JPH03203921A - Water absorbing polyurethane foam and cold reservoir - Google Patents

Abstract

PURPOSE:To obtain the subject new foam having a high rate of water absorption, free from volume increase after water absorption and capable of providing a cold reservoir excellent in water retention, etc., by dispersing a water absorbing resin in an open cell-containing polyurethane foam prepared by using a special polyol component. CONSTITUTION:An objective foam obtained by dispersing a water absorbing resin powder in an open cell-containing polyurethane foam prepared by a reaction between (A) a polyol having 2-3 average number of functional groups, 10-50wt.% oxyethylene group content and 300-10000 average molecular weight and (B) a polyisocyanate. The component (A) is recommendably obtained by addition polymerization of an alkylene oxide to a diol such as ethylene glycol or a polyvalent alcohol such as glycerin in general. As the above-mentioned water absorbing resin, e.g. a crosslinked polymer of an acrylic acid salt is used.

Description

[Detailed description of the invention] Leather chestnuts! The present invention relates to a novel water-absorbing polyurethane foam, a cold storage material using the foam as a base material, and a method for manufacturing the same. Specifically, the present invention provides a water-absorbing polyurethane foam with open cells that has a faster water-absorbing rate and better water retention than conventionally known water-absorbing polyurethane foams, and does not expand in volume even after absorbing water. The present invention relates to a cold storage material using as a base material, and also to a method for producing these materials.

Traditionally, polyurethane foam has been used not only for its insulation and cushioning properties, but also for its excellent water retention properties.
For example, it is widely used in civil engineering, architecture, food, medicine, packaging materials, household goods, etc.

However, conventionally known polyurethane foams have the disadvantage that their water retention properties are temporary and that they easily release most of the absorbed water when a slight external pressure is applied.

Therefore, in order to improve such drawbacks, for example, JP-A-53-138500, JP-A-54-37199, JP-A-55-151034, and JP-A-56. Various water-absorbing polyurethane foams containing water-absorbing resins have been proposed, such as in Japanese Patent No. 127,617. However, all of these water-absorbing polyurethane foams have problems such as volumetric expansion due to water absorption, water-absorbing resin detaching from the polyurethane foam, or slow water absorption rate, which limits their use. It is naturally limited.

It is already known that by reacting a polyol having three or more functional groups with a polyisocyanate in the presence of a water-absorbing resin, it is possible to obtain a polyurethane foam that exhibits little volumetric expansion even when water is absorbed. However, such water-absorbing polyurethane foams tend to be hydrophobic and somewhat hard, so they are superior to traditional water-absorbing polyurethane foams in terms of less volumetric expansion when water is absorbed. However, both the water absorption amount and the water absorption rate are still small, which is not satisfactory.

On the other hand, various cold storage materials are already known.

Cold storage materials are widely used in the food field, for example, for quality control, freshness preservation, energy saving, etc., because the temperature can be set arbitrarily depending on the cold storage medium they contain, and they can be reprinted. It is used.

Conventionally, such cold storage materials have been used, for example,
As described in JP-A-28505 and JP-A-57-14679, thixotropic viscous bodies made by mixing a water-soluble polymer with a cold storage medium, and polyacrylic acid cross-linked with polyvalent metal salts are used. Hydrogels obtained by this process are known. However, such a cold storage material has poor moldability, solidifies when cooled, and has poor water retention.

Therefore, in JP-A No. 62-240377, paper, cotton, nonwoven fabric, etc. are coated or impregnated with an aqueous solution containing a carboxylic acid polymer and a crosslinking agent, dried to form a base material, and this base material is used to store cold. A cold storage material impregnated with a medium has been proposed. Although this cold storage material has excellent water retention and formability, it does not have sufficient shape retention strength and may easily lose its shape retention due to external forces, or the hydrogel may separate from the base material. have

The present invention was made to solve the above-mentioned problems in conventional water-absorbing polyurethane foams, and
The purpose of the present invention is to provide a water-absorbing polyurethane foam that has a sufficiently high water absorption rate and does not undergo volumetric expansion even when it absorbs water.

Furthermore, the present invention was made to solve the above-mentioned problems with conventional cold storage materials, and aims to provide a cold storage material that has excellent water retention, moldability, shape retention, and durability. do.

Another object of the present invention is to provide a method for producing the above-described water-absorbing polyurethane foam and cold storage material.

1. The present invention is a water-absorbing polyurethane foam in which a water-absorbing resin is dispersed in a polyurethane foam having open cells, which is a reaction product of a polyol and a polyisocyanate, and has an average number of functional groups of 2. 0 or more and less than 3.0, the content of oxyethylene groups is 10 to 50% by weight, and the average molecular weight is in the range of 300 to 10,000.

The polyols used in the present invention include diols having a functional group number of 2, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, and 1,6-hexanediol, and diols having a functional group number of 3. It is obtained by addition-polymerizing alkylene oxide such as ethylene oxide or propylene oxide to polyhydric alcohol such as triol such as glycerin or trimethylolpropane, which is -
S is polyoxypropylene oxyethylene glycol or simply polyoxypropylene glycol (PPG)
This is what is called.

In the present invention, such a polyol has an average functional group number of 2.0 or more and less than 3.0, and an oxyethylene group of 1
A mixture of individual polyols is used so that the polyol has an average molecular weight of 0 to 50% by weight and an average molecular weight of 300 to 10,000, preferably 1,000 to 5,000.

When the average number of functional groups of the polyol used is less than 2.0, the reaction with the polyisocyanate does not substantially proceed, while when it is 3.0 or more, the crosslinking density of the resulting polyurethane foam is excessively high. Since it has a tendency to become tall and hard, its water absorption rate is slow. In addition, when the content of oxyethylene groups in the polyol is less than 10% by weight, the water absorption rate of the obtained polyurethane foam is poor, and when it exceeds 50% by weight, it is difficult to react with polyisocyanate in the presence of a blowing agent. , the foamability becomes unstable and the resulting polyurethane foam tends to shrink, collapse, etc., making it difficult to obtain polyurethane foam with good reproducibility.

The water-absorbing polyurethane foam having open cells according to the present invention can be obtained by producing a water-absorbing polyurethane foam by reacting a polyol and a polyisocyanate in the presence of a catalyst, a blowing agent, and a water-absorbing resin, and the average number of functional groups is 2. 0 or more and less than 3.0, the content of oxyethylene groups is 10 to 50% by weight, and the average molecular weight is 300 to 3.0.
1ooo.

It can be obtained by using a polyol within the range of as a polyol component.

Here, in the present invention, the water absorption rate is fast, and
In order to obtain a water-absorbing polyurethane foam having open cells that does not undergo volumetric expansion even when water is absorbed, the amount of water-absorbing resin to be used is determined by the volume of its total water absorption and the foaming volume of the resulting polyurethane foam, that is, the amount of water-absorbing resin used. volume of polyurethane foam.

That is, according to the present invention, the amount of water absorbent resin used is such that the volume of the total water absorption is 0 of the foaming volume of the polyurethane foam.
．． It is used so that it becomes 6 to 3.0 times. The total water absorption amount of the water-absorbing resin is the water-absorbing capacity per unit weight of the water-absorbing resin (g
It is the product of water/g resin) and the weight (g) of the water absorbent resin used.

Thus, for example, the polyurethane foam obtained is
When the water-absorbing resin is foamed to have a foaming volume of 0 m1 and has a water-absorbing capacity of 400 g/g, the water-absorbing resin has a water absorption capacity of 0.6 to 3.0 g during the reaction between the polyol and the polyisocyanate. Used in range.

When the amount of water absorbent resin used is less than 0.6g, the resulting polyurethane foam will not have sufficient water retention,
On the other hand, if it exceeds 3.0 g, the resulting polyurethane foam will expand in volume when it absorbs water. Further, when a polyol and a polyisocyanate are reacted in the presence of a water-absorbing resin, it may not be possible to obtain a sufficiently expanded polyurethane foam.

The water-absorbing polyurethane foam having open cells according to the present invention can be produced according to conventional methods. for example,
It can be produced by a so-called one-shot method in which polyisocyanate is added to a homogeneous mixture of a polyol, a blowing agent, a catalyst, a foam stabilizer, a water-absorbing resin powder, and other usual auxiliary agents and foamed.

The polyisocyanates used in the present invention are not particularly limited, and include, for example, aliphatic polyisocyanates such as hexamethylene diisocyanate, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), phenylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, etc. isocyanate, aromatic polyisocyanate such as polymethylene polyphenylene polyisocyanate, alicyclic polyisocyanate such as dicyclohexylmethane diisocyanate, [T
Examples include those conventionally used in the production of polyurethane foam, such as DI, crude MDI, and modified MDI.

Further, the water-absorbing resin used in the present invention is not particularly limited, but one having a water-absorbing capacity of about 10 to 1000 times is used. Specific examples include crosslinked products of acrylate polymers, crosslinked products of vinyl alcohol-acrylate copolymers, crosslinked products of maleic anhydride grafted polyvinyl alcohol, and crosslinked products of acrylate-methacrylate copolymers. cross-linked product of saponified methyl acrylate-vinyl acetate copolymer, cross-linked product of starch-acrylate graft copolymer, starch-acrylonyl-I
Cross-linked product of hydrolyzed product of J-ru copolymer, cross-linked product of saponified starch-ethyl acrylate graft copolymer,
Examples include carboxymethylcellulose crosslinked products. Such water-absorbing resins are already commercially available,
In the present invention, such commercially available products can be suitably used.

However, in the present invention, a water-absorbing resin containing a monomer component having a reactive hydrogen atom such as a carboxyl group in the molecule is particularly preferably used. When such a water-absorbing resin is used, when polyol and polyisocyanate are reacted in the presence of the resin to produce polyurethane foam, it is thought that it partially reacts with the polyisocyanate and becomes integrated with the polyurethane foam.
It is possible to obtain a water-absorbing polyurethane foam in which the water-absorbing resin is not detached from the polyurethane.

In the present invention, the water-absorbing resin powder used is preferably as fine as possible from the viewpoint of uniform dispersion in the resulting water-absorbing polyurethane foam and its properties, but when the particle size is 50 μm or less, Favorable results can be obtained.

As the catalyst, tertiary amines such as triethylenediamine and trialkylamine, organic tin compounds such as stannath octoate, dibutyltin dilaurate, stannous 2-ethylcaproate, and other conventionally known catalysts are used. It will be done.

In addition, as blowing agents, water, hydrous compounds such as borax, chlorofluorocarbons such as Freon-11 and Freon-12, low-boiling point solvents such as methylene chloride and ethylene chloride, bis(
A formaldehyde generating agent such as hydroxymethyl)thiourea, a nitrogen gas generating agent such as azobisisobutyronitrile, etc. are used.

Other auxiliary agents include, for example, silicone-based agents such as polysiloxane and alkylene oxide copolymers, foam stabilizers, surfactants such as sulfonated higher fatty acid salts, etc.
Inorganic or organic fillers, antioxidants, ultraviolet absorbers, flame retardants, dyes, pigments, bactericides, etc. are used as necessary.

Next, the cold storage material according to the present invention will be explained.

As described above, the cold storage material according to the present invention is a water-absorbing polyurethane foam in which water-absorbing resin powder is dispersed in a polyurethane foam having open cells, which is a reaction product of a polyol and a polyisocyanate, and includes: A water absorbent in which a polyol having an average functional group number of 2.0 or more and less than 3.0, an oxyethylene group content of 10 to 50% by weight, and an average molecular weight of 300 to 10,000 is used as a polyol component. It is characterized by being made of polyurethane foam impregnated with a liquid cool storage medium.

In the cold storage material according to the present invention, water or a mixture of water and an additive is preferably used as the cold storage medium. As the additive, various additives can be used without particular limitation as long as they have the property of absorbing thermal energy from the surroundings during the phase change from solid to liquid and are water-soluble. In particular, polyhydric alcohols are preferably used.

Examples of such polyhydric alcohols include glycols such as ethylene glycol and propylene glycol, trifunctional polyhydric alcohols such as glycerin, and polyalkylene glycols such as diethylene glycol, triethylene glycol, and polyethylene glycol. I can do it.

The mixing ratio of these polyhydric alcohols and water is not limited in any way, and may be determined as appropriate depending on the temperature at which the cold storage material is cooled, the temperature of the object to be cooled by the cold storage material, etc. .

The cold storage material according to the present invention can be obtained by impregnating the water-absorbing polyurethane foam with such a cold storage medium to form a hydrogel. By cooling such a cold storage material, it is possible to obtain an excellent cold storage effect.

The water-absorbing polyurethane foam according to the present invention has an extremely high water absorption rate, excellent water retention, and does not undergo volumetric expansion even after water absorption. Furthermore, the water-absorbing resin does not come off even after water absorption. Therefore, such water-absorbing polyurethane foam
In addition to the traditional uses of polyurethane foam, it can also be used as a water-stopping material in civil engineering and construction, a coating material, a dew prevention material (sheet), an oil-water separation material (sheet), a water-retaining material for agriculture and horticulture (sheet), and a water-absorbing material for the human body ( It can be suitably used as a sheet) or the like.

Furthermore, since the cold storage material according to the present invention uses the water-absorbing polyurethane foam as described above as a base material, there is no volumetric expansion even after impregnation with a cold storage medium, and the water-absorbing resin is desorbed from the base material. Since it does not separate, it has excellent shape retention and moldability.

Therefore, for example, it can be integrated with a storage such as a heat insulating case as a molded product.

Furthermore, according to the cold storage material of the present invention, even after thawing the cold storage medium,
Since the cold storage medium is well retained in the base material and does not flow out from the base material, it can be repeatedly used for cooling and defrosting.

2 ships ■ The present invention will be explained below by giving Examples and Comparative Examples.
The present invention is not limited in any way by these Examples.

Example 1 100 g of polyol having an average functional group number of 2, an average molecular weight of 2000, and an oxyethylene group content of 20% by weight (Polyol
shall be. ), 3.3 g of water as a foaming agent, 0.4 g of triethylenediamine (DABCO33LV, manufactured by Sankyo Air Products Co., Ltd.) as a catalyst A, 1.0 g of NUC silicone L-520 (manufactured by Nippon Unicar Co., Ltd.) as a foam stabilizer, and 1.0 g of NUC silicone L-520 (manufactured by Nippon Unicar Co., Ltd.) as a foam stabilizer. I used 5g of Aqua Keep 4S (manufactured by Jumiseika ■, water absorption capacity 400g/g) as the resin! The mixture was placed in a 2-capacity polyethylene container and stirred for 2 minutes at 5000 rpm using a disper.

Next, 39 g of Sumidur T80 (manufactured by Sumidur Bayer Urethane Co., Ltd.) was used as an isocyanate, and Stanus octoate (Neostan U-28, manufactured by Nitto Kasei Co., Ltd.) was used as a catalyst B.
0.3 g was mixed in advance, added to the container, and further stirred at 5000 rpm for 10 seconds. Thereafter, the mixture was immediately poured into a mold to obtain a water-absorbing polyurethane foam with a foaming volume of 3000 n+1. In this case, the total volume of water absorbed by the water-absorbing resin is 0.67 times the foaming volume of the polyurethane foam.

The obtained polyurethane foam was cut into a 5.0 x 50 x 20 size test piece, and its water absorption capacity, volumetric expansion rate and water retention amount were measured according to the methods shown below. In addition, the condition of the test piece during water absorption was observed. The results are shown in Table 1.

Water Absorption 1 The above test piece was immersed in ion-exchanged water for a predetermined period of time to absorb water, and the water absorption capacity was determined from the weight increase rate before and after immersion according to the following formula.

The above test piece was immersed in ion-exchanged water for 2 hours to absorb water,
The volume expansion magnification was determined from the volume increase rate before and after immersion according to the following formula.

Yumoto 1 The above test piece was immersed in ion-exchanged water for 24 hours to absorb water, and then dehydrated (100G x 90 seconds) using a centrifuge (Domestic Centrifuge Model H-120B), and the weight before and after immersion was calculated according to the following formula. The amount of water retained was determined from the weight after dehydration.

The test piece was immersed in ion-exchanged water for 24 hours to absorb water, and then its surface was visually observed. O indicates that the surface is smooth and there is no detachment of the resin from the polyurethane foam base material, △ indicates that the surface is slightly sticky, and × indicates that the surface is extremely sticky and there is no detachment of the resin from the polyurethane foam base material. Indicates that there is.

Examples 2 to 5 In Example 1, except that the following polyols were used,
In the same manner as in Example 1, water-absorbing polyurethane foam was produced using the formulations shown in Table 1.

Polyol B Average number of functional groups is 2, average molecular weight is 400, and oxyethylene group content is 20% by weight.

Polyol C: 10 parts of polyol with an average functional group number of 2, an average molecular weight of 2000, an oxyethylene group content of 20% by weight, and an average functional group number of 3
, a mixture with 90 parts of a polyol having an average molecular weight of 5000 and an oxyethylene group content of 30% by weight.

Polyol D (polyoxypropylene glycol) Polyoxypropylene glycol with an average number of functional groups of 3, an average molecular weight of 3000, and no oxyethylene groups The obtained polyurethane foam was cut into 50 x 50 x 20 square pieces to prepare test pieces. In the same manner as above, water absorption capacity, volumetric expansion capacity, and water retention capacity were measured. In addition, the condition of the test piece during water absorption was observed. Results first
Shown in the table.

Comparative Examples 1 to 4 Water-absorbing polyurethane foams were produced in the same manner as in Example 1 using the formulations shown in Table 1. Regarding the obtained polyurethane foam, the water absorption capacity, volumetric expansion rate, and water retention capacity were measured in the same manner as in Example 1 above. In addition, the condition of the test piece during water absorption was observed. The results are shown in Table 1.

Example 6 Water-absorbing polyurethane foam obtained from the formulation of Example 2 was
It was cut into a size of 40 x 160 x 50 mm, immersed in 3000 cc of a 50% by weight ethylene glycol aqueous solution for 2 hours, and then taken out from the ethylene glycol aqueous solution to obtain a cold storage material (liquid absorption amount 1500 g).

This cold storage material is cooled to -10℃ and the outer size is 310 x 220 x
The sample was placed in a commercially available foamed styrene heat insulating case with internal dimensions of 220mm and 240mm x 160mm x 160mm, and changes over time in the temperature inside the case and the temperature of the cool storage material were measured. The results are shown in Table 2.

In addition, the results of measuring the liquid absorption performance of water-absorbing polyurethane foam against a 50% by weight ethylene glycol aqueous solution were
Shown in the table.

Comparative Example 5 Using the polyurethane foam obtained with the formulation of Comparative Example 2,
A cold storage material (liquid absorption amount: 580 g) was obtained in the same manner as in Example 6. Regarding this cold storage material, the change in temperature of the cold storage material over time was measured using the same method as described above.

The results are shown in Table 2.

Furthermore, Table 3 shows the measurement results of the liquid absorption performance of the water-absorbing polyurethane foam against a 50% ethylene glycol aqueous solution.

Claims (14)

[Claims] (1) A water-absorbing polyurethane foam in which a water-absorbing resin powder is dispersed in a polyurethane foam having open cells which is a reaction product of a polyol and a polyisocyanate, and the average number of functional groups is 2.0 or more and less than 3.0. A water-absorbing polyurethane foam characterized in that a polyol having an oxyethylene group content of 10 to 50% by weight and an average molecular weight in the range of 300 to 10,000 is used as a polyol component. (2) A claim characterized in that the water-absorbing resin is used in an amount adjusted so that the volume of the total amount of water absorbed by the water-absorbing resin is 0.6 to 3.0 times the foaming volume of the polyurethane foam. The water-absorbing polyurethane foam according to item 1. (3) The water-absorbing polyurethane foam according to claim 1 or 2, wherein the particle size of the water-absorbing resin powder is 50 μm or less. (4) The water-absorbing polyurethane foam according to any one of claims 1 to 3, wherein the water-absorbing resin is a resin containing a monomer component containing a carboxyl group. (5) A polyol and a polyisocyanate are reacted in the presence of a catalyst, a blowing agent, and a water-absorbing resin powder to produce a water-absorbing polyurethane foam in which the water-absorbing resin powder is dispersed in a polyurethane foam having open cells. In the method, the average number of functional groups is 2.0 or more and less than 3.0 and the content of oxyethylene groups is 10 to 50% by weight.
A method for producing a water-absorbing polyurethane foam, characterized in that a polyol having an average molecular weight in the range of 300 to 10,000 is used as a polyol component. (6) The water-absorbing resin is used in an amount adjusted so that the volume of water absorbed by the water-absorbing resin is 0.6 to 3.0 times the foaming volume of the polyurethane foam. A method of manufacturing the water-absorbing polyurethane foam described. (7) The method for producing a water-absorbing polyurethane foam according to claim 5 or 6, wherein the particle size of the water-absorbing resin powder is 50 μm or less. (8) The method for producing a water-absorbing polyurethane foam according to any one of claims 5 to 7, wherein the water-absorbing resin is a resin containing a monomer component containing a carboxyl group. (9) A water-absorbing polyurethane foam comprising a water-absorbing resin powder dispersed in a polyurethane foam having open cells which is a reaction product of a polyol and a polyisocyanate, and having an average number of functional groups of 2.0 or more; 3. 0, the content of oxyethylene groups is 10 to 50% by weight, and the average molecular weight is in the range of 300 to 10,000.A water-absorbing polyurethane foam is impregnated with a liquid cold storage medium, and the polyol is used as a polyol component. A cold storage material that is characterized by (10) The cold storage material according to claim 9, wherein the cold storage medium is water. (11) The cool storage material according to claim 9, wherein the cool storage medium is a mixture of water and polyhydric alcohol. (12) A claim characterized in that the water-absorbing resin is used in an amount adjusted so that the volume of the total amount of water absorbed by the water-absorbing resin is 0.6 to 3.0 times the foaming volume of the polyurethane foam. The cold storage material according to item 9. (13) The cold storage material according to claim 9 or 12, wherein the water-absorbing resin powder has a particle size of 50 μm or less. (14) Claim 9, wherein the water-absorbing resin is a resin containing a monomer component containing a carboxyl group.
The cold storage material according to item 1, item 12, or item 13.