JP2015101697A - Polyester resin composition for blow molding and blow molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition having good color tone, transparency and temporal stability and being suitable for blow molding application.SOLUTION: A polyester resin composition for blow molding contains, in a polyester resin where an acid component composing the polyester comprises 50 to 98 mol% of terephthalic acid and 2 to 20 mol% of isophthalic acid and a glycol component comprises 80 mol% or more of ethylene glycol, 0.1 to 1.0 mass% of a hindered phenolic antioxidant, 5.0×10mole to 3.0×10mole of a germanium compound relative to 1 mole of the acid component in the polyester resin and 1.0×10mole to 1.0×10mole of a cobalt compound relative to 1 mole of the acid component in the polyester resin, and has an intrinsic viscosity (IV) of 0.5 or more.

Description

  The present invention relates to a polyester resin composition capable of obtaining a blow molded product excellent in color tone and transparency with high productivity.

  Polyethylene terephthalate (PET) is excellent in mechanical properties, chemical stability, transparency and the like, is inexpensive, and is widely used as various sheets, films, containers and the like. The growth in the use of hollow containers (bottles) for fruit juice drinks, liquid seasonings, edible oils, liquors, wines, etc. is remarkable. Moreover, since there is little concern about residual monomers and harmful additives in hollow molded articles made of vinyl chloride resin, and hygiene and safety are high, replacement from conventional bottles made of vinyl chloride resin and the like is also progressing.

  In the production of polyester represented by PET, germanium compounds and antimony compounds are widely used as polymerization catalysts, and germanium compounds are used for applications such as hollow containers with high demands on color and transparency. .

  On the other hand, although an antimony compound is a general-purpose polyester polymerization catalyst, when this is used, since it is inferior to a color tone and transparency than a germanium compound, a cobalt compound is often used together as a color tone improving agent.

  Patent Document 1 also proposes the combined use of three types of catalysts: germanium compound, antimony compound, and cobalt compound. However, in this method, in order to compensate for the color tone and transparency of the antimony compound, the addition amount of the cobalt compound is increased. Further, depending on the ratio of these three kinds of compounds, there is a problem that the stability with time of the polyester deteriorates.

Japanese Patent Laid-Open No. 10-67924

  An object of the present invention is to solve the above-mentioned problems and to provide a polyester resin composition having good color tone, transparency and stability over time and suitable for blow molding applications.

As a result of intensive studies to solve the above problems, the present inventor has found that a polyester containing a germanium compound, a cobalt compound, and a hindered phenol antioxidant in a specific ratio has excellent transparency and color tone. As a result, the inventors have found that the stability over time is well maintained, and have reached the present invention.
That is, the gist of the present invention is as follows.
(1) Hindered phenol in a polyester resin in which 50 to 98 mol% of the acid component constituting the polyester is terephthalic acid, 2 to 20 mol% is isophthalic acid, and 80 mol% or more of the glycol component is ethylene glycol. Containing 0.1 to 1.0% by mass of a system antioxidant and containing a germanium compound in an amount of 5.0 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol with respect to 1 mol of the acid component of the polyester resin; Blow characterized by containing a cobalt compound in an amount of 1.0 × 10 ⁻⁵ mol to 1.0 × 10 ⁻⁴ mol per mol of the acid component of the polyester resin and having an intrinsic viscosity (IV) of 0.5 or more. Polyester resin composition for molding.
(2) A blow molded product using the blow molding polyester resin composition of (1).

Since the polyester resin composition of the present invention uses a polyester having a specific composition and contains a specific amount of a specific compound, various blow molded products having excellent color tone, transparency, and stability over time can be produced with high productivity. Can be obtained.
And since the blow molded product of this invention is obtained from the polyester resin composition of this invention, it is excellent in color tone, transparency, and temporal stability, and can be used for various uses.

Hereinafter, the present invention will be described in detail.
The polyester resin composition of the present invention is suitable for blow molding, and is particularly suitable for use in forming a parison by injection molding and stretch blow molding.
The polyester resin in the polyester resin composition of the present invention requires that 50 to 98 mol% of the acid component is terephthalic acid and 2 to 20 mol% is isophthalic acid. That is, terephthalic acid is the main component and isophthalic acid is the copolymer component. Among them, the copolymerization amount of isophthalic acid is preferably 3 to 18 mol%, and more preferably 4 to 15 mol%. By copolymerizing isophthalic acid, the crystallization speed of the polyester resin can be adjusted to one suitable for blow molding, and whitening due to crystallization during blow molding can be prevented.

  If the copolymerization amount of isophthalic acid is less than 2 mol%, the crystallization speed of the resin composition will be high, and when blow molding, the molded product will crystallize and whiten, resulting in poor transparency. Become. On the other hand, when the copolymerization amount of isophthalic acid exceeds 20 mol%, the resin composition becomes amorphous, so that drying at a high temperature tends to be difficult in the chip forming step when obtaining the resin composition, or Blocking is likely to occur during high temperature drying.

  The ratio of terephthalic acid in the acid component is 50 to 98 mol%, and the ratio of terephthalic acid is preferably 60 to 95 mol%. When the proportion of terephthalic acid is less than 50 mol%, the crystallinity of the resin composition is lowered and it tends to be amorphous. On the other hand, when the proportion of terephthalic acid exceeds 98 mol%, the amount of isophthalic acid copolymerization decreases, making it difficult to adjust the crystallization speed and poor effect of preventing whitening due to crystallization during blow molding. It becomes.

  Examples of dicarboxylic acid components other than terephthalic acid and isophthalic acid include phthalic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid, and the like. Alternatively, ester-forming derivatives of these acids may be used.

  On the other hand, 80 mol% or more of the glycol component in the polyester resin is ethylene glycol, and among them, 85 mol% or more of the glycol component is preferably ethylene glycol. Examples of glycol components other than ethylene glycol include neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, diethylene glycol, 1,4-cyclohexanedimethanol, dimer diol, An ethylene oxide adduct of bisphenol A or bisphenol S can be used.

  If the proportion of ethylene glycol in the glycol component is less than 80 mol%, the crystallinity of the resin composition is lowered and it tends to be amorphous, which is not preferable.

  The polyester resin composition of the present invention uses a germanium compound and a cobalt compound in combination as a catalyst. And in order to suppress the deterioration of temporal stability which becomes a problem when two kinds of compounds are used in combination, 0.1 to 1.0% by mass of a hindered phenol-based antioxidant is contained. . Especially, it is preferable that content of a hindered phenolic antioxidant is 0.2-0.8 mass%. When the content of the hindered phenolic antioxidant is less than 0.1% by mass, the stability of the polyester resin composition with time is poor, and with a long period of time, the intrinsic viscosity is lowered and the color tone after molding is deteriorated. On the other hand, when the content of the hindered phenol antioxidant exceeds 1.0% by mass, the color tone and transparency of the polyester resin composition deteriorate.

  As the hindered phenol antioxidant, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) Propionate, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 4, 4′-butylidenebis- (3-methyl-6-tert-butylphenol), triethylene glycol-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], 3,9-bis { 2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1′-dimethylethyl} -2,4 , 10-tetraoxaspiro [5,5] undecane, etc. are used, but tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane in terms of effect and cost Is preferred.

The polyester resin composition of the present invention needs to contain a specific amount of a germanium compound and a cobalt compound as a polymerization catalyst.
The content of the germanium compound needs to be 5.0 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol with respect to 1 mol of the acid component of the polyester, and in particular, 6.0 × 10 ⁻⁵ mol. It is preferable to set it as -2.0 * 10 < ^-4 > mol. When the content of the germanium compound is less than 5.0 × 10 ^−5, it becomes difficult to obtain a polyester resin having a target degree of polymerization. On the other hand, when the amount exceeds 3.0 × 10 ⁻⁴ mol, by-product due to the reaction between the cobalt compound and the germanium compound, the stability of the polyester with time deteriorates, and the polyester resin composition after long-term storage has a reduced intrinsic viscosity and color tone. This is not preferable because the deterioration of the temperature occurs.

  Examples of the germanium compound include germanium dioxide, germanium tetrachloride, germanium tetraethoxide, and the like, and germanium dioxide is preferred from the viewpoint of polymerization catalyst activity, physical properties of the resulting polyester resin, and cost.

Content of a cobalt compound needs to be 1.0 * 10 < ^-5 > -1.0 * 10 < ^-4 > mol with respect to 1 mol of acid components of polyester, 0.2 * 10 < ^-4 > mol-0. 8 × 10 ⁻⁴ mol is preferable. When content of a cobalt compound is less than 1.0 * 10 <^-5> mol, the color tone of polyester will worsen. On the other hand, when it exceeds 1 × 10 ⁻⁴ mol, the transparency of the polyester resin is deteriorated, and further, the temporal stability of the polyester resin is also deteriorated. Examples of the cobalt compound include cobalt acetate, cobalt formate, cobalt oxide, and cobalt chloride. Cobalt acetate is preferred from the viewpoint of polymerization catalyst activity, physical properties of the resulting polyester resin, and cost.

  The intrinsic viscosity of the polyester resin composition of the present invention needs to be 0.5 or more. When the intrinsic viscosity is less than 0.5, blow molding becomes difficult, and it becomes difficult to obtain a molded product having a uniform thickness. Moreover, even if it can be molded, the resulting blow-molded product has reduced impact resistance.

Next, the manufacturing method of the polyester resin composition for blow molding of this invention is demonstrated.
After charging the esterification reactor with terephthalic acid or its ester-forming derivative as an acid component and ethylene glycol as a glycol component at a predetermined ratio, and performing an esterification reaction or transesterification reaction at a temperature of 160 to 280 ° C. under pressure , Transfer polyester oligomer to polymerization reactor, add reaction solution of isophthalic acid and ethylene glycol, or dispersion of isophthalic acid and ethylene glycol, germanium compound and cobalt compound as polymerization catalyst, hindered phenolic antioxidant, The melt polycondensation reaction is performed at a temperature of 240 to 290 ° C, preferably 250 to 280 ° C under a reduced pressure of 1 hPa or less.

  Thereafter, by performing solid phase polymerization, the intrinsic viscosity can be further increased, or the amount of oligomers contained can be reduced. In the solid-phase polymerization, after the polyester is dried and crystallized in advance, it is usually 3 to 50 hours at a temperature lower than the melting point of the polyester by 20 to 30 ° C. under reduced pressure or in an inert gas flow such as nitrogen. , By reacting the polyester in the reactor.

The blow molded product of the present invention is obtained by blow molding using the polyester resin composition of the present invention. Examples of the blow molding method include a method of molding a product in one step by injection molding or extrusion molding, or a method of stretch blow molding a parison obtained by injection molding or extrusion molding. Especially, as mentioned above, it is preferable that it is what was obtained by the method of forming a parison by injection molding and extending and blowing.
Since the polyester resin composition of the present invention has good transparency, color tone, and stability over time, the blow molded product of the present invention also has such characteristics and can be suitably used for various applications. it can.

  When the blow molded product of the present invention is produced, the product is formed in one step by injection molding or extrusion molding, or the parison obtained by injection molding or extrusion molding is stretch blow molded. At this time, after the polyester resin composition is dried, a preform is prepared using an injection molding machine in which each part of the cylinder and the nozzle temperature are 240 to 270 ° C., and the preform maintains the preheating of the injection molding or the extrusion molding. The hot parison method that moves directly to the blow molding process, or the cold parison method in which the preform injection molding machine or extrusion molding machine is separated from the blow molding machine and the preform is cooled once and then reheated and blow molded. Can be applied. The stretching ratio is suitably 1.5 to 3.5 times in the longitudinal direction and 2 to 5 times in the circumferential direction.

Next, the present invention will be described specifically by way of examples. In addition, the characteristic value of the polyester resin composition was measured as follows.
(A) Intrinsic viscosity [η]
Measurement was made at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent.
(B) Copolymerization amount of isophthalic acid, content of hindered phenol antioxidant The polyester resin composition was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20. 1H-NMR was measured with a LA-400 type NMR apparatus manufactured by JEOL Ltd., and the copolymerization amount and content were determined from the integrated intensity of the proton peak of each component of the obtained chart.
(C) Content of germanium compound, cobalt compound, antimony compound The content was measured using a fluorescent X-ray analyzer 3270 manufactured by Rigaku Corporation.

(D) Formability The thickness of the body part of the obtained molded product (20 samples) was measured, and the difference between the thickness of the thickest part and the thinnest part was up to 0.10 mm. In the case where the number of samples is 18 or more, it was evaluated as “◯”, and in the case where the number of accepted samples was 17 or less, it was evaluated as “x”. Even if the difference between the thickness of the thickest part and the thinnest part satisfies 0.10 mm, crystallization occurred in the molded product, and the molded product was whitened or the surface of the molded product was rough. The case was rejected.
(E) Color tone Sample pieces (20 pieces) were cut out from the obtained molded product, and the color tone of the sample pieces was measured using a color difference meter CR-300 manufactured by Konica Minolta. The color tone was determined with a Hunter Lab colorimeter, the b value was measured, and the average value of n number 20 was obtained. A b value of 2.0 or less was determined to be good color tone.

(F) Haze A sample piece (20 pieces) was cut out from the obtained molded product, and the turbidity was measured with a turbidimeter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0%), n number An average value of 20 was used. The smaller this value is, the better the transparency is, and if it is 5% or less, it is judged that the transparency is excellent.
(G) Time-lapse acceleration test The polyester resin composition was allowed to stand in a dryer under a normal pressure air atmosphere at 130 ° C for 120 hours. The intrinsic viscosity [η] 1 before the treatment and the intrinsic viscosity [η] 2 after the treatment were compared, and the ratio [η] 2 / [η] 1 of the intrinsic viscosity before and after the treatment was 0.90 or more.
Similarly, the sample piece whose color tone was measured in (e) (assuming that the color tone is b1) was allowed to stand in a drier at 130 ° C. under atmospheric pressure for 120 hours, and then the color tone (b2). Was measured. The difference (b2-b1) in the b value of the sample before and after the treatment was 3.0 or less.

Example 1
The esterification reactor is fed with a slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) and reacted under the conditions of a temperature of 250 ° C. and a pressure of 50 hPa for esterification. A PET oligomer having a reaction rate of 95% (number average degree of polymerization: 5) was obtained. In another esterification reaction can, a slurry (IPA / EG molar ratio = 1 / 3.1) composed of isophthalic acid (IPA) and ethylene glycol is charged, and the esterification reaction is performed at a temperature of 200 ° C. for 3 hours. A reaction solution of ethylene glycol was obtained.
Charge 55.5 kg of PET oligomer to the polymerization reactor, then 7.8 kg of reaction solution of isophthalic acid and ethylene glycol, 7.8 g of germanium dioxide as catalyst, 3.7 g of cobalt acetate as cobalt compound, hindered phenol antioxidant 120 g of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (manufactured by ADEKA: ADK STAB AO-60) was added as an agent, and the reactor was reduced in pressure to 60%. After a minute, a melt polycondensation reaction was performed at a final pressure of 0.9 hPa and a temperature of 280 ° C. for 4 hours to obtain a polyester resin composition.
After drying the obtained polyester resin composition, an injection molding machine (Nissei AG) was set at each part and nozzle temperature of 270 ° C., screw rotation speed 100 rpm, injection time 10 seconds, cooling time 10 seconds and mold temperature 15 ° C. A preform was molded using SSB Co., Ltd., ASB-50HT type. Next, this preform was stretch blow molded (adopting a hot parison method) at a blow pressure of 2 MPa in an atmosphere of 100 ° C. to produce a stretch blow molded product having an average thickness of the body portion of 300 μm and an internal volume of 1 liter.

  Table 1 shows the resin composition, characteristic values, and blow-molded product characteristic values of the obtained polyester resin composition.

Examples 2-8, Comparative Examples 1-11
Except for changing the copolymerization amount of isophthalic acid, hindered phenolic antioxidant content, catalyst content, intrinsic viscosity (adjusted by changing the melt polycondensation reaction time) as shown in Table 1, A polyester resin composition was produced in the same manner as in Example 1.
Then, stretch blow molding was performed in the same manner as in Example 1 to produce a blow molded product.

  Table 1 shows the resin compositions, characteristic values, characteristic values of blow molded products, and evaluation results of the polyester resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 11.

  As is clear from Table 1, since the polyester resin compositions obtained in Examples 1 to 8 satisfied the composition and intrinsic viscosity specified in the present invention, blow molding obtained from these resin compositions. The product was excellent in moldability without thickness unevenness, surface whitening and roughness, excellent in color tone and transparency, and good in stability over time.

  On the other hand, since the resin composition obtained in Comparative Example 1 had a low copolymerization amount of isophthalic acid, whitening occurred on the surface of the molded product during blow molding, resulting in a molded product having poor transparency. Since the resin composition obtained in Comparative Example 2 had a large amount of isophthalic acid copolymerization, fusion occurred when the resin composition was dried or when the preform was molded, and blow molding could not be performed.

  The resin composition obtained in Comparative Example 3 had a low content of hindered phenolic antioxidant, so that the stability over time was poor, and the intrinsic viscosity after heat treatment was reduced, and the resulting molding was obtained. The product had a deterioration in color after heat treatment. Since the resin composition obtained in Comparative Example 4 had a high content of hindered phenolic antioxidants, the resulting molded product was inferior in color tone and transparency.

  The resin composition obtained in Comparative Example 5 had a low intrinsic viscosity because the melt polycondensation reaction time was short, and therefore, blow molding could not be performed. Since the resin composition obtained in Comparative Example 6 had a low germanium compound content, the melt polycondensation time was prolonged, and the resulting molded product was inferior in color tone and transparency.

  The resin composition obtained in Comparative Example 7 had a high content of germanium compound, so that the stability over time was poor, and the intrinsic viscosity after heat treatment was reduced. The color tone deteriorated. Since the resin composition obtained in Comparative Example 8 had a low content of cobalt compound, the color tone was poor, and the obtained molded product was also inferior in color tone.

The resin composition obtained in Comparative Example 9 had a high content of cobalt compound, so that the stability over time was poor, and the intrinsic viscosity after heat treatment was reduced. The color tone deteriorated. Since the resin compositions obtained in Comparative Examples 10 and 11 used an antimony compound, the color tone and transparency were inferior, and the obtained molded products were also inferior in color tone and transparency.

Claims (2)

In the polyester resin in which 50 to 98 mol% of the acid component constituting the polyester is terephthalic acid, 2 to 20 mol% is isophthalic acid, and 80 mol% or more of the glycol component is ethylene glycol, hindered phenolic antioxidant 0.1 to 1.0% by mass of the agent, and the germanium compound is contained in an amount of 5.0 × 10 ⁻⁵ mol to 3.0 × 10 ⁻⁴ mol with respect to 1 mol of the acid component of the polyester resin. Blow molding polyester characterized by containing 1.0 × 10 ⁻⁵ mol to 1.0 × 10 ⁻⁴ mol per mol of acid component of the polyester resin and having an intrinsic viscosity (IV) of 0.5 or more. Resin composition. A blow-molded article obtained by using the polyester resin composition for blow molding according to claim 1.