CN108503738B - Polyvinylidene fluoride resin and preparation method and application thereof - Google Patents
Polyvinylidene fluoride resin and preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F114/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F114/18—Monomers containing fluorine
- C08F114/22—Vinylidene fluoride
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/22—Vinylidene fluoride
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/28—Hexyfluoropropene
Abstract
The invention discloses polyvinylidene fluoride resin and a preparation method and application thereof. The preparation method of the polyvinylidene fluoride comprises the following steps: the polyvinylidene fluoride resin is prepared by adopting a continuous emulsion polymerization method and is specifically divided into three stages: the first stage is as follows: homopolymerizing the vinylidene fluoride monomer to obtain homopolymerized PVDF resin; and a second stage: copolymerizing a vinylidene fluoride monomer and a modified monomer to obtain a copolymerized PVDF resin; and a third stage: homopolymerizing the vinylidene fluoride monomer and/or copolymerizing the vinylidene fluoride monomer and the modified monomer to obtain homopolymerized PVDF and/or copolymerized PVDF resin; obtaining the polyvinylidene fluoride resin. The polyvinylidene fluoride resin not only has good flexibility and toughness, but also has excellent mechanical property and barrier property of homopolymerized PVDF resin, and simultaneously has good processing property, and can be used for preparing the lining of an offshore oil delivery hose.
Description
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to polyvinylidene fluoride (PVDF) resin and a preparation method thereof.
Background
The offshore oil transportation hose needs to deal with very harsh conditions in the oil and gas transportation process, the lining of the offshore oil transportation hose needs to be in direct contact with crude oil, the transportation temperature is as high as 130 ℃, and the transportation pressure is also very high (such as 70 MPa). Therefore, the lining material is required to have excellent mechanical properties, high temperature resistance and chemical barrier properties. The hose needs to bear external forces such as bending, impact and distortion under low temperature (such as-20 ℃) during transportation, installation and operation, so that the lining material needs to have good flexibility.
In order to meet the performance requirements, various large chemical enterprises in foreign countries develop a plurality of polymer materials for hose linings, mainly comprising PE (HDPE, XLPE), PA11 and PVDF. The lining layer of the earliest oil hose is made of PE (polyethylene) materials, and is gradually replaced by PA (polyamide) materials due to low temperature resistance, and the temperature resistance of PA can only reach 80-90 ℃, so that the lining layer of the earliest oil hose is gradually developed into PVDF (polyvinylidene fluoride) materials. Compared with the former two materials, PVDF is a thermoplastic fluoropolymer with high crystallinity, and has good mechanical property, oil resistance, permeability resistance, blistering resistance and H resistance2S and CO2And the like. Meanwhile, the flexibility of the PVDF resin is seriously influenced just by the high crystallinity of the PVDF resin. On the other hand, the frame layer in the oil pipeline, which is in contact with the PVDF, is a spiral metal interlocking winding layer, a large number of gaps exist, if the molecular weight of the PVDF is too small, the fluidity is too good, polymer melt can easily permeate into the gaps of the frame layer, the flexibility of the oil pipeline is affected, and therefore the polymer melt becomes a fracture induction point, and meanwhile, in order to ensure the mechanical strength of the PVDF material, the PVDF resin for the oil pipeline hose usually adopts ultra-high molecular weight resin, which brings difficulty to downstream processing.
In the patent US 005429849, 25-75 wt% of homopolymerized PVDF and 25-75 wt% of copolymerized PVDF resin are blended to obtain a composition material with excellent low-temperature mechanical properties, and the composition material is mainly used for cables or oil pipelines. However, the combined processability obtained by this method is not ideal.
The patents US 20010055658Al and US 20160017136Al obtain PVDF compositions by blending homopolymeric PVDF with copolymeric PVDF and adding a plasticizer, and the mechanical properties, high and low temperature resistance and flexibility of the obtained compositions are all improved. However, the small molecular plasticizer adopted in the patent is easily extracted by hydrocarbons in the oil transportation process, and finally causes embrittlement of the hose and contraction and extraction at a joint, thereby bringing risks to oil transportation.
The above methods are all physical blending modification methods based on the existing PVDF resin to improve the comprehensive performance of the resin so as to meet the application on oil pipelines. However, this method requires physical blending of several different resins (or plasticizer), the mixing process is time-consuming and labor-consuming, and the uniformity of mixing is not well guaranteed.
Patent CN88100574 discloses a heterogeneous copolymer of vinylidene fluoride and chlorotrifluoroethylene, said heterogeneous copolymer consisting of elastomeric globules of vinylidene fluoride and chlorotrifluoroethylene dispersed in a matrix consisting of vinylidene fluoride quasi-polymer. However, the copolymer has good flexibility, but insufficient strength and poor processability.
Disclosure of Invention
The invention aims to provide polyvinylidene fluoride resin as well as a preparation method and application thereof.
The invention provides a first purpose of providing a preparation method of polyvinylidene fluoride resin.
The preparation method of the polyvinylidene fluoride resin provided by the invention comprises the following steps: the polyvinylidene fluoride resin is prepared by adopting a continuous emulsion polymerization method and is specifically divided into three stages:
the first stage is as follows: homopolymerizing the vinylidene fluoride monomer to obtain homopolymerized PVDF resin;
and a second stage: copolymerizing a vinylidene fluoride monomer and a modified monomer to obtain a copolymerized PVDF resin;
and a third stage: homopolymerizing the vinylidene fluoride monomer and/or copolymerizing the vinylidene fluoride monomer and the modified monomer to obtain homopolymerized PVDF and/or copolymerized PVDF resin;
obtaining the polyvinylidene fluoride resin.
In the preparation method, the comprehensive viscosity of the polyvinylidene fluoride resin can be 1.3-1.8 dL/g;
the inherent viscosities of the homopolymerized PVDF resin obtained in the first stage and the copolymerized PVDF resin obtained in the second stage can be 1.4-1.9 dL/g, such as 1.87dL/g, 1.68dL/g or 1.44 dL/g; the intrinsic viscosity of the homopolymeric PVDF and/or copolymeric PVDF resin obtained in the third stage can be 0.5 to 0.8dL/g, such as 0.53dL/g, 0.64dL/g, or 0.78 dL/g. The intrinsic viscosity is measured by preparing a PVDF resin into a N, N-Dimethylformamide (DMF) solution with the concentration of 0.4g/dL in a water bath at 30 ℃ by using an Ubbelohde viscometer.
In the preparation method, the polyvinylidene fluoride resin consists of homopolymerized PVDF resin obtained in the first stage, copolymerized PVDF resin obtained in the second stage and homopolymerized PVDF and/or copolymerized PVDF resin obtained in the third stage;
the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin obtained in the first stage is 30-90% in percentage by mass; the mass percentage of the copolymerized PVDF resin obtained in the second stage is 5-45%; and the mass percentage content of the homopolymerized PVDF and/or copolymerized PVDF resin obtained in the third stage is 5-25%.
Preferably, the total mass percentage content of the polyvinylidene fluoride resin is 100%; the homopolymerized PVDF resin obtained in the first stage is 50-70% in percentage by mass; the mass percentage of the copolymerized PVDF resin obtained in the second stage is 20-40%; and the mass percentage content of the homopolymerized PVDF and/or copolymerized PVDF resin obtained in the third stage is 10-15%.
Specifically, the polyvinylidene fluoride resin may be any one of the following 1) to 6):
1) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage is 50-70% in mass percentage; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 20-35%; the mass percentage of the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage is 10-15%;
2) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage is 50-60% in percentage by mass; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 27-35%; the mass percentage of the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage is 13-15%;
3) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage is 60-70% in mass percentage; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 20-27%; the mass percentage of the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage is 10-13%;
4) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage has the mass percentage content of 50 percent; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 35 percent; the mass percentage of the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage is 15%;
5) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage has the mass percentage content of 60 percent; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 27 percent; the mass percentage of the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage is 13%;
6) the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin prepared in the first stage has the mass percentage content of 70 percent; the mass percentage content of the copolymerized PVDF resin prepared in the second stage is 20%; and the homopolymerized PVDF and/or copolymerized PVDF resin prepared in the third stage has the mass percentage content of 10%.
In the above preparation method, in the second stage and/or the third stage, the molar content of the modified monomer in all monomers (vinylidene fluoride monomer and modified monomer) in the stage (i.e., the second stage or the second stage and the third stage, i.e., the stage in which the additional mixed monomer is added) may be 10 to 50%, specifically 10%, 40% or 50%.
In the polyvinylidene fluoride resin, the mass percentage content (the macroscopic content of the modified monomer) of the modified monomer can be 3-15%, and preferably 5-12%.
The modified monomer is a fluorine-containing vinyl monomer except vinylidene fluoride, and includes but is not limited to: at least one of vinyl fluoride, trifluoroethylene, Chlorotrifluoroethylene (CTFE), 1, 2-difluoroethylene, Tetrafluoroethylene (TFE), Hexafluoropropylene (HFP), perfluoro (alkyl vinyl) ether, perfluoro (1, 3-dioxole), and perfluoro (2, 2-dimethyl-1, 3-dioxole) (PDD); the perfluoro (alkyl vinyl) ether may be perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE), or perfluoro (propyl vinyl) ether (PPVE).
In the above preparation method, the method specifically comprises the following steps:
1) homopolymerization of a vinylidene fluoride monomer in a first stage in an emulsification system formed by water and an emulsifier to obtain homopolymerized PVDF resin;
2) supplementing mixed gas of vinylidene fluoride monomer and modified monomer into the system obtained in the step 1) to carry out second-stage copolymerization to obtain copolymerized PVDF resin;
3) supplementing vinylidene fluoride monomers or mixed gas of the vinylidene fluoride monomers and the modified monomers into the system obtained in the step 2) to carry out third-stage homopolymerization and/or copolymerization to obtain homopolymerized PVDF resin and/or copolymerized PVDF resin;
step 1) to step 3) are carried out in the presence of an initiator and a chain transfer agent;
4) taking out the emulsion obtained in the step 3), and coagulating, washing and drying to obtain the polyvinylidene fluoride resin.
In the above preparation method, the emulsifier may be sodium perfluorooctanoate, potassium perfluorooctanoate or ammonium perfluorooctanoate. The dosage of the emulsifier can be 0.05-0.5% of the total weight of all the monomers in the three stages, and specifically can be 0.08%, 0.16% or 0.32%. The addition steps of the emulsifier are as follows: is added in one portion before the reaction in the step 1).
The initiator may be an oil soluble peroxide initiator including, but not limited to: t-butyl peroxypivalate, t-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, diethyl peroxydicarbonate, etc. The dosage of the initiator can be 0.1-1% of the total weight of all the monomers in the three stages, and specifically can be 0.16%, 0.32% or 1%. The initiator addition step may be as follows: the initiator is added in batches in the reaction process, 50% of the total weight of the initiator is added before the reaction in the step 1), 20-30% (such as 20%, 25%) of the total weight of the initiator is supplemented when the monomer consumption is 1/3% of the total weight of all the monomers in the three stages in the reaction, 10-20% (such as 10%, 13%) of the total weight of the initiator is supplemented when the monomer consumption is 2/3% of the total weight of all the monomers in the three stages in the reaction, and 10-20% (such as 20%, 15%, 16%) of the total weight of the initiator is supplemented in the reaction to the third stage.
The chain transfer agent can be acetone, ethyl acetate, diethyl carbonate, diethyl malonate, diethyl succinate or dipropyl succinate. The dosage of the chain transfer agent can be 3-10% of the total weight of all the monomers in the three stages. The chain transfer agent is added in the following steps: the chain transfer agent is added in batches in the reaction process, 5-10% (such as 8% and 10%) of the total weight of the chain transfer agent is added before the reaction in the step 1) is started, 3-5% (such as 4% and 5%) of the total weight of the chain transfer agent is supplemented when the monomer consumption is 1/3% of the total weight of all the monomers in the three stages in the reaction, 2-5% (such as 4%, 3% and 5%) of the total weight of the chain transfer agent is supplemented when the monomer consumption is 2/3% of the total weight of all the monomers in the three stages in the reaction, and 80-90% (such as 84% and 80%) of the total weight.
In the preparation method, the reaction temperature in the steps 1) to 3) can be 60-100 ℃, specifically 75-85 ℃, 75 ℃, 80 ℃ and 85 ℃; the reaction pressure may be 1.0 to 3.0MPa, specifically 1.6 to 2.0MPa, 1.6MPa, 1.8MPa or 2.0 MPa.
In the step 1), stopping the reaction when the consumption of the vinylidene fluoride monomer is 50-75% of the total weight of all monomers in the three stages;
in the step 2), stopping the reaction when the consumption of the mixed monomer is 20-40% of the total weight of all monomers in the three stages;
and in the step 3), stopping the reaction when the consumption of the vinylidene fluoride monomer or the mixed monomer is 10-15% of the total weight of all monomers in the three stages.
The second purpose of the invention is to provide the polyvinylidene fluoride resin prepared by the preparation method.
The third purpose of the invention is to provide the application of the polyvinylidene fluoride resin in preparing the lining of the offshore oil transportation hose.
The fourth purpose of the invention is to provide an offshore oil transfer hose, wherein the lining material is the polyvinylidene fluoride resin.
The invention has the following beneficial effects:
the high molecular weight homopolymerized PVDF resin generated in the first stage can keep the mechanical property and the chemical barrier property of the PVDF resin; the elastic PVDF resin generated in the second stage can be used as an impact modifier to improve the impact resistance of the whole resin, and simultaneously, the overall crystallinity of the PVDF resin is reduced to a certain extent, and the flexibility of the PVDF resin is increased; the low molecular weight PVDF copolymer resin generated in the third stage can be used as a plasticizer, the processability of the resin is improved to a certain extent, and the problem of precipitation of a small molecular plasticizer can be avoided. In addition, the PVDF resin prepared by the method has good compatibility in each stage.
The test method of the invention comprises the following steps:
(1) determination of the macroscopic content of modified monomers
The macroscopic content of the modified monomer in the present invention means the mass content of the modified monomer relative to the total amount of the PVDF resin obtained by the three-stage polymerization. Dissolving PVDF resin in DMSO in deuterium band, and performing nuclear magnetic resonanceNuclear magnetic fluorine spectrum of resin19F-NMR) to calculate the modified monomer content by peak area ratio.
(2) Tensile Property test
And testing the tensile property of the resin according to the national standard GB/T1040.1-3-2006.
(3) Impact resistance test
The impact properties of the materials were tested according to ISO 179.
(4) Determination of intrinsic viscosity
Preparing high molecular weight PVDF resin into N, N-Dimethylformamide (DMF) solution with concentration (C) of 0.4g/dL, and measuring the flow-out time of pure solvent and resin solution, which are respectively T, by using Ubbelohde viscometer in water bath at 30 DEG C0And TsAnd the inherent viscosity η of the resin is calculated according to the following formula:
η＝1/C×ln(Ts/T0)
wherein C is the solution concentration in units: g/dl
(5) Critical shear rate
The critical shear rate is the shear rate at which the polymer begins to produce an unstable flow during extrusion. Unstable flow will result in rough extrudate surface, undulations, spiral distortions and even melt fracture. And (3) testing the extrusion performance of the PVDF resin by adopting a capillary rheometer at 220 ℃, observing the melt fracture condition and detecting the critical shear rate.
(6) Resistance to permeation by organic media
The resin was formed into an extruded film having a thickness of 100 μm, and the permeability of methane in the film was measured under a temperature of 130 ℃ and a pressure of 100 bar.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1 preparation of polyvinylidene fluoride resin
Adding 2500g of deionized water and an ammonium perfluorooctanoate emulsifier into a 5L vertical kettle (the rotating speed is 300rpm), heating a polymerization kettle, adding a VDF monomer, adding an initiator diisopropyl peroxydicarbonate and a chain transfer agent acetone through an auxiliary agent pump to start reaction after the kettle temperature of the polymerization kettle reaches 75 ℃ and the kettle pressure reaches 1.6MPa, wherein the adding modes of the monomer, the initiator and the chain transfer agent in the reaction process are shown in table 1, the kettle temperature and the kettle pressure of the reaction kettle are kept stable until the reaction is finished, and the reaction is stopped in the first stage when the consumption of the vinylidene fluoride monomer is 50% of the total weight of all monomers (300g of VDF) in the three stages; the second stage stops the reaction when the consumption of the mixed monomer is 35% of the total weight of all monomers in the three stages (210g of mixed monomer); the third stage stopped the reaction when the amount of mixed monomer consumed was 15% of the total weight of all monomers in the three stages (90g of mixed monomer). After the reaction is finished, the emulsion is taken out, and the PVDF resin product is obtained through the steps of coagulation, washing and drying, and the performance of the PVDF resin product is tested, and is shown in table 2.
In this example, the intrinsic viscosity of the homopolymerized PVDF obtained in the first and second stages was 1.87 dL/g; the intrinsic viscosity of the PVDF obtained in the third stage was 0.53 dL/g.
The PVDF resin product is calculated by taking the total mass percentage of the PVDF resin product as 100 percent; the mass percentage content of the homopolymerized polyvinylidene fluoride resin prepared in the first stage is 50%; the mass percentage of the copolymerized polyvinylidene fluoride resin prepared in the second stage is 35%; the mass percentage of the copolymerized polyvinylidene fluoride resin prepared in the third stage is 15%.
Example 2 preparation of polyvinylidene fluoride resin
2800g of deionized water and a potassium perfluorooctanoate emulsifier are added into a 5L vertical kettle (the rotating speed is 350rpm), then the temperature of a polymerization kettle is raised, VDF monomers are added, after the kettle temperature of the polymerization kettle reaches 80 ℃ and the kettle pressure reaches 1.8MPa, an initiator diethyl peroxydicarbonate and a chain transfer agent ethyl acetate are added through an auxiliary agent pump to start reaction, the adding modes of the monomers, the initiator and the chain transfer agent in the reaction process are shown in table 1, the kettle temperature and the kettle pressure of the reaction kettle are kept stable until the reaction is finished, wherein in the first stage, the reaction is stopped when the consumption of the vinylidene fluoride monomers is 60% of the total weight of all monomers (360g of VDF) in three stages; the second stage stops the reaction when the amount of the mixed monomer consumed is 27% by weight (160g of the mixed monomer) of the total amount of all the monomers in the three stages; the reaction was stopped in the third stage when the amount of VDF monomer consumed was 13% of the total weight of all monomers in the three stages (80g of VDF). After the reaction is finished, the emulsion is taken out, and the PVDF resin product is obtained through the steps of coagulation, washing and drying, and the performance of the PVDF resin product is tested, and is shown in table 2.
In this example, the intrinsic viscosity of the homopolymerized PVDF obtained in the first and second stages was 1.68 dL/g; the intrinsic viscosity of the PVDF obtained in the third stage was 0.64 dL/g.
The total mass percentage of the polyvinylidene fluoride resin is 100 percent; the mass percentage content of the homopolymerized polyvinylidene fluoride resin prepared in the first stage is 60 percent; the mass percentage of the copolymerized polyvinylidene fluoride resin prepared in the second stage is 27%; and the mass percentage of the homopolymerized polyvinylidene fluoride prepared in the third stage is 13%.
Example 3 preparation of polyvinylidene fluoride resin
Adding 3000g of deionized water and a sodium perfluorooctanoate emulsifier into a 5L vertical kettle (the rotating speed is 400rpm), then heating a polymerization kettle, adding a VDF monomer, adding an initiator tert-butyl peroxypivalate and a chain transfer agent diethyl carbonate into the polymerization kettle through an auxiliary agent pump to start reaction after the kettle temperature of the polymerization kettle reaches 85 ℃ and the kettle pressure reaches 2.0MPa, wherein the adding modes of the monomer, the initiator and the chain transfer agent are shown in table 1 in the reaction process, the kettle temperature and the kettle pressure of the reaction kettle are kept stable until the reaction is finished, and the reaction is stopped in the first stage when the consumption of the vinylidene fluoride monomer accounts for 70 percent (420g of VDF) of the total weight of all monomers in the three stages; the second stage stops the reaction when the consumption of the mixed monomer is 20% of the total weight of all monomers in the three stages (120g of the mixed monomer); the third stage stops the reaction when the amount of VDF monomer consumed is 10% of the total weight of all monomers in the three stages (60g of VDF). After the reaction is finished, the emulsion is taken out, and the PVDF resin product is obtained through the steps of coagulation, washing and drying, and the performance of the PVDF resin product is tested, and is shown in table 2.
In this example, the intrinsic viscosity of the homopolymerized PVDF obtained in the first and second stages was 1.44 dL/g; the intrinsic viscosity of the PVDF obtained in the third stage was 0.78 dL/g.
The total mass percentage of the polyvinylidene fluoride resin is 100 percent; the mass percentage of the homopolymerized polyvinylidene fluoride resin prepared in the first stage is 70%; the mass percentage of the copolymerized polyvinylidene fluoride resin prepared in the second stage is 20%; the mass percentage of the copolymerized polyvinylidene fluoride resin prepared in the third stage is 10%.
Comparative example 1
Similar to example 1, the only difference is that the third stage reaction is not supplemented with the additional chain transfer agent acetone. The specific formulation and process parameters are detailed in table 1.
The final properties of the product are shown in Table 2.
Comparative example 2
Similar to example 2, the only difference is that the second stage was fed with additional VDF monomer only and the product of the three stage polymerization was a PVDF homopolymer. The specific formulation and process parameters are detailed in table 1.
The final properties of the product are shown in Table 2.
Comparative example 3
Similar to example 1, the only difference is that the first stage reaction begins with the addition of additional mixed monomers of VDF and CTFE. The specific formulation and process parameters are detailed in table 1.
The final properties of the product are shown in Table 2.
Comparative example 4
Similar to example 1, the only difference is that the first stage reaction starts to supplement the mixed monomers of VDF and CTFE, and the molar ratio of the mixed monomers is VDF/CTFE 95: 5. The specific formulation and process parameters are detailed in table 1.
TABLE 2 Performance results for PVDF resin products of examples and comparative examples
The results of the examples and comparative examples in table 2 clearly show that the PVDF copolymer provided by the invention has high strength, flexibility, and good organic solvent permeation resistance, and also has good processability.
Claims (7)
1. A preparation method of polyvinylidene fluoride resin comprises the following steps: the polyvinylidene fluoride resin is prepared by adopting a continuous emulsion polymerization method and is specifically divided into three stages:
the first stage is as follows: homopolymerizing the vinylidene fluoride monomer to obtain homopolymerized PVDF resin;
and a second stage: copolymerizing a vinylidene fluoride monomer and a modified monomer to obtain a copolymerized PVDF resin;
and a third stage: homopolymerizing the vinylidene fluoride monomer and/or copolymerizing the vinylidene fluoride monomer and the modified monomer to obtain homopolymerized PVDF and/or copolymerized PVDF resin;
obtaining the polyvinylidene fluoride resin;
the first stage, the second stage and the third stage are carried out in the presence of an initiator and a chain transfer agent;
the initiator is an oil-soluble peroxide initiator;
the chain transfer agent is acetone, ethyl acetate, diethyl carbonate, diethyl malonate, diethyl succinate or dipropyl succinate;
in the second stage and/or the third stage, the molar content of the modified monomer in all monomers in the second stage and/or the third stage is 10-50%;
in the polyvinylidene fluoride resin, the mass percentage content of the modified monomer is 3-15%;
the modified monomer is at least one of vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, 1, 2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro (alkyl vinyl) ether, perfluoro (1, 3-dioxole) and perfluoro (2, 2-dimethyl-1, 3-dioxole);
the polyvinylidene fluoride resin consists of homopolymerized PVDF resin obtained in the first stage, copolymerized PVDF resin obtained in the second stage and homopolymerized PVDF and/or copolymerized PVDF resin obtained in the third stage;
the polyvinylidene fluoride resin is calculated by taking the total mass percentage of the polyvinylidene fluoride resin as 100%; the homopolymerized PVDF resin obtained in the first stage is 30-90% in percentage by mass; the mass percentage of the copolymerized PVDF resin obtained in the second stage is 5-45%; and the mass percentage content of the homopolymerized PVDF and/or copolymerized PVDF resin obtained in the third stage is 5-25%.
2. The method of claim 1, wherein: the method comprises the following steps:
1) homopolymerization of a vinylidene fluoride monomer in a first stage in an emulsification system formed by water and an emulsifier to obtain homopolymerized PVDF resin;
2) supplementing mixed gas of vinylidene fluoride monomer and modified monomer into the system obtained in the step 1) to carry out second-stage copolymerization to obtain copolymerized PVDF resin;
3) supplementing vinylidene fluoride monomers or mixed gas of the vinylidene fluoride monomers and the modified monomers into the system obtained in the step 2) to carry out third-stage homopolymerization and/or copolymerization to obtain homopolymerized PVDF resin and/or copolymerized PVDF resin;
step 1) to step 3) are carried out in the presence of an initiator and a chain transfer agent;
the initiator is an oil-soluble peroxide initiator;
the chain transfer agent is acetone, ethyl acetate, diethyl carbonate, diethyl malonate, diethyl succinate or dipropyl succinate;
4) taking out the emulsion obtained in the step 3), and coagulating, washing and drying to obtain the polyvinylidene fluoride resin.
3. The method of claim 2, wherein: the emulsifier is sodium perfluorooctanoate, potassium perfluorooctanoate or ammonium perfluorooctanoate; the dosage of the emulsifier is 0.05-0.5% of the total weight of all the monomers in the three stages; the addition steps of the emulsifier are as follows: adding the mixture once before the reaction in the step 1);
the initiator is tert-butyl peroxypivalate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate or diethyl peroxydicarbonate; the dosage of the initiator is 0.1-1% of the total weight of all the monomers in the three stages; the initiator is added by the following steps: the initiator is added in batches in the reaction process, 50% of the total weight of the initiator is added before the reaction in the step 1), 20-30% of the total weight of the initiator is supplemented when the monomer consumption is 1/3% of the total weight of all the monomers in the three stages in the reaction, 10-20% of the total weight of the initiator is supplemented when the monomer consumption is 2/3% of the total weight of all the monomers in the three stages in the reaction, and 10-20% of the total weight of the initiator is supplemented when the reaction is carried out in the third stage;
the dosage of the chain transfer agent is 3-10% of the total weight of all monomers in the three stages; the chain transfer agent is added in the following steps: the chain transfer agent is added in batches in the reaction process, 5-10% of the total weight of the chain transfer agent is added before the reaction in the step 1), 3-5% of the total weight of the chain transfer agent is supplemented when the monomer consumption is 1/3% of the total weight of all the monomers in the three stages in the reaction process, 2-5% of the total weight of the chain transfer agent is supplemented when the monomer consumption is 2/3% of the total weight of all the monomers in the three stages in the reaction process, and 80-90% of the total weight of the chain transfer agent is supplemented when the.
4. The production method according to claim 2 or 3, characterized in that: the reaction temperature of the step 1) to the step 3) is 60-100 ℃, and the reaction pressure is 1.0-3.0 MPa;
in the step 1), stopping the reaction when the consumption of the vinylidene fluoride monomer is 50-75% of the total weight of all monomers in the three stages;
in the step 2), stopping the reaction when the consumption of the mixed monomer is 20-40% of the total weight of all the monomers in the three stages;
and in the step 3), stopping the reaction when the consumption of the vinylidene fluoride monomer or the mixed monomer is 10-15% of the total weight of all monomers in the three stages.
5. The polyvinylidene fluoride resin prepared by the preparation method of any one of claims 1 to 4.
6. Use of the polyvinylidene fluoride resin of claim 5 in the preparation of an offshore oil transfer hose lining.
7. An offshore oil transfer hose, characterized in that: the polyvinylidene fluoride resin of claim 5 as a lining material.
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