JPH0347650B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a polyethylene terephthalate solution and a method for producing the same. More specifically, polyethylene terephthalate and methylene chloride/1, which are useful for producing ultrafine polyethylene terephthalate fibers,
The present invention relates to a solution comprising 1,2-trichloro-1,2,2-trifluoroerothane (hereinafter simply referred to as "trichlorotrifluoroethane") and a mixed solvent, and a method for producing the same. [Prior Art] A method of forming fibers using a solution of a polymer and a low boiling point solvent is generally known as a dry spinning method. Among these, the so-called flash spinning method, in which a solution consisting of a low boiling point solvent and a polymer is extruded from a spinning nozzle to instantaneously vaporize the solvent and form fibers, was described in Japanese Patent Publication No. 40-28125 and Japanese Patent Publication No. 41-6215. The preparation of polyethylene terephthalate solutions is also described. [Problems to be solved by the invention] When producing ultra-fine, high-strength polyethylene terephthalate fibers using the polyethylene terephthalate solution described in Japanese Patent Publication No. 40-28125 and Japanese Patent Publication No. 41-6215, the resulting fibers have low strength. However, depending on the case, the fibers may not be sufficiently thin. At present, a polyethylene terephthalate solution and its manufacturing method that are suitable for producing ultra-fine polyethylene terephthalate fibers with satisfactory strength by flash spinning have not been sufficiently established. In particular, an object of the present invention is to provide a polyethylene terephthalate solution and a method for producing the same, which are suitable for producing ultrafine, high-strength polyethylene terephthalate fibers by a flash spinning method. [Means for Solving the Problems] The present inventors have continued intensive research on a polyethylene terephthalate solution suitable for obtaining ultrafine, high-strength polyethylene terephthalate fibers by a flash spinning method. As a result, solutions prepared using specific solvents are extremely useful;
and that its solution can be prepared only under certain limited conditions. The polyethylene terephthalate solution of the present invention is
It is characterized by consisting of polyethylene terephthalate and a methylene chloride/trichlorotrifluoroethane mixed solvent. The polyethylene terephthalate used in the present invention is a mixed solvent of phenol/1,1,2,2-tetrachloroethane 60/40% by weight, and has an ηsp/c of 0.6 to 4.5 when measured at 35°C and a concentration of 1%. from low-grade fiber grades to high viscosity resins made by solid state polymerization. Other copolymerized components in the main chain, such as isophthalic acid, phthalic acid,
Glutaric acid, adipic acid, etc., and those containing up to 15 mol% of diethylene glycol, propylene glycol, 1,4-butanediol, 2,2-bis(4-hydroxyethoxyphenyl)propane, etc. as glycol components are also equivalent. It can be used for. The concentration of polyethylene terephthalate in the solution of the present invention varies depending on the degree of polymerization of the polymer, the composition of the mixed solvent, etc., and is not particularly limited, but it is usually preferably 5 to 20% by weight. The reason for this is that when this solution is used as a raw material for flash spinning, if it is less than 5% by weight, it will be difficult to manufacture continuous filaments;
This is because if it exceeds 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 to prepare the solution of 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 when used for spinning, etc. Preferably, the methylene/trichlorotrifluoroethane composition is in a weight ratio of 4:6 to 9:1. If the composition of trichlorotrifluoroethane exceeds 60% by weight, it will be difficult to dissolve polyethylene terephthalate and a uniform solution will not be formed. Furthermore, if the amount is less than 10% by weight, perhaps because the temperature of the vaporized gas of the mixed solvent becomes too low, the fibers obtained by flash spinning using this solution will not be sufficiently drawn, making it difficult to obtain high-strength fibers. The above-mentioned polyethylene terephthalate solution is made by heating the mixture of polyethylene terephthalate and methylene chloride/trichlorotrifluoroethane mixed solvent to 1.2 cc/g or less and heating it to at least 220°C or higher, preferably 250°C or higher to form a solution. It is manufactured by a method characterized by: In the production method of the present invention, the specific volume of the mixture of polyethylene terephthalate and methylene chloride/trichlorotrifluoroethane mixed solvent is 1.2 cc/g.
The following shall apply. However, when the specific volume is less than 0.9 cc/g, although a solution is formed, the system pressure increases significantly and equipment problems occur, so care must be taken when using it. Furthermore, if the specific volume exceeds 1.2 cc/g, a solution will not be formed unless the system temperature is raised to 280° C. or higher, which is undesirable as thermal decomposition of polyethylene terephthalate or thermal decomposition of the solvent may occur. In the production method of the present invention, a mixture of polyethylene terephthalate and a methylene chloride/trichlorotrifluoroethane mixed solvent is heated at a temperature of at least 220°C.
As mentioned above, a solution is preferably formed by heating to 250°C or higher, but if the heating temperature is lower than 220°C, a very long time is required to form the solution, and if the specific volume is large, it may not dissolve. At around 220°C, even if the specific volume is large, it will melt if it takes a long time, but preferably 250°C, which is close to the melting point of polyethylene terephthalate.
It can be easily dissolved in a short time by heating to a temperature above 0.degree. In the production method of the present invention, a pre-dissolved polymer and a heated solvent may be combined and dissolved. This method is effective for solution formation. Particularly, such a method is effective in a spinning method that involves continuous steps from melting to spinning. Polyethylene terephthalate and methylene chloride/
When a solution is formed from a mixture with a trichlorotrifluoroethane mixed solvent, it is unclear how the specific volume of the mixture and heating temperature interact, but the pressure change in the system as the temperature rises It is assumed that the smaller the volume, the higher the pressure itself at a certain temperature, and that it may or may not dissolve depending on the balance between the pressure and temperature of the system. The relationship between pressure and temperature is unknown, but when the specific volume of the mixture is 1.2 cc/g or less and it is heated to 220°C or higher, preferably 250°C or higher, dissolution occurs under the pressure indicated by the mixture of each specific volume. and a solution is formed. [Effects of the Invention] The solution of the present invention is suitable as a spinning dope for producing polyethylene terephthalate fibers by the flash spinning method, and can be used to produce continuous fibers consisting of extremely thin fibrils with satisfactory strength. You can get filament. Next, examples will be shown, but the examples do not limit the present invention in any way. [Example] Example 1 Polyethylene with a viscosity number (ηsp/c) of 1.28 measured at 1% concentration at 35°C using a 60/40 weight % mixed solvent of phenol/1,1,2,2-tetrachloroethane Terephthalate 19g and methylene chloride/1,
Mixed solvent of 1,2-trichloro-1,2,2-trifluoroethane (weight ratio = 50/50% by weight) 192
g was placed in a windowed autoclave with an internal volume of 200 ml and a pressure resistance of 300 Kg/cm ² G. The polymer concentration at this time was 9
The specific volume in weight percent was 0.948 cc/g. While rotating a propeller-type stirrer, the temperature of the contents was heated from room temperature to 250°C in about 30 minutes, and the temperature was maintained to proceed with dissolution. As a result of observation through a window attached to the autoclave, a uniform solution was formed in about 8 minutes after reaching 250°C. At this time, the temperature and pressure inside the autoclave were 251° C. and 216 Kg/cm ² G, respectively. Examples 2 to 6, Comparative Example 1 Using the same polyethylene terephthalate, mixed solvent, and equipment as in Example 1, the same operations as in Example 1 were performed for various specific volumes at a polymer concentration of 9% by weight. We obtained the results shown below.

[Table] *The internal pressure of the autoclave decreases as the dissolution progresses, so when the dissolution is completed,
For those that did not dissolve, the pressure was set at the time when 30 minutes had passed after reaching 250°C.
Examples 7 to 9, Comparative Examples 2 and 3 Using the same polyethylene terephthalate and equipment as in Example 1, the mixed solvent composition was varied at a polyethylene terephthalate concentration of 9% by weight and a specific volume of 1.0 cc/g. Similar operations were performed to obtain the results shown in Table.

[Table] Example 10 Polyethylene terephthalate and a mixed solvent similar to those in Example 1 were charged into an autoclave having an internal volume of 500 ml at 49 g and 501 g, respectively. (The polymer concentration was 8.9% by weight, and the specific volume was 1.0 cc/g.) The autoclave was heated while rotating a propeller-type stirrer to prepare a solution at 255° C. and 192 Kg/cm ² G. The internal pressure of the autoclave was increased to 200Kg/cm ² G with nitrogen gas, and while maintaining that pressure, the solution was heated to 0.9mmφ.
The mixture was passed through a 5 mm orifice, led to 8 mmφ and 40 mmφ conduits, and discharged into the atmosphere through a 1.0φ spinneret (L/D=1). As a result, the fineness is made up of extremely fine fibrils with a diameter of 1 to 4μ.
A continuous filament of 710d was obtained. The filament had a strength of 1.1 g/d and an elongation of 48%. Examples 11 to 16 Using the same polyethylene terephthalate and mixed solvent as in Example 1, using the same apparatus as in Example 10, and varying the polyethylene terephthalate concentration at a specific volume of 1.0 cc/g, the same operation as in Example 10 was carried out. The results shown in Table 1 were obtained.

[Table] Examples 17 to 19, Comparative Examples 4 and 5 Using the same polyethylene terephthalate as in Example 1, various mixed solvent compositions were used, and Example 10 was used at a polymer concentration of 9% by weight and a specific volume of 1.0cc/g. The same procedure as in Example 10 was carried out, except that the autoclave internal pressure was increased and maintained at 220 Kg/cm ² G using nitrogen gas immediately before spinning, and the results shown in Table 1 were obtained.

【table】

Claims (1)

[Scope of Claims] 1. A polyethylene terephthalate solution comprising polyethylene terephthalate and a mixed solvent of methylene chloride/1,1,2-trichloro-1,2,2-trifluoroethane. 2. The polyethylene terephthalate solution according to claim 1, wherein the polyethylene terephthalate concentration in the solution is 5 to 20% by weight. 3 Methylene chloride/1,1,2-trichloro-
The polyethylene terephthalate solution according to claim 1, wherein the composition of the 1,2,2-trifluoroethane mixed solvent is 4:6 to 9:1 by weight. 4 The specific volume of the mixture of polyethylene terephthalate and methylene chloride/1,1,2-trichloro-1,2,2-trifluoroethane mixed solvent is 1.2
cc/g or less and heating to at least 220°C or higher to form a solution. 5. The manufacturing method according to claim 4, wherein the concentration of polyethylene terephthalate in the solution is 5 to 20% by weight. 6 Methylene chloride/1,1,2-trichloro-
5. The method according to claim 4, wherein the composition of the 1,2,2-trifluoroethane mixed solvent is 4:6 to 9:1 by weight.