High-strength polytetrafluoroethylene dispersion resin and preparation method thereof

Abstract

The invention discloses a high-strength polytetrafluoroethylene dispersion resin and a preparation method thereof, and belongs to the technical field of chemical engineering, and the preparation method comprises the following steps: preparing a linen fiber / nano silicon dioxide microsphere filler, adding the linen fiber / nano silicon dioxide microsphere filler into a polytetrafluoroethylene dispersion stock solution to form slurry, adding a modifier into the slurry to form composite slurry, putting the composite slurry into an ultraviolet ozone reaction cabin to carry out ultraviolet / ozone synergistic modification treatment, obtaining modified composite slurry after the treatment is completed, and carrying out molding treatment on the modified composite slurry to obtain the high-strength polytetrafluoroethylene dispersion resin. Through the mode, the linen fiber / nano silicon dioxide microsphere filler and ultraviolet ozone modification treatment synergistically enhance the strength of the dispersion resin.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical industry, in particular to a high-strength polytetrafluoroethylene dispersion resin and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene dispersion resin is a kind of polymer material with excellent chemical stability, high and low temperature resistance and physical strength, which is widely used in various fields such as chemical industry, electronics and aerospace.

[0003] The prior art has made many improvements on the polytetrafluoroethylene dispersion resin and its preparation method, for example, Chinese patent CN107868162B discloses a high molecular weight polytetrafluoroethylene dispersion resin and a preparation method thereof. A stabilizer, a dispersant, an anti-adhesive and the like are added in the water medium, and a tetrafluoroethylene monomer is added under the action of a modifier under a certain temperature and pressure through an oxidation-reduction initiation system to carry out dispersion polymerization, so as to obtain a polytetrafluoroethylene dispersion resin with SSG of 2.14-2.15. The polytetrafluoroethylene dispersion resin obtained by the method has high molecular weight, narrow and uniform molecular weight distribution. However, the tensile strength of the polytetrafluoroethylene dispersion resin prepared by the above method still needs to be further strengthened.

[0004] Based on this, the present application designs a high-strength polytetrafluoroethylene dispersion resin and a preparation method thereof to solve the above problems. SUMMARY

[0005] In view of the above shortcomings of the prior art, the present application provides a high-strength polytetrafluoroethylene dispersion resin and a preparation method thereof.

[0006] To achieve the above purpose, the present application is realized by the following technical scheme: A high-strength polytetrafluoroethylene dispersion resin and a preparation method thereof, comprising the following steps: Step one, preparation of flax fiber / nano-silica microsphere filler: The flax fiber powder and nano-silica are dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution, and a mixed solution is obtained after treatment for 5-12 minutes. The mixed solution is added dropwise into a dilute sulfuric acid coagulation bath, and after the reaction is completed, the flax fiber / nano-silica mixture is obtained after filtration and washing. The washed wet flax fiber / nano-silica mixture is re-dispersed in deionized water, first irradiated in a gamma ray field, and then spray dried to obtain the flax fiber / nano-silica microsphere filler; Step two, adding microsphere filler: The polytetrafluoroethylene dispersion stock solution is placed in a high-speed shearing stirrer, and the flax fiber / nano-silica microsphere filler is added. Continuous stirring is carried out with the aid of ultrasonic dispersion to form a slurry; Step three, ultraviolet ozone synergistic modification treatment: Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose and alkyl polyglycoside are added to the slurry, and stirring is continued after addition and assisted by ultrasonic dispersion, and the composite slurry is obtained after treatment; The above composite slurry is coated on a tray to form a thin layer, and placed in a ultraviolet ozone reaction chamber, the power of ultraviolet irradiation is 20-50mW / cm 2 , oxygen is introduced while ultraviolet irradiation is carried out, the treatment time is 3-5 minutes, and the modified composite slurry is obtained after treatment; Step four, molding: After the modified composite slurry is subjected to molding treatment, a high-strength polytetrafluoroethylene dispersion resin can be obtained.

[0007] Further, the specific process of step one is: Sodium hydroxide and urea are dissolved in deionized water to obtain a sodium hydroxide / urea mixed aqueous solution, the sodium hydroxide / urea mixed aqueous solution is pre-cooled to -12℃ to -18℃, then flax fiber powder and nano-silica are dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution, mechanical stirring is continuously carried out in an ice-salt bath at a speed of 500-1000 rpm, and a mixed solution is obtained after 5-12 minutes of treatment, the mixed solution is added dropwise into a dilute sulfuric acid coagulation bath, the reaction is terminated, and the hydrogen bond of cellulose is regenerated, the nano-silica dispersed in the internal structure is coated in the regeneration process, stirring is carried out at the same time, the stirring speed is 800-1200 rpm, after the reaction is completed, the flax fiber / nano-silica mixture is obtained after filtration and washing, the washed wet flax fiber / nano-silica mixture is dispersed in deionized water again, and spray drying is carried out to obtain flax fiber / nano-silica microsphere filler.

[0008] Further, the preparation process of flax fiber powder in step one is as follows: The flax fiber is crushed by a crusher, and flax fiber powder is obtained by sieving, and the aperture of the sieve is 80-200 mesh.

[0009] Further, the particle size of nano-silica in step one is 20-50 nm.

[0010] Further, the specific process of step three is as follows: Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose and alkyl polyglycoside are added to the slurry, and stirring is continued after addition and assisted by ultrasonic dispersion, and the composite slurry is obtained after treatment;

[0011] Furthermore, in step three, the wavelengths of the main light source for ultraviolet treatment are 185nm and 254nm, respectively, and the flow rate of oxygen is 0.1-2.0L / min.

[0012] Furthermore, the specific process of step five is as follows: Add 5-15% magnesium nitrate solution as a coagulant to the modified composite slurry to completely precipitate the polytetrafluoroethylene composite particles; After filtration and washing, polytetrafluoroethylene composite particles are dried in a vacuum oven at 80-100℃ for 18-30 hours to obtain high-strength polytetrafluoroethylene dispersion resin.

[0013] To better achieve the objectives of this invention, this invention also provides a high-strength polytetrafluoroethylene dispersion resin obtained according to the above preparation method.

[0014] Compared with the prior art, the beneficial effects of this invention are as follows: 1. Flax fiber and nano silica are used together to prepare fillers and then subjected to γ-ray irradiation pretreatment, so that the two are combined to achieve biphasic synergistic reinforcement of the dispersion resin, thereby the prepared polytetrafluoroethylene dispersion resin has good mechanical strength. 2. Before molding, a modifier is added for UV / ozone synergistic modification treatment, which further improves the performance of the prepared polytetrafluoroethylene dispersion resin. 3. The synergistic effect of flax fiber / nano silica microsphere filler and UV / ozone modification treatment enhances the tensile strength and elongation at break of the dispersion resin. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] Example 1: A method for preparing a high-strength polytetrafluoroethylene dispersion resin, specifically including the following steps: Step 1: Preparation of flax fiber / nano-silica microsphere filler Flax fibers are crushed using a pulverizer and then sieved to obtain flax fiber powder. The sieve has an aperture of 80 mesh.

[0017] By weight, 7 parts sodium hydroxide and 12 parts urea were added to 81 parts deionized water to obtain a sodium hydroxide / urea mixed aqueous solution. The sodium hydroxide / urea mixed aqueous solution was first pre-cooled to -12°C. Then, flax fiber powder and nano-silica with a particle size of 20 nm were dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution. The mixture was continuously mechanically stirred at 500 rpm in an ice-salt bath for 12 minutes to obtain a mixed solution. The mixed solution was added dropwise to a 5% dilute sulfuric acid coagulation bath to terminate the reaction and regenerate the hydrogen bonds of cellulose. During the regeneration process, the nano-silica dispersed in its internal structure was coated. The mixture was stirred at 800 rpm while being added dropwise. After the reaction was completed, the mixture was filtered and washed to obtain a flax fiber / nano-silica mixture. The washed wet flax fiber / nano-silica mixture was redispersed in deionized water and irradiated in a gamma-ray field with an absorbed dose of 80 kGy. Then, it was spray-dried to obtain flax fiber / nano-silica microsphere filler.

[0018] Step 2: Add microsphere packing material The polytetrafluoroethylene dispersion stock solution was placed in a high-speed shear mixer, and flax fiber / nano silica microsphere filler was added. The mixture was continuously stirred and ultrasonically dispersed at a speed of 2000 rpm and an ultrasonic power of 500W for 30 minutes to form a slurry.

[0019] Step 3: Co-modification treatment with ultraviolet and ozone Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose, and alkyl glycosides were added to the slurry. The dosages of the three were as follows: 0.5% potassium perfluorohexyl ethyl sulfonate, 2.0% hydroxyethyl cellulose, and 0.3% alkyl glycosides by weight of the slurry. After addition, the mixture was continuously stirred and ultrasonically dispersed. The stirring speed was 3500 rpm, the ultrasonic power was 300W, and the treatment time was 60 minutes. The ultrasonic treatment was intermittent, with a 5-second working time followed by a 2-second stop. After the treatment was completed, a composite slurry was obtained. The aforementioned composite slurry was coated onto a tray to form a thin layer, which was then placed in an ultraviolet ozone reaction chamber. The main light source wavelengths were 185nm and 254nm, and the power was 20mW / cm². 2 Oxygen was introduced simultaneously with ultraviolet irradiation at a flow rate of 2.0 L / min for 3 minutes, resulting in a modified composite slurry.

[0020] Step 4: Molding Adding 5% magnesium nitrate solution as a coagulant to the modified composite slurry allows the polytetrafluoroethylene composite particles to precipitate completely.

[0021] After filtration and washing, polytetrafluoroethylene (PTFE) composite particles are dried in a vacuum oven at 80°C for 30 hours to obtain high-strength PTFE dispersion resin. The high-strength PTFE dispersion resin is then cold-pressed at 20 MPa, and subsequently heated to 380°C at a rate of 100°C / h and held at that temperature for 3 hours. Finally, it is cooled to room temperature to obtain a high-strength PTFE composite material.

[0022] Example 2: A method for preparing a high-strength polytetrafluoroethylene dispersion resin, specifically including the following steps: Step 1: Preparation of flax fiber / nano-silica microsphere filler Flax fibers are crushed using a pulverizer and then sieved to obtain flax fiber powder. The sieve has a mesh size of 200.

[0023] By weight, 7 parts sodium hydroxide and 12 parts urea were added to 81 parts deionized water to obtain a sodium hydroxide / urea mixed aqueous solution. The sodium hydroxide / urea mixed aqueous solution was first pre-cooled to -18°C. Then, flax fiber powder and nano-silica with a particle size of 50 nm were dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution. The mixture was continuously mechanically stirred at 1000 rpm in an ice-salt bath for 5 minutes to obtain a mixed solution. The mixed solution was added dropwise to a 5% dilute sulfuric acid coagulation bath to terminate the reaction and regenerate the hydrogen bonds of cellulose. During the regeneration process, the nano-silica dispersed in its internal structure was coated. The mixture was stirred at 1200 rpm while being added dropwise. After the reaction was completed, the mixture was filtered and washed to obtain a flax fiber / nano-silica mixture. The washed wet flax fiber / nano-silica mixture was redispersed in deionized water and irradiated in a gamma-ray field with an absorbed dose of 30 kGy. Then, it was spray-dried to obtain flax fiber / nano-silica microsphere filler.

[0024] Step 2: Add microsphere packing material The polytetrafluoroethylene dispersion stock solution was placed in a high-speed shear mixer, and flax fiber / nano silica microsphere filler was added. The mixture was continuously stirred and ultrasonically dispersed at a speed of 5000 rpm and an ultrasonic power of 300W for 90 minutes to form a slurry.

[0025] Step 3: Co-modification treatment with ultraviolet and ozone Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose, and alkyl glycosides were added to the slurry. The amounts of the three added were: 1.5% potassium perfluorohexyl ethyl sulfonate, 0.8% hydroxyethyl cellulose, and 1.0% alkyl glycosides by weight of the slurry. After addition, the mixture was continuously stirred and ultrasonically dispersed at a speed of 2000 rpm and a power of 500W for 30 minutes. The ultrasonic treatment was intermittent, with a 5-second working time followed by a 2-second pause. After the treatment was completed, a composite slurry was obtained. The aforementioned composite slurry was coated onto a tray to form a thin layer, which was then placed in an ultraviolet ozone reaction chamber. The main light source wavelengths were 185nm and 254nm, and the power was 50mW / cm². 2 While performing ultraviolet irradiation, oxygen was introduced at a flow rate of 0.1 L / min for 5 minutes, resulting in a modified composite slurry.

[0026] Step 4: Molding Adding 15% magnesium nitrate solution as a coagulant to the modified composite slurry allows the polytetrafluoroethylene composite particles to precipitate completely.

[0027] After filtration and washing, polytetrafluoroethylene (PTFE) composite particles are dried in a vacuum oven at 100°C for 18 hours to obtain high-strength PTFE dispersion resin. The high-strength PTFE dispersion resin is then cold-pressed at 40 MPa, and subsequently heated to 380°C at a rate of 100°C / h and held at that temperature for 2 hours. Finally, it is cooled to room temperature to obtain a high-strength PTFE composite material.

[0028] Example 3: A method for preparing a high-strength polytetrafluoroethylene dispersion resin, specifically including the following steps: Step 1: Preparation of flax fiber / nano-silica microsphere filler Flax fibers are crushed using a pulverizer and then sieved to obtain flax fiber powder. The sieve has a mesh size of 120.

[0029] By weight, 7 parts sodium hydroxide and 12 parts urea were added to 81 parts deionized water to obtain a sodium hydroxide / urea mixed aqueous solution. The sodium hydroxide / urea mixed aqueous solution was first pre-cooled to -16℃. Then, flax fiber powder and nano-silica with a particle size of 35nm were dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution. The mixture was continuously mechanically stirred at 800rpm in an ice-salt bath for 7 minutes to obtain a mixed solution. The mixed solution was added dropwise to a 5% dilute sulfuric acid coagulation bath to terminate the reaction and regenerate the hydrogen bonds of cellulose. During the regeneration process, the nano-silica dispersed in its internal structure was coated. The mixture was stirred at 1100rpm while being added dropwise. After the reaction was completed, the mixture was filtered and washed to obtain a flax fiber / nano-silica mixture. The washed wet flax fiber / nano-silica mixture was redispersed in deionized water and irradiated in a gamma-ray field with an absorbed dose of 60kGy. Then, it was spray-dried to obtain flax fiber / nano-silica microsphere filler.

[0030] Step 2: Add microsphere packing material The polytetrafluoroethylene dispersion stock solution was placed in a high-speed shear mixer, and flax fiber / nano silica microsphere filler powder was added. The mixture was continuously stirred and ultrasonically dispersed at a speed of 4000 rpm and an ultrasonic power of 350W for 60 minutes to form a slurry.

[0031] Step 3: Co-modification treatment with ultraviolet and ozone Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose, and alkyl glycosides were added to the slurry. The dosages of the three were as follows: 1.0% of potassium perfluorohexyl ethyl sulfonate, 1.2% of hydroxyethyl cellulose, and 0.6% of alkyl glycosides by weight of the slurry. After addition, the mixture was continuously stirred and ultrasonically dispersed at a speed of 2500 rpm and a power of 350 W for 40 minutes. The ultrasonic treatment was intermittent, with a 5-second working time followed by a 2-second pause. After the treatment was completed, a composite slurry was obtained. The aforementioned composite slurry was coated onto a tray to form a thin layer, which was then placed in an ultraviolet ozone reaction chamber. The main light source wavelengths were 185nm and 254nm, and the power was 40mW / cm². 2 Oxygen was introduced simultaneously with ultraviolet irradiation at a flow rate of 1.5 L / min for 4.5 minutes, resulting in a modified composite slurry.

[0032] Step 4: Molding Adding 10% magnesium nitrate solution as a coagulant to the modified composite slurry allows the polytetrafluoroethylene composite particles to precipitate completely.

[0033] After filtration and washing, polytetrafluoroethylene (PTFE) composite particles are dried in a vacuum oven at 95°C for 20 hours to obtain high-strength PTFE dispersion resin. The high-strength PTFE dispersion resin is then cold-pressed at 32 MPa, and subsequently heated to 380°C at a rate of 100°C / h and held at that temperature for 2.5 hours. Finally, it is cooled to room temperature to obtain a high-strength PTFE composite material.

[0034] Comparative Example 1: Compared with Example 3, the length of the flax fiber in step one is 50 nm.

[0035] Comparative Example 2: Compared with Example 3, step three does not involve UV ozone synergistic modification treatment.

[0036] Comparative Example 3: Compared with Example 3, the length of the flax fiber in step one is 50 nm, and the ultraviolet ozone synergistic modification treatment is not performed in step three.

[0037] Experimental Example: The following performance tests were conducted on the high-strength polytetrafluoroethylene composite materials prepared in Examples 1-3 and Comparative Examples 1-3: Tensile strength and elongation at break: GB / T 1040.3-2006; Thermal instability index: GB / T 33067-2016.

[0038] The test results are shown in Table 1: Table 1

[0039] As shown in Table 1, the high-strength polytetrafluoroethylene composite materials prepared in Examples 1-3 have tensile strengths of 35.8-37.4 MPa, indicating that the high-strength polytetrafluoroethylene composite materials have excellent strength. The elongation at break is 439-445%, indicating that the high-strength polytetrafluoroethylene composite materials have excellent toughness. At the same time, the thermal instability index is less than 0.05%, indicating that the high-strength polytetrafluoroethylene composite materials have excellent thermal stability.

[0040] As can be seen from Example 3 and Comparative Example 1, if the length of the flax fiber in step one is 50 nm, the tensile strength and elongation at break of the high-strength polytetrafluoroethylene composite material prepared in Comparative Example 1 will decrease, while the thermal instability index will increase.

[0041] As can be seen from Example 3 and Comparative Example 2, if the ultraviolet ozone synergistic modification treatment is not performed in step three, the tensile strength and elongation at break of the high-strength polytetrafluoroethylene composite material prepared in Comparative Example 2 will decrease, while the thermal instability index will increase.

[0042] As can be seen from Example 3 and Comparative Example 3, the synergistic effect of flax fiber / nano silica microsphere filler and ultraviolet ozone synergistic modification treatment on the tensile strength and elongation at break of high-strength polytetrafluoroethylene composite material is achieved.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength polytetrafluoroethylene dispersion resin, characterized in that, Includes the following steps: Step 1: Preparation of flax fiber / nano-silica microsphere filler: Flax fiber powder and nano silica were dispersed in a pre-cooled sodium hydroxide / urea mixed aqueous solution and treated for 5-12 minutes to obtain a mixture. The mixture was added dropwise to a dilute sulfuric acid coagulation bath. After the reaction was completed, the mixture was filtered and washed to obtain a flax fiber / nano silica mixture. The washed wet flax fiber / nano silica mixture was redispersed in deionized water, irradiated in a gamma-ray field, and then spray-dried to obtain flax fiber / nano silica microsphere filler. Step 2: Add microsphere packing material: The polytetrafluoroethylene dispersion stock solution was placed in a high-speed shear mixer, and flax fiber / nano silica microsphere filler was added. The mixture was continuously stirred and ultrasonically dispersed to form a slurry. Step 3: Ultraviolet-ozone synergistic modification treatment: Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose and alkyl glycosides were added to the slurry. After addition, the mixture was continuously stirred and ultrasonically dispersed. The resulting composite slurry was then obtained. The above-mentioned composite slurry was coated onto a tray to form a thin layer, and then placed in an ultraviolet ozone reaction chamber where the ultraviolet irradiation power was 20-50 mW / cm². 2 Oxygen is introduced while ultraviolet irradiation is performed, and the treatment time is 3-5 minutes. After the treatment, a modified composite slurry is obtained. Step 4: Shaping After the modified composite slurry is subjected to molding treatment, a high-strength polytetrafluoroethylene dispersion resin can be obtained.

2. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 1, characterized in that, The specific process of step one is as follows: Sodium hydroxide and urea were dissolved in deionized water to obtain a sodium hydroxide / urea mixed aqueous solution. The sodium hydroxide / urea mixed aqueous solution was pre-cooled to -12°C to -18°C. Flax fiber powder and nano silica were then dispersed in the pre-cooled sodium hydroxide / urea mixed aqueous solution. The solution was continuously mechanically stirred in an ice-salt bath at a speed of 500-1000 rpm for 5-12 minutes to obtain a mixture. The mixture was then added dropwise to a dilute sulfuric acid coagulation bath while stirring at a speed of 800-1200 rpm. After the reaction was completed, the mixture was filtered and washed to obtain a flax fiber / nano silica mixture. The washed wet flax fiber / nano silica mixture was redispersed in deionized water and spray-dried to obtain flax fiber / nano silica microspheres.

3. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 2, characterized in that, The specific process for preparing flax fiber powder in step one is as follows: Flax fibers are crushed using a pulverizer and then sieved to obtain flax fiber powder. The sieve mesh size is 80-200 mesh.

4. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 2, characterized in that, In step one, the particle size of the nano-silica is 20-50 nm.

5. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 1, characterized in that, The specific process of step three is as follows: Potassium perfluorohexyl ethyl sulfonate, hydroxyethyl cellulose, and alkyl glycosides are added to the slurry. The dosages of the three are as follows: 0.5-1.5% potassium perfluorohexyl ethyl sulfonate, 0.8-2.0% hydroxyethyl cellulose, and 0.3-1.0% alkyl glycosides by weight of the slurry. After addition, the mixture is continuously stirred and ultrasonically dispersed at a speed of 2000-3500 rpm and an ultrasonic power of 300-500W for 30-60 minutes. The resulting composite slurry is then obtained.

6. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 1, characterized in that, In step three, the wavelengths of the main light source for ultraviolet treatment are 185nm and 254nm, and the flow rate of oxygen is 0.1-2.0L / min.

7. The method for preparing the high-strength polytetrafluoroethylene dispersion resin according to claim 1, characterized in that, The specific process of step five is as follows: Add 5-15% magnesium nitrate solution as a coagulant to the modified composite slurry to completely precipitate the polytetrafluoroethylene composite particles; After filtration and washing, polytetrafluoroethylene composite particles are dried in a vacuum oven at 80-100℃ for 18-30 hours to obtain high-strength polytetrafluoroethylene dispersion resin.

8. A high-strength polytetrafluoroethylene dispersion resin obtained by the preparation method according to any one of claims 1-7.

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