JPH0429783B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a novel coated wholly aromatic polyamide fiber with improved adhesion to a matrix resin and a fiber-reinforced resin composite containing the fiber as a reinforcing component. It is something. (Prior art) Poly(p-phenylene terephthalamide), poly(3,4'-oxydiphenyl terephthalamide/p-phenylene terephthalamide) copolymer, poly(m-phenylene isophthalamide), etc. It is well known that fibers made from wholly aromatic polyamides (so-called aramid fibers) have excellent mechanical properties and heat resistance (Japanese Patent Publication No. 55-14167).
(Special Publication No. 54-43612), these fibers can be combined with various matrix resins to be used in aircraft, space equipment,
It is being used as a fiber-reinforced composite material in various fields such as automobiles and electronic equipment. In other words, in these fields, fully aromatic polyamide fibers (aramid fibers) are used in the form of unidirectionally reinforced prepregs, laminate plates using woven fabrics, honeycomb materials, filament winding moldings, pultrusion moldings, FRTP, etc. It is starting to be used. However, these wholly aromatic polyamide fibers are chemically stable or inert, as evidenced by their polymer structure, and are extremely
It has been pointed out that the adhesion with matrix resin is poor due to the high secondary transition point.
At present, no industrially effective solution is known. (Objects of the Invention) The first object of the present invention is to improve the above-mentioned drawbacks of wholly aromatic polyamide fibers and to provide fibers that have significantly improved adhesion to matrix resins. A second object of the present invention is to provide a fiber-reinforced resin composite having excellent interlaminar shear strength and containing the wholly aromatic polyamide fiber as a reinforcing component. (Structure of the Invention) In order to improve the adhesion of the wholly aromatic polyamide fiber to the matrix resin, it is necessary to add a material to the surface of the wholly aromatic polyamide fiber that has a high affinity with the wholly aromatic polyamide and is also reactive or strong with the matrix resin. A possible method is to form an adhesive layer with affinity. Therefore, the present inventor has developed an epoxy resin having a structure similar to the main chain structure of the polymer constituting the wholly aromatic polyamide fiber, and as a pendant group.
By using fully aromatic polyamide with amino groups that are reactive with the main resins used as matrix resins such as unsaturated polyester resins, phenolic resins, and polyimide resins, the heat resistance and chemical stability of the entire system can be improved. The present invention was achieved by discovering that adhesiveness can be improved without lowering the adhesive properties. That is, the present invention provides improved adhesion to a matrix resin, characterized in that the fiber surface is coated with a wholly aromatic polyamide having at least one pendant amino group in at least 10 mol% of the total repeating units. Coated wholly aromatic polyamide fiber, and fully aromatic polyamide fiber whose fiber surface is coated with a wholly aromatic polyamide having at least one pendant amino group in at least 10 mol% of all repeating units as a reinforcing component. It is a fiber-reinforced resin composite characterized by: Examples of the wholly aromatic polyamide fibers used in the present invention include fibers made of homo- or copolyamides comprising the following repeating units. Among these wholly aromatic polyamide fibers,
In particular, poly(3,4'-oxydiphenyl terephthalamide) as described in Japanese Patent Publication No. 54-43612.
It is classified as a so-called high Young's modulus and high strength fiber, represented by p-phenylene terephthalamide) copolymer fiber and poly(p-phenylene terephthalamide) fiber as described in Japanese Patent Publication No. 55-14167. Loose type wholly aromatic polyamide fibers are preferably used. The fibers may contain various additives as required, and the cross-sectional shape of the fibers may be circular, triangular, multilobal, cocoon-shaped, or any other arbitrary shape. On the other hand, the wholly aromatic polyamide having a pendant amino group used as a surface coating component of the wholly aromatic polyamide fiber in the present invention is a homo- or It is a copolyamide. Among polyamide repeating units having pendant amino groups, preferred examples include the following. Such a wholly aromatic polyamide having pendant amino groups can be produced by the method described in the specification of JP-A No. 62-7732, which was previously proposed by the present inventors. It is also possible to manufacture by a method. (a) Lower carboxyl group, amino group protected with sulfonic acid group, i.e. carboxylic acid anhydride, aldehyde group, acetamide group, phthalamide group,
an aromatic diamine having one or more sulfonamide groups, one or more azomethine groups, and two unprotected primary and/or secondary amino groups;
sometimes with other aromatic diamines,
A method for obtaining a wholly aromatic polyamide having pendant amino groups by producing a polyamide by a low-temperature polycondensation method with an aromatic dicarboxylic acid dichloride and selectively removing the protecting groups in the pendant groups of the polyamide. . (b) one or more nitro groups and primary and/or secondary
A polyamide is produced by a low-temperature polymerization method of an aromatic diamine having two aromatic amino groups, or in some cases, another aromatic diamine, and an aromatic dicarboxylic acid dichloride, and the pendant nitro groups of the polyamide are A method of converting into amino groups by reduction to obtain a wholly aromatic polyamide having pendant amino groups. (c) producing a polyamide by a low temperature polymerization method of an aromatic dicarboxylic acid dichloride having one or more nitro groups, optionally it and other dicarboxylic acid chlorides, and an aromatic diamine;
A method of converting the pendant nitro groups of the polyamide into amino groups by reduction to obtain a wholly aromatic polyamide having pendant amino groups. (d) A method of post-nitrating a wholly aromatic polyamide and reducing it to convert it into an amino group to obtain a wholly aromatic polyamide having pendant amino groups. However, in method (a) above, it is difficult to select the reaction conditions to selectively remove the protecting groups without causing hydrolysis of the fully aromatic polyamide skeletal bonds, and There is a problem in that synthesis of aromatic diamines having an amino group is troublesome, and the structures of aromatic diamines that can be synthesized are limited. In addition, in the method (b) above, in order to obtain a diamine having a nitro group, it is generally necessary to protect the amino group of the diamine and then nitrate it, and then remove the protecting group to obtain a diamine having a nitro group. The synthesis is very complicated, and diamines having a nitro group, which is a strong electron-withdrawing group, have a problem in that their reactivity decreases and it becomes difficult to increase the degree of polymerization. Furthermore, method (d) is considered to be the most advantageous method industrially because it can be obtained by directly nitrating and reducing the same polyamide used to form wholly aromatic polyamide fibers, but in reality, During nitration using mixed acids, etc., the main chain is likely to be cleaved, and it is very difficult to strictly control the number of nitro groups introduced by the reaction conditions. It is rather difficult to obtain polyamides with pendant amino groups. On the other hand, in the method (c) above, aromatic dicarboxylic acids can be easily nitrated, and nitrated aromatic dicarboxylic acids with a defined structure can generally be obtained. Since this product can be stably converted into acid chloride, the synthesis of the raw material is relatively easy, and depending on the amount of this nitrated aromatic dicarboxylic acid dichloride used, the amount of amino groups in the final polyamide can be reduced. The amount can be controlled freely. In addition, which is common to both methods (b) and (c) above, the polycondensation is carried out by a low-temperature solution polycondensation method using a so-called amide solvent such as NN'-dimethylformamide or N-methyl-2-pyrrolidone. When this is carried out, the polymer is obtained in the form of a homogeneous solution, so by further reduction of the homogeneous solution, the desired polyamide having pendant amino groups can be obtained in one pot. Therefore, from an industrial standpoint, the methods (c) and (d) above are advantageous, and in particular, the method (c) above is suitable for obtaining products of constant quality with good reproducibility. . Regarding the content of pendant amino groups in such wholly aromatic polyamides, it is appropriate to have at least one type of amino group within the range of 10 to 100 mol% of the total repeating units, but depending on the type of matrix resin used and the required The content of amino groups, etc. can be appropriately determined through experiments depending on conditions such as adhesiveness. The degree of polymerization of the wholly aromatic polyamide should also be determined through experiments, but it is often preferable to select one that can form a sufficiently durable coating film. Regarding the specific repeating unit of the wholly aromatic polyamide, in consideration of the affinity with the wholly aromatic polyamide fiber serving as the base, it is preferable that the repeating unit is similar to the structure of the wholly aromatic polyamide forming the fiber. There may be some limitations, and it is necessary to take these into consideration when using them. In order to coat a wholly aromatic polyamide fiber as a base with a wholly aromatic polyamide having pendant amino groups as described above, the fiber is dipped in a dilute solution of the wholly aromatic polyamide, squeezed appropriately, and coated as necessary. Although a method of drying the fibers by drying is preferred, a method of coating the fibers with a dilute solution of the wholly aromatic polyamide using a roller, brush, etc. may also be adopted. The optimal concentration of the solution is selected by experiment, but
Generally, a range of 0.5 to 5% by weight is preferred. The solvent preferably has a solvent composition that dissolves the wholly aromatic polyamide having pendant amino groups and has an affinity for the wholly aromatic polyamide fibers serving as the base, but does not strongly damage the fibers. From this point of view, NN′-dimethylformamide,
NN'-dimethylacetamide and water,
Those to which a diluting component such as alcohol is added are preferably used. Economically, it is particularly preferred to use water as diluent component. Thus, in accordance with the present invention, the fully aromatic polyamide fiber coated with a fully aromatic polyamide having pendant amino groups is such that the amino groups serve as the main reaction points with the matrix resin, and the fibers react with the matrix resin. Dramatically improves adhesion. That is, the fully aromatic polyamide having amino groups reacts with epoxy resin in the same way as aromatic amines used as curing agents, and reacts with unsaturated polyester resin and malein, which is a component in unsaturated polyester. It reacts with an acid component through a Michael addition type reaction and an amination reaction with an ester group. Phenol resins easily react with the methylol groups in the phenolic resin, polyimide resins containing bismaleimide compounds react by a Michael addition type reaction, and ordinary polyimide resins react by ring-opening reactions of imide groups with amino groups. Then,
Can react. In the present invention, when coating a wholly aromatic polyamide fiber having pendant amino groups, an epoxy compound, a bismaleimide compound, a polyester prepolymer having an unsaturated bond, a phenol resin-resol body, etc. are coated with a pendant amino group. After applying the fully aromatic polyamide containing polyamide to the fibers and before forming a completely dry coating layer, or after forming the coating layer and applying it as a solution to the upper layer, the specific reactivity in the matrix resin can be applied before applying the matrix resin component. It is also possible to adopt a method in which a pre-adduct is prepared by combining the ingredients. This can further improve the compatibility and reactivity with the subsequent matrix resin, and can be said to be very effective in practice. In order to produce a fiber-reinforced resin composite containing the fiber of the present invention as a reinforcing component as described above, a conventionally known composite method can be employed. For example, reinforcing fibers include continuous filaments, short fibers, yarns,
It can be present in the matrix resin in any form such as unidirectionally aligned prepreg, woven or knitted fabric, or non-woven fabric, and the ratio of resin to fiber can be appropriately selected depending on the form of the fiber and the use of the composite. . (Effects of the invention) The coated wholly aromatic polyamide fiber of the present invention as described above has a
Adhesion to the matrix resin is significantly improved, and a fiber-reinforced resin composite containing this fiber as a reinforcing component has particularly excellent tensile shear strength or interlaminar shear strength. That is, various methods have been proposed to evaluate the adhesion between reinforcing fibers and matrix resin, and generally, measurements of tensile shear strength or interlaminar shear peel strength are adopted, but the composite according to the present invention was also excellent in these measured values, indicating good fiber-resin adhesion. The fiber-reinforced composite according to the present invention has good mechanical properties and heat resistance, and has excellent fiber-resin adhesion, so it can be used as a laminate board, honeycomb material, filament winding molded product, and pultrude. In the form of rousion molded products, FRTP, etc., it can be advantageously applied to a wide range of fields such as electronic equipment, automobiles, aircraft, and space equipment. (Example) Hereinafter, the present invention will be explained in detail by giving examples. This example is for illustration of the present invention, and
The present invention is not limited thereby. Note that Reference Example 1 shows an example of manufacturing a wholly aromatic polyamide having pendant amino groups. Reference Example 1 3,4'-diaminodiphenyl ether was added in a three-necked flask equipped with a stirring blade under a stream of dry nitrogen.
9.062g of N- was dehydrated with molecular sieves.
Dissolved in methyl-2-pyrrolidone. This solution was externally cooled with ice water, 11.886 g of 2-nitroterephthalic acid chloride was added, and the poly-
3,4'-oxydiphenylene(2-nitro)terephthalamide was prepared. After neutralizing the hydrogen chloride in the above polymer solution by adding 11.3 g of lithium carbonate, 5.6 g of water and 41.7 g of hydrosulfite (Na ₂ S ₂ O ₃ ) were added to convert the pendant nitro groups of the polymer into amino groups. I gave back. The reaction mixture was precipitated with water to obtain poly-3,4'-oxydiphenylene(2-amino)terephthalamide in powder form. By changing the molar balance between the aforementioned 3,4'-diaminodiphenyl ether and 2-nitroterephthalic acid chloride, it was possible to control ηinh=0.3 to 3.5. Examples 1, 2 and Comparative Example The polymer obtained in Reference Example 1 was dissolved in N,N'-dimethylformamide and the solution obtained by adjusting the concentration as shown in Table 1 below was placed in front of the resin impregnation tank. It was placed in a pre-treatment tank. On the other hand, a matrix resin obtained by dissolving 100 parts by weight of Epicure 828 (manufactured by Yuka Ciel Co., Ltd.) and 20 parts by weight of Epicure Z (manufactured by Yuka Ciel Co., Ltd.) as a curing agent in 20 parts by weight of acetone was placed in an impregnation tank. I put it in. Poly(p-phenylene terephthalamide 3,
Fully aromatic polyamide fibers made of 4'-oxydiphenylene terephthalamide (4'-oxydiphenylene terephthalamide) copolymer are dipped in a polymer solution in a pre-treatment tank, thoroughly coated on the fibers, then introduced into a resin impregnation tank and dipped in matrix resin, and then passed through an orifice. was passed through it, and while adjusting the resin content, it was arranged in a row on a drum with a diameter of 90 cm to form a sheet-like material. The sheet-like material thus obtained was heat treated at 85 degrees for 45 minutes to remove acetone and pre-cure to obtain a unidirectionally aligned prepreg. Laminate 12 sheets of this prepreg in the 0 degree direction,
Press molding was carried out at (°C) and post-curing was further carried out at 160 (°C) for 2 hours to obtain a unidirectional fiber-reinforced composite. The interlaminar shear strength (ILSS) of the composite thus obtained was measured by a method according to ASTM D2344, and the results are shown in Table 1 as Examples and Example 2. For comparison, a unidirectional fiber-reinforced composite was similarly prepared by introducing the material into an impregnating bath without passing it through a pretreatment tank and dipping it in a matrix resin. The results of measuring the interlaminar shear strength (ILSS) of this material are shown in Table 1 as Comparative Example 1. Comparing the ILSS measurement values of Examples 1 and 2 and Comparative Example 1 in Table 1, it can be seen that the adhesiveness of the fibers of the present invention to the matrix resin is significantly improved. 【table】

Claims (1)

[Scope of Claims] 1. Improved adhesion with matrix resin, characterized in that the fiber surface is coated with a wholly aromatic polyamide having at least one pendant amino group in at least 10 mol% of all repeating units. coated fully aromatic polyamide fiber. 2. A fiber-reinforced resin characterized by containing, as a reinforcing component, wholly aromatic polyamide fiber whose fiber surface is coated with a wholly aromatic polyamide having at least one pendant amino group in at least 10 mol% of all repeating units. complex.