JP4338261B2 - Hydraulic cylinder sliding part packing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a packing for a hydraulic cylinder sliding portion. More specifically, the present invention relates to a packing for a hydraulic cylinder sliding portion that is cross-linked and molded from a polyurethane elastomer composition .
[0002]
[Prior art]
Conventionally, as the packing for hydraulic cylinder sliding parts, packing using polyurethane elastomer with excellent mechanical strength, wear resistance, etc. has been widely used. With the increase in the speed, pressure and temperature of these devices, it has become more difficult to satisfy the required life with conventional materials.
[0003]
In order for the packing to maintain the initial sealing performance, it is necessary to maintain the initial appropriate contact surface pressure distribution form and tightening allowance. The contact surface pressure distribution form changes mainly due to wear, and the tightening allowance changes depending on wear and sag. Therefore, the life of the sliding packing depends on the wear and sag.
[0004]
As a method of suppressing wear, a method of adding a filler is generally performed. However, when a filler such as graphite powder is added to a polyurethane elastomer, a large amount is obtained in order to obtain necessary wear characteristics. The addition of a large amount of fillers can reduce the rubber properties of the material, reduce the compression set properties, and can cause a significant sag as a packing. Not only is this not possible, but a large amount of expensive filler is used, resulting in an increase in cost, and there are also disadvantages such as a reduction in the machinability of the lip portion.
[0005]
Various metal compounds, glass powders, and the like can be used as the filler, but in this case as well, there are similar disadvantages such as an increase in cost, a decrease in workability, and loss of the elastic properties inherent in the elastomer.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a sliding part packing which is used for a hydraulic cylinder sliding part and has an improved durability life.
[0007]
[Means for Solving the Problems]
An object of the present invention is a polyurethane comprising 2 to 5 parts by weight of carbon fiber and 2 to 6 parts by weight of unfired tetrafluoroethylene resin powder in a total amount of 10 parts by weight or less per 100 parts by weight of a polyurethane elastomer. This is achieved by a hydraulic cylinder sliding part packing formed by cross-linking from an elastomeric composition.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The polyol component used for producing the polyurethane-based elastomer includes a polyester polyol having a molecular weight of about 500 to 3000, preferably about 1500 to 2500, a polyether polyol, an acrylic polyol, a silicon polyol, a 1,4-polybutadiene polyol, 1 , 2-polybutadiene polyol, phenolic polyol, flame retardant polyol, castor oil polyol, and the like are used.
[0009]
Among these, polyester polyols include dicarboxylic acids such as adipic acid, isophthalic acid and terephthalic acid, and polyols such as ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexanediol, trimethylolpropane and neopentyl glycol. As the polyether polyol, a polypropylene glycol-based polyol, an ethylene oxide-modified product, an amine-modified product, polyoxytetramethylene glycol, or the like is used.
[0010]
Other diisocyanates that are reaction components include aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated 4,4. Cycloaliphatic diisocyanates such as' -diphenylmethane diisocyanate or aromatic diisocyanates such as xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, 1,5-naphthylene diisocyanate Used.
[0011]
In the reaction of both of these, a chain growth agent can coexist in the reaction system. Examples of the chain growth agent include 1,4-butanediol, 1,6-hexanediol, 2,3-butanediol, p -Glycols such as phenylene di (β-hydroxyethyl) ether, p-xylylene glycol, glycerin monoallyl ether, dimethylol hydropyran, ethylenediamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane, diethyltoluylene diene Amines, diamines such as N, N′-diaminopiperidine or water are used.
[0012]
The unbaked tetrafluoroethylene resin powder and carbon fiber can be added at the prepolymer stage, but a method of compounding using a Banbury mixer or an extruder after the polyurethane-forming reaction is suitable.
[0013]
More specifically, the following method is used.
(1) After mixing these fillers with the polyol component, an excess of diisocyanate is added and reacted. A chain growth agent is added to the obtained liquid prepolymer containing the advantageous diisocyanate, injected into the mold and cured for a predetermined time, and then taken out from the mold and used as it is or after being pulverized, then an injection molding machine. After being melted by heating, the mixture is heated at a temperature of 80 to 120 ° C. for about 15 to 48 hours while being remolded in a mold.
(2) A high molecular weight dihydroxy compound, these fillers, a chain growth agent and a diisocyanate (used in an amount less than the functional group present in both the dihydroxy compound and the chain growth agent) are mixed and reacted. This reaction product can be stored and rolled and crosslinked at a later stage by mixing with other diisocyanates. When 4,4'-diphenylmethane diisocyanate is used as the diisocyanate, it can be crosslinked with a peroxide. When an unsaturated chain growth agent is used, it can be crosslinked with sulfur, formaldehyde or the like.
[0014]
The carbon fiber has a length of about 30 μm to 3 mm, preferably about 50 μm to 1 mm, and a diameter of about 1 to 50 μm, preferably about 5 to 30 μm. Used in a proportion of 5 parts by weight. If the addition ratio is smaller than this, the effect of improving the wear resistance as the object of the present invention cannot be obtained. On the other hand, if the addition ratio is larger than this, not only the cost is increased but also the workability is increased. And a decrease in flexibility becomes remarkable.
[0015]
Further, as the unbaked tetrafluoroethylene resin powder, PTFE (polytetrafluoroethylene) powder having a particle size of about 0.5 to 100 μm, preferably about 1 to 60 μm is generally used. It is used at a ratio of about 2 to 6 parts by weight per unit. If the addition ratio is less than this, the effect of improving the wear resistance as the object of the present invention cannot be obtained. On the other hand, if the addition ratio is more than this, it is not preferable in terms of cost and flexibility. Even when used in combination with carbon fibers, it is desirable that the total amount of both be reduced to about 10 parts by weight or less.
[0016]
In the polyurethane elastomer composition of the present invention containing the above components as essential components, other fillers, metal oxides or hydroxides, lubricants, antioxidants and the like are further blended as necessary. Used.
[0017]
After addition of carbon fiber or unsintered tetrafluoroethylene resin powder to the prepolymer, in the case of polyurethanation reacted with chain extenders, the polyurethane reaction performed in the mold, after molding into a sheet or the like, Secondary crosslinking (oven crosslinking) is performed at about 80 to 120 ° C. for about 15 to 48 hours .
[0018]
【The invention's effect】
The hydraulic cylinder sliding part packing according to the present invention uses a relatively small amount of carbon fiber or unvulcanized tetrafluoroethylene resin powder of about 10 parts by weight or less per 100 parts by weight of the polyurethane-based elastomer. In addition, the wear resistance is improved while being compatible with the sag resistance without substantially impairing the inherent flexibility and compression set characteristics of the polyurethane elastomer.
[0019]
More specifically,
(1) Since the effect of reducing wear can be obtained with a small amount of filling, it has superior machinability when forming a packing lip and has a more precise shape than when other fillers are blended. It can be manufactured at low cost.
(2) Even with polyurethane elastomers of a type that could not be selected due to wear problems, the wear characteristics can be improved by adding a filler that does not impair the rubber characteristics, making it suitable as a packing for hydraulic cylinder sliding parts. Can be used.
(3) By suppressing the wear and sag of the packing, it is possible to maintain the tightening allowance for a long period of time while maintaining the initial contact surface pressure distribution, thereby achieving a long life.
[0020]
【Example】
Next, the present invention will be described with reference to examples.
[0021]
Comparative Example 1
Heat a mixture of 700 g of polycaprolactone diol (OH number 56.1) and carbon fiber (Osaka Gas Chemical Product DonaCarbo S-2404N; length 30-300 μm, diameter 10-30 μm) (approx. 4 phr to the polyurethane produced) to 125 ° C. While adding 245 g of tolidine diisocyanate (molecular weight 264) and stirring under reduced pressure for about 30-40 minutes, 44 g of 1,4-butanediol was added and immediately poured onto a hot plate and cured. The cured product is pulverized, and the pulverized product is molded into a sheet (150 × 150 × 2 mm) under the molding conditions of a nozzle portion of 195 ° C. and a cylinder portion of 178 ° C. using an injection molding machine, and then about 100 to 120 ° C. Secondary crosslinking (oven crosslinking) was performed at temperature for 48 hours.
[0022]
Comparative Example 2
In Comparative Example 1 , 20 g of unsintered PTFE powder (Mitsui Fluorochemical Product PTFE 6J; particle size 470 μm) was used instead of carbon fiber (about 2 phr relative to the produced polyurethane).
[0023]
Comparative Example 3
In Comparative Example 1 , no carbon fiber was used.
[0024]
Comparative Example 4
In Comparative Example 1 , the same amount of molybdenum disulfide powder was used instead of carbon fiber.
[0025]
EXAMPLE Polycarbonate diol (OH number 55.7) and 100 g of isophorone diisocyanate (molecular weight 223.3) were reacted under reduced pressure at 80 ° C. for 30 minutes, and the resulting prepolymer was mixed with 6 g of carbon fiber (about 2 phr relative to the produced polyurethane) After adding a mixture of 6 g of calcined PTFE (PTFE 6J) (about 2 phr relative to the resulting polyurethane) and mixing, 103.2 g of trimethylene bis (4-aminobenzoate) melted by heating to about 130-135 ° C. Added. This since by injected and cured in a mold, subjected to secondary crosslinking of 15 hours at about 80 to 100 ° C. (oven crosslinked), and crosslinked molded into a sheet (150 × 150 × 2mm).
[0026]
Comparative Example 5
In the examples , carbon fibers and unfired PTFE were not used.
[0027]
Comparative Example 6
In the examples , 30 g of graphite powder (about 10 phr for the resulting polyurethane) was used instead of carbon fiber and unfired PTFE.
[0028]
About the vulcanized sheets obtained in the above examples and comparative examples , normal physical properties (according to ASTM D-412-83), compression set (100 ° C., 70 hours) and friction and wear properties (counter material SUS304, linear velocity) The dynamic friction coefficient and the wear depth were measured under the conditions of 200 mm / sec, load 20 kg / cm ² , and dry friction for 15 minutes. The results obtained are shown in the following table.
table
Measurement item ratio-1 ratio-2 ratio-3 ratio-4 Example ratio-5 ratio-6
[Normal physical properties]
Hardness (points) 88 88 87 88 93 92 95
Tensile strength (MPa) 43 42 42 46 40 38 39
Elongation (%) 482 505 480 420 560 550 380
[Compression set]
100 ° C, 70 hours (%) 32 32 33 33 37 35 44
[Friction and wear characteristics]
Coefficient of dynamic friction 0.436 0.520 0.920 0.640 0.406 0.720 0.530
Wear depth (mm) 0.37 0.58 1.10 0.67 0.40 0.81 0.58

Claims (1)

Cross-linking molding from a polyurethane elastomer composition containing 2 to 5 parts by weight of carbon fiber and 2 to 6 parts by weight of uncalcined tetrafluoroethylene resin powder in a total amount of 10 parts by weight or less per 100 parts by weight of polyurethane elastomer Packing for hydraulic cylinder sliding parts.