JP2012046589A - Polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyurethane foam that is produced without causing scorch inside block even in slabstock molding and has excellent rigidity, hardness, dimensional stability, a shock absorption property and restoration property in spite of having a low density.SOLUTION: The polyurethane foam is obtained by reacting a polyol component comprising a polyol compound, a blowing agent, a foam stabilizer and a catalyst with an isocyanate component. (A) The polyol compound is a mixed polyol of four kinds of (i) an ethylene oxide-containing polyether polyol having a number-average molecular weight of 4,000-6,000 and a hydroxy value of 20-60 mgKOH/g, (ii) a polyether polyol having a number-average molecular weight of 300-1,000 and a hydroxy value of 100-800 mgKOH/g, (iii) a polyol for open-cell foam expanded with water, having an average hydroxy value of 200-600 mgKOH/g and a viscosity of ≤1,700 mPa s and (iv) a polyhydric alcohol and is adjusted to have an average hydroxy value of 200-300 mgKOH/g. (B) The foam stabilizer is a polyether-modified polysiloxane-based foam stabilizer. (C) The isocyanate component is crude MDI having an NCO content of 28-33% and has a closed cell ratio of ≤5%.

Description

  The present invention relates to a polyurethane foam that can be produced without generating scorch inside a block in slabstock molding, and more particularly, to a polyurethane foam having both low hardness and sufficient hardness and resilience.

Rigid polyurethane foam is generally characterized by its high thermal insulation. This is due to a gas having low thermal conductivity such as chlorofluorocarbon or pentane trapped in closed cells.
Taking advantage of this feature, there are many thermal insulation materials in which hard polyurethane foam is applied by the spray method and thermal insulation boards in which hard polyurethane is foamed between the face materials.

In contrast, rigid polyurethane foams also have applications that do not require high heat insulation, such as packaging materials and automotive interior materials. In these applications, low density is preferable from the viewpoint of cost, and in addition, rigidity, hardness, dimensional stability, resilience, shock absorption, and the like are required.
However, since the low density closed cell rigid foam easily shrinks at room temperature, it is difficult to satisfy the requirements such as rigidity, hardness, dimensional stability, and recoverability.

On the other hand, an open cell foam having a low closed cell ratio has no influence of gas pressure when compressed because there is no gas in the cell, and the hardness is lower than that of the closed cell foam. Moreover, since a high molecular weight polyol generally used in flexible polyurethane foam is used as the polyol compound, the composition tends to be soft.
Therefore, there have been many problems in using conventionally known open cell foams for applications such as packing materials and automobile interior materials where rigidity and hardness are important.

In order to increase the hardness of the polyurethane foam, there are known methods such as α) increasing the hydroxyl value of the polyol compound, β) increasing the NCO content of the isocyanate compound, etc., but the polyol compound having a high hydroxyl value and the NCO content are high. Since the reaction with the isocyanate compound is dramatic, the amount of heat generated by the reaction increases, and scorch (burning) tends to occur in the urethane foam.
In addition, to reduce the density of urethane foam, there is a method of increasing the amount of water, which is a foaming agent, but water reacts dramatically with isocyanate compounds, so that, as above, scorch is likely to occur in the resulting foam. To do. This phenomenon is particularly remarkable in the case of slab stock molding for producing large block-like urethane foam, and in the worst case, there is even a risk of fire.

Furthermore, the conventional urethane foam generally loses flexibility and resilience as the hardness increases, and becomes brittle. Therefore, in applications where thin objects are processed into various shapes, cracks and buckling (a phenomenon that does not return to the original shape from a crushed state) occur, which makes it difficult to use.
For example, in automobile ceiling materials that are usually processed to have a thickness of about 2 to 10 mm, a certain degree of hardness is required when affixing to the ceiling, but if it is too hard, it is easy to break, and thus a certain degree of flexibility. Is also required. In addition, when the ceiling after construction was pushed, there was also a problem that it looked bad if left depressed.

Patent Documents 1 and 2 disclose open-celled rigid polyurethane foam suitable for automobile shock absorbers, automobile headliners, and the like.
However, the rigid polyurethane foam described in Patent Document 1 is not satisfactory in terms of density reduction and restorability, although good effects can be obtained with respect to dimensional stability at low temperatures and high temperatures.
In addition, the rigid polyurethane foam described in Patent Document 2 has a polyester polyol having a specific hydroxyl value as an essential component, and although low density has been achieved, the viscosity of the polyol is high and handling is difficult. It was easy to deteriorate under high temperature and high humidity, and its durability was inferior.

Japanese Patent No. 3522825 Patent No. 3013108

  In consideration of the above points, the present invention can be manufactured without generating scorch inside the block even in slabstock molding, and has low density, rigidity, hardness, dimensional stability, shock absorption Another object of the present invention is to provide a polyurethane foam excellent in resilience.

As a result of repeated studies to solve the above problems, the present inventor,
(A) As a polyol compound, a long-chain polyether polyol, a short-chain polyether polyol, a water-foaming polyol, a polyhydric alcohol mixture prepared by using an average hydroxyl value adjusted to a specific value,
In addition, by blending (B) a special foam stabilizer for suppressing foam shrinkage, and (C) Crude MDI as an isocyanate component,
It was found that a polyurethane foam having a low hardness and sufficient hardness and excellent resilience can be obtained.

The present invention has been achieved under such knowledge, and the gist thereof is as follows.
(1) A polyurethane foam obtained by reacting a polyol component containing a polyol compound, a foaming agent, a foam stabilizer, and a catalyst with an isocyanate component,
(A) The polyol compound comprises (i) a polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide having a number average molecular weight of 4000 to 6000 and a hydroxyl value of 20 to 60 mgKOH / g, and (ii) a number average molecular weight of 300. Polyether polyol having a hydroxyl value of 100 to 800 mg KOH / g, (iii) polyol for water foaming having an average hydroxyl value of 200 to 600 mg KOH / g and a viscosity of 1700 mPa · s or less, and (iv) a polyhydric alcohol. Four kinds of mixed polyols having an average hydroxyl value adjusted to 200 to 300 mgKOH / g,
(B) The foam stabilizer is a polyether-modified polysiloxane foam stabilizer,
(C) the isocyanate component is crude MDI having an NCO content of 28-33%,
Polyurethane foam having a closed cell ratio of 5% or less.
(2) Density is 25 to 40 kg / m ³ , hardness measured by Asker rubber hardness tester C2 type (hereinafter, sometimes simply referred to as “C2 hardness”) is 30 to 55, and compressed by 50% The polyurethane foam as set forth in (1), wherein the foam has a restoring property of recovering to 90% or more of the original thickness after 1 minute.

The polyurethane foam of the present invention can be produced without generating scorch in the block even in slabstock molding, and has low density, rigidity, hardness, dimensional stability, shock absorption and resilience. Because it is excellent, its industrial utility value is extremely high.
In particular, there is a polyurethane foam having a resilience in which a 50% compressed material recovers 90% or more after only 1 minute despite a density of 40 kg / m ³ or less and a C2 hardness of 30 or more. I didn't.
It should be noted that the polyurethane foam of the present invention can be obtained with a low density and excellent properties such as hardness and resilience, regardless of whether it is produced by molding or sprayed on site. .

The polyurethane foam of the present invention is obtained by reacting a polyol component containing a polyol compound, a foaming agent, a foam stabilizer, and a catalyst with an isocyanate component, and has a closed cell ratio of 5% or less. Is.
In the present invention, as the polyol compound (A), four types of mixed polyols of (i) a long-chain polyether polyol, (ii) a short-chain polyether polyol, (iii) a water blowing continuous polyol, and (iv) a polyhydric alcohol The average hydroxyl value is adjusted to 200 to 300 mgKOH / g.
If the average hydroxyl value of the four-type mixed polyol is too low, it is difficult to obtain a foam having a C2 hardness of 30 or more and the rigidity may be insufficient. If it is too high, the inside of the block formed by slab stock Since scorch is likely to be generated, it is preferably 205 to 280 mgKOH / g. An average hydroxyl value is the value which averaged the hydroxyl value of each polyol according to a compounding ratio.
Moreover, it is preferable that the viscosity at 25 degrees C of 4 types mixed polyol is prepared to about 3000 mPa * s or less, More preferably, it is about 2000 mPa * s or less.

  (A) In 100 parts by weight of the polyol compound, the mixture of the four kinds of polyols is as follows: (i) 30 to 70 parts by weight of the long-chain polyether polyol, (ii) 10 to 40 parts by weight of the short-chain polyether polyol, ( iii) It is preferable that the water foaming communication polyol is 10 to 40 parts by weight, and (iv) the polyhydric alcohol is 0.5 to 7 parts by weight.

(A) The polyol compound (i) long-chain polyether polyol is obtained by addition polymerization of ethylene oxide (EO) and propylene oxide (PO) having a number average molecular weight of 4000 to 6000 and a hydroxyl value of 20 to 60 mgKOH / g. Polyether polyol (hereinafter sometimes referred to as “EO-containing polyether polyol”) is used. The average number of functional groups is in the range of 2 to 4, and the preferred average number of functional groups is 3.
In polyether polyol in which EO content is 0 (zero), that is, only propylene oxide (PO) is addition-polymerized, a good foam is not obtained and easily collapses. Therefore, by appropriately adjusting the content ratios of EO and PO, Form communication is promoted.
In EO-containing polyether polyol having a number average molecular weight of less than 4000, a polyurethane foam having dimensional stability and restorability cannot be obtained, and when it exceeds 6000, the desired hardness cannot be expressed. is there.
Thus, as a long-chain polyether polyol (i), by blending an ethylene oxide (EO) -containing polyether polyol having a number average molecular weight of 4000 to 6000 and a hydroxyl value of 20 to 60 mgKOH / g, dimensional stability and restorability Will be excellent. (I) About the mixture ratio of long-chain polyether polyol, it is preferable to mix | blend 30-70 weight part in 100 weight part of (A) polyol compounds, More preferably, it is 40-55 weight part. If it is less than 30 parts by weight, it is difficult to obtain desired dimensional stability and recoverability, and if it exceeds 70 parts by weight, cell roughness tends to occur and hardness and rigidity tend to be insufficient.
As specific examples of (i), trade names “EXCENOL820”, “EXCENOL823”, “EXCENOL828”, “EXCENOL837” manufactured by Asahi Glass Co., Ltd .; trade names “FA-702”, “FA-703” manufactured by Sanyo Chemical Industries, Ltd. Trade names “VORANOL 4701”, “VORANOL CP6001” and the like manufactured by Dow Chemical Japan Co., Ltd.

(A) As the (ii) short chain polyether polyol of the polyol compound, a polyether polyol having a number average molecular weight of 300 to 1000 and a hydroxyl value of 100 to 800 mgKOH / g is used. The average number of functional groups is in the range of 2 to 4, and the preferred average number of functional groups is 3.
Polyether polyols having a number average molecular weight of less than 300 tend to shrink the foam at room temperature, resulting in lack of dimensional stability, and those having a number average molecular weight exceeding 1000 have a problem that the desired hardness cannot be expressed. , Preferably 400 to 1000.
As described above, (ii) as a short-chain polyether polyol, it is possible to improve hardness and rigidity by blending a polyether polyol having a number average molecular weight of 300 to 1000 and a hydroxyl value of 100 to 800 mgKOH / g. (Ii) About the mixture ratio of a short-chain polyether polyol, it is preferable to mix | blend 10-40 weight part in 100 weight part of (A) polyol compounds, More preferably, it is 25-30 weight part. If it is less than 10 parts by weight, it is difficult to obtain desired hardness and rigidity, and if it exceeds 40 parts by weight, it is difficult to obtain a polyurethane foam having desired dimensional stability and physical properties.
Specific examples of (ii) include product names “EXCENOL430” and “EXCENOL1030” manufactured by Asahi Glass Co., Ltd .; product names “Sanix GP-400”, “Sanix GP-600”, and “Sanniks” manufactured by Sanyo Chemical Industries, Ltd. “GP-700”, “Sanix GP-1000”; trade names “VORANOL 2070”, “VORANOL 3150” manufactured by Dow Chemical Japan Co., Ltd.

(A) Polyol compound (iii) Water-foaming connection polyol, which is generally marketed as a water-foaming blend polyol having an average hydroxyl value of 200 to 600 mgKOH / g and a viscosity at 25 ° C. of 1700 mPa · s or less Is used.
If the average hydroxyl value is less than 200 mgKOH / g, the desired hardness cannot be expressed, and if it exceeds 600 mgKOH / g, scorch may be generated inside the slabstock foam. On the other hand, the lower the viscosity, the better. When the viscosity exceeds 1700 mPa · s, it becomes difficult to mix with other polyol compounds.
(Iii) About the mixing | blending ratio of the polyol for water foaming connection, it is preferable to mix | blend 10-40 weight part in 100 weight part of (A) polyol compounds, More preferably, it is 15-25 weight part. If the amount is less than 10 parts by weight, the closed cell ratio becomes high and the foam may shrink. If the amount exceeds 40 parts by weight, the foam tends to buckle, and the mechanical strength of the foam tends to be low.
Specific examples of (iii) include trade names “ACTOCOL NFS-24”, “ACTOCOL NF-29”, “ACTOCOL NF-04”, and “ACTOCOL NF-13” manufactured by Mitsui Chemicals, Inc.

(A) The polyhydric alcohol (iv) of the polyol compound is not particularly limited as long as it is a dihydric or higher alcohol. For example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, diglycerin, trimethylolpropane And pentaerythritol. The number of functional groups is preferably in the range of 2 to 4, and the molecular weight is preferably about 50 to 200.
Such (iv) polyhydric alcohol acts as a crosslinking agent and realizes high hardness of the polyurethane foam in the present invention. (Iv) The blending ratio of the polyhydric alcohol is preferably 0.5 to 7 parts by weight, more preferably 4 to 6 parts by weight, in 100 parts by weight of the (A) polyol compound. If the amount is less than 0.5 part by weight, the action as a crosslinking agent becomes insufficient, the cell becomes rough, and sufficient hardness and strength cannot be obtained. If the amount exceeds 7 parts by weight, the foam tends to shrink. It becomes poor in stability.
Thus, the (A) polyol compound of the present invention is a four-component mixed polyol composed of (i) to (iv), and does not include a polyester polyol that is generally used to form a rigid urethane foam. Is.

In the polyol component, (B) the foam stabilizer used is a commercially available polyether-modified polysiloxane foam stabilizer having a cell open effect. The cell open effect means a foam regulating effect at the initial stage of foaming and an effect of breaking the cells at the final stage of foaming, and the resulting urethane foam achieves a closed cell ratio of 5% or less. For example, those containing a polyether-modified polysiloxane represented by the following general formula are suitable.
Examples of the foam stabilizer include trade names “TEGOSTAB B8871” and “TEGOSTAB B8526” manufactured by Evonik Degussa Japan Co., Ltd.

[Chemical 1]

_{(CH 3) 3 Si-O} - [- Si (CH _{3) 2} -O-] _n - _{[Si (CH 3) R-O-} ] m -Si (CH 3) 3

In the formula, R = — (CH ₂ ) ₃ —O— (CH ₂ —CHR′—O) _y —H where R ′ is hydrogen or a methyl group. n, m, and y are arbitrary integers.

By blending such a foam stabilizer into the (A) polyol compound consisting of the above-mentioned four kinds of mixed polyols prepared with an average hydroxyl value of 200 to 300 mgKOH / g, the cell foam breaking state becomes optimal. As a result, the closed cell ratio can be suppressed to 5% or less, shrinkage at room temperature can be completely prevented, and excellent properties (hardness, resilience, etc.) are exhibited.
The foam stabilizer is preferably 0.5 to 4 parts by weight, more preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the (A) polyol compound. If it is less than 0.5 part by weight, a sufficient foam regulating effect cannot be obtained and the foam may collapse. If it exceeds 4 parts by weight, the foam tends to shrink and the dimensional stability becomes poor.

In the polyol component, examples of the blowing agent include a mixture of at least one of water, methylene chloride, pentane, cyclopentane, hexane, cyclohexane, carbon dioxide, and the like. And a combination system of methylene chloride is desirable. The “water” is not particularly limited, and for example, ion exchange water, tap water, distilled water, or the like may be used.
When water is used as the foaming agent, the amount is preferably 2.5 to 4.5 parts by weight with respect to 100 parts by weight of the (A) polyol compound. If it exceeds 4.5 parts by weight, the amount of heat generated by the reaction with the isocyanate component increases, and scorch is generated inside the slab stock foam. If it is less than 2.5 parts by weight, the resulting foam has a high density (exceeds 40 kg / m ³ ), which is not preferable from the viewpoint of cost and weight reduction.
In addition, foaming agents other than water typified by methylene chloride have the effect of relaxing the reaction heat accumulated in the slabstock foam by the heat of vaporization, and the effect can be expected as the amount added increases. (A) 3-15 weight part is preferable with respect to 100 weight part of polyol compounds. If it exceeds 15 parts by weight, the resulting urethane foam is softened and the cells become rough. When the amount is less than 3 parts by weight, the vaporization heat cooling effect is reduced, and scorch is likely to occur inside the slab stock foam.

In the polyol component, the catalyst is for accelerating the urethanization reaction between (A) the polyol compound and (C) the isocyanate component described later. The catalyst may be about 0.1 to 3 parts by weight with respect to 100 parts by weight of the (A) polyol compound.
The catalyst may be a known one for foaming urethane foam, and is not particularly limited. For example, triethylenediamine, triethylamine, tripropylamine, triisopropanolamine, tributylamine, trioctylamine, N-methylmorpholine. An amine catalyst such as N-ethylmorpholine is preferred.
In the present invention, as the catalyst, only the above-mentioned amine-based catalyst may be used, and other catalysts may be used in combination depending on the application. Do not use at all.

(C) By using crude diphenylmethane diisocyanate (crude MDI) having an NCO content of 28 to 33% as the isocyanate component, it is possible to produce a slabstock foam with high hardness without generating scorch inside the block. It becomes possible.
With a crude MDI having an NCO content of less than 28%, the desired hardness cannot be obtained. With a crude MDI of more than 33%, the amount of heat generated by the reaction with the polyol compound increases, and scorch tends to be generated in the urethane foam. By the way, the NCO content of TDI (tolylene diisocyanate) is very high at 48.3%, the reactivity is too high, the generation of scorch cannot be suppressed, cell roughness occurs, and the hardness decreases. There is also a problem such as.
Specific examples of the component (C) include trade names “MILLIONATE MR-100”, “MILLIONATE MR-200”, “MILLIONATE MR-200S”, “CORONATE 1130” manufactured by Nippon Polyurethane Industry Co., Ltd .; trade names manufactured by Mitsui Chemicals, Inc. “COSMONATE M-50”, “COSMONATE M-100”, “COSMONATE M-200”, “COSMONATE M-300”, “COSMONATE M-2000”; manufactured by Dow Chemical Japan Ltd. “PAPI 27”, “ PAPI 94 "," PAPI 2940 "and the like.
In the present invention, if the isocyanate index is too low, the desired hardness cannot be expressed, and if it is too high, the amount of heat generated by the reaction with the polyol compound increases and scorch is easily generated in the urethane foam. It is preferable to be within the range, and more preferably 100 to 120.

As described above, the present invention includes, as described above, an infinite number of polyol compounds, foam stabilizers, and isocyanate compounds.
(A) a polyol compound prepared by mixing four kinds of a long-chain EO-containing polyether polyol, a short-chain polyether polyol, a water-foaming polyol, and a polyhydric alcohol to an average hydroxyl value of 200 to 300 mgKOH / g;
(B) a polyether-modified polysiloxane foam stabilizer having a cell open effect;
(C) By selecting and combining crude MDI having an NCO content of 28 to 33% as an isocyanate component, it has a low hardness that did not exist in the past and has sufficient hardness and excellent resilience. A polyurethane foam having a closed cell ratio of 5% or less is obtained.

  In addition to the polyol compound, the foam stabilizer, the foam stabilizer, the polyol component containing the catalyst, and the isocyanate component, the raw materials for the polyurethane foam as described above include a compatibilizer, a flame retardant, a viscosity reducer, Additives commonly used in the production of polyurethane foams, such as fillers, colorants, stabilizers, antioxidants, and UV absorbers, may be used.

  When producing the polyurethane foam of the present invention, the one-shot method in which the polyol component containing the polyol compound, the foaming agent, the foam stabilizer, and the catalyst as described above and the isocyanate component are directly reacted, or the polyol component. Any of the prepolymer methods can be employed in which a prepolymer having an isocyanate group at the terminal is obtained by reacting with the isocyanate component in advance and a polyol component is reacted therewith.

In the polyurethane foam of the present invention, the exothermic temperature at the time of foam formation can be about 170 ° C. or less.
Therefore, conventionally, in order to produce a low density and high hardness polyurethane foam, it was necessary to increase the amount of water as a blowing agent and to set the polyol hydroxyl value high, so when producing by the slabstock method As a result, the scorch due to heat storage is likely to occur inside the block, and as a result, there is a concern about the danger of fire, so it was extremely difficult to manufacture. This can reduce the risk of slabs, and can be manufactured safely using slab stock methods such as continuous slab foaming, and can effectively prevent the occurrence of scorch inside the block.

The polyurethane foam of the present invention has a closed cell ratio of 5% or less measured according to the Beckman method (ASTM D 2856 (1998)).
When the closed cell ratio exceeds 5%, the gas confined in the cell becomes smaller in volume as the temperature decreases from the exothermic temperature during foam formation, or the gas leaks from the cell. Easy to shrink at room temperature.

The polyurethane foam of the present invention preferably has a density of 25 to 40 kg / m ³ and a C2 hardness of ³⁰ to 55 as measured in accordance with JIS K7222. When the C2 hardness is less than 30, it is difficult to use it for applications such as packaging materials and automobile interior materials where rigidity and hardness are important, and when it exceeds 55, flexibility and resilience are less likely to buckle.
Moreover, in the polyurethane foam of this invention, it is preferable to have the resilience which the thickness of the foam compressed 50% recovers to 90% or more of the original thickness after 1 minute. In the case of a normal rigid urethane foam, only about 50 to 60% is recovered when the same test is performed, so that it can be seen that the polyurethane foam of the present invention is very excellent in resilience.
Furthermore, in the polyurethane foam of the present invention, the tensile strength measured according to JIS K6400-5 can be 150 kPa or more, and the elongation measured according to the JIS standard can be 20% or more.

Examples 1-7, Comparative Examples 1-14
≪Raw materials used≫
(A) Polyol compound (i) Long-chain polyether polyol. EO-containing polyether polyol having a number average molecular weight of 5100, an average number of functional groups of 3, and a hydroxyl value of 33 mg KOH / g (trade name “EXCENOL823” manufactured by Asahi Glass Co., Ltd.)
-EO-containing polyether polyol having a number average molecular weight of 6000, an average number of functional groups of 3, and a hydroxyl value of 28 mgKOH / g (trade name “EXCENOL837” manufactured by Asahi Glass Co., Ltd.)
(Ii) Short-chain polyether polyols ・ All-PO polyether polyols having a number average molecular weight of 400, an average number of functional groups of 3, and a hydroxyl value of 400 mgKOH / g (trade name “EXCENOL430” manufactured by Asahi Glass Co., Ltd.)
-All PO polyether polyol with a number average molecular weight of 1000, an average number of functional groups of 3, and a hydroxyl value of 160 mgKOH / g (trade name “EXCENOL1030” manufactured by Asahi Glass Co., Ltd.)
(Iii) Water-foaming polyol-Water-foaming polyol with an average hydroxyl group of 235 mg KOH / g and a viscosity of 800 mPa · s (trade name “ACTOCOL NFS-24” manufactured by Mitsui Chemicals, Inc.)
・ Polyol for water foaming with an average hydroxyl group of 360 mgKOH / g and a viscosity of 500 mPa · s (trade name “ACTOCOL NF-04” manufactured by Mitsui Chemicals, Inc.)
(Iv) Polyhydric alcohol, dipropylene glycol, glycerin (v) Others (polyol compounds not classified in the above (i) to (iv))
-All PO polyether polyol with a number average molecular weight of 5000 and a hydroxyl value of 34.2 mgKOH / g (trade name “ACTCOL MN-5000” manufactured by Mitsui Chemicals, Inc.)
・ Polymer polyol (product "EXCENOL941" manufactured by Asahi Glass Co., Ltd.) obtained by graft polymerization of styrene / acrylonitrile on an all-PO polyether polyol having a number average molecular weight of 3000, an average number of functional groups of 3 and a hydroxyl value of 32 mgKOH / g
-EO-containing polyether polyol having a number average molecular weight of 3000 and a hydroxyl value of 56 mgKOH / g (trade name “EXCENOL230” manufactured by Asahi Glass Co., Ltd.)
-EO-containing polyether polyol having a number average molecular weight of 6700 and a hydroxyl value of 25 mgKOH / g (trade name “EXCENOL851” manufactured by Asahi Glass Co., Ltd.)
A polyether polyol having a number average molecular weight of 200 and a hydroxyl value of 562 mg KOH / g (trade name “PEG # 200” manufactured by Lion Corporation)
-Polyester polyol having a number average molecular weight of 1000 and a hydroxyl value of 115 mgKOH / g (trade name “Teslac 2464” manufactured by Hitachi Chemical Co., Ltd.)

(B) Foam stabilizer / Polyether-modified polysiloxane foam stabilizer with cell open effect (trade name “TEGOSTAB B8871” manufactured by Evonik Degussa Japan Co., Ltd.)
・ Polyether-modified polysiloxane foam stabilizer with cell open effect (trade name “TEGOSTAB B8526” manufactured by Evonik Degussa Japan Co., Ltd.)
・ General-purpose (Polyether-modified polysiloxane type with little cell open effect) Foam stabilizer (trade name "SH-192" manufactured by Toray Dow Corning Co., Ltd.)

(C) Isocyanate compound · Crude MDI with NCO content of 31.5% (trade name “COSMONATE M-200” manufactured by Mitsui Chemicals, Inc.)
・ Crude MDI with NCO content of 24.8% (trade name “COSMONATE MC-82” manufactured by Mitsui Chemicals, Inc.)
・ TDI with NCO content of 48.3% (trade name “COSMONATE T-80” manufactured by Mitsui Chemicals, Inc.)

(D) Foaming agent / water (ion exchange water)
・ Methylene chloride (E) catalyst ・ Dipropylene glycol solution containing 33% triethylenediamine (trade name “Kao Raiser No. 31” manufactured by Kao Corporation)

The raw materials of the polyurethane foams of Examples and Comparative Examples shown in Tables 1 to 4 were mixed, stirred, and discharged onto a belt conveyor. While the belt conveyor moved, the raw material naturally foamed at room temperature and atmospheric pressure, and reacted to produce a foam continuously.
Then, it was cured (cured) in a drying furnace to obtain a polyurethane foam having a block shape (width: about 1000 mm, height: about 50 mm).

About each obtained polyurethane foam, foam properties, presence / absence of scorch, closed cell ratio (%), density (kg / m ³ ), C2 hardness, tensile strength (kPa), elongation (%), restorability, heat and humidity resistance Table 1 to 4 show the results together.

Regarding the “foam properties” and “presence / absence of scorch”, the obtained block-shaped urethane foam was cut into a predetermined length, and the appearance of the foam surface was visually evaluated.
・ Foam properties are “good” when normal foam is formed and cells are uniform in size, and “cell rough” when cells are uneven and sparse, and time after cutting As the foam shrinkage phenomenon was noticed visually over time, it was “shrinkage”, and when the foam was slightly shrunk, “fine shrinkage”, the foam collapsed during the reaction due to insufficient reaction. When the obtained foam had a low mechanical strength and was tattered, it was defined as “collapse”.
・ For the presence or absence of scorch, “○” indicates that there was no scorch, and “×” indicates that the scorch occurred.

Regarding “closed cell ratio (%)”, “density”, “C2 hardness”, “tensile strength”, “elongation”, “restorability”, “moisture and heat resistance”, the length is 300 mm × width 300 mm × thickness 10 mm. Each urethane foam cut to size was measured according to the following method.
-The closed cell ratio (%) was measured based on the Beckman method (ASTM D 2856 (1998)).
The density (kg / m ³ ) was measured based on JIS K7222.
-C2 hardness was measured with Asker rubber hardness meter C2.
-Tensile strength (kPa) was measured based on JIS K6400-5.
-Elongation (%) was measured based on JIS K6400-5.
-Restorability is that the foam thickness recovers to 90% or more of the original thickness in 1 minute after the sample is compressed 50% (ie, compressed to a thickness of 5 mm). Those with a thickness of 9 mm or more were marked with “◯”, and those with less than 90% of the original thickness (thickness less than 9 mm) were marked with “x”.
・ For heat and humidity resistance, urethane foam is subjected to an accelerated test for 30 days at a temperature of 80 ° C and a humidity of 95%, and the foam after the test maintains 70% or more of the tensile strength of the foam before the test. Was marked with “◯”, and the case of less than 70% was marked with “x”.

From Table 1, all of the polyurethane foams of Examples 1 to 7 had a density of 33 kg / m ³ or less and a C2 hardness of 35 or more. %, It can be produced without generating scorch inside the block in slabstock molding, and excellent in tensile strength, elongation, and heat and humidity resistance.

From Table 2, (A) In Comparative Example 1 where the average hydroxyl value of the polyol compound was too high, scorch was generated, while in Comparative Example 3 where it was too low, C2 hardness was poor.
Further, Comparative Example 2 has a good foam property due to the combined use of a water-foaming polyol having excellent dimensional stability and a polymer polyol obtained by graft polymerization of styrene / acrylonitrile, which is generally said to be excellent in hardness. In addition, the urethane foam having the desired hardness can be produced. (I) Since a long-chain EO-containing polyol is not blended, there is no restoration property and a polymer polyol containing a filler component is used. The strength (tensile strength, elongation) was insufficient.

(I) In Comparative Example 4 using a polyether polyol having a molecular weight of 5000 and zero EO instead of the long-chain EO-containing polyol, the foam was not formed by the urethane reaction and collapsed.
In addition, as shown in Table 4, (i) in Comparative Example 11 using an EO-containing polyether polyol having a molecular weight of 3000 instead of the long-chain EO-containing polyol, a foam was formed, but the closed cell ratio was It was 6%, slight shrinkage occurred over time, elongation was insufficient, and restoration properties could not be obtained.
Furthermore, (i) Comparative Example 12 using an EO-containing polyether polyol having a molecular weight of 6700 instead of the long-chain EO-containing polyol had insufficient hardness.

  (C) In Comparative Example 5 in which TDI having an NCO content of 48.3% was used as the isocyanate compound, cell roughening occurred and the hardness was low, and scorch was also generated (see Table 2). Further, in Comparative Example 14 using crude MDI having an NCO content of 24.8%, although a good foam was obtained, the hardness was insufficient (see Table 4).

  As shown in Table 2, in Comparative Example 6 using a general foam stabilizer with little cell open effect, the cell foam was insufficient and the closed cell rate was high, and after cutting into the aforementioned urethane foam, time elapsed A significant shrinkage phenomenon was also confirmed. When the foam shrinks in this way, the closed cell ratio cannot be measured. However, in the present invention, as shown in Example 7, when the closed cell ratio is 5% or less, the foam shrinks. I couldn't.

  As shown in Table 3, in (ii) Comparative Example 7 using a polyester polyol having a molecular weight of 1000 instead of a short-chain polyether polyol, a polyester having a low density, a high hardness and a restorability can be obtained. Due to the high viscosity of the polyol, it does not mix well with other polyols, resulting in cell roughness due to poor stirring, and inferior moisture and heat resistance due to the use of esters, and an accelerated test under high temperature and high humidity. After that, the foam softened and the strength decreased.

(Ii) In Comparative Example 8 in which the short-chain polyether polyol was not blended, the restoring property was not obtained, and the hardness and strength were insufficient (see Table 3). Further, (ii) in Comparative Example 13 using a polyether polyol having a molecular weight of 200 instead of the short-chain polyether polyol, the foam contracted (see Table 4).
(Iii) In Comparative Example 9 in which the water foaming continuous polyol was not blended, the cell foam was insufficient and the closed cell ratio was high, as in Comparative Example 6, and the urethane foam obtained over time contracted. I have.
(Iv) In Comparative Example 10 in which no polyhydric alcohol was blended, cell roughening occurred and sufficient hardness was not obtained.

  The polyurethane foam of the present invention is lightweight (low density) and high in hardness, and also has a certain degree of flexibility and resiliency. Particularly useful in the field of molded articles.

Claims (2)

A polyurethane foam obtained by reacting a polyol component containing a polyol compound, a foaming agent, a foam stabilizer, and a catalyst with an isocyanate component,
(A) The polyol compound comprises (i) a polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide having a number average molecular weight of 4000 to 6000 and a hydroxyl value of 20 to 60 mgKOH / g, and (ii) a number average molecular weight of 300. Polyether polyol having a hydroxyl value of 100 to 800 mg KOH / g, (iii) polyol for water foaming having an average hydroxyl value of 200 to 600 mg KOH / g and a viscosity of 1700 mPa · s or less, and (iv) a polyhydric alcohol. Four kinds of mixed polyols having an average hydroxyl value adjusted to 200 to 300 mgKOH / g,
(B) The foam stabilizer is a polyether-modified polysiloxane foam stabilizer,
(C) the isocyanate component is crude MDI having an NCO content of 28-33%,
And
A polyurethane foam having a closed cell ratio of 5% or less. Restoration in which the density is 25 to 40 kg / m ³ , the hardness measured with an Asker rubber hardness tester C2 type is 30 to 55, and the thickness of the 50% compressed foam recovers to 90% or more of the original thickness after 1 minute. The polyurethane foam according to claim 1, which has properties.