KR100609553B1 - Method for preparing polyethylenenaphthalate - Google Patents

Abstract

The present invention relates to a method for producing polyethylene naphthalate, and more particularly, melt polymerization of an esterification reaction product of naphthalene dicarboxylate and diol to obtain polyethylene naphthalate prepolymer, followed by solid phase polymerization to obtain high viscosity polyethylene naphthalate. In preparing a polymer, the esterification product is melt polymerized in the presence of 10 to 120 ppm Ti catalyst based on the weight of naphthalene dicarboxylate to obtain a polyethylenenaphthalate prepolymer chip, and then the prepolymer chip is 70 to 100 ° C. It is related to the method for producing polyethylene naphthalate, characterized in that it is first dried for 4 hours or more by using hot air and then subjected to solid phase polymerization for 2 hours or more at 100 to 190 ° C. under an inert gas or vacuum atmosphere. According to this, the solidification time can be shortened. It is possible to obtain a polyethylene naphthalate polymer of uniform physical properties by minimizing fusion, and the polyethylene naphthalate prepared as described above is high in radioactivity because of the low content of the polycondensation catalyst that causes the generation of deterioration during spinning Useful for the production of industrial polyethylene naphthalate fibers.

Polyethylene naphthalate, Condensation polymerization, Solid state polymerization, Fusion, Ti catalyst, Drying, Radioactive

Description

Method for producing polyethylene naphthalate {METHOD FOR PREPARING POLYETHYLENENAPHTHALATE}

The present invention relates to a method for producing polyethylene naphthalate, and more particularly, to minimize the amount of the polycondensation catalyst acting as a thermal decay during spinning, and to minimize the size of the prepolymer chip obtained from melt polymerization. The present invention relates to a method for producing polyethylene naphthalate, characterized in that the prepolymer chip is dried in two steps before solid phase polymerization in order to shorten solid phase polymerization time and reduce fusion.

Polyethylene terephthalate (hereinafter referred to as PET) grew rapidly around the world in 1953 when it was first commercialized for textile use in the United States. PET has good mechanical properties, heat resistance, chemical stability, etc. and is used in many fields. In particular, PET has a very large demand in fields such as fibers, biaxially oriented films, sheets, and beverage containers. However, these PET resins are recently being replaced by polyethylene naphthalate (hereinafter referred to as PEN) that can compensate for such demands as the product weight, high performance, high heat resistance, etc. are required.

PEN adopts a rigid naphthalene ring structure instead of the benzene ring of PET, which is very similar in structure to existing PET, but its mechanical properties such as glass transition temperature, heat resistance, tensile strength and creep resistance are higher than those of PET. It is very excellent, and gas barrier property is more than 5 times better than PET, so it is actively used for high strength thin film, barrier containers, heat-resistant containers, and the like. These properties make PEN particularly suitable as a reinforcing material for belts and hoses that require high strength, high heat resistance, chemical resistance, etc., and can exhibit optimum physical properties when applied to tire cords. PET, nylon, rayon, and aramid fibers are mainly used as a conventional tire cord material. However, rayon and aramid fibers cause environmental problems and require high manufacturing costs. There was a problem with strength and form stability. On the other hand, PEN is expected to be able to replace many industrial materials starting from the existing high performance racing tire cord material because of its high strength, heat resistance and low heat shrinkage.

Although PEN's manufacturing has a lot in common with PET manufacturing technology, it is certain that PEN's manufacturing will stand out in many industries as a substitute for PET, but so far there is a lack of general basic research on PEN's synthesis technology and physical properties. It is true.

PEN has a high melt viscosity and viscosity due to the rigid molecular chain in the main chain as described above. Therefore, it has been pointed out that it is difficult to remove unreacted materials and gases in the polymer during the polycondensation reaction, so that fusion occurs during high-phase polymerization and takes a lot of time. In addition, in the PEN fiber manufacturing process, high temperature spinning should be performed during spinning, and a large amount of heat depletion occurs in the polymer detention, causing trimming and pin yarn, which causes many problems in workability and productivity.

Looking at an example of a conventional PEN production method, US Pat. No. 4,799,772 discloses that PEN pellets are coated with alkylene carbonate (alkylene carbonnate) to crystallize at lower temperatures faster than uncoated PEN pellets. It states that fusion can be reduced during solid state polymerization. U.S. Patent No. 4,963,644 relates to a solid phase polymerization of an amorphous PEN prepolymer, wherein the prepolymer is heated in one-step in an inert gas or vacuum at 80-140 ° C. for 15 minutes to 10 hours. Next, the crystallization is performed at 150 to 260 ° C. for 1 minute to 4 hours, and then a solid phase polymerization is performed at 240 to 260 ° C. to prepare a high viscosity PEN polymer. U.S. Patent No. 5,294,695 relates to a method for producing high viscosity PEN by reacting naphthalene dicarboxylate and ethylene glycol esterification product in two steps, one step is 500 to 30 Torr, and the second step is 10 to 0.1 Melt viscosity of the polycondensation polymer was 0.4 to 1.0 dl / using one of the metal compounds containing Sb, Li, Ge, Ti, Zn, Pb, Fe, Mn, Mg, Al or Ca as the polycondensation catalyst under Torr pressure A method of performing condensation polymerization to fall within the range of g is disclosed. However, none of these methods satisfactorily solve the above-mentioned problems associated with spinning in the solid-phase polymerization and fiber manufacturing process to obtain high viscosity PEN.

The present invention is to solve the problems of the prior art as described above, fins and trimming during spinning by limiting the type and amount of the polycondensation catalyst used in the melt polymerization step of the esterification reaction product of naphthalene dicarboxylate and diol By minimizing the amount of deterioration in the polymer detention, which is the cause of the polymer, minimizing the size of the prepolymer chip obtained from the melt polymerization, and drying the chip in two stages, the fusion occurrence and polymerization time in the subsequent solid phase polymerization step are reduced. An object of the present invention is to provide a method for producing polyethylenenaphthalate which can be minimized.

That is, in the present invention, a polyethylene naphthalate prepolymer is obtained by melt-polymerizing an esterification reaction product of naphthalene dicarboxylate and diol and then subjected to solid phase polymerization to prepare a high viscosity polyethylene naphthalate polymer. Melt polymerization was carried out in the presence of 10 to 120 ppm Ti catalyst to the weight of naphthalene dicarboxylate to obtain a polyethylene naphthalate prepolymer chip, and then the prepolymer chip was first dried for 4 hours or more using hot air at 70 to 100 ° C. Provided is a method for producing polyethylene naphthalate, characterized in that the solid-phase polymerization after secondary drying at 100 ~ 190 ℃ for at least 4 hours in an inert gas or vacuum atmosphere.

Hereinafter, the present invention will be described in more detail.                     

The method for producing polyethylene naphthalate of the present invention preferably comprises the following steps:

i) polyethylene naphthalate having a melt viscosity of 0.2-0.6 dl / g by melt-polymerizing the naphthalene dicarboxylate and diol esterification reaction product in the presence of 10-120 ppm Ti catalyst by weight of the naphthalene dicarboxylate Obtaining a prepolymer chip;

ii) first drying the prepolymer chip by using hot air of 100 ° C. or lower for at least 4 hours, and then second drying the prepolymer chip at 100 ° C. or higher for at least 4 hours under an inert gas or vacuum atmosphere; And

iii) crystallizing the dried prepolymer chip by heat treatment, followed by solid phase polymerization to obtain a high viscosity polyethylenenaphthalate chip having a melt viscosity of at least 0.6 dl / g.

In the present invention, the esterification catalyst of naphthalene dicarboxylate (hereinafter referred to as NDC) and diol uses 30 ppm or more of esterification catalyst with respect to the NDC weight, and as the catalyst, Mn, K, Li, Ca, Mg, At least one of Zn, Al and Cd compounds can be used.

Since the polymerization of polyethylene naphthalate (hereinafter referred to as PEN) is carried out at a high temperature, in the present invention, a thermal stabilizer is preferably added to the esterification reaction product prior to melt polymerization. The ratio of esterification catalyst to thermal stabilizer is preferably maintained at a level of 1: 0.3 to 1: 2.0. When the ratio of esterification catalyst to thermal stabilizer is outside of the above range, it is caused by deterioration in the subsequent solid phase polymerization step. This is because a change in color tone of the polymer occurs badly. The kind of the heat stabilizer is not particularly limited as long as the object of the present invention is not impaired. Preferably, a phosphate heat stabilizer is used.

In general, one of the metal compounds containing Sb, Li, Ge, Ti, Zn, Pb, Fe, Mn, Mg, Al, Ca, etc. has been used as a catalyst for condensation polymerization of NDC and diol esterification products. The main component of the thermally decomposed polymer in the spinneret during the manufacture of PEN fibers is the polycondensation catalyst contained in the PEN polymer, and the amount of deterioration and the number of removals (times / day) vary depending on the type of catalyst used and the amount used. It is known. In addition, Sb catalysts are inexpensive and are the preferred catalyst in the art, but are not suitable for medical use due to precipitation of toxic substances in condensation polymerization reactions using Sb catalysts, and cause water pollution. In the present invention, only a Ti catalyst is used as a condensation polymerization catalyst in a small amount of only 10 to 120 ppm relative to the weight of NDC used in the esterification reaction, so that thermal degeneration is generated in the polymer mold which causes pin yarn and trimming during spinning in the PEN fiber manufacturing process. Could be minimized and further avoided the generation of toxic byproducts.

In the method of the present invention, the melt polymerization using the Ti catalyst is performed at 240 to 300 ° C. for 1 to 4 hours, and the melt viscosity of the PEN prepolymer obtained therefrom is adjusted to fall in the range of 0.2 to 0.6 dl / g. If the melt viscosity is less than 0.2 it is impossible to cut during the discharge of the melt, if it exceeds 0.6 it is difficult to discharge because of the high viscosity, the discharge time is long and the deterioration occurs.

The PEN prepolymer thus obtained preferably contains at least 90 mol% NDC units, and after cooling is cut into chips of a predetermined size, in the present invention, it is easy to remove unreacted substances and gases in the polymer in the subsequent solid phase polymerization step. In order to increase the specific surface area to shorten the solid-state polymerization time, the size of the prepolymer chip is 1.5 mm x 1.5 mm x 1.5 mm (long flat x single flat x length) or less, preferably 0.5 mm x 0.5 mm x 0.5 It is limited to mm to 1.5 mm x 1.5 mm x 1.5 mm (long flat x flat flat x length).

In addition, according to the present invention it is possible to effectively prevent the fusion in the solid phase polymerization step by performing the drying of the prepolymer chip divided into two stages. That is, conventionally, one step drying was generally performed in a vacuum atmosphere. Since the purpose is to simultaneously remove the surface of the chip and the moisture at the same time, it is easy to cause fusion during the drying process, but in the present invention, the drying step is performed in two steps. First, hot air and low temperature drying was performed to remove moisture from the surface of the chip first, and secondly, fusion was reduced by reliably removing moisture from the inside of the chip. In the present invention, the primary drying is performed at 100 ° C. or lower, preferably at 70 to 100 ° C. for 4 hours or more using hot air, and the secondary drying is at least 100 ° C. or higher, preferably 100 to 190 under an inert gas or vacuum atmosphere. At 4 ° C. for at least 4 hours. The reason for the difference between the primary drying temperature and the secondary drying temperature is that crystallization of the prepolymer occurs when the primary drying temperature exceeds 100 ° C., whereas complete drying at temperatures below 100 ° C. occurs because the secondary drying is carried out in a vacuum atmosphere. Because it is not done. In addition to the two-stage drying as described above, the addition of the prepolymer chip at 90% or less of the solid-state polymerizer capacity also helps to prevent fusion.

The dried prepolymer chip is a high viscosity PEN polymer having a melt viscosity of 0.6 dl / g or more through sequential crystallization, preliminary solid state polymerization and solid state polymerization under normal conditions.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

<Example 1>

Naphthalene dicarboxylate (hereinafter referred to as NDC) and ethylene glycol were mixed at a ratio of 1: 2.1, and then sufficiently dissolved at 190 ° C. for about 4 hours, and then esterification was started. At this time, Mn was used at a concentration of 65 ppm with respect to the NDC weight as the esterification catalyst, and reacted at 190 ° C. for 3 hours. After completion of the esterification reaction, 47 ppm of trimethylene phosphate was added to the NDC weight as a heat stabilizer, and 50 ppm of Ti catalyst was added to the NDC weight as the polycondensation catalyst, followed by melt polymerization at 290 ° C. for 60 minutes. . The prepolymer obtained therefrom is cut into chips of 1.5 mm x 1.5 mm x 1.5 mm (long flat x single flat x length) after cooling, and the first drying is carried out at 80 ° C. for 4 hours using hot air, and the second drying is carried out. After 6 hours at 120 ° C. under vacuum conditions of 2 Torr or less, the crystallization was carried out sequentially at 200 ° C. for 4 hours, and the preliminary solid phase polymerization was carried out sequentially at 245 ° C. for 6 hours. Subsequently, solid phase polymerization was performed at 250 ° C. for 17 hours to obtain a high viscosity PEN polymer chip.

<Comparative Example 1-2>

A high viscosity PEN polymer chip was prepared in the same manner as in Example 1, except that 170 ppm of the Sb catalyst was used for the NDC weight or 200 ppm for the NDC weight, instead of the Ti catalyst as the polycondensation catalyst. It was. Polymerization conditions and physical properties of the high viscosity PEN polymer chip prepared in Example 1 and Comparative Examples 1 and 2 are shown in Table 1 below.

Example One Comparative Example 1 Comparative Example 2 Polycondensation catalyst Ti catalyst Sb-based catalyst Zn-based catalyst Prepolymer Viscosity 0.3 0.3 0.3 Final polymer viscosity 0.93 0.93 0.93 Melt polymerization time 60 minutes 130 minutes 150 minutes Polycondensation Catalyst Type Ti Sb Zn  Condensation polymerization catalyst usage (ppm) 50 170 200 To the heat cargo during spinning Number of times refused by ^One) 0.5 (times / day) 4 (times / day) 5 (times / day)

1) Measure the number of trimmings during melt spinning during the day under mild conditions

<Comparative Example 3-4>

A high-viscosity PEN polymer chip was prepared in the same manner as in Example 1, except that the size of the chip was 2mm × 2mm × 2mm (long flat × flat × length) or 3mm × 3mm × 3mm (long flat × flat × length). . The total solid phase polymerization time taken in each case is shown in Table 2 below in comparison with the case of Example 1.

Example 1 Comparative Example 3 Comparative Example 4 Chip size 1.5 × 1.5 × 1.5 2 × 2 × 2 3 × 3 × 3 Solid State Polymerization Time (hr) 27 35 43

Comparative Example 5

The drying of the prepolymer chip was carried out except that one-step drying was performed at 130 ° C. for 8 hours, crystallization was performed at 200 ° C. for 2 hours, and solid phase polymerization was performed at 250 ° C. for 29 hours. A high viscosity PEN polymer chip was prepared in the same manner as in Example 1. Random extraction of a plurality of chips out of the total polymer chips produced, the number of sticking (sticking) among them It was measured and shown in Table 3 below compared with the case of the polymer chip according to Example 1.

Example 1 Comparative Example 5 In polymer chips after solid state polymerization Fusion Content  0.01%    20%

As described in detail above, according to the polyethylene naphthalate production method of the present invention can shorten the solid-state polymerization time and minimize the fusion to obtain a polyethylene naphthalate polymer of uniform physical properties, prepared by the method of the present invention Polyethylene naphthalate is useful for the production of high quality industrial polyethylene naphthalate fibers because of its low spinning property because of the low content of polycondensation catalysts that cause the generation of deterioration during spinning.

Claims (3)

The esterification product of naphthalene dicarboxylate and diol is melt polymerized to obtain polyethylene naphthalate prepolymer, and then subjected to solid phase polymerization to prepare a high viscosity polyethylene naphthalate polymer. Melt-polymerization in the presence of 10 to 120 ppm Ti catalyst by weight to obtain a polyethylene naphthalate prepolymer chip, and then the prepolymer chip was first dried for 4 hours or more using hot air at 70 to 100 ° C., followed by inert gas or vacuum atmosphere. Method for producing polyethylene naphthalate, characterized in that the solid phase polymerization after secondary drying at 100 ~ 190 ℃ for 4 hours or more. The method of claim 1, wherein the polyethylene naphthalate prepolymer has a melt viscosity of 0.2 to 0.6 dl / g. The method of claim 1, wherein the size of the polyethylene naphthalate prepolymer chip is 0.5mm × 0.5mm × 0.5mm to 1.5mm × 1.5mm × 1.5mm (long flat × flat × length). .