JP5738539B2 - Production method of polyester resin - Google Patents

Description

The present invention relates to a method for producing a polyester resin having excellent weather resistance .

  The solar cell module generally has a structure in which (sealant) / solar cell element / sealant / back sheet is laminated in this order on glass on which sunlight is incident. Conventionally, a polyester film has been used as a back sheet for this solar cell.

  In general, polyesters are produced by a condensation polymerization process of a dicarboxylic acid or an ester-forming derivative thereof and a diol component such as glycols. For example, polyethylene terephthalate (PET) is produced by condensation polymerization of terephthalic acid or a derivative thereof and ethylene glycol.

  In the commercial production process of PET, a polymerization catalyst is generally used, and an antimony (Sb) catalyst is widely used as the polymerization catalyst. However, in PET manufactured using an antimony catalyst, the antimony catalyst is reduced during melt polymerization and precipitated as metal Sb particles, and remains in the polymer. It becomes a state defect and contributes to a decrease in operability. As a polymerization catalyst that does not use an antimony catalyst, a catalyst using germanium (Ge) is known, but germanium has a problem in terms of cost because it has a small reserve and is rare.

  In view of the above circumstances, studies using a titanium compound as a polymerization catalyst have been actively conducted. Titanium compounds are relatively inexpensive, have higher catalytic activity than Sb compounds and Ge compounds, and are advantageous in that high molecular weight polymers can be obtained with a small amount of addition. Moreover, there is no generation of foreign matter such as Sb.

  In general, there are many carboxyl groups and hydroxyl groups on the surface of polyester, and hydrolysis reaction tends to occur in an environment where moisture exists, and it tends to deteriorate significantly with time. Therefore, the polyester used for the solar cell module placed in an environment that is constantly exposed to wind and rain such as outdoors is required to have resistance to hydrolysis.

  However, even if the concentration of the terminal carboxylic acid group of the polyester is lowered in order to suppress hydrolysis, the actual hydrolysis resistance is not always sufficiently obtained. For example, if the polyester has a certain degree of intrinsic viscosity (IV), the carboxylic acid is generated by heat generation (shearing heat generation) due to the application of heat and shear stress during film formation, that is, melt kneading and extrusion. As a result, the resistance to hydrolysis may not be maintained. If the IV value of the polyester is high, the resin is difficult to be extruded during melt extrusion, so that it is easily affected by shearing heat generation.

  As a technique related to the above, a polyester film containing a predetermined amount of titanium element and phosphorus element and having a terminal carboxyl group concentration of 40 equivalent / ton or less is disclosed (for example, see Patent Document 1), and is resistant to hydrolysis. It is said that environmental resistance such as weather resistance is improved.

  In addition, a biaxially oriented polyester film having a phosphorus element content in a predetermined range and a terminal carboxylic acid content of 26 equivalent / ton or less is disclosed (for example, see Patent Document 2). In this polyester film, it is described that degradation due to hydrolysis during long-term use in a high temperature and high humidity environment is prevented.

JP 2007-204538 A JP 2009-256621 A

  However, in the above-mentioned conventional polyester film, although it is presumed that the terminal carboxylic acid group is suppressed to a low level and thus exhibits a certain degree of resistance to hydrolyzability, conventionally, in order to polymerize quickly at a relatively high temperature, While the amount of carboxylic acid does not decrease so much, IV tends to increase. When IV becomes high, it becomes easy to be affected by shearing heat during melt extrusion. In the case of shearing heat generation, the resin temperature is not fixed and the amount of terminal carboxylic acid cannot be kept low, so the hydrolysis resistance with time decreases.

  The present invention has been made in view of the above, a method for producing a polyester resin capable of reducing the amount of terminal carboxylic acid while suppressing an increase in IV, and capable of producing a polyester film excellent in hydrolysis resistance, It aims at providing the polyester film excellent in hydrolysis resistance, and the solar cell backsheet and solar cell module which provided long-term durability, and makes it a subject to achieve this objective.

Specific means for achieving the above object are as follows.
<1> An esterification reaction having an intrinsic viscosity of 0.40 dL / g or more by esterifying a dicarboxylic acid component and a diol component under a catalyst containing at least one organic chelate titanium complex having an organic acid as a ligand. A reaction product generating step for generating a product and the generated esterification reaction product are heat-treated in a solid state, whereby the intrinsic viscosity is a ratio of 0.002 dL / g or more and 0.008 dL / g or less per hour. And a solid phase polymerization step of obtaining a polyester resin having an intrinsic viscosity of 0.65 to 0.90 dL / g and a terminal carboxylic acid amount of 20 equivalent / ton or less. It is a manufacturing method.

  <2> When heat-treating the esterification reaction product in a solid state, the temperature rising rate is set to 200 ° C. during the transition from the drying step of drying the produced esterification reaction product to the solid phase polymerization step. It is a manufacturing method of the polyester resin as described in said <1> which has a process made into / hour or less.

<3> the reactant generation step, a pre-Symbol pentavalent phosphoric acid ester having no aromatic ring as an organic chelate titanium complex and a magnesium compound with a substituent as a catalyst includes the step of adding in this order, further, the It is a manufacturing method of the polyester resin as described in said <1> or <2> which has a polycondensation process which carries out the polycondensation reaction of the esterification reaction product produced | generated at the reaction product production | generation process.

<4> In the reactant generation step, the value Z calculated from the following formula (i) for the organic chelate titanium complex, the magnesium compound, and the phosphate ester satisfies the following relational expression (ii): It is the manufacturing method of the polyester resin as described in said <3> to add.
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0

<5> The method for producing a polyester resin according to any one of <2> to <4>, wherein the temperature increase rate is 10 to 150 ° C./hour.
<6> The above <1> to <5, further comprising a molding step in which a polyester resin is charged into a melt extruder and melt extruded after the solid phase polymerization step to form a film having a thickness of 50 μm to 350 μm. Ru manufacturing method der polyester resin according to any one of>.

According to the present invention, it is possible to reduce the amount of terminal carboxylic acid while suppressing an increase in IV, and a method for producing a polyester resin capable of producing a polyester film excellent in hydrolysis resistance, and excellent in hydrolysis resistance. Polyester film can be provided.
Moreover, according to this invention, the solar cell backsheet and solar cell module which were provided with long-term durability can be provided.

It is a schematic sectional drawing which shows the structural example of a solar cell module.

  Hereinafter, the manufacturing method of the polyester resin of this invention, the polyester film using the same, a solar cell backsheet, and a solar cell module are demonstrated in detail.

<Method for producing polyester resin and polyester film>
The polyester resin production method of the present invention comprises a dicarboxylic acid component and a diol component (preferably an aromatic dicarboxylic acid and an aliphatic diol) under a catalyst containing at least one organic chelate titanium complex having an organic acid as a ligand. An intrinsic viscosity is obtained by heat-treating the produced esterification reaction product in a solid state with a reaction product producing step for producing an esterification reaction product having an intrinsic viscosity of 0.40 dL / g or more by esterification. Is increased at a rate of 0.002 dL / g or more and 0.008 dL / g or less per hour, and the intrinsic viscosity is 0.65 to 0.90 dL / g, the amount of terminal carboxylic acid is 20 equivalents / And a solid phase polymerization step for obtaining a polyester resin having a ton or less.
The polyester film of the present invention is produced by the method for producing a polyester resin of the present invention. In addition to the reaction product generation step and the solid phase polymerization step, the polyester resin obtained in the solid phase polymerization step is further stretched. Thus, a stretched film (uniaxial or biaxial) obtained by providing a stretching process to form a film is preferable.

In the present invention, the esterification reaction product obtained by the esterification reaction in the presence of an organic chelate titanium complex having an organic acid as a ligand as a titanium catalyst as a ligand has an intrinsic viscosity of 0.002 dL per hour. The amount of terminal carboxylic acid can be kept low without increasing the high IV by increasing the rate at a rate of not less than / g and not more than 0.008 dL / g, that is, by solid-phase polymerization at a lower speed than the conventional rate. Therefore, a polyester film showing excellent hydrolysis resistance over a long period can be produced.

-Reactant production process-
In the reaction product generation step in the present invention, the intrinsic viscosity is 0 by the esterification reaction of the dicarboxylic acid component and the diol component under a catalyst containing at least one organic chelate titanium complex having an organic acid as a ligand as the titanium compound. An esterification reaction product of 40 dL / g or more is produced.

  The reactant production step in the present invention is an esterification step in which an esterification reaction and a polycondensation reaction are provided to produce a polyester. This esterification step can be provided with (a) an esterification reaction and (b) a polycondensation reaction in which an esterification reaction product produced by the esterification reaction is polycondensed.

In this step, the esterification reaction product used in the next solid phase polymerization step is generated so that its intrinsic viscosity (IV) is 0.40 dL / g or more. If the intrinsic viscosity of the produced esterification reaction product is less than 0.40 dL / g, when the polyester resin is obtained in the subsequent solid phase polymerization step, the molecular weight of the resin becomes too low, and the powder form during solid phase polymerization A large amount of resin is generated. Since this powdery resin has a high solid-phase polymerization rate, it is unfavorable because it has a high IV and becomes a fish eye of the film. In addition, the solid phase polymerization time is long because it is economically undesirable.
In the present invention, the intrinsic viscosity of the esterification reaction product is preferably 0.45 dL / g or more, more preferably 0.48 dL / g or more, from the viewpoint of prevention of powder generation during solid phase polymerization and solid phase polymerization time. preferable. The upper limit of the intrinsic viscosity here is preferably 0.80 dL / g from the viewpoint of avoiding that the AV value tends to increase due to thermal decomposition due to shearing heat generation due to an increase in melt viscosity during melt polymerization.
Such adjustment of the IV value can be performed by adjusting the polymerization temperature, time, and vacuum degree during the liquid phase polymerization.

The intrinsic viscosity (IV: Intrinsic Viscosity) is a specific viscosity obtained by subtracting 1 from the ratio η _r (= η / η ₀ ; relative viscosity) between the solution viscosity (η) and the solvent viscosity (η ₀ ) (η _sp = η _r -1) A value obtained by dividing the value divided by the concentration into a state where the concentration is zero. IV is determined from the solution viscosity at 30 ° C. in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent.

(A) Esterification reaction In the esterification reaction at the time of polymerizing polyester, a titanium (Ti) compound, an antimony compound, a germanium compound, an aluminum compound, or the like can be used as a catalyst. Details of the catalyst will be described later. Among these, it is preferable to use a Ti compound as a catalyst. In this case, the amount of Ti compound added is preferably such that the Ti element conversion value is 1 ppm to 30 ppm, more preferably 2 ppm to 20 ppm, and even more preferably 3 ppm to 15 ppm. Is preferably performed.
When the amount of the Ti-based compound is 1 ppm or more in terms of Ti element, the polymerization rate is increased and preferable IV is obtained. If the amount of Ti compound is 30 ppm or less in terms of Ti element, the amount of terminal COOH can be adjusted to satisfy the above range, and a good color tone can be obtained.

  For the synthesis of Ti-based polyester using such a Ti compound, for example, Japanese Patent Publication No. 8-30119, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 397756, and Japanese Patent No. 396226 are disclosed. Japanese Patent No. 3997866, Japanese Patent No. 3996687, Japanese Patent No. 40000867, Japanese Patent No. 4053837, Japanese Patent No. 4127119, Japanese Patent No. 4134710, Japanese Patent No. 4159154, Japanese Patent No. 4269538, Japanese Patent No. The methods described in JP 2005-340616 A, JP 2005-239940 A, JP 2004-319444 A, JP 2007-204538 A, Japanese Patent No. 3436268, Japanese Patent No. 3780137, and the like can be applied.

  Polyesters forming the polyester film of the present invention are (A) malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, Aliphatic dicarboxylic acids such as methyl malonic acid and ethyl malonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1 , 4-Naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5 -Sodium sulfoi A dicarboxylic acid such as phthalic acid, phenylendanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, aromatic dicarboxylic acid such as 9,9′-bis (4-carboxyphenyl) fluorenic acid or an ester derivative thereof; and (B) ethylene glycol. 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, aliphatic diols such as 1,3-butanediol, cyclohexanedimethanol, spiroglycol, isosorbide Diols such as aromatic diols such as alicyclic diols such as bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxyphenyl) fluorene Esterification of compounds with known methods It can be obtained by response and / or transesterification.

It is preferable that at least one aromatic dicarboxylic acid is used as the dicarboxylic acid component. More preferably, the dicarboxylic acid component contains an aromatic dicarboxylic acid as a main component. The “main component” means that the proportion of aromatic dicarboxylic acid in the dicarboxylic acid component is 80% by mass or more. A dicarboxylic acid component other than the aromatic dicarboxylic acid may be included. Examples of such a dicarboxylic acid component include ester derivatives such as aromatic dicarboxylic acids.
Further, it is preferable that at least one aliphatic diol is used as the diol component. The aliphatic diol can contain ethylene glycol, and preferably contains ethylene glycol as a main component. The main component means that the proportion of ethylene glycol in the diol component is 80% by mass or more.

  The amount of the aliphatic diol (for example, ethylene glycol) used is in the range of 1.015 to 1.50 mol with respect to 1 mol of the aromatic dicarboxylic acid (for example, terephthalic acid) and, if necessary, its ester derivative. Is preferred. The amount used is more preferably in the range of 1.02 to 1.30 mol, and still more preferably in the range of 1.025 to 1.10 mol. When the amount used is in the range of 1.015 mol or more, the esterification reaction proceeds favorably, and in the range of 1.50 mol or less, for example, by-production of diethylene glycol due to ethylene glycol dimerization is suppressed. Many properties such as melting point, glass transition temperature, crystallinity, heat resistance, hydrolysis resistance, and weather resistance can be kept good.

  PET preferably contains 90% by mole or more of terephthalic acid and ethylene glycol, more preferably 95% by mole or more, and still more preferably 98% by mole or more.

  Conventionally known reaction catalysts can be used for the esterification reaction and / or the transesterification reaction. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Usually, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

  Among these, more preferable polyesters are polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), and still more preferable is PET. The PET is polymerized using one or more selected from a germanium (Ge) -based catalyst, an antimony (Sb) -based catalyst, an aluminum (Al) -based catalyst, and a titanium (Ti) -based catalyst. PET is preferable, and more preferable is a Ti-based catalyst in terms of good hydrolysis resistance.

  The Ti-based catalyst has high reaction activity and can lower the polymerization temperature. Therefore, in particular, it is possible to suppress the thermal decomposition of PET during the polymerization reaction and the generation of COOH, which is suitable for adjusting the amount of terminal COOH to a predetermined range in the polyester film of the present invention.

Examples of the Ti-based catalyst include oxides, hydroxides, alkoxides, carboxylates, carbonates, oxalates, organic chelate titanium complexes, and halides. The Ti-based catalyst may be used in combination of two or more titanium compounds as long as the effects of the present invention are not impaired.
Examples of Ti-based catalysts include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl Titanium alkoxide such as titanate and tetrabenzyl titanate, titanium oxide obtained by hydrolysis of titanium alkoxide, titanium-silicon or zirconium composite oxide obtained by hydrolysis of a mixture of titanium alkoxide and silicon alkoxide or zirconium alkoxide, titanium acetate , Titanium oxalate, potassium potassium oxalate, sodium oxalate, potassium titanate, sodium titanate, titanium titanate-aluminum hydroxide mixture, titanium chloride, titanium chloride-aluminum chloride Miniumu mixture, titanium acetylacetonate, an organic chelate titanium complex having an organic acid as a ligand, and the like.

Among the Ti-based catalyst, in the present invention, Ru have use of at least one organic chelated titanium complex having an organic acid as a ligand. Examples of the organic acid include citric acid, lactic acid, trimellitic acid, malic acid and the like. Among them, an organic chelate complex having citric acid or citrate as a ligand is preferable.

For example, when a chelate titanium complex having citric acid as a ligand is used, there is little generation of foreign matters such as fine particles, and a polyester resin having better polymerization activity and color tone than other titanium compounds can be obtained. Furthermore, even when using a citric acid chelate titanium complex, by adding it at the stage of the esterification reaction, a polyester resin having better polymerization activity and color tone and less terminal carboxyl groups can be obtained compared to the case where it is added after the esterification reaction. It is done. In this regard, the titanium catalyst also has a catalytic effect of the esterification reaction. By adding it at the esterification stage, the oligomer acid value at the end of the esterification reaction is lowered, and the subsequent polycondensation reaction is performed more efficiently. In addition, complexes with citric acid as a ligand are more resistant to hydrolysis than titanium alkoxides, etc., and do not hydrolyze in the esterification reaction process, while maintaining the original activity and catalyzing the esterification and polycondensation reactions It is estimated to function effectively as
Also, it is generally known that the greater the amount of terminal carboxyl groups, the worse the hydrolysis resistance. When titanium, magnesium and phosphorus are added in this order, the amount of terminal carboxyl groups decreases. Therefore, improvement in hydrolysis resistance is expected.
Examples of the citric acid chelate titanium complex are readily available as commercial products such as VERTEC AC-420 manufactured by Johnson Matthey.

  The aromatic dicarboxylic acid and the aliphatic diol can be introduced by preparing a slurry containing them and continuously supplying it to the esterification reaction step.

  In the present invention, an aromatic dicarboxylic acid and an aliphatic diol are polymerized in the presence of a catalyst containing a titanium compound, and at least one of the titanium compounds is an organic chelate titanium complex having an organic acid as a ligand. In addition, an esterification reaction step including at least a step of adding an organic chelate titanium complex, a magnesium compound, and a pentavalent phosphate ester having no aromatic ring as a substituent in this order is provided as a reactant generation step. It is preferable. In this case, in addition to the esterification reaction step, the polyester is produced by a production method comprising a polycondensation step in which a polycondensation product is produced by subjecting the esterification reaction product produced in the esterification reaction step to a polycondensation reaction. A mode in which a resin is produced is more preferable. The polycondensation step will be described later.

In this case, in the course of the esterification reaction, the addition of a magnesium compound to the presence of an organic chelate titanium complex as a titanium compound, followed by the addition order of adding a specific pentavalent phosphorus compound, thereby providing a titanium catalyst. As the result, the coloring reaction is less and the electrostatic application property is high. At the same time, a polyester resin with improved yellowing when exposed to high temperatures is obtained.
As a result, coloring during polymerization and subsequent coloring during melt film formation are reduced, and yellowishness is reduced compared to conventional antimony (Sb) catalyst-based polyester resins, and germanium catalysts having a relatively high transparency are also obtained. It is possible to provide a polyester resin having a color tone and transparency comparable to a polyester resin and having excellent heat resistance. Further, a polyester resin having high transparency and less yellowness can be obtained without using a color tone adjusting material such as a cobalt compound or a pigment.

  This polyester resin can be used for applications requiring high transparency (for example, optical film, industrial squirrel, etc.), and it is not necessary to use an expensive germanium-based catalyst, so that the cost can be greatly reduced. In addition, since foreign matters caused by the catalyst that are likely to occur in the Sb catalyst system are also avoided, the occurrence of failures and quality defects in the film forming process can be reduced, and the cost can be reduced by improving the yield.

  In the above, when the aromatic dicarboxylic acid and the aliphatic diol are mixed with a catalyst containing an organic chelate titanium complex that is a titanium compound prior to the addition of the magnesium compound and the phosphorus compound, the organic chelate titanium complex or the like is subjected to an esterification reaction. Therefore, the esterification reaction can be carried out satisfactorily. At this time, you may add a titanium compound in mixing the dicarboxylic acid component and the diol component. Moreover, after mixing a dicarboxylic acid component (or diol component) and a titanium compound, you may mix a diol component (or dicarboxylic acid component). Further, the dicarboxylic acid component, the diol component, and the titanium compound may be mixed at the same time. The mixing is not particularly limited, and can be performed by a conventionally known method.

  In the esterification reaction, a process of adding an organic chelate titanium complex which is a titanium compound and a magnesium compound and a pentavalent phosphorus compound as additives in this order is provided. At this time, the esterification reaction proceeds in the presence of the organic chelate titanium complex, and thereafter, the addition of the magnesium compound is started before the addition of the phosphorus compound.

(Phosphorus compound)
As the phosphorus compound, at least one pentavalent phosphate having no aromatic ring as a substituent is preferably used. Examples of the pentavalent phosphate ester in the present invention include trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, tris phosphate (triethylene glycol), methyl acid phosphate, and phosphoric acid. Examples include ethyl acid, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol acid phosphate.

Among pentavalent phosphates, phosphates having a lower alkyl group having 2 or less carbon atoms as a substituent [(OR) ₃ —P═O; R = an alkyl group having 1 or 2 carbon atoms] are preferable, Specifically, trimethyl phosphate and triethyl phosphate are particularly preferable.

  In particular, when a chelate titanium complex coordinated with citric acid or a salt thereof is used as the catalyst as the titanium compound, the pentavalent phosphate ester has better polymerization activity and color tone than the trivalent phosphate ester. Furthermore, in the case of adding a pentavalent phosphate having 2 or less carbon atoms, the balance of polymerization activity, color tone, and heat resistance can be particularly improved.

  The addition amount of the phosphorus compound is preferably such that the P element conversion value is in the range of 50 ppm to 90 ppm. The amount of the phosphorus compound is more preferably 60 ppm to 80 ppm, and still more preferably 65 ppm to 75 ppm.

(Magnesium compound)
Inclusion of the magnesium compound improves electrostatic applicability. In this case, although it is easy to color, in this invention, coloring is suppressed and the outstanding color tone and heat resistance are obtained.

  Examples of the magnesium compound include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among these, magnesium acetate is most preferable from the viewpoint of solubility in ethylene glycol.

  The amount of magnesium compound added is preferably such that the Mg element conversion value is 50 ppm or more, more preferably 50 ppm or more and 100 ppm or less in order to impart high electrostatic applicability. The addition amount of the magnesium compound is preferably an amount that is in the range of 60 ppm to 90 ppm, more preferably 70 ppm to 80 ppm in terms of imparting electrostatic applicability.

When a titanium compound, a magnesium compound, and a phosphorus compound are used as a catalyst, a titanium element (Ti), magnesium, which gives high electrostatic applicability and has resistance to hydrolysis and suppresses yellowing. The case where the following formula is satisfied by the element conversion ratio of the element (Mg) and the phosphorus element (P) is preferable.
3ppm ≦ Ti element content ≦ 20ppm
50ppm ≦ P element content ≦ 90ppm
50 ppm ≦ Mg element content ≦ 100 ppm

In the esterification reaction step in the present invention, the value Z calculated from the following formula (i) is calculated from the following relational expression (ii) for the titanium compound as the catalyst component and the magnesium compound and phosphorus compound as the additive. It is particularly preferable to add and perform melt polymerization so as to satisfy the above. Here, the P content is the amount of phosphorus derived from the entire phosphorus compound including the pentavalent phosphate ester having no aromatic ring, and the Ti content is the amount of titanium derived from the entire Ti compound including the organic chelate titanium complex. It is. As described above, by selecting the combined use of the magnesium compound and the phosphorus compound in the catalyst system containing the titanium compound and controlling the addition timing and the addition ratio, while maintaining the catalyst activity of the titanium compound moderately high, yellow A color tone with less taste can be obtained, and heat resistance that hardly causes yellowing can be imparted even when exposed to high temperatures during polymerization reaction or subsequent film formation (during melting).
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0
This is an index for quantitatively expressing the balance between the three because the phosphorus compound interacts not only with titanium but also with the magnesium compound.
The formula (i) expresses the amount of phosphorus that can act on titanium by excluding the phosphorus content that acts on magnesium from the total amount of phosphorus that can be reacted. When the value Z is positive, it can be said that there is an excess of phosphorus that inhibits titanium, and conversely, when it is negative, there is a shortage of phosphorus necessary to inhibit titanium. In the reaction, since each atom of Ti, Mg, and P is not equivalent, each mole number in the formula is weighted by multiplying by a valence.

  In the present invention, no special synthesis or the like is required, and the titanium compound, phosphorus compound, and magnesium compound, which are inexpensive and easily available, are used for color tone and heat while having the reaction activity required for the reaction. A polyester resin excellent in coloring resistance can be obtained.

  In the formula (ii), from the viewpoint of further enhancing the color tone and the coloration resistance to heat while maintaining the polymerization reactivity, it is preferable to satisfy + 1.0 ≦ Z ≦ + 4.0, and + 1.5 ≦ Z ≦ + 3 Is more preferable.

  As a preferred embodiment in the present invention, before the esterification reaction is completed, after adding a chelate titanium complex having 1 ppm or more and 30 ppm or less of citric acid or citrate as a ligand to the aromatic dicarboxylic acid and the aliphatic diol, In the presence of the chelate titanium complex, a magnesium salt of a weak acid of 60 ppm or more and 90 ppm or less (more preferably 70 ppm or more and 80 ppm or less) is added. And an embodiment in which a pentavalent phosphate having no aromatic ring as a substituent is added.

  The esterification reaction may be carried out using a multistage apparatus in which at least two reactors are connected in series under conditions where ethylene glycol is refluxed while removing water or alcohol produced by the reaction from the system. it can.

The esterification reaction described above may be performed in one stage or may be performed in multiple stages.
When the esterification reaction is performed in one step, the esterification reaction temperature is preferably 230 to 260 ° C, more preferably 240 to 250 ° C.
When the esterification reaction is performed in multiple stages, the temperature of the esterification reaction in the first reaction tank is preferably 230 to 260 ° C, more preferably 240 to 250 ° C, and the pressure is 1.0 to 5.0 kg / cm ² is preferable, and 2.0 to 3.0 kg / cm ² is more preferable. Temperature of the esterification reaction of the second reaction vessel is preferably from 230 to 260 ° C., more preferably from 245 to 255 ° C., the pressure is 0.5~5.0kg / cm ^2, more preferably 1.0 to 3. 0 kg / cm ² . Furthermore, when carrying out by dividing into three or more stages, it is preferable to set the conditions for the esterification reaction in the intermediate stage to the conditions between the first reaction tank and the final reaction tank.

(B) Polycondensation In polycondensation, an esterification reaction product generated by an esterification reaction is subjected to a polycondensation reaction to generate a polycondensation product. The polycondensation reaction may be performed in one stage or may be performed in multiple stages.

  The esterification reaction product such as an oligomer generated by the esterification reaction is subsequently subjected to a polycondensation reaction. This polycondensation reaction can be suitably performed by supplying it to a multistage polycondensation reaction tank.

For example, the polycondensation reaction conditions in the case of performing in a three-stage reaction tank are as follows: the first reaction tank has a reaction temperature of 255 to 280 ° C., more preferably 265 to 275 ° C., and a pressure of 13.3 × 10 ^−3. -1.3 × 10 ⁻³ MPa (100 to 10 torr), more preferably 6.67 × 10 ^{−3 to} 2.67 × 10 ⁻³ MPa (50 to 20 torr), wherein the second reaction tank is a reaction The temperature is 265 to 285 ° C., more preferably 270 to 280 ° C., and the pressure is 2.67 × 10 ^{−3 to} 1.33 × 10 ⁻⁴ MPa (20 to 1 torr), more preferably 1.33 × 10 ^{−. 3 to} 4.0 × 10 ⁻⁴ MPa (10 to ³ torr), and the third reaction vessel in the final reaction vessel has a reaction temperature of 270 to 290 ° C., more preferably 275 to 285 ° C., and a pressure of ^{1.33 × 10 -3 ~1.33 × 10 -5} MPa (10~0.1torr), Ri preferably embodiment is ^{6.67 × 10 -4 ~6.67 × 10 -5} MPa (5~0.5torr) are preferred.

In the present invention, by providing the esterification reaction step and the polycondensation step described above, the titanium atom (Ti), the magnesium atom (Mg), and the phosphorus atom (P) are included and calculated from the following formula (i). Value Z can produce a polyester resin composition satisfying the following relational expression (ii).
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0

  The polyester resin composition satisfies + 0 ≦ Z ≦ + 5.0, and the balance of the three elements of Ti, P, and Mg is appropriately adjusted, so that the polymerization reactivity is maintained, It is excellent in color tone and heat resistance (reduction of yellow coloring under high temperature) and can maintain high electrostatic applicability. Moreover, in this invention, it has high transparency, without using color tone adjusting materials, such as a cobalt compound and a pigment | dye, and can obtain polyester resin with little yellowishness.

As described above, the formula (i) is a quantitative expression of the balance between the phosphorus compound, the magnesium compound, and the phosphorus compound, and the phosphorus content acting on the magnesium from the total amount of phosphorus that can be reacted. This represents the amount of phosphorus that can act on titanium. If the value Z is less than +0, that is, if the amount of phosphorus acting on titanium is too small, the catalytic activity (polymerization reactivity) of titanium will increase, but the heat resistance will decrease, and the resulting polyester resin will have a yellowish color and polymerize. For example, it is colored at the time of film formation (melting) later, and the color tone is lowered. On the other hand, if the value Z exceeds +5.0, that is, the amount of phosphorus acting on titanium is too large, the resulting polyester has good heat resistance and color tone, but the catalytic activity is too low and the productivity is poor.
In the present invention, for the same reason as described above, the formula (ii) preferably satisfies 1.0 ≦ Z ≦ 4.0, and more preferably satisfies 1.5 ≦ Z ≦ 3.0.

  Measurement of each element of Ti, Mg, and P is obtained by quantifying each element in PET using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology). It can carry out by calculating content [ppm] from the obtained result.

Moreover, it is preferable that the produced | generated polyester resin composition satisfy | fills the relationship represented by the following relational expression (iii) further.
B value when pelletized after polycondensation ≦ 4.0 (iii)
When the polyester resin obtained by polycondensation is pelletized and the b value of the pellet is 4.0 or less, yellowness is small and the transparency is excellent. When the b value is 3.0 or less, the color tone is comparable to that of a polyester resin polymerized with a Ge catalyst.

  The b value is an index representing the color and is a value measured using ND-101D (manufactured by Nippon Denshoku Industries Co., Ltd.).

Furthermore, the polyester resin composition preferably satisfies the relationship represented by the following relational expression (iv).
Color tone change rate [Δb / min] ≦ 0.15 (iv)
When the polyester resin pellets obtained by polycondensation are melt-held at 300 ° C., the color change rate [Δb / min] is 0.15 or less, so that yellow coloring when exposed to heating is low. Can be suppressed. Thereby, when extruding with an extruder, for example, to form a film, a film with little yellow coloring and excellent color tone can be obtained.

  The color change rate is preferably as small as possible, and is particularly preferably 0.10 or less.

The color tone change rate is an index representing a color change due to heat, and is a value obtained by the following method. That is,
The pellets of the polyester resin composition are put into a hopper of an injection molding machine (for example, EC100NII manufactured by Toshiba Machine Co., Ltd.) and melted and held in a cylinder (300 ° C.). The plate b value at this time is measured by ND-101D (manufactured by Nippon Denshoku Industries Co., Ltd.). The rate of change [Δb / min] is calculated based on the change in the b value.

-Solid phase polymerization process-
In the solid phase polymerization step in the present invention, the intrinsic viscosity is slowly increased at a rate of 0.01 dL / g or less per hour by heat-treating the esterification reaction product generated in the reactant generation step in a solid state. To obtain a polyester resin having an intrinsic viscosity of 0.65 to 0.90 dL / g and a terminal carboxylic acid amount of 20 equivalents / ton or less.

  The solid-phase polymerization can be suitably performed using the polyester polymerized by the esterification reaction described above or a commercially available polyester in the form of small pieces such as pellets.

  The heat treatment performed in the solid state can be selected at any temperature, but is preferably performed at a low temperature. Among these, the temperature for the heat treatment is preferably a temperature range of 215 ° C. or lower, more preferably 150 ° C. or higher and 215 ° C. or lower, and still more preferably 170 ° C. or higher and 215 ° C. or lower. Among the above, the heat treatment is more preferably performed at 190 ° C. to 215 ° C. for 5 hours to 100 hours, more preferably 190 ° C. to 215 ° C. for 10 hours to 80 hours, particularly 190 ° C. It is preferable to carry out under the conditions of 215 ° C. or lower and 15 hours or longer and 60 hours or shorter.

The solid phase polymerization is preferably performed in a vacuum or in a nitrogen (N ₂ ) stream. Furthermore, you may mix polyhydric alcohol (ethylene glycol etc.) 1 ppm or more and 1% or less.

The solid phase polymerization in the present invention is performed in a slow range where the increase in intrinsic viscosity (IV) is 0.01 dL / g or less per hour. If the increase in IV per hour exceeds 0.01 dL / g, the concentration of terminal COOH cannot be kept low and the hydrolysis resistance is poor. That is, by performing the heat treatment so that the increase in intrinsic viscosity is suppressed to 0.01 dL / g or less, the concentration of the terminal carboxylic acid group in the polyester resin can be suppressed to a low level, thereby improving the hydrolysis resistance. To do. Thereby, the durable performance over the long term of a polyester resin can be improved.
Among these, for the same reason as described above, it is preferable to perform solid-phase polymerization in a range where the intrinsic viscosity increases at 0.002 to 0.008 dL / g per hour.

In the polyester resin after the solid phase polymerization, the intrinsic viscosity (IV) is set in the range of 0.65 to 0.90 dL / g. When the IV is less than 0.65 dL / g, the molecular weight becomes too low, causing cohesive failure at the adhesion interface and lowering the adhesion. On the other hand, when IV exceeds 0.90 dL / g, the melt viscosity is increased during film formation, it is easily decomposed by shearing heat generation, and the formation of spherulites is promoted. Therefore, the concentration of the terminal COOH group cannot be suppressed to 20 equivalent / ton or less, the AV value increases, and the extrusion characteristics at the time of melt extrusion deteriorate.
Furthermore, when IV is outside the above range, the interface with an adherend (particularly, a sealing material (for example, EVA) provided on the battery side substrate of the solar cell module) accompanying embrittlement caused by molecular weight reduction. The breakage (peeling) in can not be suppressed, and the occurrence of stretching unevenness during stretching cannot be avoided.
In order to adjust to such an IV value, it is possible to adjust the polymerization time during liquid phase polymerization in the reaction product generation step, or by solid phase polymerization.
IV can be measured by the same method as described above.

Solid-phase polymerization may be carried out in a batch mode (a method in which a resin is placed in a container and stirred while applying heat for a predetermined time), or a continuous mode (a resin is placed in a heated cylinder and this is stirred). It may be carried out by a system in which the gas is passed through the cylinder while being kept flowing for a predetermined time while being heated, and sequentially fed out.
Specifically, for example, in the case of a heated gas flow system, a low dew point nitrogen flow is preferable (for example, a dew point temperature of −40 ° C. or less is preferable due to water scrubber and zeolite adsorption).

  In the case of batch type solid phase polymerization, it is preferable to carry out under high vacuum. In the case of a high vacuum, it is preferably 50 Pa or less, more preferably 10 Pa or less, and particularly preferably 1 Pa or less.

  The amount of terminal carboxylic acid (the amount of terminal COOH) thereafter is 20 equivalent / ton or less by solid phase polymerization. When the amount of terminal COOH exceeds 20 equivalents / ton, hydrolysis resistance is lowered, and it is not possible to ensure durability that can withstand long-term use. The terminal COOH amount of the polyester resin is preferably 5 equivalents / ton or more and 20 equivalents / ton or less, more preferably 7 equivalents / ton or more and 20 equivalents / ton or less, and still more preferably 10 equivalents / ton or more. 20 equivalents / ton or less.

  The terminal COOH amount was determined by dissolving polyester completely in a mixed solution of benzyl alcohol / chloroform (= 2/3; volume ratio), using phenol red as an indicator, and using this as a reference solution (0.025N KOH-methanol mixed solution). ) And calculated from the titration amount.

-Molding-
After the solid phase polymerization step, there is provided a molding step in which the polyester resin that has been subjected to solid phase polymerization is put into a desired melt extruder and melt extruded to form a film having a thickness of 50 μm to 350 μm. Is preferred.
Here, as temperature conditions at the time of film formation, the temperature of the resin is preferably 290 ° C. or lower, and the temperature of the resin is particularly preferably 285 ° C. or lower.

In the molding step, the polyester film can be molded by melt-kneading the polyester after the solid phase polymerization step and extruding it from a die (extrusion die).
At this time, the thickness of the molten resin (melt) discharged in a strip shape before stretching is preferably in the range of 500 μm or more and 6000 μm or less. In this case, a thick polyester film can be produced by subsequent stretching treatment. The thickness of the polyester film is preferably 50 μm or more and 350 μm or less. When the thickness before stretching is 6000 μm or less, wrinkles are unlikely to occur during melt extrusion, and the occurrence of unevenness is suppressed.
Moreover, the rigidity of a required film can be acquired because the thickness before extending | stretching is 500 micrometers or more.
About the thickness before extending | stretching of a melt, the range of 500 micrometers or more and 6000 micrometers or less is preferable, More preferably, it is the range of 600 micrometers or more and 5000 micrometers or less, More preferably, it is the range of 700 micrometers or more and 4500 micrometers or less.

In this case, after drying the esterification reaction product obtained in the above solid phase polymerization step so that the residual moisture is 100 ppm or less, it can be melted using an extruder. The melting temperature is preferably 250 ° C. or higher and 320 ° C. or lower, more preferably 260 ° C. or higher and 310 ° C. or lower, and further preferably 270 ° C. or higher and 300 ° C. or lower. The extruder may be uniaxial or multi-axial. More preferably, the inside of the extruder is replaced with nitrogen from the viewpoint that generation of terminal COOH due to thermal decomposition can be further suppressed.
The melted molten resin (melt) is extruded from an extrusion die through a gear pump, a filter or the like. At this time, it may be extruded as a single layer or may be extruded as a multilayer.

-Stretching process-
After the above step, a stretched film can be suitably produced by biaxially stretching the extruded polyester film (unstretched film).

  Specifically, the unstretched polyester film is led to a group of rolls heated to a temperature of 70 ° C. or higher and 140 ° C. or lower, and stretched by 3 times or more and 5 times or less in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film). The film is preferably stretched at a rate and cooled with a roll group having a temperature of 20 ° C. or higher and 50 ° C. or lower. Subsequently, the film is guided to a tenter while gripping both ends of the film with a clip, and in an atmosphere heated to a temperature of 80 ° C. or higher and 150 ° C. or lower, the direction perpendicular to the longitudinal direction (width direction) is 3 to 5 times. Stretch at a stretch ratio.

  The stretching ratio is preferably 3 to 5 times in each of the longitudinal direction and the width direction. Moreover, it is preferable that the area magnification (longitudinal stretch magnification x lateral stretch magnification) is 9 times or more and 15 times or less. When the area magnification is 9 times or more, the reflectivity, concealability and film strength of the obtained biaxially stretched laminated film are good, and when the area magnification is 15 times or less, tearing during stretching should be avoided. Can do.

In terms of hydrolysis resistance of the film, a higher film stretch ratio is better, and the degree of plane orientation is preferably 0.15 or more, more preferably 0.16 or more, and still more preferably 0. .165 or more. When the plane orientation degree is within the above range, it is advantageous in terms of hydrolysis resistance.
Here, the degree of plane orientation indicates the degree of crystal orientation on the surface of the polyester film, and the average refractive index (n ¹ ) and thickness direction in the MD direction (transverse direction) and TD direction (longitudinal direction; Machine Direction). a value determined by the refractive index difference between the ^{(n 2) (the} absolute value of n 2 -n ^1).
Further, the degree of plane orientation can be controlled by adjusting the longitudinal and / or transverse stretching ratio, stretching temperature, heat setting temperature, and relaxation rate during stretching.

  As the biaxial stretching method, as described above, in addition to the sequential biaxial stretching method in which the stretching in the longitudinal direction (TD direction) and the width direction (MD direction) are separated, stretching in the longitudinal direction and the width direction is performed. Any of the simultaneous biaxial stretching methods performed simultaneously may be used.

  In order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and dimensional stability, the melting point (Tm) above the glass transition temperature (Tg) of the resin, which is preferably the raw material, is preferably continued in the tenter. ) Heat treatment is carried out at a temperature lower than 1 second and not longer than 30 seconds, uniformly cooled gradually, and then cooled to room temperature. In general, when the heat treatment temperature (Ts) is low, the thermal contraction of the film is large. Therefore, in order to impart high thermal dimensional stability, the heat treatment temperature is preferably higher. However, if the heat treatment temperature is too high, the orientation crystallinity is lowered, and as a result, the formed film may be inferior in hydrolysis resistance. Therefore, the heat treatment temperature (Ts) of the polyester film of the present invention is preferably 30 ° C. ≦ (Tm−Ts) ≦ 90 ° C. More preferably, the heat treatment temperature (Ts) is 40 ° C. ≦ (Tm−Ts) ≦ 80 ° C., more preferably 45 ° C. ≦ (Tm−Ts) ≦ 75 ° C.

  Furthermore, although the polyester film of the present invention can be used as a back sheet constituting a solar cell module, the ambient temperature may rise to about 100 ° C. when the module is used. For this reason, the heat treatment temperature (Ts) is preferably 160 ° C. or higher and Tm−40 ° C. (however, Tm−40 ° C.> 160 ° C.) or lower. More preferably, it is 170 degreeC or more and Tm-50 degreeC (however, Tm-50 degreeC> 170 degreeC), More preferably, Ts is 180 degreeC or more and Tm-55 degreeC (however, Tm-55 degreeC> 180 degreeC) or less.

  Moreover, you may perform a 1-10% relaxation process in the width direction or a longitudinal direction as needed.

  The polyester film can further contain additives such as a light stabilizer and an antioxidant.

  The polyester film of the present invention preferably contains a light stabilizer. By containing the light stabilizer, it is possible to prevent ultraviolet degradation. Examples of the light stabilizer include a compound that absorbs light such as ultraviolet rays and converts it into thermal energy, a material that absorbs light and decomposes when the film or the like absorbs light, and a material that suppresses the decomposition chain reaction. .

  The light stabilizer is preferably a compound that absorbs light such as ultraviolet rays and converts it into heat energy. By including such a light stabilizer in the film, it becomes possible to keep the effect of improving the partial discharge voltage by the film high for a long time even if the film is irradiated with ultraviolet rays continuously for a long time. Changes in color tone, strength deterioration, and the like due to UV rays. For example, if an ultraviolet absorber is a range in which other properties of the polyester are not impaired, any of organic ultraviolet absorbers, inorganic ultraviolet absorbers, and combinations thereof are preferably used without particular limitation. Can do. On the other hand, it is desired that the ultraviolet absorber is excellent in moisture and heat resistance and can be uniformly dispersed in the film.

Examples of the ultraviolet absorber include salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, and the like as organic ultraviolet absorbers. Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, benzotriazole 2- (2'-hydroxy-5) '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 (2H benzotriazol-2-yl) phenol], a cyanoacrylate Ethyl-2-cyano-3,3′-diphenylacrylate), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol as triazine system Hindered amine-based bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethyl Piperidine polycondensate, in addition, nickel bis (octylphenyl) sulfide, 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, and the like .
Of these ultraviolet absorbers, triazine-based ultraviolet absorbers are more preferable in that they have high resistance to repeated ultraviolet absorption. In addition, these ultraviolet absorbers may be added to the above-mentioned ultraviolet absorber alone, or a form in which an organic conductive material or a water-insoluble resin is copolymerized with a monomer having an ultraviolet absorber ability. May be introduced.

  The content of the light stabilizer in the polyester film is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.3% by mass or more and 7% by mass or less with respect to the total mass of the polyester film. More preferably, it is 0.7 mass% or more and 4 mass% or less. Thereby, the molecular weight fall of the polyester by the photodegradation over a long time can be suppressed, and the adhesive force fall resulting from the cohesive failure in the film which arises as a result can be suppressed.

  In addition to the light stabilizer, the polyester film of the present invention includes, for example, a lubricant (fine particles), an ultraviolet absorber, a colorant, a heat stabilizer, a nucleating agent (crystallization agent), and a flame retardant. Etc. can be contained as additives.

<Back sheet for solar cell>
The back sheet for a solar cell of the present invention is configured by providing the polyester film of the present invention as described above, and has an easy-adhesive layer, an ultraviolet absorbing layer, and a light-reflecting property that are easily adhered to an adherend. It can be configured by providing at least one functional layer such as a white layer. Since the polyester film described above is provided, stable durability is exhibited during long-term use.

In the solar cell backsheet of the present invention, for example, the following functional layer may be applied to a polyester film after uniaxial stretching and / or biaxial stretching. For coating, a known coating technique such as a roll coating method, a knife edge coating method, a gravure coating method, or a curtain coating method can be used.
Further, surface treatment (flame treatment, corona treatment, plasma treatment, ultraviolet treatment, etc.) may be performed before the coating. Furthermore, it is also preferable to bond together using an adhesive.

-Easy adhesive layer-
The polyester film of the present invention is a back having an easy-adhesive layer on the side facing the sealing material of the battery side substrate in which the solar cell element is sealed with a sealing agent when constituting a solar cell module. It is preferable to be configured in a sheet. Easy adhesion showing adhesion to an adherend containing a sealing agent (particularly ethylene-vinyl acetate copolymer) (for example, the surface of the sealing agent on the battery side substrate in which the solar cell element is sealed with the sealing material). By providing the conductive layer, the back sheet and the sealing material can be firmly bonded. Specifically, it is preferable that the easy-adhesive layer has an adhesive force of 10 N / cm or more, preferably 20 N / cm or more, particularly with EVA (ethylene-vinyl acetate copolymer) used as a sealing material.
Further, the easy-adhesive layer needs to prevent the backsheet from peeling off during use of the solar cell module, and therefore, the easy-adhesive layer desirably has high moisture and heat resistance.

(1) Binder The easy-adhesive layer in the present invention can contain at least one binder.
As the binder, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. Among these, acrylic resins and polyolefins are preferable from the viewpoint of durability. As the acrylic resin, a composite resin of acrylic and silicone is also preferable. The following can be mentioned as an example of a preferable binder.
Examples of the polyolefin include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals, Inc.). Examples of the acrylic resin include Julimer ET-410 and SEK-301 (both manufactured by Nippon Pure Chemical Industries, Ltd.). Examples of the composite resin of acrylic and silicone include Ceranate WSA 1060 and WSA 1070 (both manufactured by DIC Corporation), and H7620, H7630, and H7650 (both manufactured by Asahi Kasei Chemicals Corporation).
The amount of the binder is preferably in the range of 0.05-5 g / ^{m 2,} the range of 0.08~3g / ^{m 2} is particularly preferred. The binder amount is more good adhesion is obtained by at 0.05 g / m ² or more, a better surface is obtained by at 5 g / m ² or less.

(2) Fine particles The easy-adhesion layer in the present invention can contain at least one kind of fine particles. The easy-adhesive layer preferably contains 5% by mass or more of fine particles with respect to the mass of the entire layer.
As the fine particles, inorganic fine particles such as silica, calcium carbonate, magnesium oxide, magnesium carbonate, tin oxide and the like are preferably exemplified. Among these, fine particles of tin oxide and silica are preferable in that the decrease in adhesiveness when exposed to a humid heat atmosphere is small.
The particle size of the fine particles is preferably about 10 to 700 nm, more preferably about 20 to 300 nm. By using fine particles having a particle diameter in the above range, good easy adhesion can be obtained. The shape of the fine particles is not particularly limited, and those having a spherical shape, an indefinite shape, a needle shape or the like can be used.
The addition amount of the fine particles in the easy-adhesive layer is preferably 5 to 400% by mass, more preferably 50 to 300% by mass per binder in the easy-adhesive layer. When the addition amount of the fine particles is 5% by mass or more, the adhesiveness when exposed to a moist heat atmosphere is excellent, and when it is 1000% by mass or less, the surface state of the easy-adhesive layer is better.

(3) Crosslinking agent The easy-adhesion layer in this invention can contain at least 1 sort (s) of a crosslinking agent.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent is particularly preferable from the viewpoint of securing adhesiveness after wet heat aging.
Specific examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- ( 2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline) 2,2′-hexamethylene-bis- (2-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (4,4′- Methyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be mentioned. Furthermore, (co) polymers of these compounds can also be preferably used.
Further, as a compound having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS500, WS700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used.
The preferable addition amount of the crosslinking agent in the easy-adhesive layer is preferably 5 to 50% by mass, more preferably 20 to 40% by mass per binder of the easy-adhesive layer. When the addition amount of the crosslinking agent is 5% by mass or more, a good crosslinking effect is obtained, and the strength of the reflective layer is not reduced and adhesion failure hardly occurs, and when it is 50% by mass or less, the pot life of the coating liquid is further increased. I can keep it long.

(4) Additives The easy-adhesive layer in the present invention is added with known matting agents such as polystyrene, polymethylmethacrylate, silica, etc., as well as known surfactants such as anionic and nonionic types, if necessary. May be.

(5) Method for forming easy-adhesive layer As a method for forming the easy-adhesive layer of the present invention, there are a method for bonding a polymer sheet having easy adhesion to a polyester film and a method for coating. It is preferable in that it can be formed with a simple and highly uniform thin film. As a coating method, for example, a known method such as a gravure coater or a bar coater can be used. The solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

(6) Physical property Although there is no restriction | limiting in particular in the thickness of the easily-adhesive layer in this invention, Usually, 0.05-8 micrometers is preferable, More preferably, it is the range of 0.1-5 micrometers. When the thickness of the easy-adhesive layer is 0.05 μm or more, the required easy adhesion can be easily obtained, and when the thickness is 8 μm or less, the planar shape can be maintained better.
In addition, the easy-adhesion layer in the present invention may have transparency from the viewpoint of not impairing the effect of the colored layer when a colored layer (particularly a reflective layer) is disposed between the polyester film. preferable.

-UV absorbing layer-
The polyester film of the present invention may be provided with an ultraviolet absorbing layer containing the above ultraviolet absorber. An ultraviolet absorption layer can be arrange | positioned in the arbitrary positions on a polyester film.
The ultraviolet absorber is preferably dissolved and dispersed together with an ionomer resin, polyester resin, urethane resin, acrylic resin, polyethylene resin, polypropylene resin, polyamide resin, vinyl acetate resin, cellulose ester resin, and the like. The transmittance is preferably 20% or less.

-Colored layer-
The polyester film of the present invention can be provided with a colored layer. The colored layer is a layer arranged in contact with the surface of the polyester film or through another layer, and can be constituted using a pigment or a binder.

  The first function of the colored layer is to increase the power generation efficiency of the solar cell module by reflecting the light that has reached the back sheet without being used for power generation in the solar cell out of the incident light and returning it to the solar cell. is there. The second function is to improve the decorativeness of the appearance when the solar cell module is viewed from the front side. In general, when a solar cell module is viewed from the front side, a back sheet can be seen around the solar cell, and the decorativeness can be improved by providing a colored layer on the back sheet.

(1) Pigment The colored layer in the present invention can contain at least one pigment. The pigment is preferably contained in the range of 2.5 to 8.5 g / m ² . A more preferable pigment content is in the range of 4.5 to 7.5 g / m ² . When the pigment content is 2.5 g / m ² or more, necessary coloring can be easily obtained, and the light reflectance and decorativeness can be adjusted to be more excellent. When the pigment content is 8.5 g / m ² or less, the planar shape of the colored layer can be maintained better.

  Examples of the pigment include inorganic pigments such as titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, ultramarine blue, bitumen, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. It is done. Among these pigments, a white pigment is preferable from the viewpoint of constituting a colored layer as a reflective layer that reflects incident sunlight. As the white pigment, for example, titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and the like are preferable.

As an average particle diameter of a pigment, 0.03-0.8 micrometer is preferable, More preferably, about 0.15-0.5 micrometer is preferable. If the average particle size is within the above range, the light reflection efficiency may be reduced.
When a colored layer is configured as a reflective layer that reflects incident sunlight, the preferred addition amount of the pigment in the reflective layer varies depending on the type of pigment used and the average particle size, but cannot be generally stated. preferably to 15 g / ^{m 2,} more preferably about 3 to 10 g / ^{m 2.} When the addition amount is 1.5 g / m ² or more, the required reflectance is easily obtained, and when the addition amount is 15 g / m ² or less, the strength of the reflection layer can be kept higher.

(2) Binder The colored layer in the present invention can contain at least one binder. As a quantity in case a binder is included, the range of 15-200 mass% is preferable with respect to the said pigment, and the range of 17-100 mass% is more preferable. When the amount of the binder is 15% by mass or more, the strength of the colored layer can be more favorably maintained, and when it is 200% by mass or less, the reflectance and the decorativeness are lowered.
As a binder suitable for the colored layer, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. From the viewpoint of durability, the binder is preferably an acrylic resin or a polyolefin. As the acrylic resin, a composite resin of acrylic and silicone is also preferable. Examples of preferred binders include the following.
Examples of the polyolefin include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals). Examples of the acrylic resin include Julimer ET-410 and SEK-301 (both manufactured by Nippon Pure Chemical Industries, Ltd.). Examples of the composite resin of acrylic and silicone include Ceranate WSA1060, WSA1070 (both manufactured by DIC Corporation), H7620, H7630, H7650 (both manufactured by Asahi Kasei Chemicals Corporation) and the like.

(3) Additive In addition to the binder and the pigment, a cross-linking agent, a surfactant, a filler, and the like may be further added to the colored layer in the present invention as necessary.

  Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. The addition amount of the crosslinking agent in the colorant is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, per binder of the colored layer. When the addition amount of the crosslinking agent is 5% by mass or more, a good crosslinking effect can be obtained, the strength and adhesiveness of the colored layer can be maintained high, and when it is 50% by mass or less, the coating solution The pot life can be maintained longer.

As the surfactant, a known surfactant such as an anionic or nonionic surfactant can be used. 0.1-15 mg / m < ² > is preferable and, as for the addition amount of surfactant, 0.5-5 mg / m < ² > is more preferable. The amount of the surfactant added is 0.1 mg / m ² or more to effectively suppress the occurrence of repelling, and the amount added is 15 mg / m ² or less to provide excellent adhesion.

  Furthermore, a filler such as silica may be added to the colored layer in addition to the above pigment. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less per binder of the colored layer. By including the filler, the strength of the colored layer can be increased. Moreover, since the ratio of a pigment can be maintained because the addition amount of a filler is 20 mass% or less, favorable light reflectivity (reflectance) and decorativeness are obtained.

(4) Forming method of colored layer As a forming method of the colored layer, there are a method of pasting a polymer sheet containing a pigment on a polyester film, a method of co-extruding a colored layer at the time of forming a polyester film, a method by coating, and the like. Among these, the method by coating is preferable in that it can be formed with a simple and highly uniform thin film. As a coating method, for example, a known method such as a gravure coater or a bar coater can be used. The solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. However, from the viewpoint of environmental burden, it is preferable to use water as a solvent.
A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

(5) Physical property It is preferable that a colored layer contains a white pigment and is comprised as a white layer (light reflection layer). The light reflectance at 550 nm in the case of the reflective layer is preferably 75% or more. When the reflectance is 75% or more, sunlight that has passed through the solar battery cell and has not been used for power generation can be returned to the cell, and the effect of increasing power generation efficiency is high.

  1-20 micrometers is preferable, as for the thickness of a white layer (light reflection layer), 1-10 micrometers is more preferable, More preferably, it is about 1.5-10 micrometers. When the film thickness is 1 μm or more, necessary decoration and reflectance are easily obtained, and when it is 20 μm or less, the surface shape may be deteriorated.

-Undercoat layer-
An undercoat layer can be provided on the polyester film of the present invention. For example, when a colored layer is provided, the undercoat layer may be provided between the colored layer and the polyester film. The undercoat layer can be formed using a binder, a crosslinking agent, a surfactant, and the like.

  Examples of the binder contained in the undercoat layer include polyester, polyurethane, acrylic resin, and polyolefin. In addition to the binder, an epoxy, isocyanate, melamine, carbodiimide, oxazoline, or other crosslinking agent, anionic or nonionic surfactant, silica or other filler may be added to the undercoat layer.

There are no particular restrictions on the method for coating the undercoat layer and the solvent of the coating solution used.
As a coating method, for example, a gravure coater or a bar coater can be used. The solvent may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

The application may be applied to the polyester film after biaxial stretching or may be applied to the polyester film after uniaxial stretching. In this case, the film may be further stretched in a direction different from the initial stretching after coating. Furthermore, you may extend | stretch in 2 directions, after apply | coating to the polyester film before extending | stretching.
The thickness of the undercoat layer is preferably 0.05 μm to 2 μm, more preferably about 0.1 μm to 1.5 μm. When the film thickness is 0.05 μm or more, the necessary adhesiveness is easily obtained, and when it is 2 μm or less, the surface shape can be favorably maintained.

-Fluorine resin layer / silicon resin layer-
The polyester film of the present invention is preferably provided with at least one of a fluorine-based resin layer and a silicon-based (Si-based) resin layer. By providing the fluorine-based resin layer or the Si-based resin layer, it is possible to prevent contamination of the polyester surface and improve weather resistance. Specifically, it is preferable to have the fluororesin-based coating layer described in JP2007-35694A, JP2008-28294A, and WO2007 / 063698.
Moreover, it is also preferable to stick together fluorine resin films such as Tedlar (manufactured by DuPont).

  The thicknesses of the fluorine-based resin layer and the Si-based resin layer are each preferably in the range of 1 μm to 50 μm, more preferably in the range of 1 μm to 40 μm, and still more preferably in the range of 1 μm to 10 μm.

-Inorganic layer-
The polyester film of the present invention preferably further has a form in which an inorganic layer is provided. By providing the inorganic layer, it is possible to provide a moisture-proof and gas barrier function to prevent water and gas from entering the polyester. The inorganic layer may be provided on either the front or back side of the polyester film, but from the viewpoint of waterproofing, moisture proofing, etc., the side opposite to the battery-side substrate of the polyester film (the side on which the colored layer or easy-adhesion layer is formed) is opposite. It is suitably provided on the side.

Water vapor permeability of the inorganic layer as the (moisture ^{permeability), 10 0 g / m 2} · d~10 -6 g / m 2 · d , more preferably ^{10 1 g / m 2 · d~10} -5 g / ^m is ² · d, more preferably from ^{10 2 g / m 2 · d~10} -4 g / m 2 · d.
In order to form an inorganic layer having such moisture permeability, the following dry method is suitable.

  As a method of forming a gas barrier inorganic layer (hereinafter also referred to as a gas barrier layer) by a dry method, resistance heating vapor deposition, electron beam vapor deposition, induction heat vapor deposition, and vacuum vapor deposition such as an assist method using plasma or ion beam for these. , Reactive sputtering method, ion beam sputtering method, sputtering method such as ECR (electron cyclotron) sputtering method, physical vapor deposition method such as ion plating method (PVD method), heat, light, plasma, etc. Examples include chemical vapor deposition (CVD). Among these, a vacuum vapor deposition method in which a film is formed by a vapor deposition method under vacuum is preferable.

Here, when the material forming the gas barrier layer is mainly composed of inorganic oxide, inorganic nitride, inorganic oxynitride, inorganic halide, inorganic sulfide, etc., it is the same as the composition of the gas barrier layer to be formed. It is possible to directly volatilize the material and deposit it on a substrate or the like. However, when this method is used, the composition changes during volatilization, and as a result, the formed film does not exhibit uniform characteristics. There is a case. Therefore, 1) As a volatilization source, a material having the same composition as the barrier layer to be formed is used. In the case of inorganic oxide, oxygen gas, in the case of inorganic nitride, nitrogen gas, in the case of inorganic oxynitride, oxygen gas A method of volatilizing a mixed gas of nitrogen gas, halogen gas in the case of inorganic halide, and sulfur gas in the case of inorganic sulfide while being introduced into the system, and 2) inorganic substance group as a volatile source And volatilizing this, oxygen gas in the case of inorganic oxide, nitrogen gas in the case of inorganic nitride, mixed gas of oxygen gas and nitrogen gas in the case of inorganic oxynitride, and inorganic halide In the case of halogen-based gas, in the case of inorganic sulfide, sulfur-based gas is introduced into the system, and the inorganic substance and the introduced gas are reacted and deposited on the surface of the substrate. Use this To form an inorganic group layer, and in the case of inorganic oxide, it is in an oxygen gas atmosphere, in the case of inorganic nitride, in a nitrogen gas atmosphere, in the case of inorganic oxynitride, oxygen gas and nitrogen gas In a mixed gas atmosphere, in the case of an inorganic halide, a method of reacting an introduced gas with an inorganic layer by holding in a halogen-based gas atmosphere, and in the case of an inorganic sulfide, a sulfur-based gas atmosphere, and the like.
Among these, 2) or 3) is more preferably used because it is easy to volatilize from a volatile source. Furthermore, the method 2) is more preferably used because the film quality can be easily controlled. When the barrier layer is an inorganic oxide, the inorganic group is used as a volatilization source, volatilized to form an inorganic group layer, and then left in the air to naturally oxidize the inorganic group. The method is also preferable because it is easy to form.

  It is also preferable to use an aluminum foil as a barrier layer by bonding. The thickness is preferably 1 μm or more and 30 μm or less. When the thickness is 1 μm or more, water hardly penetrates into the polyester film during the lapse of time (thermo) and hardly causes hydrolysis, and when it is 30 μm or less, the thickness of the barrier layer does not become too thick, and the barrier layer The stress does not cause the film to bend.

<Solar cell module>
The solar cell module of the present invention comprises a solar cell element that converts light energy of sunlight into electric energy, a transparent substrate on which sunlight is incident, and the polyester film (back sheet for solar cell) of the present invention described above. It is arranged and arranged between. A space between the substrate and the polyester film can be configured by sealing with a resin (so-called sealing material) such as an ethylene-vinyl acetate copolymer.

  The members other than the solar cell module, the solar cell, and the back sheet are described in detail in, for example, “Photovoltaic power generation system constituent material” (supervised by Eiichi Sugimoto, Kogyo Kenkyukai, published in 2008).

  The transparent substrate only needs to have a light-transmitting property through which sunlight can pass, and can be appropriately selected from base materials that transmit light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

  Solar cell elements include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, III-V groups such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenide, and II Various known solar cell elements such as -VI group compound semiconductor systems can be applied.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
As shown below, a polyester resin is obtained by a continuous polymerization apparatus using a direct esterification method in which terephthalic acid and ethylene glycol are directly reacted to distill off water and esterify, followed by polycondensation under reduced pressure. It was.

[Reactant production step]
(1) Esterification reaction In a first esterification reactor, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol are mixed over 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. It supplied to the 1st esterification reaction tank. Further, an ethylene glycol solution of a citrate chelate titanium complex (VERTEC AC-420, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied, and the average residence time is maintained at 250 ° C. in the reaction vessel with stirring. The reaction was carried out for about 4.3 hours. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of Ti element. At this time, the acid value of the obtained oligomer was 600 eq / ton.

  This reaction product was transferred to a second esterification reaction vessel and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 200 eq / ton. The inside of the second esterification reaction tank is partitioned into three zones, and an ethylene glycol solution of magnesium acetate is continuously supplied from the second zone so that the amount of Mg added is 67 ppm in terms of element, From the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the added amount of P was 65 ppm in terms of element.

(2) Polycondensation reaction The esterification reaction product obtained above is continuously supplied to the first polycondensation reaction tank, and with stirring, the reaction temperature is 270 ° C., and the pressure in the reaction tank is 2.67 × 10 ⁻³ MPa. (20 torr) and polycondensation was carried out with an average residence time of about 1.8 hours.

Further, the mixture was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 6.67 × 10 ⁻⁴ MPa (5 torr), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.

Subsequently, it was further transferred to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature was 278 ° C., the reaction tank pressure was 2.0 × 10 ⁻⁴ MPa (1.5 torr), and the residence time was 1.5 hours. Reaction (polycondensation) was performed under conditions to obtain a reaction product (polyethylene terephthalate; hereinafter abbreviated as PET).

About obtained PET (reaction product), it measured as shown below using the high-resolution type | mold high frequency inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM by SII nanotechnology company). As a result, Ti = 9 ppm, Mg = 67 ppm, and P = 58 ppm. P is slightly reduced with respect to the initial addition amount, but is estimated to have volatilized during the polymerization process.
Moreover, the intrinsic viscosity (IV) and the amount of terminal COOH before solid-phase polymerization were measured by the method mentioned later. The measurement results are shown in Table 1 below.

  Thereafter, the obtained PET (reaction product) was vacuum-dried to a water content of 50 ppm or less. At this time, during the period from the drying to the solid phase polymerization step, the heating rate was 80 ° C.

[Solid-state polymerization process]
The above polymerized PET was pelletized (diameter 3 mm, length 7 mm), and the obtained resin pellet was subjected to solid phase polymerization in a nitrogen atmosphere. At this time, the temperature for solid-phase polymerization was 205 ° C., and the change in intrinsic viscosity per hour [ΔIV / hour] was adjusted to 0.008 as shown in Table 1 below, and solid-phase polymerization was performed.

[Extrusion molding]
The resin pellets after the solid-phase polymerization as described above are dried again to a water content of 50 ppm or less, and then put into a hopper of a single-screw kneading extruder having a diameter of 50 mm, and melted at 285 ° C. in a N ₂ stream. Extrusion was performed at a speed of 40 m / min. After passing this melt (melt) through a gear pump and a filter (pore diameter 20 μm), it was extruded from a die having a width of 0.8 m under the following conditions, and the temperature was adjusted to 10 ° C. and having a diameter of 1.5 m. Cast on a cast roll (cooling roll).
<Condition>
[1] Cooling speed on cast roll The molten polymer is cast onto a casting drum having a surface temperature of 20 ° C until the melt on the cast roll cools to 250 ° C to 120 ° C, and the air surface is air at 15 ° C. The solution was forcedly cooled by spraying and cooling.
[2] Thickness of melt (unstretched film) extruded from the die The melt thickness was adjusted to 3300 μm by adjusting the discharge amount of the extruder and the slit height of the die. The melt thickness was measured by photographing with a camera installed at the die exit.

[Stretching and winding]
The unstretched film extruded and solidified on the cooling roll by the above method was successively biaxially stretched by the following method to obtain films having the thicknesses shown in Table 2 below. The stretching was performed in the order of longitudinal stretching at 95 ° C. and transverse stretching at 140 ° C. in the order of longitudinal stretching and transverse stretching. Thereafter, the film was heat-fixed at 210 ° C. for 12 seconds and then relaxed by 3% in the lateral direction at 205 ° C. After stretching, both ends were trimmed by 10 cm, and after thicknessing was applied to both ends, 3000 m was wound around a resin core having a diameter of 30 cm. The width was 1.5 m and the winding length was 2000 m.
<Stretching method>
(A) Longitudinal stretching The unstretched film was passed between two pairs of nip rolls having different peripheral speeds and stretched in the longitudinal direction (conveying direction). The preheating temperature was 95 ° C., the stretching temperature was 95 ° C., the stretching ratio was 3.5 times, and the stretching speed was 3000% / second.
(B) Transverse stretching The longitudinally stretched film was stretched laterally under the following conditions using a tenter.
<Condition>
-Preheating temperature: 110 ° C
-Stretching temperature: 120 ° C
-Stretch ratio: 3.9 times-Stretch speed: 70% / second

  A PET film was produced as described above. Next, the following evaluation was performed using the produced PET film.

[Measurement / Evaluation]
The following measurement and evaluation were performed on the PET (polyethylene resin composition) obtained above and its pellets. The results of measurement and evaluation are shown in Tables 1 and 2 below.

(1) Element content and value Z
Using high resolution high frequency inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology), titanium element (Ti), magnesium element (Mg), and phosphorus element (P) in PET The content [ppm] was calculated from the obtained results. A value Z calculated by the following formula (i) was obtained from the obtained value.
Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight) (i)

(2) IV
The PET pellets obtained after the polycondensation are dissolved in a mixed solution of 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]), and at 25 ° C. using an Ubbelohde viscometer. The relative viscosity η ₀ was measured, the specific viscosity (η _sp ) determined from this relative viscosity and the concentration c to determine η _sp / c, and the intrinsic viscosity (IV) was calculated by a three-point method.

(3) Degree of crystal orientation (degree of orientation on the film surface)
The PET film was subjected to XD measurement, and the degree of crystal orientation on the surface of the PET film was determined from the following formula.
Degree of crystal orientation = {peak intensity at 2θ = 23 ° ((110) plane)} / {peak intensity at 2θ = 25.8 ° ((100) plane)}

(4) Amount of terminal COOH After 0.1 g of PET film was dissolved in 10 ml of benzyl alcohol, phenol red indicator was dropped into a mixed solution to which chloroform was added, and this was titrated with a reference solution (0.01 N KOH-benzyl alcohol mixed solution). did. The concentration of the terminal carboxyl group [equivalent / ton] was calculated from the amount dropped.

(5) Film-forming property About the obtained PET pellet, it formed into a film with the discharge rate of 2000 kg / hour at the film-forming temperature of 285 degreeC using the single screw extruder with a screw diameter of 250 mm. The state during film formation was evaluated according to the following evaluation criteria.
<Evaluation criteria>
(Double-circle): There was no film | membrane shake and electrostatic application nonuniformity, and the film surface shape was favorable visually.
○: Film shaking and electrostatic application unevenness were hardly observed, and the film surface shape was almost good visually.
(Triangle | delta): Although film | membrane shaking and electrostatic application nonuniformity are seen slightly, deterioration of film surface shape is seen visually, but it was a grade which is satisfactory in actual use.
X: Film shake and electrostatic application unevenness were observed, and deterioration of the film surface was observed visually.

(6) Hydrolysis resistance About the film obtained by film forming and stretching, the film was subjected to treatment at 120 ° C. under a 100% wet heat condition for a predetermined time, and then the elongation at break was measured by the JIS-K7127 method. Evaluation was performed according to the evaluation criteria.
<Evaluation criteria>
◎: Time when the breaking elongation decreases to 50% of the untreated film exceeds 100 hours ○: Time when the breaking elongation decreases to 50% of the untreated film exceeds 90 hours and is 100 hours or less Δ: Time when the elongation at break is reduced to 50% of the untreated film exceeds 80 hours and 90 hours or less X: Time when the elongation at break is reduced to 50% of the untreated film is 80 hours or less

(7) LogR
The volume resistivity value R (Ω · m) of the obtained PET was measured by the following measurement method, and the common logarithm of the obtained measurement value was LogR.
<Measurement of volume resistivity R>
After drying and crystallizing the PET pellets obtained after the polycondensation, 15 g was weighed and placed in a test tube and melted in a 290 ° C. oil bath. A measurement electrode was inserted there, and the volume specific resistance value was read with a digital multimeter (manufactured by Iwatori Measurement Co., Ltd.).

(Example 2)
In Example 1, the polycondensation reaction conditions were such that the reaction temperature of the third triple condensation tank was 278 ° C., the pressure in the reaction tank was 2.0 × 10 ⁻⁴ MPa (1.5 torr), and the residence time was 1.0 hour. A PET film was prepared in the same manner as in Example 1 except that the IV before solid phase polymerization was 0.50 and the temperature increase rate from drying to the solid phase polymerization step was changed from 80 ° C to 150 ° C. Fabricated and evaluated. The evaluation results are shown in Tables 1 and 2 below.

( Reference Example 3)
In the solid phase polymerization step of Example 1, the rate of temperature increase was changed from 80 ° C./hour to 150 ° C./hour, and the change in intrinsic viscosity per hour [ΔIV / hour] was changed from 0.008 to 0.010. A PET film was prepared and evaluated in the same manner as in Example 1 except that solid phase polymerization was performed. The evaluation results are shown in Tables 1 and 2 below.

Example 4
In Example 1, a PET film was prepared in the same manner as in Example 1 except that the rate of temperature increase was changed from 80 ° C./hour to 100 ° C./hour, and the titanium element content and the magnesium element content were changed. And evaluated. The evaluation results are shown in Tables 1 and 2 below.

(Example 5)
In Example 1, a PET film was produced in the same manner as in Example 1 except that the rate of temperature increase was changed from 80 ° C./hour to 150 ° C./hour and the magnesium element content and the phosphorus element content were changed. And evaluated. The evaluation results are shown in Tables 1 and 2 below.

( Reference Example 6)
In Example 1, the organic chelate titanium was replaced with tetra-n-butyl titanate, and the content of each element of titanium, magnesium, and phosphorus, the heating rate, and the change in intrinsic viscosity per hour [ΔIV / hour] were as follows: A PET film was produced and evaluated in the same manner as in Example 1 except that the changes were made as shown in Table 1. The evaluation results are shown in Tables 1 and 2 below.

(Examples 7 to 8)
In Example 1, except that each element content of titanium, magnesium, and phosphorus, and the heating rate were changed as shown in Table 1 below, a PET film was prepared in the same manner as in Example 1, Evaluation was performed. The evaluation results are shown in Tables 1 and 2 below.

(Comparative Examples 1-2)
In Example 1, except that the type of titanium compound, the heating rate, and the change in intrinsic viscosity per hour [ΔIV / hour] were changed as shown in Table 1 below, the same as in Example 1, A PET film was prepared and evaluated. The evaluation results are shown in Tables 1 and 2 below.

(Comparative Example 3)
In Example 1, the polycondensation reaction conditions are such that the reaction temperature in the third triple condensation tank is 278 ° C., the pressure in the reaction tank is 2.0 × 10 ⁻⁴ MPa (1.5 torr), and the residence time is 0.3 hours. By changing the IV before solid state polymerization from 0.64 to 0.30 and changing the heating rate from 80 ° C./hour to 150 ° C./hour in the same manner as in Example 1, Fabricated and evaluated. The evaluation results are shown in Tables 1 and 2 below.

(Comparative Example 4)
In Example 1, the polycondensation reaction conditions were such that the reaction temperature of the third triple condensation tank was 278 ° C., the pressure in the reaction tank was 2.0 × 10 ⁻⁴ MPa (1.5 torr), and the residence time was 1.0 hour. PET in the same manner as in Example 1 except that the IV before solid-state polymerization was 0.60, and the phosphorus element content, the heating rate, and the change in intrinsic viscosity per hour [ΔIV / hour] were changed. A film was prepared and evaluated. The evaluation results are shown in Tables 1 and 2 below.

As shown in Tables 1 and 2, by increasing the increase rate of the intrinsic viscosity per hour by solid phase polymerization while keeping it at 0.01 dL / g / hour or less, the terminal COOH is obtained without increasing the high IV. Since the amount could be reduced, shear heat generation during melt film formation was prevented, and a film with improved hydrolysis resistance could be obtained.
In Comparative Example 3 in which the IV value is too small, the molten resin from the die hangs down due to its own weight, so that uniform electrostatic application cannot be applied (that is, the surface condition is deteriorated), and the film forming property is inferior. . Moreover, in Comparative Example 4, since the IV after polymerization was too high, extrusion failure occurred.

  The polyester resin production method and the polyester film of the present invention are used, for example, for a back sheet (sheet disposed on the side opposite to the sunlight incident side with respect to the solar cell element; so-called back sheet) constituting the solar cell module. Preferably used.

DESCRIPTION OF SYMBOLS 1 ... Back sheet 2 ... Sealant 3 ... Solar cell element

Claims (6)

An esterification reaction product having an intrinsic viscosity of 0.40 dL / g or more is obtained by esterifying a dicarboxylic acid component and a diol component under a catalyst containing at least one organic chelate titanium complex having an organic acid as a ligand. A reactant generation step to be generated; and
The resulting esterification reaction product is heat-treated in a solid state to cause solid viscosity polymerization by increasing the intrinsic viscosity at a rate of 0.002 dL / g or more and 0.008 dL / g or less per hour. Is a solid phase polymerization step of obtaining a polyester resin having a terminal carboxylic acid amount of not more than 20 equivalents / ton,
The manufacturing method of the polyester resin which has this.   When heat-treating the esterification reaction product in a solid state, the temperature increase rate is 200 ° C./hour or less during the transition from the drying step of drying the produced esterification reaction product to the solid phase polymerization step. The manufacturing method of the polyester resin of Claim 1 which has the process made into. The reactant generation step includes a step of adding an organic chelate titanium complex as a catalyst, a magnesium compound, and a pentavalent phosphate ester having no aromatic ring as a substituent in this order,
Furthermore, the manufacturing method of the polyester resin of Claim 1 or Claim 2 which has a polycondensation process which carries out the polycondensation reaction of the esterification reaction product produced | generated at the said reaction product production | generation process. In the reactant generation step, the organic chelate titanium complex, the magnesium compound, and the phosphate ester are added so that a value Z calculated from the following formula (i) satisfies the following relational expression (ii): Item 4. A method for producing a polyester resin according to Item 3.
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0   The method for producing a polyester resin according to any one of claims 2 to 4, wherein the rate of temperature increase is 10 to 150 ° C / hour.   6. The method according to claim 1, further comprising a forming step of forming a film having a thickness of 50 μm to 350 μm after introducing the polyester resin into a melt extruder after the solid phase polymerization step. The manufacturing method of the polyester resin as described in a term.