethylsiloxane-polyoxyalkylene copolymer is used in combination, a hydrophilized open-cell polyurethane foam cannot be obtained. The typical polydimethylsiloxane-polyoxyalkylene copolymer having foam control used in the present invention is as follows. (In the formula, R is CH ₃ , C ₂ H ₅ , CH ₃ CO, m is an integer of 8 or more, n is an integer of 1 or more, a is an integer of 4 or more, and b is an integer of 1 or more) (In the formula, R is CH ₃ , C ₂ H ₅ C, CH ₃ CO, m is an integer of 8 or more, a is an integer of 4 or more, and b is an integer of 1 or more)

As the proportion of oxyethylene content in the total polyoxyalkylene of the polydimethylsiloxane-polyoxyalkylene copolymer having the foam-controlling property of the present invention increases, the foam is generally continuous although it depends on the formulation. It is possible to form air bubbles and at the same time improve water absorption and water retention. The preferable oxyethylene content is 50% by weight or more, and particularly preferably 60% by weight or more and 90% by weight or less, based on the polyoxyalkylene. The ratio of polyoxyethylene is 90 relative to polyoxyalkylene.
When the content is more than 100%, the polydimethylsiloxane-polyoxyalkylene copolymer becomes solid and becomes difficult to handle, and the water absorption rate at low temperature tends to decrease. The length of the oxyalkylene chain of the polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property of the present invention is generally preferably 900 to 4000 in number average, and particularly preferably 1
000-3000. Oxyalkylene chain is 900
If the amount is less than the above, the foam-stabilizing property is low, that is, coarse bubbles are formed or the bubbles are completely collapsed. If the oxyalkylene chain is 4000 or more, it becomes difficult to obtain a normal foam. The amount of the polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property used in the present invention is 0.7 to 20 parts by weight, preferably 1.5 to 10 parts by weight, based on 100 parts by weight of the polyol.

The non-foaming polydimethylsiloxane-polyoxyalkylene copolymer of the present invention has a polyoxyalkylene terminal having a C _{1 to} C ₄ alkoxy group or acetoxy group, and has a polyoxyalkylene chain length. Is less than 800 on average, preferably 700 or less. When the polyoxyalkylene chain has an average of 800 or more, it has a foam-controlling property and has no hydrophilizing ability. The length of the polydimethyloxyalkylene chain varies depending on the polyol used and the polyisocyanate used. The oxyethylene content in the polydimethylsiloxane-polyoxyalkylene copolymer having no foam control used in the present invention is 60 to 100%, preferably 70 to 100% based on the total polyoxyalkylene. As the proportion of oxyethylene in the total polyoxyalkylene chain decreases, it becomes difficult to form open cells and the hydrophilicity decreases. A typical structure example is as follows. (In the formula, R is CH ₃ , C ₂ H ₅ , CH ₃ CO, m is an integer of 1 or more, n is an integer of 1 or more, a is an integer of 1 or more, and b is 0.
Or an integer of 1 or more) (In the formula, R is CH ₃ , C ₂ H ₅ C, CH ₃ CO, m is an integer of 1 or more, a is an integer of 1 or more, and b is 0 or an integer of 1 or more)

Further details will be described in order to carry out the present invention. The polyisocyanate used in the present invention may be a polyisocyanate compound generally used industrially, for example, polymethylene polyphenylene polyisocyanate, 4.4'-diphenylmethane diisocyanate, crude polymethylene polyphenylene polyisocyanate, 2.4 tolylene diisocyanate. Isocyanate, 2.6 tolylene diisocyanate, 2.4 / 2.6 isomer mixed tolylene diisocyanate, crude tolylene diisocyanate,
There are 1.5 naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and modified products thereof, but aromatic polyisocyanates are industrially preferable, and tolylene diisocyanate (T-80, T-65) polymethylene polyphenylene is more preferable. Polyisocyanates as well as crude polymethylene polyphenylene polyisocyanates. These polyisocyanates can be used alone or with various modifications such as carbodiimide modification and / or urethane modification and / or urea modification and / or allophanate modification and / or isocyanurate modification.

The polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property defined in the present invention is a foam-controlling agent having a foam-controlling ability capable of producing a foam having normal cells when used alone. Yes, a polydimethylsiloxane-polyoxyalkylene copolymer having no foam-stabilizing property refers to one having no foam-stabilizing ability that becomes coarse cells that do not become fine cells even if the foam collapses or does not collapse when used alone. .

The hydroxy compound having a polyoxyethylene content of 20% by weight or more used in the present invention is a polyether and / or polyester polyol having an average functional group of 2.0 or more. The former preferably has an average number of functional groups of 2.0 to 5.0 and a number average molecular weight of 20,000 or less. Particularly preferred hydroxy compounds have an average number of functional groups of 2.0 to 4.0 and a molecular weight of 500 to 1000.
0 and the oxyethylene content is 50 to 90% by weight. When the oxyethylene content is 90% by weight or more, crystallization occurs at room temperature and it is difficult to handle. Examples of the hydroxy compound having an oxyethylene content of 50% by weight or more that can be used in the present invention include polyhydric alcohols, hydroxyl group-containing amine compounds, polyvalent amino compounds, polyvalent organic carboxylic acids and the like, ethylene oxide, propylene oxide and the like. There are polyethers obtained by addition-polymerizing alkylene oxide of, and more specific examples are water, glycerin, trimethylolpropane, pentaerythritol, sorbitol,
There are those obtained by addition-polymerizing alkylene oxide such as ethylene oxide with monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, tolylenediamine and the like. Further, low molecular weight hydroxy compounds, for example, low molecular weight polyols such as glycerin, trimethylolpropane, diethylene glycol and dipropylene glycol can be used, in which case the average oxyethylene content is 20% by weight or more, preferably 50%.
It is preferable to mix and blend it so as to be in the range of 90%. When the oxyethylene content is 20% by weight or less of the hydroxy compound, the above-mentioned polydimethylsiloxane-polyoxyalkylene copolymer having no foam-stabilizing property is the above-mentioned polydimethylsiloxane-polyoxyalkylene copolymer having foam-stabilizing property. The foam cannot be made hydrophilic even when it is used together. In order to obtain a particularly excellent hydrophilic open-cell polyurethane foam, the oxyethylene content in the polyhydroxy compound is preferably 50% by weight or more. Polyester polyols can also be used in the present invention. In that case, the content of ethylene oxide in all hydroxy compounds must be 50% by weight or more. The polyester polyol has an average number of functional groups of 2 to 4,
It has a molecular weight of 10,000 or less, and can be added to polycarboxylic acids such as adipic acid with ethylene glycol, propylene glycol,
The polyester polyol obtained by reacting a polyfunctional hydroxyl group-containing compound such as diethylene glycol, glycerin, and trimethylolpropane, the polyester obtained by ring-opening polymerization of caprolactone, and the like are preferable, and the polycarboxylic acid is preferably an aliphatic dicarboxylic acid.

In carrying out the present invention, even a one-shot method for producing a polyurethane foam from a general polyol and polyisocyanate is a prepolymer method in which a polyol and a polyisocyanate are reacted in advance to obtain a prepolymer having a terminal NCO group. Even if there is, you can achieve the purpose. Alternatively, a prepolymer method may be used in which a polyol and a polyisocyanate are reacted in advance to form a prepolymer having a terminal OH group, and the prepolymer is reacted with the polyisocyanate. Further, the molding foam may be a block foam, a mold foam, or any other foam. As the polyurethane-forming catalyst that can be used in the present invention, any known polyurethane-forming catalyst or isocyanurate catalyst can be used. Polyurethane catalysts include tertiary amines such as triethylenediamine, dimethylethanolamine and tetramethylpropylenediamine, or organometallic compounds such as tin octoate and dibutyltin dilaurate, or potassium acetate, sodium acetate, potassium octylate, sodium octylate, There are isocyanurate catalysts such as NN′N ″ -tris (3-dimethylaminopropyl) hexahydro-S-triazine and potassium alcoholate.

Since the hydrophilized polyurethane foam of the present invention has a high water absorption rate, a large water absorption amount, and a large holding power, it can be used as a material that needs to absorb and retain water. Specifically, it is suitable as a waste ink absorbent for printers, artificial media for raising seedlings, concrete drying prevention material, cleaning material for window glass, cosmetic puffs, hydroponic support, etc. Alternatively, it is preferable as an artificial medium for raising seedlings.

As the foaming agent used in the present invention, all the commonly used foaming agents can be used, but water is preferable. As the blowing agent other than water, a low boiling point solvent or gas such as pentane-hexane, cyclopentane, cyclohexane, dichloromethane, 1,1-dichloro-1-fluoroethane, CO ₂ gas, liquid CO ₂ , supercritical CO ₂ gas, etc. It can be used.

As the other additives that can be used in the present invention, all of the commonly used additives can be used, and general surfactants, inorganic or organic fillers, pigments, antioxidants, UV protection agents and the like can be used. is there. Particularly preferred as the hydrophilicizing aid are commonly used surfactants.
As the specific surfactant, all of anionic type, cationic type, and zwitterionic type can be used, but anionic type is preferable. For example, sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium alkyldiphenyletherdisulfonate, etc. can be added. . Examples of the inorganic filler include calcium carbonate, barium sulfate, clay, bentonite and the like, and other organic fillers include a water absorbent resin and the like. Specific examples of the water absorbent resin include crosslinked polyacrylic acid salt, isobutylene-maleic acid salt,
Starch polyacrylate, high molecular weight polyethylene oxide and the like.

[0015]

The present invention relates to a hydrophilized open-cell polyurethane foam having a large water-absorption rate and a large water-absorption amount and a large water-retaining capacity. In producing an open-cell polyurethane foam, the following two types of polydimethylsiloxane-polyoxyalkylene It is characterized in that it is used in combination with a polymer. The first polydimethylsiloxane-polyoxyalkylene copolymer is a foam stabilizer having a foam-controlling property, and is a known one which has been conventionally used for polyurethane foam. The second polydimethylsiloxane-polyoxyalkylene copolymer is a polydimethylsiloxane-polyoxyalkylene copolymer having a specific structure, which is completely different from the conventionally used foam-controlling property and has no foam-controlling property. . Conventionally, there are many cases where two kinds of silicone type foam stabilizers having a foam regulating property are used together, but a polydimethylsiloxane-polyoxyalkylene copolymer having no foam regulating property is not used together. This first,
By using the second polydimethylsiloxane-polyoxyalkylene copolymer in combination, the following effects occur. (1) The water absorption speed becomes faster. (2) The amount of water absorption increases. (3) The water retention is increased.

The polyurethane foam of the present invention does not react with a hydrophilic polydimethylsiloxane-polyoxyalkylene copolymer having a non-foaming property other than the conventional polydimethylsiloxane-polyoxyalkylene copolymer having a foaming property. Contained in. The hydrophilic polydimethylsiloxane-polyoxyalkylene copolymer having a low surface tension and having no foam-controlling property acts as a nonionic surfactant after foaming, and as a result, the surface of the cell ribs is made hydrophilic to cause capillary action. It is presumed that this will accelerate the hydrophilization and improve the water absorption rate, water absorption amount, and water retention.

[0017]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. In the following description, a polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property is referred to as "silicon having a foam-controlling property". A polydimethylsiloxane polyoxyalkylene copolymer having no foam-controlling property is referred to as a "foam-controlling property." There is no silicon ". The raw materials used in Examples and Comparative Examples are as follows. polyol-1: trifunctional polyether polyol having a molecular weight of 3300 obtained by addition-polymerizing ethylene oxide and propylene oxide at a weight ratio of 79/21 to glycerin polyol-2: having a molecular weight of 3,000 obtained by addition-polymerizing propylene oxide alone to glycerin. Trifunctional polyether polyol Silicone-1: a polydimethylsiloxane-polyoxyalkylene copolymer having a structure having a structure of (Formula 1). The weight ratio of ethylene oxide / propylene oxide in the polyoxyalkylene chain is 58/4.
2, m / n = 32/5, R = CH ₃ , MW = 2900
(Silicone Having Foam Controlling Property) Silicone-2: a polydimethylsiloxane-polyoxyalkylene copolymer having a foam controlling property having a structure of Chemical Formula 1. The weight ratio of the polyoxyalkylene chain to ethylene oxide is 65/35, m / n = 30/4, R
= _CH 3, MW = 2400 (silicon having a foam properties) Silicone-3 :(-expression 3) foam having no polydimethylsiloxane having the structure of - polyoxyalkylene copolymer. All polyoxyalkylene chains are polyethylene oxide, m / n = 18/15, R = CH ₃ , M
W = 440 (silicon without foam control) Silicone-4: polydimethylsiloxane-polyoxyalkylene copolymer having foam control. Weight ratio of ethylene oxide / propylene oxide of polyoxyalkylene chain = 60/40, terminal OH group (silicon having a foaming property) DABCO 33-LV: Sankyo Air Products triethylenediamine glycol liquid NCX-135: Sankyo Air Products NN'N "-tris (3-dimethylaminopropyl) hexahydro S-triazine DABCO T-9: Sankyo Air Products Stannas Octoate TDI-80: Mitsui Takeda Chemical Tolylene Diisocyanate PAPI-135: Dow Polyurethane Japan Co., Ltd. crude polymethylene polyphenylene diisocyanate prepolymer 1: trifunctional polyol with a molecular weight of 3200 obtained by addition-polymerizing ethylene oxide / propylene oxide at a weight ratio of 70/30 to glycerin. And 10% N reacted with tolylene diisocyanate (T-80)
CO prepolymer

The methods for measuring the physical properties of the polyurethane foams of Examples and Comparative Examples are as follows. Water absorption time (sec): One drop of pure water was dropped from a syringe equipped with a needle of needle standard 22G × 1 1/4 ”(manufactured by Nipro Co., Ltd.), and the time until the drop was completely absorbed by the foam. g): 50 mm length x 50 mm width x 40 mm height
The foam was floated on the water surface at 23 ° C. with the height surface of 40 mm vertical, and after 5 minutes, the foam was pulled up and the weight was measured. Water retention rate (%): 30% for the foam whose water absorption (A) was measured
The weight (B) is measured 24 hours after it is placed on a wire net of ° and is calculated by the following formula.

Table 1 shows the compounding formulations of Examples 1 to 5 and Table 2 shows the physical properties thereof. In Examples 1 to 5, the water absorption time, the water absorption amount, and the water retention rate were good. The high water absorption in Examples 2 to 5 is due to the swelling of the foam.

[0021]

[0022]

The polyurethane foams of Examples 2, 4 and 5 were cut into a length of 30 mm × a width of 30 mm × 35 mm, a hole having a diameter of 8 mm was opened from the central upper surface to a position of 10 mm, and further, a lower surface thereof was cut to a position of 5 mm from the lower surface. Diameter 1.
A 0 mm hole was drilled. The foam was immersed horizontally and then pulled up, and 13 leaf leek seeds were placed in the center hole.
3 times once a day after sprinkling water on this foam every day for germination
As a result of soaking in water for 0 minutes, good growth was confirmed.

The polyurethane foam of Example 3 was made to have a thickness of 1
It was cut into 0 mm x 20 mm x 20 mm length. 2 cc of waste ink for printers was continuously dropped onto this 10 mm thick sheet from a syringe equipped with a needle with a nip needle standard of 22G × 1 1/4 ″, but did not drop from the lower surface.

The compounding recipes of Comparative Examples 1 to 4 are shown in Table 3 and the physical properties are shown in Table 4. The foams of Comparative Examples 1 to 4 were not absorbed at all within the measurement time of 5 minutes even if water droplets were dropped with a syringe. Comparative Examples 1 and 2 are easily water-free unless a polydimethylsiloxane-polyoxyalkylene copolymer of (Chemical Formula 3) and (Chemical Formula 4), which has no foam-stabilizing property even if the proportion of ethylene oxide in the polyol is large, is used. Does not absorb.
In Comparative Example 3, even if the polydimethylsiloxane-polyoxyalkylene copolymer of Chemical formula 3 is used, the hydrophilization cannot be achieved when the polyoxyalkylene content in the hydroxy compound is 20% by weight or less. Comparative Example 4 is a polydimethylsiloxane having a foam-controlling property, even if the polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property and the polydimethylsiloxane-polyoxyalkylene copolymer of the chemical formula 3 are used together. Since the oxyalkylene terminal of the polyoxyalkylene copolymer was an OH group, no water was absorbed.

[0026]

[0027]

[0028]

INDUSTRIAL APPLICABILITY In the present invention, a polydimethylsiloxane-polyoxyalkylene copolymer having a foam-controlling property and a polydimethylsiloxane-polyoxyalkylene copolymer having a specific structure and having no foam-controlling property are used in combination. Hydrophilization can be achieved by. In particular, the water absorption rate, the water absorption amount, and the water retention property can be significantly improved. The hydrophilized open-cell polyurethane foam of the present invention is effective as a waste ink absorbent such as a jet printer or an artificial culture medium for raising seedlings.

Claims (4)

[Claims] 1. A polyisocyanate compound, a hydroxy compound having a polyoxyethylene content of 20% by weight or more,
A polyurethane foam produced by using a foaming agent, a catalyst, and a polydimethylsiloxane-polyoxyalkylene copolymer as essential components, the hydrophilic foamed continuous cells containing the following two types of the polydimethylsiloxane-polyoxyalkylene copolymer. Polyurethane foam. (1) The polyoxyalkylene terminal has a C _{1 to} C ₄ alkoxy group and / or an aliphatic acyloxy group, and the polyoxyalkylene chain has a number average molecular weight of 900 or more, and contains polyoxyethylene in the polyoxyalkylene. Polydimethylsiloxane-polyoxyalkylene copolymer in an amount of 50% by weight or more. (2) The polyoxyalkylene terminal has a C _{1 to} C ₄ alkoxy group and / or an acetoxy group, the polyoxyalkylene chain has a number average molecular weight of less than 800, and the ethylene oxide content is 60 of the total oxyalkylene. weight%
The above polydimethylsiloxane-polyoxaalkylene copolymer. 2. The hydrophilized open-cell polyurethane foam according to claim 1, wherein the content of polyoxyethylene in the hydroxy compound is 50% by weight or more. 3. In producing a polyurethane foam using a polyisocyanate compound, a hydroxy compound having a polyoxyethylene content of 20% by weight or more, a catalyst and a polydimethylsiloxane-polyoxyalkylene copolymer as essential components, the following 2 A method for producing a hydrophilized open-cell polyurethane foam, which comprises using two or more kinds of the polydimethylsiloxane-polyoxyalkylene copolymer in combination. (1) The polyoxyalkylene terminal has a C _{1 to} C ₄ alkoxy group and / or an aliphatic acyloxy group, and the polyoxyalkylene chain has a number average molecular weight of 900 or more, and contains polyoxyethylene in the polyoxyalkylene. A polydimethylsiloxane-polyoxyalkylene copolymer having an amount of 50% by weight or more and having a foam stabilizing property. (2) The polyoxyalkylene terminal has a C _{1 to} C ₄ alkoxy group and / or acetoxy group, the polyoxyalkylene chain has a number average molecular weight of less than 800, and the ethylene oxide content is 60% of the total polyoxyalkylene.
A polydimethylsiloxane-polyoxyalkylene copolymer having a foam control property of not less than wt%. 4. The hydrophilized open-cell polyurethane foam according to claim 1, wherein the foam is used as a waste ink absorber or an artificial medium for raising seedlings.