Fluoropolymer alloys, their preparation and application

The invention relates to fluoropolymer alloys made from melt-producible, extra-high molecular fluorinated ethylene-propylene copolymer (EHMW-FEP) and one or more other polymers, their production and use.

The fluoropolymer alloys are new materials that have different properties from the starting polymers from which they are made. It is an important way to produce new materials with a wide variety of properties because of their advantages in using available polymers, because of the simple procedure and because of the short development time. This has been of great interest for some time, cf. Sato Kawa, Plastics (Japan) 32, 69 (1981). The fluoropolymer alloys reported have been limited to mixed alloys based on polyvinylidene fluoride and on the basis of polytetrafluoroethylene (PTFE) dispersion and fluorinated ethylene-propylene copolymer (FEP) dispersion (GB-A-935 706 ( 1960); JP Patent Kokai 12521/62).

Polytetrafluoroethylene, commonly referred to as the "king of plastics", has excellent properties overall. It has very good thermal and chemical stability as well as excellent electrical insulation properties and anti-adhesive behavior. However, it could not be made by melt processing, but can only be made by cold compression and subsequent sintering. Its fatigue strength is also low. Therefore, its uses are limited.

A fluorinated ethylene-propylene copolymer with good fatigue strength is a copolymer of tetrafluoroethylene and hexafluoropropylene, it can be produced in the melt due to the presence of trifluoromethyl in the copolymer chain. The chemical inability to react and the very good electrical insulation properties of the copolymer are similar to those of polytetrafluoroethylene, but its thermal stability is not as good as that of PTFE, it can only withstand temperatures up to 200 ° C, and the manufacturing costs are higher than those of PTFE.

The object of the invention is to produce a fluorine-containing material with even more perfect properties by mixing PTFE and FEP and to obtain a polymer alloy with improved very good properties, which overcomes the disadvantages of the two starting polymers.

There are methods of making a polymer alloy from polytetrafluoroethylene and fluorinated ethylene-propylene copolymer in GB-PS 935 706 (1960) and JP-Kokai 12521/62 using the co-precipitation of these two fluoropolymer dispersions. The process is complicated and the cost is high. The mechanical properties of the fluoropolymer alloy are worse than those of PTFE and FEP; for example, their tensile strength is significantly lower than that of the two starting polymers and is only 142-213 bar (142-213 kg / cm²) at room temperature.

An important problem is the adaptation of polytetrafluoroethylene to fluorinated ethylene-propylene copolymer in order to obtain a good fluoropolymer alloy made of PTFE and FEP. These two raw fluoropolymers have different processing temperatures and different thermal stability. The temperature when compression molding an FEP melt is around 310 ° C, but the sintering temperature after cold compression of PTFE is around 380 ° C. The decomposition rate of FEP is much higher than that of PTFE at 380 ° C. In particular, when producing FEP resin having a carboxyl end group by copolymerization using perdisulfate as a starter, roasting must be carried out at 380 ° C to stabilize the end group. But after roasting, FEP resins become like dried bread or rusks and cannot be mixed with PTFE powder.

Another important problem is the mixing process when producing a polymer alloy from PTFE and FEP. In general, the mixing of polymers can be carried out in a solution mixing process, a melt mixing process or a mixing process by means of dispersion co-precipitation. Since there is no solvent for PTFE and FEP, mixing cannot be done by solution mixing. It cannot be done by melt mixing either because PTFE cannot be processed in the melt. Therefore, dispersion co-precipitation mixing was the only option used in GB-PS 935 706 and JP-Kokai 12521/62, although the cost of the polymer alloy becomes high because of producing a dispersion of PTFE and FEP an expensive fluorine-containing emulsifier must be used. Mixing by co-precipitation is also relatively complicated.

According to the present invention, fluoropolymer alloys are made available comprising melt-producible, extra-high molecular fluorinated ethylene-propylene copolymer and one or more further polymers, which are selected from the group consisting of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, Tetrafluoroethylene-ethylene copolymer, polysulfone, polyethylene, polypropylene, polyimide, polycarbonate, polyphenylene oxide and polyphenylene sulfide, the melt powder being an extra high molecular weight fluorinated ethylene-propylene copolymer which is melt-producible with 12-30% by weight hexafluoropropylene, a molecular weight of more than 2 x 10 5 on average, a melt viscosity of 1 x 10 6; P or more and a melt index less than 0.8 g / 10 min.

As a preferred embodiment, the fluoropolymer alloys have extra-high molecular fluorinated ethylene-propylene copolymer and polytetrafluoroethylene.

As a further preferred embodiment, the fluoropolymer alloys have 0.1-60% by weight extra high molecular weight fluorinated ethylene-propylene copolymer and 99.9-40% by weight polytetrafluoroethylene.

As a further exemplary embodiment, the fluoropolymer alloys contain glass fibers, graphite, molybdenum disulfide, carbon and / or metal powder.

Furthermore, according to the present invention, extra-high molecular fluorinated ethylene-propylene copolymer, which can be produced in the melt, is prepared by solution precipitation polymerization using liquid hexafluoropropylene as a solvent and charging an autoclave with 0.2-0.5 g of tetrafluoroethylene and Hexafluoropropylene per 1 ml of autoclave content, wherein the monomer mixture of tetrafluoroethylene and hexafluoropropylene contains 11-50 wt .-% tetrafluoroethylene and the weight ratio of water to monomers is 3: 1 to 1: 1 and the equivalents of the starter diisopropyl peroxydicarbonate based on the monomers 0.001-0.05 wt. -%, the polymerization pressure 20-30 bar (20-30 kg / cm²), the polymerization temperature 40-80 ° C and the polymerization time 1-5 hours per batch.

In accordance with the present invention, the polytetrafluoroethylene (PTFE) used is a commercially available resin including resins made by suspension or dispersion polymerization and has a tensile strength of more than 270 bar (270 kg / cm²) at room temperature.

According to the present invention, the other commercially available polymers such as polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer, polyethylene, polypropylene, polysulfone, polyimide, polycarbonate, polyphenylene oxide, polyphenylene sulfide for the production of a fluoropolymer alloy together with extra high molecular weight fluorinated ethylene-propylene copolymer (EHMW -FEP) can be used.

A given weight ratio of EHMW-FEP and one or more of the polymers described above is milled separately and then mixed and milled again until the two or more phases are homogeneously mixed. The mixture is passed through a 0.42-0.84 mm (40-80 mesh) sieve and is then ready for processing.

The process of blending and grinding two or more polymers can be either dry powder or wet powder. When mixing and grinding wet powder, the polymers are moistened with water, ethyl alcohol, ethyl acetate or a mixture of these solvents. After mixing is complete, the mixture of polymers must be dried and then sieved.

For the fluoropolymer alloy made of EHMW-FEP and PTFE, the weight of EHMW-FEP is 0.1-99.9% and the weight of PTFE is 99.9-0.1%. In a preferred embodiment, the weight ratios are 0.1-60% EHMW-FEP and 40-99.9% PTFE.

The fluoropolymer alloys made of EHMW-FEP and PTFE can be pressed from the melt at a temperature of 300-350 ° C and a pressure of 50-200 bar (50-200 kg / cm²) as well as PTFE. They can also be cold compressed under a pressure of 50-200 bar (50-200 kg / cm²) and then sintered at a temperature of 300-390ºC as well as PTFE.

The temperatures when pressing from the melt or when sintering the fluoropolymer alloys described above depend on the amount of PTFE contained therein. The higher the amount of PTFE, the higher the temperature.

The fluoropolymer alloys made of EHMW-FEP and PTFE according to the present invention have not only a fatigue strength like FEP, but also high tensile strength under high temperatures like PTFE. They have a tensile strength of 200-400 bar (200-400 kg / cm²) and an elongation of 300-700% at room temperature and accordingly of 50-200 bar (50-200 kg / cm²) and 300-700% at 200ºC.

Extra high molecular weight fluorinated ethylene-propylene copolymers are well compatible with polytetrafluoroethylene in the fluoropolymer alloys described above. A fluoropolymer alloy consisting, for example, of 10% EHMW-FEP and 90% PTFE has practically only one melting peak and one crystallization peak in its DSC spectrum.

All types of fluoropolymer alloys described above can be strengthened and improved by adding glass fibers, graphite, molybdenum disulfide, carbon and various metal powders.

The fluoropolymer alloys made of EHMW-FEP and PTFE according to the present invention are a type of material with very good thermal stability, chemical inertness and excellent electrical insulation properties. Using this type of fluoropolymer alloy as a material, various membranes, seals, linings for valves, pipes and pumps, various parts of pumps such as housings, wheels, wrapping wires can be manufactured. The articles made from fluoropolymer alloys have better fatigue strength than PTFE and, as a result, have a relatively long service life.

The fluoropolymer alloys described above can be used for powder coating either by the electrostatic coating process or by the fluidized bed process and can also be processed into complex articles by ram extrusion of a paste consisting of fluoropolymer alloy and petroleum ether or kerosene.

The invention is described and explained in detail with the aid of the following examples. In the examples, all parts and percentages are by weight unless otherwise specified.

example 1

20 g EHMW-FEP with a melt index of 0 g / 10 min and 180 g PTFE were successively moistened with a mixture of ethyl alcohol and ethyl acetate, ground, filtered, dried and sieved with a 40 mesh sieve. The resulting powder was cold compacted to a 2 mm thick sheet under a pressure of 80 bar (80 kg / cm²) and sintered in an oven at 350 ° C for 1 hour. After cooling, its tensile strength was 277 bar (277 kg / cm²) at room temperature.

Example 2

EHMW-FEP and PTFE were mixed in weight ratios of 1/9, 1/3, 1/1, 3/1 and 9/1, respectively, the resulting mixtures were ground separately and passed through a 0.42 mm (40 mesh ) sent, cold compressed and sintered at 80 bar (80 kg / cm²). The properties of the resulting fluoropolymer alloys are listed in Table 1. Table 1 Physical properties of alloys made of EHMW-FEP / PTFE composition sintering temperature room temp. Tensile strength elongation

Example 3

EHMW-FEP was mixed with tetrafluoroethylene-ethylene copolymer (F40) in the weight ratio shown in Table 2 by mixing dry or wetted powder, the resulting fluoropolymer alloys were cold-compressed under a pressure of 70-150 bar (kg / cm²) and then sintering or by melt pressing. Table 2 Physical properties of alloys made of EHMW-FEP and F40 composition manufacturing temp. Tensile strength bar elongation

Example 4

A mixture of 40 g EHMW-FEP, 40 g PTFE and 10 g polysulfone was moistened with acetone, homogeneously mixed by high speed stirring, ground, dried, passed through a 40 mesh sieve, cold compressed under 80 bar (kg / cm²) and then sintered for one hour at 320 ° C. The hardness (Rockwell) of the fluoropolymer alloy obtained is D50.

Example 5

EHMW-FEP was mixed with polychlorotrifluoroethylene (CTFE) in the weight ratio shown in Table 3 by mixing dry or wetted powder, the resulting fluoropolymer alloys were cold-compacted under a pressure of 70-150 bar (kg / cm²) and then sintered or made by melt pressing. Table 3 Physical properties of alloys from EHMW-FEP and CTFE composition Manufacturing temp. Tensile strength bar elongation

Example 6

EHMW-FEP was mixed with polyvinylidene fluoride (PVDF) in the weight ratio shown in Table 4 by mixing dry or wetted powder (using diisobutylacetone as a humectant), the resulting fluoropolymer alloys were cold-compressed under a pressure of 70-150 bar (kg / cm²) and subsequent sintering or by melt pressing. Table 4 Physical properties of alloys made of EHMW-FEP and PVDF composition Manufacturing temp. Tensile strength bar elongation

Example 7

EHMW-FEP was mixed with polysulfone (PS) in the weight ratio shown in Table 5 by mixing dry or wetted powder (using chloroform as a solvent), the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / cm²). Table 5 Physical properties of alloys made of EHMW-FEP and PS composition Manufacturing temp. Tensile strength bar elongation

Example 8

EHMW-FEP was mixed with polyethylene (PE) in the weight ratio shown in Table 6 by mixing dry or wetted powder (using xylene as a solvent), the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / cm²). Table 6 Physical properties of alloys made of EHMW-FEP and PE composition. Tensile strength bar elongation

Example 9

EHMW-FEP was mixed with polypropylene (PP) in the weight ratio shown in Table 7 by mixing dry or wetted powder (using decalin as a solvent), the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / c²). Table 7 Physical properties of alloys made of EHMW-FEP and PP composition manufacturing temp. Tensile strength bar elongation

Example 10

EHMW-FEP was mixed with polycarbonate (PC) in the weight ratio shown in Table 8 by mixing dry or wetted powder (using chloroform as a solvent), the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / cm²). Table 8 Physical properties of alloys made of EHMW-FEP and PC composition Manufacturing temp. Tensile strength bar elongation

Example 11

EHMW-FEP was mixed with polyphenylene oxide (PPO) in the weight ratio shown in Table 9 by mixing dry or wetted powder (using chloroform as a solvent), the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / cm²). Table 9 Physical properties of alloys made of EHMW-FEP and PPO composition Manufacturing temp. Tensile strength bar elongation

Example 12

EHMW-FEP was mixed with polyphenylene sulfide (PPS) in the weight ratio shown in Table 10 by blending dry or wetted powder, and the resulting fluoropolymer alloys were made by melt compression under a pressure of 70-150 bar (kg / cm²). Table 10 Physical properties of alloys made of EHMW-FEP and PPS composition Manufacturing temp. Tensile strength bar elongation

Example 13

EHMW-FEP was mixed with polyimide (PI) in the weight ratio shown in Table 11 by mixing dry powder or wetted powder, the resulting fluoropolymer alloys were melt-compressed under a pressure of 70-150 bar (kg / cm²) or cold compression manufactured under a pressure of 70-150 bar (kg / cm²) and sintering. Table 11 Physical properties of alloys made of EHMW-FEP and PI composition Manufacturing temp. Tensile strength bar elongation

Example 14

10 g of EHMW-FEP was mixed with 90 g of molding powder or PTFE dispersion powder, and then the resulting mixture was ground and passed through a 0.42 mm (40 mesh) sieve. The resulting dry fluoropolymer alloy powder was moistened with 200E gasoline, cold compressed, and sintered. This fluoropolymer alloy product can be used for valve and pipe linings.

Example 15

40 g Fluoropolymer alloy made of EHMW-FEP and PTFE was mixed with glass fibers in a weight ratio of 10%, 20% and 30%, respectively. The resulting mixture was separately cold-compressed under a pressure of 80 bar (kg / cm²) and sintered at 320 ° C for 2 hours. The tensile strength data of this reinforced fluoropolymer alloy are 250, 220 and 150 bar (kg / cm²) at room temperature.

Example 16

Fluoropolymer alloy of 50 g EHMW-FEP and 50 g PTFE was mixed with glass fibers in a weight ratio of 20% and graphite in a weight ratio of 3%, the resulting mixture was ground and passed through a 0.42 mm (40 mesh) sieve , cold compacted under a pressure of 80 bar (kg / cm²) and then sintered at 320 ° C for 2 hours. The tensile strength, elongation and hardness (Rockwell) of the reinforced fluoropolymer alloys are 150 bar (kg / cm²), 220% and 558, respectively.

Example 17

Process for the preparation of extra high molecular fluorinated ethylene-propylene copolymer, e.g. B. in an autoclave with a volume of 130 l: 60 l of deionized water and 45 kg of starting monomers containing hexafluoropropylene in a weight ratio of 86.6% were used in this autoclave. The contents were heated to 55-57 ° C under a pressure of 22.0 bar (kg / cm²), then 25 ml of diisopropyl peroxydicarbonate was added. The copolymerization was carried out for three hours. 7.5 kg of dry copolymer powder with a hexafluoropropylene weight ratio of 14.5%, a melt viscosity of 1.8 × 10 6. P (poises) and a melt index of 0.3 g / 10 min can be obtained. A sample of the copolymer powder was pressed into a sheet having a thickness of 2 mm at 310 ° C, which had a tensile strength of 290 bar (kg / cm²) and an elongation of 320%, and a fatigue flexural strength of more than 2 x 10 & sup5; showed at room temperature.