JP2016098271A - Manufacturing method of prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of prepreg capable of sufficiently aligning a discontinuous fiber in a thermoplastic resin with continuously manufacturing the prepreg good in linearity, a manufacturing system of an extrusion tool and the prepreg.SOLUTION: A manufacturing method of prepreg has a process for extrusion molding a composition 6 containing a discontinuous fiber 6a and a thermoplastic resin 6b in a plastic region, where the discontinuous fiber 6a has number average fiber length of 1 μm to 5 mm, number average fiber diameter of 5 nm to 30 μm and gradient of pressure to stroke when extrusion molding the composition 6 in the plastic region of 0 Pa/mm to 1.0 Pa/mm.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a prepreg manufacturing method, a prepreg, an extrusion jig, and a prepreg manufacturing system.

  Pre-pregs containing discontinuous fibers and thermoplastic resins are more flexible than prepregs containing continuous fibers and thermoplastic resins, and can easily form recesses or complex shapes without wrinkling or distorting molded products and articles. Can be manufactured. Furthermore, by disposing discontinuous fibers in one direction or randomly in the thermoplastic resin, the mechanical properties of the molded body and the article can be anisotropic or isotropic.

  Patent Document 1 discloses a method for producing an extruded product in which a resin composition comprising a vinyl chloride resin and a fibrous inorganic filler is supplied to an extruder and extruded into a mold. At this time, the elongation rate of the resin composition in the resin channel is set to 5 to 10 (1 / sec) by rapidly decreasing the cross-sectional area of the resin channel in the mold in the extrusion direction.

JP 2003-266524 A

  However, there is a problem in that a prepreg having good linearity is continuously produced and the discontinuous fibers cannot be sufficiently oriented in the thermoplastic resin.

  One aspect of the present invention is a prepreg capable of continuously producing a prepreg with good linearity and sufficiently orienting discontinuous fibers in a thermoplastic resin in view of the problems of the above-described conventional technology. An object is to provide a manufacturing method, an extrusion jig, and a prepreg manufacturing system.

  One embodiment of the present invention includes a step of extruding a composition containing discontinuous fibers and a thermoplastic resin in a plastic region in a prepreg manufacturing method, wherein the discontinuous fibers have a number average fiber length of 1 μm or more and 5 mm. The number average fiber diameter is 5 nm or more and 30 μm or less, and the gradient of the pressure with respect to the stroke when the composition is extruded in the plastic region is 0 Pa / mm or more and 1.0 Pa / mm or less.

  One embodiment of the present invention is an extrusion jig used for extrusion molding of a composition containing discontinuous fibers and a thermoplastic resin, and has an extrusion ratio of 25 or more and 45 or less.

  One aspect of the present invention is a system for producing a prepreg by extruding a composition containing discontinuous fibers and a thermoplastic resin, and means for monitoring a pressure gradient with respect to a stroke when extruding the composition. Have

  According to one aspect of the present invention, a prepreg manufacturing method, an extrusion jig, and a prepreg capable of continuously manufacturing a prepreg with good linearity and sufficiently orienting discontinuous fibers in a thermoplastic resin. The manufacturing system can be provided.

It is a graph explaining an elastic region and a plastic region. It is a schematic diagram which shows an example of the manufacturing system of a prepreg.

  Next, the form for implementing this invention is demonstrated with drawing.

  The manufacturing method of a prepreg has the process of extruding the composition containing a discontinuous fiber and a thermoplastic resin in a plastic region.

  The plastic region is a region where the pressure becomes substantially constant even when the stroke changes when an extrusion pressure is applied to the composition (see FIG. 1).

  Attempts to extrude the composition in the elastic region cannot be extruded from the extruder or the discontinuous fibers cannot be fully oriented in the thermoplastic resin.

  The elastic region is a region where the pressure increases linearly as the stroke increases when an extrusion pressure is applied to the composition (see FIG. 1).

  The pressure gradient with respect to the stroke when extruding the composition in the plastic region is 0 to 1.0 Pa / mm, and preferably 0 to 0.3 Pa / mm. When the pressure gradient with respect to the stroke when extruding the composition in the plastic region is less than 0 Pa / mm, the extrusion pressure is repelled by the composition and cannot be extruded, or the composition is continuously extruded. Therefore, it is impossible to continuously produce a prepreg with good linearity. On the other hand, when the pressure gradient with respect to the stroke when extruding the composition in the plastic region exceeds 1.0 Pa / mm, the thermoplastic resin is squeezed out of the composition or the thermoplastic resin is sufficiently softened. Therefore, a prepreg with good linearity cannot be produced continuously.

  The number average fiber length of the discontinuous fibers is 1 μm to 5 mm, and preferably 2 μm to 4 mm. When the number average fiber length of the discontinuous fibers is less than 1 μm, the degree of freedom of the discontinuous fibers in the composition increases, and the discontinuous fibers cannot be sufficiently oriented in the thermoplastic resin. On the other hand, when the number average fiber length of the discontinuous fibers exceeds 5 mm, the discontinuous fibers are easily entangled, and the discontinuous fibers cannot be sufficiently oriented in the thermoplastic resin.

  The number average fiber diameter of the discontinuous fibers is 5 nm to 30 μm, and preferably 5 nm to 20 μm. When the number average fiber diameter of the discontinuous fibers is less than 5 nm, the discontinuous fibers are easily broken and cannot be sufficiently oriented in the thermoplastic resin. On the other hand, when the number average fiber diameter of the discontinuous fibers exceeds 30 μm, fluidity and moldability are lowered when the composition is extruded.

  The discontinuous fiber is not particularly limited, but carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, natural fiber such as cellulose nanofiber, carbon nanofiber, carbon nanotube, etc. 2 or more may be used in combination.

  Content of the discontinuous fiber in a composition is 1-50 volume% normally, and it is preferable that it is 16-40 volume%. When the content of the discontinuous fiber in the composition is 1% by volume or more, the degree of freedom of the discontinuous fiber in the composition is reduced, and the discontinuous fiber can be further oriented in the thermoplastic resin. On the other hand, when the content of the discontinuous fiber in the composition is 50% by volume or less, the fluidity when the composition is extruded can be improved, and the discontinuous fiber can be further oriented in the thermoplastic resin. it can.

  The ratio in which the angle with respect to the extrusion direction of the discontinuous fibers in the prepreg is oriented in the range of 0 to 20 ° is usually 70% or more.

  The thermoplastic resin is not particularly limited, but polyamide, polypropylene, polyethylene, polystyrene, acrylic resin, polyethylene terephthalate, polyacetal, polyester, polycarbonate, polyolefin, polyphenylene sulfide, polybutylene terephthalate, polyphenylene ether, polyether ether ketone, polyamideimide , Polysulfone, ABS resin, fluorine resin and the like, and two or more kinds may be used in combination.

  The composition may further contain an additive. Thereby, electroconductivity and thermal conductivity can be provided to a prepreg.

  The additive is not particularly limited, but gold, silver, copper, iron, nickel, aluminum, magnesium and alloys thereof, silicon carbide, aluminum nitride, hexagonal boron nitride, sapphire, alumina, silicon nitride, magnesium oxide, dioxide Titanium, cermet, yttria, mullite, forsterite, cordierite, zirconia, steatite, graphite, carbon black, carbon nanotube, graphene, etc. may be mentioned, and two or more may be used in combination.

The volume ratio of the additive to the thermoplastic resin is usually 1 × 10 ^{−3 to} 0.3, and preferably 5 × 10 ^{−3 to} 0.2. When the volume ratio of the additive to the thermoplastic resin is 1 × 10 ⁻³ or more, the conductivity and thermal conductivity of the prepreg can be further improved, and when the volume ratio is 0.3 or less, the composition is extruded. The plasticity and fluidity during molding can be improved, and the discontinuous fibers can be further oriented in the thermoplastic resin.

  The composition is preferably prepared by melt-kneading a composition containing fibers and a thermoplastic resin. Thereby, discontinuous fibers can be further oriented in the thermoplastic resin. Further, it becomes easy to continuously produce a prepreg having good linearity.

  At this time, you may melt-knead the composition containing a thermoplastic resin and a fiber in multiple times using a kneader.

  The fiber may be either a discontinuous fiber or a continuous fiber. The fiber may be either virgin fiber or reuse / recycle fiber. Further, the fibers may be discontinuous fibers in which virgin fibers, reuse / recycle fibers, and roving fibers are cut with a guillotine cutter or the like. Further, the fiber may be a sizing fiber whose surface is coated with a sizing agent that improves adhesion with a thermoplastic resin.

  Although it does not specifically limit as an extruder used when extruding a composition, A pressure extruder provided with the heating mechanism for softening a thermoplastic resin, a kneader, etc. are mentioned.

  FIG. 2 shows an example of a prepreg manufacturing system.

  The prepreg manufacturing system 1 includes a pressure extruder 2, a monitor 3, an extrusion jig 4, and a heater 5 for heating the extrusion jig 4, and an extrusion molding of a composition 6 composed of discontinuous fibers 6a and a thermoplastic resin 6b. To do.

  The monitor 3 monitors the pressure gradient with respect to the stroke when the composition 6 is extruded.

  The extrusion jig 4 includes a cylinder 4a, an extrusion rod 4b, and a base 4c in which an opening is formed, and continuously squeezes and extrudes the composition 6 filled in the cylinder 4a.

  The extrusion ratio of the extrusion jig 4 is 25 to 45, and preferably 28 to 43. If the extrusion ratio of the extrusion jig 4 is less than 25, the discontinuous fibers 6a cannot be sufficiently oriented in the thermoplastic resin, and if it exceeds 45, the die 4c is clogged with the composition.

  The extrusion ratio is the ratio of the cross-sectional area S2 of the extrusion rod 4b to the cross-sectional area S1 of the opening formed in the base 4c.

  Although it does not specifically limit as a cross-sectional shape of a prepreg, A circle | round | yen, a rectangle, etc. are mentioned.

  For example, the extrusion ratio of the extrusion jig 4 and the cross-sectional shape of the prepreg can be controlled by controlling the cross-sectional area and cross-sectional shape of the opening formed in the base 4c.

  One heater 5 is fixed to each of the outer surfaces of the cylinder 4a and the base 4c. Thereby, the temperature of the cylinder 4a and the extrusion rod 4b and the temperature of the cap 4c can be controlled to 350 ° C. As a result, the temperature of the die 4c is increased and the composition 6 can be extruded in the plastic region. Moreover, since the temperature of the opening part currently formed in the nozzle | cap | die 4c can be controlled, clogging of the composition to the nozzle | cap | die 4c can be suppressed.

  The temperature of the heater 5 is preferably set so that the temperature of the base 4c is higher than the temperatures of the cylinder 4a and the extrusion rod 4b. Thereby, clogging of the composition into the die 4c can be further suppressed.

  The heater 5 may be included in the extrusion jig 4 as long as the temperature of the cylinder 4a and the extrusion rod 4b and the temperature of the base 4c can be controlled to 350 ° C.

  Three or more heaters 5 may be provided. For example, one heater 5 may be provided for each of the cylinder 4a, the extrusion rod 4b, and the base 4c, one for the cylinder 4a, and two for the base 4c.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.

Example 1
A long fiber pellet TLP1066 (manufactured by Toray Industries, Inc.) in which 22% by volume (30% by mass) of a number average fiber length of 7 mm and a discontinuous carbon fiber having a number average fiber diameter of 7 μm is coated with polyamide 6 is A composition containing discontinuous carbon fibers having a number average fiber length of 0.19 mm and a number average fiber diameter of 7 μm and polyamide 6 at a kneading temperature of 240 ° C. and a screw speed of 25 rpm. Got.

  A base 4c having an extrusion ratio of 28 is attached to the prepreg manufacturing system 1 (see FIG. 2), the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c are 260 ° C., respectively, and the composition is plastic. Extrusion molding was performed in the region to obtain a prepreg. At this time, the gradient of the pressure with respect to the stroke was 0.074 Pa / mm, and prepregs with good linearity were continuously produced. The prepreg had a discontinuous carbon fiber orientation degree of 84%.

(Example 2)
A prepreg was obtained in the same manner as in Example 1 except that the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c were changed to 280 ° C. At this time, the pressure gradient with respect to the stroke was 0.160 Pa / mm, and prepregs with good linearity were continuously produced. In the prepreg, the degree of orientation of the discontinuous carbon fibers was 86%.

(Comparative Example 1)
A prepreg was obtained in the same manner as in Example 1 except that the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c were changed to 240 ° C., respectively. At this time, the pressure gradient with respect to the stroke was −0.161 Pa / mm, and the prepreg was not continuously produced. The prepreg had a discontinuous carbon fiber orientation of 93%.

(Comparative Example 2)
A prepreg was obtained in the same manner as in Example 1 except that the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c were changed to 220 ° C., respectively. At this time, the pressure gradient with respect to the stroke was 1.232 Pa / mm, and the linearity of the prepreg was not good. The prepreg had an orientation degree of discontinuous carbon fibers of 80%.

(Comparative Example 3)
A prepreg manufacturing system 1 (see FIG. 2) is provided with a base 4c having an extrusion ratio of 28, and the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c are 240 ° C., respectively. (Toray Industries, Inc.) was extruded in a plastic region to obtain a prepreg. At this time, the pressure gradient with respect to the stroke was -0.059 Pa / mm, the linearity of the prepreg was extremely poor, and the prepreg was not continuously produced. The prepreg had a discontinuous carbon fiber orientation degree of 67%.

(Comparative Example 4)
A prepreg was obtained in the same manner as in Comparative Example 3 except that the set temperatures of the heaters 5 fixed to the outer surfaces of the cylinder 4a and the base 4c were changed to 260 ° C., respectively. At this time, the pressure gradient with respect to the stroke was -0.027 Pa / mm, the linearity of the prepreg was extremely poor, and the prepreg was not continuously produced. The prepreg had a discontinuous carbon fiber orientation degree of 62%.

<Number average fiber length of discontinuous carbon fibers contained in long fiber pellet>
After the polyamide 6 was peeled from the long fiber pellets, the discontinuous carbon fibers taken out were placed on a slide glass. Next, after unraveling the discontinuous carbon fiber with tweezers, photograph the discontinuous carbon fiber with a scale, manually measure the length of the discontinuous carbon fiber, and the number average fiber length of the discontinuous carbon fiber. Asked.

<Number average fiber length of discontinuous carbon fibers contained in the composition>
The composition was immersed in formic acid to dissolve polyamide 6, and the remaining polyamide 6 was washed away with formic acid while filtering. Next, discontinuous carbon fibers were extracted by washing out formic acid with distilled water. The number average fiber length of the discontinuous carbon fibers was determined in the same manner as the long fiber pellets except that the extracted discontinuous carbon fibers were placed on a slide glass.

<Number average fiber diameter of discontinuous carbon fibers contained in long fiber pellet>
The cross section of the discontinuous carbon fiber taken out from the long fiber pellet was photographed using a scanning electron microscope, the fiber diameter was measured manually, and the number average fiber diameter was determined.

<Number average fiber diameter of discontinuous carbon fibers contained in composition>
Since the number average fiber diameter of the discontinuous carbon fibers contained in the composition is substantially the same as the number average fiber diameter of the discontinuous carbon fibers contained in the long fiber pellets, the discontinuous carbon fibers contained in the long fiber pellets The number average fiber diameter was substituted.

<Slope of pressure with respect to stroke>
The pressure was plotted against the stroke (see FIG. 1), and the pressure gradient with respect to the stroke was calculated by linearly approximating the plastic region by the least square method.

  In Table 1, the manufacturing conditions of the prepreg of Examples 1-3 and Comparative Examples 1-3 are shown.

  Next, the properties of the prepreg and the degree of orientation of the discontinuous carbon fibers were evaluated.

<Properties of prepreg>
The properties of the prepreg were visually evaluated. In addition, the case where the prepreg with favorable linearity was manufactured continuously was set as (circle), and the case where the prepreg with favorable linearity was not manufactured continuously was set as x.

<Orientation degree of discontinuous carbon fiber>
Using an optical microscope, the surface of the prepreg was two-dimensionally photographed at a magnification of 15 times, and then the direction of 250 discontinuous carbon fibers was measured at an angle of −90 ° to + 90 ° with an extrusion direction of 0 °. did. Next, after convolving the angle of −90 ° to 0 ° to 0 ° to 90 ° and creating a histogram in the range of 0 to 90 ° with 10 ° intervals, the range of 0 to 20 ° of the discontinuous carbon fiber is created. The ratio of orientation was calculated and used as the degree of orientation of discontinuous carbon fibers.

  Table 2 shows the characteristics of the prepreg.

  Table 2 shows that Examples 1 and 2 have good prepreg properties and a high degree of orientation of discontinuous carbon fibers.

  In contrast, Comparative Examples 1 and 2 have poor prepreg properties.

  In Comparative Examples 3 and 4, in addition to the poor prepreg properties, the degree of orientation of the discontinuous carbon fibers decreases.

(Example 3)
A biaxial kneader comprising a composition comprising 30% by volume of a number average fiber length of 12 mm and a number average fiber diameter of 7 μm of chopped carbon fiber T010-012 (manufactured by Toray Industries) and CM1017 (manufactured by Toray Industries) as polyamide 6 A composition containing discontinuous carbon fibers having a number average fiber length of 0.16 mm and a number average fiber diameter of 7 μm and polyamide 6 at a kneading temperature of 240 ° C. and a screw rotation speed of 26 rpm. Obtained.

  A base 4c having an extrusion ratio of 28 is attached to the prepreg manufacturing system 1 (see FIG. 2), the set temperature of the heater 5 fixed to the outer surface of the cylinder 4a is 250 ° C., and the heater is fixed to the outer surface of the base 4c. The set temperature of 5 was 280 ° C., and the composition was extruded in the plastic region to obtain a prepreg. At this time, the pressure gradient with respect to the stroke was 0.003 Pa / mm, and prepregs with good linearity were continuously produced. The prepreg had a discontinuous carbon fiber orientation of 92%.

<Number average fiber length of chopped carbon fiber>
Chopped carbon fiber was placed on a glass slide. Next, after the chopped carbon fiber was unwound with tweezers, the chopped carbon fiber was photographed with a scale, the length of the chopped carbon fiber was manually measured, and the number average fiber length was obtained.

<Number average fiber length of discontinuous carbon fibers contained in the composition>
The composition was immersed in formic acid to dissolve polyamide 6, and the remaining polyamide 6 was washed away with formic acid while filtering. Next, discontinuous carbon fibers were extracted by washing out formic acid with distilled water. The number average fiber length of the discontinuous carbon fibers was determined in the same manner as the chopped carbon fibers except that the extracted discontinuous carbon fibers were placed on a slide glass.

<Number average fiber diameter of chopped carbon fiber>
The cross section of the chopped carbon fiber was photographed using a scanning electron microscope, the fiber diameter was manually measured, and the number average fiber diameter was obtained.

<Number average fiber diameter of discontinuous carbon fibers contained in composition>
Since the number average fiber diameter of the discontinuous carbon fibers contained in the composition is substantially the same as the number average fiber diameter of the chopped carbon fibers, the number average fiber diameter of the chopped carbon fibers was substituted.

DESCRIPTION OF SYMBOLS 1 Prepreg production system 2 Pressure extruder 3 Monitor 4 Extrusion jig 4a Cylinder 4b Extrusion rod 4c Base 5 Heater 6 Composition 6a Discontinuous fiber 6b Thermoplastic resin S1 Cross-sectional area in opening of base S2 Extrusion rod Cross section

Claims (8)

Having a step of extruding a composition containing discontinuous fibers and a thermoplastic resin in a plastic region,
The discontinuous fibers have a number average fiber length of 1 μm to 5 mm, a number average fiber diameter of 5 nm to 30 μm,
A method for producing a prepreg, wherein a gradient of pressure with respect to a stroke when the composition is extruded in a plastic region is 0 Pa / mm or more and 1.0 Pa / mm or less.   The method for producing a prepreg according to claim 1, wherein an extrusion ratio at the time of extruding the composition is 25 or more and 45 or less.   The content of the discontinuous fibers in the composition is 1% by volume or more and 50% by volume or less, and the content of the thermoplastic resin is 50% by volume or more and 99% by volume or less. Or the manufacturing method of the prepreg of 2. And further comprising a step of melt-kneading a composition containing fibers and a thermoplastic resin,
The method for producing a prepreg according to any one of claims 1 to 3, wherein the melt-kneaded composition is extruded in the plastic region. It is manufactured by the method for manufacturing a prepreg according to any one of claims 1 to 4,
The prepreg characterized in that the discontinuous fibers have an angle of 70 ° or more with an angle to the extrusion direction of 0 ° or more and 20 ° or less. An extrusion jig used for extrusion of a composition containing discontinuous fibers and a thermoplastic resin,
An extrusion jig having an extrusion ratio of 25 or more and 45 or less. A system for producing a prepreg by extruding a composition containing discontinuous fibers and a thermoplastic resin,
A system for producing a prepreg, comprising means for monitoring a pressure gradient with respect to a stroke when the composition is extruded. The prepreg manufacturing system according to claim 7, further comprising the extrusion jig according to claim 6.

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