JPH0133593B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a wholly aromatic polyamide fiber with improved adhesion to a matrix resin and a fiber-reinforced resin composite reinforced by the fiber. Prior art Poly(3,4'-oxydiphenylene terephthalamide/P-phenylene terephthalamide) copolymer, poly(P-phenylene terephthalamide), poly(m-phenylene isophthalamide) So-called "aramid fibers" made of wholly aromatic polyamides such as
Because it has good mechanical properties and heat resistance, it is widely used in fields such as aircraft, space equipment, automobiles, and electronic equipment as a fiber-reinforced composite material by combining it with various matrix resins. It is being That is, the fiber-reinforced composite material is widely used in the form of a laminate board, a honeycomb board, a filament winding molded product, a pultrusion molded product, FRTP, etc. using unidirectional prepreg or woven fabric. However, these wholly aromatic polyamide fibers are chemically stable, that is, inert, and have a very high secondary transition point, so it has been pointed out that they have poor adhesion with various resins used as matrices. has been done. However, although a method has been proposed to improve the adhesion between fully aromatic polyamide fibers and rubber when used as a composite reinforcing material in rubber products (Japanese Patent Publication No. 37473/1983), An effective method for improving adhesion is not yet known. Purpose of the Invention The purpose of the present invention is to provide fully aromatic polyamide fibers with markedly improved adhesion to matrix resins and fiber-reinforced resin composites with high tensile shear strength, delamination strength, etc., using the fibers as reinforcing components. It is about providing. Structure of the Invention In order to improve the adhesion of wholly aromatic polyamide fibers to matrix resin, it is necessary to add a material on the surface of the fibers that has a high affinity with the wholly aromatic polyamide constituting the fibers and is also reactive or strong with the matrix resin. It is considered that a method of forming an adhesive layer having affinity is suitable. Therefore, as a result of intensive research, the present inventors found that the polyamide has a main chain structure similar to the main chain structure of the polymer that forms fully aromatic polyamide fibers, and that it can be used as a matrix resin for epoxy resins, unsaturated polyester resins, etc. By using a polymer that has a carboxyl group reactive with the main thermosetting resin as a pendant group on the diamine component side as an adhesive layer forming component, the heat resistance and chemical stability of the entire system are not reduced. We discovered that the adhesion between fibers and matrix resin could be improved.
This has led to the present invention. That is, the present invention provides: (1) At least a part of the surface of the wholly aromatic polyamide fiber is a wholly aromatic polyamide fiber having at least one pendant carboxyl group on the diamine component side in an amount of 15 mol% or more of the total repeating units. A wholly aromatic polyamide fiber coated with polyamide and having improved adhesion with a matrix resin; A reinforcing material is a wholly aromatic polyamide fiber coated with a wholly aromatic polyamide having at least one pendant carboxyl group on the diamine component side in an amount of 15 mol% or more, and a thermosetting resin is used as a matrix. It is a fiber-reinforced resin composite with excellent mechanical properties. In the present invention, examples of the wholly aromatic polyamide fiber serving as the substrate (fiber to be treated) include polyamide fibers mainly consisting of the following repeating units (A) and/or (B). −CO−Ar ₁ −CO・NH−Ar ₂ −NH− ……(A) −CO−Ar ₃ −NH− ……(B) (Ar ₁ , Ar ₂ , Ar ₃ are the same or different 2 ) Such wholly aromatic polyamide fibers include poly(m-phenylene isophthalamide), poly(P-phenylene terephthalamide), poly(4,
4′-biphenylene terephthalamide), poly(P-
benzamide) and poly(3,4'-dioxydiphenyl terephthalamide/P-phenylene terephthalamide) copolymer. Poly(3,4'-dioxydiphenyl terephthalamide/P-phenylene terephthalamide) copolymer fiber and poly(P-phenylene terephthalamide)
Fibers are preferred. On the other hand, the wholly aromatic polyamide having pendant carboxyl groups on the side of the diamine component used as the coating component in the present invention generally has 1 to 2 carboxyl groups, and has primary and/or secondary carboxyl groups.
A method for obtaining a fully aromatic polyamide having pendant carboxyl groups by low-temperature polymerization of an aromatic diamine having two aromatic amino groups, and in some cases other aromatic diamines, and an aromatic dicarboxylic acid chloride. It can be manufactured by Regarding the pendant carboxyl group content of such polyamide, 15 out of the total repeating units of the polyamide
A carboxyl group having at least one, preferably one to two carboxyl groups per repeating unit in the range of ~100 mol% is used, but it depends on the type of matrix resin used in the composite, the required adhesiveness, etc. Depending on the conditions, the most appropriate one can be selected through experiments or the like. Furthermore, the optimum degree of polymerization of the polyamide should be determined through experiments, but in general it is often preferable to select one that can form a durable coating film. Regarding the repeating units of the polyamide, especially the main chain skeleton, in consideration of affinity with the wholly aromatic polyamide fiber that is the base, it is preferable to have a structure similar to that of the polyamide constituting the fiber. There may be restrictions, so it is best to take these conditions into consideration when making your selection. Preferred specific examples of the repeating unit containing a pendant carboxyl group in the polyamide used in the present invention include the following. In addition to these repeating units (1) to (3), the above polyamide also contains repeating units that do not contain pendant carboxyl groups, such as the following, for the purpose of adjusting the properties as a coating-forming polymer: It can be contained in the form of a copolymer. In order to coat at least a part of the surface of the wholly aromatic polyamide fiber with the above polyamide, a method of immersing the wholly aromatic polyamide fiber in a dilute solution of the above polyamide, squeezing it appropriately, and drying as necessary;
Alternatively, it may be carried out by applying a dilute solution of the polyamide to the surface of the fibers using a spray, brush, roller, etc., and then drying if necessary. The optimum concentration of the solution should be determined through experiments depending on the type of polyamide, the thickness and form of the base fiber, but generally it is 0.5 to 5.
Weight percent ranges are used. As the solvent, it is preferable to use a solvent composition that dissolves the above-mentioned polyamide and has an affinity for, but does not strongly attack, the wholly aromatic polyamide fibers that serve as the base.Industrially, dimethylformamide, dimethylacetamide, or these are preferred. A diluent such as water or alcohol is preferably used. Economically, it is particularly preferred to use water as diluent component. It is preferable that the coating formed on the surface of the wholly aromatic polyamide fiber be as uniform as possible. Also,
The amount of coating is generally 0.1 to 10% by weight based on the weight of the fiber.
Particularly preferred is 0.5 to 5% by weight. Thus, the surface of the fully aromatic polyamide fiber coated with the polyamide having pendant carboxyl groups has its carboxyl groups serving as the main reaction points with the matrix resin, and its adhesion to the matrix resin is greatly improved. That is, when an epoxy resin is used as the matrix resin, the carboxyl group reacts with the epoxy group of the resin, and when an unsaturated polyester resin is used, it easily reacts with the resin by forming an ester, etc. Strong adhesion is achieved. Therefore, a catalyst that facilitates such a reaction, such as a tertiary amine or a basic metal salt, may be added in advance to the dilute polyamide solution or matrix resin. The application, shaping and curing of the matrix resin to the coated wholly aromatic polyamide fibers can be carried out by conventional methods. The morphology of the wholly aromatic polyamide fibers is strand or roping, unidirectionally aligned prepreg,
It can take various forms depending on its use, such as woven fabrics, knitted fabrics, mat-like fibers, short fibers, etc. Further, if necessary, carbon fiber, silicon carbide fiber, or glass fiber may be used in combination as a reinforcing component in addition to the fully aromatic polyamide fiber. As the matrix resin, thermosetting resins are preferred, and epoxy resins and unsaturated polyester resins are particularly preferred. The fiber content P (VF) in the composite varies depending on the form of the fibers, but is generally in the range of 5 to 70% by weight, preferably 20 to 65% by weight, and more preferably 45 to 60% by weight. In the present invention, when coating wholly aromatic polyamide fibers with polyamide having pendant carboxyl groups, epoxy is applied to the fibers before or after forming a completely dry layer. It may be applied to the upper layer of a compound, unsaturated polyester prepolymer, etc. in the form of a solution, or it may be added to a solution of these polyamides and prepared in advance with the above matrix component to form a preadduct. I can do it. Thereby, the compatibility with the subsequent matrix resin can be further improved. In addition, the polyamide is added to the matrix resin in advance, and when the matrix resin is applied to the fiber, the concentration of the polyamide on the fiber surface can be increased depending on the affinity with the fiber. However, it is also possible to simultaneously coat the fibers and apply the matrix resin. Effects of the Invention The fully aromatic polyamide fiber coated with the polyamide having pendant carboxyl groups according to the present invention has good adhesion with matrix resins, especially thermosetting resins such as epoxy resins and unsaturated polyester resins, so that A fiber reinforced composite with excellent mechanical properties is formed. Various methods have been proposed for measuring the adhesion between reinforcing fibers and matrix resin in composites, and measurement is possible using any of the methods. It is common practice to measure the following. The fiber-reinforced composite obtained by the present invention is excellent in both tensile shear strength and interlaminar shear peel strength, and can be advantageously used in various forms in various applications such as aircraft, space equipment, automobiles, and electrical equipment. be able to. EXAMPLES The present invention will be described in detail with reference to Examples below, but the present invention is not limited to these Examples in any way. Example 1 Terephthalic acid chloride 100 mol%, 3,4'-
Dimiano diphenyl ether 50 mol%, 3,5-
50 mol % of dimianobenzoic acid was reacted in N-methylpyrrolidone to obtain a copolyamide having a pendant group and a logarithmic viscosity of 0.65. The obtained polymer was dissolved in dimethylformamide to prepare a solution having a polymer concentration of 2% by weight.
As a reinforcing component, a poly(3,4'-oxydiphenylene terephthalamide/P-phenylene terephthalamide) copolymer (copolymerization molar ratio 50/50) described in U.S. Pat. No. 4,075,172 is used. Aromatic polyamide fiber ["Technora" manufactured by Teijin Ltd.] was used, and 100 parts by weight of an epoxy resin matrix ["Ebicoat 828" (bisphenol A dicrycidyl ether type)] and "Epicure Z"(4,4' - 20 parts by weight of diaminodiphenylsulfone curing agent] to create a unidirectionally aligned prepreg by the drum winding method, before impregnating it with the matrix resin, immerse it in the copolyamide solution. A bath was provided to perform coating treatment with the copolyamide described above before resin impregnation. A unidirectional fiber-reinforced composite with a fiber content (VF) of 60% by weight and dimensions of 127 mm length x 125 mm width x 2 mm thickness was prepared by laminating 14 prepregs obtained in this way and using a heat press under the following curing conditions. A material plate was manufactured.

[Table] Curing after heat pressing 160℃ 2 hours under normal pressure ASTMD using the composite material thus obtained
-2344, the interlaminar shear strength was measured using the short beam three-point bending method and was found to be 7.1Kg/mm ²
The value of For comparison, the interlaminar shear strength of a composite material board made in the same manner using uncoated fibers was measured and showed a value of 6.2 Kg/mm ² , indicating that the strength of the composite material board of the present invention was improved. Example 2 In Example 1, except that poly(P-phenylene terephthalamide) fiber ["Kevlar 49" manufactured by DuPont] was used as the wholly aromatic polyamide fiber,
A composite material plate was manufactured in exactly the same manner as in Example 1. When the delamination strength of this material was measured,
It showed a value of 7.3Kg/ ^mm2 .

Claims (1)

[Scope of Claims] 1 At least a part of the surface of the wholly aromatic polyamide fiber is coated with a wholly aromatic polyamide having at least one pendant carboxyl group on the diamine component side in an amount of 15 mol% or more of the total repeating units. A wholly aromatic polyamide fiber characterized by: 2 A wholly aromatic polyamide fiber in which at least a part of the surface of the wholly aromatic polyamide fiber is coated with a wholly aromatic polyamide having at least one pendant carboxyl group on the diamine component side in an amount of 15 mol% or more of the total repeating units. A fiber-reinforced resin composite, characterized in that it is a reinforcing material and a thermosetting resin matrix.