US3734986A - Method for producing polyamide fiber having improved silky feel and lustre - Google Patents

Abstract

POLYAMIDE FIBER HAVING IMPROVED SILKY LUSTRE AND SILKY TOUCH IS PRODUCED BY MELT-SPINNING MODIFIED POLYAMIDE PELLETS OBTAINED BY DISPERSING FINE PARTICLES OF POLYALKYLENE ETHER INTO POLYAMIDE, CONTINUOUSLY DRAWING THE MELT SPUN FILAMENTS UNTIL THE BIREFRINGENCE OF SAID FILAMENT REACHES A SPECIFIC PRE-SELECTED POINT, TREATING THE DRAWN YARN WITH A SOLVENT FOR POLYALKYLENE ETHER AND RECOVERING THE SAME.

Description

May 22, 1973 TETSUYA KATO ETAL 3,734,986

METHOD FOR PRODUCING POLYAMIDE FIBER HAVING IMPROVED SILKY FEEL AND LUSTRE Filed July 31, 1970 2 Shutl-Sheet 1 50- 40- 3 v 5 9 30 g x s 2 G) V 5 IO- 0 l l I I T a, Millimol Alkylene Oxide per gram Polyomide J Z 'INVENTORS.

TETSUYA KATO TOSHIAKI HIDAKA BY CHIKATSU OKAGAWA ATTORNEYS.

May 22, 1973 TETSUYA KATO ET AL 3,734,986

METHOD FOR PRODUCING POLYAMIDE FIBER HAVING IMPROVED SILKY FEEL AND LUSTRE Filed July 51, 1970 2 Sheets-Sheet 2 REFLECTANCE MEASUREMENT IN PLANE COINCIDENT WITH YARN AXIS Fig. 3

REFLECTANCE MEASUREMENT AS YARN AXIS IS ROTATED IN PLANE COINCIDENT WITH YARN AXIS INVENTORS. TETSUYA KATO TOSHIAKI HIDAKA BY CHIKATSU OKAGAWA ATTORNEYS United States Patent 3,734,986 METHOD FOR PRODUCING POLYAMIDE FIBER HAVING IMPROVED SILKY FEEL AND LUSTRE Tetsuya Kato, Nagoya, Toshiaki Hidaka, Nishikasugaigun, and Chikatsu Okagawa, Nagoya, Japan, assignors to Toray Industries, Inc., Tokyo, Japan Filed July 31, 1970, Ser. No. 60,029 Int. Cl. B29d 27/00; D01d 5/08, 5/12 U.S. Cl. 264-49 Claims ABSTRACT OF THE DISCLOSURE Polyamide fiber having improved silky lustre and silky touch is produced by melt-spinning modified polyamide pellets obtained by dispersing fine particles of polyalkylene ether into polyamide, continuously drawing the melt spun filaments until the birefringence of said filament reaches a specific pro-selected point, treating the drawn yarn with a solvent for polyalkylene ether and recovering the same.

The present invention relates to a method for producing a polyamide fiber having improved silky lustre and silky touch, and more particularly, to a method for producing such an improved polyamide fiber by meltspinning a polyamide fiber having polyalkylene ether incorporated therein.

Polyamide fiber has been used for textile products such as are used in clothing because it has excellent strength, high anti-abrasion, excellent dyeability, and high washand wearability. (It should be noted here that fiber is used to denote both filamentary fiber and multi-filament yarn.)

However, the conventional polyamide fiber has a waxy touch and appearance which are inherent disadvantages of the synthetic fiber, and which therefore restrict the applications thereof.

Numerous attempts have been made to produce polyamide fibers having the desirable mild lustre and touch of the natural fiber most preferred in these respects, i.e., silk, by eliminating the waxy touch and appearance of the synthetic fiber.

In one example of such attempts, the cross sectional surface of the fiber is changed from circular into multilobal form. This eliminates the waxy touch of the synthetic fiber but the surface of the fiber glistens and the lustre of the synthetic fiber is completely different from that of silk.

The inventors of the present invention have found that the preferred properties of silk, in particular, silky lustre and touch can be obtained in a polyamide fiber by providing in the polyamide fiber voids of the appropriate size and volume and by appropriately making the surface of the fiber coarse.

As a method for producing voids in such fibers, there is a prior art method in which organic material and high polymer material are blended and the mixture is meltspun; thereafter the filament is treated with a solvent, to remove soluble inorganic material from the high polymer material. However, in this method, the inorganic material tends to clog the filter of the spinning machine and the melt-spinning operation is therefore very difficult.

There is another conventional method for producing voids in fiber according to which two kinds of polymers are blended, and the blended mixture is melt-spun; thereafter one of the polymers is extracted with a solvent. In one example of this method, as described in the specification of Japanese patent publication No. 25 169/ 1965, polyamide and polystyrene are blended. However, when this method is employed, the mutual solubility of the blended polymers is poor, and, in addition, fine particles of polymers cannot be easily mixed. Therefore melt-spinnability is poor, and, in addition to the above, voids of appropriate size cannot be obtained; thus the silky lustre cannot be easily attained. Furthermore, another draw back of this method is that it is necessary to use an organic solvent, which is very difiicult to handle, for producing voids by extracting one of the polymers.

On the other hand, in US. Pats. Nos. 3,329,557 and 3,475,898 a method is disclosed in which fibers of excellent antistatic property can be obtained by blending therein polyalkylene ether. At the same time, a small amount of voids can be produced by eluting a part of the fiber when refining is carried out.

The technique disclosed in the above cited United States patents is better than the other methods described above in view of the formation of voids in the fibers therein, but the object of the above cited United States patents is in the antistatic properties of the synthetic fiber, and therefore the techniques are inappropriate for simultaneously producing the most desirable silky lustre and touch.

In addition, when melt-spinning polyamide with polyalkylene ether blended therein, various kinds of drawbacks, as described hereinafter, are brought about, and it is impossible to produce fibers of high quality at a high yield in accordance with the conventional techniques.

Namely, first of all, polyalkylene ether is not dissolved into the polyamide, to say nothing of the low melting point and poor spinnability thereof, and therefore when polyamide and polyalkylene ether are merely mixed and the obtained mixture is melt-spun, the polymer melt is remarkably unstable as the polyalkylene ether of low melting point is separated from molten polyamide. As a result yarn breakage occurs and spinning becomes im possible.

Secondly, in carrying out melt-spinning of the mixture prepared by blending polyalkylene ether and polyamide, when the mixture is spun with the ordinary relatively low draft and the substantially undrawn yarn thus produced is contacted with an oiling roll where an oil finish comprising an aqueous emulsion of spinning oil is applied, the undrawn yarn fibers are also adhered to each other (this phenomenon is generally called yarn-adhesion), and, as a result, the unwinding tension of the package when the undrawn yarn is drawn becomes remarkably great producing excessively overdrawn segments in such yarn. In addition, yarn uniformity is decreased and yarn breakage is common.

The object of the present invention is to provide a method for producing polyamide fiber of excellent properties capable of smooth spinning by solving the various problems heretofore associated with the melt-spinning of polyamide fibers having polyalkylene ether blended therein.

Another object of the present invention is to provide a method for producing polyamide fiber having both silky lustre and silky touch by subjecting the modified polyamide obtained in accordance with the above mentioned method to an appropriate after-treatment.

Another object of the present invention is to provide a method for producing a polyamide fiber with a silky appearance and touch rather than the waxy touch and appearance peculiar to the usual polyamide fiber.

Further objects of this invention will become apparent from the following description of the invention.

The present invention provides a method for producing polyamide fiber having improved silky lustre and silky touch, comprising the following steps;

(1) A polyalkylene ether, of excellent thermal stability i.e., not decomposable at the melting point of the polyamide and substantially insoluble in the polyamide, is blended with polyamide in an amount governed by the Formula 1 given below and modified polyamide pellets are prepared therefrom, in which fine particles of the above blended modifier are dispersed in such a manner that at least 50% by weight of the blended modifier comprises particles having an average diameter below 20p in their cross section;

(2) The modified polyamide pellets are then meltspun;

(3) After melt-spinning, the spun filament is continuously drawn until the birfringence, Art, of the spun filament satisfies Formula 2 below;

(4) The drawn polyamide yarn is then treated with a solvent for the modifier, to extract out a part or most of the modifier, thus producing voids in the fiber.

Formulae (2) Arz l0 g49log (8a+8)32 (wherein a stands for millimols (mmols) of the recurring alkyleneoxide unit in the polyalkylene ether modifier contained in 1 gram (g) of the polyamide; All is the birefringence of a continuously melt spun, drawn yarn, taken up at 20 C. and 65% relative humidity after overnight exposure to the atmosphere, as measured by using the D-line emission of a sodium lamp.)

The fiber produced thereby, having certain specific physical properties as defined more specifically hereinafter, is also within the scope of the present invention.

When silky lustre and silky touch are produced, in accordance with the present invention, by blending polyalkylene ether along with polyamide, melt-spinning the obtained mixture into fiber, and washing the obtained fiber, to extract the polyalkylene ether modifier, one of the most important problems resides in the size and amount of the dispersed particles of polyalkylene ether contained in the modified pellets before spinning the fiber.

The polyalkylene ether is substantially insoluble in polyamide.

Further, the melting point of polyalkylene ether is low and it has poor spinnability. Therefore when polyalkylene ether is merely mixed with polyamide, it oozes out onto the surface of the polyamide pellets during the meltspinning process. This polyalkylene ether on the surface of the polyamide pellets acts as a lubricant causing the pellets to slip on the surface of the screw in the melt spinning apparatus making the feeding of pellets very difiicult. In addition to this, when the two components of the pellets are melted, the polyalkylene ether is separated from the polyamide. This causes yarn breakage at the spinneret, and substantially precludes melt-spinning.

In addition when the dispersed particles of polyalkylene ether in the modified polyamide pellets are large in size, coarse voids are produced when the yarn obtained from the pellets is washed and extracted. This makes it difificult to produce the silky lustre which is desired.

In producing the present invention, it has been found that it is necessary to melt-spin a modified polyamide containing finely dispersed modified polyamide wherein at least half of the polyalkylene ether contained in the modified polyamide is dispersed as minute particles below 20a in diameter. This makes the supply of modified polyamide pellets flow smoothly into the screw extruder when modified polyamide pellets are melt-spun. It also prevents the separation of the two components in the modified polyamide pellets and the desirable lustre when the yarn fibers are washed and extracted.

In regard to methods for finely dispersing polyalkylene ether in polyamide, there are a number of such methods.

In one such method polyalkylene ether is added before or during the polymerization of polyamide. In another method polyalkyene ether is blended with polyamide 4 pellets and thereafter the blended mixture is melt-mixed by a mixing extruder which pelletizes the mixture.

However, it is difiicult, employing only the generally adopted conditions, to blend polyalkylene ether with polyamide in such a manner that more than 50% by weight of the polyalkylene ether has a particle size below 20 When polyalkylene ether is added during polymerization, the blending operation should be carried out under such conditions that it can be uniformly dissolved into monomer or monomer solution. By so doing, finely dispersed polyamide pellets, wherein the average particle size of the modifier is around 5a, can be obtained.

On the other hand, it is preferable to carry out the pelletizing operation by using a biaxial or triaxial screw extruder in order to effect sufficient blending during the melt-kneading process.

The dispersed state of the polyalkylene ether modifier can be determined by slicing the modified polyamide pellet with a microtome. The lateral cross section and longitudinal cross section thereof are then observed with a microscope.

When the amount of the particles having a particle size below 20a is not more than 50% by weight, the blend is re-melted and the kneading operation is repeated until pellets having modifier particles with more than 50% by weight of the proper particle size are produced.

The modifier particles discussed herein include not only spherical particles, but also other particle shapes, such as rotary ellipse (elongated spherical) particles, linear, long fusiform (agglomerated) particles, etc.

As used herein particle size generally refers to the diameter of a spherical particle, or the diameter at the longitudinal midsection of a rotary ellipse particle or for odd-shaped elongated particles, such as the linear fusiform, the smallest cross-section diameter perpendicular to the axis of the particle. Collectively these may be referred to as the diameter of the cross section of each particle.

In regard to the amount of the dispersed particles, the required amount thereof varies in accordance with the size of the particles, but as is described hereinafter, the range of the amount of the dispersed particles, wherein the desired properties are attained and the fiber processability is not degraded, is from 2 to 15% by weight. This range will be discussed in more detail hereinafter.

The second problem to be faced, in carrying out the melt-spinning and fiber shaping process with polyamide containing finely dispersed polyalkylene ether particles, is the mutual yarn-adhesion of fibers as they are taken up in the aqueous emulsion of spinning oil.

This yarn-adhesion remarkably increases the unwinding tension of the package, when the undrawn yarn is drawn, causing yarn breakage or unevenness of yarn properties. As a result, the production of drawn yarn is made practically impossible.

In addition, the yarn-adhesion is retained in the final product and a coarse hand, like plait yarn, is retained in the final product.

In accordance with the present invention, the above mentioned problem can be solved by continuously drawing the melt-spun undrawn yarn, prior to taking it up, until the birefringence of the yarn satisfies Formula 2.

By so doing, the yarn-adhesion of the yarn or filament can be prevented as the modified polyamide containing polyalkylene ether is melt-spun, and has absorbed water content from the spinning oil or from the air.

The swelling elongation due to absorption of water content can be controlled by increasing the degree of orientation above some predetermined value.

In the drawings:

FIG. 1 is a schematic illustration of a melt-spinning and drawing process as used in the present invention;

FIG. 2 is a graph of modifier content versus birefringence of a drawn yarn with no yarn-adhesion in the present invention;

FIG. 3 is a diagrammatic illustration of the process used for measuring certain optical properties of the fiber of the present invention, and

FIG. 4 is a graph of certain optical properties used to determine quantitatively one important optical property of the fibers of the present invention.

Referring now to FIG. 1 there is shown a diagram of an embodiment of the device for carrying out the method of this invention for producing polyamide fiber. More specifically there is shown polyamide fiber 1 extruded by spinning nozzle 2 from a melt of modified polyamide prepared by blending polyalkylene ether in polyamide. And then it is contacted with oil roller 3 where an oil finish is applied, and is then passed from draw feed rollers 4, to drawing rollers 5 revolving at higher peripheral velocity than that of draw feed rollers 4.

The degree of orientation required for controlling the yarn-adhesion of yarn or filament can be determined from the amount of the polyalkylene ether blended with polyamide, in accordance with Formula 2 given above. The reason for this is that the yarn-adhesive is mainly caused by polyalkylene ether. A plot of this relationship is given in FIG. 2, wherein the area bounded by the parameters given in Formulas 1 and 2 is shown by slant lines.

When the amount of polyalkylene ether contained in l g. of polyamide is less than 0.2 mmol, the optical property of the fiber, with a part or all of the polyalkylene ether blended therein extracted therefrom, is not silky. When the amount of polyalkylene ether contained in 1 g. of polyamide is more than 3.5 mmol, yarn breakage or yarn-adhesion becomes excessive and spinning becomes very difficult even if the polyalkylene ether is finely dispersed in the polyamide. At the same time when the amount of polyalkylene ether is more than 3.5 mmol, yarn produced has no silky lustre but becomes chalky when the obtained yarn is washed and extracted.

As is apparent from the diagram of FIG. 2, the minimum birefringence is 40-45 1()- at maximum polyalkylene ether concentration. This birefringence is required for preventing yarn-adhesion when the polyamide which contains the possible maximum amount, i.e., 3.5 mmol/ g. of polyalkylene ether, is melt-spun. The minimum birefringence is close to that of the drawn yarn, as the amount of polyalkylene ether is lowered and the required birefringence for controlling yarn-adhesion is therefore also lowered.

On the other hand, the birefringence required for controlling yarn-adhesion, has a tendency to be more or less changed in accordance with the structure of polyalkylene ether and the kind of the matrix polyamide, but the difference is not so great as the effect of the amount thereof to be added.

In particular, when the molecular weight of polyalkylene ether is increased, the birefringence can be determined substantially by the concentration of alkylene oxide radical in the polyamide.

In the present invention, a polyalkylene ether having a molecular weight from 600 to 60,000 may be used but a molecular weight of from 1000 to 20,000 is preferred.

The structure of polyalkylene ethers having a molecular weight within the above mentioned range greatly affects the properties of the yarn product and the melt-spinnability of the modified polyamide.

As the alkylene oxides upon which the modifiers used in the present invention, eg the polyalkylene ethers or addition products thereof, are based, ethylene oxide or propylene oxide are preferred.

In accordance with the present invention, the polymer prepared by adding an alkylene oxide to organic compounds containing active hydrogen, such as a homo-or-copolymer of propylene oxide, organic amines, alcohols, acids, and compounds Whose terminal hydroxyl radicals are confined, or mixtures of said compounds, can be used as the polyamide modifier. But in order to obtain excellent spinnability, polyalkylene ether having high affinity for polyamides, such as alkylene oxide adducts of polyamide oligomers or polyamide monomers containing amido radical in the molecule thereof are preferred. The preferred compounds include ethylene or propylene oxide addition products of tetragonal through tridecagonal lactams, such as Z-piperidone, e-caprolactam, enantholactam, laurin lactam and other similar alkylene oxide addition products.

As an example of a method for making the polyalkylene oxide addition products, 1100 parts of ethylene oxide was subjected to addition polymerization along with 127 parts of enantholactam in the presence of 0.1 part of potassium hydroxide catalyst at the reaction temperature of C. under the reaction pressure of 43 kg./cm. for the reaction time of about 5 hours.

Upon analysis, it was determined that 23 mol of ethylene oxide per gram enantholactam had been added, on the average, and the product thus obtained was a light yellow paste.

Moreover, in order to prevent coloring of the polyamide caused by heat and the modifier blended therein, it is preferable to blend therewith a phosphoric ester and/ or the metal salt thereof. As the metal radical of the metal salt, mention can be made of such, for example, as the alkali metals as Na and K, the alkaline earth metals as Mg, Ca, and Ba, the transition metals as Cr, Co, Cu, Zn, Sn, Mn, and Ni, and A1, of which the most convenient are the transition metals, particularly, Mn Cu, Co, and Ni.

As examples of such phosphoric esters, monoesters, diesters, triesters or mixtures thereof can be given.

At any rate, those having high afiinity for alkylene oxide and of a structure, capable of being easily extracted with solvent, are preferred.

In the present invention, it is necessary that the meltspun and drawn modified polyamide containing polyalkylene ether be washed with a solvent which is inert against polyamide and active against the modifier blended therein so that a part or most of the modifier is extracted (from the fiber. It is also necessary that the appropriate amount of voids be formed in the fiber.

As the proportion of the modifier extracted is increased, the silky appearance and lustre effect of this invention can be attained with lower concentrations of modifier in the melt-spun fiber.

For the extraction, it is preferable to use an organic solvent such as alcohol or benzene.

In order to produce silky lustre and high non-transparency as described hereinafter, it is preferable that the extraction should be carried out in such a manner that the amount of voids in the fiber is within the range from 0.5-l3 vol percent.

When the amount of the produced voids is less than 0.5 vol percent, the silky touch and lustre is not attained.

On the other hand, in order to exceed 13 vol percent voids it is necessary to blend approximately 20 wt. percent modifier, and therefore separation of polyalkylene ether and polyamide occurs, as mentioned before and melt spinning becomes impossible. Further, the fiber product is chalky and scatters light too much.

Extraction can be carried out on yarn, but it can also be carried out on the textile product made from the yarn. Generally it is preferable to carry out extraction on the textile product from an industrial point of view. As used herein textile product is a product knitted, woven, or otherwise made up of fibers such as those of the present invention.

To further improve the lustre of the product of this invention fine white particles may be blended in the fiber forming material. This may also improve the processability of the fiber.

However, care should be taken with respect to such particles and particularly to the particle size and the blending proportion thereof so that the excellent fiber processability and silky lustre of the present invention is not lost. Namely, the diameters of circles circumscribed around these particles (e.g. the maximum diameters of the particles) should not be above or more than /a of the diameter of the melt spun fiber.

When such particles above 10a are blended in the polyamide, these particles clog the filter during meltspinning. Melt spinning thus becomes very difficult and the properties of the yarn product are remarkably degraded. The preferable size of these fine white particles is such that the diameters of circles circumscribed around the particles is from 0.1 to 4a. In order to obtain particles of preferred or acceptable particle size, a conventional method, such as hydarulic elutriation, is appropriate. A dispersing agent may be used when blending of the fine white particles is carried out during the polymerization of polyamide.

As the fine white particles which may be coemployed along with polyalkylene ether modifier in the present invention, the commercially distributed inorganic or organic white pigments can be used. But fine white particles the refractive index of which differs too greatly from the refractive index of polyamide (whose refractive index is about 1.56) scatter too much light at the interface between the particle and the polyamide matrix, making the product frosted. Therefore the silky mild lustre which is the characteristic of this invention is lost. Thus the amount of fine white particles to be blended with the polyamide is more limited if the difference of the refractive index between the particle and the polyamide is too great. As a result of detailed study into this matter by the inventors of the present invention, it has been 'found that the difference of refractive index between the polyamide matrix and the fine white particles to be blended and the amount thereof should satisfy the following Formula 3.

(wherein C is the amount of fine white particles to be blended (weight percent); d is the absolute value of the difference of refractive index between the fine white particles and the polyamide).

When fine white particles are blended by such an amount as to satisfy Formula 3, it is possible to improve the processability of the yarn by lowering its frictional coeflicient without losing the silky lustre produced in accordance with the present invention.

When the amount of the fine white particles blended into the polyamide is more than the amount defined by Formula 3, the yarn product becomes chalky and the lustre, otherwise produced in accordance with the present invention, is not obtained.

As fine white particles, the following are preferred: (The figures in parentheses show the refractive index of each type of particle.)

Halloysite (1.56)

Kalolinite (1.56)

Metakaolin (1.60) and such like kalin group Talc (1.59)

Pyrophillite (1.59)

Calcium carbonate (1.67) Magnesium carbonate (1.51, 1.70) Silica (1.4, 1.5)

Zinc oxide (2.02)

Titanium oxide (2.50 or 2.75) Zinc sulfide (2.37)

The term polyamide as used herein, refers to meltspinnable polymers of polymerizable 'monoaminomonocarboxylic acids, salts of diamine and dicarboxylic acid, or melt-spinnable fiber forming polyamides obtained from the amido forming derivatives thereof.

Copolymer of two or more of the foregoing can also be used.

The preferred polyamide used in this invention are polye capramide, polyhexamethylenedipamide, polyhexamethylenesebacamide. Other aliphatic polyamides, polyamides having aromatic rings, aliphatic rings or heterocycles in the main chain can also be used.

Heat stabilizers, light stabilizers, dyes and homologues of the foregoing polyamide materials may also be blended in the polyamides used in this invention.

The improved polyamide fibers obtained in accordance with the present invention have from 0.5 to 13% by volume of finely dispersed voids in the fibers and have a surface lustre such that the ratio of the strength of scattered light (I/I as defined hereinafter) satisfies the Formula 4 below. At the same time the lustre factor (a as defined hereinafter) satisfies the Formula 5 below.

Formula 4 Formula 5 Further, the polyamide fiber of the present invention has high non-transparency.

The polyamide fiber having such lustre properties as mentioned above, has a silky appearance, and is free of the waxy appearance peculiar to the usual synthetic fiber.

In this invention the reflectivity of the fiber is measured by the ratio of the strength of scattered light (I/I which is determined in the following manner, as illustrated in FIG. 3.

A test sample (S) is prepared by winding a test fiber on a non-reflective black panel in such a manner that the successive ends of test fiber lie in parallel and in contact with one another and there is no space between the respective adjacent test fiber ends.

This test sample (S) is set on a sample stage and white parallel light is projected onto it perpendicularly to the fiber axes of the test sample at the incident angle, O=45. The strength of reflected light (I) at the light receiving angle, 0 =45, is measured with a photoelectric photometer (Jyonan Manufacturing Co., Ltd., Model JSG-21').

The strength of reflected light (I of a standard white board of magnesium oxide (HS-Z 8722-1959) is measured under the same conditions.

When the ratio of the strengths of scattered light, N1 is high, the whole fiber is made to shine brightly by incident light. When this value is low, the brightness of the whole fiber is lower.

The lustre factor (a) of the present invention is a measure of lustre quality, and it is obtained in the following manner. The sample panel (S) is prepared by winding fibers in the same manner as described above. The light is projected onto the sample panel at the incident angle, O=45, while the sample (S) is rotated horizontally around the vertical axes of the sample plate. The reflected light (I) strength in the direction of the light receiving angle 45 (the angle of reflection on a mirror surface) is continuously measured during rotation.

The strength of reflected light (I) is plotted against the angle of rotation of sample (S) rotating in the plane of sample (S), and a curve as is shown in FIG. 4 is obtained.

The lustre factor (a) is defined as the range (AB) of the angle of rotation in which the strength of reflected light exceeds the mean strength, which is the average value of the maximum strength of reflected light (I max.) and the minimum strength of reflected light (1 min.) of said curve in any half revolution of sample (S).

The lustre factor (a) shows the angular range in which the fiber looks brighter than the mean brightness of the fiber at the angle of mirror reflection thereof.

When the lustre factor is greater, the fiber or bundles thereof look brighter when light is projected onto the fibers assembled in a textile product (wherein the axes of the fibers comprising the product are in various directions).'

On the other hand, when the lustre factor is smaller, the only fibers which appear bright are those fibers aligned in a specific direction (wherein the axis of the fiber is parallel with the plane including the projected light direction). In such a case, the product appears to have low lustre.

Therefore, unless the ratio of the strength of scattered light (l/I and lustre factor (a) satisfy the Formulae 4 and 5, a polyamide fiber having a mild and cool touch and a silky lustre, is not obtained.

The optical properties of polyamide fibers produced in accordance with the present invention are compared by taking as examples the fibers as usually used for clothes (the unit filament size being 3 denier). This comparison is graphically illustrated in FIG. 4.

As is generally known, silk has high covering power and a mild, so called, silky lustre. FIG. 4 shows the reflection pattern of silk (Curve 4) measured by the same instrument and in the same way used for polyamide fibers, as described herein.

The ratio of the strength of scattered light (I/I is high in the case of natural silk, and the lustre factor (a) is also high.

Conventional unmodified polyamide fiber (Curve 2), containing no titanium oxide, also has a high ratio of strength of scattered light. However, it has a very low lustre factor; accordingly the transparency of the conventional polyamide fiber is high and therefore when light is projected from a specific direction, it glistens and presents a waxy appearance and strong touch.

With a polyamide fiber (Curve 3) containing titanium oxide to increase the non-transparency of the fiber, the diffused reflection of light on the surface of fibers is increased and the lustre factor (a) is increased, but the ratio of the strength of scattered light (I/I within the plane inclusive of the projected light is poor. Therefore, the fiber is dull, and chalky and when such a fiber material as this is dyed, a dull pastel like lustre is obtained.

However, the improved polyamide fiber (Curve 1) of the present invention has high non-transparency, lustre factor (7) is high, and the ratio of strengths of reflected light (l/l is remarkably high. Generally, it presents a lustre similar to that of a natural silk. Therefore, when it is dyed, very brilliant colors can be obtained.

In regard to the blending of white fine particles in the fibers of the present invention, when such blending is carried out under appropriate condition in accordance with Formula 3 above, it is possible to produce the polyamide fibers which satisfy both Formulae 4 and 5 above.

It should be noted that the improved polyamide fiber of the present invention must satisfy both Formulae 4 and 5 simultaneously.

When the ratio of the strength of scattered light (I/I is less than 1.5, the amount of the reflected light is very little as light is projected onto the fiber bundle, and the fiber bundle has insutficient brightness.

On the other hand, when [/1 is larger than 15, the strength of light reflection in the position of mirror plane reflection is too high and the fiber group glistens like a mirror. This is undesirable.

When the lustre factor (a) is less than 20, the fiber bundle sparkles only in a specific direction (generally in the direction parallel with the fiber axis) as light is projected onto the fiber, and it is not preferable.

On the other hand, when lustre factor (a) is larger than 90, the whole fiber presents a dull and chalky appearance and this therefore is not desirable either.

When the polyamide fibers obtained as described in the foregoing paragraphs are used to prepare textile products, these products have a completely different lustre than that of textile products woven from conventional synthetic fibers. When the textile product woven from the From the weight of the modifier extracted by a solvent therefor and the density thereof, the volume previously occupied by the extracted modifier is determined and from this the volume percent voids is calculated.

(2) Size of void:

Void size is determined from an electron microscopic photograph of a lateral cross section of the filament.

(3) Transparency of fiber:

Fibers are associated into tow of 28,000 denier, and this tow is made into a blind the width of which is 2.5 cm.

This blind is set on a photoelectric photometer (produced by Nippon Precision Optical Co., Ltd., Model SEP-H), and the permeability or transparency (percent) with respect to white light of a tungsten lamp is measured.

(4) Dispersed state of modifier contained in polyamide pellets:

The central portion of a pellet is cut into pieces (the thickness of the lateral cross sectional surface and longitudinal cross sectional surface of each piece being respectively 5 to 10p.) and the obtained pieces are observed with a microscope to determine the diameters of the dispersed particles and the number of particles in the pellet cross section.

( 5 Birefringence Polyarnide fiber having been spun, drawn and taken up, is left out in an atmosphere of 20 C., 65% relative hu midity, for 24 hours, and then the birefringence of the fiber is measured by using the D-line emission of a sodium lamp with a polarizing microscope.

(6) Yarn-adhesion The presence or absence of yarn-adhesion is judged by the degree of flattening observable in the yarn bundle due to the mutual yarn adhesion or in the case of multifilament yarn by the unwinding tension of the yarn package.

Hn the case of the yarn bundle having adhesion, a Becke line, which is generally present on both contacting surfaces of yarn when the lateral cross section of fiber is observed with a microscope, cannot be observed; but when no adhesion is present, a Becke line can be observed.

(7) Sulfuric acid relative viscosity (777) The relative viscosity of the solution prepared by dissolving 1.0 g. of dry polymer into cc. of 98% sulfuric acid. Viscosity is then measured using an Ostwalds viscometer.

(8) Dynamic frictional coefiicient d) The sample filament yarn is worked on a frictionless roller (whose diameter is 10 mm. and fixed to the frame), and the filament yarn is twisted to give three turns thereto. Then the tension before the roller is determined to be 5 g., and while running the yarn at the speed of 300 m./ min., the tension (T) after the roller is measured, and the value obtained in accordance with the following formula is the measure of the dynamic frictional coefiicient. 10

3,734,986 11 12 EXAMPLE 1 spun, irregular extrusion was brought about right after 5 parts of ethylene oxide addition product enantholacthe Spinning Was n tiated Frequent fibe hfeakages tam (Modifier No. 1, addition product of 100 mol of curred as a result, taklhg P of the Y was Substah' ethylene oxide) was mixed along with 100 parts of polytially impossible.

TABLE 1 Drawn w g. SamplcNo; Pellets Spinning method Extruded State Drawn state (X104) Ctmtroll A Direct spinning drawing method Poor; frequentbreakage of yarn..'... Take-up impossible Example 1 B do Excellent Excellent 45 Control2 B Conventional spinning drawing ...d0 Frequent yarn breakage 48 method.

e-capramide (nylon 6) (1 r=2.46). This mixture was When Pellets B of excellent dispersion was used as in kneaded and fed to an extruder. After having been meltthe case of Control 2, extrusion was carried out normally mixed at 260 C., it was pelletized. and there was no difference from the conventional un- The pellets thus obtained (hereinafter referred to as modified nylon 6. But when the conventional drawing Pellets A) were dried at 110 (under a reduced pressure), method was used, the unwinding tension of the package and the water content was adjusted to be below 0.05%. m u drawn yarn Was remarkably great, and at the The concentration of oxyethylene radical contained in same time unevenness of drawn yarn was great. Therefore the polymer was 1.1 mmoL/g. corresponding to 4.8 yarn breakage was frequent when the yarn was drawn. i ht percent However, in Example 1 obtained in accordance with Th l t l cross section of P ll t A was ob d the present invention, uniform extrusion was very exwith a microscope and the dispersed state of said modieehehtly Carried Further, there Was 110 y breakage fier was studied. As a result of this observation, it was at the drawing Zone and uniform drawn y Could be determined that the modifier was in a linear dispersion Obtainedwherein the mean particle size was 15 and the length The drawn y p of excellent Spinning and th f was 500400,, and more than 50% by weight f drawn state produced in accordance with the method of the coarse particles were observed to have a particle size the Present invention and the unmodified nylon 6 above 20 trol 3) prepared in accordance with the same method Next, these Pellets A were revelletized, ft having as in Example 1 without blending a modifier therein were been kneaded with a biaxial screw extruder of excellent respeetlvely Wound in the form of ks. These hanks kneading property, and the newly obtained pellets (lierein- Were pp into hbt Water sutheientty shaken p after referred to as pellets B) were dried under reduced 30 minutes and then pp into hOt W t r f r pressure in the same manner as in the case of Pellets A. about 30 mthhtesy Were then dehydrated and d- The dispersed state of the modifier in these pellets was AS a result of the measurement of the Change Of Weight also studied and it was found that more than 70% by before and after the Washing of the modified nylon 6 weight of said pellets were dispersed in alinear dispersion 40 of the Present invention, it Was nd ut that about wherein the particle size was about 8;/., the length thereof 80% of the first blended modifier y Weight of was from 600 to 700,14, and coarse particles (having a nylon Was extracted y the hot Water Washing and particle size above 15,14) could hardly be observed. Voids wel'e Produced in the fibers- Pellets A and Pellets B were supplied respectively into The Void etlpaeity Was about 33% y Volumeconventional melt-spinning hi d me1t spun at 45 The lateral cross section of fibers thus obtained was 250 C. Th re ft the spun yams were taken up at 800 observed with an electron microscope and as a result of m./min., and thereafter the yarns were draw o a the microscopic observation, it was found that the averond roller running at a peripheral speed of 2,800 m./min. age diameter of these Voids Was and the maximum Then they e tak up t producs drawn yarns f 70 diameter thereof was 1.5,u. Further, it was found that there d i 24 filaments was no void with a diameter of more than (about 2,)

The drawn yarn produced by using Pellets A was made bf the diameter of the fiber- Control 1, the drawn yarn produced by using Pellets B The ratio of the Strength of Scattered o) and wa d E l 1 lustre factor (a) of the modified and unmodified nylon 6 A separate sample of yarn d d fr Pellets B fiber having been extracted as mentioned above, were was taken up as undrawn yarn at 800 m./min. in the same measured, and the results are given in Table manner as in the conventional spinning drawing process. The modified hylbh 6 fiber of the Present invention had After havi b l ft o t overnight hi yam was drawn a ratio of the strength of scattered light and lustre factor four times by using a conventional draw-twister to prowhich satisfies both Formula 4 and Formula More du e drawn yarn, over, the modified nylon 6 fiber of this invention pre- Thi yarn a th m d C t l 2 sented a bright lustre and, in addition, very excellent non- Table 1 shows the melt-spinning state of all of these transparency and y and Warm touch Were obtahledyarns, the drawing state thereof, and the birefringence on the other hand, the unmodified nylon 6 had low of the drawn yarns. ratio of strength of diffused light, low lustre factor, and

When the Pellets A, wherein polyalkylene ether is high transparency. Further it had a waxy touch and coarsely dispersed in the modified nylon 6, was meltappearance.

13 EXAMPLES 2-4 The polyalkylene ether obtained by adding 45 mol of ethylene oxide to a mole of sterylalcohol in accordance with a conventional method was phosphoric-esterified by using phosphorus pentoxide in accordance with a conventional method. This product was then neutralized with calcium hydroxide. Thus, Modifier No. 2 was prepared.

Six parts of Modifier No. 2, 100 parts of e-caprolactam,

14 The modified polyamides of Examples 24, having no yarn-adhesion and excellent spinnability were washed under the same conditions as in Example 1 to extract the modifier. Thereafter the ratio of strength of diffused light and 0.13 part of acetic acid, as a viscosity stabilizer, were mixed, and water was added to the mixture to make 75% aqueous solution. With the modifier uniformly dissolved the solution was polymerized in accordance with a conventional method.

The modified poly-e-capramide (nylon 6) product was washed with large amounts of pure water (at 9095 C.) to remove unreacted lactam and oligomer, and then dried under a reduced pressure.

The concentration of modifier was 5.2% by weight, (the concentration of oxyethylene radical was 1.2 mmol/ g.) in the modified nylon 6, and the relative viscosity of the polymer was 2.45.

The modifier was very finely dispersed in the polymer and more than 80% by weight of fine spherical particles, with a particle size of 2p, was present.

This modified Nylon 6 was supplied to a conventional spinning machine and the melt spun yarn was taken up initially at a speed of 900 m./min. Then the speed of the drawing roller was changed and the yarn prior to being taken up was drawn under such a condition that various birefringence as shown in Table 3 were obtained.

The output of extruded polymer was changed in accordance with the drawing rate so as to produce 70 denier-24 filament drawn yarn. The yarn-adhesion of the drawn yarn is shown in Table 3.

The state of extrusion was excellent in all cases, but the yarn whose birefrigence, An, was low, which was drawn under such conditions that Formula 2 was not satisfied, had great unevenness, the yarns thereof were adhered to one another, and in the extremity, yarn breakage was brought about when the yarn package was unwound.

When An goes beyond 30 10 yarn-adhesion was reduced to such a degree that it did not matter any more and unevenness of yarn was remarkably low.

When the drawing speed goes beyond 4000 m./min., yarn-adhesion is of course eliminated, but the elongation of the drawn yarn becomes extremely low, and therefore yarn breakage is frequently brought about, making fiber forming substantially impossible.

The birefringence of the limiting drawing rate was 5 2 x EXAMPLES s-s e-Caprolactam-ethylene oxide addition product having a molecular weight of 4733 (referred to as Modifier No. 3) was prepared by adding 105 mol of ethylene oxide per 1 mol of e-caprolactam. This was blended along with e-caprolactam in amounts ranging from 0.1 to 4.1 mmols of oxyethylene unit per gram of e-caprolactam as shown in Table 5.

Each of these mixtures were mixed along with water to prepare aqueous solutions.

In each case aqueous solution, which was transparent and in which the modifier was uniformly dissolved was put into a polymerization vessel and heated under atmospheric pressure, while the reaction mixture was stirred with an efiicient stirrer provided with spiral blades. The stirring operation was initiated at the point in time when the modifier began to separate and the stirring operation was continued until the polymerization was terminated.

These polymer products were melt-spun and cooled and thereafter the unreacted monomer was washed out with water and the modified poly-e-capramide thus produced contained Modifier No. 3, in amounts indicated in Table 5, which was separated from the polyamide phase and which was in the form of fine spherical particles, with an average particle size of 4a.

In the product prepared by blending 4.1 mmol/g. of modifier which is outside the range of this invention (from 0.2 mmol/g. to 3.5 mmol/ g.) the modifier and the polyamide showed a great tendency to separate, preventing the polymerization of nylon 6 and the spinning of yarn from this particular pellet material.

Examples of each of the remaining types of modified nylon 6 pellets were supplied to the screw type spinning machine, and were passed through the spinning nozzle pack, provided with a filter charged with 60 mesh and 200 mesh white Alundum, to melt-spin the modified nylon. Then the extruded fiber was taken up at a speed of 900 m./min. and thereafter it was continuously drawn.

The drawing operation was carried out on modified nylon 6 products containing Modifier No. 3 at several drawing speeds and substantially no yarn-adhesion was observed, no yarn breakage was brought about, and excellent drawn yarn was obtained.

The birefringence of the yarns thus obtained are given in Table 5.

As the amount of modifier is increased, yarn-adhesion occurs and the minimum birefringence must be increased.

Those having an insufiicient degree of orientation among the above mentioned drawn yarns, were drawn again by using a conventional draw-twister, and drawn yarn (50 denier/ 17 filament), the elongation of which was from to was obtained.

In the same manner, nylon 6 fiber (whose elongation was from 35 to 40%) was prepared by blending 0.3 and 2.0% of titanium oxide along with unmodified nylon 6 and unmodified nylon 6 containing no modifier at all was obtained.

The above prepared modified polyamide fibers were wound in hank form and dipped into 40 C. hot water. Then they were shaken and stirred for about 30 minutes.

Thereafter, they were dipped into 80 C. hot water, for about 30 minutes, to deoil the same, and then water was removed from the hanks and they were dried.

In both of the hank, from 50 to 80% of the modifier was extracted with 40 C. hot water.

As a result of microscopic observation of the lateral cross sectional surface of the fibers, voids, the mean diameter of which was 0.2 were observed in the polyamides prepared by blending modifier therein and a part of which was subsequently extracted.

The ratio of the strength of scattered light (I/I lustre factor (a), transparency, and the amount of voids in the polyamide fibers, were measured, and the results of these measurements are given in Table 5.

In the modified polyamide fiber of the present invention the amount of voids increases as the amount of modifier added increases. Along with the increase in the amount of voids, the transparency of the fibers is reduced, and the ratio of the strength of diffused light (U1 and lustre factor (a) are increased.

In the case of the modified polyamide fiber obtained in accordance with the method of the present invention, when the modified polyamide fiber of Control 9, which contains 0.2 vol percent of voids, is taken as an example, the improvement of lustre is not sufficient, and the ratio of the strength of diffused light (U1 and lustre factor (a) are also close to those of the unmodified polyamide fiber of Control 6.

However, the fibers of Examples 58 which have a sufficiently high ratio of strength of diffused light (U1 and lustre factor (a), to satisfy the requirements of the present invention, are non-transparent and have a bright lustre.

A Tricot weave of these fibers had a mild and silky lustre and, when compared with the product prepared by blending 0.3% by weight of titanium oxide, it had higher non-transparency, and presented a warmer and dryer touch.

On the other hand, the unmodified polyamide fiber of Control 6 had a lower ratio of strength of scattered light (U1 and lustre factor (a) and glistened only when observed from a specific direction. Further, it was remarkably transparent and had a waxy touch. Generally its appearance was harsher.

The polyamide fibers of Controls 7 and 8 prepared by blending titanium oxide had much lower ratios of strength of diffused light (U1 and the fibers generally presented a dull lustre. The appearances thereof was pastel colored.

At any rate, all of these controls were inferior to the modified polyamide of the present invention insofar as silky lustre is concerned.

For comparison, the lustre of natural silk having been refined with alkali in accordance with the conventional method was also measured and the result is given in Table 5.

The lustre of the polyamide fiber of the present invention is very close to that of natural silk as is apparent from Table 5.

TABLE 5 Concentra- Minimum Contents tion of birefringence of modifier oxyethylene Contents incapable of in nylon 6 units causing yarnpellet (wt. (mmol/g. titanium adhesion to percent) nylon) dioxide the yarn Control:

1. 8 0. 4 0 20Xl0- 5.3 1. 2 0 31x10- 8. 8 2.0 0 37X10- 13. 4 3. 0 0 44X10- 18. 2 4. 1 0 11 (silk) 1 No. yarn-adhesion. 1 Not polymerized.

Void in the fiber Ratio to after strength of extraction scattered Lustre Trans- (vol./ light factor parency percent) (H1 (01) (percent) EXAMPLES 9-11 A slurry composed of parts of laurolactam and 30 parts of water, was charged into an autoclave, and the mixture was heated in accordance with the conventional method, and polymerization was carried out under a high pressure.

The internal temperature of the autoclave was 300 C. and the pressure was controlled to be 18 kg./cm. Under these reaction conditions, 6 parts by weight (concentration of oxyethylene radical is 1.3 mmol/g. of lactam) of the molten ethylene oxide addition product of e-caprolactam mol ethylene oxide/mol of e-caprolactam was added thereto) was blended with the laurolactam, and the polymerization was terminated.

The modified nylon 12 pellets obtained by melt-spinning and cooling this reaction product had a sulfuric acid relative viscosity of 2.0.

These pellets were sliced and microscopic observation was carried out, as a result of which it was found that the modifier was finely dispersed in the form of fine spherical particles whose particle size was from 4 to 6a.

In the same manner as before, unmodified nylon 12 (whose relative viscosity was 2.2) was prepared without blending modifier therein.

The modified nylon 12 was supplied into an extruder type spinning machine, and it was melt-spun at 280 C. and taken up at a speed of 800 m./min. Thereafter the yarn was drawn with a drawing roller running at a peripheral speed of 2400 m./min. by using the same device as in Examples 2-4, and then the drawn yarn 30 denier/ 6 filament was taken up.

The elongation of the drawn yarn was 40%, and the birefringence thereof was 41x10? Yarn-adhesion was not observed at all and no yarn breakage was observed. The spinning operation was carried out very excellently.

This yarn was divided into four groups, and then the respective groups were wound on hanks, and the respective hanks were subjected to after-treatment.

One of the hanks was not subjected to the after-treatment and this was taken as Control 2.

The second hank was subjected to extraction by using boiling Water for 30 minutes and the hank thus treated was taken as Example 9.

The third hank was treated with 40 C. hot water for 30 minutes, and the yarn thus treated was taken as Example 10.

The last hank was boiled in a mixture of methyl alcohol and benzene, mixed at a ratio of 1:1, for 30 minutes and the yarn thus treated was taken as Example 11.

The lateral cross sections and side views of the above mentioned yarns were observed with a microscope, and as a result it was found that untreated yarn has no voids; this yarn Was also transparent. But the yarn which had been treated with boiling water, and that which had been treated with 40 C. hot water, had voids which were long and had an average diameter of 0.5

The amount of voids in the case of the latter was remarkably greater than that of the former.

The ratio of the strength of scattered light, lustre factor, and transparency of the respective yarns described above were measured using the same method used in Example 1. The results thus obtained are given in Table 6.

As is apparent from Table 6, the optical property of modified nylon 12 from which the modifier had not extracted (Control 2) was not much different from unmodified nylon 12 having no modifier.

On the other hand, modified nylon 12 treated with boiling water, warm water or organic solvent (Examples 911) presented a high ratio of strength of scattered light (I/I lustre factor, and excellent non-transparency and presented a silky lustre and a dry and desirable touch.

However, different effects were observed in the various examples depending on the solvent used to extract the modifier. Namely, when boiling water was used for extraction, the extracting effect was worse. Warm water produced a good effect, and organic solvent produced the best result.

When a large effect is to be obtained by blending a small amount of modifier, it is preferable to use organic solvent as in Example 11.

were transparent and the modifier in each case was uniformly dissolved into the nylon 6.

In the pellets prepared by adding the modifiers having the larger mole ratio of ethylene oxide in each of the pairs of addition products, the modifier was separated from the nyon 6 and the modifier was finely dispersed in the form of spherical particles the average diameter of which was from 3 to 5 The modified nylon 6 pellets containing the above mentioned modifiers were then melt spun as in Examples 2-4.

The melt temperature was 265 C., the take-up speed was 600 m./min., and the drawing speed was 1900 m./ min. Drawn yarn (70 denier/24 filament) was obtained.

The birefringence of the above modified nylon 6 products were about 45 10 and no yarn-adhesion was observed.

However, the yarn breakage of the molten polymer at the outlet of the spinning nozzle was different depending on the structure of the modifier. Remarkable yarn breakage was observed in the case of nylon '6 yarn prepared by blending the nonylphenol ethylene oxide addition product and, in addition, the modifier was separated from the a nylon 6. More specifically, it oozed out onto the surface of the pellets. This caused the supply of pellets to be very unsteady and irregular extrusion resulted.

However, in the case of the nylon 6 prepared by blending the ethylene oxide=e-caprolactam addition product, which has better aflinity for nylon 6, such problems in meltspinning did not occur and spinning was carried out excellently.

The above mentioned modified and unmodified nylon 6 yarn and unmodified nylon 6 yarn prepared by blending no modifier were extracted in the same manner and under the same conditions as in Example 1 to extract the modifiers. Thereafter the yarn products were taken up in the form of blinds, and the ratios of strength of diffused light (I/I lustre factors, and transparencies thereof were measured.

TABLE 6 Void after Ratio of the Amount of extraction strength of Lustre Transmodifier Extracting (vo1./ scattered factor parency (percent) agent percent) light (I/I) (a) (percent) Control 12.. 5.7 None None 4.1 7.7 59 Example:

9 5.7 Water (100 C.)-- 1.5 4.9 42 35 10 5.7 Water O.)- 3.5 5.7 48 24 11 5.7 Methyl alcohol- 4.3 6.2 49 20 benzene mixture (65 (3.). Control 13-. 0 None 0 6.2 6.1 58

As 15 shown in Table 7, no voids were produced 1n EXAMPLES 12-14 Each of two kinds of e-caprolactam ethylene oxide addition products (the molar ratios of ethylene oxide to caprolactam being 10 mol/mol and 40 mol/mol), each of two kinds of lauryl alcohol ethylene oxide addition products (molar ratios of ethylene oxide to lauryl alcohol, 5 mol/mol and 40 mol/mol) and each of two kinds of nonylphenolethylene oxide addition products (molar ratios of ethylene oxide to nonylphenol 5 mol/mol and 40 mol/ mol), i.e., 6 kinds in all of modifiers, were blended in a proportion of 1.3 m. mols of oxyethylene unit per gram of lactam, with e-caprolactam. These mixture were polymerized under the same conditions as in Examples 2-4 and modified nylon 6 pellets were obtained.

For the polymerization reaction, the modifiers were uniformly dissolved in an aqueous lactam solution (85% aqueous solution). Microscopic observation of cross-sections of the pellets produced indicated that pellets prepared with the modifiers having the lower mole ratio of ethylene oxide in each of the pairs of addition products the nylon 6 yarns prepared by blending modifiers which dissolved into the nylon 6 (Controls 14, 15 and 16), and therefore they presented the same properties as the unmodified nylon 6.

On the other hand, those in which modifiers could not be dissolved into the nylon 6 (Examples 12, 13, and 14) produced voids, (the diameters of the lateral cross sections thereof averaging 3n), which were long, in linear form, and as a result, the ratios of strength of diffused light, lustre factors, and non-transparency characteristics of these yarns were high and they had a silkyl lustre and a dry touch.

Since the degree of extraction varies in accordance with the kind of the modifier used, the volume of voids produced by extraction may differ even though the proportion of blended modifier is the same. This of course results in differences in optical properties.

In accordance with the present invention, more extractable modifiers (Examples 12, 13) are preferred to modifiers which are difiicult to extract (Example 14).

TABLE 7 Yarn Void after Ratio of breaka e Yarn-adhe- Solubility of extracstrength Lustre Trans- Modifier (moles ethylene (brea Biresion of modifier in tlon(vol.l of scattered factor paroncy oxide per moles adduct) age/hour) irlngenee drawn yarn polymer percent) light (a) (percent) Control:

14 None 44x10 None 0 3.4 6.2 60 15 e-Caprolactam ethylene 0.1 43 10' ...do Soluble 0 5.1 6.1 01

olxide addition product 0 Exampio12 e-Gaprolactam ethylene 0 nxur .....do Non-solublc-. 3.1 5.8 46 26 olrde addition product Control 16 Lauryl alcohol ethylene 0.5 45x10 do Soluble 0 4.9 5.0 60

ogrlde addition product Example 18..... e-Caprolaotam ethylene 0.2 44X10 -..-.do--...- Non-soluble 3.0 6.7 47 27 ((13310 addition product Control 17 Nonyl phenol ethylene 1.0 4.4X- .....do-..-.. Soluble 0 5.0 6.1 59

oride addition product Example 14-.. Nonylphenoi ethylene 0.6 43X10- ...-..do-.... Non-soluble 1.4 5.2 44 32 oxide addition product (40).

EXAMPLES 15-17 and then the tricot weaves were washed in a bath con- Hexamethylene diamine and adipic acid were reacted in accordance with conventional methods to prepare nylon 66 salt. This was dissolved in a 55%, by weight, aqueous taining nonionic active agents for minutes at C., and for 30 minutes at 80 C. These tricot weaves then presented a dry and desirable touch and the waxy touch of unmodified nylon 66 was eliminated. Moreover, the

solution and then heated to 70 C. 25 dyed products were brilliantly colored.

TABLE 8 Amount Void of after Ratio of modifier extraction strength Lustre w (v scattered factor Trans- Modifier percent) percent) light (UP) (a) parency Example 15 Laurtyl emine-EO-addition prod- 3.6 2.5 5.1 42 28 no 16 Pentaerythrlthol-EO-addition 3.6 2.4 5.1 40 28 product. 17 Ethylene oxide-propylene oxide 4.0 3.1 5. 7 45 24 copolymer.

About 4 parts each of laurylamine ethylene oxide addition product mol of ethylene oxide per mol laurylamine), ethylene oxide addition product of pentaerythritel (50 mol of ethylene oxide per mole pentaerythritol) and a 1:1 random copolymer of polyethylene oxide and polypropylene oxide (having an average of 5 monomeric units per molecule) were uniformly dissolved into separate quantities, consisting of 100 parts each, of nylon 66 salt.

The respective monomer mixtures were then polymerized in autoclaves, while vigorously stirring the same, and then they were extruded into pellets.

The dispersed states of the modifiers in the pellets thus obtained were studied and it was found that more than 70% by weight of the modifiers were dispersed finely in the form of spherical particles the average diameter of which was less than 51.1..

The concentrations of oxyalkylene radicals contained in these polymers were 0.8, 0.8 and 0.9 mmol/ gram polymer, respectively.

The modified nylon 66 pellets thus obtained were meltspun in the same manner as in Examples 2-4, and the yarns were taken up at a speed of 900 m./min. and then drawn at a drawing speed of 3,000 m./min.

Thus the drawn yarns whose birefringence were respectively 48 10- 47X l0 and 48x10 (3 denier/ 6 filament) were obtained.

In regard to the melt-spinning states of the obtained yarns, the respective yarns had excellent melt-spinning states, and no yarn breakage occurred. Further, no yarnadhesion of the drawn yarns was observed.

These yarns were extracted in the same manner and under the same conditions as in Examples 2-4, and the optical properties were studied with the results thereof shown in Table 8.

All of these yarns had a silky lustre and nontransparency.

On the other hand, unextracted yarns were woven into tricot wa es in accordance with conve t o al methods EXAMPLES 18-21 On ethylene oxide addition product of e-caprolactam (50 mol ethylene oxide per mole e-caprolactam) was phosphoric acid-esterified by using phosphorus pentoxide. The esterified addition product, neutralized with calcium hydroxide to produce metal salt, is referred to hereinafter as the modifier.

An aqueous solution was prepared by blending 5.2%, by weight, of this modifier with e-caprolactam.

On the other hand, commercially distributed metakaolin (the refractive index of which is 1.60) was mixed along with a dispersing agent (sodium pyrophosphate), and dispersed in water. After the metakaolin was deagglomerated, it was subjected to hydraulic elutriation and a slurry containing no metakaolin particles above 4,u, wherein the average diameter of circles circumscribed about the particles was 1,, was obtained.

This slurry was blended with the aqueous solution of e-caprolactam containing the above prepared modified in such a manner that a predetermined concentration of the slurry was obtained and then the mixture was sufiiciently stirred, heated and polymerized. Extraction of unpolymerized material were carried out in accordance with conventional methods and modified polycapramides containing 0.5% by weight and 1% by weight of metakaolin, and 4.8% by weight of modifier were obtained.

Other modified polycapramides, containing 0.5 and 1.0% by weight of titanium oxide (the refractive index thereof being 2.52) and 4.8% by weight of modifier were obtained through hydraulic elutriation and polymerization as described.

On the other hand, in accordance with the same polymerization method, a modified polycapramide containing 4.8% by weight of modifier alone, a polycapramide containing 0.5% by weight of metakaolin alone, and an unmodified polyamide, containing neither of them was obtained.

The above obtained polycapramides were melt-spun in accordance with the same spinning method as in Examples 24, and the yarn products were continuously drawn to produce polycapramide fibers (40 denier/10 filament) 22 mixture (dimer, trimer, and tetramer). Ethylene oxide was added to this polyamide oligomer mixture in accordance with conventional methods, (average mole ratio/ ethylene oxide per mol oligomer 50 mol) and an ethylthe birefringence of which was respectively 45 l- 5 one oxide addition product (hereinafter referred to as the Now of the yarns had irregular extrusion problems and modifier) was obtained. no yarn breakage occurred during the drawin o eration. Commerciall distributed talc (the refractive index g P Y They were excellently spun. thereof being 1.59) and kaolmite (the refractive index These drawn yams were washed ith 60 C, h t water thereof being 1.56) were dispersed in water with a dispersand th n d ied, mg agent (sodium pyrophosphate). Hydraulic elutriation The reflecting property, touch, frictional property, and Was used, In accordance With Stokes Principle, and an the amount of voids were measured for each yarn and aqueous Slurry was Obtalned containing no coarse P the r lt th f are given i T bl 9 cles wherem the average diameter of circles circumscribed The frequency of yarn breakage during tricot warpabout the Particles the Slurry was ing i l shown i T bl 9 Next, 6% by weight of the modifier was added to a These yarns were subjected to tricot warping and setmonomer mPiture composed of e'caprolactam and up in accordance with conventional methods. meFhYlene d1ammnium ,adipflte (nylon 66 Salt) in a The difi d polyamide yam prepared by blending weight ratio of 85:15. This mixture was then charged to fine white particles in an amount to satisfy Formula 3 an f as an 85% aquwus 501M191], and thermally (Examples 18-21) presented more or less lower ratio of 20 polymenleq accordance convenuonal h Strength of diffused light (U10) and lustre factor (a) The elutrlated slurry described above of fine white parthan the modified polyamide yam (Example 21) prepared ticles (talc and kaol1n1te) was added in the amount shown by blending no fine white particles, but they all satisfied m Table Whlle keepmg the reactlon temperature. at the Formulae 4 and 5, and silky lustre was obtained. 270 the pressure at 18 the Polymenzanon .In addition, the yarns had a remarkably low frictional 25 fi gig a 1 1 11 b d coefiicient between yarns, and the frequency of yarn 6 mo 1 e cope ymer my on P6 i h 0 tame breakage in the Warping process was very low Gene? were washed by the same method described 1n Examples 24, and unreacted monomer was removed. iii-g g yams showed excellent processablhty charac- 5.8% by weight of modifier was dispersed in the pellets as fine spherical partlcles the average particle size of bleggehien :g1:mg3?0:1vt2? itilfiierzlvl'ilgledgglrlgglii 17:21: 'l iiesz e il ets were melt-s un in the same manner as mula 3 (Control 18), the frictional coefiicient was low. in Examplfes 1243 to produge drawn yam (70 denier/29 Processability of the yarn was excellent but the ratio of m t) the strength of diffused light (I/I was very 10W and l iig pinning state was excellent no yarn breakage at i ifi ifi gi z figi igggg gz g d the spinning nozzle or during the drawing operation was i w n a er e yarns a ob served been, sublected to ,i dIPPed Into 9 All of the modified polyamide yarns hadabirefringence refimng bath, containing 2 g./l1tre of surface act ve agent of about 1 -3 and no yarmadhesion was observed. and 2 g./l1tre of sodium carbonate for 30 mlnutes to 40 These yarns were washed in the same manner as in extract the modlfiel and then sublected 9 l'efimng at Example 1, and a part of the modifier was extracted. Then Tilereafiel the Y Was y and finlshedthe frictional and optical properties of the yarns were Tricots obtained from the yarn of the present invention measured. presented a silky appearance and a dry touch. The modified polyamide yarns prepared by blending fine TABLE 9 Difference of Frequency of refractive yarn breakage index between when tricot Amount Void after fine white Amount Ratio of warping is of modiextraction particles and of fine strength of Lustre Trans- Dynamic carried out fier (wt. (vol. Kinds of fine polyamide white scattered factor parenc frictional (yarn breakpercent) percent) white particles (wt. percent) particles light (Illa) (a) (percent coefficient age/10 m.)

4.8 2.5 Metakaolin 0.07 0.5 4.5 38 30 0.61 0.2 4.8 2.5 o 0.07 1.0 4.3 35 2s 0. 56 0.1 2.2 2 f lgg ium oxide-.- 0. 99 0.5 2. g: 3.3g 2.:

4.8 2.5 Titanium oxide.-- 0.99 1.0 4.1 28 2A 0. 0.3 None 0 Metakaolim. 0.07 0.5 4.1 812 52 0.62 0.2 None 0 None 3.2 7.1 57 0.80 7.2

EXAMPLES 22-23 60 white particles in amounts within the range of Formula Polycapramide obtained by polymerizing e-caprolactam was extracted with hot water, and the extracted product 3 presented a silky lustre and a very low dynamic frictional coelficient.

TABLE 10 Difference of Void refractive Amount of Ratio of Amount of after exindex of fine fine white the strength modifier traction Fine white partiparticles of scattered Lustre Trans- Dynamic wt. (vol. white cles and wt. light factor parency friction percent) percent) particles polyamide percent) (III.,) (or) (percent) coefficient was dried, and the monomer (e-caprolactam) contained therein was removed to produce a polyamide oligomer What is claimed is: 1. Method for producing polyamide fiber having improved silkyl lustre and silky touch comprising the steps of (1) blending a melt spinnable polyamide with a polyalkylene ether modifier which is substantially insoluble in said polyamide and has excellent thermal stability at the melting point of said polyamide, the proportion thereof, in millimol repeating alkylene oxide unit in said modifier per gram polyamide hereinafter referred to as a being in the range 3.5 to 0.2, (2) preparing from said blend modified polyamide pellets having said modifier finely dispersed therein as minute particles at least 50%, by weight, of which have an average axial diameter in their cross-section of below 20 (3) melt-spinning said modifier polyamide pellets to prodce filaments, (4) continuously drawing said filaments until the birefringence, An, of said spun filaments is not less than 49 log 32 wherein a stands for millimols (mmols) of the recurring alkyleneoxide unit in the polyalkylene ether modifier contained in 1 gram (g.) of the polyamide; and (5) treating said drawn spun polyamide filaments with a selective solvent for said modifier said polyamide being substantially insoluble in said solvent, to produce voids in said filaments by the extraction of said modifier therefrom, said polyalkylene ether comprising an alkylene oxide adduct of amido radical-containing compounds selected from the group consisting of polyamide oligomers and polyamide monomers, said adduct having an molecular weight in the range from 600 to 60,000.

2. Method for producing polyamide fiber according to claim 1 wherein said filaments are drawn immediately after the melt spinning thereof and before being taken up.

3. Method for producing polyamide fiber according to claim 1 wherein said polyalkylene ether modifier comprises an alkylene oxide addition product, said alkylene oxide having from 2 to 3 carbon atoms.

4. Method for producing polyamide fiber according to claim 1 wherein said blending step comprises uniformly dissolving said modifier in a polyamide monomer or polyamide monomer solution and polymerizing said monomer and wherein said modifier particles in said pellets formed therefrom have an average axial diameter in their crosssection of below 5. Method for producing polyamide fiber according to claim 1 wherein fine white particles, having a refractive index of from 1.4 to 2.76 and a maximum diameter less than 10g and also less than the melt spun filament diameter, are blended into said polyamide along with said modifier, said blend proportion being within the range defined by the following formula:

(wherein C is the amount (wt. percent) of fine white particles; d is the absolute value of the difference of refractive index between said polyamide and siad fine white particles).

6. Method according to claim 5 wherein said fine white particles are selected from the group consisting of talc, kaolinite, titanium oxide and calcium carbonate.

7. Method for producing polyamide fiber according to claim 1, wherein said solvent extraction of said polyamide filaments produces voids therein totalting 0.5-13 volume percent of said filaments and the optical property of a fiber comprised of said filaments has a ratio of strength of scattered light (I/I of from 1.5 to 15 and a lustre factor (a) of from 20 to 90.

8. A method as recited in claim 7, wherein said polyalkylene ether adduct is phosphoric acid-esterified.

9. A method, as recited in claim 1, wherein said polyalkylene ether modifier has a molecular weight in the range from 1,000 to 20,000.

10. A method, as recited in claim 1, wherein said amidoradical containing compound of said polyalkylene ether comprises ethylene or propylene oxide addition products of tetragonal through tridecagonal lactams.

References Cited UNITED STATES PATENTS 3,423,491 1/1969 McLain et al. 264-49 3,551,538 12/1970 Yamamoto et al. 264-49 3,562,374 2/1971 Okamoto et al. 264-49 X 3,323,978 6/1967 Rasmussen 264-49 .UX 3,329,557 7/1967 Magat et al. 264-49 UX 3,475,898 11/1969 Magat et al. 161-180 X 3,314,919 4/1967 Most 260-37 NP X 3,405,211 10/1968 Cancio 264290 N X FOREIGN PATENTS 1,043,762 9/1966 Great Britain 264 DIG. 8

OTHER REFERENCES Miller, M. L., The Structure of Polymers, New York, Reinhold, c. 1966, pp. 566572 (Spe Polymer Science and Engineering series).

PHILIP E. ANDERSON, Primary Examiner US. Cl. X.R.

260-25 E, 2.5 M, 2.5 N, 37 NP, 37 AL, 78 S; 264-176 F, 210 F, 211, 290 N, 344, DIG. 13, DIG. 61

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