Preparation method of raw fluororubber (FKM) for tube extrusion

Abstract

The invention discloses a preparation method of raw fluororubber (FKM) for tube extrusion, and relates to the technical field of fluorine-containing polymers. The process comprises the following two steps: S1, adding high-purity water, a surfactant and a molecular weight regulator into a polymerization kettle, adjusting the temperature, adding a vinylidene fluoride, tetrafluoroethylene and perfluoropropylene mixed monomer and an initiator solution, and carrying out copolymerization reaction under specific pressure and temperature; and S2, after the polymerization reaction begins, continuously adding the mixed monomer, maintaining the pressure and the temperature, timely adding a molecular weight regulator and an auxiliary agent, stopping adding and terminating the reaction when the addition amount of the monomer reaches a specified range, recovering the unreacted monomer, and carrying out condensation, washing and drying to obtain the raw fluororubber (FKM) product for extruding the tube.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing polymers, in particular to a method for preparing fluorine rubber (FKM) for extruding pipes. Background Art

[0002] At present, there is production and research of ternary fluororubber for extruded tubes abroad. This technology is applied to the research and development of extruded fluororubber for automobile fuel pipes. The main foreign manufacturers are: DuPont's 9217, Japan Daikin G558, 3M's 5840, etc.

[0003] Patent document CN110078857B discloses a method for preparing fluororubber raw rubber, which comprises mixing fluorine-containing carbon carboxylate and ethylene glycol monomethyl ether to obtain a composite dispersant microemulsion; then adding high-purity water, pH regulator, composite dispersant microemulsion, and vulcanization point monomer into a reactor and stirring according to weight; then heating the reactor to 50-100°C, adding polymerization monomers to the reactor until the pressure in the reactor is 1-5 MPa, adding 20-50 parts of initiator to carry out polymerization reaction, and maintaining the reaction pressure constant by adding polymerization monomers during the reaction process, and adding 30-50 parts of chain transfer agent when the conversion rate of polymerization monomers is 30-40%; finally, when the solid content of the reaction liquid reaches 20-40%, the reaction is terminated, and the obtained polymer emulsion is subjected to electrolyte coagulation, washed, and dried to obtain a fluororubber raw rubber product. However, the product is not suitable for extrusion pipes.

[0004] At present, there is no manufacturer in China that can produce fluororubber for extruded fuel hoses. The domestic production of fluororubber is mainly compression molding, which makes it difficult to make fuel hoses and the efficiency of manufacturing is low. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing fluororubber raw rubber (FKM) for extruded pipes. By using this technology, ternary fluororubber with a fluorine content of ≥68% and a molecular weight distribution of M w / M n =3~20.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing fluororubber raw rubber (FKM) for extruded tubes, the operating steps are as follows:

[0008] S1: Add 2000-3000 parts of high-purity water to the polymerization kettle according to weight parts, start stirring, control the speed to 10-120rpm, add 10-50 parts of surfactant, add 0-10 parts of molecular weight regulator, adjust the temperature of the polymerization kettle to 70-95°C, add 1 mixed monomer of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene, make the pressure in the reactor reach 1.5-3.0MPa, add 1-10 parts of initiator solution to the reactor, and initiate copolymerization reaction;

[0009] S2: After the polymerization reaction starts, a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added into the polymerization kettle, the pressure of the reactor is maintained at 1.5-3.0 MPa, and the reaction temperature is controlled at 70-95°C. When the amount of the mixed monomer added reaches 300-700 kg, 0-10 parts of a molecular weight regulator and a molecular weight regulator auxiliary are added. When the amount of the mixed monomer added reaches 800-1000 parts, the addition of monomers and initiators is stopped to terminate the copolymerization reaction. After the unreacted monomers in the polymerization kettle are recovered, a fluororubber emulsion is obtained, and after coagulation, washing and drying, a fluororubber raw rubber (FKM) product for extruded pipes is obtained.

[0010] The surfactant is a trimer acid, a perfluoropolyether carboxylic acid or a mixture of the two, which is an aqueous solution with a concentration of 10-30%.

[0011] The molecular weight regulator is straight-chain alkane, branched alkane, or ester.

[0012] The straight-chain alkane molecular formula C n H 2n+2 , wherein n=2-10; the branched alkane molecular formula C n H 2n+2 , wherein n=4-10; selected from n-hexane (C 6 H 14 ), n-octane (C 8 H 18 ), n-decane (C 10 H 22 ) at least one of.

[0013] The amount of the molecular weight regulator additive added is 2-5wt% of the molecular weight regulator.

[0014] The preparation method of the molecular weight regulator auxiliary agent is:

[0015] Step 1: Amine addition reaction 1

[0016] Raw material ratio: dioctadecylamine: 25-50 parts; DMF: 300-500 parts; (+)-Ipc2B (allyl) borane: 14-33 parts, tetramethylguanidine: 2-5 parts;

[0017] Reaction conditions: Mix and stir and heat to 60-70°C; react at this temperature for 30-50 minutes;

[0018] Step 2: Amine addition reaction 2

[0019] Added raw materials: allyl dibutyltin chloride: 0.02-0.2 parts;

[0020] Reaction conditions: maintain the temperature at 60-70°C; continue the reaction for 120-180 minutes;

[0021] Post-treatment: DMF is removed by distillation to finally obtain the molecular weight regulator auxiliary.

[0022] The above molecular weight regulator additive reaction mechanism:

[0023] Dioctadecylamine reacts with (+)-Ipc2B (allyl) borane in the presence of tetramethylguanidine to form a dioctadecyl compound containing borane and butyltin chloride. This process involves two main steps:

[0024] Addition reaction: Under the catalysis of tetramethylguanidine, dioctadecylamine and (+)-Ipc2B (allyl) borane undergo an addition reaction. In this process, tetramethylguanidine acts as an alkaline catalyst, promoting the breaking of the boron-hydrogen bond and the subsequent addition reaction.

[0025] Further addition: Add allyl dibutyltin chloride to the product generated in the first step, and continue the addition reaction under the catalysis of tetramethylguanidine. Finally, a dioctadecyl compound containing borane and butyltin chloride is obtained.

[0026] The initiator is an aqueous solution or a mixed solution of ammonium persulfate or potassium persulfate, and the concentration of the initiator solution is 0.1-5%.

[0027] The ratio of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene in the mixed monomer 1 is (30-50):(10-35):(30-50).

[0028] The ratio of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene in the mixed monomer 2 is (40-70):(5-25):(10-30).

[0029] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0030] 1. The present invention solves the problem of higher strength performance and better flow extrusion performance required for tube extrusion rubber by adjusting the molecular weight distribution;

[0031] 2. The production of the ternary rubber with a high fluorine content in the present invention solves the problem that the extruded tube fluororubber requires both rapid vulcanization and a high fluorine content and good medium resistance.

[0032] 3. In the copolymerization of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene, the dioctadecyl compound containing borane and butyltin chloride is used as a chain transfer agent. It effectively controls the molecular weight of the polymer and prevents over-polymerization by quickly reacting with the growing chain free radicals, thereby maintaining the stability and controllability of the polymerization reaction.

[0033] Improve polymerization efficiency: The use of this chain transfer agent can not only accurately control the molecular weight distribution of the polymer, but also improve the efficiency of the polymerization reaction. Due to its efficient chain transfer ability, the free radical concentration in the polymerization process is kept at a relatively stable level, thereby improving the polymerization rate and product quality.

[0034] In summary, the addition reaction of dioctadecylamine with (+)-Ipc2B(allyl)borane catalyzed by tetramethylguanidine and its application in the copolymerization of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene demonstrates the importance of efficient chain transfer agents in controlling polymerization reactions and improving polymer properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the molecular weight distribution diagram of the fluororubber raw rubber of Example 1. DETAILED DESCRIPTION

[0036] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0037] Example 1

[0038] A method for preparing fluororubber (FKM) for extruded tubes comprises the following steps:

[0039] S1: Add 2500 kg of high-purity water to the polymerization kettle, start stirring, control the speed to 40 rpm, add 20 kg of surfactant perfluoro-2,5-dimethyl-3,6-dioxanononanoic acid ammonium salt, add 1 kg of molecular weight regulator diethyl malonate, adjust the temperature of the polymerization kettle to 70°C, add 1 (35:20:45) of vinylidene fluoride, tetrafluoroethylene, and perfluoropropylene mixed monomers to make the pressure in the reactor reach 1.5 MPa, add 1 kg of initiator solution to the reactor to initiate the copolymerization reaction.

[0040] S2: After the polymerization reaction starts, a mixed monomer 2 (55:20:25) of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added to the polymerization kettle, the pressure of the reactor is maintained at 1.5MPa, and the reaction temperature is controlled at 75°C. When the amount of the mixed monomer added reaches 300kg, 10kg of diethyl malonate and 0.2kg of molecular weight regulator are added. When the amount of the mixed monomer added reaches 1000kg, the monomer and initiator are stopped, the copolymerization reaction is terminated, and the unreacted monomer in the polymerization kettle is recovered to obtain a fluororubber emulsion. After condensation, washing and drying, a fluororubber raw rubber (FKM) product for extrusion pipes is obtained.

[0041] Wherein, the preparation method of molecular weight regulator auxiliary agent is:

[0042] Step 1: Amine addition reaction 1

[0043] Raw material ratio: dioctadecylamine: 25kg; DMF: 300kg; (+)-Ipc2B (allyl) borane: 14kg, tetramethylguanidine: 2kg;

[0044] Reaction conditions: Mix and stir and heat to 60°C; react at this temperature for 30 minutes;

[0045] Step 2: Amine addition reaction 2

[0046] Add raw materials: allyl dibutyltin chloride: 0.02kg;

[0047] Reaction conditions: maintain the temperature at 60°C; continue the reaction for 120 minutes;

[0048] Post-treatment: DMF is removed by distillation to finally obtain the molecular weight regulator auxiliary.

[0049] Example 2

[0050] A method for preparing fluororubber (FKM) for extruded tubes comprises the following steps:

[0051] S1: Add 2000 kg of high-purity water to the polymerization kettle, start stirring, control the speed to 60 rpm, add 50 kg of surfactant perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid ammonium salt, add 2 kg of molecular weight regulator diethyl malonate, adjust the temperature of the polymerization kettle to 70°C, add vinylidene fluoride, tetrafluoroethylene, and perfluoropropylene mixed monomer 1 (35:20:45), make the pressure in the reactor reach 1.5 MPa, add 1 kg of initiator solution into the reactor, and initiate the copolymerization reaction.

[0052] S2: After the polymerization reaction starts, a mixed monomer 2 (55:20:25) of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added to the polymerization kettle, the pressure of the reactor is maintained at 1.5MPa, and the reaction temperature is controlled at 75°C. When the amount of the mixed monomer added reaches 500kg, 10kg of diethyl malonate and 0.35kg of molecular weight regulator are added. When the amount of the mixed monomer added reaches 1000kg, the addition of monomers and initiators is stopped to terminate the copolymerization reaction. After the unreacted monomers in the polymerization kettle are recovered, a fluororubber emulsion is obtained. After coagulation, washing and drying, a fluororubber raw rubber (FKM) product for extrusion pipes is obtained.

[0053] Wherein, the preparation method of molecular weight regulator auxiliary agent is:

[0054] Step 1: Amine addition reaction 1

[0055] Raw material ratio: dioctadecylamine: 35kg; DMF: 400kg; (+)-Ipc2B (allyl) borane: 24kg, tetramethylguanidine: 3.5kg;

[0056] Reaction conditions: Mix and stir and heat to 65°C; react at this temperature for 40 minutes;

[0057] Step 2: Amine addition reaction 2

[0058] Add raw materials: allyl dibutyltin chloride: 0.1kg;

[0059] Reaction conditions: maintain the temperature at 65°C; continue the reaction for 140 minutes;

[0060] Post-treatment: DMF is removed by distillation to finally obtain the molecular weight regulator auxiliary.

[0061] Example 3

[0062] A method for preparing fluororubber (FKM) for extruded tubes comprises the following steps:

[0063] S1: Add 2000 kg of high-purity water to the polymerization kettle, start stirring, control the speed to 60 rpm, add 50 kg of surfactant perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid ammonium salt, add 2 kg of molecular weight regulator diethyl malonate, adjust the temperature of the polymerization kettle to 70°C, add vinylidene fluoride, tetrafluoroethylene, and perfluoropropylene mixed monomer 1 (35:20:45), make the pressure in the reactor reach 1.5 MPa, add 1 kg of initiator solution into the reactor, and initiate the copolymerization reaction.

[0064] S2: After the polymerization reaction starts, a mixed monomer 2 (55:20:25) of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added to the polymerization kettle, the pressure of the reactor is maintained at 1.5MPa, and the reaction temperature is controlled at 75°C. When the amount of the mixed monomer added reaches 700kg, 10kg of diethyl malonate and 0.5kg of molecular weight regulator are added. When the amount of the mixed monomer added reaches 1000kg, the monomer and initiator are stopped, the copolymerization reaction is terminated, and the unreacted monomer in the polymerization kettle is recovered to obtain a fluororubber emulsion. After condensation, washing and drying, a fluororubber raw rubber (FKM) product for extrusion pipes is obtained.

[0065] Wherein, the preparation method of molecular weight regulator auxiliary agent is:

[0066] Step 1: Amine addition reaction 1

[0067] Raw material ratio: dioctadecylamine: 50kg; DMF: 500kg; (+)-Ipc2B (allyl) borane: 33kg, tetramethylguanidine: 5kg;

[0068] Reaction conditions: Mix and stir and heat to 70°C; react at this temperature for 50 minutes;

[0069] Step 2: Amine addition reaction 2

[0070] Add raw materials: allyl dibutyltin chloride: 0.2kg;

[0071] Reaction conditions: maintain the temperature at 70°C; continue the reaction for 180 minutes;

[0072] Post-treatment: DMF is removed by distillation to finally obtain the molecular weight regulator auxiliary.

[0073] Comparative Example

[0074] A method for preparing fluororubber (FKM) for extruded tubes comprises the following steps:

[0075] S1: Add 2500 kg of high-purity water to the polymerization kettle, start stirring, control the speed to 40 rpm, add 20 kg of surfactant perfluoro-2,5-dimethyl-3,6-dioxanononanoic acid ammonium salt, add 1 kg of molecular weight regulator diethyl malonate, adjust the temperature of the polymerization kettle to 70°C, add 1 (35:20:45) of vinylidene fluoride, tetrafluoroethylene, and perfluoropropylene mixed monomers to make the pressure in the reactor reach 1.5 MPa, add 1 kg of initiator solution to the reactor to initiate the copolymerization reaction.

[0076] S2: After the polymerization reaction starts, a mixed monomer 2 (55:20:25) of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added to the polymerization kettle, the pressure of the reactor is maintained at 1.5MPa, and the reaction temperature is controlled at 75°C. When the amount of the mixed monomer added reaches 300kg, 10kg of diethyl malonate, a molecular weight regulator, is added. When the amount of the mixed monomer added reaches 1000kg, the addition of monomers and initiators is stopped to terminate the copolymerization reaction. After the unreacted monomers in the polymerization kettle are recovered, a fluororubber emulsion is obtained, and after coagulation, washing and drying, a fluororubber raw rubber (FKM) product for extrusion pipes is obtained.

[0077] The performance of the obtained fluororubber for extrusion tube was tested, and the test method was as follows:

[0078] 1. Determination of fluorine content

[0079] Weigh an appropriate amount of vulcanized fluororubber sample, crush it and mix it evenly. Use the oxygen bomb combustion method (oxygen bomb combustion coulometer), the specific steps are as follows:

[0080] 1) Place the rubber sample in an oxygen bomb and burn it in a high-pressure oxygen environment.

[0081] 2) The combustion products are absorbed by the absorption liquid.

[0082] 2. Compression deformation measurement

[0083] Prepare rubber specimens of standard size, usually cylindrical (29 mm in diameter, 12.5 mm in height), and conduct the test at 200°C.

[0084] 1) Place the sample in a compression device and keep it at a compression rate of 25% for 70 hours.

[0085] 2) After the test, remove the sample from the compression device and return it to room temperature for 30 minutes.

[0086] 3) Measure the height after recovery.

[0087] 3. Tensile strength determination

[0088] Prepare standard dumbbell-shaped rubber specimens, the dimensions of which conform to GB / T 528-2009 (ISO 37:2005) standard. Tests were performed at room temperature.

[0089] 1) Use a universal material testing machine to perform a tensile test at a constant tensile speed (such as 500 mm / min).

[0090] 2) Record the maximum tensile force of the sample.

[0091] 4. Determination of elongation at break

[0092] The dumbbell-shaped rubber specimen is the same as that for tensile strength determination. The test is carried out at room temperature.

[0093] 1) Using a universal material testing machine, continue stretching until the specimen breaks.

[0094] 2) Record the elongation at break of the specimen.

[0095] 5. Determination of medium resistance

[0096] The test was carried out in accordance with the provisions of GB / T 1690. The test time was 24 hours, the test temperature was 200°C, and the test oil was 3# standard oil.

[0097] The results of the above performance tests are shown in Table 1 below:

[0098] Table 1 Properties of fluororubber prepared in Examples 1-3

[0099]

[0100] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing fluororubber (FKM) for extrusion tube, the operating steps are as follows: S1: Add 2000-3000 parts of high-purity water to the polymerization kettle according to weight parts, start stirring, control the speed to 10-120rpm, add 10-50 parts of surfactant, add 0-10 parts of molecular weight regulator, adjust the temperature of the polymerization kettle to 70-95°C, add 1 mixed monomer of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene, make the pressure in the reactor reach 1.5-3.0MPa, add 1-10 parts of initiator solution to the reactor, and initiate copolymerization reaction; S2: After the polymerization reaction starts, a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene is continuously added into the polymerization kettle, the pressure of the reactor is maintained at 1.5-3.0 MPa, and the reaction temperature is controlled at 70-95°C. When the amount of the mixed monomer added reaches 300-700 kg, 0-10 parts of a molecular weight regulator and a molecular weight regulator auxiliary are added. When the amount of the mixed monomer added reaches 800-1000 parts, the addition of monomers and initiators is stopped to terminate the copolymerization reaction. After the unreacted monomers in the polymerization kettle are recovered, a fluororubber emulsion is obtained, and after coagulation, washing and drying, a fluororubber raw rubber (FKM) product for extruded pipes is obtained.

2. The method for preparing fluororubber (FKM) for extrusion pipe according to claim 1, characterized in that: The surfactant is a trimer acid, a perfluoropolyether carboxylic acid or a mixture of the two, which is an aqueous solution with a concentration of 10-30%.

3. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The molecular weight regulator is straight-chain alkane, branched alkane, or ester.

4. The method for preparing fluororubber (FKM) for extruded tube according to claim 3, characterized in that: The straight-chain alkane molecular formula C n H 2n+2 , wherein n=2-10; the branched alkane molecular formula C n H 2n+2 , wherein n=4-10; selected from n-hexane (C6H 14 ), n-octane (C8H 18 ), n-decane (C 10 H 22 ) at least one of.

5. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The amount of the molecular weight regulator additive added is 2-5wt% of the molecular weight regulator.

6. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The preparation method of the molecular weight regulator auxiliary agent is: Step 1: Amine addition reaction 1 Raw material ratio: dioctadecylamine: 25-50 parts; DMF: 300-500 parts; (+)-Ipc2B (allyl) borane: 14-33 parts, tetramethylguanidine: 2-5 parts; Reaction conditions: Mix and stir and heat to 60-70°C; react at this temperature for 30-50 minutes; Step 2: Amine addition reaction 2 Added raw materials: allyl dibutyltin chloride: 0.02-0.2 parts; Reaction conditions: maintain the temperature at 60-70°C; continue the reaction for 120-180 minutes; Post-treatment: DMF is removed by distillation to finally obtain the molecular weight regulator auxiliary.

7. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The initiator is an aqueous solution or a mixed solution of ammonium persulfate or potassium persulfate, and the concentration of the initiator solution is 0.1-5%.

8. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The ratio of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene in the mixed monomer 1 is (30-50):(10-35):(30-50).

9. The method for preparing fluororubber (FKM) for extruded tube according to claim 1, characterized in that: The ratio of vinylidene fluoride, tetrafluoroethylene and perfluoropropylene in the mixed monomer 2 is (40-70):(5-25):(10-30).

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