JPH11255878A - Method for producing low viscosity polyester polyol - Google Patents

Abstract

(57) [Problem] To provide a polyester polyol having a lower viscosity than that obtained by a conventional production method. SOLUTION: After completion of the esterification reaction, a low-viscosity polyester polyol is obtained by removing a low-molecular compound with a thin film evaporator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyester polyol used as a raw material for a polyurethane resin. More specifically, the method relates to a method for producing a polyester polyol having a lower viscosity than a polyester polyol obtained by a conventional production method by removing the low-molecular compound after the esterification reaction is allowed to proceed until a predetermined acid value is reached. .

[0002]

2. Description of the Related Art Polyester polyols used for polyurethane resins are subjected to dehydration polycondensation of a low molecular weight polyol and a polycarboxylic acid at a high temperature of 100 to 280 ° C. to react until a predetermined acid value and a hydroxyl value are reached. And, if necessary, a transesterification reaction. In such a production method, the molecular weight distribution of the obtained polyester polyol is widened by a side reaction such as a transesterification reaction. That is, a component having an unnecessarily high molecular weight is contained, and the viscosity (at the time of melting) tends to increase.

[0003] In the production of a polyurethane resin, a urethane prepolymer process, which is a semipolymer, is sometimes performed. When a polyester polyol obtained by a conventional method is used, the mixture cannot be uniformly mixed because the viscosity is too high, and the obtained urethane prepolymer is not uniform. For this reason, turbidity, severe insolubility, precipitation, etc. were recognized, and a uniform polyurethane resin was often not obtained.

[0004]

SUMMARY OF THE INVENTION In order to solve these problems, an object of the present invention is to provide a method for producing a low-viscosity polyester polyol. The “low-viscosity polyester polyol” referred to in the present invention means that the viscosity is lower than that of a conventional polyester polyol having the same composition and the same number average molecular weight.
The term “low-molecular compound” refers to a (by-) reactant having a number average molecular weight of 300 or less and a low-molecular polyol that has been unreacted as a result.

[0005]

That is, the present invention is a method for producing a low-viscosity polyester polyol comprising the following steps. First step: low molecular polyol, polycarboxylic acid, and
A step of adding an esterification catalyst to the reaction system and allowing the esterification reaction to proceed until a predetermined acid value is reached. Second step: Next, a step of continuously supplying the reaction solution to a thin film evaporator to evaporate the low-molecular compound into a thin film and removing it from the system.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each raw material used in the present invention will be described. Low molecular polyol used in the present invention,
It has a number average molecular weight of 200 or less and has two or more hydroxyl groups in one molecule. Specifically, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3
-Butanediol, 1,4-butanediol, 1,5-
Pentanediol, 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,6-
Hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 2-ethyl-2-n-
Butyl-1,3-propanediol, 2-ethyl-2-
Hexyl-1,3-propanediol, cyclohexanedimethanol, alkylene oxide adduct of bisphenol A, glycerin, trimethylolpropane,
Examples thereof include 2,6-hexanetriol, diglycerin, and pentaerythritol, which may be used alone or in combination.

[0007] As a partial replacement of the low-molecular polyol, one or more of diamines such as hexamethylenediamine, xylenediamine, isophoronediamine and monoethanolamine or aminoalcohols may be used in combination.

The polycarboxylic acid used in the present invention includes succinic acid, adipic acid, sebacic acid, azelaic acid, terephthalic acid, isophthalic acid, orthophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid,
Examples thereof include carboxylic acids such as hexahydroorthophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, and trimellitic anhydride, acid esters, and acid anhydrides. These may be used alone or in combination.

The esterification catalyst used in the present invention includes titanium compounds such as tetrapropyl titanate, tetrabutyl titanate and tetrastearyl titanate, dibutyltin dilaurate, dibutyltin dichloride, butyltin trichloride, dibutyltin oxide and the like. Examples include tin compounds, metal salts of alkylbenzenesulfonic acids such as sodium paratoluenesulfonate, alkylsulfonic acids such as methanesulfonic acid, cobalt hydroxide, manganese acetate, zinc oxide, and cobalt octylate. Preferred esterification catalysts in the present invention are titanium compounds and tin compounds.

In the present invention, additives and auxiliaries can be used as required. For example, pigments, dyes, dispersion stabilizers, viscosity modifiers, leveling agents, gelling inhibitors, light stabilizers, antioxidants, ultraviolet absorbers, heat resistance improvers, inorganic and organic fillers, plasticizers, lubricants, Examples include an antistatic agent and a reinforcing material.

Next, each reaction step will be described. The first step is an esterification reaction, and a known method is employed. That is, after the raw materials are charged into the reactor, they are heated and stirred.
Water starts to distill at around 100 ° C.
Heat gradually to 0 ° C, preferably 200 ° C. It is preferable to reduce the pressure from the point at which the rate of distilling water is reduced, since the distilling of water proceeds. If the pressure is rapidly reduced, bumping occurs, causing clogging of the distilling tube, etc., and therefore it is preferable to perform the pressure reduction gradually. In this way, the esterification reaction proceeds until a predetermined acid value is reached. The charging ratio between the low-molecular polyol and the polycarboxylic acid at the time of charging is determined by the target number average molecular weight of the polyester polyol. The amount of the esterification catalyst is 1 to 1,000 ppm, preferably 5 to 500 ppm, based on the total amount of the charged low-molecular polyol and polycarboxylic acid.
It is.

The final degree of reduced pressure in the esterification reaction is 5
It is at most 00 mmHg, preferably at most 300 mmHg. If the final degree of reduced pressure exceeds the upper limit, the esterification reaction time is prolonged, and the resulting polyester polyol is colored. The acid value after completion of the first step is 0.5 mgK
OH / g or less, and the hydroxyl value is preferably 105 to 170% of the target hydroxyl value, more preferably 110 to 1%.
65%. This is because a polyester polyol having an acid value exceeding the upper limit is likely to cause a prolonged urethanization reaction time during production of a polyurethane resin, a decrease in hydrolysis resistance of the polyurethane resin, and the like.

When the acid value reaches a predetermined value, the process proceeds to a second process, which is a process for removing low molecular compounds. The specific procedure of the second step lowers the temperature of the reaction solution. Next, the reaction solution is continuously supplied to a thin film evaporator to evaporate the low molecular weight compound into a thin film and remove it from the system to obtain a target polyester polyol.

The evaporator used in the present invention is a thin film formed by mechanical stirring to improve the heat transfer coefficient to efficiently evaporate the liquid. A normal vertical or horizontal type can be used. is there. In addition, steam, oil, or the like is used as a heat medium. The temperature inside the outer cylinder of the thin film evaporator is 150 to 280 ° C.
Is good.

The reaction liquid is preferably spread over the heated surface by mechanical stirring to form a thin liquid film, and it is preferred that the reaction liquid evaporate quickly. Therefore, the liquid film is advantageously thin. But,
When the liquid film is interrupted, a dry surface is exposed on the heat transfer surface and a side reaction occurs due to partial heating, so that the thickness of the liquid film is 0.1 mm to 2 mm.
The range of mm is preferred. The average residence time of the liquid can be calculated if the retained amount of the liquid is known, but it is difficult to accurately grasp the thickness of the liquid film. Therefore, expressed as a flow rate per heat transfer area, 1 × 10 ^{−4 to} 6 × 10 ⁻⁴ g / sec / cm ²
Is good. The lower the pressure, the lower the molecular weight compounds are preferably evaporated.
^{-3 to} 10 mmHg is preferred.

The timing of adding the above-mentioned additives is not particularly limited, and an appropriate stage can be selected and used.

The polyester polyol according to the present invention comprises
The reason why the viscosity is lower than that of the polyester polyol according to the conventional method is presumed as follows.

As described above, the conventional method for producing a polyester polyol is a method in which an esterification reaction is performed until a predetermined acid value and a hydroxyl value are reached, and a transesterification reaction is performed as necessary. Such a method is characterized in that the molecular weight distribution of the polyester polyol is widened. That is, in the conventional method, a polyester polyol having a high content of a low molecular compound but a high content of a polymer is obtained.

On the other hand, in the present invention, a polyester polyol having a number average molecular weight smaller than a target value is once produced, and a low molecular compound is removed while suppressing a side reaction, thereby setting the number average molecular weight to a target value. . For this reason, the polyester polyol of the present invention is characterized in that the molecular weight distribution is narrow. That is, in the present invention, a polyester polyol having a low content of a low-molecular compound and a low content of a polymer can be obtained.

Incidentally, the viscosity is correlated with the amount of the polymer present in the system. Comparing the polyester polyol obtained by the conventional method and the method according to the present invention at the same composition and the same number average molecular weight, the polyester polyol according to the conventional method has a high molecular weight component not present in the polyester polyol according to the present method. doing. Therefore, the polyester polyol obtained by the present invention has a low viscosity (when melted).

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Unless otherwise specified, “parts” and “%” in the examples mean “parts by weight” and “% by weight”, respectively.

Example 1 2 liter 4 with stirrer, distillation column, water-cooled condenser
864 g of butylene glycol, 1136 g of adipic acid, and 20 mg of tetrapropyl titanate were added to a one-necked flask, and heated with stirring. When the temperature reached 100 ° C., water began to distill. Thereafter, the esterification reaction was allowed to proceed while gradually heating to 210 ° C. Further, when the distillation rate of water became slow, the pressure was gradually reduced to 20 mmHg to promote the esterification reaction. Acid value 0.5mgKOH
/ G, the pressure was returned to normal pressure. At this time, the hydroxyl value was 143.9 mgKOH / g. Then 8
0 mg of phosphoric acid is added and stirred at 200 ° C. for about 1 hour,
The transesterification reaction was stopped, and then the temperature of the reactor was raised to 1
The temperature was lowered to 00 ° C. and supplied to a thin film evaporator. The thin film evaporator used was manufactured by Shibata Chemical, having an inner diameter of 50 mm and a length of 200 mm.
mm with a mechanical stirring type vertical stirring thin film evaporator having an outer cylinder,
The pressure inside the evaporator was 0.25 mmHg, the temperature inside the outer cylinder of the vertical stirring thin film evaporator was 240 ° C., and the rotation speed of the wiper was 200 r.
pm. The reaction was fed at 300 g per hour. The feed rate is 3.5 × 10 ⁻⁴ g / sec / cm
² The obtained polyester polyol is a colorless wax-like room temperature solid, and has a hydroxyl value of 90.1 mgK.
OH / g, acid value 0.3 mg KOH / g, viscosity 148
cSt / 75 ° C, melting point 44 ° C. The number average molecular weight of this polyester polyol was 1250, the weight average molecular weight was 2750, and the distribution was 2.2. The number average molecular weight was measured from the hydroxyl value and the acid value obtained by acetylating the terminal hydroxyl group, and the weight average molecular weight was obtained by gel permeation chromatography using polyester as a standard. The following examples,
The same applies to the comparative example.

Example 2 Nipporan 4056 manufactured by Nippon Polyurethane Industry Co., Ltd.
(Hydroxyl value 142.8 mg KOH / g, acid value 0.5 mg
KOH / g polybutylene adipate polyol)
The mixture was heated to 00 ° C. and supplied to the following thin film evaporator. The evaporator is a Smith type thin film evaporator manufactured by Shinkami Seisakusho Co., Ltd., having a heat transfer area of 3.1 m ² and a condenser area of 4.7 m ² . With the internal pressure of the evaporator set to 1 mmHg, the temperature set to 220 ° C., and the number of rotations of the wiper set to 100 rpm, Nipporan 4056 kept at 100 ° C. was 5.6 g / sec.
At a rate of The obtained polyester polyol is a colorless wax-like room temperature solid and has a hydroxyl value of 9 or less.
0.1 mgKOH / g, acid value 0.3 mgKOH / g, viscosity 148 cSt / 75 ° C, and melting point 44 ° C. The number average molecular weight is 1180, the weight average molecular weight is 2730, and the distribution is 2.
It was 3.

Example 3 In the same reactor as in Example 1, ethylene glycol 675 was added.
g, adipic acid 1325 g, tetrabutyl titanate 1
7 mg was added and heated with stirring. When the temperature reached 100 ° C., water began to distill. Thereafter, the esterification reaction was allowed to proceed while gradually heating to 220 ° C. Further, when the distillation rate of water became slow, the pressure was gradually reduced to 20 mmHg to promote the esterification reaction. Acid value is 0.4m
When gKOH / g was reached, the pressure was returned to normal pressure. At this time, the hydroxyl value was 110.5 mgKOH / g. Then, the temperature of the reactor was lowered to 100 ° C., and
Was supplied to the thin film evaporator used in step (1). Operating conditions were the same as in Example 1 to obtain a polyester polyol. This polyester polyol is a colorless wax-like solid at room temperature, and has a hydroxyl value of 74.8 mgKOH / g and an acid value of 0.5.
5 mgKOH / g, viscosity was 240 cSt / 75 ° C, and melting point was 48 ° C. The number average molecular weight of this polyester polyol is 1500, the weight average molecular weight is 3300,
The distribution was 2.2.

Example 4 A polyester polyol was obtained in exactly the same manner as in Example 1 except that the speed of feeding to the thin film evaporator was changed. The rate of supply to the thin film evaporator of this example was such that 300 g of the reaction solution was supplied in 30 minutes. This rate is 6.94 × 10 ⁻⁴ g /
Seconds / cm ² . This polyester polyol is a colorless wax-like room temperature solid, and has a hydroxyl value of 93.5 mg.
KOH / g, acid value 0.5 mgKOH / g, viscosity 13
8 cSt / 75 ° C., melting point 40 ° C. The number average molecular weight of this polyester polyol was 1150, the weight average molecular weight was 2760, and the distribution was 2.4.

Comparative Example 1 In a reactor similar to that in Example 1, 842 g of 1,4-butylene glycol, 1158 g of adipic acid and 20 mg of tetrapropyl titanate were added and heated with stirring. 10
At 0 ° C., water began to distill. Thereafter, the esterification reaction was allowed to proceed while gradually heating to 210 ° C. Further, when the distilling speed of water slows down,
The pressure was reduced to mmHg to accelerate the esterification reaction. When the acid value reached 0.4 mgKOH / g, the pressure was returned to normal pressure, and then immediately cooled, and when the temperature fell below 100 ° C., the polyester polyol was taken out of the reactor. This polyester polyol is a colorless wax-like room temperature solid, and has a hydroxyl value of 90.6 mgKOH / g.
The acid value is 0.4 mg KOH / g and the viscosity is 290 cSt / 7
The melting point was 5 ° C and the melting point was 48 ° C. The number average molecular weight of this polyester polyol was 1240, the weight average molecular weight was 3960, and the distribution was 3.2.

Comparative Example 2 In a reactor similar to that in Example 1, 1,4-butanediol 8 was added.
46 g, adipic acid 1154 g, and tetrabutyl titanate 20 mg were added, and the mixture was heated with stirring. When the temperature reached 100 ° C., water began to distill. Then gradually 210
The esterification reaction was allowed to proceed while heating to ℃. Further, at the time when the distilling speed of water becomes slow, the pressure gradually becomes 20 mmH.
g to accelerate the esterification reaction. When the acid value reached 0.5 mg KOH / g, it was returned to normal pressure. Thereafter, the mixture was immediately cooled, and the polyester polyol was taken out of the reactor when the temperature fell below 100 ° C. This polyester polyol is a colorless wax-like room temperature solid, has a hydroxyl value of 95.2 mgKOH / g,
The acid value is 0.5 mg KOH / g and the viscosity is 270 cSt / 7
The melting point was 5 ° C and the melting point was 44 ° C. The number average molecular weight of this polyester polyol was 1,180, the weight average molecular weight was 3,800, and the distribution was 3.2.

Comparative Example 3 In a reactor similar to that in Example 1, ethylene glycol 662 was added.
g, adipic acid 1641 g, tetrabutyl titanate 1
7 mg was added and heated with stirring. When the temperature reached 100 ° C., water began to distill. Thereafter, the esterification reaction was allowed to proceed while gradually heating to 210 ° C. Further, when the distillation rate of water became slow, the pressure was gradually reduced to 20 mmHg to promote the esterification reaction. Acid value 0.5m
When gKOH / g was reached, the pressure was returned to normal pressure. After that, it cooled immediately, and when the temperature fell below 100 ° C,
The polyester polyol was taken out of the reactor. This polyester polyol is a colorless wax-like room-temperature solid, has a hydroxyl value of 75.5 mgKOH / g, an acid value of 0.5 mgKOH / g, a viscosity of 350 cSt / 75 ° C.,
Melting point was 53 ° C. The polyester polyol had a number average molecular weight of 1486 and a weight average molecular weight of 510.
0, distribution 3.4.

Application Example 1 The polyester polyol obtained in Example 3 and 4,
A urethane prepolymer was synthesized by reacting 4'-diphenylmethane diisocyanate with an isocyanate group / hydroxyl group = 2/1 (molar ratio). The obtained urethane prepolymer was colorless and transparent.

Application Comparative Example 1 The polyester polyol obtained in Comparative Example 3 and 4,
A urethane prepolymer was synthesized by reacting 4'-diphenylmethane diisocyanate with an isocyanate group / hydroxyl group = 2/1 (molar ratio). The obtained urethane prepolymer was milky white.

[0031]

According to the present invention, a low-viscosity polyester polyol can be provided without using a deactivator for an esterification catalyst. When the polyester polyol according to the present invention is a solid at room temperature, since the melting point is lower than the melting point of the polyester polyol according to the conventional method, the energy cost can be reduced in actual use.
Further, when the polyester polyol obtained according to the present invention was used for producing a urethane prepolymer, the obtained urethane prepolymer was transparent, and an extremely excellent effect was recognized as a raw material for polyurethane.

Claims (1)

[Claims] 1. A method for producing a low-viscosity polyester polyol comprising the following steps. First step: low molecular polyol, polycarboxylic acid, and
A step of adding an esterification catalyst to the reaction system and allowing the esterification reaction to proceed until a predetermined acid value is reached. Second step: Next, a step of continuously supplying the reaction solution to a thin film evaporator to evaporate the low-molecular compound into a thin film and removing it from the system.