JPH01172428A - Phenol resin molding material - Google Patents

Abstract

PURPOSE:To make it possible to obtain a molded article having excellent abrasive characteristics and mechanical strengths, by compounding a specified polyacrylonitrile carbon fiber, a novolak phenol resin and a curing agent. CONSTITUTION:A polyacrylonitrile carbon fiber (A) treated by air oxidation and with a titanate coupling agent is obtd. by washing a polyacrylonitrile carbon fiber having a fiber diameter of 4-9mum and a fiber length of 1-10mm with a solvent to remove an epoxy resin with which the fiber is coated as a sizing agent, treating the fiber at 400-480 deg.C for 6-12hr in such a way that the wt. loss of the carbon fiber caused by oxidation is 5wt.% or less and then treating the fiber with 0.1-5wt.% titanate coupling agent [e.g., tetra(2,2- diallyloxymethyl-1-butyl) bis(di-tridecyl) phosphite titanate] based on the carbon fiber. 5-65wt.% component A is compounded with 25-50wt.% novolak phenol resin (B), 7-15wt.% curing agent (C) and, if necessary, a filler, a curing auxiliary etc. (D).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phenolic resin molding material. More specifically, the present invention relates to a phenolic resin molding material that provides molded products with excellent sliding properties and mechanical strength.

[Conventional technology]

In recent years, phenolic resins have been reviewed in order to reduce weight and cost by replacing metal materials with plastic materials.

In general, phenolic resin molding materials use organic materials such as wood flour and valves, and inorganic materials such as asbestos, glass fiber, and talc as reinforcing materials and fillers. However, as a substitute for metal parts, materials with excellent mechanical strength, heat resistance, and sliding properties are required, and the reinforcing materials and fillers mentioned above are unable to satisfy these required properties at the same time. It is becoming impossible to do so.

Therefore, carbon fiber, which has excellent mechanical strength and sliding properties, is used as a reinforcing material. The mechanical strength of conventional carbon fiber-reinforced phenolic resins has a drawback in that the reinforcing effect at the same content is smaller than that of glass fibers. The main reason for the low reinforcing effect of carbon fiber is that the surface of carbon fiber is chemically inert, and chemical bonding with phenolic resin cannot be expected.

One example is that the adhesive strength is low.

Therefore, in order to improve the adhesion of carbon fibers, surface treatments such as nitric acid oxidation, electrolytic oxidation, and air oxidation are carried out to generate chemically active groups on the surface. Furthermore, a silane-based coupling agent may be used in combination. However, even with the surface treatment as described above, the mechanical strength of the carbon fiber reinforced material is hardly improved, and the reinforcing effect is still small compared to glass fiber (see Reference Examples 1 and 2 below).

Therefore, current carbon fiber-reinforced phenolic resin molding materials do not take advantage of the excellent mechanical properties that carbon fibers inherently have, and the problem is that it is not possible to create molding materials that have both high strength and excellent sliding properties. There is a point.

[Problem that the invention seeks to solve]

In order to solve the problem that the reinforcing effect on the mechanical strength of carbon fibers is small in carbon fiber-reinforced phenolic resin molding materials, the present inventors focused on the following points.

(1) Improve the adhesiveness of carbon fibers and strengthen the adhesive force between carbon fibers and phenolic resin.

(2) Provide flexibility to absorb stress at the carbon fiber-phenol resin interface.

As a result of extensive research in order to obtain a phenolic resin molding material that simultaneously satisfies the above two points and has excellent sliding properties and mechanical strength, the carbon fibers were air oxidized and titanate-based coupling agents were added to the fibers. After coating, the inventors discovered that a material mixed with a novolac type phenolic resin has both excellent mechanical strength and sliding properties, leading to the completion of the present invention.

[Means for solving problems]

Therefore, the present invention relates to a phenolic resin molding material.

This phenolic resin molding material consists of polyacrylonitrile carbon fibers treated with air oxidation and a titanate coupling agent, a novolac type phenolic resin, and a curing agent.

The carbon fibers used after air oxidation treatment in the present invention may be polyacrylonitrile (PAN) carbon fibers, but those with a fiber diameter of about 4 to 9 μm and a fiber summary of 1 to 10i+n are preferably used. The epoxy resin coated as a sizing agent is removed from the carbon fibers by, for example, a cleaning method using a solvent.

The cleaned carbon fibers undergo air oxidation under heat to chemically activate the surface. The air oxidation conditions are appropriately selected from temperature-time combinations such that the weight loss rate of the fibers due to oxidation is about 5% by weight or less.
Air oxidation at 80° C. for about 6 to 12 hours provides the desired effect. On the other hand, if the weight loss rate exceeds about 5% by weight, the strength of the fibers will decrease, which is not preferable.

The amount of air oxidized carbon fiber used is preferably about 5 to 65% by weight in the phenolic resin molding material, about 5% by weight.
If the amount is less than 65% by weight, the reinforcing effect is insufficient, and even if it is used in excess of about 65% by weight, there is no change in the improving effect.

Examples of titanate coupling agents that can be used in the present invention include tetra(2,2-diallyloxymethyl-1
-butyl)bis(di-tridecyl)phosphite titanate, isopropyltris(dioctylpyrophosphate)titanate, tetraisopropylbis(dioctylphosphite)titanate, and the like. titanate coupling agents.

It has the characteristic that it can be applied to a wide range of inorganic and organic substances compared to silane coupling agents. Among titanate coupling agents, tetra(2,2-diallyloxymethyl-1
-butyl)bis(di-tridecyl)phosphite titanate is particularly preferred.

The amount of the titanate coupling agent of the present invention used is preferably about 0.1 to 5% by weight based on the carbon fiber.

If it is less than about 0.1% by weight, the effect is insufficient, and even if it is used in an amount exceeding about 5% by weight, there is no change in the improvement effect.A particularly preferable content is about 0.5 to 2% by weight.

The treatment of air oxidation treated carbon fiber with a titanate coupling agent may be either dry treatment or wet treatment.
For example, a titanate-based coupling agent is weighed in the above proportion to the air oxidized carbon fiber, and a solvent (methyl ethyl ketone, methyl ethyl ketone, Acetone, etc.) is weighed, the titanate coupling agent is dissolved in the above solvent, and this is preferably sprayed uniformly onto the carbon fibers and stirred.The proportion of the above solvent used is approximately 10%.
If it is less than 20%, it is insufficient for dissolution, and if it exceeds about 20%, it is uneconomical.

As the phenol resin, it is preferable to use a novolac type phenol resin obtained by condensing phenols and aldehydes under an acid catalyst, and the resin is blended so as to account for about 25 to 50 parts by weight of the molding material. If it is less than about 25% by weight, it becomes difficult to mix the materials on the heating roll, and if it exceeds about 50% by weight, it is difficult to obtain a high-strength molding material.

The phenolic resin molding material of the present invention comprises the above-mentioned carbon fibers,
Novolac type phenolic resin, various fillers and additives,
Hardening agent such as hexametetramine (approximately 7-15%)
and, if necessary, a hardening aid such as calcium hydroxide (maximum 5%).

An example of conditions for injection molding this phenolic resin molding material is as follows.

Mold temperature = 175℃ Screw rotation speed: 100r
p Injection pressure crab 800Kg/cd Injection time: 3
08ec mold clamping pressure: 45Ton Curing time: 4
5 sec [Effect of the Invention] By using a phenolic resin molding material containing carbon fibers treated with a titanate coupling agent after air oxidation treatment, it is possible to obtain a molded article with excellent mechanical strength and sliding properties.

[Example] Next, the present invention will be described in more detail while comparing Examples and Comparative Examples.

(Left below) Reference example 1: Comparison of properties of carbon fiber and glass fiber tensile strength
[Kgf/am”] 370 28
0 tensile modulus [Kgf/-1”] 24,000
7,000 density [g/ajl
1.77 2.49 It can be seen that the strength of the fiber itself is superior to that of carbon fiber.

Reference Example 2: Comparison of properties of carbon fiber reinforced novolac type phenolic resin and glass fiber reinforced novolac type phenol resin
ni gf/■■”] 17.0 1?
, 7 It can be seen that the carbon fiber reinforced material is inferior to the glass fiber reinforced material in terms of the strength of the reinforced material.

Example 1 [Adhesive strength test between carbon fiber and phenol resin] (1) Continuous yarn of polyacrylonitrile (PAN)-based carbonaceous carbon fiber (Toho Rayon product Besphite HTA; fiber diameter 7μ, number of filaments 6,000) was uniformly wound in the circumferential direction of a cylinder and air oxidized at 440°C for 6 hours. Weigh out 20% by weight of acetone with respect to this carbon fiber, and weigh out general formula % formula % (Ajinomoto product KR55) so that the amount is 0.5% by weight with respect to the carbon fiber, and add this titanate coupling agent. was dissolved in the above acetone.

Apply this coupling agent solution uniformly to the carbon fiber,
We made carbon fiber treated with a titanate coupling agent.

(2) Novolac type phenolic resin containing 15% by weight of hexamethylenetetramine (0/T- manufactured by Sumitomo Bakelite)
9P) to 40% by volume (
33% by weight) and completely dissolved in a small amount of methanol.

After uniformly applying this novolac type phenolic resin methanol solution to carbon fibers treated with a titanate coupling agent, air drying at 25°C for 8 hours, cutting perpendicularly to the circumferential direction of the cylinder and stretching it into a sheet. 5c■X
After cutting into Sew squares, heat drying at 65℃ for 8 hours,
A prepreg sheet with fibers arranged in one direction was created.

(3) Layer this prepreg sheet %5CIIX
Place it in a compression mold with a cross-sectional area of 5cm, adjust the thickness to 3.2+uw using a spacer, and heat at 175°C.
It was then heated and compression molded for 20 minutes.

(4) This molded product was heat-treated at 175°C for 8 hours, cooled to room temperature, and then processed with a micro cutter to a length of 16.0I.
IIIX A test piece with a width of 6.4 mm and a height of 3.2 mm was prepared. The length was taken in the direction in which the fibers were arranged, and the width and height were taken perpendicular to the direction in which the fibers were arranged.

(5) Lay on this test piece, ASTM D2344 r
StandardTest Method for A
PPARENT INTERLAMINAR5HEAR
5TRENGTHOF PARALLEL FIB
ERCOMPO5ITES BYSHORT-BEA
Adhesion was evaluated using the short beam method based on M METHODJ.

The test speed was 1.3 m/win, the distance between the supports was 9.61 times the thickness of the test piece, and the test piece was placed on a support stand so that the load was applied to the center of the test piece using a pressure wedge. ,
The test was conducted. The test results are shown in Table 1 below, along with the results of Comparative Examples 1 and 2, which will be described later.

Table 1 Here, ILSS was calculated using the following formula.

Pmax: Maximum load at the time of layer shear failure [Kg
flb = Width of test piece [I1] h: Thickness of test piece [Metal] Note that since bending failure occurred in Example 1, the apparent cage SS was calculated from the maximum load at this time.

The sheet beam method used to evaluate adhesion is to simply support both ends of a short beam using the above test piece obtained from a unidirectional fiber-reinforced material, and apply a concentrated load to the center. This is a test method that adds P. At this time, bending stress and shear road force are generated in the cross section of the "beam". The distribution of the two stress components is determined by the ratio of the thickness of the specimen to the distance between the supports (
R/b), so Q/b needs to be constant.

The fracture mode of the test piece differs depending on the adhesion state of the fiber and resin. In other words, when a fracture occurs due to shear road force caused by the adhesive force between fibers and resin, a layered shear is generated and the maximum bending stress is greater than this.Substitute the maximum shear road force at this time into the above equation. Then, ILSS is calculated. On the other hand, when the shear path force is larger than the bending stress as in Example 1 (when the adhesive force between the fiber and the resin is strong), bending failure occurs.

Comparative Example 1 (1) The continuous yarn of carbon fiber used in Example 1 was wound uniformly in the circumferential direction of a cylinder, and air oxidized at 440° C. for 6 hours.

(2) Next, a novolac type phenol resin containing 15% by weight of hexamethylenetetramine having the same specifications as in Example 1 was weighed so that the total volume with the air-oxidized carbon fiber was 40% by volume, and added to methanol. Completely dissolved.

After uniformly applying this phenolic resin methanol solution to the carbon fiber after air oxidation treatment, it was naturally dried at 25°C for 8 hours.
Cut one spot perpendicular to the circumferential direction of the cylinder, stretch it into a sheet, cut it into 5cm x 5cm squares, and then heat at 65°C.
This was heated and dried for 8 hours to create a prepreg sheet with fibers arranged in one direction.

(3) The following tests were carried out in the same manner as in section (3) of Example 1, and the test results are shown in Table 1 above.

Comparative Example 2 (1) Air oxidized carbon fibers were produced in the same manner as in section (1) of Comparative Example 1. 20% by weight based on this carbon fiber
of ethanol was weighed, and γ-aminopropyltriethoxysilane represented by the following formula (% formula %) was weighed so that it was 0.5% by weight based on the carbon fiber, and this silane coupling agent was dissolved in ethanol. . This coupling agent solution was uniformly applied to carbon fibers to produce carbon fibers treated with a silane coupling agent.

(2) Next, a novolac type phenolic resin containing 15% by weight of hexamethylenetetramine was weighed so that the total volume of the above-mentioned silane coupling agent-treated carbon fiber was 40, and a small amount of methanol was added. completely dissolved in. After uniformly applying this phenol resin methanol solution to the carbon fiber treated with a silane coupling agent,
Air-dried at 5°C for 8 hours, cut perpendicularly to the circumferential direction of the cylinder and stretched into a sheet, 5cm x 5cm.
After cutting into m square pieces, the sheets were heated and dried at 65° C. for 8 hours to create a prepreg sheet in which fibers were arranged in one direction.

(3) The following tests were carried out in the same manner as in section (3) of Example 1, and the test results are shown in Table 1 above.

Example 2 [Mechanical strength test of molded product] (1) Polyacrylonitrile (PAN)-based carbonaceous carbon fiber (Toho Rayon product Besphite HTA-C3-5)
was subjected to air oxidation treatment at 440°C for 6 hours.

(2) Weigh 20% by weight of acetone to the air oxidized carbon fiber, and weigh 1.
Tetra (
Weighing 2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)phosphite titanate,
This titanate coupling agent was dissolved in the above acetone. This coupling agent solution was uniformly sprayed onto the carbon fibers and stirred to produce carbon fibers treated with a titanate coupling agent.

(3) The treated carbon fibers were blended with the following raw material compounding agents.

Phenol resin 44.3% by weight Hexamethylenetetramine 6.7 Carbon fiber
44.3 II Asbestos (
Note 1) 4.4 #Carbon black (
Note 2) 0.5 #(ill) specific gravity 2.4
5. Moisture content 2.0-3.0%, surface area 60 2/g
, diameter 0.025 μm (i12) average particle size 24 μm,
Specific surface area: 125 m''/g, volatile content: 1.1% (4) This mixture was mixed and treated using a heated roll according to a conventional method to obtain a molding material.

(5) The above molding material was molded by a conventional method, and the mechanical strength of the obtained molded product was evaluated according to JIS K-6911. In addition, the sliding properties were measured using a precious wood type friction and wear tester under the following test conditions.

Environment: room temperature, no lubrication Load: 8 gf/cd Peripheral speed: 0.2 m/see Compatible material: 545C The obtained results are listed in Table 2 below, along with Comparative Example 3 below.

(The following is a blank space) According to Table 2 (1) Section (1) of Example 2, air oxidized carbon fibers were obtained.

(2) Weigh 5% by weight of methanol based on the above treated carbon fiber, and 2.0% by weight based on the treated carbon fiber.
γ-7minoprobyltriethoxysilane was weighed out so that the ratio would be as follows, and this aminosilane coupling agent was dissolved in the above methanol.

This coupling agent solution was uniformly sprayed and stirred onto the carbon fibers to produce carbon fibers treated with a silane coupling agent.

(3) The following tests were carried out in the same manner as in section (3) of Example 2, and the test results are shown in Table 2 above.

The mechanical strength of Example 2 is clearly improved compared to Comparative Example 3. It is also believed that the sliding properties were improved because the adhesion between the carbon fibers and the phenol resin was improved, so the detachment of the carbon fibers during sliding was reduced.

Claims (1)

[Claims] 1. A phenolic resin molding material comprising polyacrylonitrile carbon fiber treated with air oxidation and a titanate coupling agent, a novolac type phenolic resin, and a curing agent. 2. The phenolic resin molding material according to claim 1, wherein about 5 to 65% by weight of polyacrylonitrile carbon fibers treated with air oxidation and titanate coupling agent are used in the phenol resin molding material. 3. The phenolic resin molding material according to claim 1, wherein the air-oxidized polyacrylonitrile-based carbon fiber is a polyacrylonitrile-based carbon fiber that has been air-oxidized at a temperature of about 400 to 480°C.