EP-4737113-A1 - REINFORCED FIBER SUBSTRATE

EP4737113A1EP 4737113 A1EP4737113 A1EP 4737113A1EP-4737113-A1

Abstract

An object of the present invention is to provide a reinforcing fiber substrate having a resin material layer, wherein the reinforcing fiber substrate exhibiting excellent microcrack resistance and sufficient mechanical strength and further exhibiting good molding robustness; and the present invention relates to a reinforcing fiber substrate having one or more reinforcing fiber layers containing reinforcing fibers and one or more resin material layers containing fibers of a thermoplastic resin, characterized in that the thermoplastic resin has a melting point of more than 180°C and less than or equal to 250°C and a weight-average molecular weight Mw of the thermoplastic resin of 15,000 to 28,000.

Inventors

NAKAGAWA, HIROKI
OSAKI, Kohei

Assignees

TEIJIN LIMITED

Dates

Publication Date: 20260506
Application Date: 20240521

Claims (15)

A reinforcing fiber substrate, comprising one or more reinforcing fiber layers comprising reinforcing fibers, and one or more resin material layers comprising fibers of a thermoplastic resin, wherein the melting point of the thermoplastic resin is more than 180°C and 250°C or less, and wherein the weight-average molecular weight Mw of the thermoplastic resin is 15,000 to 28,000.
The reinforcing fiber substrate according to claim 1, wherein the thermoplastic resin has a polydispersity (Mw/Mn) of 1.40 to 1.80.
The reinforcing fiber substrate according to claim 1 or 2, wherein the thermoplastic resin is a polyamide resin or a polyester resin.
The reinforcing fiber substrate according to claim 1 or 2, wherein the thermoplastic resin is a polyamide resin.
The reinforcing fiber substrate according to claim 1 or 2, wherein a mean fiber diameter of the fibers of the thermoplastic resin is 1µm to 60µm.
The reinforcing fiber substrate according to claim 1 or 2, wherein the one or more resin material layers are made of a nonwoven fabric containing fibers of a thermoplastic resin.
The reinforcing fiber substrate according to claim 6, wherein the one or more resin material layers are made of a long-fiber nonwoven fabric containing fibers of a thermoplastic resin.
The reinforcing fiber substrate according to claim 1 or 2, wherein the resin material layer or each of the plurality of the resin material layers is disposed on a surface of the reinforcing fiber layer or on a surface of any of the plurality of the reinforcing fiber layers.
The reinforcing fiber substrate according to claim 1 or 2, wherein the reinforcing fiber layer is a unidirectional woven fabric having the reinforcing fibers aligned in one direction as warp yarns and an auxiliary yarn as a weft yarn.
The reinforcing fiber substrate as claimed in claim 1 or 2, wherein the reinforcing fiber substrate comprises at least two said reinforcing fiber layers stacked one on top of the other, each of said at least two reinforcing fiber layers being composed of said reinforcing fibers aligned in one direction, said at least two reinforcing fiber layers being stitched by a stitch yarn as an auxiliary yarn.
The reinforcing fiber substrate according to claim 1 or 2, wherein the reinforcing fiber is a carbon fiber.
A preform material comprising the reinforcing fiber substrate according to claim 1 or 2 and a binder resin.
A method for producing a preform material, comprising subjecting a composite body comprising the reinforcing fiber substrate according to claim 1 or 2 and a binder resin to a heat treatment under pressure.
A fiber-reinforced composite material comprising the reinforcing fiber substrate according to claim 1 or 2 and a matrix resin impregnated in the reinforcing fiber substrate.
A method for producing a fiber-reinforced composite material, comprising: impregnating the reinforcing fiber substrate according to claim 1 or 2 with a matrix resin; and subjecting the reinforcing fiber substrate impregnated with the matrix resin to a heat curing treatment, in order to obtain a fiber-reinforced composite material.

Description

FIELD The present invention relates to a reinforcing fiber substrate and a method for producing the same. The present invention also relates to a preform material and a fiber-reinforced composite material having the reinforcing fiber substrate, and to methods for producing them. BACKGROUND Fiber-reinforced composite materials (also referred to as fiber-reinforced resin composite materials or composites) have been used in a wide range of fields, such as sports and leisure applications including fishing rods and golf shafts, and industrial applications including automobiles and aircraft, due to their light weight, high strength, and high rigidity. The fiber-reinforced composite material can be produced, for example, by impregnating a reinforcing fiber substrate (in particular, a reinforcing fiber substrate composed of carbon fibers) with a matrix resin, and then curing it. Methods of molding a fiber-reinforced composite material include a method of impregnating a reinforcing fiber substrate with a resin in advance and then molding it into the form of a sheet to form a prepreg (an intermediate substrate) which is molded into a fiber-reinforced composite material, and a method of impregnating a reinforcing fiber substrate disposed in a mold with a liquid resin (i.e., for example, an uncured curable resin or a molten thermoplastic resin) and curing or solidifying it to obtain a fiber-reinforced composite material (Resin Transfer Molding method; RTM method). The reinforcing fiber substrate often comprises a plurality of reinforcing fiber layers, in particular reinforcing fiber sheets. Examples of the reinforcing fiber layer include a woven fabric in which reinforcing fibers as warp yarns and weft yarns have been woven by plain weaving, satin weaving, etc. In such a woven fabric, for example, reinforcing fibers as warp yarns and reinforcing fibers as weft yarns run orthogonally. It is also possible to use a unidirectional (UD) reinforcing fiber layer in which reinforcing fibers are aligned in one direction. Such unidirectional reinforcing fiber layers include a unidirectional woven fabric (a UD-woven fabric). The unidirectional woven fabric is a woven fabric composed of reinforcing fibers aligned in one direction as warp yarns and auxiliary yarns as weft yarns, and is a so-called cord fabric. Further, a non-crimp fabric may also be used as a reinforcing fiber substrate. In the non-crimp fabric, a plurality of reinforcing fiber layers made of reinforcing fibers aligned in one direction are stacked, and the stacked reinforcing fiber layers are stitched by a stitching yarn as an auxiliary yarn. In the non-crimp fabric, a stack of reinforcing fiber sheets made of reinforcing fibers aligned in one direction is integrated by being stitched with an auxiliary yarn (which is in particular referred to as a "stitch yarn"), wherein the auxiliary yarn penetrates the stack in the thickness direction. In such a reinforcing fiber substrate, it is known to use a resin material layer (also referred to as a veil layer) such as a nonwoven fabric. The resin material layer is generally composed of thermoplastic resin fibers. For example, a nonwoven fabric containing thermoplastic resin fibers as a resin material layer can be disposed on a reinforcing fiber layer and/or between reinforcing fiber layers. The resin material layer may bring about advantageous effects in terms of interlayer fracture toughness, impact resistance, resin permeability, and substrate morphological stability. Patent Literature 1 (PTL1) describes a reinforcing element for a curable composition, which comprises a resin-soluble thermoplastic veil suitable for being located between reinforcing fiber layers. Patent Literature 2 (PTL2) describes an intermediate material, which is intended to be combined with a thermosetting resin to produce a composite part. The intermediate material is composed of a unidirectional layer of carbon fibers, each side of which is combined with a web of thermoplastic fibers having a specific thickness. Patent Literature 3 (PTL3) describes a reinforcing fiber substrate; wherein the reinforcing fiber substrate has a reinforcing fiber aggregate and a mesh-like resin material disposed on at least one side surface thereof; wherein the resin material is a copolymer polyamide containing at least two polyamide components selected from polyamide 6, polyamide 6-6, polyamide 6-10, polyamide 12, polyamide 6-I; and wherein the melting point of the resin material is within the range from 80 to 180 °C. [Citation List] [Patent Literature] [PTL 1] JP 2008-540766A[PTL 2] JP 2012-506499A[PTL 3] JP 2019-99987A [Technical Problem] For the reinforcing fiber substrate, the fiber-reinforced composite material produced from the reinforcing fiber substrate is required to have excellent microcrack resistance and sufficient mechanical strength. In addition, it is also required to have good molding robustness. However, with the conventional reinforcing fiber substrate