KR101126283B1 - Method of solid-state polymerization of polyethyleneterephthalate - Google Patents

Abstract

The present invention relates to a solid phase polymerization method of polyethylene terephthalate, wherein during a solid phase polymerization reaction of a polyethylene terephthalate, oxygen is injected during a solid phase polymerization reaction by injecting a piece of polyethylene terephthalate molding containing an oxygen scavenger into the solid phase polymerization reactor together with the polyethylene terephthalate pellet. The concentration can be controlled very low, effectively preventing the discoloration of the produced product.

Solid State Polymerization, Polyethylene Terephthalate, Molded Part, Discoloration, Oxygen Scavenger

Description

Solid phase polymerization method of polyethylene terephthalate {METHOD OF SOLID-STATE POLYMERIZATION OF POLYETHYLENETEREPHTHALATE}

1 is a schematic of a batch type (vacuum type) solid state polymerization apparatus according to the prior art.

The present invention relates to a solid phase polymerization method of polyethylene terephthalate for producing a polyethylene terephthalate product having excellent color.

Polyethylene terephthalate (hereinafter, abbreviated as 'PET') is widely used as a fiber, a beverage container, a film, or a tire cord. Among them, the amount of PET used for bottles, such as beverage containers, is increasing rapidly.

In the manufacture of bottles using PET, a stretch blow molding method is adopted, and for this purpose, a high molecular weight PET is generally used. In order to manufacture high molecular weight PET, a solid phase polymerization method is widely used.

1 is a schematic diagram of a solid-state polymerization reactor of a batch vacuum method conventionally used. The solid phase polymerization reactor is maintained in the temperature range of 200 ~ 240 ℃ through a suitable device, and rotates at a speed of 20 ~ 60 rpm for the even stirring effect of the PET reactant in the solid pellet state and fusion prevention during the crystallization process . A vacuum pump is connected to maintain the pressure inside the reactor during the reaction in a vacuum for effective discharge of reaction byproducts. Therefore, the solid phase polymerization reactor lowers the oxygen concentration by accelerating the vacuum and promotes the diffusion of reaction by-products. Since the pressure in the system is lower than that of the outside due to the vacuum system, a small amount of oxygen may be introduced into the system when a minute gap occurs in the reaction equipment. This exists. In particular, the use of the actual solid-state polymerization equipment inevitably leads to the occurrence of minute gaps. Oxygen, once introduced into the reactor, causes an oxidation reaction on the surface of the PET pellets, thereby discoloring the color of the PET product, thereby degrading the quality of the product.

Mossi & Ghisolfi, in the international patent WO 03/010226 A1, contains various metal particles such as iron, calcium, magnesium, titanium, and cobalt having a diameter of less than 25 microns and a density of 0.97 to 3.4 g / cm ³ in polyester to polymerize Through the method of polymerizing the ester resin, it was found that the contained metal particles have an effect as an oxygen scavenger for removing oxygen.

W.R. Grace & Co.-Conn discloses a method of using an ethylenically unsaturated hydrocarbon polymer at a concentration of 0.01-1.0 equivalent per 100 g of transition metal and polymer as an oxygen scavenger in US Pat.                         

Advanced Oxygen Technologies, Inc. discloses a method of using salicylic acid chelate or its transition metal complex as an oxygen scavenger in US Pat. No. 53,64,555.

However, a technique for effectively preventing color discoloration of a polyethylene terephthalate product by controlling the oxygen concentration during a solid state polymerization reaction using a molding including an oxygen scavenger is not known.

An object of the present invention is to prevent discoloration of polyethylene terephthalate products by oxygen introduced into the solid-state polymerization reactor.

Accordingly, the present inventors have completed the present invention by finding that the color change of the polyester resin after the solid phase polymerization is lowered by injecting a piece of polyethylene terephthalate molded article containing an oxygen scavenger in the solid phase polymerization reactor in the solid phase polymerization process.

In order to achieve the above object,

The present invention comprises the steps of injecting and crystallizing together a piece of polyethylene terephthalate molding comprising a polyethylene terephthalate pellet and an oxygen scavenger into a solid-phase polymerization reactor; Solid-phase polymerization of the crystallized polyethylene terephthalate molding pieces and polyethylene terephthalate pellets; And separating and removing the polyethylene terephthalate molded pieces from the solid phase polymerized polyethylene terephthalate molded pieces and the polyethylene terephthalate pellets.

The polyethylene terephthalate molded pieces are prepared by mixing 1 to 20 parts by weight of an oxygen scavenger with respect to 100 parts by weight of the solid-state polymerized PET resin and injection molding to obtain a preform, and then blow molding the preform and then cut the bottle to a certain size. .

In addition, the polyethylene terephthalate molding pieces are mixed with 1 to 20 parts by weight of an oxygen scavenger with respect to 100 parts by weight of the solid-state polymerized PET resin and extruded to obtain a sheet (sheet) or film, the sheet or film to a certain size It can be cut and manufactured.

When the oxygen scavenger is used in less than 1 part by weight with respect to 100 parts by weight of the PET resin, the oxygen removal performance is poor, so it is difficult to expect the effect as an oxygen scavenger, if it exceeds 20 parts by weight when producing a PET molding containing the oxygen scavenger There is a problem that makes molding difficult.

The oxygen scavenger uses a transition metal such as iron, calcium, and cobalt, and an ethylenically unsaturated hydrocarbon polymer such as Amosorb of Colormatrix Co.

The polyethylene terephthalate resin containing the oxygen scavenger may be introduced into the solid-state polymerizer in the form of bottle scraps, various sheets or film pieces, and in particular in the form of scrap PET beer bottles to be reused. It can be attached inside the reactor through a mechanical design.

The crystallization process is carried out for 30-120 minutes at a temperature of 120-195 ℃, the solid phase polymerization process is carried out for 4-20 hours at a temperature of 200-230 ℃.

If the crystallization temperature is lower than 120 ° C. in the crystallization process, the crystallization rate is very slow and crystallization is difficult to proceed. If the crystallization temperature is higher than 195 ° C., there is a risk of fusion and yellowing, and thus, a stable process is difficult to achieve. Similarly, if the temperature of the solid phase polymerization process is lower than 200 ℃, the solid phase polymerization rate is too slow and difficult, and if the solid phase polymerization temperature is higher than 230 ℃ fusion phenomenon occurs it is difficult to proceed to normal solid phase polymerization.

The crystallization process is carried out by putting PET pellets in an amorphous phase into the reactor and rotating them, and maintaining the temperature of the reactor at the crystallization temperature of the PET resin. By maintaining the temperature of the reactor at the crystallization temperature, the PET resin provides thermal energy for the crystallization to proceed, and by rotating the reactor to continue the collision between the pellets to prevent fusion between the pellets.

When the crystallinity of the PET pellets is 30 to 40% through the crystallization process, the solid phase polymerization can be stably performed without fusion between the PET pellets even at the solid phase polymerization reaction temperature. The solid phase polymerization process transfers an internal substance in which the reactant diffuses chemical reactions between polymer ends in solid PET, especially in the amorphous phase, and by-products ethylene glycol, water, and acetaldehyde, which are the result of this reaction, to the outside of the PET pellets in the solid phase. And an external material transfer step of discharging the by-products diffused to the PET pellet surface out of the system.

In addition, the polyethylene terephthalate molded article is separated from the solid phase polymerized polyethylene terephthalate molded article and the polyethylene terephthalate pellet.

When separating pieces of polyethylene terephthalate moldings containing an oxygen scavenger, a screening process can be used utilizing the size difference of the pellets. For example, if a piece of polyethylene terephthalate molding containing an oxygen scavenger is 0.7 mm in diameter and a normal polyethylene terephthalate pellet is 0.3 mm in diameter, a piece of solid state polymerized polyethylene terephthalate molding and polyethylene tere using a screen having a diameter of 0.5 mm are used. Only polyethylene terephthalate pellets can be separated from the mixture of phthalate pellets.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are merely examples of the present invention and the present invention is not limited by these examples.

<Production Example>

300 Kg of PET pellets having an intrinsic viscosity of 0.60 dl / g were prepared through a conventional polyester melt polymerization method. At this time, germanium oxide (Germanium oxide) was used as a polymerization catalyst, and the color of the produced PET product was measured. As a result, Color L value 88, a value 0, and b value were -1. The PET product obtained by the manufacture example is abbreviated as sample A below.

Comparative Example

10 Kg of Sample A obtained in the Preparation Example was introduced into the solid-state polymerization apparatus of FIG. 1, subjected to a crystallization process at 180 ° C. for 30 minutes, and then subjected to a solid-state polymerization reaction at 215 ° C. for 10 hours to intrinsic viscosity 0.80 dl / g PET resin was obtained. The color of the obtained solid state PET resin was measured, and as a result, Color L value 94, a value 0, and b value were +3.4.

&Lt; Example 1 >

10 g of the solid-state polymerized PET resin obtained in the comparative example was evenly mixed with 300 g of iron powder having a size of 325 mesh, and then injected at 285 ° C. to obtain a preform, which was blow molded to prepare a PET bottle. The side wall of the PET bottle containing iron powder was cut into a size of 3 × 3 cm to prepare a PET bottle piece containing an oxygen scavenger. The PET bottle fragment containing the oxygen scavenger thus produced is hereinafter abbreviated as sample B.

10 Kg of Sample A obtained in the Preparation Example and 1 Kg of Sample B obtained above were added together to the solid phase polymerization apparatus of FIG. 1, and the crystallization step (180 ° C., 30 minutes) and the solid phase polymerization step (215) were carried out in the same manner as in Comparative Example. ℃, 10 hours) to obtain a solid-phase polymerized PET resin. Sample B containing an oxygen scavenger was removed and removed, and the intrinsic viscosity and color of only the remaining solid polymerized PET resin were measured. As a result, the intrinsic viscosity was 0.805 dl / g, and the Color-L value was 95 and color-. a value 0.3 and color-b value 1.7.

<Example 2>

10Kg of solid-state polymerized PET resin produced in Comparative Example was mixed with 1Kg of Amosorb DFC4020 product provided by Color matrix, and then injected at 285 ° C to obtain a preform. The preform was blow molded to prepare a PET bottle. The side wall of the PET bottle was cut to a size of 3 × 3 cm to prepare a bottle piece containing an oxygen scavenger. The bottle fragment containing the oxygen scavenger thus produced is referred to below as sample C.

10 Kg of Sample A obtained in the Preparation Example and 1 Kg of Sample C obtained above were added together to the solid phase polymerization apparatus of FIG. ℃, 10 hours) to produce a solid-phase polymerized PET resin. The sample C containing the oxygen scavenger was separated and removed, and the intrinsic viscosity and color of the remaining solid polymerized PET resin were measured, and the intrinsic viscosity was 0.803 dl / g, and the Color-L value 94, color -a value was 0.1 and color-b value was 1.9.

<Example 3>

10 kg of the solid-phase polymerized PET resin produced in the comparative example was mixed with 300 g of the iron powder used in Example 1 and 1 Kg of the Amosorb DFC4020 product provided by the Color matrix used in Example 2, and then injected at 285 ° C. for preform. The preform was blow molded to produce a PET bottle. The PET bottle containing the oxygen scavenger was prepared by cutting the side wall of the PET bottle thus prepared to a size of 3 × 3 cm. The PET bottle fragment containing the oxygen scavenger thus produced is abbreviated as sample D.

10 Kg of Sample A obtained in Preparation Example and 1 Kg of Sample D obtained above were added together to the solid phase polymerization apparatus of FIG. 1, and the crystallization step (180 ° C., 30 minutes) and the solid phase polymerization step (215) were performed in the same manner as in Comparative Example. ℃, 10 hours) to produce a solid-phase polymerized PET resin. The sample D containing the oxygen scavenger was separated and removed, and the intrinsic viscosity and color of the remaining solid polymerized PET resin were measured. As a result, the intrinsic viscosity was 0.803 dl / g and the Color-L value 94, color The value of -a was 0.1 and the color-b was 0.8.                     

<Example 4>

After purchasing commercially available PET beer bottles of OB Beer Co., Ltd. and washing them with water, the side walls of the beer PET bottles were cut to a size of 3 × 3 cm to prepare pieces of PET bottles containing an oxygen scavenger. The PET bottle fragment containing the oxygen scavenger thus produced is hereinafter abbreviated as sample E.

10 Kg of Sample A obtained in Preparation Example and 1 Kg of Sample E obtained above were added together to the solid phase polymerization apparatus of FIG. 1, and the crystallization step (180 ° C., 30 minutes) and the solid phase polymerization step (215) were performed in the same manner as in Comparative Example. ℃, 10 hours) to produce a solid-phase polymerized PET resin. The sample E containing the oxygen scavenger was separated and removed, and the intrinsic viscosity and color of the remaining solid polymerized PET resin were measured, and the intrinsic viscosity was 0.801 dl / g, and the Color-L value 94, color It was -a value 0.2 and color-b value 2.5.

As described above, according to the present invention, during the solid state polymerization of polyethylene terephthalate, the oxygen concentration is controlled very low during the solid state polymerization by injecting a piece of polyethylene terephthalate molding containing an oxygen scavenger together with the polyethylene terephthalate pellets. This can effectively prevent color discoloration of the produced product.

Claims (7)

Injecting and crystallizing together pieces of polyethylene terephthalate molding comprising polyethylene terephthalate pellets and an oxygen scavenger into a solid phase polymerization reactor; Solid-phase polymerization of the crystallized polyethylene terephthalate molding pieces and polyethylene terephthalate pellets; And Separating and removing the polyethylene terephthalate molding pieces from the solid-phase polymerized polyethylene terephthalate molding pieces and the polyethylene terephthalate pellets Solid phase polymerization method of polyethylene terephthalate comprising a. The method of claim 1, wherein the polyethylene terephthalate molding pieces are mixed with 1 to 20 parts by weight of an oxygen scavenger based on 100 parts by weight of the solid-phase polymerized polyethylene terephthalate resin and injection molded to obtain a preform, and after blow molding the preform Solid phase polymerization method of polyethylene terephthalate, characterized in that the bottle is cut to a certain size. The method of claim 1, wherein the polyethylene terephthalate molding pieces are mixed with 1 to 20 parts by weight of an oxygen scavenger with respect to 100 parts by weight of the solid-phase polymerized polyethylene terephthalate resin to obtain a sheet or film, the sheet Or a solid phase polymerization method of polyethylene terephthalate, characterized in that to cut the film to a certain size. The method of claim 1, wherein the polyethylene terephthalate molding piece is a waste polyethylene terephthalate beer bottle containing an oxygen scavenger. The solid phase polymerization method of polyethylene terephthalate according to claim 4, wherein the oxygen scavenger is at least one selected from iron, calcium, transition metals and ethylenically unsaturated hydrocarbons. The solid phase polymerization method of polyethylene terephthalate according to claim 1, wherein the crystallization process is performed at a temperature of 120-195 ° C for 30-120 minutes. The solid phase polymerization method of polyethylene terephthalate according to claim 1, wherein the solid phase polymerization process is performed for 4-20 hours at a temperature of 200-230 ° C.

Images