Polyester chip for producing low-scratch release protective film and preparation method thereof

Abstract

The preparation method comprises the following steps: 1, completing an esterification reaction of terephthalic acid and ethylene glycol in an esterification reaction kettle according to a semi-continuous polyester synthesis process, and ensuring that the esterification rate is not lower than 96% by controlling the water yield; 2, introducing the fully esterified intermediate high-temperature solution into a secondary esterification kettle, uniformly adding quantitative self-prepared spherical coated silicon dioxide additive suspension, controlling the temperature, and continuously stirring and dispersing for not less than 30 minutes; and 3, heating the uniform slurry in the secondary esterification reaction kettle to a certain temperature, introducing the slurry into a polycondensation reaction kettle after passing through a melt filter of 15-25 microns, completing a polymerization reaction in the polycondensation reaction kettle by controlling parameters such as temperature, pressure and stirring rate, and synthesizing a polyester chip melt capable of producing the low-scratch release protective film, and pelletizing the polyester chips by using an underwater pelletizing system, drying and sub-packaging to obtain the target modified polyester chips.

Description

Technical Field

[0001] The invention relates to the technical field of polyester chips, in particular to a polyester chip for producing a low-scratch release protective film and a preparation method thereof. Background Art

[0002] In recent years, BOPET release protective film has attracted more and more attention in the material processing industry due to its excellent peeling effect, relatively favorable price, easy to obtain and very easy to recycle and reuse. Its scope of use has also been continuously expanded. From small mobile phone films and circuit board release protection to large building window films, car window films, car clothing films, etc., BOPET release protective film is generally the first choice. With the continuous expansion of application fields, problems are gradually exposed. In order to achieve a good peeling effect, traditional release protective films need to add silica additives as opening agents. In this way, there will be a very high risk of scratches for release protective bodies with high requirements for surface defects and softer surface layers, which will affect the appearance and application of the release protective body. In this way, the demand for low-scratch release protective films came into being. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a polyester chip for producing a low-scratch release protective film and a preparation method thereof, wherein the layer is softer, the film surface roughness is more uniform, and the scratch probability is very low.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a polyester slice for producing a low-scratch release protective film, comprising the following steps:

[0005] ① In a slurry mixing kettle, the slurry is mixed according to the molar ratio of PTA and EG of 1:1.2-1.3, and pumped into an esterification reactor through a slurry supply pump, and the esterification reaction temperature is controlled at 255-265°C to generate a 3-6 polymer mixture of BHET;

[0006] ② Transfer the materials that have completed the esterification reaction and meet the material feeding requirements to the diesterification reactor, start stirring, and after the temperature stabilizes, add an appropriate amount of ethylene glycol to cool down, control the temperature at 225-230°C, continue to maintain the constant temperature for 10-20 minutes, and pump in the spherical coated silica additive suspension at a uniform speed. After the addition is completed, raise the temperature to 240-250°C, during which nitrogen replacement protection is used. Add the catalyst and stabilizer 10-20 minutes before feeding;

[0007] ③ The uniform slurry obtained in step ② is pressed into the polycondensation reactor by nitrogen through a 15-25 μm stainless steel melt filter, and the polycondensation stirring, vacuum system, and heating system are started. The material reaction vacuum degree is controlled to be ≤30Pa, the internal temperature is 275-285°C, and the reaction is carried out for 3-5 hours. The polymerization viscosity is predicted by the current and power of the stirring reaction. After reaching the preset value, the material is discharged and the polyester slices for producing the low-scratch release protective film are obtained through the underwater pelletizing system, dryer, vibrating screen, and silo.

[0008] The temperature of the slurry feeding reaction process during the whole esterification reaction is controlled at 255-265° C., and the esterification rate is not less than 96%, and the esterification water output is not less than 21% of the PTA feed amount.

[0009] The spherical coated grade silica additive suspension is prepared as follows: a certain amount of silica powder is added into a dispersion tank filled with ethylene glycol, the mass ratio of silica to ethylene glycol is 1:(4-9), and a hydrophilic dispersant is added, the amount of the dispersant added is 0.05‰-0.5‰ of the mass of silica; firstly, the powder is dispersed for 2 hours by high-speed stirring at 3000-6000r / min and colloid mill, filtered through a 5-15μm stainless steel filter, a certain amount of the filtered suspension is added into a closed dispersion tank filled with a certain amount of ethylene glycol, the mass ratio of the suspension to the ethylene glycol in the dispersion tank is 1:(1-19), then the stirring rate is adjusted to 1500-2000r / min, the powder is dispersed for 4 hours by the colloid mill, and then filtered through a 1-5μm stainless steel filter and two 1μm wire-wound filters to obtain a spherical coated grade silica additive suspension with a final dispersed particle size of 0.1-0.5μm.

[0010] The added amount of the spherical coated silicon dioxide powder is 0.5%-1.5% of the theoretical polyester chip output, the powder particle size is 0.1-0.5 μm, and the particle size deviation range is controlled within M±0.02 μm.

[0011] The catalyst is a compound of ethylene glycol antimony and germanium oxide, the compounding mass ratio of ethylene glycol antimony: germanium oxide = (1-4): 1, the overall catalyst addition amount is 100-200ppm of the theoretical polyester chip output; the stabilizer is trimethyl phosphate, the addition amount is 100-150ppm of the theoretical polyester chip output.

[0012] In the step ②, in addition to adding the catalyst and the stabilizer, red and blue dyes are also added, the mass ratio of red and blue dyes is 1: (1-2), and the total amount added is 1-2ppm of the theoretical polyester chip output.

[0013] The vacuum degree is reduced from normal pressure to within 30 Pa, and the time is controlled to be 1-1.5h.

[0014] The above preparation method produces polyester chips for producing low-scratch release protective films.

[0015] The beneficial effects of the present invention are as follows: the low-scratch release protective film produced by the present invention has the same peeling effect as the release protective film modified by the traditional silica opening agent, and the surface layer is softer, the film surface roughness is more uniform, and the scratch probability is very low; compared with the release protective film modified by PMMA microsphere coating, the film drawing process is simplified, the film drawing cost is low, the film surface opening agent has high reliability, good durability, and the single material recycling has more environmental value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an electron photograph of the surface of the spherical coated silica modified membrane of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with specific embodiments:

[0018] The method for preparing a polyester chip for producing a low-scratch release protective film of the present invention comprises the following steps:

[0019] ① In a slurry mixing kettle, the slurry is mixed according to the molar ratio of PTA and EG of 1:1.2-1.3, and pumped into an esterification reactor through a slurry supply pump, and the esterification reaction temperature is controlled at 255-265°C to generate a 3-6 polymer mixture of BHET;

[0020] ② Transfer the materials that have completed the esterification reaction and meet the material feeding requirements to the diesterification reactor, start stirring, and after the temperature stabilizes, add an appropriate amount of ethylene glycol to cool down, control the temperature at 225-230°C, continue to maintain the constant temperature for 10-20 minutes, and pump in the spherical coated silica additive suspension at a uniform speed. After the addition is completed, raise the temperature to 240-250°C, during which nitrogen replacement protection is used. Add the catalyst and stabilizer 10-20 minutes before feeding;

[0021] ③ The uniform slurry obtained in step ② is pressed into the polycondensation reactor by nitrogen through a 15-25 μm stainless steel melt filter, and the polycondensation stirring, vacuum system, and heating system are started. The material reaction vacuum degree is controlled to be ≤30Pa, the internal temperature is 275-285°C, and the reaction is carried out for 3-5 hours. The polymerization viscosity is predicted by the current and power of the stirring reaction. After reaching the preset value, the material is discharged and the polyester slices for producing the low-scratch release protective film are obtained through the underwater pelletizing system, dryer, vibrating screen, and silo.

[0022] The polyester chips for producing low-scratch release protective films and the preparation method thereof are characterized in that the temperature of the slurry feeding reaction process during the entire esterification reaction is controlled at 255-265°C, the esterification rate is not less than 96%, and the esterification water output is not less than 21% of the PTA feed amount.

[0023] The spherical coated silica additive suspension is prepared as follows: a certain amount of silica powder is added into a dispersion tank filled with ethylene glycol, the mass ratio of silica to ethylene glycol is 1:(4-9), and a hydrophilic dispersant is added, the amount of the dispersant added is 0.05-0.5‰ of the mass of silica; firstly, the powder is dispersed for 2 hours by high-speed stirring at 3000-6000 r / min and colloid mill, filtered through a 5-15 μm stainless steel filter, a certain amount of filtered suspension is added into a closed dispersion tank filled with a certain amount of ethylene glycol, the mass ratio of the suspension to the ethylene glycol in the dispersion tank is 1:(1-19), then the stirring rate is adjusted to 1500-2000 r / min, the powder is dispersed for 4 hours by the colloid mill, and then filtered through a 1-5 μm stainless steel filter and two 1 μm wire-wound filters to obtain a spherical coated silica additive suspension with a final dispersed particle size of 0.1-0.5 μm.

[0024] The polyester chips for producing low-scratch release protective films and the preparation method thereof are characterized in that the addition amount of the spherical coated silica powder is 0.5%-1.5% of the theoretical polyester chip output, the powder particle size is 0.1-0.5 μm, and the particle size deviation range is controlled within M±0.02 μm;

[0025] The polyester chips for producing low-scratch release protective films and the preparation method thereof are characterized in that the catalyst is a compound of ethylene glycol antimony and germanium oxide, the compounding ratio of ethylene glycol antimony: germanium oxide = (1-4): 1, the overall amount of the catalyst added is 100-200ppm of the theoretical polyester chip output; the stabilizer is trimethyl phosphate, and the amount added is 100-150ppm of the theoretical polyester chip output.

[0026] The polyester chips for producing low-scratch release protective films and the preparation method thereof are characterized in that in the step ②, in addition to adding a catalyst and a stabilizer, a red-blue dye is also added, the red-blue dye is added in a ratio of 1:(1-2), and the total amount added is 1-2ppm of the theoretical polyester chip output.

[0027] The polyester chips for producing low-scratch release protective films and the preparation method thereof are characterized in that the vacuum degree is reduced from normal pressure to within 30 Pa, and the time is controlled within 1-1.5 hours.

[0028] The method of the present invention has the following characteristics:

[0029] 1. High esterification rate control in the first esterification reaction kettle: First, the molar ratio of ethylene glycol to terephthalic acid in the first esterification reaction kettle is controlled; second, the higher temperature range of the esterification feed is controlled; third, the residence time after the feed is completed is controlled. Through these process control means, the esterification rate is ultimately achieved to be no less than 96%, which facilitates the addition of spherical coated silica additives in the second esterification reaction, effectively avoiding the impact of low esterification rate on water-based dispersants, and thus avoiding problems such as uneven dispersion and agglomeration of additives;

[0030] 2. The spherical coated silica particles have a higher uniformity, and the surface coating can cover the sharp edges of silica to form a smooth surface. Compared with conventional silica-modified films, the film surface opening agent has fewer edges and corners, and is less likely to scratch the release protection body, which is also the key to the low scratching of the product of the present invention;

[0031] 3. The particle size fluctuation range of spherical coated silica is extremely small. After film formation, the film surface roughness is more uniform and the film surface adhesion is higher. Compared with the release protective film modified by PMMA microsphere coating, it is less likely to fall off, more durable after repeated friction, and has higher thermal stability. In addition, the film processing steps are fewer and the cost is lower.

[0032] 4. In the diesterification stage, by controlling the slurry temperature when the spherical coated silica additive is added, the solid components in the additive are integrated into the slurry to the maximum extent, which is more conducive to the dispersion of the additive;

[0033] 5. In the polycondensation reaction stage, by extending the low vacuum time, enough time is reserved for the materials to complete the pre-polycondensation reaction, and the added spherical coated silica additive can be fully mixed to form a uniform dispersed phase with the esterified short chain to the maximum extent;

[0034] 6. The use of compound catalysts, especially the addition of germanium oxide, can better control the hue of polyester chips and provide support for a good appearance after film formation.

[0035] After the polyester slices synthesized by the above method are formed into films, the product film surface has uniform opening agent, uniform film surface roughness, fewer raised edges and corners, and a lower chance of scratches. The film surface is also resistant to friction, not easy to lose points, and has excellent weather resistance.

[0036] Example 1

[0037] First, prepare a self-prepared spherical coated silica additive suspension with a particle size of 0.30 μm:

[0038] Take 25 kg of spherical coated silica powder with a particle size of 0.3 μm (provided by Changxing Special Materials (Zhuhai) Co., Ltd., D50 particle size 0.3 μm), add it to a 175 kg ethylene glycol dispersion tank, and add 0.005 kg of hydrophilic dispersant (provided by Suzhou Polydi Materials Technology Co., Ltd., model AA55 dispersant), first disperse it for 2 hours by high-speed stirring at 3000-6000 R / min and colloid mill, filter it through a 5 μm stainless steel filter, take 100 kg of the filtrate and add it to a closed dispersion tank filled with 150 kg of ethylene glycol, then adjust the stirring rate to 1500-2000 R / min, continue to disperse it through the colloid mill for 4 hours, and then pass it through a 2 μm stainless steel filter and two 1 μm wire-wound filters to obtain a spherical coated silica additive suspension with a final dispersed particle size of 0.3 μm;

[0039] ① An esterification reaction stage: 1000 kg of PTA was added into the slurry mixing kettle, and 430 L of EG was added through a pipeline. After uniform mixing, it was pumped into an esterification reaction kettle at a uniform speed through a pipeline pump. The esterification reaction was carried out at 257 ° C to obtain a uniform mixed slurry of BHET and its derivatives. The mixture was kept for 30 minutes to maintain the temperature. The water output was 208 L, which met the process requirements.

[0040] ② The slurry obtained in step ① was heated to 262°C and pressed into the diesterification reactor by nitrogen through a pipeline. The diesterification was started and stirred. 30L of ethylene glycol was added to cool the mixture. When the temperature dropped to 228°C, 115Kg of a self-prepared spherical coated silica additive suspension with a particle size of 0.30 μm was added. During the addition, the column top was fully refluxed and the internal temperature was controlled at 230°C. After the solution was added, the temperature was raised to 245°C, 100g of antimony glycol, 100g of germanium oxide, 120mL of trimethyl phosphate, 1g of red dye and 1.5g of blue dye were added, and stirring was continued for 10 minutes.

[0041] ③ The mixed slurry obtained in step ② is pressed into a polycondensation reactor through a 15 μm stainless steel filter using nitrogen for polymerization reaction, the internal temperature is controlled at 280°C, the vacuum degree is ≤30 Pa, and after the reaction reaches the characteristic viscosity after 3.5 hours, the final product is produced through a casting head, underwater pelletizing system, drying system, screening system, and packaging system.

[0042] ④ The polyester chips obtained in step ③ were tested for their intrinsic viscosity of 0.635 dl / g, b value of 6.30, melting point of 261° C. The chips had a good appearance, uniform particles, light white and transparent, and no other colors.

[0043] According to the method of steps ① to ④, other 2-4 examples were implemented. The specific data are shown in Table 1. The dosages of PTA and EG remained unchanged, and the types of added catalysts and auxiliary materials remained unchanged. Only the addition amounts of the catalyst and the spherical coated silica additive suspension and the control conditions of each reaction stage were adjusted.

[0044] Table 1

[0045]

[0046]

[0047] The polyester chips for producing the low-scratch release protective film of the present invention have a lower scratch probability compared with the conventional silica-modified release protective film; compared with the PMMA microsphere-coated release protective film, it has a simpler processing procedure, a lower processing cost, and a more durable anti-friction performance.

[0048] The following is explained in conjunction with specific embodiments:

[0049] The polyester slices of the low-scratch release protective film produced in Examples 1-4 above were tested for multiple physical and chemical indicators, and then processed into a 40μm three-layer co-extruded release protective film. The film was compounded with the window film and subjected to a peeling test. The number of scratches (≥1mm) on the 1㎡ window film was counted, and the four groups of experimental results were compared. The test results are summarized in Table 2 below (based on the test machine data):

[0050] Table 2

[0051]

[0052] Electronic photo of spherical coated silica modified membrane surface (0.5% content) Figure 1 .

[0053] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A method for preparing a polyester chip for producing a low-scratch release protective film, characterized in that: The following steps are involved: ① In a slurry mixing kettle, the slurry is mixed according to the molar ratio of PTA and EG of 1:1.2-1.3, and pumped into an esterification reactor through a slurry supply pump, and the esterification reaction temperature is controlled at 255-265°C to generate a 3-6 polymer mixture of BHET; ② Transfer the materials that have completed the esterification reaction and meet the material feeding requirements to the diesterification reactor, start stirring, and after the temperature stabilizes, add an appropriate amount of ethylene glycol to cool down, control the temperature at 225-230°C, continue to maintain the constant temperature for 10-20 minutes, and pump in the spherical coated silica additive suspension at a uniform speed. After the addition is completed, raise the temperature to 240-250°C, during which nitrogen replacement protection is used. Add the catalyst and stabilizer 10-20 minutes before feeding; ③ The uniform slurry obtained in step ② is pressed into the polycondensation reactor by nitrogen through a 15-25 μm stainless steel melt filter, and the polycondensation stirring, vacuum system, and heating system are started. The material reaction vacuum degree is controlled to be ≤30Pa, the internal temperature is 275-285°C, and the reaction is carried out for 3-5 hours. The polymerization viscosity is predicted by the current and power of the stirring reaction. After reaching the preset value, the material is discharged and the polyester slices for producing the low-scratch release protective film are obtained through the underwater pelletizing system, dryer, vibrating screen, and silo.

2. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 1, characterized in that: The temperature of the slurry feeding reaction process during the whole esterification reaction is controlled at 255-265° C., and the esterification rate is not less than 96%, and the esterification water output is not less than 21% of the PTA feed amount.

3. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 1, characterized in that: The spherical coated grade silica additive suspension is prepared as follows: a certain amount of silica powder is added into a dispersion tank filled with ethylene glycol, the mass ratio of silica to ethylene glycol is 1:(4-9), and a hydrophilic dispersant is added, the amount of the dispersant added is 0.05‰-0.5‰ of the mass of silica; firstly, the powder is dispersed for 2 hours by high-speed stirring at 3000-6000r / min and colloid mill, filtered through a 5-15μm stainless steel filter, a certain amount of the filtered suspension is added into a closed dispersion tank filled with a certain amount of ethylene glycol, the mass ratio of the suspension to the ethylene glycol in the dispersion tank is 1:(1-19), then the stirring rate is adjusted to 1500-2000r / min, the powder is dispersed for 4 hours by the colloid mill, and then filtered through a 1-5μm stainless steel filter and two 1μm wire-wound filters to obtain a spherical coated grade silica additive suspension with a final dispersed particle size of 0.1-0.5μm.

4. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 3, characterized in that: The added amount of the spherical coated silicon dioxide powder is 0.5%-1.5% of the theoretical polyester chip output, the powder particle size is 0.1-0.5 μm, and the particle size deviation range is controlled within M±0.02 μm.

5. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 1, characterized in that: The catalyst is a compound of ethylene glycol antimony and germanium oxide, the compounding mass ratio of ethylene glycol antimony: germanium oxide = (1-4): 1, the overall catalyst addition amount is 100-200ppm of the theoretical polyester chip output; the stabilizer is trimethyl phosphate, the addition amount is 100-150ppm of the theoretical polyester chip output.

6. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 1, characterized in that: In the step ②, in addition to adding the catalyst and the stabilizer, red and blue dyes are also added, the mass ratio of red and blue dyes is 1: (1-2), and the total amount added is 1-2ppm of the theoretical polyester chip output.

7. The method for preparing a polyester chip for producing a low-scratch release protective film according to claim 1, characterized in that: The vacuum degree is reduced from normal pressure to within 30 Pa, and the time is controlled to be 1-1.5h.

8. The polyester chips for producing low-scratch release protective films obtained by the preparation method according to any one of claims 1 to 7.

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