JPS60161415A - Preparation of polyurethane - Google Patents

Abstract

PURPOSE:To obtain a polyurethane having improved curing properties and water resistance, by reacting a polyol containing a specific OH terminal urethane prepolymer as at least part of the polyol with an organic polyisocyanate. CONSTITUTION:A OH terminal urethane prepolymer of (A) an organic polyiso cyanate (e.g., toluene diisocyanate, etc.), (B) a polyether polyol having 20-120 hydroxyl number (e.g., compound obtained by adding an alkylene oxide to a compound containing two active hydrogen atoms, etc.), and (C) a primary OH- containing low-molecular diol (e.g., diethylene glycol, etc.) is used as at least part of polyol, and reacted with an organic polyisocyanate optionally in the presence of a blowing agent (e.g., water and/or flon), to give the desired polyurethane. USE:Panels for instruments, steering wheel of automobiles, various bumpers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyurethane, specifically a method for producing polyurethane having improved curing properties and water resistance, and in particular, a method for producing polyurethane having improved cure properties and water resistance, and particularly a method for producing polyurethane having improved cure properties and water resistance.
It is abbreviated as Mi. ) The present invention relates to a method for producing polyurethane that provides excellent curing properties and water resistance when molded with polyurethane.

In recent years, the RIM process has been put to practical use as a means of making urethane moldings for applications such as instrument panels, automobile steering wheels, various bumper and shock absorber materials, and the like. When producing urethane molded products for the above-mentioned uses using the RIM method, excellent curing properties are required. Generally, it is known that in order to improve curing properties, a polyoxyalkylene polyol containing a hydrophilic polyoxyethylene chain is used as one of the main raw materials; The molded products manufactured using this method have poor water resistance, and a product that can be used satisfactorily for automotive exterior materials such as bumpers has not yet been developed. As a result of studies to eliminate the above-mentioned drawbacks, the present inventors have found that It has been discovered that a polyurethane with excellent curing properties and excellent water resistance can be obtained by using the OH-terminated urethane prepolymer of

That is, the present invention provides a method for producing polyurethane by reacting an organic polyisocyanate and a polyol, if necessary in the presence of a blowing agent, in which at least a part of the polyol contains an organic polyincyanate (a) and a polyol having a valence of 0 to 20.
120 polyether polyol (b) and primary OH
A method for producing polyurethane characterized by using an OH-terminated urethane prepolymer with a low-molecular-weight diol (c) containing the polyurethane (first invention); This is a method for producing polyurethane (second invention) characterized by producing a molded product.

Production of the polyurethane of the present invention [The polyether polyol (1), which is the raw material for the OH-terminated urethane prepolymer used here, is commonly used in the production of polyurethane, and contains at least two active hydrogen atoms. (e.g. polyhydric alcohols, polyhydric phenols,
Compounds having a structure in which one or more alkylene oxides are added to polycarboxylic acids, amines) and mixtures thereof 75E can be mentioned. The above polyhydric alcohols include ethylene glycol, propylene glycol, 1
, 4-phytanediol, 1,6-hexanedio7J, dihydric alcohols such as diethylene glycol and neopentyl glycol, octahydric alcohols such as glycerin, trimethylolpropane, hexanetriol, and trimethylolethane, pentaerythritol, sorbitol, and methyl glucoside. Any polyhydric alcohol with a valence of 4 or more; examples of polyhydric phenols include polyhydric phenols such as pyrogallol and hydroquinone, as well as bisphenols such as bisphenol A;
Examples of polycarboxylic acids include aliphatic polycarboxylic acids such as succinic acid and adipic acid.

Aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, and trimellitic acid; and amines such as ammonia, monoamines (alkylamines, aniline, etc.), and polyamines (ethylenediamine).

diethylenetriamine, tolylenediamine, piperazine, aminoethylpiperazine, etc.), and alkanolamines (triethanolamine, tripropaturamine, etc.). Two or more kinds of the above-mentioned active hydrogen atom-containing compounds can also be used. Among these, preferred are polyhydric alcohols (especially ethylene glycol,
, 4-butanediol, neopentyl glycol, glycerin, trimethylolpropane) and polyhydric phenols (especially hydroquinone, bisphenol). As the alkylene oxide, ethylene oxide, propylene oxide, 1.2-, 1.8- or 2,
Examples include 8-butylene oxide, tetrahydrofuran, styrene oxide, and dichlorohydrin.

The alkylene oxides may be used alone or in combination of two or more, and in the latter case, block addition, random addition, or a mixture of both may be used. Among these alkylene oxides, propylene oxide and its combination with ethylene oxide (random and/or block) are preferred, but other alkylene oxides (butylene oxide, tetrahydrofuran) may be used depending on the required properties. , styrene oxide, etc.) is also preferred. The proportion of ethylene oxide in the alkylene oxide is preferably 80% (weight %, the same applies hereinafter) or less, particularly 20% or less. If it exceeds 80%, the water resistance of the resulting polyurethane decreases, which is not preferable. Also, a primary OH-containing polyol having a terminal oxyethylene chain (tipped type, balanced type, etc.; terminal oxyethylene chain content of 5 to 80 chains (preferably 8 to 20%)).

1st class 0 ■ Content rate 10-90% (preferably 80-80%
)], and by using this, the time required for prepolymerization can be shortened.

Moreover, in the present invention, as the polyether polyol (b), it is possible to balance the physical properties of vinyl polyurethane instead of or together with the above-mentioned ordinary polyether polyol.

Ethylenically unsaturated monomers used in the production of polymer polyols include (a) acrylic acid, methacrylic acid, and derivatives thereof: acrylonitrile, methacrylonitrile.

Acrylic acid, methacrylic acid and their salts, methyl acrylate, methyl methacrylate, dimethylamine ethyl methacrylate, acrylic acid amide.

Methacrylic acid amide, etc.; (b) aromatic vinyl monomer:
Styrene, α-methylstyrene; (Cl olefinic hydrocarbon monomer: ethylene, propylene.

Butadiene, imbutylene, imprene, 1,4-pentadiene, etc.; (dl vinyl ester monomer: vinyl acetate, etc.; (e) vinyl halide monomer: vinyl chloride, vinylidene chloride, etc.; (f) vinyl ether monomer : vinyl methyl ether, etc. Among these, preferred are acrylonitrile, methyl methacrylate, styrene, and butadiene. Particularly preferred are acrylonitrile, a combination of acrylonitrile and styrene (styrene:acrylonitrile weight ratio 0:100-60:
40). The ratio of the polyether polyol and monomer used in the polymer polyol can be varied over a wide range, but usually the ethylenically unsaturated monomer (or polymer) is used per 100 parts (parts by weight, same hereinafter) of the polyether polyol. It is 2 to 70 parts, preferably 5 to 40 parts. The content of ethylenically unsaturated monomers (polymers) in the entire polyether polyol (b) used for producing the OH-terminated prepolymer is usually 80% or less, preferably 20% or less. The preparation of polymeric polyols from polyols and ethylenically unsaturated monomers can be carried out by one conventional method.

For example, a method in which an ethylenically unsaturated monomer is polymerized in a polyol in the presence of a polymerization catalyst (radical generator, etc.)
U.S. Patent No. 8888851, Japanese Patent Publication No. 89-24787
No., Special Publication No. 47-47999, Japanese Patent Publication No. 1589-1989
No. 4) and a method in which a polymer obtained by pre-polymerizing the above monomers and a polyol are subjected to craft polymerization in the presence of a radical generator (Japanese Patent Publication No. 47-47597). The former method is preferred. Polymerization catalysts (radical generators) used in polymerization reactions include azo compounds,
Peroxides, persulfates, perborates, etc. can be used, but
Practically speaking, azo compounds are preferred. The amount used is not particularly limited, and is, for example, 01 to 20 parts by weight, preferably 01 to 15 parts by weight, per 100 parts by weight of the ethylenically unsaturated monomer (or polymer). The above polymerization can also be carried out in solvents such as toluene.

It can also be carried out in the presence of xylene or the like. The reaction temperature is usually 50-170"C, preferably 90-150"C.

The OH value of the polyether polyol (b) is generally 20 to
120, preferably 25-80. When the OH value is less than 20, the reactivity during polyurethane production is significantly reduced, resulting in insufficient curing. When the OH value exceeds 120, the reactivity is high and the workability of polyurethane production becomes poor.

Another raw material for the urethane prepolymer is, for example, alkylene glycol and/or di- or polyalkylene glycol having a molecular weight of 400 or less and having 2 to 4 carbon atoms, such as ethylene glycol.

Propylene glycol, 1,4-butanediol.

Examples include diethylene glycol, low molecular weight polyethylene glycol, and the like. The molecular weight of the low-molecular polyalkylene glycol (polyethylene glycol, etc.) can be varied depending on the required physical properties of the urethane, but generally a molecular weight of 200 or less is preferred.

In the case of polyethylene glycol, if the molecular weight is too high,
The increased hydrophilicity causes the water resistance of the produced polyurethane to decrease significantly. Among low molecular weight diols, terminal 1 is preferable.
grade OH, especially diethylene glycol.

The organic polyisocyanate (a) used as a raw material for the OH-terminated urethane prepolymer in the present invention includes:
Those conventionally used in polyurethane production can be used. For example, aliphatic polyinsyanate (hexamethylene diisocyanate).

lysine diisocyanate, etc.), alicyclic polyisocyanates (hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, etc.), aromatic polyisocyanates [tolylene diisocyanate (TDI) and its isomer mixture (TDI-
and mixtures thereof. Among these, aromatic diisocyanates are preferred, and TDI is particularly preferred.

It is MDI. These polyisocyanates are crude polyisocyanates, such as crude TDI, crude MDI [
Phosgenated product of crude diaminodiphenylmethane (a mixture of diaminodiphenylmethane, a condensation product of formaldehyde and an aromatic amine or a mixture thereof, and a small amount (for example, 5 to 20% by weight) of an octafunctional or higher polyamine): polyallyl polyisocyanate ( PAPI) ),
or modified polyisocyanates such as liquefied MD
I (carfoshiimito-modified, trihydrocarbylphosphate-+-modified, etc.) can also be used.

OH-terminated urethane prepolymer is polyisocyanate (
Reacting al, polyether polyol (b) and low molecular diol (C1) in any order [for example (b)
and (c) are reacted with (a), (al and (b)
(C) or (C) to produce an NCO-terminated prepolymer and then react it with (C) or (b), or a combination thereof; preferred is one whose ends are capped with (C). , that is, it has the residue (b) bonded to the urethane bond inside and the formula -N at the end.
It has a group represented by H-COO-A-OH [where A is a residue of (C)], and such an OH-terminated prepolymer has a group represented by (b) [or (b) and (c)]. part of]
It can be produced by reacting C with N(30-terminated prepolymer) [or an OH-terminated prepolymer of (C) with (a)].

Such an OH-terminated prepolymer has the following general formula Q.
), (2), and mixtures containing the same.

(T-E), 1(T-A)mon)X=1 (in formula 21,
T is -000-NH-polyisocyanate residue -Nu-
A group represented by COO-, A is a residue of a low molecular weight diol, E
is the residue a of the polyether diol, E' is the residue of the X-valent polyether polyol, X is the number of functional groups of the polyether polyol (2, 8, 4, . . . ), and m.

m', l, n are integers of 0 or 1 or more (Multiple m, m', n in a molecule may be the same or different, respectively.) However, at least a part (preferably all) of m is an integer greater than or equal to 1.

In producing the OH-terminated prepolymer, (a).

The proportions of (b) and (C) can be varied as long as an OH-terminated prepolymer can be produced.
The equivalence ratio (NCO10H ratio) with b) and (c) is usually 1/1・1~3, OR'E shi<ha 1/1.1~2
．． 0, the equivalent ratio of (a) and (b) is usually 12-25/
1, preferably 1.8 to 2.2/1, and the equivalent ratio of (b) to (C1) is usually 1105 to 30, preferably 171.5 to 1.
2.5. If the ratio of (a) to (b) and (C) is smaller than the above range, the prepolymer will have a significantly high viscosity and will be difficult to handle, and if it is larger than the above range, the oral stability of the prepolymer will decrease, which is undesirable. . If the proportion of (b) is too high, the prepolymer will have a significantly high viscosity and will be difficult to handle.
) is undesirable, as the reactivity during polyurethane production increases and the elongation of the molded product decreases when it is made into a molded product.

In the present invention, the OH-terminated urethane prepolymer may be modified with a vinyl polymer. Such modification can be carried out at any stage in the production of the above-mentioned OH-terminated prepolymers, and in addition to those using the above-mentioned polymer polyols, for example OH-terminated prepolymers or their intermediates [the above-mentioned NCO-terminated prepolymers] , an OH-terminated prepolymer of (C) and (a), a mixture of (b) and (C), etc.)]. As the ethylenically unsaturated monomer used for modification, those listed in the section regarding polymer polyols can be used. The conditions of the polymerization method 9 may be the same as those for producing the polymer polyol, except that an OH-terminated prepolymer or an intermediate thereof is used instead of the polyether polyol. (However, in the case of an NCO-terminated prepolymer, a monomer without active hydrogen is used.) Although the proportion of monomers (polymers) used for modification can be varied, the reaction and/or Usually 50 parts or less, preferably 2 to 40 parts, more preferably 5 to 25 parts per 100 parts of unmodified polyether polyol present in the mixture.
Department.

The OR value of the OH-terminated urethane prepolymer is usually 20 to 6.
0, preferably 20 to 50. If the OH number is lower than the above, the curing properties will be poor, and if it is higher than the above, the compression set of the foam will be poor, which is not preferable. The urethane group content of the prepolymer is usually 5p to 17p.

In carrying out the method for producing polyurethane of the present invention, it is necessary to react the above-mentioned O-terminated urethane prepolymer with an organic polyisocyanate, alone or in combination with other high-molecular polyols and/or low-molecular polyols. Other polymer polyols that may be used include polyether polyols, polyester polyols, polymer polyols, etc., and commonly used types of these polyols can be used.Polyether polyols As, the above OH
Those described as the raw material (b) for the terminal prepolymer can be mentioned. Those having an oxyethylene chain content of 25 or less are preferred. In addition, low-molecular polyols include those described as the raw material (C) above and/or polyols with a valence of 8 or more; )
Alkylene oxide (02-4) low molar adducts of the active hydrogen atom-containing compounds listed as raw materials for the above examples.

In the present invention, the amount of the OH-terminated urethane prepolymer used in the polyol can be varied depending on the required water resistance, curing properties, foam properties, etc.;
Generally, it is usually 5 to 100% based on the weight of the polyol, preferably 80 to 70 inches, and most preferably 20 to 50 inches. The amount of low molecular weight polyol is usually 80% of the total polyol.
% or less, preferably 5 to 25 inches. The average OH number of the polyol (total) is usually 20 to 120, preferably 25
~80.

Polyols may optionally be used in combination with polyamines. Tolylenediamine is a polyamine.

Xylylenediamine, diaminodiphenylmethane.

Methylenebis-〇-chloroaniline is mentioned.

The amount used can be varied depending on the required rigidity, etc., but 1
0% or less, preferably 5% or less.

The organic polyisocyanate used in the method for producing polyurethane of the present invention includes raw materials for the OH-terminated prepolymer (those listed as al) and/or obtained by reacting an excess polyisocyanate (TDI, MDI, etc.) with a polyol. Polyols used in the production of the NOO-terminated prepolymer include polyols having an equivalent weight of 30 to 200, such as glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; Examples include triols such as methylolpropane and glycerin; high-functional polyols such as pentaerythritol and sorbitol; and alkylene oxide (ethylene oxide and/or propylene oxide) adducts of these. Among these, preferred are those having 2 to 8 functional groups. The content of free incyanate groups in the above prepolymer is usually 1 to 10.
38 inches, preferably 15 to 30 inches, particularly preferably 25 to 30 inches
It is 80%.

The amount of organic polyisocyanate can be varied over a wide range depending on the required physical properties of the polyurethane, but it is generally used in such an amount that the incyanate index is usually 80 to 115, preferably 100 to 110.

In carrying out the process of the invention, the reaction may be carried out in the presence of a blowing agent to produce foams, or elastomers and foams may be produced without the use of blowing agents.

You may also manufacture sheets, paints, adhesives, etc.

Examples of the blowing agent that may be used if necessary include water and/or halogen-substituted aliphatic hydrocarbon blowing agents (fluorocarbons such as trichloromonofluoromethane). The amount of blowing agent used depends on the density of the foam.

The amount of water can be varied depending on the physical properties, but in the case of water, for example, 2 to 5 parts of water can be used based on the total amount of polyol.

Further, when water and a halogen-substituted aliphatic hydrocarbon blowing agent are used together, the halogen-substituted aliphatic hydrocarbon blowing agent can be used in an amount of, for example, 20% or less based on the total polyol.

Further, if necessary, the reaction can be carried out in the presence of a catalyst, a surfactant (such as a silicone surfactant), or other auxiliary agents. These auxiliaries include those commonly used in polyurethane production [for example, Polyurethane J (19
You can use the one listed in 1960 (published by Makishoten). Specifically, the catalysts include amine catalysts such as triethylenediamine, tetramethylethylenediamine, and tetramethylhexylene diamine; tin catalysts such as stannath octoate, dibutyltin dilaurate, and stannath oleate; and lead catalysts such as lead naphthenate. manufactured by Nion Carbide) and Toray Silicone 8H192, 5)i
190 (Toreshiri: manufactured by Iez).

Pigments are used as necessary when producing polyurethane.

Fillers, solvents, thixotropic agents, etc. can also be added.

The polyurethane production method may be the same as the conventional one, and the one-shot method and prepolymer pouring can also be applied.

For example, ``Polyurethanes: Chemistry and Technology'' and ``Polyurethanes: Chemistry and Technology,'' Bart 1. This can be carried out by the method described in Chemistry J (published by Interscience Publishers, 1962).

In the present invention (second invention), a method for manufacturing a polyurethane molded product by molding by RIM method can be carried out by a conventional method. For example, a cross-linking agent, a catalyst, a blowing agent (water or Freon 11) if necessary, a pigment, and a foam stabilizer are added to the polyol and mixed uniformly to form the A liquid, and an organic isocyanate is prepared in advance as the B liquid. Fill the A and B liquid tanks of the foaming machine. The injection nozzle of the high-pressure foaming machine and the injection port of the mold are connected in advance, and liquids A and B are mixed with a mixinog head and injected into a closed mold, and after curing, the mold is demolded.

The polyurethane manufacturing method of the present invention is particularly useful for molding by the RIM method, but other methods such as RIM
Molding other than the method (molding by open mold).

It can also be applied to various methods such as PVC integral molding method, vacuum molding, cold cure and hot cure), slab method, on-site construction, spray method, injection, coating-impregnation, etc.

Forms of polyurethane include foam and skin foam (integral method, mold coat method).

Examples include Enstomer and Sicilant.

According to the present invention, the above (al, (bl and (C1) OH
By reacting a terminal urethane prepolymer with an organic polyisocyanate, a polyurethane with excellent curing properties and excellent water resistance can be obtained. Furthermore, polyurethane having sufficient rigidity can be obtained with a smaller amount of crosslinking agent than in the conventional method. Furthermore, since the OR-terminated prepolymer has high activity, it has excellent curing properties and requires only a small amount of catalyst, thereby avoiding deterioration of the physical properties of polyurethane due to the use of a large amount of catalyst.

A method of reacting the OH-terminated prepolymer and an organic polyisocyanate according to the present invention and molding by RIM method (Second
The invention) is superior to the conventional method in the following points: (1) Because it has excellent curing properties, it is effective in shortening the cycle time from injection to demolding, which is the original purpose of the RIM method. Extremely effective◎ (11) Excellent curing properties even with a small amount of catalyst, so the increase in viscosity when reacted with polyisocyanate is moderate, preventing insufficient filling and voids in molded products due to poor flowability. generation etc. can be avoided.

(Il+) When producing polyurethane with 1i111 properties, it is possible to achieve the same stiffness with a smaller amount of crosslinking agent than the conventional method, and therefore it has superior temperature characteristics (physical properties change from low to high temperatures) compared to the conventional method. Polyurethane molded products can be obtained.

(Song) In the conventional RIM method, a polyether polyol with a high content of oxyethylene chains was used to increase the curing property, resulting in a decrease in the water resistance of the molded product.
In the RIM method of the present invention, by using an OH-terminated prepolymer with a low content of oxyethylene chains, a decrease in water resistance of the molded article can be avoided.

Furthermore, in addition to the RIM method, the method of the present invention can be applied to various types of polyurethane molded products (foams, elastomers, sealants, coating agents, etc.), especially polyurethane manufacturing methods that conventionally required relatively large amounts of catalysts, and crosslinking agents. It exhibits excellent effects in the polyurethane manufacturing method used.

The polyurethane obtained by the present invention is particularly useful for applications requiring water resistance, such as automobile exterior materials such as bumpers and air spoilers, and automobile interior materials such as automobile seat cushions, crash pads, and steering wheel covers. materials, other vehicles (trains, etc.)
It is useful in various application fields such as exterior and interior materials for aircraft, ships, etc.

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. (The parts shown in the examples indicate parts by weight.) The urethane prepolymers and polyols containing terminal hydroxyl groups used in the following examples and comparative examples are as follows: 28 polypropylene glycol 4000.9 (1 mol) and tolylene diisocyanate (TDI-80) 848 g (2 mol) were charged and reacted at 75 to 85°C for 12 hours until the NCO content became 1.8 to 19%. After that, diethylene glycol 2
12 g (2 mol) was added and reacted for a further 7 hours to form the prepolymer ■ 51 4-tulocolbene with polyoxypropylated glycerol 800J9 (1 mol) having an OH value of 28 Todolylene diisocyanate (TDI-80) 261.9 (8 mol) and the NOO content was 12 to 1 at 75 to 85°C.
After reacting for 18 hours with 8-tinynaruma, diethylene glycol 15J9 (8 mol) was added and the reaction was further continued for 9 hours.

Prepolymer m 51 4-tulocolben, solid content (polymer) content 20% produced from polyokine propylated glycerol (OH value 8B) and acrylonitrile, polymer polyol 800J9 (1 mol) with OH value 28 and tolylene diisocyanate. (TDI-80) 261y (8MoJL') was charged and reacted at 75-85°C for 18 hours until the NCO content became 12-13g, and then diethylene glycol 15
9 g (8 mol) was added and the reaction was further continued for 9 hours.

Polyol A: 76 parts of propylene glycol and 8 parts of propylene oxide
0HV28 polyether polyol obtained by adding 470 parts of ethylene oxide and further adding 900 parts of ethylene oxide.

Polyol B A polyether polyol with an OHV of 88 obtained by adding 4,698 parts of propylene oxide to 92 parts of glycerin and further adding 900 parts of ethylene oxide.

Polyol C A polymer polyol with an OH value of 28 obtained by charging and polymerizing 200 parts of acrylotrile to 8,800 parts of polyol.

These analytical values are shown in Table 1.

Table 1 Examples 1 to 4 and Comparative Examples 1 to 2 According to the foaming recipe shown in Table 2, flexible urethane foam and RIM molded products were manufactured under the foaming and molding conditions shown in Table 8.

Table 4 shows the physical properties of the obtained polyurethane. In addition, the hardness reduction rate due to water absorption rate and humidity is 1 or less (1), (
Measurement was carried out as in 2): (1) The test piece was immersed in 40°C warm water for 240 hours, then the water was wiped off with gauze and the weight was measured.

(2) Leave the test piece in a constant temperature and humidity chamber at 50°C x 95% RH for 80 minutes, and immediately measure the 25 inch compressive strength (#/814m) after taking it out.Table 8

Claims (1)

[Scope of Claims] 1. A method for producing polyurethane by reacting an organic polyisocyanate and a polyol, if necessary in the presence of a blowing agent, wherein at least a part of the polyol contains an organic polyisocyanenite (a) and an OH compound. A process for producing polyurethane, characterized in that it uses an OH-terminated urethane prepolymer with a polyether polyol (b) having a molecular weight of 20 to 120 and a primary OH-containing low-molecular diol (C). 2. The prepolymer has f bonded to a urethane group internally.
b) with the formula -NH-000-A-OH at the end
The manufacturing method according to claim 1, which has a group represented by [where A is a residue of a low molecular weight diol (c)]. 3. The production method according to claim 1 or 2, wherein the prepolymer and another high molecular weight polyol and/or low molecular weight polyol are used as the polyol. 4. The prepolymer is added to
The manufacturing method according to any one of claims 1 to 3, wherein 100% by weight is used. 5. The manufacturing method according to any one of claims 1 to 4, wherein the organic polyisocyanate, the prepolymer, and, if necessary, other high molecular weight polyols and/or low molecular weight polyols are reacted and foamed in the presence of a foaming agent. 6. In a method for producing polyurethane by reacting an organic polyisocyanate and a polyol in the presence of a blowing agent if necessary, organic polyisocyanate (a) and a polyether polyol having an OH value of 20 to 120 are used as at least a part of the polyol. (b) and a primary OH-containing low-molecular-weight diol (C1) using a 0■-terminated urethane prepolymer and reacting with the reactor injection molding method to produce a polyurethane molded product. 7. The prepolymer has internally bonded urethane groups (
bl residue, with the formula -NH-Coo-A-OH at the end
The manufacturing method according to claim 6, which has a group represented by [where A is a residue of a low molecular weight diol (C)]. 8. The manufacturing method according to claim 6 or 7, wherein the organic polyisocyanate and the polyol are reacted in the presence of a foaming agent and foam-molded.