JPS6245662A - Synthetic resin composition for sliding member - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having excellent rate characteristics and moldability and a low coefficient of static friction, by blending a thermoplastic synthetic resin, a fatty acid and a phosphate salt powder. CONSTITUTION:A thermoplastic synthetic resin (A) selected from among polyoxymethylene, polyamide, polybutyleneterephthalate, polyethylene tere phthalate, PP, PE, polyurethane and polyether ester, 1-10wt% at least one fatty acid (B) selected from among 10C or higher normal satd. fatty acids and 12C or higher unsaturated fatty acids (e.g. stearic acid), 1-20wt% water- insoluble phosphate salt powder (C) (e.g. calcium phosphate powder), pref. fine powder passing through a 150-mesh size, such as secondary or tertiary phosphate salt, metaphosphate salt or pyrophosphate salt, and optionally lubricating oil (D) selected from among mineral, vegetable oil and synthetic oil in an amount of 1/10-2 times that of the satd. fatty acid are blended together.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synthetic resin composition for sliding members suitable for use in bearings, cams, gears, sliding plates, liner tubes for flexible shafts, and the like.

[Conventional technology]

Plastic bearings modified by blending lubricating oil with thermoplastic synthetic resin to further improve self-lubricating properties and wear resistance so that they can withstand long-term use without lubrication are disclosed in Japanese Patent Publication No. 46-5321, for example. Special Publication No. 46-42217, Special Publication No. 42615, Special Publication No. 47-29374
No., Special Publication No. 52-4301, Japanese Patent Publication No. 49-99740
It is known by the number etc.

Specifically, Japanese Patent Publication No. 46-5321 relates to a method for manufacturing polyacetal (polyoxymethylene) and polyamide bearings containing lubricating oil, and according to this,
This reduces the friction coefficient of the plastic used and significantly improves its wear resistance, but on the other hand, the method of adding lubricating oil has some drawbacks in terms of production technology.

Special Publication No. 46-42217 and Special Publication No. 47-4261
No. 5 relates to a method for manufacturing a synthetic resin bearing made of oil-impregnated polyacetal (polyoxymethylene) that has improved the above-mentioned problems, and also significantly improves the friction and wear characteristics. There were problems such as the need for modification.

As mentioned above, the oil-impregnated polyacetal (polyoxymethylene) related to the conventional technology significantly improves the friction and wear characteristics in terms of performance as a sliding member. coefficient)
The sliding speed is not as low as expected, and the sliding speed is approximately 25.
When the speed exceeds m 2 /min, there remain problems such as a decrease in friction and wear characteristics, and as the amount of lubricating oil to be contained increases, the molding surface becomes rough (appearance of flow marks).

Also, Japanese Patent Publication No. 47-29374 and Japanese Patent Publication No. 49-9
No. 9740 is polyacetal (polyoxymethylene)
When the lubricating oil is contained in the lubricating oil, polyethylene having an affinity for the lubricating oil is used as a lubricating oil retainer.

These products are effective in that the addition of polyethylene prevents the lubricating oil from separating, which tends to occur during molding, so there is no need to modify the heating cylinder of the molding machine, and it can be molded using an ordinary molding machine. However, the use of polyethylene inevitably reduces the load bearing capacity of the sliding member, and as the polyethylene becomes a thin foil and is dispersed on the molding surface and into the molded product, the mechanical strength is impaired. However, there is a drawback that the molding surface tends to become rough.

Furthermore, Japanese Patent Publication No. 52-4301 relates to a sliding member made of a blend of polybutylene terephthalate, potassium titanate fiber, unburned polytetrafluoroethylene powder, and mineral oil as a lubricating oil, and its friction coefficient and wear resistance. is significantly improved compared to the non-blended version, but as in the case of polyacecool mentioned above,
There is a problem in that as the sliding speed increases, friction and wear characteristics deteriorate.

In addition, various improvements and developments have been made to plastic compositions for sliding parts that contain lubricants, but problems remain, such as generally lacking speed characteristics and high coefficients of static friction. is the reality.

[Problem that the invention sought to solve]

The present invention solves the drawbacks of sliding members in the prior art, namely, lack of speed characteristics, large coefficient of static friction, rough molding surfaces, and poor moldability.

[Means for solving problems]

As a result of intensive research to solve the above-mentioned problems, the inventors obtained knowledge based on the following experimental discoveries, and came up with the present invention.

In other words, a) Adding a certain amount of fatty acids to a thermoplastic synthetic resin has the same or better effect than adding lubricants such as mineral oil in terms of reducing the coefficient of friction and improving wear resistance. Furthermore, the difference from the case of adding mineral oil is that it significantly contributes to lowering the static friction coefficient, and therefore the friction coefficient is low and stable from the time of startup. 2) There is no separation of the lubricant during molding, and the moldability is excellent (without modification of the heating cylinder of the molding machine, etc.). It was confirmed that the molded surface was beautiful without causing any roughness.

However, although fatty acid-added products exhibit excellent performance in the high-speed range, in the low-speed range where the sliding speed is several meters/minute or less, they stabilize at a low level at a certain point as the sliding time passes. There is a tendency for the coefficient of friction to rise rapidly. This is similar to a sudden increase in the coefficient of friction that occurs when you run out of oil.
Therefore, it has been found that products containing only fatty acids have a practical problem in that durability remains unstable in the low speed range. As a result of further research aimed at improving the instability of the coefficient of friction in the low speed range, it was discovered that adding phosphate in addition to fatty acids solved these problems at once.

That is, e) by adding phosphate powder in addition to fatty acids, the drawbacks regarding the coefficient of friction in the low speed region are completely eliminated without impairing the above-mentioned properties a) to b),
Furthermore, it was confirmed that the abrasion resistance and load resistance of the molded product were also improved.

Incidentally, the effect of stabilizing the coefficient of friction in the low speed wi range due to the addition of phosphate mentioned in e) is due to the effect of adding graphite, molybdenum disulfide, or metal oxide powder, which are widely used as additives for this type of plastic. In addition,
To say the least, no effect was observed for 0.

On the other hand, this does not occur when adding unsaturated fatty acids that are liquid at room temperature, but when adding saturated fatty acids that are solid at room temperature, if the molded product is left in the atmosphere for a long time, It was found that a very thin white powdery film was formed on the surface.

Analysis revealed that this was the added saturated fatty acid itself.

Therefore, there is no problem in using it as it is as a sliding member; in fact, the presence of this powdery film, which has a lubricating effect, is preferable from the viewpoint of preventing initial staining.

However, this powdery film is not firmly attached to the surface of the molded product, and can be easily removed from the surface by rubbing it with your fingertips or touching it with another object, so Even if the presence of a powdery film is desirable from this point of view, it is not only difficult for those who actually handle the molded product to handle it, but also may be undesirable from the viewpoint of aesthetics as a product. As will be described in detail, by adding a small amount of lubricating oil that dissolves saturated fatty acids, it was possible to avoid the formation of this powdery film without impairing the desirable performance as a sliding member.

Therefore, if it is necessary to avoid the formation of this powdery film, the use of lubricating oil can be effectively employed.

The present invention will be explained in detail below.

The thermoplastic synthetic resin used in the present invention has mechanical properties and chemical properties that are desirable and required for sliding members, and also has wear resistance and self-lubricating properties. It is even more preferable if the Furthermore, depending on the application, it may be preferable to use rubber elasticity that can absorb vibrations.

From the viewpoint of productivity, it is also important that injection molding and extrusion molding, which are excellent in mass production, are possible.

Examples of such thermoplastic synthetic resins include polyoxymethylene, polyamide, polybutylene terephthalate, polyethylene terephthalate, polypropylene, polyethylene,
Preferred examples include thermoplastic elastomers such as polyurethane, polyetherester, other polyamide-based elastomers, and polyolefin-based elastomers.

As sliding members, polyoxymethylene and polyamide are effective for general purposes, and polybutylene terephthalate and polyethylene terephthalate have a service limit temperature of approximately 150° C. and are effective for heat-resistant applications.

Unlike the above-mentioned resins, polypropylene and polyethylene are compatible with lubricating oil, so their application as sliding members is likely to be limited.Excluding special cases, polypropylene and polyethylene are generally used at low speeds and under light loads. suitable for the purpose.

Polyurethane, polyether ester, and the like having rubber elasticity are used as so-called elastomers, and one example of a preferable application is push related to steering of an automobile.

In obtaining the resin composition of the present invention, each of the above-mentioned thermoplastic synthetic resins can be effectively used in the form of fine powder, flakes, or pellets.

The fatty acids used in the present invention are higher fatty acids that are waxy or oily at room temperature, and both saturated and unsaturated fatty acids can be used.

As the saturated fatty acid, a normal saturated fatty acid that is waxy at room temperature and has at least 10 carbon atoms was used.

For example, capric acid (CIO), lauric acid (
C12), myristic acid (C14), palmitic acid (016), stearic acid (C18), arachidic acid (
C20), behenic acid (C22), cerotic acid (C
26), montanic acid (028), myricin fi (C
30) etc.

The unsaturated fatty acid used was one that was oily at room temperature and had 12 or more carbon atoms.

- Examples include lauroleic acid (C12), myristoleic acid (C14), oleic acid (C18) + gadolenic acid (C20).

In addition to this, unsaturated fatty acids include linoleic acid (018)
etc. can also be used.

Addition of 1% by weight of fatty acid produces an effect of reducing the coefficient of friction, but the content is preferably 3 to 5% by weight. If added in a large amount exceeding 10% by weight, the strength of the molded product will be impaired.

These fatty acids are added to the resin raw material in the form of powder, granules, butter, or oil and are mixed uniformly. When using solid fatty acids, it is preferable to stir them at a temperature that is high enough to dissolve them.Also, these fatty acids can be mixed in advance with the phosphate powder described below as a resin raw material. A method of mixing can also be adopted.

The phosphates used in the present invention are preferably secondary and tertiary phosphate powders, metaphosphates, and birophosphate powders that are insoluble or almost insoluble in water. Preferred examples include calcium phosphate, calcium hydrogen phosphate, barium phosphate, lithium phosphate, calcium metaphosphate, and zinc birophosphate.

All of these are mixed into the resin raw material in the form of fine powder that passes through 150 meshes. Due to the synergistic effect with the fatty acids mentioned above, addition of 1% by weight produces a stabilizing effect on the coefficient of friction in the low speed range. However, from the standpoint of improving wear resistance and load carrying capacity, addition of 3 to 15% by weight is recommended. preferable.

However, if added in excess of 20% by weight, not only the moldability deteriorates but also the toughness of the molded product is impaired, so in the present invention, the upper limit of addition is set at 20% by weight.

A desired molded product can be obtained by injection or extrusion molding using a predetermined amount of each of the above-mentioned components as a molding material.

Even if a screw-in-line molding machine is used, there is no need to modify a part of the heating cylinder as described in the description of the prior art, and no melting and separation of fatty acids is observed during molding.

Moreover, the surface of the molded product obtained is smooth and glossy.
There are no flow marks or rough skin that are often seen in prior art moldings.

As already mentioned, when a molded product obtained by adding saturated fatty acids is left in the air for a long time, a thin powdery film is formed on its surface.

It is not clear why the powdery film does not form when the molded product is cooled to room temperature after molding, but instead forms after a long period of time.

It has been found that the formation of a powdery film can be prevented by mixing a small amount of lubricating oil into the molded product, but the amount of mixing is 1/2 to 1 of the amount of saturated fatty acid added. It was confirmed that it is preferable to set the amount to /10.

However, it has been revealed that when the lubricating oil is contained in the total composition in an amount exceeding 2% by weight, it not only impairs moldability but also has a negative effect on the effect of reducing the coefficient of static friction.

This static friction coefficient problem is hardly a problem in applications where the sliding member is incorporated into a machine or device and once it starts operating, it continues to operate in one direction for a long time.
This often becomes a problem in applications where activation and stopping are repeated, or where forward and reverse rotations are frequently performed.

This is because the evaluation of friction performance as a sliding member is determined by the static friction coefficient rather than the dynamic friction coefficient.

In addition, if the difference between the static friction coefficient and the kinetic friction coefficient is large, it often causes a "stick-slip" phenomenon with the mating material (rotating shaft, etc.), which causes abnormal friction noise and chatter vibration. tends to occur.

Applications under these conditions include bush bearings used in ratchet and cam mechanisms, bush bearings and slide plates for office equipment and measuring equipment, various joint bearings, ball seats in ball joints, wiper bearings, flexible shafts, etc. Examples include bearings used in liner tubes of control cables, swinging parts of pendulum shafts, and reciprocating parts such as carriages.

The lubricating oil used to prevent the formation of a powdery film on the surface of the molded product mentioned above may be any commonly used lubricating oil, including mineral oils such as machine oil and engine oil, vegetable oils such as castor oil, and ester oils. Synthetic oil is used.

We also conducted experiments to determine whether unsaturated fatty acids, which are liquid at room temperature, could be used as lubricating oils for this purpose.

Compared to mineral oil, it is slightly less effective in preventing the formation of a powdery film, but it is effective in limiting the amount added to saturated fatty acids (1/2 to 1/10) and limiting the amount added in the total composition (2 It has been found that there is an advantage that there is no need to take into account
The synthetic resin composition for sliding members of the present invention, which can also be used as a lubricating oil, is as described above, but it can also be used for purposes such as improving wear resistance and load carrying capacity. In addition to this ingredient, graphite, which is commonly used in the past,
There is no problem in adding up to 3% by weight of molybdenum disulfide and tungsten disulfide, respectively, and an appropriate amount of pigment for the purpose of coloring.

〔Example〕

Examples of the present invention will be described below.

Examples 1 to 4: Polyoxymethylene (abbreviated as POM) manufactured by Polyplastics "Duracon? 190 J Flakes"
The mixed powder obtained by mixing 5% by weight of calcium phosphate powder that passes through 150 mesh with 100% by weight of stearic acid powder and stirring with a high-speed mixer (accompanied by heat generation due to friction of 80 to 100°C during stirring) is used as a molding material. This is then processed using a screw in-line injection molding machine.
Unfilled PO? Almost the same molding conditions as I (molding temperature 1
60~200'C1 injection molding pressure 900 kg/c
The molded product was molded in step d) to obtain a plate-shaped molded product with 30 squares in length and width and 3 squares in thickness.

Examples 5-7: Polybutylene terephthalate powder (abbreviated as PBT).

Toyobo Co., Ltd. rN-! 040J'), 5% by weight of calcium phosphate powder containing 150 mSOIL and 1 to 10% by weight of montanic acid powder were mixed, and the following Example 1 was prepared.
A mixed powder was obtained in the same manner as in ~4, and this was molded using a screw in-line injection molding machine under almost the same molding conditions as unfilled PBT (molding temperature 200-240゛t, injection molding pressure 500 kg/cj). Examples 8 to 12 in which a plate-shaped molded product with a length and width of 30 m and a thickness of 3 mm was obtained.
: 5% by weight of stearic acid powder and 1 to 20% by weight of lithium phosphate powder that passes through 150 meshes were mixed with POM, and the same method as in Examples 1 to 4 was carried out to form 3% by weight each in the vertical and horizontal directions.
Examples 13 to 1 in which a plate-shaped molded product with a thickness of 3fi was obtained.
5: Add 5% by weight of stearic acid powder to POM flakes.
Calcium phosphate powder passing through 0 mesh 5% by weight and 5AE No. 30 engine oil 0.5 without AL, 1.0% by weight
A mixed powder obtained by stirring the mixture with a high-speed mixer was used as a molding material, and the same procedure as in Examples 1 to 4 was carried out to obtain a plate-shaped molded product having a length and width of 30 fl and a thickness of 3 fi.

Examples 16-18: PBT powder mixed with 5% by weight of montanic acid, 5% by weight of calcium phosphate powder passing through 150 mesh, and 0.5 to 1.0% by weight of 5AE No. 30 engine oil was mixed in a high speed mixer. The mixed powder obtained by stirring was used as a molding material, and in the same manner as in Examples 5 to 7, 300
A plate-shaped molded product with a thickness of 3 mm was obtained.

Example 19: Polyester elastomer (abbreviated as TPEE) manufactured by Toyobo Co., Ltd. "Belprene P150B J pulverized product" was added with 5% by weight of montanic acid powder, 5% by weight of calcium phosphate powder passing through 150 meshes, and 5AE No. 30 engine oil 0
．． 7% by weight to obtain a mixed powder in the same manner as in Examples 1 to 4. This was molded using a screw in-line injection molding machine under almost the same conditions as unfilled TPEH (
Molding temperature 200-240℃, injection molding pressure Too kg/
aa), length and width each 3Qnm, thickness 3um
A plate-shaped molded product was obtained.

Example 20: POM mixed with 5% by weight of oleic acid and 5% by weight of calcium phosphate powder that passes through 150 meshes was stirred with a high-speed mixer, and a mixed powder obtained was used as a molding material, and the following Example 1- In the same manner as in Step 4, a plate-shaped molded product with a length and width of 300mm and a thickness of 3mm was obtained.

Comparative Example 1: POM flakes were molded at a molding temperature of 180 to 200° C. and an injection molding pressure of 900 kg/csl to obtain a plate-shaped molded product having a length and width of 30 fl each and a thickness of 3N.

Comparative example 2: PO? 5% by weight of 5AE No. 30 engine oil in l flakes
The mixture was stirred and mixed using a high-speed mixer, and the mixture was injection-molded using a screw-in-line injection molding machine under the following conditions to obtain a plate-shaped molded product with 30 cranes in each length and width and a thickness of 3 fl.

Heating cylinder supply section of the molding machine = 70°C Compression section: 170
°C Measuring part: 190°C Nozzle part: 190°C Comparative example 3: 5% by weight of calcium phosphate powder and 5% by weight of 5AE No. 30 engine oil passing through 150 meshes on POM flakes
The mixture was stirred and mixed with a high-speed mixer, and then molded under the same conditions as in Comparative Example 2 to obtain a plate-shaped molded product with 30 mm in each direction and 3 μ in thickness.

Comparative example 4: PR? Molding the powder at a temperature of 220 to 250°C and an injection molding pressure of 5
00 kg/- to obtain a plate-shaped molded product with a length and width of 3 mm each and a thickness of 3 mm.

Comparative Example 5: 5% by weight of 5AE No. 30 engine oil was added to the PBT powder and mixed with a high speed mixer, and this was injection molded using a screw-in-line injection molding machine under the following conditions. A plate-shaped molded product was obtained.

Heating cylinder supply section near 0℃ compression section of the molding machine; 200
°C Measuring part: 240 °C Nozzle part: 235 °C Comparative example 6: FB? 5% by weight of calcium phosphate powder that passes through 150 meshes and 5% by weight of 5AE No. 30 engine oil were added to the powder, stirred and mixed in a high-speed mixer, and molded under the same conditions as in Comparative Example 5 to form a mold with a length and width of 3011 mm and a thickness of 31 m. A plate-shaped molded product was obtained.

Comparative Example 7: TPEE powder was molded at a molding temperature of 200 to 240°C and an injection molding pressure of 700 kg/cj, and the length and width were 30 dragons each.
A plate-shaped molded product with a thickness of 3 frames was obtained.

Comparative Example 8: 5% by weight of 5AE No. 30 engine oil was added to the TPEE powder and mixed with a high speed mixer, and this was injection molded using a screw-in-line injection molding machine under the following conditions. A plate-shaped molded product of 3 tl was obtained.

Heating cylinder supply section near 0℃ compression section of the molding machine: 200
°C Measuring part: 240 °C Nozzle part: 230 °C Comparative Example 9: POM was mixed with 5% by weight of stearic acid powder, and the mixed powder obtained by stirring with a high-speed mixer was used as a molding raw material, and the following Examples 1-4 and In the same manner, a plate-shaped molded product of 30 pieces in length and width and 3 pieces in thickness was obtained.

Comparative Example 10: A mixed powder obtained by mixing PO)'I with 5% by weight of oleic acid and stirring with a high-speed mixer was used as a molding raw material, and then molded in the same manner as in Example 1-4 for 30 cm in each length and width. Thickness 3f
A plate-shaped molded product of i was obtained.

The table shows the performance of the molded products of each example and comparative example.

In the table, in the fatty acid column, ☆ indicates that stearic acid was used, ★ indicates that montanic acid was used, and # indicates that oleic acid was used.

The Δ mark in the phosphate column indicates calcium phosphate, the mu mark indicates lithium phosphate, and the lubricant type: 5AII: No. 30 engine oil is used.

The * mark in the dynamic friction coefficient column indicates the lowest friction coefficient (0,08)
After reaching , the slip time to maintain this value is short, indicating that the friction coefficient tends to rise rapidly thereafter.

In the Moldability/Surface Properties column, this mark indicates that a white powdery film is formed on the surface of the molded product, but the surface of the molded product is beautiful with no roughness. The mark ** indicates that the moldability is "fair" under the condition that the heating cylinder of the molding machine is subjected to the specific temperature control described in each comparative example.

The test related to the coefficient of friction was conducted using carbon w4 (345
C) The end face of a cylinder made of 2.7m/win, load 30kg/am'', Example 5
-18 and Comparative Examples 1 to 6 have a sliding speed of 30 m/l1in.
- Load of 20 kg/c+w'', and Example 19 and Comparative Example 7.8 were tested at a sliding speed of 5 m/cm and a load of 301 cg cm''.

The dynamic friction coefficient is the value when a steady state is reached after the start of the test, and the static friction coefficient is the value when the rotation is stopped and restarted after the dynamic friction coefficient reaches the steady state. The tensile strength value is ^S'TM D 638
It was obtained in accordance with the test method.

FIG. 1 shows the molded products of Example 3 and Comparative Example 9, and FIG. 2 shows the molded products of Example 20 and Comparative Example 10.
3 is a graph showing the relationship between friction time and friction coefficient, respectively.

As can be understood from each graph, it can be seen that the effect of adding phosphate is significant under the low sliding speed condition of 2.7 m/1n.

In each figure, the curves shown with broken lines are those of Comparative Example 9.
．． For composition 10, the sliding speed was 30 s/w.
This is a plot of the friction coefficient when in is shown, indicating that there is no sudden increase in the friction coefficient at high speeds.

〔Effect of the invention〕

As explained above, the synthetic resin composition for sliding members of the present invention has a stable friction coefficient from a low speed range to a relatively high speed range with respect to sliding speed, and has a low static friction coefficient.

Regarding moldability, there is no melting and separation of fatty acids during molding, and the molding property is excellent, and the molded product surface is beautiful with no roughness or flow marks.

Although wear resistance is not indicated, for example, Comparative Example 2
7 In other words, compared to ordinary lubricating oils, it has become clear that lubricating oils using fatty acids improve not only the coefficient of friction but also the speed characteristics related to wear.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between friction time and friction coefficient for the molded products of Example 3 of the present invention and Comparative Example 9, and FIG. 2 is a graph showing the relationship between the friction time and the friction coefficient for the molded products of Example 20 of the present invention and Comparative Example 10. It is a graph showing the relationship between friction time and friction coefficient.

Claims (1)

[Claims] 1) 1 to 10% by weight of fatty acid in a thermoplastic synthetic resin;
A synthetic resin composition for a sliding member, which is uniformly mixed with 1 to 20% by weight of phosphate powder. 2) The thermoplastic synthetic resin is any type of synthetic resin selected from polyoxymethylene, polyamide, polybutylene terephthalate, polyethylene terephthalate, polypropylene, polyethylene, and thermoplastic elastomers such as polyurethane and polyether ester. A synthetic resin composition for a sliding member according to claim 1. 3) The synthetic resin composition for a sliding member according to claim 1, wherein the fatty acid is one selected from saturated fatty acids and unsaturated fatty acids, or a mixture of two or more. 4) The sliding member according to claim 3, wherein the saturated fatty acid is a normal saturated fatty acid having at least 10 carbon atoms, and the unsaturated fatty acid is an unsaturated fatty acid having at least 12 carbon atoms. Synthetic resin composition for use. 5) The synthetic resin composition for a sliding member according to claim 1, wherein the phosphate is a phosphate that is insoluble or almost insoluble in water. 6) 1 to 10% by weight of saturated fatty acids, 1 to 20% by weight of phosphate powder, and 2% by weight or less and 1/10 to 1/2 of saturated fatty acids to a thermoplastic synthetic resin. A synthetic resin composition for sliding members, which is uniformly mixed with lubricating oil in a blended amount. 7) The synthetic resin composition for a sliding member according to claim 6, wherein the lubricating oil is mineral oil, vegetable oil, or synthetic lubricating oil.