CN111154121A - Water-based polytetrafluoroethylene powder material and preparation method thereof - Google Patents
Water-based polytetrafluoroethylene powder material and preparation method thereof Download PDFInfo
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- CN111154121A CN111154121A CN201911405308.3A CN201911405308A CN111154121A CN 111154121 A CN111154121 A CN 111154121A CN 201911405308 A CN201911405308 A CN 201911405308A CN 111154121 A CN111154121 A CN 111154121A
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- C08F259/00—Macromolecular compounds obtained by polymerising monomers on to polymers of halogen containing monomers as defined in group C08F14/00
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- C08G12/26—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds
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- C08J2451/08—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
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Abstract
The invention discloses a water-based polytetrafluoroethylene powder material and a preparation method thereof, wherein the water-based polytetrafluoroethylene powder material is prepared from the following raw materials in parts by weight: 15-50 parts of polytetrafluoroethylene micro powder, 0.5-1 part of melamine, 0.25-0.5 part of formaldehyde, 5-25 parts of grafting monomer, 0.06-0.35 part of emulsifier, 0.25-1.5 parts of initiator and 40-80 parts of deionized water; the coating is prepared by grafting hydrophilic groups, so that the grafting rate of the hydrophilic groups is higher, the polytetrafluoroethylene powder has better hydrophilicity, and the hydrophilic groups can be grafted with various hydrophilic groups, so that the raw materials are various, the coating is more suitable for industrial production, and the coating has a positive effect on large-scale application of the aqueous polytetrafluoroethylene powder material in aqueous paint.
Description
Technical Field
The invention relates to the field of high polymer materials, in particular to modification of a high polymer material, and specifically relates to a water-based polytetrafluoroethylene powder material and a preparation method thereof.
Background
Polytetrafluoroethylene (PTFE) is a material with excellent physical and chemical properties, and is widely applied to chemical corrosion prevention, engineering plastics and other composite materials, even biomedicine and the like. However, because PTFE has extremely high hydrophobicity, PTFE fine powder is insoluble and difficult to disperse in water and almost all solvents, which makes it difficult to prepare a coating from PTFE fine powder, and is also a main reason why PTFE is not widely used in the field of coatings. In order to improve the hydrophilicity of PTFE micro powder, two methods are commonly used at present, one is that the surface of PTFE is subjected to chemical or radiation treatment to generate an activated group, and then a hydrophilic group is grafted on the surface of PTFE; another approach is to add a large amount of surfactant to reduce the surface tension of the PTFE, thereby increasing its hydrophilicity.
Chinese patent CN101223231A discloses an aqueous PTFE dispersion containing a plurality of specific fluorine-containing carboxylic acid salts (APFO), which improves the friction stability of PTFE to provide a good aqueous dispersion, thereby preventing thickening and cracking of the coating film, and a method for producing the same.
Chinese patent CN102086243A discloses a method for preparing a high-gloss polytetrafluoroethylene dispersion concentrate, which comprises the steps of adding deionized water, an initiator, a dispersant, a stabilizer and a polymerization monomer into a high-pressure reaction kettle to carry out emulsion polymerization reaction to obtain a modified polytetrafluoroethylene polymerization solution, and carrying out post-treatment concentration to obtain a polytetrafluoroethylene dispersion concentrate which has better hydrophilicity.
Chinese patent CN102977276A discloses a water-based polytetrafluoroethylene material, a preparation method and application thereof, in the method, electron beams or cobalt sources are utilized to irradiate PTFE micro powder, then the PTFE micro powder and acrylic acid are subjected to grafting reaction, and water dispersion of a grafting product is obtained through post-treatment, wherein the polytetrafluoroethylene material in the dispersion has better hydrophilicity.
Chinese patent CN107266631A discloses a preparation method of a modified polytetrafluoroethylene micropowder material, which comprises the step of carrying out grafting reaction on polytetrafluoroethylene micropowder in a mixed solution of monomer acrylic acid, 2-acrylamide-2-methylpropanesulfonic Acid (AMPS), fluorocarbon surfactant and water to prepare modified PTFE micropowder with high grafting rate, wherein the modified PTFE micropowder also has good hydrophilicity.
Although the prior art achieves the purpose of improving the hydrophilicity of the PTFE micro powder material or the dispersibility of the PTFE micro powder material in water, the PTFE dispersion liquid or the modified PTFE micro powder has the defects of low monomer grafting rate, single grafting monomer raw material, need of activating treatment on the PTFE micro powder, complex subsequent treatment process, poor hydrophilicity of PTFE products, incapability of large-scale production and the like, and the large-scale production and application of the PTFE micro powder in the water-based paint are seriously limited.
Disclosure of Invention
The invention aims to overcome the defect of poor hydrophilicity of the existing hydrophilic modified PTFE product, and provides a water-based polytetrafluoroethylene powder material and a preparation method thereof; the water-based polytetrafluoroethylene powder material is prepared by coating and grafting hydrophilic groups, the grafting rate of the hydrophilic groups is higher, so that the polytetrafluoroethylene powder has better hydrophilicity, and can be grafted with various hydrophilic groups, so that the raw materials are various, the water-based polytetrafluoroethylene powder material is more suitable for industrial production, and has a positive effect on large-scale application of the water-based polytetrafluoroethylene powder material in water-based paint.
In order to realize the purpose, the invention provides a water-based polytetrafluoroethylene powder material which is prepared from the following raw materials in parts by weight: 15-50 parts of polytetrafluoroethylene micro powder, 0.5-1 part of melamine, 0.25-0.5 part of formaldehyde, 5-25 parts of grafting monomer, 0.06-0.35 part of emulsifier, 0.25-1.5 parts of initiator and 40-80 parts of deionized water.
The aqueous polytetrafluoroethylene powder material of the invention is prepared by the reaction of melamine and formaldehyde to generate melamine formaldehyde resin prepolymer, which is coated with polytetrafluoroethylene micropowder and simultaneously carries out grafting and crosslinking reaction with a grafting monomer, and a stable shell with a large amount of hydrophilic groups is formed on the surface of the polytetrafluoroethylene micropowder, so that the hydrophilicity of the polytetrafluoroethylene micropowder is obviously improved, and the aqueous polytetrafluoroethylene powder material can be applied to aqueous coatings on a large scale.
Wherein, the grain diameter of the polytetrafluoroethylene micro powder can influence the grafting effect, the larger the grain diameter is, the more difficult the coating is, the poorer the grafting effect is, and the poorer the hydrophilicity is; the smaller the particle size, the more difficult the dispersion, the easy agglomeration, and the same influence on the grafting effect, therefore, the proper particle size can lead the polytetrafluoroethylene micro powder to have better grafting effect, and the hydrophilicity of the product is better. Preferably, the particle size of the polytetrafluoroethylene micro powder is 0.5-50 microns.
Wherein the emulsifier is one or more of nonionic emulsifier and/or ionic emulsifier; through emulsification, the dispersion of the polytetrafluoroethylene micro powder is facilitated, and meanwhile, an emulsification environment is provided for coating and grafting reaction; preferably, the emulsifier is a mixed emulsifier consisting of a nonionic emulsifier and an ionic emulsifier in a mass ratio of 0.5-1: 1. Wherein the nonionic emulsifier is one or more of OP10 and Tween 80; the ionic emulsifier is one or more of SDS and SDBS. The preferable emulsifier has better emulsifying effect and is beneficial to the coating and grafting reaction.
The grafting monomer is a monomer organic matter containing a hydrophilic group and capable of performing grafting and/or crosslinking reaction with melamine formaldehyde resin prepolymer, and can significantly improve the hydrophilicity of the polytetrafluoroethylene micropowder through the grafting and crosslinking reaction with the grafting monomer, preferably, the grafting monomer comprises but is not limited to one or more of acrylic monomers or acrylate monomers, further preferably, the grafting monomer comprises but is not limited to one or more of Methyl Methacrylate (MMA), Butyl Methacrylate (BMA), α -methacrylic acid (α -MAA), Acrylic Acid (AA), Butyl Acrylate (BA), Vinyl Acetate (VAC), pentaerythritol triacrylate and styrene (PS), more preferably, the grafting monomer is a mixed grafting monomer composed of one or more of acrylic monomers and one or more of acrylate monomers according to the mass ratio of 1-4: 1, the grafting ratio is higher, and the obtained polytetrafluoroethylene micropowder has better hydrophilicity.
Wherein the initiator is one or more of potassium persulfate, benzoyl peroxide and azobisisobutyronitrile; preferably, the initiator is potassium persulfate and benzoyl peroxide in a mass ratio of 1: 1. The preferable initiator composition has the advantages of more thorough grafting and crosslinking reaction, higher reaction speed, higher grafting rate and better hydrophilicity of the obtained polytetrafluoroethylene micropowder.
Preferably, the aqueous polytetrafluoroethylene powder material is prepared from the following raw materials in parts by weight: 15-30 parts of polytetrafluoroethylene micro powder, 0.5-1 part of melamine, 0.25-0.5 part of formaldehyde, 6-10 parts of grafting monomer, 0.06-0.24 part of emulsifier, 0.25-1.5 parts of initiator and 50-60 parts of deionized water.
Furthermore, in order to achieve the above object, the present invention provides a method for preparing an aqueous polytetrafluoroethylene powder material, comprising the steps of:
(1) mixing melamine, formaldehyde and deionized water, stirring and heating for reaction to prepare a melamine formaldehyde resin prepolymer solution;
(2) adjusting the pH value of the melamine formaldehyde resin prepolymer solution to 9-10, adding an emulsifier, stirring and emulsifying, adding polytetrafluoroethylene micro powder, and stirring and dispersing uniformly to obtain a mixed solution;
(3) and adding an initiator and a grafting monomer into the mixed solution, stirring for grafting and crosslinking reaction, and after the reaction is finished, carrying out suction filtration, washing, drying and crushing to obtain the water-based polytetrafluoroethylene powder material.
Wherein, in the step (1), the heating reaction temperature is 70-90 ℃ and the time is 3-5 h; the reaction temperature is too high, the reaction time is too long, the reaction of the melamine formaldehyde resin prepolymer is excessive, the polymerization degree is too large, and the later coating, grafting and crosslinking reaction is not facilitated; preferably, the temperature for heating reaction is 85 ℃ and the time is 4 h. Wherein the stirring speed is 100-300 rpm; the stirring speed is too high, which is not beneficial to polymerization reaction, and the speed is too low, which is easy to agglomerate; preferably, the stirring speed is 100 rpm.
Wherein in the step (2), the emulsifying temperature is 80-95 ℃ and the time is 20-40 min; the emulsification temperature is too low, the time is too short, the emulsification is not thorough, the emulsification effect is poor, and the subsequent reaction is not facilitated; the emulsification temperature is too high, the time is too long, the energy is wasted, and the production cycle is long. Wherein the stirring speed is 200-400 rpm; the stirring speed is too high, which is not beneficial to the emulsification; the speed is too slow, and the emulsifying speed is slow; preferably, the stirring speed is 300 rpm.
Wherein in the step (2), the stirring speed for stirring and dispersing is 400-800 rpm, and the time is 0.5-1.5 h; the preferred stirring speed is 700rpm and the time is 1 h; the preferable stirring speed and time have better dispersing effect and short production period.
Wherein in the step (3), the temperature of grafting and crosslinking reaction is 85-95 ℃ and the time is 6-10 h; preferably, the temperature of grafting and crosslinking reaction is 90 ℃, and the time is 6-8 h; the preferable reaction temperature and time have the advantages of more thorough reaction, higher grafting ratio and better hydrophilicity of the obtained polytetrafluoroethylene powder material. Wherein the stirring speed in the reaction process is 300-800 rpm; preferably, the stirring speed is 500 to 800 rpm.
Wherein in the step (3), the drying temperature is 100-120 ℃, and the drying time is 8-12 h; good drying effect, low energy consumption and short production period.
Compared with the prior art, the invention has the beneficial effects that:
1. in the aqueous polytetrafluoroethylene powder material, the melamine formaldehyde resin prepolymer and the grafting monomer are subjected to grafting and crosslinking reaction, so that the grafting efficiency of the hydrophilic groups is remarkably improved (the grafting rate is more than 20 percent), the number of the hydrophilic groups on the surface of the polytetrafluoroethylene micro powder is remarkably increased, and the hydrophilicity of the polytetrafluoroethylene powder is remarkably enhanced.
2. In the aqueous polytetrafluoroethylene powder material, the melamine formaldehyde resin prepolymer is coated on the surface of the polytetrafluoroethylene micro powder, so that the stability of a hydrophilic group on the surface of the polytetrafluoroethylene is better, and the polytetrafluoroethylene micro powder can be modified by more types of grafting monomers in a hydrophilic manner due to higher chemical activity of the melamine formaldehyde resin prepolymer, thereby being beneficial to improving the product yield (the yield is more than 96 percent) and being more suitable for industrial production.
3. The preparation method of the water-based polytetrafluoroethylene powder material has the advantages of high controllability, simple process, mild reaction conditions, high reaction efficiency and high product yield, and is suitable for large-scale and industrial production of the water-based polytetrafluoroethylene powder material.
Figures and table description:
FIG. 1 is an infrared spectrum of an example 1 of the present invention, a comparative example 1 and an unmodified PTFE fine powder (JH 300);
FIG. 2 is an infrared spectrum of example 1 of the present invention, comparative example 2 and unmodified PTFE fine powder (JH 300);
FIG. 3 is an infrared spectrum of example 1 of the present invention;
FIG. 4 is an infrared spectrum of example 2 of the present invention;
FIG. 5 is an infrared spectrum of example 3 of the present invention;
FIG. 6 is an infrared spectrum of example 4 of the present invention;
FIG. 7 is an infrared spectrum of example 5 of the present invention;
FIG. 8 is an infrared spectrum of example 6 of the present invention;
FIG. 9 is an infrared spectrum of example 7 of the present invention;
FIG. 10 is an infrared spectrum of example 8 of the present invention;
FIG. 11 is a graph showing the dispersion of polytetrafluoroethylene powder in water in example 1, comparative example 2 and comparative example 2 of the present invention (number 1 on the beaker is example 1, 02 is comparative example 1, 03 is comparative example 2);
FIG. 12 is a graph showing the dispersion of polytetrafluoroethylene powder in water in examples 1, 2, 3, 4, 5, 6, 7 and 8 of the present invention (numbers on the beaker: 1-8 correspond to examples 1-8, respectively).
Fig. 13 is a graph showing the results of the contact angle test.
Detailed Description
The present invention will be described in further detail with reference to test examples and specific embodiments, but it should not be construed that the scope of the above-described subject matter of the present invention is limited to the following examples, and that techniques realized based on the contents of the present invention are within the scope of the present invention.
Example 1:
(1) mixing 0.8 part of melamine, 0.4 part of formaldehyde and 60 parts of deionized water, and reacting at 85 ℃ and a stirring speed of 200rpm for 4 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 9 by using a 30% sodium carbonate solution, adding 0.05 part of OP10 and 0.1 part of SDS, emulsifying at the temperature of 85 ℃ and the stirring speed of 300rpm for 25min, adding 35 parts of polytetrafluoroethylene micro powder, and stirring and dispersing at the stirring speed of 600rpm for 1h to obtain a mixed solution;
(3) adding 0.25 part of potassium persulfate and 0.25 part of benzoyl peroxide into the mixed solution, adding 5 parts of acrylic acid and 5 parts of butyl acrylate, carrying out grafting and crosslinking reaction for 8 hours at the temperature of 90 ℃ and the stirring speed of 500rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/AA _ BA).
Example 2:
(1) mixing 0.8 part of melamine, 0.4 part of formaldehyde and 60 parts of deionized water, and reacting at 85 ℃ and a stirring speed of 200rpm for 4 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 9 by using a 30% sodium carbonate solution, adding 0.05 part of OP10 and 0.1 part of SDS, emulsifying at the temperature of 85 ℃ and the stirring speed of 300rpm for 25min, adding 40 parts of polytetrafluoroethylene micro powder, and stirring and dispersing at the stirring speed of 600rpm for 1h to obtain a mixed solution;
(3) adding 0.25 part of potassium persulfate and 0.25 part of benzoyl peroxide into the mixed solution, adding 5 parts of acrylic acid and 5 parts of vinyl acetate, carrying out grafting and crosslinking reaction for 8 hours at the temperature of 90 ℃ and the stirring speed of 500rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/AA _ VA).
Example 3:
(1) mixing 0.5 part of melamine, 0.25 part of formaldehyde and 40 parts of deionized water, and reacting at the temperature of 70 ℃ and the stirring speed of 100rpm for 5 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 10 by using a 30% sodium carbonate solution, adding 0.06 part of Tween 80, emulsifying at the temperature of 95 ℃ and the stirring speed of 400rpm for 20min, adding 45 parts of polytetrafluoroethylene micro powder, and stirring and dispersing at the stirring speed of 400rpm for 1.5h to obtain a mixed solution;
(3) adding 0.25 part of azodiisobutyronitrile, 5 parts of pentaerythritol triacrylate and 5 parts of α -methacrylic acid into the mixed solution, carrying out grafting and crosslinking reaction for 6 hours at the temperature of 95 ℃ and the stirring speed of 800rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/PETA _ MAA).
Example 4:
(1) mixing 1 part of melamine, 0.5 part of formaldehyde and 70 parts of deionized water, and reacting at the temperature of 90 ℃ and the stirring speed of 300rpm for 3 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 9 by using a 20% sodium carbonate solution, adding 0.15 part of tween 80 and 0.15 part of SDBS, emulsifying for 30min at the temperature of 80 ℃ and the stirring speed of 200rpm, adding 35 parts of polytetrafluoroethylene micro powder, and stirring and dispersing for 0.5h at the stirring speed of 800rpm to obtain a mixed solution;
(3) adding 0.75 part of potassium persulfate and 0.75 part of benzoyl peroxide into the mixed solution, adding 10 parts of acrylic acid, carrying out grafting and crosslinking reaction for 10 hours at the temperature of 85 ℃ and the stirring speed of 300rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/AA).
Example 5
(1) Mixing 0.5 part of melamine, 0.25 part of formaldehyde and 50 parts of deionized water, and reacting at 85 ℃ and a stirring speed of 100rpm for 5 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 10 by using a 40% sodium carbonate solution, adding 0.06 part of SDBS, emulsifying for 30min at the temperature of 95 ℃ and the stirring speed of 200rpm, adding 30 parts of polytetrafluoroethylene micro powder, and stirring and dispersing for 0.5h at the stirring speed of 500rpm to obtain a mixed solution;
(3) 0.25 part of benzoyl peroxide and 8 parts of α -methacrylic acid are added into the mixed solution, grafting and crosslinking reaction are carried out for 6h at the temperature of 95 ℃ and the stirring speed of 800rpm, and the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/MAA) is obtained after suction filtration, water washing, drying and crushing.
Example 6:
1) mixing 1 part of melamine, 0.5 part of formaldehyde and 60 parts of deionized water, and reacting at 85 ℃ and a stirring speed of 200rpm for 4 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 9 by using a 30% sodium carbonate solution, adding 0.05 part of OP10 and 0.1 part of SDS, emulsifying at the temperature of 85 ℃ and the stirring speed of 300rpm for 25min, adding 35 parts of polytetrafluoroethylene micro powder, and stirring and dispersing at the stirring speed of 600rpm for 1h to obtain a mixed solution;
(3) adding 0.25 part of potassium persulfate and 0.25 part of benzoyl peroxide into the mixed solution, adding 10 parts of vinyl acetate, carrying out grafting and crosslinking reaction for 8 hours at the temperature of 90 ℃ and the stirring speed of 500rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/VA).
Example 7:
(1) mixing 1 part of melamine, 0.5 part of formaldehyde and 70 parts of deionized water, and reacting at the temperature of 90 ℃ and the stirring speed of 300rpm for 3 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 9 by using a 20% sodium carbonate solution, adding 0.15 part of tween 80 and 0.15 part of SDBS, emulsifying for 30min at the temperature of 80 ℃ and the stirring speed of 200rpm, adding 45 parts of polytetrafluoroethylene micro powder, and stirring and dispersing for 0.5h at the stirring speed of 800rpm to obtain a mixed solution;
(3) 0.75 part of potassium persulfate and 0.75 part of benzoyl peroxide are added into the mixed solution, 10 parts of α -methacrylic acid and 5 parts of methyl methacrylate are added, grafting and crosslinking reaction are carried out for 10 hours at the temperature of 85 ℃ and the stirring speed of 300rpm, and the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/MMA _ MAA) is obtained after suction filtration, water washing, drying and crushing.
Example 8
(1) Mixing 0.8 part of melamine, 0.4 part of formaldehyde and 70 parts of deionized water, and reacting at the temperature of 70 ℃ and the stirring speed of 300rpm for 5 hours to prepare a melamine-formaldehyde resin prepolymer solution;
(2) adjusting the pH value of a melamine formaldehyde resin prepolymer solution to 10 by using a 30% sodium carbonate solution, adding 0.35 part of OP10, emulsifying for 25min at the temperature of 80 ℃ and the stirring speed of 400rpm, adding 30 parts of polytetrafluoroethylene micro powder, and stirring and dispersing for 0.5h at the stirring speed of 600rpm to obtain a mixed solution;
(3) adding 0.3 part of azobisisobutyronitrile, 5 parts of α -methacrylic acid and 5 parts of styrene into the mixed solution, carrying out grafting and crosslinking reaction for 10 hours at the temperature of 95 ℃ and the stirring speed of 400rpm, carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as MF/PTFE/MAA _ PS).
Comparative example 1:
(1) adding 0.15 part of Tween 80 and 0.15 part of SDBS into 70 parts of water, emulsifying for 30min at the temperature of 80 ℃ and the stirring speed of 200rpm, adding 35 parts of polytetrafluoroethylene micro powder, and stirring and dispersing for 0.5h at the stirring speed of 800rpm to obtain a mixed solution;
(2) adding 0.75 part of potassium persulfate and 0.75 part of benzoyl peroxide into the mixed solution, adding 5 parts of acrylic acid and 5 parts of butyl acrylate, carrying out grafting and crosslinking reaction for 10 hours at the temperature of 85 ℃ and the stirring speed of 300rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as PTFE/AA _ BA).
Comparative example 2:
(1) adding 0.15 part of tween 80, 0.15 part of SDBS and 1 part of silane coupling agent KH550 into 70 parts, emulsifying at the temperature of 80 ℃ and the stirring speed of 200rpm for 30min, adding 35 parts of polytetrafluoroethylene micro powder, and stirring and dispersing at the stirring speed of 800rpm for 0.5h to obtain a mixed solution;
(2) adding 0.75 part of potassium persulfate and 0.75 part of benzoyl peroxide into the mixed solution, adding 5 parts of acrylic acid and 5 parts of butyl acrylate, carrying out grafting and crosslinking reaction for 10 hours at the temperature of 85 ℃ and the stirring speed of 300rpm, and carrying out suction filtration, washing, drying and crushing to obtain the aqueous polytetrafluoroethylene powder material (marked as KH550/PTFE/AA _ BA).
Experimental example:
1. infrared spectrum experiment: the polytetrafluoroethylene fine powders prepared in the above examples 1 to 8, comparative example 1 and comparative example 2 were measured by an infrared spectrometer (Nicole iS 10FT-IR spectrometer (Thermo Scientific)), and the infrared spectra were shown in the attached figures 1 to 10 of the specification.
And (4) analyzing results: by analyzing the infrared chart 1 and 2, the following results can be obtained: the surface of the polytetrafluoroethylene fine powder in example 1 of the present invention was indeed coated or grafted with a large amount of melamine formaldehyde resin and acrylic resin. Whereas in comparative examples 1 and 2 only a small amount of hydrophilic groups was present.
The analysis of the infrared chart 3-10 shows that: the surfaces of the aqueous polytetrafluoroethylene powder materials prepared in the embodiments 1-8 of the invention are grafted with a large amount of acrylate groups successfully.
2. Product yield and grafting rate experiments: the polytetrafluoroethylene fine powders prepared in the above examples 1 to 8, comparative example 1 and comparative example 2 were subjected to analysis of product yield and graft ratio of acrylate resin, and the raw materials and the product were weighed respectively and then calculated according to the following formulas, and the results are shown in table 1.
Table 1 is a summary of the product yields and the acrylate resin grafting ratios of examples 1-8 and comparative examples, and the specific calculation formula is shown below: formula 1-product yield equals product mass/feed mass x 100%;
formula 2-the grafting ratio of the acrylate resin is equal to the grafting mass of the acrylate resin/the mass of the unmodified polytetrafluoroethylene powder multiplied by 100 percent;
description of the drawings: the mass of the material fed in the formula 1 is the mass of the unmodified polytetrafluoroethylene micro powder, the mass of melamine, the mass of formaldehyde and the mass of acrylate; in formula 2, the grafting ratio of the acrylate resin is defined: the ratio of the mass of the acrylic ester grafted onto the PTFE fine powder to the mass of the unmodified polytetrafluoroethylene powder to be grafted is referred to. The theoretical acrylic resin grafting rate, which is the mass of the added acrylic monomer/the mass of the unmodified polytetrafluoroethylene micro powder multiplied by 100%, refers to the highest acrylic resin grafting rate, and indicates that the added acrylic monomer is completely grafted to the polytetrafluoroethylene micro powder. In formula 2, the grafting mass of the acrylate resin is product mass-melamine formaldehyde resin mass-unmodified polytetrafluoroethylene fine powder mass, wherein at a low melamine formaldehyde resin solid content, specifically in the examples, the melamine formaldehyde resin mass is calculated as (melamine mass + formaldehyde mass) × 50%.
TABLE 1 product yield and graft results
And (4) analyzing results: as can be seen from Table 1, the acrylic resin grafting ratio and the product yield of the system with the melamine formaldehyde resin prepolymer in examples 1-8 are higher and obviously higher than those of comparative examples 1 and 2 without the melamine formaldehyde resin prepolymer, wherein the product yield is higher than that of examples 1 and 3 by over 99%, the improvement of the acrylic resin grafting ratio is helpful for improving the hydrophilicity of the polytetrafluoroethylene powder, and the corresponding verification is obtained during the dispersion test.
3. Water dispersion experiment: the polytetrafluoroethylene fine powders obtained in the above examples 1 to 8 and comparative examples 1 and 2 were subjected to a water dispersion test (test conditions in which 0.2 g of modified PTFE fine powder was added to 50ml of deionized water and stirred at normal temperature and 200rpm for 10 minutes), and the test results are shown in FIG. 11 and FIG. 12.
And (4) analyzing results: as can be seen from the dispersion experiments in FIGS. 11 and 12, the aqueous polytetrafluoroethylene powder materials prepared in examples 1-8 of the present application have significantly better aqueous dispersion effects than comparative examples 1 and 2. The addition of the melamine formaldehyde resin prepolymer can improve the hydrophilicity of the aqueous polytetrafluoroethylene powder material, so that the aqueous polytetrafluoroethylene powder material can be dispersed in water more easily.
4. Contact angle test: the polytetrafluoroethylene fine powders obtained in examples 1 to 8 and comparative examples 1 and 2 were subjected to contact angle test (test conditions, about 1min under 10MPa pressure, sheet formation with a tablet press, measurement of water contact angle at room temperature using TST-U805 optical automatic water contact angle measuring instrument), and the test results are shown in fig. 13 and table 2.
Table 2 contact angle test results
| JH300 | Comparative example 1 | Comparative example 2 | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 | Example 7 | Example 8 |
| 132.8° | 97.4° | 91.4° | 83.7° | 83.8° | 80.1° | 85.4° | 74.5° | 83.7° | 83.5° | 88.4° |
And (4) analyzing results: as can be seen from fig. 13 and table 1, JH300 (unmodified polytetrafluoroethylene micropowder) has relatively good hydrophobicity, examples 1 to 8 have significantly improved wettability to water, the contact angle is less than 89 °, comparative examples 1 and 2 have lower wettability to water than the examples, and the contact angle is greater than 91 °, which indicates that the modified polytetrafluoroethylene powder of the present invention has significantly improved hydrophilicity.
Claims (10)
1. The water-based polytetrafluoroethylene powder material is characterized by being prepared from the following raw materials in parts by weight: 15-50 parts of polytetrafluoroethylene micro powder, 0.5-1 part of melamine, 0.25-0.5 part of formaldehyde, 5-25 parts of grafting monomer, 0.06-0.35 part of emulsifier, 0.25-1.5 parts of initiator and 40-80 parts of deionized water.
2. The aqueous polytetrafluoroethylene powder material according to claim 1, wherein the particle size of the polytetrafluoroethylene micropowder is 0.5 to 50 μm.
3. The aqueous polytetrafluoroethylene powder material according to claim 1, wherein the emulsifier is a mixed emulsifier consisting of a nonionic emulsifier and an ionic emulsifier in a mass ratio of 0.5-1: 1.
4. The aqueous polytetrafluoroethylene powder material according to claim 1, wherein the grafting monomer comprises but is not limited to one or more of acrylic or acrylate monomers.
5. The aqueous polytetrafluoroethylene powder material according to claim 4, wherein the grafting monomer includes but is not limited to one or more of methyl methacrylate, ethyl acrylate, propyl acrylate, hydroxyethyl acrylate, butyl acrylate, α -methacrylic acid, acrylic acid, butyl acrylate, vinyl acetate, pentaerythritol triacrylate, and styrene.
6. The aqueous polytetrafluoroethylene powder material according to claim 5, wherein the initiator is one or more of potassium persulfate, benzoyl peroxide and azobisisobutyronitrile.
7. The aqueous polytetrafluoroethylene powder material according to claim 1, wherein the aqueous polytetrafluoroethylene powder material is prepared from the following raw materials in parts by weight: 25-45 parts of polytetrafluoroethylene micro powder, 0.5-1 part of melamine, 0.25-0.5 part of formaldehyde, 6-20 parts of grafting monomer, 0.06-0.24 part of emulsifier, 0.25-1.5 parts of initiator and 50-70 parts of deionized water.
8. A preparation method of the water-based polytetrafluoroethylene powder material as set forth in any one of claims 1-7, characterized by comprising the following steps:
(1) mixing melamine, formaldehyde and deionized water, stirring and heating for reaction to prepare a melamine formaldehyde resin prepolymer solution;
(2) adjusting the pH value of the melamine formaldehyde resin prepolymer solution to 9-10, adding an emulsifier, stirring and emulsifying, adding polytetrafluoroethylene micro powder, and stirring and dispersing uniformly to obtain a mixed solution;
(3) and adding an initiator and a grafting monomer into the mixed solution, stirring for grafting and crosslinking reaction, and after the reaction is finished, carrying out suction filtration, washing, drying and crushing to obtain the water-based polytetrafluoroethylene powder material.
9. The method for preparing the aqueous polytetrafluoroethylene powder material according to claim 8, wherein in the step (1), the heating reaction is carried out at 70-90 ℃ for 3-5 hours.
10. The preparation method of the water-based polytetrafluoroethylene powder material according to claim 8, wherein in the step (3), the temperature of the grafting and crosslinking reaction is 85-95 ℃ and the time is 6-10 hours.
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