JP2884088B2 - Method for producing polyurethane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyurethane. More particularly, the present invention relates to a process for producing a polyurethane having excellent flexibility at a low temperature obtained by reacting an organic diisocyanate compound with a polycarbonate diol compound having a low melting point, which is liquid or easily melted at room temperature and has excellent workability. .

[Prior Art] Polyurethane resins are used in many fields such as foams, adhesives, fibers, elastomers and paints, and the main raw materials are polyisocyanates and polyol compounds.

Examples of the polyol compound include polyether polyols such as polypropylene glycol and polytetramethylene glycol, polyester polyols derived from dihydric carboxylic acids such as adipic acid and polyhydric alcohols, and lactones obtained by reacting with alcohols. Polylactone polyols and the like are used, and are properly used for various applications according to the required performance.

However, since a polyether polyol has an ether bond, a polyurethane produced using the same has a drawback that heat resistance and weather resistance are poor.

On the other hand, since polyester polyols and polylactone polyols have ester bonds, polyurethanes produced using them have the disadvantage that they have poor water resistance. In order to obtain a new polyurethane overcoming these disadvantages, it has been proposed to use a polyol having a carbonate bond in a molecular structure as a raw material. Currently, the most widely used polycarbonate polyol, that is, a polyol having a carbonate bond in a molecular structure, has 1,6-hexanediol as a basic skeleton in the molecular structure as shown by the following formula (I).

Polycarbonate diol having a 1,6-hexanediol structure in the basic skeleton is a polyurethane obtained by using the polycarbonate diol, which is very balanced in mechanical strength, heat resistance, moisture resistance, etc. It also has the advantage of being easily manufactured.

[Problems to be Improved by the Invention] However, the polycarbonate diol having only the 1,6-hexanediol structure in the basic skeleton has a melting point.
Since it is a wax-like solid at 40 ° C. to 50 ° C., that is, at room temperature, it is usually necessary to heat it to a liquid state using a melting tank or the like before use. In addition, the use of a heating and melting tank or the like requires keeping the temperature of the tanks and pipes, which is disadvantageous not only in thermal economy but also in facility economy.

In order to improve such disadvantages, Japanese Patent Laid-Open Publication No. 61-11592 (title of invention: method for producing polyurethane) proposes a random copolymer of dialkyl carbonate such as diethyl carbonate and dimethyl carbonate and ε-caprolactone. Have been.

However, this random copolymer has a low melting point and is a liquid polyol, but it has one of the characteristics of polyurethane synthesized from polycarbonate diol because ester bonds caused by ε-caprolactone are present in the molecule. Is significantly reduced.

The present inventors have solved these problems and have excellent workability because polycarbonate diol has a low melting point.
In addition, as a result of studying the development of an excellent polyurethane having flexibility at a low temperature, it was found that a polycarbonate diol having a specific composition should be used, and the present invention was reached.

[Constitution of the Invention] That is, the present invention provides a method for producing a polyurethane by reacting an organic diisocyanate compound with a compound having two or more active hydrogens in a molecule, wherein the compound having active hydrogen used is phosgene or A polycarbonate diol obtained by reacting an aliphatic diol with one selected from the group consisting of bischloroformate, alkylene carbonate, diaryl carbonate, and dialkyl carbonate, wherein the aliphatic diol is trimethyl-1,6-hexane 20 to 80 mol% of diol, 80 to 20 mol% of 1,6-hexanediol [However, when bischloroformate is used,
Is a diol residue derived from bischloroformate and 1,
The total amount of the 6-hexanediol residues is 80 to 20 mol%.] A process for producing a polyurethane having excellent flexibility at a low temperature characterized by using a carbonate diol compound composed of an aliphatic diol mixed in a ratio of: It is.

When producing a polycarbonate diol compound which is one of the components used in the method for producing a polyurethane of the present invention, phosgene, bischloroformate, alkylene carbonate, and dialkyl carbonate are used.

Examples of the alkylene carbonate include ethylene carbonate, 1,2-propylene carbonate, and 1,2-butylene carbonate.

Examples of the diaryl carbonate include diphenyl carbonate and dinaphthyl carbonate. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate. Each of these can be reacted with a polyhydric alcohol described below to form a polycarbonate diol by a known method.

Among the aliphatic diols constituting the polycarbonate diol compound which is one of the components used in the method for producing the polyurethane of the present invention, 2,2,4-trimethyl-1,6-hexanediol or 3,3,5-trimethyl-1 It is essential to use 2,6-hexanediol.

These may be used alone or in combination of two or more.

These trimethyl-1,6-hexanediols are 20 to 8
0 mol% and 1,6-hexanediol are charged and reacted at a ratio of 80 to 20 mol%. Trimethyl-1,6-
When the amount of hexanediol is less than 20 mol%, the melting point of the obtained polycarbonate diol becomes high, and the desired performance of the polyurethane obtained by the production method of the present invention cannot be obtained.

Further, when the number of moles of trimethyl-1,6-hexanediol is more than 80% by mole, the characteristics of 1,6-hexanediol are lost, and the polyurethane of the present invention synthesized using this loses mechanical strength and the like. No longer available.

As the dialkyl carbonate which is one component of the polycarbonate diol which is one component used in the production method of the present invention, dimethyl carbonate and diethyl carbonate are preferable.

The reaction for obtaining the polycarbonate diol used in the method for producing a polyurethane of the present invention is generally represented as follows.

(R is an alkyl group, R 'is an alkylene group) A chemical reaction formula for producing a polycarbonate diol using bischloroformate is as follows.

(However, R and R ″ represent an alkylene group.) At this time, the two polyhydric alcohols used as the raw materials are randomly incorporated into the carbonate diol compound molecule, that is, into the polyurethane molecule by a carbonate bond.

If one is HO-R1-OH and the other is HO-R2-OH React randomly and are present in the molecule.

This randomness breaks down the crystallinity of the 1,6-hexanediol skeleton and liquefies the obtained carbonate diol.

Then, dialkyl carbonate was used as another raw material for reacting trimethyl-1,6-hexanediol with an aliphatic diol in which both 20-80 mol% of 1,6-hexanediol were mixed with 80-20 mol%. The situation, such as the reaction procedure, will be described in detail.

For the reaction, a catalyst usually used in transesterification can be used.

For example, metals such as lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, zinc, aluminum, titanium, cobalt, germanium, tin, lead, antimony, arsenic and cerium and alkoxides thereof. Examples of other suitable catalysts include carbonates of alkali and alkaline earth metals, zinc borate, zinc oxide, lead silicate, lead arsenate, lead carbonate, antimony trioxide, germanium dioxide, cerium trioxide, And aluminum isopropoxide.

Particularly useful and preferred catalysts are magnesium organic acids,
Organic metal compounds such as metal salts of calcium, cerium, barium, zinc, tin, titanium and the like.

The amount of catalyst used is 0.0001% to 1.0% of the total weight of starting materials
Is appropriate.

Preferably it is 0.001-0.2%. Reaction temperature is 80 ° C ~ 22
About 0 ° C. is preferable.

In the early stage of the reaction, the reaction is carried out at a temperature near the boiling point of the dialkyl carbonate. As the reaction proceeds, the temperature is gradually raised and the reaction further proceeds.

A device capable of separating the produced alcohol from the raw material dialkyl carbonate is usually a reactor equipped with a distillation tower, in which the reaction is carried out while refluxing the dialkyl carbonate, and the alcohol produced as the reaction proceeds is distilled off.

At this time, the dialkyl carbonate is partly azeotropically dissipated together with the alcohol distilled off, so that it is better to allow for this dissipated amount when the raw materials are measured and charged.

According to the above reaction formula, the theoretical molar ratio of aliphatic diol (n + 1) to n mol of dialkyl carbonate is, but in practice, the molar ratio of dialkyl carbonate / aliphatic diol is preferably 1.1 to 1.3.

The reaction can be carried out at normal pressure, but can be carried out under reduced pressure, for example, at 1 mmHg to 200 mmHg in the latter half of the reaction to speed up the progress of the reaction.

The molecular weight of the polycarbonate diol, which is one of the components used in the polyurethane production method of the present invention, can be adjusted by changing the reaction molar ratio of the raw material aliphatic diol to a dialkyl carbonate, a dialkylene carbonate or the like.

That is, the molecular weight can be controlled by adjusting n in the above formula.

In addition, various components constituting the polycarbonate diol, which is one of the components used in the polyurethane production method of the present invention, are obtained by hydrolyzing the produced polyurethane and analyzing the decomposition products by gas chromatography or NMR to obtain trimethyl. It can be confirmed that 1,6-hexanediol is used in a combination of 20 to 80 mol% and 1,6-hexanediol is used in a combination of 80 to 20 mol%.

The following are examples of the organic diisocyanate compound that can be used.

That is, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tolidine diisocyanate, xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4 4,4'-Dicyclohexylmethane diisocyanate, 1,5-naphthalenediisocyanate, carbodiimide-modified MDI, xylylene diisocyanate, and the like, and one or more kinds can be used.

At this time, a chain extender may be allowed to coexist in the above mixture, if necessary.

Examples of the chain extender include low molecular weight compounds having active hydrogen, and specific examples thereof include the following.

Ethylene glycol, propylene glycol, 1,4-
Butylene glycol, 2-methylpropanediol, neopentyl glycol, pentanediol, 1,6-hexanediol, ethylenediamine, propylenediamine, hydrazine, isophoronediamine, metaphenylenediamine, 4,4'-diaminodiphenylmethane, diaminodiphenylsulfone, 3 , 3'-Dichloro-4,4'-diaminodiphenylmethane.

In the present invention, as a method for producing a polyurethane, a polyol is reacted with an excess of organic diisocyanate to produce a prepolymer having a terminal isocyanate group, and then a chain extender such as a diol or a diamine is reacted to form a polyurethane. Any method such as a polymer method or a one-shot method in which all components are added simultaneously to form a polyurethane can be used.

These reactions can be carried out without solvent or in a solvent.

It is preferable to use an inert solvent. Specific examples include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, dimethylformamide, and tetrahydrofuran.

In the urethanization reaction, a urethanization catalyst can be used.

For example, an organic tin compound such as tin octylate and dibutyltin dilaurate, or a tertiary amine such as N-methylmorpholine and triethylamine can be used.

[Effect of the Invention] The polyurethane obtained by the production method of the present invention thus obtained not only has excellent low-temperature properties without impairing other properties, but also has a good balance of mechanical strength, wet heat resistance and the like. It is a thing. The polyurethane obtained by the production method of the present invention can be used in a very wide range of applications such as spandex, thermoplastic urethane elastomer, thermosetting urethane elastomer, hard / soft urethane foam, adhesive, synthetic leather, and paint.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited by the Examples and Comparative Examples.

"Synthesis Example-1" In a 2 liter round bottom flask equipped with a stirrer, a thermometer and a ten-stage plate distillation column, 814 g of dimethyl carbonate (9.
04 mol), 564 g (4.78 mol) of 1,6-hexanediol,
3,3,5-trimethyl 1,6-hexanediol (TMHD)
29.6 g (9.56 mol) and 0.16 g of tetrabutyl titanate as a catalyst were charged, and the reaction was carried out under normal pressure under boiling dimethyl carbonate to distill off produced methanol. The temperature of the reaction vessel gradually increased and reached 200 ° C., and when the distillation of methanol was almost stopped, the pressure reduction operation was started.Unreacted substances were distilled off under a reduced pressure of final 20 mmHg, and the molecular weight was determined as a reaction product. Of 2000 polycarbonate diol (PCD).

"Comparative Synthesis Example-1" A polycarbonate diol (PCD) was similarly obtained using the same apparatus as in "Synthesis Example-1" and using 100% of 1,6-hexanediol as a polyhydric alcohol component.

Table 1 shows the properties of the polycarbonate diol (PCD) obtained in "Synthesis Example-1" and "Comparative Synthesis Example-1".

"Example-1" and "Comparative Example-1" A polyurethane was synthesized from the polycarbonate diol (PCD) obtained in "Synthetic Example-1" and "Comparative Synthetic Example-1" under the following reaction conditions, Create a 150 micron thick urethane film from this polyurethane,
Physical properties were evaluated.

 Table 2 shows the results.

[Polyurethane reaction conditions] (1) Blending composition Polyol 100 parts 1,4BG 8.3 parts MDI 35.6 parts Solvent (DMF) 267.3 parts Note) Polyol having a molecular weight of 2,000, 1,4-butylene glycol (1 , 4BG) as methylene diisocyanate (MD
I) was used.

NCO / OH = 1.03 The hydroxyl equivalent ratio of polyol to 1,4BG is about 2 (2) Cooking schedule 100 parts of polyol, 8.3 parts of 1,4BG, and 144 parts of solvent are charged into a reactor and heated to 60 ° C. .

Then, add 35.6 parts of MDI and heat further. When the temperature of the reactor reaches 80 ° C., the reaction is continued for several hours. Thereafter, the temperature of the reactor is removed until it reaches 60 ° C. 60
When the temperature reaches ° C, 123.3 parts of a solvent is added and the mixture is aged at the same temperature.

(3) Properties of polyurethane Non-volatile content is 35% VIS (cp / 25 ° C): 60,000 to 80,000 Solvent: DMF (4) Preparation of film A polyurethane solution is coated on release paper and dried by force.

 Finished film thickness: 150 microns (5) Physical property measurement JIS No. 3 dumbbell punching Measurement device: Shimadzu Autograph The obtained results are shown in Table-2.

In the numerical values shown in Table 2, the polyurethane of Example 1 synthesized using the PCD of Synthesis Example 1 was superior in the low-temperature characteristics to the polyurethane of Comparative Example 1 synthesized using the PCD of Comparative Synthesis Example 1. Is shown.

This is apparent from the fact that the polyurethane of Example 1 has smaller modulus values at -10 ° C and -30 ° C than the polyurethane of Comparative Example 1. That is, the polyurethane of Example 1 is flexible even at a low temperature.

Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) C08G 18/00-18/87 C08G 64/00-64/42 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. An organic diisocyanate compound and 2
In producing a polyurethane by reacting with a compound having two or more active hydrogens, the compound having active hydrogen used is selected from the group consisting of phosgene or bischloroformate, alkylene carbonate, diaryl carbonate, and dialkyl carbonate. A polycarbonate diol obtained by reacting a kind with an aliphatic diol, wherein the aliphatic diol is 20 to 80 mol% of trimethyl-1,6-hexanediol and 80 to 20 mol% of 1,6-hexanediol [ However, if bischloroformate is used,
Is a diol residue derived from bischloroformate and 1,6
-The total of hexanediol residues is from 80 to 20 mol%]. A process for producing a polyurethane having excellent flexibility at low temperatures, characterized by using a carbonate diol compound composed of an aliphatic diol mixed in a ratio of: