JPH0220725B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention uses a spinneret composed of a spinning solution guide rod that is fitted into a spinning hole and protrudes from the discharge surface. The present invention relates to a method for producing polyester fibers at a spinneret temperature lower than the spinneret temperature at which the fibers are produced. More specifically, the present invention relates to a method for producing polyester fibers that have spinnability comparable to polyester fibers produced at normal spinneret temperatures even when melt-spun at such low spinneret temperatures. <Prior art> Synthetic fibers made from thermoplastic polymers such as polyester are produced by extruding the polymer through the pores of a spinneret at a temperature above its melting point, cooling it and thinning it into a linear solid before taking it off or winding it. It is manufactured by the so-called melt spinning method. Usually, the spinneret pores (hereinafter referred to as discharge holes) have a diameter of 0.1 to 0.8
mm, usually a circular thin tube (nozzle) with a length of several mm, and its discharge tip is cut parallel to the discharge surface of the nozzle and perpendicular to the thin tube axis. In the process of spinning using such a normal spinneret, it is said that stress is concentrated and the polymer stream undergoes rapid deformation when it leaves the discharge surface. Melting point, melt viscosity, spinneret temperature, discharge hole shape, etc. play important roles. In particular, if the spinneret temperature is too low, the melt viscosity will increase, and in extreme cases, this will lead to weakened yarns and increased yarn breakage, leading to phenomena called shark skin and melt fracture. In a normal spinneret, when the spinneret temperature is lowered, there is a temperature at which the yarn breaks, which is called the weakening spinneret temperature or the lower limit spinning spinneret temperature, but normally in the case of polyethylene terephthalate, the intrinsic viscosity [η] A die temperature of approximately between 280 and 300° C. is employed in conjunction with polymer properties such as f. This spinneret temperature is 25°C or more higher than the melting point of polyethylene terephthalate, which is 254 to 260°C, and even the spinning temperature at the lower limit of spinnability is approximately 278°C or higher, about 25°C higher than the melting point. There is usually one. In general, when polyester is exposed to high temperatures above its melting point for a long period of time, thermal deterioration such as thermal decomposition causes a decrease in melt viscosity and molecular weight, so efforts are made to shorten the thermal history time at high temperatures as much as possible. ing. In particular, when spinning a high [η]f polymer to obtain high strength and high modulus fibers, in order to achieve stable spinning using a normal spinneret, the spinneret temperature described above must be set to a fairly high temperature to maintain an appropriate melt viscosity. At that time, the molecular weight reduction ([η]f reduction) due to high-temperature thermal history is usually much larger than that of [η]f polymers, and polymers with less [η]f reduction or high Significant efforts have been made to produce high [η]f polymers. On the other hand, in order to modify polyethylene terephthalate and give it functionality, various additives are mixed into it, and composite spinning with physically and chemically different thermoplastic polymers such as copolyester and other types of polymers is carried out. Although this method is widely used, strict spinning conditions are required to achieve stable spinning due to the thermal stability of additives and coexisting polymers and the current spinneret temperature.
This is a major obstacle to expanding the possibilities of modifying polyethylene terephthalate. <Object of the invention> Therefore, the object of the present invention is to enable spinning of polyester terephthalate at a low spinneret temperature (low temperature spinning), which has been a long-held dream for those skilled in the art, thereby preventing thermal deterioration [η] Improve the performance potential of polyethylene terephthalate itself by preventing the decrease in f, and facilitate the wide expansion of various composite spinning technologies for modifying polyethylene terephthalate.
In addition, the aim is to significantly reduce the amount of effort currently being invested. <Structure of the Invention> In view of the above circumstances, the present inventors have made intensive studies to realize low-temperature spinning of polyethylene terephthalate, and have developed a spinneret in which a spinning solution guide rod passes through a discharge hole and protrudes downstream of the discharge surface. It was discovered that low-temperature spinning can be easily performed by using this method, leading to the present invention. That is, the present invention provides a polyester polymer (melting point +
30) After completely melting at a melting temperature of ℃ or higher, the spinning solution is placed in a spinneret plate having at least one spinning hole consisting of a spinning solution introduction hole and a spinning solution discharge hole connected to the spinning solution introduction hole, and the spinning solution has a needle-shaped lower part. A guide rod is fitted into each spinning hole, and the axis of the guide rod is aligned with the axes of the introduction hole and the discharge hole at least over a range from the lower part of the spinning solution introduction hole through the discharge hole to the tip, Moreover, melt spinning is performed at a spinneret temperature T (°C) of (melting point +5)°C or more and (melting point +20)°C or less by using a spinneret in which the guide rod projects downward from the discharge surface through the discharge hole. This is a method for producing polyester fiber characterized by the following. Here, the words and symbols used in the present invention will be explained. (a) Intrinsic viscosity [η] f is measured using a spun yarn obtained by melt spinning, and is determined by the following formula. [η] f = Lim ^C → ⁰ l _o (ηrel)/C [(ηrel) is the ratio of the viscosity of a dilute solution of polyester using o-chlorophenol as a solvent to the viscosity of the solvent measured in the same temperature unit. and C is the number of grams of polyester in 100 c.c. solution. (b) Melting point Tm (°C) is determined by measuring polyester polymer chips at a heating rate of 10 using a differential thermal measurement device.
It is the peak temperature of melting as measured in °C/min. The present invention will be explained in more detail. To summarize, the present invention has the following two main features. That is, the spinneret is different from a normal spinneret, and is a spinneret in which a needle-shaped spinning solution guide rod is arranged so as to pass through a discharge hole and protrude downstream of the discharge surface; Spinneret temperature must be above (melting point + 5)°C and below (melting point + 20)°C. In other words, since the lower limit spinneret temperature for normal spinnerets is approximately equivalent to (melting point + 20)°C, melt spinning should be performed at a temperature lower than the lower limit spinneret temperature for normal spinnerets. The polyester referred to in the present invention may be a copolymerized polyester in which 85 mol% or more of the repeating units are polyethylene terephthalate, and if necessary, copolymerized with at least one copolymer component, or a matting agent. , antistatic agent, flame retardant, lubricant,
It may also contain additives such as heat stabilizers. Although the present invention will be specifically explained using a polyethylene terephthalate polymer, it is easily understood that certain embodiments of the present invention are generally applicable to melt-spun thermoplastic polymers. It is a place where Intrinsic viscosity of polyester used in the present invention [η]
f is not particularly limited, and [η]f within a practical range is used regardless of clothing or non-clothing. Furthermore, the melting point (Tm) of the polyester is not particularly limited, and any polymer can be used as long as it has a Tm that can withstand practical use. The first important thing in the present invention is that the spinneret is different from a normal spinneret in that it has a needle-shaped spinning solution guide rod that is arranged so as to pass through the discharge hole and protrude downstream of the discharge surface. It is necessary.
The features of the spinneret of the present invention will be explained in detail below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of essential parts of a spinneret according to the present invention, FIG. 2 is a perspective view showing an embodiment of a spinning solution guide rod fitted into the spinneret of the present invention, and FIG. FIG. 1 is a longitudinal cross-sectional view (a) of a main part and a cross-sectional view (b) of a main part of a spinneret in which the spinning solution guide rod shown in the figure is inserted. As shown in FIG. 1, the spinneret of the present invention has at least one spinning hole 3 consisting of a spinning solution introduction hole 1 having a large diameter at the top and a gradually decreasing diameter at the bottom, and a spinning solution discharge hole 2 connected thereto. Spinneret plate 4 having or more
As shown in Fig. 2, a plurality of (four in this example) blades 5 are provided at equal intervals in the circumferential direction of the upper part, and the lower part 6 is shaped like a uniform needle (in this example, circularly shaped). )
A spinning solution guide rod 7 is fitted into each spinning hole 3 as shown in FIG. 3, and the upper part of the guide rod 7 including the blades 6 is fixed to the large diameter upper part of the spinning solution introduction hole 1. Furthermore, as shown in FIG. 3, the axis of the guide rod 7 extends from at least the lower part 8 of the spinning solution introduction hole 1 through the discharge hole 2,
The introduction hole 1 and the discharge hole 2 extend all the way to the tip 6.
The guide rod 7 is projected downward from the discharge surface 9 through the discharge hole 2. According to the spinneret of the present invention having such a structure, the spinning solution is surrounded by the upper blade 5 of the spinning solution guide rod 7 fitted and fixed in each spinning hole 3 and the inner wall 10 of the large diameter portion of the introduction hole 1, and A plurality of passages 11 formed at equal intervals
, and then enters an annular passage 13 formed by the upper part 12 of the tip 6 of the guide rod 7, the lower part 8 of the introduction hole 1, and the discharge hole 2, and from the tip of this annular passage 13, the spinning solution guide rod It flows along the outer periphery of the columnar part 12 of No. 7, is pulled out from the tip 6, and is spun into a fiber. In the spinneret of the present invention, the shape of the spinning hole 3 shown in FIG. Adopted. The diameter of the large diameter part of the spinning solution introduction hole 1 shown in FIG.
It is necessary to have a size that allows the spinning solution guide rod 7 shown in FIG. The diameter of the discharge hole 2 and the diameter of the columnar part 1 are preferably about 0.1 mm or more larger than the diameter of the columnar part 12 of No.
It goes without saying that the combination of the two diameters can be adjusted as desired. The upper part of the spinning solution guide rod 7 shown in FIG. The purpose is to form or hold a passage leading to the discharge hole 2, and the shape of the upper part is not limited in any way. A shape in which spinning solution inflow holes are provided at equal intervals may also be used. The shape from the lower columnar part 12 to the tip 6 of the spinning solution guide rod 7 shown in FIG. It may be a conical shape, or it may be a polygonal prism (cone) such as an ellipse (cone), a triangle (cone), a pentagonal prism (cone), or any other irregular cross-section prism (cone). . Furthermore, by using a guide rod in the shape of a circular tube, a polygonal tube, or a hollow tube with various other irregular cross sections, it is possible to spin hollow fibers. If the guide rod 7 is arranged so as to roughly divide the range from the inlet to the tip of the discharge hole 2 into two, a side-by-side type composite yarn can be obtained, and it can also be used in a normal sheath-core type composite spinneret. It is also possible to apply the spinning solution guide rod of the invention. What is important in the combined structure of the spinning hole 3 and the spinning solution guide rod 7 in the spinneret of the present invention shown in FIG.
The range from the lower part 8 to the distal end 6 via the discharge hole 2 is substantially aligned with the axis of the introduction hole 1 and the discharge hole 2. If the axis of the guide rod is extremely eccentric, or the spinning solution passes through the passage 13 shown in FIG. 3, unevenness will occur in the flow velocity, causing bending or the like immediately after exiting the discharge surface 9, which is undesirable. The next important thing is that the lower end 6 of the columnar part 12 of the guide rod 7 protrudes from the discharge surface 9, as shown in FIG. The degree of this protrusion is determined by the diameter of the discharge hole 2, the diameter of the columnar part 12 of the guide rod 7, the viscosity of the spinning solution,
1 to 30 mm, depending on discharge rate, spinneret temperature, etc.
Preferably it is about 2 to 20 mm. If the degree of protrusion is small, the stress deformation of the spinning solution immediately after the discharge surface 9 will be rapid, as is the case with a normal spinneret, and if the spinneret temperature is lowered below normal, weak yarn or yarn breakage will occur even under conditions where the temperature is not lowered that much. This makes stable spinning difficult, and the effect of low-temperature spinning cannot be obtained sufficiently. On the other hand, if the degree of protrusion is extremely large, the spinning solution will cool as it flows down from the columnar part 12 of the guide rod 7 along the tip 6, and in extreme cases, the spinning solution will solidify. This is not preferable because it may make it impossible to thread the thread. The second important thing in the present invention is that the spinneret temperature T (°C) as shown in FIG.
The spinning must be carried out under the conditions of ℃ or more and (melting point + 20) ℃ or less, in other words, the minimum spinneret that can be spun with a normal spinneret is approximately equivalent to (melting point + 25) ℃. Melt spinning is performed at a temperature lower than the temperature. <Function> Although the detailed principle by which low-temperature spinning is enabled by the spinneret of the present invention is not clear, it is probably due to the following reasons. In general, the flow of a polymer melt can be divided into flow under shear stress (mainly due to shear flow) and flow under elongation stress.When considering the spinning process of synthetic fibers, the former is the flow in the spinning hole, especially the discharge hole. The latter is the flow outside the spinning hole. Although it is well known that fiberization of synthetic fibers occurs under elongation stress outside the spinning hole, it is also true that the flow characteristics within the spinning hole have various effects on fiberization. In a normal spinneret, the shear deformation received during the process of passing through the spinning hole, especially the discharge hole, moves in the direction of relaxation after leaving the discharge hole, but the subsequent elongation stress causes the polymer melt to melt. undergoes rapid deformation and becomes thinner. Therefore, when the spinneret temperature decreases, the polymer melt becomes highly viscous and highly elastic, and as a result, rapid deformation due to elongation stress extends to the vicinity of the spinneret, and in extreme cases, to the inside of the discharge hole. It is thought that the polymer flow in the polymer in the spinneret is disturbed, resulting in a weak yarn or breakage. On the other hand, in the spinneret of the present invention, even after exiting the discharge surface, the shear deformation received in the spinning hole is gently relaxed during the process in which the polymer flow flows down along the spinning solution guide rod, and then The effect of the elongation stress on the polymer flow also increases as you move upstream from the tip of the guide rod.
Because the polymer flow gradually decreases, the deformation experienced by the polymer flow becomes more gradual in the long region flowing along the guide rod, and it is thought that when it leaves the tip of the guide rod, it transitions more smoothly to the next elongation stress deformation process. It will be done. Therefore, the spinneret temperature is kept fairly low;
Even if the polymer flow becomes highly viscous and highly elastic, it is considered that spinning is possible because it is unlikely to undergo rapid deformation as in a normal spinneret. There is a natural limit (lower limit) to the spinneret temperature in the present invention.In other words, at a spinneret temperature at which the polymer flow solidifies during the process of flowing down the guide rod, elastic deformation due to elongation stress leads to brittle fracture and spinning becomes impossible. Therefore, (melting point of polyester polymer +
5) A cap temperature of ℃ or higher is required. On the other hand, the upper limit of the spinneret temperature in the present invention is
Normally, the spinneret temperature should be kept below the lower limit of spinnability, and the usefulness of the present invention can be found below this lower spindle temperature. Therefore, the upper limit of the die temperature in the present invention is set to approximately correspond to the above-mentioned lower limit spinneret temperature (melting point of polyester polymer +20°C). The fineness (De) and spinning speed of the spun yarn obtained in the method for producing polyester fiber of the present invention as described above are not particularly limited, but the fineness of the spun yarn is from so-called ultrafine fibers having a fineness of about 1 de. tens of de
It is possible to spin ultra-thick fibers in the range of 100 to 100 m/min, and the spinning speed depends on the fineness of the spun yarn and the spinneret temperature, but in general, it ranges from a low spinning speed of several tens of m/min to a high spinning speed of several thousand m/min. Can be spun up to a wide range. Note that, after the spun yarn according to the present invention is once wound up in the spinning process, it may be subjected to drawing in the next process, etc., or may be directly delayed (SDY), and is not particularly specified. <Effects> Regarding the effects and usefulness of the present invention, spinning is possible at the spinneret temperature of a normal spinneret.
That is, since low-temperature spinning is possible, stable spinning of polyesters containing additives with poor heat resistance, blended or copolymerized polyesters, polyesters with a lot of spindle stains and foreign matter, etc. can be easily performed. Furthermore, composite spinning between different types of polyesters having considerably different melting points can be performed more easily than before because the spinning temperature of the higher melting point polyester is lowered. Since the melt viscosity of the polymer can be increased by lowering the spinneret temperature, it is possible to spin low [η]f polyester, which was previously considered difficult. It is possible to spin fibers with fineness ranging from extremely fine to extremely thick without having to significantly change the shape of the spinning hole of the spinneret or the spinning solution guide rod. High viscosity polyesters and highly crystalline polyesters can be spun without the need to raise the temperature of the spinneret to a high temperature as in a normal spinneret. Therefore, the inherent characteristics of high viscosity and highly crystalline polymers can be effectively utilized. Threads spun at low temperatures using the spinneret of the present invention tend to have lower elongation and lower NDR than normally spun yarns obtained at the same spinning speed using a normal spinneret. By doing so, it is possible to easily obtain a spun mixed fiber yarn having an arbitrary difference in elongation. The spun yarn obtained by the present invention tends to be dyed more deeply than the yarn of the same elongation from the spinneret, and this tendency also occurs in yarns that have been subjected to drawing heat treatment or false twisting under the same conditions. Yes, the coloring is better than usual. As described above, the present invention can overcome several problems that are difficult to achieve by conventional spinning, and brings about industrially extremely significant effects. The present invention will be explained below with reference to Examples. Example 1 Spinneret plate 3 (large diameter 5 of introduction hole 1) shown in FIG.
mm; the diameter of the discharge hole 2 is 1.3 mm, the length is 1.0 mm; the number of discharge holes 2 is 12), and the spinning solution guide rod 7 shown in FIG. 2 (the diameter of the columnar part 12 is 1.0 mm, the length is 5 mm) is combined. ,
Polyethylene terephthalate having an intrinsic viscosity [η] f of 0.60 and a melting point of polymer chips of 255°C is melted at a melting temperature of 295°C using the spinneret shown in Fig. 3 (length of the guide rod protruding downward from the discharge surface 9: 3 mm). Melt spun at °C. The single yarn De after drawing the spun yarn is approximately 3de,
Adjust the discharge amount so that the elongation at break is approximately 25%,
Table 1 shows the results of spinning with various spinneret temperatures and spinning speeds. As a comparative example, a normal mouthpiece (discharge hole diameter 0.3mm,
Using the same polyethylene terephthalate as above at a melting temperature of 295℃,
Table 1 also shows the results of spinning at different spinneret temperatures and spinning speeds.

[Table] (Note) * indicates a comparative example other than the present invention.
In Table 1, Experiments Nos. 1 to 13 were conducted using the spinneret of the present invention and examining spinnability and yarn physical properties by changing the spinneret temperature and spinning speed. No. 1 has a cap temperature of 255
Because the temperature was so low, yarn breakage occurred frequently at an experimental spinning speed of 2000 m/min, and spinning could not be completed. No. 2 to 5 are the results at a cap temperature of 260℃,
At a spinning speed of 4000 m/min (elongation 67%), single yarn breakage occasionally occurred and the yarn became weak, but spinning was possible over a wide range of lower spinning speeds. No. 6 to 13 have a cap temperature of 265 and 275℃
As a result, it was possible to perform spinning without any particular problem within the range of the experimental spinning speed (4000 m/min) or lower. A characteristic feature of Nos. 2 to 13 is that when the spinneret temperature is lowered, the elongation of the spun yarn obtained at the same spinning speed tends to decrease. On the other hand, Nos. 14 to 23 are samples obtained by using a normal spinneret and changing the spinneret temperature and spinning speed. When the spindle temperature is 283℃ (No. 21 to 23), which is the temperature normally used, single yarn breakage occurs at a spinning speed of 6000 m/min (elongation 66%), but a wide spinning speed range below this This allows stable spinning. When the spinneret temperature is lowered to 275°C, as shown in Nos. 17 to 20, although spinning is possible at low spinning speeds, single yarn breakage occurs at high spinning speeds, and in extreme cases, yarn breakage occurs frequently and spinning is impossible. Further, when the spinneret temperature is lowered to 270° C. (Nos. 14 to 16), yarn breakage occurs and spinning becomes difficult, and even if spinning is possible at a low spinning speed (No. 14), wraps tend to occur during drawing. As described above, it can be seen that according to the present invention, stable spinning is possible even at a considerably low spindle temperature. In addition, as can be seen in Table 1, the pithing effect of the low-temperature spinning of the present invention results in lower elongation than that of normally spun yarn at the same spinning speed. It has the usefulness of producing average yarn. Example 2 In the spinneret used in Example 1, the length l of the guide rod protruding below the discharge surface was 3, 10,
No changes other than 15 and 20 mm, and Example 1
Table 2 shows the results of melt spinning using the same polyethylene terephthalate as above at a melting temperature of 295°C, a spinneret temperature of 275°C, a single filament denier of the spun yarn of about 5 de, and a spinning speed of 1500 m/min.

[Table] As can be seen from Table 2, increasing the length of the guide rod promotes the cooling effect of the polymer flowing down the guide rod, resulting in a spun yarn with a considerably lower elongation than the spinning speed. It will be done. In Example No. 27, the spinning speed is low (1500
m/min), while the intermediate orientation system (so-called
It is a low elongation yarn similar to POY (spinning speed 3300 to 3500 m/min). In this way, depending on the combination of the guide rod length, die temperature, and spinning speed, it is possible to obtain spun yarn having any elongation over a fairly wide range. As explained above in the examples, according to the present invention, stable spinning is possible at a much lower spindle temperature than normal spinning, and the physical properties of the obtained spun yarn have characteristics not found in normal spinning yarn. The industrial significance of the present invention is extremely great.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of essential parts of a spinneret according to the present invention, FIG. 2 is a perspective view showing an embodiment of a spinning solution guide rod in a spinneret according to the present invention, and FIG. FIG. 2 is a vertical cross-sectional view of a main part of a spinneret in which a spinning solution guide rod shown in FIG. 1: Spinning solution introduction hole; 2: Spinning solution discharge hole; 3: Spinning hole; 4: Spinneret plate; 5: Vane; 6: Guide rod tip; 7: Guide rod; 8: Lower part of introduction hole; 9: Discharge surface ;
10: Inner wall of large diameter part of introduction hole; 11: Passage; 12: Guide rod columnar part; 13: Annular passage.

Claims (1)

[Claims] 1. When producing polyester fibers containing ethylene terephthalate units as a main component by melt spinning, after the polyester polymer is completely melted at a melting temperature of (melting point + 30) °C or higher, a spinning solution introduction hole and a In a spinneret plate having at least one spinning hole consisting of a spinning solution discharge hole, a spinning solution guide rod with a needle-shaped lower part is fitted into each spinning hole, and the guide rod has an axis that is at least The range from the lower part of the spinning solution introduction hole through the discharge hole to the tip is aligned with the axes of the introduction hole and the discharge hole, and the guide rod is made to protrude downward from the discharge surface through the discharge hole. A method for producing polyester fiber, which comprises performing melt spinning using a spinneret such that the spinneret temperature (T° C.) satisfies the following formula. Tm+5≦T≦Tm+20 (°C) [However, Tm is the melting point (°C) of the polyester polymer, which is expressed as the peak temperature of melting in differential thermal measurement of the polymer chip. ]