US3404204A - Method of producing high-shrinkage acrylic fibers - Google Patents

Description

United States Patent 3,404,204 METHOD OF PRODUCING HIGH-SHRINKAGE ACRYLIC FIBERS Kazumi Nakagawa, Keitaro Shimoda, and Koji Miyashita,

Saidaiji, Japan, assignors to American Cyanamid Company, Stamford, -Conn., a corporation of Maine N0 Drawing. Filed Mar. 1, 1965, Ser. No. 436,285 Claims priority, application Japan, Mar. 7, 1964, 39/ 12,693; Mar. 9, 1964, 39/ 13,169 4 Claims. (Cl. 264-210) ABSTRACT OF THE DISCLOSURE In the process of preparing fibers of acrylonitrile polymer comprising the steps of wet-spinning said polymer to form a tow of wet gel fibers, stretching the wet gel fibers in said tow, dehydrating and collapsing the wet gel fibers in said tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about 110 C. to about 140 C., and drying the thus relaxed fibers; the improvement comprising: (a) subsequent to stretching the wet gel fibers and prior to relaxing the fibers with steam, preheating said fibers with an aqueous medium to between 60 C. to 95 C. and mechanically crimping the thus preheated fibers and (b) restretching the dried relaxed fibers 1.15 to 1.35 at 100 C. to 260 C. in a dry atmosphere.

This invention relates to a process for preparing fibers of acrylonitrile polymer having the combined characteristics of high shrinkage and stabilized crimp and, more particularly, for preparing such fibers by appropriate modification of a known wet-spinning process.

Previously, it was known to prepare acrylic fibers by a wet-spinning process comprising the steps of wet-spinning the acrylonitrile polymer to form a tow of wet gel fibers, stretching the wet gel fibers in the tow, dehydrating and collapsing (or unstructurizing) the Wet gel fibers in the tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about 110 C. to about 140 C., and drying the thus relaxed fibers. When desired to prepare high-shrinkage fibers by such a process, it was known to restretch the dried relaxed fibers at elevated temperatures to produce fibers capable of shrinking upon subsequent exposure to elevated temperatures, as in boiling water or dye bath. In order that such fibers be processable on conventional textile handling equipment, it is known to crimp them by use of any of several types of mechanical crimpers.

Such high-shrinkage fibers, when blended with lowsrinkage fibers, are used to produce yarns and fabrics which will become bulky on subsequent exposure to elevated temperatures due to the shrinkage of the high-shrinkage fibers causing'the low-shrinkage fibers to form loops, curves, and waves. However, it has been observed that the crimp in such fibers tends to disappear during heat treatment and, therefore, the bulkiness of such yarns and fabrics is less than would have been expected from the fibers provided with a crimp stable to such heat treatment. Also, in such yarns, the high-shrinkage fibers tend to concentrate' in the core of the yarn while the low-shrinkage fibers lie loosely around the core making the yarn liable to lean out or become thin or slim, a tendency which 'ice detracts materially from the saleability and value of these bulky yarns.

It is an object of the present invention to prepare high-shrinkage fibers of acrylonitrile polymer which are free of the aforementioned defects and which can be used to make bulky yarns which resist leaning out to a much greater extent than prior products. It is a further object to make such fibers by suitable modifications of the wet-spinning process for preparing acrylic fibers, which modifications will not unduly complicate or add to the costs of preparing acrylic fibers.

We have found that the above objects, and others as will appear hereinafter, can be achieved by suitable modification of the process of preparing fibers of acrylonitrile polymer comprising the steps of wet-spinning said polymer to form a tow of wet gel fibers, stretching the wet gel fibers in said tow, dehydrating and collapsing the Wet gel fibers in said tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about 110 C. to about 140 C., and drying the thus relaxed fibers. T=his modification comprises (a) subsequent to the stretching step and prior to the steam relaxation step, preheating the fibers with an aqueous medium to between 60 C. and 95 C. and mechanically crimping the thus preheated fibers combined with (b) restretching the dried relaxed fibers 1.15 X to 1.35 X at 100 C. to 260 C. in a dry atmosphere.

In one preferred embodiment of this invention, the Wet gel fibers, subsequent to the stretching step and prior to the dehydration and collapsing step, are preheated with an aqueous bath to between 60 C. and 85 C. and mechanically crimped in the wet gel state. In a second preferred embodiment of this invention, the dehydrated and collapsed fibers prior 't-O' the relaxation step, are preheated with an aqueous medium to between C. and 95 C. and mechanically crimped. In either modification, the mechanical crimping may be conventional stufiing box crimpers or intermeshing gear crimpers, for example.

The foregoing modification of the wet-spinning process for preparing fibers of acrylonitrile polymers produces fibers which, upon treatment with a hot aqueous environment, are capable of substantial shrinkage with recovery of crimp. It must be noted that the restretching step serves to pull Quit the crimp imparted in this process, but the memory of that crimp lingers on and serves to reproduce the crimp upon later exposure to a hot wet environment.

Frequently, in order to provide better handling characteristics to these restretched fibers in textile processing equipment, they are provided with a mechanically produced crimp subsequent to the restretching step. However, this later crimping step must not be confused with the crimping step of the present invention since the crimps imparted by the crimping of the restretched fibers are easily lost during treatment with a hot wet environment.

For a clearer and more detailed understanding of this invention, reference may be had to the following description of the two preferred embodiments mentioned above.

In the first embodiment, wherein the wet gel fibers were preheated and crimped while in the wet gel state, it is preferred that the preheating be done in an aqueous medium between 60 C. and C. in order to impart sufficient crimps to the fibers. When preheated at a temper ature exceeding about 85 C., the fibers become soft and tend to be agglutinated with each other because of the pressure given during crimping and also tend to change in fiber cross-section. Moreover, preheating wet gel fibers at above this temperature is not preferable, because it In order to determine the amount of restretch needed during the final hot drawing treatment in the process of this invention, acrylic fiber tow which had been processed in accordance with this embodiment of the invention was gives shrinkage to the fibers in the wet gel state and restretched various amounts as shown in Table 2 after bedeprives them of transparency. Crimps are not acquired ing relaxed in steam at 125 C. and being passed between fully at a temperature below about 60 C., and an effort two hot plates heated to 150 C. to make forced crimps by raising the crimper pressures TABLE 2 may greatly damage the fibers. R fib t h h: kin fib fie These crimped Wet gel b are then P Ratio of hot h t draw i ng t iiifier heat ifig in h ot witer tf 1 00 0. collapsed. Suitable dehydration and collapsing conditions drawing under dry condition) for acrylonitrile polymer fibers are disclosed in US. Patdry condltw Number Degree of Number Degree of Shrinkage 6111'. NO. 2,984,912 and Japanese Patent NO. 245,665. F01 ."of crimping of crimping amouut the present invention, it is considered preferable to use cnmps (percent) clumps (percent) (percent) that pOrtiOn of the temperature-humidity range of con- 15.5 14.0 ditions disclosed in these references which lies between i: fig about 110 C. and 130 C. dry bulb temperature and be- 1.31 12.8 tween about C. and about C. we-t bulb tempera- 3:2 33 ture in order to provide maximum stabilization of the 114s 6.2 29 crimps in the fibers. If this collapsing is not accomplished 20 v during the dehydration step, the high-shrinkage fibers As is apparent from the results in Table 2, the amount have a poor luster and have undesirable properties due of shrinkage of high-shrinking fiber produced by treatto the formation of numerous voids in the fiber structure. ment in hot water is too small whenthe drawing ratio is In order to further stabilize the crimps in these fibers below 1.15 and in consequence a bulky yarn using this against loss in hot water, it is necessary that these dehy- 25 fiber does not show sufiicient bulkiness after bulking has drated and collapsed fibers be treated in a relaxed freebeen carried out. On the other hand, when the drawing to-shrink condition with steam at about 110 C. to about ratio exceeds 1.35, the ability of the fiber after being 140 C. The fibers thus relaxed are drawn by hot drawtreated in hot water to recover its crimps drops as shown ing under dry conditions after being dried. above, with the result that a bulky yarn made of this Table 1 shows the amount of shrinkage and the char- 3() fiber tends to lean out. As the drawing temperature acteristics of the crimps which appeared when fibers made varies depending upon the spacing of hot plates, the from a copolymer comprised of by weight acryloniwidth, thickness and drawing velocity of a tow to be trile and 10% by weight methyl aorylate were processed treated, it preferably is set within the range of to under various conditions including hot drawing under dry 260 C. condition at a temperature of 150 C. and when they were 35 Generally a tow is mechanically crimped after having subsequently heated for 10 minutes in hot water having been restretched by hot drawing under dry condition, a temperature of 100 C. but this mechanical crimping is carried out for the pur- TABLE 1 Amount of shrinkage water at 100C.

Treatment in steps of non-structurization and heat- Number of Degree of Ratio of Number of Degree of Amount of treatment crimps crimping hot-drawing crimps crimping shrinkage (per inch) (percent) under dry (per inch) (percent) (percent) condition A. Crimped and non-structurized after yarn drawn 12 12. 2 14. 8 1. 05X 4. 9 6. 1 6 B. Crimped and non-structurized after yarn drawn and heat-treated 10 minutes in saturated steam at C 19 12. 0 12.8 1. 15X 12.0 10. 0 13 C. Crimped and non-strueturized after yarn drawn and heat-treated 10 minutes in saturated steam at C 23 14. 0 13. 6 1. 15X 13. 2 14.0 13 D. Orirnped and non-structurized after yarn drawn and heat-treated 10 minutes in saturated steam at C 28 14. 5 13. 6 1. 20X 14. 0 15. 1 17 E. Non-Structurized after yarn drawn and I heat-treated in 10 minutes in saturated steam and crimped 28 16. 5 14. 5 1. 20X 7. 2 4. 0 10 *Fiber prior to being drawn by hot drawing under dry condition.

Because high-shrinking fibers A were treated by nonstructurization alone, they lost most of their crimps when they were drawn by hot drawing under dry condition and treated in hot water having a temperature of 100 C. High-sh inking fibers E spun by the conventional technique have shown a great decrease in their crimps when treated in hot water. Such a sharp decrease in the degree of crimping makes the leaning out of bulky yarn marked. In contrast to the preceding result, high-shrinking fibers C and D provided by the process of this invention show the same value as they did when they were raw in the degree of crimping after they were treated in hot water, being exceedingly fine in reproductive capability of crimps. B-is slightly inferior to C and D in point of reproductive capability of crimps. In order to improve this. reproductive capability, the temperature at which heat-treatment is carried out should be higher than 110 C. and the total amount of shrinkage in the step in the process of non-structurization and heat-treatment should be higher than 20%.

and then heated in hot water, crimps are not reproduced;-

but also by the fact, that, as'shown above, the fibers produced by the process of this invention wherein hot drawing under dry condition is effected but mechanical crimping is not applied to the thus restretched fibers, acquire crimps in hot water. r I

In the second embodiment, wherein the dehydrated and collapsed fibers were preheated and crimped prior to.

relaxation in steam, it is preferred that the preheating be done in an aqueous medium between 80 C. and 95 C. Table 3 shows the amount of shrinkage and the crimp characteristics of the acrylic fibers manufactured under various conditions from a copolymer of 90% ,by weight of acrylonitrile and '10% by weight of methyl acrylate when they are stretched under dry, hot conditions at 150 Usually, the tow after the dry-heat treatment is me chanically crimped, but this is done to improve the interlocking property of the web or sliver at the subsequent carding or drawing operation, and as such .has nothing to C. and, then, treated in hot water at 100 C. for 10 min- 5 do with our crimp that is reproduced upon hot-water utes. treatment of the fiber which has been stretched under TABLE 3 Raw fiber* High-shrinking fibers treated in hot 1 Total percent shrinkage Ratio of water at 100 C.

during unstructurirestretching, Treatment zation and heat Number Degree hot dry Number Degree Amount treatment ofcrimp1s. of crimping conditions of crimps of crimping of shrinkage (per inc (percent) (per inch) (percent) (percent) F. Unstructurized, crimped, and treated with saturated water vapor at 105 G. g for 10 min 19 15. 3 13.8 1.15x 1417 10.0 13- G. Unstructurized, crimped, and treated with saturated water vapor at 110 C. for 10 min 23 16.5 14. 5 1. 15x 15. 3 13. 8 13 H. Unstructurized, crimped, and treated with saturated water vapor at 120 C. for 10 min 28 16.8 15.3 1. x 15.2 14.0 17 J Unstructurized, and treated with saturated water vapor at 120 C. for 10 min 28 16.5 14.5 1. 20x 7.2 4.0 16

Fiber before treatment by stretching under hot and dry conditions. I v I High-shrinking fiber I, which was manufactured by the dry hot conditions. This is apparent from the fact that conventional method, lost a substantial part of its crimp no crimp will be produced in the tow prepared in the when it was treated in hot water. It will be particularly conventional manner even if it is stretched under dry, hot apparent that such a drastic reduction in thedegree of conditions, mechanically crimped, and, finally, treated crimping makes the reduction in volume of the bulky yarn with hot water, and that as described hereinbefore, the more pronounced. In contrast, high-shrinking fibers G and fiber of this invention which has bee-n stretched under H, which were prepared according to this invention, were dry, hot conditions but not crimped mechanically does excellent in crimp re-development, their crimp charaeredevelop its crimp in hot water. teristics after the hot-water treatment being almost the The acrylic fiber to be employed for the purpose of same as those of the raw fiber. Fiber F is somewhat lnthis invention may be a polymer or copolymer containferior to fibers G and H in tendencies t0 redeve op ing at least 80 percent of acrylonitrile. The monomer crimps, and in order to improve this characteristic, it is which can be a component of the above-mentioned acrylpreferred that the temperature of heat treatment be at ic fiber, other than acrylonitrile, may be a member of the least 110 C. and the combined rate of shrinkage of fiber class consisting of various ethylenically unsaturated after .the unstructurization and heat treatment be more monomers such as vinyl acetate, vi-nyl propionate, methyl than 20 percent. v acrylate, ethyl acrylate, vinyl pyridines, acrylsulfonic The range of levels of restretchmg of fiber to be conacid, methacrylsulfonic acid, acrylic acid, methacrylic ducted under dry, hot conditions in order to manufacture id, d th lik the desired high-shrinking fiber should be llmited to The relative amount of the high-shrinking fiber of this l.15 to 1.35X for the following reason. T )W 0f 'aeryll invention to be incorporated in a bulky yarn should vary fibers of a copolymer of 90% acrylonitrlle a according to the type and denier of the low-shrinking methyl acryl w ich havebeen stretched under fiber to be blended therewith and the desired hand or humid conditions, unstructurlzed, crimped, and treated feel of the final bulky yarn, but it may range from 20 W Saturated Steam at are stftcheq WTIPHS to 70 percent, and, preferably, from 30 to percent. a u under y, hot fihh and the resulhhg hlgh' If the percentage is, below 20, the bulky yarn will be Shrinking fibers are treated h hot Water at h ill-shaped, while no bulk will be obtained if the percentage crimp characteristics of these fibers are summarized n i more h h 1 h -inki,ng fib to be blended Table which Shows t Wheathe stretchlqg a 18 50 with the high-shrinking fiber of this invention may be below the fate o shhlhkage 111 hot Water 10W selected from the class consisting of various natural fibers and the bulky Y cohtalhlng Such a h Wl1 1 not such as wool and cotton, as well as low-shrinking (the V6101J a sufilchiht u dhnhg h bulk'lmpartlng treata rnount of shrinkage being below about 5% in hot water ment described hereinbefor e. It w ll also be apparent from at 100 C) li and other synthetic fib the table that if the stretching ratioexceeds 1.35, the ten- For f th understanding of this invention and the of Q to redevhlop crlmP p h? two embodiments described above, reference may be had ment f adversely affected so'that the bulky Y cohtahlto the following examples, wherein all parts are by weight ing the fiber is liable to lose its bulk and lean out. unless otherwise ifi d TABLE 4 60 Example 1 Raw fibers ggigg g fi g 10 parts of a copolymer comprised of of acrylo- Stretching v nltrile and 10% ofmethyl acrylate are dissolved in 90 who Number Degree Number Degree ,Shrmkage parts of a 48% aqueous solution of sodium thiocyanate. (dry, hot) oi of of amount ()fimps crimping crimps crimping (percent) A Spllll'llllg solution thus obtained is spun into a 10% (Percent) (Percent) 5 aqueous solution of sodium thiocyanate at a tempera- While the stretching temperature should vary according to the gap between the hot plates, the width and thickness of the tow to be stretched and other factors, it preferably lies somewhere between C. and 260 C.

ture of 0 C., washed in water in the wet gel state while being drawn to twice its length, and drawn again 5 times its length in hot water having a temperature of 98 to 100 C. The denier of the drawn monofilaments is 2.1 d. and the total denier of the tow is 55,000 d., with a water content of 86% (against dry yarns). This tow is continuously passed through water having a temperature of 80 C. and fed into a stuifing-box crimper for crimp: ing and thereafter is dehydrated and collapsed in an atmosphere having a dry-bulb temperature of C.

and a relative humidity of 20% for 10 minutes. The tow thus treated has a water content of 2.3%. This tow is subjected to steaming for 10 minutes in saturated steam at a temperature of 120 C., treated with oil, and thereafter dried, to yield a 3 denier fiber K. The fiber K is drawn 1.31 times its length between hot plates at a temperature of 150 C., cooled, then crimped and cut in 89 mm., to yield a high-shrinking yarn L. In order to obtain a high-shrinking fiber by the conventional technique for a contrast test, processing was carried out under the same conditions as with L, except that no crimping was effected after hot drawing under wet condition but after steaming was completed crimping was carried out. Thus a conventional high-shrinking fiber M was obtained. The foregoing L or M is mixed with merino wool at a ratio of 50 to 50, to yield 2/34 yarn. The yarn obtained is treated in a state of relaxation with boiling water for 10 minutes, cooled gradually to a temperature of 60 C. and dried. The bulky yarn produced from L was a highbulk spun yarn, while the bulky yarn obtained from M showed leaning out and was exceedingly bad in sense of touch and appearance. In order to compare the degree of bulkiness between the two samples, hanks of bulky yarns were placed in a channel 20 cm. wide in parallel therewith, and the thickness of the hanks was measured while a load of 50 g./cm. was applied to the top of the hanks. The comparative thickness of the two computed in terms of the same count shows a ratio of 87 in the case of M to 100 in the case of L.

Example 2 A low-shrinking fiber K which was not treated by hot drawing under dry condition as described in Example 1 is cut in 89 mm. lengths and mixed with L and M in a ratio of 50 to 50 to spin a bulky yarn. The bulky yarn thus spun is dyed with cationic dyestuff in the hank dyeing machine. The temperature at which dyeing was started was 60 C. and gradually raised to 100 C. which temperature was maintained for 40 minutes, and then gradually cooled to 60 C. The yarn was therefore subjected to bulkiness treatment simultaneously with the dyeing. After washing and treating with finishing oil, the yarn was dried. The bulky yarn produced by mixing K with L was highly solid and beautiful in lay, while that obtained by mixing K with M was slightly inferior in solidness and showed partial thinning or leaning out. The same test on bulkiness as was conducted in Example 1 showed that the comparative thickness of the hanks was in a ratio of 92 in the case of M to 100 in the case of L.

Example 3 Ten parts of a copolymer consisting of 90% acrylonitrile and 10% methyl acrylate was dissolved in 90 parts of a 48% aqueous solution of sodium thiocyanate to prepare a spinning solution, which was extruded into a 10% aqueous solution of sodium thiocyanate at C. The tow was washed with water while it was stretched to 200% of its initial length. Then, the tow was further stretched in hot water at 98100 C. to 500% of its length. The fibers after the two cycles of stretching were 2.1 d. and the tow 55,000 d., with its moisture content being 86% (based on dry fiber). This tow was unstruc turized in hot air streams at a dry-bulb temperature of 110 C. and a relative humidity of 20% for minutes. The unstructurized tow was passed through hot water at 90 C. and then fed to a crimper of the stuffing-box type, where it was crimped. The tow was further steamed with saturated water vapor at 120 C. for 10 minutes in a steaming tank, followed by oiling and drying. The above procedure gave a 3 d. fiber N. This fiber was stretched to 1.31 by hot plates at 150 C. After cooling, the fiber was crimped and cut to 89 millimeters to prepare a high shrinking fiber P. As a control, a high-shrinking fiber of the conventional type Q was prepared under the same conditions as those used in the preparation of fiber P,

except that this fiber was not crimped immediately after said unstructurization but was crimped only after the steaming operation.

A spun yarn was prepared by mix-spinning the above high-shrinking fiber P or Q with merino wool on a fifty fifty basis and this yarn so prepared was treated with boiling water for 10 minutes in the form of a hank. The yarn was all-owed to cool d ownto 60 C. and dried. The bulky yarn containing fiber P had a neat twist and good bulk, whereas the bulky yarn containing fiber Q had a poor hand and was found to be liable to lose its bulk. To measure the relative bulkiness of the two yarns, the hank was placed in a 20 mm. wide channel in parallel relation and a load of grams per square centimeter was applied from above. In this manner, the thickness of the hank under the above load was measured. The relaive thickness of the hank as converted into the same denier basis was 89 for the bulky yarn containing fiber Q as against 100 for the bulky yarn containing fiber P.

Example 4 A low-shrinking fiber, which was prepared in the same manner as Example 3 except that it Was not stretched under dry, hot conditions, was cut to 89 millimeters. This fiber was mix-spun with fiber P or Q on a fifty-fifty basis to prepare a bulky yarn, which was dyed with a cationic dyestutf in a hank-dyeing machine. Starting at C., the temperature was gradually increased to 100 C., where it was held for 40 minutes after which it was gradually lowered to 60 C. In this manner, the yarn was concurrently dyed and bulked. The yarn was finally washed with water, finished with oil, and dried. The bulky yarn containing fiber P had a good bulk and attractive twist, whereas the yarn containing fiber Q was somewhat inferior in bulkiness, showing local slimness. The relative thickness of the hank measured in the same manner as Example 3 was 93 for the bulky yarn containing fiber Q as against 100 for the bulky yarn containing fiber P.

What is claimed is:

1. In the process of preparing fibers of acrylonitrile polymer comprising the steps of wet-spinning said polymer to form a tow of wet gel fibers, stretching the Wet gel fibers in said tow, dehydrating and collapsing the wet gel fibers in said tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about 110 C. to about 140 C., and drying the thus relaxed fibers; the improvement comprising:

(a) subsequent to stretching the wet gel fibers and prior to relaxing the fibers with steam, preheating said fibers with an aqueous medium to between 60 C. to 95 C. and mechanically crimping the thus preheated fibers and (b) restretching the dried relaxed fibers 1.15 to 1.35X at C. to 260 C. in a dry atmosphere.

2. In the process of preparing fibers of acrylonitrile polymer comprising the steps of wet-spinning said polymer to form a tow of wet gel fibers, stretching the wet gel fibers in said tow, dehydrating and collapsing the wet gel fibers in said tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about C. to about 140 C., and drying the thus relaxed fibers; the improvement comprising:

(a) subsequent to stretching the wet gel fibers and prior to dehydrating and collapsing the wet gel fibers, preheating the wet gel fibers with an aqueous bath to between 60 C. and 85 C. and mechanically crimping the tow of preheated wet gel fibers and (b) restretching the dried relaxed fibers 1.15 to 1.35 at 100 C. to 260 C. in a dry atmosphere.

3. A process as defined in claim 2 wherein said fibers are dehydrated and collapsed by exposure to an environment at a dry bulb temperature between about 110 C. and about C. and a wet bulb temperature between about 70 C. and about 80 C.

4. In the process of preparing fibers of acrylonitrile polymer comprising the steps of wet-spinning said polymer to form a tow of wet gel fibers, stretching the wet gel fibers in said tow, dehydrating and collapsing the wet gel fibers in said tow, treating the thus dehydrated and collapsed fibers in a relaxed free-to-shrink condition with steam at about 110 C. to about 140 C., and drying the thus relaxed fiber; the improvement comprising:

(a) subsequent to dehydrating and collapsing the wet gel fibers and prior to relaxing the fibers with steam, preheating the dehydrated and collapsed fibers with an aqueous medium to between 80 C. and 95 C. and mechanically crimping the thus preheated fibers and (b) restretching the thus dried and relaxed fibers 1.15 to 1.35 at 100 C. to 260 C. in a dry atmosphere.

References Cited UNITED STATES PATENTS Terpay 264182 Melchore et al 264182 Robertson et al. 264182 Ryan et al. 264-168 Knudsen et a1 264-182 Fukushima et a1. 264-168 Fujita et al. 264-182 DONALD J. ARNOLD, Primary Examiner.