JPS61263714A - Curing of resin-impregnated product - Google Patents

Abstract

PURPOSE:To obtain a cured product with high reliability electrically and mechanically by a method wherein the residual stress in the cured product is relieved by producing such a temperature gradient that the temperature at the lower part of resin is higher than that at its upper part by means of a heat source equipped in a mold vessel. CONSTITUTION:Firstly, fiber material 1 is wound around a mandrel 2. Secondly, the resultant wound fiber material 1 is placed in a mold 3. Thirdly, the total assembly is placed in a tank 4 in order to pour resin 6 through a resin well 5 installed outside the tank 4. Fourthly, heaters at lower position among vertically split heaters 7, which are mounted on the inner peripheral side of the mandrel 2, are energized so as to control the temperature at the lower part of the resin higher by 5-20 deg.C than that at its upper part. After that, heaters 7 at higher position are successively energized. Because the temperature at the lower part of the resin is made higher than that at the upper part of the resin, the resin at the lower part starts to cure earlier than that at the upper part. At this time, the cure shrinkage has already started. However, because un-cured resin exists above the cured resin, the un-cured resin flows in the shrunk portion and consequently no substantial cure shrinkage exists and the major portion of strain due to the cure shrinkage can be released.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for curing a resin impregnated material, which is employed for producing insulating cylinders, insulating plates, etc. made of glass fiber reinforced synthetic resin. .

[Technical background of the invention and its problems]

Fiber-reinforced plastics (hereinafter referred to as FRP) are used in the field of high voltage as structural electrical insulators with high mechanical strength per weight.

The scope of application of the demand for lighter weight and smaller equipment is expanding as it contributes to energy and resource conservation.

Therefore, it is strongly desired to improve both the electrical and mechanical properties of FRP, which is an electrical insulator.

Various molding methods have been developed as methods for manufacturing FRP, including a hand lay-up method, a filament winding method, a press method, a vacuum impregnation method, and others.

When molding is performed in the atmosphere, air is taken into the insulating layer and remains as bubbles in the FRP even after heating and curing. As is well known, air bubbles in solid insulators are prone to discharge, so
F1'LP manufactured by these methods has the disadvantage that the designed electric field must be kept low.

Therefore, from an electrical point of view, it can be said that the vacuum impregnation method, which involves molding in a vacuum, is the most desirable.

The mechanical properties of FRP vary greatly depending on the type, thickness, weaving method, orientation of the fiber material, type of treated resin, and degree of impregnation of the reinforcing fibers.

However, if the vacuum impregnation method described above is adopted, cracks may occur in the layer after curing or during use due to residual strain caused by curing shrinkage of the resin. The disadvantage was that it was easy for this to occur.

The production of a conventional insulating tube will be explained below with reference to FIG.

Fig. 5 shows that after a fiber material 1 which is not impregnated with resin is wound around a mandrel 2, it is put into a mold 3, the whole is put into a vacuum impregnation tank (hereinafter referred to as tank) 4, and the resin is poured from outside of the tank 4. 5 is a cross-sectional view of a manufacturing method using a so-called vacuum impregnation method in which resin 6 is injected through 5.

In this method, a large amount of resin is generally used, and a heat-curable resin with a long pot life is used so that the impregnation time can be extended. Since the impregnation time for a large insulating cylinder is long, it is necessary to use a resin with a long pot life.

After impregnating with the resin, in order to harden the impregnated resin 6, the impregnated resin 6 is cured by a predetermined heat treatment in the tank 4 using a heat source installed in the tank or in separately prepared drying equipment.

In order to suppress the amount of curing shrinkage of the impregnated resin 6, it is first cured at a low temperature, and then 1. Post-curing is then performed at high temperatures to prevent rapid curing reactions.

However, even if hot air circulation drying equipment is used, which is said to have a good temperature distribution, the temperature distribution between the top and bottom of the impregnated material is high in the upper part and low in the lower part. In addition, in the case of the impregnated material shown in Fig. 5, in the case of the mandrel 2,
Since the heat medium does not circulate sufficiently, there is a problem that the temperature is lower than that of the outer peripheral part 8. - Since the curing of the impregnated resin starts from the high-temperature area, it will harden sequentially from the top, outer periphery, center, and around the mandrel. In this case, since the upper resin hardens first, this layer 1 forms a kind of lid θ, and this lid and mandrel 2
And the volume surrounded by mold 3 is determined. after that,
The resin in this enclosed area, which occupies most of the volume, hardens, but curing shrinkage occurs due to the phase change from liquid to solid, and most of the curing shrinkage strain is caused by mold 3 which has been released. Although the stress is alleviated by the phenomenon of delamination, some of the stress remains in the FRP body in the form of residual stress or deforms. Further, since the area around the mandrel 2 hardens the slowest, the residual stress is also the largest. This residual stress and deformation is alleviated during cooling, processing, and use, sometimes through the phenomenon of cracking.

[Purpose of the invention]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for curing a resin-impregnated material that can minimize residual strain caused by curing shrinkage of the resin.

[Summary of the invention]

The method of the present invention: In the curing of a resin-impregnated product in which a fiber material or the like is placed in a mold and impregnated with a resin.

A heater or the like is installed to raise the temperature of the lower part of the mold higher than that of the upper part, so that the curing reaction starts from the resin located at the lower part of the mold.

Curing shrinkage occurs during curing, but due to gravity or external pressure applied to the uncured resin on the top of the contracted area,
Flow into.

Sequential upper layer: Curing progresses, reducing curing shrinkage within the impregnated material (
Residual stress caused by shrinkage can be alleviated, and a cured product with high electrical and mechanical reliability can be obtained.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to the drawings.

Fig. 1 shows a process in which a fiber material 1 that is not impregnated with resin is wrapped around a mandrel 2 and then put into a mold 3 &:, the whole is put into a tank 4, and a resin 6 is injected from outside the tank 4 through a resin reservoir 5. This shows the production of an insulating tube using the vacuum impregnation method.

Next, it is placed in the tank 4 or in a separately prepared drying facility and heated. The upper temperature at this stage is set 5 to 20°C lower than the target curing temperature.

Next, among the vertically divided heaters 7 attached to the inner circumferential side of the mandrel, the lower part is energized, and the temperature is controlled to be 5 to 20° C. higher than the upper part. When curing is completed, the heaters 7 located above are sequentially energized to cure the impregnated resin in the lower part and then the resin in the upper part, and after the entire resin is cured, post-curing is performed by a conventional method.

[Effect of the embodiment]

First, electricity is applied from the lower part of the heater 7 to make the temperature of the resin in the lower part higher than that of the resin in the upper part, so that the resin in the lower part begins to harden more quickly.

At this time, curing shrinkage has already begun, but since there is uncured resin at the top, the resin flows into the contracted area, resulting in virtually no curing shrinkage. Since curing proceeds sequentially from the top, curing shrinkage within the impregnated material can be kept extremely low.

In the present invention, since the resin corresponding to curing shrinkage can be replenished from the upper part, most of the distortion caused by curing shrinkage can be canceled. There is no problem as this is normally a processing fee.

In addition to the position of the heater 7 shown in FIG.
Although the outer peripheral surface of the mandrel 2 can be considered, when considering the residual stress within the product, the inside of the mandrel 2 shown here is optimal.

In addition, since it is difficult to move the resin impregnated inside the fiber material, if the entire impregnated material is cured under pressure conditions of 5 to 7) #/- or more, it will be easier to replenish the resin and reduce distortion inside the fiber material. It will be canceled.

As another example, as shown in FIG. 2, a steam pipe 8 may be installed. In this case, if the steam inlet is at the bottom and the outlet is at the top, only the source pressure condenser is used. Easy to operate as there is a natural temperature gradient.

Furthermore, as shown in FIG. 3, in order to further facilitate temperature control, the heater wires or steam pipes may be arranged densely at the bottom and sparsely arranged toward the top. Although the insulating tube has been described here, it is not limited to a cylindrical shape, and may be modified as appropriate.

FIG. 4 shows an example in the case of a laminated plate.

〔Effect of the invention〕

As explained above, according to this method, a heat source is provided in the mold container of the resin-impregnated material during heat curing, and a temperature gradient is created such that the temperature at the bottom is high and the temperature at the top is low, so that the resin does not harden. The resin-impregnated material progresses from the bottom to the top, and the curing shrinkage is absorbed by the liquid part that has fluidity, and the residual stress due to faecal shrinkage in the cured resin-impregnated material is alleviated, and electrical/mechanical A highly reliable cured product can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing how the curing method of one embodiment of the present invention is applied; FIGS. 2, 3, and 4 are cross-sectional views showing how other embodiments of the present invention are applied; FIG. The figure shows a conventional curing method. 1... Fiber material, 2... Mandrel, 3...
...Mold, 4.-Impregnation tank, 5.-Resin reservoir, 6.-Resin, 7.-Heater,
8...Steam piping. &m person*m+ Fill: 斤 'Jli
Thou rl” FA, 1 &) Fig. 1 Fig. 2 WJ 3rd WJ Fig. 4 [ Fig. 5

Claims (1)

[Claims] 1. In a method of impregnating a fiber material or the like with a thermosetting resin using a container or mold and then curing it by heating, a heating device is attached to the container or mold to adjust the temperature of the lower part of the impregnated material. A method for curing a resin-impregnated material, characterized in that the resin is cured sequentially from the lower part to the upper part by raising the temperature of the resin to a higher temperature than that of the upper part. 2. The method for curing a resin-impregnated material according to claim 1, wherein the heat curing is carried out under pressure equal to or higher than atmospheric pressure. 3. The method for curing a resin-impregnated material according to claim 1, characterized in that the heating devices are arranged densely in the lower part of the container or mold and sparsely arranged in the upper part.