JP2013166874A - Copolymerized polyester resin, and coating, coating agent, and adhesive using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolymerized polyester resin that has long term thermal stability and an extremely advanced heat resistance.SOLUTION: A copolymerized polyester resin includes a dicarboxylic acid component and a glycol component, contains at least 3 mole% of isosorbide as a glycol component, and satisfies the following requirement (1). (1) The total metal element content is at most 150 ppm based on the mass of the polyester resin.

Description

  The present invention relates to a copolyester resin excellent in heat resistance and a paint, a coating agent, and an adhesive using the same. Specifically, the present invention relates to a copolyester resin excellent in heat resistance and weather resistance suitable for outdoor use such as a solar cell backside sealing sheet, and a paint, coating agent, and adhesive using the same.

  In general, the performance of a polyester resin gradually decreases due to degradation of the polyester resin. In particular, since solar cell members and electrical insulation members are kept under high temperature and high humidity for a long period of time, higher heat resistance is required for the polyester resins used and paints, coating agents, and adhesives using the same. ing.

  Degradation and degradation of the copolyester resin under high temperature and high humidity can be considered by dividing into thermal degradation and hydrolysis.

  First, it is considered that decomposition of the copolyester resin by heat proceeds by the following reaction. That is, the ester bond is first cleaved by heat and the polymer chain is cleaved to generate a carboxyl terminal group and a vinyl ester terminal. Subsequently, acetaldehyde is eliminated by further reaction from the vinyl ester terminal.

  Moreover, it is thought that hydrolysis with water or water vapor proceeds by the following reaction. That is, the polymer chain is split by the hydrolysis reaction of the ester bond due to the nucleophilic attack on the ester bond of the water molecule, and the carboxyl group terminal and the hydroxyl terminal are formed, and then the generated terminal hydroxyl group causes back-biting. Furthermore, the polymer chain continues to be decomposed. In this reaction, the terminal carboxyl group plays a catalytic role in the hydrolysis reaction of the polymer, and the hydrolysis is accelerated as the amount of the terminal carboxyl group increases.

  Many polyester resins with a small amount of terminal carboxyl groups have been proposed in order to suppress decomposition by heat, water, and water vapor. However, long-term decomposition suppression was insufficient only by reducing the amount of terminal carboxyl groups.

  Therefore, a method of suppressing the molecular motion at high temperature by increasing the glass transition temperature of the resin by making the polymer chain stiff is also used. In this case, however, the solvent solubility of the resin is reduced or the heat at normal temperature is reduced. In the pressure bonding, since the fluidity of the resin is low, the adhesion to the base material may not be exhibited, and there remains a problem as a paint or an adhesive.

  In recent years, 1,4: 3,6-dianhydro-D-sorbitol (hereinafter referred to as “isosorbide”) is a glycol component having an effect of increasing the glass transition temperature of a resin by copolymerizing with polyester and improving heat resistance. Is attracting attention. Isosorbide is a glycol component that can be easily synthesized from glucose and starch, and can be produced using renewable resources as raw materials, while petroleum resources are feared to be exhausted.

  It is already known that copolymerizing isosorbide has an effect of increasing the heat resistance and durability of the copolymerized polyester resin. Patent Documents 1 and 2 disclose a crystalline resin for molding in which isosorbide is copolymerized, and a polyester resin excellent in heat resistance can be made. In Patent Document 3, a film using polyester copolymerized with isosorbide has transparency and can be used in food packaging and the like. Patent Document 4 discloses a hot fill bottle that makes use of transparency and heat resistance. Patent Document 5 discloses that isosorbide is treated as an aqueous solution to increase the efficiency of polyester polymerization. However, none of the documents describes the catalyst for the copolymerized polyester resin composition, and the copolymerized polyester resin composition is decomposed by the residual catalyst under the condition of being exposed outdoors for a long time, such as for solar cell modules. There is a concern that performance will not develop.

  On the other hand, Patent Document 6 contains 40 mol% or more of aromatic dicarboxylic acid and 3 to 80 mol% of isosorbide, and has a concentration of 10 wt% in a 2-butanone / toluene mixed solvent (mass ratio 1/1) at 25 ° C. A soluble copolyester resin that dissolves in 1 is disclosed and seems to be used for paints and coatings with high heat resistance. However, although several types of polyester resins copolymerized with isosorbide are disclosed in Patent Document 6, the number average molecular weight, glass transition temperature, and solubility in two specific solvents are only shown. Although heat resistance and durability assumed to be used for outdoor use are not evaluated at all, Sn and Ti are used in combination in the examples, and the total metal amount of Sn and Ti greatly exceeds 150 ppm, It can be easily imagined that it is not suitable for outdoor use. Similarly, Patent Documents 1 to 5 do not describe a catalyst for the copolymerized polyester resin composition, and the total metal amount in the examples exceeds 150 ppm.

Japanese Patent No. 3413640 Japanese Patent No. 3399465 Special table 2007-508812 Special table 2007-504352 gazette JP 2006-506485 A JP 2010-95696 A

  Conventionally, as a measure for improving the durability of the copolyester resin, improvement of heat resistance by increasing the glass transition temperature of the resin has been proposed as described in the above patent document. However, applications used outdoors, such as solar cell modules, are exposed to high temperatures for a long time. In addition, there is an increasing demand for long-term thermal stability that can withstand high-level and long-term heat generation by improving the output of electronic devices and solar cell modules. Therefore, it was thought that sufficient durability could not be achieved only by improving the conventional heat resistance. Furthermore, in recent years, the environment exposed to the outdoors has become more severe, and a copolyester resin composition used for solar cell backside sealing or electrical insulation has been proposed in the above patent document. With such heat resistance, sufficient durability may not be obtained. Moreover, in order to improve heat resistance, the method of raising a glass transition temperature may not satisfy physical properties, such as adhesiveness.

  In view of the above problems, an object of the present invention is to provide a copolyester resin having long-term thermal stability and extremely high heat resistance.

  As a result of intensive studies to solve the above problems, the present inventor senses that the residual metal element of the polyester affects thermal degradation and hydrolysis, and makes the amount of the residual metal element extremely low. Thus, the present invention has been found as an effect of exhibiting excellent long-term heat resistance as an outdoor application such as for sealing the back surface of a solar cell. That is, the configuration of the present invention is as follows.

  The gist of the present invention is as follows.

[1] A copolyester resin comprising a dicarboxylic acid component and a glycol component, comprising 3 mol% or more of isosorbide as a glycol component and satisfying the following requirement (1).
(1) The total metal element content is 150 ppm or less with respect to the mass of the polyester resin.

[2] The copolyester resin according to [1], which further satisfies the following requirements (2) and (3).
(2) The phosphorus element content is 100 ppm or less with respect to the mass of the polyester resin. (3) The TODΔ reduced viscosity represented by the following formula is 0.03 dl / g or less (TODΔ reduced viscosity) = (heat Reduced viscosity before oxidation test)-(Reduced viscosity after thermal oxidation test)
(Thermal oxidation test)
A polyester resin sample is freeze-pulverized to a powder of 100 mesh or less, and vacuum-dried at 70 ° C. for 12 hours and 1 Torr or less. 0.3 g of this is weighed, put into a glass test tube, and heat-treated at 200 ° C. for 60 minutes under air.

[3] The copolymerized polyester resin according to [1] or [2], wherein the catalyst during polymerization of the copolymerized polyester is an aluminum compound and a phosphorus compound.

[4] The copolyester resin according to any one of [1] to [3], which has a glass transition temperature of 70 ° C. or lower.

[5] A paint using the copolyester resin according to any one of [1] to [4].

[6] A coating agent using the copolyester resin according to any one of [1] to [4].

[7] An adhesive using the copolymer polyester resin according to any one of [1] to [4].

  The copolyester resin of the present invention is excellent in long-term thermal stability. Therefore, it is useful as a constituent member for solar cell applications used outdoors.

  The copolymerized polyester resin of the present invention contains a catalyst (metal element) in the copolymerized polyester, and is a kind of composition. However, since the catalyst is a trace amount, it is expressed as “resin”. The copolymer polyester resin of the present invention is characterized in that the total metal element content is 150 ppm or less with respect to the mass of the polyester resin. When a lot of metals are contained in the polyester, the thermal decomposition reaction of the polyester is accelerated at a high temperature, which may cause thermal degradation of the polyester. Therefore, in the present invention, the content of the metal element is set to 150 ppm or less from the viewpoint of maintaining the long-term thermal stability of the copolyester resin. Furthermore, the content of the metal element is preferably 100 ppm or less, more preferably 80 ppm or less, and further preferably 50 ppm or less. The content of the metal element is preferably small from the viewpoint of reducing the thermal deterioration of the copolyester resin. However, in order to accelerate the polymerization reaction during the production of the polyester, a transition metal or a typical one is used as a catalyst within the concentration range. It is desirable to add a metal element. Therefore, the lower limit of the content of the metal element is preferably 1 ppm or more, more preferably 5 ppm or more, and further preferably 10 ppm or more. From the viewpoint of polyester productivity, it is desirable to select an appropriate catalyst type as described later in order to achieve sufficient catalytic activity while being within the above-mentioned content range.

  The copolymerized polyester resin of the present invention is mainly composed of a dicarboxylic acid component and a glycol component, and is obtained by copolymerizing three or more functional components as necessary.

  The type of dicarboxylic acid used in the copolymerized polyester resin of the present invention is not particularly limited, but from the viewpoint of heat resistance, the copolymerization ratio of the aromatic dicarboxylic acid to the total polyvalent carboxylic acid component is 20 mol% or more. Is preferably 30 mol% or more, more preferably 40 mol% or more, and may be 100 mol%. When the proportion of aromatic dicarboxylic acid decreases and the proportion of aliphatic dicarboxylic acid increases, the ester group consisting of aliphatic dicarboxylic acid and glycol component decomposes by heat and moisture, and the resulting copolyester resin is heat resistant. Inferior in resistance to hydrolysis and may not be suitable for outdoor use.

  Examples of the aromatic dicarboxylic acid copolymerized with the copolymerized polyester resin of the present invention include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 4,4′-dicarboxybiphenyl, and 5-sodium sulfoisophthalic acid. It is done. Of these, terephthalic acid and isophthalic acid are preferably used in order to obtain heat resistance and hydrolysis resistance.

  Examples of other polycarboxylic acids copolymerized with the copolymerized polyester resin of the present invention include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 2,5-norbornene. Alicyclic dicarboxylic acids such as dicarboxylic acid and tetrahydrophthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, octadecanedioic acid, fumaric acid, maleic acid And aliphatic dicarboxylic acids such as itaconic acid, mesaconic acid, citraconic acid and dimer acid.

  Isosorbide is copolymerized in the copolymerized polyester resin of the present invention. Isosorbide has a rigid alicyclic structure as shown in (Formula 1). Since isosorbide is a secondary alcohol, it is less reactive than a primary alcohol and tends to remain at the end of the polymer. When the polymer terminal becomes an isosorbide residue, the secondary hydroxyl group having low reactivity becomes the polymer terminal, and the polymer chain near the polymer terminal becomes rigid, so that the polymer main chain is hardly subjected to back-biting. In addition, since the isorubide residue copolymerized inside the polymer main chain is three-dimensionally bulky, the neighboring ester bond portion is less susceptible to nucleophilic attack, and the degradation of the polymer chain is suppressed. Thus, since isosorbide is used as a copolymerization component, decomposition of the copolymerized polyester resin is suppressed, so that it is a preferred copolymerization component as a resin for outdoor use that requires heat resistance. Isosorbide can be easily obtained from sugars and starch. For example, isosorbide can be obtained by hydrogenating D-glucose and performing a dehydration reaction.

  The copolymerization ratio of isosorbide used in the copolymerized polyester resin of the present invention needs to be 3 mol% or more, preferably 5 mol% or more, based on the total polyhydric alcohol component. If it is less than 3 mol%, there is almost no effect of increasing the heat resistance, which is not preferable. On the other hand, since isosorbide has low reactivity, increasing the copolymerization amount tends to increase the polymerization time, which is disadvantageous in terms of production cost. Therefore, the copolymerization amount of isosorbide is preferably less than 60 mol%, and more preferably less than 55 mol%.

  Other glycol components used in the copolymerized polyester resin of the present invention are not particularly limited, but ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1,3-propanediol 1,10-decanediol, dimethyloltricyclodecane, diethylene glycol, triethylene glycol and other aliphatic glycols, bisphenol A, bisphenol S, bisphenol C, bisphenol Z, bisphenol AP, ethylene oxide addition of 4,4'-biphenol Or propylene oxide adduct 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, alicyclic glycols such as 1,4-cyclohexane dimethanol, polyethylene glycol, polypropylene glycol, and the like.

  The copolymerized polyester resin of the present invention can be copolymerized with a trifunctional or higher functional carboxylic acid or a trifunctional or higher functional alcohol component as required for appropriate flexibility and improved adhesion. The copolymerization ratio of the tri- or higher functional monomer is suitably about 0.2 to 5 mol% with respect to the total carboxylic acid component or total glycol component. If the copolymerization ratio of the trifunctional or higher monomer is too low, the effect of copolymerization is not exhibited, and if the copolymerization ratio is too high, gelation may be a problem. Tri- or higher functional carboxylic acids include trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid, trimesic acid and other aromatic carboxylic acids, 1, 2, Examples include aliphatic carboxylic acids such as 3,4-butanetetracarboxylic acid. Examples of the tri- or higher functional alcohol component include glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, and sorbitol.

  Furthermore, you may add hydroxycarboxylic acid, lactones, monocarboxylic acid, and monoalcohol as a copolymerization component to the copolymerization polyester resin of this invention. Examples of hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, o-hydroxybenzoic acid, lactic acid, glycolic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyiso Examples include butyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, and 10-hydroxystearic acid. . Examples of lactones include β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, and the like. Examples of monocarboxylic acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane acid, 4-hydroxyphenyl stearic acid. Examples of the monoalcohol such as acid include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, 2-phenoxyethanol and the like.

  The polymerization method of the copolyester resin includes a transesterification method using a diester carboxylic acid component and a glycol component as starting materials, and a direct esterification method using a dicarboxylic acid component and a glycol component as starting materials. In the transesterification method, a catalyst such as Zn, Ca, Mg, etc. is added at the time of transesterification in order to ensure productivity, so the concentration range may not be satisfied. Therefore, the polyester polymerization method in the present invention is a direct esterification method. Is preferred.

  As described above, since isosorbide has a secondary hydroxyl group and is inferior in reactivity, oligomer physical properties before polycondensation are important to ensure reactivity with a small amount of metal. Specifically, it is preferable to carry out esterification without a catalyst, add a catalyst after esterification, homogenize by stirring, and then enter the polycondensation step at a stage where the oligomer acid value is 100 eq / ton or more. When the oligomer acid value is 100 eq / ton or more, in addition to the catalytic activity of the metal, the proton of the oligomer acts as a polycondensation catalyst to ensure productivity. The oligomer acid value is preferably 200 eq / ton or more, and more preferably 300 eq / ton or more. In terms of proton catalytic ability, the higher the oligomer acid value, the better. However, when the oligomer acid value exceeds 600 eq / ton, polymerization may not proceed due to poor esterification, and the molecular weight may not increase.

  The polymerization catalyst for polymerizing the copolymerized polyester resin of the present invention is preferably not a heavy metal from the viewpoint of environmental load, and more preferably an aluminum compound from the viewpoint of polymerization activity and polyester physical properties.

  As the aluminum and / or aluminum compound, known aluminum compounds can be used in addition to metal aluminum.

  Specific examples of aluminum compounds include carboxylates such as aluminum formate, aluminum acetate, basic aluminum acetate, aluminum propionate, and aluminum oxalate; inorganic acid salts such as aluminum chloride, aluminum hydroxide, and aluminum hydroxide chloride; Aluminum alkoxide such as aluminum methoxide, aluminum ethoxide, aluminum iso-propoxide, aluminum n-butoxide, aluminum t-butoxide, aluminum chelate compounds such as aluminum acetylacetonate, aluminum acetylacetate, trimethylaluminum, triethylaluminum, etc. Examples thereof include organoaluminum compounds and partial hydrolysates thereof, and aluminum oxide. Of these, carboxylates, inorganic acid salts and chelate compounds are preferred, and among these, aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride and aluminum acetylacetonate are particularly preferred.

  However, the aluminum compound alone has a low polymerization activity, and in order to ensure productivity, it is necessary to add 150 ppm or more to all constituent units of carboxylic acid components such as polyester dicarboxylic acid and polycarboxylic acid. Therefore, in order to control the total metal element content to 150 ppm or less with respect to the polyester, it is preferable to add a phosphorus compound as a promoter for the purpose of increasing the polymerization activity.

  In this invention, it is preferable that the density | concentration of the phosphorus compound which should be used as said promoter is 100 ppm or less with respect to the mass of a polyester resin as phosphorus element content. When the phosphorus element content with respect to the polyester exceeds the above range, the phosphorus compound may be incorporated into the main chain of the polyester in the polymerization reaction of the polyester, and the durability of the polyester may decrease. The phosphorus element content relative to the polyester is more preferably 95 ppm or less, and even more preferably 90 ppm or less. When used as the cocatalyst, the polyester element content is preferably 1 ppm or more and more preferably 3 ppm or more for the purpose of increasing the polymerization activity. In addition, although the kind and the addition amount of the preferable phosphorus compound which should be used in this invention are mentioned later, it displays as an addition amount with respect to all the structural units of a carboxylic acid component as the addition amount of a phosphorus compound in that case.

  The phosphorus compound used as the co-catalyst is not particularly limited, but it is preferable to use one or two or more compounds selected from the group consisting of phosphonic acid compounds and phosphinic acid compounds because the effect of improving catalytic activity is great. Among these, when one or two or more phosphonic acid compounds are used, the effect of improving the catalytic activity is particularly large and preferable. Especially, the phosphorus compound which has a phenol part in the same molecule from the point of improving the thermal oxidation stability of polyester is especially preferable.

  The copolyester resin of the present invention is, as a phosphorus compound containing a phenol moiety used as a cocatalyst, specifically 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ethyl, 3,5- Methyl di-tert-butyl-4-hydroxybenzylphosphonate, isopropyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, phenyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, Octadecyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, lithium [3,5-di-tert-butyl-4-hydroxy Ethyl benzylphosphonate], sodium [3,5-di-tert-butyl-4-hydride Ethyl xylbenzylphosphonate], sodium [3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid], calcium bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ethyl], calcium Bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid], 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid diethyl, 3,5-di-tert-butyl-4- And diphenyl hydroxybenzylphosphonate. Of these, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate commercially available as Irganox 1222 (manufactured by Ciba Specialty Chemicals) and commercially available as Irganox 1425 (manufactured by Ciba Specialty Chemicals) Especially preferred is calcium bis [3,5-di-tert-butyl-4-hydroxybenzylphosphonate].

  The polyester of the present invention can also use titanium as a catalyst. Even when titanium is used as a catalyst, productivity can be secured with a small amount of addition, but titanium has high catalytic activity, so thermal oxidation degradation of polyester tends to occur under heating, and long-term thermal stability cannot be obtained. There is. Therefore, in the present invention, it is preferable to use a catalyst species other than titanium as the polyester catalyst species.

Since the copolymerized polyester resin of the present invention can be suitably obtained using the above-described catalyst species, the total amount of metal elements relative to the polyester resin can be reduced to 150 ppm or less. Therefore, the polyester resin of the present invention is excellent in thermal oxidation stability and can exhibit long-term thermal stability. The polyester resin of the present invention preferably has a TODΔ reduced viscosity represented by the following formula, which is an index of thermal oxidation stability, of 0.03 dl / g or less.
(TODΔ reduced viscosity) = (reduced viscosity before thermal oxidation test) − (reduced viscosity after thermal oxidation test)
(Thermal oxidation test)
A polyester resin sample is freeze-pulverized to a powder of 100 mesh or less, and vacuum-dried at 70 ° C. for 12 hours and 1 Torr or less. 0.3 g of this is weighed, put into a glass test tube, and heat-treated at 200 ° C. for 60 minutes under air.

  The TODΔ reduced viscosity is more preferably 0.025 dl / g or less, and still more preferably 0.020 dl / g or less. The lower the total metal content, the more advantageous the thermal oxidation stability. However, when the metal content is small, that is, the catalyst amount is small, it is disadvantageous in terms of productivity. Therefore, it is preferable to use a small amount of an aluminum compound and a phosphorus compound as a cocatalyst together to ensure polymerization activity. Further, the phosphorus compound preferably has a phenol moiety. Furthermore, a phosphorus moiety-containing phosphorus compound is particularly preferable because it has an effect of suppressing polyester degradation that decomposes under a radical mechanism under oxygen. In order to enhance this function, it is preferable that the phenol moiety has a hindered phenol skeleton that is sterically and electronically stabilized and expresses more radical trapping ability. The TODΔreduced viscosity is preferably small, and the lower limit is 0.

  When used in outdoor applications where long-term stability is required, it is considered important that the viscosity decrease after leaving the resin at 105 ° C. and 100% RH for 24 hours as an accelerated test is 0.03 dl / g or less. . The viscosity change after being left at 105 ° C. and 100% RH for 24 hours and the TODΔ reduced viscosity are almost the same. Therefore, if the TODΔ reduced viscosity is 0.03 dl / g or less, it can be judged that it is suitable for outdoor use. .

  Moreover, the higher the glass transition temperature of the resin, the more advantageous the thermal oxidation stability. However, when the glass transition temperature is high, it does not dissolve in a general-purpose solvent, which is disadvantageous when used as a paint, coating agent, or adhesive. When dissolved in a general-purpose solvent and used as a polyester solution, the solution concentration is preferably 15 to 50% by mass, and more preferably 15 to 40% by mass. Moreover, as a preferable solvent, at least 1 type or 2 types of mixed solvents which consist of cyclohexanone, 2-butanone, toluene, and ethyl acetate are mentioned. Of these, a mixed solvent of 2-butanone / toluene is generally preferable because of its high solubility, and most preferably has a mass ratio of 8/2 to 2/8. Considering dissolution in these general-purpose solvents, the glass transition temperature of the resin is preferably 70 ° C. or lower, more preferably 60 ° C. or lower, and further preferably 50 ° C. or lower. From the viewpoint of the handleability of the resin, the lower limit of the glass transition temperature is considered to be -20 ° C.

  In order to set the glass transition temperature of the copolyester resin to 70 ° C. or less, as a copolymer component constituting the copolyester resin, the ratio (mol%) of the aromatic dicarboxylic acid component in the total polyvalent carboxylic acid component and The ratio (mol%) of the straight aliphatic glycol component having 6 or more carbon atoms and the linear aliphatic dicarboxylic acid glycol component having 6 or more carbon atoms from the sum of the ratios (mol%) of the isosorbide components in the total polyhydric alcohol components. The value obtained by subtracting the ratio (mol%) is preferably 110 (mol%) or less. This numerical value is preferably 100 (mol%) or less, and more preferably 95 (mol%) or less. The upper limit of this value is 200 (mol%). Since it is necessary to use 20 mol% or more of aromatic dicarboxylic acid from the viewpoint of heat resistance, the lower limit of this value is considered to be -154 (mol%). Furthermore, considering that the lower limit of the glass transition temperature is −20 ° C., the lower limit is considered to be 10 (mol%). That is, the optimum range of this numerical value is 10 to 110 (mol%). Both the aromatic dicarboxylic acid component and the isosorbide component have the effect of increasing the glass transition temperature of the copolyester resin obtained by copolymerization. On the other hand, a linear aliphatic glycol component having 6 or more carbon atoms and a linear aliphatic dicarboxylic acid component have the effect of lowering the glass transition temperature of the copolymerized polyester resin obtained by copolymerization.

  The copolyester resin of the present invention also has an effect of excellent stability when stored in a general-purpose solvent and stored for a long time. In other words, the polyester resin metal catalyst itself or the metal catalyst accelerates the decomposition of the polyester resin, and the oligomer produced by the decomposition causes the polyester solution that was transparent immediately after dissolution to precipitate or become cloudy over time. It is known to be caused by a decrease in sex. The copolymerized polyester resin of the present invention is excellent in storage stability because of its low metal content.

  The number average molecular weight of the copolyester resin of the present invention is preferably 4,000 or more, and more preferably 8,000 or more. A number average molecular weight of less than 4,000 is not preferable because the heat resistance is lowered.

  The copolymer polyester resin of the present invention may further contain a curing agent in order to improve heat and moisture resistance and adhesion strength to the substrate.

  As a hardening | curing agent mix | blended with the copolymerization polyester resin of this invention, an isocyanate compound, an epoxy compound, an acid anhydride, a melamine compound, a phenol resin, etc. are raised. Among these, the isocyanate compound is preferable in that it can be cured at a low temperature, and the use of aliphatic hexamethylene diisocyanate or alicyclic isophorone diisocyanate is preferable in that yellowing with time in outdoor use can be reduced. There are various types of isocyanurates, biurets and adducts, but isocyanurates are preferred.

  The compounding ratio of the copolymerized polyester resin of the present invention and the isocyanate compound is 1 to 20 parts by weight, preferably 5 to 10 parts by weight, based on 100 parts by weight of the copolymerized polyester. If it is 1 part by weight or less, the crosslinking density is too low and there is a possibility of affecting the adhesion and heat-and-moisture resistance. If it is 20 parts by weight or more, the crosslinking density of the coating film is too high and the adhesiveness may be inferior.

  Further, a curing catalyst may be added to increase the reactivity of these curing agents. Examples of the curing catalyst include tin-based and zinc-based other organic metal compounds, amines, Lewis acids, and alkaline compounds.

  In the copolymerized polyester resin of the present invention, a terminal blocking agent such as a carbodiimide compound, an oxazoline compound, or an epoxy compound is added at an arbitrary ratio in order to block a carboxyl group that is generated when decomposition degradation occurs at high temperature and high humidity. You may mix.

  The copolymerized polyester resin of the present invention may contain known additives such as an ultraviolet absorber for imparting weather resistance, an antioxidant for preventing oxidative degradation, a release agent, and a lubricant as necessary. .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In addition, each measured value described in the Example is measured by the following method.

(1) Reduced viscosity (ηsp / c)
It was determined from the solution viscosity at 25 ° C. in a mixed solvent of parachlorophenol / tetrachloroethane = 6/4 (weight ratio).

(2) TODΔReduced Viscosity A polyester resin sample is freeze-pulverized to a powder of 100 mesh or less, vacuum-dried at 70 ° C. for 12 hours and 1 Torr or less, weighed 0.3 g, put into a glass test tube, and air The heat treatment was performed at 200 ° C. for 60 minutes, the reduced viscosity was measured by the same method as described above, and the TODΔ reduced viscosity was calculated from the following formula.
(TODΔ reduced viscosity) = (reduced viscosity before thermal oxidation test) − (reduced viscosity after thermal oxidation test)

(3) Glass transition temperature (Tg)
The copolyester resin vacuum-dried at room temperature was placed in an aluminum pan for DSC, heated at 160 ° C. for 20 minutes, and then cooled with liquid nitrogen. The copolymer polyester resin pretreated as such was measured using DSC2920 manufactured by TA Instruments. Two samples derived from the glass transition in the obtained temperature rise curve observed in the middle of the sample 7.5 mg, heated in the range of −50 to 250 ° C. at 20 ° C./min in a nitrogen atmosphere An intermediate value of the bending point temperature was determined and used as the glass transition temperature (Tg).

(4) Polyester resin composition Determination of the composition and composition ratio of the polyester resin was performed by ¹ H-NMR measurement (proton nuclear magnetic resonance spectroscopy) with a resonance frequency of 400 MHz. The measuring apparatus used was an NMR apparatus 400-MR manufactured by VARIAN, and deuterated chloroform / trifluoroacetic acid = 85/15 (mass ratio) was used as the solvent.

(5) Content of all metal elements in polyester resin sample (ppm)
Phosphorus was determined by the fluorescent X-ray method. The other metals were determined by high-frequency plasma emission analysis and atomic absorption analysis after ashing / dissolving the polymer.

(6) Acid value of oligomer before polycondensation ・ AV (AVo)
An oligomer (OLG) before polycondensation was collected, and the OLG was pulverized and dried under reduced pressure at 70 ° C. for 15 hours or more. About 1 g of the sample was precisely weighed, 20 ml of pyridine was added, and the mixture was boiled and refluxed for 15 minutes for dissolution. After dissolution, 10 ml of pure water was added, allowed to cool to room temperature, and titrated with N / 10-NaOH using phenolphthalein as an indicator. The same operation was performed on a blank without a sample. In addition, when OLG did not melt | dissolve in a pyridine, it carried out in benzyl alcohol.
AVo (eq / ton) was calculated according to the following formula.
AVo = (A−B) × 0.1 × f × 1000 / W
(A = drop constant (ml), B = blank drop constant (ml), f = factor N / 10-NaOH, W = weight of sample (g))

(Preparation of polycondensation catalyst solution)
(Preparation of Irganox 1222 in ethylene glycol)
Irganox 1222 (manufactured by Ciba Specialty Chemicals) was added as a phosphorus compound while adding 2.0 liters of ethylene glycol to a flask equipped with a nitrogen introduction tube and a cooling tube at room temperature and normal pressure and stirring at 200 rpm in a nitrogen atmosphere. 200 g was added. Further, 2.0 liters of ethylene 1 glycol was added, the jacket temperature was changed to 196 ° C., the temperature was raised, and the mixture was stirred under reflux for 60 minutes from the time when the internal temperature reached 185 ° C. or higher. Thereafter, the heating was stopped, the solution was immediately removed from the heat source, and the solution was cooled to 120 ° C. or less within 30 minutes while maintaining the nitrogen atmosphere.

(Preparation of aqueous solution of aluminum compound)
After adding 5.0 liters of pure water to a flask equipped with a cooling tube at room temperature and normal pressure, 200 g of basic aluminum acetate was added as a slurry with pure water while stirring at 200 rpm. Further, pure water was added so as to be 10.0 liters as a whole, and the mixture was stirred at room temperature and normal pressure for 12 hours. Thereafter, the jacket temperature was changed to 100.5 ° C., the temperature was raised, and the mixture was stirred under reflux for 3 hours from the time when the internal temperature reached 95 ° C. or higher. Stirring was stopped and the mixture was allowed to cool to room temperature to obtain an aqueous solution.

(Preparation of ethylene glycol mixed solution of aluminum compound)
After adding an equal volume of ethylene glycol to the aqueous aluminum compound solution obtained by the above method and stirring for 30 minutes at room temperature, the internal temperature is controlled to 80 to 90 ° C., and the pressure is gradually reduced to reach 27 hPa while stirring for several hours. Water was distilled off from the system to obtain an ethylene glycol solution of an aluminum compound at 20 g / l. The peak integration value ratio of ²⁷ Al-NMR spectrum of the obtained aluminum solution was 2.2.

(Preparation of ethylene glycol solution of antimony compound)
Antimony trioxide was dissolved in an ethylene glycol solution to obtain an ethylene glycol solution of 14 g / l antimony trioxide.

(Preparation of aqueous solution of germanium compound)
Germanium dioxide was dissolved in water to obtain an aqueous solution of 8 g / L germanium dioxide.

(Preparation of TMPA ethylene glycol solution)
Trimethyl phosphoric acid (TMPA) was dissolved in an ethylene glycol solution to obtain a 20 g / l TMPA ethylene glycol solution.

(Preparation of 1-butanol solution of TBT)
Tetra-n-butoxy titanium (TBT) was dissolved in 1-butanol to obtain a 1-butanol solution of 68 g / l TBT.

(Preparation of ethylene glycol solution of Co acetate)
Co acetate was dissolved in ethylene glycol to obtain an ethylene glycol solution of 20 g / l Co acetate.

(Preparation of ethylene glycol solution of Mn acetate)
Mn acetate was dissolved in ethylene glycol to obtain an ethylene glycol solution of 20 g / l Mn acetate.

(Preparation of hydroxybutyltin oxide solution)
Hydroxybutyltin oxide was dissolved in ethylene glycol to obtain 20 g / l of hydroxybutyltin oxide in ethylene glycol.

Example 1
High-purity terephthalic acid 185.2 g (1.12 mol), sebacic acid 96.7 g (0.48 mol), isosorbide 28.0 g (0.19 mol), ethylene glycol 141 in a 2-liter stainless steel autoclave with a stirrer .5 g (2.28 mol) and neopentyl glycol 99.6 g (0.96 mol) were charged, the esterification reaction was carried out under a pressure of 0.25 MPa for 150 minutes while raising the temperature to 220 ° C. And oligomer AV (AVo) was measured. Thereafter, an ethylene glycol solution of Irganox 1222 and an ethylene glycol mixed solution of an aluminum compound were added so as to have a predetermined residual amount, and the temperature of the reaction system was gradually lowered while heating up to 270 ° C. over 60 minutes. , 13.3 Pa (0.1 Torr), and polyester polycondensation reaction was further performed at 270 ° C. and 13.3 Pa for 60 minutes. After releasing the pressure, the resin under slight pressure is discharged into cold water in a strand form and rapidly cooled, then held in cold water for 20 seconds, and then cut to obtain a cylinder-shaped pellet having a length of about 3 mm and a diameter of about 2 mm. It was. The properties of this polyester pellet are shown in Table 1.

Example 2
In a 2 liter stainless steel autoclave with a stirrer, 219.3 g (1.13 mol) of dimethyl terephthalate, 111.6 g (0.48 mol) of dimethyl sebacate, 28.3 g (0.19 mol) of isosorbide, ethylene glycol 143 .3 g (2.31 mol), neopentyl glycol 100.9 g (0.97 mol), a predetermined amount of an ethylene glycol solution of Mn acetate prepared as a catalyst was added, and the temperature was raised to 220 ° C. and 180 ° C. under normal pressure. A transesterification reaction was performed for a minute to obtain an oligomer mixture, and oligomer AV (AVo) was measured. Thereafter, polycondensation was performed in the same manner as in Example 1 to obtain pellets. The properties of this polyester pellet are shown in Table 1. Since Mn was contained as a transesterification catalyst, the thermal oxidation stability was inferior to that of Example 1.

Example 3
Polycondensation was performed in the same manner as in Example 1 except that the esterification time was 240 minutes. Since the oligomer AV (AVo) was low, the reduced viscosity was low, and it could not be formed into a strand shape and pellets could not be obtained. The properties of this polyester are shown in Table 1.

Example 4
Pellets were obtained in the same manner as in Example 1 except that a predetermined amount of the prepared Co acetate was added after esterification. The properties of this polyester pellet are shown in Table 1.

Example 5
The polycondensation was carried out for 60 minutes in the same manner as in Example 1 except that Irganox 1222 was changed to a 1-butanol solution of TBT prepared from an ethylene glycol solution of an aluminum compound and an ethylene glycol mixed solution of aluminum compound. Ethylene glycol was added, and after stirring for 10 minutes, pellets were obtained in the same manner as in Example 1. The properties of this polyester pellet are shown in Table 1.

Example 6
Pellets were obtained in the same manner as in Example 5 except that TMPA ethylene glycol was not added. The properties of this polyester pellet are shown in Table 1.

Examples 7-12
According to the polymerization method of Example 1, except that the types and blending ratios of the raw materials were changed, copolymer polyester resin examples 7 to 12 were produced. The composition of the obtained resin, the amount of residual metal, and physical properties are shown in Table 1. They showed good thermal oxidation stability.

Comparative Example 1
Pellets were obtained in the same manner as in Example 2, except that the Irganox 1222 ethylene glycol solution and the aluminum compound ethylene glycol mixed solution were changed to an antimony trioxide ethylene glycol solution and Co acetate ethylene glycol solution. The physical properties are shown in Table 1. Since the metal residual amount exceeds 500 ppm, it is understood that the thermal oxidation stability is poor and the TODΔreduced viscosity is 0.03 or more, which is not suitable for outdoor use.

Comparative Example 2
Pellets were obtained in the same manner as in Example 1 except that the Irganox 1222 ethylene glycol solution and the aluminum compound ethylene glycol mixed solution were changed to an antimony trioxide ethylene glycol solution and Co acetate ethylene glycol solution. The physical properties are shown in Table 1. Since the residual metal amount is 320 ppm, the thermal oxidation stability is poor, and the TODΔreduced viscosity is 0.03 or more, indicating that the resin is not suitable for outdoor use.

Comparative Example 3
Pellets were obtained in the same manner as in Example 1 except that the Irganox 1222 ethylene glycol solution and the aluminum compound ethylene glycol mixed solution were changed to an aqueous solution of germanium dioxide. The physical properties are shown in Table 1. Since the residual metal amount is 260 ppm, the thermal oxidation stability is poor and the TODΔreduced viscosity is 0.03 or more, indicating that the resin is not suitable for outdoor use.

Comparative Example 4
Polycondensation was carried out for 60 minutes in the same manner as in Comparative Example 3, then, the pressure was returned from the reduced pressure to normal pressure, TMPA ethylene glycol was added, and after stirring for 10 minutes, pellets were obtained in the same manner as in Comparative Example 3. Since the metal is deactivated by the phosphorus compound, the thermal oxidation stability is better than that of Comparative Example 3, but since the TODΔreduced viscosity is 0.03 or more, the resin may not be suitable for outdoor use. I understand.

Comparative Example 5
Pellets were obtained in the same manner as in Example 1 except that the ethylene glycol solution of Irganox 1222 and the ethylene glycol mixed solution of the aluminum compound were changed to an ethylene glycol solution of hydroxybutyltin oxide and a 1-butanol solution of TBT. The physical properties are shown in Table 1. Since the amount of remaining metal is 540 ppm, it can be seen that the thermal oxidation stability is poor and the TODΔreduced viscosity is 0.03 or more, which is not suitable for outdoor use.

Comparative Example 6
Pellets were obtained in the same manner as in Example 1 except that the addition amount of the ethylene compound mixed solution of the aluminum compound was increased and the remaining amount was changed to 300 ppm. The physical properties are shown in Table 1. Since the residual metal amount is 300 ppm, the thermal oxidation stability is poor, and the TODΔreduced viscosity is 0.03 or more, indicating that the resin is not suitable for outdoor use.

  The copolyester resin of the present invention is excellent in long-term thermal stability. Therefore, it is useful as a component for solar cell applications used outdoors and has a great industrial utility value.

Claims (7)

A copolyester resin comprising a dicarboxylic acid component and a glycol component, comprising 3 mol% or more of isosorbide as a glycol component and satisfying the following requirement (1).
(1) The total metal element content is 150 ppm or less with respect to the mass of the polyester resin. The copolyester resin according to claim 1, further satisfying the following requirements (2) and (3).
(2) The phosphorus element content is 100 ppm or less with respect to the mass of the polyester resin. (3) The TODΔ reduced viscosity represented by the following formula is 0.03 dl / g or less (TODΔ reduced viscosity) = (heat Reduced viscosity before oxidation test)-(Reduced viscosity after thermal oxidation test)
(Thermal oxidation test)
A polyester resin sample is freeze-pulverized to a powder of 100 mesh or less, and vacuum-dried at 70 ° C. for 12 hours and 1 Torr or less. 0.3 g of this is weighed, put into a glass test tube, and heat-treated at 200 ° C. for 60 minutes under air.   The copolymer polyester resin according to claim 1 or 2, wherein a catalyst at the time of copolymerization polyester polymerization is an aluminum compound and a phosphorus compound.   The copolyester resin according to any one of claims 1 to 3, which has a glass transition temperature of 70 ° C or lower.   The coating material using the copolyester resin in any one of Claims 1-4.   The coating agent using the copolyester resin in any one of Claims 1-4. The adhesive agent using the copolyester resin in any one of Claims 1-4.