JPH0615654B2 - Resin molding material for injection molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a phenol resin molding material for injection molding suitable for a sliding member (hereinafter, referred to as a molding material), which gives a molded article having particularly excellent sliding characteristics and high Charpy impact strength. , Abbreviated as a sliding material). This sliding material is used for bearings, bushings, pistons, sliding members such as magnet switches,
Drive transmission members such as gears, cams, pulleys, rollers,
Wheels, transport members such as casters, reels, handles,
It can be used for joints, packings, washers, heat-resistant fans, caps, lamp housings, and other thin sliding members.

2. Description of the Related Art Thermosetting resin molding materials such as phenol resin molding materials have been widely used as materials for sliding materials, and thermoplastic resins such as polyacetal resins and polyamide resins have been widely used recently. These materials for sliding materials have so-called self-lubricating properties, and although there is a difference in friction coefficient and wear resistance depending on the materials for sliding materials, even if a lubricating oil is not used, a sliding member such as a bearing is used. It has low friction and abrasion resistance required to some extent.

In addition, the present inventors previously applied for a patent for a phenol resin molding material that can obtain a high impact strength molded product having particularly excellent Charpy impact strength without lowering the Charpy impact strength even in continuous injection molding (special Wish
59-113204). This phenol resin molding material has a solubility parameter (SP ... "Adhesion Encyclopedia (above)" written by Ichiro Shibasaki, published by Kobunshi Kogakukai, 51st edition, page 33) 9.0 to 11.
5 to 150 parts by weight of polyvinyl alcohol fiber (hereinafter abbreviated as vinylon fiber) having a tensile strength of 6.0 g / denier or more and 100 parts by weight of phenol resin of 0 and 2 to 50 parts by weight of a lubricating filler are blended. It is something that can be done. In the following description, the solubility parameter is 9.0
As the phenol resin of 1 to 11.0, a benzylic ether type phenol resin (hereinafter abbreviated as BE resin) is exemplified, but it goes without saying that the phenol resin is not limited to BE resin.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, conventional thermoplastic resins such as polyacetal resin and polyamide resin have low surface hardness of these resins themselves, and thus have poor load resistance, for example, drive transmission members such as gears and cams. When a metal is combined as a mating material,
There is a limit to long-term use such as metal biting and dimensional change resulting in poor meshing. Further, it has poor heat resistance, and therefore has a problem that it cannot withstand use at high temperature or high PV value. Further, these resins are excellent in self-lubricating property and wear resistance, and also have good mechanical strength to some extent, but the range of use in which these excellent self-lubricating property and wear resistance properties can be sufficiently exhibited is It is limited to low speed and low surface pressure areas, and in these areas it is sufficiently used even without lubrication, but at high speed and high surface pressure areas, seizure and flow occur due to friction heat, There is a problem that it cannot withstand use under conditions of high speed and high surface pressure. Under such harsh high speed conditions, phenomena such as softening or welding of the working surface or seizure often occur, and even if the product is used for a short period of time, it may not be able to withstand it and does not always exhibit satisfactory performance. .

On the other hand, a conventional phenol resin molding material as a material for a sliding material has a high surface hardness, a high heat deformation temperature, etc., and is excellent in load resistance and thermal characteristics as compared with the thermoplastic resin, In the low speed and low surface pressure range, although it has good sliding properties to some extent, conventional phenol resin molding materials generally have a problem of low impact strength and brittleness, and general Charpy impact strength of phenol resin molding materials is 2-3
It is about kgf · cm / cm ² . Thus, the conventional phenol resin molding material has a low Charpy impact strength,
Notches or scratches on the sliding member are fatal, and some parts of the sliding member are liable to be damaged, which makes it difficult to apply to sliding members that require some mechanical strength. . Therefore, in order to improve the mechanical strength of the phenol resin molding material, glass fiber and rock wool are also mixed to reinforce the strength of the phenol resin molding material. However, it causes a serious defect in friction characteristics that it is easily exposed to the friction surface to damage the mating material.

Further, the above-mentioned prior-art phenol resin molding material is based on the discovery of a surprising phenomenon that the Charpy impact strength cannot be lowered even in continuous injection molding by adding a lubricating filler to BE resin mixed with vinylon fiber. It is a thing. However, this material is excellent in the minimum baking time, the residence time, the volume of the molding material, etc., which become the bottleneck of injection molding, for example, when a thin molded product having a thickness of about 2 to 6 mm is obtained. For example, it has been found that there is a problem in molding that a molded product having a thickness of about 8 to 15 mm is slightly difficult and not always good. Further, this material has a problem that the molding shrinkage rate is rather large.

The present invention has been made by eliminating the above-mentioned problems of the prior art and finding a factor that can further improve the good injection moldability and molding shrinkage of the phenolic resin molding material of the prior application. A problem to be solved is to provide a sliding material having a high Charpy impact strength and excellent in sliding characteristics even under high speed and high surface pressure conditions.

Means for Solving the Problems In view of the problems of the above-mentioned conventional techniques, the present inventors have improved the brittleness, which is an important drawback of phenol resin molding materials, and further improved the conventional thermoplastic engineering plastics (hereinafter referred to as engineering plastics). As a result of various studies to develop a self-lubricating material that overcomes the drawbacks and limitations of use, it is difficult to be affected by use conditions such as contact pressure, surface speed of rotating shaft, temperature, composition of atmosphere, In addition, as shown in the following examples, a self-lubricating material capable of obtaining a sufficiently high limit PV value was found in a phenol resin molding material,
The present invention has been accomplished. Further, in view of the above-mentioned problems of the phenolic resin molding material of the prior application, the minimum baking time, the residence time and the volume of the molding material, which are the necks of continuous injection molding, can be solved very well by using the novolac type phenolic resin. It has been found that the present invention, the purpose is to blend graphite with novolak type phenolic resin, and vinylon fiber of high tensile strength, has the same impact strength as engineering plastic, and high speed, An object of the present invention is to provide a sliding material that gives excellent sliding characteristics even under high surface pressure conditions.

By the way, vinylon fiber is hardly dissolved in BE resin, but it is partially dissolved in novolac type phenol resin at the time of heating, and the fiber itself is melted or lubricated particularly when heated for several minutes or more at the time of molding such as injection molding. Then, since the tensile strength of itself is lowered, the impact strength is hardly improved, and it is extremely difficult to produce a sliding material having high mechanical strength particularly in injection molding. However,
As a result of intensive studies by the present inventors, by blending graphite, surprisingly, the vinylon fiber was hardly dissolved in the novolac type resin even in the injection molding and the tensile strength of the vinylon fiber was maintained, and the tensile strength thereof was maintained. The present invention has been completed by finding that a sliding material having a high impact strength in which the strength is uniquely reflected can be obtained.

That is, the phenolic resin molding material for injection molding suitable for the sliding member according to the present invention has a solubility parameter of 9.0 or less.
-30% by weight of unmodified novolac type phenolic resin outside the range of -11.0, 2-45% by weight of vinylon fiber having a tensile strength of 6.0 g / denier or more and 5-40% by weight of graphite. is there.

Hereinafter, the present invention will be specifically described.

The "sliding member" defined in the present invention is a general term for members used in the fields such as sliding, driving transmission, and transportation as described above.

The phenolic resin used to construct the sliding material of the present invention is a novolac type phenolic resin. This phenolic resin is an unmodified straight novolac type phenolic resin which is different from the phenolic resin having an SP value in the range of 9.0 to 11.0 used in the phenolic resin molding material of the previous application. Compared with other phenolic resin molding materials, the minimum baking time during injection molding is shortened,
The chargeability of the material in the hopper is improved, and the molding shrinkage is reduced, so that the injection moldability is further improved.

The amount of the phenolic resin used in the present invention is
Generally in the range of 30 to 60% by weight, preferably 35 to 50
It is in the range of% by weight. If this amount is less than 30% by weight,
It is not preferable because the mechanical strength is low and the moldability is adversely affected. Conversely, if it is blended in a large amount exceeding 60% by weight, a sliding material suitable for injection molding cannot be obtained, and further the mechanical strength is impaired. It is not preferable.

In the present invention, the vinylon fiber used to improve the impact strength of the sliding material as high as engineering plastic is 6.0 g.
/ Having a tensile strength of denier or more, more preferably having a tensile strength of 7.5 g / denier or more. If the tensile strength of the vinylon fiber is less than 6.0 g / denier, the impact strength is not substantially improved even if a large amount of vinylon fiber is used, which is not preferable. The fiber length of the vinylon fiber used in the present invention is not particularly limited, but the generally used one having a length of 1 to 6 mm is suitable.

The phenol resin molding material of the present invention contains the vinylon fiber in an amount of 2 to 45% by weight, preferably 10 to 40% by weight, more preferably 25 to 35% by weight. If the content is less than 2% by weight, the Charpy impact strength is not significantly improved, and if it exceeds 45% by weight, the sliding material becomes bulky and injection molding becomes difficult, which is not preferable. In addition to the vinylon fiber described above, the molding material of the present invention, in consideration of heat resistance, bending strength, tensile strength, etc., is generally used in phenol resin molding materials such as celluloses and organic fibers such as synthetic fibers. It is also effective to use as a reinforcing material.

Examples of the graphite used in the present invention include ordinary natural graphite such as scaly graphite, scaly graphite, and earth graphite, or artificial graphite. In the molding material of the present invention, the above graphite is blended in the range of 5 to 40% by weight, preferably 7 to 30% by weight. The amount of graphite is 5% by weight
If it is less than 40%, the sliding characteristics will be greatly varied, and the effect of graphite, which will hinder local heat generation in injection molding, will not be fully exerted. Conversely, if it exceeds 40% by weight, the sliding material will slip. It is not preferable because the mixing property and the moldability of the molding material are remarkably deteriorated and the material becomes difficult to be injection-molded.

Incidentally, in the molding material of the present invention, an inorganic powder such as calcium carbonate, aluminum hydroxide, silica or the like may be blended with the sliding material as another filler.

The sliding material of the present invention enables continuous injection molding,
It is characterized in that the impact strength does not decrease even after continuous injection molding, the molded product has high mechanical strength and excellent sliding characteristics.

The sliding material of the present invention can be manufactured by a usual method. An example thereof will be described, but it goes without saying that the method for producing the sliding material of the present invention is not limited to this.
That is, novolac type phenolic resin 30 to 60% by weight, 6.0
Vinylon fibers having a tensile strength of g / denier or more 2 to
45% by weight and 5-40% by weight of graphite are blended, and if necessary, an appropriate amount of organic fibers such as cellulose, inorganic powder such as calcium carbonate and curing agent, curing catalyst, release agent, colorant, etc. The additive is mixed with an appropriate amount of a solvent in a Henschel mixer, and the mixture is kneaded and granulated under heating and high-speed stirring to granulate the material with a volume of 30 to 40 cc / 20 g and a diameter of 2 to 8 mm. The desired sliding material in granular form can be produced.

Action Here, the action of graphite, which is one component of the sliding material of the present invention, will be described. As described above, the vinylon fiber that improves the mechanical strength of the sliding material of the present invention is a novolac type phenol resin when heated. Swells or dissolves in
The tensile strength of itself cannot be maintained, and a sliding material having high impact strength cannot be obtained in injection molding.

However, the present inventors have surprisingly found that by adding graphite to this, it is possible to obtain a sliding material having a high impact strength that sufficiently reflects the tensile strength of the vinylon fiber. This is because graphite, which is a solid lubricant, slides the material well and minimizes the heat generated by friction in sprues and runners in the cylinder of the injection molding machine, molds, etc. It is considered that the fever was suppressed. Further, although the same effect is considered in the Henschel mixer at the time of manufacturing the material, the heat generation is suppressed, so that a sliding material having high impact strength can be obtained. In addition, graphite has the effect of improving the heat conduction when the sliding material is filled in the mold and shortening the minimum baking time, and the sliding property of the sliding material in the cylinder of the injection molding machine, that is, the fluidity is good. And has the effect of extending the residence time range that enables stable long-term injection molding.
Further, it has an effect of improving the sliding property by improving the lubricating property such as lowering the friction coefficient of the sliding material and increasing the limit PV value.

Further, the vinylon fiber itself does not show any lubricity, but it has an action of enhancing mechanical properties by being mixed with a phenol resin. That is, the tensile strength of the vinylon fiber and the Charpy impact strength of the sliding material obtained by using the vinylon fiber are unique, and when the vinylon fiber having high strength is used, the sliding material having high impact strength can be obtained. Further, the addition of vinylon fiber has a function of improving the sliding material performance without causing the deterioration of the sliding material performance due to the increase of the friction coefficient as seen in the addition of the inorganic fiber such as glass fiber or rock wool.

Further, the novolac type phenol resin has an effect of accelerating the minimum baking time, which is a neck of injection molding, as compared with the BE resin in the presence of graphite which is used for the phenol resin molding material of the above-mentioned prior application. The minimum baking time in the present invention is the air generated during curing on the surface of the molded article by changing the baking time from the end of injection of the material to the mold opening,
It is the time until the phenomenon such as uncured blistering caused by water vapor and volatile components is completely absent.This minimum baking time depends on the structure of the mold, heat conduction of the material, thickness of the molded product, and heating. It depends on the method, etc., and is affected by temperature and pressure. Generally, the lower the activation energy, the shorter the activation energy.

The activation energy of novolac type phenolic resin is about 18
~ 20Kcal / mol, that of BE resin is about 24Kcal / m
ol. That is, the use of the novolac type phenol resin shortens the minimum baking time by an amount that the activation energy is smaller by about 4 to 6 Kcal / mol than the BE resin.

Further, since the novolac type phenol resin has a short minimum baking time, it has an effect that it is sufficiently cured under standard molding conditions to obtain a sliding member having a small molding shrinkage ratio.

Examples Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples.

The physical properties in the examples were measured by the following methods.

Charpy impact strength: According to JIS K 6911.

Limit PV value: A sliding test was conducted under the following conditions using a thrust type friction wear tester to measure the limit PV value.

Minimum baking time: Dimension 90x15m using family mold
A Charpy impact strength test piece having a thickness of 15 mm and a thickness of 15 mm was used as a thick molded product and its minimum baking time was measured.

Examples 1 to 6 By blending the components shown in Table 1 in the indicated proportions with a suitable amount of a solvent in a Henschel mixer to uniformly disperse and mix, and further heating and high speed stirring to knead and granulate. A granular sliding material having a diameter of 2 to 8 mm was obtained.

Molding conditions generally used with this sliding material (injection pressure 1000-1200 kg / cm ² , mold temperature 170-180 ° C)
Then, injection molding (manufactured by MEIKI, RJ-140C injection molding machine) was performed to mold a Charpy impact strength test piece and a thrust type friction wear test piece, and the Charpy impact strength and the limit PV value were measured. Further, the Charpy impact strength test piece was used as a molded article of a thick material, and the minimum baking time was measured. The results are shown in Table 2. Regarding other physical properties
Table 2 shows the results of measurement based on JIS K 6911.

Comparative Example 1 Each physical property of only the polyacetal resin was measured. The results are shown in Table 2.

Comparative Examples 2 to 5 Sliding materials were obtained in the same manner as in Example 1, except that the compounding ingredients mixed in the proportions shown in Table 1 were obtained, and each test piece was molded to measure each physical property. The results are shown in Table 2.

Effects of the Invention 1. As described above, according to the present invention, there is provided a sliding member that can be suitably used in any environment, not only under severe conditions of high speed and high surface pressure, but also under low speed and particularly heavy load. When the mating material is a metal, the limit PV value of the resulting sliding material is about three times higher than that of a sliding member made of a polyacetal resin, and when the mating material is a plastic material, the polyacetal resin is About 5 compared to sliding members made of
It has an excellent effect on sliding characteristics, such as about 10 times higher than sliding members obtained from conventional general phenol resin materials.
Therefore, there is an effect that a sliding material can be obtained which provides a sliding member having excellent friction and wear characteristics such as preventing foreign matter from being caught, slurry, welding, and seizure.

2. Further, the sliding material according to the present invention has an effect that the Charpy impact strength does not decrease even in continuous injection molding, and a material having a high impact strength can always be obtained.

3. The sliding material of the present invention has an effect that a material suitable for injection molding can be obtained such that the minimum baking time is short, the residence time range that enables stable long-term injection molding is long, and the volume of the sliding material is small.

4. In addition, there is an advantage that the surface hardness is high and scratches are unlikely to occur even when the mating material is a metal or plastics. It also has a high impact resilience, is less likely to be charged, and is free from dust. It has the advantage of being oil-free and non-greasy with oil.

Claims (1)

[Claims] 1. A non-modified novolac type phenolic resin having a solubility parameter outside the range of 9.0 to 11.0, 30 to 60% by weight, 2 to 45% by weight of polyvinyl alcohol fiber having a tensile strength of 6.0 g / denier or more, and graphite 5. ~
Phenolic resin molding material for injection molding, containing 40% by weight, suitable for sliding parts.