JP2014201659A - Pultrusion method for fiber-reinforced plastic and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced plastic which uses carbon fiber large tow and allows an irregular-shape pultrusion molding.SOLUTION: A fiber-reinforced plastic consists of a fiber bundle of reinforcing fibers having a number of filaments of 25,000-80,000 and a hardened product of an epoxy resin composition containing an epoxy resin and an epoxy resin hardening agent, has a strength development rate of the reinforcing fiber of 90% or higher and is capable of suppressing meander of fibers and exerting good mechanical characteristics not only when the cross sectional shape of the filament is perfectly circular but also when it is, e.g., elliptical, ovoid, horse-bean-shaped or three-leafed.

Description

  The present invention relates to a pultruded product, a fiber reinforced plastic, and a pultrusion method using a carbon fiber large tow.

  In the fiber reinforced plastic pultrusion method, the reinforcing fibers meander due to the resin viscosity and the frictional resistance of the mold wall surface, and the strength of the obtained pultruded product in the fiber direction may decrease. As a method of molding while maintaining the straightness of the reinforcing fiber, a method of increasing the tension of the reinforcing fiber from the resin impregnation to the molding die (die) or slowing the molding speed is known. Moreover, the method of suppressing a fiber meander is known by suppressing the resistance with respect to the fiber at the time of mold | die approaching by using low-viscosity resin (patent document 1).

JP 2008-38082 A

  However, the method disclosed in the above patent is preferably applied when the cross-sectional shape of the filament of carbon fiber is almost perfect circle in order to obtain good tensile strength as a pultruded product, but the cross-sectional shape is irregular. For filaments that have wrinkles or have wrinkles on the surface, there are concerns about in-process troubles such as fuzz and thread breakage due to thread breakage due to rubbing between filaments, and reduction in strength of pultruded products, It was not easy. Furthermore, fiber bundles made of filaments having wrinkles tend to contain resin, causing excess of the resin drawn when entering the mold to cause fiber meandering when backflowing from the mold, thus reducing the mechanical properties of the composite material. Thus, it was difficult to obtain a composite material having good strength development. On the other hand, pultrusion using large tow carbon fibers with 25,000 filaments or more is expected to have a merit of cost reduction due to simplified process setup, but as long as the conventional technology is used, productivity and performance are high. Large tow pultrusion has not been realized.

  As a result of intensive studies to solve the above problems, the present inventor has reached the present invention.

  That is, the present invention is a fiber reinforced plastic comprising a fiber bundle of reinforcing fibers having 25000 to 80000 filaments and a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, and the strength expression rate of the reinforcing fibers. Is a fiber reinforced plastic having 90% or more.

  According to the pultrusion method of the present invention, not only when the cross-sectional shape in the cross-section perpendicular to the fiber direction of the filament (hereinafter simply referred to as “cross-sectional shape”) is almost a perfect circle, but also an ellipse, egg shape, and empty bean shape. Even when using a fiber bundle made of filaments having ridges and having a cross-sectional shape such as a trilobal shape, the back flow of the resin and the resulting meandering of the fiber when entering the mold are suppressed, and high mechanical A fiber reinforced plastic exhibiting properties can be obtained. The present invention is a technique applicable to a wide variety of reinforcing fibers. Furthermore, since the problem of fiber meandering and impregnation failure can be avoided even when large tow carbon fibers are used, production at a low cost is possible by simplifying the molding setup by employing large tows.

It is a figure explaining the outline | summary of the pultrusion molding of this invention.

  The present invention is a fiber reinforced plastic comprising a fiber bundle of reinforcing fibers having 25,000 to 80000 filaments and a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, and the strength expression rate of the reinforcing fibers is Realized by fiber reinforced plastic that is 90% or more.

(Reinforcing fiber)
The reinforcing fiber used in the present invention is preferably a fiber such as a glass fiber, an aramid fiber, a carbon fiber, or a boron fiber, but it is preferable to use a carbon fiber having excellent strength. Further, it is preferable to use carbon fiber having a tensile strength of 3000 to 6000 MPa as a fiber reinforced plastic for general industrial use. In the present invention, the tensile strength of carbon fiber refers to the strand strength measured according to JIS R7601.

  The reinforcing fiber used in the present invention contains 0.01 to 5 mass of a substance having one or more functional groups selected from an epoxy group, a hydroxyl group, an amino group, a carboxyl group, a carboxylic anhydride group, an acrylate group, and a methacrylate group. %, And can be used as a sizing agent for improving the convergence of the fiber bundle and the adhesion between the reinforcing fiber and the matrix resin when the fiber reinforced plastic is used.

  The reinforcing fiber used in the present invention can be suitably used in the form of a reinforcing fiber bundle called a large tow and having 25,000 to 80,000 filaments. By using large tow, process setup can be simplified and cost can be reduced.

  The reinforcing fiber used in the present invention may have a perfect cross-sectional shape of the filament, or may have an elliptical shape, an oval shape, an empty bean shape, a trilobal shape or the like. Moreover, any may be sufficient also about the presence or absence of a fiber surface wrinkle.

  As the reinforcing fibers used in the present invention, those having a roundness of 1 to 3 in the cross-sectional shape of the filament can be suitably used. The roundness referred to in the present invention is represented by the ratio of the maximum diameter / minimum diameter of the filament. Here, the maximum diameter is a width at a rotation angle at which the width of projection onto a plane parallel to the fiber axis is maximum during one rotation of one filament around the fiber axis. The width at the rotation angle at which the projection width is minimized, and the maximum diameter and the minimum diameter of the reinforcing fiber can be easily obtained by observing the cross-sectional shape of the fiber with an optical microscope or a scanning electron microscope (SEM). . According to the pultrusion method of the present invention, even if the cross-sectional shape of the filament is a perfect circle, even if the roundness is greater than 1.1, it is possible to maintain high productivity even if it is a so-called irregular cross-section. is there.

  An epoxy resin that is liquid at room temperature is used as the epoxy resin used in the present invention. Glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin and phenol novolac type epoxy resin, glycidyl amine type epoxy resins such as glycidyl aniline and tetraglycidyl methylene dianiline, and glycidyl of aminophenol skeleton Epoxy resins such as ether and glycidylamine type can be used and can be appropriately used according to the purpose. The epoxy resin of the present invention may be one kind, but two or more kinds of epoxy resins may be mixed and used as necessary. It is also possible to use a viscous or solid epoxy resin dispersed or dissolved in a liquid epoxy resin at room temperature.

As the epoxy resin used in the present invention, a so-called reactive diluent or the like can be suitably used together with the above epoxy resin. A reactive diluent is a low-viscosity compound having one or more epoxy groups in the molecule. For example, ethylene glycols, propylene glycols, butylene glycols, neopentyl glycols, 1,6-hexanediols, Di (6-hydroxyhexyl) ether, 1,8-octanediol, di (8-hydroxyhexyl) ether, 1,10-decanediol, di (10-hydroxydecyl) ether, phenyleneethylene glycol, di (phenylethyleneglycol) In addition to diglycidyl etherified products of diols having 2 to 15 carbon atoms such as glycerol), glycerol triglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane glycidyl ether, etc., and propylene oxide adducts of trimethylolpropane Triglycidyl ethers, triglycidyl ethers of propylene oxide adducts of pentaerythritol, diglycidyl ethers of hydrogenated bisphenols, and carboxylic acids such as hexahydrophthalic anhydride, tetrahydrophthalic anhydride, dimer acid, benzoic acid, etc. And glycidyl ester.
The reactive diluent used in the present invention preferably has a low viscosity at room temperature. Due to the low viscosity, the resistance due to the back flow of the resin is reduced, which is effective in suppressing fiber meandering.

(Epoxy resin curing agent Lewis acid)
As the epoxy resin curing agent used in the present invention, a complex of Lewis acid and base can be used. Examples of the complex of Lewis acid and base include those that dissociate at a high temperature to produce a Lewis acid. As the Lewis acid, boron halides such as boron trifluoride and boron trichloride, phosphorus pentafluoride, antimony pentafluoride and the like are preferable. The base is preferably an organic amine. Specifically, boron trifluoride / aniline complex, boron trifluoride / p-chloroaniline complex, boron trifluoride / ethylamine complex, boron trifluoride / isopropylamine complex, boron trifluoride / benzylamine complex, three Boron fluoride / dimethylamine complex, boron trifluoride diethylamine complex, boron trifluoride / dibutylamine complex, boron trifluoride / piperidine complex, boron trifluoride / dibenzylamine complex, boron trichloride / dimethyloctylamine complex Etc.
When a complex of Lewis acid and base is used as the epoxy resin curing agent, the curing agent may be 0.1-15% by mass with respect to all epoxy resins including the reactive diluent contained in the epoxy resin composition. preferable. More preferably, it is 2-10 mass%.
A Lewis acid and base complex may be used alone or in combination of two or more. When using 2 or more types, it is preferable that the sum total is the said compounding quantity.

(Epoxy resin curing agent, acid anhydride curing agent)
As the epoxy resin curing agent used in the present invention, an acid anhydride curing agent can be used. There are no particular restrictions on the acid anhydride curing agent that can be used, but there are no restrictions on cyclic aliphatic acids such as tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl nadic anhydride, dodecyl succinic anhydride, hexahydrophthalic anhydride, etc. Anhydrides and anhydrides of aromatic fatty acids such as phthalic anhydride, trimellitic anhydride and pyromellitic anhydride are preferably used. The acid anhydride type curing agent curing agent may be used alone or in combination of two or more. The addition amount of the acid anhydride curing agent is preferably such that the number of moles of acid anhydride groups is 50 to 120% with respect to the number of moles of all epoxy groups contained in the epoxy resin composition, More preferably, it is 100%.

(Epoxy resin curing agent Polyamine curing agent)
As the epoxy resin curing agent used in the present invention, a polyamine curing agent can be used. The polyamine curing agent that can be used is not particularly limited, but aliphatic polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and diethylaminopropylamine, and fats such as mensendiamine, isophoronediamine, and N-aminoethylpiperazine. Aromatic polyamines such as cyclic polyamines, diethyltoluenediamine, metaphenylenediamine, diaminodiphenylsulfone, metaxylenediamine, dicyandiamide, adipic acid dihydrazite, and polyamidoamines obtained by reacting dimer acid with aliphatic polyamines are preferably used. The polyamine curing agent may be used alone or in combination of two or more. The addition amount of the polyamine-based curing agent is preferably such that the number of moles of active hydrogen of the amino group is 80 to 120% with respect to the number of moles of all epoxy groups contained in the epoxy resin composition, % Is more preferable.

(Other epoxy resin curing agents)
Tertiary amine compounds, imidazole compounds, and polyphenols can be used as the epoxy resin curing agent used in the present invention. The tertiary amine compound that can be used is not particularly limited, but benzyldiethylamine, 2- (dimethylaminomethyl) phenol, and 2,4,6-tris (diaminomethyl) phenol are preferably used. The imidazole compound that can be used is not particularly limited, but 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, and the like are preferably used. The polyphenol that can be used is not particularly limited, but bisphenol A, bisphenol F, and phenol novolac are preferably used.

(Curing accelerator)
When acid anhydrides are used as the epoxy resin curing agent, a curing accelerator may be added to the epoxy resin composition for the purpose of accelerating the curing reaction. Examples of the curing accelerator include imidazoles, tertiary amines, organic phosphine compounds, or salts thereof. Here, a suitably usable curing accelerator is preferably liquid at room temperature, one having a melting point equal to or lower than the curing temperature of pultrusion molding, or one easily dissolved in an epoxy resin group. More preferably, the melting point is 60 ° C. or lower.
The addition amount of the curing agent accelerator is preferably in the range of 0.5 to 5% by mass with respect to all epoxy resins including the reactive diluent contained in the epoxy resin composition, and 0.5 to 3% by mass. % Is more preferable.

(Additive)
An additive may be blended in the epoxy resin composition used in the present invention as long as the physical properties of the pultruded product are not significantly lowered. For example, you may disperse | distribute or melt | dissolve the powder of thermoplastic resins, such as polyvinyl formal for adjusting the viscosity of an epoxy resin composition, a phenoxy resin, and nylon. In addition, in order to improve flame retardancy, a metal hydroxide such as aluminum hydroxide, a metal oxide such as alumina, titanium oxide or magnesium oxide, a flame retardant such as phosphorus compound or antimony trioxide can be added. In addition, the resin adhesion to the die inner wall that occurs during pultrusion can be suppressed to improve the appearance of pultruded products, the resistance during pultrusion operation can be reduced, and the time for stable and continuous operation can be extended. Therefore, an internal mold release agent may be added as appropriate. In addition, pigments, pigments and the like may be added.

(Viscosity of epoxy resin composition)
The viscosity of the epoxy resin composition used in the present invention is preferably 300 to 1000 mPa · s at 28 ° C. which is a normal resin bath temperature. If the viscosity at 28 ° C. is less than 300 mPa · s, the amount of resin adhering to the reinforcing fiber is too small and voids are observed in the molded product, or irregularities due to the shape of the fiber are generated on the surface of the molded product. There is a possibility of appearance failure. Also, if it exceeds 1000 mPa · s, impregnation failure may occur when large tow is used, and there is a concern that the occurrence of fiber meandering due to the shearing force acting on the inner wall surface of the mold and the fibers may be significant. . The viscosity at 28 ° C. of the epoxy resin composition is more preferably 400 to 600 mPa · s.

(Viscosity measurement)
A flat plate-flat plate viscometer was used, and the temperature rising viscosity of the epoxy resin composition was measured at a temperature rising rate of 2 ° C./min in the temperature range of 25 to 130 ° C. AR-G2 made by TA Instruments Japan Co., Ltd. was used as a measuring device. For the measurement, a φ34 parallel plate was used, and the gap between the plates was 0.5 mm.

(Resin backflow volume, backflow rate)
During the pultrusion, the mass per 1 m of the pultruded product length of the resin overflowing from the mold entrance when the reinforcing fiber bundle impregnated with the epoxy resin composition enters the mold is called the resin back flow amount. . The value (backflow rate) calculated by dividing the resin backflow amount by the mass of the resin in the pultruded product having a length of 1 m is preferably 4.5 times or less. If it is more than that, fiber meandering due to backflow becomes prominent. The smaller the backflow rate is 0 or more, the fewer resin compositions discarded by pultrusion molding are advantageous. However, when the backflow rate is 1.0 or less, there is a possibility that defects such as voids are included in the molded product.

(Strength rate)
In the present invention, the strength expression rate refers to the ratio of the breaking stress of the reinforcing fiber estimated from the tensile strength of the fiber reinforced plastic to the tensile strength of the reinforcing fiber obtained by measurement according to JIS R7601 and the like.
If the tensile strength (fracture stress) of the unidirectional reinforcing fiber reinforced plastic whose volume content (Vf) of the reinforcing fiber is x% is σ _UD and the tensile strength of the reinforcing fiber is σ _ST , the strength expression rate ( %) Is expressed by the following equation.
(Σ _UD / (x / 100)) / σ _ST × 100

(Pulling process)
An outline of the pultrusion process is shown in FIG. The reinforcing fiber bundle is pulled out from the spool (1), introduced into the resin bath (3) through the guide roll (2), adhered with the epoxy resin composition, and then rubbed with the guide bar (4). Then, the reinforcing fiber bundle is impregnated with the epoxy resin composition and a part of the excess epoxy resin composition is removed. Furthermore, the position of the reinforcing fiber is determined one by one with the guide (5), thereby allowing it to enter the pultrusion mold (die) (6) having a desired cross-sectional shape with good balance. Resin that cannot pass through the die together with the reinforcing fiber and eventually becomes surplus is backflowed from the mold and dropped from the die entrance to be removed.
The general pultrusion conditions are that the tension of the reinforcing fiber bundle reaching the resin bath is about 0.2 N with respect to 1 g of mass per 1 m of the length of the reinforcing fiber bundle, and the mold temperature is about 100 to 250 ° C. It is preferable to lower the entrance and gradually increase the curing temperature toward the rear of the mold. The pultrusion speed is generally 0.1 to 1.0 m / min, preferably 0.2 to 0.3 m / min. A suitable time for the reinforcing fiber and the resin composition to pass through the mold is 0.5 to 10 minutes. When the mold length is constant, if the speed is too high, poor curing tends to occur, and if it is too slow, Productivity is poor, and sticking inside the mold tends to occur. In pultrusion molding, even if the resin is not completely cured while passing through the mold, after-curing at 130-150 ° C for about 2 hours may cause insufficient curing of the matrix resin of the fiber reinforced plastic that is the final product. This is more preferable because it can be eliminated and the speed of pultrusion can be increased.

  EXAMPLES Hereinafter, although an Example and a comparative example are demonstrated concretely about this invention, this invention is not limited to these Examples.

As the resin material, the following epoxy resin and epoxy resin curing agent were used and prepared according to the blending ratio shown in Table 1 and used as an epoxy resin composition.
(Epoxy resin)
jER828
“Product Name” jER828
"Ingredients" Bisphenol A epoxy resin "Manufacturer" Mitsubishi Chemical Corporation CY184
“Product Name” CY184
"Components" Alicyclic epoxy resin "Manufacturer" Huntsman Japan Co., Ltd. (Epoxy resin curing agent)
LS-81K
"Product name" LS-81K
“Component” Acid anhydride curing agent “Manufacturer” Lindau Chemical
DY9577
"Product name" DY9577
"Components" Boron trichloride amine complex (Lewis acid)
"Manufacturer" Huntsman Japan Co., Ltd.

The following carbon fiber bundle was used as the reinforcing fiber bundle.
(Carbon fiber bundle)
TRH50-60M
"Product name" TRH50-60M
60000 filaments, tensile strength 4700 MPa
"Manufacturer" Mitsubishi Rayon Co., Ltd. TRW40-50L
"Product name" TRW40-50L
Number of filaments 50000, tensile strength 4100 MPa
"Manufacturer" Mitsubishi Rayon Co., Ltd. TR50S-12L
"Product name" TR50S-12L
12,000 filaments, tensile strength 4900 MPa
"Manufacturer" Mitsubishi Rayon Co., Ltd.

(Measurement method of resin coverage)
After pulling out the reinforcing fiber bundle from the spool while maintaining a tension of about 0.7 N, the reinforcing fiber bundle is opened by impregnating the resin by immersing in the resin with a φ10 guide bar in a resin bath at 28 ° C. The reinforcing fiber bundle coming out of the resin liquid surface is wound up with a gap in a ridge on one side while maintaining the tension, and the fiber direction of the reinforcing fiber bundle is kept vertical for 5 minutes to discharge excess resin. . Thereafter, the reinforcing fiber bundle is cut at a constant length, the mass of the reinforcing fiber bundle including the resin is measured, the mass per 1 m of the reinforcing fiber bundle is obtained, and the mass per unit area of the reinforcing fiber bundle (per 1 m of reinforcing fiber bundle) is obtained. The value obtained by dividing by the mass of the reinforcing fiber) was taken as the resin coverage. The resin used for the measurement is product name: jER807 (Mitsubishi Chemical, bisphenol F type liquid epoxy resin).

(Measurement of fiber meander ratio)
The meandering of the reinforcing fiber is evaluated by polishing a cross section (longitudinal section) parallel to the direction of the reinforcing fiber of the fiber reinforced plastic obtained by pultrusion and observing the reflected image with an optical microscope at a magnification of 50 times. In the observation of the longitudinal section of the fiber-reinforced plastic obtained by pultrusion, generally, the meandering of the reinforcing fiber is observed near the outer peripheral surface of the fiber-reinforced plastic, and the portion where the reinforcing fiber meanders is the direction of the reinforcing fiber. Is specified as a band-like region having a substantially constant width. By observing several longitudinal sections, the position, area, and shape of the portion (meandering area) where the reinforcing fibers meander in the cross section (cross section) perpendicular to the reinforcing fibers of the fiber reinforced plastic obtained by pultrusion The distribution is estimated, the ratio of the total area of the meandering region to the area of the cross section is calculated, and the meandering ratio (%) of the fiber reinforced plastic obtained by pultrusion molding.
When the fiber reinforced plastic is a round bar obtained by pultrusion using a circular die, the fiber meandering is performed by observing an arbitrary longitudinal section passing through the central axis of the round bar under a microscope and assuming cylindrical symmetry. Percentage can be estimated.

Example 1
Ten carbon fiber bundles TRH50-60M were used, and a mixture of 7 parts by mass of DY9577 (boron trichloride amine complex) and 100 parts by mass of CY184 (alicyclic epoxy resin) was used for the epoxy resin composition. The pultrusion process was performed with a drawing die (die) diameter of 6 mm, a mold temperature of 190 ° C., a drawing speed of 0.25 m / min, and after-curing at 135 ° C. for 2 hours. The volume content Vf of the reinforcing fiber in the obtained fiber reinforced plastic was 64.3%, and the resin mass per 1 m length of the molded product was 11.9 g. The mass of the backflow resin that flowed out from the mold entrance was 48.6 g per 1 m of fiber reinforced plastic, and the backflow rate was 4.1 times. The resin coverage of TRH50-60M was 3.2 times.

  When the tensile strength of the fiber reinforced plastic obtained by pultrusion was subjected to a tensile test according to the test method of ASTM D3039 tensile properties, the tensile strength was 2718 MPa. Since the strand strength of TRH50-60M is 4700 MPa, the strength expression rate was 90%.

  In other examples and comparative examples, the resin compounding ratio was in accordance with Table 1, and various measurements of the fiber reinforced plastic obtained by the same pultrusion process as in Example 1 were performed in the same manner as in the examples. The results are summarized in Table 1.

Comparison between Example 1 and Comparative Examples 1 and 2 shows that in pultrusion using a reinforcing fiber bundle having 60000 filaments, a high strength expression rate is obtained by adjusting the backflow rate to 4.5 times or less. As a result, the strength development rate tends to decrease as the backflow rate increases. Further, from the comparison between Examples 1 and 2 and Comparative Example 3, the strength expression rate is 90% or more even in the pultrusion molding using the reinforcing fiber bundle of 60000 filaments of Examples 1 and 2, and Comparative Example 3 A strength development rate equivalent to that obtained when a reinforcing fiber bundle having 12,000 filaments was used could be obtained. Since an equivalent strength expression rate can be obtained, more efficient pultrusion can be performed by using a reinforcing fiber bundle having 60000 filaments, and higher productivity can be obtained.

Claims (2)

It is a fiber reinforced plastic comprising a fiber bundle of reinforcing fibers having 25000 to 80000 filaments and a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, and the strength expression rate of the reinforcing fibers is 90% or more. A fiber reinforced plastic. A unidirectional reinforcing fiber reinforced plastic composite material, characterized in that the ratio of the area of the meandering portion of the fiber to the area of the cross section in a cross section perpendicular to the direction of the reinforcing fiber is 25% or less And unidirectional reinforced fiber reinforced plastic.