JP2005193379A - Method for manufacturing polyester preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyester preform efficiently reduced in the content of acetaldehyde by compression-forming a general-purpose polyester resin low in intrinsic viscosity. <P>SOLUTION: A melt of a polyester resin due to melt polymerization is subjected to degassing treatment to reduce the concentration of acetaldehyde of the polyester resin and the intrinsic viscosity (IV) of the polyester resin is substantially increased. The melt after treatment is compression-formed to form the polyester preform. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a polyester preform used for producing a polyester container such as a bottle or a cup, and more specifically, a method for producing a preform by compression molding using a general-purpose polyester resin having a low intrinsic viscosity. About.

Stretch blow molded plastic containers, in particular biaxially stretched polyester containers, are now commonplace, and liquids such as liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc. due to their excellent transparency and moderate gas barrier properties. In addition to products such as foods, they are widely used in carbonated beverages such as beer, cola, and cider, and other beverage containers such as fruit juice and mineral water.
When forming a biaxially stretched polyester container, a bottomed preform having a size considerably smaller than the final container and having an amorphous polyester is formed in advance by injection molding of a polyester resin, and the preform is brought to its stretching temperature. A method of preheating, stretching in the axial direction in the blow mold and blow-stretching in the circumferential direction is employed (for example, Patent Document 1).

As the shape of the bottomed preform, a mouth-and-neck portion corresponding to the mouth-and-neck portion of the container and a bottomed cylindrical portion to be stretch blow molded are generally used, and the shape as a whole is a test tube. The mouth / neck portion is formed with, for example, a sealing opening end or an engaging means with a lid. In addition, a gate portion that protrudes outward from the center of the bottom portion is always formed on the bottom portion because of the necessity of injection molding.
However, in general, in the manufacture of a preform by injection molding, the melt-plasticized resin is injected into the cavity through the nozzle, sprue, runner, and gate, so that the residence time of the resin in the injection molding machine is long. A long stay in a simple molding machine may cause deterioration of the resin. In particular, the polyester resin has a problem in that satisfactory mechanical strength cannot be obtained because the intrinsic viscosity and molecular weight decrease due to thermal decomposition.
Further, acetaldehyde is generated during the thermal decomposition of the polyester resin, and the acetaldehyde remaining in the polyester causes a decrease in the flavor retention of the bottle.

From such a viewpoint, it has already been proposed to produce a bottomed preform by compression molding of a resin. For example, Patent Document 2 discloses a female mold in which a molten resin mass extruded from an extruder is cut and held. A method for manufacturing a preform is described, which comprises supplying a male mold into the female mold and compressing the female mold into the female mold after being supplied into the female mold.
However, in the manufacture of a preform by compression molding, even if the whitening tendency of the gate part is eliminated as in the case of a preform manufactured by injection molding, the tendency to draw down the molten resin mass extruded from the extruder is suppressed. Therefore, it is necessary to use a polyester resin by solid phase polymerization having a high intrinsic viscosity, and it is also desired from the viewpoint of cost to produce a preform by compression molding using a polyester resin by melt polymerization having a low intrinsic viscosity.

  A method for producing a polyester preform in which the melt-polymerized polyester resin melt is formed by reducing the concentration of acetaldehyde by a degassing treatment without substantially increasing the intrinsic viscosity, and molding the melt after the treatment into a preform. Has been proposed (Patent Document 3).

JP-A-4-154535 JP 2000-280248 A JP 2000-117819 A

According to Patent Document 3, since the melt-polymerized polyester resin can be used directly, there is no need to remelt the resin chip by solid-phase polymerization, and the acetaldehyde concentration is reduced, so that the flavor retention is also improved. Although there is an advantage that an excellent preform can be formed, since the deaeration treatment is performed without substantially increasing the intrinsic viscosity, it is necessary to draw a molten resin mass for application to the production of a preform by compression molding. In order to suppress the down tendency, it is necessary to use a polyester resin having a high intrinsic viscosity before the deaeration treatment.
In general, the ease of removal of acetaldehyde contained in a polyester melt is related to the intrinsic viscosity, and the higher the intrinsic viscosity, the more difficult the acetaldehyde escapes. In the above method, the acetaldehyde is removed by stirring little by little in a twin-screw extruder. I was not satisfied with the efficiency of deaeration.

Accordingly, an object of the present invention is to provide a production method by compression molding of a preform in which acetaldehyde is efficiently reduced using a general-purpose polyester resin having a low intrinsic viscosity.
Another object of the present invention is to provide a production method capable of molding a preform having a reduced acetaldehyde concentration and excellent in flavor retention by compression molding.

According to the present invention, the melt of the polyester resin by melt polymerization substantially increases the intrinsic viscosity (IV) of the polyester resin in the extruder and decreases the concentration of acetaldehyde by the degassing treatment. There is provided a method for producing a preform, characterized in that a preform is formed by compression molding an article.
In the method for producing the preform of the present invention,
1. The intrinsic viscosity (IV) of the polyester resin by melt polymerization is 0.55 to 0.64 dL / g,
2. 2. The intrinsic viscosity (IV) of the polyester resin after deaeration or compression molding is 0.65 to 0.85 dL / g. Increasing the intrinsic viscosity of the polyester resin after completion of the degassing treatment of acetaldehyde,
4). Performing the deaeration treatment of acetaldehyde and the treatment for increasing the intrinsic viscosity of the polyester resin separately in the same extruder,
Is preferred.

  The present invention also provides a preform manufactured by the above-described manufacturing method, and a polyester container formed by stretching the preform.

According to the preform manufacturing method of the present invention, a polyester resin having a low intrinsic viscosity by melt polymerization can be used, so that the production cost can be reduced by using an inexpensive raw material.
In addition, the polyester resin obtained by melt polymerization can be used directly without going through solid phase polymerization, and the degassing treatment can be performed efficiently, so that the productivity is excellent.
Further, since the polyester resin after deaeration has a high intrinsic viscosity, the tendency of the molten resin lump to be drawn down is suppressed, and the preform can be molded by compression molding with high productivity.
In addition, the preform molded by the manufacturing method of the present invention has advantages that there is no flow orientation distortion at the bottom, no gate part or other trimming operations are required, and the acetaldehyde concentration is reduced. A polyester container formed by stretching is excellent in flavor retention.
Further, according to the method of the present invention, since acetaldehyde removal by degassing treatment of the polyester melt is performed in a remarkably short time, the productivity is high, the apparatus and the operation cost are low, and the polyester chip by the melting method is used. There is no need for solidification, solid phase polymerization, remelting for molding into a preform, and so on, which has many advantages such as simplifying the process and saving energy costs.

In the preform manufacturing method of the present invention, the melt of the polyester resin by melt polymerization is reduced by degassing the concentration of acetaldehyde, and the intrinsic viscosity of the polyester resin is substantially increased. It is an important feature to form a preform by compression molding.
The ease of removal of acetaldehyde contained in the polyester melt is closely related to the intrinsic viscosity (IV) of the polyester, and the higher the intrinsic viscosity (IV), the more difficult it is to escape.
In the present invention, by using a polyester melt having a low intrinsic viscosity (IV) subjected to a degassing treatment, acetaldehyde in the molten polyester is efficiently removed, and then acetaldehyde is sufficiently reduced. In this state, by increasing the intrinsic viscosity of the molten polyester resin, it is possible to increase the reduced acetaldehyde without increasing the acetaldehyde and to suppress the preform drawdown tendency. This makes it possible to directly use a molten polyester resin having a low viscosity.
In particular, as the polyester melt subjected to the degassing treatment, an intrinsic viscosity (IV) having an intrinsic viscosity (IV) of 0.55 to 0.64 dL / g, preferably 0.57 to 0.62 dL / g will be described later. It is desirable in terms of easily increasing the intrinsic viscosity of the polyester resin.

In order to increase the intrinsic viscosity of the polyester resin in the production method of the present invention, it can be carried out simultaneously with the deaeration treatment of acetaldehyde, but it is preferably carried out after the deaeration treatment of acetaldehyde. In this case, the acetaldehyde removal treatment and the polymerization treatment can be performed by separate apparatuses, but can also be performed by forming a degassing zone and a polymerizable zone in a single extruder.
That is, the relationship between the melt degassing time and the acetaldehyde concentration in the polyester melt is such that the acetaldehyde concentration decreases monotonically with the melt degassing time, but the degree of decrease gradually decreases with time and eventually saturates. Tend. On the other hand, the relationship between the melt degassing time and the intrinsic viscosity of the polyester is such that the intrinsic viscosity hardly increases while the time is short, but after a certain time, the intrinsic viscosity increases with the treatment time due to condensation polymerization. . Therefore, it is possible to simultaneously perform the acetaldehyde removal treatment and the intrinsic viscosity increasing treatment by performing a deaeration treatment until the intrinsic viscosity increases. In this case, however, the treatment time is prolonged and the polyester resin is colored. Another problem may occur.

  FIG. 1 shows an example of a preform manufacturing process according to the present invention. The equipment used in this manufacturing process includes a polyester continuous melt polymerization apparatus 11, an acetaldehyde removal apparatus 12, a polyester intrinsic viscosity increasing apparatus 13, and a preform. It consists of a compression molding device 14. The polyester melt polymerized to have an intrinsic viscosity in the range of 0.55 to 0.64 dL / g in the melt polymerization apparatus 11 is continuously sent to the acetaldehyde removal apparatus 12 and kept under degassing conditions. To remove acetaldehyde in the polyester melt. The polyester melt from which acetaldehyde has been removed is sent from the removing device 12 to the intrinsic viscosity increasing device 13 and polymerized until it has an intrinsic viscosity in the range of 0.65 to 0.85 dL / g. The molten polyester resin whose intrinsic viscosity has been increased to the above range is supplied to the compression molding device 14 by the conveying device 15 and molded into a preform 16 for forming a bottle.

(polyester)
The polyester resin used in the present invention is a polyester resin derived from a carboxylic acid component mainly composed of one or more aromatic dicarboxylic acid components and an alcohol component mainly composed of one or more glycol components. Polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and the like are typical examples, and polyethylene terephthalate is preferable.

  The polyethylene terephthalate is a linear polyester resin containing 85 mol% or more of ethylene terephthalate units as a main repeating unit, and preferably a linear polyester resin containing 95 mol% or more.

  Examples of the dicarboxylic acid component incorporated into the polyethylene terephthalate by copolymerization include aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, and diphenoxyethanedicarboxylic acid, and their functions. Oxyacids such as p-oxybenzoic acid and oxycaproic acid and their functional derivatives; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, glutaric acid and their functional derivatives, cyclohexanedicarboxylic acid And alicyclic dicarboxylic acids and functional derivatives thereof.

  Examples of the glycol component incorporated into the polyethylene terephthalate by copolymerization include aliphatic glycols such as diethylene glycol, trimethylene glycol, tetramethylene glycol, and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, bisphenol A, and bisphenol A. Examples include aromatic glycols such as alkylene oxide adducts.

Further, as other copolymer components composed of polyfunctional compounds that can be incorporated into a polyester resin composed of polyethylene terephthalate, examples of the acid component include trimellitic acid, pyromellitic acid, and the like, and glycerin as the glycol component. And pentaerythritol. The amount of the copolymer component composed of these polyfunctional compounds must be such that the polyester resin is substantially kept linear.
The polyester resin preferably has a melting point (Tm) of less than 265 ° C., particularly 220 to 255 ° C. The glass transition point is preferably 30 ° C. or higher, particularly 50 to 120 ° C.
In addition, a colorant, an ultraviolet absorber, an antioxidant, an antistatic agent, a lubricant, a nucleating agent, a release agent, and the like are added to the polyester resin used in the present invention as long as the purpose of the present invention is not impaired. can do.

(Melt polymerization process)
The polyester used in the present invention is produced by any melt polymerization method known per se. Each raw material is esterified in the presence of an esterification catalyst and then liquid phase polymerized in the presence of a polymerization catalyst to reach a predetermined molecular weight. Examples of the production method include a batch method and a continuous method (single can method, multistage method).
In the present invention, it is preferable that the intrinsic viscosity (IV) of the melt of the thermoplastic polyester before the deaeration treatment is low, particularly in the range of 0.55 to 0.64 dL / g, and the acetaldehyde concentration is based on the polyester. It is preferably 25 ppm to 80 ppm.

If the intrinsic viscosity of the polyester by melt polymerization before the deaeration treatment exceeds the above range, it is difficult to suppress the acetaldehyde concentration of the final preform to 25 ppm or less even if the deaeration treatment is performed. The polyester container may cause a problem in flavor retention. On the other hand, when the intrinsic viscosity of the polyester is below the above range, it takes a long time to increase the intrinsic viscosity.
In general, the concentration of acetaldehyde in the polyester melt by the melt polymerization method is not 25 ppm or less, and is generally 30 ppm or more. However, if the acetaldehyde concentration exceeds 80 ppm, it is difficult to suppress the acetaldehyde concentration of the preform to 25 ppm or less even if the degassing treatment of the present invention is performed, which is not preferable in terms of flavor retention of the polyester container.

The thermoplastic polyester melt before degassing treatment preferably has a phosphorus-containing compound content (as phosphorus element) of 1 to 1000 ppm based on the polyester. More preferably, it is 10-500 ppm, More preferably, it is 20-300 ppm.
In general, when dealdehyde is removed from a resin using an extruder equipped with a vent, the resin is considerably colored compared to the conventional melt polymerization or solid state polymerization after melt polymerization. This is a characteristic phenomenon when dealdehyde is removed from the resin using a vented extruder. Shear heat generation between the screw and barrel of the extruder, local temperature rise due to heating of the heater part of the barrel, decompression Even so, it is considered that the resin deteriorates due to the fact that the air leaks from the barrel connecting portion and the resin is easily exposed to oxygen.
By adding a phosphorus-containing compound, the above-mentioned coloring problem can be effectively prevented. When the phosphorus content is less than 1 ppm, the anti-coloring effect is not sufficient. When the phosphorus content exceeds 1000 ppm, not only the effect as a stabilizer is saturated, but also problems such as a decrease in reaction rate occur.

  Examples of phosphorus-containing compounds include trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, and the like, triphenyl phosphite, trisdodecyl phosphite, trisnonylphenyl. Preferred examples include phosphites such as phosphites, acid phosphates such as methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, and dioctyl phosphate, and phosphoric acid and polyphosphoric acid. . The phosphorus-containing compound may be added during the esterification reaction step or may be added during the polycondensation reaction step. Furthermore, it may be added either in the extruder with a vent or until it is supplied to the extruder with a vent. Of course, it may be added sequentially for each step.

The melt of the thermoplastic polyester before the degassing treatment has an acid value of 20 to 80 equivalent / ton, particularly preferably 35 to 60 equivalent / ton.
When the acid value is lower than 20 equivalents / ton, the amount of aldehyde generated by the resin decomposition increases, and it is necessary to further improve the performance of the vented extruder for reducing the acetaldehyde amount of the preform to 25 ppm or less. In other words, it is not economical, and the amount of aldehyde generated in the molding process is large, resulting in an increase in the aldehyde content of the molded product.
Further, when the acid value exceeds 80 equivalents / ton, there is a problem that the reaction rate of the polycondensation becomes slow and the residence in the polycondensation reactor until the desired intrinsic viscosity is reached becomes long. Coloring occurs and impurities due to resin decomposition increase. Thus, by appropriately adjusting the acid value of the resin, it is possible to balance the amount of acetaldehyde generated and the polymerization rate and efficiently obtain a polyester resin having a low acetaldehyde amount and a high molecular weight.
The acid value can be adjusted by adjusting the acid / diol ratio charged in the polyester resin production process by polycondensation reaction. Any known method such as adding an acid component in the late stage of the reaction, adding an acid anhydride or the like before the completion of the reaction, and converting the terminal to a carboxylic acid can be employed.

  The polyester resin used in the present invention includes compounds containing at least one metal element selected from alkali metals, alkaline earth gold layers, Zn, Mn, and Co, particularly Mg, Ca, Zn, and Mn. It is preferable that at least one compound containing at least one metal element selected from Co and Co is contained. By containing these components, the transparency and color tone can be further improved. The content of these compounds is preferably 1 to 1000 ppm, more preferably 3 to 500 ppm, and particularly preferably 5 to 300 ppm with respect to the polyester resin as a value obtained by adding the weights of the respective elements.

  In general, when a resin after melt polymerization is directly molded into a preform without passing through a solid phase, the temperature rise crystallization temperature is higher than that of a resin that has passed through a solid phase, and for example, the mouth is thermally crystallized. In the case of a bottle preform or the like, the temperature rise crystallization temperature of the mouth part exceeds 180 ° C., and the productivity of the preform may be inferior. By adding the phosphorus element-containing compound and the metal element-containing compound, the temperature rising crystallization temperature required for the crystallization treatment of the resin can be lowered to 140 to 180 ° C.

(Acetaldehyde removal step)
According to the present invention, the concentration of acetaldehyde in a thermoplastic polyester melt having a low intrinsic viscosity, preferably 0.55 to 0.64 dL / g, formed by melt polymerization is reduced by degassing.
The deaeration treatment is performed at a temperature not lower than the melting temperature of the thermoplastic polyester and not higher than 320 ° C. under a reduced pressure of 0.01 to 10 torr so as to remove acetaldehyde in a short time of 0.1 to 10 minutes. Good. The resin temperature during the degassing treatment is preferably in the range of 250 ° C to 290 ° C.

  The deaeration treatment should be performed in as short a time as possible in order to prevent the polyester resin from being colored. For this purpose, the treatment should be performed under the above-mentioned temperature and reduced pressure. If the pressure during decompression exceeds the above range, it is difficult to effectively remove acetaldehyde, and the hue of the polyester resin tends to decrease. Moreover, when the resin temperature at the time of a process exceeds the said range, it will also become difficult to remove acetaldehyde effectively, and the hue of a polyester resin also tends to fall.

  The apparatus used for the deaeration treatment is not particularly limited as long as the kneading of the molten resin and the deaeration of acetaldehyde are performed effectively. However, an extruder with a vent is preferable in terms of acetaldehyde removal efficiency. As the extruder with a vent, either a single-screw extruder or a twin-screw extruder can be used, but a twin-screw extruder is preferable because of high stirring efficiency and acetaldehyde reduction efficiency. Note that the screw of the twin-screw extruder may be any of a meshing type, a non-meshing type, and an incomplete meshing type, or any of the same direction and different direction rotations.

  The design and operating conditions of the apparatus for deaeration treatment are also set so that acetaldehyde is efficiently performed in a short time treatment, the screw rotation speed is 50 to 250 rpm, and the place for deaeration is 10 in L / D. Best performed in a -60 vented twin screw extruder.

(Intrinsic viscosity increasing process)
In the present invention, the melted polyester resin in which the acetaldehyde concentration is reduced by the degassing treatment is subjected to a polymerization step, whereby an intrinsic viscosity in a range in which drawdown does not occur during compression molding, preferably 0.65 to Increase to an intrinsic viscosity in the range of 0.85 dL / g.
The polymerization treatment is preferably carried out at a temperature not lower than the melting temperature of the thermoplastic polyester and not higher than 300 ° C., preferably at a temperature of 270 to 290 ° C. for 5 to 30 minutes, particularly 10 to 20 minutes. Also in this case, it is preferable to perform polymerization while degassing under a reduced pressure of 0.01 to 10 torr in order to prevent the reduced acetaldehyde concentration from increasing.

  The apparatus used for the polymerization is not particularly limited as long as the molten resin can be kneaded effectively, but a vented extruder is preferable in that acetaldehyde accompanying polymerization can be removed. As the extruder with a vent, the same one as used for the deaeration process can be used, and a separate one from the deaeration process may be used, but preferably a single twin-screw extruder is used. The temperature condition and the residence time can be changed, and the degassing zone and the polymerization zone can be used separately.

In the method of the present invention, the intrinsic viscosity of the polyester after deaeration and polymerization is preferably 0.65 to 0.85 dL / g, thereby suppressing the drawdown at the time of melt extrusion and up to the compression molding step. In addition to improving transportability, the preform can be efficiently molded in the next compression molding process, such as stringing when cutting the molten polyester resin to obtain drops and improving upright stability in the compression mold. It becomes.
Moreover, it is preferable that the acetaldehyde density | concentration of the melt of the thermoplastic polyester after deaeration and a polymerization process is 25 ppm or less on the basis of polyester. Thereby, the flavor retention of a final bottle can be improved notably.

(Compression molding process)
In the present invention, the degassed and polymerized molten polyester is transferred from a vented extruder and supplied to a compression molding machine.
That is, the extruder continuously extrudes the melt and cuts it to produce a molten resin lump (drop) that is a preformed preform for a preform in a molten state. The molten resin lump is compression molded. It is put into the cavity mold of the machine, and this is compression molded with the core mold. When a large number of compression molding dies are circumferentially arranged on the rotating turret, the preform can be molded with high efficiency in an intermittent but close to continuous state.
In the method for producing a preform of the present invention, the melt extrusion temperature of the molten polyester resin is preferably in the range of Tm + 5 ° C. to Tm + 40 ° C., particularly Tm + 10 ° C. to Tm + 30 ° C., based on the melting point (Tm) of the polyester resin. At a temperature lower than the above temperature, the shear rate becomes too high, and it may be difficult to form a uniform melt extrudate. On the other hand, at a temperature higher than the above range, the degree of thermal degradation of the resin increases. Or the drawdown becomes too large, and it becomes difficult to form a preform having the above-mentioned characteristics.

  FIG. 2 is an explanatory view showing a compression molding apparatus used for molding the preform of the present invention. The compression molding apparatus generally indicated by 1 has an intrinsic viscosity of 0.65 to 0 after the deaeration and polymerization treatment described above. Resin A for inner and outer layers composed of a polyester resin of .85 dL / g is continuously supplied from the main extruder 2, and an intermediate layer resin B such as a gas barrier resin is intermittently supplied from the sub-extruder 3, The composite melt extruded by the cutting means 6 which is melt-extruded from the nozzle 5 provided below the multilayer die 4 so that the resin A encloses the resin B by being merged in the multilayer die 4 and moved in the horizontal direction. The resin 7 is cut into a predetermined dimension at a portion where the intermediate layer does not exist. The cut composite molten resin lump 8 is conveyed into a female mold 9 of a compression molding apparatus composed of a female mold 9 and a male mold 10 immediately after cutting, sandwiched between jigs. The composite molten resin mass 8 in the female mold 9 is compression-molded by the male mold 10 to form a multilayer preform in which the intermediate layer is sealed with the inner layer and the outer layer.

(preform)
The preform of the present invention is obtained by compression-molding the molten polyester resin that has been subjected to the above-described degassing and polymerization treatment. Of course, a multilayer preform having a layer made of another thermoplastic resin in a layer made of this polyester resin may be used.
As the thermoplastic resin other than the polyester resin, any resin can be used as long as it is a resin that can be stretch blow molded and thermally crystallized, and is not limited thereto. However, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene- Examples thereof include olefin resins such as vinyl alcohol copolymers and cyclic olefin polymers, and polyamide resins such as xylylene group-containing polyamide. In addition, oxygen-absorbing gas barrier resin compositions containing diene compounds and transition metal catalysts in polyamides containing xylylene groups, recycled polyesters (PCR (resin that recycles used bottles), SCRs (generated in production plants) Resin) or a mixture thereof) can also be used. These recycled polyester resins preferably have an intrinsic viscosity (IV) measured by the method described above in the range of 0.65 to 0.75 dL / g.

The recycled polyester can be used alone or as a blend with virgin polyester. When the recycled polyester has a reduced intrinsic viscosity, it is preferably used by blending with the virgin polyester. In this case, the ratio of the recycled polyester: virgin polyester is 1: 5 to 5: 1. Preferably there is.
Moreover, in order to adhere | attach an inner layer or an outer layer, and an intermediate | middle layer, adhesive resin can also be interposed. As the adhesive resin, an acid-modified olefin resin obtained by graft polymerization of maleic acid or the like, an amorphous polyester resin, a polyamide resin, or the like can be used.
Moreover, various additives for resin can be mix | blended with thermoplastic resins other than the said polyester resin similarly to the said polyester resin for compression molding.

Although the layer structure of the multilayer preform of the present invention is not limited to this, the following can be exemplified. The following abbreviations in the multilayer structure are: PET: polyester resin that has been subjected to degassing treatment and intrinsic viscosity increasing treatment according to the method of the present invention, GBR: gas barrier resin, PCR: recycled polyester resin, ADR: adhesive resin, OAR : Oxygen-absorbing resin composition, COC: Cyclic olefin copolymer.
Three-layer structure: PET / GBR / PET, PET / PCR / PET
PET / (PET + PCR) / PET
Four-layer structure: PET / GBR / PCR / PET,
PET / GBR / OAR / PET,
PET / GBR / COC / PET
Five-layer structure: PET / ADR / GBR / ADR / PET
PET / ADR / OAR / ADR / PET
PET / GBR / PCR / GBR / PET
PET / ADR / (GBR + OAR) / ADR / PET
Six-layer structure: PET / ADR / GBR / AR / PCR / PET
PET / ADR / OAR / ADR / PCR / PET
Seven-layer structure: PET / PCR / ADR / GBR / ADR / PCR / PET
PET / ADR / GBR / ADR / OAR / ADR / PET

  FIG. 3 is a cross-sectional view of an example of a multilayer preform among the preforms of the present invention. The multi-layer preform indicated as a whole by 20 consists of a mouth-and-neck part 21, a trunk part 22 and a bottom part 23. In the specific example shown in the figure, the preform is formed by compression molding having no gate portion at the bottom, and the portion excluding the end portion 21a of the mouth and neck portion 21 is the same as the three layers of the inner layer 24, the intermediate layer 25 and the outer layer 26. It has a structure.

(Polyester container)
The polyester container of the present invention can be obtained by stretching the preform.
In the stretch blow molding, the preform of the present invention is heated to a stretching temperature, the preform is stretched in the axial direction, and biaxial stretch blow molding is performed in the circumferential direction to produce a biaxially stretched container.
The preform molding and the stretch blow molding can be applied to a hot parison system in which stretch blow molding is performed without completely cooling the preform, in addition to the cold parison system. Prior to stretching blow, if necessary, the preform is preheated to an appropriate stretching temperature by means of hot air, an infrared heater, high frequency induction heating or the like. In the case of polyester, the temperature range is 85 to 120 ° C., particularly 95 to 110 ° C.

The preform is supplied into a publicly known stretch blow molding machine, set in a mold, stretched in the axial direction by pushing a stretching rod, and stretched in the circumferential direction by blowing a fluid. In general, the mold temperature is preferably in the range of room temperature to 190 ° C. However, as described later, when heat setting is performed by the one mold method, the mold temperature is preferably set to 120 to 180 ° C.
The draw ratio in the final polyester container is suitably 1.5 to 25 times in terms of area magnification. Among these, the axial draw ratio is 1.2 to 6 times, and the circumferential draw ratio is 1.2 to 4.5. It is preferable to double.

The polyester container of the present invention can be heat-set by a means known per se. The heat setting can be performed by a one-mold method performed in a blow molding die, or can be performed by a two-mold method performed in a heat fixing die separate from the blow molding die. The temperature for heat setting is suitably in the range of 120 to 180 ° C.
As another stretch blow molding method, as illustrated in Japanese Patent No. 29178851 of the present applicant, a preform is subjected to primary blow molding having a size larger than that of a final molded product using a primary blow mold. A two-stage blow molding method may be employed in which the primary blow molded body is heated and shrunk, and then stretch blow molding is performed using a secondary blow mold to obtain a final molded product.

  An example of the multilayer structure of the polyester container of the present invention is shown in FIG. In FIG. 4, the biaxially stretched container generally indicated by 40 has a bottle shape and is composed of a mouth part 41, a body part 42, and a bottom part 43. The body part 42 and the bottom part 43 are composed of an inner layer 44a and an outer layer 44b. It consists of the intermediate | middle layer 45 enclosed in. The mouth portion 41 is formed of only the inner and outer layer resins as in the multilayer preform described above.

[Example 1]
The polyethylene terephthalate resin after melt polymerization was subjected to degassing and intrinsic viscosity (IV) increasing treatment as it was, and supplied to a compression molding machine to form a preform. When IV measurement was performed at 30 ° C. in a phenol / tetrachloroethane having a weight ratio of 1: 1, it was 0.55 dL / g after melt polymerization and 0.66 dL / g after compression molding.
Conveyance of the molten resin mass during compression molding was stable, and the formability to the preform was also good. Further, after water extraction at 60 ° C. for 2 hours, the amount of acetaldehyde (AA) measured by gas chromatography was 21 ppm.

[Example 2]
After melt polymerization, molding and evaluation were performed in the same manner as in Example 1 except that the IV in the degassing / intrinsic viscosity (IV) increasing treatment was 0.60 dL / g and 0.70 dL / g, respectively.
Conveyance of the molten resin mass during compression molding was stable, and the formability to the preform was also good. Further, after water extraction at 60 ° C. for 2 hours, the amount of acetaldehyde (AA) measured by gas chromatography was 23 ppm.

[Example 3]
After melt polymerization, molding and evaluation were carried out in the same manner as in Example 1 except that the IV in the degassing / intrinsic viscosity (IV) increasing treatment was 0.64 dL / g and 0.82 dL / g, respectively.
Conveyance of the molten resin mass during compression molding was stable, and the formability to the preform was also good. Further, after water extraction at 60 ° C. for 2 hours, the amount of acetaldehyde (AA) measured by gas chromatography was 24 ppm.

[Comparative Example 1]
When the same operation as in Example 1 was performed using a polyethylene terephthalate resin having an intrinsic viscosity (IV) of 0.50 dL / g after melt polymerization, the IV after the deaeration / intrinsic viscosity (IV) increasing treatment was 0.63 dL. / G, and the conveyance of the molten resin mass during compression molding became unstable.

[Comparative Example 2]
When a polyethylene terephthalate resin having an intrinsic viscosity (IV) after melt polymerization of 0.70 dL / g was used and the same operation as in Example 1 was performed, the IV after degassing / increased viscosity (IV) increasing treatment was 0.88 dL. / G and the shapeability at the time of compression molding was not sufficient, and a good preform could not be molded.

[Comparative Example 3]
The same operation as in Example 1 was performed, except that the deaeration / intrinsic viscosity (IV) increase treatment was not performed. As a result, the preform IV became 0.56 dL / g and the transport of the molten resin mass became unstable. The acetaldehyde (AA) concentration in the preform was 50 ppm.

  The results of the above examples and comparative examples are shown in Table 1.

It is a figure which shows an example of the manufacturing process of this invention. It is a figure which shows an example of the compression molding machine used for shaping | molding of the preform of this invention. It is a figure which shows an example of the preform of this invention. It is a figure which shows an example of the polyester container of this invention.

Claims (7)

  The melt of the polyester resin by melt polymerization is reduced by degassing the acetaldehyde concentration and the inherent viscosity (IV) of the polyester resin is substantially increased, and the melt after the treatment is compression molded to form a preform. A method for manufacturing a preform.   The process according to claim 1, wherein the intrinsic viscosity (IV) of the polyester resin by melt polymerization is 0.55 to 0.64 dL / g.   The production method according to claim 1 or 2, wherein the intrinsic viscosity (IV) of the polyester resin after deaeration or compression molding is 0.65 to 0.85 dL / g.   The production method according to any one of claims 1 to 3, wherein the intrinsic viscosity of the polyester resin is increased after completion of the degassing treatment of acetaldehyde.   The manufacturing method in any one of Claims 1 thru | or 4 which performs the deaeration process of acetaldehyde and the process which increases the intrinsic viscosity of a polyester resin separately in the same extruder.   A preform manufactured by the manufacturing method according to claim 1.   A polyester container obtained by stretching the preform according to claim 6.

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