JPH024692B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing polyethylene terephthalate fiber. More specifically, a solution consisting of polyethylene terephthalate and a mixed solvent of methylene chloride/1,1,2-trichloro-1,2,2-trifluoroethane (hereinafter simply referred to as "trichlorotrifluoroethane") is used to form ultrafine particles. The present invention relates to a method for producing polyethylene terephthalate fibers. <Prior art> As a method for producing ultrafine fibers, a so-called melt blowing method is used in which a polymer melt is extruded from a spinning nozzle and then pulled and thinned by a heated fluid jet;
A method of removing some polymer components (for example, sea components in the fiber cross-sectional structure) with a solvent after spinning a fiber (which has an island structure); There is a so-called flash spinning method in which a solution of a low boiling point solvent and a polymer is extruded from a spinning nozzle and the solvent is instantaneously vaporized as described in . <Problems to be Solved by the Invention> When producing ultra-fine polyethylene terephthalate fibers using these methods, the melt-blowing method does yield extremely thin fibers, but the fibers are thinned in the polymer melt state. Therefore, there is a problem that the stretching orientation and crystallization of the fibers are insufficient, and the strength of the obtained fibers is extremely low. Also,
The method of removing some component polymers of a multicomponent filament requires a troublesome step of eluting the polymers. Special Publication No. 40-28125 and Special Publication No.
In the method described in No. 41-6215, thin fibers with satisfactory strength are obtained from polyethylene, but only extremely weak fibers are obtained from polyethylene terephthalate. 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 the 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. the result,
We have 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, the present invention provides a method for producing polyethylene terephthalate fibers, which comprises extruding a solution consisting of polyethylene terephthalate and a mixed solvent of methylene chloride/trichlorotrifluoroethane through a spinning nozzle, instantaneously vaporizing the solvent, and forming fibers. It is. The polyethylene terephthalate used in the present invention is a mixed solvent of 60/40% by weight of phenol/1,1,2,2-tetrachloroethane, and has an ηSP/C of 0.6 to 0.6 when measured at a concentration of 1% at 35°C. They range from fiber grades of about 4.5 to high viscosity resins made by solid state polymerization. Other copolymerized components in the main chain,
For example, acid components include isophthalic acid, phthalic acid, glutaric acid, adipic acid, etc.; glycol components include diethylene glycol, propylene glycol, 1,4-butanediol, 2,2-bis(4-hydroxyethoxyphenyl)propane, etc. Those containing up to 15 mol% can equally be used. Although 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., 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 manufacture a continuous filament, and at a high concentration of more than 20% by weight, the filament becomes spongy or foamed, not ultrafine fibers, and has extremely low strength. 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. 4:6~9:1
It is preferable that 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 drawn sufficiently, probably because the vaporized gas temperature of the mixed solvent becomes too low. It is difficult to become a fiber with high strength. The temperature of the solution used in the present invention is not necessarily limited depending on the composition of the mixed solvent, polymer concentration, etc., but usually
A range of 220°C to 280°C is preferred. The temperature of the solution is
If the temperature exceeds 280°C, thermal deterioration of the polymer tends to occur. Furthermore, if the temperature is lower than 220°C, the resulting fibers cool and solidify quickly, and the fibers cannot be drawn sufficiently, resulting in a failure to exhibit high strength or difficulty in forming fibers. The pressure of the solution is not necessarily limited depending on the composition of the mixed solvent, polymer concentration, temperature of the solution, etc.
Generally, 80 kg/cm ² G or more is preferable. If it is less than 80Kg/cm ² G, it may be difficult to obtain high-strength fibers due to low fiber orientation, or the solution may not be discharged uniformly, or the form of the generated fibers may be discontinuous due to fiber breakage from foamed filament. The fibers become non-uniform, even fibrillar fibers. The most important feature of the present invention is that ultrafine, high-strength fibers are produced using a solution of polyethylene terephthalate in a methylene chloride/trichlorotrifluoroethane mixed solvent. There is. First, in order to sufficiently enhance the ability to form ultrafine fibers, sufficient dissolution must be achieved. This is the first reason why a mixed solvent of methylene chloride and trichlorotrifluoroethane is necessary. Next, in the present invention,
The stretching and orientation of the fibers is achieved by the expansion force associated with the vaporization of the solvent, and the strength of the fibers is approximately determined by whether the fibers are sufficiently stretched and oriented.
In the flash spinning method, phase separation of the solution occurs within an extremely short time of 0.1 seconds or less, the polymer concentration increases as the solvent is eliminated, and finally the solvent is almost completely eliminated and the polymer is formed. precipitation occurs. Therefore, it is necessary to form fibers and simultaneously apply sufficient stretching within this extremely short period of time. In addition, it is desirable that crystallization also occur. Although it is presumed, the initial fibrous material is formed from a concentrated solution containing a solvent and has the fluidity and fiber shape retention necessary for stretching to a certain extent, and then further loss of fluidity occurs due to desolvation and cooling. . It is thought that the degree of stretching orientation is determined by the balance between this fluidity (which changes due to solvent removal and cooling) and the expansion force accompanying vaporization of the solvent. That is, it is important whether the fibrous material initially formed within an extremely short period of time has fluidity that allows it to be easily drawn and oriented, and whether it is under the conditions necessary for crystallization. In other words, the affinity between the solvent and polymer, which is thought to control fluidity,
The ejection power of the solvent gas and the vaporization temperature of the solvent gas play important roles. It seems that if the affinity between the solvent and the polymer is high, phase separation of the initial solution will not occur in a very short time, and the ultrafine fibers of the present invention will not be produced. Considering the process of forming ultrafine fibers as described above, it is thought that appropriate values for the solvent type, solvent composition, polymer concentration, solution temperature, and solution pressure are determined. <Effects of the Invention> According to the present invention, highly strong polyethylene terephthalate fibers made of ultrafine fibrillar fibers can be obtained at high speed, which is very advantageous industrially. Next, examples will be shown. <Example> Example 1 Polyethylene with a viscosity number (ηSP/C) of 1.28 measured at 1% concentration at 35°C using a 60/40 wt% mixed solvent of phenol/1,1,2,2-tetrachloroethane Terephthalate 49g and methylene chloride/1,
501 g of 1,2-trichloro-1,2,2-trifluoroethane (weight ratio 50/50) mixed solvent was charged into an autoclave with an internal volume of 550 ml, heated, and 255
A solution was prepared at 192 Kg/cm ² G at ℃. While maintaining the autoclave internal pressure at 200Kg/cm ² G with nitrogen gas,
The solution was introduced into a 8mmφ, 40mm conduit through a 0.9mmφ, 5mm orifice, and was introduced into a 1.0mmφ (L/D=
1) was released all at once into the atmosphere through the spinneret.
As a result, a continuous filament with a fineness of 710 d consisting of extremely fine fibrils with a diameter of 1 to 4 μm was obtained. The strength of this filament is 1.1g/d,
The elongation was 48%. Examples 2 to 7 Using the same polyethylene terephthalate and mixed solvent as in Example 1, and using the same apparatus as in Example 1, the same operations as in Example 1 were carried out while varying the polyethylene terephthalate concentration. We obtained the results shown below.

[Table] Examples 8 to 10, Comparative Examples 3 to 5 Example 1 was prepared by using the same polyethylene terephthalate as in Example 1, setting the polyethylene terephthalate concentration to 9% by weight, and varying the mixed solvent composition.
Using the same equipment and performing the same operations <Table-
The results shown in > were obtained.

[Table] Examples 11 to 14, Comparative Examples 6 to 7 Using the same polyethylene terephthalate and mixed solvent as in Example 1, the polyethylene terephthalate concentration was adjusted to 9% by weight, and a solution was prepared by heating to 255°C. Using the same apparatus and operation as in Example 1, the results shown in Table 1 were obtained by varying the temperature of the sample by cooling and heating.

[Table] Using the same polyethylene terephthalate and mixed solvent as in Examples 15 to 17, Comparative Example 8, and Example 1, the polyethylene terephthalate concentration was 9% by weight, and the temperature of the solution was 255°C.
The pressure of the solution was varied variously, and the inside of the autoclave was pressurized with nitrogen gas to a pressure approximately 5 kg/cm ² G higher than the pressure of the solution using the apparatus of Example 1, and then the solution was released into the atmosphere. The following results were obtained.

【table】

Claims (1)

[Claims] 1. A solution consisting of polyethylene terephthalate and a mixed solvent of methylene chloride/1,1,2-trichloro-1,2,2-trifluoroethane is extruded from a spinning nozzle, and the solvent is instantaneously vaporized, A method for producing polyethylene terephthalate fiber, the method comprising forming a fiber. 2. The method according to claim 1, wherein the concentration of polyethylene terephthalate in the solution is 5 to 20% by weight. 3 Methylene chloride/1,1,2-trichloro-
2. The method according to claim 1, wherein the composition of the 1,2,2-trifluoroethane mixed solvent is in a weight ratio of 4:6 to 9:1. 4. The method according to claim 1, wherein the temperature of the solution is in the range of 220°C to 280°C. 5. The method according to claim 1, wherein the pressure of the solution is 80 kg/cm ² G or more.