JP2005068345A - Method for producing polyester resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently and stably producing a polyester resin that has enhanced crystallization speed at the stopper neck part, when a bottle is molded. <P>SOLUTION: After the completion of polymerization reaction between the terephthalic acid component and/or the naphthalenedicarboxylic acid component and the ethylene glycol component, the resultant polyester resin is brought into contact with a molded plastic product, and then pelletized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a modified polyester resin. More specifically, in a heat-resistant container that has heat resistance and flavor properties as a beverage container used as a hollow container, and further requires a crystallization treatment for the stopper part of the bottle container, the injection molding process of the container molding process is performed. The present invention relates to a method for producing a polyester resin, which can increase the crystallization speed at the time of heating the plug portion of the renovation, thereby stabilizing production and improving production efficiency.

  Conventionally, as bottle containers for carbonated drinks, fruit juice drinks, alcoholic drinks, drinks such as tea and mineral water, liquid seasonings, edible oils, liquid detergents, cosmetics, etc., in addition to their excellent mechanical and chemical properties, Polyester resins have attracted attention because of their excellent transparency, gas barrier properties, low flavor, safety and health. In particular, the production volume of bottle containers of poly (ethylene terephthalate) resin has shown remarkable growth. This polyethylene terephthalate resin bottle container is usually formed by subjecting an injection-molded preform to stretch blow molding in a blow mold. In particular, in heat-resistant bottle containers that require hot filling such as fruit juice beverages, a polyethylene terephthalate resin is usually polycondensed using a germanium compound as a catalyst in order to place importance on its transparency, resulting in a high crystallization temperature. Is used. In this resin, in order to increase the adhesion and heat resistance of the stopper part of the bottle container, the stopper part is crystallized by heat treatment at the stage of the preform or the bottle container.

  Conventionally, in the production of bottle containers, in order to effectively utilize defective moldings that occur in the molding process, what is called repro material obtained by pulverizing these is partially mixed with the raw material polyethylene terephthalate resin and used. There were many cases. This repro material is once melted and undergoes a molding process. Since the intrinsic viscosity is lowered and a part of the resin is stretched and oriented, crystallization is faster than that of a polyethylene terephthalate resin that has not undergone the molding process. By utilizing this point, adjusting the mixing ratio of the repro material, the crystallization speed of the plug portion of the preform was promoted and stabilized. However, in recent years, with a significant increase in demand centered on small bottle containers, the use of dedicated lines and high-speed molding lines for small bottle container forming facilities are progressing. Along with this, there is a problem that even if the repro material itself is reduced, or even if the repro material is mixed, there is a problem that the crystallization of the stopper portion of the bottle container will be insufficient in the predetermined heat treatment time, and the crystallization of the polyethylene terephthalate resin itself There is a strong demand for speed improvements.

  As a method for improving the crystallization speed of the polyethylene terephthalate resin, generally, addition of an inorganic nucleating agent, blending or copolymerization of higher aliphatic compounds and polyether compounds is well known. However, in bottle container forming applications, there are problems of concern such as transparency, coloring due to thermal stability deterioration, flavor properties of fillers due to agent-decomposing components, and hygiene, and satisfactory products are not obtained. On the other hand, as a means for solving this problem, a method of adding or adding a trace amount of a different type of thermoplastic resin such as polypropylene or polyethylene, such as polyolefin, has been proposed (for example, see Patent Documents 1 to 5). In these proposals, the transparency of the bottle container is certainly good and the effect of increasing the crystallization speed of the polyethylene terephthalate resin is large, but these different types of thermoplastic resins are basically poorly compatible with the polyethylene terephthalate resin. Therefore, there is a problem that it is very difficult to uniformly disperse a minute amount, and thus there is a large variation in crystallization speed. In addition, a large amount of equipment investment or equipment modification is required for a method of adding or mixing a small amount of this polyolefin-based different thermoplastic resin as a crystallization accelerator. Furthermore, there is a serious problem in actual commercial production that it is difficult to make the crystallization speeds that are optimal for each customer and brand of polyethylene terephthalate resin as a product. For example, as a method for treating polyethylene terephthalate resin with polyolefin, a method is disclosed in which polyethylene terephthalate resin is brought into contact with polyethylene by making a part of a SUS pneumatic transportation pipe that transports the polymer chipped after melt polymerization into a polyethylene pipe. (For example, refer to Patent Document 3). Also disclosed is a method in which the interior of a polyethylene terephthalate resin production apparatus is coated with a crystalline resin such as polyethylene and is made to contact with polyethylene by production using these (see, for example, Patent Document 6). In these methods, when there is a need to provide a resin with a high crystallization rate to a certain customer and a resin with a low crystallization rate to another customer, the polyethylene member is removed or the polyethylene member is removed. A production line that bypasses the contact area is required. Also, if polyethylene parts wear out and need to be replaced as production continues, the reactor and piping must be opened and replaced, and production is stopped or contacted with polyethylene. It is economically disadvantageous because it is necessary to install a plurality of parallel devices or pipes. Furthermore, there was a problem that the loss at the time of switching the apparatus or piping could not be ignored and the yield also deteriorated.

JP-A-8-302168 JP-A-9-183430 JP-A-9-071639 JP-A-9-151308 Japanese Patent Laid-Open No. 9-194697 JP 2002-317052 A

  The object of the present invention is to solve the above-mentioned problems, while maintaining the heat resistance and flavor required for a bottle container for beverages, while having a fast crystallization rate at the plug part and good polyester for heat-resistant bottle container applications. It is to provide a production method capable of producing a resin efficiently and stably.

  As a result of intensive studies in view of the above problems, the present inventors brought a polyester obtained from a terephthalic acid component and / or a naphthalenedicarboxylic acid component and an ethylene glycol component into contact with a plastic molded article after the polymerization reaction was completed. The above-described problems can be achieved by a method for producing a polyester resin to be chipped, and the present invention has been achieved.

  According to the method for producing a polyester resin of the present invention, it is possible to efficiently and stably produce a polyester resin having a high crystallization speed required for a stopper part of a bottle container.

  Hereinafter, the present invention will be described in detail. The polyester resin obtained by the present invention comprises a polyester obtained from a terephthalic acid component and / or a naphthalenedicarboxylic acid component and an ethylene glycol component. Naphthalenedicarboxylic acid contains all possible structural isomers, but 2,6-naphthalenedicarboxylic acid can be preferably used. A more preferable polyester is a polyester mainly composed of ethylene terephthalate and / or ethylene naphthalate units, and the total of ethylene terephthalate units and ethylene naphthalate units is 80 mol% or more of the total repeating units. is there. In other words, the polyester resin in the production method of the present invention may contain a repeating unit other than polyethylene terephthalate and polyethylene naphthalate units as a copolymerization component in a range of less than 20 mol%. The copolymer component is a compound used as a raw material such as phthalic acid, isophthalic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-phenylic acid. Dioxy acids such as range oxydiacetic acid, malonic acid, succinic acid and adipic acid or ester bond-forming derivatives thereof, oxyacids such as p-hydroxybenzoic acid or glycolic acid, or ester bond-forming derivatives thereof, 1,2- Propanediol, 1,3-propanediol, 1,4-butanediol, aliphatic glycols such as pentamethylene glycol, hexamethylene glycol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, or bisphenol A or bisphenol Aroma such as S Dihydroxy compound or an ester bond-forming derivatives. Although not described in detail, structural isomers of these compounds are also included. Here, the ester bond-forming derivative is a derivative that easily forms an ester bond by reaction, and specific examples thereof include lower alkyl esters, phenyl esters, acid halides, and the like. More preferably, the polyester is composed of 90 mol% or more of polyethylene terephthalate or polyethylene naphthalate.

  The polyester in the present invention is preferably produced using terephthalic acid and / or naphthalenedicarboxylic acid (hereinafter referred to as “terephthalic acid etc.”) or a lower alkyl ester thereof and ethylene glycol as main raw materials. These acid components and / or other glycol components may be used together as raw materials.

  A raw material containing terephthalic acid or the like or an ester-forming derivative thereof and ethylene glycol as described above is converted into bis (β-hydroxyethyl) terephthalate by esterification or transesterification in the presence of an esterification catalyst or transesterification catalyst. And / or naphthalate or an oligomer thereof is formed, and then subjected to melt polycondensation under high temperature and reduced pressure in the presence of a polycondensation catalyst and a stabilizer to obtain a polyester. The esterification catalyst is not particularly required because terephthalic acid or the like becomes an autocatalyst for the esterification reaction. On the other hand, as the transesterification catalyst, alkaline earth metal salts such as magnesium and calcium, and metal compounds such as titanium, zinc and manganese are preferably used. For the purpose of ensuring the transparency of the bottle container, titanium is used. A manganese compound is particularly preferred. As the polycondensation catalyst, germanium compounds, antimony compounds, titanium compounds, cobalt compounds, or tin compounds are generally known. However, the polycondensation catalyst used in the present invention has color tone, transparency, and hygiene. From the point of satisfaction, germanium dioxide is preferable. It is also preferable to use a titanium compound as a transesterification catalyst and also use it as a polycondensation catalyst. The use ratio of the above-mentioned various catalysts is usually in the range of 5 to 1000 ppm, preferably 10 to 500 ppm as the weight of the metal element in the catalyst in all the polymerization raw materials.

  In addition, stabilizers added during polymerization include phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, and triphenyl phosphate, phosphites such as triphenyl phosphite and trisdodecyl phosphite, methyl acid phosphate, and dibutyl phosphate. Phosphorus compounds such as acidic phosphoric acid esters such as monobutyl phosphate, phosphoric acid, phosphorous acid, hypophosphorous acid and polyphosphoric acid are preferred. The use ratio of these stabilizers is usually in the range of 10 to 1000 ppm, preferably 20 to 500 ppm, as the weight of phosphorus atoms in the stabilizer in all the polymerization raw materials.

  The catalyst and the stabilizer can be supplied at any stage of the esterification reaction or transesterification reaction in addition to the preparation of the raw slurry. Further, it can be supplied at the beginning of the polycondensation reaction step. The reaction temperature during the esterification reaction or transesterification reaction is usually 240 to 280 ° C., and the reaction pressure is normal pressure to 0.3 MPa. Moreover, the reaction temperature at the time of melt polycondensation is usually 250 to 300 ° C., and the reaction pressure is usually preferably 60 to 0.1 KPa. Such esterification reaction, transesterification reaction, and melt polycondensation reaction may be performed in one step or in multiple steps. By carrying out such a method, a polyester having an intrinsic viscosity of 0.45 to 0.70 dl / g can be obtained.

  Next, in general, the polyester after the completion of the melt polymerization reaction is discharged from the outlet of the polymerization reactor, brought into contact with water and cooled. In general, since the polymer is in a strand state at this time, it is a feature of the present invention that chips are formed after contacting the polymer with a plastic molded product. In the present invention, after the polymer is discharged, it may be cooled first by contacting with a plastic molded product and then with water. The material of the molded product used as the plastic molded product here is preferably a plastic molded product selected from the group consisting of polytetrafluoroethylene, polytrifluoroethylene, polyvinylidene fluoride, polyamide, polyolefin, and polycarbonate. . Further, specific examples of the polyolefin here include polyethylene such as high density polyethylene, low density polyethylene, or linear low density polyethylene, polypropylene such as high density polypropylene, or low density polypropylene, or other olefins such as propylene and ethylene. These copolymers are preferably used. Examples of the polyamide include 6-nylon and 6,6-nylon. Polycarbonate is preferably a polycondensate of bisphenol A and phosgene or a carbonic acid diester.

  In this case, the shape of the plastic molded product is not particularly limited, and may be any of a flat plate shape, a roll shape, and other shapes. In particular, it is preferable that the polyester strand slides on the flat plate or roll, and the contact treatment with the plastic molded product is performed. Further, in the production method of the present invention, after contact with a plastic molded product or after cooling with water, chips are formed by a conventional method. The average particle diameter of the polymer chip is usually in the range of 2.0 to 5.5 mm, preferably 2.2 to 4.0 mm.

  Next, it is also preferable that the polymer obtained by melt polycondensation as described above is usually subjected to solid phase polymerization. Usually, a polymer chip subjected to solid phase polymerization is preliminarily crystallized by heating to a temperature lower than the temperature at which solid phase polymerization is performed in advance, and then subjected to solid phase polymerization. The pre-crystallization process always flows a polymer chip in an amorphous state or a low crystallinity at a temperature of usually 120 to 200 ° C., preferably 130 to 180 ° C. so as not to cause fusion due to heat generated by chip crystallization. Under certain conditions, it is preferable to crystallize by one or two or more heating steps. The time for crystallization is preferably at least 15 minutes. The solid phase polymerization step after the preliminary crystallization treatment is composed of at least one stage, and is usually at a polymerization temperature of 190 to 230 ° C., preferably 195 to 225 ° C., under a reduced pressure of 0.05 to 5 kPa, or from an atmospheric pressure to 0.00. It is preferable to carry out under an inert gas flow such as nitrogen, argon, carbon dioxide under the condition of 1 MPa. The solid phase polymerization time may be shorter as the polymerization temperature is higher, but is usually 1 to 50 hours, preferably 5 to 30 hours, and more preferably 10 to 25 hours. The intrinsic viscosity of the polymer obtained by solid phase polymerization is usually in the range of 0.7 to 0.90 dl / g.

  In addition, after the completion of the polymerization reaction of the solid phase polymerization, it is also included in the production method of the present invention to melt again and perform a contact treatment with the above-mentioned plastic molded product to form a chip.

  In the present invention, the content or copolymerization amount of the diethylene glycol component constituting the polyester resin obtained by the above production method is preferably 0.7 to 2.0 wt% with respect to all diol units constituting the polyester, More preferably, it is 1.0-1.5 wt%. When the content or copolymerization amount is too small, the transparency of the bottle container body after molding is deteriorated, and when it is too large, the heat resistance is lowered and the effect of promoting the crystallization rate is further reduced. Examples of a method for adjusting the diethylene glycol content within the above range include using diethylene glycol as a polymerization raw material. As another method, since ethylene glycol used as a main raw material partially produces diethylene glycol as a by-product, there is a method of adjusting the amount of by-product by controlling the amount of ethylene glycol used as a polymerization raw material and other reaction conditions. Can be mentioned.

  Moreover, it is desirable to reduce as much as possible the oligomer component which is contained in the polymer and causes mold contamination during molding of the bottle container, and the acetaldehyde component which affects the taste and odor of the filling in the bottle container. The oligomer component content is preferably 0.5 wt% or less, and particularly preferably 0.4 wt% or less. On the other hand, the acetaldehyde content is preferably 5 ppm or less, and particularly preferably 2 ppm or less. Since the oligomer and acetaldehyde reduction treatment is performed simultaneously in the above-described solid phase polymerization step, the IV (inherent viscosity), solid phase polymerization time, and solid phase polymerization temperature of the polymer after melt polymerization are adjusted. To reach the target level.

  Further, it is particularly preferable that the concentration of the terminal carboxyl group in the polymer is in the range of 15 to 25 eq / ton. If the concentration of the terminal carboxyl group is less than the above range, solid phase polymerization is poor and it may take a long time to increase the intrinsic viscosity. In some cases, the effect of reducing oligomers such as cyclic trimer (CT) is small. In order to make the concentration of the terminal carboxyl group within this range, it can be achieved by appropriately adjusting the reaction conditions such as the time for performing the esterification reaction or the transesterification reaction.

  By such a polyester resin production method, it is easy to make a polyester resin with a high crystallization speed and a polyester resin with a low crystallization speed, and easy replacement when a member for promoting the crystallization speed is worn. become. This is because, after melt polymerization, the polyester polymer is discharged from the pores at the outlet of the polymerization reactor, brought into contact with water, cooled, and cut into strands in the form of chips in the melt polymerization and solid phase polymerization processes. This is because the polyester polymer is the only part exposed outside the reactor except for the shipment of the product chip. By using the production method of the present invention in which the treatment for promoting the crystallization speed is performed by contacting the plastic molded article at this portion, brand switching between polyesters having different crystallization speeds can be easily performed. For example, when a polyester resin having a high crystallization speed is manufactured and a resin having a low crystallization speed is required, the resin can be easily removed by removing the plastic molded product and stopping the contact treatment between the polyester and the plastic molded product. Moreover, it can implement simply compared with the case where a plastic coating is applied to part or all of the piping of a process, or the internal surface of a reaction tank, and contact processing is performed. Also, replacement of the molded product when the plastic molded product is worn can be carried out very easily without the need to open the reactor or piping and stop production. These contribute to the efficiency and stabilization of polyester resin production.

  The polyester resin obtained by the present invention is a crystallization temperature at the time of temperature rise (hereinafter abbreviated as “Tc”) when a molded product obtained by injection molding at a molding temperature of 280 ° C. is measured with a differential scanning calorimeter. .) Is preferably in the range of 140 to 146 ° C. When Tc is less than the above range, when the body portion of the preform obtained by molding is heated for blow molding, whitening due to crystallization is likely to occur, and the preform for imparting sufficient heat resistance It cannot be heated to a temperature, resulting in insufficient heat resistance, and the shoulder and trunk may be whitened to impair transparency. On the other hand, when Tc exceeds the above range, heating for a long time is required to heat and crystallize the plug part to the target crystallinity, resulting in reduced productivity and large crystallization equipment for the plug part. You will not get. By satisfying the Tc condition, the crystallinity and transparency of the molded product and the heat resistance imparted to the bottle container can be made more preferable. Within the range of Tc, in the contact treatment with the above-mentioned plastic molded product, it can be achieved by appropriately adjusting the type of plastic molded product used and the contact time depending on the type of polyester.

  The polyester resin obtained by the production method of the present invention is suitable for forming bottle containers and other hollow containers, and can be formed into a bottle container or the like by employing a commonly used melt molding method. More specifically, for example, a parison is once molded by injection molding or extrusion molding, and the stretched blow molding method such as the hot parison method or the cold parison method is applied as it is or after processing the plug portion and the bottom portion and reheating. To do. In this case, the molding temperature (specifically, the temperature of each part of the cylinder of the molding machine and the nozzle) is usually 260 to 300 ° C, and the stretching temperature is usually 70 to 120 ° C. The draw ratio is usually 1.5 to 3.5 times in the longitudinal direction and 2 to 5 times in the circumferential direction.

  The obtained bottle container can be used as it is, but in the case of filling liquids that require hot filling, such as fruit juice drinks and oolong tea, generally heat-fixed in a heated blow mold to give further heat resistance Used. The heat setting is usually performed at a mold temperature of 100 to 200 ° C. for several seconds to several minutes under tension by compressed air or the like. Alternatively, a bottle container larger than the final shape is formed, the body is crystallized by shrinking by heating, and then blow molded in a final shape mold to obtain a product bottle container.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. In the examples and comparative examples, “parts” represents parts by weight. In this example and comparative example, the method for measuring the crystallization temperature of the polyester resin was as follows.

(A) Crystallization temperature of polyester resin A sample cut from a portion corresponding to the top of the stopper portion of the preform bottle container was measured from room temperature to 285 ° C. with a differential scanning calorimeter (“DSC220C” manufactured by Seiko Denshi). The temperature was raised at a rate of 20 ° C./min until the temperature of the top of the crystallization peak observed during the crystallization (crystallization temperature at the time of temperature rise, Tc) was measured.

[Example 1]
A slurry composed of 13.0 parts of terephthalic acid and 5.82 parts of ethylene glycol is supplied to a polycondensation tank and subjected to an esterification reaction at 250 ° C. under normal pressure, and bis (β-hydroxyethyl) having an esterification reaction rate of 95%. ) Terephthalate and its low polymer were prepared. Thereafter, 0.012 part of orthophosphoric acid and 0.012 part of germanium dioxide were added, and melt polymerization was performed at 280 ° C. under a reduced pressure of 0.133 kPa (1 mmHg). The polyester produced after the completion of the melt polymerization is drawn out in the form of a strand from the discharge port provided directly connected to the cooling water tank at the bottom of the melt polymerization tank, cooled in water, then slid on the polytetrafluoroethylene roll and then into a chip shape. Into a polymer chip. Subsequently, the obtained polymer chip was transferred to a stirring crystallizer (type of Bepex), and the surface of the polymer chip was heated and crystallized at 150 ° C., and then dried at 140 ° C. for 3 hours under a nitrogen flow. Subsequently, it was transferred to a stationary solid phase polymerization tower and subjected to solid phase polymerization at 210 ° C. for 20 hours under a nitrogen flow to produce a chip-like polyethylene terephthalate resin. The obtained chip was dried at 130 ° C. for 10 hours with a vacuum dryer, and then with an injection molding machine (“FE-80S” manufactured by Nissei Plastic Industry Co., Ltd.), the cylinder temperature was 275 ° C., the screw rotation speed was 120 rpm, and the primary. A cylindrical preform having an outer diameter of about 30 mm, an inner diameter of about 20 mm, a length of 165 mm, and a weight of about 60 g was injection molded at a pressure time of 1.0 second and a mold temperature of 20 ° C. The resulting preform was measured for crystallization temperature (Tc) and the results are shown in Table 1.

  In addition, when producing a polyethylene terephthalate resin that does not require modification of the crystallization speed, it is stably produced only by a simple operation of replacing a roll made of polytetrafluoroethylene with a roll made of stainless steel (for example, SUS304). I was able to.

[Comparative Example 1]
The polyester obtained after the completion of the melt polymerization is taken out in the form of a strand from the discharge port provided directly connected to the cooling water tank at the bottom of the melt polymerization tank and cooled with water, and then the strand slides on a stainless steel (SUS304) roll. A preform was injection-molded in the same manner as in Example 1 except that the chip was cut. The resulting preform was measured for crystallization temperature at elevated temperature, and the results are shown in Table 1.

  According to the method for producing a polyester resin of the present invention, in a heat-resistant container that maintains heat resistance and flavor properties required for a beverage bottle container and requires a crystallization treatment of a bottle plug part, It is possible to efficiently and stably produce a polyester resin having a high crystallization rate when heating the. In particular, in the same equipment process, it is possible to switch brands very easily when producing polyester resins having different crystallization speeds. As a result, it is possible to stabilize production and improve production efficiency, and its industrial significance is great.

Claims (2)

  A method for producing a polyester resin, in which a polyester obtained from a terephthalic acid component and / or a naphthalenedicarboxylic acid component and an ethylene glycol component is brought into contact with a plastic molded article after completion of the polymerization reaction.   2. The production method according to claim 1, wherein the plastic molded product is a plastic molded product selected from the group consisting of polytetrafluoroethylene, polytrifluoroethylene, polyvinylidene fluoride, polyamide, polyolefin, and polycarbonate.