JPH04316807A - Long fiber reinforced resin pellet - Google Patents

Abstract

PURPOSE:To form a compact, which can bear filler, modifier and the like, and is dynamically excellent by a method wherein the pellet concerned has two phase structure consisting of reinforced resin core, in which reinforcing fibers are arranged to the longer direction of the pellet, and fiber un-reinforced resin sheath made of the same material as of the core. CONSTITUTION:Fiber reinforced resin core 2, in which reinforcing fibers are arranged to the longer direction of pellet and uniformly dispersed, is formed. Fiber un-reinforced resin sheath 4 is made of the same resin as that constituting the core. The long fiber reinforced resin pellet has two phase structure consisting of the core 2 and the sheath 4. In this case, the content of resin in fiber reinforced resin part 1 is 20-80wt.%. Further, the resin composing the fiber un-reinforced resin sheath 4 contains additive. As the additive, filler, modifier, antioxidant, antistat, flame retardant and the like, which allow to give various characteristics requiring for pellet, are employed.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to long fiber reinforced resin pellets having a two-phase structure that can be used for injection molding, and particularly to long fiber reinforced resin pellets having a two-phase structure that can be molded into molded products with excellent mechanical properties. This invention relates to fiber-reinforced resin pellets.

0002

[Prior Art] Fiber-reinforced thermoplastic resin pellets used in injection molding are conventionally made by melt-kneading a base resin, reinforcing fibers, other additives, etc., and then discharging the molten mixture from the nozzle tip of a die and cutting it. It was produced by pelletizing it. However, due to the shearing force applied to the molten mixture in the melt extruder, the reinforcing fibers added are cut short, and when the resulting pellets are used to make a molded product, the mechanical properties and other properties of the molded product are developed. I had a problem in doing so.

[0003] Furthermore, in order to homogenize the mixture, the extrusion operation is repeated two or more times during pellet production, but this tends to significantly shorten the length of the reinforcing fibers. The original length of the reinforcing fibers used in the production of the above-mentioned fiber-reinforced resin pellets is usually from several mm to several mm, but the average residual fiber length in the molded product is about 0.0 mm in the case of glass fibers. It is generally said to be about 3 to 0.5 mm, and about 0.1 to 0.2 mm in the case of carbon fiber. By the way, the mechanical properties of a molded product obtained by injection molding are determined by the length of the remaining fibers (critical fiber length: meaning a length equal to or greater than Lcr) when the adhesion at the interface between the matrix resin and the reinforcing fibers is good. However, current methods of manufacturing formed bodies have reached their limits in improving mechanical properties.

[0004] In recent years, the development of long fiber reinforced resin pellets has been studied in order to improve the mechanical properties of molded articles formed using these fiber reinforced resin pellets. In other words, the length of the reinforcing fibers present in the fiber reinforced resin pellet is 3~
The length of the reinforcing fiber bundle is approximately 13 mm, each single fiber of this reinforcing fiber bundle is uniformly dispersed in the matrix resin, and the reinforcing fibers are arranged parallel to the length direction of the pellet. In the field of short fiber-reinforced thermoplastic composite materials (abbreviated as FRTP), the use of longer fibers and higher Vf in fiber-reinforced resin pellets is being studied.

[0005] By the way, the method for producing long fiber reinforced resin pellets is generally based on the pultrusion molding method of unidirectionally reinforced thermoplastic resin with continuous fibers, but the resin supply method is generally a powder impregnation method or a solution method. It is roughly divided into three types: impregnation method and melt impregnation method. The first powder impregnation method involves immersing reinforcing fibers in polymer fine powder of several microns to several hundred microns, and attaching the polymer fine powder to each single fiber that makes up the reinforcing fibers, or applying electrostatic powder to spread fiber bundles. This is a method of applying charged polymer fine powder using a body coating machine. After adhering the polymer fine powder, the fiber bundle is drawn into a high-temperature furnace or a high-temperature mold to melt the polymer and impregnate the fibers.

[0006] In the second solution impregnation method, a reinforcing fiber bundle that has been opened is passed through a lacquer in which a polymer is dissolved in a solvent and impregnated with the lacquer, and then the solvent is scattered in a dryer. In this method, several of the polymer-attached fiber bundles obtained in this way are drawn into a high-temperature mold to completely coat each single fiber in the fiber bundle with the polymer. The third melt impregnation method is the most common method, and involves extruding matrix resin into a mold attached to the tip of a melt extruder, and then drawing reinforcing fibers into this mold to impregnate the fibers with resin. This is the way to try.

Furthermore, JP-A-2-292008 discloses a method of injection molding a thermoplastic resin composition containing long fibers using an injection molding machine in which the depth of the screw groove is greater than a specified value. A method of injection molding using an injection molding machine having a diameter of 6 mm or more is proposed in JP-A-2-292009.

[0008]

[Problem to be solved by the invention] However, the above FR
The conventional technology for TP is FR, which is a grade mainly based on mechanical properties.
This is an attempt to improve TP, and the current situation is that it has not yet achieved performance that satisfactorily satisfies the other elements, workability, appearance, electrical properties, thermal properties, etc. required of FRTP molded products as products. Further, the above-mentioned powder impregnation method has the problem that it is difficult to obtain inexpensive high molecular weight polymer fine powder, and it is also difficult to simultaneously supply various additives at the time of impregnating the polymer into fibers.

Furthermore, the solution impregnation method described above cannot be called a general method because the polymers to be used are limited from the viewpoint of polymer solubility. Moreover, even when the polymer is dissolved in a solvent, the solubility of the polymer is around 20% by weight, and there is a problem that the amount of polymer that can be attached to the reinforcing fiber cannot be increased. Moreover, as in the case of the powder impregnation method, there is a drawback that various additives cannot be supplied simultaneously during polymer impregnation.

Furthermore, in the above melt impregnation method, since the thermoplastic resin used generally has a high melt viscosity (approximately tens of thousands of poise), it is extremely difficult to wet each single fiber constituting the reinforcing fibers with the resin. be. Further, although this method has the advantage that various additives can be simultaneously supplied to the matrix resin, when various additives are actually added, the melt viscosity tends to further increase, which is not preferable. Therefore, in the case of the melt impregnation method, a method is used in which the reinforcing fibers are impregnated with the resin and then re-impregnated using a heated roll or heated die, but such re-impregnation method tends to damage the reinforcing fibers; This is not preferable because it tends to cause fuzz. Moreover, when re-impregnating using a heated roll, the reinforcing fibers may be wrapped around, resulting in problems in workability. Furthermore, defects such as voids tend to remain in the resulting pellets due to insufficient resin impregnation, which is disadvantageous.

On the other hand, the injection molding methods proposed in JP-A-2-292008 and JP-A-2-292009 require complicated molding conditions, and it is difficult to control the injection molding conditions. The problem is that it is difficult. As mentioned above, the long fiber reinforced resin pellets produced by the prior art are far from general-purpose grade pellets that also contain various additives, and the injection molding method requires special conditions.

In view of the above-mentioned current situation, the present inventors have developed a molding method with excellent mechanical properties that fully utilizes the excellent properties inherent in a long fiber reinforced thermoplastic resin composition without using special injection molding conditions. The present invention was arrived at as a result of intensive studies aimed at obtaining long fiber reinforced pellets as a product.

[0013]

[Means for Solving the Problems] The gist of the present invention is to provide a fiber-reinforced resin core in which reinforcing fibers are arranged in the length direction of a pellet, and a fiber-reinforced resin core made of the same resin as the core. It is a long fiber reinforced resin pellet having a two-phase structure composed of a reinforced resin sheath.

A typical structure of the long fiber reinforced resin pellet having a two-phase structure according to the present invention will be schematically explained with reference to the drawings. FIG. 1 is a perspective view of a pellet with a cylindrical structure, and FIG. 2 is a perspective view of a pellet with a rectangular structure. In FIGS. 1 and 2, 1 represents reinforcing fibers, 2 represents a fiber reinforced resin core, 3
4 indicates a resin, and 4 indicates a fiber-unreinforced resin sheath.

The most significant feature of the present invention is that, unlike the conventional long fiber reinforced resin pellets which are simply formed by blending long fibers into a thermoplastic resin, the present invention has a fiber reinforced resin core as described above and a fiber-free pellet. Composed of reinforced resin sheath part 2
It has a phase structure, and by having such a structure, more resin constituting the fiber-unreinforced resin sheath can be impregnated into the reinforcing fibers in the core. Moreover, various additives can be contained in the resin constituting the sheath, and as a result, by injection molding using the long fiber reinforced resin pellets of the present invention, the resin uniformly impregnates the reinforcing fibers, Furthermore, it has an excellent effect as a general-purpose grade in that various additives are uniformly dispersed in the resulting molded product, and molded products with excellent mechanical properties, appearance, electrical properties, thermal properties, etc. can be obtained.

The reinforcing fibers used in the present invention include glass fibers, aramid fibers, alumina fibers, silicon carbide fibers, tyranno fibers, pitch-based carbon fibers, and PA fibers.
Examples include N-based carbon fibers, and among these, PAN-based carbon fibers are preferred. It is also possible to use a hybrid of PAN-based carbon fiber and other reinforcing fibers.

[0017] The resins constituting the core and sheath used in the present invention include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, 6-nylon, 6,
Examples include polyamide resins such as 6-nylon, polyetherimide resins, polyetheretherketone resins, polyetherketoneketone resins, and polyphenylene sulfide resins.

In carrying out the present invention, the same resin is used for the fiber-reinforced resin core and the non-fiber-reinforced resin sheath. This further improves the impregnation of the reinforcing fibers with the resin. Note that the resin content in the fiber-reinforced resin core is preferably in the range of 20 to 80% by weight. If the resin content is within this range, it is possible to perform molding without losing the fluidity of long fiber reinforced resin pellets, and to suppress fiber breakage as much as possible during injection molding, increasing the average residual fiber length in the molded product. This is preferable because it makes it possible to

Furthermore, in the present invention, additives can be incorporated into the resin constituting the fiber-unreinforced resin sheath as described above. With the manufacturing technology of fiber-reinforced resin pellets, it is now possible to make long fiber-reinforced resin pellets carry fillers, etc., which were difficult to add due to operational reasons.
It is possible to impart the characteristics of a general-purpose grade that satisfies the various requirements required for injection molding pellets to the special grade type long fiber reinforced resin pellets that have so far focused on mechanical properties.

Additives that can be used in carrying out the present invention include fillers, modifiers, mold release agents, pigments, antioxidants,
Examples include antistatic agents, nucleating agents, low shrinkage agents, flame retardants, specific gravity regulators, flow regulators, etc., and these can be used singly or in combination of two or more depending on the purpose.

Next, a typical method for manufacturing the long fiber reinforced resin pellets having a two-phase structure according to the present invention will be described below with reference to an example in which carbon fibers are used as the reinforcing fibers. The following manufacturing method examples can also be applied when other reinforcing fibers are used.

First, a fiber-reinforced resin core is created in which the reinforcing fibers are arranged in the length direction of the pellet and uniformly dispersed in the resin, but this core can be easily formed by the process shown in FIG. 3, for example. can be implemented. That is, first, for example, a carbon fiber bundle with a size amount of 0.5% by weight is introduced into an impregnation bath containing a thermoplastic resin powder 6 having a particle diameter of not more than a number + μ, and when the resin powder 6 is attached to the fibers, the fiber bundle 5 becomes Spread and widen.

Next, the widened fiber bundle 5 is impregnated by dipping in a lacquer 7 in which about 10% by weight of the same thermoplastic resin as the resin powder 6 is dissolved in a solvent, and then introduced into a hot air dryer 8. The solvent is volatilized to obtain a widened carbon fiber tow to which the resin is attached. The amount of resin attached to the fiber tow has a roughly linear relationship with the width of the tow, and by controlling the tow width of the spread tow, the apparent amount of resin attached can be set appropriately in the range of several percent to 80%. As described above, the amount of the attached resin is preferably in the range of 20 to 80% by weight.

Next, the resin-attached fiber bundle 5 obtained in this manner
Several of the tubes are guided to the inlet 11 of a mold 10 heated to a high temperature attached to the tip of an extruder 9 as shown in FIG. After that, the fiber bundle 5 is pulled out from the outlet 12 of the mold, and at the same time,
Resin pellets prepared separately by adding various additives are supplied from a hopper (not shown) of an extruder 9, and the resulting mixture is melt-kneaded and attached to the tip of the extruder 9.
The resin-attached fiber bundle 5 is coated around the resin-attached fiber bundle 5 to form a resin sheath, and then pulled out from the outlet 12 of the mold 10.

[0025] The resin-attached fiber bundles 5 led to the entrance 11 of the mold 10 are melted and bonded to each other immediately after being led to the entrance 11, so this becomes a core and various additives are contained around it. A resin is coated within the mold 10 as described above to form a resin sheath. After leaving the mold 10, the continuous rod-shaped product having a two-phase structure in which the sheath portion is formed is cooled and cut into lengths of about 10 mm using a guillotine cutter to obtain long fiber-reinforced resin pellets having a two-phase structure. In the present invention, it is possible to change the resin content of the entire pellet by changing the thickness of the resin sheath during the preparation of the pellet.

[0026] There is a wire coating technique that is similar to the technique for preparing long fiber reinforced resin pellets described above, but when pellets are prepared using such a technique, the reinforcing fibers in the core are hardly wetted with the coating resin. When the obtained pellets are used for injection molding, various problems occur such as fragmentation of the unimpregnated portion of the fibers, generation of thread balls, and non-uniformity of the molded product. However, when preparing the long fiber-reinforced resin pellets of the present invention, by employing the method described above, it is possible to provide excellent pellets without any of the problems presented by the prior art.

[0027] The length of the reinforcing fibers in the long fiber reinforced resin pellets having a two-phase structure of the present invention is substantially the same as the length of the pellet, and the length of the pellet is usually 3
Those having a diameter of mm or more, preferably 5 mm or more are suitably used.

[0028]

[Examples] The present invention will be explained in detail with reference to Examples below. Example 1 PAN-based carbon fiber (Pyrofil TR30, 12K, a registered trademark manufactured by Mitsubishi Rayon Co., Ltd.) in the form of a tow with a size amount of 0.5% by weight was used as a reinforcing fiber, and granules were prepared by the process shown in Figure 3. The carbon fiber tow was introduced into an impregnating tank containing polycarbonate resin powder (registered trademark Iupilon ALO71, manufactured by Mitsubishi Gas Chemical Co., Ltd.) with a diameter of several tens of microns or less, and was spread and expanded. Thereafter, the spread and widened carbon fiber tow was dipped and impregnated in a lacquer prepared by dissolving about 10% by weight of polycarbonate resin (Novarex 7025A, manufactured by Mitsubishi Kasei Corporation) in 1,2-dichloroethane, and then the impregnated carbon The fiber tow was passed through a hot air circulation dryer at 130° C. to volatilize 1,2-dichloroethane and dry it. Furthermore, the carbon fiber tow after drying is 200~3
The impregnation of the polycarbonate resin was improved by passing it through a dryer at 00°C. In this way, carbon fiber tape-like products containing polycarbonate resin were continuously manufactured. The amount of resin attached to this tape-like material was about 50% by weight.

Four tape-shaped carbon fibers impregnated with the polycarbonate resin thus obtained are fed from the inlet 11 of a drawing mold attached to the tip of an extruder as shown in FIG. The four supplied tapes were melted and bonded together. On the other hand, modified polycarbonate resin pellets prepared separately by blending fillers, modifiers, pigments, and mold release agents with polycarbonate resin are fed into the hopper of an extruder, melt-kneaded, and then heated to 300°C for drawing. The aggregate of the carbon fiber tape-like material transferred and supplied into the mold and previously melt-bonded is pulled out through a pulling device provided outside the front of the mold, thereby forming a surface of the carbon fiber tape-like material aggregate. The modified polycarbonate resin was continuously coated.

A continuous film having a two-phase structure consisting of a core made of an aggregate of carbon fiber tapes impregnated with the polycarbonate resin obtained in this manner and a sheath made of a modified polycarbonate resin layer. After the bar exited the mold, it was cooled and continuously wound on a winder. After that, the wound continuous rod was cut into lengths of approximately 10 mm using a guillotine cutter to obtain a two-phase structure consisting of a carbon fiber-reinforced resin core in which carbon fibers were arranged in the length direction, and a resin sheath. Long carbon fiber reinforced resin pellets were obtained.

[0031] This long carbon fiber reinforced resin pellet was injection molded using an injection molding machine to prepare a test piece. The molding conditions during injection molding were: compression ratio 2, L/D = 10 (L: screw length, D: screw outer diameter), screw rotation speed 40 r.
pm Below, the injection speed was 4 mm/min and the runner gate opening was made as large as possible. Using the obtained test piece, JIS
As a result of conducting a bending test in accordance with K 7055,
Flexural modulus: 3 ton/mm2, bending strength: 40 kg/
It was mm2. Further, the average residual carbon fiber length in the test piece was 3 mm, and the carbon fiber content was 40% by weight.

Example 2 The carbon fiber tow used in Example 1 was spread using a spreader roll. Next, using the electrostatic powder coating machine shown in FIG. 5, 50% by weight of the same polycarbonate resin powder as that used in Example 1 was applied to the spread carbon fiber tow. Thereafter, the carbon fiber tow impregnated with the polycarbonate resin powder was passed through a heating furnace set at 240 to 300°C to melt and adhere the polycarbonate resin powder to the carbon fiber tow. Next, the four carbon fiber tows thus obtained were supplied from the inlet 11 of the drawing die attached to the tip of the extruder as shown in FIG. 4 in the same manner as in Example 1, and The four supplied carbon fiber tows were pulled out from No. 12 and melted and bonded.

On the other hand, the modified polycarbonate resin used in Example 1 was continuously coated on the surface of the melt-bonded carbon fiber tow by the same method as in Example 1, and a core portion impregnated with the polycarbonate resin was formed. The continuous rod had a two-phase structure consisting of a sheath portion made of a modified polycarbonate resin layer.

[0034] After this continuous rod came out of the mold, it was cooled and continuously wound on a winder. After that, the wound continuous rod is cut into lengths of about 10 mm each with a guillotine cutter, and has a two-phase structure consisting of a carbon fiber reinforced resin core part and a resin sheath part, in which carbon fibers are arranged in the length direction. Long carbon fiber reinforced resin pellets were obtained. Using this long carbon fiber reinforced resin pellet, injection molding was performed using the same injection molding machine and molding conditions as in Example 1 to prepare a test piece. A bending test in accordance with JIS K 7055 was carried out using the obtained test piece, and as a result, the bending elastic modulus was 2.8 ton/mm2 and the bending strength was 41 kg/mm2. Further, the average carbon fiber length in the test piece was 2.8 mm, and the carbon fiber content was 39% by weight.

[0035]

Effects of the Invention Since the long fiber reinforced resin pellets of the present invention have the above-mentioned structure, (a) fillers, modifiers, mold release agents, etc., which were difficult to produce using conventional long fiber reinforced pellet production techniques, can be removed; Additives can be supported on long fiber reinforced resin pellets, making it a general-purpose product that satisfies the various requirements required for injection molded pellets in addition to special grade types of long fiber reinforced resin pellets focused on mechanical properties. (b) Additives can be contained in the resin sheath, and these additives can be uniformly mixed with the matrix resin of the long fiber reinforced resin core during injection molding. (c) without losing fluidity as long fiber reinforced resin pellets,
In addition, it is possible to perform molding in which cutting of reinforcing fibers is suppressed as much as possible during injection molding, and (d) excellent effects such as being able to mold a molded article with overall excellent mechanical properties are achieved.

[0036]

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views of embodiments of long fiber reinforced resin pellets having a two-phase structure according to the present invention.

[Figure 1] Perspective view of a cylindrical structured pellet

[Figure 2] Perspective view of rectangular structured pellet

[Figure 3] Diagram showing an example of a process for creating a fiber-reinforced resin core

[Fig. 4] A diagram showing an example of a process for forming a fiber-reinforced resin core and a resin sheath together.

[Figure 5] Schematic diagram of electrostatic powder coating machine

[Explanation of symbols]

1 Reinforcing fiber
2 Fiber reinforced resin core 3 Resin
4 Resin sheath part 5 Fiber bundle
6
Fine polymer powder 7 Lacquer
8 Dryer 9 Extruder
10 Mold 11
Mold reinforcing fiber inlet 12
Mold outlet 13 Two-phase structure long fiber reinforced resin rod 14
Pulling device

Claims (3)

[Claims] Claim 1: The pellet has a two-phase structure consisting of a fiber-reinforced resin core in which reinforcing fibers are arranged in the length direction of the pellet, and a non-fiber-reinforced resin sheath made of the same resin as the resin constituting the core. Long fiber reinforced resin pellets. [Claim 2] The resin content of the fiber reinforced resin core is 20
Pellet according to claim 1, characterized in that it is 80% by weight. 3. The pellet according to claim 1, wherein the resin constituting the fiber-unreinforced resin sheath contains an additive.