JPH0625374A - Production of hydrophilic and water absorptive rigid urethane foam - Google Patents

Abstract

PURPOSE:To produce an open-cell type rigid urethane foam excellent in hydrophilic property and water absorptivity and exhibiting a low volume increase and a low deformation in water absorption. CONSTITUTION:A composition composed of 100 pts.wt. polyol, a crude MDI (NCO index; 50 to 90), 8 pts.wt. water, 1.5 pts.wt. foam stabilizer and 1 pts.wt. amine-based catalyst is used. The polyol is obtained by blending 55 pts.wt. polyol (A) with 35 pts.wt. polyol (B) and 10 pts.wt. polyol (C) respectively described below. The polyol (A); a glycerol-based polyether polyol having 3 functional groups, 500 to 1500 molecular weight and ratio (mol%) of (PO/EO)=100/0. The polyol (B); a glycerol-based polyol having 3 functional groups, 3000 to 6000 molecular weight and ratio of (PO/EO)=(50/50) to (10/90). The polyol (C); an ethylenediamine-based polyether polyol having 4 functional groups, 100 to 500 molecular weight and ratio of (PO/EO)=(100/0).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrophilic / water-absorbent rigid urethane foam, and more specifically, a method for producing a rigid urethane foam which has little volume expansion / shape change upon water absorption and is excellent in hydrophilicity and water absorption. Regarding INDUSTRIAL APPLICABILITY The present invention is used for manufacturing soil substitutes and the like.

[0002]

2. Description of the Related Art There are many known methods for producing urethane foam exhibiting water absorbency and hydrophilicity, such as a prepolymer method in which a polyol having a high ethylene oxide content is reacted with a polyisocyanate in advance, and a foam breaking property. There is known a method of adding a foam stabilizer having a viscosity (Japanese Patent Laid-Open No. 2-1.
4209, JP 63-145362 A, JP 62-13427 A, JP 59-64620 A,
58-76417, 56-143227, 51-62899, etc.).

The above conventional manufacturing method is for manufacturing a flexible urethane foam having elasticity. Therefore, when this foam absorbs water, moisture penetrates between the molecular structures of the resin, causing swelling and volume expansion, which is suitable for hydroponic cultivation represented by kaiware radish, but for planting. The following problems were encountered when using soil replacement in planters for the purpose of weight reduction. 1) Since it is an elastic body, it can be bent by a small load. 2) Since the volume swelling of the foam causes water to be taken in between the molecular structures, the foam absorbs water more strongly than the water drains, and cannot smoothly move water from the foam to the soil due to capillary action. Further, for example, Japanese Patent Laid-Open No. 62-134
In Japanese Patent No. 27, the cells become coarse and absorb water, but there is a problem that the water retention is poor. On the other hand, among urethane foams, rigid urethane foams have a high closed cell rate, so it is extremely difficult to allow water to enter the foams. From the above, it is desired to manufacture an open-celled rigid urethane foam which is excellent in hydrophilicity and water absorption.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and meets the above requirements. It is a non-elastic body having the characteristics of rigid urethane foam, and has a volume expansion due to swelling even when absorbing water, It is an object of the present invention to provide a method for producing a hydrophilic / water-absorbing urethane foam with little change in shape.

[0005]

The method for producing a hydrophilic / water-absorbent rigid urethane foam of the present invention is to produce a hydrophilic / water-absorbent polyurethane foam from a composition containing a polyol, an isocyanate, a foaming agent, a foam stabilizer and a catalyst. In the method described above, as the above-mentioned polyol, the above-mentioned polyols A, B and C are used, and when the polyol A is 100 parts by weight, the polyol B is 40 to 80 parts by weight and the polyol C is 10 to 30 parts by weight. Compounded, the NCO index of the isocyanate is 50 to 90, the blowing agent is water, and 3 per 100 parts by weight of the polyol.
˜15 parts by weight are blended.

As the "polyols A and C", those having 3- to 4-functionality and a short molecular weight are used so as not to give elasticity to the foam. The “polyol B” has a large molecular weight and has a large molecular weight because it breaks the reaction balance with the polyols A and C and opens the cell.
O) Use a high content.

The above-mentioned "isocyanate" is usually
Known examples of rigid polyurethane foams include crude or polymeric diphenylmethane diisocyanate (MDI), modified MDI, tolylene diisocyanate (TDI) prepolymer, and the like. The NCO index of this isocyanate is 50-
When it is out of the range of 90, the appearance of the foam shrinks and the water retention amount becomes insufficient.

If the amount of water as the "foaming agent" is less than 3 parts by weight, a closed cell structure is formed and the foam shrinks. If the amount exceeds 15 parts by weight, the foam will collapse,
Or, the closed cell structure is formed and the foam shrinks. As the above-mentioned “foam stabilizer”, known compounds can be used, and examples thereof include block copolymers of dimethylsiloxane and polyether which are generally used for urethane foam.
As the above-mentioned "catalyst", known ones can be used, and examples thereof include amine derivatives and morpholine derivatives.

[0009]

The urethane foam of the present invention has an open cell structure and each cell structure is fine, so that a physical action called capillarity occurs and water can be easily absorbed. In addition, since the hydroxyl groups having hydrophilicity can be left in excess of the isocyanate groups during the urethane reaction, the urethane foam is excellent in hydrophilicity. Further, since it is a rigid foam, it does not bend up to a compressive load of breaking strength, and it is less likely that water will be taken in between the molecular structures of the resin and the volume will expand. Furthermore, in the case of using a foam stabilizer having a strong foam stabilizing activity, the foam can be formed into a fine cell structure and thus has excellent water absorption, and therefore, a pseudo action of smooth water movement of soil due to a capillary phenomenon can be performed.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples. First, each composition component shown in Table 1 is blended in the blending ratio shown in Table 1 to prepare a predetermined composition (Test Examples No. 1 to 4).

[0011]

[Table 1]

"Polyol A" shown in Table 1 has 3 functional groups, a molecular weight of 1000, and an OH value of 160 (mgKOH /
g), a glycerin-based polyether polyol having a propylene oxide (PO) / ethylene oxide (EO) ratio (mol%) = 100/0. "Polyol B"
Has 3 functional groups, molecular weight 5000, OH value = 33 (mg
KOH / g), PO / EO ratio (mol%) = 20/80
Is a glycerin-based polyether. "Polyol C"
Has 4 functional groups, molecular weight 300, OH value = 750 (mg
KOH / g), PO / EO ratio (mol%) = 100/0
Is an ethylenediamine-based polyether polyol.

"SF-2910" (trade name, manufactured by Toray Silicone Co., Ltd.) for "foam stabilizer" and DM for "amine catalyst"
CHA (dimethylcyclohexylamine), "isocyanate" is crude MDI (NCO% = 31%, NC
O index = 40-100) was used for each. Further, as other foam stabilizers, "SH-190", "SH-
192 "(Toray Silicone Co., Ltd.), other catalysts are N
MM (normal methyl morpholine) or the like may be used.

The above composition was foamed and molded under the following conditions to give a urethane foam (shape: 270 × 2).
70 × 250 mm) was manufactured. [Foaming and molding conditions] Liquid foam; 20 ° C, room temperature; 20 ° C, humidity; 60% Injector: "MU-212" (manufactured by Polyurethane Engineering Co., Ltd.)

Each test example No. The appearance and water retention of the foams 1 to 4 are shown in the same table. According to this result, the best performance was exhibited when the NCO index was 60 (No. 2). "Shrinkage" as the foam appearance means that the foam shrinks and deforms by the day after foaming, and is "good".
Means that there is no such contraction. Further, this foam was an open-cell type, and its average cell diameter was as small as about 0.2 mm and was uniform. The evaluation of the "open cells" was carried out by a water absorption test (described below) and a Beckman air-comparison hydrometer 930 type. The evaluation of the “average bubble diameter” was performed with a general magnifying glass and a microscope. Furthermore, this best No. When the results of changes in the density, compressive strength and water retention amount of the foam of No. 2 were examined, the following results were obtained. Density: 0.023 g / cm ³ , compressive strength: 1.9 length
N / cm ^2, horizontal 1.6 N / cm ^2, water retention amount 0 hours after: 100%, 24 hours after 94%, after 1 week: 63
%.

As the measurement sample, a sample was taken from a hand-foamed product in a 270 × 270 × 250 (mm) foam bag on a 3 × scale. And the measurement of the density was based on JIS K7222. The compression strength was measured according to JIS K 7220. The measurement of the water retention capacity is as follows. That is, first, 100 × 100
The mass (WF) and volume (V) of a 25 mm sample are measured. After that, the sample was immersed in water at 25 ° C for 1 hour, then gently taken out, and the mass (W0) of the sample immediately after that was measured, and the standard temperature / humidity state grade 3 (temperature; 2
The mass (WT) is measured again by leaving it to stand in a room at 1 ° C and humidity (R, Hum); 65% for a certain time (24 hours or 1 week). The water retention capacity is calculated by the following formula. Water retention after 0 hours (%) = (WO-WF) / V Water retention after 24 hours or one week (%) = (WT-WF)
/ V

The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0018]

As described above, according to the production method of the present invention, a non-elastic material having the characteristics of a rigid urethane foam is less likely to undergo volume expansion and shape change due to swelling even when absorbing water, and further has hydrophilicity and water retention. It is possible to produce a foam excellent in Therefore, this foam can be suitably used as a soil substitute or the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area C08L 75:04

Claims (1)

[Claims] 1. A polyol, an isocyanate, a foaming agent,
In the method for producing a hydrophilic / water-absorbent rigid polyurethane foam from a composition containing a foam stabilizer and a catalyst, the above-mentioned polyols include the following polyols A and B.
And C, and when the polyol A is 100 parts by weight, 40 to 80 parts by weight of the polyol B and 10 to 30 parts by weight of the polyol C are blended, and the NCO index of the above isocyanate is 50 to 90.
Wherein the foaming agent is water, and 3 to 15 parts by weight is blended with 100 parts by weight of the polyol, and a method for producing a hydrophilic / water-absorbent rigid urethane foam. Polyol A; Functional group number 3, Molecular weight 500 to 1500,
Propylene oxide / ethylene oxide ratio (mol%) = 100/0 glycerin-based polyether polyol Polyol B; Functional group number 3, Molecular weight 3000 to 600
0, propylene oxide / ethylene oxide ratio (mol%) = 50/50 to 10/90 glycerin-based polyether polyol Polyol C; number of functional groups 4, molecular weight 100 to 500, propylene oxide / ethylene oxide ratio (mol%) = 100 / 0 ethylenediamine-based polyether polyol