JP2992059B2 - Short metal fiber powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a metal short fiber powder which is mixed into plastics and the like to contribute to improvement of wear resistance, heat resistance, mechanical strength, etc. It can be used for a wide range of applications such as base materials for friction materials such as plates and clutch plates, composite materials for various structures such as conductive plastics and shielding materials, and other base materials for porous sintering.

[Conventional technology]

Recently, short metal fiber powders having a large aspect ratio have been developed, and application to a wide range of applications as a high-performance new material has been attempted. This metal short fiber powder is used as a metal filler for a heat-resistant and wear-resistant plastic composite material, taking advantage of the properties of the metal powder, especially abrasion resistance, heat resistance and flexibility. It has begun to be used as.

These short metal fiber powders effectively and uniformly disperse and distribute while forming a network in the plastic substrate, and impart a reinforcing effect such as wear resistance and heat resistance to the plastic. In order to fulfill such a role, it has intermediate characteristics between long fibers having a large aspect ratio and excellent reinforcing properties, and powder particles having a small aspect ratio and excellent dispersibility. 2-10mm,
Short metal fiber powder having a fiber diameter of 30 to 100 μm is used.

As a prior art related to such a metal short fiber powder, there is a chatter vibration-cut metal short fiber (hereinafter abbreviated as chatter fiber) obtained by Japanese Patent Publication No. 56-51050.

This method of producing chatter fiber utilizes self-excited vibration in cutting, and the resulting short metal fiber powder has a fiber length equal to the tool width used as the fiber shape, and a triangular cross-sectional shape. It has a high pull-out resistance to plastic and has excellent features as a metal filler for plastic reinforcement. However, since the shape of the short metal fibers is uniform and linear, the fibers in the fiber assembly intersect each other linearly, and entanglement occurs in a form in which the movement of each fiber is restricted, forming a bridge. There is an easy disadvantage. In such a case, the uniform dispersibility required for the composite with the plastic is impaired, and the reinforcing property for the plastic is reduced. In addition, the shape of each fiber is needle-like and easy to handle, and there is a problem in workability.

In addition, when short metal fibers are generated by the self-vibration of the cutting tool, high-temperature cutting heat is generated, and in the dry process, there are problems such as burning of fibers and shortening of tool life. Therefore, the cutting process is a wet process using a cutting oil, and has a disadvantage that extra processes such as cleaning, dehydration, rust prevention, and drying are required.

[Problems to be solved by the invention]

The present inventors, when mixed into plastics and the like, are uniformly dispersed, and furthermore, have little entanglement, do not generate bridges, and furthermore, variously examine short metal fiber powders which are not inferior to hand. In the process, the present inventors completed the present invention as a result of variously examining the shape of the metal short fiber, paying attention to the fact that the larger the difference between the apparent density and the tap density of the metal short fiber powder, the smaller the above-mentioned defects.

[Means for solving the problem]

That is, the present invention has a fiber diameter of 30 to 100 μm, a fiber length of 2 to 10 mm, a fiber cross-sectional shape of a quadrilateral, and
At least 70 wt% of metal short fibers that are curved in the longitudinal direction and have an arcuate shape as a fan-shaped arc with a central angle of 45 to 180 °
A metal short fiber powder characterized by containing the above.

The short metal fibers may be curved in the longitudinal direction, have an arc shape, and have a twist in the longitudinal direction.

[Action]

The fiber diameter of the short metal fibers in the present invention needs to be 30 to 100 μm. When this is 30 μm or less, the flexibility when mixed with plastic is significantly reduced, and is shortened by being broken by the stirring blade when mixed with plastic,
Aspect ratio becomes small, network-like dispersibility cannot be obtained, and reinforcing property for plastics is unfavorably reduced. On the other hand, if the fiber diameter is 100 μm or more, the aspect ratio becomes small due to the relationship with the fiber length described below, and the reinforcing property when mixed with plastic is undesirably reduced.

It is necessary that the fiber length of the short metal fiber is 2 to 10 mm. If this is less than 2mm, the aspect ratio will decrease,
When mixed with plastic, network-like dispersibility cannot be obtained, and reinforcing properties for plastic cannot be obtained, which is not preferable. On the other hand, in the case of 10 mm or more, when segregated into plastic as long fibers, significant segregation occurs in the distribution state,
It is not preferable because the reinforcing property to the plastic varies.

It is necessary that the cross-sectional shape of the short metal fiber is quadrilateral. If this is a triangle, the entanglement of the short metal fibers becomes larger, which makes it easier to form a bridge, and at the same time, when mixed into plastics, the corners become sharper, resulting in notches and lowering the strength of the plastic composite material. May be undesirable. On the other hand, if the shape is polygonal or circular, the resistance to pulling out the plastic decreases, and the reinforcing property for the plastic decreases, which is not preferable.

The fiber shape of the short metal fiber is required to be curved in the longitudinal direction as a sector-shaped arc having a central angle of 45 to 180 ° to have an arc shape. The central angle of a fan-shaped arc made of short metal fibers is 45
弓 In the case of the following bow shape, the fiber shape is not changed to a linear shape, and short metal fibers are entangled to form a bridge, which is not preferable. The state in which such bridges are formed can be represented by the packing density of the metal short fiber powder, and in the case of direct short fibers, the tap density after applying vibration by the apparent density at the time of natural filling and a predetermined number of tappings. There is almost no difference with density. In this case, the bridge has already been formed in a state of natural filling. However, in the case of the arcuate short fibers according to the invention,
It can flow like a powder particle while drawing an arc according to the shape, the restraining force of each fiber is smaller than the linear short fiber, the short fiber moves due to tapping vibration, and the apparent density and tap density The difference becomes large.

On the other hand, in the case of a circular arc of a short metal fiber with a central angle of 180 ° or more, the short metal fibers become ring-shaped and entangled in a chain, and when mixed with plastic, uniform dispersion is obtained. This is not preferable because the reinforcing property for plastic is reduced.

In this way, the metal short fiber which is curved in the longitudinal direction as a sector-shaped arc having a central angle of 45 to 180 ° and exhibits an arc shape is difficult to form a bridge, and when mixed into plastic, uniform dispersibility is obtained, It is preferable because the reinforcing property with respect to plastic is improved, and since it is not needle-like, it is hard to touch the hand and is also preferable in terms of workability.

In producing the short metal fiber powder having the above-mentioned fiber shape and exhibiting a bow shape curved in the longitudinal direction as a sector-shaped arc having a central angle of 45 to 180 °, there is a case where twisting occurs in the longitudinal direction depending on production conditions. When the short metal fibers having the twist are mixed in plastics or the like, the pullout resistance increases, and the strength of the composite material increases, which is preferable.

The short metal fiber powder, which is an aggregate of the short metal fibers as described above, has an excellent advantage that it is less entangled and does not form a bridge. This advantage is obtained when the short metal fibers are present in at least 70 wt% or more. Can be obtained. In the case of the metal short fiber powder in which the metal short fiber does not exist in less than 70% by weight, the metal short fibers are entangled with each other to form a bridge, and when mixed into the plastic, uniform dispersibility is not obtained. Variations occur in sex.

Next, a method for producing short metal fiber powder according to the present invention will be described. The metal short fiber powder of the present invention is basically obtained by cutting a metal foil. At the time of this cutting, the cutting edge of the shearing blade 1 is arranged at right angles to the feeding direction of the metal foil as shown in FIG. 1, and the cutting edge is set to a shear angle θ _{1 with} respect to the plane of the metal foil as shown in FIG. By inclining in the range of 15 to 35 °, a metal arc having a central angle of 45 to 180 °, a curved arc in the longitudinal direction and an arc shape, and a short metal fiber having a twist in the longitudinal direction are obtained. Can be

FIG. 1 shows an example of the apparatus for producing short metal fiber powder according to the present invention. In more detail, the metal foil 5 is supplied in a plurality of coils and has a predetermined width of 2 to 10 mm in a stacked state. As shown in FIG. 2, while a predetermined number of pieces are cut by a slitter 4 having a disk-shaped periphery and having a cutting edge on the periphery, and a predetermined number of pieces are fed by two pairs of pinch rollers 3 by the thickness of the metal foil to be used, as shown in FIG. the linear vertical reciprocation of shearing blades 1 having 15 to 35 ° predetermined shear angle theta _1, the metal short fibers obtained by shearing between the lower blade 6. In the drawing, reference numeral 2 denotes a foil press that moves up and down together with the shear blade 1.

Next, in order to produce the metal short fiber powder according to the present invention more efficiently, instead of the shearing method of cutting by reciprocating motion of one blade shown in FIG. 1, a spiral shape as shown in FIG. A cutting method using a rotary blade that continuously cuts through a lower blade on the normal line of a spiral end mill 7 having a plurality of outer peripheral cutting blades is used. Further, as a means for more efficiently producing the metal short fiber powder according to the present invention, as shown in FIG. 4, the slitter 4 in FIG. 1 is omitted, and the spiral end mill 7 is fed while feeding the laminated strip foil itself. It can also be obtained by using a cutting tool (Katinic end mill) 9 shown in FIG. Reference numeral 8 in the figure denotes a guide plate for preventing the metal foil from floating. The above cutting is performed on the normal line of the rotary tool. At this time, the cutting edge of the outer peripheral cutting edge is cut at right angles to the feeding direction of the foil at the point of contact with the lower blade and in the thickness direction of the metal foil, Then, a repulsive force acts in the opposite direction from the lower blade, the metal foil is fixed, and the amount of the metal foil is cut off as a cutting amount per one blade of the rotary cutting tool. Also,
Twist angle θ ₂ of the outer peripheral cutting edge must be 15 to 35 degrees,
At the same time the center angle theta ₃ as shown in FIG. 6 in this range exhibits an arcuate curved in the longitudinal direction as the fan-shaped arc is 45 to 180 °, the resulting metal short fibers having a twisted theta ₄ in the longitudinal direction .

〔Example〕

Example (1) As shown in FIG. 1, three copper foil strips 5 each having a width of 50 mm and a thickness of 45 μm and wound around a paper tube in a coil shape are stacked and transferred by a pinch roller 3 for transferring copper foil. In the middle of the cutting, the four slitters 4 provided at intervals of 10 mm between the front and rear pinch rollers 3, 3 are cut into 10 mm width in the longitudinal direction, and the shearing blade moves up and down with a shear angle of 20 ° above the lower blade 6. 50m by 1
μ was cut. In this case, the feed rate of copper foil is 12mm / mi
n, the number of cuts of the shear blade 1 was 240 times / min.

About 200 g of metal short fiber powder produced in this way,
Among 50 short metal fibers result of measuring the degree of extraction curved randomly, sector central angle theta ₃ shown in FIG. 6 is located average 160 °, the variation was ± 5 ° arc-shaped material . The short metal from one end in the longitudinal direction of the fiber twisted about 40 ° at the other end theta ₄ had occurred as Figure 7. To investigate the properties of the metal short fiber powder obtained as described above was measured for apparent density and tap density, respectively 1.2 g / cm ^3, it was 1.5 g / cm ^3. In addition, as for these measuring methods, the inner diameter is 5.0 cmφ, the depth is 5.1 cm, and the volume is 100 cm ^3.
In the case of apparent density, the fiber is filled into the container in a natural fall state, and in the case of tap density, the naturally filled container is further vibrated by tapping.
The density was calculated by dividing the filling weight by the volume and adding each 100 times to the closest packing.

Example (2) As in Example (1), in a state where three copper foils each having a thickness of 45 μm, each of which is chopped with a width of 10 mm in the longitudinal direction and stacked, are spirally twisted as shown in FIG. Cutting was performed with the lower blade 6 using a spiral end mill having a diameter of 40 mm having six 20 mm outer peripheral cutting blades. As a processing condition in this case, the cut amount per sheet is 50 μm as in the embodiment (1).
The feeding speed of the copper foil was 105 mm / min, and the rotation speed of the end mill was 350 rpm so that m was obtained.

This way, the metal to produce short fiber powder 200 g, Among 50 short metal fibers result of measuring the degree of extraction curved randomly, as shown in FIG. 6, average sector central angle theta ₃ 160 And the variation was ± 5 °. When checking apparent density and tap density to investigate the properties of the metal short fiber powder obtained as described above, respectively 1.2 g / cm ^3, it was 1.5 g / cm ^3. The short metal from one end in the longitudinal direction of the fiber twisted about 40 ° at the other end theta ₄ had occurred as Figure 7.

As described above, even when the spiral end mill was used, the same short metal fiber powder as in the shearing method of Example (1) was obtained.

Embodiments (3) to (6) According to the method shown in FIG. 4, the width is constant at 240 mm and the thickness is 35,5.
Examples of four kinds of strip-shaped copper foils wound in a coil shape on a paper tube at 0,70,100 μm, each in a state of three sheets stacked
The step of cutting in the longitudinal direction with the slitter performed in steps 1 and 2 was omitted, and the leading edge of the copper foil was directly twisted at a twist angle of 25 as shown in FIG.
゜, the length of the cutting edge is 3 mm, the groove length for cutting chips is 1 mm, and the diameter is 8 with 8 peripheral cutting edges provided at equal intervals
Cutting was carried out using a 0 mm Katnicnic end mill 9. As the processing conditions in this case, the feeding speed of the copper foil and the number of revolutions of the catenic end mill were selected as shown in Table 1 so that the cutting amount per blade becomes the foil thickness of each copper foil.

With respect to 200 g of each of the four types of short metal fiber powders having different fiber diameters, 50 metal short fibers were randomly extracted and the degree of curvature was measured. Also, as a comparative example, a conventional copper chatter fiber was added,
The apparent density and the tap density were measured to compare the characteristics. The results are shown in Table 1. First, the degree of curvature tends to decrease as the fiber diameter of the short metal fiber increases, and the central angle θ _{3 of the} sector having the short metal fiber as an arc is shown.
Varies from 135 ゜ to 105 ゜ on average. The 40-50 ° twisted theta ₄ has occurred at the other end from one end in the longitudinal direction in each of the short metal fibers. Next, the apparent density and tap density of each short metal fiber powder tend to slightly increase in accordance with the fiber diameter of each short metal fiber. However, the tap density of each of the metal short fiber powders is larger than the apparent density by 0.3 to 0.4 g / cm ³ . In the case of linear copper chatter fiber, this difference is as small as 0.1 g / cm ³ .

Examples (7) to (11) As metal foils other than copper foil, aluminum, brass, pure iron,
Example (3)-for stainless steel and nickel foil
As a result of cutting under the same manufacturing conditions as in (6), as shown in Table 2, all had tap density / apparent density of 1.3 to 1.4 and had good properties as metal short fiber powder for mixing with plastic.

[Effect of the Invention] As described above, the short metal fiber powder according to the present invention has an aspect ratio of an appropriate size, and the shape of each short metal fiber exhibits a bow shape curved in the longitudinal direction,
In particular, when it is twisted in the longitudinal direction, when it is mixed with plastic, it has excellent uniform dispersibility and reinforcing properties, and is effectively used as a metal filler of a heat-resistant and wear-resistant plastic composite material such as a disc brake pad.

[Brief description of the drawings]

FIG. 1 is a side view showing a main part of an apparatus for cutting a metal foil after cutting it by a slitter, and FIG. 2 is an explanatory view of an inclination angle (shear angle) θ ₁ of the shear blade in FIG. FIG. 4 is an explanatory view showing a blade portion of a spiral end mill, FIG. 4 is a side view showing a main part of an apparatus for cutting a metal foil by a Kathinikondo mill, and FIG. FIG. 6 is an explanatory view showing a central angle θ ₃ of a metal short fiber curved in the longitudinal direction and having an arc shape obtained by the present invention, and FIG. 7 is a torsion angle θ _{4 of the} metal short fiber obtained by the present invention. FIG. 1 shear blade 2 foil holder 3 pinch roller 4 slitter 5 metal foil 6 lower blade 7 spiral end mill 8 guide plate 9 catenic end mill θ ₁ shear angle θ ₂ ...... twist angle θ ₃ ...... central angle θ ₄ ...... twist angle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-274701 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22F 1/00

Claims (2)

(57) [Claims] 1. A fiber having a fiber diameter of 30 to 100 μm and a fiber length of 2 to 1
A metal having a fiber cross section of 0 mm, a quadrilateral shape, and at least 70 wt% or more of metal short fibers which are curved in the longitudinal direction as a sectoral arc having a central angle of 45 to 180 ° and exhibit an arc shape. Short fiber powder. 2. The short metal fiber powder according to claim 1, wherein the short metal fibers are curved in the longitudinal direction, have an arc shape, and have a twist in the longitudinal direction.