JP2003212983A - Method for treating polyester resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating a polyester resin which can effectively reduce the amount of oligomers such as a cyclic trimer and, simultaneously, can render the residual amount of the entrainer in the resin small. <P>SOLUTION: In the method for treating a polyester by subjecting the polyester resin to contact treatment with a mixed fluid of a supercritical fluid and an entrainer, a poor solvent for polyester oilgomers is used as the entrainer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating a polyester resin by contacting a mixed fluid of a supercritical fluid and an entrainer, and more specifically, it can effectively reduce the amount of an oligomer such as a cyclic trimer. At the same time, the present invention relates to a method for treating a polyester resin capable of minimizing the amount of residual entrainer in the resin.

[0002]

2. Description of the Related Art Conventionally, polyester resins, such as polyethylene terephthalate resins, have been injection molded by taking advantage of their excellent transparency, gas barrier properties, safety and hygiene properties, in addition to their excellent mechanical and chemical properties. As a bottle or the like formed by stretch blow molding of a reform, a tray or a cup formed by thermoforming an extruded sheet, or a film or the like obtained by biaxially stretching the sheet, it shows remarkable growth particularly in the food packaging field. Among them, as a beverage bottle that requires heat sterilization filling such as juice drink, after reheating the injection-molded preform to soften it, or before heating the blow mold during stretch blow molding, Alternatively, by heat setting the bottle with a heating die separately provided after the stretch blow molding, the elongation of the bottle to which the oriented crystal of the molecular chain is fixed by the stretching and the heat resistance is imparted is particularly remarkable.

On the other hand, during molding of polyethylene terephthalate resin, for example, during molding of the heat-resistant bottle, molding equipment such as a heating mold for heat setting is easily contaminated, and the surface smoothness of the obtained bottle is impaired. There is a problem that the transparency is inferior and the productivity is greatly reduced due to cleaning of molding equipment such as molds. On the other hand, the cause of mold contamination is, for example, terephthalic acid and ethylene. In a polyethylene terephthalate resin produced by melt-polycondensing a glycol as a main raw material in the presence of a polycondensation catalyst, and solid-phase polycondensation, a by-product such as a cyclic trimer is a melt polycondensed resin. It is usually contained in an amount of 1 to 2% by weight, and a solid-phase polycondensation resin is usually contained in an amount of about 0.5 to 1% by weight. Furthermore, even during melt molding such as injection molding, a cyclic trimer or the like is contained in the resin. It is considered that products are generated and those cyclic trimers and the like migrate to the mold surface during molding and heat setting in stretch blow molding, and in order to prevent them, for example, extension of solid phase polycondensation time. , A method of reducing the content of by-products such as cyclic trimer contained in the resin by a method such as increasing the amount of the polycondensation catalyst and modifying the main chain, and heating the resin after the polycondensation Methods such as catalyst deactivation by contact with water, and methods such as modification of end groups are known to reduce the generation of by-products such as cyclic trimers during melt molding. Although it is certainly recognized, there is a strong demand for improved productivity and further reduction of mold contamination.

On the other hand, the polyester resin molded product is contacted with a mixed fluid of a supercritical fluid and a good solvent for a polyester oligomer such as chloroform or xylene as an entrainer, the latter having a concentration of 10 to 99.9% by weight. A method of extracting and removing an oligomer such as a cyclic trimer has been proposed (for example, JP-A-3-217).
See Japanese Patent No. 422. ). According to the study of the present inventors, this method is certainly effective in reducing the amount of oligomer, but the entrainer used remains in the polyester resin, and when used as a bottle or the like, the content of the beverage It has been found that problems such as impairing flavor are likely to occur.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned state of the art in the prior art. Therefore, the present invention is directed to a process of bringing a mixed fluid of a supercritical fluid and an entrainer into contact with a polyester resin. It is an object of the present invention to provide a method for treating a polyester resin, which can effectively reduce the amount of an oligomer such as a cyclic trimer and the amount of the entrainer remaining in the resin can be minimized.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by using a poor solvent for a polyester oligomer as an entrainer, and arrived at the present invention. That is, that is, the present invention is a method of treating a polyester resin in which a poor solvent for a polyester oligomer is used as an entrainer in the treatment of bringing a mixed fluid of a supercritical fluid and an entrainer into contact with the polyester resin. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin in the present invention is not particularly limited, but it is a polyester resin having an ethylene terephthalate unit as a main repeating constitutional unit, and terephthalic acid or its alkyl (having 1 to 1 carbon atoms) is used. (About 4) obtained by polycondensing a dicarboxylic acid component containing an ester-forming derivative such as an ester as a main component and a diol component containing ethylene glycol as a main component through an esterification reaction or a transesterification reaction. Is a polycondensation product of a dicarboxylic acid component in which terephthalic acid or an ester-forming derivative thereof accounts for 95 mol% or more of the total dicarboxylic acid component and a diol component in which ethylene glycol accounts for 95 mol% or more of the total diol component. Of ethylene terephthalate units by Ri is intended returns accounts for at least 90 mol% of structural units is preferred. When the ethylene terephthalate unit is less than 90 mol%, the polyester resin tends to have poor mechanical strength and heat resistance.

The polyester resin having an ethylene terephthalate unit as a main repeating constitutional unit is a dicarboxylic acid component other than terephthalic acid and its ester-forming derivative, such as phthalic acid, isophthalic acid,
1,4-phenylenedioxydicarboxylic acid, 1,3-phenylenedioxydiacetic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid,
4,4'-diphenylketone dicarboxylic acid, 4,4'-
Aromatic dicarboxylic acids such as diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, and amber Acids, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid and other aliphatic dicarboxylic acids, and alkyls of these dicarboxylic acids (having about 1 to 4 carbon atoms) One or more kinds of ester-forming derivatives such as ester may be used as a copolymerization component.

Examples of diol components other than ethylene glycol include trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, polyethylene glycol, polytetramethylene. Aliphatic diols such as methylene ether glycol, 1,
2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,
A cycloaliphatic diol such as 4-cyclohexanedimethylol,
And xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis (4-hydroxy) One or more aromatic diols such as phenyl) sulfone and bis (4-β-hydroxyethoxyphenyl) sulfonic acid may be used as a copolymerization component.

Further, for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t- Butylbenzoic acid, benzoylbenzoic acid, and other monofunctional components, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, and other polyfunctional compounds. One kind or two or more kinds of functional components may be used as a copolymerization component.

The polyester resin is subjected to polycondensation of a dicarboxylic acid component containing terephthalic acid or its ester-forming derivative as a main component and a diol component containing ethylene glycol as a main component through an esterification reaction or a transesterification reaction. It is produced by polycondensation in the presence of a catalyst, but basically by a conventional method for producing a polyester resin. That is, the dicarboxylic acid component containing terephthalic acid or an ester-forming derivative thereof as a main component and the diol component containing ethylene glycol as a main component were added to a slurry preparation tank together with a copolymerization component used as necessary. And mixed under stirring to form a raw material slurry, which is obtained by carrying out an esterification reaction in an esterification reaction tank under normal pressure to increased pressure and under heating, or an ester exchange reaction in the presence of an ester exchange catalyst. The low molecular weight polyester as an esterification reaction product or a transesterification reaction product is transferred to a polycondensation tank, and melted under a reduced pressure such as a normal pressure to a gradually reduced pressure under heating in the presence of a polycondensation catalyst. It is produced by condensation, usually followed by transfer to a solid phase polycondensation device, and solid phase polycondensation under heating. These may be continuous or batch type, and the esterification reaction tank, the polycondensation tank, and the solid-phase polycondensation apparatus may each be one-stage or multi-stage.

In the above-mentioned production method, the esterification reaction or transesterification reaction is carried out at a temperature of about 200 to 270 ° C. and a pressure of about 1 × 10 ⁵ to 4 × 10 ⁵ Pa, and the esterification reaction rate is Usually 90% or more, preferably 93% or more, and then transferred to melt polycondensation, the melt polycondensation, in the presence of a polycondensation catalyst, preferably in the presence of a phosphorus compound, a temperature of about 240 ~ 290 ℃, 13.3 to 133
It is performed under a reduced pressure of about 3 Pa.

As the polycondensation catalyst, a catalyst conventionally used as a polycondensation catalyst for polyester resins is used, and examples thereof include germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, and germanium tetraethoxide. Germanium compounds such as germanium tetra-n-butoxide, antimony trioxide,
Antimony compounds such as antimony pentoxide, antimony acetate, methoxyantimony, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-
Titanium compounds such as butyl titanate, titanium oxalate, and potassium potassium oxalate are used alone or in combination, or in addition, organic acid salts such as magnesium and cobalt are also used in combination. The amount used is preferably 10 to 400 ppm with respect to the theoretical yield of the polyester resin, and particularly preferably 30 to 300 ppm.

During polycondensation, a phosphorus compound such as orthophosphoric acid, tris (triethylene glycol) phosphate, ethyl diethylphosphonoacetate, ethyl acid phosphate, triethylene glycol acid phosphate, phosphorous acid, etc. is stabilized together with the polycondensation catalyst. It is preferable to coexist as an agent. The amount used is preferably 10 to 1,000 ppm, and more preferably 20 to 200 ppm, based on the theoretical yield of the polyester resin.

The resin after melt polycondensation is usually drawn out in a strand form from an outlet provided at the bottom of the polycondensation tank and cut into pellets, chips or the like while being cooled with water or after water cooling and cut with a cutter. Although it is a granular body, prior to the subsequent solid phase polycondensation, the granular body after the melt polycondensation, in a dry state, or under an inert gas atmosphere such as nitrogen, carbon dioxide, argon, or under a steam atmosphere, Alternatively, it is preferable that the surface of the resin granules be crystallized by heating at a temperature of about 120 to 200 ° C. for 1 minute or more under a water vapor-containing inert gas atmosphere.

The solid phase polycondensation is carried out at a temperature of about 180 to 240 ° C., in an atmosphere of an inert gas such as nitrogen, carbon dioxide, argon, and / or under a reduced pressure of about 13.3 to 1333 Pa. By this solid-phase polycondensation, it is possible to further increase the degree of polymerization of the resin and to reduce the reaction by-products such as cyclic trimers.

The polyester resin thus obtained by melt polycondensation or solid phase polycondensation has an intrinsic viscosity ([η]) measured at 30 ° C. in a solution of a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1). , Usually 0.1-1.5d
1 / g, preferably 0.4 to 1.2 dl / g. If the intrinsic viscosity is less than the above range, the mechanical strength of the polyester resin tends to be poor. On the other hand, if it exceeds the above range, the melt moldability is lowered and a large amount of an oligomer such as a cyclic trimer due to heat generation in the molding machine. As a result, it tends to be difficult to reduce the amount of oligomer even by contact treatment with an entrainer described later.

The polyester resin obtained by melt polycondensation or solid phase polycondensation has a cyclic trimer content of 6,
000 ppm or less is preferable, 5,000 pp
It is particularly preferably m or less. If the content of the cyclic trimer exceeds the above range, it tends to be difficult to reduce the content even by contact treatment with a mixed fluid of a supercritical fluid and an entrainer described later.

The method for treating the polyester resin of the present invention is as follows:
The above polyester resin is subjected to a treatment of bringing a mixed fluid of a supercritical fluid and an entrainer into contact therewith to extract and remove an oligomer such as a cyclic trimer in the resin. It is essential to use a poor solvent for the polyester oligomer.
Except for the poor solvent, it tends to be difficult to minimize the amount of residual entrainer in the resin.

Here, the supercritical fluid is a fluid in a state of a critical temperature or higher and a critical pressure or higher, and includes a single fluid and a mixed fluid. As the critical fluid, for example, carbon monoxide, carbon dioxide, nitrogen, nitrous oxide, ethane, propane, butane, ethylene, benzene, toluene, diethyl ether and the like are used. Carbon is preferred.

The poor solvent for the polyester oligomer as an entrainer refers to a solvent in which the solubility of the cyclic trimer at the boiling point is 1,000 ppm or less, and examples thereof include alcohols having 1 to 4 carbon atoms such as methanol and ethanol. Is preferred.

The concentration of the poor solvent in the mixed fluid of the supercritical fluid and the poor solvent as an entrainer is preferably 0.1 to 10% by weight, and 0.5 to 10% by weight.
More preferably, it is 3% by weight.

The temperature and pressure of the mixed fluid differ depending on the type of supercritical fluid and entrainer used, but the temperature is from the critical temperature of the fluid to 160 ° C. and the pressure from the critical pressure of the fluid to 60 MPa. For example, when carbon dioxide is used as the supercritical fluid and methanol is used as the entrainer, the temperature is preferably 40 to 160 ° C., and 60 to 12 ° C.
Particularly preferably, the temperature is 0 ° C., and the pressure is 7.4 to 60M.
Pa is preferable, and 20 to 40 MPa is particularly preferable. The treatment time is usually about 1 minute to 10 hours, preferably about 10 minutes to 4 hours.

The device for these contact treatments is not particularly limited, but for example, a pressure vessel for contact treatment, a high pressure pump for supplying a supercritical fluid to the pressure vessel, It is preferable to provide a separation tank equipped with a decompression valve for separating the fluid containing the extract into the extract and the fluid.

The contact treatment in the present invention may be applied to the granular polyester resin obtained by the melt polycondensation or the solid phase polycondensation, or a molded product formed into a bottle, a sheet, a film or the like. Although it may be applied to, it is preferable to apply to the granular material obtained by pulverizing the granular material obtained by the melt polycondensation or solid phase polycondensation, as the granular material,
The average particle size as a value when the integrated percentage is 50% in the integrated distribution curve created by the method described in JIS K0069 is preferably 20 to 1,000 μm, and particularly preferably 50 to 500 μm.

The polyester resin granules which have been subjected to the contact treatment as described above are, if necessary, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, lubricants, blocking agents which are usually added to polyester resins. Anti-fog, anti-fog, nucleating agent,
It is prepared as a molding material by adding a plasticizer, a colorant, a filler and the like, and melt-kneading the mixture by a conventional method. Then, for example, by molding into a preform by injection molding and then stretch blow molding, or by blow molding a parison molded by extrusion molding, a bottle or the like is obtained, or a sheet is molded by extrusion molding. After that, it is thermoformed into a tray, a container, or the like, or a uniaxially or biaxially stretched sheet is formed into a stretched film or the like, or is formed into a fibrous shape to be various fiber processed bodies.

Among them, the present invention is suitable for molding an injection blow bottle in which a preform is molded by injection molding and then biaxially stretched in a blow molding die and stretch blow molded to mold a bottle. For example, it is preferably used as a container for carbonated drinks, fruit juice drinks, alcoholic drinks, drinks such as tea and mineral water, liquid seasonings such as soy sauce, sauces, mirin, and dressings.

[0028]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 9710 parts by weight of dimethyl terephthalate and 6207 parts by weight of ethylene glycol were mixed with manganese acetate tetrahydrate 1.
9 parts by weight was charged into an esterification reaction tank, the temperature was gradually raised from 160 ° C. to 220 ° C. over 4 hours to carry out an ester exchange reaction, and then the obtained transesterification reaction product was transferred to a polycondensation tank, Orthophosphoric acid (1.4 parts by weight) and germanium dioxide (1.2 parts by weight) were added, and the temperature was gradually raised from 220 ° C and the atmospheric pressure was gradually reduced to 275 ° C, 50P.
Melt polycondensation was performed under reduced pressure of a for a total polymerization time of 3 hours,
A molten polycondensation resin was produced in the form of strands from a polycondensation tank, which was drawn out in a strand form from an outlet provided in the bottom, cooled with water, and then cut with a cutter. The obtained resin has an intrinsic viscosity of 0.6 as measured by the following method.
It was 3 dl / g and the cyclic trimer content was 11,000 ppm.

<Intrinsic Viscosity> About 0.25 g of a resin sample was dissolved in about 25 ml of a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1) at 110 ° C. to a concentration of 1.0% by weight, and then 30 It cooled to 30 degreeC, and measured at 30 degreeC with the fully automatic solution viscometer ("2CH type DJ504" by a central Rika company).

<Content of cyclic trimer> 200 mg of resin sample
Was dissolved in 2 ml of a mixed solvent of chloroform / hexafluoroisopropanol (volume ratio 3/2), 20 ml of chloroform was further added to dilute the solution, and 10 ml of methanol was added to the solution for precipitation, followed by filtration to obtain a filtrate. Was evaporated to dryness, dissolved in 25 ml of dimethylformamide, and the cyclic trimer (cyclotriethylene terephthalate) in the solution was quantified by liquid chromatography (“LC-10A” manufactured by Shimadzu Corporation).

Subsequently, the molten polycondensation resin chips obtained above were placed in a stirring crystallization machine (Bepex) for 12 hours.
After the surface was crystallized at 0 ° C., it was transferred to a stationary solid-state polycondensation tower, dried at 120 to 160 ° C. for 3 hours under a nitrogen gas flow of 20 liter / kg · hour, and then 21
A solid phase polycondensation polyester resin in the form of chips was produced by solid phase polycondensation at 0 ° C. for 20 hours. The obtained resin had an intrinsic viscosity of 0.78 dl / g and a cyclic trimer content of 5,200 pp measured by the same method as described above.
It was m.

Next, the obtained solid-phase polycondensed polyester resin chips were pulverized by using a freeze pulverizer so as to be a granular material having an average particle diameter of 220 μm measured by the following method. <Average particle size> The value when the cumulative percentage in the cumulative distribution curve created by the method described in JIS K0069 was 50% was defined as the average particle size.

The solid phase polycondensed polyester resin powder obtained was used to prepare an inner diameter of 60 mm, a depth of 400 mm and a capacity of 1,100.
In a cc pressure resistant container, a mixed fluid of carbon dioxide as a supercritical fluid and 1% by weight of methanol as an entrainer was circulated in the container at 80 ° C. and 40 MPa to give a polyester resin. The contact treatment was performed for 1.5 hours.

In the polyester resin after the contact treatment,
The cyclic trimer content measured by the same method as above is 2,5
The residual amount of the entrainer measured by the method described below was 2 ppm. <Remaining amount of entrainer> 20 ml of 1.0 g of resin sample
The sample was placed in a sample vial, the headspace temperature was set to 160 ° C., and the methanol separated and collected for 30 minutes was quantified by gas chromatography.

Examples 2 to 8 and Comparative Examples 1 to 2 The average particle size of the polyester resin powder, the entrainer species and concentration in the mixed fluid, and the contact treatment temperature, pressure and time are shown in Table 1. Otherwise, the polyester resin powder is contact-treated in the same manner as in Example 1,
At that time, the content of cyclic trimer in the polyester resin after the contact treatment and the residual amount of entrainer were measured by the same method as described above, and the results are shown in Table 1.

[0037]

[Table 1]

[0038]

According to the present invention, the amount of oligomers such as cyclic trimers can be effectively reduced and the amount of oligomers can be effectively reduced in the treatment of bringing the mixed fluid of the supercritical fluid and the entrainer into contact with the polyester resin. It is possible to provide a method for treating a polyester resin capable of minimizing the residual amount of the trainer in the resin.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J029 AA01 AB04 AC01 BA02 BA08                       BA09 BA10 BB04A BB10A                       BB12A BB13A BD03A BD04A                       BH02 CA01 CA02 CA04 CA05                       CA06 CB04A CB05A CB06A                       CB07A CB10A CB11A CC06A                       DB07 KE02 KE05 KH00 KH05

Claims (6)

[Claims] 1. A method for treating a polyester resin, wherein a poor solvent for a polyester oligomer is used as an entrainer in the treatment of bringing a mixed fluid of a supercritical fluid and an entrainer into contact with the polyester resin. 2. The method for treating a polyester resin according to claim 1, wherein the entrainer is an alcohol having 1 to 4 carbon atoms. 3. The method for treating a polyester resin according to claim 1, wherein the concentration of the entrainer in the mixed fluid is 0.1 to 10% by weight. 4. A polyester resin having an average particle size of 20 to 1,
The method for treating a polyester resin according to claim 1, wherein the polyester resin has a particle size of 000 μm. 5. The contact treatment is performed at a temperature from the critical temperature of the fluid used to 160 ° C. and 60 times the critical pressure of the fluid used.
The method for treating a polyester resin according to any one of claims 1 to 4, which is performed under a pressure up to MPa. 6. The difference (CT ₁ -ppm) between the cyclic trimer content before the contact treatment (CT ₁ ; ppm) and the cyclic trimer content after the contact treatment (CT ₂ ; ppm) in the polyester resin. CT
_{2. The} method for treating a polyester resin according to claim 1, wherein ₂ ) is 1,000 ppm or more.