JP2010285575A - Method for producing short fiber oriented prepreg - Google Patents

Abstract

Provided is a method for producing a short fiber oriented prepreg that can easily provide a short fiber oriented prepreg that exhibits sufficient mechanical properties when formed into a fiber reinforced resin molded article.
A method for producing a short fiber oriented prepreg according to the present invention includes a sheet for forming a prepreg containing a thermosetting resin and reinforcing fibers having a length of 200 mm or more oriented in one direction in the length direction of the reinforcing fibers. This is a method of drawing and reinforcing fibers. In the manufacturing method of the short fiber orientation prepreg F of this invention, it is preferable to cool when extending | stretching the sheet | seat for prepreg formation.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a prepreg containing short fibers oriented in one direction (hereinafter referred to as short fiber oriented prepreg).

As a prepreg used for obtaining a fiber reinforced resin molded product, a unidirectional prepreg in which a reinforcing fiber oriented in one direction is impregnated with a thermosetting resin is known. As the reinforcing fiber contained in the unidirectional prepreg, a long fiber is usually used.
On the other hand, Patent Document 1 discloses a method for producing a sheet-like material in which short fibers are oriented using a short fiber dispersion, and the sheet-like material obtained thereby is used as a reinforcing material for a composite material. It also describes what is possible.
Patent Document 2 describes a method for obtaining a sheet-like material containing reinforcing fibers oriented in one direction by drafting carbon fibers, making them into a sliver, and then impregnating with a resin. .

Japanese Patent Laid-Open No. 61-12995 Japanese Patent Laid-Open No. 7-118412

  However, in the method of Patent Document 1, since a short fiber dispersion is used, only a sheet-like material having a small basis weight can be obtained, and in order to obtain a carbon fiber basis weight in a known prepreg, it is possible to laminate ten or more sheets. It was necessary. Moreover, in the method of Patent Document 2, since the carbon fiber is not crimped, it was very difficult to handle it as a sliver.

By the way, the fiber-oriented prepreg is usually produced by impregnating a fiber bundle of fibers with a thermosetting resin. In the production of the prepreg, a treatment for opening the fiber bundle is performed in order to uniformly impregnate the thermosetting resin. In the process of opening the fiber bundle, in the case of a long fiber, a large tension can be applied to the fiber bundle, and the fiber bundle can be opened. The interval between the short fibers becomes longer. When the thermosetting resin was impregnated in such a state, it was easy to form a portion where the reinforcing fiber was insufficient and the reinforcement was insufficient in the obtained prepreg. When a fiber reinforced resin molded product is molded using a prepreg having a portion with insufficient reinforcement, mechanical properties such as tensile strength tend to be lowered. Therefore, it was practically difficult to apply tension to the fiber bundle of short fibers.
Therefore, it is conceivable to reduce the tension applied to the short fibers by applying a method of irradiating the fiber bundle with ultrasonic waves, a method of sucking the fiber bundle, etc. as the opening method. As it becomes finer, it is not easy to break even with a small tension. In addition, when the above opening method is applied, it is difficult to sufficiently open the fiber, so that the thermosetting resin cannot be impregnated uniformly and while maintaining the orientation. A prepreg exhibiting physical properties could not be obtained.
The present invention has been made in view of the above circumstances, and provides a method for producing a short fiber oriented prepreg that can easily provide a short fiber oriented prepreg that exhibits sufficient mechanical properties when formed into a fiber reinforced resin molded product. The purpose is to do.

The present invention has the following configuration.
[1] A short fiber orientation in which a prepreg-forming sheet containing a thermosetting resin and reinforcing fibers having a length of 200 mm or more oriented in one direction is stretched in the length direction of the reinforcing fibers to check the reinforcing fibers. A method for producing a prepreg.
[2] The method for producing a short fiber oriented prepreg according to [1], wherein the sheet is cooled when the prepreg-forming sheet is stretched.
In addition, in this invention, a long fiber is a fiber with a length of 200 mm or more, and a short fiber is a fiber with a length of less than 200 mm.

  According to the method for producing a short fiber oriented prepreg of the present invention, a short fiber oriented prepreg that exhibits sufficient mechanical properties when formed into a fiber-reinforced resin molded product can be easily obtained.

It is a schematic diagram which shows the manufacturing apparatus used by one Embodiment of the manufacturing method of the short fiber orientation prepreg of this invention.

An embodiment of a method for producing a short fiber oriented prepreg of the present invention will be described.
In the manufacturing method of the short fiber oriented prepreg of this embodiment, the manufacturing apparatus 1 shown in FIG. 1 is used.
The manufacturing apparatus 1 obtains a sheet-like fiber bundle B by opening a fiber bundle feeding means 10 for feeding a fiber bundle A of reinforcing fibers and a fiber bundle A fed from the fiber bundle feeding means 10. Opening means 20, resin film feeding means 30a, 30b for feeding a resin film C coated with a thermosetting resin on one side of a release paper, and two resin films C, C on a sheet-like fiber bundle B Pressure bonding means 40 for obtaining a laminate D in which a sheet-like fiber bundle B is sandwiched between two resin films C, C, a heating means 50 for heating the laminate D, and a long fiber obtained by heating and transfer means 60 for transferring the oriented prepreg E, a peeling means 70 to obtain a sheet F prepreg formed by peeling off the release paper C ₁ from the long fiber orientation prepreg E, a stretching means 80 for stretching the sheet F prepreg formation, Cool around the stretching means 80 Cooling means 90.

The fiber bundle feeding means 10 in the manufacturing apparatus 1 is a plurality of creels 11, 11,.
The fiber opening means 20 is made by pressing the fiber bundle A against the bar 21 by bending the traveling direction of the fiber bundle A.
The resin film feeding means 30a and 30b are feeding rolls to which the winding of the resin film C is attached and are driven to rotate.
The crimping means 40 includes a pair of rolls 41 and 41 that are arranged in parallel with each other and are driven to rotate. The clearance between the rolls 41 and 41 is set so that the resin film C can be crimped to the sheet-like fiber bundle B.
The heating means 50 is a heating element such as a resistance heating element, for example.
The transfer means 60 includes a pair of rolls 61 and 61 that are arranged in parallel with each other and are driven to rotate. The clearance between the rolls 61 and 61 is set so as not to crush the long fiber oriented prepreg E.
Stripping means 70 includes a bar 71 that bends the release paper _C 1, _{C 1,} a roll 72 for the winding for winding the release paper _C 1, _{C 1.}
The stretching means 80 includes three stretching roll units 80 a, 80 b, and 80 c each including a main drive roll 81 that is rotationally driven and two driven rolls 82 and 82 adjacent to the main drive roll 81. The three extending roll units 80a, 80b, 80b are arranged in parallel to each other, and are set so that the rotational speed of the main roll 81 increases from the upstream side toward the downstream side. In each of the stretching roll units 80a, 80b, and 80c, the prepreg-forming sheet F passes between the main roll 81 and the driven roll 82.
The cooling means 90 includes a housing 91 that houses the stretching means 80 and a cooler 92 that cools the atmosphere in the housing 91.

The manufacturing method of the short fiber orientation prepreg using the said manufacturing apparatus 1 is demonstrated.
In this manufacturing method, first, the fiber bundle A of reinforcing fibers is fed by the fiber bundle feeding means 10. Here, as the reinforcing fiber, for example, glass fiber, aramid fiber, carbon fiber or the like can be used. Among these, carbon fibers are preferable because they are excellent in specific strength and specific rigidity.
Next, the fiber bundle A is squeezed and opened by the bar 21 of the fiber opening means 20 to obtain a sheet-like fiber bundle B.

Further, the resin films C and C are fed by the resin film feeding means 30a and 30b so that the thermosetting resin is in contact with the sheet-like fiber bundle B.
As the thermosetting resin in the resin film C, for example, epoxy resin, phenol resin, bismaleimide resin, vinyl ester resin, unsaturated polyester resin, benzoxazine resin, and the like can be used. However, these resins are uncured. Among thermosetting resins, an epoxy resin is preferable because of excellent mechanical properties. The thermosetting resin contains a curing agent, a curing accelerator, and the like.
As the release paper, it is possible to use, for example, a paper substrate whose one side is subjected to a release treatment with a release agent such as silicone.

Thereafter, the sheet-like fiber bundle B and the two resin films C and C are crimped by the crimping means 40 to obtain a laminate D.
Next, the laminate D is heated by the heating unit 50, and the long fiber oriented prepreg E is transferred by the transfer unit 60.
Thereafter, the release paper C ₁ of the long fiber oriented prepreg E is peeled off by being bent by the bar 71, and taken up by the take-up roll 72. Thereby, the sheet | seat F for prepreg formation is obtained.

Next, the prepreg forming sheet F is passed through the stretching roll units 80a, 80b, and 80c in which the rotational speed of the main driving roll 81 is increased toward the downstream side. By passing the prepreg-forming sheet F through these stretching roll units 80a, 80b, and 80c, a tensile force can be applied in the length direction. Then, the prepreg-forming sheet F is stretched in the longitudinal direction of the reinforcing fibers by the tensile force, and the reinforcing fibers in the prepreg-forming sheet F are checked by the stretching. In addition, at the time of extending | stretching, since the thermosetting resin of the sheet | seat F for prepreg formation is not fully hardened, its restoring force is high and it is not cut | disconnected.
As described above, only the reinforcing fibers of the prepreg forming sheet F are cut to obtain the short fiber oriented prepreg G.

  The draw ratio of the prepreg-forming sheet F depends on the thermosetting resin and the reinforcing fibers used, but when the thermosetting resin is an epoxy resin and the reinforcing fibers are carbon fibers, 1.05 to 1.7. It is preferable to double. If the draw ratio is 1.05 times or more, the reinforcing fibers can be cut reliably, and if it is 1.7 times or less, the distance between the short fibers in the length direction is prevented from becoming long, and a fiber-reinforced resin molded product. It is possible to reliably exhibit sufficient mechanical properties.

In this embodiment, the prepreg-forming sheet F is cooled by the cooling means 90 during the stretching. Specifically, the inside of the container 91 is cooled by the cooler 92, thereby cooling the prepreg forming sheet F in the container 91. Here, the cooling is a temperature lower than room temperature.
When the fluidity of the thermosetting resin of the prepreg-forming sheet F is high, the rolls 81, 82, 83 of each of the stretching roll units 80a, 80b, 80c slide and idle with the thermosetting resin. Difficult to stretch. However, if the prepreg-forming sheet F is cooled during stretching, the fluidity of the thermosetting resin of the prepreg-forming sheet F is lowered, so that each roll 81, 82, 83 slides with the thermosetting resin. Can be prevented, and the reinforcing fiber can be reliably stretched and cut.

  When the prepreg forming sheet F is stretched, it naturally becomes thin. Therefore, it is preferable to appropriately adjust the thickness of the thermosetting resin in the resin film C so that the thickness of the obtained short fiber oriented prepreg G becomes a target value.

  The short fiber oriented prepreg G obtained by the above production method is preferably protected by laminating a new release paper.

As described above, in this production method, the reinforcing fiber in the prepreg forming sheet F is cut by stretching the prepreg forming sheet F by the stretching means 80. According to this method, the distance between the short fibers in the length direction can be easily adjusted, and the formation of a portion insufficiently reinforced by the reinforcing fibers can be prevented. Moreover, in the said manufacturing method, since the conventional fiber opening method can be applied, the fiber bundle A can be opened uniformly. Therefore, the thermosetting resin can be impregnated sufficiently while maintaining the fiber orientation.
Therefore, according to the said manufacturing method, the short fiber orientation prepreg G which exhibits sufficient mechanical property when it is set as a fiber reinforced resin molded product can be obtained easily.
Moreover, since the obtained short fiber oriented prepreg G is excellent in formability, wrinkles are not easily generated in the fiber-reinforced resin molded product.

In addition, the manufacturing method of the short fiber orientation prepreg of this invention is not limited to the said embodiment example. For example, the cooling at the time of extending the prepreg forming sheet F may be performed by means such as bringing only the prepreg forming sheet F into a cooling atmosphere or bringing it into contact with the cooling plate instead of cooling the atmosphere in the container 91. You may apply and the roll unit 80a, 80b, 80c for extending | stretching can also be used as a cooling roll.
Moreover, you may abbreviate | omit the cooling in the case of extending | stretching. However, in order to cut | disconnect the fiber in the sheet | seat for prepreg formation reliably, it is preferable to cool.
Moreover, in the manufacturing method of the short fiber orientation prepreg of this invention, the process of peeling a release paper from the long fiber orientation prepreg E, and extending the sheet F for prepreg formation is continued until the long fiber orientation prepreg E is obtained. There is no need to carry out these steps individually, and these may be carried out independently. When each of them is carried out independently, the long fiber oriented prepreg E can be wound up once and stored and transported.
Further, as the prepreg forming sheet F, a commercially available prepreg containing long fibers oriented in one direction may be used. The prepreg forming sheet F may be stretched in a state where a cover film such as polyethylene or polypropylene is laminated on one or both sides, and the reinforcing fibers may be checked.

There may be two stretching roll units of the stretching means 80, or four or more.
In addition, the stretching of the prepreg-forming sheet may not be performed using the stretching means 80 provided with a roll whose rotational speed is sequentially increased. For example, the prepreg-forming sheet may be stretched by gripping both ends in the length direction of the prepreg-forming sheet with a gripping tool and moving the gripping tools away from each other. However, in this case, the number of checkouts of the reinforcing fibers decreases at the grip portion.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 10 Fiber bundle feeding means 11 Creel 20 Opening means 21 Bar 30a, 30b Resin film feeding means 40 Crimping means 41 Roll 50 Heating means 60 Transfer means 61 Roll 70 Peeling means 71 Bar 72 Winding roll 80 Stretching Means 80a, 80b, 80c Stretching roll unit 81 Driving roll 82 Followed roll 90 Cooling means 91 Container 92 Cooler A Fiber bundle B Sheet fiber bundle C Resin film D Laminate E Long fiber oriented prepreg F Sheet for forming prepreg G Short fiber oriented prepreg

Claims (2)

  Manufacture of a short fiber oriented prepreg in which a prepreg-forming sheet containing a thermosetting resin and reinforcing fibers having a length of 200 mm or more oriented in one direction is stretched in the length direction of the reinforcing fibers to check the reinforcing fibers. Method.   The manufacturing method of the short fiber orientation prepreg of Claim 1 cooled when extending | stretching the sheet | seat for prepreg formation.

Images