245results about How to "Good swelling properties" patented technology

The invention relates to a method for dissolving cellulose in a CO2 switchable ionic compound or a mixed system composed of a CO2 switchable ionic compound and an organic solvent. Various anti-solvents are added into the system, or a gas is introduced into the system or heating is conducted to destroy the structure of a CO2 switchable solvent. The dissolved cellulose regenerates in various physical structure forms. By adjusting the CO2 pressure, and selecting organic amine or alcohol of cations and anions able to compose a CO2 switchable ionic compound or the structure of an assistant organic solvent, the solubility of cellulose and various properties of the solution can be controlled.

The invention discloses a organic silicon compound containing silicon-silicon bond, silicon-carbon bond, silicon-halogen bond and ceramics precursor poly carbon silicon alky synthesized under high pressure and with medium in supercritical fluid status which uses mixture of the aforementioned compound as raw material, uses solvent soluble of poly carbon silicon alky as supercritical fluid medium. Ceramics precursor poly carbon silicon alky with different molecular weight and different softening point can be obtained by controlling reaction condition of synthesis. The inventive method effectively improves uniformity of heat transfer and reaction, with short reaction time, high synthesis efficiency, high synthesis yield. The produced poly carbon silicon has a high molecular weight, high content of bonds of silicon and hydrogen and uniform distribution of molecular weight. The inventive method can be widely used in preparation of SiC fibre, SiC composite, heat resistant alloy with high strength, ceramic binder, SiC membrane, nano-wire, nano-pipe and nano-powder and so on.

A preparation method of polyvinyl alcohol / hydroxyapatite (PVA / HA) composite microspheres belongs to preparation methods of composite water-in-oil emulsion system microspheres. PVA and HA precursors are used as raw materials to prepare a clear and transparent mixed solution; the clear and transparent mixed solution is dispersed into an oil phase containing a surfactant to form a homogeneous water-in-oil microemulsion; and the PVA / HA composite microspheres can be finally obtained by successive crosslinking reaction under acid-catalyzed conditions, HA deposition under alkaline conditions, product centrifugation, washing, drying and other processes. The method has the advantages of simple process, good repeatability, low energy consumption and low cost, and effectively solves the problems that inorganic nanoparticles are easy to agglomerate in the microspheres to cause uneven structures and poor comprehensive performances and the like. The composite microspheres prepared by the method have the advantages of regular morphology, high dispersibility, uniform microstructure, good biocompatibility, biological activity and adsorption performance, and can be used as drug carrier materials, bone repair materials, environmental water treatment materials, cosmetics or food additives and the like.

The invention relates to an aramid fiber-reinforced rein-based composite material and a preparation method thereof. Aramid fibers coated with an acrylic ester derivative polymer are prepared with a biological enzyme treatment method. A composite material is molded according to different substrate resins by adopting the conventional molding processes of fiber-reinforced resin-based composite materials such as die pressing, laminating, a hot pressing tank and the like or liquid phase molding processes such as resin transfer molding (RTM), a resin film infiltration (RFI) process and the like, so that the aramid fiber-reinforced rein-based composite material is obtained. Compared with a composite material prepared with unmodified aramid fibers, the composite material provided by the invention has the advantage that: the interlaminal shear strength is raised by 10-25 percent. The technical scheme of the invention has the characteristics of small fiber damage, mild reaction conditions, simple and practicable process, environmental friendliness and high industrial production benefit.

The invention discloses fruit residue dietary fiber and a preparation method thereof. According to the preparation method, fruit peel residues and fruit flesh residues produced in the processing processes of fruit juice and fruit cans are taken as raw materials and prepared into a high-purity and high-physiological activity dietary fiber product by the process steps and equipment of impurity removal, ultrafine crushing, enzymolysis, centrifuging, concentrating, decoloring, ethanol precipitation, drying and the like. The product has the characteristics of high purity, high water holding capacity, strong swelling performance and the like.

The invention relates to a spinning process for a high-strength and high-modulus ultrahigh molecular weight polyethylene fibre. The spinning process is a one-step swelling and dissolving continuous type spinning process. Compared with the prior art, the spinning process adopts the one-step swelling and dissolving continuous type spinning process and has good swelling effect; the concentration of a spinning solution is increased from the prior 5 to 8 percent to 10 to 15 percent; the production efficiency is improved by more than 30 percent; the quality of a product is greatly improved; the high-strength (more than 35 g / d) ultrahigh molecular weight polyethylene fibre is obtained; the spinning process solves the problem of quality fluctuation caused by intermittent type operation in the prior process, has the advantages of simple process, strong manoeuvrability, high production efficiency and the like, and realizes the continuity of the production process and the excellence of the product quality of the high-strength and high-modulus ultrahigh molecular weight polyethylene fibre.

The invention discloses amino acid grafted GMA-DVB copolymer chelate resin and a preparation method and application. (1) GMA is used as a monomer, DVB is used a coupling agent, polyving akohol is used as a dispersing agent, azodiisobutyronitrile is used as an initiating agent, methylbenzene and n-heptane are used as a mixed pore-foaming agent, and GMA-DVB bipolymer crosslinked microspheres taking the GMA as the main monomer are prepared with a suspension polymerization method; (2) N,N-dimethyl formamide is taken as a swelling agent, amino acid is used for surface grafted modification of the GMA-DVB bipolymer crosslinked microspheres, and the amino acid grafted GMA-DVB copolymer chelate resin is obtained. The amino acid grafted GMA-DVB copolymer chelate resin and the preparation method and the application have the advantages that the synthesis process is simple, the preparation cost is low, the toxicity is small, the resin particle diameters are uniform, separation and recycling are easy, the resin can be reused for multiple times and the like.

The invention discloses a methanol diesel oil additive and simultaneously discloses methanol diesel oil with the methanol diesel oil additive. The methanol diesel oil prepared by the invention is prepared by mixing 0.04-0.07 part of ferrocene, 2-5 parts of acetone, 4 parts of diemethyl carbonate, 2-3 parts of isobutanol, 2-3 parts of toluene, 70 parts of diesel oil and 20-25 parts of methanol. The methanol diesel oil has the advantages of low corrosion, good intersolubility and swelling property, uniform texture, high flash point, low condensation point and high cetane number, is safe to use and meets all indexes of automobile diesel oil GB19147-2009. The methanol diesel oil can be applied to internal-combustion engines, general engines, power plant fuels, burner substances and the like, thus the applicable range of the methanol diesel oil is wide.

The invention provides a novel preform body for bone porcelain and a preparation process of the preform body. The novel preform body for bone porcelain comprises the following components in percentage by weight: 50-55% of bone meal, 24-28% of kaolin, 9-11% of quartz, 8-10% of feldspar, 0.38-0.52% of lithium chinastone, 0.8-1.6% of zircon sand and 0.4-0.8% of nano-aluminum oxide. The preparation process comprises the following steps: mixing various ground materials with proper granularity to prepare the preform body, and calcining once again before the bone meal is mixed. The preform body prepared in the invention is good in thermal shock resistance, high in strength, uniform in structure, compact in toughness and excellent in overall performance.

The invention relates to hydrophobic swelling polyurethane foam and a preparation method and use thereof, and belongs to the field of high-molecular-weight materials. In the invention, the high-hydrophobicity swelling polyurethane foam is prepared by introducing a polysiloxane chain into unsaturated hydroxyl-terminated polybutadiene (unsaturated hydroxyl-terminated polyisoprene) on the basis of the high hydrophobicity of silicon rubber and the high swelling performance of the silicon rubber in organic materials and petroleum products and reacting with isocyanate to prepare the high-hydrophobicity swelling polyurethane foam. In the invention, the polyurethane foam is prepared by mixing the isocyanate, polyol, a catalyst, a foam stabilizer, a foaming agent, a pore-forming agent and a flame retardant, foaming and aging; the prepared polyurethane foam fills pores and swells a substrate while absorbing leaked liquid organic matters and petroleum products; and thus, the leaked liquid organic matter and petroleum product absorption power of the polyurethane foam is improved, and the polyurethane foam can selectively absorb oil and organic matters from liquid pollutants leaking onto water surface so as to separate oil from water.

The invention discloses a polymer-coated aramid fiber and a preparation method thereof. The preparation method comprises the following steps: 1, mixing an inorganic salt with an inorganic alkali solution, and diluting with water to prepare a buffer solution; 2, placing an aramid fiber in the buffer solution under the protect of nitrogen, adding a solvent, horseradish peroxidase and an acrylic acid monomer, adding hydrogen peroxide drop by drop, and carrying out washing and vacuum drying after finishing a reaction to obtain the polymer-coated aramid fiber. By adopting above technical scheme of the invention, the enzyme inactivation rate is low, and the surface of the aramid fiber has a good swelling effect in a reaction medium, so the full contact of the biological enzyme and the fiber is guaranteed, and the grafting rate is improved; and the formed coating which contains active groups allows the cohesiveness of the fiber with other materials to be effectively improved, so a large space is provided for the further modification of the fiber. The technical scheme adopted in the invention has the characteristics of low damage to the fiber, mild reaction condition, simple and easily implemented technology, environmental protection, and high benefit of the industrialization production.

PCT No. PCT / SE96 / 00123 Sec. 371 Date Mar. 8, 1996 Sec. 102(e) Date Mar. 8, 1996 PCT Filed Feb. 2, 1996 PCT Pub. No. WO96 / 24359 PCT Pub. Date Aug. 15, 1996The invention relates to a pharmaceutical composition for topical administration comprising a combination of foscarnet and an antiinflammatory glucocorticoid, in admixture with a carrier based on galactolipids and a polar solvent. The pharmaceutical composition can be used in a prophylactic and / or curative treatment of herpesvirus infections in mammals including man. The invention also relates to the use of said pharmaceutical composition in the manufacture of a medicament for said prophylactic or curative treatment.

The invention discloses a N-doped porous carbon / NiO composite material and a preparation method therefor. The preparation method comprises the following steps: first, coal-based polyaniline is prepared through a in-situ polymerization method; second, nickle powder and coal-based polyaniline are mixed uniformly to obtain a mixture, the mixture is subjected to pyrolysis and a N-doped porous carbon / Ni composite material is obtained; third, hydrogen peroxide and sulfuric acid are mixed uniformly and a mixed solution A is obtained; fourth, the N-doped porous carbon / Ni composite material is added in the mixed solution A, after mixing processing is carried out, the pH value is adjusted to 7-8 through ammonium hydroxide, next a urea aqueous solution is added drop by drop, insulation stirring is carried out, pumping filtration is carried out after cooling, a filter cake is washed, the filter cake is calcined, and a N-doped porous carbon / NiO composite material is obtained. N-doped porous carbon in the N-doped porous carbon / NiO composite material prepared through the method shows pore structure characteristics of meso pores as the main and macropores as the part and NiO in the composite material exists in a form of nanosheets or nanospheres.

The invention discloses a method for preparing crosslinking-oxidization jointly modified starch, which comprises the following steps: (1) adding water into rice starch to prepare starch milk, adding 0.01 to 0.03 percent of NaCl into the starch milk and uniformly mixing the starch milk and the NaCl; (2) adjusting the pH value of the mixture to 9.0 to 11.0, adding epoxy chloropropane in an amount which is 0.1 to 0.9 percent of the weight of the rich starch for performing reaction at 20 to 50 DEG C for 2 to 5 hours, adjusting the pH value of the mixture obtained after reaction to 6.0 to 7.0 to obtain crosslinked rice starch; (3), adjusting the reaction temperature to 30 to 50 DEG C and adjusting the pH value of the crosslinked rice starch to 8 to 10; and (4) adding sodium hypochlorite solution of which the mass concentration of active chlorine is 7 to 10 percent in an amount which is 40 to 50 percent of the weight of the rice starch for performing further reaction for 20 to 40 minutes, removing excessive chlorine in the reactants by using solution of sodium bisulfate, adjusting the pH value of the resulting product to 6.0 to 6.5, filtering the resulting product, washing the resulting product and drying the resulting product. The crosslinking-oxidization jointly modified rice starch has a viscosity of more than or equal to 1,800cP, a shearing stress at 30 DEG C of up to 1,200dy / cm2, high swelling performance, high transparency and stability.

The invention relates to a lithium-ion-battery composite material and a preparing method of a composite electrode of a lithium ion battery. Nanometer silicon is added into a dopamine hydrochloride solution, and a polydopamine wrapping layer is formed on the surface of silicon; meanwhile, graphene quantum dots are prepared with the one-step solvothermal method, and are doped into sodium alginate binding agent, and a composite electrode material is prepared. In the lithium-ion-battery composite material and the preparing method of the composite electrode of the lithium ion battery, the polydopamine wrapping layer can buffer enormous volume expansion of a silicon ball, and the stability of a silicon-based cathode material is effectively improved. As the graphene quantum dots are doped, a binding agent layer has the higher mechanical performance and the elasticity, the product has the more lasting swelling property in electrolyte accordingly, and can develop the reversible buffering effecton enormous volume changes of silicon after multiple times of cycling, and the structural integrity of an electrode in the charging and discharging process is further guaranteed; meanwhile, the graphene quantum dots have certain conductivity, and therefore the conductivity of the binding agent layer is improved. The electrode shows the good electrochemical performance, and can be widely applied to various high-capacity lithium ion batteries.

The invention relates to a production method and applications of cyclic carbonate. According to the present invention, the used catalyst is a multifunctional biomimetic heterogeneous catalyst formed by an organic porous copolymer based on metalloporphyrin and a quaternary phosphonium salt, the catalyst carrier is formed by carrying out mixed polymerization on alkylene-functionalized metalloporphyrin and a quaternary phosphonium salt, and the active component of the catalyst comprises metalloporphyrin (as a Lewis acid activation epoxy compound) and a quaternary phosphonium salt (as a ring-opening nucleophilic reagent) functional group; the obtained multifunctional biomimetic heterogeneous catalyst can be used for fixed beds, slurry beds, kettle type reactors, trickle beds and other reactors; the obtained multifunctional biomimetic heterogeneous catalyst has good performance, extremely high activity (2000-6000 h<-1>), good selectivity (more than 99%) of the formed cyclic carbonate and strong substrate applicability in the cyclic carbonate production reaction between the epoxy compound and the carbon dioxide, further has good stability, and can be simply and efficiently separated fromthe substrate and the product.

The invention provides a powdery casting coating as well as a preparation method and a use method thereof. The powdery casting coating provided by the invention is composed of the following components in percentage by weight: 89-92% of refractory aggregates, 2.6-3.6% of sodium bentonite, 0.64-1.3% of rosin, 0.58-0.75% of polyvinyl butyral, 0.15-0.25% of hydroxypropyl methyl cellulose, and 4.0-5.1% of water. The powdery casting coating provided by the invention is alcohol-free, and capable of being mutually infiltrated and fused with alcohol in use to obtain a qualified coating.

The invention discloses a semi-interpenetrating network nano hybrid hydrogel and a preparation method and an application thereof. Firstly, chitosan is modified to prepare water soluble carboxymethyl chitosan (CMCS); then N-isopropylacrylamide (NIPAM), CMCS and (carboxyl functionalized) carbon nanotubes are subjected to in-situ free radical crosslinking polymerization reaction, and the semi-interpenetrating network nano hybrid hydrogel with different composition ratios of NIPAM, CMCS and the nanotubes is obtained. The prepared novel nano hybrid hydrogel has relatively high swelling rate, appropriate volume phase transition temperature and pH phase transition point, and high drug loading amount and continuous controllable drug release behavior. The hydrogel pharmaceutical preparation can be used as a promising hydrophilic oral drug carrier, is used for targeted release of oral vaccines, polypeptides, proteins and anticancer drugs, has low toxicity, and can be used for long-term treatment of colon cancer and the like.

An absorbable and expandable closure member used to occlude or exclude a body lumen or cavity, such as a blood vessel, fallopian tube, duct, aneurysmal sac, etc., comprising a closure member comprising one of more sheets of a biomaterial that are rolled, stacked, or folded to form a multilayer construct of a generally cylindrical configuration for deployment through a delivery system, either as a singularly or part of a multiplicity of closure members. The biomaterial is derived from a source material, such as small intestinal submucosa or another remodelable material (e.g., an extracellular matrix) having properties for stimulating ingrowth of adjacent tissue into the biomaterial deployed within the bodily lumen. The closure member is deployed to the bodily lumen from a delivery sheath, cartridge, and / or over a inner guiding member, such as a wire guide or catheter.

The invention discloses a preparation method of a cellulose based conductive hydrogel. The preparation method comprises the following steps: (1) dissolving microcrystalline cellulose (MCC) with 1-Butyl-3-methylimidazolium chloride, reacting in a N2 protective atmosphere, and adding N,N-methylenebisacrylamide and benzoyl peroxide to prepare a pure microcrystalline cellulose hydrogel; and (2) soaking the pure microcrystalline cellulose hydrogel obtained in the step (1) in a mixed solution of FeCl3 and sodium p-benzenesulfonate, and immersing in a pyrrole water solution to prepare the cellulose based conductive hydrogel. The cellulose based conductive hydrogel prepared by the method has the advantages of uniform stable network structure, excellent conductivity, swelling property and heat stability, favorable electric conductivity and favorable swelling property; and the equilibrium swelling rate can be up to about 500%.

The invention relates to a coating rubber sizing material of a dual-purpose printing rubber roller for UV (ultraviolet) ink and common ink. The sizing material consists of pre-plasticized butadiene-acrylonitrile rubber / polyvinyl chloride blend rubber, silicone rubber compound, precipitation-process white carbon black, zinc methacrylate, a polyester plasticizer, a plasticizer TP-95, a plasticizer TP-90B, sulfur, an accelerant, dicumyl peroxide and other auxiliaries. The sizing material provided by the invention has the characteristics that the swelling property is relatively good in the UV ink and cleaning agent thereof and common ink and cleaning agent thereof, and the physical property is equivalent to that of the coating rubber sizing material of the UV ink printing rubber roller and common ink printing rubber roller. The dual-purpose printing rubber roller made from the coating rubber sizing material can be conveniently replaced between the UV ink and the common ink, and can be applied to UV ink printing as well as common ink printing.

The invention discloses a bone china and a preparation method thereof, relates to a bone china and provides a bone china with better performance and a preparation method thereof. The blank raw materials of the bone china are 45-55 percent of bone powder, 255-34 percent of clay, 85-14 percent of feldspar and 85-12 percent of quartz. The preparation method comprises the following steps of: drying and calcinating the bone powder, cooling along with a furnace, ball milling and washing and then drying; carrying out ball milling on the clay, the feldspar and the quartz; mixing bone powder, clay powder, feldspar powder and quartz power which are subjected to ball milling; adding a dispersant and grinding to obtain a bone china sizing agent; pouring the bone china sizing agent into a mold and molding, then demolding and drying to obtain a blank; and repairing the bland, pouring the blank into the furnace and sintering to obtain the bone china. The invention solves the problems that the sizing agent molded by grouting has instability, low strength, easy crack and the like, caused by overhigh viscosity of the bone china sizing agent, improves the mechanical strength and the transmittance of the bone china, enables the comprehensive performance index of a bone body to reach an optimal balance by adopting a proper sintering system, avoids the production problem of higher production cost and has considerable market prospect.

The invention provides a method for preparing a compound material of modified polyvinyl chloride resin and thermosetting resin. The method adopts the solution blending process to obtain modifier-PVC blended solution and then the blended solution is precipitated to obtain PVC modified resin powder with high porosity. The resin powder is blended with the thermosetting resin and a curing agent at room temperature, and then molding and curing are carried out to obtain the compound material with better comprehensive performance. The solution blending method is adopted for obtaining the inorganic nanoparticle modified PVC resin powder, thereby avoiding the degradation of the PVC caused by high-temperature melt blending method, and the method can particularly ensure the own performance of the PVC resin and simultaneously achieve the nano-compound with modified particles to the maximum extent for the PVC with high degree of polymerization. The obtained modified PVC resin has good absorption and swelling abilities for plasticizers and the thermosetting resin and good adaptability with molding process. The impact strength of the material prepared by compound of the modified PVC resin and the thermosetting resin is improved by more than 2 times.

The invention belongs to the technical field of functional macromolecule material preparation and in particular relates to a method for preparing nano compound temperature-sensitive hydrogel by using frontal polymerization technology. The method comprises the following steps of: organizing nano-scale sodium-based montmorillonite with a cationic modifier first and then dissolving or dispersing a temperature-sensitive monomer, a crosslinking agent, the nano-scale sodium-based montmorillonite and an initiator into a dimethylsulfoxide solvent, and heating the mixture at the upper end of a tubular reactor to allow the initiator to decompose with heat; removing the heat source after the reaction beings, and allowing the heat generated by the polymerization per self to spread to a non-reacted area to form a polymerization front; allowing the polymerization front to spread automatically to gradually convert the raw materials into polymers; and rinsing the polymerization product with de-ionized water to obtain the nano compound temperature-sensitive hydrogel. The method has the advantages of low cost, quick reaction and simple process; and the prepared nano compound temperature-sensitive hydrogel has the characteristics of high strength and sensitive response.

The invention discloses a hydrophilic antibacterial composite nano fibrous membrane and a preparation method of the hydrophilic antibacterial composite nano fibrous membrane. The preparation method comprises the steps of: preparing a primary-spun polysulfone fibrous membrane by adopting an electrostatic spinning method, carrying out heat treatment on the primary-spun polysulfone fibrous membrane, and carrying out padding treatment on the polysulfone fibrous membrane with glutaric dialdehyde / chitosan solution after oxygen plasma treatment so that the solution entrainment rate is 80-100%; and hanging the padded membrane, drying at 30-40 DEG C, then immersing in 1-3% NaOH solution for treating for 1-2h, taking out, washing with deionized water to be neutral and drying at 35-50 DEG C. According to the invention, the hydrophilicity of the membrane is improved, the mechanical property of the membrane is effectively improved, the average pore size of the fibrous membrane is reduced and the filtering effect is improved.

The invention relates to a multifunctional biomimetic heterogeneous catalyst formed by an organic porous copolymer based on metalloporphyrin and a quaternary phosphonium salt, and a preparation methodthereof, wherein the metalloporphyrin and the quaternary phosphonium salt functional group are used as the main active component of the heterogeneous catalyst, the metalloporphyrin group is used as aLewis acid, the halogen ion in the quaternary phosphonium salt is used as a nucleophilic reagent, and the organic porous copolymer carrier containing metalloporphyrin and a quaternary phosphonium group is formed by carrying out co-polymerization on alkylene-functionalized metalloporphyrin and a quaternary phosphonium salt monomer. According to the present invention, the heterogeneous catalyst isused for the coupling reaction process of epoxy compounds and carbon dioxide, wherein the abundant N and P atoms in the polymer skeleton can increase the adsorption of CO2; and the porous organic polymer material can seal and limit the reaction substrate in the nano-scale pores and increase the concentration of the substrate at the catalytic site, such that the catalyst has double advantages of extremely high activity and extremely high stability.

The invention relates to the technical field of concrete and particularly relates to a preparation process of anti-cracking concrete. The preparation process comprises the following steps: (1) designing a concrete ratio; (2) uniformly stirring a mixture, wherein the stirring temperature is 15-40 DEG C; (3) pouring concrete: alternatively injecting the concrete and a high-strength steel-imitated fiber net into a template, and carrying out cement plastering treatment in the process; and (4) cutting and polishing the concrete: polishing by adopting a water grinding method, and adding a polishing medium. The preparation method of the anti-cracking concrete, provided by the invention, has the characteristics of easiness of obtaining raw materials, low cost, good performance and the like; all components are reasonably matched, and a high admixture use amount ratio and a low gel material use amount ratio are used as main characteristics; and the concrete which has good workability, high strength, good anti-cracking performance, good anti-seepage performance and long service life and is suitable for a seabed working condition is finally formed.

The invention discloses polyurethane / chitosan self-healing hydrogel based on Schiff base, which is prepared by crosslinking aldehyde polyurethane and chitosan serving as raw materials through an iminebond. Wherein the molar ratio of an aldehyde group in the aldehyde polyurethane to an amino group in the chitosan is 1: (1-3); wherein the solid content of the self-healing hydrogel is 8%-12%. The polyurethane / chitosan self-healing hydrogel based on the Schiff base has good mechanical property, excellent antibacterial property, good self-healing property, swelling property and pH responsiveness,is convenient to use, and can prolong the service life of the hydrogel.

The present invention aims to provide an electrode mixture which shows little change in viscosity even after 24 hours from the preparation of the mixture and enables production of an electrode having a high electrode density and excellent flexibility and is capable of giving excellent electric properties to the resulting cell. The present invention relates to an electrode mixture including a powdery electrode material; a binder; and an organic solvent, the binder including polyvinylidene fluoride and a fluorine-containing polymer including a polymer unit based on vinylidene fluoride and a polymer unit based on tetrafluoroethylene, the fluorine-containing polymer including the polymer unit based on vinylidene fluoride in an amount of 80.0 to 90.0 mol % based on all the polymer units, the polyvinylidene fluoride having a number average molecular weight of 150,000 to 1,400,000.