KR20010018933A - Process for producing polyamideimide varnish for coating enamel wire by using Blocked -Isocyanate method and catalyst - Google Patents

Abstract

PURPOSE: Provided is a process for producing polyamideimide vanish for enameled wire coating, which is improved durability, and also the cost of production is reduced by more than 50 percent and the time of production is shorten. CONSTITUTION: The polyamideimide vanish is obtained by the steps of: i) purging a chamber with a tube to be injected nitrogen gas, with nitrogen gas; ii) reacting methylene diisocyanate with m-cresol in N-methyl pyrrolidone to make m-methylene diisocyanate; iii) reacting m-methylene diisocyanate with trimellitic acid anhydride in N-methyl pyrrolidone and diluting it with dimethyl formamide; and then iv) coating it on the enameled wire and hardening it at the high temperature.

Description

Process for producing polyamideimide varnish for coating enamel wire by using Blocked -Isocyanate method and catalyst}

The present invention is an insulation varnish of coil copper wire, which is a main component of yoke coils of various motors or TV CRTs, which are electrically exerted in rotational force, in particular, various electric tools or machines that are repeatedly opened or closed and a high voltage is always applied. It relates to a manufacturing method of varnish for coating coating of phosphoric polyamideimide. In this case, the coated coil is generated heat due to various mechanical and electrical factors such as the passage of the energization time and overload, so in the case of devices using such enameled copper wire, A heat resistant insulator coating is required.

Therefore, the high heat resistance characteristics of the enameled copper wire, which is one of the coils used in electronics, electrics, automobiles, various electric machines, communication machines, and electronic grand machines, are important factors in determining the reliability and safety of the equipment. The development of the high heat resistance enamel wire varnish coat | covered with such an copper wire as an insulation material is calculated | required.

However, general enamelled copper coating varnish uses cresol, NMP (N-methylrrolidone), or xylene (xylene), which is a toxic organic solvent, to recover these solvents or completely burn them when drying copper wire coating. In order to prevent contamination around the production facilities, in practice, mainly the combustion method is used, and platinum catalyst is usually used for complete combustion. The heat of combustion can be reused as dry heat during copper wire coating, but part of the solvent due to the economic loss of burning organic solvents that are more expensive than combustible fuels and the large amount of CO ₂ and odor of unburned solvent. Research and efforts to replace H with H ₂ 0 have continued until recently. This conventional basic approach dissolves polyamide acid (Polyamic acid), a precursor of imide, to the NMP, dimethyl formamide (DMF), etc., which are polar solvents, and ammonia, tetramethylamino alcohol (Me ₂ N CH ₂ CH). _It reacts with ₂ OH) to make amic acid salt and dilutes it with water, which increases the solubility in water and reduces the use of toxic solvents. It is applied to all imide varnishes such as PESI, PAI, PI, etc. come.

In the conventional case, however, these amine groups are detached from the amic acid salt and an imide ring is formed to form a film while passing through a process such as drying and curing after coating on the copper wire. This method is also of great interest in terms of improving the shelf life of polyamic acid, a polyimide enamel varnish, but it is caused by the use of water and the disadvantage of deteriorating the heat resistance and electrical properties of the enameled wire prepared from the aqueous phase. Problems such as improvement of coating equipment and operating system and bad smell of amine by-products are obstacles to full-scale commercialization. In addition, high solid varnishes, which greatly reduce the amount of solvent in conjunction with pollution problems, It is announced.

However, in the case of high concentration type, the coating process of enamel varnish on copper wire is very different from the existing one, so the coating equipment is required to be remodeled or re-installed, and the operating conditions are difficult. In addition, extrusion coating, powder coating, and radiation coating are being researched and announced, but they are not as excellent in heat resistance and insulation as existing products. It is rarely used due to the disadvantages such as cost increase, difficulty in coating conditions, and raw material price, which is much more expensive than conventional methods.

As described above, PAI (Polyamideimid) -based resin having excellent heat resistance, which is most often used as an insulation coating material for copper wire, has a chemical structure as a reactant of trimellitic acid anhydride (TMA) and aromatic diamine (diamine).

In general, PAI manufacture mainly uses isocyanate method for reacting trimellitic acid anhydride (TMA) with Methylene diisocyanate (MDI) and acid chloride method for reacting TMAC with MDA, and is used for wire insulation coating agent. The isocyanate method is mainly used for the production of these compounds. However, PAI synthesized by the acid chromide method is mainly used for molding rather than copper clad coating and is relatively expensive. On the other hand, PAI synthesized by the isocyanate method is mainly used as a lead coating material and few examples are used for molding.

This is because unreacted -NCO or urea is present in the PAI manufactured by this manufacturing method, so that cross-linking occurs during the reheating process for molding and thus the process cannot be performed. However, this unreacted material (MDI, etc.) crosslinking reaction is rather suitable for coating because it lowers the solubility of the coated film and increases the heat resistance.

However, if a large amount of unreacted materials is present, the viscosity of the solution increases with time or excessive crosslinking occurs during the coating process, resulting in a decrease in flexibility of the coating film. As a method of forming this PAI, PAI can be produced by the following various chemical formulas,

PAI coating solution can be prepared by the above formula. By the way

In general, as the solvent of PAI, NMP, DMSO (dimethyl sulfoxide), DMAC (N, N-dimethyl acetamide), sulfolane, cresol, etc. may be used. However, since PAI coating solution is easy to obtain a relatively high concentration (25% or more) of the reaction stock solution, it is examined in connection with problems such as monomer reactivity with solvent, phase separation at high concentration, storage stability, coating property and coating processability. And economic issues cannot be overlooked.

On the other hand, since dimethyl formamide (DMF) is decomposed at high temperature and reacts with monomers, cresol has been limited in use due to problems such as reactivity and phase separation, DMAc, and sulfolane, such as price and high film forming temperature.

Almost all commercially available solvents for PAI insulating coatings are mainly made of NMP, which is a great burden on the cost of coating solutions. Therefore, it is necessary to replace with a low cost coating solvent for reducing the price. For reference, the characteristics that an enamel line should have are shown in the table below.

Table 1. Required Properties of Enamelled Wire

In addition to these, flexibility is also an important factor, which is essentially determined by the molecular structure, but in the case of crosslinked varnish also depends on the degree of crosslinking. In other words, when the degree of crosslinking is high, a dense film is formed, but the film is easily broken.However, when the degree of crosslinking is too low, proper insulation is required because of poor insulation and heat resistance. This problem does not occur because it is not used, but if the film is excessively hardened, physical properties may decrease due to carbonization.

Therefore, the present invention adopts the blocked-isocyanate method instead of the conventional polyamideimide varnish production method in order to solve the above-mentioned problems of the prior art, and the production cost by improving the overall specific method. It is also possible to lower even more cheaply.

The present invention to solve the conventional problems as described above and to produce a product which is cheaper and has excellent electrical characteristics

Refrain from the way that conventional TMA (trimellitic acid anhydride) and MDI (methylene diisocyanate) react directly in NMP to produce the final material, and also refrain from coating the final material on enameled wire and curing at high temperature. To prepare a coating polyamideimide (PAI) solution, after purging the inside of a container having a certain volume equipped with a nitrogen gas extractable tube with nitrogen gas, methylene diisocyanate (MDI) And m-cresol are reacted in N-methyl pyrrolidone (NMP) to form m-MDI, and then the m-MDI is trimellilic acid anhydride (TMA). ) And the enmethylpyrrolidone to make a primary product, which is diluted with dimethyl formamide (DMF) to prepare a secondary product, which is coated on an enamel wire and then The method of producing the polyamide-imide varnish for the block-isoyanate and enamel wire coating which was hardened to obtain a final product was obtained.

To this end, the inventors changed the synthetic reaction route as follows: MDI and m-cresol were reacted in NMP to form m-MDI. Next, m-MDI is reacted with TMA and NMP (N-methyl pyrrolidone) to make a primary product, which is diluted with DMF to prepare a secondary product, which is coated on an enameled wire and cured at high temperature. The present invention is also characterized in that the final product is produced. In addition to the TMA and MDI, the monomer required for the synthesis was added m-cresol, and the temperature required for the completion of the reaction was lowered from the conventional 180 ° C to 130-140 ° C.

In preparing the PAI solution, the catalyst may be appropriately used depending on the product, the use, and the viscosity of the solution. In this case, however, if the catalyst is used incorrectly, for example, the viscosity of the PAI solution gradually increases, which may impair storage stability.

In order to describe the present invention in more detail, an example is given as follows.

Example

First of all, the PAI manufacturing formula implemented in the present invention

To this end, in order to prepare about 600ml of 30% by weight PAI coating solution, the inside of the container was filled with nitrogen gas in a constant volume, followed by injection of TMA (Trimellitic acid anhydride) and NMP, and then at a rotational speed of about 300 RPM. While stirring, another flask filled with nitrogen, MDI (Methylene diisocyanate (Diphenylmethane-4, 4'-diisocyanate) and m-cresol completely dissolved in NMP m-cresol and some MDI combined m- The MDI solution was slowly added dropwise over a period of one hour using a dropping funnel, and after the addition was completed, the mixture was further stirred at a rotational speed of 300 RPM for about 30 minutes and then the solution was gradually heated to 70 ° C. over two hours. The solution was then heated to 140 ° C. over about 2 hours (10 ° C./20 mim) and then stirred by rotating at a rotational speed of 300 RPM for about 30 minutes while maintaining the temperature of 140 ° C., and the reaction was completed. After slowly lowering the temperature to 40 ℃ was added to DMF (dimethyl formamide) was diluted to 25% by weight concentration was stirred for about 4 hours to prepare a coating solution PAI solution.

For reference, the structure of the polymer synthesized in the present invention was confirmed using H'-NMR and FT-IR, and the molecular weight was dissolved in NMP at a concentration of 0.5 g / dl and measured at 30 ° C. using a Penskviscometer. In addition, the viscosity of the solution was measured at room temperature using a Brookfield viscometer.

The thermal properties of the resin were evaluated by DSC and TGA (heating rate 10 ° C / min) analysis under nitrogen atmosphere.

In addition, in order to evaluate the characteristics of the PAI solution (coating solution) prepared as described above, after the PAI solution was made of enamel coated copper wire in a pilot line, the dielectric breakdown voltage, elongation, pinhole, and film flaw of the wires were prepared. As a result of measuring and evaluating various properties such as adhesion, heat shock resistance and elongation pinhole properties, the physical properties and mechanical properties of PAI varnishes prepared by the conventional methods were better.

Table 2. Electric Wire Result from Pilot Line

The PAI was prepared by evaluating this at a high equivalent weight (equivalent ratio of 100 mol%), and in order to confirm the tensile strength according to the molecular weight, the film forming conditions of PAI were established, and the prepared tensile strength was measured and compared with the conventional sample. It was as follows.

Table 3.

That is, when the reaction temperature was lowered to 140 ° C. by using the MCR of 30 mol% in the equivalent ratio of 100 mol%, which is the condition set in the present invention, the intrinsic viscosity was about 0.35 dL / g, but it was possible to manufacture a film showing excellent physical properties. In other words, a film having a more dense, tougher physical property can be produced when the film is formed at a high temperature without gelation during the reaction.

According to the present invention, half of the expensive amount of NMP required for synthesis could be replaced with DMF, and the temperature required for the completion of the reaction could be lowered from 180 ° C. to 130 ° C. to 140 ° C., thus reducing the power consumption. In addition, the time required for reaction and synthesis was shortened from approximately 9 hours to approximately 5 hours, and in particular, the tensile strength of the final product was increased to 1200kg / cm ² or more from the conventional 1100kg / cm ² level, thereby improving durability of the product. Could.

As a result, the manufacturing cost can be reduced by more than 50%.

In other words, the present invention is to achieve a significant productivity and manufacturing cost reduction compared to the conventional method.

Claims (1)

In order to prepare a polyamideimide (PAI) solution for enamelled copper wire coating, after purging the inside of a container having a certain volume equipped with a nitrogen gas extractable tube with nitrogen gas, methylene diisocyanate: MDI) and m-cresol are reacted in N-methyl pyrrolidone (NMP) to form m-MDI, and then the m-MDI is trimellilic acid anhydride. : TMA) reacted with the en methylpyrrolidone to make a primary product, which was diluted with dimethyl formamide (DMF) to prepare a secondary product, which was coated on an enameled wire and cured at high temperature. A method for producing a polyamideimide varnish for block-isoyanate and enamel wire coating to obtain a final product.