JPH01306431A - Production of substrate for composite material consisting of polybenzoxazole fiber - Google Patents

Abstract

PURPOSE:To obtain the subject substrate, excellent in adhesion to matrix resins and capable of providing a composite material excellent in strength, etc., by treating the surface of a polybenzoxazole fiber or molded product thereof with a plasma, then applying and reacting a surface treating agent consisting of a specific compound therewith. CONSTITUTION:The surface of a polybenzoxazole fiber (preferably containing >=80wt.% recurring units expressed by formula I or II) or a molded product thereof is treated with a plasma and then a surface treating agent consisting of a compound (e.g., glycidyl methacrylate) having a group (preferably mercapto group) reactive with the above-mentioned fiber surface or a compound having a group (preferably amino group, etc.,) reactive with an epoxy resin which is a matrix resin is applied and reacted therewith (preferably by heating). The unreacted surface treating agent is preferably removed by washing with water, etc., to afford the objective substrate, excellent in elastic modulus, water and fatigue resistance, etc., and capable of providing a composite material suitable as sports tools, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a base material for a composite material made of polybenzoxazole fibers used in a composite material having an epoxy resin as a matrix.

[Conventional technology]

Examples of substrates for composite materials that have been put into practical use industrially include glass fibers, aramid fibers, and carbon fibers, which are used in fields such as sporting goods, aircraft, automobiles, and ships. In addition, in the field of advanced composite materials, such as those in the aircraft and space industries, these conventional materials are used to further improve the strength, modulus of elasticity, heat resistance, impact resistance, fatigue resistance, etc. of composite materials. In addition, research into new materials is also being conducted.

Under these circumstances, heterocyclic aromatic fibers, which have excellent strength, elastic modulus, heat resistance, etc., and are lightweight, are expected to be used as base materials for advanced composite materials.

Among them, polybenzoxazole fibers are excellent in terms of high and 7 degrees. A method for producing polybenzoxazole fiber, which is a type of heterocyclic aromatic fiber, is disclosed in Japanese Patent Application Laid-Open No. 61-501452.

As a surface treatment for the composite material, U.S. Patent No. 4.58
1.437, there is a method of heat treatment in a specific oxygen atmosphere.

[Problem that the invention seeks to solve]

-i In the case of composite materials, the quality of adhesion between the base material and the matrix resin greatly influences the physical properties of the composite material including the two, such as strength, elastic modulus, fatigue resistance, and water resistance. Therefore, in order to improve these physical properties of composite materials, it is said to be extremely important to improve the adhesiveness between the base material and the resin.

However, as described in U.S. Pat. No. 4,58L437, polybenzoxazole fibers have poor adhesion to thermosetting resins, and even the use of epoxy resins, which have relatively good adhesion, is not sufficient. . for that,
The excellent characteristics of fibers are not well reflected in the physical properties of composite materials.

1. Although the method of heat treatment in an oxygen atmosphere described in the patent publication does improve adhesion, it has not reached the point where the physical properties of the composite material are significantly improved.

Therefore, in order to improve the physical properties of composite materials using epoxy resin as a matrix, such as strength, elastic modulus, water resistance, and fatigue resistance, the present inventors developed a composite material base material made of polybenzoxazole fibers. As a result of extensive research into manufacturing methods, the present invention has been completed.

[Means for solving problems]

The present invention involves subjecting polybenzoxazole fibers or molded products thereof to plasma surface treatment, and then surface-treating the surface with a compound that has both a group capable of reacting with the modified fiber surface and a group capable of reacting with an epoxy resin in its molecule. This is a method for producing a base material for a composite material made of polybenzoxazole fibers, which is characterized in that the polybenzoxazole fibers are applied as an agent and reacted.

The base material obtained by the method of the present invention exhibits a remarkable effect particularly on composite materials having an epoxy resin as a matrix.

Polybenzoxazole fiber in the present invention (hereinafter referred to as
(referred to as PBO fiber) is a polymer having one or more types of repeating units represented by the following structural formulas I, ■, and ■, in which these repeating units account for 80% by weight or more of the total weight. Fibers made of these copolymers can be obtained by polymerization and spinning using well-known methods, and they have 1. high strength and high modulus of elasticity. Unexamined Japanese Patent Publication 1986
The method described in JP-A-501452 is preferred.

Further, in the present invention, PBO fibers having the following structural formula (1) or (2) as a main component are preferably used in terms of high strength and high elastic modulus.

Structural formula of polybenzoxazole Examples of molded products of the above fibers include nonwoven fabrics, woven fabrics, chopped strands, and the like. Furthermore, the molded product may be composed of two or more types of PBO fibers, and reinforcing materials for composite materials other than PBO fibers, such as carbon fibers, glass fibers, alumina fibers, aramid fibers, and heterocyclic aromatic fibers, may also be used. etc. may be included. However, in order to take advantage of the light and strong characteristics of PBO fibers, the content of reinforcing materials other than PBO fibers is preferably 30% or less based on the base material. In addition, when using molded products containing reinforcing materials other than PBO fibers for electrical circuit wiring board applications,
It is also necessary to consider their electrical properties such as insulation and dielectric constant.

In the present invention, plasma surface treatment not only cleans the surface of the substrate, increases the surface area by etching, and crosslinks the surface layer, but also modifies the surface so that it can chemically bond with the surface treatment agent applied in the next step. This is done to ask questions. Plasma treatment can be performed by a known method. Examples of the atmospheric gas include gases such as air, nitrogen, hydrogen, carbon dioxide, argon, helium, ammonia, -carbon oxide, methane, ethane, propane, and methylamine, and mixed gases thereof. however,
01917 Less deterioration in operability due to corrosion of surface treatment equipment, contamination with polymers, etc. ■Good plasma stability;
and the reactivity with the zero-order surface treatment agent increases.
For this reason, it is preferable that the atmospheric gas contains argon, helium, nitrogen, air, or a mixed gas thereof as a main component. The pressure is usually 0.02 to 5 torr, preferably 0.05 to 1 torr. The discharge power source can be a high frequency power source or a low frequency power source as long as it can provide a stable plasma state.The discharge power (discharge voltage x current) is usually 10 to 1000 watts, but it can be used to The plasma irradiation time is preferably 10 to 300 watts in terms of activating the plasma.The plasma irradiation time needs to be selected depending on conditions such as the type of gas, discharge power, pressure, etc., and is usually 5 seconds to 10 minutes.Plasma device is not particularly specified, and may be a batch type or a continuous type.

In the present invention, following plasma surface treatment, a compound having in its molecule both a group capable of reacting with the modified fiber surface and a group capable of reacting with an epoxy resin is applied to the PBO fiber or a molded product thereof, and reacted. . As a result, the groups that can react with the fiber surface react with the base material activated by the plasma surface treatment, but the groups that can react with the epoxy resin remain unreacted. chemically bond and, as a result, improve the physical properties of the composite material.

Examples of groups that can react with the fiber surface include unsaturated groups such as maleimide groups, vinyl groups, styryl groups, methacrylic groups, allyl groups, and acetylene groups; unsaturated groups such as mercapto groups, amino groups, and imidazole groups; Examples include groups that can react. In terms of reaction with the surface of the base material, styryl groups, methacrylic groups, and mercapto groups are preferred, and among them, mercapto groups with low polymerizability are the best.

Groups that can react with epoxy resins include, for example, amino groups, imidazole groups, epoxy groups, phenolic hydroxyl groups,
Examples include groups having an acid anhydride skeleton. In terms of reactivity with epoxy groups and hydrolysis of bonds formed by the reaction, amino groups, imidazole groups, and epoxy groups are preferred. Examples of such compounds include glycidyl methacrylate, 5-, mercapto-2-amino-1,
3゜4 triazole, 2-mercaptoimidazole, 2
-Mercaptoethylamine and their salts, etc.
Also, reaction products of glycidyl methacrylate and ammonia, reaction products of glycidyl methacrylate and diaminodiphenylmethane, reaction products of p-vinylbenzyl chloride and n-butylamine, reaction products of p-vinylbenzyl chloride and benzylamine. There are also things.

As long as the compound has at least one group capable of reacting with the fiber surface as a functional group and has at least one group capable of reacting with an epoxy resin, it may have three or more types of these functional groups. . A plurality of compounds may be used as a mixture, and other radically polymerizable compounds such as styrene, methyl methacrylate, acrylonitrile, acrylamide, fumaric acid, maleic acid, maleic anhydride, maleimide, etc. may be used as a mixture. Good too. However, from the viewpoint of effectively bonding the surface treatment agent and the base material, the mixing ratio of these radically polymerizable compounds is preferably 50% or less.

Methods for applying these compounds include, for example, methods in which they are applied in the form of a gas, an aqueous solution, an organic solvent, or an emulsion solution. From an industrial perspective, an aqueous solution is superior in that it is inexpensive, easy to produce, and reduces unevenness in processing. For example, water-soluble surface treating agents such as 2-mercaptoethylamine and its salts are preferably used.

The amount of the surface treatment agent applied is not particularly limited, but is preferably 0.5% by weight or less, more preferably 0.01 to 0.3% by weight, based on the base material.

The reaction between the surface of the substrate and the surface treatment agent can be carried out by conventional methods such as heating, irradiation with ultraviolet rays, irradiation with electron beams, and the like.

However, industrially, it is advantageous to apply the solution using a solution, and in this case, since the solvent is heated during the drying process, it is preferable to carry out the reaction at this time.

The base material to which the surface treatment agent has been applied and reacted as described above improves the mechanical properties of the composite material, but in order to further improve the physical properties of the composite material against heat or thermal history, It is preferable to remove unreacted surface treatment agent. Since not all of the applied surface treatment agent reacts and is grafted onto the surface of the substrate, the amount that has simply adhered remains on the surface of the substrate. This inhibits the reaction between the grafted surface treatment agent and the matrix resin, and reduces the adhesion between the base material and the resin. As a result, the S of the composite material
Although it does not have a very significant effect on mechanical properties, it does reduce the physical properties of the composite material against heat or thermal history, such as interlayer adhesion after moisture absorption, thermal shock resistance 1, and heat-and-moisture cycling resistance. To prevent such problems, unreacted surface treatment agents are removed. For example, water,
This can be carried out by washing with an aqueous detergent solution, organic solvent, etc. (wet method), vacuum drying, volatilization by heating, etc. (dry method). However, in consideration of removal efficiency, decomposition of the graft portion, etc., a wet method is preferable, and furthermore, it is preferable to use water or an aqueous solution because it is industrially easy.

〔Example〕

Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited by the Examples.

In this example, a heat treatment system made of a polymer represented by the following structural formula was used as the polybenzoxazole fiber.

Structural Formula of Polymer This fiber was prepared based on the description in Japanese Patent Application Laid-Open No. 61-501452, and will be explained below by citing the example numbers described in that publication.

Polymerization was carried out according to Example 13 in the publication, adjusting the amount of monomer charged so that the polymer concentration was 11% by weight. The intrinsic viscosity of the obtained polymer was 204!
/g. The spinning was carried out with reference to Example 119 in the publication, using a spinneret (pore diameter o, 25 at φ, number of holes 5), dope temperature 120'', and a drawing ratio during spinning of C1 of 13/1.The obtained fiber The heat treatment was performed in a nitrogen atmosphere at 500°C for 1 minute under a tensile force of 2 g/d.The physical properties of the single yarn in the heat treatment system were as follows: strength: 32 g/d, elastic modulus: 1290 g/d
, elongation 2.6% T: Atta. In addition, the physical properties of the single yarn are
Measured based on ASTM-D-3379.

Example 1 and Comparative Example The heat treatment system consisting of polybenzoxazole was heated to 0.05
Plasma surface treatment was performed for 5 minutes at a frequency of 5 KHz and a discharge power of 100 W in an argon gas atmosphere of 11 g of mm, immersed in an aqueous solution of 3 g/l of mercaptoethylamine hydrochloride, squeezed with a rubber roll, and dried in a hot air dryer at 120 °C. and dried for 10 minutes. Then, it was washed with running water at room temperature for 15 minutes.

The resulting heat treatment system was made of 100 parts of Epikote 604 (an epoxy resin manufactured by Shell Chemical Co., Ltd.), 40 parts of 4,4'-diaminodiphenylsulfone, 1 part of boron trifluoride monoethylamine complex, and 50 parts of methyl ethyl ketone. The solution was impregnated and the silicone was wound at regular intervals onto a drum pre-wrapped with a coated release paper. The release paper was removed from the drum and dried in a drying layer at 70° C. for 30 minutes to produce a prepreg with a resin content of 40% by volume.

The obtained prepregs were laminated in one direction and the pressure was 4 kg/I.
11'', was cured at a temperature of 140° C. for 2 hours to create a unidirectional composite material.

From the composite material thus obtained, length 7011,
A test piece with a width of 25 mm and a thickness of 2.7 fins was prepared, and a bending test in the fiber direction was conducted using an autograph under the conditions of a span distance of 43 mm and a crosshead speed of 3 m/min. As a water resistance test, using a pressure vessel,
Those exposed to water vapor at 120'C for 50 hours ('P
C-50hr) was also subjected to a bending test in the same manner. The test results are shown in Table 1. Note that the comparative example shows the results of a heat treatment system in which the method of the present invention was not performed.

This result shows that the method of the present invention is effective in improving the physical properties of composite materials. In particular, it shows remarkable effects on physical properties after moisture absorption.

Example 2 and Comparative Examples The heat treatment system consisting of polybenzoxazole was heated to 0.05
9. Under argon gas atmosphere of 11g of dragon, frequency of 5KII2, discharge power of 100W. Plasma surface treatment was performed for 5 minutes, immersed in an aqueous solution of 3 g/β mercaptoethylamine hydrochloride, squeezed with a rubber roll, and dried in a hot air dryer at 120° C. for 10 minutes.

The resulting heat treatment system was prepared from 100 parts of Epikote 604 (an epoxy resin manufactured by Shell Chemical Co., Ltd.), 40 parts of 4,4'-diaminodiphenylsulfone, 1 part of boron trifluoride monoethylamine complex, and 50 parts of methyl ethyl ketone. A release paper impregnated with a solution containing silicone and coated with silicone was wound onto a pre-wound drum at regular intervals. The release paper was removed from the drum and dried in a drying dish at 70°C for 30 minutes to produce a prepreg with a resin content of 40% by volume. The obtained prepregs were laminated in one direction and the pressure was 4k.
g/Ryu 2 and cured at a temperature of 140° C. for 2 hours to create a unidirectional composite material.

A test piece with a length of 70 mm, a width of 25 mm, and a thickness of 2.7 H was prepared from the composite material thus obtained, and using an autograph, the distance between spans was 43 mm, and the crosshead speed was 311/min. A bending test in the fiber direction was conducted under the following conditions. In addition, as a water resistance test, using a pressure vessel,
Those exposed to water vapor at 120°C for 50 hours (PC-5
0 hr) was similarly subjected to a bending test. The test results are shown in Table 2. Note that the comparative example shows the results of a heat treatment system in which the method of the present invention was not performed.

This result shows that the method of the present invention is effective as a base material for composite materials. In particular, it exhibits remarkable effects on physical properties after moisture absorption.

〔Effect of the invention〕

The base material for a composite material produced by the method of the present invention is excellent in the following points when used as a composite material having an epoxy resin as a matrix.

(1) Since the base material and the epoxy resin matrix are chemically bonded, the mechanical properties of the composite material are improved, such as bending strength, elastic modulus, water resistance, heat cycle resistance, thermal shock resistance, and environmental resistance. It is possible to improve sexual performance, etc.

(2) In recent years, in order to improve the physical properties of the composite material Nemi 1, research has been conducted on the use of composite reinforcing materials, such as aramid fibers and glass fibers, aramid fibers and carbon fibers, etc. In the present invention, the base material Since the surface is activated by plasma surface treatment,
Base materials other than polybenzoxazole fibers can also be activated at the same time. Therefore, it is also effective as a surface treatment for base materials such as woven fabrics of carbon fibers, aramid fibers, glass fibers, etc. and polybenzoxazole fibers.

(3) Resistance to delamination due to thermal shock after moisture absorption, which is a disadvantage in printed electrical circuit wiring board applications that take advantage of the insulation properties, low dielectric constant, negative coefficient of thermal expansion, and low water absorption of polybenzoxazole fibers. (soldering heat resistance). This effect is particularly noticeable when the unreacted surface treatment agent is further removed in the method of the present invention.

The composite material substrate produced by the method of the present invention can be used, for example, in sports equipment, leisure equipment, various appliances, parts, etc., as well as aircraft that require lightness and excellent properties such as strength, elastic modulus, and heat resistance. It is effective in composite materials used in the space industry, automobiles, and ships.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] After subjecting polybenzoxazole fibers or molded products thereof to plasma surface treatment, a compound having in the molecule both a group capable of reacting with the modified fiber surface and a group capable of reacting with an epoxy resin is applied as a surface treatment agent. A method for producing a base material for a composite material made of polybenzoxazole fibers, characterized by reacting the polybenzoxazole fibers with