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Method and process for preparing dilute UHMWPE solution and detecting its solubility

发布日期:2020-01-07 13:12 Document serial number: 19641812 Release date: 2020-01-07 13:12

The present invention relates to the field of organic chemical materials, particularly relates to a process for the preparation and the degree of dissolution of one uhmwpe dilute solution to be detected.



Background technique:

In recent years, the processing of ultra-high molecular weight polyethylene (uhmwpe) resins and small-molecule solvents has been widely used in the field of high-strength fibers and lithium battery separators. Due to the tightly entangled structure of uhmwpe macromolecular chains, its dissolution is very difficult. If the resin is not completely dissolved in the solvent, transparent "gel" particles appear in the solution (formed because the physical entanglement points between the molecular chains have not been completely unentangled in the solvent, unlike a gel formed by a crosslinked network ), Specifically manifested in the surface of fibers or films prepared by uhmwpe resin, such as black spots, crystal points or holes, which greatly affect the performance and quality of the product. In addition, gel particles in the solution affect its processing stability Sex. Therefore, the preparation of a uniform uhmwpe solution becomes an important link in the entire production process of fibers and separators, so that the uhmwpe molecular chains are fully entangled in the solvent to form a uniform solution, which has a decisive effect on the performance of the fibers or separators.

The preparation of a uniform uhmwpe dilute solution and the detection of its solubility have become the key to the processing process and product performance.

Patent cn109721892a discloses a vinylidene fluoride thermoplastic resin, a preparation method and application thereof, which involves a method for testing the gel content of a polymer: after the polymer is extruded into a film, it can be determined by the number of defects visible to the naked eye. The film is transparent or opaque, and the defects reflect or refract light and appear as (more) opaque areas (usually shown as dark or black areas or spots). The gel content of the polymer was obtained by recording the number of such spots per m 2 film by imaging software. The size of the defect is about 0.06mm to 1.00mm. This method has high requirements on the test sample, and needs to be able to form a film and have certain requirements for light transmission. In addition, this method can only measure the gel particles on the surface of the film, which has a certain deviation from the actual results.

Patent cn109153809a discloses a molecular modification method of polyethylene resin, which involves a method of extracting crosslinked polyethylene with boiling xylene through a Soxhlet extraction device, and drying and weighing to calculate the gel content of the crosslinked polyethylene. The method is refluxed at a high temperature for a long time to achieve complete dissolution of the uncrosslinked polyethylene portion, but this method is not suitable for difficult-to-dissolve "gel" particles formed by the physical entanglement of macromolecular chains, because After a high temperature reflow for a long time, the "gel" formed by the physical entanglement point will be completely dissolved in the solvent.

Patent cn102605440a discloses a method for preparing a high-concentration ultra-high-molecular-weight polyethylene spinning solution, which comprises adding ultra-high-molecular-weight polyethylene powder with a molecular weight of 5 to 8 million and an antioxidant together into a solvent, dissolving at high temperature, and preparing the product. A low-concentration ultra-high molecular weight polyethylene solution is obtained; a low-concentration ultra-high molecular weight polyethylene high-temperature solution is concentrated at 190 to 220 ° C to obtain a uniform and completely dissolved 10% to 20% high-concentration ultra-high molecular weight polyethylene solution. It does not disclose a quantitative method for measuring the degree of dissolution and cannot clearly determine the dissolution of ultra-high molecular weight polyethylene.



Technical realization elements:

The purpose of the present invention is to provide a method for preparing a uhmwpe dilute solution and a method for detecting its solubility in order to solve the above-mentioned problems, and to solve the problem that the insoluble "gel" content formed by the physical entanglement points of the macromolecular chains is not measured at present. Status quo.

The object of the present invention is achieved by the following technical solutions:

A method for preparing a dilute uhmwpe solution and measuring its dissolving degree. The method is to weigh dry uhmwpe powder or fine fragments, with a mass of m1, mix uhmwpe with a solvent, and leave the mixed solution at a high temperature and constant temperature for a period of time. , Mechanical stirring, until the torque of the stirring is stable (the torque value changes with time within 10 minutes to reach a stable state within 10 minutes); then the mixture is quickly filtered through a filter to collect the uhmwpe gel on the filter The mass of the particles after the extraction solvent and vacuum drying is m2, and the value of m2 / m1 is used as a parameter to determine the solubility of uhmwpe. The smaller the value of m2 / m1, the better the solubility; otherwise, the larger the value of m2 / m1 , Indicating the worse the solubility. The experimental results show that the value of m2 / m1 is from 0 to 0.5%, which indicates that the solubility of uhmwpe is better. At this time, the content of "gel" particles is low and the particle size is small, which will hardly affect the performance and appearance of the product.

Preferably, the solvent is selected from one or more of decalin, paraffin oil, toluene, xylene or trichlorobenzene.

Preferably, the solvent contains an antioxidant, and the antioxidant is selected from one or more of a phenol-type antioxidant, an amine-type antioxidant, and a heterocyclic antioxidant. The concentration range is 0 to 1 wt.%.

Preferably, the gel particles are obtained after solvent extraction and drying. The extractant is selected from one of dichloromethane or hydrocarbon extractant, the extraction ratio is 50, and the vacuum drying temperature is 60-80. ℃.

Preferably, the viscosity average molecular weight range of the uhmwpe resin is 0.5 × 10 6 to 5.8 × 10 6 g / mol, and the concentration range is 0.05 to 0.5 wt.%.

Preferably, the temperature range of the high temperature and constant temperature of the mixed liquid is 130 to 200 ° C, and the standing time is 0.5 to 3h, and the temperature is more preferably 150 to 170 ° C, and the standing time is 1 to 2h. The organic solvent in this temperature range The solubility to uhmwp is large, which can ensure that uhmwpe particles do not exist due to saturation in the formed uhmwpe dilute solution; too long standing time will cause the "gel" formed by the physical entanglement point to be completely dissolved in the solvent.

Preferably, the rotation speed of the mechanical stirring is 100-200 rpm.

Preferably, the mesh size of the filter is 180-220 mesh, and the mesh size of the filter is selected according to the molecular size of uhmwpe to avoid filtering other impurities that are not in the particle size range.

Preferably, the filter screen is a metal filter screen. When filtering, the metal filter screen is immersed in a uhmwpe dilute solution subjected to a high-temperature constant temperature bath, and after filtering, the uhmwpe gel particles on the filter screen are collected.

Preferably, the filtering time is 20-30 seconds, and the filtering is completed quickly. When the filter is used for filtering, the filter will be taken out of the dilute solution. At this time, the temperature of the filter will be reduced, and the dilute solution attached to the surface of the filter will also be cooled, which may cause the uhmwpe section to analyze. Quick filtering can reduce this. The occurrence of such situations reduces the impact on the evaluation results.

The present invention is different from the test for gel content of polymers formed by chemical cross-linking networks. The present invention creatively sets the value of m2 / m1 (that is, the mass of uhmwpe gel particles) / (uhmwpe resin powder Quality)) as the ratio of the parameter to determine the solubility of uhmwpe as the physical "gel" content, used to quantitatively evaluate the solubility of uhmwpe. The lower the value, the better the solubility in the solvent. Processing has important guiding significance. Different polymers with cross-linked structures cannot be dissolved in the solvent by increasing the temperature or prolonging the dissolution time. The "gel" particles in this patent fail to completely resolve in the solvent through the physical entanglement points between the macromolecular chains. Formed by entanglement, such "gel" particles cannot be dissolved in the solvent for a short time, and increasing the temperature or prolonging the dissolution time may fully dissolve in the solvent. For actual production, too long a dissolution time will affect its production efficiency, and an increase in temperature will cause the polymer to decompose. Therefore, in order to not affect the performance of the product during processing time, it is necessary to make the ultra-high molecular weight polyethylene resin not completely dissolved. The "gel" particle content is minimized.

Compared with the prior art, the method used in this patent is different from the current detection of flaws such as transparent spots of manufactured products to determine the processability (dissolution degree) of ultra-high molecular weight polyethylene. The method used in this patent was first proposed in The ratio of raw materials can realize the quantitative characterization of the solubility of ultra-high molecular weight polyethylene resin, which helps to accurately screen the raw materials and improve the yield of industrial production.

Compared with the prior art, the dilute uhmwpe solution prepared by the present invention has a uniform concentration, a simple preparation process, a simple and efficient detection method, and the detection standard accurately reflects the "coagulation" of the uhmwpe resin which is difficult to dissolve due to the physical entanglement of the macromolecular chains "Gum" particle content.

detailed description

The present invention is described in detail below with reference to specific embodiments.

A method for preparing ultra-high molecular weight polyethylene (uhmwpe) dilute solution. The preparation method is specifically: weighing uhmwpe resin powder, an organic solvent and an antioxidant, and adding them to a container to form a dilute solution. The container is placed in a high temperature constant temperature bath, and then stirred to assist dissolution to form a uniform uhmwpe dilute solution. The temperature range of the high temperature constant temperature bath is 130 to 200 ° C, and the standing time is 0.5 to 3 hours. The stirring time is 0.5 to 3 hours. Among them, the method for detecting the degree of dissolution is specifically: immersing the metal filter in a uhmwpe dilute solution subjected to a high-temperature constant temperature bath, leaving it for a period of time, and then filtering and collecting the uhmwpe gel particles on the filter, and the uhmwpe gel particles Weigh after extraction and filtration, and use the ratio of (mass of uhmwpe gel particles) / (mass of uhmwpe resin powder) to evaluate the solubility of uhmwpe. The smaller the ratio, the higher the solubility. The mesh number of the metal filter is 180 ~ 220 mesh, and the filtering time is 20 ~ 30s.

Example 1

Weigh 0.025 g of uhmwpe (viscosity average molecular weight 0.5 × 10 6 g / mol) resin powder, weigh 49.95 g of paraffin oil, add antioxidant 168 (concentration 1 wt.%), And mix uhmwpe powder, paraffin oil, and antioxidant Add it to a glass container to form a dilute solution (uhmwpe concentration is 0.05wt.%). Put the mixed solution of uhmwpe / paraffin oil in a 150 ° C thermostatic bath and let it stand for 1 hour, and then add slow mechanical stirring to dissolve it for 2 hours. The time curve does not show obvious large fluctuations, indicating that uhmwpe dissolves to form a uniform dilute solution. The homogeneous solution was then quickly (within 30 s) filtered through a 200-mesh metal mesh to the high-temperature uhmwpe solution (150 ° C). The uhmwpe gel particles on the mesh were collected, and the solvent was extracted and dried to weigh the gel particle mass 0 g. , The content of the physical "gel" particles is 0%.

Example 2

Weigh 0.05 g of uhmwpe (viscosity average molecular weight 1.2 × 10 6 g / mol) resin powder, weigh 49.95 g of decalin, add antioxidant 168 (concentration 1 wt.%), And mix uhmwpe powder, decalin, Antioxidant was added to a glass container to form a dilute solution (uhmwpe concentration was 0.1wt.%). The mixed solution of uhmwpe / decahydronaphthalene was placed in a constant temperature bath at 150 ° C for 1 hour, and then dissolved by mechanical stirring for 1.5 hours. Until the torque is stable, visually observe that uhmwpe is uniformly dissolved in the solvent to form a uniform solution. The homogeneous solution was then quickly (within 30 s) filtered through a 200-mesh metal mesh to the high-temperature uhmwpe solution (150 ° C). The uhmwpe gel particles on the mesh were collected, and the solvent was extracted and dried to weigh the gel particle mass 0 g. , The content of the physical "gel" particles is 0%.

Example 3

Weigh 0.25g of uhmwpe (viscosity average molecular weight 2.1 × 10 6 g / mol) resin powder, weigh 49.75g paraffin oil, add antioxidant 168 (concentration 0.5wt.%), And mix uhmwpe powder, paraffin oil, anti- The oxidant was added to the glass container to form a dilute solution (uhmwpe concentration was 0.5wt.%). The mixed solution of uhmwpe / decahydronaphthalene was placed in a 160 ° C constant temperature bath for 1 hour, and then dissolved by mechanical stirring for 1.5 hours until it was dissolved. The torque is stable, and the uhmwpe is uniformly dissolved in the solvent to form a uniform solution. The homogeneous solution was then quickly (within 30s) filtered through a 200-mesh metal mesh to the high-temperature uhmwpe solution (160 ° C). The uhmwpe gel particles on the mesh were collected, and the solvent was extracted and dried to weigh the gel particle mass 0.008. g, the content of the physical "gel" particles is 3.2%.

Example 4

Weigh 0.25 g of uhmwpe (viscosity average molecular weight 3.5 × 10 6 g / mol) resin powder, weigh 49.75 g of decalin, add antioxidant 168 (concentration 0.6 wt.%), And mix the powder of uhmwpe and decalin 1. Add the antioxidant to the glass container to form a dilute solution (uhmwpe concentration is 0.5wt.%). Put the mixed solution of uhmwpe / decahydronaphthalene in a constant temperature bath at 150 ℃ for 1h, and then add mechanical stirring to dissolve for 1.5h. Until the torque is stable, visually observe that uhmwpe is uniformly dissolved in the solvent to form a uniform solution. The homogeneous solution was then quickly (within 30 s) filtered through a 200-mesh metal mesh to a high-temperature uhmwpe solution (150 ° C). The uhmwpe gel particles on the mesh were collected, and the solvent was extracted and dried to weigh the gel particle mass 0.015. g, the content of the physical "gel" particles is 6%.

Example 5

Weigh 0.25g of uhmwpe (viscosity average molecular weight 5.8 × 10 6 g / mol) resin powder, weigh 49.75g paraffin oil, add antioxidant 168 (concentration 1wt.%), Mix uhmwpe powder, paraffin oil, antioxidant Add it to a glass container to form a dilute solution (uhmwpe concentration is 0.5wt.%). Put the mixed solution of uhmwpe / decahydronaphthalene in a 180 ° C thermostatic bath and let it stand for 1 hour, and then add mechanical stirring to dissolve it for 2 hours until the torque is stable. , Visual inspection uhmwpe uniformly dissolved in the solvent to form a uniform solution. Then the homogeneous solution was quickly (within 30s) filtered through a 200-mesh metal mesh to the high-temperature uhmwpe solution (180 ° C). The uhmwpe gel particles on the mesh were collected, and the solvent was extracted and dried to weigh the gel particle mass to 0.021. g, the content of the physical "gel" particles is 8.4%.

The foregoing description of the embodiments is to facilitate understanding and use of the invention by those skilled in the art. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications that do not depart from the scope of the present invention within the scope of the present invention.

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