JP2005350507A - Polyester prepolymer, method for producing the same, and polyester resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester prepolymer having a good color tone and capable of being decreased in formation of foreign matter, to provide a method for producing the same, to provide a polyester, and to provide a molded article therefrom. <P>SOLUTION: This polyester prepolymer contains ethylene terephthalate as a main repeating unit and has an intrinsic viscosity of 0.45-0.70 and a water content of ≤ 500 mass ppm, wherein the polyester prepolymer contains a germanium compound in an amount of 20-70 mass ppm converted into atoms and a phosphorus compound in an amount of 10-80 mass ppm converted into atoms and has retention percentages of contents of ≥ 90% in both the germanium compound and the phosphorus compound converted into the atoms, when the polyester prepolymer is heat-treated at a degree of reduced pressure of ≤200 Pa at 200°C for 20 hr and the contents are compared with the contents before heat treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyester prepolymer (hereinafter referred to as prepolymer), a production method thereof, a polyester resin obtained by solid-phase polymerization of the prepolymer, and a molded product thereof, and more specifically, production of a polyester resin. The present invention relates to a prepolymer having a good color tone and reduced generation of foreign matter, a polyester resin obtained therefrom, and a molded product thereof.

  Polyester resins such as polyethylene terephthalate (hereinafter referred to as PET) are excellent in mechanical strength, chemical stability, transparency, etc., and are lightweight and inexpensive, so various sheets, films, containers In particular, the use of containers for carbonated drinks, fruit juice drinks, liquid seasonings, edible oils, liquors, wines, etc. has been growing significantly.

Polyester resins used for molded articles are generally solid-phase polymerized in order to improve strength and reduce oligomers and aldehydes inside the resin. In order to obtain a molded product from this solid-phase polymerized PET, for example, in the case of a hollow container, it is generally supplied to a molding machine such as an injection molding machine to form a preform, and after heating the preform, a predetermined shape is obtained. A hollow container can be obtained by inserting into a mold and stretching blow.
However, there is a problem that foreign matters are often generated in the molded product and adhere to the product. In addition to oligomers such as ethylene terephthalate cyclic trimer, this foreign matter may contain foreign matters such as catalyst elements aggregated and deteriorated in the polyester resin chip inside and outside the chip. It may occur as a foreign matter. Therefore, it is desired to produce not only oligomers but also polyester resins that hardly generate such catalyst-derived foreign matter.

  As a method for removing foreign matter, a method of treating a polyester resin or a prepolymer thereof with water has been proposed (see, for example, Patent Documents 1 and 2). However, when the prepolymer is water-treated, foreign matters derived from the catalyst can be reduced, but the water temperature is high and the contact time is long, so the catalyst is deactivated, the solid-phase polymerization rate is significantly reduced, and the productivity is lowered. There was a problem to do. In addition, when the polyester resin is treated with water, it is not possible to remove the catalyst-derived foreign matter that has adhered to the chip or submerged inside the chip in the solid phase polymerization step, and the foreign matter removing effect is low.

As a method for removing foreign substances, a method of using cooling water containing a predetermined amount of mineral when a prepolymer strand is chipped has been proposed (see, for example, Patent Documents 3 and 4). However, in this case, the moisture content in the chip becomes high, the residual heat is added, the catalyst is deactivated, the solid-phase polymerization rate may decrease, or the mineral aggregates and the transparency of the molded product decreases. There was a case.
JP 08-253563 JP 2000-319490 A JP2003-064173 JP2003-073465

  An object of the present invention is to solve such problems, and to provide a prepolymer having a good color tone and reduced generation of foreign matter, a method for producing the same, a polyester resin, and a molded product thereof.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the gist of the present invention is as follows.
(1) In a polyester prepolymer having a main repeating unit of ethylene terephthalate, an intrinsic viscosity of 0.45 to 0.70, and a water content of 500 ppm by mass or less, a germanium compound is 20 to 70 ppm by mass in terms of atoms, and a phosphorus compound is in terms of atoms When the polyester prepolymer is heat-treated at a pressure of 200 Pa or less and a temperature of 200 ° C. for 20 hours, both the germanium compound and phosphorus compound content retention ratios in terms of atoms are 90%. A polyester prepolymer characterized by being at least%.
(2) In producing the polyester prepolymer described in (1), the strand or chip after liquid phase polymerization is contacted with water in the range of 5 to 60 ° C. for 3 seconds to 10 hours, and then dehydrated and contacted with water. And a step of drying to a moisture content of 500 mass ppm or less in a drying temperature range of 10 to 100 ° C. under an air flow, an inert gas flow, or a reduced pressure within 20 hours from the start. The manufacturing method of the polyester prepolymer as described in (1).
(3) A polyester resin obtained by solid-phase polymerization of the polyester prepolymer according to (1) in the range of 180 to 240 ° C. under an inert gas flow or under reduced pressure.
(4) When the polyester resin described in (3) is heat-treated at a temperature of 200 ° C. for 20 hours at a reduced pressure of 200 Pa or less, both the content retention ratios in terms of atoms of the germanium compound and phosphorus compound are 90% or more. A polyester resin characterized by being.
(5) The polyester resin according to (3), wherein the content of the ethylene terephthalate cyclic trimer is 5000 ppm by mass or less.
(6) A polyester molded product obtained by molding the polyester resin according to (3) by injection molding or extrusion molding.

  According to the present invention, it is possible to obtain a prepolymer having good color tone and reduced generation of foreign matter, a polyester resin obtained by solid-phase polymerization of the prepolymer, and a molded product thereof.

Hereinafter, the present invention will be described in detail.
In the prepolymer of the present invention, the main repeating unit is ethylene terephthalate.
The prepolymer of the present invention may be copolymerized with the following compounds as long as the properties of the polyester resin of the present invention are not impaired. That is, such compounds include isophthalic acid, phthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, parahydroxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4 ′ -Diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, eicosanedioic acid, lactic acid, succinic acid, dimer acid, 2- (9,10-dihydro-9-oxa-10-oxide -10-phosphaphenanthrene-10-yl) methylsuccinic acid, bis- (2-hydroxyethyl) -ester, 3-methylphosphinicopropionic acid, 1,4-cyclohexanedicarboxylic acid, ε-caprolactone, δ-valerolactone , Diethylene glycol, triethylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol 1,9-nanonediol, polyethylene glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S, 1,3-bis (2-hydroxyethoxy) Examples include benzene.

  Further, the intrinsic viscosity of the prepolymer of the present invention needs to be 0.45 to 0.70, preferably 0.55 to 0.70, and more preferably 0.60 to 0.68. If the intrinsic viscosity is less than 0.45, the amount of powdered polyester resin having a high melting point increases during solid phase polymerization, and unmelted white foreign matter is generated in the molded product, which is not preferable. An intrinsic viscosity exceeding 0.70 is not preferable because the color tone of the polyester tends to deteriorate.

  The prepolymer of the present invention can contain additives such as pinning agents, pigments, antioxidants, antifoaming agents, antistatic agents and the like within a range that does not change the essential properties of the polymer. Magnesium acetate, potassium acetate, etc. as pinning agents, carbon black, titanium dioxide, etc. as pigments, hindered phenols, etc. as antioxidants, silicone oils, etc. as antifoaming agents, sodium alkyl sulfonates as antistatic agents Examples include, but are not limited to, salts.

  The water content of the prepolymer needs to be 500 ppm by mass or less, more preferably 300 ppm by mass or less, and most preferably 100 ppm by mass or less. If the water content exceeds 500 ppm by mass, the reaction rate of solid phase polymerization becomes slow, and the content of ethylene terephthalate cyclic trimer (hereinafter referred to as CT) in the polyester resin tends to increase. It is not preferable.

  Further, it is necessary that the content of the germanium compound contained in the prepolymer is in the range of 20 to 70 ppm by mass in terms of germanium atoms, preferably in the range of 30 to 70 ppm by mass, in the range of 40 to 60 ppm by mass Is most preferred. Exceeding 70 mass ppm is not preferable because foreign matter is generated in the molded product. If less than 20 mass ppm, the intrinsic viscosity is hardly increased at the time of solid-phase polymerization, and productivity is lowered and CT in the polyester resin is hardly reduced. Therefore, it is not preferable.

  Further, it is necessary that the content of the phosphorus compound contained in the prepolymer is in the range of 10 to 80 mass ppm in terms of phosphorus atom, preferably in the range of 15 to 60 mass ppm, and in the range of 20 to 50 mass ppm Is more preferable, and the range of 25 to 40 ppm by mass is most preferable. Exceeding 80 mass ppm is not preferable because foreign matter is generated in the molded product, and less than 10 mass ppm is not preferable because the color tone of the polyester resin is deteriorated.

  Furthermore, the content retention in terms of atoms of the germanium compound before and after the heat treatment when the prepolymer is heat-treated at a temperature of 200 ° C. for 20 hours at a reduced pressure of 200 Pa or less is required to be 90% or more, 95% or more Is more preferable, and 97% or more is most preferable. If the retention is less than 90%, a germanium compound is precipitated during solid-phase polymerization and foreign matters are mixed in the molded product, which is not preferable.

  In addition, when the prepolymer is heat-treated at a pressure of 200 Pa or less and a temperature of 200 ° C. for 20 hours, the content retention in terms of atoms of the phosphorus compound before and after the heat treatment needs to be 90% or more, and 95% or more More preferably, 97% or more is most preferable. A retention of less than 90% is not preferable because a phosphorus compound precipitates during solid phase polymerization and foreign matters are mixed into the molded product.

These retention rates can be calculated, for example, by the following method. That is, 100 g to 1 kg of prepolymer is put into a box-type or tumbler-type dryer, and heat treatment is performed at a temperature of 200 ° C. for 20 hours under a reduced pressure of 200 Pa or less. The sample before heat treatment and the sample after heat treatment are each measured for content of germanium or phosphorus with a fluorescent X-ray analyzer, and the retention rate is calculated by the following formula.
Retention rate (%) = 100 × M ₁ / M ₀
(However, M ₁ represents the phosphorus or germanium content of the sample after the heat treatment, and M ₀ represents the phosphorus or germanium content of the sample before the heat treatment.)
Next, a method for producing a prepolymer will be described.

  The prepolymer in the present invention is produced through a liquid phase polymerization process, a water treatment process, a dehydration process, and a drying process. The liquid phase polymerization step includes, for example, a product obtained by esterifying terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG), or dimethyl terephthalate (hereinafter referred to as EG). A method of polycondensation reaction of a product obtained by transesterification of DMT) and EG is preferably used.

The polycondensation reaction is carried out in the presence of a catalyst, usually under a reduced pressure of about 1 to 1,300 Pa, at a temperature of 265 to 300 ° C., preferably at 270 to 290 ° C., until a predetermined intrinsic viscosity is reached.
As a catalyst, it is necessary to use a germanium compound, but a metal compound such as antimony, tin, titanium, zinc, aluminum, magnesium, calcium, manganese, cobalt, 5-sulfosalicylic acid, o-sulfobenzoic anhydride It can be used in combination with organic sulfonic acid compounds such as The amount of the catalyst added is preferably 1 × 10 ^{−5 to} 5 × 10 ⁻³ mol, and 5 × 10 ⁻⁵ to 1 × 10 to 1 mol of the acid component constituting the prepolymer in the case of combined use. ⁻³ mol is more preferable, and 1 × 10 ^{−4 to} 5 × 10 ⁻⁴ mol is particularly preferable. As the germanium compound, for example, a solution obtained by dissolving germanium dioxide in EG or another organic solvent, or a reaction product can be used.

Moreover, it is necessary to add a phosphorus compound as a heat stabilizer. The amount of the phosphorus compound added is preferably 7 × 10 ^{−5 to} 5 × 10 ⁻⁴ mol, more preferably 1 × 10 ⁻⁴ to 4 × 10 ⁻⁴ mol, with respect to 1 mol of the acid component constituting the prepolymer. 1.3 × 10 ^{−4 to} 3 × 10 ⁻⁴ mol is particularly preferable. As the type of phosphorus compound, phosphoric acid, triethyl phosphate, trimethyl phosphate and the like are preferably used.

  The molten polymer that has been reacted to a predetermined intrinsic viscosity by the above method is discharged in a strand shape, and then cooled and cut into a chip shape.

Next, a water treatment process is demonstrated.
The strand or chip discharged as described above is brought into contact with water having a temperature in the range of 5 to 60 ° C. for 3 seconds to 10 hours.

  In order to make contact with water, there is a method in which chips or strands are put into a silo type water tank or a bathtub type water tank and brought into contact with water, and either a batch system or a continuous system may be used. A shower of water can be sprayed so that the water can contact more effectively.

  The temperature of the water to be contacted needs to be in the range of 5 to 60 ° C, more preferably in the range of 15 to 50 ° C, and most preferably in the range of 25 to 45 ° C. When the water temperature is less than 5 ° C., it is not preferable because scattering of the germanium compound or phosphorus compound from the chip cannot be sufficiently suppressed during solid phase polymerization, and foreign matters are mixed into the molded product. On the other hand, when the water temperature exceeds 60 ° C., the catalytic activity of germanium is deactivated, CT cannot be sufficiently reduced by solid phase polymerization, and white powder precipitates at the time of molding, which is not preferable.

  The time for contact with water needs to be in the range of 3 seconds to 10 hours, preferably in the range of 20 seconds to 8 hours, more preferably in the range of 1 minute to 6 hours, and in the range of 10 minutes to 2 hours. A range is most preferred. A contact time of less than 3 seconds is not preferable because it is physically difficult, and a contact time of more than 10 hours is not preferable because CT does not sufficiently decrease during solid phase polymerization and white powder adheres to a molded product. The bath ratio is preferably 0.5 to 10 kg of water and more preferably 1 to 5 kg of water with respect to 1 kg of chips.

  Next, the dehydration process will be described.

  The dehydration method is not particularly limited. For example, in the case of chips, it can be dropped on a sieve to dehydrate the water. In the case of a strand, it can be dehydrated by pulling it up from the water tank. However, the strand needs to be cut into chips before or after dehydration, and when it is cut before dehydration, it is handled in the same manner as the chip dehydration method.

Next, the drying process will be described. However, the drying step referred to in the present invention is distinguished from preliminary drying performed to prevent the chips from fusing during solid phase polymerization. If the water content is sufficiently reduced in this drying step, the preliminary drying can be omitted.
As the dryer, a dryer such as a box dryer, a tumbler dryer, a fluidized bed dryer, or the like, or a method of blowing air through a silo or a pipe is used, but is not limited thereto. The drying atmosphere is either air circulation, inert gas circulation, or reduced pressure, and can be appropriately selected in consideration of the characteristics of the dryer, drying conditions, and the like. In the case of reduced pressure, the degree of reduced pressure is preferably 200 Pa or less.

  The drying temperature needs to be in the range of 10 ° C to 100 ° C, more preferably 20 ° C to 90 ° C, further preferably 30 ° C to 80 ° C, and most preferably 40 ° C to 70 ° C. If the drying temperature is 10 ° C. or lower, the catalyst cannot be sufficiently dried, and if it exceeds 100 ° C., the catalyst may be deactivated.

In the present invention, the entire process from the water treatment process to the drying process, or the dehydration process and the drying process may be performed continuously or individually. In any case, the time from contact with water until the moisture content of the chip or strand is at least 500 ppm by mass must be within 20 hours, preferably within 18 hours, preferably within 15 hours Is more preferable.
Exceeding 20 hours is not preferable because CT does not decrease sufficiently during solid-phase polymerization and white powder adheres to the molded product. As a practical drying step, the time when the drying step is completed after the start of the water treatment is within 20 hours, and the water content at the end of the drying step may be at least 500 ppm by mass or less.

  In order to produce the prepolymer of the present invention, not only the liquid phase polymerization, water treatment, dehydration, and drying steps as described above, but also after the water content is 500 ppm by mass or less, A step of high-temperature drying at a temperature exceeding the temperature, a step of crystallization, and the like may be added as appropriate.

Next, the prepolymer having been subjected to the above treatment is subjected to solid phase polymerization.
In the present invention, the temperature of the solid phase polymerization needs to be 180 to 240 ° C, preferably 190 to 240 ° C, and more preferably 195 to 235 ° C. Above 240 ° C, the polymer may melt, which is not preferable. Moreover, if it is less than 180 degreeC, since the decreasing rate of CT is remarkably slow, it is not preferable.

  In the present invention, solid phase polymerization needs to be carried out under an inert gas flow or under reduced pressure. This inert gas means a gas that does not cause deterioration of the polyester resin obtained after solid-phase polymerization, and it is generally preferable to use inexpensive nitrogen. The amount of water in the inert gas may be in a range where the intrinsic viscosity of the polyester does not decrease during solid phase polymerization, and is usually 500 ppm by mass or less. When solid-phase polymerization is performed under reduced pressure, the degree of reduced pressure is usually 0.07 MPa or less.

  The solid phase polymerization apparatus can uniformly heat prepolymers such as a rotary solid phase polymerization apparatus, a tower stationary solid phase polymerization apparatus, a fluidized bed type solid phase polymerization apparatus, and a solid phase polymerization apparatus having various stirring blades. Those are preferred.

The intrinsic viscosity of the polyester obtained by solid phase polymerization is preferably 0.7 or more, and more preferably 0.75 or more. If the intrinsic viscosity is less than 0.7, the strength properties of the molded article are inferior, which is not preferable.
Further, the CT content in the polyester is required to be 5000 mass ppm or less, more preferably 4000 mass ppm or less, and most preferably 3500 mass ppm or less. Exceeding 5000 ppm by mass is not preferable because an oligomer precipitates on a molding die and moves to a molded product.

  In addition, when the polyester resin is heat-treated at 200 ° C. for 20 hours at a reduced pressure of 200 Pa or less, the content retention in terms of atoms of the germanium compound before and after the heat treatment needs to be 90% or more, and 95% or more More preferably, 97% or more is most preferable. If the retention is less than 90%, a germanium compound is precipitated during solid-phase polymerization and foreign matters are mixed in the molded product, which is not preferable.

  Further, when the polyester resin is heat-treated at a temperature of 200 ° C. for 20 hours at a degree of vacuum of 200 Pa or less, the content retention in terms of atoms of the phosphorus compound before and after the heat treatment needs to be 90% or more, and 95% or more More preferably, 97% or more is most preferable. A retention of less than 90% is not preferable because a phosphorus compound precipitates during solid phase polymerization and foreign matters are mixed into the molded product.

These retention rates can be calculated, for example, by the following method.
That is, 100 g to 1 kg of polyester resin is put into a box-type or tumbler-type dryer, and heat treatment is performed at a temperature of 200 ° C. for 20 hours under a reduced pressure of 200 Pa or less. The sample before heat treatment and the sample after heat treatment are each measured for germanium or phosphorus content with a fluorescent X-ray analyzer, and the retention rate is calculated by the following formula.

Retention rate (%) = 100 × M ₁ / M ₀
(However, M ₁ represents the phosphorus or germanium content of the sample after heat treatment, and M ₀ represents the phosphorus or germanium content of the sample before heat treatment.)
A polyester molded product can be obtained by injection molding or extrusion molding using the polyester resin obtained as described above. Molded products include hollow containers formed by biaxial stretch blow molding after injection molding, sheet-like materials obtained by extrusion molding, stretched films formed by stretching the sheet-like materials in at least one direction, and the like. Can be mentioned.

  In producing a hollow molded body, a preform molded from the polyester resin of the present invention is stretch blow molded, and an apparatus conventionally used in blow molding of PET can be used. Specifically, for example, a preform is once formed by injection molding or extrusion molding, and the plug portion and the bottom portion are processed as they are, and then reheated, and then an injection blow method, a hot parison method or a cold parison method. A biaxial stretch blow molding method is applied. The stretching temperature is 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio may be 1.5 to 3.5 times in the longitudinal direction and 2 to 5 times in the circumferential direction.

  The obtained hollow container can be used as it is, but in the case of a liquid content requiring heat filling, such as a fruit juice beverage, generally, it is generally further in the same blow mold used for molding or separately. It is used by improving heat resistance by heat fixing in the mold provided. This heat setting method is generally 100 to 200 ° C., preferably 120 to 180 ° C., usually 2 to 2 hours, preferably 10 to For 30 minutes.

  Moreover, a polyester film can be obtained by film forming. That is, for example, a lubricant is added, the polyester resin is melt-extruded, discharged from a die, formed into a film, and then biaxially stretched and heat-set to form a biaxially stretched film.

Examples of the lubricant include silicon dioxide, kaolin, clay, calcium carbonate, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, and silicone particles, and inorganic lubricants are preferable.
In addition to the lubricant, the polyester resin may contain additives such as a stabilizer, a colorant, an antioxidant, an antifoaming agent, and an antistatic agent as necessary.

  The stretching temperature is usually 40 to 170 ° C, preferably 70 to 140 ° C. The stretching may be uniaxial stretching or biaxial stretching, but biaxial stretching is preferred from the standpoint of film strength. In the case of uniaxial stretching, the draw ratio is usually 1.1 to 10 times, and preferably 1.5 to 8 times. In the case of biaxial stretching, simultaneous biaxial stretching or sequential biaxial stretching may be used, but the stretching ratios in the machine direction and the transverse direction are usually 1.1 to 8 times, preferably 1.5 to 5 times. Further, the vertical / horizontal magnification is usually 0.5 to 2, preferably 0.7 to 1.3.

  The obtained film is preferably heat-set. The heat setting is usually performed at 120 ° C. or higher and a melting point or lower, preferably 150 ° C. or higher and 230 ° C. or lower under tension for several seconds to several minutes.

  The thickness of the polyester film is usually 10 to 30 μm.

  It is considered that the phosphorus compound and germanium compound content in the chip is decreased by the heat treatment test in the present invention because the phosphorus compound and germanium compound on the chip surface are sublimated. A similar phenomenon occurs in the solid-phase polymerization, and it is estimated that the sublimated material aggregates and forms foreign matter. Therefore, it is desirable to increase the retention rate of the phosphorus compound and the germanium compound when the prepolymer or polyester heat treatment test is performed in order to reduce the generation of foreign matter.

  As a means for increasing the retention rate, it is effective to treat the prepolymer with water. It is presumed that the water treatment can wash off the phosphorus compound and germanium compound in the vicinity of the polymer surface. However, if the temperature of the water treatment is high or the contact time is too long, the catalytic activity of the internal germanium compound that cannot be washed out is lowered, and CT is not sufficiently reduced during solid phase polymerization. Therefore, it is necessary to select mild water treatment conditions.

  In addition, the water-treated prepolymer needs to be dehydrated and dried at an early stage. If this time is extended, the catalytic activity is lowered by residual moisture, and CT is not sufficiently reduced during solid phase polymerization.

Next, the present invention will be specifically described with reference to examples. In the examples, the characteristic values of polyester were measured as follows.
(1) Intrinsic viscosity [η]
Measurement was made at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent.
(2) CT content Prepolymer or polyester resin pellets, films, or hollow containers are dissolved in hexafluoroisopropanol / chloroform (volume ratio 1/1), and acetonitrile is added to precipitate the polymer components. The filtrate was filtered through a sfilter and analyzed by high performance liquid chromatograph (Waters Alliance 2695 system). The unit is expressed in ppm by mass.
(3) Presence of mold contamination The injection molding, stretch blow molding, and heat setting molds after continuously molding 1000 1L hollow containers from a polyester resin were visually observed to check for oligomer precipitation.
(4) Existence of foreign matter
The 1 L hollow container was visually observed to check whether foreign matter was mixed.
(5) Moisture content 5 g of chips are introduced into a 180 ° C moisture vaporizer (VA-06 model manufactured by Mitsubishi Chemical Corporation), and moisture is measured with nitrogen gas using a coulometric titration moisture content analyzer (CA-06 manufactured by Mitsubishi Chemical Corporation). Type) and titrated to determine the water content.
(6) Color tone Measured using a color difference meter ND-Σ80 manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined using a Hunter Lab colorimeter. A b value of 1.0 or less was accepted.
(7) A germanium compound, phosphorus compound retention rate prepolymer or 100 g of polyester was put into a box-shaped drier, and heat-treated at a drier temperature of 200 ° C. for 20 hours under a reduced pressure of 200 Pa or less. The pre-heat treatment sample and the heat-treated sample were each measured for germanium or phosphorus content with a fluorescent X-ray analyzer (type 3270E manufactured by Rigaku Corporation), and the retention rate was calculated according to the following formula.
Retention rate (%) = 100 × M ₁ / M ₀
(However, M ₁ represents the phosphorus or germanium content of the sample after heat treatment, and M ₀ represents the phosphorus or germanium content of the sample before heat treatment.)
(8) Germanium or phosphorus content Germanium or phosphorus content was measured with a fluorescent X-ray analyzer (type 3270E manufactured by Rigaku Corporation).
Example 1
A slurry of TPA and EG (TPA / EG = 1 / 1.6, molar ratio) was continuously fed to an esterification reactor in which bis (β-hydroxyethyl) terephthalate and its low polymer existed, at a temperature of 250 ° C. The reaction was carried out for 8 hours under the condition of a pressure of 50 hPaG to continuously obtain a reaction product having an esterification reaction rate of 96%.

To 60 kg of this reaction product, 3 × 10 ⁻⁴ mol of germanium dioxide and 2.6 × 10 ⁻⁴ mol of phosphoric acid are added to 1 mol of the total acid component, and the pressure is reduced in a polymerization reactor, finally at 67 Pa and 270 ° C. Polycondensation was performed. After reaching a predetermined stirring power value, the polymer obtained by a conventional method is discharged from a mouthpiece having 58 circular small holes with a diameter of 9 mm at the bottom of a polymerization reaction tank pressurized to 200 kPa, a cold water shower, and It was rapidly cooled in a water bath and taken up at a take-up speed of 75 m / sec, and the discharged strand was cut into chips.

This chip was put into a stainless steel container containing 60 kg of water at 20 ° C., kept at a water temperature of 20 ° C. for 0.5 hr, dehydrated, and dried under reduced pressure at an internal temperature of 60 ° C. for 8 hr to obtain a prepolymer. This prepolymer has an intrinsic viscosity of 0.55, a moisture content of 210 mass ppm, a germanium (Ge) content of 49 mass ppm, a phosphorus (P) content of 42 mass ppm, and a CT content of 10000 mass ppm. The time from the start to the end of drying was 10 hours.
The prepolymer had a Ge retention of 93% and a P retention of 92%.

  This prepolymer was charged into a rotary solid phase polymerization apparatus and crystallized at a reduced pressure of 133 Pa at 130 ° C. for 4 hours, and then subjected to solid phase polymerization at 230 ° C. for 10 hours. The obtained polyester resin had an intrinsic viscosity of 0.78, a CT content of 3800 mass ppm, a Ge retention of 95%, a P retention of 94%, and a b value of 0.6.

  Using this polyester resin, preforms were made on an injection molding machine IS-60B manufactured by Toshiba Corporation, set to 280 ° C in front, middle, and rear of the cylinder, screw rotation speed 100rpm, injection time 10 seconds, mold cooling water temperature 20 ° C. Was molded.

The resulting preform was blow-molded with a stretch blow molding machine set at a preheating furnace of 90 ° C, a blow pressure of 2 MPaG and a molding cycle of 10 seconds to form a hollow container with an average body pressure of 300 µm and an internal volume of 1 L, followed by 160 ° C. Compressed and tensioned in the mold set to, and heat set for 10 seconds.
Further, 1000 hollow containers were continuously molded, but no contamination of the mold was observed in any of injection molding, stretch blow molding, and heat setting.

Further, the appearance of the bottle surface was observed, but no unmelted foreign matter was observed.
Example 2
Chips were obtained by melt polymerization in the same manner as in Example 1, and then put into a stainless steel container containing 60 kg of water at 50 ° C., held at a water temperature of 50 ° C. for 7 hours, dehydrated, and dried air at 25 ° C. was chipped. The prepolymer having the characteristic values shown in Table 1 was obtained.
This prepolymer was subjected to solid phase polymerization and injection molding in the same manner as in Example 1. Table 1 shows the characteristic values of the polyester and the bottle.
Example 3
Chips were obtained by melt polymerization in the same manner as in Example 1 except that 3.5 × 10 ⁻⁴ mol of germanium dioxide and 4.4 × 10 ⁻⁴ mol of phosphoric acid were added to 1 mol of all acid components. This chip was processed in the same manner as in Example 1 except that the conditions shown in Table 1 were changed, and a prepolymer having the characteristics shown in Table 1 was obtained.
This prepolymer was subjected to solid phase polymerization and injection molding in the same manner as in Example 1. Table 1 shows the characteristic values of the polyester and the bottle.
Example 4
Except for adding 2 × 10 ⁻⁴ mol of germanium dioxide and 1.0 × 10 ⁻⁴ mol of phosphoric acid to 1 mol of all acid components, melt polymerization was performed in the same manner as in Example 1 and the polymer was discharged, followed by cold water at 20 ° C. It cut | disconnected with the shower and the 20 degreeC water bath, was chipped, and it dehydrated with the dicer. The time during which the chip was immersed in the water bath was 10 seconds. This chip was blown into a silo with air at 25 ° C., and allowed to dry while flowing air at 25 ° C. through the silo to obtain a prepolymer. The time for starting to air and allowing it to stand and dry was 4 hours.

This prepolymer was subjected to solid phase polymerization and injection molding in the same manner as in Example 1. Table 1 shows the characteristic values of the polyester and the bottle.
Comparative Examples 1-12
As shown in Table 1, solid-state polymerization and injection molding were carried out in the same manner as in Example 1 except that the conditions were changed. Table 1 shows the characteristic values of the polyester and the bottle.

As is clear from Table 1, all of the characteristic values of the polyesters obtained in Examples 1 to 4, the foreign matter in the bottle, and the mold contamination were excellent.

  In Comparative Example 1, since the intrinsic viscosity of the prepolymer was too low, a powdery chip was generated and the melting point was increased, or a white unmelted product was observed in the bottle.

  In Comparative Example 2, since the drying temperature was too low, the moisture content of the prepolymer was too high, and the catalyst was deactivated by that effect, so CT did not decrease sufficiently by solid phase polymerization, and mold contamination was observed during bottle molding. It was.

  In Comparative Example 3, the drying temperature was too high, and the catalyst was deactivated due to the influence. Thus, solid phase polymerization did not sufficiently reduce CT, and mold contamination was observed during bottle molding.

  In Comparative Example 4, the drying time and the time from contact with water to the end of drying were too long, and the catalyst was deactivated due to the influence. Therefore, CT was not sufficiently reduced by solid phase polymerization, and the mold was formed at the time of bottle molding. Contamination was observed.

  In Comparative Example 5, since the P content was too small, the color tone of the polyester failed.

  In Comparative Example 6, since there was too much P content and the fall of P retention could not be suppressed, the brown foreign material was recognized in the bottle. When this brown foreign material was measured with an X-ray microanalyzer (type 733 manufactured by JEOL Ltd.), phosphorus element was strongly detected.

  In Comparative Example 7, since the Ge content was too high and the decrease in the Ge retention rate could not be suppressed, brown foreign matter was observed in the bottle. When this brown foreign material was measured with an X-ray microanalyzer (type 733 manufactured by JEOL Ltd.), germanium element was strongly detected.

  In Comparative Example 8, since the Ge content was too small, CT was not sufficiently reduced by solid phase polymerization, and mold contamination was observed during bottle molding.

  In Comparative Example 9, the water treatment temperature was too high, and the catalyst was deactivated due to the influence. Therefore, CT was not sufficiently reduced by solid phase polymerization, and mold contamination was observed during bottle molding.

  In Comparative Example 10, the water treatment temperature was too low, the water treatment effect was not obtained, and the decrease in both the P retention rate and the Ge retention rate could not be suppressed, and brown foreign matter was observed in the bottle. When this brown foreign material was measured with an X-ray microanalyzer (type 733 manufactured by JEOL Ltd.), both germanium and phosphorus elements were strongly detected.

  In Comparative Example 11, the water treatment time was too long, and the catalyst was deactivated due to the influence. Therefore, CT was not sufficiently reduced by solid phase polymerization, and mold contamination was observed during bottle molding.

In Comparative Example 12, the liquid color polymerization time was increased to increase the intrinsic viscosity of the prepolymer, and the color tone of the polyester deteriorated.

Claims (6)

In the polyester prepolymer having a main repeating unit of ethylene terephthalate, an intrinsic viscosity of 0.45 to 0.70, and a water content of 500 mass ppm or less, the germanium compound is 20 to 70 mass ppm in terms of atoms, and the phosphorus compound is 10 to 80 in terms of atoms. The content retention in terms of atoms of the germanium compound and phosphorus compound before and after heat treatment when the polyester prepolymer is heat-treated at a reduced pressure of 200 Pa or less and a temperature of 200 ° C. for 20 hours is 90% or more in both cases. A polyester prepolymer characterized by being. In producing the polyester prepolymer according to claim 1, the strand or chip after liquid phase polymerization is contacted with water at a temperature in the range of 5 to 60 ° C. for 3 seconds to 10 hours, then dehydrated and contacted with water. Characterized in that it includes a step of drying within a period of 20 hours from air, under an inert gas stream, or under reduced pressure until the moisture content is 500 mass ppm or less within a drying temperature range of 10 to 100 ° C. The manufacturing method of the polyester prepolymer of Claim 1. A polyester resin obtained by solid-phase polymerization of the polyester prepolymer according to claim 1 in the range of 180 to 240 ° C under an inert gas flow or under reduced pressure. When the polyester resin according to claim 3 is heat-treated at a pressure of 200 Pa or less and a temperature of 200 ° C. for 20 hours, the content retention in terms of atoms of the germanium compound and the phosphorus compound before and after the heat treatment is both 90% or more. A polyester resin. The polyester resin according to claim 3, wherein the content of the ethylene terephthalate cyclic trimer is 5000 ppm by mass or less. A polyester molded product obtained by molding the polyester resin according to claim 3 by injection molding or extrusion molding.