JPS62250220A - Production of polyethylene terephthalate fiber - Google Patents

Abstract

PURPOSE:To obtain the titled ultra-fine fiber having high strength in high stability, suppressing the decomposition of polymer, by extruding a dope composed of a polyethylene terephthalate and a specific mixed solution through a spinning nozzle under a specific condition and instantaneously evaporating the solvent to form fibers. CONSTITUTION:A solution having a specific volume of <=1.0cc/g and composed of 5-20wt% polyethylene terephthalate and a mixed solvent consisting of methylene chloride and 1,1,2-trichloro-1,2,2-trifluoroethane at a weight ratio of 4:6-9:1 is heated at 240-280 deg.C, passed through an orifice under a pressure (P1, kg/cm<2>G) and a temperature (T1, deg.C) condition satisfying the formula I, introduced into a pipe having a pressure P2 and a temperature T2 satisfying the formula II (P2 is higher than the vapor-liquid equilibrium pressure and P1>P2) and abruptly released through a spinning nozzle into atmosphere to effect the instantaneous vaporization of the solvent and obtain the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyethylene terephthalate fibers. More specifically, polyethylene terephthalate and methylene chloride/1,1.2-1-lichloro 1.2.2
- Trifluoroethane (hereinafter simply referred to as "trichlorotrifluoroethane") and a mixed solvent.

[Conventional technology]

As a method for producing ultrafine fibers, a polymer melt is extruded from a spinning nozzle using methylene chloride/1,1, and then pulled with a jet of heated fluid to make it thinner. A method in which a part of the polymer component (for example, a sea component in the fiber cross-sectional structure) is removed using a solvent after spinning a fiber (which has an island structure);
Examples include methylene chloride/1,1 extruding a solution of a low boiling point solvent and polymer from a spinning nozzle, as described in No. 5, and the so-called flash spinning method in which the solvent is instantaneously vaporized.

[Problem that the invention seeks to solve]

When ultra-fine polyethylene terephthalate fibers are produced using these methods, although the melt-blowing method does yield extremely thin fibers, since the fibers are thinned in the polymer melt state, the drawing orientation and crystallization of the fibers are difficult. The problem is that the strength of the obtained fibers is extremely low. In addition, the method of removing some component polymers of a multicomponent filament requires a troublesome step of eluting the polymer. The methods described in Japanese Patent Publication No. 40-28125 and Japanese Patent Publication No. 41-6215 yield polyethylene fibers that are thin and have satisfactory strength, but polyethylene terephthalate fibers yield only extremely weak fibers. As described above, at present, a method for producing polyethylene terephthalate fibers that are extremely fine and have satisfactory strength has not been sufficiently established industrially.

An object of the present invention is to provide an efficient and industrially advantageous method for producing ultra-fine, high-strength polyethylene terephthalate fibers.

[Means for solving problems]

The present inventors have focused on the flash spinning method and have continued intensive research in producing ultra-fine, high-strength polyethylene terephthalate fibers. As a result, they discovered that ultrafine, high-strength polyethylene terephthalate fibers can be obtained by using a solution of polyethylene terephthalate prepared in a specific solvent. That is, a solution consisting of polyethylene terephthalate and a methylene chloride/trichlorotrifluoroethane mixed solvent is extruded from a spinning nozzle.
1,1, Discovery of a method for producing polyethylene terephthalate fibers characterized by instantaneous vaporization of the solvent to form fibers Methylene chloride/1,1, Patent application 1986-2405
It was set at 79. However, it was found that it was difficult to stably obtain ultrafine, high-strength polyethylene terephthalate fibers using the method of the prior application. In order to solve this problem, we conducted further research and completed the present invention. That is, a specific specific volume is required to obtain ultra-fine, high-strength polyethylene terephthalate fibers.

Polyethylene terephthalate is dissolved in methylene chloride/1.1 at temperature and pressure, and then spun under conditions that match the specific volume, temperature and pressure mentioned above.The present invention will now be described in detail.

The polyethylene terephthalate used in the present invention is 60% of phenol/1.1.2.2-tetrachloroethane.
/40% by weight mixed solvent, from fiber grades with ηSP/C of about 0.6 to 4.5 (100cc/g) measured at 35°C and 1% concentration to high viscosity resins made by solid phase polymerization. belongs to.

The main chain contains other copolymerized components, such as acid components such as isophthalic acid, phthalic acid, geltaric acid, adipic acid, etc., and glycol components such as diethylene glycol, propylene glycol, 1.4-7'tanediol, and 2.2-bis( 15 4-hydroxyethoxyphenyl)propane, etc.
Those containing up to mol % can equally be used.

The polyethylene terephthalate concentration of the solution used in the present invention and the composition of the methylene chloride/trichlorotrifluoroethane mixed solvent are as described in the earlier Japanese Patent Application No. 60-240579, and are shown below.

That is, the concentration range of the solution used in the present invention is not necessarily limited depending on the degree of polymerization of the polymer, the composition of the mixed solvent, etc., but it is usually preferably 5% by weight to 20% by weight.

At a low concentration of less than 5% by weight, it is difficult to produce a continuous filament, and at a high concentration of more than 20% by weight, it becomes spongy,
It becomes a foamed filament and does not become an ultra-fine fiber, and its strength becomes extremely weak.

The composition of the methylene chloride/trichlorotrifluoroethane mixed solvent used in the present invention is not necessarily limited depending on the degree of polymerization of the polymer, the concentration of the solution, the temperature of the solution, etc., but the composition of methylene chloride/trichlorotrifluoroethane is usually the weight ratio. It is preferable that 4=6 to 9:1. When the composition of trichlorotrifluoroethane exceeds 60% by weight, it becomes difficult to dissolve polyethylene terephthalate, and when it becomes less than 10% by weight, the resulting polyethylene terephthalate fibers are not sufficiently stretched, probably because the vaporized gas temperature of the mixed solvent becomes too low. Therefore, it is difficult to form fibers with high strength.

In the present invention, the specific volume of the mixture of polyethylene terephthalate and methylene chloride/trichlorotrifluoroethane is set to 1.0 cc/g or less and methylene chloride/1,1,24
The solution is heated to 0°C or more and 280°C or less, and the pressure P + (kg/ciG) and temperature T + ('c) are P1
≧2.8 T + 532 (kg / cj G
) Preferably, the pressure P z (kg/c
rA G ), the temperature Tz ('C) is P z < 2.
8 Tt 471 Preferably pi <2.8TZ -532 (However, methylene chloride/1,1, P2 is above the vapor-liquid equilibrium pressure and P+>Pz) and led to a conduit that satisfies pi <2.8TZ -532 (methylene chloride/1,1, P2 is above the vapor-liquid equilibrium pressure and P+>Pz) and released into the atmosphere at once through the spinneret. It is characterized by

The specific volume of the mixture of polyethylene terephthalate and methylene chloride/trichlorotrifluoroethane mixed solvent is 1.
By setting it to 0 cc/g, the solution pressure can be made sufficiently high and the dissolution of methylene chloride/1,1, polyethylene terephthalate can be made extremely fast. Furthermore, the temperature at which polymer≠dissolution is lowered, and decomposition of the polymer can be suppressed. For example, to explain using FIG. 1, a mixed system (PET 15 wt%
, MC/F-113=515), the temperature is 250℃
Specific volume], 2 cc/g shows a pressure of about 90 kg/c4G, whereas if the specific volume is 1.0 cc/g, the pressure is 150
kg/cd G in methylene chloride/1,1, the solubility is greatly improved. Also, with a specific volume of 1.2 cc/g, the temperature must be 295°C to obtain a pressure of 150 kg/cal G, but with a specific volume of 1.0 cc/g, the temperature must be 295°C.
0°C is sufficient. In addition, a mixed solvent of methylene chloride/trichlorotrifluoroethane in a weight ratio of 9/1 and ηSP/
7.0wt of polyethylene terephthalate with C of 0.73
% mixture shows 260 kg/cdG at 242°C with a specific volume of 0.93 cc/g, methylene chloride/1,1, polyethylene terephthalate dissolves very quickly. It has been found that dissolving polyethylene terephthalate in a short time can suppress the decomposition of polyethylene terephthalate and is extremely effective in increasing the strength of the fiber after spinning.

The temperature of the solution is set to 240° C. or higher and 280° C. or lower in order to finish dissolving the polyethylene terephthalate in a short time and suppress the decomposition of the polyethylene terephthalate. Temperatures exceeding 280°C are unsuitable for methylene chloride/1,1, which significantly accelerates the decomposition of polyethylene terephthalate. At temperatures below 240° C., polymer dissolution slows down, leading to polymer decomposition.

Additionally, the strength of the fibers decreases.

In the production method of the present invention, a pre-melted polymer and a heated solvent may be combined and dissolved. This method is effective for solution formation. Such a method is particularly preferred in a manufacturing method that continuously involves dissolving the polymer and spinning it.

The solution is heated at a pressure P1 (kg/crAG) and a temperature Tl ('
The relationship c) is P1≧2.8. T, -532 Preferably, from the conditions satisfying P, upper 2°8T, -471, the conduit between the orifice and the spindle is heated through the orifice to a pressure Pz (kg/cnl
G), temperature 72 ('C) satisfies Pz < 2.8 Tz 471, preferably P2 < 2.8T2 532 (however, P2 is equal to or higher than the vapor-liquid equilibrium pressure and P+>Pg), and is passed through the spinneret. If released all at once into the atmosphere, a high-strength fiber consisting of extremely thin, uniform fibrils can be obtained. PI<2.8 guns.

Release of the solution into the conduit from the range -I=F532 (kg/csA G ) results in weaker fibers of fibrils with non-uniform thickness. In addition, if the inside of the conduit is P2≧2.
In the range of 8T471 (kg/cnlG), the fibrils tend to form a film-like fiber with adhesive methylene chloride/1,1, and the strength also decreases. In extreme cases, broken and discontinuous filaments result. As mentioned above, the pressure P2 in the conduit needs to be Pt < 2.8 T2 471 preferably Pt < 2.87g 532 and must be equal to or higher than the gas-liquid equilibrium pressure. Below the vapor-liquid equilibrium pressure, the result is a low-strength fiber consisting of thick, non-uniform fibrils.

In the present invention, polyethylene terephthalate is now properly dissolved, a more uniform solution is achieved before flash spinning, and this is considered to be a necessary process for fiber formation. Optimization of phase separation conditions is thought to be the reason why ultrafine, high-strength polyethylene terephthalate fibers can now be stably produced.

〔Effect of the invention〕

According to the present invention, it has become possible to obtain a spun fiber by suppressing the decomposition of the polymer, which has made it possible to achieve high strength fibers and to use polymer raw materials with lower molecular weights. became. Furthermore, by making the solution more uniform before spinning and by strictly controlling the conditions of the spinning process, it has become possible to obtain ultra-fine fibers. From the above, it has become possible to stably obtain high-strength polyethylene terephthalate fibers consisting of ultra-fine fibrils, and the method has high utility as an industrial production method.

[Examples 1 and 2, Comparative Examples 1 to 5] Phenol/1,1,2.2-tetrachloroethane 6
Using a 0/40% by weight mixed solvent, 49.9g of polyethylene terephthalate having a viscosity number (ηSP/C) of 1.28 measured at 35°C and a concentration of 1% and methylene chloride/1,1.
2-) 504 g of a mixed solvent of dichlorol and 2,2-trifluoroethane (9/1 weight ratio) was charged into an autoclave having an internal volume of 532 cc. (Polymer concentration is 9.0%1
t%, the specific solubility is 0.96 cc/g. ) Heating the autoclave while rotating the propeller type stirrer, methylene chloride/1,1, contents at 250℃, 235kg/cJ
I put it in the state of G.

235 kg/ct with nitrogen gas inside the autoclave
Pressure methylene chloride/1,1 in A G, and while maintaining the pressure, pass the solution through a Q, 7 mmφ, 5 pal orifice with methylene chloride/1,1,8 mφ.

4Qwl conduit, 0.8mφ, hole length/hole diameter (L/
D) was released into the atmosphere at once through a spinneret of 1. The pressure and temperature inside the conduit are each 130 kg/cnlG,
The temperature was 240°C (P2 is within the appropriate conditions.p
, =130 < 2.8 x240-471 =20
1 (kg/cJG). As a result, a continuous filament with a fineness of 680 d consisting of extremely fine fibrils with a diameter of 0.5 to 4 μm was obtained. This filament had a strength of 1.0 g/d and an elongation of 57%. (Example 1
) The amount of polymer and mixed solvent charged was 51.4 g each.

Increased to 521g methylene chloride/1,1, (specific volume 0.93
cc/g) The same procedure as in Example 1 was performed except that the orifice diameter was set to 0.65 mmφ. The results are shown in Table 1. (Example 2) The amount of raw material charged was 517g (specific volume 1.
03cc/g) and similarly (polymer concentration 9.0wt%
, use the same mixed solution) Prepare the solution at 250℃, 155
kg/colG), 155 kg/ with nitrogen gas
Pressurized methylene chloride/1,1 was applied to aa G, and as a result of flash spinning in the same manner while maintaining the pressure, filaments with non-uniform fibril sizes were obtained, and the strength was 0.5 g/1.
It decreased to d. (Comparative example 1: Pressure P is not within the appropriate value. P, = 155 < 2.8 X250-5
32=168) The strength and elongation of the filament was measured using an Instron type tensile tester, and the filament was tested 300 times/
Measurements were made with 360 dragon twists applied.

Table 1 shows Comparative Examples 2 to 5, which were carried out in the same manner by changing the amounts of polymer and solvent charged, solution temperature, solution pressure, and temperature and pressure of the conduit after the orifice. The pressure and temperature of the conduit after the orifice were varied by changing the orifice hole diameter and the combination of spinnerets, and by heating the conduit section.

In Comparative Example 2, the conduit pressure was too high to form a continuous filament. (Pg = 220 > 2.8 X24
5-471 = 215) In Comparative Example 3, the solution temperature was too low, resulting in a filament consisting of non-uniform fibrils, and the tensile strength was as low as 0.4 g/d.

In Comparative Example 4, the specific volume was too large and the solution pressure was too low, so very fine fibrils were not formed and thick fibers were formed in a foamed state.

In Comparative Example 5, it is thought that the solution temperature was too high and thermal decomposition of the polymer occurred, and the filaments produced were yellowish brown colored methylene chloride/1,1 fibrils in close contact.

The following blank space [Example 3, Comparative Example 6.7] 73.6 g of the same polyethylene terephthalate used in Example 1 and methylene chloride/1,1.2-)lichloro-1,2,2-trifluoroethane (weight 492 g of a mixed solvent with a ratio of 713) was charged into an autoclave having an internal volume of 532 cc. (Polymer concentration is 13.0-t%, specific volume is 0
．． While rotating the propeller type stirrer, the autoclave was heated to methylene chloride/1,1 and the contents were brought to 268° C. and 310 kg/calG. The temperature of the solution was set to 260℃ and methylene chloride/1,1, the solution was slightly removed from the autoclave and the pressure was 270 kg.
/ cd G. temperature.

Due to the relationship between pressure and specific volume, the specific volume of the solution is 1.0 cc/g or less. Next, the inside of the autoclave was filled with 270 kg of nitrogen gas.
Pressurize methylene chloride/1,1 to /cJ, and while maintaining the pressure, pass the solution through a 0.8 φ, 51 μl orifice, and 81 sφ.

The mixture was introduced into a 40 liter conduit and discharged all at once into the atmosphere through a spinneret with a diameter of 0.9 and a hole length/hole diameter of 1. The pressure and temperature inside the conduit were 140 kg/cnlG and 251°C, respectively. (pg = 140<2.8X251-47
1.232) As a result, a continuous filament with a fineness of 790 d consisting of extremely thin fibrils was obtained. This filament had a strength of 0.9 g/d and an elongation of 62%.

After preparing a polymer solution in the same manner, (260°C.

270 kg/cnl r), shape B), 311φ
, Methylene chloride/1,1, passed through an orifice with L/D=1.
Similarly, flash spinning resulted in broken, discontinuous fibers. Pressure inside the conduit is 257 kg/cal G
, the temperature was 258°C. (Comparative example 2: Pressure P2 is not an appropriate value. Pg = 257 > 2.8 X258-4
71 = 251 ”) After preparing a polymer solution in the same manner, the solution was taken out of the autoclave and was heated to 175 kg/c at a temperature of 260°C.
dG and pressurized methylene chloride/1,1 with nitrogen' gas to 175 kg/cjG. As a result of flash spinning using the same orifice and spinning hole as in Example 2, the fibril thickness became filaments with uneven thickness, and the strength decreased to 0.4 g/d. (Comparative Example 3: Pressure P is not appropriate.

P, = 175< 2.8 X260 -53
2 = 196)

[Brief explanation of drawings]

In Figure 1, ηSP/C= 1.28 (100cc/g
) mixed system of polyethylene terephthalate and methylene chloride/trichlorotrifluoroethane (PE77771
15 wt%, MC/F-113-515) temperature,
Specific volume. It is a graph showing the relationship between pressures.

Claims (1)

[Claims] 1. A mixture of 5 to 20% by weight of polyethylene terephthalate and methylene chloride/1,1,2-trichloro-1,2,2-trifluoroethane in a weight ratio of 4:6 to 9:1. A method for producing polyethylene terephthalate fibers, which comprises extruding a solution consisting of a solvent from a spinning nozzle, instantaneously vaporizing the solvent, and forming fibers. The specific solubility of the mixture with 1,2,2-trifluoroethane is 1.0 cc/g or less, and the temperature is 240°C or higher and 280°C.
The solution is heated to a pressure of P_1 (kg/cm^
3G) and temperature T_1 (℃) satisfy P_1≧2.8T_1-532 (kg/cm^2G), through the orifice, pressure P_2 and temperature T_2 become P_2<2.8T_2-471 (kg/cm^ 2G)(
However, the method for producing polyethylene terephthalate fibers is characterized in that P_2 is higher than the vapor-liquid equilibrium pressure and P_1>P_2) is guided into a conduit and discharged into the atmosphere at once through a spinneret.