JPH0615655B2 - Resin molding material for injection molding - Google Patents

Description

TECHNICAL FIELD The present invention provides a molded product having particularly excellent heat resistance and high Charpy impact strength and having extremely excellent sliding characteristics, that is, high sound, high speed, and high surface pressure. The present invention relates to a phenol resin molding material for injection molding (hereinafter abbreviated as a sliding material), which is suitable for a sliding member and can be preferably used under the above condition. This sliding material includes bearings, bushings, pistons, sliding members such as magnet switches, drive transmission members such as gears, cams and pulleys, transfer members such as rollers, wheels and casters, reels, handles, joints, packing, washers, It can be used for heat resistant fans, caps, lamp housings, and other thin sliding members.

2. Description of the Related Art Thermoplastic resin molding materials such as phenol resin molding materials have been widely used as resin 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 a so-called self-lubricating property, and even without using a lubricating oil,
Although there are differences in the coefficient of friction and wear resistance depending on the material for the sliding material, it has a certain degree of low friction and wear resistance required for sliding members such as bearings.

Further, the inventors separately applied for a patent for a phenol resin molding material for injection molding, which is suitable for a sliding member that can obtain a molded product having excellent sliding characteristics and high Charpy impact strength in injection molding. This phenol resin molding material is a novolac type phenol resin 30 to 60% by weight, polyvinyl alcohol fiber (hereinafter abbreviated as vinylon fiber) 2 to 45% by weight and graphite 5 to 40% by weight having a tensile strength of 6.0 g / denier or more. %, And is a phenol resin molding material for injection molding which is particularly suitable for sliding members.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, conventional thermoplastic resins such as polyacetal resins and polyamide resins have poor heat resistance, and therefore have limitations in use at high temperatures or at high PV values. Since the surface hardness is low, the load resistance is poor,
For example, when a metal is combined with a drive transmission member such as a gear or a cam as a mating material, the metal bites into the metal, causing a dimensional change, which makes it difficult to engage with each other. 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 the low speed, low surface pressure and low temperature areas, and it can be used satisfactorily even in the absence of lubrication in these areas. There is a problem that it causes flow and cannot withstand use under high speed, high surface pressure and high temperature conditions. 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, phenolic resin molding materials as materials for sliding materials
It has relatively good thermal characteristics and load bearing capacity such as high heat deformation temperature and high surface hardness compared to the above thermoplastic resins, and has some good sliding characteristics in the low speed and low surface pressure regions. It is a thing. However, there is a limit to use under high temperature, high speed, and high surface pressure conditions, and under such severe conditions, phenomena such as seizure occur and the performance is not always satisfactory. Furthermore, phenol resin molding materials generally have a basic problem of low impact strength and brittleness. General phenol resin molding materials have Charpy impact strength of about ^{2 to 3} kgf · cm / cm ² , and notched Izod impact strength of 1 to It is about 2 kgf · cm / cm. In this way, the conventional phenol resin molding material has low Charpy impact strength and Izod impact strength with notch, so the notch or scratch on the sliding member is fatal and it is easy to damage such as chipping of the sliding member. Therefore, it was difficult to apply it to a sliding member that requires some mechanical strength. Therefore, in order to improve the mechanical strength, a method of supplementing the mechanical strength by blending glass fiber or rock wool is also used. However, these glass fibers and rock wool are exposed on the friction surface and the mating material is exposed. It has a serious defect in friction characteristics that it is easily damaged.

Further, a phenol resin molding material for injection molding suitable for the sliding member of the above-mentioned separate application (hereinafter simply referred to as another application)
Solves the basic problem of low impact strength and brittleness of general phenolic resin molding materials.In another invention of this application, vinylon fiber is injected by blending vinylon fiber and graphite with novolac type phenolic resin. In the discovery of a surprising phenomenon that the tensile strength of vinylon fiber is maintained almost without being dissolved in novolac type phenolic resin even during molding, and a high impact strength sliding material that uniquely reflects the tensile strength is obtained. It was made based on. However, the sliding member obtained from this sliding material has high Charpy impact strength and good sliding characteristics, but has a low heat distortion temperature when used under conditions of high temperature, high speed and high surface pressure. It was found that there is a limit to heat resistance.

The present invention has been made by eliminating the above-mentioned problems of the prior art and finding factors that can further improve the injection strength and the molding shrinkage such as the mechanical strength and the minimum baking time of the sliding material of another application. The problem to be solved is to provide a sliding material having a remarkably high heat deformation temperature and high Charpy impact strength, and having extremely excellent sliding characteristics even under conditions of high temperature, high speed and high surface pressure. That is.

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. In view of the problems of the sliding material of another application, the phenol resin has a number average molecular weight of at least
If you use the novolac type phenolic resin which is 650,
Surprisingly, they have found that the heat resistance is significantly improved regardless of the presence or absence of after-cure, and have completed the present invention.

That is, the phenol resin molding material for injection molding suitable for the sliding member according to the present invention has a number average molecular weight of at least
30-60% by weight of novolac type phenolic resin which is 650,
It comprises 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.

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 comprise the sliding material of the present invention has a molecular weight of at least 650, preferably 700.
It is a novolac type phenolic resin having a relatively high molecular weight of about 5000 to 5000, more preferably 800 to 1500. The use of a novolac type phenolic resin having a molecular weight of at least 650 according to the present invention surprisingly results in a sliding material with significantly improved heat resistance, both with and without after cure. This is probably because the cross-linking density of the resulting sliding member is high due to the high molecular weight of the phenol resin, but vinylon fiber
Despite shrinking at 0 ° C and softening at 220 ° C, mysteriously, the heat distortion temperature after the post-cure is remarkably improved, and the Charpy impact strength at high temperature is not significantly decreased. After cure is usually
It is carried out when it is used continuously at high temperature or when it is subjected to temporary high temperature treatment such as soldering. Further, surprisingly, when the above-mentioned phenol resin is used, the vinylon fiber is hardly dissolved in the phenol resin, and sliding having a high Charpy impact strength and a high limit PV value uniquely reflecting the tensile strength of the vinylon resin. The material is obtained. Furthermore, mechanical properties such as Charpy impact strength and Izod impact strength are improved compared to the sliding material of another application, the minimum baking time during injection molding is shortened, and the chargeability of the material in the hopper is improved. Therefore, the injection moldability is further improved such that the molding shrinkage is small. The number average molecular weight of the phenol resin is determined by high-speed GPC (Gel Permeation Chromatography) according to the conventional method.
To measure.

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 consideration of the fluidity of the resulting sliding material, a novolac type phenol resin having a number average molecular weight of less than 650 may be used together.

The vinylon fiber used to improve the impact strength of the sliding material in the present invention has a tensile strength of 6.0 g / denier or more, more preferably 7.5 g.
/ It has a tensile strength of not less than denier. 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 improvement of mechanical strength such as Charpy impact strength or Izod impact strength is significantly small, and if it exceeds 45% by weight, the sliding material is bulky and injection molding is difficult. It is not preferable because it becomes a material. 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.
For example, 30 to 60% by weight of a novolac type phenolic resin having a number average molecular weight of at least 650 is mixed with 2 to 45% by weight of vinylon fiber having a tensile strength of 6.0 g / denier or more and 5 to 40% by weight of graphite. If necessary, an appropriate amount of organic fibers such as cellulose, inorganic powder such as calcium carbonate and a curing agent, a curing catalyst, a release agent, a colorant and other additives are mixed, and this is mixed with an appropriate amount of a solvent in a Henschel mixer. Then, the desired sliding material in the form of granules having a volume of the material of 30 to 40 cc / 20 g and a diameter of 2 to 8 mm can be produced by uniformly dispersing and mixing in (1) and kneading under heating and high speed stirring.

Action The action of the novolac type phenolic resin having a number average molecular weight of at least 650 used for the sliding material of the present invention will be explained. By using such a phenolic resin, the presence or absence of after cure is surprising. It has been found that a sliding material having a significantly high heat distortion temperature can be obtained regardless of the above. This is probably due to the action of increasing the crosslink density of the obtained sliding member due to the high molecular weight of the phenol resin, and increasing the heat resistance such as the heat distortion temperature before and after after-curing. However, it has a role of a skeleton that enhances various strengths. Vinylon fiber
Even if it is softened at 220 ° C, it is considered that the function of the reinforcing fiber is already lost at a temperature lower than this. Nevertheless, the heat distortion temperature, especially after after-cure, is 250
The phenomenon that the temperature rises to ~ 270 ° C and the Charpy impact strength decreases only slightly, and it is a fortunate finding, and the present inventors can make some inferences about its action, but it is still demonstrable. Has not arrived.

Further, the vinylon fiber imparted to increase the mechanical strength of the sliding material according to the present invention swells or dissolves in an ordinary novolac type phenol resin when heated, and the tensile strength of itself cannot be maintained, and thus the injection is performed. In molding, a sliding material having high impact strength could not be obtained. However, probably because the viscosity is increased by using the novolac type phenolic resin having the number average molecular weight of at least 650, the solubility of vinylon fiber, which has a unique relationship with the viscosity of the resin, is reduced, which is surprising. The phenol resin hardly dissolves the vinylon fiber, and therefore has a function of improving mechanical properties such as a sliding material having high Charpy impact strength being obtained.

Further, the phenolic resin, compared to the sliding material of another application,
It has the effect of further shortening the minimum baking time, which is the neck of injection molding. The minimum baking time in the present invention will be specifically described in the following examples, but the baking time from the completion of injection of the material to the opening of the mold is changed to occur during curing on the surface of a thick molded product. It is the time until no phenomena such as uncured swelling caused by air, water vapor, or volatile matter are observed, and the minimum baking time is the mold structure.
It depends on the heat conduction of the material, the thickness of the molded product, the heating method, etc., and is affected by temperature and pressure. Generally, the lower the activation energy, the shorter the activation energy.

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

Next, explaining the action of graphite, the tensile strength of vinylon fiber tends to decrease due to heat history in the phenol resin at the time of heating, but by adding graphite, at the time of injection molding, the cylinder of the injection molding machine or It is thought that graphite, which is a solid lubricant, slides the material well and minimizes the heat generated by friction, especially at high temperature places such as sprue and runner in the mold, but local heat generation of the material is suppressed, Therefore, the vinylon fibers are hardly swollen or dissolved, so that a sliding material having high impact strength can be obtained. In addition, impact strength does not decrease even in continuous injection molding. 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. In addition, it has the effect of lengthening the residence time range that enables stable and long-term injection molding of the sliding material. 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 function of the vinylon fiber will be explained. Although the vinylon fiber itself does not show lubricity at all, it has the function of being incorporated into a phenol resin to enhance mechanical properties.
That is, the tensile strength of vinylon fiber and the Charpy impact strength of the sliding material obtained by using it are unique,
When high-strength vinylon fiber is used, a 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. In addition, the elongation of vinylon fiber is added to increase the Izod impact strength, and a sliding material having higher Izod impact strength than conventional phenol resin general materials can be obtained, and a thin sliding member in which V notches are hard to enter is obtained. To be

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 and notched Izod impact strength:
According to JIS K 6911.

Heat distortion temperature: Measured under a load of 18.6 kgcm ² according to ASTM D648.

(Standard condition for after cure: room temperature to 200 in 5-10 hours
Heat up to ℃ and keep at 200 ℃ for 2 hours. ) Limit PV value: A sliding test was performed 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 7 Compounds blended in the proportions shown in Table 1 were uniformly dispersed and mixed with an appropriate amount of solvent in a Henschel mixer, and further heated and stirred at high speed, and kneaded and granulated to give particles of diameter 2 to 2.
An 8 mm granular sliding material was obtained.

Molding conditions generally used with this sliding material (injection pressure 1000-1200 kg / cm ² , mold temperature 170-180
Injection molding (MEIKI, RJ-140C injection molding machine) at 50 ° C) to form Charpy impact strength test pieces, Izod impact strength test pieces, heat distortion temperature test pieces, and thrust type friction wear test pieces, and Izod impact The strength test pieces were notched, and the Charpy impact strength, the notched Izod impact strength, the heat distortion temperature before and after after-curing, and the limiting PV value were measured. The Charpy impact strength was measured as a thick molded product and its minimum baking time was measured. The results are shown in Table 2. Regarding other physical properties
The results measured according to JIS K 6911 are also shown in Table 2.

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 an effect that a sliding member having a remarkably high heat distortion temperature and excellent heat resistance regardless of the presence or absence of after-cure and capable of being suitably used under high temperature conditions can be obtained.

2. The sliding material according to the present invention has an effect that the Charpy impact strength is high, 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. Further, the sliding material according to the present invention can provide a sliding member which can be suitably used not only under severe conditions of high speed and high surface pressure but also at low speed and under particularly heavy load regardless of various atmospheres. However, when the mating material is a metal, the limit PV value of this sliding material is about 6 as compared with the sliding member made of polyacetal resin.
When the mating materials are plastics, the sliding characteristics are about 10 times higher than sliding materials made of polyacetal resin and about 20 times higher than sliding materials obtained from conventional phenol resin general materials. Has excellent effect. 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.

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

5. INDUSTRIAL APPLICABILITY The sliding material of the present invention has a higher Izod impact strength than conventional phenol resin general materials, and has an effect that a thin sliding member in which V notches are hard to be obtained can be obtained.

6. 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. Further, it has high impact resilience, and is advantageous in that it is difficult to be charged, does not get dust, is oil-free, and is not sticky with oil.

Claims (1)

[Claims] 1. A novolac type phenolic resin having a number average molecular weight of at least 650, 30 to 60% by weight, polyvinyl alcohol fiber having a tensile strength of 6.0 g / denier or more, 2 to 45% by weight, and graphite, 5 to 40% by weight. A phenol resin molding material for injection molding, which is suitable for sliding members.