JP3330402B2 - Method for producing fiber-reinforced thermoplastic resin structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fiber-reinforced thermoplastic resin structure, and more particularly, to a fiber-reinforced thermoplastic resin having excellent adhesion between a reinforcing fiber and a resin and an extremely excellent reinforcing effect by the reinforcing fiber. The present invention relates to a method for manufacturing a thermoplastic resin structure.

[0002]

2. Description of the Related Art Conventionally, a method for producing a thermoplastic resin reinforced by fibers is roughly classified into the following two methods.

(1) One of the methods is to dry blend a reinforcing fiber having a length of, for example, about 3 mm into a thermoplastic resin,
Further, this is a method of kneading and granulating the mixture with an extruder. (2) Another method is a method in which continuous reinforcing fibers are passed through a die, a thermoplastic resin melted by an extruder is guided into the die, the reinforcing fibers are coated, and after cooling, cut.

At present, most commercially available fiber reinforced thermoplastic resins are produced by the method (1). In this method, the reinforcing fibers are crushed by kneading with a screw of an extruder, and the reinforced fibers are crushed. The reinforcing effect is not always sufficient. Further, the amount of fibers that can be blended is limited to at most about 40% by weight.

[0005] On the other hand, in the method (2), since the fiber length of the pellets is equal to the length of the pellets, the reinforcing effect by the fibers should be extremely excellent. However, it is difficult to cover and impregnate the filaments constituting the fibers with the thermoplastic resin only by passing the reinforcing fibers through the high-viscosity molten thermoplastic resin, and the reinforcing fibers fall off the pellets and scatter. Further, the molded products obtained from these pellets have a problem that the reinforcing fibers are not uniformly dispersed and become pills and are scattered throughout the molded products. Further, in order to uniformly disperse the reinforcing fibers of the pellet obtained by the method (2), a large shearing force is required at the time of molding. For this reason, there is a problem that the cutting of the reinforcing fibers is remarkable and the reinforcing effect is not sufficient. JP-B-63-37694 describes a method of impregnating a reinforcing fiber bundle with a molten polymer by pulling the surface of a rod or bar located in the molten polymer. However, in this method, the take-up speed of the reinforcing fiber is at most 3 m / min, which is not necessarily an industrially high-productivity method. Good mechanical properties may be impaired.

[0006]

Therefore, the present invention utilizes the method (2), which is excellent in principle, to reduce the thermal degradation of the polymer and to prevent the fibers from falling off from the fiber reinforced structure. It is an object of the present invention to provide a method for obtaining a fiber-reinforced thermoplastic resin structure having good fiber dispersibility during molding and excellent mechanical properties with high productivity.

[0007]

The method for producing a fiber-reinforced thermoplastic resin structure according to the present invention comprises a specific production step, namely, (a) immediately before coating and impregnating a reinforcing fiber with a molten thermoplastic resin. Preheating the reinforcing fibers above the melting temperature of the thermoplastic resin. (B) After coating the molten thermoplastic resin on the reinforcing fibers, the reinforcing fibers are heated above the melting temperature of the thermoplastic resin and arranged alternately up and down. In the case where the reinforcing fibers are glass fibers, the fiber width is widened by static electricity due to friction before the step (a) when the reinforcing fibers are glass fibers. The above object is achieved by combining these steps.

Hereinafter, the method and structure of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 2 denotes a roving fiber fed out from a roving bobbin 1. The roving fiber 2 includes glass fiber, carbon fiber, and the like.
Roving in which a large number (several tens to thousands) of filament fibers (several μ to several tens μ) of polyester fiber, nylon fiber, aromatic polyamide fiber and the like are bundled using a small amount of binder in general. Fiber is used. It is preferable that the amount of the binder is small to facilitate the opening of the roving fiber. However, even if the amount of the binder is large and tightly bundled, the rollers and bars are arranged in multiple stages after being unwound from the roving bobbin 1. Then, the roving fiber 2 can be used by applying tension thereto.

Further, when the roving fibers 2 to be used are glass fibers, as shown in FIG. 2, rollers or bars 11 whose surface material is an insulating material such as Teflon are arranged in multiple stages, and a pair of rolls is further provided. One of them has a rectangular notch parallel to the roll axis. Through the process of being taken by the drive roller 12, the fiber can be greatly opened. This is because the surface material is passed through a roller or bar 11, which is an insulating material such as Teflon, so that the binding force between the filaments by the binder is weakened, and at the same time, static electricity is generated in the glass roving fiber by a frictional force proportional to the tension,
Further, one of the pair of rolls has a rectangular cutout parallel to the roll axis, and the tension and relaxation of the tension are repeated by the drive roller 12, whereby a large fiber opening can be achieved.

In FIG. 1, a roving fiber 2 fed from a roving bobbin 1 is passed through a comb-like or annular yarn path 3 and aligned in a predetermined shape, for example, a thin strip, and then introduced into a preheating furnace 4. You. The preheating furnace 4 uses radiant heat such as a commonly used nichrome wire heater, hot air, a far infrared heater, and a heated die. At the outlet of the preheating furnace 4, the roving fibers 2 are coated with a thermoplastic resin 8
, The impregnation of the roving fiber 2 with the molten thermoplastic resin 8 is promoted, the speed of taking off the roving fiber 2 can be increased, and high productivity can be achieved.

The roving fiber 2 heated to a temperature higher than the melting temperature of the thermoplastic resin 8 is introduced into a coating die 5 and is covered with the thermoplastic resin melted and plasticized by an extruder 7.

The thermoplastic resin usable in the present invention is not particularly limited as long as it is softer and has a lower melting point than the reinforcing fibers.
Any material may be used in combination with the reinforcing fiber, for example, specifically, polyamide, polypropylene, polyester, polyarylene sulfide, polyacetal, etc., and fiber reinforced heat obtained by the production method of the present invention. Other resins, elastomers, inorganic fillers, coloring agents, heat stabilizers, plasticizers, lubricants, release agents, flame retardants, etc. can be added as long as the properties of the plastic resin structure are not impaired.

The extruder 7 is an extruder generally used for thermoplastic resin, and any extruder capable of supplying the plasticized and molten thermoplastic resin to the coating die 5 in a stable state without discharge unevenness. Extruders can also be used.

The coating die 5 is a roving fiber 2
This is a die for coating a molten thermoplastic resin, and may be a die usually used for covering an electric wire, etc., but a predetermined shape, for example, a thin band shape is maintained by a comb-shaped or annular yarn path 3 to melt the resin. It is preferable to use a coating die that is introduced into a bath of a thermoplastic resin that has been melted, is coated with a molten thermoplastic resin, and has a structure that can be pulled out while maintaining its shape. Furthermore, depending on the production speed, the structure of the coating die is such that the internal pressure of the resin is increased, and the pressure of the extruded resin is reduced in the direction of reducing the pulling force of the roving fiber coated with the molten thermoplastic resin. A die having such a structure as to act on is preferable. The amount of the thermoplastic resin coated with the coating die is 30 to 80% by weight. If the content is less than 30% by weight, the resin impregnation is insufficient, and the sufficient effect of the reinforcing fiber is not exhibited. 80% by weight
If the ratio exceeds, the reinforcing effect of the reinforcing fibers is small, and is not the object of the present invention.

The roving fiber coated with the molten thermoplastic resin is introduced into an uneven die 6 having convex portions arranged alternately up and down and heated to a temperature higher than the melting temperature of the thermoplastic resin and lower than the decomposition temperature. , And contact with and pass through the convex portion. FIG. 3 shows a schematic view of the concavo-convex die. In FIG. 3, 1
Reference numeral 3 denotes an uneven die convex portion, and 14 denotes a fiber passage covered with a molten resin. It is preferable that the degree of protrusion from the yarn path in the concavo-convex die 6 (the difference in height between the lower convex and the upper convex) is large because the impregnation of the molten thermoplastic resin into the roving fiber can be promoted. Although it depends on the viscosity and amount of the thermoplastic resin, it cannot be too large in terms of fluffing of the roving fiber, further cutting or reduction of the take-up speed, and increase of the take-up tension. However, by increasing the number of protrusions in the concave and convex die 6, even if the degree of protrusion is small, it is possible to promote the impregnation of the roving fiber with the molten thermoplastic resin.
The number of the convex portions is preferably 8 or more, and below that, unless the degree of convexity is further increased, the expected impregnation of the thermoplastic resin cannot be obtained, and the fluffing of the roving fiber as described above,
Furthermore, cutting or an increase in take-off tension occurs. The shape and arrangement of the projections 13 of the die are set so as not to damage the reinforcing fibers coated with the molten resin. For example, a convex with a convex radius of 12.5 to 25 mm is changed to a convex of 10 mm to 50 mm.
It is preferable to arrange them at mm intervals.

According to the manufacturing method of the present invention, a fiber-reinforced thermoplastic resin structure such as a tape, a string, or a sheet in which reinforcing fibers composed of reinforcing fibers and a thermoplastic resin are arranged in parallel according to the shape of the outlet of the concavo-convex die 6. The body is obtained.

In particular, the roving fiber coated with the molten thermoplastic resin and passed through the concavo-convex die 6 is a mold having a perforation such as a forming nozzle, which is heated to a temperature higher than the melting temperature of the thermoplastic resin and lower than the decomposition temperature. After being formed into a strand, it is cooled and solidified by the cooling device 9, and the strand is cut into a desired length by the cutter 10.

[0019]

EXAMPLES The method for producing the fiber-reinforced thermoplastic resin structure of the present invention will be described in detail in the following examples, taking as an example the case where polyamide 6/6 is used as the thermoplastic resin and glass fiber is used as the reinforcing fiber roving. . These examples are given by way of illustration and the invention is not limited thereto.

The evaluation of the fiber-reinforced thermoplastic resin structure described in the examples was carried out according to the following method.

(1) Roving fiber content The fiber-reinforced thermoplastic resin structure was placed in an electric furnace at 650 ° C for 4 hours.
After charging for 5 minutes, the resin content was incinerated and calculated from the weight before and after that.

(2) Dropping rate of roving fiber In order to quantify the degree of impregnation of the roving fiber with the thermoplastic resin, about 1 g of a sample obtained by the following method was used.
Weigh, put into a 100 ml Erlenmeyer flask and shake for 5 minutes.

Next, the sample from which the fibers have fallen off by shaking is taken out of the flask, and the amount of the fibers that have fallen off is calculated from the weights before and after that. The roving fiber shedding rate was determined by the following equation.

ES (%) = (Mf / Ms) / Wf × 10000 where Mf: amount of dropped fibers (g) Ms: sample amount (g) Wf: roving fiber content (%)

Next, a method for preparing a sample will be described. The pellet obtained by cutting the strand is cut at a length of 5 mm at right angles to the direction in which the fibers are arranged (taken), and the pellet cross section is reduced by 1 / along the direction in which the fibers are arranged.
2 and a sample having a semicircular section with a length of 5 mm was used.

(3) Mechanical Properties Using a IS150E injection molding machine manufactured by Toshiba Machine Co., Ltd., dumbbells having a thickness of 3 mm and test pieces of tanzaku were molded. Next, a tensile test, a bending test, and a notched Izod impact test were performed according to ASTM D638, D790, and D256.

Example 1 In this example, a pellet-shaped fiber-reinforced thermoplastic resin structure was manufactured using the apparatus shown in FIG.

First, glass roving fiber [1150 t
ex, Asahi Fiberglass Co., Ltd., diameter 16μ, FT5
94], and four roving bobbins were prepared. Feed out glass roving fiber from this roving bobbin,
Zigzag wrapped around four 25 mm diameter bars with Teflon sheet wound, and the upper roll was about 102 mm diameter,
It was pulled up by a driving roller having three notches of 2 mm depth and 55 mm width at equal intervals. At this time, each of the four glass roving fibers was spread from a width of 5 mm to a maximum of 120 mm from a width of 35 mm. Next, the glass roving fiber was introduced into a hot air preheating furnace and heated to about 300 ° C.

On the other hand, Leona 1200 manufactured by Asahi Kasei Corporation
(Polyamide 6/6, melting point: 263 ° C.) was plasticized and melted using a single screw extruder, and supplied to a coating die. The above-mentioned four glass roving fibers are introduced into the die, and coated with molten polyamide 6/6.
2. The degree of protrusion from the yarn path is 3 mm and the protrusion radius is 12.5 m
m, the distance between the protrusions is 12.5 mm, and it passes through an uneven die set at a surface temperature of 285 ° C., and is further formed into a strand through a nozzle having a tip hole diameter of 3 mm set at a surface temperature of 290 ° C., and then cooled with water. Then, the mixture was solidified and cut into a length of about 10 mm to obtain a glass fiber reinforced polyamide 6/6 in a pellet form. The transaction speed was 20 m / min. Table 1 shows the results of the evaluation of the sample by the method described above.

Comparative Example 1 A pellet-shaped glass fiber reinforced polyamide 6/6 was obtained in the same manner as in Example 1 except that the number of protrusions of the concave-convex die was reduced to 7. The take-off speed was 20 m / min.
However, the pellets suffered severe cutting defects, glass fibers protruded from the end faces of the pellets, and could not be molded because they did not cut into the cylinder from the hopper of the injection molding machine. Table 1 shows the results of the evaluation of the sample by the method described above.

Comparative Example 2 The number of protrusions of the concavo-convex die was reduced to 7, and the take-off speed was 10 m / min.
A pellet-like glass fiber reinforced polyamide 6/6 was obtained in the same manner as in Example 1 except that However, as in Comparative Example 1, the pellets were significantly defective in cutting and could not be molded. Table 1 shows the results of the evaluation of the sample by the method described above.

Example 2 A pellet-shaped glass fiber reinforced polyamide 6/6 was obtained in the same manner as in Example 1 except that the number of protrusions of the concave-convex die was 9, and the take-off speed was 10 m / min. Table 1 shows the results of the evaluation of the sample by the method described above.

Comparative Example 3 A pellet-shaped glass fiber reinforced polyamide 6 was prepared in the same manner as in Example 1 except that the number of protrusions of the concavo-convex die was reduced to 7, the degree of protrusion was 4 mm, and the take-off speed was 10 m / min. / 6
However, the strand was cut, which was considered to be due to a large amount of fluff and an increase in tensile tension, and a sample that could be molded was not obtained. Table 1 shows the results of the evaluation of the sample by the method described above.

Reference Example 1 Leona 1300 pellets and glass fiber chopped strands manufactured by Asahi Kasei Kogyo Co., Ltd. [Asahi Fiber Glass Co., Ltd.]
And a filament diameter of 13 μm and a length of 3 mm] were dry-blended to obtain glass fiber-reinforced polyamide 6/6 pellets by a conventional method using a single screw extruder. The glass fiber content of the pellet was 60% by weight. In the production of this pellet, vent up and pulsation are observed,
Driving was unstable. Table 1 shows the results of the evaluation of the sample by the method described above.

[0035]

[Table 1]

[0036]

According to the method of the present invention, a fiber-reinforced thermoplastic resin structure having excellent adhesion between a reinforcing fiber and a resin and having a very excellent reinforcing effect by the reinforcing fiber can be obtained with high productivity. Having.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of an apparatus used in the method of the present invention.

FIG. 2 is a schematic diagram showing the configuration of a fiber opening device inserted before a preheating step (step (a)) when reinforcing fibers are glass roving fibers.

FIG. 3 is a schematic view showing one example of a structure of a concavo-convex die used in the present invention.

[Description of Signs] 1 Roving fiber bobbin 2 Roving fiber 3 Yarn 4 Preheating furnace 5 Coating die 6 Concavo-convex die 7 Extruder 8 Thermoplastic resin 9 Cooling device 10 Cutter 11 Bar whose surface material is insulating material 12 In the roll axis direction Drive roller having notch 13 Uneven die, convex part 14 Fiber passage covered with molten resin

Continuation of front page (56) References JP-A-5-162135 (JP, A) JP-A-63-264326 (JP, A) JP-A-3-230943 (JP, A) JP-A-3-183353 (JP) JP-A-2-151407 (JP, A) JP-A-4-138219 (JP, A) JP-A-6-47825 (JP, A) JP-A-63-37694 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 70/00-70/88 B29B 11/00-11/16 B29B 13/00-13/10 B29B 15/00-15/14

Claims (3)

(57) [Claims] 1. A method for producing a fiber-reinforced thermoplastic resin structure in which a molten thermoplastic resin is coated and impregnated while pulling continuous reinforcing fibers, wherein (a) the reinforcing fiber is coated with the molten thermoplastic resin. Preheating the reinforcing fiber to a temperature equal to or higher than the melting temperature of the thermoplastic resin immediately before impregnation; (b) heating the reinforcing fiber with the molten thermoplastic resin to a temperature equal to or higher than the melting temperature of the thermoplastic resin; A method of producing a fiber-reinforced thermoplastic resin structure, wherein the fiber-reinforced thermoplastic resin structure is caused to contact with and pass through a convex part in a passage having eight or more convex parts arranged alternately above and below. 2. The fiber according to claim 1, wherein the continuous reinforcing fiber glass is fiber roving, and before the step (a), static electricity is generated in the glass fiber by friction to increase the width thereof. A method for producing a reinforced thermoplastic resin structure. 3. The method for producing a fiber-reinforced thermoplastic resin structure according to claim 1, wherein after the step (b), the fiber-reinforced thermoplastic resin structure is formed into a strand and cooled and cut.