JPS6227490B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a flyback transformer by insulating a polybutadiene resin composition, particularly a flyback transformer in which a bobbin, a diode, a coil, a focus resistor, a capacitor, and a case are integrated. A flyback transformer (FBT) for a television receiver, for example, consists of a primary coil, 1
It consists of parts such as a secondary coil with split winding similar to the primary coil, a resistor for focus voltage adjustment, an epoxy resin molded capacitor, and a case, while wiring three or more glass molded diodes. The finished product is made by insulating it with cast resin. When insulating FBT as described above, there are large differences in the coefficient of thermal expansion of each of its component parts. Complex stress is generated between the mold and the resin, resulting in cracks and peeling. Since high voltage is applied to each component of the FBT, cracks and peeling of these components can cause corona discharge, leading to dielectric breakdown of the FBT. Conventionally, insulating materials such as thermosetting epoxy resin, unsaturated polyester resin, and silicone rubber have been used as casting resins. This is because these resins have excellent mechanical and insulating properties, and although silicone rubber is a completely different rubber elastic body from these resins, it has excellent flame retardant and dielectric properties. It is. However, although epoxy resins and unsaturated polyester resins have excellent mechanical properties, they are sensitive to heat shock and often crack due to rapid temperature changes, resulting in a lack of product reliability. Additionally, the resin contracts during heating and curing, and the resin hardens while stress remains inside. This is called hardening strain. This trend is
It is particularly strong against unsaturated polyester resins, which has become a major problem. As a solution to these problems, it is often taken to impart flexibility to the resin, but imparting flexibility to the resin may lead to deterioration of the dielectric properties, which may be fatal as an insulating material. Silicone rubber is a material with a low dielectric constant and dielectric loss tangent, and has excellent properties as an insulating material, such as excellent flexibility.
In general, its use is limited due to high cost and high moisture permeability. On the other hand, polyester-based, polyether-based, and castor oil-based materials exist as urethane-based insulating materials, but all of them have poor water resistance and do not have sufficient ability to be used as insulating materials, have poor dielectric properties, and are flame retardant. Although it has sex, it is not used in FBT. In addition, there is a polybutadiene-based material as a special urethane-based insulating material, which has superior water resistance and dielectric properties compared to the above-mentioned urethane, but urethane-based insulating materials generally have a high reactivity with the polyol component of the isocyanate component. is too high compared to other materials, the pot life is short, and the viscosity of the mixture of both components increases rapidly, resulting in insufficient resin impregnation between the coils, leading to dielectric breakdown of the FBT. It was hot. However, although masked isocyanate has low reactivity at room temperature, it cannot be used because the reaction temperature is too high, voids occur, and dielectric properties deteriorate. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to provide a cured resin composition with excellent flexibility, and to improve the adhesion between it and FBT components, the water resistance and dielectric properties of the resin, and to improve the flexibility of the cured resin composition. FBT bobbins, diodes, coils, focus resistors, and capacitors are made of polybutadiene resin compositions that have good flame retardancy, have moderately low reactivity, have a long pot life, and have good impregnation properties between coils. ,
The purpose of the present invention is to provide a method for manufacturing an FBT by simultaneously insulating the case. In order to achieve the above object, the inventor investigated various polybutadiene resin compositions and found that (a) a liquid polybutadiene homopolymer having hydroxyl groups at both ends of the molecule, or a liquid styrene-butadiene copolymer having hydroxyl groups at both ends of the molecule; Alternatively, a liquid acrylonitrile butadiene copolymer having hydroxyl groups at both ends of the molecule, or a mixture thereof; (b) a short chain diol and/or a short chain triol; (c) an isocyanate having the chemical formula shown below; However, l = 2 to 10, m = 2 to 10, n = 2 to 10 (d) hydrated alumina, (e) red phosphorus powder.
It was revealed that this can only be achieved by insulating the bobbin, diode, coil, focus resistor, capacitor, and case at the same time. That is, the present invention simultaneously insulates each of the above components with the above polybutadiene resin composition.
FBT is characterized in that the cured resin composition of FBT obtained by this process has excellent flexibility, adhesion between it and FBT components, water resistance of the cured resin, and dielectric properties. , has good flame retardancy, and the resin liquid has moderately low reactivity, has a long pot life, and has good impregnation properties between coils, so FBT has excellent withstand voltage characteristics and is highly reliable. Become. Next, materials used in the present invention will be explained.
The liquid polybutadiene, which is one component of the polyol, is effective in any of the following liquid polybutadienes: a polybutadiene homopolymer, a styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer, each having a molecular weight of 500 to 10,000 and having hydroxyl groups at both ends of the molecule. These are, for example, R-45HT, R-
It is commercially available from Idemitsu Petrochemical Co., Ltd. under the trade names 45M, CS-15, and CN-15. The remaining polyol components and short chain diols and short chain triols which are also crosslinking agents include the following. Short chain diols such as 2-ethyl-1,3-hexanediol, butanediol, N,N-bis(2-hydroxypropyl)aniline, 1,2,6
- Short chain triols such as hexanetriol and glycerin. These may be used alone or in combination. If only polybutadiene polyol is used, it will have a soft hardness and its physical properties, especially at high temperatures, will be impaired, and if too much is added, it will become too hard, so 3-30% by weight (97-70% by weight) should be added as a polyol component.
It is desirable to incorporate polybutadiene polyol). As the isocyanate, those with the chemical formula shown below are good because the reaction rate is moderately slow and the pot life is long, and the blending amount is 0.6 to 1.3 equivalents per equivalent of active hydrogen of the above two types of polyol components. is desirable in terms of characteristic saturation. In the above formula, l, m, and n are l = 2 to 10, m = 2 to 10,
It is preferable that n = 2 to 10. If l, m, and n are smaller than 2, the reactivity will be too high, resulting in poor impregnation, and if larger than 10, the reactivity will be too low, resulting in poor curing, resulting in poor mechanical and electrical properties. It becomes insufficient. The hydrated alumina may be one having the chemical formula Al ₂ O ₃ .3H ₂ O, and commercially available products can be used. This material has flame retardant properties.
The effective blending amount is 40 to 150 parts by weight based on 100 parts by weight of the total amount of the above two types of polyol components. That is, if it is less than 40 parts by weight, the flame retardant effect will be low, and if it exceeds 150 parts by weight, the dielectric constant and dielectric loss tangent will deteriorate, and workability will decrease due to increased viscosity. Red phosphorus powder is effective in providing flame retardancy, particularly when used in combination with hydrated alumina, which exhibits excellent flame retardancy due to a synergistic effect. By blending this, the blending amount of hydrated alumina can be reduced to a predetermined amount, and flame retardance can be imparted without deteriorating the dielectric constant and dielectric loss tangent. The blending amount is preferably 10 parts by weight or more, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the two types of polyol components in total. That is, if the amount was less than 10 parts by weight, the flame retardant effect was small, and even if it exceeded 30 parts by weight, the effect did not change. In addition, esters, oils (hydrocarbon oils and halogenated oils), epoxidized fatty acids, and the like may be added as viscosity modifiers, if necessary. Further, in order to improve the properties, other inorganic fillers, silane coupling agents, antifoaming agents, coloring agents, etc. can be added as necessary. Next, methods for measuring various characteristics will be described. (1) Flexibility of cured resin product: Test piece with a C-shaped annealed copper washer (inner diameter 8 mm, outer diameter 22 mm, thickness 5 mm, cut width 2 mm) embedded in a resin composition (wall thickness of cured resin product 7 mm) ), the upper limit temperature is 100
A heat shock test was carried out with the lower limit temperature kept at a constant temperature of 40°C and the temperature was lowered by 10°C every cycle (each temperature was held for 2 hours), and the temperature at which a crack occurred in the test piece was measured for 10 tests. The average value was taken as the crack generation temperature and used as a measure of flexibility. That is, the resin with a lower crack generation temperature has excellent flexibility. (2) Adhesion: A 12 mm x 12 mm x 3 mm polybutylene terephthalate (PBT) plate is sandwiched between an aluminum rod (diameter 11.3 mmφ, adhesive area 1 cm ² ), and the adhesive layer between the aluminum rod and the PBT plate is approximately 50 μm.
A resin composition was applied to the sample and cured by heating to obtain a test piece. After the tensile test, the fracture surface was observed and it was confirmed that the resin and PBT plate peeled off in all test pieces. Measured values are measured at 25℃
The average value of 10 values was taken as the average value. (3) Water resistance: According to JIS K6911, the water absorption rate (%) of the cured resin product was measured for three samples at 23°C after 24 hours, and the average value was used as a guideline for water resistance. Resins with lower water absorption have excellent water resistance. (4) Dielectric properties: According to JIS K6911, 90℃, 10KHz
I asked for it. For the three samples, those with a dielectric constant of 4 or less and a dielectric loss tangent of 2% or less were rated "O", and the other samples were rated "X". (5) Pot life: The time it takes for the viscosity of the resin to double at 40℃. The average value of three samples is shown. (6) Physical properties at high temperatures: Mechanical properties were determined at 90°C according to JIS K6301. Of the five samples, those with a tensile strength of 50 kg/cm ² or more and an elongation of 200% or more were rated "O", and the others were rated "X". (7) Flame retardancy: Measured using a 1/16 inch thick test piece in accordance with the UL94 standard. Those that passed UL94V-O were designated as "V-O", and those that failed were designated as "combustion". (8) Impregnability: The impregnability of the resin between the coil windings can be determined by cutting the coil winding part of FBT that has been cast and cured with resin, and observing the cross section with a microscope at about 50x magnification. The ratio of the resin impregnated to the area between the coils was investigated. A score of 95% or higher was considered a pass. The curing conditions for all resins were 60°C/3 hours + 100°C/2 hours. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 The crack occurrence temperature, adhesion,
The water absorption rate, dielectric properties, pot life, mechanical properties at high temperatures, and flame retardancy were measured, and the results shown in Table 2 were obtained. FBT casting resin cannot be used unless its crack generation temperature is lower than -50°C. Examples Nos. 1 to 10 are lower than -70℃, and comparative examples are also lower than No. 2.
Except for No. 4, the temperature was lower than -70℃, which is satisfactory from the standpoint of flexibility. However, Comparative Examples No. 2 and No. 4, which have a high blending ratio of short-chain diols, are too hard, have a high clutch generation temperature of -20°C, and have poor flexibility, so they cannot be used for FBT. Looking at the adhesion properties, both the Examples and Comparative Examples are satisfactory, being higher than 100 Kg/cm ² . In addition, the water absorption rate was 100Kg/
cm ² higher and more satisfying. From the perspective of the dielectric properties of the resin, Examples
Both comparative examples are good and satisfactory. For FBT resin, it is essential to impregnate the space between the coil windings with resin. For this purpose, it is important that the reactivity after mixing the glycol component and the isocyanate component is appropriately low. The pot life is used as a guideline; the longer the pot life, the lower the reactivity. Based on actual results, the pot life should be at least 5 hours at 40°C. Comparative Examples No. 9 and No. 10, which did not use the isocyanate of the present invention, both had a pot life of less than 1 hour. However, both Examples using the isocyanate of the present invention and other comparative examples were good for longer than 5 hours. In terms of mechanical properties at high temperatures, Comparative Examples No. 1 and No. 3, which did not contain any short chain diol, were poor. However, both Examples containing short chain diols and Comparative Examples other than those mentioned above were good. Flame retardancy is also an important property for FBT.
Only resins that pass UL94V-O can be used. Comparative example No. 5 with a small amount of hydrated alumina, Comparative example No. 7 with a small amount of red phosphorus
Both failed in terms of flame retardancy. However, both Examples and Comparative Examples other than those mentioned above, in which the required amounts of hydrated alumina and red phosphorus were blended, both satisfied flame retardancy. In Comparative Example No. 8, red phosphorus was added in excess of the necessary amount, and although the flame retardance did not particularly deteriorate, the excess amount was wasteful. Resin compositions that can satisfy all of the above characteristics are Examples Nos. 1 to 10.

【table】

【table】

【table】

[Table] Example 2 In a 10 mmHg vacuum container, the primary bobbin 2, secondary bobbin 3, diode 4, primary coil 5, secondary coil 6, focus resistor 7, and capacitor 8 are housed in the case 9 as shown. Place the FBT that was
The resin compositions shown in Examples Nos. 1 to 10 and Comparative Examples Nos. 1 to 7, 9, and 10 in the table were poured, returned to normal pressure, and then cured under predetermined conditions. A cross-sectional view of the FBT after casting and hardening is shown. 9 in the figure is a cast resin. FBT using Comparative Examples No. 1 and No. 3 suffered from breakage of the cured resin during handling operations such as high-temperature operation.
Dielectric breakdown occurred during the operation test. FBT using Comparative Examples No. 2 and No. 4 was conducted at 100℃/2h.
After 20 cycles of heating and cooling at -50°C for 2 hours, a crack appeared near the core, and dielectric breakdown occurred during an operation test. The FBTs using Comparative Examples No. 5 and No. 7 failed the combustion test according to the Electricity Control Law. In the FBT using Comparative Example No. 6, the dielectric properties of the resin were poor and dielectric breakdown occurred during operation. In the FBTs using Comparative Examples No. 9 and No. 10, the pot life of the resin was short and the reactivity was high, so the impregnation of the resin between the coil windings was extremely poor and dielectric breakdown occurred during operation. On the other hand, no abnormality was observed in FBT using the resin compositions of Examples Nos. 1 to 10 in Table 1. As described above, the polybutadiene resin composition according to the present invention has moderately low reactivity, has a long pot life, and has good impregnability between FBT coils, and has a high flexibility of the cured resin composition. , not only the adhesive properties but also the water resistance, dielectric properties, and flame retardance of the resin are significantly improved, so the obtained FBT has high withstand voltage properties, dielectric properties, flame retardance, and reliability. Therefore, it has great industrial value.

[Brief explanation of the drawing]

The figure shows a cross section of a flyback transformer. 1... Casting resin, 2... Primary bobbin, 3...
Secondary bobbin, 4... diode, 5... primary coil, 6... secondary coil, 7... focus resistor,
8... Capacitor, 9... Case.

Claims (1)

[Scope of Claims] 1 (a) Liquid polybutadiene homopolymer having hydroxyl groups at both molecular ends, liquid styrene-butadiene copolymer having hydroxyl groups at both molecular ends, liquid acrylonitrile butadiene copolymer having hydroxyl groups at both molecular ends, or the like. (b) a short-chain diol and/or a short-chain triol; (c) an isocyanate having the chemical formula shown below; However, l = 2 to 10, m = 2 to 10, n = 2 to 10 (d) hydrated alumina, (e) red phosphorus powder. Manufacturing method of back transformer.