JPH01139866A - Fluorine type fiber for composite material - Google Patents

Abstract

PURPOSE: To obtain the subject fibers with specific oxygen-contg. functional groups on the fiber surface, capable of giving composite materials having excellent high-frequency characteristics, mechanical strength and durability and also usable in ICs or the like through composite formation with matrix resins. CONSTITUTION: The fluorocarbon fibers are obtained by incorporating the fluorocarbon fiber surface with oxygen-contg. functional groups bound to the fiber-forming polymeric molecular chains pref. by low-temperature plasma treatment. In the above fibers, it is preferable that, for the oxygen-contg. functional groups, the atom number ratio O1s /C1s (the number of moles of oxygen atoms per mol of carbon atom) in terms of ESCA measurements is >=0.02 higher than that inside the fiber (at least >=0.5 μm in depth from the fiber surface).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a fluorine-based fiber for composite materials (FRP) having excellent high frequency properties.

[Prior art] In recent years, the field of FRP has made remarkable progress, and has come to be used in a wide range of fields, including premium sports products such as golf club shafts and fishing rods, lightweight vessels such as leisure boats, automobiles, and aviation applications. .

However, the reality is that FRP using fluorine-based fibers has hardly been applied to date because its adhesiveness is too weak.

[Problems to be Solved by the Invention] The present invention makes it possible to improve adhesion with a matrix resin in a practical manner by subjecting polytetrafluoroethylene (hereinafter referred to as PTFE) fibers to low-temperature plasma modification. By improving the dispersibility and homogeneity of this modified PTFE fiber, we were able to provide a composite material with extremely excellent high frequency properties.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, (1) A fluorine-based fiber for a composite material, which has an oxygen-containing functional group bonded to the fiber-forming polymer molecular chain on the surface of the fluorine-based fiber.

(2) The fluorine-based fiber for composite materials according to claim (1), wherein the oxygen-containing functional group is produced by low-temperature plasma treatment.

(3) The concentration of the oxygen-containing functional group is 01.0 as measured by ESCA. /C1, (the number of moles of oxygen atoms per mole of carbon atoms) is 0.02 or more higher than the value inside the fiber (at least 0.5 μm or more deep from the surface). The present invention is a fluorine-based fiber for composite materials as described in item (1).

In the present invention, the hydrophilic group consisting of an oxygen-containing functional group introduced by low-temperature plasma treatment contains at least one functional group selected from an imide group, an epoxy group, and an unsaturated group on the surface of the fluoropolymer. The present invention has been able to provide a base material that functions favorably as a composite with a specific resin that has excellent high frequency properties. Such a base material was provided for the first time by the present inventors.

That is, oxygen in the air reacts with the surface of the fiber whose surface has been activated by low-temperature plasma treatment, and oxygen-containing functional groups (for example, peroxide groups) directly bonded to the i-fiber polymer molecules are formed.

When this oxygen-containing functional group is mixed with a resin containing at least one functional group selected from an imide group, an epoxy group, and an unsaturated group and a resin formation reaction proceeds, the oxygen-containing functional group is used as a radical polymerization initiator or a resin. It was discovered that the radicals generated in the process exert a strong chemical bonding force.

The fluorine-based fiber of the present invention refers to a fiber made of a fluoroalkylene resin mainly made of tetrafluoroethylene. That is, fibers made of a homopolymer of tetrafluoroethylene or a copolymer in which 90 mol% or more, preferably 95 mol% or more of the total amount is tetrafluoroethylene can be mentioned.

Monomers that can be copolymerized with tetrafluoroethylene include fluorinated vinyl compounds such as trifluoroethylene, trifluorochloroethylene, tetrafluoropropylene, and hexafluoropropylene, as well as propylene, ethylene, isobutylene, styrene, acrylonitrile, etc. Examples include vinyl compounds, but there is no need to limit it to these. Among these seven polymers, vinyl fluoride compounds, especially compounds with a high fluorine content, are preferred from the viewpoint of fiber properties.

There are the following two methods for producing such a PTFE fiber composite fiber.

(1) A mixed solution of viscose and PTFE dispersion is used as a spinning stock solution, which is discharged into a coagulation bath, coagulated, and then washed and refined with water. After scouring, the shuns are dipped in alkaline water and squeezed, then dried or sent directly to the firing process for 30 minutes.
Calcinate at 0-450'C and at least 5-10'C
Stretch twice. Next, this fired fiber is produced by oxidative aging in a high temperature atmosphere of 300 to 340°C.

<2) Produced by melt-spinning a polyurethane resin melted at a temperature higher than the melting point of the PTFE copolymer resin.

The fluorine-based fiber of the present invention may be produced by any of the above methods, but according to the method (1), fibers with a diameter of 3 d or less, or even 1 d or less can be produced. For the composite material of the present invention, fibers of (1) are preferably selected because they have smaller fineness, packing density, and high frequency characteristics.

In the present invention, fibers other than PTFE fibers may be used in combination as necessary within a range that does not impede the object of the present invention. Such blended fibers include, for example, inorganic fibers such as carbon fibers and glass fibers, natural fibers such as cotton, hemp, silk, and wool, ordinary thermoplastic synthetic fibers such as polyester, polyamide, polyacrylic, and polyolefin; High strength thermoplastic synthetic fibers such as those drawn at a high magnification, aromatic polyamide fibers, and thermosetting synthetic fibers such as polyamideimide, polyimide, polysulfone, and polysulfide can be used. The high-strength drawn thermoplastic synthetic fibers include polyacrylic, polyethylene, and polyvinyl alcohol fibers of at least 8
Examples include fibers obtained by stretching more than twice as much.

The epoxy resin used in the present invention is a linear low-molecular compound having glycidyl ethyl groups (epoxy groups) at least at both ends, and is formed from, for example, bisphenol A and epichlorohydrin. The above bisphenol A
Instead, it can also be produced using resorcinol, cashew nut oil phenol, sulfonamide, etc. When producing such a resin, a copolymerizable compound containing at least one epoxy group in the molecule, such as phenylglycidyl ether, allylglycidyl ether, styrene oxide, glycidylglycerol, or bisglycidyl diphenylpropane, is used as a diluent and a constituent component. Also included are resins that. These epoxy resins use polybasic acids and their acid anhydrides, inorganic and organic bases, polyamines, polyamides, etc. as curing agents. Examples include polyamines such as guanidine, triethitanolamine, and hexamethylene diamine, initial condensates such as dicyandiamide, melamine, trimethyl cyanurate, polyamide, and urea resin.

The unsaturated group-containing resin referred to in the present invention is a resin containing a radically polymerizable unsaturated group, and includes unsaturated dicarboxylic acid compounds such as maleic acid, fumaric acid, and itaconic acid, and ethylene glycol, propylene glycol, and neopentyl glycol. unsaturated polyester resin obtained by polymerizing diol compounds such as terephthalic acid, isophthalic acid, etc., and saturated dicarboxylic acids such as terephthalic acid and isophthalic acid; vinyl ester resin consisting of divinyl ester mainly composed of bisphenol A1 epichlorohydrin polymer; Examples include silicone resins contained therein, but are not limited thereto.

The fluorine-based fiber of the present invention is the most suitable material for composite with the above two types of resins, but it is also possible to composite with polyimide resin. Examples of such polyimide resins include polycondensates derived from pyromellitic dianhydride and aromatic diamines (such as diaminodiphenyl ether), and polyamides based on trimellitic anhydride and aromatic diamines. Imide resin is also included in this polyimide resin.

The low-temperature plasma treatment of the present invention is a treatment in which fibers are exposed to glow discharge in a specific gas atmosphere.

Glow discharge is usually less than 50 torr, roughly 20 torr.
It is generated by applying a photovoltage in a gas atmosphere under a reduced pressure of less than 10 mm, preferably 0.01 to 10 orr, and the treatment time is selected depending on the type of fiber and processing equipment, but it is usually a few seconds. to several minutes, preferably about 1 second to 5 minutes.

Examples of gases that give an activation effect include Ar, N,
2. He, CO2, Co, 02. H2O.

CF4. NH4, H2, air, etc. and mixtures thereof can be used, but Ar, He, N2゜H2, Co, NH, which do not have a particularly strong etching effect, can be used.
4 etc. are preferable.

Through such plasma treatment, the surface of the fluorine-based fiber (300
The number of oxygen-containing functional groups bonded to molecular chains (within 0) increases. Examples of such oxygen-containing functional groups include carbonyl groups, carboxyl groups, hydroxyl groups, and hydroxyperoxide.

The surface concentration of such functional groups was measured under the following conditions.

The ESCA measurement value is 01. /C1, the atomic ratio (number of moles of oxygen atoms per mole of carbon atoms) is 0°18 or more,
It is preferably 0.35 or less, particularly 0.18 to 0
．． 29 is preferred.

(ESCA measurement conditions) Equipment: Shimadzu X-ray photoelectron spectrometer ESCA750
) Output -8KV-30mA Measurement vacuum -1, OX 10-50a Measurement temperature...20℃ Sampling...Fixed to sample stand with double-sided adhesive tape Horizontal axis correction...C1S main peak binding energy value 2
It was adjusted to 84.6 eV.

If the atomic ratio is less than 0.18, it is difficult to obtain sufficient effects, and if it exceeds 0.35, insufficient effects may not be obtained due to a decrease in the strength of the fiber surface layer.

In addition, as radical polymerization initiators added to promote the resinization reaction of unsaturated polyester resin, bezoyl peroxide, t-butyl peroxyisobutyrate, t-butyl peroxy acetate, t-butyl peroxy Examples include, but are not limited to, benzoate, methyl ethyl ketone peroxide, dicumyl peroxide, and di-1-butyl hydroperoxide.

A composition comprising such low-temperature plasma-treated fluorine-based fibers, a resin containing at least one of an imide group, an epoxy group, and an unsaturated group, and a radical polymerization initiator is molded by a conventional method.

That is, it is molded by heating using a method such as an extrusion molding method, an injection molding method, or a lamination method.

The PTFE fibers of the present invention can be applied in the form of filaments, stables, spun yarns made of staples, or fibrous materials such as woven or knitted fabrics or nonwoven fabrics made of these. Note that by applying PTFE fiber yarn, a composite material having a desired stiffness can be obtained.

The present invention will be explained in detail below with reference to Examples.
The present invention is not limited to this.

[Example] Toyoflon (manufactured by Bunshi ■, polytetrafluoroethylene,
A woven fabric (plain weave, vertical and horizontal density: 60 fibers/inch) consisting of 300 multifilaments was woven, and scouring was performed under the following conditions to remove the oil and sizing agent adhering to the fibers.

(Scouring conditions) Nonionic activator 2Q/n soda ash
2 (80°C in a 17/ff bath)
Shun was treated for 20 minutes, then washed twice with hot water and cold water.
Dry.

This fabric was subjected to low temperature plasma treatment under the following conditions.

(Low temperature plasma processing conditions) Gas used Argon processing pressure 0.7 torr frequency
110 KH2 Applied voltage: 2.5 KV Processing time: 3, 5, 7.15, 30, 60° 600 seconds Next, this treated woven fabric was impregnated with unsaturated polyester resin (#4500, manufactured by Bunsashi ■). After that, it is molded,
A molded product with a fiber content of 60% was obtained.

At the same time, the same molding process was performed on the woven fabric that was not subjected to plasma treatment to improve the adhesion between the fiber and resin.
The bending strength was evaluated based on -7203 and is shown in Table 1.

Table 1 From the above, the comparison example has an increase in the atomic ratio of O15/C1, and the bending strength is low. Also, among the embodiments of the present invention, 0
．． 02 or higher, a significant effect of improving adhesiveness was obtained. It has been found that the composite material made of such PTFE-based fibers exhibits excellent high frequency characteristics and is a material for high-performance IC substrates and LSI substrates.

[Effects of the invention] The PTFE fiber for composite materials of the present invention exhibits excellent high frequency characteristics when combined with a matrix resin, has excellent strength and durability during use, and is capable of increasing the density of ICs and LSIs. It provides highly reliable materials.

Claims (3)

[Claims] (1) A fluorine-based fiber for composite materials, which has an oxygen-containing functional group bonded to the fiber-forming polymer molecular chain on the surface of the fluorine-based fiber. (2) The fluorine-based fiber for composite materials according to claim (1), wherein the oxygen-containing functional group is generated by low-temperature plasma treatment. (3) The concentration of the oxygen-containing functional group is an ESCA measurement value, and the atomic ratio of O_1_s/C_1_s (the number of moles of oxygen atoms per mole of carbon atoms) is within the fiber (at least 0.5 μm or more deep from the surface). ) is 0.0 compared to the value of
The fluorine-based fiber for composite materials according to claim (1), which is higher than 2 or more.