JP2012076457A - Method of molding hollow container by blow molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superior method of molding a hollow container comprising polyethylene terephthalate capable of carrying out continuous blow molding without cleaning a mold for a long period of time, in which productivity is enhanced, cost is lowered, and working environment is enhanced.SOLUTION: In the method, the hollow containers are continuously molded 10,000 times or more part per mold without cleaning the blow molding mold using polyethylene terephthalate polymerized using a phenol group containing phosphorous compound and aluminium compound as a catalyst or polyethylene terephthalate polymerized using aluminium salt of phenol group containing phosphorous compound as the catalyst.

Description

  The present invention relates to a method for forming a hollow container made of polyethylene terephthalate (PET). More specifically, the present invention relates to a method for forming a heat-resistant blow-molded hollow container for beverage made of PET.

  Hollow containers made by blow molding of PET are used as containers for various purposes. In particular, it is very often used as a container (bottle) for beverages such as juice, tea, and mineral water.

  These beverage containers are roughly classified into pressure-resistant bottles for carbonated beverages, aseptic bottles for aseptic filling, and heat-resistant bottles for high-temperature filling.

  Since heat-resistant bottles are filled with fillings at a high temperature around 80 ° C, the bottles are also required to have heat resistance that does not deform at this filling temperature, and the heat resistance is achieved by crystallizing the cap and body of the bottle. ing.

  The body is crystallized by heating the preform and then performing blow stretching in a mold heated to 130 to 180 ° C., and holding the bottle in the mold for about 0.5 to 10 seconds. The crystallization of the part is increased.

  At this time, oligomers such as cyclic trimer (CT) in PET migrate to the mold surface, contaminate the mold surface, and contamination is accumulated by repeating molding, and is obtained after a certain number of moldings. It was necessary to clean the mold because the bottle was cloudy and lost its commercial value.

  Cleaning the mold requires manual wiping with a solvent, and since large commercial blow molding machines have multiple blow molds, all molds must be cleaned. It took several hours to a day, and improvements were required in terms of productivity reduction and work environment.

On the other hand, a technique of molding a bottle using PET whose CT is reduced by solid phase polymerization has been known (for example, see Patent Document 1). However, such a conventional technique has a problem in that CT is generated again at a high temperature during molding and a sufficient effect of reducing mold contamination cannot be obtained.
Furthermore, a technique of preventing the regeneration of the above CT by treating with hot water after solid phase polymerization to deactivate the catalyst has been known (see, for example, Patent Document 2). However, a facility for deactivating the catalyst is required, and it is impossible to manufacture or increase the cost unless it is a dedicated facility.

  Furthermore, it has been known that by blending a small amount of a crystalline resin such as polyethylene with PET or adjusting the amount of fine powder of PET, the crystallization speed is accelerated and the mold contamination is reduced (for example, (See Patent Document 3).

  However, even in these conventional techniques, there is a problem that it is necessary to clean the mold by continuous molding of 20000 to 30000 times, and it is insufficient.

Japanese Patent Laid-Open No. 53-5259 JP-A-3-17441 JP 2000-163293 A

  The present invention has been made against the background of such prior art problems. That is, the object of the present invention is to enable continuous blow molding without cleaning the mold over a long period of time, and to improve the productivity, lower the cost, and improve the working environment. The object is to provide a method for forming a container.

The present invention is as follows.
(1) Using polyethylene terephthalate polymerized by using a phenol group-containing phosphorus compound and an aluminum compound as a catalyst, or polyethylene terephthalate polymerized by using an aluminum salt of a phenol group-containing phosphorus compound as a catalyst, blowing more than 10,000 times per mold A method of continuously forming a hollow container without cleaning the molding die.

(2) The method for forming a hollow container according to (1), wherein the phenol group-containing phosphorus compound is a compound having the following structural formula.

(X1 and X2 each represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a monovalent or higher metal. X1 is a metal that is divalent or higher and X2 may not be present. An anion corresponding to the surplus valence of the metal with respect to the phosphorus compound may be arranged.)

(3) The method for molding a hollow container according to (1) or (2), wherein the concentration of phosphorus element in polyethylene terephthalate is 5 to 300 ppm and the concentration of aluminum element is 3 to 100 ppm.

(4) The content of the cyclic trimer in polyethylene terephthalate is 0.2 to 0.6% by mass, and the intrinsic viscosity of polyethylene terephthalate is 0.6 to 0.95 dl / g (1) A method for forming the hollow container according to any one of to (3).

(5) A step of molding a preform, a step of crystallizing the plug portion, a step of reheating the preform, a step of blow-drawing the reheated preform in a mold, and a blow-drawn hollow molded body The method of shape | molding the hollow container in any one of (1)-(4) including the process of heat-setting in the metal mold | die heated.

(6) The hollow container according to (5) is formed, wherein the magnification in the bottle length direction in blow stretching is 1.5 to 6 times, and the magnification in the bottle circumferential direction is 2 to 6 times. Method.

  According to the present invention, in the formation of a hollow container made of polyethylene terephthalate, it is possible to perform continuous blow molding without cleaning the mold for a long time without deactivating the polyethylene terephthalate catalyst, improving productivity. Cost reduction and work environment can be improved.

It is a related figure of the frequency | count of shaping | molding in an Example and a comparative example, and bottle haze.

First, polyester used for bottle molding will be described.
(Polyester composition, physical properties)
The polyester is a polyester whose main repeating unit is ethylene terephthalate, preferably a linear polyester containing 90 mol% or more of ethylene terephthalate units, more preferably 95 mol% or more, particularly preferably. It is a linear polyester containing 97% mol or more. It should be noted that the inclusion of 90 mol% or more of ethylene terephthalate units means that the product of the number of moles of terephthalic acid component and the number of moles of ethylene glycol when the number of moles of all carboxylic acid components and all glycol components is 1, respectively. It represents 0.9 or more.

As dicarboxylic acids as copolymerization components other than terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid 2,7-naphthalenedicarboxylic acid, diphenyl-4,4-dicarboxylic acid, 4,4′-biphenyl ether dicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p′-dicarboxylic acid, anthracene dicarboxylic acid, etc. Aromatic dicarboxylic acids, succinic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1, 3-cyclobutanedicarboxylic acid, 1,3-si Fats exemplified by lopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, dimer acid, hydrogenated dimer acid, etc. An unsaturated dicarboxylic acid such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, fumaric acid or itaconic acid can be used. Of these, isophthalic acid is most preferred.
These dicarboxylic acids can be used in the range of preferably 10 mol% or less, more preferably 5.0 mol% or less, and most preferably 3 mol% or less of the carboxylic acid component.

Examples of the glycol as a copolymer component other than ethylene glycol include propylene glycol, 1,3-propanediol, 1,4-butylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2, 3-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 2-methyl-1,3 -Propanediol, 2-ethyl-1,3-pro Diol, neopentyl glycol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-n-butyl-1,3-propanediol 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propane Diol, 2,2-di-n-hexyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, polyethylene glycol, poly Aliphatic glycols such as trimethylene glycol, polytetramethylene glycol and polypropylene glycol, hydroquinone, 4 4′-dihydroxybisphenol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-bis (β-hydroxyethoxyphenyl) sulfone, bis (p-hydroxyphenyl) ether, bis (p-hydroxyphenyl) sulfone , Aromatic glycols such as bis (p-hydroxyphenyl) methane, 1,2-bis (p-hydroxyphenyl) ethane, bisphenol A, alkylene oxide adducts of bisphenol A, and the like. Of these, diethylene glycol is most preferred.
These glycols can be used in the range of preferably 10 mol% or less, more preferably 5.0 mol% or less, and most preferably 3 mol% or less of the glycol component. By-product diethylene glycol is also included in this copolymer glycol.

  The lower limit of the intrinsic viscosity · IV (dl / g) of the polyester is preferably 0.6, more preferably 0.63, still more preferably 0.65, and particularly preferably 0.67. The upper limit of IV (dl / g) is preferably 0.95, more preferably 0.8, still more preferably 0.77, and particularly preferably 0.75. If the IV is lower than this range, the mechanical strength and impact resistance of the container are insufficient. On the other hand, if the IV is higher than the above range, injection molding into a bottomed preform is difficult or blow molding is difficult. There is a tendency to become.

The cyclic trimer (CT) content of PET is usually about 1% by mass after melt polymerization. Even PET having a high CT content only by melt polymerization, the PET obtained using the catalyst is less likely to contaminate the mold during blow molding, and many times (10,000 times without cleaning the mold). More than once) is possible.
However, by reducing the CT content by solid phase polymerization, contamination of the mold can be further suppressed, and the mold cleaning interval can be lengthened.

The lower limit of the CT content (% by mass) of the polyester is preferably 0.2, more preferably 0.25, and still more preferably 0.27. If it is less than the above, solid-phase polymerization takes a long time, and productivity may be reduced.
The upper limit of the CT content (% by mass) is preferably 0.6, more preferably 0.5, and still more preferably 0.4. If the above is exceeded, mold contamination may become strong.

Since the heat-resistant bottle is filled with the contents at a high temperature, the stopper portion is crystallized to have heat resistance. In order to control in the crystallization step, the temperature rising crystallization temperature (Tc1) is preferably within a specific range.
The lower limit of the temperature rising crystallization temperature (Tc1) of the polyester is preferably 130 ° C, more preferably 140 ° C, and even more preferably 150 ° C. If it is less than the above, the stopper crystallization is too fast and the stopper dimensional stability is deteriorated, and the bottle transparency may be lowered.
The upper limit of Tc1 is preferably 172 ° C, more preferably 170 ° C, and even more preferably 168 ° C. When the above is exceeded, crystallization of the plug part is slow and productivity may be lowered. Tc1 can be adjusted by adjusting the catalyst. Moreover, it can adjust by adding crystalline resins, such as polyethylene, or performing a contact process.

  Increase amount of medium molecular weight PET (weight average molecular weight 1000-6000) when polyester is heated at 170 ° C. for 20 hours is preferably 6% by mass or less, more preferably 5% by mass or less, and further preferably 4% by mass. % Or less, most preferably 3% by mass. When the increase amount of the medium molecular weight PET (weight average molecular weight 1000 to 6000) when the polyester is heated at 170 ° C. for 20 hours exceeds 6% by mass, the mold contamination tends to become strong. By using a phenol group-containing phosphorus compound or aluminum compound as a catalyst, even if heated for a long time at the mold temperature at the time of blow molding, since the medium molecular weight PET generated by thermal decomposition is small, mold contamination can be effectively prevented. It is considered a thing.

  The amount of acetaldehyde in the polyester is preferably 20 ppm or less, more preferably 10 ppm or less, still more preferably 8 ppm or less, and particularly preferably 5 ppm or less. If the above is exceeded, the fragrance retention of the contents may be lowered.

(Polyester catalyst)
As an aluminum compound which comprises a polyester polymerization catalyst, a well-known aluminum compound can be used without limitation.

  Specific examples of the aluminum compound include aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, aluminum acetylacetonate, and organoaluminum compounds such as aluminum oxalate and their parts. Examples include hydrolysates. Among these, carboxylate, inorganic acid salt and chelate compound are preferable, and among these, aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride and aluminum acetylacetonate are more preferable, Aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide and aluminum hydroxide chloride are more preferred, and aluminum acetate and basic aluminum acetate are most preferred.

The amount of the aluminum compound used for the polyester polymerization catalyst as an aluminum atom is preferably 3 to 100 ppm, more preferably 5 to 70 ppm, still more preferably 7 based on the total weight of the polyester obtained. -50 ppm, particularly preferably 8-40 ppm.
Below the above, catalyst activity may be poor, and above the above, foreign matter may be generated, and the transparency of the bottle may be reduced, or the crystallization control of the plug may be difficult. is there.
In addition, when the phosphorus compound containing the following phenol group is Al salt, an aluminum compound does not need to be used separately.

  The phosphorus compound constituting the polyester polymerization catalyst contains a phenol group. The phenol group preferably has a hindered phenol structure, and a particularly preferred form is a phosphorus compound having a hindered phenol structure represented by the following chemical formula (formula A).

In Formula A, X1 and X2 each represent hydrogen, an alkyl having 1 to 4 carbon atoms, or a monovalent or higher metal. X1 is divalent or higher in metal, and X2 may not be present. Alternatively, an anion corresponding to the surplus valence of the metal may be arranged with respect to the phosphorus compound.
As the metal, Li, Na, K, Ca, Mg, and Al are preferable. In addition, when it is Al as a metal, the said aluminum compound does not need to be.

  Examples of the compound represented by the chemical formula (formula A) include phosphorus compounds represented by the chemical formulas (Chemical Formula 1) and (Chemical Formula 2).

  Irgamod 295 (manufactured by BASF) is commercially available as the compound represented by the above chemical formula (Chemical Formula 1), and Irgamod 195 (manufactured by BASF) is commercially available as the compound represented by (Chemical Formula 2). It can be used.

The amount of the phosphorus compound used is preferably 5 to 300 ppm as phosphorus atoms with respect to the total weight of the resulting polyester, more preferably 10 to 200 ppm, still more preferably 15 to 150 ppm, and particularly preferably. Is 20 to 100 ppm.
When the amount of the phosphorus compound added is small, the catalytic activity may be poor or foreign matter may be generated. Even if the amount is too large, the catalytic activity as a polyester polycondensation catalyst may be reduced. Varies depending on the amount of aluminum added. When the catalytic activity is poor, a large temperature time product in the polycondensation is required, which is economically disadvantageous.

The ratio P / Al (molar ratio) between the phosphorus atom of the phosphorus compound and the aluminum atom of the aluminum compound contained in the polyester is preferably 1 ≦ P / Al ≦ 100, more preferably 1.2 ≦ P /. Al ≦ 50, more preferably 1.3 ≦ P / Al ≦ 20, particularly preferably 1.4 ≦ P / Al ≦ 10, and most preferably 1.5 ≦ P / Al ≦ 5. .
If P / Al is too low, the catalyst activity as a polyester polycondensation catalyst may be reduced or foreign matter may be generated. If it is too high, the catalyst activity as a polyester polycondensation catalyst may also be reduced.

  In the polycondensation catalyst of the present invention, other polycondensation catalysts such as an antimony compound, a germanium compound, and a titanium compound may coexist within a range of addition amounts that do not cause problems in products such as polyester characteristics, processability, and color tone. However, it is preferable that these are not substantially contained.

  It is preferable that an antimony compound is 30 ppm or less as an antimony atom with respect to the polyester obtained by polycondensation. More preferably, it is 20 ppm or less, More preferably, it is 10 ppm or less, Most preferably, it is 5 ppm or less. If the amount of antimony added exceeds 30 ppm, metal antimony is precipitated and Tc1 may be removed, which is not preferable.

  The germanium compound is preferably in an amount of 10 ppm or less as germanium atoms with respect to the polyester obtained by polycondensation. More preferably, it is 5 ppm or less, More preferably, it is 3 ppm or less, Most preferably, it is 2 ppm or less. If the amount of germanium added exceeds 10 ppm, it is not preferable because it is disadvantageous in terms of cost.

  It is preferable that a titanium compound is 3 ppm or less as a titanium atom with respect to the polyester obtained by polycondensation. More preferably, it is 2 ppm or less, More preferably, it is 1 ppm or less. If the amount of titanium added is more than 3 ppm, the resulting polyester will be markedly colored, and the thermal stability will be significantly reduced.

  The sodium compound is preferably in an amount of 20 ppm or less as sodium atoms with respect to the polyester obtained by polycondensation. More preferably, it is 10 ppm or less, More preferably, it is 5 ppm or less, Most preferably, it is 2 ppm or less. If the amount of sodium added exceeds 20 ppm, the haze at the time of molding the resulting polyester deteriorates, and the hydrolysis resistance and thermal stability deteriorate, which is not preferable.

  The magnesium compound is preferably in an amount of 100 ppm or less as magnesium atoms with respect to the polyester obtained by polycondensation. More preferably, it is 50 ppm or less, More preferably, it is 20 ppm or less, Most preferably, it is 10 ppm or less. If the amount of magnesium added exceeds 100 ppm, the thermal oxidation stability of the resulting polyester deteriorates, which is not preferable.

  The lithium compound is preferably in an amount of 50 ppm or less as lithium atoms with respect to the polyester obtained by polycondensation. More preferably, it is 20 ppm or less, More preferably, it is 10 ppm or less, Most preferably, it is 5 ppm or less. If the amount of lithium added exceeds 50 ppm, it is not as good as a sodium compound, but the haze at the time of molding the resulting polyester deteriorates, and the thermal stability decreases, which is not preferable.

(Polyester polymerization method)
The polyester according to the present invention can be produced by a method having a conventionally known process using a polyester polymerization catalyst comprising an aluminum compound and a phosphorus compound as a catalyst. For example, in the case of producing PET, a direct esterification method in which terephthalic acid, ethylene glycol and, if necessary, other copolymerization components are directly reacted to distill water to esterify, followed by polycondensation under reduced pressure, or It is produced by a transesterification method in which dimethyl terephthalate is reacted with ethylene glycol and other copolymerization components as required to distill off methyl alcohol for transesterification, followed by polycondensation under reduced pressure.
Furthermore, it is preferable to carry out solid phase polymerization in order to increase the intrinsic viscosity and reduce the CT amount as necessary. In order to accelerate crystallization before solid-phase polymerization, the melt-polymerized polyester may be heated and crystallized after moisture absorption, or steam may be sprayed directly onto the polyester chip to heat and crystallize.
The melt polycondensation reaction may be either a batch reactor or a continuous reactor.

(Catalyst adjustment)
When an aluminum compound and a phosphorus compound are used as a catalyst, it is preferable to add them in powder form, a slurry form in a solvent such as water or glycol, or a solution form such as water or glycol.

  It is preferable to add the aluminum compound solution and the phosphorus compound solution simultaneously after the esterification reaction or transesterification reaction and before the polycondensation. It is preferable that the system is uniformly mixed immediately after the addition.

  By these methods, foreign matter can be reduced and Tc1 can be increased to around 170 ° C. or higher. Moreover, Tc1 can be made high by making polycondensation temperature as low as possible.

(Molding bottle)
In blow molding of a heat-resistant bottle, a bottomed precursor generally called a preform is prepared, this preform is blow-drawn in a mold, and further heat set.
For producing the preform, methods such as compression molding and injection molding are used. Taking injection molding as an example, a preform can be obtained by heating and melting at 260 to 300 ° C. and injecting it into a preform mold.
Usually, the preform has a thick test tube shape and has a gate portion at the bottom, and a cap screw is engraved on the plug portion.

  In the heat-resistant bottle, the plug portion of the obtained preform is crystallized. Even when the high-temperature contents are filled by crystallization, the plug portion can be prevented from being deformed. Crystallization of the plug portion is preferably performed by heating to 130 to 200 ° C, more preferably 140 to 190 ° C. As a heating method, an infrared heater, hot air, induction heating, immersion in an oil bath, or the like can be used. It is preferable to use an infrared heater from the viewpoint of productivity. The heat crystallization of the plug portion may be after blow molding.

The preform is heated, and the preform is stretched in the bottle length direction and blown in the circumferential direction to obtain a bottle. In the longitudinal direction, it is usually stretched with a rod-shaped stretching rod, and in the circumferential direction, a pressurized gas such as air or nitrogen is used. The pressurized gas is preferably 1 to 10 MPa. A method in which pressurized gas is blown while a stretching rod is inserted and stretching in the length direction and the circumferential direction is preferred, but stretching in the length direction may be followed by stretching in the circumferential direction.
For the heating, an infrared heater, hot air, induction heating or the like is used. The heating temperature is usually 80 to 130 ° C, preferably 90 to 120 ° C.

The lower limit of the draw ratio in the bottle length direction is preferably 1.5 times, more preferably 2 times. If it is less than the above, stretching unevenness may occur.
The upper limit of the draw ratio in the length direction is preferably 6 times, more preferably 5 times, and further preferably 4 times. If the above is exceeded, tearing or the like easily occurs.

The lower limit of the stretching ratio in the circumferential direction of the bottle is preferably 2 times, more preferably 2.5 times. If it is less than the above, stretching unevenness may occur.
The upper limit of the stretching ratio in the circumferential direction is preferably 6 times, more preferably 5 times, and further preferably 4 times. If the above is exceeded, tearing or the like easily occurs.

  When heat setting is continued in the same mold after blow molding, the lower limit of the mold temperature of blow molding is preferably 80 ° C., more preferably 120 ° C., further preferably 130 ° C., most preferably 140 ° C. If it is less than the above, sufficient heat treatment is not performed in the heat setting performed later, so that the heat resistance is insufficient, or it is necessary to take a long heat setting time, resulting in a decrease in productivity.

  The upper limit of the mold temperature is preferably 200 ° C, more preferably 190 ° C, still more preferably 180 ° C, and particularly preferably 170 ° C. When the mold temperature increases, mold contamination increases, and the number of continuous moldings may decrease.

The blow molded bottle is then heat set in the mold. The lower limit of the heat setting time is preferably 0.5 seconds, more preferably 1 second, and even more preferably 1.5 seconds. If it is less than the above, sufficient crystallization is not promoted and heat resistance may be insufficient.
The upper limit of the heat set time is 90 seconds, preferably 15 seconds, more preferably 10 seconds, and even more preferably 5 seconds. A long heat set time is not only inferior in productivity, but in the case of a rotary blow molding machine, it is necessary to prepare a large number of molds, and if the apparatus becomes large, the economy may be inferior.
After heat setting in the mold, additional heat setting may be performed by further heating with infrared rays, hot air, induction heating, or the like.

  It is also possible to perform blow molding in a mold at 5 to 50 ° C. and subsequently heat set in a heating mold. The temperature of the heat set mold in this case is the same as the mold temperature in the above case.

  The blow molding apparatus may be provided with a single mold, but in the case of mass production, it is provided with a plurality of molds, and these molds are places where the heated preform is set in the mold, It is preferable to use a method of sequentially moving a stretching place, a heat setting place, and a bottle discharging place.

  In addition, although the cold parison method which reheats the cooled preform was demonstrated above, the hot parison method which performs blow molding, without completely cooling a preform is also possible.

The inner volume of the bottle to be molded is preferably 200 mL to 6 L. The thing of 300mL-2L is especially preferable.
The shape of the bottle body can be any shape such as a circle, a quadrangle (including a shape with a cut corner), and a hexagon.

  Usually, when PET in which the catalyst is not deactivated is used, when the molding is performed several thousand to slightly less than 10,000 times with one blow mold, the mold surface is forced to be cleaned. However, blow molding using polyethylene terephthalate polymerized with phenol group-containing phosphorus compound and aluminum compound as catalyst can unexpectedly reduce the contamination of the mold and clean the mold. It was found that blow molding can be performed continuously 10,000 times or more per mold without performing the above process. Further, it was found that continuous molding can be continued without cleaning the mold even after continuous molding of 15000 times or more and 20000 times or more.

  Moreover, even with PET in which the catalyst has been deactivated with hot water, it has been necessary to stop the molding after 20000 to 30000 continuous molding, but it is necessary to clean the mold, but 25000 times or more, and further 30000 times or more continuous molding. However, it was found that molding can continue without cleaning the mold.

  In addition, for PET in which the catalyst is not deactivated, 3 g of a dried polyester chip having a CT content of 0.5% by mass or less is put in a glass test tube and immersed in a 290 ° C. oil bath for 60 minutes in a nitrogen atmosphere and melted. In this case, the CT increase amount (ΔCT) is 0.1% by mass or more. When blow molding is performed using a phenol group-containing phosphorus compound, polyethylene terephthalate polymerized by using an aluminum compound as a catalyst, or polyethylene terephthalate polymerized by using an aluminum salt of a phenol group-containing phosphorus compound as a catalyst, such a deactivation is caused. Even with no PET, the contamination of the mold can be very low. Even if ΔCT is 0.15% by mass or more, and further 0.2% by mass or more, contamination of the mold can be kept low.

According to the study of the present inventors, the mold contamination of the bottle is not mainly CT as has been said until now, but the mold is mainly made of medium molecular weight PET having a molecular weight of about 3000 to 5000. It was found that it adhered and CT was mixed with it.
PET polymerized using a phenol group-containing phosphorus compound and aluminum compound as a catalyst has little medium molecular weight PET generated by thermal decomposition even when heated for a long time at the mold temperature of blow molding. It is thought that it can prevent.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
The main characteristic value measurement methods will be described below.

(1) Intrinsic viscosity of polyester (IV)
The viscosity was calculated from the solution viscosity at 30 ° C. in a 1,1,2,2-tetrachloroethane / p-chlorophenol (1: 3 weight ratio) mixed solvent.

(2) Temperature rising crystallization temperature of polyester (Tc1)
Measured with a differential thermal analyzer (DSC), RDC-220, manufactured by Seiko Electronics Industry Co., Ltd. The temperature was raised at a rate of temperature rise of 20 ° C./minute and held at 290 ° C. for 3 minutes, then the temperature was lowered from 290 ° C. to 240 ° C. at 10 ° C./minute, and further from 240 ° C. to 130 ° C. at 7 ° C./minute. The temperature dropped. The peak temperature of the crystallization peak observed at the time of temperature rise is defined as the temperature crystallization temperature (Tc1).
The Tc1 of various polyester molded bodies used in Examples and Comparative Examples uses 4 mg ± 1.0 mg of samples from the following preform mouths. A total of five measurements were taken and the average value was taken.

(3) Aluminum determination method (X-ray fluorescence analysis)
Using a stainless steel ring having a thickness of 5 mm and an inner diameter of 50 mm, it was melted and smoothed in a melting oven melting oven at 300 ° C. for 15 minutes. After cooling, the ring was removed, and the sample was scraped with a razor blade to remove surface contamination, and used as a measurement sample. Catalyst quantification was carried out using a calibration curve obtained in advance from a sample having a known aluminum element amount.
Measuring device: RIGAKU ZSX100e (4.0 kW Rh tube)
Measuring ball: 30mmφ

(4) Phosphorus compound quantification method (X-ray fluorescence analysis)
Using a stainless steel ring, it was melted and smoothed in a melting oven at 300 ° C. for 15 minutes. After cooling, the ring was removed, and the sample was scraped with a razor blade to remove surface contamination, and used as a measurement sample. Catalyst quantification was performed using a calibration curve obtained in advance from a sample having a known phosphorus element amount.
Measuring device: RIGAKU ZSX100e (4.0 kW Rh tube)
Measuring ball: 30mmφ

(5) Diethylene glycol content (DEG)
After 0.1 g of polyester was thermally decomposed at 250 ° C. in 2 ml of methanol, it was quantitatively determined by gas chromatography.

(6) Content of cyclic trimer (hereinafter referred to as “CT content”)
The sample is dissolved in a hexafluoroisopropanol / chloroform mixture, and further diluted with chloroform. Methanol is added to this to precipitate the polymer, followed by filtration. The filtrate was evaporated to dryness, made constant with dimethylformamide, and a cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(7) Acetaldehyde content (hereinafter referred to as “AA content”)
Sample / distilled water = 1 g / 2 cc of glass ampoule substituted with nitrogen was sealed and subjected to extraction treatment at 160 ° C for 2 hours. After cooling, acetaldehyde in the extract was measured by high-sensitivity gas chromatography. The concentration was expressed in ppm.
(8) Medium molecular weight PET (weight average molecular weight 1000-6000) increase The sample was extract | collected from the mouth of the extending | stretching hollow molded object shape | molded by the said method, and it freeze-ground and made it the powder of 20 mesh or less. This powder was vacuum-dried at 130 ° C. for 12 hours, and 300 mg of the powder was placed in a glass test tube having an inner diameter of about 8 mm and a length of about 140 mm and vacuum-dried at 70 ° C. for 12 hours. Next, a drying tube containing silica gel is attached to the upper part of the test tube, and after being immersed in a salt bath at 170 ° C. for 20 hours and heated for 20 hours, the amount of increase in medium molecular weight PET (weight average molecular weight 1000 to 6000) is increased by the GPC method. Was calculated.
Measurement Conditions (Sample Preparation) A sample solution was prepared by dissolving 1 mg of a sample in 0.2 mL of chloroform / hexafluoroisopropanol = 3/2 (vol%) and then diluting with 3.8 mL of chloroform.
(Eluent) Chloroform / hexafluoroisopropanol = 98/2 (vol%)
(Equipment) TOSOH HLC-8220GPC manufactured by Tosoh Corporation
(Column) TSKgel SuperHM-H × 2 + TSKgel SuperH2000 manufactured by Tosoh Corporation
(Standard polystyrene) TSK standard polystyrene manufactured by Tosoh Corporation (measurement conditions) Measurement temperature 40 ° C., flow rate 0.6 mL / min (detector) UV detector 254 nm
(Molecular weight conversion) Calculation was performed in terms of standard styrene.
(Integration range) The peak start was set to 700 with standard polystyrene, and the peak end was set to 700 with standard polystyrene.

(9) Hollow container continuous molding evaluation method The sample polyester was dried in a vacuum dryer to a moisture content of 100 ppm or less, a 150C-DM type injection molding machine manufactured by Meiki Seisakusho and a mold for preforms (mold temperature 5 ° C). ) Was used to mold a bottomed preform (PF).
As plasticizing conditions by the M-150C-DM injection molding machine, the feed screw rotation speed is 70%, the screw rotation speed is 120 rpm, the back pressure is 0.5 MPa, the cylinder temperature is 45 ° C., 250 ° C. and the nozzle in order from directly below the hopper. The cylinder temperature after the inclusion (hereinafter referred to as Sx) was set to 280 ° C. Further, the injection pressure and the holding pressure were adjusted so that the weight of the molded product was 28.4 ± 0.2 g.
Next, the plug portion of the preform was heated and crystallized using an NC-01 plug portion crystallization apparatus manufactured by Frontier Corporation.
Furthermore, the preform was blown biaxially with a SBO LabN ° 1045 type 1 Lab blow molding machine manufactured by Sidel. The reheating of the preform was adjusted to about 105 ° C. While blowing air at a pressure of 36 bar in a mold whose temperature was adjusted to 150 ° C., biaxial stretching blow was performed at a ratio of 2.5 times in the longitudinal direction at 750 bph and a magnification of 3.8 times in the circumferential direction in a molding cycle of 30 seconds. Subsequently, a 500 ml bottle having a shape having six flat surfaces on the side surface was obtained by contacting the hot mold for 2.3 seconds in the mold.
Before the molding, the blow mold was wiped clean, and thereafter the molding was repeated continuously without cleaning the mold.

(10) Haze of the stretched hollow molded body (degree%)
Of the substantially flat part of the bottle body obtained in (9), the center of the part corresponding to the joint part of the mold was cut out so as to be 22 mm wide x 55 mm long and used as a measurement sample. The thickness of the sample was about 0.4 mm. This sample was measured with a Nippon Denshoku Co., Ltd. haze meter, model NDH2000. A total of five measurements were taken at different locations and the average value was taken.

(11) Increase amount of cyclic trimer during melting of polyester (ΔCT amount)
3 g of the dried polyester chip was put in a glass test tube and immersed in an oil bath at 290 ° C. for 60 minutes in a nitrogen atmosphere and melted. The amount of increase in cyclic trimer at the time of melting was determined by the following formula.
Increase amount of cyclic trimer at the time of melting (wt%) =
Cyclic trimer content after melting (wt%)-cyclic trimer content before melting (wt%)

  Next, production of PET will be described.

(Production of PET-A)
The reaction was carried out using a polycondensation apparatus consisting of three continuous esterification reactors and three polycondensation reactors. As the catalyst, an ethylene glycol solution of basic aluminum acetate (hydroxyaluminum diacetate) and an ethylene glycol solution of Irgamod 295 (manufactured by BASF) as the phosphorus compound were added before the polycondensation step.
In the esterification step, the temperature of each reaction vessel is raised between 250 and 268 ° C., and in the polycondensation, the degree of vacuum is increased while raising the temperature of the nuclear reaction vessel between 270 and 275 ° C., and the IV is 0.554 dl / g of PET was obtained. The polyester was extruded in a strand shape, cooled in water and then cut into chips having an average particle weight of 36 mg.
The catalyst was added so that the amount of migration after completion of polycondensation was 45 ppm as phosphorus atoms so that the amount of aluminum atoms was 15 ppm as aluminum atoms relative to the acid component in the polyester.

Subsequently, the obtained chip was transported to a continuous solid phase polymerization apparatus. Crystallization was performed at about 155 ° C. in a nitrogen atmosphere, and after preheating to about 200 ° C. in a nitrogen atmosphere, the mixture was sent to a continuous solid-phase polymerization reactor and subjected to solid phase polymerization at about 207 ° C. in a nitrogen atmosphere.
Continued in the vibration sieving step and the airflow classification step to remove fines and film-like materials, and part of the gravity transport piping made of SUS304 connected to the shipping container filling step installed under the airflow classification step, A contact device in which ten rod-like bodies each having a diameter of about 1 cm made of linear low density polyethylene (MI = about 0.9 g / 10 min, density = about 0.923 g / cm ³ ) are attached in a total of 5 stages. Inside the attached pipe, the PET chip, from which fines and the like were removed, was dropped to perform contact treatment with polyethylene.

  The intrinsic viscosity of the obtained PET-A was 0.74 dl / g, the DEG content was 2.5 mol%, the cyclic trimer content was 0.31 wt%, and the cyclic trimer increase was 0.35. % By weight, AA content is 2.4 ppm, polyethylene content is about 20 ppb. The polyethylene content is a value calculated from the amount of PET treated and the weight loss of the polyethylene rod-like body when PET is treated for a long period of time with this apparatus using PET under other catalysts and polymerization conditions.

(PET-B)
A solution of an aluminum compound and a phosphorus compound was prepared in the same manner as PET-A, except that the migration amount after the completion of polycondensation was 10 ppm as an aluminum atom and 23 ppm as a phosphorus atom with respect to the acid component in the polyester. It was. The polymerization time and pressure were adjusted slightly to match PET-A.

(PET-C)
The same procedure as in PET-A was performed, except that the solution of the aluminum compound and the phosphorus compound was added so that the migration amount after completion of the polycondensation was 30 ppm as an aluminum atom and 90 ppm as a phosphorus atom with respect to the acid component in the polyester. It was. The polymerization time and pressure were adjusted slightly to match PET-A.

(PET-D)
The same as PET-A except that the contact treatment to polyethylene was not performed.

(PET-E)
The melt polymerization conditions were changed to change the PET IV after melt polymerization to 0.65 dl / g, and the solid phase polymerization conditions were changed to obtain 0.72 dl / g PET.
(PET-F)
The same as PET-A, except that Irgamod 195 (manufactured by BASF) was used as the phosphorus compound.

(Production of PET-G)
A slurry of high-purity terephthalic acid and ethyl glycol was continuously supplied to a two-can esterification reactor, and the reaction was conducted at 250 to 260 ° C. with stirring. The catalyst crystalline germanium dioxide was dissolved in water by heating, ethylene glycol was added to the catalyst, and the heat-treated catalyst solution and phosphoric acid in ethylene glycol were continuously fed separately to the second esterification reactor. . The esterification reaction product was supplied to a 3-can type polycondensation reactor, and polycondensed with stirring at about 265 to 275 ° C. and a final pressure of 0.5 to 1 torr. The melt polycondensation reaction product was cut in a semi-solid state while being cooled with cooled ion-exchanged water, converted into chips, and then transported to a continuous solid phase polymerization apparatus. Crystallization was performed at about 155 ° C. in a nitrogen atmosphere, and after preheating to about 200 ° C. in a nitrogen atmosphere, the mixture was sent to a continuous solid-phase polymerization reactor and subjected to solid phase polymerization at about 207 ° C. in a nitrogen atmosphere.

Further, the obtained solid-phase polymerization chip was continuously supplied to a hot water treatment apparatus in which ion exchange water at 95 ° C. was circulated, and the catalyst was deactivated.
After the deactivation treatment, it is dried continuously with heated dry air, then processed in the vibration sieving step and airflow classification step to remove fine and film-like materials, and the transport container installed under the airflow classification step A part of gravity transport piping made of SUS304 connected to the filling process is a rod-shaped rod made of linear low density polyethylene (MI = about 0.9 g / 10 min, density = about 0.923 g / cm ³ ) with a diameter of about 1 cm. A PET chip from which fines and the like were dropped was dropped inside a pipe to which a contact device having 10 bodies in one stage, a total of 5 stages, was attached, and contact treatment with polyethylene was performed.

  The obtained PET-G has an intrinsic viscosity of 0.74 dl / g, a DEG content of 2.5 mol%, a cyclic trimer content of 0.30 wt%, and a cyclic trimer increase of 0.04. % By weight, AA content is 2.3 ppm, polyethylene content is about 20 ppb. Further, the residual amount of Ge measured by fluorescent X-ray analysis was 47 pm, and the residual amount of P was 30 ppm.

(Production of PET-H)
PET-G was obtained in the same manner as PET-G except that the catalyst deactivation treatment with hot water was not performed.

(Examples 1-7, Comparative Examples 1-3)
Continuous bottle molding was performed using PET-A to H. The haze measurement of the trunk | drum with a bottle was performed for every fixed molding frequency. The results are shown in Table 1.
In Example 1, even after 35,000 times, the increase in the bottle haze was small, and when the molding was observed after 35,000 times, the mold was not stained.
Furthermore, it is considered that continuous molding of 40000, 50000 times, 60000 times or more is possible. FIG. 1 shows the relationship between the number of moldings and bottle haze in each of the examples and comparative examples. Considering the limit of continuous molding when the haze exceeds 5%, it is predicted that continuous molding of 100,000 times or more is possible.

Also in Examples 2 to 6, the increase in bottle haze after 20000 times molding is the same as in Example 1, and continuous molding equivalent to that in Example 1 is possible. When the mold was taken out and observed, there was almost no dirt on the mold.
In Example 7 and Comparative Example 3, the mold temperature was 170 ° C. In Example 7, compared with Example 1, the mold contamination increased, but when the mold was taken out and observed after molding, there was no large mold contamination, and it can be predicted that continuous molding of 35,000 times or more is possible. .

In Comparative Example 1, the haze exceeded 6% after 35,000 continuous moldings, making continuous molding difficult.
In Comparative Example 2, haze exceeded 6% after 10,000 continuous moldings, making continuous molding difficult.

  The method for molding a hollow container according to the present invention is capable of continuous blow molding without cleaning the mold for a long period of time, and is extremely useful for improving productivity, reducing costs, and improving the working environment. .

Claims (6)

  Using polyethylene terephthalate polymerized by using phenol group-containing phosphorus compound and aluminum compound as catalyst, or polyethylene terephthalate polymerized by using aluminum salt of phenol group-containing phosphorus compound as catalyst, blow molding mold more than 10,000 times per mold A method of continuously forming a hollow container without cleaning. The method for forming a hollow container according to claim 1, wherein the phenol group-containing phosphorus compound is a compound having the following structural formula.

(X1 and X2 each represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a monovalent or higher metal. X1 is a metal that is divalent or higher and X2 may not be present. An anion corresponding to the surplus valence of the metal with respect to the phosphorus compound may be arranged.)   The method for molding a hollow container according to claim 1 or 2, wherein the concentration of phosphorus element in polyethylene terephthalate is 5 to 300 ppm and the concentration of aluminum element is 3 to 100 ppm.   The content of the cyclic trimer in polyethylene terephthalate is 0.2 to 0.6% by mass, and the intrinsic viscosity of polyethylene terephthalate is 0.6 to 0.95 dl / g. The method to shape | mold the hollow container in any one.   The step of molding the preform, the step of crystallizing the plug portion, the step of reheating the preform, the step of blow-drawing the reheated preform in the mold, the blow-drawn hollow molded body being heated The method of shape | molding the hollow container in any one of Claims 1-4 including the process of heat-setting within the metal mold | die.   6. The method for forming a hollow container according to claim 5, wherein the bottle length direction magnification in blow stretching is 1.5 to 6 times and the bottle circumferential direction magnification is 2 to 6 times.