JPS6212839B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in solid lubricants and methods for producing the same. Hitherto, solid lubricants of this type containing lead as a main component have been developed, such as Japanese Patent Publication No. 51-3859 and Japanese Patent Publication No. 43-9498, which have achieved considerable success in their respective intended uses. In the case of solid lubricants used by being embedded in grooves or holes drilled in the sliding surface of a bearing, the solid lubricant is easily introduced into the sliding surface by the sliding of the mating material, and there is a strong bond there. It is desired that a film is formed, and that the formed film can withstand repeated friction for a long period of time, and that it also has excellent self-repairing properties in the event that the film breaks. The ability of solid lubricants to be introduced into sliding surfaces or to self-repair depends on several factors, such as the arrangement and embedding of the solid lubricant on the sliding surface, and the properties of the solid lubricant itself. However, at least when used under high load conditions or relatively high temperature atmospheres, or when used in combination with lubricants such as grease, solid lubricants themselves have considerable mechanical It has physical strength, heat resistance, and oil resistance, so it can prevent solid lubricants from sinking into holes in which they are embedded, leaking onto sliding surfaces, or being exposed to grease. It is desirable that the function will not be impaired due to dissolution. The solid lubricant disclosed in Japanese Patent Publication No. 51-3859 is made of lead (however, stamped lead as an example), lead monoxide, PTFE, and wax, with polyethylene disposed thereon. Solid lubricant pellets have a large elastic strain limit,
Moreover, it is molded under an extremely high molding pressure (at least 2 tons/cm ² , especially 5 to 7 tons/cm ² ), and as a result of the relaxation of the compressive pressure stress, it can be molded over time (even more quickly in a heated state). b) The solid lubricant has the property of expanding as a whole. When the solid lubricant expands inside the buried hole,
Since expansion is restricted in areas other than the sliding surface, the solid lubricant expands so as to protrude from the sliding surface. In this way, good contact between the solid lubricant and the mating material is maintained. However, solid lubricants and the holes in which they are buried generally do not have very precise dimensions;
There is a small gap between the solid lubricant and the buried hole, and especially under high load conditions, the solid lubricant flows to fill the gap, causing the solid lubricant to have the above-mentioned effect. Even if such expansibility were to remain, our objective of good contact with the mating material would no longer be satisfactorily achieved. The polyethylene component in the solid lubricant shown in Japanese Patent Publication No. 51-3859 is microscopically dispersed in the form of particles, and the component present at the grain boundaries of these polyethylene particles and lead particles is wax. Therefore, the mechanical strength is not great, and the oil resistance is not necessarily sufficient. The present invention has been made to solve such problems. In other words, the object of the present invention is to provide excellent lubrication performance;
Moreover, it is an object of the present invention to provide a pellet-like solid lubricant having high mechanical strength. Another object of the present invention is to provide a solid lubricant obtained by molding, particularly a solid lubricant obtained by injection molding that can be mass-produced. Yet another object of the present invention is to provide a solid lubricant that is difficult to dissolve in lubricating oils, greases, and the like. Yet another object of the present invention is to mix the components of atomized lead powder, PTFE powder, polyolefin resin powder, and waxes, stir and knead until the polyolefin component in the mixture is at least partially melted, and then stir and knead the mixture until the polyolefin component in the mixture is at least partially melted. The object of the present invention is to provide a method for efficiently producing a solid lubricant by heating and press-molding a powdery mixture obtained by cooling the polyolefin component to a temperature below the melting point of the polyolefin component. Hereinafter, the composition of the solid lubricant of the present invention and its manufacturing conditions will be explained in more detail. Composition In the present invention, the atomized lead powder has a substantially granular particle shape, and is preferably a powder that passes 200 meshes, particularly 250 meshes, on a Japanese Industrial Standards standard sieve. This atomized lead powder differs from stamped (crushed) lead powder, which has an irregular particle shape, in that it has a large apparent density and extremely low agglomeration in the same powder size distribution. For example, stamped lead powder that passes 90% or more of 250 mesh has an apparent density of 1.9 to 2.4 g/cm ³
On the other hand, the atomized lead powder has the same particle size distribution of 5.2 to 5.8 g/cm ³ . According to experiments conducted by the present inventors, the atomized lead powder has excellent miscibility with other components of the present invention, a homogeneous dispersion can be obtained, and the powder has excellent fluidity after being made into a mixture. It was also found that it has the advantage of having a significantly low tendency to oxidize under heated conditions. These various characteristics are extremely important in that they enable the application of techniques with high mass productivity such as injection molding when producing the solid lubricant of the present invention, and the reason for this is as explained below. It will become clear. The blended amount of atomized lead powder is 77-90% by weight.
If the amount exceeds 90%, the friction coefficient will increase in applications where the load is not very large. Moreover, if it is less than 77%, not only the ability to form a solid lubricating film on sliding surfaces decreases, but also the mechanical strength when formed into pellet-like solids decreases. The PTFE powder used in the present invention has a particle size of several tens of microns or less, preferably several microns to several tens of microns, and has excellent dispersibility and powder flowability. Powder Yunon P (trade name), fluorine resin lubricating powder TLP-10F (trade name) manufactured by Mitsui Fluorochemical Co., Ltd., etc. are preferable. These PTFE powders differ from the PTFE powders used as molding materials (referred to as "Raw Teflon (trade name)" to distinguish them from the ones mentioned above), and have no interparticle cohesiveness (but It is a fine powder with a smooth feel (the material itself does not have moldability). Therefore, these PTFE powders do not contribute to improving the strength of the solid lubricant as a component of the solid lubricant of the present invention. Therefore, by adding the above-mentioned "Raw Teflon" powder to these PTFE powders, it is possible to improve their mechanical strength, but this will impair the dispersibility and moldability of the powder components, so even if they are used together. The amount added is preferably 20% or more by weight based on the total amount of PTFE components. These PTFE powder or mixed powder components are blended in an amount of 7.5 to 1.5% by weight based on the total weight. 15%
If the amount exceeds 7.5%, the mechanical strength of the solid lubricant will be impaired, and if it is less than 7.5%, good lubrication performance will not be exhibited. Polyolefin resin is unique as a solid lubricant component of the present invention. Its first function is to substantially increase the mechanical strength of the solid lubricant by acting as a binder. However, if this polyolefin resin component is simply blended as a powder and dispersed in the composition while maintaining granularity, it is not possible to improve the mechanical strength. Desirably, the polyolefin resin component needs to be softened and melted during the stirring and kneading process of each component, and especially during the molding process. By going through such a softening and melting process, the polyolefin resin component does not simply take on a granular shape and is dispersed in the structure, but instead exists in an amorphous shape so as to fill the grain boundaries of the component particles.
This difference from the state of existence of polyethylene resin components in solid lubricants in Japanese Patent Publication No. 51-3859,
Experiments confirmed that it greatly contributed to improving mechanical strength. The second function of the polyolefin resin component is to effectively utilize the property of polyolefin resin to be compatible with wax, which will be described later, to prevent excessive supply of only the wax component from the solid lubricant to the sliding surface, or to prevent the machine from heating during heating. The purpose is to prevent a decline in the strength of the target. Polyolefin resin becomes significantly more compatible with waxes at temperatures above its softening and melting temperature, and is also compatible with waxes that have little compatibility at room temperature, and after this thermal history returns to room temperature. In this state, waxes are held inside the polyolefin resin. Examples of the polyolefin resin used in the present invention include polyethylene resin, polypropylene resin, and polybutene resin, and low-density polyethylene resin whose molecular weight is not very large is particularly desirable. The particle size may be several microns or less from the viewpoint of miscibility, and the blending amount is preferably 1 to 3% by weight. If the amount exceeds 3%, not only will it have a negative effect on film forming ability and lubrication performance, but it will also be difficult to obtain a pallet with good dimensional accuracy.
If it is less than 1%, the binding effect is poor and it does not contribute to improving the strength of the solid lubricant. The waxes used in the present invention have the role of reducing the coefficient of friction as a component of the solid lubricant and helping to supply the solid lubricant to the sliding surface, and also have the effect of increasing the fluidity of the mixture when molded. It also has a mold release effect. Waxes are wax-like waxes with a melting point of approximately 50°C or higher, including hydrocarbon waxes,
In addition to higher fatty acids and higher fatty acid derivatives, higher alcohols and polyhydric alcohols can be used alone or in combination of two or more. As the hydrocarbon wax, paraffin waxes with a carbon number of approximately 24 or more, olefin waxes with a carbon number of 26 or more, alkylbenzenes with a carbon number of 2 g or more are suitable, and crystalline microcrystal waxes can also be effectively used. As higher fatty acids, saturated fatty acids having approximately 14 or more carbon atoms, such as myristic acid and stearic acid, and unsaturated fatty acids having approximately 1 g or more carbon atoms, such as parinaric acid, can be effectively used. Examples of higher fatty acid derivatives include higher fatty acid esters such as methyl and ethyl esters of higher fatty acids having 22 or more carbon atoms, esters of higher fatty acids having approximately 16 or more carbon atoms and higher monohydric alcohols having approximately 15 or more carbon atoms, Mono- and diglycerides of higher fatty acids with carbon numbers of approximately 12 or more, triglycerides of higher fatty acids with carbon numbers of 14 or more, As others, higher fatty amides, keto fatty acids and their esters can be effectively used. In addition, polyhydric alcohols such as sorbitan and mannitan, and their oleic acid esters are effective as waxy substances. The amount of wax component blended is 1.5 to 5% by weight.
is desirable. If it exceeds 5%, the mechanical strength as a solid lubricant will be impaired, and if it is less than 1.5%, the moldability and low friction properties as a solid lubricant will also be impaired. Manufacturing conditions The polyolefin resin component begins to melt at least partially by passing the powder component having the composition described above through a heated roll or using a mixer equipped with a high-speed stirring blade and a heating/cooling device (especially a cooling device). Knead or stir to a moderate degree. When high-speed stirring is used, melting of the resin component proceeds due to frictional heat generated during stirring of the mixture. When the resin component begins to melt, the rotational torque of the stirring shaft increases rapidly. This can be confirmed by the pointer of a torque meter or ammeter. Therefore, the contents are forcedly or naturally cooled and at the same time the rotational speed of the stirring blade is reduced. Most of the wax component is absorbed into the resin component during the stirring and mixing process involving the resin component. The powdery mixture thus obtained is molded under heat and pressure either as it is or through a granulation step to form a solid lubricant such as pellets. Although the solid lubricant pellets of the present invention can be obtained by compression molding, they are particularly characterized by the fact that they can be molded by injection molding, which is particularly suitable for mass production. In this molding process, the molding temperature must be higher than the temperature at which the polyolefin resin component softens.
This is particularly necessary for improving the mechanical strength of the resulting pellet solid lubricant. Compared to a plunger type injection molding machine, a screw type injection molding machine can easily knead and melt the molding material simultaneously and sufficiently. Therefore, in the process from mixing the powder components of the solid lubricant of the present invention to molding, the melting of the polyolefin resin component is left only to this molding step, and the mixed powder is molded without melting the resin in the mixing step. It is to be used as a material. The melting of the polyolefin resin component in the powder mixing process described above improves the uniformity of the obtained mixed powder, improves moldability due to the progress of granulation of the powder, and improves ease of handling as a molding material. be. Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto. Examples All weight ratios are as follows: Japanese Industrial Standard Standard Sieve (JIS)
85% atomized lead powder passing through 200 meshes of Z-8801), 10.5% PTFE powder (fluoropolymer lubricating powder TLP-10F manufactured by Mitsui Fluorochemical Co., Ltd.), density
0.920, a polyethylene powder that passes through a 45 mesh with a melting point of 105 to 111°C (manufactured by Steel Chemical Co., Ltd., Frozen)
G701) 1.5%, 125° lower paraffin wax 2 to 3% mixed wax of 1 part by weight of lithium stearate was stirred and mixed at 1000 revolutions/min using a high speed mixer equipped with a cooling device. After 7 minutes, the rotational torque of the stirring shaft suddenly increased (the temperature of the contents was 120℃), so we cooled the contents by passing cold water through the cooling device, lowered the rotation rate to 500 rpm, and continued stirring for 15 minutes. The mixture was removed from the mixer when the temperature reached 65°C or lower. The powdery mixture thus obtained was molded using a screw-type injection molding machine at a temperature of 120 to 140°C for the rear part, 140 to 180°C for the middle part,
Molding was carried out under the following conditions: 150 to 170° C. Injection pressure: 1400 Kg/cm ² Mold temperature: 40° C. Screw rotation speed: 80 revolutions/min to obtain cylindrical pellets with a diameter of 14 mm and a height of 16 mm. Example The powdery mixture obtained in the example was molded using a compression molding machine under the following conditions: Preheating temperature of the powdery mixture: 110-115℃ Molding pressure: 300Kg/cm ² Mold temperature: 40℃ A cylindrical pellet of 14 mm and height of 16 mm was obtained. Examples All weight ratios are as follows: Japanese Industrial Standard Standard Sieve (JIS)
84% atomized lead powder passing through 200 meshes of Z-8801), PTFE powder (Teflon manufactured by Mitsui Fluorochemical Co., Ltd. for Yunon P10 manufactured by Nihon Valqua Co., Ltd.)
1 part by weight of 7J) 11.5%, density 0.920, melting point 105
1.5% of polyethylene powder (Frosene G701, manufactured by Seitetsu Kagaku Co., Ltd.) and 3% of higher fatty acid amide (a mixture of 75 parts by weight of stearic acid amide, 22 parts by weight of palmitic acid amide, and 3 parts by weight of oleic acid amide) were cooled and passed through a 45-mesh mesh at ~111°C. Using a high speed mixer with equipment
The mixture was stirred and mixed at 1000 revolutions/minute. After 6 minutes, the rotational torque of the stirring shaft suddenly increased (the temperature of the contents was 115°C), so cold water was passed through the cooling device to cool the contents, the rotation speed was lowered to 450 rpm, and stirring was continued for about 15 minutes. The powdery mixture thus obtained is molded using a plunge-type injection molding machine at temperatures: 150℃ for the rear, 150℃ for the middle, and 155℃ for the front.Injection pressure: 1200Kg/ ^cm2.Mold temperature: 30℃. The pellets were molded at ℃ to obtain cylindrical pellets with a diameter of 14 mm and a height of 16 mm. The results of experiments regarding the physical and mechanical properties and lubricating performance of the pellet solid lubricant of the present invention thus obtained are shown in the table. In the table, the products of the present invention are those according to Examples, and the comparative products are solid lubricants according to Japanese Patent Publication No. 51-3859. The friction coefficient values are: Load: 300Kg/cm ² , Thrust load sliding speed: 1.02m/min Test piece: Aluminum manganese bronze sliding surface, solid lubricant

[Table] Pellets are embedded to account for 27% of the gold sliding surface. Compatible material: Chromium molybdenum steel type 22. Induction hardened material, Rockwell hardness C50~51 Test time: 2000 cycles (measurement time) As can be seen from the table, the solid lubricant of the present invention has excellent physical and mechanical strength, and the compressive strength is It is more than twice as hard as the other products, and has a high hardness and a high compressive deformation rate that leads to destruction. In other words, the toughness is significantly greater than that of comparative products. This characteristic is thought to be due to the fact that the polyethylene component used undergoes a melting process during the production of solid lubricant pellets, and plays the role of bonding other components together. According to experiments conducted by the present inventors, in the molding process of solid lubricants containing lead, if the molding temperature is high (for example, below 200°C) or the residence time in the barrel of the molding machine is long, Often, the lead component oxidizes and the formation of yellow lead oxide is observed, but when atomized lead powder was used, such adverse effects could be completely avoided. Lead oxide powder (PbO) is itself a low-friction substance, so there is no problem in terms of lubricity, but as a solid lubricant component of the present invention, the production or mixing of this powder will only impair mechanical strength. It should be excluded because it causes uneven color tone. Incidentally, if stamp powder is used instead of atomized powder as the lead component in the same composition of the present invention, injection molding itself will not be possible, and the lead component in the barrel will change to lead oxide (yellowing) and end up. Ta. When atomized lead powder is used, injection molding is possible despite the fact that both the amount of wax and the amount of polyolefin are small compared to comparative products, and oxidation (yellowing) of the lead component is not observed. The improvement in oil resistance is thought to be due to the fact that the wax component in the solid lubricant of the present invention contains a small amount of this wax component, and also because the polyolefin component used in combination has absorbed most of this wax component. As explained above, the solid lubricant of the present invention is
The performance is significantly improved compared to conventional lubricants, and it is particularly effective as an embedded solid lubricant.

Claims (1)

[Scope of Claims] 1. A solid lubricant comprising 77-90% by weight of atomized lead powder, 7.5-15% of tetrafluoroethylene resin, 1-3% of polyolefin resin, and 1.5-5% of waxes. 2 A mixed powder consisting of 77 to 90% by weight of atomized lead powder, 7.5 to 15% of tetrafluoroethylene resin, 1 to 3% of polyolefin resin, and 1.5 to 5% of waxes is heated to a temperature above the softening point of the polyolefin component. A solid lubricant made by heating and pressure molding. 3 A mixed powder consisting of 77 to 90% by weight of atomized lead powder, 7.5 to 15% of tetrafluoroethylene resin, 1 to 3% of polyolefin resin, and 1.5 to 5% of waxes is heated at a temperature higher than the softening point of the polyolefin component. A method for producing a solid lubricant, which comprises heating and press molding. 4. Atomized lead powder 77-90%, tetrafluoroethylene resin powder 7.5-15%, polyolefin resin powder 1-3%, and waxes 1.5-5% by weight.
After mixing the powders of each component and stirring and kneading the mixture until at least the polyolefin component begins to melt, the whole is cooled to a temperature below the melting point of the polyolefin component. A method for producing a solid lubricant, which comprises heating and press molding at a temperature above the softening point of the ingredients. 5. The method according to claim 4, further characterized in that the heat and pressure molding is injection molding.