JPH0641164B2 - Heat-fixed stretched polyester hollow container and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester hollow container and a method for producing the same,
More specifically, the present invention relates to a molecularly oriented heat-fixing polyester hollow container which is excellent in surface gloss and prevents the surface of the container from being roughened, and a method for producing the same.

(Prior Art) A biaxially stretch blow-molded container made of a thermoplastic polyester such as polyethylene terephthalate (PET) has excellent transparency and surface gloss, and also has impact resistance, rigidity and gas barrier property required for a bottle. It has and is used as a bottling container for various liquids.

However, the polyester container has the drawback of being poor in heat resistance, and for the purpose of hot filling the contents,
Since heat deformation and shrinkage deformation of volume occur, it is required to heat set (heat set) the biaxially stretched blow container after molding.

As for the method of heat setting, as seen in Japanese Patent Publication No. 60-56606, a molded product obtained by stretch blow molding is taken out from a molding blow mold and then held in a mold for heat setting to perform heat setting. As is known from Japanese Patent Publication No. 59-6216, a method of performing heat setting at the same time as stretch blow molding in a blow mold is known. In addition, JP-A-5
JP-A-7-53326 describes a method in which heat treatment is performed simultaneously with stretch blow molding in a temporary mold, and a molded product is taken out and blow molded in a secondary treatment mold without cooling the molded product. .

(Problems to be solved by the invention) In the polyester hollow container, from the viewpoint of improving the above-mentioned various physical properties, it is required that the polyester constituting the vessel wall is highly biaxially molecularly oriented, and the heat resistance is high. From the viewpoint of highly improving the heat resistance, it is required to perform the heat setting reliably at a higher temperature.

However, the heat-fixed stretched polyester hollow container has a lower surface gloss than the unheated stretched polyester hollow container, and in particular, in order to increase the degree of heat-fixing, the mold temperature is increased and It has been found that when the reforming temperature is increased, the decrease in surface gloss, that is, the occurrence of rough skin and cloudiness is particularly remarkable in the container body corresponding to the smooth portion of the mold.

Therefore, an object of the present invention is to prevent the surface gloss of a heat-set stretched polyester hollow container from being lowered, that is, to prevent the occurrence of rough skin and cloudiness.

Another object of the present invention is to provide a polyethylene terephthalate hollow container which has a high degree of biaxial molecular orientation and heat resistance and is also excellent in surface gloss, and a method for producing the same.

Still another object of the present invention is to provide a method capable of producing a heat-fixed stretched polyester container having the above characteristics with high productivity, without the need for complicated and troublesome operations such as mold cleaning.

(Means for Solving the Problems) According to the present invention, a neck portion, a shoulder portion obtained by stretch blow molding a thermoplastic polyester preform mainly composed of ethylene terephthalate units and thermally fixing the orientation, A container comprising a body and a closed bottom, wherein the container is formed from polyester having an intrinsic viscosity of 0.70 to 0.85 dl / g and a cyclic trimer content of 0.55% by weight or less, and the surface of the body is In the part of, the refractive index in the thickness direction on the inner surface side is 1.52
The molecule is oriented so that it becomes 00 or less, and it is heat-set so that the crystallinity by the density method becomes 30% or more.
Containers are provided that are characterized by having a gloss of 0% or greater.

According to the invention, it is also composed of a thermoplastic polyester mainly composed of ethylene terephthalate units and has an intrinsic viscosity of 0.
Crystallized pellets with 70 to 0.85 dl / g, a cyclic trimer content of 0.55% by weight or less, and a crystallinity of 40% or more by a density method are converted into bottomed preforms in a substantially amorphous state. A step of melt injection molding, a step of stretch blow-molding the bottomed preform into a hollow body in a blow mold at a stretching temperature, and a hollow body to be formed in the blow mold or a heat treatment mold different from the blow mold. A process for producing a heat-set stretched polyester hollow container having an excellent surface gloss is provided, which comprises a step of heating under tension and heat-setting.

(Operation) The inventors of the present invention have found that the decrease in surface gloss in the heat-set stretched polyester hollow container is caused by the migration and accumulation of certain components contained in the hollow body during the heat-setting treatment of the hollow body. , The pattern of this accumulation is transferred to the surface of the hollow body, which leads to a decrease in surface gloss, that is, the occurrence of rough skin and cloudiness; the component that is transferred to and accumulated on the mold surface is polyethylene terephthalate. It is a specific component having a high melting point among the monomer or oligomer components contained in a relatively large amount; and if the cyclic trimer component (CT) in the polyethylene terephthalate thus used is suppressed below a certain standard. , That the reduction of the surface gloss of the heat-set stretched polyester container can be effectively suppressed.

Generally, polyethylene terephthalate (PET) has the following formula using dimethyl terephthalate (DMT) and ethylene glycol (EG) as raw materials. Bis-β-hydroxyethyl terephthalate (BHET) is produced by the transesterification reaction shown in
HET or its low polycondensate is represented by the following formula It can be obtained by polycondensation as shown in.

This polycondensation reaction is carried out by melt polymerization or a combination of melt polymerization and solid phase polymerization.

Thus, polyethylene terephthalate contains various monomers and oligomers as shown below.

Ethylene glycol (hereafter EG) HOCH ₂ CH ₂ OH Terephthalic acid (hereafter TPA) Bishydroxyethyl terephthalate (hereinafter referred to as BHET) Monohydroxyethyl terephthalate (hereinafter referred to as MHET) Dimethyl terephthalate (hereinafter referred to as DMT) Monomethyl hydroxyethyl terephthalate (hereinafter MMMH
Called ET) Ring trimer (hereinafter referred to as CT) Cyclic tetramer Cyclic pentamer The content of these monomers or oligomers in PET is
Depending on the polycondensation conditions and the molecular weight of the produced PET, MHET and BHET are, for example, 5 to 100.
ppm order, 1-20 ppm EG, TPA
While the amount is 0.5 to 5 ppm, CT is a significantly large amount of 0.1 to 2.0% by weight. However, the above monomers generally have low melting points (other than TPA), whereas CT has a high melting point of 320 ° C.

However, according to the study by the present inventors, it is the cyclic trimer component, not the monomer component contained in a large amount in PET, that is attached and accumulated on the mold surface during the heat setting treatment. Was found as a result of chemical analysis. In addition, when the transfer of the monomer or oligomer to the surface was examined in the melted state of PET, it was found that the composition was about half of the monomers and about half of the cyclic trimer, despite the difference in the content described above. It turned out to be a transition. From the above, the cyclic trimer migrates to the mold surface together with the monomers even during the heat setting treatment, but the monomers volatilize and the cyclic trimer having a high melting point is formed on the mold surface. It was confirmed that the polymer (CT) remained attached.

Based on the above findings, the present invention significantly reduces migration and accumulation of foreign matter on the mold surface during heat setting treatment by reducing the CT content in PET to be used, and rough skin on the surface of the hollow body and generation of cloudiness. And the surface glossiness can be remarkably suppressed.

The content of PET cyclic trimer (CT) used should be 0.55 wt% or less, especially 0.51 wt% or less, most preferably 0.47 wt% or less, whereby highly biaxial molecular orientation is achieved. 90% or more, especially 130%, of the surface glossiness of the body of the PET hollow container that is highly heat-set
It becomes possible to maintain above. Although the CT content of PET constituting the wall of the hollow container increases slightly during the preform melt injection molding step, it is generally 0.55% by weight or less,
It is 0.51% by weight or less.

The intrinsic viscosity [η] of PET used is 0.70 to 0.85 dl / g,
In particular, it should be in the range of 0.75 to 0.82 dl / g. That is,
When the viscosity is lower than this range, the mechanical strength and impact resistance of the container are insufficient, while when it is higher than the above range, injection molding into a bottomed preform tends to be difficult.

The polyester hollow container according to the present invention is excellent in surface gloss while being subjected to a high degree of molecular orientation and a high degree of heat setting, but the planar portion of the body part has a thickness direction on the inner surface side. It is important that the molecular orientation is such that the refractive index of is 1.5200 or less, especially 1.5100 or less, otherwise, whitening occurs during heat setting, or impact resistance, gas barrier property, mechanical strength, The transparency and the like will be reduced.
The planar portion of the body has a crystallinity of 3 by the density method.
It is also important that the heat setting is 0% or more, particularly 33% or more, which significantly improves the heat resistance of the container, hot fills the contents, or bottles and pasteurizer sterilization. It is possible to improve the thermal deformation and the thermal contraction when applied.

The polyester container of the present invention is a conventionally known molding method using the above-mentioned PET, for example, after forming a preform by injection molding, and then biaxially stretch blow molding by a so-called one-mold method or two-mold method, It can be molded by heat fixing.

(Preferred Embodiment of the Invention) Polyester Hollow Container In FIG. 1 (side view), FIG. 2 (bottom view) and FIG. 3 (cross-sectional view) showing an example of the container of the present invention, this heat-set biaxially stretched polyester container is shown. 1 comprises an unstretched nozzle (neck) 2, a frustoconical shoulder 3, a tubular body 4 and a closed bottom 5. A pillar-shaped convex portion 7 having a relatively large diameter and a short circumferential length is provided at a main portion of the body portion 4.
And a plurality of panel-shaped recesses 6 having a relatively small diameter and a long circumferential length are alternately provided in the circumferential direction via short connecting portions 8. The pillar-shaped convex portion 7 extends in the axial direction (height direction) of the container, and therefore the panel-shaped concave portion 6 is formed in the pillar-shaped convex portion 7.
It has a rectangular shape with long corners rounded in the axial direction of the container partitioned by.

As can be seen from the sectional view of FIG. 3, the panel-shaped recess 6
It is possible to expand (project) radially outward by increasing the internal pressure and contract inward (concave) by decreasing the internal pressure, which has the effect of alleviating the internal pressure change.

In the specific example shown in the drawings, a bulging ring portion 9 having a relatively large diameter and a groove-shaped ring portion 10 having a relatively small diameter adjacent to the bulging ring portion 9 are provided above the panel-shaped recess installation portion. Therefore, a slight deformation in the axial direction of the container is allowed. In addition, there is a star-shaped inward recess 11 in the center of the bottom portion 5 so that outward buckling due to pressure or thermal deformation of the bottom portion 5 can be prevented.

In the heat-set stretched polyester container of the present invention, the thickness of the body is preferably in the range of 0.20 to 1.00 mm, particularly 0.25 to 0.80 mm, while the size of the panel-shaped recess varies depending on the size of the container. , Generally with a circumferential dimension of 10 to 5
0 mm, and the axial (height) dimension is preferably in the range of 40 to 160 mm. Further, the step difference between the pillar-shaped convex portion having a large diameter and the panel-shaped concave portion having a small diameter, that is, the difference in diameter is preferably within the range of 1 to 8 mm.

In this heat-set stretching container, it is the trunk portion 4, particularly the pillar-shaped convex portion 7 and the panel-shaped concave portion 6 that the surface gloss is most likely to be reduced. This problem can be solved by using PET.

Raw Material Polyester According to the present invention, PET having a CT content suppressed within the above-mentioned range is used as a raw material.

For the synthesis of polyethylene terephthalate, most methods generally used for the synthesis of saturated polyester can be applied, but the synthesis by the melting method is also easy to obtain the raw material, and not only the operation is simple compared to other methods, Almost all of them have been synthesized by the melting method today because they can be easily obtained with an arbitrary molecular weight and have high polymer purity and therefore excellent thermal stability.

The synthesis of polyethylene terephthalate by the melting method is usually divided into two steps: (A) a step of synthesizing bis-β-hydroxyethyl terephthalate (BHET) or a low polycondensate thereof, and (B) further It comprises a step of condensing to synthesize polyethylene terephthalate having an arbitrary degree of polymerization. However, the usual melt polymerization method has a disadvantage that when the degree of polymerization, that is, the viscosity is increased, the content of the cyclic trimer increases as the viscosity increases.

The raw material PET preferably used in the present invention is, of course, not limited to this, but generally PET obtained by melt polymerization is crystallized, and the crystallized PET is solid-phase polymerized to obtain an intrinsic viscosity of 0.70 in the final PET. To 0.85dl / g, the content of cyclic trimer is 0.55wt% or less, and the crystallinity by the density method is 4
It is obtained by setting it to 0% or more. Hereinafter, this method will be described.

In the melt polymerization, starting materials are dimethyl terephthalate and ethylene glycol, and oxides, carbonates, sulfides, and water of metals such as antimony, zinc, calcium, cerium, cadmium, lead, lithium, zirconium, aluminum, tin, and titanium. By heating and transesterifying in the presence of a catalyst such as an oxide or a carboxylate, bis-β-hydroxyethyl terephthalate (BHET)
Is synthesized. At this time, the concentration of the catalyst is about 1 to 1000.
ppm, preferably about 100-1000 ppm, more preferably about 500 ppm or less is suitable. These amounts are based on the ester feedstock fed to the reaction.

These substances were placed in a transesterification reactor at atmospheric pressure at 16
The reaction is carried out at a temperature of 0 to 230 ° C, especially 180 to 210 ° C. The low polycondensate, especially the cyclic trimer, which easily adheres to the surface of the container and the heat-fixing mold has a high melting point of 320 ° C., but when polymerized at a reaction temperature higher than the melting point of the cyclic trimer, thermal deterioration is remarkable. It is not preferable because a colored product is generated in association with this. The reaction time is dependently determined by these reaction temperature and pressure, but is generally 1 to 5 hours, especially 2
Allow to react for ~ 4 hours. The reaction product that has passed through a filter is placed in a melt polycondensation reaction tank at 10 to 0.1 mmH.
260 to 300 at a vacuum degree of g, especially 1 to 0.1 mmHg
The polycondensation reaction is carried out at a temperature of ° C, especially 270 to 280 ° C. The reaction time in this case is also determined depending on these reaction temperature and pressure, but is generally 1 to 4 hours, especially 2 hours.
Polycondensation is carried out by reacting for 3 hours.

The PET obtained by this melt polymerization is generally 0.5 to 0.8 dl
It has an intrinsic viscosity of / g.

The PET is pelletized and the pellets are heated to the crystallization temperature of PET to cause PET crystallization. PE
With the crystallization of T, the CT contained inside protrudes to the outside and the CT content decreases. This crystallization temperature has an optimum range for reducing the CT content, and is generally 100 to 140 ° C., particularly 115 to 125 ° C., and the treatment time is 100 to 180 minutes, particularly 120.
Approximately 150 minutes is suitable. The heat treatment for crystallizing the PET pellets can be carried out in a fluidized bed or a fixed bed using a heated inert gas such as heated nitrogen gas,
It can also be carried out in a vacuum heating furnace.

Then, the crystallized PET pellets are solid-state polymerized. In this solid-state polymerization, unlike the case of melt polymerization, the CT content decreases as the intrinsic viscosity increases. Also, in general, as the solid-state polymerization temperature increases, CT
The content decreases, and the CT content decreases as the polymerization time increases. The solid phase polymerization is generally carried out at a temperature of 160 to 260 ° C., particularly 180 to 200 ° C. for 2 to 10 hours,
It is particularly desirable to carry out for 4 to 6 hours. The heating during solid-state polymerization may be the same as in the case of crystallization, except that the temperature is changed. Crystallization of PET also proceeds to some extent during this solid-state polymerization.

As PET, in addition to PET homopolymer, a small amount of other glycols such as hexahydroxyrylene glycol may be contained as a glycol component, or other dibasic acid such as isophthalic acid or hexahydroterephthalic acid may be used as a dibasic acid component. So-called modified PET containing a small amount of components
Etc. are used. These polyesters can be used alone or in the form of blends with other resins such as nylons, polycarbonates or polyarylates.

Molding method In the present invention, the preform used in the stretch blow molding method can be manufactured by an injection molding method. Injection conditions are not particularly limited, but generally 260
A bottomed preform can be molded at an injection temperature of ˜300 ° C. and an injection pressure of 30˜60 kg / cm ² .

In order to impart heat resistance to the preform thus obtained, the neck and neck portion having the screwing portion, the fitting portion, the supporting ring, etc. may be crystallized and whitened by heat treatment at the stage of the preform. After completion of bottle molding, the mouth and neck of the unstretched part may be crystallized and whitened.

Bring the prepared preform to the stretch molding temperature. Preform The heat applied to the preform of the injection machine, that is, residual heat, is used to adjust the temperature range to a stretching temperature of 85 to 125 ° C., or in the case of a cold parison, reheating is performed and the temperature is adjusted to 85
Preheat to a stretching temperature range of ~ 125 ° C.

Stretch blow molding and heat setting can be performed by a one-mold method or a two-mold method. In any of these cases, the stretching operation involves blowing a pressurized fluid into the preform, performing axial tensile stretching and circumferential expansion stretching with a stretching rod, and the axial stretching ratio is 1.3 to 3.5 times, particularly 1.5 to It is preferable that the stretching ratio is 3 times, and the stretching ratio in the circumferential direction is 2 to 5.5 times, particularly 3 to 5 times.

In the case of the one-mold method, the blow mold is 110 to 230 ° C., preferably 120 when biaxially stretching with the blow mold.
The mold is heated to 210 ° C., and the heat treatment (heat setting) is started at the same time when the outside of the wall of the stretch-blown preform contacts the inner surface of the mold. After a predetermined heat treatment time, the blowing fluid is switched to the internal cooling fluid to start cooling the inside. The heat treatment time, which varies depending on the thickness and temperature of the blow-molded product, brings about the above-mentioned crystallinity in PET, and is generally 0.5 to 30 seconds, especially 1.0.
To the order of 20 seconds. On the other hand, the cooling time also varies depending on the heat treatment temperature and the type of cooling fluid, but is generally 1 to 3
On the order of 0 seconds, especially 2 to 20 seconds.

INDUSTRIAL APPLICABILITY The present invention is particularly remarkable in the improvement effect when performing high-magnification drawing and high-temperature heat-setting by using a relatively high-temperature preform and a high-temperature blow mold in the one-mold method. The stretching speed is 3.0 times / second or more, particularly 4.0 times / second or more, and the stretching speed in the circumferential direction is 5.0 times / second or more, especially 6.0 times / second or more.
A high-speed drawing such that the speed is double / second or more is advantageously used.
Further, as the pressurized fluid blown at the time of stretch blow molding,
It is preferable to use a hot fluid that is at least 10 ° C. above the preform temperature.

As the cooling fluid, various cooled gases, for example, -4
In addition to nitrogen, air, carbon dioxide, etc. at 0 ° C to room temperature, chemically inert liquefied gases such as liquefied nitrogen gas, liquefied carbon dioxide, liquefied trichlorofluoromethane gas, liquefied dichlorodifluoromethane gas, other liquefied aliphatic carbonization Hydrogen gas or the like is also used. A liquid mist having a large heat of vaporization, such as water, can be allowed to coexist with this cooling fluid. By using the cooling fluids mentioned above, significantly higher cooling rates can be obtained.

In the case of the two-mold method, using a blow mold heated to a high temperature, the stretch blow-molded hollow body is taken out to the outside without being cooled, and this hollow body is put into a second mold, and this mold is used. For example, a blowing method is used to adjust the shape inside. Stretching blow conditions and heat treatment conditions can be based on the one-mold method.

(Effect of the invention) According to the present invention, by reducing the CT content in the PET used, migration and accumulation of foreign matter on the mold surface during heat setting treatment is significantly reduced, and the surface of the hollow body is roughened. It is possible to suppress the occurrence of fogging and significantly suppress the surface glossiness.

The lowering of the surface gloss of the PET container becomes more remarkable as the degree of stretching and the degree of heat fixing increase, but according to the present invention, the surface of the PET container has a high degree of biaxial molecular orientation and heat resistance. It becomes possible to provide a polyethylene terephthalate hollow container having excellent gloss and a method for producing the same, and a heat-fixed stretched polyester container having the above-mentioned properties without the need for complicated and troublesome operations such as mold cleaning. Can be produced with high productivity.

(Example) The method for evaluating and measuring the characteristic value of the container of the present invention is as follows.

(1) Intrinsic viscosity 200 sample taken from preform or bottle
mg is dissolved in 20 ml of a phenol / tetracurethane mixed solvent (weight ratio 1: 1) at 105 ° C. for 20 minutes with stirring. The solution viscosity is measured with an Ubbelohde viscometer in a constant temperature water bath at 30 ° C., and the intrinsic viscosity is calculated from this.

t: falling time (sec) _t of the solution _o: solvent falling time (sec) specific viscosity η _SP = η _re1 -1 k ′: Huggins constant (0.33) c: Solution concentration [g / 100 ml] (2) Content of cyclic trimer (CT) About 0.10 g of sample is precisely weighed and dissolved in about 1.0 ml of hexafluoroisopropanol. (Room temperature x 16 hours). Tetrahydrofuran is mixed little by little, the polymer content is reprecipitated, and the whole is filtered to dilute the total amount to 25 ml, followed by gel permeation chromatography (GPC) measurement.
(The content is calculated based on the peak area value when CT is 100%.) GPC measurement conditions Device: Toyo Soda Industry Co., Ltd., HLC-8020 Column: Toyo Soda Industry Co., Ltd., G2000H8 + G1000H8 Detector: Differential refractometer Eluent: tetrahydrofuran (3) Refractive index RJSAMUELS (Journal of Applied Pol) using NaD line as a light source and Abbe's refractometer and deflector as a refractometer.
ymer Science.Vol.26.1383 (1981)), the sample cut from the bottle, the axial direction of the bottle, the circumferential direction,
Refractive indexes n _z , n _y , and n _x in the thickness direction were measured.

In this case, of the samples, the refractive index on the side in contact with the main prism can be selectively measured, and the result of the biaxially stretched polyethylene terephthalate bottle thus measured is M.CA.
Reported by KMAK et al. (ANTEC'84, P920).

(4) Crystallinity An n-heptane-carbon tetrachloride-based density gradient tube (Ikeda Rika Co., Ltd.) was prepared and the density of the sample was determined under the condition of 20 ° C. Thus, the crystallinity was calculated according to the following formula.

ρ: Measured density (g / cm ³ ) ρ _am : Amorphous density (1.335 g / cm ³ ) ρ _c : Crystal density (1.455 g / cm ³ ) (5) Glossiness It is cut out and the glossiness of the outer surface is measured with a 60 degree mirror surface (JIS Z 8741).

Apparatus: Suga Test Co., Ltd. Digital variable angle gloss meter (UGV-5K) (6) Surface roughness The panel is cut out, and the center line average roughness Ra (JIS B0601) of the outer surface is measured.

Device: Tokyo Seimitsu Co., Ltd. Surface Roughness Measuring Machine (Surfcom 400A) Measuring conditions: Cutoff value 0.8 mm Example 1 A far infrared heater is a preform (weight 59 g) injection-molded using crystallization pellets of polyethylene terephthalate. After heating at 1, the material was stretch-blown and heat-set (heat-set) to prepare a container having an internal volume of about 1.5 and having the shape shown in FIG. 1 (mean wall thickness 0.35 mm). When the pellets used are measured by the method described in the specification, the intrinsic viscosity is 0.77 dl / g,
Content of cyclic trimer 0.51% by weight (Fig. 4), crystallinity 6
It was 0%.

After cleaning the mold, the measurement results of the glossiness and surface roughness on the outer surface side of the body panel-shaped recess of the 300th and 30,000th stretch blow molded containers are shown in Table 1 and FIG. 6 (a), Shown in (b).

It can be seen that both the A and B containers have good gloss. This is because, as is clear from FIG. 6, the surface roughness is very small, that is, the skin is not roughened.
Since no deposits were observed on the blow mold during A and B molding, the use of pellets with a low cyclic trimer content is recommended for the monomers and cyclic trimers in the pellets. It can be seen that the transfer to the mold surface is prevented or reduced, and as a result, a container having excellent gloss is obtained.

Comparative Example 1 In the same manner as in Example 1, after cleaning the mold, 600th and 20th
An evaluation was performed on the container molded on the 00 side. However, the inherent viscosity of the pellets used was 0.77 dl / g, the content of cyclic trimer was 0.59% by weight (Fig. 5), and the crystallinity was 57%. The results are shown in Table 2 and FIGS. 7 (a) and 7 (b).

Here, in the 600th container, the glossiness is already as bad as 76%, and it is remarkably inferior to the 2000th container. This is because the deposits accumulated on the mold, the traces of which were transferred to the bottle, and the surface roughness became large. When pellets are used in this way, operations such as mold cleaning must be frequently performed in order to obtain a container with excellent glossiness, and the necessary heat-fixed stretched polyester container can be produced with high productivity. It cannot be manufactured.

Example 2 Table 3 shows the measurement results of the crystallinity and gloss of the containers obtained by using the same pellets as in Example 1 and changing the heat setting mold temperature. The container was collected at the 30,000th line after cleaning the mold in the same manner as in Example 1.

In order to increase the heat resistance, it is necessary to raise the temperature of the mold and fix it by heat.At this time, monomers and cyclic trimers are transferred from the container material to the mold. The chance of producing a kimono increases.

However, as is clear from Table 3, the glossiness was good even when the mold temperature was high. Therefore, the use of pellets having a low content of cyclic trimer is important for producing a container having high heat resistance and high gloss.

Example 3 and Comparative Example 2 The panel portions of several types of polyester hollow containers were evaluated by the method described in the specification. The results are shown in Table 4. The container was collected by the method of Example 1 at the 2000th line after cleaning the mold.

Example 3 is a polyester hollow container excellent in surface gloss while having a high degree of molecular orientation and a high degree of heat setting. This shows the effect of the low content of the cyclic trimer. is there. In order to reduce the content of the cyclic trimer, it is necessary to increase the intrinsic viscosity at the time of solid phase polymerization, so that the value of the intrinsic viscosity is also in a relatively high range.

In Comparative Example 2I, excellent gloss is exhibited despite the large content of the cyclic trimer. However, because of its low crystallinity, this container has low heat resistance.
That is, since the temperature of the mold container is low, the cyclic trimer and the monomers do not migrate to and accumulate in the mold and show a good glossiness.

Regarding J, D, and K, they have a high degree of molecular orientation and show crystallinity that can have heat resistance, but it is understood that the glossiness is poor due to the large content of cyclic trimer. it can.

[Brief description of drawings]

1 is a side view of an example of the container of the present invention, FIG. 2 is a bottom view of the container of FIG. 1, FIG. 3 is a cross-sectional view of the container of FIG. 5 and 5 show GPC showing CT content in pellets.
FIGS. 6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b) are diagrams showing the surface roughness of the container panel portion. Reference numeral 1 is a biaxially stretched polyester container, 2 is a nozzle portion, 3 is a shoulder portion, 4 is a body portion, 5 is a bottom portion, 6 is a panel-shaped concave portion, and 7 is a pillar-shaped convex portion.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B29L 22:00 4F

Claims (2)

[Claims] 1. A neck portion, a shoulder portion obtained by stretch-blow molding a thermoplastic polyester preform mainly comprising ethylene terephthalate units and heat-fixing the orientation,
A container comprising a body and a closed bottom, wherein the container is formed from polyester having an intrinsic viscosity of 0.70 to 0.85 dl / g and a cyclic trimer content of 0.55 wt% or less, The part is molecularly oriented so that the refractive index in the thickness direction on the inner surface side is 1.5200 or less, and is heat-set so that the crystallinity by the density method is 30% or more and the glossiness of 90% or more ( A container having a gloss. 2. A thermoplastic polyester mainly composed of ethylene terephthalate units and having an intrinsic viscosity of 0.70 to 0.
Crystallized pellets having 85 dl / g, a content of cyclic trimer of 0.55% by weight or less, and a crystallinity of 40% or more by a density method,
A step of melt injection-molding a bottomed preform in a substantially amorphous state; a step of stretch-blow molding the bottomed preform into a hollow body in a blow mold at a stretching temperature; A process for producing a heat-set stretched polyester hollow container having excellent surface glossiness, which comprises the step of heating under heat in a blow mold or in a heat treatment mold other than this to heat-fix.