US3391181A - Preparation of methylolated carbamates - Google Patents

Description

United States Patent ice 3,391,181 PREPARATION OF METHYLOLATED CARBAMATES Donald R. Schenerl, Franklin Lakes, N.J., assignor to .l'. P. Stevens 81 Co., Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 13, 1965, Ser. No. 440,938 5 Claims. (Cl. 260-482) ABSTRACT OF THE DISCLOSURE A method of preparing dimethylolated aliphatic carbomates in improved yield and substantially free from both monomethylolated contaminant and formaldehyde, comprising the steps of (l) Admixing an essentially anhydrous reaction mixture of alkyl carbamate containing at least two methylolatable amido hydrogens selected from the group consisting of monoalkyl carbamates and alkylene bis-carbamates, paraformaldehyde in an amount corresponding to from about 0.9 to about 1.1 equivalent weight of paraformaldehyde for each amido hydrogen atom in said carbamates, and sufiicient basic catalyst to maintain the pH from about 8.0 to about 11.0 during the reaction, and

(2) Heating the reaction mixture between about 50 C.to about 85 C. until a substantial quantity of dirnethylolated product is produced and isolating the product contained therein.

This invention relates to an improved method for preparing finishing agents for cellulosic textile fabrics. More particularly, it relates to the preparation of methylol carbomates.

Cellulosic textile fabrics can be treated with cross-linking agents in order to impart to such fabrics enhanced wrinkle resistance and improved smooth drying after laundering. Among the cross-linking agents which have been demonstrated to be effective are methylolated carbamates which are usually prepared by reacting an organic carbamate with aqueous formaldehyde in an alkaline medium. In this methylolation reaction, the amido hydrogen atoms of the carbamate are replaced by methylol groups. In order to obtain cross-linking of the cellulosic fabric treated with the carbamate, it is necessary that the methylolated carbamates contain two or more reactive mcthylol groups. It has been found, however, that the preparation of dimethylolated carbamates by aqueous formaldehyde treatment is usually unsatisfactory in that the yield of the dimethylol compound is lowered by the incomplete conversion of the monomethylol compound to the dimethylol carbamate, with the result that mixtures of the monomethylol and dimethylol compounds are obtained. It has been necessary, consequently, to react excess formaldehyde with the carbamate in order to drive the methylolation reaction further to completion.

The use of excess formaldehyde in methylolation reactions presents serious processing shortcomings. The presence of free (i.e., unbound) formaldehyde, a serious irritant, in the reaction mixture presents a safety hazard not only to the personnel running the reaction, but also to personnel subsequently using the reaction product in the treatment of textile materials. Moreover, t .e use of large amounts of formaldehyde inevitably results in waste of the reagent. Further, the presence of free formaldehyde may cause variations in the properties of treated cellulosic textiles due to undesirable side reactions between the formaldehyde and cellulose. Lastly, the utilization of aqueous reaction mixtures increases the cost of preparing, handling, and shipping the methylolated materials.

In addition to the failings outlined above, methods em- 3,391,181 Patented July 2, 1968 ploying aqueous formaldehyde solutions exhibit a further disadvantage. Even though excess equivalents of formaldehyde are used in the reaction, the conversion of a carbamate to a dimethylolated compound is seldom substantially complete. If the reaction product ratio is expressed as the number of moles of bound formaldehyde per mole of carbamate nitrogen, a CH O/ N ratio of 2.0 corresponds to complete conversion to N, N-dimethylol alkyl carbamate, and a CHQO/ N ratio of 1.0 represents N-methylol alkyl carbamate. It has been found that use of exactly 2 moles of formaldehyde solution (the stoichiometric amount) in the methylolation reactions hitherto used yields a product having a CH O/N ratio of from 1.3 to 1.5, rather than the theoretical value of 2.0.

It is an object of this invention to provide a method for the essentially anhydrous preparation of N-methyh olated carbamates.

Another object of this invention is to provide a safe, economical, and effective method for preparing N-methylolated carbamates, said carbamates subsequently being used in the cross-linking of cellulosic textiles.

A further object of this invention is to provide a reaction for preparing mixtures of N-methylol and N, N- dimethylol carbamates wherein a major amount of N- methylol carbamate is converted to N, N-dimethylol carbamate.

Other objects and the advantages of this invention will be apparent from the description that follows hereinafter.

In accordance with this invention, an alkyl carbamate is reacted with paraforrnaldehyde under basic conditions to yield the corresponding N-methylolated carbamate. This reaction may be carried out under essentially anhydrous conditions, and thereby circumvents the undesirable features characteristic of prior art methods utilizing aqueous formaldehyde treatment.

Exemplary of the carbarnates which may be used in the process of this invention are those compounds represented by the formula wherein R is hydrogen; R may be hydrogen, straight or branched chain-lower alkyl having from 1 to 4 carbon atoms; X may be alkylene having up to 20 carbon or an ethylenically unsaturated group having from 3 to 6 carbon atoms, such as, e.g., CH=CH-CH or the residue of a branched chain alkyl group having up to 20 carbon atoms; and Z may the hydrogen, halogen, alkoxy,

i -o- N\ where R and R are as defined above. Also suitable for use in this invention are biscarbamates of primary diamines represented by the formula if t t i R3OCN-X-N-CO-Rs wherein R is a straight or branched chain-lower alkyl group having from 1 to 4 carbon atoms and X is as defined above.

As was mentioned previously, the methylolation reaction of this invention is carried out under basic conditions which may be attained by use or" such basic catalysts as the hydroxides of the alkali and alkaline earth metals, and preferably sodium hydroxide. Sufiicient amounts of catalyst are used to maintain the pH of the reaction from about 8 to about 11, with the preferred range being from 9.5 to 10.5.

The temperature at which the reaction proceeds may vary within a wide range, e.g., from about C. to about 100 C. It is preferred, however, to maintain the reaction temperature from 50 C. to 85 C. in order to minimize side reactions and achieve rapid reaction. The duration of heating is not critical and can vary within wide limits, e.g., from 10 minutes to 10 hours. The preferred reaction time, however, is about 2 hours.

The amount of paraforrnaldehyde to be employed in the process of this invention will be determined by the degree of conversion desired, as well as by the number of amide hydrogen atoms present in the earbamate. It is preferred to employ one equivalent weight of paraformaldehyde for each amide hydrogen present in the earbamate, although the ratio of paraformaldehyde to amide hydrogen may range from about 0.9 to about 1.1. The use of stoichiometric quantities of paraformaldehyde in this invention will give a substantial yield of dimethylol carbamate, so that an excess amount of paraforrnaldehyde serves no purpose.

In carrying out the process of this invention, anhydrous conditions or essentially anhydrous conditions can be used. In one embodiment of the process, the dry ingredients are charged to a suitable reactor, the catalyst added, and the mixture is heated. The mixture becomes fluid and stirrable at a temperature of from to C. and is thereafter stirred at the desired elevated temperature for from about 2 to about 4 hours. If less than substantially complete conversion is desired, the time of heating may be reduced accordingly. In another embodiment of this invention, a low melting carbamate, e.g., ethyl carbamate (melting point C.) may be melted hefore addition thereto of paraformaldehyde and the basic catalyst. The mixture remains fluid after addition of the paraformaldehyde and catalyst and may be stirred. Alternatively, small amounts of water may be added to assist in fluidizing the reaction mixture. However, the process of this invention eliminates the necessity of using even slight amounts of water in the reaction and consequently avoids the disadvantages inherent in such usage.

The N,N-dimethylolated alkyl carbamates produced by the process of this invention are stable indefinitely. These carbamates may also be used directly after preparation or the reaction mixture may be neutralized with an acid to a pH of from about 6.5 to about 7.5 and subsequently stored.

The methylolated carbamates of this invention may be applied to cellulosic textiles by any of the conventional means known to the practitioner. Using these carbamates, cross-linked textiles are obtained which exhibit enhanced smooth drying after laundering and good resistance to wrinkling.

In summary, then, the process of this invention enables carbamates to be methylolated without the use of aqueous formaldehyde solutions. Accordingly, the hazards, as well as the expense, of employing these aqueous solutions have been effectively circumvented. At the same time, the process of this invention yields carbamates having an increased degree of methylolation. As was mentioned previously, these carbamates find widespread application in the cross-linking of cellulosic textiles.

The following examples will further illustrate the embodiments of this invention. All parts given are by weight unless otherwise indicated.

Example 1 N,N-dimethylol ethyl carbamate was prepared by reaction of 178 grams ethyl carbamate (2 moles) with grams paraformaldehyde (4 moles) using 1 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was agitated and heated slowly starting at 25 C. When the temperature reached 27 C. a fiuid slurry was ob tained which cleared at 65 C. The reaction mixture was held at 6570 C. for 5 hours, after which time the pH thereof was about 10.2. On standing overnight the product was found to contain 4.8% free formaldehyde and 40.06% total formaldehyde (theoretical=40.1% representing a CH O/N ratio of 1.76.

Example 2 N,N-dimethylol ethyl carbamate was prepared by melting 1780 grams ethyl carbamate (20 moles) and adding to this at 53 C. 1200 grams of paraformaldehyde (40 moles). To this fluid slurry were charged 10 grams aque ous 50% sodium hydroxide. An immediate temperature increase was observed from 5367 C. in 3 minutes. The reaction mixture was held at 6466 C. for 3 hours and a portion neutralized to pH 7.1 with concentrated 37% hydrochloric acid. The pH of the mixture before neutralization was about 10.1. The neutralized product was found to contain 4.56% free formaldehyde, which corresponds to a CH O/N ratio of 1.77. The remaining portion of the reaction was found to contain 4.2% free formaldehyde after standing for 3 days which corresponds to a CH O/N ratio of 1.79.

Example 3 N,N-dimethylol methyl carbamate was prepared by reaction of grams methyl carbamate (2 moles) with 120 grams of paraformaldehyde (4 moles) using 1.0 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was agitated and heated slowly starting at 26 C. When the temperature reached 33 C., a fluid slurry was obtained which was clear at 68 C. The reaction mixture was held at 60-68 C. for 3 hours and then cooled. Neutralization to a pH of 7.12 was carried out using 1 gram of 37% hydrochloric acid. The pH of the mixture before neutralization was about 10. The product was found to contain 7.3% free formaldehyde, which corresponds to a CH O/N ratio of 1.67.

Example 4 N,N-din1ethylo1 methylene bis (ethyl carbamate) was prepared by reaction of grams of methylene bis (ethyl carbamate) (1 mole) with 60 grams of paraformaldehyde (2 moles) using 1.0 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was agitated and heated slowly starting at 25 C. When the temperature reached 48 C., a fluid slurry was obtained which became clear at 65 C. The reaction mixture was held at 65-73 C. for 3 hours, after which time the pH of the mixture was about 9.5. The reaction was allowed to cool overnight and Was found to contain 4.9% free formaldehyde, which corresponds to a CH O/N ratio of 1.59.

Example 5 This example illustrates the superior results obtained when the process of the present invention is employed rather than a prior art process.

The method set forth in Examples 14 was followed in preparing Formulations 2, 3 and 5, whereas Formulations 1 and 4 were prepared according to an exemplary prior art method. In carrying out the prior art technique, a 30% aqueous solution of a carbamate in formaldehyde was prepared by dissolving the carbamate in 4 times its weight of water and then adding sufiicient 37% formaldehyde solution to afford a ratio of formaldehyde to the carbamate of 2:1. The reactants, their ratio, and the CH O/N ratio present in the final product are set forth in the table below.

formaldehyde (2).

From the results presented hereinabove, it can be seen that the product of the present invention contains a significantly higher proportion of the dimethylolatcd compound.

Example 6 N,N-dimethylol allyl carbamate was prepared by reaction of 50.5 grams of allyl carbamate (0.5 mole) with 30 grams of paraformaldehyde (1 mole) using 0.25 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was agitated and heated slowly, starting at 24 C. The temperature rose exothermically to 33 C., and the mixture was heated to 60 C. at which point it cleared. It was held at 60 C. for two hours, and was found to contain 7.45% free formaldehyde. The reaction mixture was cooled and filtered to yield a clear water-white viscous liquid. The CH O/N ratio based on free formaldehyde analysis was 1.60.

Example 7 N,N-dimethylol 2-ethylhexyl carbamate was prepared by reaction of 52 grams of Z-ethylhexyl carbamate (0.3 mole) with 18 grams of paraformaldehyde (0.6 mole) using 0.25 grams of 50% aqueous sodium hydroxide as catalyst. The mixture was heated to 80 C. and was clear at this temperature. The reaction mixture was held at 6070 C. for two hours and cooled, whereupon a viscous oil was obtained which showed 3.6% fere formaldehyde, corresponding to a CH O/ N ratio of 1.72.

Example 8 N,N-dimethylol cetyl stearyl carbamate (this carbamate is actually an equimolar mixture of cetyl carbamate and stearyl carbamate) was prepared by reaction of 60 grams of cetyl stearyl carbamate with 12 grams of paraformaldehyde, using 0.25 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was initially heated to 60 C. and, on further heating to 80 C., gave a clear liquid. The reaction mixture was held for two hours at 80 C. and cooled. A solid white product was obtained which showed 3.3% free formaldehyde, corresponding to a CH O/N ratio of 1.60.

Example 9 N,N-dimethylol 2-chloroethyl carbamate was prepared by the reaction of 49.2 grams of 2-chloroethyl carbamate (0.4 mole) with 24.0 grams of paraformaldehyde (0.8 mole) using 0.2 gram of 50% aqueous sodium hydroxide as catalyst. The mixture was heated to 50 C. with stirring. It was held at this temperature for one hour where- 6 upon a product having a CH O/N ratio of 1.70 was obtained.

Example 10 N,N-dimethylol 2-methoxyethyl carbamate was prepared by reaction of 143.0 grams of Z-methoxyethyl carbamate (1.2 moles) with 72 grams of paraformaldehyde (2.4 moles) using 0.25 gram of aqueous sodium hydroxide as catalyst. The mixture was agitated and heated for one hour at -65 C. The reaction mixture was cooled to room temperature and found to contain 5.85% free formaldehyde. The CH O/N ratio of the product based on free formaldehyde analysis was 1.66.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the invention as defined by the following claims.

What is claimed is: 1. A method of preparing dimethylolated aliphatic carbamates in improved yield and substantially free from both monomethylolated contaminant and formaldehyde, comprising the steps of (1) admixing an essentially anhydrous reaction mixture of alkyl carbamate containing at least two methylolatable amido hydrogens selected from the group consisting of monoalkyl carbamates and alkylene biscarbarnates, paraformaldehyde in an amount corresponding to from about 0.9 to about 1.1 equivalent weight of paraformaldehyde for each amido hydrogen atom in said carbamates, and sufiicient basic catalyst to maintain the pH from about 8.0 to about 11.0 during the reaction, and

(2) heating the reaction mixture between about 50 C.

to about C. until a substantial quantity of dimethylolated product is produced and isolating the product contained therein.

2. The method of claim 1 wherein said basic catalyst is selected from the group consisting of alkali metal hy droxides and alkaline earth metal hydroxides, the pH is maintained between about 9.5 and 10.5, and the reaction time varies between about 2 to about 5 hours.

3. The method of claim 2 wherein the carbamate used is a monoalkyl carbamate.

4. The method of claim 3 wherein the monoalkyl carbamate is selected from the group consisting of ethyl carbamate, methyl carbamate, Z-ethylhexyl carbamate, cetyl stearyl carbamate, 2-chloroethyl carbamate, Z-methoxyethyl carbamate and 'alkyl carbamate.

5. The method of claim 1 wherein the bis alkyl carbamate is methylene bis(ethyl carbamate).

References Cited UNITED STATES PATENTS 2,297,531 9/1942 Bock 260-584 2,760,977 8/1956 Fener et a1. 260-561 2,864,861 12/1958 W-ohnsiedler 260561 3,144,299 8/1964 Frick et a1. 3,226,428 12/1965 Vail et a1. 260-482 LORRAINE A. WEINBERGER, Primary Examiner.

A. P. HALLUIN, Assistant Examiner.