JP2010100756A - Polyester composition and bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a polyester composition having less clouding degree even if it is thin-molded and excellent in tensile strength and tensile modulus of elasticity; its manufacturing method; and a thin bottle obtained by melting-molding the polyester composition. <P>SOLUTION: In the polyester composition comprising aromatic polyester and spherical silica, an average particle diameter of the spherical silica is 20-180 nm, and 0.01-0.6 wt.% of the spherical silica is contained based on the whole weight of the polyester composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyester composition and a bottle comprising the same. More specifically, the present invention relates to a polyester composition having excellent tensile strength and tensile modulus even when thin-walled, a method for producing the same, and a bottle comprising the composition.

  Polyester has excellent mechanical strength, heat resistance, transparency, and gas barrier properties, and is suitable for use as a material for films, sheets, fibers, etc., as well as bottle materials for beverage filling containers such as juices, soft drinks, and carbonated drinks. Has been.

In recent years, molding manufacturers and beverage manufacturers have been conducting research and development focused on reducing the cost of PET bottles (see, for example, Patent Document 1). Of particular note are thin-walled PET bottles that are reduced by about 30% by weight from the amount of conventional polyester resin used. However, by reducing the weight of the bottle, the thickness of the bottle body may be reduced, resulting in a serious drawback that the bottle strength is greatly reduced.
JP 2003-119257 A

  An object of the present invention is to provide a polyester composition excellent in tensile strength and tensile modulus even when thin-walled, a method for producing the same, and a thin-wall bottle formed by melt-molding the polyester composition. More specifically, the object is to provide a polyester composition that is less cloudy, excellent in transparency, and excellent in hue of a molded product.

  In order to solve the above-mentioned problems, the present inventor has conducted intensive research on nanoparticles used for increasing the strength of polyester resin. As a mineral, silica resin and alumina are used so that the polyester resin has excellent tensile strength and tensile elastic modulus. The present invention has been solved by finding that it can be produced.

  That is, an object of the present invention is a polyester composition comprising an aromatic polyester and spherical silica, the average particle diameter of the spherical silica is 20 to 180 nm, and the spherical silica is 0.01 based on the total weight of the polyester composition. This can be solved by a polyester composition containing ˜0.6% by weight.

  According to the present invention, since a polyester composition having sufficient strength can be obtained even if thin-wall molding is performed, it is possible to provide a beverage bottle that is thinner-walled than the prior art, and the amount of resin to be used can also be reduced. Therefore, cost reduction and environmental load are reduced. In a still more preferred embodiment, a thin bottle excellent in transparency and hue can be provided.

Hereinafter, the present invention will be described in detail.
The aromatic polyester used in the present invention is an aromatic polyester obtained by polycondensation reaction of an aromatic dicarboxylic acid or an ester moldable derivative thereof and an aliphatic diol. An ester moldable derivative of an aromatic dicarboxylic acid refers to a lower dialkyl ester having 1 to 6 carbon atoms, a lower diaryl ester having 6 to 8 carbon atoms, and a diacid halide. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 4,4′-diphenylmethanedicarboxylic acid. , Diphenyl ketone dicarboxylic acid, and 4,4′-diphenyl sulfone dicarboxylic acid. Specific examples of the aliphatic diol include ethylene glycol, 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, heptamethylene glycol, hexamethylene glycol, diethylene glycol, dipropylene glycol, bis (trimethylene glycol), bis (Tetramethylene glycol), triethylene glycol, 1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol. Among them, it is preferable that 80 mol% or more per all repeating units constituting the aromatic polyester is an ethylene terephthalate unit or an ethylene naphthalate unit obtained by polycondensation reaction of terephthalic acid or the like or naphthalene dicarboxylic acid and the like with ethylene glycol. . More preferably, it is 90 mol% or more. Among these, the preferred diol for carrying out the present invention is ethylene glycol, and the preferred carboxylic acid ester is dimethyl terephthalate. In addition, preferred polyesters for the practice of this invention are polyethylene terephthalate or polyethylene naphthalate.

  The mineral particles suitable for constituting the polyester composition of the present invention are spherical silica having an average particle size of 20 to 400 nm (nanometers). According to a preferred embodiment, it is more preferably 21 to 180 nm, still more preferably 22 to 80 nm, and most preferably 23 to 50 nm. Convenient particulate minerals are preferably metal oxides such as silicon dioxide, alumina, titanium dioxide. These are preferably surface-treated. This surface treatment is preferably carried out for the purpose of improving the dispersibility of the particles in the glycol component and the polyester polymer. If the average particle size is smaller than this range, the effect of improving the strength, which is the subject of the invention, is not seen. If the average particle size exceeds this range, the molded product becomes cloudy when melt-molded. This is not preferable.

  Silica is a suitable particle for the practice of the present invention. Mainly silica sol is particularly suitable for obtaining a composition having good dispersibility of the particles and is suitable for the purpose of the present invention. The weight concentration of the spherical silica particles in the polyester composition is 0.01 to 0.6% by weight, preferably 0.05 to 0.4% by weight, based on the total weight of the polyester composition. If the concentration range in the polyester composition is less than this range, the effect of improving the strength, which is the subject of the invention, is not seen, and if the concentration range exceeds this range, the molded product should be melt molded. It is not preferable because cloudiness may occur.

  The spherical silica particles can be introduced into the polymer according to a known method for introducing a mineral filler into the polymer. The first method is to introduce the particles into the polyester synthesis medium prior to initiation of polymerization. The polymerization is then carried out in the presence of spherical silica particles. The spherical silica particles can be introduced in a form dispersed in a powder or liquid medium. A second method is to obtain a uniform dispersion by introducing spherical silica particles into a molten polymer as a powder, and applying a shearing force and mixing. This operation can be carried out by a kneader having a uniaxial or biaxial screw. The third method is that spherical silica particles can be introduced into the molten polymer by a so-called masterbatch method (in the form of a kneaded mixture). Intimate mixtures can be prepared by conventional methods. The intimate mixture can be introduced into the molten polymer by a mixing device having a twin screw. In the masterbatch method, a polyester composition containing 1 to 30% by weight of the silica particles based on the total weight of the polyester composition is prepared in advance, and at least one diol and at least one aromatic dicarboxylic acid or aromatic are prepared. In a method for producing a polyester composition comprising a step of subjecting a mixture with a dicarboxylic acid ester to esterification or transesterification, and then polycondensing the obtained esterification reaction product or transesterification reaction product under reduced pressure. It can manufacture by adding in the process after a polycondensation process. Addition and melt mixing can be preferably employed in the polycondensation step in the reaction tank, or in the subsequent mixing (kneading) step using a single or twin screw extruder (kneader).

  According to an advantageous embodiment of the invention, the spherical silica particles are introduced into the polyester synthesis medium in the form of a sol. The sol may be an aqueous sol or a glycol sol, and the glycol sol is particularly suitable for the practice of the present invention. In a more preferred embodiment, a silica sol containing spherical silica having an average particle size of 20 to 400 nm is introduced into a mixture of at least one diol and at least one aromatic dicarboxylic acid or aromatic dicarboxylic ester, In this method, a polyester composition is obtained by carrying out an esterification reaction or a transesterification reaction and then polycondensing the resulting esterification reaction product or transesterification reaction product under reduced pressure.

The method for preparing the composition according to this embodiment is as follows.
A silica sol having an average particle size of 20 to 400 nm or less is introduced into a mixture of at least one diol and aromatic dicarboxylic acid or aromatic dicarboxylic acid ester, and esterification of aromatic dicarboxylic acid or aromatic dicarboxylic acid ester with diol or An ester exchange reaction is performed, and the esterification product or the ester exchange reaction product is polycondensed under reduced pressure. The production method of this polyester composition is the same as the conventional method except that silica sol is introduced. The esterification reaction step or the transesterification reaction step is a step that is widely practiced by an industrial method of a polyester production method. These two methods are used, for example, for the production of polyethylene terephthalate. Hereinafter, the case of producing polyethylene terephthalate will be mainly described.

  The first preparation method is a methyl terephthalate (DMT) method, that is, a transesterification method. The molten DMT is dissolved in excess ethylene glycol (EG) at a molar ratio of EG / DMT = 1.9 to 2.2, and the transesterification reaction is carried out at a temperature of 130 to 250 ° C. under normal pressure. A catalyst such as manganese acetate is required for the transesterification reaction. Methanol produced by the transesterification reaction is removed by distillation. Unreacted ethylene glycol is removed by evaporation after the transesterification reaction. The product obtained by this transesterification is bis-β-hydroxyethyl terephthalate (BHET).

  The second preparation method is a direct esterification method, in which an esterification reaction of terephthalic acid with ethylene glycol is performed. This esterification reaction is carried out at a temperature of 190 to 280 ° C., preferably 200 to 260 ° C., in a molar ratio of EG / terephthalic acid = 1 to 1.5. In this esterification reaction, since terephthalic acid itself can contribute as a catalyst, no further catalyst compound need be added. An appropriate esterification catalyst compound can be added as needed. The product obtained by this transesterification is bis-β-hydroxyethyl terephthalate (BHET) or an oligomer of ethylene terephthalate that has undergone further reaction.

  Next, a polycondensation step is performed. Generally, the polycondensation step is performed by using a germanium catalyst compound such as germanium dioxide, germanium tetraethoxide, germanium tetra-n-butoxide, an antimony catalyst compound such as antimony trioxide, or titanium tetrabutoxide. A titanium catalyst compound such as can be used.

  The polyester composition of the present invention can be used for forming a bottle. A general method for producing a bottle from a thermoplastic polymer can be suitably employed for molding the polyester composition of the present invention. In particular, a method of performing injection molding and then blow molding is generally preferred. If the polyester composition of the present invention is used for molding, the resulting bottle can easily have a haze of 0.5% or less. The bottle can be suitably used as a beverage bottle.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

[Example 1]
1. Manufacture of polyester composition [Manufacture of master chip]
In a mixture of 20,000 g (103.2 mol) of dimethyl terephthalate and 12800 g (206.2 mol) of ethylene glycol, 5.0 mmol% of titanium trimellitic acid as a titanium atom with respect to dimethyl terephthalate, a stirrer, a rectifying tower And a methanol container that is equipped with a methanol condenser and capable of pressure reaction, pressurizes to 0.08 MPa, gradually raises the temperature from 140 ° C., and accumulates methanol generated as a result of the reaction outside the system. The transesterification reaction was carried out while allowing When the distillation of methanol is completed and the internal temperature reaches 235 ° C., 10% by weight of spherical silica particles having an average particle diameter of 25 nm is 2.0% by weight with respect to the obtained polyester composition (master chip). Glycol sol (purchased from Catalyst Kasei Co., Ltd., trade name: Oscar special product) was added. Next, when the internal temperature reached 248 ° C., sodium acetate was 5.0 mmol% as terephthalic acid dimethyl ester, germanium dioxide was dimethyl terephthalic acid as a sodium atom, 35 mmol% as germanium dioxide molecules and positive phosphorus. The acid was added to terephthalic acid dimethyl ester in an amount of 30.0 mmol% as a phosphorus atom, and the reaction was terminated after stirring for 5 minutes.

Subsequently, the obtained reaction product is transferred to a reaction vessel equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and gradually heated from 210 ° C. to 280 ° C., and from a normal pressure to a high vacuum of 50 Pa. The polycondensation reaction was carried out while reducing the pressure. While tracing the melt viscosity of the reaction system, the polycondensation reaction was terminated when the intrinsic viscosity reached 0.58 dL / g. The molten polymer was extruded in the form of a strand from the bottom of the reactor into cooling water, and was cut into pellets using a strand cutter.
The average particle size of the silica particles was measured by the manufacturer of the product, and the product was judged by the value displayed on the test certificate attached at the time of delivery.

[Addition of master chip: Production of polyester composition]
The chips produced by the above production method were blended so that the spherical silica particles had the concentrations shown in Table 2 (0.1% by weight, 0.5% by weight) with respect to the weight of the Teijin polyester (polyethylene terephthalate) resin. Two types of polyester compositions having different spherical silica contents were obtained.

2. Evaluation method [Molding]
Each of the polyester compositions was dried at 160 ° C. for 5 hours or more, and then injection / blow molded.

[transparency]
The molded product was confirmed with a haze meter. Compared with the bottle formed without adding spherical silica particles, the haze of 0.5% or less was evaluated as ◯, and the value exceeding 0.5% was evaluated as ×.

[Strength / Elastic modulus]
A No. 2 test piece was created from the body of the molded product, and the tensile strength and tensile modulus were evaluated using an autograph manufactured by Shimadzu Corporation. Moreover, it compared similarly with the molded product without spherical silica addition.

[Dispersibility]
A thin piece was prepared from the body of the molded product, and the dispersibility of the spherical silica particles was evaluated with a transmission electron microscope TECNAI G2 (manufactured by FEI) at an acceleration voltage of 120 kV. Transmission electron micrographs of bottles added with spherical silica having an average particle size of 25 nm and 120 nm are shown in FIG. 1 (Example 1) and FIG. 3 (Example 3), respectively. Other physical property evaluation results are shown in Table 2.

[Hue]
The appearance of the molded bottle was observed, a bottle having a good hue was judged as ◯, and a bottle having a yellow hue was judged as x.

[Examples 2-3]
The same operation as in Example 1 was carried out except that spherical silica particles having an average particle size shown in Table 1 were used, and a polyester composition and a bottle were obtained. However, the content of spherical silica was one type of 0.1% by weight. The transmission electron micrograph of the sample of Example 2 is shown in FIG. Other physical property evaluation results are shown in Table 2.

[Comparative Example 1]
Except for not adding the spherical silica particles, the polyester composition and the bottle forming operation and the evaluation method thereof were the same as those in Example 1 to obtain a polyester composition and a bottle. The results are shown in Table 3.

  According to the present invention, since a polyester composition having sufficient strength can be obtained even if thin wall molding is performed, it is possible to provide a beverage bottle that has been molded thinner than the prior art, and the amount of resin to be used can be reduced. The load on the environment and the environment will be reduced. In a still more preferred embodiment, a thin bottle excellent in transparency and hue can be provided. The knowledge of these matters has great industrial significance.

It is the SEM photograph of the surface which shaved the surface layer of the bottle surface obtained in Example 1 flatly. The horizontal black bar at the bottom left represents 1 μm. It is a SEM photograph of the surface which shaved flatly the surface layer of the bottle surface obtained in Example 2. The horizontal black bar at the bottom left represents 0.2 μm. It is the SEM photograph of the surface which shaved the surface layer of the bottle surface obtained in Example 3 flatly. The horizontal black bar at the bottom left represents 2 μm. It is the SEM photograph of the surface which shaved flatly the surface layer of the place different from FIG. 3 with the bottle surface obtained in Example 3. FIG. The horizontal black bar at the bottom left represents 2 μm.

Claims (8)

  A polyester composition comprising an aromatic polyester and spherical silica, the average particle diameter of the spherical silica is 20 to 180 nm, and the spherical silica is 0.01 to 0.6% by weight based on the total weight of the polyester composition. Polyester composition included.   The polyester composition according to claim 1, wherein the aromatic polyester is polyethylene terephthalate or polyethylene naphthalate.   The polyester composition according to claim 1 or 2, wherein the spherical silica has an average particle size of 23 to 50 nm.   The polyester composition according to any one of claims 1 to 3, wherein the spherical silica is contained in an amount of 0.05 to 0.4% by weight based on the total weight of the polyester composition.   A silica sol containing spherical silica having an average particle size of 20 to 180 nm is introduced into a mixture of at least one diol and at least one aromatic dicarboxylic acid or aromatic dicarboxylic acid ester, and esterification reaction or transesterification reaction is performed. The method for producing a polyester composition according to any one of claims 1 to 4, further comprising a step of polycondensing the esterification reaction product or the transesterification reaction product obtained under reduced pressure.   A mixture of at least one diol and at least one aromatic dicarboxylic acid or aromatic dicarboxylic acid ester is subjected to esterification reaction or transesterification reaction, and then the obtained esterification reaction product or transesterification reaction product is obtained. In a method for producing a polyester composition including a step of polycondensation under reduced pressure, a polyester composition comprising 1 to 30% by weight of spherical silica having an average particle diameter of 20 to 180 nm based on the total weight of the polyester composition is polycondensed. It adds in the process after a process, The manufacturing method of the polyester composition of any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a polyester composition according to claim 5 or 6, wherein a titanium catalyst or a germanium catalyst is used in the step of polycondensation.   A bottle having a haze of 0.5% or less formed by molding the polyester composition according to any one of claims 1 to 4.