A high-performance TPU film material and its preparation method

Abstract

The present invention discloses a high-performance TPU film material and a preparation method thereof. The preparation method includes: semi-plasticizing TPU particles through a single-screw extruder, and setting the temperature of the single-screw extruder between 120 °C and 160 °C; adding the semi-plasticized TPU melt to a two-roll mill for kneading, controlling the temperature of the two-roll mill between 130 °C and 150 °C, and simultaneously adding TPU particles and lubricants between the rolls of the two-roll mill; the added TPU particles account for 10 wt% - 50 wt% of the total amount of the TPU melt being kneaded, so that the TPU in the two-roll mill is always in a semi-plasticized state; feeding the kneaded TPU melt material into a calender roll, controlling the roll temperature of the calender roll between 120 °C and 140 °C, pulling out the film through the calender roll, and shaping and winding it through a cooling roll to obtain a high-performance TPU film material. The present invention solves the problems of the development of kneaded TPU products, the development of kneading and calendering processes, as well as the problems of TPU roll wrapping and large internal heat generation.

Description

Technical Field

[0001] The present invention relates to the technical field of the production of thermoplastic polyurethane elastomer (TPU) films, and particularly relates to a high-performance TPU film material and a preparation method thereof. Background Art

[0002] At present, the production processes of TPU films mainly include extrusion blow molding, casting, melt coating, calendering, etc. First, the TPU pellets are melted at a high temperature, and then the melt is shaped into a film by means of blow molding, calendering, etc. However, few TPUs can be processed by the method of open milling like rubber. The main reasons include:

[0003] 1) The processing window of open milling and calendering of TPU is narrow. If the temperature is too low, plasticization cannot be achieved. If the temperature is too high, it is easy to stick to the roll. After sticking to the roll, cleaning consumes a lot of manpower and material resources, and the production efficiency is low.

[0004] 2) The open milling equipment currently used in China is very small. The length of the open milling rolls is generally about 1 m, and the longest does not exceed 2 m. The production efficiency is very low, and the output is low (far lower than the production capacity of processes such as blow molding and casting), and mass production cannot be achieved. Larger open milling rolls cannot process TPU. One reason is that the output of large rolls is large, but the internal heat generation of TPU is not easy to control, and it is easy to stick to the roll. The other reason is that there is currently no mature TPU product available for open milling and calendering, and there is no mature TPU open milling processing technology.

[0005] At the present stage, most of the polymer materials that can be calendered are rubbers, and there are also plastic products such as PVC. Because they can achieve high filling and have poor temperature sensitivity, the problem of sticking to the roll basically does not occur during the open milling process, and the processing window is relatively wide.

[0006] Currently, the most efficient production method of TPU films is extrusion casting, and there are few open milling and calendering processes and products.

[0007] The current situation of TPU open milling and calendering in the prior art is listed as follows:

[0008] (1) There is currently no TPU product specifically applied to open milling and calendering. The TPU products on the market are difficult to achieve effective open milling operations. Because the processing window of TPU used as a calendering material is the temperature range between the softening temperature and the viscous flow temperature. Below the softening temperature, plasticization cannot be carried out. Above the viscous flow temperature, it sticks to the roll and cannot be calendered into a shape. The calendering temperature range of conventional TPU is about 15 °C. However, within this range, the plasticization effect will become worse when approaching the softening temperature, and the problem of sticking to the roll will occur when approaching the viscous flow temperature. Therefore, the actual processing temperature window of TPU on calendering equipment is very narrow.

[0009] (2) Currently, there is a lack of a dedicated TPU open mill production process. The problem of TPU sticking to the rolls during the open mill process is a difficult problem in the industry. If too much lubricant is added, it is difficult for TPU to be stably extruded and there is a risk of precipitation. If too little lubricant is added, it will not work.

[0010] (3) To obtain high-strength products from conventional TPU cast films, high-viscosity and high-performance TPU particles are required.

[0011] The patent specification with the publication number CN 103756287 A discloses a modified TPU calendered film and its preparation method, which includes the following components: TPU resin, TPO resin, TPSiV resin, TPU masterbatch, light stabilizer, antioxidant, mildew and antibacterial agent, flame retardant, processing lubricant, etc. The preparation method of the modified TPU calendered film includes the following steps: Put the raw materials of each component into a high-speed mixer according to the formula dosage, stir evenly at a high speed, control the temperature at 80-90 °C, then enter the internal mixer, the internal mixing time is 3-5 min, and after mixing, pass through the rolling mill, extrude and filter, and transport it to the four rolls for calendering to obtain the film product. This patent technical solution does not optimize the TPU resin itself, but improves the processing performance of TPU by adding other types of resins additionally, and does not improve the process. Summary of the Invention

[0012] The present invention provides a preparation method of a high-performance TPU film material, which solves the problems of providing TPU calendered products and developing an open mill calendering process. Through the present invention, the application of TPU products in the field of open mill calendering can be greatly improved, and TPU can be produced by a larger open mill roll (for example, with a length of 3-5 m), and the production capacity is greatly improved. More importantly, the TPU film produced by the open mill calendering process of the present invention has higher strength compared to the cast film. The present invention simultaneously solves the problems of developing open mill TPU products and developing an open mill calendering process, and better solves the problems of TPU roll entanglement and large internal heat. Through the cooperation of the product and the process, a TPU film product with better performance and higher output is produced.

[0013] The specific technical solution is as follows:

[0014] A preparation method of a high-performance TPU film material, including:

[0015] Step 1, semi-plasticize the TPU particles through a single-screw extruder, and set the temperature of the single-screw extruder between 120-160 °C;

[0016] Step 2: Add the semi-plasticized TPU melt to the open mill for mixing. The temperature of the open mill is controlled between 130 - 150 °C. Meanwhile, add TPU particles and lubricants between the rollers of the open mill. The added TPU particles account for 10wt% - 50wt% of the total amount of the TPU melt being mixed in the open mill, keeping the TPU in the open mill in a semi-plasticized state all the time, ensuring that there is no problem of roll wrapping after the TPU melt enters the open mill.

[0017] Step 3: Feed the well-mixed TPU melt material into the calender roll. The temperature of the calender roll is controlled between 120 - 140 °C. Draw out the film through the calender roll, and then shape and wind it up through the cooling roll to obtain the high-performance TPU film material.

[0018] The reason why the TPU film obtained in the present invention has high performance is that the present invention makes good use of the internal stress of the TPU product. Processes such as extrusion casting use high-temperature plasticization of the TPU product for processing, which not only cannot avoid the degradation of TPU at high temperature resulting in performance decline, but also completely eliminates the internal stress of the TPU product. The processing temperature of the present invention is relatively low, which preferably prevents the degradation of the TPU product and does not eliminate the internal stress of the product, greatly improving the strength of the TPU film.

[0019] For the preparation method of the high-performance TPU film material described above, the purpose of Step 1 is to make the TPU have the plasticity for mixing in the open mill without sticking to the rolls.

[0020] For the preparation method of the high-performance TPU film material described above, in Step 1, the hardness of the TPU particles is preferably 80A - 95A to ensure the appropriate hardness of the TPU product.

[0021] As a preference, for the preparation method of the high-performance TPU film material described above, in Step 1, the raw material composition of the TPU particles includes polyol, isocyanate, chain extender, lubricant, etc. The number-average molecular weight of the polyol is 500 - 1500 g / mol; the actual processing temperature window for mixing the TPU particles is 30 - 50 °C.

[0022] Further preferably, the small molecule diol for synthesizing the polyol is a diol with 2 - 4 carbon atoms.

[0023] By controlling the molecular weight of the above-mentioned polyol and selecting the synthesis raw materials, the softening point and melting point of the TPU product can be reduced, enabling the product to be processed at a lower temperature and within a wider processing temperature range.

[0024] Further preferably, the lubricant in the raw materials of the TPU particles is at least one of erucic acid amide lubricants, oleic acid amide lubricants, and stearic acid lubricants, and its addition amount is 0.02% - 0.3% of the mass of the polyol.

[0025] Preferably, in the preparation method of the high-performance TPU film material, in step one, the TPU particles are obtained by reactive extrusion granulation, and the reaction temperature (i.e., the temperature of the reaction zone of the extrusion equipment) is controlled at 120-180°C.

[0026] In the preparation method of the high-performance TPU film material, the purpose of adding TPU particles in step two is to eliminate the endothermic heat during the open mill process, so that the TPU is always in a semi-plasticized state, and the lubricant is added to prevent sticking to the rolls.

[0027] Preferably, in the preparation method of the high-performance TPU film material, in step two, the lubricant is at least one of erucic acid amide lubricants, oleic acid amide lubricants, and stearic acid lubricants, and the addition amount is 0.05wt%-0.6wt% of the total amount of the TPU melt.

[0028] In a preferred example, in the preparation method of the high-performance TPU film material, in step three, 50%-70% of the open-milled TPU melt material is cut off and fed into the calender rolls, and the remaining TPU melt remains in the open mill and continues to be open-milled with the newly added semi-plasticized TPU melt and TPU particles. In this way, continuous production is carried out by cycling. Cutting off a part rather than all of the melt is for two reasons. One is to ensure the continuity and stability of production, and the other is to ensure that the TPU has the same plasticized state, so that the product performance is uniform and stable.

[0029] In the preparation method of the high-performance TPU film material, in step three, the calender roll temperature is controlled at 120-140°C, one is to ensure the calendering plasticity, and the other is to ensure that the product has sufficient internal stress.

[0030] In the preparation method of the high-performance TPU film material, in step three, the temperature of the cooling roll is preferably -10 to 20°C.

[0031] The present invention also provides a high-performance TPU film material prepared by the preparation method described above.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] By combining the open mill method with the characteristics of TPU particles, the performance of the TPU film prepared by the present invention is greatly improved. The present invention has developed a special lubricant addition process, which involves the addition of lubricants in the raw materials for preparing TPU particles and the addition of lubricants between the rolls during the open mill process. The present invention has opened up a new direction for the market application of TPU such as the preparation of TPU films by open mill calendering. Specific Embodiments

[0034] The following will further illustrate the present invention in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0035] For the operation methods without specified conditions in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0036] Example 1

[0037] Select poly(ethylene adipate)diol (Mn = 1000), 4,4'-diphenylmethane diisocyanate (MDI), and 1,4-butanediol as the chain extender. 0.1% of oleic acid amide (calculated based on the mass of the polyol) is added to the polyol in advance. A TPU product with a hardness of 90A is produced through formula calculation. The temperature of the reaction extruder is controlled at 120 °C (pouring port temperature zone), 150 °C (first reaction zone), 160 °C (second reaction zone), 170 °C (third reaction zone), 175 °C (fourth reaction zone), 170 °C (fifth reaction zone), 150 °C (sixth reaction zone), 130 °C (cooling zone), 100 °C (cooling zone), 100 °C (cooling zone), 100 °C (cooling zone). Then it is extruded, granulated, and packaged and stored in the warehouse.

[0038] Take 3 kg of the finished pellet material and put it into the drying hopper. After drying at 70 °C for 3 h, take it out. Use a small open mill to verify the temperature range in which the product can be normally processed by open milling, and confirm the film-forming situation and heat-resistant yellowing performance of the product.

[0039] After verifying that it can be used, dry 1000 kg of the TPU product at 70 °C for 3 h, and then conduct preliminary plasticizing extrusion through an extruder. The temperature of the extruder is set at 140 °C. Immediately draw the semi-plasticized TPU melt to an open mill for open milling, and at the same time add the dried TPU particles and the lubricant oleic acid amide. The TPU particles are added at 10 wt% of the total melt amount, and the lubricant is added at 0.5 wt% of the total melt amount. After normal film-forming, cut off 70% of the amount and draw it to the calender roll. The temperature of the calender roll is controlled at 135 °C, and the film thickness is controlled at 0.3 mm. After stabilization, draw it to the cooling roll for shaping and winding. The temperature of the cooling roll is 5 °C.

[0040] Take samples of the formed film, cut them, and test their physical properties.

[0041] Example 2

[0042] Dry 100 Kg of the TPU particles prepared in Example 1 at 70 °C for 3 h, and then put them into a casting machine for extrusion and film casting. The film thickness is controlled at 0.3 mm. The temperature of the casting machine is set from the feeding port to the die head as 170 °C - 180 °C - 190 °C - 200 °C - 195 °C. If the temperature is too low, the effect of the extruded film is poor, and the transparency and plasticizing effect are not good. If the temperature is too high, normal film winding cannot be carried out. After multiple verifications, the effect of extruding and casting the film is the best at this temperature. The cast film is cooled and shaped by the cooling roll and normally wound. The temperature of the cooling roll is controlled at 10 °C.

[0043] Take samples of the formed film for cutting and test its physical properties.

[0044] Example 3

[0045] Select polyethylene adipate glycol (Mn = 1000), 4,4'-diphenylmethane diisocyanate (MDI), and choose 1,4-butanediol as the chain extender. Add 0.1% of oleic acid amide (calculated based on the mass of the polyol) to the polyol in advance. Produce a TPU product with a hardness of 90A through formula calculation. Control the temperature of the reactive extruder at 120°C, 150°C, 160°C, 170°C, 175°C, 170°C, 150°C, 130°C, 100°C, 100°C, 100°C. Extrude, pelletize, and package for storage.

[0046] Take 3 kg of the finished pellet material and put it into the drying hopper. After drying at 70°C for 3 hours, take it out. Use a small open mill to verify the temperature range in which the product can be normally processed by open milling, and confirm the film-forming situation and heat-resistant yellowing performance of the product.

[0047] After verification of usability, dry 1000 kg of TPU product at 70°C. After drying for 3 hours, conduct preliminary plasticizing extrusion through an extruder. Set the temperature of the extruder at 140°C. Immediately draw the semi-plasticized TPU melt to an open mill for open milling. Only add the lubricant oleic acid amide, and add 0.5 wt% of the lubricant to the total melt. When open milling normally, the phenomenon of roll entanglement occurs. After applying a certain amount of lubricant to the rolls in advance, the roll entanglement problem is alleviated. Supplement the lubricant addition amount by 0.1 wt% of the total melt. After film formation, cut off 70% of the amount and draw it to the calender roll. Control the roll temperature of the calender roll at 135°C, control the film thickness at 0.3 mm, and then draw it to the cooling roll for shaping and winding. The roll temperature of the cooling roll is 5°C.

[0048] Take samples of the formed film for cutting and test its physical properties.

[0049] Example 4

[0050] Select polyethylene adipate glycol (Mn = 1000), 4,4'-diphenylmethane diisocyanate (MDI), and choose 1,4-butanediol as the chain extender. Produce a TPU product with a hardness of 90A through formula calculation. Control the temperature of the reactive extruder at 120°C, 150°C, 160°C, 170°C, 175°C, 170°C, 150°C, 130°C, 100°C, 100°C, 100°C. Extrude, pelletize, and package for storage.

[0051] Take 3 kg of the finished pellet material and put it into the drying hopper. After drying at 70°C for 3 hours, take it out. Use a small open mill to verify the temperature range in which the product can be normally processed by open milling, and confirm the film-forming situation and heat-resistant yellowing performance of the product.

[0052] After verification of availability, 1000 kg of TPU products were dried at 70 °C for 3 hours. After 3 hours of drying, they were preliminarily plasticized and extruded through an extruder. The temperature of the extruder was set at 140 °C. The semi-plasticized TPU melt was immediately drawn to a two-roll mill for mixing. However, the problem of roller entanglement occurred in the two-roll mill, making it impossible to mix normally.

[0053] Example 5

[0054] Polyethylene adipate glycol (Mn = 2000), 4,4'-diphenylmethane diisocyanate (MDI), and 1,4-butanediol were selected as the chain extender. 0.1% of oleic acid amide was added in advance to the polyol (calculated based on the mass of the polyol). Through formula calculation, a TPU product with a hardness of 90A was produced. The temperature of the reactive extruder was controlled at 120 °C, 150 °C, 160 °C, 170 °C, 175 °C, 170 °C, 150 °C, 130 °C, 100 °C, 100 °C, 100 °C, and then extruded, pelletized, and packaged and stored in the warehouse.

[0055] 3 kg of the finished pellet was placed into the drying hopper and dried at 70 °C for 3 hours and then taken out. A small two-roll mill was used to verify the temperature range in which the product could be normally processed by mixing, and to confirm the film-forming situation and heat-resistant yellowing performance of the product.

[0056] The processing window verified in the small test was found to be relatively narrow, so no on-line verification was carried out.

[0057] Example 6

[0058] Polyethylene adipate glycol (Mn = 1000), 4,4'-diphenylmethane diisocyanate (MDI), and 1,4-butanediol were selected as the chain extender. 0.1% of oleic acid amide was added in advance to the polyol (calculated based on the mass of the polyol). Through formula calculation, a TPU product with a hardness of 90A was produced. The temperature of the reactive extruder was controlled at 150 °C, 180 °C, 190 °C, 200 °C, 190 °C, 180 °C, 160 °C, 150 °C, 130 °C, 100 °C, 100 °C, and then extruded, pelletized, and packaged and stored in the warehouse.

[0059] 3 kg of the finished pellet was placed into the drying hopper and dried at 70 °C for 3 hours and then taken out. A small two-roll mill was used to verify the temperature range in which the product could be normally processed by mixing, and to confirm the film-forming situation and heat-resistant yellowing performance of the product.

[0060] After verification, 1000 kg of TPU products are dried at 70 °C. After 3 hours of drying, they are preliminarily plasticized and extruded through an extruder. When the temperature of the extruder is set at 140 °C, the extrusion effect is slightly poor. When the temperature is increased by 5 °C, the extrusion effect is close to that of Example 1. The semi-plasticized TPU melt is immediately drawn to a two-roll mill for mixing. At the same time, the dried TPU particles and lubricant are added. The TPU particles are added at 10 wt% of the total melt amount, and the lubricant is added at 0.5 wt% of the total melt amount. There is a slight phenomenon of sticking to the rolls. After appropriate cooling, the problem is not serious. After normal mixing and film formation, 70% of the amount is cut off and drawn to a calender roll. The temperature of the calender roll is controlled at 135 °C, and the film thickness is controlled at 0.3 mm. After stabilization, it is drawn to a cooling roll for shaping and winding. The temperature of the cooling roll is 5 °C.

[0061] The formed film is sampled and cut to test its physical properties.

[0062] Table 1 Comparison table of mixing performance data for different examples

[0063] Example 1 Example 5 Example 6 Pilot-scale open mill temperature range / °C 122-155 180-190 135-155 Yellowing condition after 20 min of pilot-scale open milling The film does not turn yellow The film does not turn yellow The film does not turn yellow Yellowing condition after 40 min of pilot-scale open milling The film does not turn yellow The film turns significantly yellow The film does not turn yellow Yellowing condition after 60 min of pilot-scale open milling The film does not turn yellow The film turns yellow severely The film turns slightly yellow

[0064] The larger the mixing temperature range, the easier it is to control during extrusion and mixing, and the less likely it is to have problems such as roll entanglement. As can be seen from the comparison of the above examples, the effect of Example 1 is the best. In Example 5 produced according to normal TPU production, due to the relatively high molecular weight of the polyol, the product forms quickly and has a relatively high melting point, resulting in a narrow processing window. Moreover, because the mixing processing temperature is relatively high, the film is more likely to turn yellow during the mixing process, and its heat resistance becomes worse; in the production process of Example 6, the temperature control is relatively high, the TPU particle product reacts well, and the molecular weight is relatively high, resulting in a reduction in the mixing temperature range of the product. The optimal processing temperature during specific mixing is relatively high, resulting in poor yellowing resistance performance.

[0065] Table 2 Comparison table of film strength data for different examples

[0066] Example 1 Example 2 Example 3 Example 6 Longitudinal strength of the film / MPa 70.34 54.34 68.73 65.34 Transverse strength of the film / MPa 68.56 50.43 65.44 64.33

[0067] Comparing Example 1 and Example 2, it can be seen that for TPU products with the same formula produced by the present invention, due to different processing technologies of the products, the performance differences are obvious. In Example 3, because no TPU particles were added to eliminate the aggregation of reaction heat, roll entanglement occurred during mixing. This scheme is only used for experimental evaluation, and the solution to the roll entanglement problem needs to be reconsidered in actual production. The aggregation of reaction heat is a challenge to the heat resistance of the product, and the film strength is slightly lower; comparing Example 1 and Example 6, in Example 6, because the reaction temperature is higher during the TPU production process, the product reacts more fully, the molecular weight is higher, and both the melting point and viscosity have increased, and the film strength has weakened slightly.

[0068] Moreover, it can be seen from the above data comparison that for the film products obtained by open mixing, the strength difference between the longitudinal and transverse directions is significantly reduced. For cast films, the longitudinal strength is generally higher due to the influence of stretching and orientation crystallization, and the transverse strength is significantly poorer. However, the products obtained by open mixing have high strength in both the longitudinal and transverse directions.

[0069] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A preparation method of a high-performance TPU film material, characterized in that, Including: Step 1: Semi-plasticize the TPU particles through a single-screw extruder, and the temperature of the single-screw extruder is set between 120 - 160 °C; the raw material composition of the TPU particles includes polyol, isocyanate, chain extender, and lubricant; the lubricant in the raw materials of the TPU particles is at least one of erucic acid amide lubricant, oleic acid amide lubricant, and stearic acid lubricant, and its addition amount is 0.02% - 0.3% of the mass of the polyol; the number-average molecular weight of the polyol is 500 - 1500 g / mol; the actual open mill processing temperature window of the TPU particles is 30 - 50 °C; the TPU particles are obtained by reactive extrusion granulation, and the reaction temperature is controlled between 120 - 180 °C; Step 2: Add the semi-plasticized TPU melt to an open mill for open milling. The temperature of the open mill is controlled between 130 - 150 °C. Meanwhile, add TPU particles and lubricant between the rollers of the open mill; the added TPU particles account for 10wt% - 50wt% of the total amount of the TPU melt being open milled, so that the TPU in the open mill is always in a semi-plasticized state; Step 3: Feed the open-milled TPU melt material into a calender roll. The temperature of the calender roll is controlled between 120 - 140 °C. Pull out the film through the calender roll, and shape and wind it up through a cooling roll to obtain the high-performance TPU film material.

2. The preparation method of the high-performance TPU film material according to claim 1, characterized in that, In Step 1, the hardness of the TPU particles is 80A - 95A.

3. The preparation method of the high-performance TPU film material according to claim 1, wherein The small molecule diol for synthesizing the polyol is a diol with 2 - 4 carbon atoms.

4. The preparation method of the high-performance TPU film material according to claim 1, characterized in that, In Step 2, the lubricant is at least one of erucic acid amide lubricant, oleic acid amide lubricant, and stearic acid lubricant, and the addition amount is 0.05wt% - 0.6wt% of the total amount of the TPU melt.

5. The preparation method of the high-performance TPU film material according to claim 1, characterized in that, In Step 3, 50% - 70% of the open-milled TPU melt material is cut and fed into the calender roll, and the remaining TPU melt stays in the open mill and continues to be open milled with the newly added semi-plasticized TPU melt and TPU particles. In this way, continuous production is carried out in a cycle.

6. The preparation method of the high-performance TPU film material according to claim 1, characterized in that, In Step 3, the temperature of the cooling roll is -10 to 20 °C.

7. A high-performance TPU film material prepared by the preparation method according to any one of claims 1 - 6.