JPH04202324A - Production of polyester imide and wire enamel - Google Patents

Abstract

PURPOSE:To obtain the subject compound containing isocyanurate bond in the molecular structure without using expensive isocyanurate compound by reacting a specific polyester with an imide-forming component under heating. CONSTITUTION:The objective compound is produced by reacting (A) a polyester produced by reacting a polyhydric alcohol (preferably ethylene glycol or propylene glycol), a polyethylene terephthalate and a cyanuric acid (isomer) with (B) an imide-forming component (preferably trimellitic anhydride and 4,4-diaminodiphenylmethane) under heating.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a novel method for producing polyesterimide and wire enamel using the same. This invention relates to a new manufacturing method and wire enamel using the same.

(Prior Art) Polyester resins have been prized as general-purpose wire enamels for their good electrical, thermal, and mechanical properties. Recently, with the miniaturization and higher performance of electrical equipment, the performance required of wire enamel has also increased.As a result, there is a demand for wire enamel using polyesterimide as a polyester resin with high heat resistance and a good balance of properties. It has increased.

As a method of imparting heat resistance to polyesterimide, a method of introducing isocyanurate bonds into the molecular structure using tris (2-hydroxyethyl) isocyanurate (hereinafter abbreviated as THE I C) as a polyhydric alcohol has been patented in the UK. It was proposed in Box 1,082°181 and has been implemented for at least the past 20 years.

THEIC, the raw material for heat-resistant polyesterimide, is produced on a commercial scale by the reaction of cyanuric acid and ethylene oxide, and to avoid accidents that may occur due to the use of ethylene oxide, TI (E I
There are very limited places to manufacture THE I C, and therefore there are only a limited number of factories around the world that manufacture THE I C.
It is also expensive.

For this reason, there has been a strong desire to develop an economical method for producing heat-resistant polyesterimide having an isocyanurate bond in its molecular structure.

Conventionally, in the production of polyester, there has been a method of directly using cyanuric acid and reacting it with other reaction components all at once, as described in Japanese Patent Publication No. 35-18,676, Japanese Patent Publication No. 47-29.399,
This is suggested and proposed in U.S. Patent No. 4,849,465 and the like. However, application development of polyesterimide, which emphasizes heat resistance and a balance of properties, has not yet been achieved.

(Problems to be Solved by the Invention) Therefore, the object of the present invention is to provide a new method for producing heat-resistant polyesterimide having an isocyanurate bond in its molecular structure without using THEIC in the production of polyesterimide, and to provide a method for producing heat-resistant polyesterimide having an isocyanurate bond in its molecular structure. The purpose of the present invention is to provide wire enamel using the following methods.

(Means for solving the problem) These various methods include polyester obtained by reacting polyhydric alcohol, polyethylene terephthalate (hereinafter abbreviated as PET), and cyanuric acid or its isomer (hereinafter abbreviated as cyanuric acid). This is achieved by a method for producing polyester imide, which is characterized by subjecting imide-forming components to a heating reaction.

Furthermore, it can also be achieved with a wire enamel containing polyesterimide obtained by the above method.

(Function) That is, as a method for introducing isocyanurate bonds into the molecular structure of polyesterimide, instead of THEIC,
This is achieved by a method for producing a polyesterimide, which is characterized in that a polyester obtained by heating and reacting cyanuric acid with a polyhydric alcohol and an imide-forming component are heated and reacted.

In order to develop an economical method for producing polyesterimide having an isocyanurate bond in its molecular structure, the present inventors discovered that in the process of researching a method for directly using cyanuric acid as a raw material, When cyanuric acid was added to the commercially practiced method of thermally reacting polyester-forming components and imide-forming components all at once, it was difficult to obtain a good reaction product due to problems in the uniformity of the reaction. However, it was found that it was difficult to obtain good properties as a wire enamel.

The reasons for this are that when the polyester-forming component and the imide-forming component are heated together, (1) cyanuric acid comes into direct contact with the aromatic diamine in the alkaline component, that is, the imide-forming component; THE
Unlike IC, it does not have a melting point and does not dissolve into the reaction system if unreacted, so this is a phenomenon well known to those skilled in the art that occurs when the reaction system is caused by an amic acid generated from aromatic tricarboxylic acid and aromatic diamine, which are imide-forming components. (3) When cyanuric acid comes into contact with water at high temperatures, it tends to cause side reactions as shown in the following equation, In the case of reaction, there are many opportunities for contact with water, so it is presumed that the decomposition of cyanuric acid is large, making it difficult to obtain the desired molecular structure.

/′. \HN Nil +4.5H20-i, 5(NH,l)2 CO3
÷1.5CO2 Therefore, the present inventors conducted intensive research on improvement measures such as reducing the chances of contact between cyanuric acid and water as much as possible, and performing the esterification reaction with cyanuric acid in as homogeneous a system as possible. As a result, the combination of (1) carrying out the reaction process in two steps, polyesterification and imide esterification with the addition of an imide-forming component, and (2) using PET as the aromatic carboxylic acid feedstock, resulted in the production of wire enamel. It has been found that a good polyesterimide with excellent properties can be produced.

In the production method of the present invention, only cyanuric acid generates water in the polyesterification stage, and there is no influence from other components, and in the imide esterification stage, cyanuric acid is almost completely incorporated into the polymer skeleton. Because of this, the reaction proceeds stably and a good polyesterimide resin is provided.

That is, the present invention relates to the synthesis of heat-resistant polyesterimide having an isocyanurate bond in its molecular structure.
The present invention relates to a new method for producing polyesterimide and wire enamel, which is characterized in that a polyester obtained by thermally reacting T, a polyhydric alcohol, and cyanuric acid, which is a crude raw material for THEIC, and an imide-forming component are thermally reacted. .

The method for producing heat-resistant polyesterimide of the present invention takes the following embodiments, but these are only -
It should be understood that this is an example, and the order of addition of reaction components and the reaction temperature and characteristics of each step are not limited to the example and can be changed in various ways.

For example, when reacting the polyester and the imide-forming component in these embodiments, it is also possible to add glycol to the polyhydric alcohol to lower the viscosity of the reaction system, if necessary. Naturally, the polyhydric alcohol used is accounted for in the overall composition.

In addition, in these embodiments, common solvents such as cresylic acid and N-methylpyrrolidone are used as reaction solvents, and hydrocarbons are used to quickly remove produced water from the reaction system by azeotropic distillation. I can do something.

Further, in these embodiments, it is possible to use a catalyst to accelerate the reaction, examples of catalysts that can be used include titanate esters such as tetrabutyl titanate, tetracresyl titanate, and dibutyltin oxide, There are tin compounds such as stannath oxide, and organic acid metal salts such as zinc acetate, lead acetate, and zinc propionate, and two or more of these can be used in combination. Usually, it is used at an addition level of less than 2% by weight relative to the total number of reactants.

(1) PET, polyhydric alcohol and cyanuric acid are charged into a reaction vessel in the presence or absence of a catalyst, and heated to 150°C.
Above, preferably by heating at 180 to 270°C, PET
Ester decomposition and esterification with cyanuric acid proceed in parallel to obtain polyester. Next, add this hatch to 15
Cool to below 0'C, add imide-forming components, and heat again at 15°C.
A heating reaction is carried out at 0 to 2700C to obtain a predetermined polymerized polyesterimide.

(2) PET and polyhydric alcohol are charged into a reaction vessel in the presence or absence of a catalyst, and heated at 150 to 220°C to deesterify PET.

Cyanuric acid is added to this batch at a temperature below 200°C, and the reaction is heated preferably at 180 to 270°C.
Obtain polyester. The batch is then cooled to below 150°C, imide-forming components are added, and the temperature is again reduced to 150-270°C.
A heating reaction is carried out at °C to obtain a predetermined polymerized polyesterimide.

(3) Charge a part of PET and a polyhydric alcohol into a reaction vessel in the presence or absence of a catalyst,
PET is deesterified by heating at °C. This batch is brought to a temperature of 200 DEG C. or lower, cyanuric acid, the remainder of PET and, if necessary, an additional polyhydric alcohol are added, and the mixture is heated and reacted preferably at 180 DEG to 270 DEG C. to obtain a polyester. Next, this batch is cooled to 150°C or lower, an imide-forming component is added thereto, and the mixture is heated and reacted again at 150 to 270°C to obtain a predetermined polymerized polyester imide. In addition, in these embodiments, the preparation of the reaction solvent is as follows:
This can be done either at the beginning or during the reaction.

The preferred degree of polymerization of the polyester for blending the imide-forming component is such that at least cyanuric acid crystals have almost or completely disappeared from the reaction system. The condition is such that the acid value of the solid content is 100 or less, more preferably 20 or less.

The progress of the reaction as a polyesterimide can be controlled by monitoring the amount of recovered water, the viscosity of the reactant, or the acid value of the solid content. The reactant is dissolved in a solvent such as cresol, and the viscosity is measured at a predetermined concentration and temperature. The set value of the reaction stopping viscosity differs depending on the composition, but at least the reaction continues until the crystals of the reaction components disappear from the reaction system and the reaction system becomes uniform, and the liquid dissolved in a solvent such as cresol becomes completely stable even after cooling. It is necessary.

Polyhydric alcohols that can be used in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, -1, Examples include 6-hexanediol, N,N-bishydroxyethyl-5,5-monodimethylhydantoin, cyclohexane dimetatool, glycerin, diglycerin, and preferably ethylene glycol or propylene glycol.

Cyanuric acid has a tautomeric relationship as shown in the following formula, and when heated to 150° C. or higher, it assumes the structure of isocyanuric acid. Therefore, when blending, any structure of the isomers can be used, and recently there are powder and granule shapes, which can be used depending on the equipment.

j11 10\ -1→ 10\ -→ Isocyanuric acid (triketo type) (diketo type) Cyanuric acid (monoketo type) (trienol type) PET has recently been produced in large quantities and is used for forming bottles and films. Supplied in pellet form. For handling purposes such as preventing blocking during storage, it is preferable to have a degree of polymerization with an intrinsic viscosity (IV) of 0.45 or higher;
Alternatively, scraps from film formation, or even fiber scraps, etc., can also be used, and are more preferably used in terms of cost.

As imide-forming components, aromatic tricarboxylic acid or its anhydride and aromatic diamine are blended, but examples of aromatic tricarboxylic acid or its anhydride include trimellitic acid or its anhydride, 3゜4.4'-benzophenone tricarboxylic acid, and aromatic tricarboxylic acid or its anhydride. Among them, trimellitic acid or its anhydride is most preferred from the viewpoint of versatility.

Aromatic diamines include 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3
'-diethyl-4,4'-diaminodiphenylmethane,
4.4-diaminodiphenyl ether, 4,4'-diaminodiphenylcyclohexane, 4,4'-diaminodiphenylsulfone, 1,4-phenylenediamine,
Although 1,3-phenylenediamine and the like are used, 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl ether are preferably used.

Imide forming components For example, trimellitic acid or its anhydride and aromatic diamine react to produce a carboxylic acid containing an imide bond, but the actual molar ratio of both components is 1 part amine to 1 part trimellitic acid. Or its anhydride 2. Both components produce a diimidodicarboxylic acid with the following structural formula:

O (The example formula is when the diamine is 4,4'-diaminodiphenylmethane) From this, aromatic tricarboxylic acid or its anhydride is calculated as monovalent when calculating the OH/C0OH ratio. The blending ratio of aromatic tricarboxylic acid or its anhydride is preferably as described above, but diamine 1
A blending range of about 1.9 to 2.1 mol of aromatic tricarboxylic acid or its anhydride per mol is acceptable. When the diamine is in excess, some amide bonds are formed, and when the aromatic tricarboxylic acid or its anhydride is in excess, it reacts with glycol as a trivalent carboxylic acid to form a triester.

These diimide dicarboxylic acids are generally produced during the production of polyesterimide by blending aromatic tricarboxylic acids or their anhydrides with imide raw materials such as aromatic diamines, but they can also be synthesized separately and produced as diimide dicarboxylic acids. It is equally possible to blend dicarboxylic acids prepared in advance.

In this case, an aromatic diisocyanate suitable for each aromatic diamine, such as diphenylmethane diisocyanate, can also be used as the imide-forming component.

Is it possible to change the Kura G ratio of imide in polyester imide or change the properties of polyester imide?
For the purpose of h, an imide content of 10% or more, particularly 20 to 40%, is preferable. The calculation method is described in British Patent No. 1.
No. 082.181 and is a method well known to those skilled in the art.

In the present invention, the ratio of hydroxyl groups/acid groups used during polyester imide production is determined through polyester synthesis and imide esterification. The ratio of diimidodicarboxylic acid produced from terephthalic acid and imide-forming components to the total acid groups is 1.2 to 2.0.

If it is less than 1.2, the viscosity of the reaction system will be too high and the reaction will not progress smoothly, and the molecular weight of the reaction product will be too small, making it difficult to stabilize the coating as a wire enamel and not only resulting in poor curing. I can't.

The present invention also provides a method for introducing isocyanurate bonds into the molecular structure of polyesterimide using conventional THE
Cyanuric acid is used in place of IC to react with the hydroxyl groups liberated by decomposition of polyhydric alcohol and PET.
The ratio of the acid groups of cyanuric acid to the total acid groups of diimide dicarboxylic acid produced from cyanuric acid, terephthalic acid constituting PET, and imide forming components is 20 to 20.
If it is less than 20%, the heat resistance will be poor and the stability of the paint as a wire enamel will be poor. If it exceeds 60%, the viscosity of the reaction system will be high, making it difficult to control the reaction, and the cured film will be difficult to control. It is brittle and difficult to obtain good characteristics. Further, in practical terms, a preferable range is 40 to 55%.

The polyesterimide produced by the above method can be collected in solid or semi-solid form, and these resins are finally dissolved in a suitable solvent and used as wire enamel. Also, instead of collecting in solid or semi-solid form, these resins are dissolved in the same solvent as the wire enamel forming solvent at the end of the reaction. In this case, cool the reaction system to below 240°C, add the solvent directly to the reaction vessel, and
Mix evenly. Then, it can be transferred to another container or cooled to 150° C. or less in the same container, and mixed with an additional solvent to adjust the solid content and viscosity to a target range to form a wire enamel.

Solvents that can be used as wire enamel forming solvents include:
N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylcaprolactam, commercially available cresylic acids, m- and p-cresol mixtures, acetophenone, methylbenzoate, γ-butyrolactone, glycol ethers,
Although aliphatic dicarboxylic acid lower alkyl esters such as dimethyl adipate can be used, commercially available cresylic acids are generally preferred. Additionally, aromatic hydrocarbons such as aliphatic and aromatic naphthas and xylene can be used in combination as diluents.

The polyester imide wire enamel thus prepared can be used as it is for producing enameled wire, but in order to obtain better properties, the curing agent and modifier used in conventional polyester imide wire enamel can be mixed and used. For example, organic acid metal salts such as zinc naphthenate and zinc octylate, and titanate esters such as tetraisopropyl titanate, tetrabutyl titanate, tetracresyl titanate, triethanolamine titanate, etc. can be used as curing catalysts, and the amount of blending is 0.5 to 15% by weight, especially 1 to 15% by weight based on the imide resin content
A range of 10% by weight is preferred.

Modification can be achieved by blending up to 20% by weight of cresol formaldehyde resin in terms of solid content with respect to the polyesterimide resin content.

Furthermore, instead of the cresol formaldehyde resin, a phenol formaldehyde resin, a xylenol formaldehyde resin, or a mixture formaldehyde resin of phenols can be used.

Modification can be achieved by blending a stabilized polyisocyanate in an amount of up to 20% by weight in terms of solid content with respect to the polyesterimide resin content. Examples of the stabilized polyisocyanate include a phenol-blocked product of diphenylmethane diisocyanate, a phenol-blocked product of 3 moles of diphenylmethane diisocyanate or an adduct of toluylene diisocyanate and trimethylolpropane, and a cyclic trimer of phenols of toluylene diisocyanate. There are blocks. From the viewpoint of heat resistance, a cyclic trimer of toluylene diisocyanate is preferable, and a commercially available product is Desmodur CT (D
esmodur CT) and Mobay Chemical Company's Mondur SH (Mondur SH) can be used equivalently.

(Example) Examples are shown below to explain the present invention in more detail. Note that the examples shown below are shown as preferred specific examples of the present invention, and the present invention is not limited to these examples, and various changes and modifications can be made within the spirit and scope of the present invention. It will be clear to those skilled in the art that

In the examples, the following abbreviations are used:

EG = ethylene glycol CA = cyanuric acid TPA = terephthalic acid T MA = trimellitic anhydride DAM = 4.4'' diaminodiphenylmethane TPT = tetraisopropyl titanate TBT = tetrabutyl titanate THE I C = tris(2-hydroxyethyl) isocyanate Nurate PET = Polyethylene terephthalate 5W1000 = Aromatic naphtha "Swazol 1000" manufactured by Maruzen Sekiyu Co., Ltd. Desmodur CT - Cyclic trimeric phenol block compound of toluylene diisocyanate manufactured by Bayer Co., Ltd. Mondur SH = Toluylene diisocyanate manufactured by Mobay Chemical Co., Ltd. A method for calculating the decomposition rate of cyclic trimeric phenol blocked cyanuric acid.

(1) Measure the specific gravity of the recovered product water and compare it with the [Relationship table of “concentration and specific gravity” of ammonium carbonate aqueous solution] described in the literature (Chemical Handbook, page 436, published by Maruzen on April 15, 1952). The amount of ammonium carbonate in the produced water was calculated.

(2) The calculated amount of ammonium carbonate was substituted into the following equation to determine the decomposition rate of cyanuric acid.

Decomposition of anuric acid ↓ (%) Example 1 353 g of EG and 353 g of CA22 were placed in a 2 g flask equipped with a stirrer, a thermometer, and a distillation condenser for recovering produced water.
6g of PET (IV=0.75), 398g of PET (IV=0.75), and 3g of TBTo as a catalyst were charged, and heating and stirring was started.

The temperature was raised while collecting the produced water, and the reaction proceeded at a maximum temperature of 235 °C. Sampling was started when CA crystals disappeared from the reaction system, and heating was stopped when the acid value of the reactant decreased to 15. The process was stopped and the temperature was cooled to below 150°C to obtain polyester. The recovered produced water weighed 91 g and had a specific gravity of 1.030, indicating that it contained 9% ammonium carbonate, and the calculated CA decomposition rate was only 3.3%.

Next, 303 g of TMA and 156 g of DAM were added as imide-forming components to the obtained polyester, and heating was started again. The reaction system became cake-like at around 140°C, and distillation of produced water started at around 150°C. As the reaction progressed, the cake state gradually unraveled. The reaction was continued at a maximum temperature of 225°C while collecting the produced water, and sampling was started from around the point where the reaction system became transparent. Heating was stopped when the acid value of the reactant became 10 or less. The reactant was transferred to a tin can, cooled, and ground.
Polyesterimide was obtained.

Reference Example 1 EG155. IgTHE
IC457g, TPA344g, T~lA303g, D
56 g of AMl and 13 g of TBTO as a catalyst were charged, and heating and stirring were started. The temperature was raised while collecting the produced water, and the reaction was continued at a maximum temperature of 225°C, and TP was removed from the reaction system.
Sampling was started near where the crystals of A had disappeared, and when the acid value of the reactant reached 10 or less, heating was stopped, and the reactant was transferred to a tin can and cooled and ground to obtain polyesterimide. The amount of recovered water was 129g, and its specific gravity was 1.
It was 001.

Comparative Example 1 EG480g, CA226 in the same flask as Example 1
g%TPA344gSTMA303g.

156 g of DAM and 3 g of TBTo as a catalyst were charged, and heating and stirring were started. The reaction system became cake-like at around 110°C, and distillation of produced water started around 150°C. The cake was quite hard and took time to unravel, and when it came apart, a gel-like substance was observed adhering to the wall of the flask.

The temperature was raised while collecting the produced water, and the reaction was continued at a maximum temperature of 235°C. Sampling was started from the vicinity where the CA crystals disappeared from the reaction system, and when the acid value of the reactant became 10 or less. Heating was stopped, and the reaction product was transferred to a tin can, cooled, and pulverized to obtain polyesterimide. The gel on the walls of the flask had disappeared at this point. The amount of recovered water is 2
26g, its specific gravity is 1.033, and 1 ammonium carbonate
The calculated decomposition rate of CA was 8.4%, which was a very large value.

Example 2 A polyester having an acid value of 13.5 was obtained in the same manner as in Example 1 except that 433.4 g of PG was used as the glycol instead of EGO. The recovered product water weighed 98 g and had a specific gravity of 1.033, indicating that it contained 9.8% ammonium carbonate, and the calculated CA decomposition rate was 3.8%.

Next, the obtained polyester was reacted with an imide forming component in the same manner as in Example 1 to obtain a polyester imide having an acid value of 10 or less.

Example 3 Into a 3 g flask equipped as in Example 1, E.
G317.2g, cresylic acid 235g.

374 g of PET (IV=0.68) and 7872 g as a catalyst were charged, and heating and stirring was started.

After treatment at 190 to 210° C. for 2 hours to perform ester decomposition and completely dissolve PET, 100 g of cresylic acid was added and the temperature was lowered to 190° C., 219 g of CA was added, and heating was started again. The temperature was raised while collecting the produced water, and the reaction proceeded at a maximum temperature of 235°C, and heating was stopped when the CA crystals disappeared and 87 g of produced water was recovered (95% of the theoretical value recovered, corresponding to an acid value of around 17). and cooled to below 150°C. The recovered product water had a specific gravity of 1.020, indicating that it contained 6% ammonium carbonate, and the CA decomposition rate calculated at this point was about 2.2%.

Next, 286 g of TMA and 147 g of DAM were added to the obtained polyester, and heating and temperature raising was started again. The reaction system became cake-like at around 140°C, and distillation of produced water resumed at around 150°C. As the reaction progressed, the cake state gradually loosened.

The temperature was raised while collecting the produced water, and the reaction proceeded at a maximum temperature of 225° C., and sampling was started from the vicinity where the reaction system became transparent.

2 of a 30% concentration m-, p-cresol solution of the reactants.
Heating was stopped when the Gardner viscosity at 5° C. reached Z4, and 836 g of m-cresylic acid was added to stop the reaction and uniformly mixed with stirring. Thereafter, 555 g of m-cresylic acid was added and mixed uniformly to obtain a solution of polyesterimide in cresylic acid having a concentration of about 40% by weight, which was cooled and collected in a tin can.

The total recovered amount of produced water was approximately 146 g, with a specific gravity of 1°013, indicating that it contained 4% ammonium carbonate.
The calculated decomposition rate of CA was 2.4%.

Example 4 In a flask similar to Example 1, EG435gSPET, (
IV=0.55), 215 g of CA, and 70.5 g of TB as a catalyst were charged, and heating and stirring was started. The temperature was increased while collecting the produced water, and the reaction proceeded at a maximum temperature of 235° C., and sampling was started from the vicinity where the CA crystals disappeared. Heating was stopped when the acid value of the reactant became 30 or less, and the mixture was cooled to 150° C. or less to obtain a polyester.

Next, 288 g of TMA and 148 g of DAM were added to the obtained polyester, and heating and temperature raising was started again. The temperature was raised while collecting the produced water, and the reaction proceeded at a maximum temperature of 225° C., and sampling was started from the vicinity where the reaction system became transparent. When the oxidation level of the reactant reached 10 or less, heating was stopped, the reactant was placed in a tin can, cooled and pulverized to obtain polyesterimide. The recovered amount of produced water was 145g and the specific gravity was 1.015, indicating that it contained 4.6% ammonium carbonate, and the calculated CA decomposition rate was 2.8%.
Met.

Comparative Example 2 EG557g, CA215 in the same flask as Example 1
g, TPA 328g, TMA 288g.

148 g of DAM and 5 g of TBTo as a catalyst were charged, and heating and stirring were started. The reaction system became cake-like at around 120°C, and distillation of produced water began at around 150°C. The cake was quite hard (it took some time to separate, and by the time it had separated, a gel-like substance could be seen adhering to the walls of the flask).

The temperature was raised while collecting the produced water, and the reaction was continued at a maximum temperature of 235°C. Sampling was started from the vicinity where CA crystals disappeared from the reaction system, and heating was started when the acid value of the reactant became 10 or less. The reaction mixture was stopped, and the reaction product was transferred to a tin can, cooled and ground to obtain polyesterimide. The gel on the walls of the flask had disappeared at this point. The amount of recovered water is 2
20g, its specific gravity is 1.035, and 1 ammonium carbonate
The calculated decomposition rate of CA was 9.6%, which was a very large value.

Examples 5-8, Reference Example 2 and Comparative Examples 3-4 Polyesters obtained in Examples 1-4, Reference Example 1 and Comparative Examples 1-2 in a flask with a capacity of 21 equipped with a stirrer, a thermometer and a condenser. Wire enamel was prepared using imide.

Polyesterimide with m-cresylic acid and SWI
The mixture was heated and stirred together with 000 naphtha to 150°C to uniformly dissolve it, then cooled to IC 10°C, a modifier was added, and the mixture was mixed uniformly. Thereafter, the mixture was cooled to 90° C. or lower and filtered using qualitative filter paper to obtain a polyester imide wire enamel. Table 1 shows the composition of the obtained polyester imide wire enamel and the coating properties.

The polyester imide wire enamels obtained in Examples 5 to 8, Reference Example 2, and Comparative Examples 3 to 4 were heated in an electric furnace with an effective furnace length of 3 m, a center baking temperature of 430°C, 6 coats, and a drawing speed of 6 m.
A steel wire with a diameter of 1 mm was baked under the conditions of /min. The line characteristic measurement results are shown in Table 2.

As is clear from Table 2, as the aromatic dicarboxylic acid feedstock, PET and/or polyhydric alcohol
The polyesterimide wire enamel of the present invention is made of a polyesterimide obtained by heat-reacting a polyester obtained by heat-reacting an oligomer obtained by ester decomposition of ET with a polyhydric alcohol and cyanuric acid and an imide-forming component, Compared to other methods, the heat resistance properties are better balanced, and even compared to the reference example using THE I C, the properties are equivalent or better.

(Effects of the Invention) From the various properties of the polyester imide wire in the examples, it was found that THE
It is shown that comparable heat resistant polyesterimide wire enamels can be prepared using I C.

Moreover, since cheap cyanuric acid is used instead of expensive THEIC, the cost can be extremely reduced. Furthermore, depending on the content of the polyhydric alcohol used in the reaction, a polyesterimide having an isocyanurate structure containing a corresponding side chain can be easily produced, which is of great significance.

Claims (5)

[Claims] (1) A method for producing polyester imide, which comprises heating and reacting a polyester obtained by reacting a polyhydric alcohol, polyethylene terephthalate, and cyanuric acid or an isomer thereof with an imide-forming component. (2) The method for producing polyesterimide according to claim 1, wherein the polyhydric alcohol is ethylene glycol and/or propylene glycol. (3) The imide-forming components are trimellitic anhydride and 4,
The method for producing polyesterimide according to claim 1, wherein the polyesterimide is 4'-diaminodiphenylmethane. (4) A wire enamel containing the polyesterimide obtained by the method according to claim 1. (5) The wire enamel according to claim 4, which contains a curing agent and/or a modifier.