JPH0753803B2 - Phenolic resin molding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a phenolic resin molding material. More specifically, it relates to a phenolic resin molding material that gives a molded article excellent in sliding characteristics and mechanical strength.

[Conventional technology]

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

Generally, phenolic resin molding materials use organic substances such as wood powder and pulp as reinforcing materials and fillers, and inorganic substances such as asbestos, glass fibers and talc. However, as a substitute material for metal parts, a material that has excellent sliding properties in addition to mechanical strength and heat resistance is required, and the above-mentioned reinforcing materials and fillers must satisfy these required properties at the same time. Is becoming impossible.

Therefore, carbon fiber having excellent mechanical strength and sliding characteristics is used as a reinforcing material. The mechanical strength of conventional carbon fiber reinforced phenolic resin has a drawback that the reinforcing effect at the same content is smaller than that of glass fiber. The reason why the reinforcing effect of the carbon fiber is small is mainly that the surface of the carbon fiber is chemically inactive, a chemical bond with the phenol resin cannot be expected, and the adhesive force is small.

Therefore, in order to improve the adhesiveness of carbon fibers, surface treatment such as nitric acid oxidation, electrolytic oxidation, and air oxidation is performed to generate chemically active groups on the surface. In addition, a silane coupling agent may be used together. However, even if the surface treatment as described above is performed, the mechanical strength of the carbon fiber reinforced material is hardly improved, and the reinforcing effect is still smaller than that of the glass fiber (see Reference Examples 1 and 2 below).

Therefore, the current carbon fiber reinforced phenolic resin molding material does not take advantage of the excellent mechanical properties inherent in carbon fiber, and it is not possible to make a molding material that has both high strength and excellent sliding properties. There is a point.

[Problems to be solved by the invention]

In order to solve the problem that the carbon fiber reinforced phenolic resin molding material has a small reinforcing effect on the mechanical strength of the carbon fiber, the present inventor has paid attention to the following.

(1) Improve the adhesiveness of carbon fiber and strengthen the adhesive force between carbon fiber and phenol resin.

(2) The carbon fiber-phenolic resin interface has flexibility to absorb stress.

As a result of earnest studies to satisfy the above two points at the same time and obtain a phenol resin molding material having excellent sliding characteristics and mechanical strength, carbon fiber was subjected to air oxidation treatment, and a titanate coupling agent was applied to this fiber. After that, they found that the material mixed with the novolac type phenolic resin had both excellent mechanical strength and sliding characteristics, and completed the present invention.

[Means for solving problems]

Therefore, according to the phenol resin molding material of the present invention, the phenol resin molding material comprises a polyacrylonitrile-based carbon fiber that has been air-oxidized and treated with a titanate-based coupling agent, a novolac-type phenol resin, and a curing agent.

The carbon fiber used for air oxidation treatment in the present invention may be polyacrylonitrile (PAN) -based carbon fiber,
A fiber having a fiber diameter of about 4 to 9 μm and a fiber length of about 1 to 10 mm is preferably used. Epoxy resin applied as a sizing agent is removed from the carbon fibers by, for example, a cleaning method using a solvent.

The washed carbon fibers are air-oxidized under heating to chemically activate the surface. The conditions for air oxidation are appropriately selected from the combination of temperature and time such that the weight loss rate of the fibers due to oxidation is about 5% by weight or less. For example, about 400-480 ℃
After air-oxidizing for about 6-12 hours, the desired effect is obtained.
On the other hand, if the weight reduction rate exceeds 5% by weight, the strength of the fiber is reduced, which is not preferable.

The amount of the air-oxidized carbon fiber used is preferably about 5 to 65% by weight in the phenol resin molding material. If it is less than about 5% by weight, the reinforcing effect is insufficient, and if it exceeds 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, isopropyl tris (dioctylpyrophosphate) titanate, tetraisopropylbis (dioctylphosphite) titanate, and the like. The titanate-based coupling agent has a feature that it can be applied to a wide range of inorganic substances and organic substances as compared with the silane-based coupling agent. Among the titanate coupling agents, tetra (2,2-diallyloxymethyl-1-butyl) bis (diethyl) -di (dibutyloxymethyl-1-butyl) bis (diethyl) -di (diphenyloxymethyl-1-butyl)- -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. about
If the amount is less than 0.1% by weight, the effect is insufficient, and even if the amount exceeds about 5% by weight, the improving effect remains unchanged. Particularly preferably, it is about 0.5 to 2% by weight.

The air-oxidation-treated carbon fiber with a titanate-based coupling agent may be treated by either dry treatment or wet treatment.
For example, the titanate coupling agent is weighed so that the above ratio is obtained with respect to the air-oxidation-treated carbon fiber, and the solvent (methyl ethyl ketone, acetone, etc.) is adjusted so as to be about 10 to 20% by weight with respect to the carbon fiber. ),
It is preferable that the titanate-based coupling agent is dissolved in the above-mentioned solvent, and this is uniformly sprayed and stirred on the carbon fiber. If the proportion of the above solvent used is less than about 10%, the dissolution is insufficient, 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 in the presence of an acid catalyst, which is blended so as to account for about 25 to 50% by weight of the molding material. If it is less than about 25% by weight, it will be difficult to knead the material with a 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 is the above carbon fiber,
Novolac type phenolic resin, various fillers and additives,
Hardener such as hexamethylenetetramine (about 7-15%),
And, if necessary, a hardening aid such as calcium hydroxide (up to about 5%) is mixed and mixed.

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

Mold temperature: 175 ℃ Screw speed: 100 rpm Injection pressure: 800Kg / cm ² Injection time: 30sec Mold clamping pressure: 45Ton Curing time: 45sec [Effect of the invention] Carbon treated with titanate coupling agent after air oxidation treatment The phenol resin molding material containing fibers makes it possible to obtain a molded product having excellent mechanical strength and sliding characteristics.

〔Example〕

Next, the present invention will be described in more detail by comparing Examples and Comparative Examples.

Reference Example 1: Comparison of characteristics between carbon fiber and glass fiber It can be seen that the strength of the fiber itself is superior to that of the carbon fiber.

Reference Example 2: Comparison of characteristics between carbon fiber reinforced novolac type phenolic resin and glass fiber reinforced novolac type phenolic resin Regarding the strength of the reinforcing material, it can be seen that the carbon fiber reinforced material is inferior to the glass fiber reinforced material.

Example 1 [Adhesive strength test of carbon fiber and phenolic resin] (1) Polyacrylonitrile (PAN) -based carbonaceous carbon fiber (Besphite HTA manufactured by Toho Rayon Co., Ltd .; fiber diameter 7 μm, number of filaments 6,000) It was wound evenly in the circumferential direction and air-oxidized at 440 ° C. for 6 hours. Weigh 20% by weight of acetone with respect to this carbon fiber, and set it to 0.5% by weight with respect to the general formula. Tetra (2,2-diallyloxymethyl-1) represented by
-Butyl) bis (di-tridecyl) phosphite titanate (Ajinomoto KR55) was weighed and the titanate coupling agent was dissolved in the above acetone.

Apply this coupling agent solution evenly to the carbon fiber,
A carbon fiber treated with a titanate coupling agent was prepared.

(2) Novolac-type phenol resin containing 15% by weight of hexamethylenetetramine (Sumitomo Bakelite 0 / T-9P)
Was weighed so as to be 40% by volume (33% by weight) with respect to the total amount of the above carbon fibers, and completely dissolved in a small amount of methanol.

This methanol solution of novolac type phenolic resin was uniformly applied to the carbon fiber treated with titanate coupling agent, and naturally dried at 25 ° C for 8 hours, cut at one place perpendicular to the circumferential direction of the cylinder and stretched into a sheet. Then, it was cut into 5 cm × 5 cm squares and then heated and dried at 65 ° C. for 8 hours to prepare a prepreg sheet in which fibers were arranged in one direction.

(3) This prepreg sheet was overlaid, put in a compression molding die having a cross-sectional area of 5 cm x 5 cm, adjusted to a thickness of 3.2 mm using a spacer, and heated and compression molded at 175 ° C for 20 minutes. .

(4) This molded product was heat treated at 175 ° C for 8 hours, allowed to cool to room temperature, and then processed with a micro cutter, length 16.0 mm × width 6.
A test piece of 4 mm x 3.2 mm in height was prepared. The length was taken in the fiber array direction, and the width and height were taken at right angles to the fiber array direction.

(5) For this test piece, refer to ASTM D2344 “Standard T
est Method for APPARENT INTERLAMINAR SHEAR STRENGT
H OF PARALLEL FIBER COMPOSITES BY SHORT-BEAM METH
Adhesion was evaluated by the short beam method based on “OD”.

The test speed is 1.3 mm / min, and the distance between fulcrums is 3 of the thickness of the test piece.
The test piece was placed on a support so that the load was applied to the center of the test piece by a pressure wedge and the test piece was doubled in size to 9.6 mm. The test results are shown in Table 1 below together with the results of Comparative Examples 1 and 2 described below.

Here, ILSS was calculated by the following equation.

Pmax: Maximum load when interlaminar shear failure [Kgf] b: Width of test piece [mm] h: Thickness of test piece [mm] Since bending failure occurred in Example 1, The apparent ILSS was calculated from the maximum load.

The short beam method used for the evaluation of adhesiveness means that both ends of a short "beam (short beam)" using the above-mentioned test piece obtained from a unidirectional fiber reinforced material are simply supported and a concentrated load P is applied to the center. This is the test method to be added. At this time, bending stress and shear stress are generated in the cross section of the “beam”. Since the component distributions of the two stresses vary depending on the ratio of the thickness of the test piece and the distance between fulcrums (l / b), it is necessary to keep I / b constant.

The fracture mode of the test piece differs depending on the adhesion state of the fiber and resin. That is, when fracture occurs due to shear stress due to the adhesive force between the fiber and the resin, interlaminar shear occurs and the maximum bending stress is larger than this. The maximum shear stress at this time is substituted into the above equation to calculate ILSS. On the other hand, when the shear stress is larger than the bending stress (when the adhesive force between the fiber and the resin is strong) as in Example 1, bending failure occurs.

Comparative Example 1 (1) The continuous yarn of carbon fiber used in Example 1 was evenly wound in the circumferential direction of the 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 as to be 40% by volume with respect to the total amount of the air-oxidized carbon fiber, and completely mixed with methanol. Dissolved in.

This phenol resin methanol solution was evenly applied to carbon fiber after air oxidation treatment, then air-dried at 25 ° C for 8 hours, cut at one place perpendicular to the circumferential direction of the cylinder and stretched into a sheet shape, 5 cm × After being cut into 5 cm square pieces, it was heated and dried at 65 ° C. for 8 hours to prepare a prepreg sheet in which fibers were arranged in one direction.

(3) Hereinafter, the same method as in (3) and subsequent steps of Example 1 was performed, and the test results are shown in Table 1 above.

Comparative Example 2 (1) An air-oxidation-treated carbon fiber was produced in the same manner as in (1) of Comparative Example 1. 20% by weight of ethanol was weighed out with respect to this carbon fiber, and γ-amino represented by the following formula H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ was prepared so as to be 0.5% by weight based on the carbon fiber. Propyltriethoxysilane was weighed and this silane coupling agent was dissolved in ethanol. This coupling agent solution was uniformly applied to carbon fibers to prepare carbon fibers treated with a silane coupling agent.

(2) Next, a novolac type phenol resin containing 15% by weight of hexamethylenetetramine is weighed so as to be 40% by volume based on the total amount of the carbon fibers treated with the silane coupling agent, and a small amount of methanol is added. Completely dissolved. This phenol resin methanol solution is uniformly applied to carbon fibers treated with a silane coupling agent, then naturally dried at 25 ° C for 8 hours, cut at one location perpendicular to the circumferential direction of the cylinder and stretched into a sheet. , 5 cm × 5 cm square, and then heat-dried at 65 ° C. for 8 hours to prepare a prepreg sheet in which fibers are arranged in one direction.

(3) Hereinafter, the same method as in (3) and subsequent steps of Example 1 was performed, 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 Vesphite HTA-C3-S) was used at 440 ° C.
And air-oxidized for 6 hours.

(2) 20% by weight of acetone was weighed with respect to the air-oxidized carbon fiber, and tetra (2,2) used in Example 1 was used so that the ratio was 1.0% by weight with respect to the air-oxidized carbon fiber.
-Diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate was weighed and this titanate coupling agent was dissolved in the above acetone. This coupling agent solution was uniformly sprayed onto the carbon fibers and stirred to prepare titanate coupling agent-treated carbon fibers.

(3) The treated carbon fiber was blended with the following raw material compounding agents.

Phenol resin 44.3% by weight Hexamethylenetetramine 6.7 〃 Carbon fiber 44.3 〃 Asbestos (Note 1) 4.4 〃 Carbon black (Note 2) 0.5 〃 (Note 1) Specific gravity 2.45, Moisture content 2.0-3.0%, Surface area 60m ² / g, Diameter 0.025μm (Note 2) Average particle size 24μm, specific surface area 125m ² / g, volatile matter
1.1% (4) This compound was mixed and processed by a conventional method using a heating roll to obtain a molding material.

(5) The above molding material was molded by a conventional method, and the resulting molded product was evaluated for mechanical strength according to JIS K-6911. The sliding characteristics were measured under the following test conditions with a Suzuki type friction and wear tester.

Environment: room temperature, unlubricated load: 8 Kgf / cm ² peripheral speed: 0.2 m / sec Counterpart material: S45C The obtained results are shown in Table 2 below together with Comparative Example 3 described later.

Comparative Example 3 (1) According to the item (1) of Example 2, an air-oxidation-treated carbon fiber was obtained.

(2) 5% by weight of methanol is weighed with respect to the treated carbon fiber, and γ-aminopropyltriethoxysilane is weighed so as to have a ratio of 2.0% by weight with respect to the treated carbon fiber. The coupling agent was dissolved in the above methanol. This coupling agent solution was uniformly sprayed onto carbon fibers and stirred to prepare silane coupling agent-treated carbon fibers.

(3) Hereinafter, the same method as in (2) and subsequent steps of Example 2 was carried out, and the test results are shown in Table 2 above.

The mechanical strength of Example 2 is clearly improved as compared with Comparative Example 3. Further, it is considered that the sliding property is also improved because the detachment of the carbon fiber during sliding is reduced because the adhesive force between the carbon fiber and the phenol resin is improved.

Claims (3)

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