KR20020055840A - Method for preparing highly polymerized polyethylene naphthalate - Google Patents

Abstract

PURPOSE: Provided is a method for preparing a polyethylene having high degree of polymerization which inhibits a fusion phenomenon in solid state polymerization. CONSTITUTION: The method comprises the steps of: (i) producing PEN having medium molecular weight by melt polymerization; (ii) adding 0.005-0.05 wt% of at least one of fine powder selected from the group consisting of oxides, sulfate and chloride of group II metal to the molten PEN during or after the melt polymerization, and homogeneously mixing the PEN with the powder; and (iii) solid state polymerizing the molten polymer containing the powder.

Description

Method for preparing highly polymerized polyethylene naphthalate

The present invention relates to a method for producing a high degree of polymerization of polyethylene naphthalate (PEN), and more particularly, (i) preparing a PEN having a moderate molecular weight by melt polymerization; (ii) adding 0.005 to 0.05% by weight of one or more fine powders selected from the group consisting of oxides, sulfates and chlorides of Group II metals to the PEN in the molten state during or after the melt polymerization step and mixing them uniformly. step; And (iii) solid-phase polymerization of the molten polymer to which the fine powder is added.

Polyethylene naphthalate (PEN) has a glass transition point of 125 ° C and a melting point of 268 ° C, which is higher than the polyethylene terephthalate (PET) by about 50 ° C and a melting point of about 10 ° C or more. It is very useful as a raw material for molded products.

PEN first transesterifies naphthalenedicarboxylate and ethylene glycol to form an ethylene naphthalate monomer or prepolymer, followed by melt polymerization to increase the degree of polymerization by vacuum in the presence of a suitable catalyst at a temperature above the melting point. After preparing a polymer having a molecular weight of about a degree, a high-polymerization PEN is prepared by solid-phase polymerization, in which an inert gas (N ₂ ) is injected into the reactor at a temperature below the melting point or subjected to high vacuum to further increase the degree of polymerization of the molten polymer. It is possible to do

When PEN is produced by melt polymerization, PEN has a high viscosity in a molten state, and thus it is difficult to proceed with polymerization while stirring, and it takes a long time to discharge the molten polymer after completion of polymerization. Therefore, it is difficult to obtain a degree of polymerization or more by the melt polymerization method, and uniformity is not sufficient in the degree of polymerization and the like.

On the other hand, since the polymerization is carried out at a relatively low temperature, the solid phase polymerization method has considerably fewer pyrolysis reactions as side reactions and only the polymerization reaction proceeds, whereby a very high degree of polymerization PEN can be easily obtained. However, this solid phase polymerization method has the disadvantage that (i) the reaction is performed at a low temperature, the polymerization reaction rate is slow, and (ii) fusion between polymers occurs frequently.

In other words, in order to polymerize PEN into a solid phase, it is necessary to maintain the reaction temperature at least 240 ° C. or higher and at most 260 ° C. or lower. If solid phase polymerization is performed at such a temperature, fusion between polymers is likely to occur. When fusion occurs, the polymerization does not proceed any more, or the degree of polymerization of the final polymer becomes uneven, and there is a problem when the fused polymer is used as a molding material such as a film or plastic.

In order to prevent this fusion phenomenon, a method of pre-heating and crystallizing the polymer particles prior to solid phase polymerization has been proposed. However, the use of such a preheated crystallized polymer results in a small but still fusion as compared with the non-preheated treatment.

The present invention is to solve the problems of the prior art as described above, and an object of the present invention is to provide a method for producing a high degree of polymerization polyethylene naphthalate (PEN) is prevented fusion phenomenon during solid phase polymerization.

That is, the present invention comprises the steps of (i) producing a PEN having a medium molecular weight by melt polymerization; (ii) adding 0.005 to 0.05% by weight of one or more fine powders selected from the group consisting of oxides, sulfates and chlorides of Group II metals to the PEN in the molten state during or after the melt polymerization step and mixing them uniformly. step; And (iii) provides a method for producing a high degree of polymerization polyethylene naphthalate (PEN) comprising the step of solid-phase polymerization of the molten polymer to which the fine powder is added.

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

Method for producing a high degree of polymerization polyethylene naphthalate (PEN) of the present invention comprises the steps of (i) preparing a PEN having a moderate molecular weight by melt polymerization; (ii) adding fine powder to the molten PEN during or after the melt polymerization step and mixing uniformly; And (iii) solid phase polymerizing the molten polymer to which the fine powder is added.

Referring to the manufacturing method of the present invention in more detail as follows.

In the present invention, first, a PEN having a moderate molecular weight to be provided for solid phase polymerization according to a conventional melt polymerization method is prepared. For example, 2,6-naphthalene dicarboxylic acid and ethylene glycol are transesterified to form an ethylene naphthalate monomer or prepolymer, which are melt polymerized under reduced pressure at a temperature above the melting point, preferably at 290 to 300 ° C. Let's do it.

If the intrinsic viscosity of the molten polymer obtained therefrom is too high, the melt viscosity is too large, so that uniform polymerization is difficult during subsequent solid phase polymerization or the properties of the obtained polymer tend to be nonuniform, so the intrinsic viscosity of the molten polymer is 0.50 or less. Preferably, 0.35 to 0.45. Since the particle size of the molten polymer also affects the rate of solid phase polymerization, it is necessary to use a certain size, but since it is desirable to obtain high viscosity in a short time, the particle size of the molten polymer is preferably about 1.5 g / 100ea. .

In this manner, during the melt polymerization, various additives such as catalysts and phosphorus compounds, which are usually used in the production of PEN, may be optionally added within a range not departing from the characteristics of the present invention as necessary.

According to the method of the present invention, during or after the preparation of the PEN molten polymer having a medium molecular weight as described above, 1 is selected from the group consisting of oxides, sulfates and chlorides of Group II metals in the molten PEN. Fine powder or more, preferably magnesium oxide, barium oxide, calcium oxide, magnesium sulfate, barium sulfate, calcium sulfate, magnesium chloride, barium chloride, calcium chloride, calcium carbonate, calcium phosphate, barium terephthalate, calcium naphthalene, naphthalenedicar 0.005 to 0.05% by weight, preferably 0.01 to 0.03% by weight of calcium carbonate, barium naphthalenedicarboxylic acid, or a mixture thereof is added and mixed uniformly.

If the size of the fine powder is too large, it is difficult to uniformly disperse in the PEN, it is preferable that the average particle size is 5 ~ 10㎛.

The fine powder may be added at any stage during the PEN polymerization or in the molten state after the polymerization as long as it can be uniformly dispersed in the PEN, but is preferably added at the beginning of the melt polymerization.

If the added amount of the fine powder is less than 0.005% by weight, there is no effect of improving the fusion phenomenon, and if it exceeds 0.05% by weight, the effect of improving the fusion phenomenon no longer increases, but it is not good because it lowers the physical properties of the final solid polymer.

As described above, the finely added PEN molten polymer uniformly finely sized to 1.0 to 2.0 g / 100ea, preferably 1.5 g / 100ea, if necessary, and then a cylindrical polymerization vessel or a rotating drum type with a stirring device. It is put in a polymerization vessel, and solid phase polymerization is carried out while removing by-product glycol and water at 240 to 250 ° C. under high vacuum having a vacuum degree of 1 mmHg or less, preferably 0.5 to 1 mmHg, outside the reaction system. The solid polymer thus obtained has a very high and uniform degree of polymerization.

According to the method of the present invention, in order to maximize the effect of preventing fusion phenomenon, it is possible to further introduce a step of preheating the granulated molten polymer after the granulation step at a temperature of 180 to 200 ° C. for at least 4 hours.

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.

Examples and Comparative Examples :

A reaction mixture consisting of 302 parts by weight of 2,6-naphthalene dicarboxylic acid, 156 parts by weight of ethylene glycol, 0.09 part by weight of manganese acetate, 0.03 part by weight of cobalt acetate, and 0.12 part by weight of antimony trioxide was heated at 160 to 240 ° C. for about 3 hours. After exiting at least about 70 parts by weight, 0.6 parts by weight of trimethyl phosphate and fine powder (average particle diameter of 5 ~ 6㎛) were quantitatively added and mixed as shown in Table 1 below, and the reactor was gradually heated up under reduced pressure to reach 290 ° C. The polymerization was carried out for 100 minutes while maintaining the pressure reduction degree at about 0.5 to 1.0 mmHg to obtain a molten polymer having the indicated intrinsic viscosity (η). The molten polymer was granulated to about 1.5 g / 100ea and then preheated at 200 ° C. for 4 hours.

The preheated molten polymer particles were introduced into a cylindrical polymerization vessel with a stirrer heated to have an internal temperature of 245 ° C., and then subjected to a solid phase polymerization reaction under a reduced pressure of 0.5 to 1.0 mmHg for 12 hours while stirring at a speed of 1 rpm. The ultimate viscosity and fusion rate of the high-polymerization PEN thus prepared are shown in Table 1 below.

Fine powder Addition amount (% by weight) Ultimate viscosity of PEN after melt polymerization ^* (η) PEN after solid phase polymerization Intrinsic viscosity ^* (η) Fusion rate ^** (%) Example 1 Barium sulfate 0.1 0.42 0.62 1.9 Example 2 Calcium phosphate 0.1 0.42 0.62 1.1 Example 3 Calcium phosphate 0.5 0.40 0.60 1.1 Example 4 Calcium oxide 0.1 0.42 0.62 2.1 Example 5 Calcium oxide 0.5 0.40 0.60 1.9 Example 6 Barium carbonate 0.1 0.42 0.62 1.8 Comparative Example 1 No addition - 0.45 0.64 12.0

^* : PEN was dissolved in a mixed solution of phenol: tetrachloroethane = 6: 4 at 130 ° C. for 20 minutes, and then cooled to 25 ° C. and expressed as a viscosity measured.

^** : The weight ratio of the solid polymer not passing through the 8 mesh to the total solid polymer.

As can be seen from Table 1, the PEN to which the fine powder was not added was not able to continue the solid phase polymerization because the incidence of fusion during the solid phase polymerization was quite high even after preheating.

As described in detail above, according to the method of the present invention, fusion of PEN is prevented during the solid-phase polymerization, so that PEN having a high degree of polymerization having a small quality difference can be easily provided.

Claims (5)

(i) preparing a PEN having a moderate molecular weight by melt polymerization; (ii) adding 0.005 to 0.05% by weight of one or more fine powders selected from the group consisting of oxides, sulfates and chlorides of Group II metals to the PEN in the molten state during or after the melt polymerization step and mixing them uniformly. step; And (iii) solid phase polymerizing the molten polymer to which the fine powder is added. The method of claim 1, The fine powder is magnesium oxide, barium oxide, calcium oxide, magnesium sulfate, barium sulfate, calcium sulfate, magnesium chloride, barium chloride, calcium chloride, calcium carbonate, calcium phosphate, barium terephthalate, calcium naphthalate And calcium naphthalenedicarboxylic acid, barium naphthalenedicarboxylic acid, or mixtures thereof. The method of claim 1, The solid phase polymerization is a method of producing a high degree of polymerization polyethylene naphthalate, characterized in that the temperature is 240 ~ 250 ℃ and under a reduced pressure of 0.5 ~ 1mmHg. The method of claim 1, Method for producing a high degree of polymerization polyethylene naphthalate further comprises the step of refining the molten polymer to which the fine powder is added to the size of 1.0 ~ 2.0g / 100ea before the solid phase polymerization step. The method of claim 4, wherein After the granulation step further comprises the step of preheating the granulated molten polymer at 180 ~ 200 ℃ 4 hours or more characterized in that the method of producing a polyethylene naphthalate.