JPH06207315A - Yarn for reinforcing composite material - Google Patents

Abstract

PURPOSE:To obtain the subject yarn providing excellent toughness and crack resistance by subjecting a specific polyimide and a polyether imide to dry mixed spinning. CONSTITUTION:(A) A polyimide comprising a structure of formula I and/or formula II as a main repeating unit and (B) a polyether imide comprising a structure of formula III (1, m and n are integer) as a main repeating unit are subjected to dry mixed spinning. A molding of composite material obtained from a thermosetting matrix resin and reinforcing yarn can be provided with toughness and crack resistance without damaging thermal properties and mechanical properties by arranging a proper amount of the prepared yarn on the surface and in the interior of prepreg.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite material reinforcing fiber used for imparting excellent toughness and crack resistance to a composite material molded product obtained from a thermosetting matrix resin and a reinforcing fiber.

[0002]

2. Description of the Related Art Composite materials having high-strength and high-elasticity fibers such as carbon fibers as reinforcing fibers have been widely used for sports applications because of their excellent specific strength and specific elasticity.
Usually, thermosetting resins such as epoxy resins and bismaleimide resins, which are used as matrix resins, have various characteristics, but have a drawback of poor toughness, and therefore their applications are considerably limited. It was

In order to improve the defects of the thermosetting resin, a method of adding a rubber component or a thermoplastic resin is generally used, but in order to obtain a sufficient effect of improving the toughness, it is necessary to add a large amount and heat resistance. As a result, solvent resistance and handleability are deteriorated.

Further, a method called interleaf has been proposed in which a toughness of a molded article is improved by inserting a film of an adhesive or a thermoplastic resin into a laminate of prepregs in which reinforcing fibers are impregnated with a thermosetting resin. However, it has not been put to practical use because the fiber content cannot be increased and the workability is poor.

As an alternative method, for example, it has been proposed to localize fine particles of a thermoplastic resin on the surface of a prepreg to provide the same effect as the interleaf (Japanese Patent Laid-Open No. 110537/1999). Even in this case, not only the tack of the prepreg is significantly decreased, but also the process is complicated and the quality control is complicated.

In addition, the resin-based composite material has a problem that cracks are generated due to thermal stress during molding or thermal cycle due to the difference in thermal expansion coefficient between the resin and the reinforcing fiber (carbon fiber). Although attempts have been made to increase the elongation of the resin for these, satisfactory results have not been obtained as the current three-dimensional woven fabrics have higher reinforced fiber structures.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems and impairs excellent thermal properties and mechanical properties of a composite material molded product obtained from a thermosetting matrix resin and a reinforcing fiber. The present invention provides a composite reinforcing fiber used for imparting excellent toughness and crack resistance.

[0008]

Means for Solving the Problems The present inventors have used a specific thermoplastic fiber in combination with a composite material composed of a reinforcing fiber and a matrix resin. 1) A suitable amount can be easily arranged on the surface and inside of the prepreg. You can 2) It is easy to control the tack level of the prepreg. 3) The conventional prepreg manufacturing process can be used as it is without having to handle high-viscosity materials. 4) The crack resistance of the molded product is improved. The present invention has been achieved by finding out that various effective characteristics can be obtained.

That is, the gist of the present invention is that a polyimide having a structure of the general formula I as a main repeating unit,
This is a composite material-reinforcing fiber obtained by dry-mixing and spinning a polyetherimide having a structure of the general formula II as a main repeating unit.

[0010]

[Chemical 2]

The polyimide having the structure of the general formula I as the main repeating unit used in the present invention comprises 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride as the main component of the aromatic dianhydride. 5 (6) as the main component of diamine
-Amino-1- (4'-aminophenyl) -1,3,3
-Manufactured by a known condensation reaction using trimethylindane.

The reaction can be carried out in the molten state above the melting point of at least one of the components or in a suitable solvent. By carefully adjusting the molar amounts of aromatic dianhydride and diamine, it is possible to adjust the molecular weight of the resulting polyimide in a fairly wide range. As a catalyst
It is effective to accelerate the formation of polyimide by using pyridine or the like.

The aromatic dianhydride used is 3,3 ',
4,4'-benzophenone tetracarboxylic acid dianhydride as a main component, that is, 3,3 'in aromatic dianhydride
4,4'-benzophenonetetracarboxylic dianhydride is contained in an amount of 90 mol% or more, and other aromatic dianhydrides include, for example, pyromellitic dianhydride 3,
Examples thereof include 3'-bisphthalyl ether dianhydride.

As the diamine, 5 (6) -amino-1
-(4'-aminophenyl) -1,3,3-trimethylindane as a main component, that is, 5 in diamine
(6) -amino-1- (4′-aminophenyl) -1,
3,3-trimethylindane is contained in an amount of 90 mol% or more, and other diamines include, for example, 1,
Examples thereof include 6-hexanediamine, 2,2,4-trimethylhexane-1,6-diamine 1,6-bis [4-aminophenyl] hexane and 4,4′-methylenedianiline. 3,3 ', 4 in aromatic dianhydride
When the amount of 5 (6) -amino-1- (4'-aminophenyl) -1,3,3-trimethylindane in 4'-benzophenonetetracarboxylic dianhydride and diamine is less than the above-mentioned number of moles, it will be described later. It is not preferable because the solubility in a solvent may decrease.

The molecular end of the polyimide used in the present invention is

[0016]

[Chemical 3]

Or a monofunctional capping agent that is reactive with amino or anhydride functional groups. The obtained polyimide is in a solid state.

The polyetherimide having the structure of the general formula II as a main repeating unit used in the present invention is, for example, bisphenol A bisphthalic acid dianhydride represented by the following structural formula 1 as a main component of aromatic dianhydride. object

[0019]

[Chemical 4]

It is produced by a known condensation reaction using 1,3-phenylenediamine as the main component of diamine and diamine.

The reaction can be carried out in the molten state at a temperature above the melting point of at least one of the components or in a suitable solvent. By carefully adjusting the molar amounts of aromatic dianhydride and diamine, it is possible to adjust the molecular weight of the resulting polyetherimide in a fairly wide range. It is effective to promote the generation of polyetherimide by using pyridine or the like as the catalyst.

The aromatic dianhydride used is mainly composed of bisphenol A bisphthalic acid dianhydride represented by structural formula 1, that is, bisphenol A represented by structural formula 1 in aromatic dianhydride. It contains 90 mol% or more of bisphthalic dianhydride, and other aromatic dianhydrides include, for example, pyromellitic dianhydride, 3,3 ′.
Examples thereof include bisphthalyl ether dianhydride.

The bisphenol A bisphthalic acid dianhydride represented by the structural formula 1 is produced by a known method. That is, a bisetherimide compound produced by the etherification reaction of 4-phenyl-4-nitrophthalimide with an alkali metal salt of bisphenol A, which is obtained by the reaction of 4-nitrophthalic anhydride and aniline, is hydrolyzed to form a dehydrated ring. It can be manufactured by

The diamine has 1,3-phenylenediamine as a main component, that is, 1,3 of the diamine.
-Containing 90 mol% or more of phenylenediamine, and other diamines include, for example, 1,6-
Hexanediamine, 2,2,4-trimethylhexane-
1,6-diamine 1,6-bis [4-aminophenyl]
Hexane, 4,4'-methylenedianiline, 5 (6)-
Amino-1- (4′-aminophenyl) -1,3,3-
Examples include trimethylindane. When the bisphenol A bisphthalic acid dianhydride represented by Structural Formula 1 in the aromatic dianhydride and the 1,3-phenylenediamine in the diamine are less than the above-mentioned number of moles, the solubility in a solvent described below is lowered. Is not preferred.

The molecular end of the polyetherimide used in the present invention is

[0026]

[Chemical 5]

It may be a monofunctional capping agent which is or is reactive with amino or anhydride functional groups. The resulting polyetherimide is in solid form.

As the polyether imide, a commercially available product known as Ultem 1000 manufactured by GE (General Electric Company), for example, Ultem 1000 can be used. As the average molecular weight of the polyimide and polyetherimide used, any one of the number average molecular weight, the weight average molecular weight and the Z average molecular weight in terms of standard polystyrene determined by gel permeation chromatography (GPC) is 10,000 or more, more preferably 200 or more.
It is 00 or more. When it is less than 10,000, during spinning,
There is a risk that problems such as yarn breakage may occur, or the fibers may become intolerable in strength afterwards.

The solvent used is one which can dissolve polyimide and polyetherimide uniformly, and the viscosity of the solution measured by a B-type rotational viscometer is 10 ² to 1 at a temperature of 25 ° C.
0 ⁵ as long as it poises solution can be produced, for example, dichloromethane, dichloroethane, chloroform, tetrachloroethane, tetrahydrofuran, dioxane, acetophenone, cyclohexanone, m- cresol, .gamma.-butyrolactone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, It is possible to increase N-methylpyrrolidone or a mixture thereof, a mixture of these solvents and another solvent, and the like. Preferred are dichloromethane, dichloroethane, chloroform, tetrachloroethane, etc., and the solvent is preferably a mixture of methanol and dichloromethane because the solvent is easy to evaporate, the solution viscosity is easy to adjust, and the fluctuation of the solution viscosity is small. Is particularly preferably dichloromethane / methanol = 99-80 / 1-20 weight ratio.

As a method for obtaining a mixed solution of polyimide and polyetherimide, a method in which the polyimide and polyetherimide are individually dissolved and adjusted using the above solvent is mixed, and both are mixed in a powder state in advance. After that, any method such as dissolving in the solvent and mixing may be used.

As a method of dissolving the polyimide or polyether imide, or a mixture thereof, in a solvent,
It can be performed by a known method such as kneader mixing. It is preferable to cool the container in order to suppress the rise in the solution temperature due to the generation of heat of dissolution, and attention should be paid to the increase in viscosity due to the volatilization of the solvent. The mixing ratio of the polyimide and the polyetherimide is not particularly limited. It may be appropriately determined in consideration of heat resistance and the like.

The viscosity of the resulting solution is 10 ² to 10 ⁵ at room temperature (25 ° C.) measured by B-type rotational viscosity.
Poise should preferably be on the order of 10 ³ poise. Depending on the molecular weight of the polyimide and polyetherimide used, dichloromethane / methanol = 99-8
In the 0/1 to 20 weight ratio mixed solvent, the solution concentration of the mixture of polyimide and polyetherimide is most preferably 15 to 35% by weight in terms of spinning stability (spinning) solution.

As a specific method for dry spinning using the thus prepared solution, for example, the solution is fed into a cylinder whose temperature is controlled by a preheater by a gear pump or the like, and filtered by a filter to remove foreign matters. After that, it is continuously extruded from a spinning nozzle into a temperature-controlled atmosphere, passed through a temperature-controlled drying oven at a temperature above the boiling point of the solvent to evaporate and remove the solvent, and then wound at a constant speed. The method is adopted.

An appropriate oil agent may be added to prevent troubles during winding and to prevent static electricity, but it is preferable that no oil agent is attached in order to avoid adverse effects in the subsequent compounding. In addition, the interlace treatment is a preferable method for improving the handleability. The form of the fiber yarn may be either monofilament or multifilament.

The main cross-sectional shape of the composite material-reinforcing fiber thus obtained is an irregular cross-sectional shape having three or more branches, as shown in FIG. Due to such a modified cross-sectional shape, uneven distribution of the fibers due to the impregnation movement of the resin is avoided after the fibers for reinforcing the composite material of the present invention are uniformly dispersed and mixed in a bundle of reinforcing fibers such as carbon fibers, and the fibers are uniformly A good mixed state is maintained. Also, due to such a modified cross-sectional shape, a space through which the resin can penetrate is sufficiently taken, the fiber for reinforcing the composite material and the resin are well mixed, and since the specific surface area is large, it is easy to adapt to the resin and the prepreg When placed on the surface, it has a feature that it is difficult for it to get inside.

Further, it is preferable that it is solid, but even if it is hollow or porous, the conditions for the subsequent compounding process,
It can be used without any particular problem, such as in the case where inconvenience such as molding failure does not occur due to molding conditions and selection of matrix resin.
The fiber diameter may also be set according to the application according to the spinning nozzle diameter and manufacturing conditions. Further, stretching treatment is also effective.

[0037]

The present invention will be described in more detail with reference to the following examples.

Examples 1-3 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 5 (6) -amino-1- (4'-aminophenyl) -1,3,3-trimethyl A polyimide resin was obtained from Indan based on the method described in US Pat. No. 3,857,752. The number average molecular weight of the obtained polyimide resin measured by gel permeation chromatography (GPC) is 2900.
0, mass average molecular weight 65,000, Z average molecular weight 1100
At 00, it was a yellow powder.

On the other hand, a commercially available Ultem 1000 (manufactured by GE) was used as the polyetherimide and mixed at a polyimide / polyetherimide = 70/30 weight ratio, and further mixed with a dichloromethane / methanol (91/9 weight ratio) mixed solvent. A polymer solution having a concentration of 23% by weight was well mixed by stirring at room temperature to prepare a uniform solution. When the viscosity of this solution was measured with a B-type rotational viscometer, it was 1500 poise.
After briefly filtering this solution with a non-woven fabric filter, the temperature is approximately 60 ° C.
40 ° C. to 90 ° C., which is heated at a temperature of 18 ° C. and discharged from a spinning nozzle having a nozzle hole diameter of 38 μm and a hole number of 52 at a discharge rate of 18.70 cc / min.
The solvent was removed by evaporation under the atmosphere described above, and the solvent was taken up at 250 m / min and wound up without applying an oil agent.

The obtained composite material-reinforcing fiber has a fineness of 19
2 denier / 52 filaments Maximum tensile strength 150g
/ Denier Maximum tensile elongation 112% Yield strength 80g /
It was denier. As a result of electron microscope observation of the cross section,
The cross-sectional shape was mainly the cross-sectional shape having three or more branches as shown in FIG. The following investigations were conducted using the composite material reinforcing fibers thus obtained. First, high strength medium elasticity carbon fiber (MR-made by Mitsubishi Rayon Co., Ltd.)
50K, tensile strength 5600MPa, elastic modulus 300GP
A unidirectional prepreg was produced from a) and the resin composition shown in Table 1 by a hot melt method. The carbon fiber areal weight of the prepreg was 145 g / m ² , and the resin content was 28% by weight.

The above-mentioned composite material-reinforcing fiber was added to both sides of the prepreg by the filament winding method in the same direction as the carbon fiber (2.0 mm) so that the fiber basis weight per one surface was 11 g / m ^2. Winded at intervals) and then lightly embedded in the prepreg. From this prepreg, cut a small piece of a predetermined size (+ 45 °
After laminating on _4S , a test piece for measuring post-impact compression strength was molded under the molding conditions shown in Table 1.

Using this test piece, SACMA (Supp
liers of Advanced Composi
tes Materiala Associate
n) Recommended Method SRM2
The compressive strength after 270 lb-in impact was measured according to -88, and the results shown in Table 1 were obtained.

Comparative Examples 1 to 3 The resin content of the prepreg was adjusted to 36% by weight,
A unidirectional prepreg is manufactured in the same manner as in Examples 1 to 3,
It was evaluated without adhering the composite reinforcing fiber of the present invention. The results are also shown in Table 1.

From the above results, it is clear that the use of the composite material-reinforcing fiber of the present invention has high compressive strength after impact and exhibits excellent impact resistance.

Example 4 The composite material-reinforcing fiber obtained in Example 1 and the high-strength medium-elastic carbon fiber (MR-50K manufactured by Mitsubishi Rayon Co., Ltd., tensile strength 5600 MPa, elastic modulus 300 GPa) are uniformly mixed. And rolled it up. In this case, the mixing ratio is as follows: composite material reinforcing fiber / carbon fiber = 3 bundles / 1 bundle (weight ratio 12/10
0).

Further, the mixed fiber bundle thus obtained,
Resin composition of Example 1 (resin film basis weight 56 g /
prepreg was produced from m ² ) by the hot melt method. After the resin was impregnated, the cross section of the prepreg was observed with a microscope. As a result, the composite material reinforcing fiber showed excellent dispersibility. Furthermore, 6 g / fiber per side of composite material reinforcing fiber
The prepreg was obtained by winding the filaments at equal intervals to obtain m ² . A small piece having a predetermined size was cut out from the obtained prepreg, and a test piece for compressive strength measurement after impact was molded and evaluated in the same manner as in Example 1. A compressive strength after impact of 270 MPa was obtained.

For the cycle test (+ 45 / -45 / 0
_8/90) was laminated to the _2S molding. This test piece is -52 ° C
(10 minutes) ← → 132 ° C. (10 minutes) 1 cycle 40 minutes Total 10 cycles Thermal shock was applied. After that, the cross section was polished and the presence or absence of cracks was evaluated by an optical microscope. No cracks were found.

Comparative Example 4 When a thermal cycle test piece was prepared from the prepreg of Comparative Example 1 and evaluated in the same manner as in Example 4, cracking was observed after thermal shock.

[0049]

[Table 1]

[0050]

EFFECTS OF THE INVENTION By using the fiber for reinforcing a composite material of the present invention, excellent toughness and crack resistance are imparted to a molded product without impairing the excellent thermal properties and mechanical properties of the thermosetting matrix resin. And is preferably used as a structural material for aircraft.

[Brief description of drawings]

FIG. 1 shows a main cross-sectional shape of a composite material reinforcing fiber of the present invention.

Front page continuation (72) Inventor Akihiro Ito 4-chome, Sunadabashi, Higashi-ku, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Fumio Sawada 3 Kaigan Dori, Toyama City, Toyama Prefecture Mitsubishi Rayon Co., Ltd. Toyama Office

Claims (4)

[Claims] 1. A fiber for reinforcing a composite material, which is obtained by dry-mix-spinning a polyimide having a structure of general formula I as a main repeating unit and a polyetherimide having a structure of general formula II as a main repeating unit. [Chemical 1] 2. The fiber for reinforcing a composite material according to claim 1, wherein the polyimide and polyetherimide used have an average molecular weight of 10,000 or more. 3. A mixed solvent of dichloromethane and methanol as a solvent (dichloromethane / methanol = 99-8)
0/1 to 20% by weight), and the composite material reinforcing fiber according to claim 1, obtained by dry spinning at a mixed solution concentration of polyimide and polyetherimide of 15 to 35% by weight. 4. The fiber for reinforcing a composite material according to claim 1, wherein the main shape of the cross section is a modified cross section having three or more branches.