JP2004067964A - Method of treating polyethylene terephthalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating polyethylene terephthalate for a remarkable reduction of the problem of white powder adhesion to a mold in a molding process and for obtaining a wrapping material for films or vessels which is excellent in increasing productivity, transparency, heat resistance and mechanical strengths. <P>SOLUTION: To reduce an oligomer contained in pellets of polyethylene terephthalate, which is obtained by using a titanium compound as a condensation polymerization catalyst, by bringing the pellets into contact with water in an arbitrary stage of applying it to a solid state condensation polymerization. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has a remarkable effect on the reduction of white powder caused by oligomers, which is problematic when adhered to a mold or the like at the time of molding, and improves the productivity, transparency, heat resistance and mechanical strength of a film or container. The present invention relates to a method for treating polyethylene terephthalate, from which a packaging material can be obtained.
[0002]
[Prior art]
Polyesters, especially polyethylene terephthalate, are widely used in the form of fibers, films, industrial resins, bottles, cups, trays, etc. due to their excellent mechanical and chemical properties.
[0003]
However, in the molding process, for example, the oligomers present in the polyester during the fiber spinning or the oligomers generated during the molding adhere to the stretching roller, the heat treatment roller, etc. The problem of contamination, such as the contamination of various rollers as well as the fibers during film formation, and the problem of causing product defects such as so-called dropouts on magnetic tape, is further problematic when molding hollow containers and industrial resins. In addition, the molding die is contaminated, and the oligomer adheres to the pent portion and causes sink marks, so that a satisfactory molded product cannot be obtained. In addition, there are various problems such as oligomers generated during stretching and heat treatment adhering to a mold or the like, and the transfer significantly impairs the transparency of the molded article.
[0004]
In order to solve these problems, methods for reducing the amount of oligomers contained in the polyester have been studied, and many proposals have been made. For example, a method of heat-treating the polyester at a temperature lower than its melting point in a high vacuum ( JP-A-48-101462, JP-A-51-48505), and a so-called solid phase such as a method in which a polyester is heat-treated at a temperature lower than its melting point in an inert gas atmosphere (JP-A-55-189331). An oligomer reduction method by a polycondensation reaction method has been proposed.
[0005]
However, when the oligomer is reduced by this method, the polymer has a white powder reducing effect for a polymer having a relatively large amount of the oligomer, but cannot exert the white powder reducing effect for a polymer having a relatively small amount of the oligomer. Or, conversely, white powder may increase.
[0006]
In connection with this technique, Japanese Patent Application Laid-Open No. 3-47830 proposes treating polyethylene terephthalate after the solid-phase polycondensation reaction with water in order to reduce oligomers generated during molding. Since the liquid is water, a relatively high temperature or a long-time treatment using low-temperature water had to be performed to obtain a sufficient effect.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems of the above-mentioned conventional technology, to significantly reduce the amount of white powder that becomes a problem by adhering to a mold during molding, and to improve productivity, transparency, heat resistance, and mechanical strength. It is an object of the present invention to provide a method for treating polyethylene terephthalate, which can obtain a packaging material such as a film or a container.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in view of the above-described conventional technology, and as a result, completed the present invention.
[0009]
That is, the object of the present invention is to
A polyethylene terephthalate polymer pellet obtained using a titanium compound as a polycondensation reaction catalyst is brought into contact with water at an arbitrary stage before subjecting to a solid-phase polycondensation reaction to reduce oligomers contained in the pellet. This can be achieved by a processing method for polyethylene terephthalate.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The polyethylene terephthalate of the present invention is a polyester whose main acid component is a terephthalic acid component and whose main glycol component is an ethylene glycol component. Here, “main” means that the component accounts for 85 mol% or more.
[0011]
Therefore, the ester component other than the terephthalic acid component and the ethylene glycol component can be contained in the range of 15 mol% or less. Examples of such a copolymer component include terephthalic acid, a dicarboxylic acid component other than ethylene glycol, a diol component, and an oxy component. Acid components can be mentioned. Specifically, examples of the aromatic dicarboxylic acid component include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfondicarboxylic acid, diphenylketonedicarboxylic acid, and sodium-sulfoisophthalic acid. Acid, dibromoterephthalic acid, etc., as an aliphatic dicarboxylic acid component, for example, decalin dicarboxylic acid, hexahydroterephthalic acid, etc., as an aliphatic dicarboxylic acid, for example, malonic acid, succinic acid, Such as phosphate can be mentioned.
[0012]
Examples of the glycol component include aliphatic diol components such as diethylene glycol, trimethylene glycol, tetramethylene glycol, and hexamethylene glycol, and aromatic diol components such as vitronone, catechol, naphthalene diol, resorcinol and 4,4 ′. -Dihydroxy-diphenyl-sulfone, bisphenol A [2,2'-bis (4-hydroxyphenyl) propane], tetrabromobisphenol A, bishydroxyethoxybisphenol A, etc., and a cycloaliphatic diol component such as cyclohexanediol. Examples of the aliphatic oxycarboxylic acid component include glycolic acid, hydroacrylic acid, and 3-oxypropionic acid, and examples of the alicyclic oxycarboxylic acid component include asiatic acid and quinova. Etc., aromatic oxycarboxylic acid components as such as salicylic acid, m- oxybenzoate, p- hydroxybenzoic acid, mandelic acid, and the like atrolactic acid.
[0013]
Further, a polyfunctional compound having a valence of 3 or more, such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, and tricarbaryl, is used as long as the polymer chains constituting the polyester are substantially linear. An acid or gallic acid may be copolymerized, and a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added as necessary.
[0014]
The polyester may be produced using a conventionally known method for producing polyethylene terephthalate. For example, an esterification reaction is performed using terephthalic acid and ethylene glycol, or a lower alkyl ester of terephthalic acid (eg, dimethyl ester) and ethylene glycol are used. The transesterification reaction is carried out using the compound (A), and the obtained reaction product is further subjected to a polycondensation reaction.
[0015]
When producing these polyesters, it is preferable to use a transesterification catalyst, a polycondensation reaction catalyst, a stabilizer and the like. As these transesterification catalysts, stabilizers and the like, those known as transesterification catalysts and stabilizers for polyesters, particularly polyethylene terephthalate, can be used, and titanium compounds are used as polycondensation reaction catalysts. The effect of the present invention can be obtained only when there is.
[0016]
For example, when a germanium-based compound is used as a polycondensation reaction catalyst, the germanium-based compound loses its catalytic activity by contact with water, and does not function as a polycondensation reaction catalyst in the subsequent solid-phase polycondensation reaction. The method cannot be applied.
[0017]
Of course, other additives such as a coloring agent, an antioxidant, an ultraviolet absorber, an antistatic agent and a flame retardant may be used as needed.
[0018]
In the present invention, it is necessary to directly contact the polyethylene terephthalate pellets at any stage before the solid-phase polycondensation reaction with water.
[0019]
The method of contacting water may be any of a batch type and a continuous type, and in the case of a batch type, a method in which water and polyethylene terephthalate pellets before the solid-phase polycondensation reaction are put into a treatment device and brought into contact with each other is used. In the case of a continuous system, a method in which water is continuously supplied in countercurrent or cocurrent and brought into contact with pellets can be exemplified.
[0020]
The above-mentioned treatment conditions may be appropriately selected depending on the proper immersion treatment time depending on the water temperature and the like, the intrinsic viscosity of polyethylene terephthalate to be subjected to the solid-phase polycondensation reaction, the oligomer content, the size of the pellets, and the like. When water is supplied continuously, the flow rate of water and whether it is countercurrent or cocurrent may be appropriately selected.
[0021]
After the pellets treated by these methods are dried, they are subjected to a solid-phase polycondensation reaction, and this drying treatment can be carried out by a commonly used drying treatment method for polyethylene terephthalate.
[0022]
The dried pellets must be subjected to a polycondensation reaction in at least one solid phase polycondensation reaction step, and any conventionally known method may be employed for the solid phase polycondensation reaction.
[0023]
At this time, the intrinsic viscosity of the polyethylene terephthalate pellet after completion of the solid-phase polycondensation reaction is preferably 0.65 or more from the viewpoint of the mechanical strength of the molded article, and the oligomer (cyclic trimer) contained in the polymer is preferably used. Is preferably 0.35% by weight or less.
[0024]
【The invention's effect】
Polyethylene terephthalate obtained by the treatment method of the present invention has a remarkable reduction in white powder which is attached to a mold at the time of molding, which is problematic, and is a film or container excellent in productivity, transparency, heat resistance and mechanical strength. Packaging material can be obtained.
[0025]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each value in an Example was calculated | required by the following method.
1) Intrinsic viscosity:
According to a conventional method, the measurement was performed at 35 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio: 60/40).
2) Oligomer (cyclic trimer) content:
The sample was quantified in a fixed volume, dissolved in hexafluoroisopropanol / chloroform = 1/1 (volume ratio), diluted with chloroform, and subjected to GPC (gel permeation chromatography (ALC / GPC744 manufactured by Waters)). Measured and determined.
3) Regeneration amount of oligomer:
An oligomer (circular ring) of a pellet and an extruded sample subjected to melt shearing treatment (using a flow tester (using a flow tester CFT-500 manufactured by Shimadzu Corporation) at 305 ° C. for 6 minutes, holding die 0.5 mm diameter × 2.0 mm, load 110 kg) Monomer) content difference.
[0026]
[Example 1]
179 parts of high-purity terephthalic acid and 95 parts of ethylene glycol were mixed in a reactor in which 225 parts of the oligomer had been retained in advance under stirring and under a nitrogen atmosphere at 255 ° C. and under normal pressure. The prepared slurry was fed at a constant rate, and while the water and ethylene glycol generated in the reaction were distilled out of the system, the esterification reaction was carried out for 4 hours to complete the reaction. At this time, the esterification ratio was 98% or more, and the degree of polymerization of the produced oligomer was about 5 to 7.
[0027]
225 parts of the oligomer obtained by this esterification reaction was transferred to a polycondensation reaction tank, and 0.018 parts by weight of tetrabutoxytitanate was charged as a polycondensation reaction catalyst. Subsequently, the reaction temperature in the system was increased from 255 ° C. to 280 ° C., and the reaction pressure was gradually increased and reduced from normal pressure to 60 Pa. The polycondensation reaction was performed while removing water and ethylene glycol generated in the reaction outside the system. Was done.
[0028]
The progress of the polycondensation reaction was confirmed by monitoring the load on the stirring blades in the system, and the reaction was terminated when the desired degree of polymerization was reached. Thereafter, the reactants in the system were continuously extruded from the discharge section into a strand, cooled and cut to obtain granular pellets of about 3 mm. At this time, the polycondensation reaction time was 110 minutes, and the intrinsic viscosity of the obtained polyethylene terephthalate pellets was 0.52.
[0029]
1 kg of the obtained pellet (oligomer (cyclic trimer) 0.30 wt%) was placed in a 5 liter processing apparatus containing water at 90 ° C., and was subjected to contact treatment for 0.5 hour, followed by removal of water. Thereafter, drying was performed at 160 ° C. for 5 hours under a nitrogen stream.
[0030]
The dried pellets were subjected to a solid-state polycondensation reaction under vacuum at 220 ° C. for 15 hours. As a result, the intrinsic viscosity of the obtained pellets was 0.75. Table 1 shows the results.
[0031]
[Examples 2 to 3]
The same operation as in Example 1 was performed except that the water treatment conditions were changed. The results are shown in Table 1 together with the results.
[0032]
[Comparative Example 1]
In Example 1, the same operation was performed except that the contact treatment between the polyethylene terephthalate pellets and water was not performed. Table 1 shows the results.
[0033]
[Comparative Example 2]
225 parts of the oligomer obtained by carrying out the esterification reaction in the same manner as in Example 1 were transferred to a polycondensation reaction tank, and 0.10 parts by weight of germanium dioxide was charged as a polycondensation reaction catalyst. Subsequently, a polycondensation reaction was carried out in the same manner as in Example 1.
[0034]
The progress of the polycondensation reaction was confirmed by monitoring the load on the stirring blades in the system, and the reaction was terminated when the desired degree of polymerization was reached. Thereafter, the reactants in the system were continuously extruded from the discharge section into a strand, cooled and cut to obtain granular pellets of about 3 mm. At this time, the polycondensation reaction time was 112 minutes, and the intrinsic viscosity of the obtained polyethylene terephthalate pellets was 0.52.
[0035]
1 kg of the obtained pellet (oligomer (cyclic trimer) 0.31 wt%) was placed in a 5 liter processing apparatus containing water at 90 ° C., and subjected to contact treatment for 0.5 hour, followed by removal of water. Thereafter, drying was performed at 160 ° C. for 5 hours under a nitrogen stream.
[0036]
The dried pellets were subjected to a solid-state polycondensation reaction at 220 ° C. for 15 hours under vacuum, but the reaction hardly proceeded, and the intrinsic viscosity of the obtained pellets was 0.57. Table 1 shows the results.
[0037]
[Table 1]

Claims (1)

A polyethylene terephthalate polymer pellet obtained using a titanium compound as a polycondensation reaction catalyst is brought into contact with water at an arbitrary stage before subjecting to a solid-phase polycondensation reaction to reduce oligomers contained in the pellet. A method for treating polyethylene terephthalate.