JP2006213838A - Polyethylene terephthalate giving molded articles having small cyclic trimer content - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polyethylene terephthalate having a small amount of oligomers causing the staining in the molds of molding machines. <P>SOLUTION: This polyethylene terephthalate contact-treated with an aqueous potassium gluconate solution having a concentration of 1 ppm to 10 mass%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyethylene terephthalate capable of obtaining a molded product having a low content of a cyclic trimer oligomer that causes mold contamination during molding.

  Polyester, particularly polyethylene terephthalate, is widely used after being molded into fibers, films, industrial resins, bottles, cups, trays, and the like because of its excellent mechanical properties and chemical properties. However, when the polyethylene terephthalate resin is melted and molded, the oligomers contained in the resin, especially the cyclic trimer, adhere to and remain on the mold and become mold stains, which transfer to the molded product and impair the appearance of the molded product. Sometimes. In order to prevent this, it is necessary to stop the molding operation and clean the mold. However, since it is necessary to lower the temperature for safety reasons, the workability and productivity are significantly reduced.

In order to solve these problems, a method of reducing the oligomers contained in the polyester has been studied, and the polyethylene terephthalate after solid phase polymerization is treated with water in order to reduce the oligomers and acetaldehyde generated during molding. Has been proposed (see, for example, Patent Document 1), but since the treatment liquid is water, in order to obtain a sufficient effect, the treatment liquid must be made relatively hot or treated for a long time using cold water. In addition, when the polymerization catalyst is a titanium compound other than the germanium compound, there is no effect.
JP-A-3-72524 (Claims)

  An object of the present invention is to provide a poly (ethylene terephthalate) that eliminates the problems of the prior art and has a low content of oligomers that cause mold contamination of a molding machine.

As a result of intensive studies in view of the above prior art, the present inventors have completed the present invention.
That is, the object of the present invention can be achieved by polyethylene terephthalate characterized in that polyethylene terephthalate is contact-treated with an aqueous solution of potassium gluconate having a concentration of 1 ppm to 10% by mass.

  Polyethylene terephthalate obtained by the treatment method of the present invention is remarkably reduced in white powder, which is attached to the mold during molding and becomes a problem, and is excellent in productivity improvement, transparency, heat resistance and mechanical strength. Therefore, a packaging material such as a polyethylene terephthalate film or a container excellent in these characteristics can be obtained.

  Hereinafter, the present invention will be described in detail. The polyethylene terephthalate of the present invention is a polyester in which the main acid component is a terephthalic acid component and the main glycol component is an ethylene glycol component. Here, “main” means that 85 mol% or more of all repeating units of the polyester is occupied by a component in which the acid component is terephthalic acid and the glycol component is ethylene glycol.

  Therefore, other ester units other than the terephthalic acid component and the ethylene glycol component can be contained in the remaining 15 mol% or less. Examples of such copolymer components include dicarboxylic acid components other than terephthalic acid, and diol components or oxyacid components other than ethylene glycol. Specifically, examples of the aromatic dicarboxylic acid component include isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, sodium-sulfoisophthalic acid, and dibromoterephthalic acid. be able to. Examples of the aliphatic dicarboxylic acid component include decalin dicarboxylic acid and hexahydroterephthalic acid, and examples of the aliphatic dicarboxylic acid include malonic acid, succinic acid, and adipic acid.

  Examples of the glycol component include diethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol and the like as the aliphatic diol component. As aromatic diol components, for example, vitronone, catechol, naphthalenediol, resorcin, 4,4′-dihydroxy-diphenyl-sulfone, bisphenol A [2,2′-bis (4-hydroxyphenyl) propane], tetrabromobisphenol A, Examples thereof include bishydroxyethoxybisphenol A. Examples of the alicyclic diol component include cyclohexanediol. Examples of the aliphatic oxycarboxylic acid component include glycolic acid, hydroacrylic acid, and 3-oxypropionic acid. Examples of the alicyclic oxycarboxylic acid component include asiatic acid and quinobaic acid. Examples include salicylic acid, m-oxybenzoic acid, p-oxybenzoic acid, mandelic acid, and atrolactic acid.

  Further, a polyfunctional compound having three or more valences within the range in which the polymer chain constituting the polyester is substantially linear, such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, tricarbaryl. An acid, gallic acid, or the like may be copolymerized, and a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added as necessary.

  The polyester may be produced using a conventionally known method for producing polyethylene terephthalate. For example, the polyester is esterified with terephthalic acid and ethylene glycol, or a lower alkyl ester of terephthalic acid (for example, dimethyl ester) and ethylene glycol. Can be produced by subjecting the resulting reaction product to a polycondensation reaction. An appropriate copolymer can be produced by adding the copolymer component before the transesterification reaction or before the polycondensation reaction.

  It is preferable to use a transesterification catalyst, a polymerization catalyst, a stabilizer and the like when producing these polyesters. As these catalysts and stabilizers, those known as polyesters, particularly polyethylene terephthalate catalysts, stabilizers and the like can be used. Of course, other additives such as colorants, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants and the like may be used as necessary.

  The obtained polyethylene terephthalate may be pelletized and then further polycondensed in the solid phase polymerization step, and any conventionally known method may be adopted as the solid phase polymerization method.

  In the present invention, it is necessary to contact polyethylene terephthalate with an aqueous solution of potassium gluconate. Here, the aqueous solution of potassium gluconate needs to have a concentration of 1 ppm to 10% by mass. If the concentration is less than 1 ppm, the effect of reducing oligomers during molding is insufficient, and if it exceeds 10% by mass, the cost increases. A preferable range of the concentration is 10 ppm to 5% by mass, and more preferably 100 ppm to 2% by mass.

  As a method for bringing the potassium gluconate aqueous solution and the polyester into contact treatment, either a batch type or a continuous type may be used. For example, in the case of a batch type, the method etc. which put a potassium gluconate aqueous solution and a polyethylene terephthalate chip | tip in a processing apparatus and make it contact can be illustrated. Moreover, in the case of a continuous type, the method etc. which supply potassium gluconate aqueous solution continuously or countercurrently, and make it contact with a pellet can be illustrated. Furthermore, when polyethylene terephthalate obtained by the polymerization reaction is chipped, a method in which an aqueous potassium gluconate solution is brought into contact with molten polyethylene terephthalate to be cooled and solidified may be used. In addition, if there is an organic solvent capable of dissolving potassium gluconate at a sufficient concentration in place of the potassium gluconate aqueous solution, the organic solvent can be used.

  Moreover, the form of the polyethylene terephthalate to be contacted is not limited to the chip, and may be, for example, a sheet. In this case, for example, a method of continuously introducing a polyethylene terephthalate sheet into a continuous processing apparatus and contacting with a potassium gluconate aqueous solution can be exemplified. The temperature at which the potassium gluconate aqueous solution and polyethylene terephthalate are brought into contact with each other is not particularly limited, but usually it is preferably brought into contact with being heated at about 10 to 60 ° C. The contact time is usually about 5 minutes to 10 hours, preferably about 10 minutes to 8 hours, and more preferably about 30 minutes to 6 hours. In particular, it is preferable to perform contact treatment with a potassium gluconate aqueous solution in the form of a chip because it can be easily performed.

The polyethylene terephthalate treated by these methods is preferably dried, but a commonly used method for drying polyethylene terephthalate can be used, and it is not dried using a spinning machine with a vacuum suction device. May be spun into.
The various processing conditions described above may be appropriately selected depending on the production amount, intrinsic viscosity, form (chip or sheet, etc.), form size, etc. of the polyethylene terephthalate to be produced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive any limitation by this.

[Example 1]
In a reactor in which 225 parts by mass of oligomers are retained in advance, 179 parts by mass of high-purity terephthalic acid and 95 parts by mass of ethylene glycol were stirred and maintained under a nitrogen atmosphere at 255 ° C. and normal pressure. The slurry prepared by mixing was supplied at a constant rate, and the esterification reaction was completed for 4 hours while water and ethylene glycol generated in the reaction were distilled out of the system to complete the reaction. The esterification rate at this time was 98% or more, and the polymerization degree of the produced oligomer was about 5 to 7.

  225 parts by mass of the oligomer obtained by this esterification reaction was transferred to a polycondensation reaction tank, and 0.018 parts by mass of tetrabutoxy titanate and 0.016 parts by mass of monobutyl phosphate were added to ethylene glycol in advance as a polycondensation catalyst and heated. Then, the reaction product was added. Subsequently, the reaction temperature in the polycondensation reaction tank is increased from 255 to 280 ° C., and the reaction pressure is gradually increased and reduced from normal pressure to 60 Pa, respectively. A condensation reaction was performed.

  The degree of progress of the polycondensation reaction was confirmed without monitoring the load on the stirring blade in the polycondensation reaction tank, and the polycondensation reaction was terminated when the desired degree of polymerization was reached. Thereafter, the reactant in the polycondensation reaction tank was continuously extruded in a strand form from the discharge part, cooled and cut to obtain a granular pellet of about 3 mm. The polycondensation reaction time at this time was 110 minutes, and the intrinsic viscosity of the obtained polyethylene terephthalate pellets was 0.52.

  Subsequently, the obtained polyethylene terephthalate pellets were subjected to solid phase polymerization at 220 ° C. for 15 hours under vacuum. 1 kg of the obtained pellets (intrinsic viscosity 0.75) was placed in a treatment apparatus having a volume of 5 liters containing 2.5 kg of an aqueous 980 ppm potassium gluconate solution at 25 ° C. and contact-treated for 4 hours. Subsequently, after removing the potassium gluconate aqueous solution and drying in a nitrogen stream at 160 ° C. for 5 hours, a preform molded body was molded by the following method.

  5 kg of polyethylene terephthalate was dried for 3 hours under the conditions of 160 ° C., normal pressure and N 2 inflow, and the dried polyethylene terephthalate was injected with an injection molding machine (FN-2000 manufactured by Nissei Plastic Industrial Co., Ltd., cylinder temperature 280 ° C., cycle 30 seconds). A cylindrical preform having an outer diameter of about 28 mm, an inner diameter of about 19 mm, a length of 136 mm, a body thickness of 4 mm, and a weight of about 56 g was injection molded.

  A sample piece is cut out from the mouth of the molded preform, freeze-ground, and the sample is pulverized with a pulverizer, weighed in a certain amount, once dissolved in a small amount of hexafluoroisopropanol / chloroform mixture, and then fixed in chloroform (50 g). / L). This sample was subjected to gel permeation chromatography (GPC, Waters ALC / GPC244 type) to detect a low molecular weight region and its peak, and a calibration curve obtained from a standard sample of cyclic trimer (Cy-3). Was used to determine the cyclic trimer content of polyethylene terephthalate.

[Comparative Example 1]
In Example 1, the same operation was performed except that the contact treatment with the potassium gluconate aqueous solution was not performed. The results are shown in Table 1.

[Comparative Example 2]
In Example 1, the same operation was performed except that water was placed in the treatment apparatus as a contact treatment liquid and high-temperature hot water treatment was performed. The results are shown in Table 1.

[Comparative Example 3]
In Example 1, the same operation was performed except that a potassium acetate aqueous solution was used instead of the potassium gluconate aqueous solution. The results are shown in Table 1.

[Comparative Example 4]
In Example 1, the same operation was performed except that the gluconic acid aqueous solution was used instead of the potassium gluconate aqueous solution. The results are shown in Table 1.

[Comparative Example 5]
In Example 1, the same operation was performed except that a sodium gluconate aqueous solution was used instead of the potassium gluconate aqueous solution. The results are shown in Table 1.

  The poly (ethylene terephthalate) obtained by the treatment method of the present invention is remarkably reduced in white powder, which becomes a problem due to adhesion to the mold during molding, and is excellent in productivity improvement, transparency, heat resistance and mechanical strength. Therefore, it is possible to obtain a packaging material such as a polyethylene terephthalate film or a container excellent in these characteristics, and the industrial significance is great.

Claims (1)

  Polyethylene terephthalate obtained by contacting polyethylene terephthalate with an aqueous potassium gluconate solution having a concentration of ppm to 10% by mass.