JP2009185193A - Polyester composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester composition being excellent in heat resistance and having less content of ethylene terephthalate cyclic trimer using a titanium catalyst. <P>SOLUTION: In the polyester composition, the polyester includes 90 mol% or more of an ethylene terephthalate unit, a polymerization catalyst metal compound is a titanium compound, and a polymerization cocatalyst is a specific phosphorous compound. The content of the ethylene terephthalate cyclic trimer is 0.4 wt.% or less, the concentration of a terminal carboxyl group is from 25 eq/T to 50 eq/T, and intrinsic viscosity is 0.50 dl/g to less than 0.70 dl/g. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyester composition. Specifically, the present invention relates to a polyester composition having excellent transparency and a low ethylene terephthalate cyclic trimer content. Films produced with this polyester composition are excellent in transparency and smoothness, and can be used as raw materials for films for various industrial materials such as optical, packaging, mold release, and steel sheet laminating. Suitable as a raw material.

  The polyester composition is obtained by polycondensation of a dicarboxylic acid component and a diol component, and is a linear polymer produced from terephthalic acid or an ester-forming derivative thereof and ethylene glycol, and is excellent in versatility and practicality. And is suitably used as a material for films, sheets, fibers and the like.

  However, precipitation of cyclic compounds is a problem in polyester molding processes and the like. For example, in the case of a base film for magnetic recording materials, the cyclic compound forms coarse protrusions by precipitation, thereby inhibiting magnetic recording. In the case of an optical base film, the cyclic compound is precipitated by heating in the processing step. If it is a film for laminating steel sheets, it will cause cloudiness in the appearance after being laminated to the steel sheet.

  Various reports have been made on these cyclic compounds. For example, for polyethylene terephthalate, the main component of the cyclic compound is ethylene terephthalate cyclic trimer (hereinafter sometimes referred to as cyclic trimer). For example, Non-Patent Documents 1 and 2 report that a polycondensation reaction of polyethylene terephthalate is generated by an equilibrium reaction.

  Further, in the production of these polyethylene terephthalates, antimony compounds are mainly used as polycondensation catalysts. However, a polyester composition polymerized using an antimony compound as a polycondensation catalyst is a rate at which the cyclic trimer increases during melt molding even when using a polyester with a reduced content of the cyclic trimer by solid phase polymerization or the like. , The amount of cyclic trimer contained in the molded product tends to increase. Therefore, it is desired that antimony is not used at all or even if it is used, the amount is extremely low, or other metals are used.

  A polyester composition polymerized by using a germanium compound instead of an antimony catalyst is also known. However, although the rate of increase of the cyclic trimer at the time of melt molding is slightly slower than that of the antimony compound, the germanium compound is very expensive because it has a small reserve, and a catalyst that can be used as an alternative is desired. It was. Therefore, various polyester compositions polymerized using an inexpensive titanium compound have been proposed. Titanium catalysts are more active than antimony catalysts and germanium catalysts, and can be used in small quantities. Furthermore, the rate of increase of cyclic trimers during melt molding is slower than antimony catalysts and germanium catalysts. The composition is an industrially valuable consideration.

  In order to solve the above problems, a method for solid-phase polymerization of a polyester chip polymerized with a specified amount and a specified type of polymerization catalyst (Patent Document 1), specific viscosity and terminal carboxyl group concentration are set to specific values (Patent Document 2). Methods are being studied. However, in these methods, since the amount of the cyclic trimer in the obtained polyester fluctuates, it is very difficult to industrially obtain a certain quality polyester.

  In addition, the technology for reducing the number of cyclic compounds by such a solid-state polymerization method is also unsuitable as a raw material for producing molded articles with a low content of cyclic compounds because the polycondensation reaction of the polyester proceeds at the same time and the degree of polymerization increases. Met.

  That is, when the degree of polymerization of the polyester increases, the viscosity of the polymer at the time of molding increases during molding, which increases the load during extrusion, and the polymer temperature rises due to shearing heat generation, causing problems such as thermal decomposition. Will occur.

  Then, the heat processing which reduces a cyclic compound by heating in inert gas atmosphere are implemented. However, a polyester composition polymerized using a titanium catalyst requires a long-time heat treatment because the cyclic trimer reduction rate is remarkably slow even when heat-treated.

  As a result of intensive studies, the present inventors have clarified that polyesters polymerized with a titanium catalyst do not sufficiently reduce the cyclic trimer because the crystallization rate is not sufficient. That is, the crystallization of polyester starts around the crystal nucleus, but the titanium catalyst does not produce a metal metal like other polymerization catalysts and does not have a crystal nucleus, so that the crystallization rate is not sufficient.

  As a result of further studies, the addition of a crystal nucleating agent significantly increases the rate of reduction of the cyclic trimer during the heat treatment, and can reduce the cyclic trimer content of the polyester to 0.4 wt% or less. I found it.

Moreover, when a titanium compound is used as a polymerization catalyst, side reactions are also promoted due to its high activity, resulting in problems such as poor thermal stability and yellowing of the polymer. The fact that the polymer is yellowish is an unfavorable characteristic when, for example, polyester is used as a fiber, particularly when used as a fiber for clothing or when used for an optical film. In order to solve such a problem, studies have been widely made to improve the heat resistance and color tone of a polymer by adding a phosphorus compound together with a titanium compound. This method suppresses the activity of titanium that is too high by the phosphorus compound, and improves the heat resistance and color tone of the polymer. For example, in (Patent Document 3), in a polyester using a titanium compound as a catalyst, phosphoric acid or phosphorous acid is added as a phosphorus compound, and in (Patent Document 4), phosphate or phosphorous acid is used as a phosphorus compound. In the method of adding a salt and (Patent Document 5), a method of adding a phosphinic acid compound, a phosphine oxide compound, a phosphonous acid compound, a phosphinic acid compound, and a phosphine compound as a phosphoric acid compound is clearly shown. ing. However, if these methods are used, a certain factory can be seen in the heat resistance of the polymer, but if a phosphorus compound is added in a certain amount or more, the polymerization activity of the titanium compound is too suppressed, and the target degree of polymerization is reached. It has not been reached, or the polymerization reaction time has been remarkably increased, resulting in a problem that the color tone of the polymer is deteriorated. On the other hand, (Patent Document 6) discloses a method for defining the molar ratio (Ti / P) of the titanium compound and the phosphorus compound within a certain range. According to this method, although the deactivation of the catalyst of the titanium compound can be prevented, heat resistance and color tone exceeding a certain level cannot be obtained. As described above, it has been necessary to solve the contradictory problem of suppressing side reactions without impairing the polymerization reaction activity of the titanium compound. Therefore, as a result of intensive studies on improving the above problems in the present invention, the inventors have obtained the knowledge that the object of the present invention can be achieved by adding a specific phosphorus compound in the step of obtaining a polyester using a titanium compound as a polymerization catalyst. .
P.J.Flory "Polymer Chemistry" (Oka Koten, Kanamaru Kyodo, Maruzen Publishing Co., Ltd.) P90-97 Yuki Kazuo Saturated Polyester Resin Handbook (Nikkan Kogyo Shimbun) P167-178 JP 2001-048966 A JP 2006-096840 A JP-A-6-100680 JP 2000-143789 A JP 2004-292657 A Japanese Patent Laid-Open No. 2000-256442

  An object of the present invention is to solve the above-described conventional problems, to provide a polyester composition that uses a titanium catalyst, is excellent in transparency, and has a low ethylene terephthalate cyclic trimer content.

  An object of the present invention described above is a polyester comprising 90 mol% or more of ethylene terephthalate units, the polymerization catalyst metal compound is a titanium compound, the polymerization promoter is a phosphorus compound represented by the formula 1 described later, and ethylene terephthalate The cyclic trimer content is 0.4 wt% or less, the terminal carboxyl group concentration is more than 25 eq / T, 50 eq / T or less, and the intrinsic viscosity is 0.50 dl / g or more and less than 0.70 dl / g. This is achieved by a polyester composition characterized by being.

  According to the present invention, it is possible to provide a polyester composition that uses a titanium catalyst, is excellent in transparency, and has a low ethylene terephthalate cyclic trimer content. The polyester composition of the present invention can prevent defects due to precipitation of a cyclic trimer during use of a molded body, and can be effectively used for fibers, films, bottles and the like. In particular, it is effective as an optical base material application such as an optical film, a food container, a steel sheet bonding, a packaging application, or a release film. Among these, it is suitable as an optical film. By using the polyester composition of the present invention, it becomes possible to prevent contamination of the oil agent during spinning by the cyclic trimer, contamination of casting / drawing equipment during film formation, and the like.

  The polyester composition of the present invention is preferably polyethylene terephthalate, and polyethylene terephthalate may be copolymerized, but 90 mol% or more of the polyester structural units must be ethylene terephthalate units. When the ethylene terephthalate component is less than 90 mol%, the crystallinity of the polyester is deteriorated, and it may be difficult to satisfy the crystallinity in the method for producing a polyester composition of the present invention.

  Examples of copolymer components of these polyesters include dicarboxylic acid components, glycol components, and polyfunctional components. Examples of dicarboxylic acid components include terephthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, phthalic acid, and isophthalic acid. , Aromatic dicarboxylic acid components such as sodium sulfoisophthalate and alkyl esters thereof, aliphatic dicarboxylic acid components such as adipic acid, sebacic acid, and alkyl esters thereof, fats such as 1,4 cyclohexane dicarboxylic acid and alkyl esters thereof Mention may be made of cyclic dicarboxylic acid components. Examples of the glycol component include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4 cyclohexanedimethanol, neopentyl glycol, spiro glycol, ethylene oxide adduct of bisphenol A, isosorbate, and the like. Examples of the polyfunctional component include polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid, and polyfunctional alcohols such as trimethylolpropane and pentaerythritol. Furthermore, hydroxycarboxylic acids such as p-hydroxybenzoic acid may be used as a copolymerization component.

  Furthermore, the above polyester contains at least one of an alkali metal salt derivative of a sulfonic acid that is non-reactive with the polyester, a polyalkylene glycol substantially insoluble in the polyester, and the like so as not to exceed 5% by weight. Or it may be copolymerized.

  In the method for producing the polyester of the present invention, it is essential to add the phosphorus compound represented by the formula 1 as a phosphorus compound at an arbitrary time.

(In the above formula 1, X represents a hydrocarbon group having 1 to 10 carbon atoms or sulfur. The hydrocarbon group may contain one or more alicyclic structures, aromatic ring structures and double bonds, or substituted. R _{1 to} R ₄ each independently represents a hydrocarbon group having 1 to 30 carbon atoms including a hydroxyl group and an alkoxy group, wherein the hydrocarbon group is an alicyclic structure or an aliphatic group. R _{5 to} R ₈ each independently represents a hydrocarbon group having 1 to 10 carbon atoms including a hydroxyl group and an alkoxy group, and may contain at least one group branched structure, aromatic ring structure and double bond. And the hydrocarbon group may contain one or more of an alicyclic structure, an aliphatic branched structure, an aromatic ring structure and a double bond, wherein a + b and c + d are integers of 0 to 4.)
In the method of obtaining a polyester by polycondensation in the presence of a titanium-based polycondensation catalyst, when the phosphorus compound represented by Formula 1 is added, surprisingly the color tone and heat resistance of the resulting polymer are dramatically improved. The Coloring of polyester and deterioration of heat resistance are caused by a side reaction of polyester as clearly shown in a saturated polyester resin handbook (Nikkan Kogyo Shimbun, first edition, P.178-198). In the side reaction of this polyester, carbonyl oxygen is activated by a metal catalyst, and β hydrogen is extracted, thereby generating a vinyl end group component and an aldehyde component. By forming a polyene by this vinyl end group, the polymer is colored yellow, and since an aldehyde component is generated, the main chain ester bond is cleaved, so that the polymer has poor heat resistance. In particular, when a titanium compound is used as a polymerization catalyst, the side reaction due to heat is very strongly activated, so that many vinyl end group components and aldehyde components are generated, resulting in a yellow colored polymer having poor heat resistance. The conventional phosphorus compound has adjusted the activity of the titanium catalyst by allowing the phosphorus compound to appropriately interact with the titanium compound. However, with conventional phosphorus compounds, it is inevitable that the polymerization activity is reduced as well as the side reaction activity of the titanium compound. However, in the phosphorus compound represented by Formula 1 of the present invention, it is possible to keep only the side reaction activity extremely small while sufficiently maintaining the polymerization activity of the titanium compound. Although this effect is not completely clarified at present, a phosphorus compound having two or more phosphorus atoms in one molecule across a bisphenol-type skeleton, such as the phosphorus compound of formula 1, has a mutual effect on the titanium compound. As a result of the action, it is estimated that a titanium-phosphorus compound is formed in the reaction system that does not affect the catalytic activity for the polymerization reaction but significantly reduces only the catalytic activity for thermal decomposition, which is a side reaction. ing. This is essentially different from the effect of the conventional phosphorus compound on the titanium compound, or at least cannot be achieved sufficiently with the conventional phosphorus compound.

  Especially, it is preferable from the surface of a color tone or heat resistance that it is a phosphorus compound represented by Formula 2-Formula 4.

(In the above formulas 2 to 4, R _{1 to} R ₄ , R ₁₁ , R ₁₂ , R ₁₅ and R ₁₆ each independently represents a hydrocarbon group having 1 to 30 carbon atoms including a hydroxyl group and an alkoxy group. The hydrocarbon group may contain one or more of an alicyclic structure, an aliphatic branched structure, an aromatic ring structure, and a double bond R _{5 to} R ₈ , R ₁₃ , R ₁₄ , R ₁₇ , R ₁₈ each independently represents a hydrocarbon group having 1 to 10 carbon atoms including a hydroxyl group and an alkoxy group, and the hydrocarbon group has 1 alicyclic structure, aliphatic branched structure, aromatic ring structure and double bond. A + b, c + d, e + f, and g + h are each an integer of 0 to 4. R ₉ and R ₁₀ each represents hydrogen or a hydrocarbon group having 1 to 10 carbon atoms. Is alicyclic structure, aliphatic branched structure, aromatic ring structure and double bond One or more of them may be included.)
In particular, R _{1 to} R ₄ , R ₁₁ , R ₁₂ , R ₁₅ and R ₁₆ are each a hydrocarbon group having 5 to 20 carbon atoms, R _{5 to} R ₈ , R ₁₃ , R ₁₄ , R ₁₇ and R ₁₈ . It is preferable that the hydrocarbon group having 1 to 5 carbon atoms and R ₉ and R ₁₀ are each hydrogen or a hydrocarbon group having 1 to 5 carbon atoms because the color tone and heat resistance are good.

Examples of the phosphorus compound represented by the above formula 2 include 4,4′-isopropylidene-diphenol alkyl (C12-C15) phosphine as compounds of a + b = 0, c + d = 0, R ₉ , R ₁₀ = methyl group. This compound is available as ADK STAB 1500 (Asahi Denka) or JA-805 (Johoku Chemical). In addition, as a compound of a, c = 1 (R ₅ , R ₇ = methyl group), b, d = 1 (R ₆ , R ₈ = tert-butyl group), R ₉ = hydrogen, R ₁₀ = propyl group, 4 , 4'-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, which is available as ADK STAB 260 (Asahi Denka).

Examples of the phosphorus compound represented by Formula 3 include a, c, e = 1 (R ₅ , R ₇ , R ₁₃ = methyl group), b, d, f = 1 (R ₆ , R _8). , R ₁₄ = tert-butyl group) R ₉ = hydrogen, R ₁₀ = 1,1,3-tris (2-methyl-4-di-tridecyl phosphite-5-tert-butylphenyl) as a compound of isopropyl group Butane is available as ADK STAB 522A (Asahi Denka). These compounds may be used alone or in combination.

  When a phosphorus compound is added to the polyester composition of the present invention, the phosphorus compound may be added alone, or may be added in a state dissolved or dispersed in a diol component such as ethylene glycol.

  The polyester production method of the present invention is preferably added to the polymer from which the titanium compound is obtained so as to be 1 to 50 ppm in terms of titanium atoms excluding the titanium oxide particles. When it is 1 to 30 ppm, the thermal stability and color tone of the polymer become better, and it is more preferably 2 to 10 ppm. Moreover, it is preferable to add the manufacturing method of polyester of this invention so that a phosphorus compound may be 1-500 ppm in conversion of a phosphorus atom with respect to polyester with a titanium compound. In addition, the amount of phosphorus added is preferably 1 to 200 ppm, more preferably 5 to 75 ppm, from the viewpoint of thermal stability and color tone of polyester during yarn production and film formation.

  As a titanium catalyst used as a polymerization catalyst for the polyester of the present invention, a titanium chelate compound or a tetraalkoxytitanium compound is preferable. For example, titanium chelates such as titanium acetylacetonate, titanium tetraacetylacetonate, titanium octylene glycolate, titanium lactate, titanium ethyl acetoacetate, titanium citrate, titanium oxalate, titanium lactate, titanium peroxocitrate ammonium ammonium and tetraisopropyl Alkyl titanates such as titanate, tetrabutyl titanate, tetra (2-ethylhexyl) titanate, and tetramethyl titanate can be mentioned. Among them, titanium chelate and tetrabutyl titanate are preferably used.

  In the polyester of the present invention, a magnesium compound can be added at any time as a promoter. This is added in order to control the thermal resistivity, the cyclic trimer content, the intrinsic viscosity, the color coordinate b value, the volume resistivity, etc., particularly the volume resistivity in a preferable range. Examples of the compound include oxides, hydroxides, alkoxides, acetates, carbonates, oxalates, and halides such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. . Of these, magnesium acetate is preferred. These can be used alone or in combination.

  The addition amount of magnesium is preferably 0.1 to 100 ppm in terms of magnesium metal amount with respect to the obtained polyester resin. More preferably, it is 10-80 ppm, Most preferably, it is 20-70 ppm. In the case of 0.1 ppm or less, the value of volume resistivity may not be sufficiently reduced, and in the case of more than 100 ppm, it tends to form a foreign matter defect of the film or incur a disadvantage in thermal stability. is there.

  The crystal nucleating agent may be inorganic or organic. Specifically, for example, clays such as talc and clay; metal oxides such as zinc oxide, magnesium oxide, alumina, and iron oxide; carbonates (eg, magnesium carbonate), silicates, sulfates (eg, barium sulfate) Etc.), inorganic salts such as phosphates; metal salts of monocarboxylic acids (eg lithium salts, sodium salts, magnesium salts, calcium salts, barium salts etc.), metal salts of benzoic acids (eg sodium salts, potassium salts, calcium) Organic acid salts such as metal salts of organic phosphorus compounds (eg, magnesium salts and zinc salts); polymer powders such as ionomers, alkali metal salts of polyester oligomers, wholly aromatic polyesters; carbon black, graphite, An inorganic simple substance powder such as aluminum can be mentioned. These crystal nucleating agents can be used alone or in combination of two or more. Of these crystal nucleating agents, sodium acetate is preferred. The one having an average particle diameter of 0.1 to 100 μm is most preferably used.

  In order to obtain a polyester composition containing 0.1 to 1000 ppm of crystal nuclei in the present invention, it is preferable to add 0.05 to 800 ppm, more preferably 50 to 600 ppm, of a crystal nucleating agent with respect to PET. When the addition amount is 0.05 ppm or less, the amount of crystal nuclei generated in the polymer is not sufficient, the crystallization rate is slow during the heat treatment, and the rate of reduction of the cyclic trimer is reduced. Moreover, when 800 ppm or more is added, the amount of crystal nuclei generated in the polymer is too large, which is not preferable because it becomes a foreign matter. Moreover, it is preferable that the addition amount of a crystallization accelerator is 1-1000 ppm with respect to PET.

  A crystallization accelerator can also be added. As the crystallization accelerator, a low molecular compound or a high molecular compound that acts as a plasticizer for PET can be used, and those having a melting point of 80 ° C. or less can be preferably used. Examples of the low molecular weight compound include ketones such as benzophenone; halogenated hydrocarbons such as tetrachloroethane; esters such as neopentyl glycol dibenzoate, triphenyl phosphate and phthalate; amides such as N-substituted aromatic amides. There can be mentioned. Examples of the polymer compound include caprolactone and other various aliphatic polyesters; end-capped aliphatic polyesters; polyglycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; end-capped polyglycols; alicyclic carboxylic acid Mention may be made of polyolefins such as modified polyolefins; polyamides such as nylon 6. These crystallization accelerators can be used alone or in combination of two or more.

  The amount of the crystallization accelerator added varies depending on the type of PET used. However, if the amount is too small, the degree of crystallization tends to be small. On the other hand, if the amount is too large, the degree of crystallization increases. The physical properties are likely to be impaired, and the mechanical strength of the obtained molded product tends to decrease.

  A metal salt soluble in ethylene glycol such as sodium acetate can be obtained by heating ethylene glycol to 50 to 100 ° C., stirring it for 30 minutes or more, and then adding it to the reaction system to obtain a crystal nucleus having an excellent particle size. When it is 50 ° C. or lower or 100 ° C. or higher, crystal nuclei are not formed well. The ethylene glycol solution can be added before or during melt polycondensation.

  The polyester composition before the heat treatment has a terminal carboxyl group concentration of more than 25 eq / T and 50 eq / T or less, more preferably more than 25 eq / T, 40 eq / T or less, most preferably 28 to 40 eq / T. . If it is 25 eq / T or less, the terminal carboxyl group concentration of the polyester after the heat treatment is small, which causes tearing during film formation. Moreover, when it is 50 eq / T or more, the decreasing rate of the cyclic trimer at the time of heat processing becomes slow, and is not preferable.

  The polyester composition before the heat treatment has an intrinsic viscosity in the range of 0.50 dl / g or more and less than 0.70 dl / g. If it is less than 0.50 dl / g, the cyclic trimer tends to decrease, but the obtained polyester molded product has insufficient mechanical properties. When the intrinsic viscosity is 0.70 dl / g or more, the rate of decrease of the cyclic trimer is slow, and a long-time heat treatment is required, which is economically disadvantageous. A preferable intrinsic viscosity is in the range of 0.55 dl / g or more and less than 0.70 dl / g, and more preferably in the range of 0.60 to 0.68 dl / g. A polyester composition having such an intrinsic viscosity can be obtained by controlling the polymerization stirring torque in ordinary melt polymerization.

  A method for obtaining the above-described polyester composition will be described below.

  In the case of polyethylene terephthalate, for example, it can be produced by any of the following processes. (1) A process in which terephthalic acid and ethylene glycol are used as raw materials, a low polymer is obtained by direct esterification reaction, and a high molecular weight polymer is obtained by subsequent polycondensation reaction, and (2) dimethyl terephthalate and ethylene glycol are used as raw materials. In this process, a low polymer is obtained by a transesterification reaction, and a high molecular weight polymer is obtained by a subsequent polycondensation reaction. In the present invention, either method (1) or (2) can be adopted. In either method (1) or (2), the crystal nucleating agent and the crystallization accelerator are used before and / or during the esterification reaction or transesterification reaction and / or during and / or during the polycondensation reaction. Can be added. Furthermore, an antioxidant, an antiblocking agent, etc. can be added before reaction during reaction as needed.

  The intrinsic viscosity of the polyester composition can determine the end point of polymerization by the stirring torque of the polymer. When the stirring torque is high, the polymer has a high melt viscosity and a high intrinsic viscosity. What is necessary is just to set the end point determination stirring torque of a superposition | polymerization apparatus so that it may become the target intrinsic viscosity.

  The obtained polyester composition after completion of the polymerization may be discharged in the form of a strand from the lower part of the polymerization apparatus and cut with a cutter while cooling with water.

  The obtained polyester composition is preferably dried before heat treatment. Drying may be performed by heating the chip to 120 ° C. to 180 ° C. under reduced pressure or flowing hot air for 2 hours or more. By such a drying step, the crystallinity of the polyester composition can be increased to 30% or more.

  A heat treatment method for obtaining a polyester composition excellent in moldability and film forming property from the polyester composition of the present invention will be described below.

  A method of heating at a temperature of 190 ° C. or more and 250 ° C. or less for 0.5 hours or more and 60 hours or less in an inert gas atmosphere with a pressure of 960 hPa or more and 1160 hPa or less and a flow rate of less than 0.1 liter / hr per kg of polyester. Can be preferably employed.

  Examples of the inert gas atmosphere include rare gases such as helium, neon, and argon, nitrogen gas, and carbon dioxide gas. Of these, nitrogen gas is easily available and can be preferably used. The concentration of oxygen or water contained in these inert gases is preferably 500 ppm by volume or less. When the concentration of oxygen or water exceeds 500 ppm, the polyester is likely to be deteriorated, which causes coloring of the polyester.

  In the above treatment, the terminal carboxyl group concentration tends to increase as the pressure increases. If the pressure exceeds 1160 hPa, the terminal carboxyl group concentration increases excessively, or the film winding property deteriorates and the film is damaged. And the precipitation of the cyclic trimer tends to increase.

  On the other hand, the lower the pressure, the closer to the solid phase polymerization, the lower the terminal carboxyl group concentration tends to decrease. When the pressure is less than 960 hPa, the adhesion between the stretching roll and the film decreases in the film forming process, and it becomes slippery. The film surface tends to be damaged, and it tends to be difficult to suppress the precipitation of the cyclic trimer. 1000 hPa-1100 hPa is more preferable.

  When the flow rate of the inert gas is 0.1 liter / hr or less per kg, so-called solid-phase polymerization does not occur. Therefore, the terminal carboxyl group concentration of the polyester does not decrease, and the suppression of the cyclic trimer is preferable. .

  The temperature at which the heat treatment is performed is in the range of 190 ° C to 250 ° C. If it is less than 190 ° C, the cyclic trimer reduction rate is slow, so that the treatment time is long, which is economically disadvantageous. On the other hand, if the treatment temperature exceeds 250 ° C, the polyester composition is likely to be fused, Since heat deterioration also occurs, the coloring of the polyester becomes intense. A preferable temperature range is 200 ° C to 240 ° C, and further a range of 220 ° C to 235 ° C is preferable.

  The time for performing the heat treatment is in the range of 0.5 to 60 hours. Although the time varies depending on the amount of the polymerization catalyst remaining in the polyester composition and the treatment temperature, it is difficult to sufficiently reduce the cyclic trimer in less than 0.5 hours, and economically in the case of exceeding 60 hours. Disadvantageous. By the above production method, only the cyclic trimer can be reduced without increasing the degree of polymerization of the polyester and without coloring it. More preferably, it is 10 to 50 hours, and most preferably 15 to 35 hours.

  The polyester composition subjected to the heat treatment has a crystallinity of 30% or more. Since the cyclic trimer exists in the amorphous part of the polyester composition, the cyclic trimer is concentrated in the amorphous part as crystallization proceeds. In the polyester in such a state, the cyclic trimer supersaturated in the amorphous part is reduced to the equilibrium amount, so that the amount of the cyclic trimer as the whole polyester composition can be reduced. When the degree of crystallinity is less than 30%, a large cyclic trimer reduction effect cannot be expected because the supersaturation degree of the cyclic trimer in the amorphous part is insufficient. Note that the crystallinity can be increased even during the heat treatment, and it is preferable that the crystallinity be 70% or higher in the end. In the method of setting the crystallinity to 30% or more, it is preferable to provide a crystallization treatment step before the heat treatment. For example, the polyester composition is heated at 120 to 180 ° C. for 2 hours or more under reduced pressure or hot air flow. It is preferable. You may combine this process with a drying process.

The crystallinity of the polyester composition can be confirmed by a change in density. For example, if the density of the completely amorphous part is 1.335 g / cm ³ and the crystal density is 1.455 g / cm ³ , the crystallinity = ( The chip density can be obtained by (chip density minus 1.335) / (1.455-1.335).

  As the heat treatment apparatus used for the above heat treatment, those capable of uniformly heating the polyester are preferable. Specifically, a stationary dryer, a rotary dryer, a fluid dryer, a dryer having various stirring blades, a continuous tower dryer, or the like can be used.

  The polyester composition after the heat treatment has a terminal carboxyl group concentration of less than 25 equivalents / T and 50 equivalents / T or more. In the case of 25 equivalents / T or less, in the film forming step, the adhesion between the stretching roll and the film is reduced and the film becomes slippery, and the film surface is easily damaged. Furthermore, the adhesiveness when processing the film surface is insufficient. On the other hand, when it exceeds 50 equivalent / T, the winding property of the film is lowered, the film is likely to be damaged, and the precipitation of the cyclic trimer tends to increase. The preferred range is 25 equivalents / T or more and 40 equivalents / T or less, and the most preferred range is 28-40 equivalents / T.

  The polyester composition after the heat treatment has an intrinsic viscosity in the range of 0.50 dl / g or more and less than 0.70 dl / g. In the present invention, the intrinsic viscosity is measured at 25 ° C. using orthochlorophenol as a solvent, but if it is less than 0.50 dl / g, it becomes insufficient mechanical properties as a molded product, while 0.70 dl / g or more. In some cases, shear exotherm becomes significant during melt extrusion, which may induce thermal decomposition of the polymer. A preferred range is 0.55 dl / g or more and less than 0.70 dl / g, more preferably 0.60 to 0.68 dl / g.

  The content of the cyclic trimer in the polyester composition after the heat treatment is 0.4% by weight or less, preferably 0.3% by weight or less. When the content of the cyclic trimer in the polyester composition exceeds 0.4% by weight, the content of the cyclic trimer exceeds 0.6% by weight when molding a film or the like. Since a cyclic trimer precipitates and the precipitate becomes a surface defect, it is not preferable.

  The polyester composition after the heat treatment is cooled and taken out from the tank.

  When forming into a film, the polyester composition is put into an extruder, and a molten sheet is continuously extruded from a slit die provided in the extruder. The extruded molten sheet is brought into close contact with the mirror cooling drum by an electrostatic application method to obtain an amorphous cast sheet. In addition, when setting it as a laminated | multilayer film, a polymer can be fuse | melted using two or more extruders, and the fuse | melted polymer can be united and laminated | stacked within a laminated block or a nozzle | cap | die.

  The obtained amorphous sheet is then stretched biaxially by various stretching methods such as a roll stretching method or a tenter stretching method and wound up. The order of stretching may be either sequential or simultaneous.

  Here, stretching in the longitudinal direction refers to stretching for imparting a molecular orientation in the longitudinal direction to the film. For example, the stretching is performed by using a stretching roll depending on a difference in peripheral speed of the roll. This stretching may be performed in one stage, or may be performed in multiple stages using a plurality of roll pairs. The stretching ratio is preferably 2 to 15 times, more preferably 2.5 to 7 times.

  Stretching in the transverse direction refers to stretching for giving the film an orientation in the width direction. For example, the film is stretched in the width direction by using a tenter while gripping both ends of the film with clips. The stretching ratio is preferably 2 to 10 times.

  In the case of simultaneous biaxial stretching, the film is stretched simultaneously in the longitudinal direction and the lateral direction while being conveyed while being gripped by clips in the tenter, and this method may be used.

  The biaxially stretched film is preferably subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in the tenter in order to impart flatness and dimensional stability. After uniform cooling, the film is cooled to room temperature and wound. In the film of the present invention, the heat treatment temperature is preferably 120 to 240 ° C. from the viewpoints of flatness and dimensional stability.

  In addition, when forming an easy-adhesion layer, particle layer, etc., the coating components may be applied in-line before stretching or between longitudinal stretching and lateral stretching using a coating technique such as gravure coating or metering bar. It is also possible to perform off-line coating after stretching.

  The content of the cyclic trimer in the polyester film is preferably less than 0.60% by weight, and preferably less than 0.50% by weight. Since the cyclic trimer cannot exist in the crystal part of the polyester, if the crystallization of the polyester proceeds during the film forming process, it will be unevenly distributed in the amorphous part. The cyclic trimer unevenly distributed at a high concentration in the amorphous part is in a state of being easily precipitated on the polyester surface, and is precipitated when the amount of the cyclic trimer in the amorphous part exceeds about 1.2% by weight. For this reason, if the crystallinity of the polyester composition is c% (volume%), the content (% by weight) of the cyclic trimer is smaller than 1.2 × ((100−c) / 100). Is preferred. Therefore, if the film has a crystallinity of 50%, the content of the cyclic trimer is preferably less than 0.60% by weight, and more preferably less than 0.50% by weight.

  In the polyester film obtained from the polyester composition of the present invention, the cyclic trimer is hardly deposited on the film surface even during long-term storage, and the cyclic trimer is deposited on the film surface even when the film is processed in a heated state. Therefore, it is suitable for magnetic recording media, optical films, and packaging films. If it is desired to suppress the precipitation of the cyclic trimer only on the specific surface of the film, a laminated film can be formed. If the polyester composition is laminated, not only the laminated surface but also the cyclic trimer precipitation on the non-laminated surface can be reduced. When laminating, it is preferable that at least one surface contains the above-described polyester composition of the present invention.

  The polyester composition and the polyester film are suitable for a release film, an optical substrate film, a steel sheet laminating film, and a packaging film.

Hereinafter, the present invention will be described in more detail with reference to examples.
(1) Measurement of cyclic trimer in polyester
A 20 mg sample is dissolved in OCP (orthochlorophenol) at 150 ° C. for 30 minutes and cooled at room temperature. Thereafter, 1,4-diphenylbenzene is added as an internal standard, 2 ml of methanol is added, the polymer is separated with a high-speed centrifuge, and the liquid layer portion is measured.

Device: Shimadzu LC-10ADvp
Column: YMC-Pack ODS-2 150 mm x 4.6 mm
Column temperature: 40 ° C
Flow rate: 1.3ml / min
Injection amount: 10 μm
Detector: UV240nm
Eluent: Liquid A (pure water): Liquid B (methanol) = 25: 75
(2) Measurement of crystal nucleus content Polyester was dissolved in ortho-cresol / chloroform (weight ratio 7/3) at 90-100 ° C. and centrifuged with a centrifuge, and the precipitate was ortho-cresol / chloroform (weight ratio 7). / 3), and after drying, the weight was measured.
(3) Intrinsic viscosity
Measurement was performed at 25 ° C. using orthochlorophenol.
(4) Terminal carboxyl group concentration
The polyester was dissolved in orthocresol / chloroform (weight ratio 7/3) at 90 to 100 ° C., and the potential difference was measured with an alkali.
(5) Polymer color tone (b value)
The Hunter b value was measured using a color difference meter (SM color computer type SM-T45, manufactured by Suga Test Instruments Co., Ltd.).
(6) Precipitation amount of cyclic trimer A film of 5 cm square in length and width was heated in a hot air oven at 150 ° C. for 30 minutes, and then the surface of the film was observed with a scanning electron microscope, and the diameter per 100 μm square was 1 μm or more. The number of cyclic trimer precipitates was counted.
(Reference Example) Method for synthesizing sodium lactate sodium chelate compound
Lactic acid (226.8 g, 2.52 mol) was dissolved in warm water (371 g) in a 3 L flask equipped with a stirrer, condenser and thermometer. To this stirred solution, titanium tetraisopropoxide (285 g, 1.00 mol) was slowly added from a dropping funnel. The mixture was heated to reflux for 1 hour to produce a cloudy solution from which the isopropanol / water mixture was distilled under reduced pressure. The product was cooled to a temperature below 70 ° C. and a 32 wt / wt% aqueous solution of NaOH (380 g, 3.04 mol) was slowly added via a dropping funnel to the stirred solution. The resulting product was filtered and then mixed with ethylene glycol (504 g, 80 mol) and heated under reduced pressure to remove isopropanol / water and a slightly cloudy light yellow product (titanium content 5 .6% by weight). {Titanium lactate sodium chelate compound}
Example 1
About 100 kg of bis (hydroxyethyl) terephthalate was previously charged in a slurry of 82.5 kg of high-purity terephthalic acid (Mitsui Chemicals) and 35.4 kg of ethylene glycol (Nippon Shokubai Co., Ltd.), temperature 250 ° C., pressure 1.2 × The esterification reaction tank maintained at 10 ⁵ Pa was sequentially supplied over 4 hours, and after the completion of the supply, the esterification reaction was continued for another 1 hour, and 101.5 kg of this esterification reaction product was put into the polycondensation tank. Transferred.

  Here, 441.1 ppm (50 ppm in terms of magnesium atom) of magnesium acetate and 0.025 kg of sodium acetate were added to 1.0 kg of ethylene glycol after stirring at 80 ° C. for 1 hour. Next, a titanium lactate sodium chelate compound prepared in a reference example corresponding to 5 ppm (weight) relative to the polymer as a titanium element and 4,4′-isopropylidene-diphenolalkyl equivalent to 400 ppm (20 ppm in terms of phosphorus atom) relative to the polymer 30 minutes before adding (C12-C15) phosphite (manufactured by Asahi Denka Co., Ltd., ADK STAB 1500), the mixture was premixed in another mixing tank and stirred at room temperature for 30 minutes, and then the mixture was added.

  While stirring the low polymer at 30 rpm, the reaction system was gradually heated from 235 ° C. to 285 ° C. and the pressure was reduced to 130 Pa. The time to reach the final temperature and final pressure was both 90 minutes. When the predetermined stirring torque was reached, the reaction system was returned to normal pressure with nitrogen gas, the polycondensation reaction was stopped, discharged into cold water as a strand, and immediately cut to obtain a polyester chip.

  The obtained polyester chip had an intrinsic viscosity of 0.64, a terminal carboxyl group concentration of 34 equivalents / T, and a cyclic trimer content of 1.2% by weight.

  This polyester was dried at 170 ° C. under reduced pressure to obtain a polyester having a crystallinity of 60%. Next, 100 kg of dried chips were charged into a rotary heat treatment machine, and the internal pressure was set to 1024 hPa. Next, the temperature in the tank was raised, and after maintaining the temperature for 20 hours from 230 ° C., the chip was taken out.

  The obtained chip had an intrinsic viscosity of 0.64 dl / g, a terminal carboxyl group concentration of 34 equivalent / T, a cyclic trimer amount of 0.25 wt%, and a crystallinity of 70%. Other characteristics are shown in Table 1.

  The processed chip was put into an extruder, melted at 285 ° C., and extruded from the die into a sheet. The molten sheet was cooled by being brought into close contact with a mirror drum whose surface temperature was controlled at 25 ° C. by an electrostatic application method. Next, the obtained amorphous polyester sheet was stretched 3.3 times in the longitudinal direction by a stretching roll heated to 90 ° C., and then stretched 3.8 times in the width direction at 110 ° C. by a tenter type stretching machine. The stretched film was heat-set at 230 ° C. and wound on a roll. The film thickness was 30 μm, and the content of the cyclic trimer contained in the film was 0.42% by weight. When the amount of cyclic trimer precipitation was measured, no cyclic trimer precipitation was observed.

Examples 2-5
Polymerization was carried out in the same manner as in Example 1 except that only the amount of magnesium acetate added in Example 1 was changed, and a film was formed after solid phase polymerization.

Examples 6-9
Only the amount of sodium acetate added in Example 1 was changed, and polymerization was carried out in the same manner, followed by solid phase polymerization to form a film.

Examples 10 and 11
A film was formed in the same manner as in Example 1 except that the polymerization end determination torque was changed and the intrinsic viscosities were changed to 0.50 dl / g and 0.69 dl / g, respectively.

  Since the intrinsic viscosity of the polymer is low or high, it is difficult to make the thickness of the extruded sheet uniform, and tearing may occur during film formation.

Example 12
A film was formed in the same manner as in Example 1 except that the heat treatment conditions were changed as shown in Table 1.

Example 13
The solid state polymerization conditions were changed as shown in Table 1. Some fusion was observed on the chip. A film was formed in the same manner as in Example 1 except for the solid phase polymerization conditions.

Examples 14-17
A film was formed in the same manner as in Example 1 except that the heat treatment conditions were changed as shown in Table 1.

Comparative Example 1
A film was obtained in the same manner as in Example 1 except that sodium acetate was not added. A large amount of cyclic trimer was deposited, which was not suitable as a product.

Comparative Example 2
Polymerization was carried out in the same manner as in Example 1 except that 4,4′-isopropylidene-diphenolalkyl (C12-C15) phosphite in Example 1 was changed to phosphoric acid, and a film was formed after heat treatment. The color was yellowish and unsuitable for the product.

  The results are summarized in Table 1.

Claims (4)

90 mol% or more is a polyester comprising ethylene terephthalate units, the polymerization catalyst metal compound is a titanium compound, the polymerization promoter is a phosphorus compound represented by the following formula 1, and the content of ethylene terephthalate cyclic trimer is 0 Polyester composition characterized by having a terminal carboxyl group concentration exceeding 25 eq / T, 50 eq / T or less, and an intrinsic viscosity of 0.50 dl / g or more and less than 0.70 dl / g. .

(In the above formula 1, X represents a hydrocarbon group having 1 to 10 carbon atoms or sulfur. The hydrocarbon group may contain one or more alicyclic structures, aromatic ring structures and double bonds, or substituted. R _{1 to} R ₄ each independently represents a hydrocarbon group having 1 to 30 carbon atoms including a hydroxyl group and an alkoxy group, wherein the hydrocarbon group is an alicyclic structure or an aliphatic group. R _{5 to} R ₈ each independently represents a hydrocarbon group having 1 to 10 carbon atoms including a hydroxyl group and an alkoxy group, and may contain at least one group branched structure, aromatic ring structure and double bond. And the hydrocarbon group may contain one or more of an alicyclic structure, an aliphatic branched structure, an aromatic ring structure and a double bond, wherein a + b and c + d are integers of 0 to 4.)   The polyester composition according to claim 1, wherein the titanium compound that is a polymerization catalyst metal compound is a chelate metal compound containing an alkali metal.   3. The polyester composition according to claim 1, comprising 0.1 to 100 ppm of magnesium as a magnesium element.   The polyester composition according to any one of claims 1 to 3, comprising 0.1 to 1000 ppm of a crystal nucleating agent.