US2999106A - Method of storing 4,4'-methylenediphenylisocyanate - Google Patents

Description

United States Patent-D a 3 06. ME'IHGDOFSIORING '4,4'-MEI'HYLENE- DIPHENYLISOEYANAT-E Robert M. Prosser, Wilmington, Del., and Charles A. Seibert, -Jr.,'Salem, N.J., -assignors to E. -I.-du -Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware v No Drawing. Filed Apr. 17, 1959,-Ser. No. 807,039

' 5 Claims. ((11.260-453) This invention relates to the substantial prevention of 2,999,106 Patented Sept. 5, 1961 2 tion, wherein the 4,-4'-methylenediphenylisocyanate is maintained in a liquid state at a temperature of between about 40-50 C., the formation of insoluble residues would be substantially prevented.

In general, it is desirable to prevent the formation of;

insoluble residues in 4,4-methylenediphenylisocyanate for a periodof time from about 1 up to about 4 weeks the formation of insoluble residues in 4,4'-.methylenediphenylisocyanate' and more particularly to maintaining 4,4-methylenediphenylisocyanate in the liquid state at a temperature of between about 40 C. and 50 C.

4,4-methylenediphenylisocyanate is highly useful asan intermediate in the preparation .o'fmany polymeric ma-- terials. Inthe formation of these polymeric materials it is essential that the 4,4-methylenediphenylisocyanate be substantially free "from impurities. This is particularly true when 4,4-methylenediphenylisocyanate is used, for reaction with polymeric glycols 'to form linear, substantially non-crosslinkedpolyurethane polymers, r-However, 4,4'-methylenediphenylisocyanate under normal storage conditions develops varying amounts of insoluble residues which are clearly visible when solid 4,4-methylenediphenylisocya'nate is melted prior to use. These insoluble residues, unless removed from the .,4-methyl'enediphenylisocyanate, will interfere with normal condensation polymerization reactions, whereby inferior polymers are produced from this .diisocyanate. From the standpoint of the preparation of good linear polymers using 4,4methylenediphenyliso'cyanate as an intermediate, it is highly desirable that the amount. of insoluble residues be 11 greater than about 0.02% by weight;

Heretofore, in order to substantially prevent the jformation of these insoluble residues, it has been necessary,

immediately after the 4,4-methylenediphenylisocyanate is prepared, to chill and maintain it during shipping and storage at temperatures of about 0 C. or lower.- Thus,

as 4.,4-methylenediphenylisocyanate Iisprepared itlis colenediphenylisocyanate during shipping and/or storage. A further :object is to provide a process-whereby l theiformation of insoluble residues in 4,4-methylenediphenylisocyanate is substantially prevented. Other objects will appear hereinafter.

These and other objects of this invention are accomplished by substantially preventing the formation of insoluble residues in 4,4'-methylenediphenylisocyanate during shipping and/ or storage, by maintaining the 4,4'-methylenediphenylisocyanate in the liquid state at a temperature of between about 40 C. and 50 C. until it is to be used.

As mentioned above, it has been the practice to take special precautions to reduce the formation of insoluble residues by maintaining 4,4'-methylenediphenylisocyanate at temperatures of 0 C. or lower. The fact that the amount of insolubles' formed at these low temperatures was appreciably less than that formed at room temperature is not unexpected since one would ordinarily expect the rate of chemical reaction to decrease markedly when the temperature is drastically reduced. On the other hand, it is entirely unexpected that in the present inven- .mate use. -amples, by maintaining the 4,4'-methylenediphenylisosince this provides a reasonable time between the preparation of the 4,4-methylenediphenylisocyanate and its ulti- As will be noted from the accompanying excyanate in a liquid state -at-a temperature of between about 40-.50 C., the formation of insoluble residues can be substantially prevented for a period'of time up to about 28 days. vThe preferred temperature at which the 4;4'-methylenediphenylisocyanate is to be maintained accordingto the process of the present invention is at about "45 "Cr-and at this temperature the formation ofinsolu'ble residues is substantially completely prevented. At a temperature of about 45C.'it would be possible to store the 4,4-methylenediphenylisocyanate for a much longer .period than 28 days.

lnsaccordance with the present invention, the 4,4.-meth- .ylenediphenylisocyanate, after preparation and final distillation, may be discharged from the receiver as a liquid into a container which may 'be closed and maintained at 4010 50 C. This avoids any solidification of the 'diis'ocyanatebetween its manufacture and use. Since 4,4- methylenediphenylisocyanate is normally transported and stored in containers whichare-closed or sealed in order to prevent atmospheric moisture from reacting with the diisocyanate, the present invention contemplates a container or package which comprises a closed container having 4,4'=methylenediphenylisocyanate therein, said' cyanate-stabilizer composition maintained at a temperature of between about 40 C. and 50 C. until ready for use. It has been determined that the presence of a stabilizer will assist in the prevention of insoluble residue formation. The amount of stabilizer which may be used may range fromabout 0. 1% to 0.5% by weightbased on the weight of the -4,4-methylenediphenylisocyanate. Suitable stabilizers which may be used include organic acyl halides and phosphoroushalides. The organic acyl halides are preferred. Representative acyl halides include acetyl chloride, fumaryl chloride, propionyl chloinide, succinyl chloride; adipyl chloride and benzoyl chloride. Representative phosphorous halides include phos phorous trichloride, phosphorous pentachloride and phosphorous oxychlon'de.

The following examples will better illustrate the nature of the present invention; however, the invention is not intended to be limited to these examples. Parts and percents are by weight unless otherwise indicated.

Example 1 tubes from each temperature was removed and the tolu 3 ene insolubles determined on the entire sample using the procedure of American Society for Testing Materials procedure ASTM D-269-52 with the modification that the weight of the sample was 8-10 grams and [the toluene was not heated. The percent toluene insolubles at the beginning of the experiment was nil. A dash indicates that no analysis was made.

At the end of 4 weeks, the samples stored at 40 and 45 showed no visible solids, as compared with those stored at other temperatures. At the end of 2 weeks, the samples stored at 40, 45 and 50 C. showed less insolubles than those stored at room temperature, 35 and 70 C. At about 0.02% and above the solids are visible as cloudiness 0r settled solids in the molten isocyanate.

Example 2 4,4-methylenediphenylisocyanate prepared as in Example 1 was recrystallized by dissolving in the minimum amount of hot benzene, adding hot hexane until a cloudy precipitate began to form, and then adding hot benzene until the formed precipitate just redissolved and then cooling to crystallize. The product was then recrystallized the same way and finally distilled undervacuum (boiling point 169 C. at 1 mm. of mercury pressure). The purified product melted at 4l42 C. and was essentially colorless. Y

The product was placed in clean, dry l0-ml. Pyrex tubes as in Example 1 and held at the temperatures for the times shown below. As in Example 1, one tube was taken for analysis for toluene insolubles.

The samples stored at 0 C. and 45 C. showed no visible solids at the end of 27 days, as compared with those stored at 70 C. and room temperature.

Example 3 A sample of commercially available 4,4'-methylenediphenylisocyanate was distilled under reduced pressure as in Example 2 and stored in similar glass vials at the temperatures shown below. The toluene insolubles were determined as in Example 1 at the intervals shown:

There were no visible solids in the samples stored at 0 C. and 45 C. after 4 weeks.

As many widely diife'rent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

What is claimed is:

1. A method of storing- 4,4'-methylenediphenylisocyanate so as to substantially prevent the formation of insoluble residues therein which consists of maintaining the 4,4-methylenediphenylisocyanate in a closed container in the liquid state at a temperature of between 40C. and 50 C.

2. A method according to claim 1 wherein the temperature is maintained at about C. y

3. The process of substantially preventing the formation of insoluble residues in, 4,4'-methylenediphenylisocyanate which consists of maintaining the 4,4'-meihylenediphenylisocyanate in the liquid state at a temperature of between 40 C. and C.

4. The process according to claim 3 wherein the temperature is maintained at about 45 C.

5. 'The process according to claim 4 wherein the 4,4- methylenediphenylisocyanate contains from about 0.1% to 0.5% of a halide selected from the group consisting of acetyl' chloride, fumaryl chloride, propionyl chloride, succinyl chloride, adipyl chloride, benzoyl chloride, phosphorous trichloride, phosphorous pentachloride and phosphorous oxychloridc.

References Cited in the file of this patent MonsantoTechnical Bulletin, No. P-125, March 1953, Is0cyanates," pp. 1 and 10.

Du Pont Elastomers Div. Pub. HR-S, December 1955, Hylene M, Hylene M-50, Organic Isocyanates, p. 2.

Claims (1)

1. A METHOD OF STORING 4,4''-METHYLENEDIPHENYLISOCYANATE SO AS TO SUBSTANTIALLY PREVENT THE FORMATION OF INSOLUBLE RESIDUES THEREIN WHICH CONSISTS OF MAINTAINING THE 4,4''-METHYLENEDIPHENYLISOCYANATE IN A CLOSED CONTAINER IN THE LIQUID STATE AT A TEMPERATURE OF BETWEEN 40*C. AND 50*C.