JPH01500123A - Method for surface modification of polytetrafluoroethylene, modified molded products of polytetrafluoroethylene and their use - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Surface modification method of polytetrafluoroethylene, Modified molded bodies and their use The present invention focuses on the application of easily hydrolyzed volatile compounds and Polytetrafluoroethylene or mainly polytetrafluor due to the action of moisture A method for surface modification of a copolymer composed of oleoethylene, and the modification method The present invention therefore relates to modified molded bodies and their use.

Polytetrafluoroethylene and copolymers containing it in major amounts are Due to its excellent mechanical and chemical properties, it is particularly suitable for the production of shaped bodies and e.g. metal coatings. It is used as a coating material for coatings. Polytetrafluoroethylene is chemically It is characterized by being extremely inert chemically, and is not susceptible to the corrosive effects of most organic solvents. Only fluorine-containing hydrocarbons cause polytetrafluoroethylene to swell. but without destroying its tissue, especially after treatment with fluorohydrocarbons. is a zero element that does not change the adhesion/wetting properties of polytetrafluoroethylene. Fluorine or chlorotrifluoride reacts with polytetrafluoride at high temperature and pressure. When in contact with ethylene, a disintegration reaction occurs. polytetrafluoroethylene It is completely resistant to inorganic fluorides such as uranium hexafluoride. Kunststoffhandbuch (plastic handbuch) Fluorhaltige Polymerisate (Fluorine-containing Polymer) J, Vol, 11. Cap, 4. See p. 271, Karl.

Carl-Hanser Publishing, Munich].

This chemically inert property makes the surface modification of polytetrafluoroethylene extremely making it difficult. However, the surface of products made of polytetrafluoroethylene making it hydrophilic and improving its wettability, especially by polar liquids such as water is often desirable. In addition, by surface modification, organic coating It is often necessary to change the adhesion or tackiness to the material. This is particularly Important in forming layered composite materials. By making it hydrophilic, it also has better coloring and antistatic properties. Resistance and certain electrical properties such as surface resistance may also be improved or changed.

, on the surface of products made of polytetrafluoroethylene, e.g. nonionic wetting agents, Apply hydrophilic substances such as cationic active antistatic agents or anionic active compounds. This is publicly known. However, these substances are It does not adhere to the lens surface and may therefore be washed away. polytetra Permanent surface property modification of fluoroethylene products is desired.

Furthermore, the surface of polytetrafluoroethylene was treated with corona discharge or chromium sulfate. It is also known to carry out oxidation treatment depending on the purpose. However, this kind of processing It only reaches its limits, consumes time, creates wastewater treatment problems, and overall It is unsatisfactory. Sodium treatment in liquid ammonia or other solvents The process is the same, and in that case, etching is further affected by ultraviolet rays and heat. This has the added disadvantage of lowering the value.

U.S. Pat. No. 2,898,299 describes the active use of fluorocarbon polymer surfaces. The sexualization method is mentioned. In this method, for example, polytetrafluoroethylene The polymer object was first heated for about 1 hour, with the polymer surface substantially unaffected. The heated surface is then heated to a surface temperature of 50°C in the presence of moisture. in contact with vapors of easily hydrolyzable volatile compounds of silicon, titanium or germanium. Let me touch it. Examples of such easily hydrolyzable volatile compounds are given in this patent specification. , titanium tetrachloride, germanium tetrachloride and silicon tetrachloride. Lido as well as tetraisopropyl titanate are mentioned. Preferably volatile Treatment with vapors of chemical compounds is carried out. In this patent specification, these It is stated that the compound reacts with moisture present on the surface of the object to form an oxide. ing. Objects treated in this way lose their usual slipperiness. unprocessed table Unlike the surface, adhesive adheres to the treated surface. Epoxy resin also adheres to the surface. It can be improved in the same way. From U.S. Pat. No. 3,666.741, Polytet Additional methods of surface treatment of lafluoroethylene are known.

In this method, a fluorocarbon polymer object is heated with rhenium hexafluoride. in a liquid metal fluoride selected from the group of olide and molybdenum hexafluoride. Soak in. This soaking is continued until the desired penetration is achieved. Next, Hydrolyzes molybdenum hexafluoride or molybdenum hexafluoride. So A black conductive coating forms during this process. Finally, U.S. Patent No. 3,122,445 Methods for processing fluorocarbon polymer moldings are known from the literature. This method smells In order to change the surface properties of the polymer, the object was treated with boron trifluoride and acid. Process it plain. However, the problem in this case is the oxidation process.

Processing of pure polytetrafluoroethylene polymers is not a problem.

By current state of the art methods, polytetrafluorocarbons are used to improve wettability. It is possible to modify the surface of molded products made of polyethylene. However, publicly known In this method, only a thin layer near the surface of the object can be treated, so it is difficult to modify the material. Therefore, the permanence of the properties brought about or changed is insufficient. It is clear that

Therefore, the object of the present invention is to cover not only the layers near the surface but also to In order to extend the modification to a deeper layer than before, we used a polytetrafluoroethylene counter. A copolymer composed primarily of polytetrafluoroethylene. Particularly, the object of the present invention is to provide a method for modifying the surface of Improved persistence of effects. Modified surface basically does not cause discoloration damage .

According to the present invention, silicic acid forms a pseudo-interpenetrating polymer network in the layer adjacent to the surface. Polytetrafluoroethylene or its copolymer system incorporated in the form of A modified molded product is produced.

The above object is solved according to the invention by the method according to claim 1. be done. Other preferred embodiments are described in Section 2 and below.

These desirable modifications surprisingly result in easily hydrolyzable volatile compounds. , achieved by using silicon, germanium, phosphorus or arsenic fluorides. will be accomplished. These fluorides can be prepared at a temperature of at least 150°C, similar to known methods. The temperature is applied to an object composed of a fluorocarbon polymer. However, 25 It is preferable to select a temperature between 0°C and 300°C as the working temperature. 0 Working time depends on the temperature of the surface on which the action takes place.9If the surface temperature is chosen high, In particular, the 6 effects can shorten the action time by that much, from a few minutes to about 2 It is carried out with working times ranging from ~3 hours.

A preferred embodiment of the method of the invention is characterized in that silicon tetrafluoride is used as the fluoride. or the highest valence fluoride of germanium, phosphorus or arsenic. It is characterized by its use. Such fluoride is germanium tetra chloride, phosphorus pentafluoride or arsenic pentafluoride. but However, among these fluorides, silicon tetrafluoride is particularly preferred. , which is the easiest method to use during the assembly of polytetrafluoroethylene molded products. Penetrates and is hydrolyzed by steam or water to form silicic acid, which forms polytetrafluorocarbons. Silicon, germanium, phosphorus or arsenic in a special form in fluoroethylene moldings The action of water or steam on the fluoride-treated surface is in one step (i.e. , together with the action of fluoride), but also these water Alternatively, the treatment with water vapor can be carried out after the surface treatment of the molded product with Fluleolide. You can also do that. Therefore, a preferred embodiment of the method of the invention provides that in the first step Silicon, germanium, phosphorus or arsenic fluorides are applied to the polymer surface. and then exposing the treated polymer to the action of water or steam. It is in. At this time, the polymer that has undergone the above treatment is treated with cold water, especially water at a temperature below 10°C. It has been found that it is particularly effective to Use a chilled salt solution By doing so, it is possible to lower the treatment temperature to below the freezing point of water. This allows you to The networks formed from silicic acid can be fixed particularly well in the shaped articles.

Polytetrafluoroethylene or its copolymers can be used as powders, particles, foils or fibers. in the form of textiles, flat knitted or woven fabrics, or in the form of gears, pulleys, bearings, etc. It can be in the form of a molded article.

Copolymers in the sense of the present invention are hexafluoroallopyrene, chlorotri Fluoroethylene, perfluorovinyl ether, vinylidene fluoride, vinyl Copolymerization of up to 50% by weight from the group of fluoride, ethylene and/or propylene It is a copolymer with copolymer monomers. Particularly preferred is 30% by weight or less of the above. It is a copolymer with monomers.

Fluorides of Si, Ge, P and As can be dissolved into polytetrafluoride at a given temperature. fluorine-containing hydrocarbons penetrate into the surface limiting layer of polyethylene, and similarly, fluorine-containing hydrocarbons It is presumed that it swells tetrafluoroethylene and its copolymers. centre Luolides are hydrolyzed under the action of water vapor to produce hydroxyl groups. the In particular, the silicic acid produced during the hydrolysis of SiF4 is affected by free hydrogen fluoride. In this case, perhaps Physics of polysilicic acid in the surface layer matrix of swollen polytetrafluoroethylene A tightly bound polymeric network is formed, which firmly adheres to the polymer inside and out. It is thought that it will stick.

Polytetrafluoroethylene or copolymers thereof treated according to the present invention Both the properties and the physical investigation, e.g. by ESC analysis, indicate that silicic acid has a pseudo-phase. Interpenetration - fully expected to be incorporated in the form of a polymer network. Ru.

The processed product can be modified by hydrolysis and optionally by the incorporation of condensation products of fluoride. It has been modified in the form of, in particular, made hydrophilic. In this case, in particular The following characteristics are observed for the manufactured products: In other words, it has not undergone the above processing. Polytetrafluoroethylene fibers, foil pieces or powders are coated with surface-active When placed in water containing agents, they remain floating on the surface of the water, but the treatment according to the invention In contrast, similar fibers, fragments, etc. that have been made hydrophilic by this process quickly become wet. , it will sink to the bottom.

The thin voile treated according to the invention then becomes transparent.

Verifying the structural differences between unmodified polytetrafluoroethylene and polyester fibers Under conditions such as those used to Falkai), 5ynthesefasern (synthetic fibers), Gemmy Publishing, Einheim et al. (1982), p. 418], if treated with disperse dyes (e.g. ) Oron Marine Blue S-201), the surface is colored, but the hydrophilic The modified sample absorbs very little disperse dye.

The method of the present invention is different from the method of U.S. Pat. No. 2,898,229, etc. The silicon, germanium, phosphorous or arsenic fluoride selected in the case is It is said that it penetrates much deeper into the surface layer of modified polytetrafluoroethylene molded products. This is particularly advantageous in this respect. Geite tetrachloride or germanium tetrachloride shows insufficient penetration depth; the hydrolysis products produced by water penetration are based on Essentially incorporated only on the outer surface and therefore easily removed by mechanical action may be done. In contrast, silicon, germanium, phosphorus or arsenic fluorescein Luolides penetrate much deeper into the modified article. Hydrolysis that occurs during hydrolysis The polymer network of water decomposition products is particularly effective in settling into the molding matrix. , and therefore much more mechanically resistant. This excellent penetration depth is gradually layered using a microtome from the surface of the molded product treated according to the present invention. is peeled off and the wettability of the surface is tested using ink with a predetermined surface tension. It can be easily demonstrated by The depth of penetration is limited by the current state of the art, especially the method of U.S. Pat. No. 2,898,229. This shows that the level is much higher than that of molded products that have undergone treatment.

When inspecting the surface of a molded product treated by the method of the present invention, spectroscopic analysis was performed. , it can be confirmed that silicon atoms and oxygen atoms are arranged on the surface. . Polytetrafluoroethylene molded products with a porous structure are modified by the method of the present invention. In some cases, scanning electron microscopy shows that porous structures can be detected even in treated molded products. is verified to be maintained.

The pores are not blocked by silicic acid produced during hydrolysis.

When the product obtained by the method of the present invention is exposed to the action of hot water, the modified molded product properties are maintained despite the hydrothermal treatment, i.e. the effect achieved It is confirmed that the sustainability of the project is high. Therefore, the polymer produced by hydrolysis -Acid is not only physically integrated into the object, but also solidified on the inside and outside surfaces of the object. He is wearing it.

The product obtained according to the invention is therefore suitable for the following uses: wife Due to its self-lubricating properties, the molded article modified according to the present invention can be used, for example, in small models. It can be used as a mechanical structural component in motors, and also in self-lubricating switchgears. It can also be used in manufacturing. Lubricating properties are maintained even in high vacuum conditions. Asymmetric diaphragms can be obtained from foils that are hydrophilized on one side. m fiber Finishing shaped products into cloths with a hydrophilic surface, for example for filter cloths can be given. The processed product has reactive hydroxyl on its surface.

The surface of the molded article or foil that has undergone the above treatment can be easily bonded with an organic compound using a customary adhesive. Can be laminated with synthetic resins, thereby preparing e.g. laminate structures 0 Hydroxyl groups on the surface of the polymer treated according to the present invention Isocyanate-based adhesives, which can interact, are particularly suitable.

The following examples demonstrate the method according to the invention as well as the products produced by the method. Describe the characteristics in detail.

Example I V4A-Steel cylinder (bottom diameter 30e-1, top opening diameter 10cm, height 50 cm) is equipped with a clamp device at the upper end opening, and a cylindrical port is attached to the device. Fixes processed products made of litertrafluoroethylene.

A mixture of powdered fluorite and quartz sand is placed at the bottom of the cylinder, and a concentrated mixture is placed at the bottom of the cylinder. Sulfuric acid is added dropwise onto the mixture. Steam is blown into the cylinder through the inlet. You can

Sulfuric acid should be used so that the unit area load due to passing gas is 5 to 500 m/+e2h. supply to. The temperature of the workpiece was 250°C during the treatment with silicon tetrafluoride. ℃ to 260℃, then the processed product is kept at -10℃ to 0℃ due to the action of water vapor. Cool to ℃.

When using silicon tetrafluoride and water vapor at the same time, the water in the gas chamber must be Adjust the minute content to 6-600 g/m. The unit area load is again 5 to 500. Select the value of m/+m2. The action time of SiF4 and/or water is from several minutes to several hours can be varied between.

As shown by the ESC analysis, silicon is present on the surface of the processed workpiece. atoms and oxygen atoms are present.

Surface tension is graded, such as used to investigate pretreatment backfilling of foil surfaces. General commercially available PE-test ink [manufacturer, e.g. Druckfarbenfibrik Gebr, Schmidt br, Schmidt) G bH, 6000 Frankfurt 96] Ru. For all test inks in the range of 30-50 nN/plow, the treated material In the case of materials, closed membranes are obtained.

When an aqueous surfactant solution (sodium sulfonate wetting agent 1%) is added dropwise, the It can be seen that it spreads to the surface over time.

Peel the foil from 0.02 mm thick to 1-plow from the workpiece.

The above-mentioned tests (ESC analysis, PE test ink application, surfactant aqueous solution) (wetting) is repeated with these foils with the same results.

Foil is a synthetic fiber by B. von Falkai. , Verlag Chemie, Weinheim, 1 981, p. 418, of Boron Marine Blue S-2Gl. Colored with disperse dyes commonly available under the name In this case, the untreated foil should be The color is clearly darker than that of voile that has been treated. Saponify anionic detergent by boiling In this case, the colored pigment in the treated foil disappears completely again. On the other hand, Most of the colored pigments in the treated foil remain.

A piece of foil with an area of 1 cwh2 was soaked in a surfactant aqueous solution (sodium sulfonate-based wet 1%). Untreated polytetrafluoroethylene - sample is water Samples treated with the present invention retain their superior wetting properties while remaining suspended on surfaces. Due to its nature, it will sink immediately.

A white porous foil (porosity 40%, thickness 0.25 mm) was soaked in a surfactant aqueous solution ( Soak in 1% commercially available detergent. The foil becomes transparent immediately after immersion.

Polytetrafluoroethylene treated according to the invention and untreated polytetrafluoroethylene fluoroethylene is heated above its melting temperature, cooled to room temperature, and then freshly added again. When heated, they exhibit identical DSC spectra.

Maximum tensile strength and Measure the maximum tensile strain 0 Maximum tensile strain of the material treated according to the invention The maximum tension of the treated material decreases to about 60% (relative) of the untreated material, while the The tensile strength still amounts to at least 80% of the original material.

Example 2 The steel cylinder clamping device described in Example 1 is Fix the foil with a thickness of 0.02 to 1-0.Then, the foil was fixed in the same way as in Example 1. Process. The foil exhibits the same properties as described in Example 1.

Example 3 Replace the clamping device of the steel cylinder described in Example 1 with a closed steel mesh. do. On this net, fiber materials of various shapes (flock, spun, filament yarn, cloth) are coated. If necessary, use another wire mesh to remove the material from the other side. These materials are then treated as in Example 1. m fiber material , after treatment, exhibits the same properties as described for the foil of Example 1.

Example 4 During the opening of the steel cylinder described in Example 1, a polytetra trough to a height of 1.5 cm was Insert a V4A-steel Buchner funnel filled with fluoroethylene powder (dia. (9.5 cm, height 5 cm, porosity 20%) Treat with ion tetrafluoride. After treatment, the powder was treated in a manner similar to that described in Example 1. Show characteristics.

Example 5 Repeat the tests described in Examples 1 to 4, but substituting 7. silicon tetrafluoride. , gaseous germanium tetrafluoride, phosphorus bentafluoride or arsenic Use pentafluoride. Injecting gas directly into the cylinder from a pressurized container .

Other conditions (temperature on the gas flow side of the molded product, unit area load due to flowing gas) are in Example 1. - Select as described in Example 4.

The modification occurring on the polymer surface is verified in the same manner as in Examples 1-4. all sun A pull indicates a hydrophilized polar surface.

These are easily wetted with polar liquids such as water or alcohol.

Example 6 Place the workpiece in a V4A-autoclave (volume 1.71).

By blowing silicon tetrafluoride, the pressure in the autoclave is brought to 1 atm. 0 Next, the autoclave is heated to 250°C, at a pressure of 2.2~ The pressure rises to 2.4 atmospheres. After 2-3 hours of treatment, drain the autoclave with ice/saline solution. Cool rapidly to 0°C. Then, put it in a cooled autoclave at -15°C on ice/ Push in the saline from below and let it work for 1 minute to 1 hour.

The test described in Example 1 is repeated with the same results.

Example 7 Repeat the test described in Example 6, but select a treatment temperature of 330°C In addition to trafluoride, silicon tetrachloride at the same molar concentration was used in parallel tests. use.

Repeating the test to determine material properties as described in Example 1 yields the same results. It will be done.

A microtome was used to measure the penetration depth of silicic acid from both samples. Strip the surface in layers. PE-test in each case on the newly obtained surface. to check whether the hydrophilic effect of silicic acid is still detected.

In 5iC14-treated samples, the effect of silicic acid was up to > I MIS. Is recognized. In the case of 5iF4-treated samples, already <0.1 mm; A hydrophilic effect can no longer be recognized.

international search report ANNEX τQ THE INTERNATIONAL 5EARCHREP ORT 0NUS-A-36667413010S/72 NoneCB-A- 11517461410S/69 US-A-34427000610S/69

Claims (11)

[Claims] 1. Effects of easily hydrolyzable volatile compounds and moisture on heated surfaces of polymers polytetrafluoroethylene or primarily polytetrafluoroethylene In the method for surface modification of copolymers composed of using silicon, germanium, phosphorus and/or arsenic fluorides as A surface modification method characterized by: 2. As fluoride, SiF4 or germanium, phosphorus or arsenic atoms The method according to claim 1, characterized in that the highest valence fluoride is used. Method. 3. In the first step, silicon, germanium, phosphorus and/or arsenic fluorinated The treated polymer is then subjected to a second process step. Claim 1, or The method described in Section 2. 4. A claim characterized in that the treated polymer is treated with water at a temperature of 10°C or less. The method described in item 3 of the scope of the request. 5. In the first step, silicon, germanium, phosphorus and/or arsenic fluorinated The treated polymer is preferably heated to a temperature below the freezing point of water. Claims 1 to 3, characterized in that the treatment is carried out with a cold salt solution cooled below. The method described in any of Section 3. 6. The action of silicon, germanium, phosphorus and/or arsenic fluorides can be reversed by according to claim 2, characterized in that: is carried out together with the action of water vapor. Method. 7. When the fluoride is applied, the polymer is heated to at least 150°C, preferably Preferably, the method is heated to 250°C to 300°C. The method according to any of paragraph 7. 8. Incorporation of silicic acid in the layer adjacent to the surface in the form of a pseudo-interpenetrating polymer network Polytetrafluoroethylene or its copolymer-based modified molded products. 9. The molded product modified by the method described in claims 1 to 7. Use as a lubricating structural member. 10. A foil modified on one side by the method described in claims 1 to 7. Use as an asymmetric diaphragm. 11. Fibers modified on one side by the method described in claims 1 to 7. , use in the production of fleeces and cloths with hydrophilic surfaces.