US2392103A - Mixed thio ethers - Google Patents

Description

UNITED STATES PATENT OFFICE MIXEDTHIOETHEBS ware No Drawing. Application November 24, 1942, Serial No. 466,830

4 Claims. (01. 260. 217) This invention relates to the production of cellulosic products and has for its general object the provision of certain improvements in carrying out one or more of the processing steps used in the production of such products. The invention aims particularly to suppress or minimize the formation of incrustations, sometimes referred to as craters, formed in spinneret oriflees. The invention further contemplates, as a new article of manufacture, a chemically prepared wood pulp having incorporated therein a mixed thio ether containing a polyethylene oxide radical and an aliphatic hydrocarbon radical containing more than 7 carbon atoms.

In one of its important aspects, the invention involves the use of chemically prepared wood pulp as a source of cellulose in the preparation of cellulosic solutions for viscose processes in which extruded regenerated cellulose is produced, and has for a particular object the use of the mixed thio ethers to improve the spinning operatlon.

The invention is especially applicable to the spinning of viscose rayon in which chemically prepared wood pulp (hereinafter called "wood pulp) is used as a source of cellulose and the invention will be described with reference to that process, it being understood that it is also applicable to the spinning of other aqueous cellulosic solutions where clogging of the spinneret orifices due to incrustations tends to occur.

Wood pulp as usually prepared as a sourceof cellulose for the viscose and related spinning industries is of various degrees of purity, and is generally supplied for use in the form of sheets. Normal dissolving wood pulp in present use consists mainly of cellulose and contains an appreciable amount of non-cellulosic impurities, such as hemi-celluloses, fats, resins, waxes, etc. One of the main objects in the manufacture of highly refined dissolving pulp is to remove as much as possible of the non-cellulosic impurities so that a whiter, purer pulp results which is capable in the manufacturing of rayon of producing a higher grade yarn.

We find that there are impurities present in pulp which has not been highly refined which have marked efiects, both favorable and adverse,

on the formation of incrustations in the orifices of the spinnerets during spinning. In theory, the problem of malnng a good pulp could be solved by removing all the undesirable impurities while retaining those impurities which facilitate the step of spinning. I practice such a cleancut separation is diflicult to accomplish directly. We

have discovered that better results are obtainable by removing most or all of the impurities, including those which affect spinning, either positively or negatively, and then causing to be present in the viscose, materials of a class entirely different from the natural impurities originally present, and which greatly aid the step of spinning.

White, highly purified or refined wood pulps are very advantageous for the production of high grade rayon yarns of superior strength and color, and for this reason, are highly esteemed by the trade. Such highly refined pulps are in generaicharacterized by having an ether extract lower than 0.15% where such values refer to the amount of natural ether extractable material left in the pulp after the purification processes. While our invention is particularly applicable to such highly refined pulp containing not more than 0.15% of ether extractable material, it may be applied with certain advantages to the processing of normal dissolving pulps containing more than 0.15% of ether extractable material, although such pulps do not generally yield the highest grade yarns.

In accordance with the invention a small quantity of a mixed thio ether containing a polyethylene oxide radical, and an aliphatic hydrocarbon radical containing more than '1 carbon atoms, is incorporated in the materials used in producing the cellulosic solution prior to regenerating the cellulose to improve the characteristics of the spinning solution and the spinning operation. For use in our invention, the mixed thio ethers are preferably substantially soluble in water. Such compounds will generally contain a polyethylene oxide radical, having at least a third as many ethenoxy groups as there are carbon atoms in the hydrocarbon radical. Practically, it is believed there is no upper limit for the number of ethenoxy groups in the polyethylene oxide radical. Materials with a polyethylene oxide group containing up to 157 ethenoxy groups may be satisfactorily used.

While the mixed thio ethers used in our invention are preferably substantially water soluble, it is possible to obtain the advantages of the invention in part using compounds of only slight solubility. Thus, mixed thio ethers containing even the simplest possible polyethylene oxide radical composed of two ethenoxy groups, may be used. Even though such products do not have a great solubility they still possess a suflicient tendency to emulsify so that they may be dispersed in a finely divided state in the viscose yielding in part the advantages of the invention. If, however, a high degree solubili in water is desired with such agents, as for example, in the preparation of concentrated stock solutions for application to the pulp or in the viscose process, it may be advantageous to combine them amount of sodium. Thismay readily be accomplished by addition of a solution of the theoretical amount of sodium in liquid ammonia to an ether solution of the mercaptan, or by addition or liquid ammonia to an ether solution of the mercaptan followed by subsequent addition of with dispersing agents. Such additional. (118- persing agents should preferably be of a nonionic nature, for example, a mixed thio ether containing a higher proportion of ethenoxy groups. In the preferable form of our invention, however, sumcient ethenoxy groups will be present in the polyethylene oxide radical so that the products will be substantiall water soluble without the aid of any additional dispersing agents.

Furthermore, our most preferred class of compounds are those mixed thio ethers containing a polyethylene oxide radical with from 9 to 20 ethenoxy groups and a normal primary aliphatic hydrocarbon radical-with from 12 to 18 carbon atoms. Such compounds are particularly effective in suppressing or minimizing formation of incrustations in the spinneret orifices during spinning. While the mixed thio ethers may be used in connection with any of the steps inproducing regenerated cellulose, they are especially beneficial when in contact with the spinneret due to their presence either in the spinning solution or in the spin-bath.

In the usual viscose process the sheets are first subjected to a steeping step to convert the cellulose to alkali cellulose, and the pressed sheets of alkali cellulose are then shredded to form a fiufiy mass of fibers. The fiufiy mass is xanthated, dissolved in dilute caustic soda and the solution commonly known as viscose filtered to remove undissolved fibers and gel-like materials, and ripened to impart the desired properties for satisfactory spinning. A

Viscose solutions used in making rayon are usuall spun through metal spinnerets having orifices varying from 0.002 to 0.004 of an inch in I diameter. The incrustations form on the inside walls of the hole of the metal spinnerets, especially in acid spin-baths containing high proportions of such salts as sodium, zinc and magnesium sulphates and seriously impair the spinning operation. It is a particular object of this invention to employ the mixed thio others so that they are in contact with the metallic spinneret during spinning, and so that the formation of the craters is greatly minimized. The mixed thio ethers exert such a powerful influence on the materials present that only very small quantitles are necessary to accomplish, the results sought. The extremely efiective suppression of the craters is illustrated in some operations by a reduction of from to percent in the crater formation. I

The mixed thio ethers of the invention may be prepared by any of the known methods for adding ethylene oxide on to a mercaptan. Or the mixed thio ethers may be prepared by condensation reactions as, for example, by reacting a sodium salt of the mercaptan with a halogen hydrin of a polyethylene glycol.

We prefer, however, to react ethylene oxide at moderately elevated temperatures with aliphatic fatty mercaptans containing more than 7 carbon atoms under conditions in which at least part of the mercaptan may be considered to be present as mercaptide.

Rapid reaction with the ethylene oxide may be obtained by transforming the fatty mercaptan into a mercaptide containing the theoretical metallic sodium. vThe solvents are then evaporated ofi. .Vacuum may be used to remove the final traces although a product containing a small amount of ether may be satisfactorily used. During the last stages of solvent removal, particular care is taken that the product does not take up any apprecable amount of moisture. Instead of preparing a mercaptide b means of sodium and liquid ammonia other methods suitable for the preparation of the mercaptide in a dr condition may be used.

Instead of actually preparing and isolating a mercaptide containing the theoretical amount of sodium, it suffices to add a small amount of concentrated aqueous caustic soda to the mercaptan, e. g., about 0.5% by weight of 48% caustic soda. This is a less expensive method particularly suited to the preparation of derivatives containing a relatively short polyethylene oxide chain.. When aqueous caustic soda is so used some of the ethylene oxide is probably consumed to form polyethylene oxide. The presence of polyethylene oxide is, however. not harmful to our invention in that it has an anti-cratering action of its own, though to a considerably lesser degree. Furthermore, the presence of the polyethylene oxide may be even beneficial, especially when the material is to be added to the pulp prior to use or at the latest to the viscose process prior to the comletion of shredding. The presence of polyethylene oxide in such cases is actually favorable in that it has a beneficial effect on the shredding operation, the efi'ect being very marked when using highly refined pulp.

After forming a mercaptide, as for example by the method described, or after adding a small portion of concentrated caustic soda to the mercaptan as described, the material is placed in an autoclave and heated with agitation in contact with the required amount of ethylene oxide until the pressure drops approximately to atmospheric pressure. When using a mercaptide containing the theoretical amount of alkali the reaction should be carried out at a relatively low temperature, e. g., about 65 0.; otherwise the reaction may proceed too rapidlyand surge to completion in a few minutes with explosive violence resulting in a less pure product. When, however, using only small amounts of sodium in the form of strong aqueous caustic soda considerably higher temperatures should be used. c. g., about 0.

Example 21.2 gm. of lauryl mercaptide, prepared by the sodium-ether-ammonia method described above were placed in a small autoclave with 50 gm. of

. product was isolated by evaporating off the benzene, finally applying vacuum. I

This product which is particularly eifective is predominately a compound represented by the probable iormula 012E258 (C2340) 123.

In the preparation of the above product, mixtures of mercaptans prepared from technical lauryl alcohol, which is a mixture in which Cm predominates, may be used, and in basins the amount of ethylene oxide, it suflices to consider the whole material as having the molecular weight of lauryl mercaptan. Furthermore, the exact twelve ethenoxy units shown are not essential and could range according to the description given above for the most preferred compounds, from 9 to 20 residues.- Also, other mercaptan mixtures prepared from commercial mixtures oi alcohols derived by hydrogenating fats and oils are suitable and practical for conversion to thio others for use in the invention.

The mixed thio ethers may be incorporated in the finished wood pulp, or during the formation er the pulp sheet, or at any stage of the viscose process. A most practical and convenient methpd of securing the presence 01 the desired amount of the mixed thio ether during spinning is to incorporate the mixed thio ether in the wood pulp while it is on the sheet-forming machine. when the agent is so incorporated in the wood pulp, by the pulp manufacturer thereof, the pulp comes to the rayon manufacturer in a form calculated to secure the full advantages of the inconcentrations than 0.2 percent which include the causing of excessive softness in the sheet resulting in mechanical difliculties in steeping. excessive ball formation in xanthation, difliculties in the dissolving operation du both to the excessive ball formation in the xanthating step and due to excessive foaming in the viscose solution. Also there will be considerable difliculty in obtaining a completely de-aerated viscose which is absolutely necessary for satisfactory spinning. Larger percentages also cause the surface tension of the viscose to be too low, resulting in unsatisfactory spinning.

When it is desired to suppress the formation oi! incrustations in the orifices of the spinneret without incorporating the mixed thio ether in any of the materials prior to extrusion through the spinneret, the mixed thio ether may be added directly to the spin-bath in relatively small quantities. Suitable quantities oi the compounds in this adaptation oi the invention vary from 0.001 to 0.1 percent by weight based on the weight of th spin-bath.

The mixed thio ethers, whether in the spinning solution or in the spin-bath, 'come into direct contact with the orifices oi the spinneret and suppress the formation of incrustations on the walls of the orifices.

We claim:

1. As a new article 01' manufacture a chemically prepared wood pulp having incorporated therein from 0.01 to 0.2 percent by weight based on the bone dry weight ofthe pulp of a water soluble mixed thio ether containing a polyethylene oxide radical and an aliphatic hydrocarbon radical containing more than 7 carbon atoms.

2. An article of manufacture according to claim 1 in which the mixed thio ether contains a polyethylene oxide radical in which there are at least one-third as many ethenoxy residues as carbon atoms in the alkyl chain.

3. An article of manufacture according to claim 1 in which the mixed thio ether contains a polyethylene oxide radical with from 9 to 20 ethenoxy residues and a normal primary aliphatic hydrocarbon radical with from 12' to 18 carbon atoms.

4. As a new article or manufacture, a chemically prepared wood pulp containing not more than 0.15 percent natural ether extractable ma- 0 terial and having incorporated therein from 0.01 to 0.2 percent by weight based on the bone dry weight of the pulp of a water soluble mixed thio ether containing a polyethylene oxideradi- PAUL HENRY SCHLOSSER. KENNETH RUSSELL ,GRAY.