JPH04351543A - Manufacture of double-layered bearing material made of polyacetal resin composition - Google Patents

Abstract

PURPOSE:To improve adhesiveness by coating a sintered base material consisting of a rear metal and a sintered alloy layer on the rear metal with a polyacetal resin compsn. with a particle diameter of 295mum or smaller, passing through the polyacetal resin compsn. of the sintered base material between upper and lower roils under a heated and melted condition and pushing it into the sintered base material. CONSTITUTION:A sintered base material consisting of a rear metal 1 and a sintered alloy layer 2 on the rear metal 1 is coated with a polyacetal resin compsn. with a particle diameter of 295mum or smaller. Then, the polyacetal resin compsn. with which the sintered base material is coated is melted by heating at 170-200 deg.C and 18 pressed into the sintered base material by passing through it between upper and lower rolls under this condition to make it into a double layer to obtain a required double-layered bearing material made of the polyacetal resin compsn.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing a multilayer bearing with good adhesion consisting of a steel back metal, a sintered alloy layer, and a polyacetal resin composition layer. A method for manufacturing a polyacetal resin composition multi-layer bearing material, in which a solid lubricant etc. are added to this to form a composition, and this composition is evenly impregnated into the cavities of a sintered base material. Related.

0002

[Prior Art] Polyacetal resin is used as a bearing material because it has a high level of balance in mechanical properties, heat resistance, and durability, and also has high crystallinity, chemical stability, and excellent self-lubricating properties. It is widely used. Bearing materials are roughly divided into two types. One is a single molded bearing material made of polyacetal resin manufactured by injection molding, and the other is an indented (oil sump) polyacetal resin bearing material as described in British Patent No. 1,091,710. It is a multilayer bearing material. The manufacturing method for this multilayer bearing material is to create a sheet of a polyacetal resin composition with a predetermined thickness by melt blending, then laminate this sheet onto a sintered base material, and form this laminate into a predetermined size. - The key point of the technology is the so-called sheet method, in which the material is passed through a patterned indentation roll for indentation.

[0003] By the way, in multi-layering in which polyacetal resin composition sheets are laminated on a sintered base material, when the sintered layer is dense, that is, the porosity is small, or when the alloy has a complicated shape, The resin may not be sufficiently filled into the cavity, and
At this time, air remains at the interface between the sintered base material and the resin layer, which may cause problems such as blistering or peeling of the resin layer when used as a product. In addition, the extrusion molding method is used to form sheets, and there is a problem in that the burden of initial equipment investment and running costs cannot be ignored.

0004

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems, and specifically focuses on the problems of the conventional sheet method. The adhesiveness between the polyacetal resin composition and the sintered base material is good, and there is no blistering or peeling.
It is an object of the present invention to propose a method for manufacturing a multilayer bearing material made of a polyacetal resin composition, which can obtain a multilayer bearing material made of a polyacetal resin composition without particularly providing a device for converting the polyacetal resin composition into a composite material.

[0005]

[Means for Solving the Problems] That is, the present invention coats a polyacetal resin composition having a particle size of 295 μm or less on a sintered base material consisting of a backing metal and a sintered metal layer on the backing metal.
Then, the polyacetal resin composition of the coated sintered base material is heated and molten and passed between upper and lower rolls and press-fitted into the sintered base material to form a multilayer. shall be.

[0006]

[Operation] According to the present invention, a polyacetal resin composition is coated on a sintered base material, and the coated resin composition on the sintered base material is heated and molten by rolling. Since it is press-fitted into the sintered base material, the filling of the sintered base material is increased.

[0007] Hereinafter, the configuration of the means of the present invention will be explained in more detail along with its operation.

[0008] The present inventors investigated the problem of poor adhesion between polyacetal resin compositions and sintered substrates, and found that this problem often occurs during multi-layering, and that many of the causes are This is because the air on the sintered base material is not sufficiently expelled. In particular, it has been found that in the conventional stacking of sheets, air remains at the interface between the sheet and the sintered base material, and this portion remains as a defective portion due to poor adhesion of the resin powder filling.

In the present invention, we believe that the biggest problem with residual air in a series of multi-layer treatments for polyacetal resin composition laminated bearing materials lies in whether or not it is possible to remove air during roll processing. As a result of investigating a powder method that allows air to freely enter and exit, we were able to confirm its effectiveness in removing air. However, since the powder method contains a lot of air and the polyacetal resin is easily thermally decomposed, it is difficult to apply a homopolymer type due to the appearance and finish, and a copolymer type polyacetal resin is preferable. Understood.

The structure of a polyacetal resin composition multilayer bearing according to one embodiment of the present invention will be explained below with reference to the drawings.

FIG. 1 shows a longitudinal cross-sectional view of a multilayer bearing material, and reference numeral 1 indicates a backing metal, and the porosity sintered on this backing metal is 30.
~50% alloy layer 2, on which is a polyacetal resin based composition layer 3. The back plate 1 is generally made of steel and has the functions of maintaining the mechanical strength of the bearing material and dissipating heat generated on the bearing surface. The alloy layer 2 serves to hold the polyacetal resin with an anchor effect and to release heat generated on the bearing surface to the backing metal. Therefore, the alloy layer 2 may be made of either general bronze or lead bronze, but considering the possibility of seizure if the sliding surface reaches the alloy layer due to extreme wear, the latter lead bronze has better seizure resistance. It is preferable to use The powder lamination method of the present invention can be applied to both irregular and spherical shapes of the alloy, but from the viewpoint of press-fitting of the polyacetal resin composition, spherical shapes are more desirable, and the average particle size is 80 to 150 μm.
A range of m is preferred. In addition, the alloy layer 2 has a molecular weight of 200~
A range of 400 μm is preferred. The reason for this is that if it is too thick, there is a risk of poor adhesion, and if it is too thin, the anchoring effect for the resin will be insufficient.

The polyacetal resin composition layer 3 is a material that plays a key role in the sliding function of the bearing material. Polyacetal resins are classified into homopolymer types and copolymer types based on their structure; the former is polymerized using formaldehyde as a starting material, and the latter is a copolymer synthesized from, for example, trioxane and ethylene oxide. This copolymer type has a "-C-C-" bond in the middle of the molecule, so even if depolymerization begins due to heat or chemicals, the first "-C-C- -”
It has the property of stopping decomposition upon bonding. In the powder method of the present invention, a homopolymer type polyacetal resin containing a large amount of air (oxygen) that promotes decomposition and having poor thermal stability can be used at any temperature.
Even under long-term conditions, vent holes for decomposed gas are left on the resin surface after roll forming. Therefore, there are many problems in terms of sliding properties, and it is difficult to use this powder method. On the other hand, copolymer-type polyacetal resins may also decompose depending on the processing conditions;
Due to the characteristics of the molecular structure as mentioned above, the heating temperature is 170~20°C.
A good appearance finish was shown under the treatment conditions of 0° C. and a holding time of 5 to 20 minutes, and this will be explained in detail in Examples below. The thickness of the resin layer is not particularly limited, but from the viewpoint of durability, heat dissipation, cost, etc., it is preferably in the range of 10 to 400 μm.

A solid lubricant can be added to the copolymer-type polyacetal resin according to the present invention in order to further improve sliding properties. Solid lubricants are broadly classified into inorganic and organic types; examples of the former include graphite (C), molybdenum disulfide (MoS2), zinc oxide (ZnO), calcium fluoride (CaF2), and lead iodide (PbI2). ), cadmium sulfide (CdS), etc.; examples of the latter include polyethylene, trifluoride resin, PTFE (polytetrafluoroethylene), etc. Note that polyacetal resin tends to undergo thermal decomposition in the presence of acid or alkali, so for example, when MoS2 or PbI2 is blended, the blending amount should be 2 parts by weight or less per 100 parts by weight of resin. preferable.

The polyacetal resin used in the present invention has high crystallinity and a high glass transition temperature, so it can be pulverized at room temperature. However, when pulverized at room temperature, there are concerns about chemical deterioration due to the heat generated during pulverization. Therefore, low-temperature pulverization is desirable.

[0015] Table 1 shows the experimental results showing the relationship between the sieve size and yield of powder ground at -196°C using liquid nitrogen. This shows that as the particle size becomes finer, the yield becomes worse and the price becomes higher. For example, with a 400 mesh sieve, the yield is only 18 wt%. From this result, it can be seen that it is desirable to use powder with a larger particle size in terms of cost.

[0016]

[Table 1]

For example, PbI2 was added as a solid lubricant to each of the powders obtained in Table 1, and the filling properties into the sintered base material and the appearance finish (presence or absence of color unevenness) were evaluated. The particle size is 495 μm or less, preferably 295 μm or less.
It was found that it was less than μm.

[0018]

[Example] The method of the present invention will be explained by the following example.

Example 1. Homopolymer type polyacetal resin (product name: “Tenac 4010” manufactured by Asahi Kasei Industries, Ltd.)
) and copolymer-type polyacetal resin (product name "Tenac C4510" manufactured by Asahi Kasei Industries, Ltd.) were cryogenically ground at -196°C, and then classified using an 80-mesh sieve to obtain particles with a particle size of 175 μm or less. A fine powder was obtained. Next, lead iodide (PbI) is added to this fine powder as a solid lubricant.
2 parts by weight of 2) were blended with 100 parts by weight of polyacetal resin and mixed and dispersed for 10 minutes using a high speed mixer to obtain two types of yellow fine powder resin compositions for coating. This fine powder was made into a spherical lead bronze with a width of 150 mm and a length of 250 mm (
(Cu85wt%, Sn10wt%, Pb5wt%) alloy was sprinkled on a sintered base material (total thickness 0.98mm) with a porosity of 40% and a thickness of 200μm, and was evenly leveled with a glass rod. The coating layer was 1 mm thick. This coated plate was heated in a heating furnace under the conditions shown in Tables 2 and 3. Immediately after the treatment, it was taken out of the heating furnace and heated between upper and lower rolls 6 and 6' as shown in the explanatory diagram in Figure 2. A laminate 7 was obtained by press-fitting a coating plate on which polyacetal preparation powder 5 was sprinkled onto a bonding base material 4.

As shown in Table 2, the homopolymer type polyacetal resin undergoes thermal decomposition at any temperature, leaving gas vent holes on the resin surface, making it unsuitable for practical use. On the other hand, if copolymer-type polyacetal resin is heat-treated at excessively high temperatures or for a long time, it will suffer from the same phenomenon as homopolymer-type polyacetal resin, but if the temperature and time are set to the specified conditions, multilayer materials with a good external finish can be produced. was found to be obtained. In addition, Table 2
The melting points of the resins used in Table 3 were 179°C for the homopolymer type and 167°C for the copolymer type.

[0021]

[Table 2]

[0022]

[Table 3]

Example 2. Comparative Example Copolymer-type polyacetal resin powder obtained by the method shown in Table 1 (trade name: ``Tenac C4510'' manufactured by Asahi Kasei Industries, Ltd.)
), lead iodide (P) per 100 parts by weight of resin, respectively.
2 parts by weight of bI2) were blended and dispersed and mixed in the same manner as in Example 1 to obtain 11 types of yellow fine powder resin compositions for coating. On the other hand, as a comparative example, 2 parts by weight of lead iodide was blended into the same resin pellets as above, and a yellow film with a thickness of 0.4 mm was obtained by melt blending using an extruder. Next, these powders and films were placed on the same substrate as in Example 1, heat treated in a heating furnace at 190°C for 10 minutes, immediately taken out, and rolled in the same manner as in Example 1 to form a multilayer structure. Table 4 shows the results of evaluation based on the filling properties of the resin into the sintered base material and the appearance finish (degree of dispersion of PbI2). In the powder method, there is a tendency that the finer the powder, the better the filling properties and the better the appearance finish, but in practice it is understood that the particle size should be 495 μm or less, preferably 295 μm or less. On the other hand, in film lamination, the appearance finish is extremely good due to melt blending, and the dispersibility of PbI2 is good, but the filling of the resin into the sintered base material is not necessarily good, and there are concerns about adhesion. remains.

[0024]

[Table 4]

Example 3. 99 parts by weight of copolymer-type polyacetal resin powder (trade name "Tenac C4510" manufactured by Asahi Kasei Corporation) obtained by the method shown in Table 1 and lead iodide (P
A yellow fine powder resin composition for coating was obtained in the same manner as in Example 1 except that 1 part by weight of bI2) was blended. Next, this resin composition was treated in the same manner as in Example 1 except that the treatment time and temperature were changed, and the results are shown in Table 5 and FIG. As is clear from Table 5 and Figure 3, the temperature is 17
It has been found that when the temperature rises from 0°C to 200°C, the processing time can be shortened. Note that since the heating temperature of the resin is 160° C., which is below the melting point, the resin becomes unmolten or semi-molten, making it impossible to form multiple layers. Further, when the heating temperature of the resin was 210° C., the melting and thermal decomposition temperatures were close to each other, making it difficult to form multiple layers.

[0026]

[Table 5]

[0027]

Effects of the Invention As explained in detail above, the present invention provides a method for coating a polyacetal resin composition with a particle size of 295 μm or less on a sintered base material consisting of a backing metal and a sintered metal layer on the backing metal. Then, the polyacetal resin composition of the coated sintered base material is heated and molten and passed between upper and lower rolls and press-fitted into the sintered base material to form a multilayer. shall be.

According to the present invention, since the conventional sheet or film lamination method has been changed to a powder method, the resin composition can be more completely filled into the sintered base material, resulting in excellent adhesion. We are able to provide products of stable quality to our customers, and because the specified material can be obtained by mechanically blending powders together in a very short time, capital investment is also small. Since there is no need to
Running costs are also low, allowing us to provide customers with low-cost products.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a multilayer bearing material made of a polyacetal resin composition according to one embodiment of the method of the present invention.

FIG. 2 is an explanatory diagram showing a state in which a polyacetal resin composition according to the present invention is press-fitted into a sintered base material.

FIG. 3 is a graph showing the relationship between temperature and time showing the processing conditions for polyacetal according to the present invention.

[Explanation of symbols]

1　Secret money 2 Alloy layer 3 Polyacetal resin composition layer 4 Sintered base material 5　Polyacetal adjusted powder 7 Composite layer

Claims (3)

[Claims] Claim 1: A sintered base material consisting of a back metal and a sintered metal layer on the back metal, and a polyaceter with a particle size of 295 μm or less.
The polyacetal resin composition of the coated sintered base material is then heated and melted at 170 to 200°C, and in this state upper and lower rolls are applied. A method for producing a multilayer bearing material made of a polyacetal resin composition, which comprises press-fitting a polyacetal resin composition into a sintered base material to form a multilayer bearing material. 2. The method for producing a polyacetal resin composition multilayer bearing material according to claim 1, wherein the polyacetal resin is a copolymer type resin. [Claim 3] Claim 1, wherein the sintered alloy is lead bronze consisting of copper, tin, and lead, and has an average grain size of 80 to 150 μm.
Or the method for producing a polyacetal resin composition multilayer bearing material according to 2.