Continuous coagulation process of polytetrafluoroethylene or modified polytetrafluoroethylene finely divided powder, polytetrafluoroethylene or modified polytetrafluoroethylene finely divided powders prepared by this method

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to the continuous method for preparing polytetrafluoroethylene (PTFE) or modified PTFE finely divided powders. The continuous method for preparing PTFE or modified PTFE finely divided powders involves the following steps: (a1) dilution of PTFE-latex of modified PTFE-latex prepared in polymerization in the dispersion-emulsion to the concentration from 5 to 25 wt.-% of PTFE or modified PTFE with possible filtration of the prepared diluted latex; (b1) molding latex with inert gas to the relative pressure with respect to atmosphere pressure in the range 3-40 kg/cm2 (0.3-4 MPa); (c1) addition of acid electrolyte solution to latex in the line-flow mixer at pH value 1-4; (d1) feeding the latex flow from the mixer through capillary tube under condition of turbulent current with the Reynolds number above 3000; (e1) gel prepared at step (d1) is coagulated onto granules at mechanical stirring with the specific power 1.5-10 kWt/m3 and stirring is maintained up to flotation of finely divided powder; (f1) below water is separated from the finely divided powder. PTFE of modified PTFE finely divided powders that can't be processed by thermal method prepared by abovementioned method show the following indices: apparent density is ≥ 470 g/l; average diameter of particles (D50) is above 200 mcm; distribution of particles by diameter determined as ratio between particles mass with diameter from 0.7 to 1.3 times with respect to average particles diameter and the total particles mass above 50%. Invention provides preparing powders without using the complex and expensive equipment, and powders possess the improved fluidity and show the apparent density and narrow distribution of particles by the diameter index.

EFFECT: improved preparing method.

9 cl, 1 tbl, 1 dwg, 6 ex

 

The present invention relates to a continuous method of coagulation of the polytetrafluoroethylene ((PTFE)(PTFE)), obtained by the method of polymerization in dispersion or emulsion, with getting wet fine powders of non-recoverable thermally PTFE (or modified PTFE).

More specifically, the invention relates to a continuous method of coagulation of fine powders of PTFE, including aggregation/gelation PTFE latex using capillary tubes and subsequent granulation (coagulation) with mechanical stirring.

Rest thermally fine powders of PTFE or modified PTFE, obtained by the method of the present invention, are characterized by high apparent density ≥470 g/l, a mean diameter (D50) more than 200 μm, preferably from 400 to 600 microns, and characterized by a narrow distribution of particle diameter, and the specified distribution, defined as the ratio between the mass of particles having a diameter in the range of 0.7 to 1.3 times the average diameter of particles and the total mass of the polymer particles is greater than 50%, preferably greater than or equal to 60%.

In the existing technique, it is known that fine powders of PTFE produced by polymerization in dispersion. In this way use a fairly high amount of the surface of the but-active substances with the to stabilize colloidal particles of PTFE, and the weak mixing used in the polymerization process, to avoid coagulation (precipitation) of the polymer. Then the latex obtained from the above method, coagulums, and the powder obtained by coagulation, called "fine powder". The traditional method of coagulation contains the following stages:

- dilution of the latex with water, perhaps adding a destabilizing electrolyte;

mechanical mixing of the latex with the formation of aggregates/gels;

- granulation (coagulation) units/gels under mechanical stirring;

flotation PTFE from water;

mechanical separation of the wet powder from coagulates water.

These fine powders of PTFE is processed by the method of extrusion sizing with obtaining molded products.

The method of extrusion sizing is much more productive and easily automated, a large part of the fine powders are free-flowing and have a high apparent density. In addition, the average particle diameter is preferably more than 400 μm, and the distribution of particle diameter, as defined above, should be at least above 50%, preferably greater than or equal to 60%, with improved fluidity.

In the modern technology world who have different ways of obtaining fine powders as periodic, and continuous way. In the case of periodic ways to get the apparent density of approximately 400 g/l (see comparative examples) or a little higher and the average particle diameter (D50) in the required interval. However, the fine powders have the disadvantage of having a distribution of particle diameter, as defined above, below 50%, and therefore are unsuitable. Another disadvantage of periodic methods is that, from the industry point of view, they are more expensive than continuous methods. Experts know that it is usually impossible periodic methods of obtaining fine powder PTFE convert to continuous methods.

In USP 3046263 described continuous method of coagulation of PTFE latexes containing the following stages:

- stage a strong mechanical agitation polymerization of latexes using specific capacity 1-100 must be selected to satisfy ×/gallon (196-19600 kJ/m3), preferably using a centrifugal pump with an average stay of latex in the pump 2C;

- aggregation or gelation when passing through the capillary tube having a hydraulic resistance of 0.5 to 20 psig (˜3,4-136 kPa);

- granulation in the presence of air under mechanical stirring with a power density of 0.25-50 CL· ×/gallon (49-9800 kJ/m3 );

- subsequent separation of fine PTFE powder from the water.

The disadvantage of this method is that the capillary tube is easily blocked, resulting method must often be interrupted for cleaning the capillary tube. In addition, it was found by the Applicant that at the first stage of obtaining the latex, which must be introduced into the capillary tube to gelation, there is a partial formation of pellets of PTFE, causing clogging centrifugal pump. This is an additional disadvantage of the above method.

Another continuous method, which avoids the disadvantages described in the previous patent, discussed in USP 5977295. In the specified way of the capillary tube is not used, since it is considered unsuitable for continuous way by the above-mentioned disadvantages. PTFE latex obtained from the polymerization in emulsion, served in wysokosciowe device having rotating elements for the units/gels (gel phase). Thus obtained gel phase is fed to the phase of coagulation in the column with the application of shear force to a gel phase. According to USP 5977295 in this way receive a high apparent density, good average particle diameter, but the distribution of particle diameter is not specified. The disadvantage of this method with the her is that is a very complex and expensive high shear device that requires a peripheral speed of the rotor of the order of 2-30 m/s and the free space between the stator and rotor of approximately 0.5 mm, It requires dilution with water on rotating parts for proper operation of the shear device and the described method. In addition, despite the fact that you use such a complex device, the shift is not completely homogeneous, so it is impossible to obtain a narrow distribution of particle diameter. This leads to the above-mentioned disadvantages.

Felt the need to have available a continuous method of getting wet PTFE fine powders, overcoming the disadvantages of the known prior art and do not require complex and costly devices for high shifts to reduce the heterogeneity of the obtained fine powders and allowing to obtain fine powders of PTFE with improved fluidity and high apparent density and a narrow distribution of particle diameter, as defined above, above 50%, preferably greater than or equal to 60%.

The object of the present invention is a continuous method of coagulation of fine powders of PTFE or modified PTFE containing:

A1) dilution in the lift latex PTFE or modificarea the aqueous PTFE, obtained by polymerization in a dispersion (emulsion) to a concentration of from 5 to 25% wt./wt. PTFE, preferably from 8 to 20% wt./wt. PTFE or modified PTFE; and possibly filtering the obtained diluted latex;

b1) obessolivanie latex in the lift with an inert gas, preferably air, to the relative pressure with respect to atmospheric pressure in the range of 3-40 kg/cm2(0.3 to 4 MPa), preferably from 5 to 20 kg/cm2(0.5 to 2 MPa) and more preferably from 7 to 15 kg/cm2(0.7 to-1.5 MPa);

C1) adding the acid electrolyte solution, preferably nitric acid to the latex of PTFE or modified PTFE in continuous mixer so that the pH is from 1 to 4, preferably from 1.5 to 3; the concentration of the latex and the pH are such as not to cause formation of aggregates/gels in the continuous mixer;

d1) the flow of latex from the mixer through a capillary tube under conditions of turbulent flow having a Reynolds number higher than 3000, preferably above 5000;

e1) granulation (coagulation) of the gel obtained in stage d1), under mechanical stirring with a power density of 1.5 to 10 kW/m3with keeping mixing before flotation of fine powder;

f1) the Department is below the water from the wet powder.

On stage d1) to obtain y the th turbulent flow of latex are preferably as follows:

- the capillary tube has an internal diameter that the total hydraulic resistance of the capillary tube in terms of the way causes a pressure drop between the ends of the capillary tubes from 3 to 40 kg/cm2(0.3 to 4 MPa), preferably from 5 to 20 kg/cm2(0.5 to 2 MPa) and more preferably from 7 to 15 kg/cm2(0.7 to-1.5 MPa);

- the length of the capillary tube is from 0.1 to 30 m, preferably from 0.3 to 15 m and more preferably from 1 to 10 m;

- speed/latex gels inside the capillary tube is in the range of 2-15 m/s;

the diameter of the capillary tube is usually from 2 to 20 mm, preferably from 3 to 10 mm.

In a preferred embodiment, the length of the capillary tube is in the range from 0.1 to 3 m, better still from 0.2 to 1 m

The combination of the diameter of the capillary tube, the concentration of the latex, the pH of the electrolyte and the linear velocity of latex through the capillary tube must be such as to provide a turbulent flow of latex inside the capillary tube.

On stage d1) is the aggregation/gelation. The length of the capillary tube, as defined above, is such as to ensure full aggregation/gelation of the latex and the absence of granule formation fine powder inside the capillary tube.

The drawing shows a preferred variant of the device containing the cap is Larney pipe, to produce the polymer gel from the original latex. The figures have the following meanings:

1 - inlet for latex.

2 - mixing chamber.

3 - pipe for feeding electrolyte.

4 - section converging from 2.

5 is a capillary tube.

6 - section differences.

7 - release gel.

Latex coming from 1, is mixed with the electrolyte coming from 3 in the mixing chamber 2. Then the latex is mixed with the electrolyte in the chamber 2, is supplied in section 4 connecting the mixing chamber 2 with capillary tube 5. The angle of the profile section of convergence 4 may be from about 5 to 15°preferably 10°. Then the latex mixture flows into the capillary tube 5, in which the gelation. The so formed gel takes place in section 6. Angle profile this section is not specifically limited, and in General ranges from 10 to 20°. The gel at the end of 6 through issue 7 enters the granulation device (stage E1) of the method of the invention).

Under units/gels is understood that the polymer particles are immersed in the liquid phase and are connected by transverse relationship so that they form a dense grid. Properties of aggregates/gels are significantly dependent on the interaction of these two components (polymer and liquid). The liquid prevents the transformation of the polymer network in a dense mass, and the polymer prevents the flow of segregated/gels. Depending on the chemical composition and other factors, the consistency of units/gels ranging from liquids to fairly hard - hard condition

At the end of stage b1), when pre-opressovannyh latex is discharged into the mixer stage C1), a second lift, which is fed into the latex, diluted in accordance with stage A1). When the first lift is emptied, latex, submitted to the second lift is at the end of stage b1), and therefore, the latex is applied again in the first lift.

At stage E1) are, for example, with the columns described in the prior art, in order to have a continuous way, for example, vessels that relate the height/diameter > 2, equipped with a stirrer (see the methods described in the above patents).

Fine powders of PTFE or modified PTFE, obtained by the method of the present invention are particularly suitable for processing by extrusion with sizing with obtaining molded products.

Under PTFE according to the present invention realize a homopolymer TPV, under the modified PTFE understand copolymers TPV with one or more comonomers having at least one unsaturation of ethylene type, in an amount of from 0 to 3 mol.%, preferably from 0.01 to 1 mol.%.

The comonomers that can be used are hydrogenated, and fluorinated type.

Among the hydrogenated comonomers may be mentioned ethylene, propylene, acrylic monomers, e.g. methyl methacrylate, (meth)acrylic acid, butyl acrylate, hydroxyethylmethacrylate, styrene monomers, such as styrene.

Among the fluorinated comonomers can be specified;

- C3-C8the perfluoroolefins, such as HEXAFLUOROPROPYLENE ((HFP)(FNV);

- hydrogenated With2-C8-ferritine, for example, viniferin ((VF) (VF)), vinylidenefluoride ((VDF) (WDF)), triptorelin, hexafluoroisobutene, perftorpolietilena CH2=CH=Rfwhere Rfis1-C6-perfluoroalkyl;

- C2-C8-chlorine-and/or bromo-and/or golftrolley, such as chlorotrifluoroethylene ((CTFE) (HTFA));

- (per)peralkaline ethers ((PAVE) (PAVE)) CF2=CFORfwhere Rfis1-C6-(TRANS)floralcy, for example, CF3C2F5With3F7;

- (per)peroxyacetylnitrate esters CF2=CFOX, where X represents C1-C12-alkyl or C1-C12-oxyalkyl or1-C12-(TRANS)peroxyacyl having one or more ether groups, for example PERFLUORO-2-propoxyphenyl;

- portixol, preferably peritoneoscopy;

- unpaired diene type:

CF2=CFOCF2CF2CF=CF2,

FX 1=CX2OCX3X4OCX2=CX1F,

where X1and X2the same or different from each other, represent F, Cl or H; X3and X4the same or different from each other, represent F or CF3that in the polymerization process cyclopolymerization;

- corviniana ethers ((MOVE)(SER)), General formula

CFXAI=CXAIOCF2ORAI(A-I)in which RAIis2-C6-a linear, branched or5-C6-cyclic (per)foralkyl group or2-C6-a linear, branched (per)peroxyacids containing from one to three oxygen atoms; when RAIis foralkyl or peroxyacetate, as stated above, it can contain from 1 to 2 atoms, equal or different, selected from the following: H, Cl, Br, I; XAI=f, H; the compounds of General formula:

CFXAI=CXAIOCF2OCF2CF2YAI(A-II)in which yAI=F, OCF3; -XAIas described above, are preferred; in particular, SER I, CF2=CFOCF2OCF2CF3(A-III) and SER II CF2=CFOCF2OCF2CF2OCF3(A-IV) are preferred.

Continuous method of the present invention, as described, allows to obtain fine powders of PTFE having a narrow distribution frequent the C diameter (as defined above), the resulting fine powders show improved fluidity. This property combined with a high apparent density and average diameter of the particles, preferably above 400 microns.

Continuous method of the invention gives fine powders with reproducible properties. In the capillary tube used in the method according to the present invention, clogging does not occur even after long periods of work. In addition, from a manufacturing point of view, the method does not require very expensive devices with high shear, as described above.

The following examples illustrate the invention but without limiting its scope.

Examples.

Methods of characterization.

The distribution of particle diameter (%).

The distribution of particle diameter is calculated by determining the relations of mass between particles, having a diameter in the range from 0.7 to 1.3 times the average diameter of the particles on the total weight of the particles and multiplying by 100. Particle diameter determined by laser scattering using an instrument Coulter LS 230. The device directly gives the distribution curve. According to the distribution curve can directly calculate the mass of the particle distribution having a diameter in the above range.

Determination of apparent density.

Use a method ASTM D4895-89.

Set is the average of particle diameters (D 50).

Fine powder PTFE is dispersed in water with nonionic surface-active agent Triton X100 and particle diameter determined by laser scattering using an instrument Coulter LS 230. The device directly gives the distribution curve at which the device calculates the D50and distribution, as described above.

The determination of the density variance.

The density of dispersion calculated as the average density by the following formula:

in which

x is the percentage by mass of water in the dispersion;

y is the percentage by weight of PTFE in the dispersion.

The calculation of the viscosity.

The viscosity of the dispersion is determined by the following formula (formula Einstein):

viscosityenvironment×(1+2,5F),

in which

viscosityenvironmentis the viscosity of water, and

F is the volumetric concentration of PTFE in the dispersion.

Example A.

Getting PTFE latex.

600 parts by weight of degassed water, 1,33 including an aqueous solution of performanta of ammonia at 30% wt./wt. in performante ammonium, 3 hours an aqueous solution of ammonium persulfate at 0.2% wt./wt. the ammonium persulfate is served in a reactor equipped with a mechanical stirrer, pre-summed up by the vacuum. The reactor presoviet TPV to a pressure of 20 bar (2 MPa) when temperature is 30° C. Then served 3 o'clock aqueous solution of (NH4)2Fe(SO4)2×6N2(Salt Mora) at a concentration of 0.3 wt.%.

When the pressure in the reactor is reduced to 0.5 bar (5×104PA), start feeding TPV in order to maintain a constant pressure of 20 bar inside the reactor. The average internal temperature of the reactor is increased to 85°With speed equal to 1°C/min In the reaction in the reactor serves to 3.5 hours above aqueous solution of performanta ammonium (surfactant).

After 50 min after the start of supply of the TPV its stop, the reactor ventilate, cool and finally unloaded. Unloaded latex has a concentration of 510 g PTFE/l of water.

Example 1.

The method according to the present invention when diluted at the stage A1) latex to a concentration of 120 g/l, using on stage b1) pressure 15 bar (1.5 MPa) and at stage d1) capillary tube length 7 m (diameter 3 mm).

The latex obtained as in example a, diluted in Elevator (lift 1)having a capacity of 500 l, to obtain a concentration of 120 g/l (10.7% of dry matter), and the latex is diluted so that the temperature is maintained at 22°C.

After dilution lift 1 presoviet compressed air at a pressure of 1.5 MPa relative to the atmospheric pressure.

Latex are mixed in a continuous mixer with a solution of HNO 3when 3 wt.% and get a latex having a concentration of 110 g/l with a pH of 2, and the temperature is 22°C.

The aggregation/gelation of the latex in the process of the last mentioned stage is not observed.

Latex enable flow through a capillary tube having a diameter of 3 mm, a length of 7 m from a speed of 6.4 m/s When working in this way ensures a complete aggregation/gelation of the latex in the absence of granules coagulated polymer (fine powder).

The obtained gel granularit under mechanical stirring, with a specific power of 2.1 kW/m3to complete granulation and flotation of fine powder. Wet fine powder is separated from the water and dried.

The obtained fine powder has properties apparent density, average particle diameter and distribution of particle diameter, as shown in the table.

When the content of the Elevator 1 ends, enter lift 2, having the same capacity with lift 1 in order to have a continuous method.

Example 2.

The method according to the present invention when diluted at the stage A1) latex to a concentration of 120 g/l, using on stage b1) pressure 10 bar (1.0 MPa) and at stage d1) capillary tube length 7 m (diameter 3 mm).

Working as in example 1, but with the following changes.

Latex, receive the config, as in example a, diluted in the lift with capacity 500 l, to obtain a concentration of 120 g/l (10.7% of dry matter), and the latex is diluted at a temperature of 22°C.

After dilution lift presoviet compressed air at 1 MPa relative to the atmospheric pressure.

Latex are mixed in a continuous mixer with a solution of HNO3when 3 wt.% and get a latex having a concentration of 110 g/l with a pH of 2, and the temperature is 22°C. In these conditions, the gelation of the latex is missing.

The latex is then able to flow through a capillary tube having a diameter of 3 mm, a length of 7 m from a speed of 5 m/s When working in this way ensures complete gelation of the latex in the absence of granules coagulated polymer (fine powder).

The obtained gel granularit under mechanical stirring, with a power density of 2.5 kW/m3to complete granulation and flotation of fine powder. Wet fine powder is separated from the water and dried.

The obtained fine powder has properties apparent density, average particle diameter and distribution of particle diameter, as shown in the table.

Example 3.

The method according to the present invention when diluted at the stage A1) latex to a concentration of 80 g/l, using on stage b1) pressure is of 15 bar (1.5 MPa) and at stage d1) capillary tube length of 19 m (diameter 3 mm).

Working as in example 1, but with the following changes.

The latex obtained as in example a, diluted in the lift with capacity 500 l, to obtain a concentration of 80 g/l (7.4% of dry matter), and the latex is diluted at a constant temperature of 22°C.

After dilution lift presoviet compressed air at a pressure of 1.5 MPa relative to the atmospheric pressure.

Latex are mixed in a continuous mixer with a solution of HNO3when 3 wt.% and get a latex having a concentration of 75 g/l with a pH of 2.5, and the temperature is 22°C. In these conditions, the gelation of the latex is missing.

Latex enable flow through a capillary tube having a diameter of 3 mm, a length of 19 m, with a speed of 4 m/s When working in this way ensures complete gelation of the latex in the absence of granules coagulated polymer (fine powder).

The obtained gel granularit under mechanical stirring, with specific power 2.2 kW/m3to complete granulation and flotation of fine powder. Wet fine powder is separated from the water and dried.

The obtained fine powder has properties apparent density, average particle diameter and distribution of particle diameter, as shown in the table.

Example 1C (comparative).

Periodic pic is b obtain fine powder PTFE latex according to the prior art without capillary tubes.

In a 50-liter reactor load 15 l of the latex from example a and water to obtain 22 l latex having a concentration of 160 g/l (13.7% of dry matter). The latex is diluted so that after dilution the temperature is 22°C.

To the mixture was added with stirring a solution of HNO3when 20 wt.% in order to bring the pH of the latex to 2.5.

Mechanical agitation causes the aggregation of colloidal particles. First is gelation, and then granulation and finally flotation coagulated powder. The obtained fine powder is separated from the water and dried.

The obtained fine powder has properties apparent density, average particle diameter and distribution of particle diameter, as shown in the table.

Get powder having an apparent density below 470 g/l and the distribution of particle diameter of below 50%.

Example 2 (comparative).

Continuous method according to USP 3046263.

Working as in example 1, but with the following changes.

The latex obtained in example a And diluted to obtain a concentration of 120 g/l (10.7% of dry matter). The latex is diluted so that the final temperature after dilution is 22°C. To this mixture with stirring, a solution of HNO3when 20 wt.% in order to bring the pH of the latex to 2.5.

Latex is served in a capillary tube (diameter 3 mm, length 7 m) with ISOE what Itanium centrifugal pump. When working this way, the pump and the capillary tube are sealed, and it becomes impossible to proceed further.

Table. The concentration of the diluted latex, the relative pressure in the lift, the pH after dilution in the mixer with a solution of HNO3pH and length of the capillary tube and the relevant properties of the obtained fine powders: apparent density, average particle diameter (D50) and wt.% powder particles having a diameter of from 0.7 to 1.3 times the average particle diameter of powders.

470
ExampleConc. latex after Rabaul. (g/l)Rel. pressure (bar)pHLength capill. pipe (m)Each. density (kg/m3)D50(µm)The distribution of particles (wt.%)
1120152751042065
2120102748047060
380152,51952050068
1C EUR.160-2,5-41045
2C EUR.120-2,57---

1. Continuous production of fine powders of polytetrafluoroethylene (PTFE) or a modified polytetrafluoroethylene (PTFE), which

A1) diluted PTFE latex or modified PTFE latex obtained by polymerization in dispersion-emulsion to a concentration of from 5 to 25% wt./wt. PTFE or modified PTFE; and may filter the received diluted latex;

b1) pressed latex inert gas to a relative pressure with respect to atmospheric pressure in the range of 3-40 kg/cm2(0.3 to 4 MPa);

C1) add the acid electrolyte solution to the latex in the continuous mixer, so that the pH is from 1 to 4;

d1) serves the flow of latex from the mixer through a capillary tube under conditions of turbulent flow having a Reynolds number above 3000;

e1) coagulated in the granules of the gel obtained in stage d1) under mechanical stirring with a power density of 1.5 to 10 kW/m3support mixing before flotation of fine powder;

f1) is located below the water from the fine powder.

2. The method according to claim 1, wherein the inert gas is air./p>

3. The method according to claim 1, wherein the acid electrolyte solution is nitric acid.

4. The method according to claim 1, wherein to obtain turbulent flow of latex on stage d1) are as follows:

the total hydraulic resistance of the capillary tube in terms of the way causes a pressure drop between the ends of the capillary tubes from 3 to 40 kg/cm2(0.3 to 4 MPa);

the length of the capillary tube is from 0.1 to 30 m;

speed/latex gels inside the capillary tube is in the range of 2-15 m/s;

the diameter of the capillary tube is from 2 to 20 mm.

5. The method according to claims 1 to 4, in which polytetrafluoroethylene (PTFE) or a modified polytetrafluoroethylene (PTFE) contain one or more comonomers hydrogenated and/or fluorinated type, having at least one unsaturation of ethylene type, in an amount of from 0 to 3 mol.%, preferably, from 0.01 to 1 mol.%.

6. The method according to claim 5, in which the hydrogenated comonomers are selected from ethylene, propylene, acrylic monomers, preferably, methyl methacrylate, (meth)acrylic acid, butyl acrylate, hydroxyethylmethacrylate, styrene monomers.

7. The method according to claim 5, in which the fluorinated comonomers are selected from the following:

With3-C8-perfluoroolefins, preferably HEXAFLUOROPROPYLENE ((HFP)(FNV);

p num="160"> hydrogenated With2-C8-pterolepis selected from winifrida ((VF)(VF)), vinylidenefluoride ((VDF) (WDF)), triptorelin, hexafluoroisobutene and performancerating CH2=CH=Rfwhere Rfrepresents C1-C6-perfluoroalkyl;

With2-C8-chlorine - and/or bromo - and/or golftrolley, preferably, chlorotrifluorethylene ((CTFE) (HTFA));

(per)peralkaline ethers ((PAVE) (PAVE)) CF2=CFORfwhere Rfis1-C6-(TRANS)foralkyl, preferably, CF3C2F5With3F7;

(per)peroxyacetylnitrate esters CF2=CFOX, where X represents C1-C12-alkyl, C1-C12-oxyalkyl or1-C12-(TRANS)peroxyacyl having one or more ether groups, preferably PERFLUORO-2-propoxyphenyl;

portixol, preferably, peritoneoscopy;

unpaired diene type:

CF2=CFOCF2CF2CF=CF2,

CFX1=CX2OCX3X4OCX2=CX1F,

where X1and X2identical or different, represent F, Cl or H; X3and X4identical or different, represent F or CF3that in the polymerization process cyclopolymerization;

corviniana ethers ((MOVE)(SER)), General formula

CFXAI=X AIOCF2ORAI(A-I)in which RAIis2-C6-a linear, branched or5-C6-cyclic (per)alkyl fluoride group or2-C6-a linear, branched (per)peroxyacyl group containing from one to three oxygen atoms; when RAIrepresents alkyl fluoride or peroxyacyl group, as described above, it can contain from 1 to 2 atoms, equal or different, selected from the following: H, Cl, Br, I; XAI=F, H; the compounds of General formula

CFXAI=CXAIOCF2OCF2CF2YAI(A-II)in which YAI=F, OCF3; XAIas described above, are preferred; in particular, SER I, CF2=CFOCF2OCF2CF3(A-III) and SER II CF2=CFOCF2OCF2CF2OCF3(A-IV) are preferred.

8. Rest thermally fine powders of polytetrafluoroethylene (PTFE) or a modified polytetrafluoroethylene (PTFE)obtained by the method according to claims 1 to 7, with

apparent density ≥470 g/l;

average particle diameter (D50) more than 200 microns;

the distribution of particle diameter, defined as the ratio between the mass of particles having a diameter of from 0.7 to 1.3 times the average diameter of particles and the total mass of particles above 50%./p>

9. Rest thermally fine powders of polytetrafluoroethylene (PTFE) or a modified polytetrafluoroethylene (PTFE) of claim 8, having: average particle diameter (D50) more than 400 to 600 μm; the distribution of particle diameter, defined as the ratio between the mass of particles having a diameter of from 0.7 to 1.3 times the average diameter of particles and the total mass of particles greater than or equal to 60%.



 

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18 cl, 2 tbl, 14 ex

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to the continuous method for preparing polytetrafluoroethylene (PTFE) or modified PTFE finely divided powders. The continuous method for preparing PTFE or modified PTFE finely divided powders involves the following steps: (a1) dilution of PTFE-latex of modified PTFE-latex prepared in polymerization in the dispersion-emulsion to the concentration from 5 to 25 wt.-% of PTFE or modified PTFE with possible filtration of the prepared diluted latex; (b1) molding latex with inert gas to the relative pressure with respect to atmosphere pressure in the range 3-40 kg/cm2 (0.3-4 MPa); (c1) addition of acid electrolyte solution to latex in the line-flow mixer at pH value 1-4; (d1) feeding the latex flow from the mixer through capillary tube under condition of turbulent current with the Reynolds number above 3000; (e1) gel prepared at step (d1) is coagulated onto granules at mechanical stirring with the specific power 1.5-10 kWt/m3 and stirring is maintained up to flotation of finely divided powder; (f1) below water is separated from the finely divided powder. PTFE of modified PTFE finely divided powders that can't be processed by thermal method prepared by abovementioned method show the following indices: apparent density is ≥ 470 g/l; average diameter of particles (D50) is above 200 mcm; distribution of particles by diameter determined as ratio between particles mass with diameter from 0.7 to 1.3 times with respect to average particles diameter and the total particles mass above 50%. Invention provides preparing powders without using the complex and expensive equipment, and powders possess the improved fluidity and show the apparent density and narrow distribution of particles by the diameter index.

EFFECT: improved preparing method.

9 cl, 1 tbl, 1 dwg, 6 ex

FIELD: chemistry.

SUBSTANCE: present invention refers to emulsion rubber recovery from latex and can be used in chemical rubber industry. There is disclosed method of emulsion rubber recovery from latex through coagulation with using bivalent metal salts from magnesium chloride, magnesium sulphate, calcium chloride. Thereafter rubber crumb is separated from serum, it is followed with wringing and drying, differing that mixing latex and bivalent metal salt is preceded with pre-acidification of latex with diluted sulphuric acid concentrated 0.3-4% to pH 2.5-7.0 units. Within mixing range of acidulous latex and bivalent metal salt, concentration of the latter is kept within 0.05-0.8%, while produced rubber crumb is wrung out thus maintaining pH of wringing water within 2.5-6.9 units with sulphuric acid supplied to pre-acidification of latex.

EFFECT: making uniform rubber compatible with the requirements of related GOST and rubber TOR specifications in characteristics - mass fraction of organic acid soaps and mass fraction of organic acids, improved technological effectiveness and ecological compatibility of process.

2 cl, 1 tbl, 14 ex

FIELD: chemistry.

SUBSTANCE: rubber is extracted from latex continuously by mixing latex with a coagulant. Consumption of coagulant is varied depending on the given turbidity value of serum (primary serum), which is maintained by the amount of coagulant fed. The given turbidity value of primary serum is adjusted depending on the turbidity of the serum released (secondary serum) towards the minimum consumption of coagulant to obtain minimum turbidity of the released serum.

EFFECT: method of controlling the coagulation process enables to reduce contamination of waste water through loss of partially coagulated latex with minimum consumption of coagulants.

2 dwg, 6 ex

FIELD: chemistry.

SUBSTANCE: method of extracting butadiene-nitrile rubber from latex is carried out by feeding sodium sulphite or sodium bisulphite or sodium pyrosulphite in amount of 0.05-0.8 wt % per latex, into a stream of latex degassed beforehand, into which an antioxidant emulsion is also fed. Further, the stream of latex, containing sulphite, is directed into a coagulation apparatus into which aqueous sulphuric acid and an organic amine coagulant in form of a quaternary polymer ammonium salt are also simultaneously fed, said salt being selected from: polydimethyl diallyl ammonium chloride, a methacrylamide and dimethyl aminoethyl methacrylate hydrochloride copolymer, and polydiethyl aminoethyl methacrylate hydrochloride. The amount of the polymer ammonium salt varies from 0.2-0.5 wt %, per rubber, depending on content of leukanol content in latex in the range of 0.1-0.4 wt %, per rubber, at coagulation pH 3-6 and temperature 30-70°C.

EFFECT: invention improves environmental friendliness of the process, specifically reduces content of unreacted monomer - free acrylic acid nitrile, avoids excess synthetic coagulant and the amount of salt used for coagulation.

3 tbl, 7 ex

FIELD: chemistry.

SUBSTANCE: described is nitrile rubber which contains repeating units of at least one α,β-unsaturated nitrile and at least one conjugated diene, and also contains magnesium ions in concentration of 100-180 ppm and calcium ions in concentration of 50-145 ppm, respectively, with respect to nitrile rubber. Described is a method of producing said nitrile rubber via emulsion polymerisation of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerisable monomers selected from a group comprising α,β-unsaturated mono- or dicarboxylic acids, esters and amides thereof, in the presence of at least one molecular weight regulator, with the latex which is obtained during polymerisation and contains nitrile rubber being subjected to coagulation and the coagulated nitrile rubber subsequently being washed, wherein (i) the latex obtained during emulsion polymerisation has a pH of at least 6 before the coagulation, (ii) coagulation of the latex is carried out using at least one magnesium salt, up to 40 wt % of which is optionally replaced with a calcium salt, as precipitant, (iii) the coprecipitant used during coagulation of latex is gelatine, (iv) temperature of latex before reacting with the coprecipitant (iii) is kept higher than 50°C, and then raised to 100°C, and (v) coagulation of latex and/or treatment of the coagulated latex is carried out using water containing calcium ions, under the condition that coagulation is carried out without a calcium salt as a precipitant. Treatment of nitrile rubber obtained using the method described above is described, wherein nitrile rubber is subjected to (i) either a metathesis reaction only or (ii) a metathesis reaction and subsequent hydrogenation, or (iii) hydrogenation only, to obtain optionally hydrogenated nitrile rubber. Described is use of said nitrile rubber, optionally hydrogenated nitrile rubber, to obtain vulcanised mixtures, obtained by mixing at least one nitrile rubber or at least one optionally hydrogenated nitrile rubber, at least one cross-linking agent and optionally other additives. Described is a method of making moulded articles, such as a seal, a cap, a hose or a diaphragm, in particular an O-ring seal, a flat seal, a dynamic seal, a sealing sleeve, a sealing cap, a cap for protection from dust, a plug seal, a thermal insulation hose (with or without a PVC additive), an oil cooler hose, an air hose, a servo control hose or a pump diaphragm, through vulcanisation during moulding, via pressure casting of said vulcanised mixture.

EFFECT: special nitrile rubber, characterised by high stability during storage and high rate of vulcanisation is obtained.

25 cl, 15 tbl, 38 ex

FIELD: chemistry.

SUBSTANCE: described is nitrile rubber which contains repeating units of at least one α,β-unsaturated nitrile and at least one conjugated diene and has chlorine content in the range of 4 to 25 ppm with respect to nitrile rubber. Described is a method of producing said nitrile rubber by emulsion polymerisation of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more other copolymerisable monomers selected from a group comprising α,β-unsaturated mono- or dicarboxylic acids, esters and amides thereof, in the presence of a molecular weight regulator, with the latex which is obtained during polymerisation and contains nitrile rubber being subjected to coagulation and the coagulated nitrile rubber subsequently being washed, wherein (i) the latex obtained during emulsion polymerisation has a pH of at least 6 before the coagulation, (ii) coagulation of the latex is carried out using at least one salt of a mono-, di- or trivalent metal, which is optionally a chloride, as precipitant, (iii) coagulation of the latex is carried out in the presence of polyvinyl acetate, which is optionally partially or fully saponified, as coprecipitant, and (iv) coagulation of latex and/or treatment of the coagulated latex is carried out using water containing chloride ions under the condition that the salt of the mono-, di- or trivalent metal (ii) is not a chloride. A method of treating nitrile rubber obtained using the method described above is described, wherein nitrile rubber is subjected to (i) either a metathesis reaction only or (ii) a metathesis reaction and subsequent hydrogenation, or (iii) hydrogenation only, to obtain optionally hydrogenated nitrile rubber. Described is use of said nitrile rubber, optionally hydrogenated nitrile rubber, to obtain vulcanised mixtures, obtained by mixing at least one nitrile rubber or at least one optionally hydrogenated nitrile rubber, at least one cross-linking agent and optionally other additives. Described is a method of making moulded articles in form of a seal, a cap, a hose or a diaphragm, in particular an O-ring seal, a flat seal, a dynamic seal, a sealing sleeve, a sealing cap, an oil cooler hose, a hydraulic booster hose, an air conditioner hose, a thermal insulation hose, a diaphragm for hydro bearings or a diaphragm for a diaphragm pump, through vulcanisation during moulding, preferably via pressure casting of said vulcanised mixture.

EFFECT: nitrile rubber characterised by high stability during storage and high rate of vulcanisation are obtained, as well as with a preferable profile of properties, mainly with respect to contact of moulded articles based on such vulcanised rubber with metal structural components.

25 cl, 15 tbl, 5 dwg, 5 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing fine polytetrafluoroethylene powder, as well as fine powder obtained using said method. The method of producing fine polytetrafluoroethylene powder involves emulsion polymerisation of tetrafluoroethylene in the presence of an aqueous medium, a fluorinated surfactant and a radical polymerisation initiator to obtain an aqueous emulsion of polytetrafluoroethylene and coagulation thereof in the presence of at least one apparent density-reducing compound selected from a group consisting of ammonia, an ammonium salt and urea, in amount ranging from 0.4 to 10 pts.wt per 100 pts.wt polytetrafluoroethylene. The fine polytetrafluoroethylene powder obtained using said method has standard specific mass from 2.140 to 2.180 and paste extrusion pressure from 10 to 25 MPa.

EFFECT: method of obtaining fine polytetrafluoroethylene powder which is capable of paste extrusion at low pressure using a simple method.

10 cl, 1 tbl, 10 ex

Nitrile rubber // 2479591

FIELD: chemistry.

SUBSTANCE: nitrile rubber contains repeating units of at least one α,β-unsaturated nitrile and at least one conjugated diene and has ionic index in the range of 7-26 ppm×mol/g. The nitrile rubber is obtained by emulsion polymerisation. The obtained latex, which contains nitrile rubber, is coagulated and the coagulated nitrile rubber is washed. Polymerisation is carried out in the presence of at least one alkylthiol. Before coagulation, the pH of the latex is set to at least 6, and coagulation is then carried out in the presence of at least one salt of a monovalent metal. The latex coagulation temperature ranges from 60 to 90°C and the washing temperature ranges from 50 to 90°C. The obtained nitrile rubber is used to obtain curable mixtures which contain said rubber and at least one cross-linking agent. The curable mixtures are cured by moulding to obtain moulded articles.

EFFECT: nitrile rubber has excellent curing rate and exceptional properties of cured products.

26 cl, 7 tbl, 13 ex

Nitrile rubbers // 2491296

FIELD: chemistry.

SUBSTANCE: invention relates to nitrile rubber, method of its obtaining and products, obtained from it. Claimed nitrile rubber contains structure repeat units of, at least, one α,β- unsaturated nitrile and, at least, one conjugated diene, and has ion indicator in range 0-60 ppm×mole/g. Nitrile rubber is obtained by emulsion polymerisation. Obtained latex, which contains nitrile rubber, is subjected to coagulation, and then coagulated nitrile rubber is washed. Polymerisation is carried out in presence of, at least, one alkylthiolate. Before coagulation value of latex pH is set at level, at least, 6, and then is coagulated in presence of, at least, one magnesium salt. Temperature of latex before adding at least one salt of magnesium is set at value 45°C. Obtained nitrile rubber is applied for obtaining capable of vulcanisation mixtures, which contain claimed rubber, at least, one linking agent and, if necessary, additional target additives to rubbers. Capable of vulcanisation mixtures are vulcanised by casting with obtaining cast products.

EFFECT: claimed nitrile rubbers have exclusive speed of vulcanisation, as well as exclusive properties of vulcanisates.

24 cl, 13 tbl, 17 ex

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to the continuous method for preparing polytetrafluoroethylene (PTFE) or modified PTFE finely divided powders. The continuous method for preparing PTFE or modified PTFE finely divided powders involves the following steps: (a1) dilution of PTFE-latex of modified PTFE-latex prepared in polymerization in the dispersion-emulsion to the concentration from 5 to 25 wt.-% of PTFE or modified PTFE with possible filtration of the prepared diluted latex; (b1) molding latex with inert gas to the relative pressure with respect to atmosphere pressure in the range 3-40 kg/cm2 (0.3-4 MPa); (c1) addition of acid electrolyte solution to latex in the line-flow mixer at pH value 1-4; (d1) feeding the latex flow from the mixer through capillary tube under condition of turbulent current with the Reynolds number above 3000; (e1) gel prepared at step (d1) is coagulated onto granules at mechanical stirring with the specific power 1.5-10 kWt/m3 and stirring is maintained up to flotation of finely divided powder; (f1) below water is separated from the finely divided powder. PTFE of modified PTFE finely divided powders that can't be processed by thermal method prepared by abovementioned method show the following indices: apparent density is ≥ 470 g/l; average diameter of particles (D50) is above 200 mcm; distribution of particles by diameter determined as ratio between particles mass with diameter from 0.7 to 1.3 times with respect to average particles diameter and the total particles mass above 50%. Invention provides preparing powders without using the complex and expensive equipment, and powders possess the improved fluidity and show the apparent density and narrow distribution of particles by the diameter index.

EFFECT: improved preparing method.

9 cl, 1 tbl, 1 dwg, 6 ex

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