JP6985698B2 - Polyester resin and blow molded products - Google Patents

Description

The present invention relates to a polyester resin having characteristic values suitable for blow molding.

Polyethylene terephthalate (PET) has excellent mechanical properties, chemical stability, transparency, etc., is inexpensive, and is widely used as various sheets, films, containers, etc. Especially in recent years, carbonated drinks, The growth of hollow container (bottle) applications such as fruit juice beverages, liquid seasonings, cooking oil, liquor, and wine is remarkable. Moreover, since there is less concern about residual monomers and harmful additives as in the case of hollow molded products made of vinyl chloride resin, and the hygiene and safety are high, the replacement of conventional bottles made of vinyl chloride resin or the like is progressing.

Generally, when manufacturing plastic bottles, melt-plasticized resin is used as a die orifice because of its ease of molding, high productivity, and relatively low equipment costs for molding machines and dies. A so-called direct blow molding method is adopted in which a cylindrical parison is formed by extruding through a mold, sandwiched between molds, and air is blown into the inside. In the case of this direct blow molding, it is necessary to prevent the parison extruded in the molten state from drawing down during blow molding in order to carry out the molding smoothly, and therefore, a high melt viscosity is required for the resin used. Will be done. Therefore, as a resin having a high melt viscosity, vinyl chloride resin, polyolefin resin and the like are widely used in direct blow molding.

Although replacement of vinyl chloride resin with polyester resin is being considered for direct blow molded products, polyester resin generally does not have a high melt viscosity suitable for direct blow molding. For this reason, there is a problem that the extruded parison draws down during blow molding and cannot be blown molded, and crystallization is likely to occur during blow molding, so that whitening occurs even if molding is possible, and transparency is improved. There was the problem of being inadequate. Therefore, it is considered to introduce a copolymerization component into PET, and for example, in the dicarboxylic acid component containing terephthalic acid as a main component, a copolymerized polyester resin using isophthalic acid as a copolymerization component and a bottle made of the copolymerized polyester resin have been proposed. (See, for example, Patent Document 1).
Further, in a polyester containing terephthalic acid and ethylene glycol as main components, a copolymerized polyester resin using 1,4-cyclohexanedimethanol as a copolymerization component and a bottle made of the same have been proposed (see, for example, Patent Document 2).

Generally, when the above-mentioned copolymerized polyester resin is produced, it goes through a melt polymerization step and a solid phase polymerization step, but foreign matter is generated in the reaction step. These foreign substances are carbides generated in the reaction can derived from catalysts and additives, gel-like substances generated during melt polymerization, and deteriorated polyester resins. However, it is difficult to prevent the generation of these foreign substances, and when the polymerization step is carried out by a normal production method, such foreign substances are generated to some extent in the obtained polyester resin. If the number of foreign substances increases, it may cause troubles during blow molding, the quality of the obtained blow molded product may deteriorate, or even if the appearance is not affected at first glance, the resistance of the blow molded product may be reduced. There was a problem that the impact resistance was reduced.

Japanese Unexamined Patent Publication No. 2015-101679 Japanese Patent No. 6038571

The present invention solves the above problems, can be suitably used for blow molding, has a small number of foreign substances during molding, has good blow moldability, is excellent in molding cycle, and is excellent in impact resistance. It is an attempt to provide a polyester resin capable of obtaining a blow-molded product.

As a result of diligent studies to solve the above problems, the present inventors have specified the polymerization conditions for obtaining the polyester resin, so that the number of foreign substances is small and the density is equal to or less than the specific numerical value. We have found that a polyester resin can be obtained, and have reached the present invention.
That is, the gist of the present invention is the following (1) to (2).
(1) When ethylene terephthalate is the main repeating unit and the total amount of all glycol components is 100 mol%, ethylene glycol is 80 to 97 mol% and 1,4-cyclohexanedimethanol is 2 to 15 mol% as a copolymerization component. A polyester resin containing 85 mol% or more of terephthalic acid when the total amount of all acid components is 100 mol%, having an ultimate viscosity of 0.9 to 1.4 and a thickness at 280 ° C. Polyester characterized in that the number of foreign substances having a diameter of 300 μm or more present in the sheet obtained by melt-extruding a 20 μm sheet is 3 pieces / m ² or less, and the resin density is 1.370 g / cm ^{3 or less.} resin.
(2) A blow-molded product obtained by blow-molding using the polyester resin according to (1) .

Since the polyester resin of the present invention is a copolymerized polyester resin having a specific composition and satisfies a specific extreme viscosity, density, and number of foreign substances, it can be suitably used for blow molding. In other words, the number of foreign substances during molding is small, productivity is good, the molding cycle is excellent, there is no drawdown problem during blow molding, thermal stability is excellent, and impact resistance is excellent. A blow molded product can be obtained.
Since the blow-molded product of the present invention contains the polyester resin of the present invention, it has an excellent transparent appearance and impact resistance, and can be used for various purposes.

Hereinafter, the present invention will be described in detail.
The polyester resin of the present invention (hereinafter, may be abbreviated as the resin of the present invention) is suitable for molding, and above all, is suitable for the direct blow molding method.

The polyester resin of the present invention is a copolymerized polyester resin satisfying a specific composition. The copolymerized polyester resin in the present invention contains ethylene terephthalate as a main repeating unit and 1,4-cyclohexanedimethanol as a copolymerization component in an amount of 2 to 15 mol%.
The acid component of the polyester resin of the present invention preferably contains 85 mol% or more of terephthalic acid, and more preferably 95 mol% or more of terephthalic acid. When the proportion of terephthalic acid is less than 85 mol%, the crystallinity and heat resistance of the obtained polyester resin tend to be inferior.

Examples of the acid component other than terephthalic acid contained in the copolymerized polyester resin include phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, anhydrous phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid and the like. , Two or more of these may be used in combination, or ester-forming derivatives of these acids may be used.

On the other hand, the glycol component contains ethylene glycol as a main component and 1,4-cyclohexanedimethanol as a copolymerization component.
First, the content of 1,4-cyclohexanedimethanol, which is a copolymerization component, is 2 to 15 mol% of the glycol component, and more preferably 3 to 8 mol%.

When the content of 1,4-cyclohexanedimethanol is less than 2 mol%, the crystallization rate of the resin composition is high, so that the obtained direct blow molded article is crystallized and whitened. On the other hand, if it exceeds 15 mol%, it becomes amorphous and it becomes difficult to dry it at a high temperature or solid-phase polymerization. Alternatively, it is not preferable because blocking is likely to occur during high temperature drying or in the solid phase polymerization step.

The content of ethylene glycol as a main component is preferably 80 to 97 mol%, particularly preferably 85 to 95 mol% of the glycol component. When the content of ethylene glycol is less than 80 mol%, the crystallinity and heat resistance of the obtained polyester resin are inferior. On the other hand, if it exceeds 98 mol%, the proportion of 1,4-cyclohexanedimethanol becomes small, it becomes difficult to adjust the crystallization rate, and the effect of preventing whitening due to crystallization during blow molding is poor.

The total content of ethylene glycol and 1,4-cyclohexanedimethanol in the glycol component is preferably 90 mol% or more, and more preferably 95 mol% or more of the total glycol component.
Glycol components other than these three types include, for example, diethylene glycol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1 , 6-Hexamethylene diol, dimer diol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S and the like can be used.

The polyester resin of the present invention may contain a catalyst at the time of polymerization, and may contain various additives and the like as described later as long as the effect is not impaired. However, in order to prevent foreign substances from being present in the polyester resin, it is preferable that the polyester resin does not contain various additives.

Various additives that may be added to the polyester resin of the present invention include, for example, phosphoric acid, fluoric acid, trimethylphosphite, triethylphosphine, triphenylphosphine, tridecylphosphine, as anticoloring agents. Phosphorus compounds such as trimethyl phosphate, triethyl phosphate, triphenylphosphine, and tridecyl phosphate can be mentioned. These phosphorus compounds may be used alone or in combination of two or more. The amount of the phosphorus compound used is preferably 1.0% by mass or less.
Further, in order to suppress coloring due to thermal decomposition of polyester resin, additives such as cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, anthraquinone dye compounds, copper phthalocyanine compounds, phenolic antioxidants, and phosphate compounds are used. Antioxidants such as antioxidants and thioether-based antioxidants can be used, and these may be used alone or in combination of two or more.

Next, the characteristic values of the polyester resin of the present invention will be described.
First, the ultimate viscosity of the polyester resin is 0.99 to 1.40. The ultimate viscosity (IV) is measured at a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.
If the ultimate viscosity is less than 0.90, the drawdown during blow molding becomes large and molding becomes difficult. On the other hand, when the ultimate viscosity exceeds 1.40, it is necessary to raise the molding temperature, and the color tone and transparency of the obtained molded product deteriorate.

The polyester resin of the present invention is characterized by having a small number of foreign substances. The foreign substance referred to in the present invention refers to a carbide generated in a reaction can derived from a catalyst or an additive, a gel-like substance generated during melt polymerization, or a deteriorated substance of a polyester resin.
Specifically, the number of foreign substances in the polyester resin is obtained by melt-extruding the polyester resin of the present invention at 280 ° C. to prepare a sheet having a thickness of 20 μm, and counting the number of foreign substances having a diameter of 300 μm or more existing in the sheet. be. At this time, ME20 / 2800V3, CR9, and FSA200 manufactured by OCS are used to prepare a sheet and detect a foreign substance having a diameter of 300 μm or more.

The diameter of the foreign substance means the diameter equivalent to a circle (the diameter of a perfect circle corresponding to the area of a figure drawn on an image or the like).
In the polyester resin of the present invention, the number of foreign substances having a diameter of 300 μm or more present in the sheet is 3 / m ² or less, and more ^{preferably 2.5 / m 2} or less.
When the number of foreign substances is less than or equal to the above, the number of foreign substances is small and the moldability is good, and a molded product having excellent impact resistance can be obtained. On the other hand, if the number of foreign substances exceeds the above, the moldability becomes inferior due to the foreign substances at the time of molding, and the obtained molded product has poor appearance quality or is inferior in impact resistance even if the appearance is not bad at first glance. Become.

Further, the polyester resin of the present invention has a density of 1.370 or less, and more preferably 1.365 or less. The method for measuring the density in the present invention is as follows.
It is obtained from the average value of three points excluding the maximum and minimum values obtained after five measurements using AUX220 and SMK-401 manufactured by Shimadzu Corporation.
By reducing the number of foreign substances in the polyester resin to the above number or less and the density to 1.370 or less, the molded product obtained when the weight is constant may be thick and impact resistant. It is possible to obtain an excellent molded product.

Then, in order to obtain the resin of the present invention having the above-mentioned characteristics, it is preferable to obtain a copolymerized polyester resin by a production method as described later.

The method for producing the polyester resin of the present invention will be described. First, an acid component and a glycol component constituting the copolymerized polyester resin are charged to carry out an esterification reaction, but the esterification reaction is carried out without particular limitation, and a known technique can be used.

Next, the melt polymerization is preferably carried out at a temperature of 240 to 290 ° C., preferably 250 to 280 ° C. under a reduced pressure of 1 hPa or less for 4 to 8 hours. Here, it is important that the time required from the normal pressure to the reduced pressure of 1 hPa or less is 75 to 120 minutes, and the melt polymerization temperature during that period is 240 to 270 ° C. A resin that satisfies the number and density of foreign substances specified in the present invention as described above by melt-polymerizing with the time required for reducing the pressure to 1 hPa or less to 75 to 120 minutes and the temperature during that period to 240 to 270 ° C. Can be obtained.
If the time required to reduce the pressure from normal pressure to 1 hPa or less is less than 75 minutes, or if the melt polymerization temperature during this period exceeds 270 ° C, the depressurization rate becomes faster and the contents in the polymerization can are foamed. The number of foreign substances having a diameter of 300 μm or more increases due to the collection of foreign substances such as carbides in the polymerization can and the formation of gel-like substances. In addition, the density of the obtained polyester resin becomes high.
On the other hand, if the time required from normal pressure to a reduced pressure of 1 hPa or less exceeds 120 minutes, or if the melt polymerization temperature during this period is less than 240 ° C., the total melt polymerization reaction time becomes long, so that the polyester obtained can be obtained. The resin deteriorates.

It is preferable to carry out solid-phase polymerization after obtaining a prepolymer by carrying out the melt polymerization reaction as described above. The ultimate viscosity of the prepolymer obtained by the melt polymerization reaction is preferably 0.55 to 0.70.

The polymerization catalyst in the case of melt polymerization is not particularly limited, and generally used antimony-based, germanium-based, titanium-based, and aluminum-based catalysts can be used. A germanium compound is preferable from the viewpoint of transparency of the obtained molded product.
Examples of the germanium compound include germanium dioxide, germanium tetrachloride, germanium tetraethoxydo and the like, and germanium dioxide is preferable from the viewpoint of polymerization catalytic activity, physical properties of the obtained polyester resin and cost.

Subsequently, a solid phase polymerization reaction is carried out using the prepolymer obtained by the melt polymerization reaction to obtain a polyester resin having a target maximum viscosity. In solid phase polymerization, after the prepolymer is dried and crystallized in advance, it is usually carried out under reduced pressure or under the flow of an inert gas such as nitrogen at a temperature 20 to 30 ° C. lower than the melting point of the polyester resin for 3 hours. It is carried out by reacting in the reactor for 50 hours.

When other resins or additives are added to the polyester resin obtained as described above, they are mixed (dry blended) in a solid state such as pellets, granules or powders before molding and melted. The kneading method is preferable. Alternatively, the polyester resin is melt-kneaded with a single-screw or twin-screw extruder during the molding process, and another resin or additive is added and kneaded in a temperature range of 250 to 300 ° C.

The polyester resin of the present invention is particularly suitable for direct blow molding, but even if an injection molding or stretching method is adopted, a molded product (injection molded body, sheet, film, etc.) having excellent color tone and transparency can be produced. Obtainable.

Next, the direct blow molded article of the present invention is made of the polyester resin of the present invention. The direct blow molded product of the present invention can be manufactured using a general-purpose direct blow molding machine, and the temperature of each cylinder portion and nozzle of the molding machine is preferably in the range of 240 to 290 ° C.

Next, the present invention will be specifically described with reference to Examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
(A) Extreme viscosity The measurement was carried out in the same manner as described above.
(B) Copolymerization amount of copolymerization component The obtained polyester resin was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20, and JNM-ECZ manufactured by JEOL Ltd. 1H-NMR was measured with a −400R type NMR apparatus, and the amount of copolymerization was determined from the integrated intensity of the proton peaks of each component in the obtained chart.
(C) Number of foreign substances The obtained polyester resin is melt-extruded at 280 ° C. using ME20 / 2800V3, CR9, and FSA200 manufactured by OCS to melt and extrude a sheet having a thickness of 20 μm, and the diameter (equivalent to a circle) existing in the obtained sheet. ) A foreign substance of 300 μm or more was detected.
(D) Density The obtained polyester resin was obtained from the average value of three points excluding the maximum and minimum values obtained after five measurements using AUX220 and SMK-401 manufactured by Shimadzu Corporation. ..
(E) Moldability The obtained molded product (100 samples) was visually observed and evaluated by the number of molded products containing foreign matter in the following three stages.
Within 1 ... ○
2 to 4 ... △
5 or more ... ×
(F) Impact resistance The obtained molded product (100 samples) was filled with 400 ml of water, and the number of molded products that cracked when dropped from a height of 150 cm was evaluated in the following three stages. did.
Within 1 ... ○
2 to 4 ... △
5 or more ... ×

Example 1
[Polyester resin]
A slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) is supplied to the esterification reactor and reacted under the conditions of a temperature of 250 ° C. and a pressure of 50 hPa for esterification. A reaction product (number average degree of polymerization: 5) having a reaction rate of 95% was obtained.
60.3 parts by mass of the reaction product of TPA and EG was charged into the polymerization reactor, followed by 3.9 parts by mass of 1,4-cyclohexanedimethanol, 0.008 parts by mass of germanium dioxide as a polymerization catalyst, and triethyl phosphate 0. .016 parts by mass and 0.004 parts by mass of cobalt acetate were added, and the reactor was depressurized to a final pressure of 0.9 hPa at 270 ° C. over 120 minutes, and then a melt polymerization reaction was carried out at a temperature of 280 ° C. for 5 hours. A polyester resin having an ultimate viscosity of 0.66 was obtained.
Next, this prepolymer was pre-dried at 150 ° C. for 5 hours and then solid-phase polymerized at 210 ° C. for 30 hours in a nitrogen stream to obtain a polyester resin.
[Blow molded article]
The obtained polyester resin is used, dried, and then molded using a direct blow molding machine at an extrusion temperature of 260 ° C., a parison diameter of 3 cm and a length of 25 cm, and a 500 ml hollow container (direct blow molded product). ) Was obtained.

Examples 2-3, Comparative Examples 1-3
The copolymerization amount of 1,4-cyclohexanedimethanol was changed as shown in Table 1, and the time until the pressure reached 1 hPa or less at the time of melt polymerization, the melt polymerization temperature at that time, and the total melt polymerization time. Was changed as shown in Table 1, and a polyester resin was obtained in the same manner as in Example 1.
Using the obtained polyester resin, a direct blow molded product was produced in the same manner as in Example 1.

Comparative Example 4
A slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) is supplied to the esterification reactor and reacted under the conditions of a temperature of 250 ° C. and a pressure of 50 hPa for esterification. A reaction product (number average degree of polymerization: 5) having a reaction rate of 95% was obtained.
60.3 parts by mass of the reaction product of TPA and EG was charged into the polymerization reactor, followed by 3.9 parts by mass of 1,4-cyclohexanedimethanol, 0.008 parts by mass of germanium dioxide as a polymerization catalyst, and tetrakis as an additive. [Methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] 0.12 parts by mass of methane (Irganox-1010 manufactured by Ciba Specialties) was added, and the reactor was added for 60 minutes. After reducing the pressure to a final pressure of 0.9 hPa at 260 ° C., a melt polymerization reaction was carried out at a temperature of 280 ° C. for 4 hours to obtain a copolymerized polyester resin composition having an ultimate viscosity of 0.72.
Using the obtained polyester resin composition, a direct blow molded product was produced after performing solid phase polymerization in the same manner as in Example 1.

Table 1 shows the characteristic values and the evaluation results of the moldability of the polyester resin and the molded product obtained in Examples 1 to 3 and Comparative Examples 1 to 4.

As is clear from Table 1, the polyester resins obtained in Examples 1 to 3 satisfy the range of the present invention in the number of foreign substances and the density, so that the container has good moldability and excellent impact resistance. I was able to get.

On the other hand, in Comparative Example 1, the melt polymerization temperature until the pressure reached 1 hPa or less at the time of melt polymerization was too high, so that the obtained polyester resin had a large number of foreign substances and a high density. Therefore, the blow moldability was poor, and the obtained molded product was inferior in impact resistance.
In Comparative Example 2, the time required to reach the pressure of 1 hPa or less at the time of melt polymerization was long, and the melt polymerization temperature was too high, so that the obtained polyester resin had a large number of foreign substances, a high density, and was also high. Deterioration also occurred. Therefore, the blow moldability was poor, and the obtained molded product was inferior in impact resistance.
In Comparative Example 3, it took a long time to reach the pressure of 1 hPa or less at the time of melt polymerization, and the melt polymerization temperature was too low, so that the total melt time became long, and the obtained polyester resin contained foreign matter. There was a lot of deterioration. Therefore, the blow moldability was poor, and the obtained molded product was inferior in impact resistance.
In Comparative Example 4, the time required to reach the pressure of 1 hPa or less at the time of melt polymerization was short, and the polyester resin contained an antioxidant, so that the obtained polyester resin composition had the number of foreign substances. The density was high. Therefore, the blow moldability was poor, and the obtained molded product was inferior in impact resistance.

Claims (2)

When ethylene terephthalate is the main repeating unit and the total amount of all glycol components is 100 mol%, ethylene glycol is contained in an amount of 80 to 97 mol% and 1,4-cyclohexanedimethanol is contained in an amount of 2 to 15 mol% as a copolymerization component. A polyester resin containing 85 mol% or more of terephthalic acid when the total amount of total acid components is 100 mol%, having an ultimate viscosity of 0.9 to 1.4, and a thickness of 20 μm at 280 ° C. A polyester resin having a diameter of 300 μm or more and a foreign matter having a diameter of 300 μm or more and having a diameter of 3 pieces / m ² or less and a resin density of 1.370 g / cm ³ or less in a sheet obtained by melt-extrusion. A blow-molded product obtained by blow-molding using the polyester resin according to claim 1 .