JP2013039809A - Method and apparatus for manufacturing natural fiber reinforced resin strand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple manufacturing apparatus that can increase the strength by sufficiently impregnating resin between fibers when manufacturing strands and pellets of natural fiber reinforced resin for injection molding.SOLUTION: A yarn bundle of natural fibers is passed through a preheating pipe 4, and preheated close to the melting temperature of resin to be coated thereon. Molten resin is coated on the yarn bundle preheated by passing through a crosshead die 1. When a resin-impregnated part C with a plurality of pins being disposed in a ladder shape in the axial direction is held at the temperature close to the melting temperature of the resin, and passed in a cylindrical heater 5, the resin-impregnated part is stretched over the pins in a zigzag manner. Through the slidable rubbing above and below the pins, the resin is sufficiently impregnated between the fibers of the yarn bundle. The yarn bundle is preheated to the temperature close to the melting temperature of the resin in the preheating pipe 4, and the resin is excellently coated on the yarn bundle.

Description

  The present invention relates to a method and an apparatus for producing a natural fiber reinforced resin strand, and more particularly, a natural fiber reinforced resin strand for simple injection molding in which resin impregnation is applied to an electric wire coating system in which a resin coating apparatus is attached to an extrusion molding machine. The present invention relates to a manufacturing method and a manufacturing apparatus.

  Fiber reinforced plastic (FRP) is excellent in strength, heat resistance, and corrosion resistance, and is used as a structural member in various industrial and consumer devices including automobiles and aircraft. As a typical example, glass fiber reinforced plastic (GFRP) is often used. However, this has a problem that the energy consumption is large in the production process and the environmental load at the time of disposal is high. On the other hand, a natural fiber reinforced resin using a high-strength plant fiber as a reinforcing material, so-called green composite, has attracted attention and is used from the viewpoint of environmental load.

  In general, fiber reinforced resin strands for injection molding use natural fibers together with resin in an extrusion molding machine to form extruded strands through a kneading process, and pellets obtained by cutting the strands are used for injection molding. For fiber reinforced resin, the critical fiber length is the minimum length that can reach a level equivalent to the stress caused by loading the continuous fiber when the short fiber embedded in the resin is loaded along the fiber axis. The fibers were cut by the shearing force generated when the screw was rotated in the extruder, and it was difficult to produce a long fibrous composite material exceeding the critical length. Therefore, an apparatus for producing long fiber pellets using continuous fiber filaments such as glass fibers using an electric wire coating system has been developed. The following document discloses the fiber reinforced resin strand and pellet manufacturing technology.

  Patent Document 1 discloses that a filament yarn is immersed in a resin bath (resin tank) and the resin is infiltrated between fibers via a roller, a pin, or the like. Since this method is entirely made of resin, the resin easily penetrates between the fibers. However, as the number of rollers or pins increases, a large amount of extra resin is required, leading to resin loss. Further, once the resin components are determined, there is a difficulty in that the components in the tank cannot be controlled thereafter.

  In Patent Document 2, a long reinforcing fiber bundle is immersed in a molten resin in a crosshead so that the fiber bundle is impregnated with resin. Discloses a method for producing a fiber reinforced resin strand impregnated with a resin. Glass fiber is used as the reinforcing fiber in this manufacturing method, and it is not applied to the one using natural fiber twisted yarn as the reinforcing fiber. The natural fiber twisted yarn is used as the reinforcing fiber by this manufacturing method. It cannot be sufficiently impregnated with resin.

  In Non-Patent Document 1, when producing fiber reinforced resin strands using natural fibers as reinforcing fibers and using an extrusion molding machine, the twist of the fibers is loosened and the resin is infiltrated into the gaps of the fibers to interpenetrate the fibers. It has been shown to enhance resin impregnation. According to this method, the device for untwisting the natural fiber twisted yarn is provided with one unit for each twisted yarn, and the entire device cannot be constructed at low cost.

Japanese Utility Model Publication No. 5-22563 Japanese Patent No. 3114311

Kobe Steel Technical Report / Vol.51, No.2,2001, pp62-66 “Application to Long Fiber Pellet Production Equipment Natural Composite (Eco-Composite)”

  In order to increase the strength of the fiber reinforced resin, it is required to sufficiently impregnate the reinforced fiber with the resin in the production process of the fiber reinforced resin strand for injection molding. In the case of using a natural fiber twisted yarn as a reinforcing fiber, the resin may not be sufficiently impregnated between the fibers depending on the process in the case of using an artificial fiber such as a glass fiber as the reinforcing fiber. In this case, an effective method is required.

  A strand in which the twisted yarn is coated with a resin is formed by taking a process of continuously pulling the twisted yarn through the molten resin in accordance with the electric wire coating system without administering the natural fiber twisted yarn to the extruder. A fiber-reinforced resin pellet is obtained by cutting. In such a system, the resin only covers the periphery of the twisted yarn, the impregnated yarn is not impregnated at all, and voids remain between the fibers, and sufficient strength as a fiber-reinforced resin pellet cannot be provided. In order to give sufficient strength as a fiber reinforced resin pellet, it is necessary to sufficiently impregnate the resin so as to fill the space between the fibers.

  As described above, in the production of fiber reinforced resin strands for injection molding as a fiber reinforced resin or a forming material thereof using natural fibers as reinforced fibers, it is required to sufficiently impregnate the resin into the natural fiber twisted yarn as the reinforced fiber, This has not been proposed in the past with respect to an effective method for that purpose and to construct a simple device therefor.

The present invention has been made to solve the above-described problems, and the method for producing a natural fiber reinforced resin strand according to the present invention is a method in which a twisted fiber bundle is coated on a twisted yarn bundle in which a plurality of natural fiber twisted yarns are combined. A method for producing a natural fiber reinforced resin strand impregnated with a resin,
A preheating step of preheating the twisted bundle to near the temperature of the molten resin to be coated, a resin coating step of covering the preheated twisted bundle with the molten resin, and impregnating the resin between the fibers of the twisted bundle coated with the resin A resin impregnation step, wherein in the resin impregnation step, the twisted yarn bundle in which the resin is coated is pinched in a zigzag manner on a plurality of pins arranged in a ladder shape in the axial direction in a cylindrical heater. The twisted yarn bundle held at a temperature close to the melting temperature of the resin in the cylindrical heater is rubbed on the top and bottom of the pin in a state where the resin is coated, so that the resin is interposed between the fibers of the twisted yarn bundle. It is impregnated.

  The apparatus for producing natural fiber reinforced resin strands according to the present invention is an apparatus for producing natural fiber reinforced resin strands in which a molten resin is coated on a twisted yarn bundle in which a plurality of natural fiber twisted yarns are combined and the resin is impregnated between the twisted fibers. A preheating part that includes a preheating pipe for passing the twisted yarn bundle, preheats the molten yarn that is covered with the twisted yarn bundle to a temperature close to the temperature, and a resin-coated portion that supplies the molten resin and coats the molten resin on the preheated yarn bundle And a resin impregnated portion in which a plurality of pins are arranged in a ladder shape in the axial direction in a cylindrical heater having a temperature control means, and the twisted yarn bundle coated with resin in the resin impregnated portion The twisted yarn bundle, which is held in a zigzag manner on the numerous pins and is held at a temperature close to the melting temperature of the resin in the cylindrical heater, slides up and down the pins while the resin is coated. Rubbing In which resin is impregnated in between the fibers of the twisted bundle by being.

  In the present invention, during the production of the natural fiber reinforced resin strand, the twisted bundle is preheated to near the melting temperature of the resin covered with the twisted bundle of natural fibers, and in the process resin impregnation step, the shaft is placed in the cylindrical heater. A plurality of pins arranged in a ladder shape in a direction are advanced by the twisted yarn bundle covered with the resin being zigzag hung, and the twisted yarn bundle covered with the resin is melted in the cylindrical heater By being rubbed above and below the pin while being held at a nearby temperature, the resin is sufficiently impregnated between the fibers. Thereby, the strength of the natural fiber reinforced resin pellet and the pellet obtained by cutting it is increased. There is no need to newly add a device for continuously untwisting the natural twisted yarn bundle, and the device for manufacturing the fiber-reinforced resin Tosland can be made inexpensive without being complicated.

FIG. 1 is a diagram showing a configuration of a natural fiber reinforced resin strand manufacturing apparatus according to the present invention. FIG. 2 is a diagram illustrating a configuration of a resin impregnating unit in the natural fiber reinforced resin strand manufacturing apparatus of FIG. 1. FIG. 3 is a graph showing the stress-strain characteristics measured for pellets obtained from the generated strands when the temperature in the resin impregnation step is changed. FIG. 4 is a cross-sectional photograph of a fiber reinforced resin strand produced by applying a preheating step and a resin impregnation step, and (b) is a partially enlarged photograph of (a). FIG. 5 is a cross-sectional photograph of a fiber reinforced resin strand produced without applying a preheating step and a resin impregnation step, and (b) is a partially enlarged photograph of (a).

A preferred embodiment of a production method and production apparatus for a natural fiber reinforced resin strand for injection molding according to the present invention will be described.
[Production equipment for natural fiber reinforced resin strands]
FIG. 1 shows the overall structure of a production apparatus for natural fiber reinforced resin strands. This apparatus coats a twisted yarn bundle with resin and impregnates the resin between fibers to form a twisted strand.

  The apparatus for producing natural fiber reinforced resin strands includes a resin coating part A for coating a resin on a natural fiber twisted bundle, a preheating part B for preheating a natural fiber twisted bundle to be coated with a resin, and a resin coated on a natural fiber twisted yarn. Are provided with a resin-impregnated portion C for impregnating resin between fibers and a cooling portion D. The twisted yarn supply source of natural fibers includes a plurality of supply bodies of twisted yarn F, and the twisted yarn bundle of the plurality of twisted yarns F is a preheating portion. B, the resin coating part A, the resin impregnation part C, and the cooling part D are configured to pass through in order.

  The resin coating portion A includes a crosshead die 1 for coating the molten resin MR while the natural fiber twisted yarn bundle passes, and an extruder 2 that supplies the molten resin to the crosshead die 1. An attachment portion 3 for attaching the preheating tube 4 of the preheating portion B is attached to the inlet side of the natural fiber twisted yarn bundle of the crosshead die 1. A shaping die (not shown) for shaping the twisted yarn coated with the resin is preferably provided outside the outlet of the crosshead die 1. As the extruder 2, a simple uniaxial extruder is used.

  The preheating pipe 4 is attached to the attachment portion 3 to the crosshead die 1 and preheats the twisted yarn bundle passing through the inside while the preheating pipe 4 itself is heated. The preheating pipe 4 can be made of a material having high thermal conductivity such as aluminum, and the residual heat of the crosshead die 1 can be transmitted through the mounting portion 3 to increase the temperature. It is good also as a form provided with an original heat source.

  As shown in FIG. 2, the resin-impregnated portion C has a large number of pins P in the cylindrical heater 5 attached to the outlet side of the crosshead die 1 and is spaced in the direction in which the twisted yarn bundle coated with the resin passes. And arranged in a ladder shape. In the case where a molding die is installed outside the outlet of the crosshead die 1, a resin impregnated portion C is disposed following the molding die. As shown in FIG. 2, the twisted yarn bundle coated with the resin is alternately zigzag around the pins P and advances in the cylindrical heater 5. The twisted yarn coated with the resin is given a tension by a tensile force applied from the downstream side, and is rubbed on the upper and lower sides of the pin so that a contact pressure acts to impregnate the resin. In the resin impregnation step, maintaining the twisted yarn bundle coated with the resin at a predetermined temperature is important for improving the properties of the generated strand, and therefore, it has a means for controlling the heating temperature by the cylindrical heater.

  In FIG. 1, the twisted yarn bundle that has passed through the resin-impregnated portion C and is coated with the resin is in a state in which the resin is impregnated between the fibers, and is then twisted by a pair of twisting rollers 6 that rotate in opposite directions, and cooled. The natural fiber reinforced resin strand ST is formed by cooling in the part D. Reference numeral 10 denotes a feeding roller for supplying a bundle of a plurality of twisted yarns F to the preheating part B, and 20 denotes a drawing roller for the strand ST. The formed strand ST may be wound on a spool (not shown) and wound after being wound for a predetermined length. However, the strand ST is provided with a cutter for cutting the strand ST after passing through the drawing roller 20. It is good also as a form to produce. Moreover, it is possible even if there is no twisting roller 6 in preparation of the pellet, and it may be omitted depending on the situation.

[Strand manufacturing process]
The strand manufacturing process by the natural fiber reinforced resin strand manufacturing apparatus shown in FIG. 1 will be described. Although the example using a ramie twisted yarn is demonstrated as the natural fiber twisted yarn F, you may use other natural fibers, such as a flux, hemp, jute, and Kefna. As the resin for covering the twisted yarn, a thermoplastic material such as polypropylene or polyethylene is used.

  As a twisted yarn supply source, a plurality of ramie twisted yarns F (manufactured by Tosco Corp .; single yarn 16th) are provided, and in the example shown in the figure, six ramie twisted yarns are combined into one twisted yarn bundle. Then, the preheating pipe 4 of the preheating part B, the crosshead die 1 of the resin coating part A, and the cylindrical heater 5 of the resin impregnation part C are inserted. In order to perform this insertion, the tip of the twisted yarn bundle is attached to the leading needle and inserted, and the tubular heater 5 is divided and opened in the longitudinal direction, and the twisted yarn bundle is as shown in FIG. It is preferable that the cylindrical heater 5 is closed after the zigzag is hung on the ladder-like pin P. The twisted yarn bundle is further passed through the twisting roller 6 and the cooling part D so as to be sandwiched between the drawing rollers 20.

  In the preheating part B, the twisted yarn bundle is preheated to near the melting temperature of the resin coated on the twisted yarn bundle passing through the preheating pipe 4. If the twisted yarn bundle is at a temperature much lower than the temperature of the molten resin (about 195 ° C.), the resin is solidified when the molten resin comes into contact with the twisted bundle at the resin coating portion A, and good coating is not performed. The length of the preheating pipe is about 300 mm, and it is preferable not to increase the temperature rapidly from the initial stage, but to gradually increase the temperature so as to reach the resin melting temperature at the end of the preheating.

  After the twisted yarn bundle is inserted, the molten resin MR is supplied from the extruder 2 to the crosshead die 1 side, the drawing roller 20 is driven to rotate, and the resin is applied to the twisted yarn bundle that has passed the preheating portion C in the crosshead 1. Pull out the twisted yarn bundle while coating. In the example using polypropylene (manufactured by Prime Polymer Co., Ltd.) as the resin and MAPP (maleic acid modified polypropylene; manufactured by Kayaku Akzo Co., Ltd.) as the compatibilizing agent, the temperature of the cylinder part in the extruder 2 is 190 ° C., the resin outlet The temperature of the part is 195 ° C., the temperature of the crosshead die 1 is 190 ° C., and the screw speed is about 7.0 rpm. The twisted yarn coated with the resin by the crosshead die 1 is rubbed up and down with a ladder-like pin P in the resin impregnation portion C, and contact pressure acts to impregnate the resin between the twisted fibers.

  In order to sufficiently impregnate the resin between the fibers, it is necessary to make the length of the cylindrical heater 5 and the number of pins P appropriate. As an example of a twisted bundle of six ramie twisted yarns and polypropylene as the resin, it is appropriate that the length of the cylindrical heater 5 is 1000 mm, the interval between the pins P is 40 mm, and the number of pins is 22. In fact, it has been confirmed that in the form of the impregnated portion as described above, it is almost combined when passing through the 15th to 16th pins. However, this situation can change if the yarn diameters are different.

  In the resin impregnation step in the resin impregnation portion, maintaining the twisted yarn bundle coated with the resin at a predetermined temperature is important for improving the properties of the generated strand. Fig. 6 shows the results of measuring the stress-strain characteristics of a pellet obtained by changing the temperature conditions in the resin impregnation step to produce a 30 wt% ramie twisted yarn / polypropylene fiber reinforced resin and cutting it to a length of 2 mm. 3 shows. As a result, the tensile strength of the resin impregnated at a resin melting temperature of 195 ° C. is particularly high, but the tensile strength decreases at a high temperature of 205 ° C. or higher.

  This is thought to be due to the deterioration of the ramie fibers due to overheating. Further, when the temperature in the impregnation step is lowered to 185 ° C. or lower, the tensile strength is also lowered. Thus, in the resin impregnated portion C, the temperature is raised to a temperature close to the resin melting temperature (temperature within the range of 10 ° C. with the resin melting temperature as the center) by heating with the cylindrical heater through which the twisted yarn bundle coated with the resin passes. It is preferable that the impregnation is performed in a wet state.

  FIG. 4 is a cross-sectional photograph of a fiber reinforced resin strand produced by applying a preheating process and a resin impregnation process according to the present invention, and (b) is an enlarged photograph of an enclosure part of (a). The muscle inside the fiber represents the lumen (lumen), indicating that the resin is impregnated between the fibers. FIG. 5 is a cross-sectional photograph of a fiber reinforced resin strand produced without applying a preheating process and a resin impregnation process, and (b) is an enlarged photograph of the enclosure part of (a). In this case, no resin is impregnated between the fibers in the twisted yarn, and voids are seen between the fibers.

  As described above, in the production of the natural fiber reinforced resin strand according to the present invention, the twisted bundle is preheated to near the melting temperature of the resin covered with the twisted bundle of natural fibers, and in the process resin impregnation step, A plurality of pins arranged in a ladder shape in the axial direction are hung in a zigzag manner on the twisted yarn bundle covered with the resin, and the twisted yarn bundle covered with the resin is made of resin in the cylindrical heater. The resin is impregnated between the fibers by rubbing up and down the pin while being held at a temperature close to the melting temperature, and the resin is satisfactorily impregnated between the fibers of the twisted bundle. The

  The strands formed by coating a resin on a plurality of twisted yarn bundles and impregnating the resin are described as rod-like strands, but the twisted yarn bundles are arranged in a horizontal line and flat with the resin covered It may be a shape. In the case of such a tape-like fiber-reinforced resin body, no twist is applied after resin coating and impregnation.

DESCRIPTION OF SYMBOLS 1 Crosshead die 2 Extruder 3 Mounting part 4 Preheating pipe 5 Cylindrical heater 6 Twisting roller 10 Feeding roller 20 Drawing roller A Resin coating part B Preheating part C Resin impregnation part D Cooling part F Twisted yarn ST Strand MR Molten resin P Pin

Claims (2)

A method for producing a natural fiber reinforced resin strand in which a twisted yarn bundle comprising a plurality of natural fiber twisted yarns is coated with a molten resin and then impregnated with resin between the twisted fibers,
A preheating step for preheating the twisted yarn bundle to near the temperature of the molten resin to be coated;
A resin coating step of coating the preheated twisted yarn bundle with a molten resin;
A resin impregnation step of impregnating the resin between the fibers of the twisted yarn bundle coated with the resin;
In the resin impregnation step, the twisted yarn bundle in which the resin is coated on a plurality of pins arranged in a ladder shape in the axial direction in the cylindrical heater proceeds in a zigzag manner, and the cylindrical heater The twisted yarn bundle held at a temperature close to the melting temperature of the resin is rubbed on the top and bottom of the pin in a state where the resin is coated, so that the resin is impregnated between the fibers of the twisted yarn bundle. A method for producing a natural fiber reinforced resin strand. A device for producing a natural fiber reinforced resin strand in which a twisted bundle of a plurality of natural fiber twisted yarns is coated with a molten resin and impregnated with resin between the twisted fibers,
A preheating section that includes a preheating pipe that passes the twisted yarn bundle and preheats the twisted yarn bundle to near the temperature of the molten resin that is coated;
A resin-coated portion for coating the molten resin on the twisted bundle that has been preheated by supplying the molten resin;
A resin impregnated portion in which a plurality of pins are arranged in a ladder shape in the axial direction in a cylindrical heater having a temperature control means;
In the resin impregnated portion, the twisted yarn bundle coated with the resin is applied in a zigzag manner to the numerous pins, and the twisted yarn is maintained at a temperature near the melting temperature of the resin in the cylindrical heater. An apparatus for producing a natural fiber reinforced resin strand, wherein the bundle is impregnated with resin between the fibers of the twisted bundle by rubbing the top and bottom of the pin in a state where the resin is coated.