JPH07242769A - Oil-containing porous material - Google Patents

Abstract

PURPOSE:To obtain an oil-contg. porous body suitable for a bearing, an oil retainer, etc., by impregnating a porous molding obtd. from a polytetrafluoroethylene molding powder with an oil. CONSTITUTION:This oil-contg. porous body is obtd. by baking a polytetrtafluoroethylene molding powder and impregnating the resulting porous molding with an oil. A lubricating or edible oil is used for the impregnation. The porous molding is pref. obtd. from the powder having baking densification indexes P10, P25, and P50 each not higher than 0.2. The porous molding of any desired shape can be easily obtd. by premolding the powder under a low pressure and baking the resulting molding at the m.p. of polytetrafluoroethylene or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polytetrafluoroethylene impregnated with lubricating oil (hereinafter referred to as PTFE).
The present invention relates to an oil-containing porous body. More specifically, PTF after firing
E relates to a PTFE oil-containing porous body, which is obtained by impregnating a porous molded body with a lubricating oil or the like.

The present invention also relates to a PTFE oil-containing porous material impregnated with edible oil or the like. More specifically, the present invention relates to a PTFE oil-containing porous body obtained by impregnating edible oil or the like into a PTFE porous molded body after firing.

[0003]

2. Description of the Related Art PTFE has excellent heat resistance, chemical resistance,
It has water and oil repellency, non-adhesiveness, nonflammability, low friction coefficient, weather resistance, etc., and is used as a sealing material such as packing and gaskets, and various sliding members such as bearings.

Further, in addition to the above-mentioned properties of PTFE, various inorganic and organic fillers are mixed with unsintered PTFE powder, compression-molded, and sintered to impart lubricity, wear resistance, load resistance and the like. Composite materials have been put to practical use in various fields.

On the other hand, oil-impregnated bodies in which a synthetic resin contains oil are known, and these are particularly durable bearing materials and oil retainers (for example, polyethylene resin moldings and It is used as a mixture of lubricating oil and molded).

Further, on the surface of a fixing roller of an electronic copying machine or the like, for the purpose of preventing offset, a coating such as a fluororesin or an offset preventing liquid such as oil is applied to impart non-adhesiveness. At present, such a fixing roller is required to be usable for a long period of time without oil supply.

[0007] Further, there is a cooking utensil such as a frying pan which is surface-treated with a fluorine-based paint for the purpose of preventing charring during cooking, which utilizes the non-adhesiveness of the fluororesin. In these cooking utensils, the fluororesin used for the surface treatment may be damaged and peeled off. Since there is a problem such as burning and adhesion of food on the peeled part of the treatment and propagation of various bacteria in the adhered food, it is recommended to prevent burning and adhesion of cooking utensils and replace it in consideration of hygiene There is a demand for a non-sticky surface that can be used.

Further, impregnating oil for impregnating a fluororesin foam has also been proposed (for example, JP-A-63-256).
693 gazette), but among the fluororesins, PTFE
Because of its high melt viscosity, extrusion molding and injection molding cannot be performed, and foams and porous bodies cannot be obtained by ordinary methods. Therefore, impregnated porous bodies such as lubricating oil are known. There wasn't.

As a method for producing a PTFE porous molded article, for example, an unsintered PTFE film is stretched at a temperature not higher than the melting point of PTFE to make it porous, and then a temperature not lower than the melting point of PTFE while maintaining the stretched state. A method of firing at is known. However, the porous molded body obtained by this method is usually only a film having a thickness of several microns to several hundreds of microns, and a porous molded body having an arbitrary shape cannot be obtained.

Therefore, attempts have been made to obtain a porous body by using PTFE molding powder as a raw material, low-pressure compression-molding it, and then firing it at a temperature not lower than the melting point of PTFE, but increasing the density in the firing process. It is extremely difficult to obtain a uniform porous molded product having a high porosity due to its large size.

On the other hand, unsintered PTFE molding powder is calcined once at a temperature equal to or higher than the melting point of PTFE, the calcined powder is crushed, the obtained powder is compression molded, and then P
A method has also been proposed in which a porous body is obtained by firing at a temperature equal to or higher than the melting point of TFE (see, for example, JP-A-61-66730). However, it is difficult to say that this method is economical and can be used economically because the steps until obtaining the sintered PTFE powder are complicated, and it is difficult to obtain a sufficiently homogeneous porous body.

Further, PT containing an inorganic substance or the like which is not compatible with PTFE and can be removed in a later step as a filler.
A method has also been proposed in which a PTFE porous molded article is obtained by preparing a molded body from FE powder, decomposing the filled substance with heat or a chemical agent, or dissolving it in a solvent to remove it, but the filled substance remains. Therefore, not only the manufacturing process but also the product inspection process is complicated.

[0013]

[Background of the Invention] In the background that there has been no PTFE porous molded body impregnated with lubricating oil or the like until now, since PTFE cannot be melt processed in general, the porous molded body can be easily manufactured. It is considered that one of the reasons was that it was difficult to obtain, and that even if it was obtained, it was difficult to obtain a homogeneous porous molded article.

The present invention is a PTF composed of a porous molded body obtained from a PTFE molding powder which can be suitably used as a bearing, an oil retainer and the like.
E is intended to provide an oil-containing porous body.

A further object of the present invention is to provide a PTFE oil-containing porous body comprising a porous molded body obtained from PTFE molding powder, which can be suitably used as a cooking sheet or the like.

[0016]

The present invention relates to an oil-containing porous body characterized in that a porous molded body obtained from PTFE molding powder is impregnated with oil.

The present invention provides a PTFE produced by the above method.
It is possible to use a porous molded body, but it is easy to use PT.
As a method for obtaining a FE porous body, the firing densification index P ₁₀ , P ₂₅ and P ₅₀ described in detail in JP-A-1-131217 are described.
It is more preferable to use a PTFE molding powder (hereinafter referred to as HM-PTFE), each of which is 0.2 or less. This powder is preformed at low pressure, and the preformed body is fired at a temperature equal to or higher than the melting point of PTFE. By doing so, a PTFE porous molded body having an arbitrary shape can be easily obtained.

[0018] The molding pressure when preforming at a low pressure in the present invention is usually 100 kgf / cm ² or less of molding pressure, preferably it refers to a molding pressure of 1~50kgf / cm ^2.

The PTFE porous molded article according to the present invention has an apparent density of 0.2 to 1.8, preferably
Say something from 0.6 to 1.6. If the apparent density is larger than 1.8, the oil content will be small, which is not preferable.

The firing densification index means PTFE powder
It means the density change before and after firing in a block in which 10 g was filled in a mold having a diameter of 30 mm and preformed at 23 to 25 ° C. under a molding pressure of 10, 25 or 50 kgf / cm ² for 2 minutes, and Pn = | d− d ₀ | [where, Pn: firing densification index of block preformed with nkgf / cm ² d: density after firing (g / cm ³ ) d ₀ : density before firing (g / cm ³ ) ] Is shown.

The thus obtained PTFE porous molded article is put into, for example, a lubricating oil, and after applying a reduced pressure, the pressure is returned to normal pressure to obtain an oil-impregnated porous body of the present invention impregnated with the lubricating oil.

The lubricating oil used is not particularly limited,
For example, a diester-based, silicone-based, polyalkylene glycol-based, or fluorine-based lubricating oil can be used, and preferably a fluorine-based, for example, a low polymer of trifluoroethylene chloride or a perfluoropolyether-based lubricating oil. Yes, and more preferably perfluoropolyether lubricating oil. In addition, thickeners can be added to adjust the viscosity of the lubricating oil if necessary. Also, if necessary,
In order to improve oil retention, it is possible to use a block or graft polymer of these lubricating oils and PTFE (see, for example, JP-A-1-284542).

The oil-containing porous body of the present invention is used for bearings of various power machines, oil retainers, fixing rollers of copying machines and facsimiles, bridges, and so-called sliding of buildings.
It can be used for applications such as pads.

The PTFE porous molded article can be used as a cooking sheet by processing it into a sheet and impregnating it with edible oil or the like. At this time, the thickness of the sheet is 0.1 to 10 mm, preferably 0.5 to 5 mm. When the thickness is more than 10 mm, there is a problem in that heat conduction is poor, and when it is less than 0.1 mm, there is a problem in sheet holding stability, and further there is a problem in that the oil content is small.

The edible oil used at this time is not particularly limited, but examples thereof include corn oil, safflower oil, olive oil, vegetable oil such as rapeseed oil or salad oil, animal oil such as lard, or edible oil such as butter and margarine. It can be used and is preferably salad oil or butter, more preferably salad oil.

When the cooking sheet of the present invention is laid on or joined to the surface of a metallic cooking utensil,
As a raw material for the PTFE porous molded body, a method in which a powder of permanent magnet (hard magnetic material) such as carbon steel, cobalt steel, and alnico is added to PTFE molding powder is used, and the end of the PTFE oil-containing porous body is folded back to make a frying pan, etc. By using a method such as fitting and fixing to the edge of the cooking utensil, the adhesion between the cooking utensil and the cooking sheet is increased, and it can be used more effectively.

[0027]

EXAMPLES The present invention will be described more specifically below with reference to examples.

Example 1 HM-PTFE molding powder was compression-molded at a preforming pressure of 10 kgf / cm ² using a mold having a cylindrical cavity having an inner diameter of 1 mm and an outer diameter of 3 mm, and a height of 30 mm was measured. An HM-PTFE preform having a working density of 1.05 was obtained. 380 this
PTFE with an apparent density of 1.04 after firing for 30 minutes in a heating furnace at ℃
A porous compact was obtained. This molded product is a perfluoropolyether lubricating oil in a container (“Demnum” manufactured by Daikin Industries, Ltd.).
S-200 ”), the pressure in the container was reduced to 10 ⁻³ mmHg, and after sufficiently releasing air, the pressure was returned to normal pressure. Thus
Specific gravity 2.00 with the porous space almost completely replaced with the lubricating oil
An oil-containing porous body of was obtained.

This sample was cut into pieces of 10 mm each in the length direction, and an actual idle load rotation test was conducted with a DC motor set as a bearing for a small motor. During the 24-hour continuous operation with the voltage set at 6000 rpm, no abnormalities such as changes in the number of revolutions were observed.

Comparative Example 1 The same experiment as in Example 1 was conducted without impregnating the PTFE porous molded article prepared in Example 1 with lubricating oil. At this time, the initial rotation speed at the same voltage was 5200 rpm, and after 24 hours changed to 6100 rpm, indicating abnormal wear.

Example 2 HM-PTFE molding powder was compression-molded at a preforming pressure of 5 kgf / cm ² using a mold having a cylindrical cavity having an inner diameter of 30 mm and an outer diameter of 40 mm, and a height of 2.5 mm, An HM-PTFE preform having an apparent density of 0.83 was obtained. 38 this
Firing was performed in a heating furnace at 0 ° C. for 2 hours to obtain a cylindrical HM-PTFE porous molded body having an apparent density of 0.85. Example 1
In the same manner as above, lubricating oil was impregnated, and this was mounted as an oil retainer in contact with the retainer of the ball bearing and the outside was fixed.

The bearing exhibited stable performance without abnormal wear and noise due to oil shortage even when operated in an atmosphere of 150 ° C.

Example 3 Using a mold having a cylindrical cavity with a cross section of 30 mm in diameter,
4 g of HM-PTFE molding powder was compression molded at a preforming pressure of 10 kgf / cm ² and fired for 30 minutes in a heating furnace at 380 ° C., a diameter of about 30 mm, a thickness of about 5 mm, and an apparent density of 1.10.
An M-PTFE porous molded body was obtained. This was immersed in perfluoropolyether lubricating oil (“Demnum S-200” manufactured by Daikin Industries, Ltd.) in the container, and the inside of the container was 10 ⁻³ mmH.
The pressure was reduced to g and then returned to normal pressure. Thus, an oil-containing porous body in which the porous space was almost completely replaced with the lubricating oil was obtained.

Example 4 The HM-PTFE porous molded article prepared in Example 3 was replaced with a silicone lubricating oil (Shin-Etsu Silicone KF96 10 manufactured by Shin-Etsu Chemical Co., Ltd.) in place of the perfluoropolyether lubricating oil.
0 ”) was used, impregnation with lubricating oil was carried out in the same manner as in Example 3 to obtain an oil-containing porous body in which the pore spaces were almost completely replaced with oil.

Example 5 PTFE molding powder (Daikin Industries, Ltd.)
"M-12" manufactured by Mfg. Co., Ltd. is baked for 30 minutes in a heating furnace at 380.degree. Between meshes
Screened with 500μm sieve (hereinafter gelled and crushed PTF
E molding powder) is used as a raw material for obtaining the PTFE porous body, and a mold having a cylindrical cavity with a cross section of 30 mm in diameter is used for compression molding at a preforming pressure of 10 kgf / cm ² and heating at 380 ° C. Baking in a furnace for 30 minutes, diameter about 30m
A PTFE porous molded body having m, a thickness of about 5 mm and an apparent density of 0.80 was obtained. This was immersed in a perfluoropolyether lubricating oil (“Demnum S-200” manufactured by Daikin Industries, Ltd.) in the container, the pressure in the container was reduced to 10 ⁻³ mmHg, and the pressure was returned to normal pressure again. Thus, an oil-containing porous body in which the porous space was almost completely replaced with the lubricating oil was obtained.

Example 6 The gelled and pulverized PTFE porous molded article prepared in Example 5 was replaced with a perfluoropolyether lubricating oil and a silicone lubricating oil (Shin-Etsu Silicone KF 9 manufactured by Shin-Etsu Chemical Co., Ltd.).
6 100 ") was used to impregnate a lubricating oil in the same manner as in Example 5 to obtain an oil-containing porous body.

With respect to the four types of oil-containing porous bodies of Examples 3 to 6, the oil separation rate in a state of standing on a glass petri dish under an air atmosphere of 100 ° C. and 200 ° C. The weight of the spilled oil relative to the weight of the oil was shown in wt%). The measurement results are shown in FIGS.
◯ indicates a porous molded body made of HM-PTFE impregnated with perfluoropolyether oil, and ● indicates HM-PTF.
A porous molded body made of E impregnated with silicone oil, □ a porous molded body made of gelled and crushed PTFE impregnated with perfluoropolyether oil, and ■ made of gelated crushed PTFE A porous molded body impregnated with silicone oil is shown).

With respect to the oil-containing porous body made of the HM-PTFE molding powder, the oil separation rate of the impregnated oil reaches a certain value in a short time and does not flow out more than any oil. There wasn't. On the contrary,
The amount of oil separation from the oil-containing porous body made of the gelled and pulverized PTFE molding powder increased with the passage of time, and the oil flowed out at a substantially constant rate within the measurement time.

This is because, in the PTFE oil-containing porous body of the present invention, a molded article made of gelled and pulverized PTFE molding powder has a larger pore size than the molded article made of HM-PTFE. In contrast to the fact that the viscosity of the oil that is flowing out easily flows out from the pores, the molded product made of HM-PTFE has a small pore diameter, so only the thermal expansion of the impregnated oil flows out and more It is considered that this is because it is difficult to flow out.

Due to the difference in these properties, the oil-containing porous body obtained from the gelled and pulverized PTFE molding powder can be used as an oil-containing porous body obtained from HM-PTFE for applications requiring continuous oil supply (outflow) at high temperatures. The body is
It can be used for applications where oil supply (outflow) is required only when the temperature rises.

Example 7 In order to perform a test as a fixing roller for an electronic copying machine or a facsimile, a fixing roller covered with a PTFE porous molded body was prepared as follows.

The aluminum roller body having an outer diameter of 40 mm and a length of 340 mm was subjected to usual undercoating treatment (blast treatment, primer application) in order to coat it with a fluororesin. Next, using a mold having a cylindrical cavity with an outer diameter of 50 mm and an inner diameter of 40 mm, HM-PTFE molding powder
260 g was compression molded at a preforming pressure of 10 kgf / cm ² . With the roller inserted in this preform, by firing in a heating furnace at 380 ° C. for 2 hours, the circumference of the H
An aluminum roller covered with the M-PTFE porous molding was obtained. The HM-PTFE porous molded body coating layer of this roller was cut to obtain an aluminum roller covered with the HM-PTFE porous molded body having a thickness of 0.5 mm.
Perfluoropolyether oil (“Demnum S-200” manufactured by Daikin Industries, Ltd.) was dropped into this to uniformly impregnate it to obtain a fixing roller.

Example 8 An aluminum roller coated with a 0.5 mm-thick HM-PTFE porous molded body prepared in Example 7 was replaced with a silicone oil (Shin-Etsu Chemical Co., Ltd.) in place of perfluoropolyether oil. "Shin-Etsu Silicone KF 96 100") was added dropwise and uniformly impregnated into a fixing roller.

Comparative Example 2 Using the mold used in Example 7, PTFE molding powder ("M-12" manufactured by Daikin Industries, Ltd.) was compression molded at a preforming pressure of 300 kgf / cm ² . The obtained PTF
E With the aluminum roller prepared in Example 7 inserted in the preformed body, the aluminum roller was baked in a heating furnace at 380 ° C. for 2 hours to obtain an aluminum roller whose periphery was covered with a PTFE molded body of about 5 mm. It was PTFE of this roller
The molded body coating layer is cut to give an apparent density of 2.10 and a thickness of 0.5 m.
An aluminum roller covered with m PTFE molding was obtained.

The rollers obtained in Examples 7 and 8 and Comparative Example 2 were attached to a dry copying machine as a heat fixing roller, and copying was performed under the conditions of a fixing temperature of 180 to 200 ° C. and a copying speed of 180 mm / sec. In the roller of Comparative Example 2, A4 paper 1000
Toner offset occurred on one sheet, but in Examples 7 and 8
No toner offset occurred on any of the rollers even after copying 10,000 sheets of A4 paper.

Example 9 Using a mold having a cylindrical cavity with a cross section of 22 cm in diameter,
60 g of HM-PTFE molding powder was molded at a preforming pressure of 10 kgf / cm ² to obtain a preform. 38 this
Baking at 0 ℃ for 30 minutes, diameter 22cm, thickness 1.5mm, apparent density 1.
05 porous molded body was obtained. Edible oil was added dropwise to this porous molded body to uniformly impregnate it with the porous molded body to obtain an oil-containing porous body. When this oil-containing porous body was heated on a metal frying pan to make tamagoyaki on the oil-containing porous body, it could be cooked without burning. The eggs were cooked 5 more times in succession without supplementing the cooking oil, and all were cooked without burning.

[0047]

Since the oil-containing porous body of the present invention is excellent in heat resistance and low friction, it can be suitably used as a bearing or an oil retainer used in a high temperature atmosphere.

Further, the oil-containing porous material of the present invention is excellent in heat resistance and non-adhesiveness, and therefore can be suitably used as a cooking sheet.

[Brief description of drawings]

FIG. 1 shows HM-PTFE and gelled ground PTF.
100 g of the oil-containing porous body obtained from E on a glass petri dish
The oil separation rate when left standing for about 4 hours at 0 ° C is shown.

FIG. 2 shows HM-PTFE and gelled crushed PTF.
The oil-containing porous body obtained from E is put on a glass petri dish for 200
The oil separation rate when left standing for about 4 hours at 0 ° C is shown.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C08L 71/02 LQE // C08J 5/16 CEW 9267-4F C10M 111/04 9159-4H (C10M 111 / 04 107: 38 105: 54) C10N 40:02 50:08 50:10

Claims (11)

[Claims] 1. An oil-containing porous body, characterized in that a porous molded body obtained from polytetrafluoroethylene molding powder is impregnated with oil. 2. The oil-containing porous body according to claim 1, wherein the oil is a lubricating oil. 3. The oil-containing porous body according to claim 1, wherein the oil is edible oil. 4. The oil-containing porous body according to claim 2, wherein the porous molded body is obtained from a polytetrafluoroethylene powder having a firing densification index P ₁₀ , P ₂₅ and P _{50 which} are all 0.2 or less. 5. The oil-containing porous body according to claim 3, wherein the porous molded body is obtained from a polytetrafluoroethylene powder having a firing densification index P ₁₀ , P ₂₅ and P ₅₀ all of which are 0.2 or less. 6. The lubricating oil is a fluorine-containing compound.
Or the oil-containing porous body according to 4. 7. The oil-containing porous body according to claim 6, wherein the fluorine-containing compound is a perfluoropolyether compound. 8. A bearing comprising the oil-containing porous body according to claim 2, 4, 6, or 7. 9. An oil retainer comprising the oil-containing porous body according to claim 2, 4, 6, or 7. 10. A fixing roller for an electronic copying machine, comprising the oil-containing porous body according to claim 2, 4, 6, or 7. 11. An oil-containing sheet for cooking, comprising the oil-containing porous body according to claim 3 or 5.