JP3263107B2 - Method for producing urethane prepolymer with excellent thermal stability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a urethane prepolymer, and more particularly to a method for producing a urethane prepolymer having excellent heat stability which is useful for obtaining a polyurethane elastomer.

[0002]

2. Description of the Related Art Conventionally, polyurethane elastomers are produced by tolylene diisocyanate and polyols such as polytetramethylene ether glycol, polyoxypropylene glycol and polyester polyol as represented by adiprene, vibracene, and cyanaprene. Is known. A method is known in which a urethane prepolymer having an isocyanate group at the molecular terminal obtained by reacting with an aromatic polyamine such as methylenebis (o-chloroaniline) is reacted and cured by heating. These polyurethane elastomers are widely used in industrial products such as rolls, solid tires and belts because of their excellent abrasion resistance, mechanical strength and rebound resilience.

When a polyurethane elastomer is molded, the urethane prepolymer is preliminarily used to improve the workability by lowering the viscosity of the urethane prepolymer and to prevent precipitation when mixing and stirring the heated and melted aromatic amine and the urethane prepolymer. It is necessary to heat to １００100 ° C. However, when the urethane prepolymer is 60 to 10
When heated at 0 ° C. for a long time, the urethane prepolymer tends to deteriorate, and the physical properties of the obtained polyurethane elastomer tend to deteriorate. For the purpose of improving the heat resistance of the urethane elastomer, a method using various stabilizers is known, but there is little known about a method for preventing the thermal deterioration of the urethane prepolymer as described above. Attempts have been made to slightly add an acid such as benzoyl chloride, but the effect is not sufficient.

[0004]

Although the mechanism of thermal degradation of the urethane prepolymer has not been elucidated, in general, preheating when using the urethane prepolymer and heating in the feed tank to the molding machine are performed under nitrogen. Since the reaction is performed in an atmosphere, it is considered that the deterioration is not caused by a so-called oxidation reaction but is caused by a side reaction involving an isocyanate group.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for improving the thermal stability of a urethane prepolymer. As a result, a urethane having an isocyanate group at a molecular terminal by reacting an organic polyisocyanate with a polyhydroxy compound is disclosed. In producing the prepolymer, the general formula
(RO) ₂ POH or (RO) ₂ PH = O (wherein, R represents. An alkyl group or an aryl group having 1 to 18 carbon atoms) at least organopolyphosphite one or more phosphite represented by Isocyanate and polyhydroxy compound
It has been found that the coexistence during the reaction significantly improves the thermal stability of the urethane prepolymer, and the present invention has been completed.

The production of the urethane prepolymer is carried out by reacting an organic polyisocyanate with a polyhydroxyl compound according to a known method. At this time, the above phosphite may be coexisted. 2,4-tolylene diisocyanate as an organic polyisocyanate,
2,6-tolylene diisocyanate and its mixture (abbreviation TDI, the same applies hereinafter), diphenylmethane diisocyanate (MDI), or its carbodiimide derivative (liquid MDI), and its mixture, xylylene diisocyanate (XDI), paraphenylene diisocyanate (PP
DI), isophorone diisocyanate (IPDI), methylene bis (4-cyclohexyl isocyanate) (H
MDI), 1,6-hexamethylene diisocyanate (HDI), cyclohexane diisocyanate (CHD)
I) and the like are used.

Examples of the polyhydroxyl compound include polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran, polyether such as polyoxyalkylene polyol obtained by adding propylene oxide and / or ethylene oxide to water, propylene glycol, glycerin and the like. Polyols, ethylene glycol, propylene glycol, diethylene glycol,
One or two of 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, etc.
More than species and malonic acid, maleic acid, succinic acid, adipic acid, glutaric acid, pimelic acid, sebacic acid, phthalic acid,
Polyester polyols obtained by dehydration condensation of one or more of isophthalic acid and terephthalic acid; polyester polyols obtained by ring-opening polymerization of propiolactone, butyrolactone, caprolactone, and the like; hydroxyl-terminated liquid polybutadiene; Castor oil polyols and the like. In addition, one or more of ethylene glycol, propylene glycol, diethylene glycol, 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, and the like can be used in combination.

The general formula (RO) ₂ PO used in the present invention
H or (RO) ₂ PH = O (where R represents 1 carbon atom)
-18 represents an alkyl group or an aryl group. As the phosphite represented by the formula (2), di-2-ethylhexyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen hydrogen phosphite and the like can be used. When the number of carbon atoms is 19 or more, the melting point increases and the solubility in the urethane prepolymer deteriorates. The amount of the phosphite used is 0.01 to 0.01% based on the urethane prepolymer.
10% by weight is suitable. Among them, a particularly preferred range is 0.1 to 5% by weight. Further, existing antioxidants represented by hindered phenols, benzoyl chloride and the like can be used in combination.

[0009]

The present invention will be specifically described below with reference to examples and comparative examples. Table 1 collectively shows Examples and Comparative Examples.

[0010]

[Table 1]

Example 1 A three-necked flask equipped with a stirrer, a thermometer and a nitrogen inlet tube was charged with 2,4-tolylene diisocyanate (80% by weight).
348 g of tolylene diisocyanate containing 20% by weight of 2,6-tolylene diisocyanate was mixed with polytetramethylene ether glycol 1 having an average molecular weight of 1,000.
2,000 g, 6.7 g of di-2-ethylhexylhydrogen phosphite (trade name: Chelex H-8: manufactured by Sakai Chemical Industry Co., Ltd.) at 80 ° C. for 4 hours in a nitrogen stream,
Viscosity of 7,500 containing 6.2% by weight of terminal NCO groups
A cps / 25 ° C. urethane prepolymer was obtained. 100 parts by weight of the urethane prepolymer thus obtained is
After degassing under reduced pressure at 100 ° C., methylene bis (o-chloroaniline) previously dissolved at 120 ° C. was added so that the equivalent ratio of the NCO group to the NH ₂ group became 1.1, and the mixture was stirred without adding bubbles. Cast into a mold heated to ℃ 10
Cured at 0 ° C. for 24 hours. The physical properties of the cured product of the obtained polyurethane elastomer were measured in accordance with JIS K-6301. For the measurement of tan δ, a viscoelastic spectrometer SDM5500 (manufactured by Seiko Instruments Inc.) was used. After heating the urethane prepolymer in a hot air circulating drier adjusted to 100 ° C. for 12 hours, the physical properties of the cured product were measured in the same manner. The results were 100 as shown in Table 1.
Even when the urethane prepolymer was heated at 12 ° C. for 12 hours, a good retention was shown as compared with the cured material properties of a blank in which the urethane prepolymer was not heated.

Example 2 The amount of Chelex H-8 used in Example 1 was 27 g.
A urethane prepolymer was manufactured in the same manner as in Example 1 except that the cured product was measured for physical properties. The results, as shown in Table 1, showed that even when the urethane prepolymer was heated at 100 ° C. for 12 hours, a good retention was obtained as compared with the cured material properties of a blank in which the urethane prepolymer was not heated.

Example 3 Chelex H-8 in Example 1 was replaced with dilauryl hydrogen phosphite (trade name: Chelex H-1).
2: Sakai Chemical Industry Co., Ltd.), except that a urethane prepolymer was produced in the same manner as in Example 1 and the physical properties of the cured product were measured. The results, as shown in Table 1, showed that even when the urethane prepolymer was heated at 100 ° C. for 12 hours, a good retention was obtained as compared with the cured material properties of a blank in which the urethane prepolymer was not heated.

Comparative Example 1 A urethane prepolymer was produced in the same manner as in Example 1 except that Chelex H-8 in Example 1 was not used, and the physical properties of the cured product were measured. As shown in Table 1, as shown in Table 1, when the urethane prepolymer was heated at 100 ° C. for 12 hours, the retention was deteriorated as compared with the cured material properties of the blank in which the urethane prepolymer was not heated.

Comparative Example 2 Chelex H-8 in Example 1 was replaced with 2,6-di-t
A urethane prepolymer was produced in the same manner as in Example 1 except that -butyl-p-cresol (trade name: BHT: manufactured by Yoshitomi Pharmaceutical Co., Ltd.) was used, and the cured product properties were measured. As shown in Table 1, as shown in Table 1, when the urethane prepolymer was heated at 100 ° C. for 12 hours, the retention was deteriorated as compared with the cured material properties of the blank in which the urethane prepolymer was not heated.

Comparative Example 3 A urethane prepolymer was produced in the same manner as in Example 1 except that ChelexH-8 in Example 1 was changed to dilaurylthiodipropionate (trade name: DLTDP: manufactured by Yoshitomi Pharmaceutical Co., Ltd.). The physical properties of the cured product were measured. Table-
As shown in FIG. 1, when the urethane prepolymer was heated at 100 ° C. for 12 hours, the retention was deteriorated as compared with the cured material properties of the blank in which the urethane prepolymer was not heated.

Comparative Example 4 Chelex H-8 in Example 1 was replaced with octadecyl-
3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name: IRGANOX107
6: CIBA-GEIGY)
A urethane prepolymer was produced in the same manner as described above, and the physical properties of the cured product were measured. The results were as shown in Table 1, 100 ° C.
When the urethane prepolymer was heated for 12 hours at, the retention was deteriorated as compared with the cured material properties of a blank in which the urethane prepolymer was not heated.

[0018]

[0019]

[0020]

According to the method of the present invention, a urethane prepolymer having excellent heat stability can be produced. By using this prepolymer, a polyurethane elastomer having excellent physical properties can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-129256 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 18/00-18/87

Claims (1)

(57) [Claims] In producing a urethane prepolymer having an isocyanate group at a molecular terminal by reacting an organic polyisocyanate with a polyhydroxy compound, a general formula (RO) ₂ POH or (RO) ₂ PH = O (wherein , R represents an alkyl group or an aryl group having 1 to 18 carbon atoms.) Wherein at least one phosphite is represented by an organic polyisocyanate and a polyhydroxy compound.
A method for producing a urethane prepolymer having excellent thermal stability, wherein the urethane prepolymer is allowed to coexist when reacting .