JPH0555535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for treating polyamide molded articles.

[Conventional technology]

Polyamide is usually an acid amide bond (-
Nylon is a general term for polymers having CONH-), among which linear polymers with fiber-forming ability are called nylon, such as nylon 6, nylon 46, nylon 66, nylon 610, nylon 7, nylon 8,
Nylon 9, Nylon 10, Nylon 11, Nylon
It is already well known that a large number of compounds such as 12 or their copolymers or mixtures are produced on an industrial scale. Compared to other plastics and metal materials, polyamides have excellent mechanical strength, especially wear resistance, self-lubricating properties, light weight, moldability, heat and cold resistance,
It is excellent in many aspects such as silence, chemical resistance, non-toxicity, and dyeability, and is widely used in the field of plastic materials for various equipment parts such as bearings, bushes, gears, automobiles and other vehicle parts. . It is also well known that in the field of textile materials, it is considered important as a synthetic fiber that can replace silk. However, this polyamide has oxygen in the carbonyl group (=C=O) in the main chain and its adjacent amino group (=NH).
Molecular forces (hydrogen bonds) act between hydrogen and these groups, and because these groups are hydrophilic, they absorb moisture when left in humid air, or absorb moisture when left in dry air. Released, absorption rate is 0~
The absorption amount varies within a range of about 14%, and although the degree varies depending on the type of polymer, the mechanical properties of the molded product are greatly affected by the amount of absorption, so it is a relatively large amount. Even if a molded product has excellent mechanical properties such as abrasion resistance, lubricity, and impact resistance after absorbing water, its performance deteriorates as the amount of water absorbed decreases, making it unusable. , which often causes various troubles. Therefore, such water absorption of polyamide is a fatal flaw, and conventionally, in order to enhance wear resistance and lubricity, water lubrication, solid lubricants (such as molybdenum disulfide, graphite, Methods such as adding metal soap, etc.) and oil lubrication have been adopted, but there have been few attempts to essentially adjust and stabilize water absorption and improve wear resistance, lubricity, and impact resistance. I couldn't help it.

Therefore, the inventor of the present invention proposed a polyamide machine part and a molded part characterized in that a water and lubricating oil permeation layer is provided on the surface of the patent application No. 58-69818 (Japanese Patent Application Laid-open No. 59-193930). A method for producing mechanical parts made of polyamide is disclosed, which is characterized by carrying out post-water absorption treatment and dehydration treatment, and further heating and infiltrating a water-based emulsion type lubricating oil. When a water and lubricating oil permeation layer is provided on the surface of a polyamide molded product in this way, it significantly improves the inherent lubricity of polyamide, and at the same time improves impact resistance and abrasion resistance due to fluctuations in water absorption, which are disadvantages of polyamide. It also showed a remarkable effect in preventing deterioration of mechanical performance such as, etc., and the dimensional stability after post-processing was also significantly improved. However, the method disclosed for producing such polyamide molded products usually involves immersing or enclosing the polyamide molded product in an atmosphere of hot water of about 70°C or higher or steam of about 120°C or lower for several hours to several tens of hours. After forcibly absorbing water, the water is heated to, for example, about 70 to 120°C, and then the pressure is reduced to, for example, several tens of mm-Hg or lower to remove the absorbed water, and then the water-based emulsion is applied to the molded product. Although this method heats and infiltrates mold lubricating oil, it has the drawback that the water absorption treatment and dehydration treatment after molding, which are pretreatments, are extremely complicated.

[Problem that the invention seeks to solve]

As described above, although a polyamide molded article with significantly improved properties can be obtained in the conventional techniques, there is a problem in that the processing method for obtaining it is complicated.

[Means for solving problems]

In order to solve the above problems, this invention adopts a method of treating the polyamide molded product by infiltrating the water-based emulsion type lubricating oil after molding, fixing the lubricating oil sufficiently at room temperature or under heating, and then drying it. This is what I did. The details will be described below.

First, the water-based emulsion type lubricating oil in this invention is a lubricant that is liquid or semi-solid (grease-like) at room temperature (for example, a petroleum-based lubricant mainly containing high molecular weight hydrocarbon components, olefin polymerized oil, diester oil, polyester oil, etc.). Synthetic oils such as alkylene glycol oils, halogenated hydrocarbon oils, and silicone oils, animal and vegetable oils alone or in combination of two or more of these oils, or groups reactive to acid amide groups in these oils, such as hydroxyl groups. , those modified by introducing carboxyl groups, epoxy groups, etc.
Furthermore, it is made by adding a modifier required as a lubricant) and dispersing it in water by adding an emulsifier. It is also possible to dissolve the lubricating oil in water in a transparent state. Here, depending on the type of lubricating oil, a third substance having a catalytic effect may be added to cause a polymerization reaction within the permeation layer to change the lubricating oil having a larger molecular weight. Furthermore, if the lubricating oil emulsion is appropriately colored, it is possible to color the surface of the molded article and obtain a color effect, and at the same time it is convenient for knowing the thickness of the permeation layer on the surface of the molded article.

Next, the polyamide used in the present invention is not particularly limited in type, and may contain carbon black or other pigments, fillers, reinforcing materials, etc., and has been widely used in the fields of engineering plastics and fiber materials. It can be any one as long as it is provided. Polyamides are usually processed through injection molding, extrusion molding, spinning, etc., which are performed at temperatures of approximately 200 to 320°C, as well as blow molding, film (sheet) molding, sinter molding, centrifugal casting, powder coating, and monomer casting. ,
Various types of molded products can be obtained by machining and the like.

In addition, the polyamide molded product is preferable because the elapsed time after molding is short, and the drier the atmosphere in which it comes into contact with the molded product, the less water absorption the molded product will have. When infiltrating a water-based emulsion type lubricating oil into such a molded product, there are no particular restrictions on temperature or time, but generally speaking, the lower the temperature, the longer the processing time needs to be, and the longer the processing time Although high temperatures are desirable in order to shorten the temperature, the higher the temperature, the higher the equipment costs, expenses, etc., resulting in an economic disadvantage. Apply a water-based emulsion-type lubricant to the molded product or immerse the molded product in the water-based emulsion-type lubricant, and keep the surface of the molded product sufficiently covered with the lubricant emulsion for several tens of hours or less. Just keep it. Next, the molded article that has been subjected to such treatment is preferably subjected to a fixing treatment for the penetrating lubricating oil at room temperature or under heating, after removing the excess lubricating oil emulsion that has adhered thereto. The behavior of the lubricating oil during this fixing process is not entirely clear, but it is formed through the bonding of the lubricating oil itself or the bonding of reactive groups naturally or artificially introduced into the lubricating oil molecule with polyamide. It is presumed that a new, strong structure is formed in the parts of the product where the lubricating oil has penetrated. Generally, the higher the temperature (lower than the softening point of the molded product), the faster the various reactions during the fixing process, which is advantageous.
When the lubricant has a complicated shape or the lubricating oil is easily deteriorated by heat, it is preferable to carry out the process at room temperature.

Furthermore, after such a fixing process, a drying process is performed, which is a process to make the fixing of the lubricant more complete and at the same time remove excess water, and as an extension of the fixing process. Alternatively, it may be carried out separately under different conditions, and the specific method may be a normal method using dry air, warm air, hot air, etc., and the end point is the point at which the weight of the molded product stops changing. good.

In addition, for bearings, bushes, gears, and other molded products that require high precision, machining may be performed again for finishing at the end.

〔Example〕

Examples and comparative examples are shown below.

Example: Polyamide [manufactured by Toray Industries, Inc.: Nylon CM1017] was injected into a mold at a cylinder temperature of 270 to 280°C, cooled to 80°C in the mold, and then taken out to form an outer diameter of 19 mm, an inner diameter of 7 mm, and a width of 9 mm. On both sides of the car, there are three fan-shaped depressions with a depth of about 2.5 mm in three places.
Sliding wheels arranged concentrically at intervals of mm were obtained. This wheel was heated to 80°C with a silicone oil-dissolved water solution (silicone oil [manufactured by Toray Industries, Ltd.: Silicone
TK20#] was uniformly dispersed using a hydrophilic surfactant, and a small amount of coloring agent was added to make it a brown liquid to make it easier to detect the thickness of the penetration layer. The wheels were immersed for about 48 hours while being maintained at the same temperature to allow the wheel surface layer to sufficiently absorb water and silicone oil, forming a permeated layer with a thickness of about 0.1 mm.
Thereafter, this was placed in a heating furnace and heated to approximately 120°C, and at the same time as the lubricating oil that had penetrated was fixed, a drying process was performed to evaporate the moisture. The time required was approximately 10 hours. In order to evaluate the mechanical properties of the obtained wheels, a rotation test with a load of 3000 kg was attempted, and as a result, the wheels obtained in the examples according to the present invention were still able to withstand the load even after 8 months had passed. Furthermore, the wheel according to the present invention is not affected by the humidity in the atmosphere.
This method had various characteristics that were comparable to the method disclosed in No. 2003-12201, in which water absorption treatment and dehydration treatment are performed as pretreatments. The above-mentioned tendency was the same even when treated with a lubricating oil other than silicone oil, such as cottonseed oil.

Comparative Example: A wheel obtained by injection molding under the same conditions as in the above example was immersed in the same aqueous silicone oil solution under the same conditions for the same period of time, and then taken out and immediately subjected to a rotation test under a load of 3000 kg.

As a result, wear began immediately and the shape changed due to increased frictional temperature.

〔effect〕

The polyamide molded article of the present invention subjected to the above treatment significantly improves the inherent lubricity of the polyamide through the action mechanism of the water and lubricant permeation layer formed within the structure of the molded article. It has a remarkable effect on preventing deterioration of mechanical properties such as impact resistance, abrasion resistance, and tensile strength due to fluctuations in water absorption, which is a disadvantage of polyamide, and also improves dimensional stability after post-processing. It is extremely excellent. Since such good results can be obtained through simple processing, it can be said that the significance of this invention is extremely large.

Claims (1)

[Claims] 1. A method for treating a polyamide molded article, which comprises impregnating a polyamide molded article with a water-based emulsion type lubricating oil, sufficiently fixing the lubricating oil at room temperature or under heating, and drying to evaporate water.