JPH08253549A - Production of open-cell rigid polyurethane foam - Google Patents

Abstract

PURPOSE: To produce an open-cell rigid polyurethane foam excellent in moldability, workability, mechanical properties and dimensional stability. CONSTITUTION: A polyol mixture comprising 10-60wt.% hydroxyl-terminated reaction product (c) obtained by reacting an organic polyisocyanate (a) having an average functionality of 1.6-2.9 with a polyether polyol (b) having an average functionality of 2.0-6.0, an average molecular weight of 700-6000 and acontent of oxyethylene units of 10wt.% or below in such a ratio as to provide 1.3-10.0 equivalents of the hydroxyl groups of (b) per equivalent of the isocyanato groups of (a) and 20-90wt.% polyol (d) having an average molecular weight of 150-1200 and a content of oxyethylene units of 10wt.% or below is reacted with an organic polyisocyanate having an average functionality of 2.0-2.8 in the presence of a catalyst, a blowing agent and a foam stabilizer.

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 an open-cell rigid polyurethane foam which is excellent in moldability, workability, mechanical properties and dimensional stability.

[0002]

2. Description of the Related Art Rigid polyurethane foam is widely used as a heat insulating material, structural member, vibration damping material, and filling material in refrigerators, cold storage, heat storage, interior and exterior materials, heat insulation pipes, heat insulation tanks, bathtubs, sports equipment, etc. Has been. In the production of rigid polyurethane foam, it is common to add a foaming agent to the raw material in order to adjust the foaming degree and foam density. Conventional foaming agents such as CFC-11 and HCFC-
Fluorocarbons such as 123 and HCFC-141b have been used, but a method of reducing the amount of chlorofluorocarbons has been studied in recent years in consideration of the adverse effect of fluorocarbons on the environment.

[0003]

A method of utilizing carbon dioxide generated by the reaction of water and isocyanate added to a raw material polyol for foaming is well known. This method makes it possible to reduce the amount of CFCs used or to eliminate CFCs at all. However, if a large amount of water is used to reduce the foam density (apparent density) of rigid polyurethane foam, it Due to the reaction, a large amount of urea bonds are formed in the polyurethane resin,
The brittleness of the resin deteriorates. Therefore, there are molding problems such as peeling of the foam surface and deterioration of the adhesiveness to the surface material. Further, in a polyurethane foam produced by carbon dioxide foaming, the diffusion rate of carbon dioxide in the foam cell is faster than the air permeation rate, so the inside of the foam cell is in a reduced pressure state and shrinks when the foam density is low. Easy to cause. Therefore, there is also a problem that the dimensional stability is worse than that of a polyurethane foam using CFC as a foaming agent.

As a method for improving the dimensional stability of a polyurethane foam using water as a foaming agent, a method of improving shrinkage by making the polyurethane foam into open cells and eliminating the pressure difference between the inside and the outside of the foam is known. For example, it is described in Japanese Patent Publication No. 4-487 and Japanese Patent Laid-Open No. 25375/1994. According to these methods, the molecular weight per hydroxyl group in the raw material polyol is about 600 to about 20.
No. 00 polyoxyalkylene polyol and a polyoxyalkylene polyol having a molecular weight of less than about 600 per hydroxyl group are mixed to form a cell membrane of a foam having a weak strength portion or a high surface tension. By making parts, the cells were made into open cells in the process of producing polyurethane foam. However, in these methods, it is necessary to add about 30% by weight or more of polyoxyalkylene polyol having a molecular weight of about 600 or more per hydroxyl group to the mixed polyol. Therefore, there is a drawback that the degree of crosslinking of the polyurethane resin is lowered and the foam physical properties such as compressive strength and bending strength are significantly lowered as compared with the closed-cell foam.

US Pat. No. 5,250,57
No. 9, No. 5312846, etc., a fine component that is insoluble in polyol and isocyanate in the raw material and has a surface free energy of less than 23 mJ / m ² is added, A method for performing open cell formation is described. However, the polyurethane raw material to which such a component is added is non-uniform and is difficult to use and store. It is conceivable to add such a component as a third component when mixing the isocyanate and the polyol without adding it to the raw material at the storage stage, but it requires complicated production control and modification of the production equipment. . Further, the above-mentioned conventional techniques have not solved the problems such as brittleness of the resin surface and deterioration of adhesion with the face material. In other words, without making a major modification to the conventional manufacturing equipment,
Using water as the main foaming agent, there are no molding problems such as brittleness of the resin surface and deterioration of adhesion with the surface material, and because it has open cells, it has good dimensional stability, but it is a conventional CFC foam. A method for producing a rigid polyurethane foam that does not deteriorate the physical properties of foam has been heretofore known.

[0006]

The present invention has been made to solve the above problems of a rigid polyurethane foam which uses water as a foaming agent, and can be manufactured by a conventionally used manufacturing facility. The purpose of the present invention is to provide an open-celled rigid polyurethane foam having excellent properties, workability, physical strength and dimensional stability.

The present invention relates to a method for producing an open-cell rigid polyurethane foam obtained by reacting a polyol mixture (A) with an organic polyisocyanate (B) in the presence of a catalyst, a foaming agent and a foam stabilizer. (A)
Is an organic polyisocyanate (a) having an average number of functional groups of 1.6 to 2.9, an average number of functional groups of 2.0 to 6.0, an average molecular weight of 700 to 6000, and an oxyethylene unit content of 1
0% by weight or less of the polyether polyol (b) and 1 equivalent of the NCO group of (a) to 1.
10 to 60% by weight of a hydroxyl group-terminated reaction product (c) obtained by reacting in the range of 3 to 10.0 equivalents, and an average molecular weight of 1
50-1200, oxyethylene unit content 10% by weight
It is a mixture containing 20 to 90% by weight of the following polyol (d), and the organic polyisocyanate (B) is an organic polyisocyanate having an average functional group range of 2.0 to 2.8. The method for producing an open-cell rigid polyurethane foam, wherein water is used as a blowing agent in the range of 3 to 12 parts by weight with respect to 100 parts by weight (A) of the polyol mixture.

The average number of functional groups used in the present invention is 1.6 to 2.9.
The organic polyisocyanate (a) in the range of is, for example, polymethylene polyphenyl polyisocyanate, 4,
4'-diphenylmethane diisocyanate, 2,4'-
Diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, paraphenylene diisocyanate, metaxylene diisocyanate, 1,5-naphthylene diisocyanate, 3,
3′-dimethyl-4,4′-biphenylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, etc., and further reacting these organic polyisocyanates with carbodiimide-modified polyisocyanates and isocyanate-reactive hydrogen atom-containing compounds. A compound having an isocyanate group at the terminal obtained can also be used. One of these may be used alone or two or more of them may be mixed to give an average number of functional groups of 1.6.
It can be used by adjusting it to be about 2.9.

When the average number of functional groups of the organic polyisocyanate (a) is less than 1.6, a continuous cell rigid polyurethane foam having good dimensional stability even when reacted with the polyether polyol (b) is produced. Therefore, an effective reaction product cannot be obtained. When the average number of functional groups exceeds 2.9, the viscosity of the reaction product becomes extremely high, which is not preferable in handling.

The average number of functional groups used in the present invention is 2.0 to 6.
0, an average molecular weight of 700 to 6000, and an oxyethylene unit content of 10 wt% or less, the polyether polyol (b) has a polyhydric alcohol having an average number of functional groups of 2.0 to 8.0, a hydroxyl group-containing amine compound, A polyether polyol obtained by addition-polymerizing an alkylene oxide such as ethylene oxide or propylene oxide with a polyvalent amino compound so that the oxyethylene unit content is 10% by weight or less alone or with an average functional group number of 2 0.0-6.0, average molecular weight 700-6000
As described above, they can be appropriately mixed and used.

Examples of polyhydric alcohols having an average number of functional groups of 2.0 to 8.0 include glycerin, propylene glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, methylglucoside, sorbitol, mannitol and sucrose. And so on. Examples of the hydroxyl group-containing amine compound include monoethanolamine, diethanolamine, triethanolamine and the like. Examples of polyvalent amino compounds include ethylenediamine, tolylenediamine, diethylenetriamine, and the like.

When the average molecular weight of the polyether polyol (b) is less than 700, it is effective for producing an open cell rigid polyurethane foam which has good dimensional stability even when reacted with the organic polyisocyanate (a). Reaction product cannot be obtained. Oxyethylene unit content is 1
The same applies when the content exceeds 0% by weight. Average molecular weight is 6
In the case of a polyether polyol having a oxyethylene unit content of more than 000 and an oxyethylene unit content of 10% by weight or less, production problems may occur.

The above-mentioned organic polyisocyanate (a) and polyether polyol (b) are mixed with NCO group 1 of (a).
The hydroxyl group-terminated reaction product (c) is obtained by reacting the OH group of (b) within the range of 1.3 to 10.0 equivalent with respect to the equivalent. (A)
When the OH group of (b) is less than 1.3 equivalent to 1 equivalent of NCO group of, the viscosity increase due to the increase in molecular weight is remarkable, and it is not preferable in handling, and the invention is intended when it exceeds 10.0 equivalent. Can not be obtained. In the reaction between the organic polyisocyanate (a) and the polyether polyol (b), a plasticizer, a surfactant, a flame retardant, a coloring agent, a catalyst and the like can be added, if necessary.

As the polyol (d) having an average molecular weight of 150 to 1200 and an oxyethylene unit content of 10% by weight or less, for example, glycerin, propylene glycol, dipropylene glycol, trimethylolpropane, triethanolamine, pentaerythritol, methyl glucoside. Polyhydric alcohols such as sorbitol, mannitol and sucrose, hydroxyl group-containing amine compounds such as monoethanolamine and diethanolamine, polyvalent amino compounds such as ethylenediamine, tolylenediamine and diethylenetriamine, ethylene oxide and propylene oxide Polyether polyol obtained by adding alkylene oxide such as, polycondensation of polyfunctional carboxylic acid and polyfunctional hydroxy compound, hydroxy Polycondensation of carboxylic acid, ring-opening polymerization of cyclic esters, polyester polyols obtained by a method such as transesterification can be used. Further, polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran is used as a polyol (d).
Can also be used. These polyols may be mixed and used so that the average molecular weight is 150 to 1200 and the oxyethylene unit content is 10% by weight or less.

In the present invention, the polyol mixture (A) is 10 to 60% by weight of the hydroxyl group-terminated reaction product (c) obtained above, and the average molecular weight is 150 to 120.
0, 20-90% by weight of polyol (d) having an oxyethylene unit content of 10% by weight or less. When the amount of the hydroxyl group-terminated reaction product (c) is less than 10% by weight, an open cell rigid polyurethane foam having good dimensional stability cannot be obtained. The amount of the reaction product (c) is 6
When it exceeds 0% by weight, a rigid polyurethane foam having uniform cells cannot be obtained, and the compressive strength of the foam,
Mechanical properties such as bending strength are reduced. When the amount of the polyol (d) is less than 20% by weight, sufficient mechanical properties cannot be obtained, and when it exceeds 90% by weight, an open cell rigid polyurethane foam having good dimensional stability cannot be obtained.

In the present invention, within the range which does not deviate from the effect of the present invention, it is possible to use by adding a polyol, an active hydrogen atom-containing compound or the like which is not included in the range defined as the polyol (d) to the polyol mixture. it can. Examples of these polyols or compounds include glycerin, diethanolamine, tolylenediamine and the like. These components are used as necessary for the purpose of improving the strength of the obtained rigid polyurethane foam and improving the compatibility of the polyol mixture with the catalyst, the foaming agent, the foam stabilizer, and the like.

Examples of the organic polyisocyanate (B) having an average number of functional groups of 2.0 to 2.8 to be reacted with the polyol mixture include, for example, polymethylene polyphenyl polyisocyanate, 4,4'-diphenylmethane diisocyanate,
2,4'-diphenylmethane diisocyanate, 2,
2'-diphenylmethane diisocyanate, 2,4'-
Tolylene diisocyanate, 2,6-tolylene diisocyanate, paraphenylene diisocyanate, metaxylene diisocyanate, 1,5-naphthylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, isophorone diisocyanate, 1,
6-hexamethylene diisocyanate and the like,
Furthermore, a compound having an isocyanate group at the terminal, which is obtained by reacting these organic polyisocyanates with a carbodiimide-modified polyisocyanate or an isocyanate-reactive hydrogen atom-containing compound, can also be used. Among these, one kind can be used alone, or two or more kinds can be mixed and adjusted so that the average number of functional groups becomes 2.0 to 2.8 and used.

For the reaction between the polyol mixture (A) and the organic polyisocyanate (B), an amine catalyst known as a urethanization reaction catalyst or a tin-based or lead-based organometallic catalyst can be used. Examples of amine catalysts include pentamethyldiethylenetriamine, hexamethylenediamine, tetramethylhexamethylenediamine, and the like. Examples of organic metal catalysts include dibutyltin dilaurate and stannas octoate.

The preferred blowing agent in the process of the present invention is water. Water as a foaming agent is a polyol mixture (A) 1
It is preferably used in the range of 3 to 12 parts by weight with respect to 00 parts by weight. The foam density of the product rigid polyurethane foam can be adjusted by changing the amount of water used. Further, if necessary, HCFC-based halogenated hydrocarbons such as 1,1-dichloro-1-fluoroethane, H such as 1,1,1,2-tetrafluoroethane, etc.
Low boiling point liquids such as FC halogenated hydrocarbons, pentane and hexane can be used together. Further, in the method of the present invention, as the foam stabilizer, an organic siloxane copolymer known in the production of polyurethane foam can be used. In the present invention, additives such as a flame retardant and a coloring agent can be used if necessary.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the description of the following examples unless it exceeds the gist. 1. Preparation of Hydroxyl-Terminated Reaction Product (c) A hydroxyl-terminated reaction product (c) was prepared using the following organic polyisocyanate (a) and polyether polyol (b). The polyol (bA, bB) does not belong to the range defined in the present invention.

Isocyanate (a1): A mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. Mixing ratio is 2,4-body / 2,6-body = 80
/ 20, average number of functional groups 2.0 NCO group content 48.2% Isocyanate (a2): 4,4'-diphenylmethane diisocyanate, average number of functional groups 2.0, NCO group content 33.6% Isocyanate (a3): poly Methylene polyphenyl polyisocyanate, average number of functional groups 2.8, NCO group content 31.1%

Polyol (b1): a polyether polyol obtained by adding propylene oxide to dipropylene glycol, having an average molecular weight of 2000 and a hydroxyl value of 56 mg KO.
H / g, average functional group 2.0 polyol (b2): polyether polyol obtained by adding propylene oxide to dipropylene glycol, average molecular weight 3000, hydroxyl value 37 mgKOH / g, average functional group 2.0 polyol (b3 ): Polyether polyol obtained by adding propylene oxide to glycerin, average molecular weight 3000, hydroxyl value 56 mg KOH / g, average number of functional groups 3.0 Polyol (b4): Polyether polyol obtained by adding propylene oxide to glycerin With an average molecular weight of 5000, a hydroxyl value of 34 mgKOH / g, and an average number of functional groups of 3.0 Polyol (b5): a polyether polyol obtained by adding propylene oxide to pentaerythritol, an average molecular weight of 900, a hydroxyl value of 250 mgKOH / g, an average number of functional groups 4.0 Polyol (b6): sorbitol Polyether polyol obtained by adding propylene oxide has an average molecular weight of 1530, hydroxyl value of 220 mgKOH / g, and average number of functional groups of 6.0 polyol (bA): Polyether polyol obtained by adding propylene oxide to glycerin has an average molecular weight of 600. , Hydroxyl value 280 mg KOH / g polyol (bB): polyether polyol obtained by adding propylene oxide and ethylene oxide to glycerin, average molecular weight 4800, hydroxyl value 34 mg KOH /
g, oxyethylene unit content 16%

Examples 1 to 9 and Comparative Examples A and B 160 parts by weight of polyol (b1), polyol (b3)
Isocyanate (a1) whose temperature was adjusted to 40 ° C. with stirring by mixing 240 parts by weight and adjusting the temperature to 40 ° C. 13.
9 parts by weight were added. After continuing stirring under a nitrogen stream for 8 hours, the whole container was stored in a constant temperature bath at 70 ° C. for 44 hours, and the viscosity was measured. Further, it was stored in a constant temperature bath at 70 ° C. for 48 hours, and the viscosity was measured again. The viscosity was 3640 centipoise at 25 ° C. both at the first and second times. This reaction product is designated as (c1). The reaction product was a uniform and transparent liquid, and its properties did not change even after storage at room temperature for 3 months.
From the reaction products (c2) to (c
9), and (cA) and (cB) were prepared. Table 1 shows the amounts of the reaction components used in Examples 1 to 9 and the physical properties of the obtained reaction products. Table 2 shows the amounts of the reaction components used in Comparative Examples A and B and the physical properties of the obtained reaction products.

[0024]

[Table 1]

[0025]

[Table 2]

2. Production of Rigid Polyurethane Foam Reaction products (c1 to c9) obtained in Examples 1 to 9
And the polyether polyols (d1) to (d
3) is mixed to prepare a polyol mixture, and water, a catalyst, and
Foam stabilizers and flame retardants were added to prepare the polyol compounded liquids shown in Examples 10 to 26.

Polyol (d1): Polyether polyol obtained by adding propylene oxide to tolylenediamine, average molecular weight 483, hydroxyl value 465 mg KOH / g Polyol (d2): Obtained by adding propylene oxide to monoethanolamine. Polyether polyol having an average molecular weight of 337 and hydroxyl value of 500 mgKOH / g Polyol (d3): Polyether polyol obtained by adding propylene oxide to ethylenediamine, having an average molecular weight of 351 and hydroxyl value of 640 mgKOH / g

Catalyst A: Tetramethylhexamethylenediamine, Kao Riser No. manufactured by Kao Corporation 1 Catalyst B: pentamethyldiethylenetriamine, Kao Riser No. manufactured by Kao Corporation. 3 Foam stabilizer: B-8017 made by Gold Schmidt Flame retardant: Tris chloropropyl phosphate

A polyol compounding liquid and a polymethylene polyphenyl polyisocyanate (both made by Mitsubishi Kagaku Dow PAPI-1) whose temperature was adjusted to 20 ° C.
35, NCO group content rate 31.1%) and immediately stirred for 5 seconds at 3000 rpm with a stirring blade attached to a motor, and then put into a wooden frame with a polyethylene sheet on the inner surface. A free foam was obtained. Tables 3 and 4 show the composition (parts by weight) of the polyol blended liquid, the reactivity, and the density of the obtained foam.

Similarly, a polyol mixture was prepared by using the reaction products (cA, cB) obtained in Comparative Examples A and B, the polyols (b3, d1 and d2), and the polyols (d4 and e1) shown below. To produce a free-foamed foam. These are shown in Table 5 as Comparative Examples C to I.

Polyol (d4): Polyether polyol obtained by adding propylene oxide to ethylenediamine, average molecular weight 590, hydroxyl group 380 mgKOH / g Polyol (e1): Polyether polyol obtained by adding propylene oxide to glycerin, average Molecular weight 1500, hydroxyl value 112 mg KOH / g

Similarly, using the reaction products (c2, c7) and the polyols (d1, d3) obtained in Examples 2 and 7, a polyol mixture was prepared and an attempt was made to prepare a free-foamed foam. Was degassed during the foaming process and collapsed. These are shown in Table 5 as Comparative Examples J and K. In Comparative Examples J and K, the content of the reaction products (c2, c7) in the polyol mixture is outside the scope of the present invention.

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

In Tables 3, 4 and 5, the cream time is the time from the start of mixing the reaction solution to the time when the reaction solution becomes creamy and starts foaming, and the unit is seconds. The tack-free time is the time from the start of mixing the reaction solution to the time when the foaming apparently stops and the reaction solution stops adhering even if it touches the foam surface lightly. The unit is seconds. The core density was measured by cutting the center portion of the obtained foam into a cube having a side length of about 10 cm and using the ASTM-D-1622 method. The unit is kg / m ² . In Comparative Examples J and K, the foam collapsed during the foaming process. The number with *) indicates the time from the start of mixing the reaction solutions to the depression, and the unit is seconds.

The foams obtained in Examples 10 to 26 and Comparative Examples C to I were evaluated by the following methods. The evaluation results are shown in Table 6. After molding the foam, it was left at room temperature for 30 minutes, then taken out from the wooden frame, the polyethylene sheet was peeled off, and the cured state of the foam surface was observed. In the case where the surface cure was insufficient, a part of the foam skin adhered to the polyethylene sheet side and the foam skin was peeled off. Further, when the foam skin remaining on the foam side was rubbed with a finger, it showed brittleness. Judging the quality of the surface cure by this observation,
A: good, B: almost good, C: somewhat bad, D: bad 4
It was classified into stages. Cut the center of the foam into cubes of 10 cm square, and after 1 day and 1 week at room temperature, 70 ℃
The rate of dimensional change in the direction perpendicular to the foaming direction was measured after 1 week. + Indicates that the foam has expanded, and-
Indicates that the foam has shrunk. The closed cell ratio of the center of the foam which did not shrink is determined by ASTM-D-28.
The compressive strength was measured by the method 56 and the JIS-A-9514 method. Since the foams of Comparative Examples C, D, E, and F had remarkable shrinkage, the closed cell ratio and the compressive strength could not be measured.

[0038]

[Table 6]

As shown in the above table, the open-cell rigid polyurethane foam of the present invention does not decrease the brittleness of the foam surface even when water is used as the foaming agent, and is further excellent in dimensional stability and physical properties.

[0040]

EFFECTS OF THE INVENTION According to the present invention, in particular, in the production of rigid polyurethane foam using water as a foaming agent, using the production equipment conventionally used, moldability, workability,
It is possible to obtain an open cell rigid polyurethane foam having excellent physical strength and dimensional stability. When the rigid polyurethane foam obtained according to the present invention is used as an exterior or interior member of a building, it maintains stable dimensional accuracy against environmental changes such as temperature and humidity, and further has good impact resistance and load deformation. . In addition, the brittleness of the foam surface, which is a problem when water is used as the foaming agent, and the resulting peeling at the interface between the surface material and the polyurethane foam are significantly improved. Therefore, the productivity and interface adhesion at the time of producing a composite material by foaming polyurethane on a face material such as paper, aluminum and iron are improved. This method can be used for manufacturing laminated boards, siding, and the like.

Claims (2)

[Claims] 1. A method for producing an open-cell rigid polyurethane foam obtained by reacting a polyol mixture (A) with an organic polyisocyanate (B) in the presence of a catalyst, a foaming agent and a foam stabilizer, wherein the polyol mixture (A) is used. However, the average number of functional groups is 1.6 to 2.9.
Of the organic polyisocyanate (a) having an average number of functional groups of 2.0 to 6.0, an average molecular weight of 700 to 6000, and an oxyethylene unit content of 10% by weight or less (a). 10 to 60% by weight of a hydroxyl group-terminated reaction product (c) obtained by reacting the OH group of (b) in the range of 1.3 to 10.0 equivalents with respect to 1 equivalent of the NCO group, and an average molecular weight of 150 to 1200. A polyol (d) having an oxyethylene unit content of 10% by weight or less
A process for producing an open-cell rigid polyurethane foam, which is a mixture containing 90% by weight, and the organic polyisocyanate (B) is an organic polyisocyanate having an average functional group range of 2.0 to 2.8. . 2. The method for producing an open-cell rigid polyurethane foam according to claim 1, wherein water is used as a foaming agent in a range of 3 to 12 parts by weight with respect to 100 parts by weight of the polyol mixture (A). .