JP2000017162A - Polyester resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester resin composition capable of providing a bottle excellent in transparency, heat and pressure resistance, and moldability even by a high-speed bottle production apparatus. SOLUTION: This polyester resin composition obtained by kneading (A) a polyethylene terephthalate with (B) a polyethylene naphthalate is regulated so that (a) the content of an ethylene naphthalate unit may be 5-15 mol.% based on the total of the components A and B, (b) the proportion of the exchanged ester may be <=20%, and (c) the content of diethylene glycol ester in the polyethylene terephthalate may be <=1.5 mol.% based on the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin composition containing polyethylene terephthalate and polyethylene naphthalate, and more particularly to a raw material resin composition for forming a polyester bottle which is excellent in transparency, moldability and heat and pressure resistance.

[0002]

2. Description of the Related Art Plastic bottles are widely used as packaging containers for various liquids because of their excellent lightness and impact resistance. Among them, bottles formed by drawing and blowing polyethylene terephthalate are easy to mold. Because of its excellent transparency and mechanical strength, it is widely used as a container for filling beverages such as juices, soft drinks, and carbonated drinks.

[0003] In recent years, in order to meet the demands for filling contents under high-temperature sterilization conditions and for prolonging the storage period of the contents, better heat-resistant pressure resistance, gas barrier properties, transparency and the like have been desired. I have. To solve such a problem, polyethylene naphthalate, which is known to be a material excellent in heat resistance and gas barrier properties than polyethylene terephthalate, is blended with polyethylene terephthalate, and has excellent heat resistance, gas barrier properties, and heat pressure resistance. Obtaining a packaging material is disclosed in JP-A-50-122549.

[0004]

However, the compatibility between polyethylene terephthalate and polyethylene naphthalate is inferior, so that their mixture usually has a milky white color and is inferior in transparency. Therefore, in order to obtain a transparent blend of polyethylene terephthalate and polyethylene naphthalate, melt mixing is performed to cause a transesterification reaction,
The molecular structure needs to be close to the random copolymer structure, and a long-term reaction at a temperature equal to or higher than the melting point of the resin is required to obtain sufficient transparency. As a method of melt mixing, we examined a method to obtain a transparent blend by directly mixing and molding polyethylene terephthalate and polyethylene naphthalate using an injection molding machine. Because you can take a long time,
Although a transparent blend can be obtained, in a recently developed high-speed bottle production facility in which the output amount exceeds 300 kg per unit time, there is a restriction on the reaction time, so that a transparent molded article can be obtained. I got the knowledge that there is no. Also, in the conventional method of melt-mixing polyethylene terephthalate and polyethylene naphthalate in a kneading extruder, high-speed production equipment for the same reason,
It was difficult to obtain a transparent molded product.

The inventor of the present invention has conducted intensive studies in order to obtain a transparent bottle even in a high-speed bottle production facility, and kneaded polyethylene terephthalate and polyethylene naphthalate under predetermined conditions to obtain a transesterification rate lower than that of the conventional one. Invented a polyester resin composition having excellent transparency despite being low, and filed a patent application (Japanese Patent Application No. 9-1).
94766).

[0006]

However, regarding the heat resistance of a bottle obtained by biaxially stretch-blow-molding the composition, particularly the heat resistance of the bottle cap, the heat resistance of a bottle filled with a carbonated beverage or the like is considered. Since heat and pressure are intensively applied in the filling sterilization process, further improvement is desired. In order to increase the heat resistance, the method of crystallizing the plug portion, which is widely performed in polyethylene terephthalate biaxially stretched bottles, requires a long time, and lowers the production speed. aside from that,
A method of raising the glass transition temperature of the raw material resin can be considered. This is based on the fact that since the bottle cap is not stretched, the heat deformation resistance of this portion is mainly determined by the glass transition temperature (Tg) of the raw material resin.

As a method for increasing the Tg, it is conceivable to mix more polyethylene naphthalate having a higher Tg than polyethylene terephthalate. However, polyethylene naphthalate is expensive. On the other hand, if the content of polyethylene naphthalate exceeds 20 mol% of the whole resin, the crystallinity is reduced, and the material is not suitable for biaxial stretch blow molding. Therefore, there is a limit to the solution by adding a large amount of polyethylene naphthalate.

The present inventors have paid attention to the content of diethylene glycol ester units in the resin composition as a factor affecting Tg, in addition to the above mixing ratio. The unit is a unit derived from the reaction of terephthalic acid, naphthalenedicarboxylic acid or an ester derivative thereof with diethylene glycol or a derivative thereof. The present inventors investigated the relationship between the unit content and the resin Tg, by using a resin whose unit content is within a certain amount or less, Tg is high,
It has been found that a resin composition having excellent heat deformation resistance is obtained, and the present invention has been accomplished.

[0009]

That is, the present invention provides:
In the polyester resin composition obtained by melt-kneading (A) polyethylene terephthalate and (B) polyethylene naphthalate, the content of ethylene naphthalate unit is 5 to 5 with respect to the total amount of (A) and (B). B) the transesterification rate is 20% or less, and c) the content of diethylene glycol ester units in (A) polyethylene terephthalate is 1.5 mol% of (A).
It is a polyester resin composition characterized by the following.

Further, the content of diethylene glycol ester units in the polyester resin composition is preferably 1.5 mol% or less based on the total amount of (A) and (B).

It is preferable that the content of the ester unit other than the ethylene naphthalate component in the polyethylene naphthalate (B) is 8 mol% or less.

It is preferred that (B) polyethylene naphthalate is polyethylene-2,6-naphthalenedicarboxylate. In particular, it is preferable that the polyethylene naphthalate (B) is a polyethylene terephthalate naphthalate copolymer containing an ethylene terephthalate component of 8 mol%.

[0013] In addition, the present invention relates to a polyester bottle comprising any of the polyester resin compositions described above.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene terephthalate used in the present invention is substantially linear and has an ethylene terephthalate unit derived from terephthalic acid or an ester derivative thereof and ethylene glycol or an ester derivative thereof as a main component. The polyethylene terephthalate is
It preferably does not contain units derived from other dicarboxylic acids and / or other dihydroxy compounds.

Further, the polyethylene terephthalate used in the present invention must have a diethylene glycol ester unit content of not more than a certain amount. The unit can be formed by the reaction of diethylene glycol, a by-product in the production of polyethylene terephthalate, with terephthalic acid or an ester derivative thereof, and has a structure represented by chemical formula (1) (2-ethyleneoxyethylene terephthalate residue). ). The present inventors have repeatedly studied various polyethylene terephthalates regarding the relationship between the content of the unit and the Tg of the resin. As a result, by using polyethylene terephthalate having a content of the unit of 1.5 mol% or less, preferably 1.4 mol% or less, the raw material polyester resin blend composition can be used without depending on means for increasing the blend amount of polyethylene naphthalate. Succeeded in achieving high Tg.

[0016]

Embedded image In the present invention, in preparing the resin composition, the content of the above units is measured for each lot of polyethylene terephthalate, and the content in polyethylene terephthalate is 1.
Use less than 5 mol%. The measurement is performed, for example, by NMR.
The spectroscopic method can be carried out by using the peak of the proton in the diethylene group of the aromatic carboxylic acid diethylene glycol ester, the details of which will be described later.

The polyethylene terephthalate used in the present invention has an intrinsic viscosity [η] (30 in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1: 1).
C.) (measured at .degree. C.) of 0.6 to 1.2 (dl / g), preferably
7 to 0.9 (dl / g).

The polyethylene naphthalate used in the present invention contains, as a main component, an ethylene naphthalate unit derived from naphthalenedicarboxylic acid and ethylene glycol. As naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,
There are 2,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid and the like, and 2,6-naphthalenedicarboxylic acid is particularly preferred.

The above-mentioned polyethylene naphthalate is
Contains 15 mol% or less, preferably 10 mol% or less, more preferably 8 mol% or less of ester units derived from dicarboxylic acids other than naphthalenedicarboxylic acid and / or dihydroxy compounds other than ethylene glycol. May be. Other dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, and ester derivatives thereof. Other dihydroxy compounds include trimethylene glycol,
Aliphatic glycols such as propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, dodecamethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; alicyclic glycols such as cyclohexanedimethanol; bisphenols; hydroquinone; Diols, such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane, and their ester derivatives.

The other ester unit is preferably contained in the form of a naphthalate copolyester polymer,
Particularly, a copolyester polymer with ethylene terephthalate is preferred. This is because such a copolyester polymer has a melting point closer to that of polyethylene terephthalate than polyethylene naphthalate homopolymer, and thus is easier to melt-mix with polyethylene terephthalate. The content of the other ester component in the copolyester is 15 mol% or less, preferably 10 mol% or less.
Mol% or less. Particularly preferred is a polyethylene terephthalate-ethylene-2,6-dinaphthalate copolymer containing 8 mol% of ethylene terephthalate units.

The polyethylene naphthalate used in the present invention preferably has an intrinsic viscosity [η] (measured in a mixed solvent of phenol and tetrachloroethane at a volume ratio of 1: 1 at 30 ° C.) of 0.4 to 1.0, More preferably, it is 0.4 to 0.8 (dl / g).

In the present invention, the content of the diethylene glycol ester unit in the finally obtained resin composition is more preferably 1.5 mol% or less.
The content of diethylene glycol ester units in the polyethylene naphthalate is also preferably not more than a certain amount. The diethylene glycol ester unit in polyethylene naphthalate is considered to have a structure in which a benzene ring is substituted by a naphthalene ring in the above chemical formula (1). Further, in the case of a copolymer with terephthalate, Structures can also be included. Preferably, the content of diethylene glycol ester units in polyethylene terephthalate as a base polymer in the resin composition is 1.4 mol% or less, and the content of diethylene glycol ester components in polyethylene naphthalate is 2.0 mol% or less.

The mixing ratio of (A) polyethylene terephthalate and (B) polyethylene naphthalate used in the present invention is such that the ethylene naphthalate unit is 5 to 15 mol% based on the total amount of (A) and (B). Range, preferably 7
~ 13 mol%. If the ethylene naphthalate unit is less than the above lower limit, the heat resistance and gas barrier properties of the bottle are insufficient. On the other hand, if the amount is larger than the upper limit, the crystallization characteristics of the blended resin composition are lost, and problems such as fusion of the pellets occur during dehumidification and drying before the secondary melt molding of the resin pellets of the present invention. Not preferred.

The method for producing the resin composition of the present invention comprises the steps of (A)
For example, polyethylene terephthalate and (B) polyethylene naphthalate are weighed, for example, in the form of pellets, and then melt-mixed at a temperature equal to or higher than the melting point of the resin mixture by a kneading extruder. The kneading extruder is preferably a deaeration type, for example, a twin screw extruder with a vent.
Polyethylene terephthalate and polyethylene naphthalate are desirably dried in advance, but according to a degassing-type kneading extruder, they can be melt-mixed undried. The temperature of the melt mixing is set to be equal to or higher than the melting point of the resin mixture, for example, 290 to 330 ° C. at the resin temperature. Extrusion conditions include
The ratio of the amount of extrusion to the screw speed of the extruder is 0.5 to 1.4k
g / hr · rpm, preferably 0.7 to 1.0 kg
/Hr.rpm. When the ratio is smaller than the lower limit, the heat generated by the resin is increased due to the high shearing force of the extruder, and the resin is deteriorated. Further, mass productivity is impaired due to a decrease in the amount of extrusion. On the other hand, if this ratio is greater than the upper limit,
Transparency worsens. The obtained resin composition can be formed into a pellet shape, for example.

In the present invention, the transesterification rate means the transesterification rate between polyethylene terephthalate and polyethylene naphthalate, and can be determined by NMR spectroscopy. Details of the measuring method will be described later. The transesterification rate of the resin composition of the present invention is 20
% Or less, preferably from the viewpoint of mass productivity, resin deterioration, etc.
18% or less. In a resin composition in which polyethylene terephthalate and polyethylene naphthalate are blended by a conventional injection molding method, the transesterification ratio is usually 2%.
If it is less than 0%, it is opaque, and if it is not more than 30%, it is not transparent. In order to reach an exchange rate of 30% or more, a high-temperature and long-time molding process is required, which leads to resin deterioration, heat resistance,
Bottle moldability and the like are also likely to decrease.

Next, the pellets are heated at 110 to 130 ° C.
After heating in air for 2 to 4 hours to crystallize at least the surface layer, dehumidifying and drying at 140 to 160 ° C. for 3 to 6 hours can usually reduce the water content in the pellets to 50 ppm or less.

The resin composition may contain various additives such as weathering stabilizers, pigments or dyes as long as the object of the present invention is not impaired.

The polyester bottle of the present invention can be produced from the above pellets by a known bottle production method. Preferably, a bottle preform is formed from the pellets by an injection molding method, and the preform is biaxially stretch blow-molded. In molding a bottle preform, the molten resin temperature is the melting point of the resin + 5
To 40 ° C, preferably +10 to 20 ° C. When the temperature of the molten resin is lower than the melting point of the resin + 5 ° C., the melt viscosity is too high and injection molding is difficult. On the other hand, when the melting point is higher than + 40 ° C., the generation of thermal decomposition products such as acetaldehyde increases, and the quality of the beverage bottle may be deteriorated.

The injection molding machine is preferably a vent type which has a high kneading effect and can remove thermal decomposition products such as acetaldehyde generated in the melting process out of the system by decompression or vacuum suction. Can also be used.

If the preform is at a suitable stretching temperature, the biaxial stretch blow molding may be carried out in the course of cooling from the melting temperature or after cooling to near room temperature and then reheating.

[0031]

EXAMPLES Hereinafter, the polyester resin composition and the polyester bottle of the present invention will be described in detail with reference to examples.

(I) The intrinsic viscosity of the resin used and the content of the diethylene glycol ester unit are as follows.

(A) Polyethylene terephthalate: a. Example 1 and Comparative Examples 1 and 2 Intrinsic viscosity 0.83 (dl / g) Diethylene glycol ester unit 1.3 mol% b. Reference Example 1 Intrinsic viscosity 0.83 (dl / g) Diethylene glycol ester unit 1.7 mol% c. Reference Example 2 and Comparative Example 3 Intrinsic viscosity 0.83 (dl / g), diethylene glycol ester unit 3.2 mol% (B) polyethylene naphthalate: ethylene-2,6-
Copolymer consisting of 92 mol% of naphthalene dicarboxylate units and 8 mol% of ethylene terephthalate units, intrinsic viscosity 0.50 (dl / g) 1.8 mol% of diethylene glycol ester units

(II) Preparation of Resin Composition Example 1 The above-mentioned polyethylene terephthalate and polyethylene naphthalate were supplied in a constant weight at a ratio of 85 to 15% by weight (ethylene naphthalate unit: 11.4 mol%). Direction twin screw extruder TEX65 (screw diameter φ65mm,
Using L / D = 42), blended resin pellets were formed under the kneading conditions of an extrusion rate of 250 kg / hr and an extrusion rate to screw rotation speed ratio of 0.9.

Reference Example 1 Diethylene glycol ester unit content 1.7 mol%
Was melt-mixed under the same conditions as in Example 1 except that polyethylene terephthalate was used to obtain a blended resin pellet.

Reference Example 2 Diethylene glycol ester unit content was 3.2 mol%
Was melt-mixed under the same conditions as in Example 1 except that polyethylene terephthalate was used to obtain a blended resin pellet.

[0037] The same polyethylene terephthalate and polyethylene naphthalate and Comparative Example 1 Example 1, a constant weight supplied at a ratio of 85-to 15 wt%, Japan Steel Works, Ltd. the same direction biaxial extruder TEX65
(Screw diameter φ65 mm, L / D = 42) using an extrusion rate of 250 kg / hr, a ratio of the extrusion rate to the screw rotation speed =
Under kneading conditions of 0.09, a blended resin pellet having a transesterification rate of 28.2% was formed.

Comparative Example 2 The same polyethylene terephthalate and polyethylene naphthalate as in Example 1 were supplied at a constant weight ratio of 70 to 30% by weight (ethylene naphthalate: 23.6 mol%), and biaxially oriented in the same direction manufactured by Nippon Steel Works, Ltd. Extruder TEX65 (screw diameter φ
65 mm, L / D = 42) and the extrusion rate is 250 kg / h.
Under the kneading conditions of r, the ratio of the extruded amount to the screw rotation speed = 0.9, the blended resin pellets were formed.

Comparative Example 3 Using the same polyethylene terephthalate as in Reference Example 2,
A constant weight feed is provided at a ratio of 0 to 30% by weight (ethylene naphthalate 23.6 mol%), and a twin screw extruder TEX65 manufactured by Nippon Steel Works (screw diameter φ65 mm, L / D = 42).
The blended pellets were molded under the conditions of kneading with an extrusion rate of 250 kg / hr and an extrusion rate to screw rotation ratio = 0.9.

(III) Evaluation of Resin Composition (a) The pellets prepared under the above conditions were measured for glass transition temperature, intrinsic viscosity, ester exchange rate, and diethylene glycol ester unit content by the following methods.

(1) Glass transition temperature Using a scanning calorimeter DSC220C manufactured by Seiko Denshi Kogyo KK, the glass transition temperature was determined from a chart obtained by heating at a rate of 10 ° C./min.

(2) Intrinsic Viscosity 0.5 g of a polyester resin is dissolved in 100 cc of a mixed solution of phenol and 1,1,2,2-tetrachloroethane in a volume ratio of 1: 1 at 30 ° C. using an Ubbelohde viscometer. It was measured.

(3) Transesterification Rate An appropriate amount of a sample was dissolved in a mixed solution of trifluoroacetic acid and chloroform at a volume ratio of 1: 1 using FT-NMR (manufactured by JEOL) and mixed with tetramethylsilane as a standard. And the proton NMR spectrum was measured, and the naphthalate-ethylene-terephthalate bond, naphthalate-ethylene-
The integrated value of the peak derived from each of the naphthalate bond and the terephthalate-ethylene-terephthalate bond is determined, and the abundance ratio of each bond is determined. The reaction rate was calculated from the respective binding ratios according to the following formula.

(Equation 1)

(4) Content of Diethylene Glycol Ester Unit Proton NMR spectrum was measured in the same manner as in the transesterification rate.
Aromatic carboxylic acid diethyleneglycol appearing around ppm
The integral value of the peak derived from the proton in the diethylene group in the ester unit was determined, and the diethylene glycol ester unit component content was calculated from the ratio.

(B) Further, from each blended pellet,
Using a SH-150A injection molding machine manufactured by Sumitomo Heavy Industries, a 2mm x 110mm square sheet is injection molded at a cylinder temperature of 280 ° C.
A test piece was cut from the sheet and the following heat resistance was measured.

(1) Tan δ peak temperature in dynamic viscoelasticity A test piece was prepared by cutting a sheet to a width of 12 mm, and a dynamic viscoelasticity was measured under the following conditions using a rheometric viscoelasticity measuring device RDA2. The tan δ peak temperature was determined by elasticity measurement. Heating rate: 23 ℃ → 130 ℃, 2 ℃ / min Frequency: 10Hz torsion

(2) Small constant load elongation test A test piece obtained by cutting the injection molded sheet to a width of 2 mm was measured for a deformation rate with respect to a tensile load using a small constant load elongation tester manufactured by Intesco Corporation. Sample size: 2mm × 2mm × 50mmL Load: 20kg / cm ² Heating pattern: 30 → 65 ° C (4 ° C / min), then constant at 65 ° C Deformation rate: Deformation rate after 65 ° C × 30 minutes

(IV) Preparation and Evaluation of Polyester Bottle From each of the above blended pellets, using an injection molding machine SH-150A manufactured by Sumitomo Heavy Industries, Ltd. at a cylinder temperature of 280 ° C. and a weight of 31
g preform, reheat it to 110 ° C and use Krupp Corpoplast LB-01E blower
A 500 ml bottle was molded and subjected to a bottle hot water filling test and evaluation of bottle moldability.

(1) Bottle hot water filling test The obtained bottle was filled with hot water of 85 ° C and capped.
After standing for 3 minutes, the mixture was cooled with water, and the inner diameter of the plug was measured with a vernier caliper to determine the dimensional change rate compared to the inner diameter before filling.

(2) Bottle Formability Five bottles prepared under each condition were visually evaluated immediately after molding. If all five pieces are faithfully formed into a mold and stand upright on a flat part,
When even one of the rods was tilted when standing, it was rated as △, and when it was apparent that the shape was not faithful to the mold, it was rated as ×. Table 1 summarizes the evaluation results.

[0051]

[Table 1]

Comparing Example 1 with Reference Example 1 or 2, the resin composition of Example 1 has a high Tg and tan δ peak temperature, a deformation rate in a minute constant load test, and a hot water filled bottle at 85 ° C. Has a small rate of change in plug and excellent heat resistance.
In Comparative Example 1, the same resin as in Example 1 was used. However, since the resin was kneaded until the transesterification rate was increased, the crystallinity of the resin was reduced, and the bottle moldability was poor. In contrast, the composition of the present invention of Example 1 not only has good bottle moldability, but also has a low transesterification rate of 7.3%, but has sufficient transparency and a short production cycle. In Comparative Example 2, the blending amount of polyethylene naphthalate was large. Although the Tg of the resin was high, the inherent viscosity was low and the moldability of the bottle was poor. Comparative Example 3 also contained a large amount of polyethylene naphthalate, but was unable to obtain Tg corresponding to the amount of the mixture due to a high content of diethylene glycol ester units, and had poor bottle moldability.

[0053]

As described above, the resin composition of the present invention provides: a) a bottle having a high Tg of the resin and a high heat and pressure resistance because the content of the diethylene glycol ester unit is low; b) a low polyethylene naphthalate. Since the compounding amount has a high Tg, the bottle formability is not impaired; c) A bottle with sufficiently high transparency is obtained even if the transesterification rate is 20% or less; and d) Bottles in high-speed production equipment Production is possible.

Claims (6)

[Claims] 1. A polyester resin composition obtained by melt-kneading (A) polyethylene terephthalate and (B) polyethylene naphthalate, wherein (a) the content of ethylene naphthalate units is the total of (A) and (B) B) the transesterification rate is 20% or less, and c) the content of diethylene glycol ester units in (A) polyethylene terephthalate is 1.5 mol of (A) polyethylene terephthalate. % Or less. 2. The polyester resin according to claim 1, wherein the content of diethylene glycol ester unit in the polyester resin composition is 1.5 mol% or less based on the total amount of (A) and (B). Composition. 3. The polyester resin composition according to claim 1, wherein the content of the ester component other than the ethylene naphthalate component in the polyethylene naphthalate is 8 mol% or less. 4. The polyester resin composition according to claim 1, wherein (B) the polyethylene naphthalate is polyethylene-2,6-naphthalenedicarboxylate. 5. The (B) polyethylene naphthalate is a polyethylene terephthalate naphthalate copolymer containing 8 mol% of an ethylene terephthalate component.
5. The polyester resin composition according to any one of items 4 to 4. 6. A polyester bottle comprising the polyester resin composition according to claim 1.