JPH024542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of cutting synthetic resin reinforcing fibers into a certain length, and particularly relates to a method of cutting glass fibers into a certain length of 2.0 mm or less.

Fibers such as glass fiber are widely used as reinforcing materials for synthetic resins. Glass fibers for reinforcing synthetic resins can be classified by length into continuous long fibers such as roving, cut short fibers such as chopped strands,
There are powdered short fibers such as milled fibers. Cut short fibers are produced by cutting roving or the like into a certain length, and the length is usually about 1 cm or more. Powdered short fibers such as milled fibers are manufactured by crushing cut short fibers with a ball mill, etc.
Its average length is usually less than 5 mm. Glass fibers having a length of about 0.2 to 2 mm are currently required in certain applications. This is reaction injection molding (hereinafter referred to as RIM) of polyurethane and other synthetic resins.
It is used as a reinforcing material when molded by this method.
The RIM method is a molding method in which at least two liquid components, at least one of which has a reinforcing material dispersed therein, are ejected from nozzles, the two are mixed by collision, and the mixed liquid is injected into a mold and hardened. In this method, the liquid component in which the reinforcing material is dispersed is pressurized, flows through the pipe, and is ejected from the nozzle, so the reinforcing material must not easily clog the pipe or the nozzle. Therefore, the reinforcing material for this purpose needs to be short to a certain extent, and on the other hand, it needs to be long to a certain extent in order to fully exhibit its reinforcing effect as a reinforcing material. Considering both of these requirements, it is currently considered that a length of approximately 0.2 to 2 mm is appropriate for the reinforcing material.

Glass fibers of about 0.2 to 2.0 mm can be produced by pulverization in the same manner as the method for producing milled fibers described above. However, the average length is 0.2-2.0
Milled fibers between mm are not fully satisfactory as reinforcement materials for use in the RIM process. The reason is that the fiber length distribution in the milled fiber is too wide. for example,
Milled fibers with an average length of 2.0 mm contain a large amount of long fibers with a length of more than 2.0 mm and short fibers with a length of less than 2.0 mm. Therefore, the presence of a large amount of long fibers exceeding 2.0 mm tends to cause the above-mentioned clogging problem. Similarly, milled fibers with an average length of 0.2 mm contain a large amount of shorter fibers that have less reinforcing effect. parable,
Even in milled fibers with an average length of 1.0 mm, the amount of fibers outside the range of 0.2 to 2.0 mm is so large that it cannot be ignored.
It is not uncommon for it to exceed % by weight.

As a method for producing short fibers having a sufficiently narrow fiber length distribution, it is thought that a method of cutting long fibers into a certain length, similar to chopped strands, is considered to be appropriate. However, conventionally, the lower limit of the length of chopped strands is about 3 mm, and it has been difficult to manufacture chopped strands shorter than that. The reason for this was found to be a problem with the method of cutting the fibers. Chopped strands of glass fiber are manufactured by being continuously cut by a cutting device called a roll cutter, which combines a cutter roll with embedded blades and a contact roll. When the spacing between the blades of this cutter roll is set to 2 mm or less, it becomes difficult for the roving to be drawn between the cutter roll and the contact roll. This is because the function of the cutter roll and the contact roll to press and fix the roving in the gap between the blades stops working as the gap between the blades becomes shorter. Second, even if the roving could be advanced between the two rolls by some means, the cut fibers would accumulate between the blades, and the blade would become buried within a short period of time, making it impossible to cut the roving. Therefore, it seems extremely difficult to continuously produce short fibers of 2 mm or less using a roll cutter unless these problems are solved.

From the above viewpoint, the present inventor investigated a method for manufacturing glass fiber having a length of 2 mm or less, and found that
We have discovered a method for cutting glass fibers etc. intermittently using a cutting board equipped with multiple blades. In this method, a roving or the like is placed almost perpendicularly to the blade between a cutting board with a large number of blades arranged at regular intervals and a contact board, and the two are brought close together to cut the roving into a large number of short fibers. It's a method. According to this method, the first problem with the roll cutter described above is solved. Furthermore, in order to deal with the second problem, the present inventor provided a method in which a discharge tool is provided between each two blades, and the cut fibers accumulated between the blades are pushed out from between the blades after cutting. I found it.
The gist of the present invention is this cutting method,
That is, in a method of cutting fibers for reinforcing synthetic resin into lengths of 2.0 mm or less, a blade cutting board and a contact board, in which a plurality of blades are arranged parallel to each other at regular intervals, are relatively reciprocated. By bringing the two close together, the fibers located between them are cut, and after cutting the fibers, a discharge tool placed between the plurality of blades is moved in a different manner relative to the movement of the cutting board to cut the plurality of fibers. This is a method for cutting fibers for reinforcing synthetic resin, characterized in that the cut fibers held between the blades are discharged from between the blades.

An example of the method of the present invention will be explained using the drawings.
FIGS. 1-2 show an example of a cutting device using the method of the present invention. Fig. 1 is a partial cross-sectional view of the cutting device showing a plane cut through the cutting board in a direction parallel to the blade, and Fig. 2 is a partial cross-sectional view of the cutting board taken along a cross section A-A' in a direction perpendicular to the blade. . In Fig. 1, the left half of the center dot-dash line A-A' shows the B-B' section in Fig. 2, and the right half shows the C-C' section. The status of the device is partially different. The blade 1 that cuts the fiber is the first blade.
In the figure, a large number of fibers are arranged in parallel in the direction perpendicular to the plane of the paper, and the fibers arranged in the direction perpendicular to the plane of the paper in FIG. 1 are cut between the cutting plate 2 and the contact plate 3. Second
As shown in the figure, a large number of blades 1, 1', 1'', etc. are arranged at regular intervals with spacers 4, 4', 4'', etc. The distance between the tips of the two blades 1-1' etc. determines the length of the cut fiber, so in the present invention the distance between the tips of the two blades is determined.
2.0 mm or less, especially 0.2 to 1.8 mm. Normally, all the blades 1,
The distance between the tips such as 1' and 1'' is determined. The cutting board 2 can be reciprocated up and down by the movement of the piston 5. Therefore, the fibers positioned between the cutting board 2 and the contact board 3 are After the cut fibers are removed by moving the contact plate 2 in the horizontal direction (perpendicular to the plane of the paper in Figure 1), the fibers are placed between the two poles again, and the same process Intermittently cut fibers are produced.

In the above cutting process, the cutting blades 1, 1',
Since cut fibers are easily retained between 1" and the like, the discharge rod 6, which is a type of discharge tool in the present invention,
The cut fibers are discharged from between the blades 1, 1', 1'', etc. with the blades 6', 6'', etc. Figure 1 shows the discharge rods 6, 6',
6" etc. are shown protruding from the tip of the blade, and Figure 2 shows the state where it is drawn in between the blades. When cutting fibers, it is done in the state shown in Figure 2. After cutting, the cut fibers are discharged from between the blades 1, 1', 1'', etc. by setting the state as shown in FIG. The movement of the discharge rods 6, 6', 6'', etc. is carried out as follows.A large number of discharge rods 6, 6', 6'', etc.
6'' etc. are fixed to discharge rod holders 7 provided at both ends of the lower part of the cutting board 2, and the discharge rod holders 7 are connected to rods 8 slidably attached to both ends of the cutting board 2. Each of these rods 8 is urged upward by a spring 9, but in the state shown in FIG. When separated from the upper stopper 10, the force of the spring 9 causes the ejection rod 6, 6'6'' etc. to move towards the blade 1,
1', 1", etc., resulting in the state shown in Fig. 2. On the left and right sides of the contact plate 3, lower parts are installed to further ensure the retraction of the ejection rods 6, 6', 6", etc. Although a stopper 11 is provided, it is not necessarily necessary when the force of the spring 9 is strong. In addition, from the discharge rod holder 7 to the lower stopper 11
The first set and the other set are in the front part of Figure 1.

1 and 2 are examples of an apparatus that can carry out the method of the present invention, and the apparatus can be further applied in various ways. For example, if the direction in which the spring 9 is biased is downward, contrary to that shown in FIG. 1, and the discharge rods 6, 6', 6'', etc.
1" or the like, and can be pushed up toward the lower stopper 11.
In this case, the upper stopper 10 is not necessarily required. Since it is preferable that a large number of blades 1, 1, ', 1'' etc. cut the fibers at the same time, the surface formed by the tips of the large number of blades is preferably a flat surface or a cylindrical surface convex upward or downward. It is particularly preferable that it be flat.Of course, if it is not necessary to cut fibers at the same time, the position of the tip of the blade may be slightly irregular.The surface of the contact plate is also a surface that corresponds to the shape of the surface of the tip of the blade. It is preferable that the two blades are parallel to each other, and a flat surface is particularly preferable.Although it is preferable that two adjacent blades be parallel to each other, if the range of the length distribution of the cut fibers may be somewhat wide, the strictly parallel state is not necessarily required. For the same reason, it is preferable that the intervals between the tips of the plurality of blades be constant, but there may be cases where the intervals between the tips of the blades are slightly different.

The shape of the ejector is not limited to the illustrated rod-shaped body, but may be a linear body such as a metal wire, for example. The ejector may also not be movably attached to the cutting board. For example, a device attached to a contact plate or other fixed object and stretched above the surface of the contact plate,
When the cutting board moves downward to cut the fibers, it may be positioned between the blades as shown in Figure 2. In this case, it may be possible to contact the cutting board or its spacer portion and move downward to some extent.

The number of blades is not particularly limited and may be at least two. Usually, the cutting efficiency improves as the number of blades increases, so tens to hundreds of blades or more are attached to the cutting board. Preferably, the ejector is provided between all of these blades. Furthermore, the blades can be provided not only on the cutting plate but also on the contact plate, in which case the fibers are cut between the tips of the two upper and lower blades. However, the fibers are relatively brittle and can be cut with the tip of a single blade and the surface of the contact plate. In order to facilitate cutting, the surface of the contact plate is preferably made of a somewhat elastic material such as rubber. Further, in order to take out the cut fibers from the cutting device, it is preferable that the contact plate is moved after cutting. Preferably, this direction of movement is perpendicular to the direction of movement of the cutting board.

The cutting plate and the contact plate can be relatively moved back and forth. That is, in contrast to the case where the cutting board is moved as shown in the figure, the contacting board can be moved, or both can be moved.
It is also possible to change the positions of the cutting board and the contact board, positioning the cutting board below and the contact board above, making either or both movable. In these cases, the ejector can be appropriately modified according to the specific examples and application examples described above.

As described above, various devices can be used to carry out the method of the present invention, but the most preferred device is the one shown in the drawings.

The most preferred fiber is glass fiber, but other inorganic fibers such as carbon fiber, synthetic fibers such as vinylon, etc. may also be used. The fibers before cutting are preferably long fibers having a length at least equal to the distance between both ends of the blade, and continuous long fibers such as roving are particularly preferable. The average length of the desired cut short fibers is 2.0 mm or less, especially a certain length within the range of 0.2 to 1.8 mm, and the length distribution is particularly centered around the desired length. It is preferable that the range is as narrow as possible. In particular, it is preferable that the amount of cut short fibers having a length exceeding 2.0 mm be as small as possible. More preferably, the average length of the cut short fibers is within the range of 0.4 to 1.6 mm.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a cutting device to which the method of the present invention is applied, and the cutting board portion is shown along the lines B-B' and C-C' in FIG. FIG. 2 is a partial sectional view showing a section AA' of the cutting board shown in FIG. 1. 1, 1', 1''...blade, 2...cutting board, 3...contact board, 4...spacer, 6, 6', 6"...discharge tool.

Claims (1)

[Claims] 1. A method for cutting fibers for reinforcing synthetic resin into lengths of 2.0 mm or less, in which a cutting board in which a plurality of blades are arranged in parallel at regular intervals and a contact board are relatively connected. By reciprocating the two to bring them close together, the fibers located between them are cut,
After cutting the fibers, a discharge tool placed between the plurality of blades is moved in a different manner relative to the movement of the cutting board, and the cut fibers held between the plurality of blades are discharged from between the blades. A method for cutting fibers for reinforcing synthetic resin, characterized by: 2. The method according to claim 1, wherein the tip of the ejection tool is made to protrude above the height of the blade by a spring or a stopper when the cutting board starts or stops retracting. 3. The method of claim 1, wherein the fibers are glass fibers.