JPS5817221B2 - Phenolic resin composition for molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phenolic resin composition for molding that can produce molded products with little variation in strength (excellent reliability).

Phenolic resin molding materials are widely used because they have a good balance of properties such as strength, electrical insulation, and heat resistance, are low cost, and have good molding workability.

In particular, so-called general-purpose grade phenolic resin molding materials that use a large amount of vegetable fibrous powder fillers such as wood flour and pulp flour as fillers are in great demand because of their excellent moldability such as injection and filling properties.

On the other hand, for molded products such as structural parts that require strength, a certain level of strength is required not only due to design factors such as shape and thickness and size of corner radius, but also from the material.

If particularly high strength is required, it is possible to increase the strength by using, for example, glass fibers or pulp long fibers.

However, such materials have high material costs and
Because the shape and bulk of the material increases, an inefficient compression molding method is required, and the biggest drawback of fiber-reinforced materials is that the strength variation (σ: standard deviation) due to orientation is wide (lack of reliability). .

In addition, when trying to obtain a constant strength as a molded product, it is easy to increase the average strength value N by increasing the thickness, for example, but in this case, the variation σ also increases in proportion to X.

That is, the magnitude of σ is important when trying to obtain a constant level of strength by taking into account variations such as X-3σ.

The present invention has been made to solve the above problems and provides a highly reliable material with a small σ.

As a result of intensive studies on molded product strength and materials, the inventors found that 30 to 100 parts by weight of phenolic resin
In a phenolic resin composition comprising parts by weight of a plant fiber powder filler and additives such as a curing agent, a mold release agent, a coloring agent, and a plasticizer, 10 parts by weight of the plant fiber powder filler in the entire composition It has been found that by setting the particle size of the part by weight of -20 to 120 mesh or more and the remaining part to 200 mesh or less, the above-mentioned σ and -3σ can be significantly reduced.

This will be explained in detail below.

(Parts are parts by weight.) Vegetable fiber powder filler 30~
100 parts is the amount to obtain a material with good molding workability; if it is more than 100 parts, the fluidity is poor (and if it is less than 30 parts, the flow is too large).

Further, the inorganic filler can be added in a range of 0 to 100 parts depending on purposes such as combustibility and specific gravity adjustment.

On the other hand, as a result of thorough investigation of the strength, particularly the variation σ, it was found that fibrous fillers increase σ.

It is presumed that this is because there is a limit to the uniformity of orientation during the molding process.

Inorganic fibers such as glass and asbestos, which have a particularly high modulus of elasticity, cannot be used because they increase σ, and when an inorganic filler is used in the composition of the present invention, it is limited to granular or plate-like materials of 200 mesh or less.

The effect of vegetable fibers varies depending on the particle size, and the larger the particle size, the better the average strength X, but the σ also tends to increase.

As a result of studying the particle size distribution of vegetable fibers, the present inventors found that by reducing the weight of 120 meshes or more to 10 to 20 meshes of the total amount to 200 meshes or less, the average strength value X could not be reduced. We have found that the variation σ can be significantly reduced.

Here, when the mesh size is 120 or more and it is less than 10%, X decreases, and when it is more than 20%, σ becomes thicker.

Also, when 120 to 200 meshes are used as the remaining amount, σ is large, and when 120 to 200 meshes are used alone, σ is
is thick (again, low).

That is, by combining 120 mesh or more, which has a large reinforcing effect, and 200 mesh or less, which reduces σ, within the above range, it is possible to reduce σ without reducing X.

In addition, for fillers with a mesh size of 120 or more, if the particle size is large, the smoothness of the surface of the molded product will be poor.
Metsushi is preferred.

'The particle size of the filler was determined using a JIS standard sieve.

The phenol resin used in the present invention is a resin made of phenols such as phenol, cresol, xylenol, and formaldehyde, and may be a resol resin using an alkali catalyst or a novolak resin using an acid catalyst.

The molding material is made by blending these resins with curing agents such as hexamethylenetetramine and paraform, the above-mentioned fillers, and mold release agents such as stearic acid, zinc stearate, and wax, as well as colorants and plasticizers as necessary. The mixture is heated and mixed using a mixing roll, kneader, panburi mixer granulator, etc., and then pulverized.

Figure 1 shows the molded product used for strength measurements.

Table 1 shows the molding conditions.

For strength measurement, as shown in FIG. 2, the molded product was placed on a ring-shaped jig 1, and a load was applied using a cylindrical jig 2 at a speed of 0.5 mm Z to determine the breaking strength.

The vegetable fibers used in the present invention include powdered fibers containing cellulose, such as wood flour, pulp powder, rice husk powder, and ground powder of resin-impregnated products such as ground powder of paper phenol laminates, and abrasive powder. say.

When an inorganic filler is used, it is preferably granular or plate-like with a mesh size of 200 or less, such as silica powder, calcium carbonate, clay, and tank.

This will be explained below using specific columns.

Formalin/phenol molar ratio 0.79, hydrochloric acid 0.8
% as a catalyst, the temperature was raised to 80°C while stirring in a flask.
After refluxing at 100℃ for 90 minutes and 60 minutes at 100℃, it was dehydrated by heating under reduced pressure, and when it reached 135℃, it was taken out and the softening point was 9.
Novolac resin A at 0°C was obtained.

Examples 1 to 3 The compositions shown in Table 2 were premixed using a Henschel mixer (manufactured by Mitsui Miike Seisakusho), heated and mixed for 5 minutes using a mixing roll at 80°C, and then cooled and pulverized to obtain materials.

Furthermore, molding and strength measurements were performed under the conditions described above.

Comparative Examples 1 to 4 With the compositions shown in Table 2, materials were produced in the same manner as in the Example, and their strengths were measured.

Example rows 1 to 3 are examples in which no fibrous inorganic filler was used and 10 to 20% of wood flour of 120 mesh or more was used, and the magnitude of σ was approximately 173 compared to the comparison row. .

Therefore, it is possible to obtain a product with excellent strength compared to the lower limit of the distribution, such as X-3σ, and with high reliability.

Comparison row 1 is an example using glass fiber, and compared to practical row 1, X
Although it is 10 times stronger, it is inferior to X-3σ because σ is large.

Comparison row 2 is a row using 30% wood flour of 80 to 120 mesh, and also has a large σ.

Comparison row 3 is a row using wood flour of 200 mesh or less, and σ
is small, but inferior to X.

Comparative Example 4 is a row in which 120 to 200 meshes of wood flour is used in combination, and σ is larger than when 200 meshes or less is used in combination.

[Brief explanation of the drawing]

Figure 1 is a front view and a surface view of the molded product used for strength measurement.
FIG. 2 is an explanatory diagram of the intensity measurement method. Explanation of symbols 1...Ring-shaped jig, 2...Cylindrical jig.

Claims (1)

[Claims] 1 30 to 100 per 100 parts by weight of phenolic resin
In a phenolic resin composition comprising parts by weight of a plant fiber powder filler and additives such as a curing agent, a mold release agent, a coloring agent, and a plasticizer, 10 parts by weight of the plant fiber powder filler in the entire composition A phenolic resin composition for molding, characterized in that the particle size of the part by weight is 120 meshes or more, and the remaining part is 200 meshes or less.