US3749751A - Reducing free formaldehyde content in methylolated carbamates - Google Patents

Abstract

THE FREE FORMALDEHYDE CONTENT OF METHYLOTATED CARBAMATES IS REDUCED BY CONTACTING AN AQUEOUS SOLUTION OF THE METHYLOLATED CARBAMATE WITH A NITROGENOUS CARBONYL COMPOUND HAVING A CC(O)N(H) GROUP, E.G., A PYRROLIDONE, IN THE PRESENCE OF A CAUSTIC.

Description

United States Patent 3,749,751 REDUCING FREE FORMALDEHYDE CONTENT IN METHYLOLATED CARBAMATES Panemangalore S. Pai, Charlotte, N.C., assignor to BASF Wyandotte Corporation, Wyandotte, Mich. No Drawing. Filed Aug. 30, 1971, Ser. No. 176,318 Int. Cl. C07c 125/04 US. Cl. 260-482 C 10 Claims ABSTRACT OF THE DISCLOSURE The free formaldehyde content of methylolated carbamates is reduced by contacting an aqueous solution of the methylolated carbamate with a nitrogenous carbonyl compound having a CC(O)N(H) group, e.g., a pyrrolidone. in the presence of a caustic.

BACKGROUND (1) Field of the invention This invention relates to textile finishes based on methylolated carbamates which have a reduced free formaldehyde content.

(2) Description of the prior art Formaldehyde has long known as a cross-linking agent for cellulosic materials and has been known to impart crease resistance and dimensional stability to such materials. As a reactant, it is known that formaldehyde is difficult to control to achieve uniform results and in addition is difficult to work with due to its ability to sensitize workman and its potent disagreeable odor. Moreover, formaldehyde can seriously etfect initially tensile strength values for cellulosic materials finished therewith. Therefore, efforts have been made to prepare methylolated compositions, that is compositions wherein the formaldehyde is bound, to overcome the objections of using free formaldehyde. Compositions such as dimethylolurea and ureaformaldehyde condensates having a high ratio of moles of combined formaldehyde per mole of urea have been developed. While in general terms there are suggestions that highly methylolated ureas such as tetramethylol urea have been prepared, successful processes for making the product as a useful textile finishing agent have been few in number.

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, the use of large amounts of formaldehyde inevitably results in the waste of the reagent. Further, the presence of free formaldehyde may cause variation in the properties of treated cellulosic textiles due to undesirable side reactions between the formaldehyde and cellulose.

In recent years various methylolated carbamates have become very popular in the textile industry as finishing agents. However, as pointed out 'by I. D. Reid et al. in the American Dyestuif Reporter, 59 (5), 26 et seq., June 1970, the use of carbamate finishing agents in the postcurable press process has been inhibited by the relatively high free formaldehyde content of solutions of these agents. They thought compounds that react to bind free 3,749,751 Patented July 31, 1973 formaldehyde chemically offer some promise for further development. While they were able to obtain decreases in free formaldehyde with various reagents, they obtained some undesirable side effects, notably in the resistance to chlorine damage of a fabric treated with a modified finishing solution.

Therefore, it is an object of this invention to provide a process for reducing the free formaldehyde content of methylolated carbamates which is free of undesirable side reactions injurious to the finished fabric.

It is still another object of this invention to provide a simple process which is conveniently carried out for the reduction of free formaldehyde in methylolated carbamates.

The foregoing objects and other objects will become readily apparent to those of ordinary skill in the art upon reading of the following specification including the examples appended thereto.

SUMMARY OF THE INVENTION In accordance with this invention there is provided a method for reducing the free formaldehyde content of methylolated carbamates comprising contacting an aqueous solution of the methylolated carbamate with a nitrogenous carbonyl compound having a CC(O)N(H) group, a total of from 2 to 6 carbon atoms and a carbonyl wave number from about 1650 to 1700 cm? in the presence of a caustic.

DESCRIPTION OF PREFERRED EMBODIMENTS Methylolated carbamates useful as textile finishing agents are well known and include monomethylol monoalkyl carbamates, dimethylol monoalkyl carbamates, dimethylol carbamates of ether alcohols, monomethylol carbamates of ether alcohols, alkylene bis(N-methylol- N-alkyl) carbamates and alkylene bis(N-methylol carbamates). Typical monomethylol monoalkyl carbamates wherein the alkyl group contains 1 to 6' carbon atoms include methylol methyl carbamate, methylol isopropyl carbamate and methylol butyl carbamate. Illustrative of the dimethylol monoalkyl carbamates wherein the alkyl group contains from 1 to 6 carbon atoms includes dimethylol methyl carbamate, dimethylol n-propyl carbamate, dimethylol ethyl carbamate, dimethylol isopropyl carbamate and dimethylol n-butyl carbamate. Representative of tetramethylol carbamates is the tetramethylol derivative of butane diol dicarbamate and the tetramethylol derivative of diglycol dicarbamate. Among the dimethylol carbamates of ether alcohols can be mentioned ethoxyethyl N,N-dimethylol carbamate, methoxyethyl N,N-dimethylol carbamate, propoxyethyl N,N-dimethylo1 carbamate, isopropoxyethyl N,N-dimethylol carbamate, isobutoxyethyl N,N-dimethylol carbamate, pentoxyethyl N,N-dimethylol carbamate, butoxyethyl N,N-dirnethyl0l carbamate, N,N-bis(isopropoxymethylol) methoxyethyl carbamate and hexoxyethyl N,N-dimethylol carbamate. Representative monomethylol carbamates of ether alcohols include N-methylol methoxy methyl carbamate, N- methylol Z-methoxy ethyl carbamate, N-methylol ethoxyethyl carbamate, N-methylol Z-propoxyethyl carbamate, N-methylol 2-isobutoxyethyl carbamate and N-methylol Z-hexoxyethyl carbamate. Alkylene bis(N-methylol N-allyl carbamates) are exemplified by ethylene bis(N-methy1ol N-methyl carbamates) and atkylene bis(N-methylol carbamates) are exemplified by ethylene bis(N-methylol carbamates). Further elucidation of the foregoing carbamates may be found in US. Pats. 3,144,299; 3,391,181 and 3,524,876 and articles appearing in the American Dyestuff Reporter 50 (22) at pages 37-41, Oct. 30, 1961 and 54 (13) pages 54-60, June 21, 1965, which are incorporated herein by reference.

The nitrogenous carbonyl compounds of this invention are a select group of carbonyl compounds characterized by the carbonyl group being joined to a carbon atom and also a nitrogen atom which is part of either an amide or imide group. Structurally then these compounds are characterized by the group which is also noted as CC(O)N(H). For convenience unless otherwise noted the special carbonyl compounds of this invention will be referred to as pyrrolidone. The pyrrolidone compounds are further characterized as having a total of from 2 to 6 carbon atoms and a single nitrogen atom. The carbonyl wave number of the pyrrolidone compounds is from about 1650 to about 1700 cm.- Illustrative of the pyrrolidone compounds are 2-pyrrolidone, acrylamide, methacrylamide, acetamide, 2-piperidone, caprolactam and succinimide.

Since the methylolated carbamates are either prepared and/or used as an aqueous dispersion or solution, it is convenient to treat the methylol methylolated carbamate for removal of formaldehyde while in an aqueous dispersion. The total solids content of the dispersion is a matter of choice being governed by considerations such as ease of processing of lower dispersions balanced against the large volumes required when low total solids content dispersions are being handled. It has been found that total solids contents of 50 to 70% are very conveniently handled in this process.

In carrying out the process the pH of the solution should be at least 9 and a pH of 9 to 10.5 is preferable. The pH is obtained and maintained by the use of a caustic selected from the group of alkali hydroxides and alkaline earth hydroxides. The alkali hydroxides of the first column of the periodic table are preferred and particularly sodium hydroxide and potassium hydroxide.

The method of this invention is carried out by heating the aqueous dispersion of carbamate to a temperature of from about to about 45 C. and preferably from about 32 to about 42 C. To the warm dispersion is added pyrrolidone (especially preferred is 2-pyrrolidone) in an amount of about 0.5 to 1.0 mole for each mole of free formaldehyde contained in the methylolated carbamate. In keeping with good chemical engineering practices the reaction mixture is stirred so as to insure complete recontact and reaction. The length of time of treatment that is maintained will depend upon the volume of methylolated carbamate being treated, the amount of free formaldehyde contained therein and the amount of pyrrolidone charged. In a typical commercial scale operation a contacting or residence time of 1 to 2 hours has been found satisfactory.

The pyrrolidone adds to the formaldehyde to produce N-methylol derivatives which are unobjectionable to the textile finishing agent use for which the methylolated carbamate is intended.

The following examples are included to illustrate the process of the present invention but are not to be considered limiting. Unless otherwise stated, all parts are by weight and all temperatures are in degrees centigrade.

EXAMPLE I An aqueous dispersion (1000 parts) of N-methylol 2- methoxyethyl carbamate (about 52% solids) was charged to a reactor. The pH was adjusted to a pH of 9 to 9.5 with the use of potassium hydroxide. The free formaldehyde (100%) content of the dispersion was 2.5%. To the reactor was added 62 parts of 2-pyrrolidone. The reaction mixture was stirred for 1 to 2 hours at a temperature of 35 to 40 C. After treatment was discontinued the free formaldehyde content was again determined and found to be 1.1%. The total solids content was adjusted to 50% by the addition of 62 parts of water. After adjusting the pH of the product to 7.0-7.5 with hydrochloric acid, the product was ready for textile use.

The product obtained was then applied on swatches of polyester/cotton sheeting material and cured. N-methylol Z-methoxyethyl carbamate which had not been treated by the process of this invention was applied to and cured on control swatches of polyester/cotton sheeting material. In each case 225 g./l. of specified carbamate was added to an aqueous dispersion of 20 g./l. of a non-ionic fatty blend liquid softener, 20 g./l. of a non-ionic polyethylene emulsion, 45 g./l. of an activated magnesium chloride hexahydrate (64% solution) and 2 g./l. of a non-ionic wetting agent, the balance of the bath being water. In each case the wet pick-up was 65%. The swatches were dried 60 seconds at 225 F. and then cured for seconds at 360 F. The swatches with the product of this invention had an accelerator abrasion loss (1 minute at 3,000 r.p.m.) of 5.9% whereas the swatches with untreated carbamate had a loss of 8.6%. Thus the product produced by this invention reduced the dusting of the sheeted material. Both samples gave no chlorine scorches after five home and five commercial washes, chlorine scorch being determined after 30 seconds at 635 F.

Comparable results are obtained by the substitution of acrylamide for the 2-pyrrolidone of this example.

EXAMPLE II To a reactor was charged an aqueous dispersion (920 parts) of N-methylol 2-methoxyethyl carbamate (about 52% total solids) and 80 parts of 2-pyrrolidone. The dispersion contained 3.2% free formaldehyde The pH of the solution was adjusted by adding a 50% solution of sodium hydroxide until a pH of 10.3-10.5 was obtained. The reaction mixture (temperature 35 to 37 C.) was stirred for l to 2 hours. The treated carbamate was cooled to room temperature and free formaldehyde content was found to be 1.3-1.5%.

In place of the 2-pyrrolidone of this example an equal amount of methacrylamide can be employed to obtain satisfactory results.

The foregoing examples have been described for the purpose of illustration and not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art based on this disclosure. These are intended to be comprehended as within the scope of this invention.

Having thus described the invention, what it is desired to claim and secure by Letters Patent is:

1. A method for reducing the free formaldehyde content of methylolated carbamates comprising contacting the free formaldehyde in an aqueous solution of methylolated carbamate with an amide compound containing 2 to 6 carbon atoms characterized by a CC(O)N(H) group and having a carbonyl wave number from about 1650 to about 1700 cm.- in the presence of caustic and at a temperature from about 25 to about 45 C.

2. The method of claim 1 wherein the amide is 2- pyrrolidone.

3. The method of claim 1 wherein the carbamate is treated for a period of 1 to 2 hours.

4. The method of claim 1 wherein the treatment is carried out at a temperature of about 32 to about 42 C.

5. The method of claim 1 wherein the caustic is an alkali metal hydroxide.

5 6 6. The method of claim 5 wherein the caustic is sodium References Cited hydroxide.

7. The method of claim 5 wherein the caustic is potas- UNITED STATES PATENTS Sium hydroxide 3,556,713 1/1971 Kullman 260-482 C 8. The method of claim 1 wherein 0.5 to about 1.0 moles of the amide is added for each mole of free 5 LORRAINE WEINBERGER Pnmary Examiner formaldehyde. P. I. KILLOS, Assistant Examiner 9. The method of claim 1 wherein the pH of the aqueous solution is from about 9.0 to about 10.5.

10. The method of claim 1 wherein the amide is acryl- 10 amide.