KR940011773B1 - Polyethylene therephthalate and process for preparation thereof - Google Patents

Abstract

The polyethylene terephthalate copolymer is produced by: mixing the monomers of formula (I), (II) and (III) by the mixing mole ratio of 1.0 < (II)+(III)/(I) < 2.0; melt-polymerizing the mixture with a polymerization catalyst to obtain a medium polymer of 0.4-0.7 intrinsic viscosity; and solid-polymerizing the medium polymer. In the formulas, R1 is OH or OCH3; R2 is H or COCH3. The copolymer has a good transparency and heat resistance, and is used in the manufacture of carbonated drink containers, food packaging films and thick transparent containers.

Description

Polyethylene terephthalate copolymer and preparation method thereof

The present invention relates to a polyethylene terephthalate copolymer and a method for producing the same, and more particularly, thermoplastics such as polyethylene terephthalate having excellent transparency and heat resistance have excellent mechanical and thermal properties in terms of their structural properties, thereby producing fibers and films. In recent years, the application of food packaging materials and carbonated beverage containers has been expanded.

In order for plastic materials to be used as food packaging or containers, the food must be blocked from the external environment, the contents of the packaged food must be transparent so that the contents can be directly identified from the outside, and the container is not deformed by thermal changes. It shall be a requirement that the contents of the container not enter or dissolve in the food and contaminate the food.

In general, when manufacturing a container for food packaging with polyethylene terephthalate resin, since the amorphous polymer is stretched to prepare the container, the strength of the container and the barrier property of air are increased, but the crystallization is simultaneously accompanied by the crystallization during the stretching of the polymer. There is a problem that is reduced.

Another problem that arises in the use of polyethylene terephthalate resins in food packaging is acetaldehyde, which is caused by thermal decomposition of polymers.

When the acetaldehyde generated in this way is eluted from the packaging material, it not only degrades the taste and aroma of the food, but also the long-term intake of acetaldehyde adversely affects health, so the concentration of the acetaldehyde is less than 5 ppm. It is strictly regulated.

In order to solve these problems, attempts have been made to increase the content of diethylene glycol in the polymerization of polyethylene terephthalate to improve transparency, and to reduce the decomposition of polymers by performing solid phase polymerization.

For example, in order to improve the transparency of polyethylene terephthalate resin, French Patent No. 79/10061 and US Patent No. 4,340,721 are added with comonomers such as isophthal, to delay the crystallization of the polymer, A method of increasing the content of diethylene glycol has been proposed, but the resin produced by this method has a problem in that dyeability and heat resistance are reduced.

In addition, to reduce the production of acetaldehyde by thermal decomposition of polyethylene terephthalate resin, US Pat. The method of performing solid phase polymerization which advances a reaction is shown, In addition, French patent No. 78/23635 and 79/11981 crystallize 4-5 hours in 180-230 degreeC and inert gas atmosphere, and then solid-phase polymerization is performed. A method of doing this is shown.

But. The polyethylene terephthalate copolymers produced by these methods still have problems such as not having sufficient heat resistance to prevent the polymer from thermally decomposing when heated.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide a polyethylene terephthalate copolymer having excellent transparency and heat resistance and a method of manufacturing the same.

In order to achieve the above object, the present invention is a polyethylene obtained by mixing the monomers represented by the following general formulas (I), (II) and (III) at a fixed ratio to perform melt polymerization, followed by solid phase polymerization. Provided are terephthalate copolymers.

(Wherein R ₁ is an OH group or an OCH ₃ group, and R ₂ is an H or COCH ₃ group.)

The mixing ratio of the monomers (I), (II) and (III) described above is in molar ratio. (II) :( III) is preferably in the range of 99: 1 to 50:50.

Moreover, it is preferable that the intrinsic viscosity of the intermediate polymer after melt polymerization of the said monomer is the range of 0.4-0.7.

As the polymerization catalyst, it is preferable to use catalysts such as phosphorus, manganese and antimony.

According to other embodiment of this invention, this invention mixes the monomer represented by following General formula (I), (II), and (III) by predetermined ratio, and performs melt polymerization, and the intrinsic viscosity is 0.4-0.7 intermediate It provides a method for producing a polyethylene terephthalate, characterized in that the polymer is obtained, followed by solid phase polymerization to obtain a final polymer.

(Wherein R ₁ is an OH group or an OCH ₃ group, and R ₂ is an H or COCH ₃ group.)

Hereinafter, the present invention will be described in detail.

The polyethylene terephthalate copolymer of the present invention can be produced by a known polyester polycondensation reaction using monomers represented by the following general formulas (I), (II) and (III).

(Wherein R ₁ is an OH group or an OCH ₃ group, and R ₂ is an H or COCH ₃ group.)

In this case, the polycondensation reaction may be composed of two steps, transesterification reaction and polymerization reaction, in the molar ratio of each equivalent to be added to the reaction (II) :( III) is preferably in the range of 99: 1 to 50:50.

The monomers (II) and (III) used may be either diol forms such as ethylene glycol, resorcinol, or acetate forms such as ethylene glycol acetate, resorcinol diacetate, but acetate forms are preferred because of the fast reaction rate.

In addition, the catalyst and heat resistant material which can be used for this invention can use what is used for conventional polyester manufacture as it is.

In the present invention, the polyethylene terephthalate copolymer having an intrinsic viscosity in the range of 0.4 to 0.7 is obtained by performing direct melt polymerization of the above monomers. The molecular weight of this copolymer does not exceed 90% of the molecular weight theoretically obtained.

Next, the polyether terephthalate copolymer prepared by the molten polymer is subjected to solid phase polymerization in a vacuum or inert gas atmosphere under a temperature range not exceeding its melting point, thereby carrying out condensation polymerization, and thereby the desired polyethylene terephthalate. Obtain a copolymer.

In the physical properties of the polyethylene terephthalate copolymer prepared according to the present invention, in the melt polymerization, it shows excellent heat resistance even in the solid phase polymerization step, the amount of acetaldehyde generated by the thermal decomposition of the polymer is low, blow molding, injection molding ( Transparency is maintained in processing processes such as injection molding and extrusion molding.

In addition, the final polymer exhibits a high glass transition temperature and is excellent in heat deformation resistance, and thus may be particularly useful in the manufacture of thick transparent containers and the like.

Next, a preferred embodiment of the present invention is described. However, these examples are only presented to more easily understand the present invention, the present invention is not limited only to these examples.

Example 1

Into a reaction tube equipped with a distillation tube and a nitrogen inlet, 166 g (1 mol) of terephthalic acid (I), 62 g (1 mol) of ethylene glycol (II), and 1.96 g (0.11 mol) of resorcinol diacetate (III) were added thereto. Polymer was prepared through the polycondensation reaction. In this case, phosphorus, manganese, antimony, etc. were used as the catalyst. The inherent viscosity of the polymer obtained through direct melt polymerization was 0.57. The obtained polymer was subjected to solid phase polymerization at 220 ° C. for 12 hours through drying and precrystallization to prepare a polyethylene terephthalate copolymer having a desired molecular weight. The intrinsic viscosity after solid state polymerization was 0.66.

EXAMPLES 2-7

Except that the mixed amount of terephthalic acid (I), ethylene glycol (II), resorcinol diacetate (III) was added as shown in Table 1, Desired polyethylene terephthalate copolymers were prepared. Intrinsic viscosity of the copolymer before and after solid phase polymerization was measured and shown in Table 1 as a result.

In addition, the molar ratio of the compounds (I), (II), (III) used in Examples 1 to 7 described above, And the values of (II) / (III) are also shown in Table 1.

Comparative Example 1

166 g (1 mole) of terephthalic acid (I) and 93 g (1.5 mole) of ethylene glycol (II) were substantially the same as in Example 1 above except that resorcinol diacetate (III) was used. Treatment produced a polyethylene terephthalate polymer.

Comparative Example 2

A polyethylene terephthalate copolymer was prepared in the same manner as in Comparative Example 1 except that 5 g (0.03 mol) of isophthalic acid was further added.

Comparative Example 3

A polyethylene terephthalate copolymer was prepared in the same manner as in Comparative Example 1 except that 8.76 g (0.06 mol) of diethylene glycol was further added.

The molar ratios of the compounds (I), (II), (III) and the like used in Comparative Examples 1 to 3 described above and the intrinsic viscosity before and after solid phase polymerization of the obtained polymer were measured and the results are also shown in Table 1. The intrinsic viscosity was measured at a concentration of 1% (weight / volume) at a temperature of 25 ° C. using a mixed solvent of phenol / tetrachloroethane.

The properties of the polyethylene terephthalate resins prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated by the following methods, and the results were shown.

[Assessment Methods]

1) Heat resistance of polymer

The heat resistance of the polymer was evaluated by measuring the generation rate of the acetaldehyde remaining in the polymer and the acetaldehyde under high temperature.

(1-1) amount of remaining acetaldehyde

The polymer was ground to 800 μm, then heated in a closed flask to a temperature of 160 ° C. for 30 minutes, and then the amount of acetaldehyde that was vaporized was measured by gas chromatography (Gas-Chromatography).

(1-2) Acetaldehyde Generation Rate

The polymer powder (prepared in 1-1) was heated at a temperature of 220 DEG C for 30 minutes in the presence of nitrogen to remove residual acetaldehyde, and then the amount of acetaldehyde was changed every 3 hours as in (1-1). Measured by.

2) transparency

The polymer was melted completely at a temperature of 290 ° C. and then injected to make test specimens with a thickness of 2 to 10 mm. The maximum thickness of the cloudy state by crystallization was made into a transparent thickness, and compared to each other. At this time, the temperature of the mold was 40 ℃, the larger the thickness of the transparent indicates the slower.

3) Heat deformation

Using the resin of the present invention to improve the container of 1 L, filled with hot water of varying temperature in each container, and then left at room temperature for 24 hours to measure the degree of shrinkage of the container to the highest shrinkage rate of 1% or less It is expressed in temperature.

TABLE 1

TABLE 2

As can be seen in Tables 1 and 2, the polyethylene terephthalate resin prepared according to the invention has a lower acetaldehyde remaining rate, incidence rate and excellent transparency and higher heat resistance deformation characteristics than the resin produced by the conventional method. Indicates.

Due to the physical properties of the polyethylene terephthalate copolymer prepared according to the present invention it can be very useful for the production of carbonated beverage containers, food packaging films, thick transparent containers.

Claims (4)

The polyethylene terephthalate copolymer obtained by mixing the monomer represented by following General formula (I), (II), and (III) by predetermined ratio, carrying out melt polymerization, and then performing solid phase polymerization. (Wherein R ₁ is an OH group or an OCH ₃ group, and R ₂ is an H or COCH ₃ group.) The mixing ratio of the monomers (I), (II) and (III) according to claim 1, in a molar ratio. Satisfies the above, wherein the molar ratio of (II) :( III) is in the range of 99: 1 to 50:50. The polyethylene terephthalate copolymer according to claim 1, wherein the intrinsic viscosity of the intermediate polymer after melt polymerization of the monomer is in the range of 0.4 to 0.7. The monomers represented by the general formulas (I), (II) and (III) shown in claim 1 are mixed at a predetermined ratio, followed by melt polymerization to obtain an intermediate polymer having an inherent viscosity of 0.4 to 7.0, which is then solid phase. Method for producing polyethylene terephthalate, characterized in that the polymerization to obtain a final polymer.