JPH04348912A - Manufacture of prepreg - Google Patents

Abstract

PURPOSE:To prevent cavities from remaining in the inner part of prepreg obtained by impregnating and drying resin varnish into a sheet base material, and smooth the surface of the prepreg. CONSTITUTION:The space encircled by a bank of rolls is connected to a vacuum pump 1 so as to be a depressurized chamber 2. Following the decompression chamber 2, the space encircled by a bank of rolls that rotate in contact with each other is made a resin varnish impregnation chamber. A pair of rolls among a bank of rolls constituting the impregnation chamber 3 is connected to the entrance of the depressurized drying chamber 4. A continuous sheet base material 7 passes through the depressurized chamber 2 and impregnation chamber 3 and then is dried by radiant heat at the depressurized drying chamber 4. The pressure in the depressurized drying chamber 4 is of the order of 50mmHg. After the depressurized drying, hot air drying is effected as required.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing prepreg used for manufacturing laminates, etc.

0002

BACKGROUND OF THE INVENTION A laminate is manufactured by stacking a predetermined number of prepregs obtained by impregnating a sheet-like base material with a thermosetting resin varnish and drying the prepregs and molding them under heat and pressure. Prepreg is made by heating and drying a thermosetting resin impregnated into a sheet-like base material to a semi-cured state, and the drying is performed by blowing hot air into a drying oven. Further, impregnation with a resin varnish prior to drying is generally performed under atmospheric pressure by a roll coating method, a dip coating method, or the like.

0003

[Problem to be solved by the invention] In the above conventional method,
Insufficient impregnation or air bubbles contained in the resin varnish may leave voids inside the prepreg, and laminates formed using such prepreg may not be filled with resin during molding, leaving voids. , which caused a decline in quality. The problem to be solved by the present invention is to prevent voids from remaining inside the prepreg and to make the surface of the prepreg smooth.

0004

[Means for Solving the Problems] In order to solve the above problems, the method according to the present invention includes a step of impregnating a sheet-like base material with a resin varnish through a reduced pressure atmosphere, and then drying it with radiant heat in a reduced pressure atmosphere. It is characterized by going through the process of performing. Further, the second invention includes a step of impregnating a sheet-like base material with a resin varnish through a reduced pressure atmosphere, a step of drying it in a reduced pressure atmosphere with radiant heat until the surface becomes sticky, and a step of drying with hot air. It is characterized by passing through.

[0005]

[Operation] In the method according to the present invention, before impregnation with the resin varnish, the base material is passed through a reduced pressure atmosphere to remove air trapped inside the base material, and the resin varnish is impregnated in this state. Therefore, the resin varnish penetrates into the inside of the base material. In addition, in drying using radiant heat, heating is carried out from within the base material, so in combination with drying in a reduced pressure atmosphere, the solvent and gas inside the base material can easily escape, making it possible to prevent voids from remaining inside the prepreg. can do. Furthermore, in drying using radiant heat in a reduced pressure atmosphere, there is no flow of hot air, so the surface of the prepreg does not bubble and can be made smooth.

[0006]

Embodiments An embodiment of the present invention will be described together with the apparatus used. A space surrounded by a group of rolls rotating in contact with each other is connected to a vacuum pump 1 to form a decompression chamber 2. Further, a space surrounded by a group of rolls that rotate in contact with each other following the decompression chamber 2 is defined as a resin varnish impregnation chamber 3. Then, one pair of the roll group constituting the impregnation chamber 3 contacts the entrance of the reduced pressure drying chamber 4. A pair of exit rolls 5 are also in contact with the exit of the reduced pressure drying chamber 4. 6 is a radiant heat plate. The elongated sheet-like base material 7 is guided to the decompression chamber 2 from an appropriate location of the rotating roll group, and the air included in the sheet-like base material 7 is removed here. The pressure in the reduced pressure chamber 2 is approximately 50 mmHg. Then, it is sent as it is to the impregnation chamber 3, where it is impregnated with resin varnish. The sheet-like base material 7 is then sent to the reduced-pressure drying chamber 4 and dried by heat from the radiant heat plate 6. The pressure inside the reduced pressure drying chamber 4 is also about 50 mmHg.

[0007] All the drying can be completed by drying only in the reduced pressure drying chamber 4, but the amount of heat added by heating with radiant heat alone is small and the length of the drying chamber must be made long. Therefore, drying in the reduced pressure drying chamber 4 is carried out to the extent that the surface of the sheet-like base material 7 impregnated with resin varnish loses its stickiness.
The base material coming out of the reduced pressure drying chamber 4 is guided to a hot air drying furnace 8,
Final drying may be performed here. Once the surface is no longer sticky, it will not bubble when exposed to hot air.

[0008]

Effects of the Invention As described above, the prepreg obtained by passing through a reduced pressure atmosphere, impregnating it with a resin varnish, and drying it under reduced pressure using radiant heat has no internal voids and has a smooth surface. A laminate formed using such prepreg has no voids and is of excellent quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment according to the present invention.

Claims (2)

[Claims] 1. A method for producing a prepreg, which comprises the steps of impregnating a sheet-like base material with a resin varnish in a reduced pressure atmosphere, and then drying it with radiant heat in a reduced pressure atmosphere. [Claim 2] A step of impregnating a sheet-like base material with a resin varnish in a reduced pressure atmosphere, followed by a step of drying in a reduced pressure atmosphere with radiant heat until the surface becomes sticky, and then a step of drying with hot air. A method for producing prepreg characterized by: