US3254059A - Treatment of chips of polycarbonamide containing organic derivative of hypophosphorous acid - Google Patents

Description

ceptivity of filaments made therefrom.

United States Patent TREATMENT 0F CHIPS 0F POLYCARBONAMIDE CONTAINHNG ORGANIC DERIVATIVE 0F HYPO- PHOSPHURQUS ACID George H. Brinkman, Jr., and Gerald W. Sovereign, Gulf Breeze, Fia., assignors to Monsanto Company, a corporation of Delaware No Drawing. Filed Feb. 12, 1962, Ser. No. 172,773 7 Claims. (Cl. 260-78) The present invention relates to a process of treating chips of a polycarbonamide, i.e., nylon, containing an organic derivative-of hypophosphorous acid. More particularly, the present invention relates to a process of treating chips of a specific polycarbonamide, namely polyhexamethylene adipamide, commonly termed nylon- 66, containing a phenyl derivative of hypophosphorous acid or salt thereof added during the polycondensation of the polymer-forming material to enhance the dye receptivity of filaments made therefrom.

Manufacture of fiber-forming polyamides by polycondensation of diamines and dibasic acids is broadly known. A commercially important polyamide of the aforesaid class is polyhexamethylene adipamide, known generally as nylon-66. In the preparation of nylon-66, hexamethylene diammoniumadipate (the salt of hexamethylene diamine and adipic acid) is heated under suitable polycondensation conditions to produce a fiber-forming polyamide having molecular weights represented by intrinsic viscosity values of about 0.3 to 1.3.

Filaments are normally made from the fiber-forming polyamides by conventional melt spinning techniques. Unfortunately, such filaments have a limited aflinity to certain dyes. This limited afiinity of the filaments for dyes not only restricts the depth of obtainable color, but also greatly limits the range of dyes which can be employed.

It is known that certain additives can be incorporated in the fiber-forming polyamides to enhance the dye re- It has been suggested recently to polycondense polyamide-forming substances in the presence of a small amount of a phosphinic compound selected from the group consisting of monoand di-alkyl, monoand di-aryl, and monoalkyl monoaryl phosphinic acids, and diamine salts of these phosphinic acids. The resulting polymers prepared in the presence of these additives exhibit greater dye receptivity. However, when the polymers containing the aforesaid phosphinic additives are melt spun, obnoxious fumes heretofore have developed during melt spinning giving rise to a health hazard to operators attending the melt spinning operation.

It is an object of the present invention to provide a method of treating nylon chips containing an organic derivative of hypophosphorous acid or diamine salt thereof to minimize the formation of obnoxious fumes normally occurring during melt extrusion of the chips into filaments or the like.

It is a further object of the present invention to provide a method of treating nylon-66 chips containing a phenylphosphinic compound to minimize the formation of obnoxious fumes normally occurring during melt spinning of the chips into filaments or the like.

Other objects may become apparent from the follow ing detailed description.

In general, the objects are accomplished by polycondensing a nylon-forming substance in the presence of a small amount of a phosphinic additive. The phosphinic additive can be a compound selected from the group consisting of monoand di-alkyl, monoand di-aryl, and monoalkyl monoaryl phosphinic acids, and the diamine salts of these phosphinic acids. Preferably, the additive Patented May 31, 1966 is benzenephosphinic acid or hexamethylene diammoniumphenylphosphinate and the nylon-forming substance is hexarnethylene diammoniumadipate. The resulting nylon polymer is extruded and quenched in the form of a ribbon which is thereafter cut into flakes, chips, granules, or like particulate form. The chips are scoured to reduce the water soluble content of the phosphinate additive. The scoured chips are dried and then melted. The resulting polymer melt is extruded into filaments by conventional melt spinning. The thus-produced filaments exhibit an enhanced dye receptivity. Obnoxious phosphorous-containing fumes normally attendant with melt spinning of chips which have not been scoured is minimized. Surprising is the fact that the dye receptivity of the filaments is not reduced significantly by the scouring.

At least one of the above-defined phosphinic additives is introduced into the polymerization vessel with the nylon-forming substance for the purpose of enhancing the dye receptivity of filaments made from the ultimate polymer. The phosphinic additives generally are used in an amount of about 0.7 to 14.0 mol percent based on the weight of the nylon-forming substance With about 0.7 to 2.0 mol percent being preferred. The additive should be a member of the class of phosphinic compounds as above defined. For example, metal phosphinates, such as sodium phenylphosphinate, to a substantial extent do not improve the dye saturation level of nylon prepared in the presence thereof. Commercially important of the dye enhancing phosphinic additives are benzenephosphinic acid or such acid which has been reacted with a suitable diamine such as hexarnethylene diamine to form hexamethylene diammoniumphenylphosphinate. In a preferred embodiment hexamethylene diammoniumadipate and benzenephosphinic acid are charged to a polymerization vessel conventionally used in preparing nylon polymer. Nylon-forming reaction conditions are employed. That is, the reactants are heated at a temperature from about 180 C. to 300 C., and preferably from 200 C. to 295 C. until the product has a sufficiently high molecular weight to exhibit fiber-forming properties. This condition is reached when the nylon polymer possesses an intrinsic viscosity of at least 0.3.

In a conventional manner the resulting nylon polymer is castinto a ribbon which is quenched. As is normally the case where filaments are spun in accordance with the heated grid spinning procedure, the ribbon is diced into chips or flakes of the usual size. ent invention the chips are scoured. That is, they are contacted with a solvent so that soluble phosphinic compound is partly or totally removed from the chips. It has been found that Water or water containing a small amount of an alkaline substance gives excellent results as a material with which the chips can be scoured. The scouring can be accomplished in a variety of ways. In one procedure the chips can be soaked in or drenched with water. For best results the scouring water has a pH of about 6 to 12.5, preferably 6 to 8, and a temperature of about 20 C. to 100 C. and higher. Preferably the scouring is carried out at or near the boiling point of water. The-scouring time normally will be between about 5 and minutes to reduce the soluble phosphinic compound to a minimum practical value.

An alkaline substance which has been found to give good results is trisodium phosphate. It is believed that the scouring operation removes the part of the phosphinic additive which has not become an integral part of the nylon polymer. However, the presence of the part of the soluble phosphinic additive is not really needed in the deeper dyeing filaments, since filaments prepared with and without the scouring of the chips exhibit comparable dye receptivities.

However, in the pres- The scoured chips are dried in a suitable manner without degrading the polymer to a substantial extent. For example, the chips can be dried in a vacuum oven at a temperature of 65 C. to 90 C. or centrifuged until .a moisture content of about two percent or lower is reached. The chips need not be dried completely, since the presence of some water can be used to create a static pressure head of steam normally maintained in melting Examples [-111 A stainless steel autoclave was charged with 406 parts of hexamethylene diammoniumadipate dissolved in an equal weight of water. A sufficient amount of acetic acid was added to stabilize the viscosity of the ultimate polymer at a relative viscosity of 34. The autoclave which-had been purged of air by steam was pressurized and heated. When a temperature of 170 C. was reached, 3.1 parts of benzenephosphin-ic acid was added. The heating of the ture to a temperature of 243 C. while the pressure was 1 held constant. At this point, the pressure reduction cycle was begun with the pressure being reduced to atmospheric pressure over a period of 105 minutes. The polymerforming material was held at this temperature and at atmospheric pressure for an additional 30 minutes. The molten polymer thus obtained was then extruded in the form of a ribbon using a conventional casting wheel. After being cooled, the ribbon was cut into flakes suitable for melting and spinning into filaments by means of a melt spinning assembly including a heated grid.

The polymer flakes were divided into three equal portions. One portion of the flakes was placed in an extraction tray wrapped with an aluminum screen and suspended in a clean tank. The tank was rectangular with an open top having a capacity of approximately 50 gallons. The bottom and sides of the tank were jacketed for reception of steam. The tank was then filled with deionized water having a pH of 6.7. The Water was heated to boiling and this condition was continued for a period of 30 minutes. Thereafter, the steam was turned off and the water drained from the tank. This extraction procedure was then repeated twice after which the flakes were removed from the tank and transferred to a vacuum oven. The flakes were dried therein for a period'of 8 hours at 75 C; under vacuum.

The thus-prepared water-scoured flakes were then spun into textile filaments using a conventional melt spinning apparatus. The air employed to solidify the filaments was analyzed for phosphorous content and was found to contain less than 0.05 ppm. phosphorous.

The second portion of the flakes was spun into textile filaments by-passing the scouring and drying steps of the present invention. The air employed to solidify the filaments had a pungent obnoxious phosphorous-like odor.

The third portion of the flakes was placed in a bag constructed of loosely woven nylon yarn. The bag was placed in boiling water containing 2.5 gms./ liter trisodium phosphate for 30 minutes. The pH of the water containing the trisodium phosphate was 11.4. The flake was then dried in a vacuum oven for 8 hours at 75 C. The thus-scoured flakes were spun into textile filaments using a conventional melt spinning apparatus. The air employed to solidify the filaments was analyzed for phosphorous content and was found to contain less than 0.05 p.p.m. phosphorous.

There were no significant differences in the physical properties of the filaments prepared from the scoured flakes and the unscoured flakes. The filaments obtained by spinning scoured flakes and unscoured flakes were separately fabricated into 4 inch length samples of knit tubing. Tests were .then run on each of the fabric samples to determine their relative dye saturation levels. In the procedure used, each of the samples was dyed with equal concentrations of the commercial dyestutf Scarlet 4'RA (C.I. Acid Red 18). The dyeing was continued over a period of two hours in a bath having a liquor to fiber ratio of 40:1. A temperature of C. was maintained in the bath. After completing the dyeing, the amount of .dye absorbed by each sample was determined by spectrophotometrically measuring the change in dye bath concentration, i.e., the difference between the original dye concentration in the bath and the exhausted dye concentration.- It was found that the amount of dye absorbed by the filaments spun from scoured flakes was substantially the same as the amount absorbed by the filaments spun from unscoured flakes. Values obtained averaged 1.95 percent dye absorbed for scoured sample-s vs. 2.08 percent for unscoured samples vs. 1.04 percent for samples not containing the phosphinic additive.

Example IV Another batch of polymer was prepared as described in Example I. The flakes were poured into a tray and immersed in boiling deionized water. After 30 minutes the tank was drained and refilled with fresh deionized water. The temperature of the water was raised to the boiling point and the extraction process was repeated. After repeating the extraction a third time, the chips were removed from the tray and dried.

- The washed and dried chips were placed in a conventional grid melter and the resulting melt extruded into filaments. The occurrence of the obnoxious fumes was reduced below the detectable level.

As can be seen from the above, the present invention affords several advantages. Nylon polymer to which a phosphinic compound has been added during the polycondensation thereof can be spun without the normal obnoxious phosphorous-containingfumes being formed during melt spinning of the polymer. The dye receptivity induced by the phosphinic compound is not sacrificed by the scouring of the nylon flakes. The health hazards of the fumes are obviated. Other advantages will be noted.

It is not intended that the invention be limited solely to the details of the embodiments set forth above. It will be recognized that numerous modifications conforming to the spirit of the invention may be made. Therefore, it is intended that the invention be limited only by the scope of the following claims.

What is claimed is:

1. A process of treating chips of polyhexamethylene adipamide polycondensed in the presence of about 0.7 to 14.0 mol percent based on the weight of the polymer forming substance of a dye-enhancing benzenephosphinic additive comprising the steps of:

(a) scouring said chips in water; and

(b) drying the scoured chips; whereby obnoxious phosphorous-containing fumes normally attendant with melt spinning of such polymer is minimized.

2. The process of claim 1 wherein the additive is ben-.

zenephosphinic acid.

3. The process of claim 2 wherein the pH of the scouring water is about 6 to 12.5.

4. The process of claim 3 wherein the temperature of the scouring water is about 20 C. to 100 C.

5' 6 5. The process of claim 2 wherein boiling Water of 21 2,927,841 3/1960 Ben 26()-78 pH of about 6 to 8 is employed during the scouring. 2,978,439 4/1961 Kersting 260--78 6. The process of claim 5 wherein a small amount of 2,981,715 4/1961 Ben 26078 an alkaline substance is present in the scouring water. 3,078,248 2/ 1963 Ben 26,078

7. The process of claim 6 wherein boiling water con- 5 OTHER REFERENCES taining a small amount of trisodium phosphate is employm during the scouring Beilstein: Organische Chemie, vol. 16, pp. 791 and 803 A I relied on. References Cited by the Examiner WILLIAM H SHORT P E e UNITED STATES PATENTS 10 "7 2,510,777 6/1950 Gray 260-78 LOUISE QUAST Examme" 2,739,959 3/ 19-56 ;Ney et al. 26078 H. D. ANDERSON, Assistant Examiner. 2,891,038 6/1959 Barnes et al. 26078

Claims (1)

1. A PROCESS OF TREATING CHIPS OF POLYHEXAMETHYLENE ADIPAMIDE POLYCONDENSED IN THE PRESENCE OF ABOUT 0.7 TO 14.0 MOL PERCENT BASED ON THE WEIGHT OF THE POLYMER FORMING SUBSTANCE OF A DYE-ENHANCING BENZENEPHOSPHINIC ADDITIVE COMPRISING THE STEPS OF: (A) SCOURING SAID CHIPS IN WATER; AND (B) DRYING THE SCOURED CHIPS; WHEREBY OBNOXIOUS PHOSPHOROUS-CONTAINING FUMES NORMALLY ATTENDANT WITH MELT SPINNING OF SUCH POLYMER IS MINIMIZED.