A PET base film for transfer printing and its preparation method

Abstract

This invention discloses a PET base film for transfer printing and its preparation method. A pretreated PET film is obtained by corona treatment of a PET composite film, followed by treatment with a processing solution to obtain the PET base film for transfer printing. Flexible organosilicon segments are embedded in the PET main chain, significantly improving the chain segment mobility and elastic recovery, resulting in a soft feel and the ability to stretch and contract synchronously with substrates such as cotton fibers. The flexibility of the organosilicon segments endows the material with excellent resistance to dynamic fatigue. The hyperbranched disulfide bond structure enhances the toughness of the PET base film through dynamic sacrificial bonds. Simultaneously, the embedding of organosilicon segments ensures that the PET base film does not experience a decrease in stability during long-term high-speed printing. Corona treatment followed by treatment with a processing solution grafts sodium sulfonate groups onto the surface, improving ink adhesion.

Description

Technical Field

[0001] This invention relates to the field of PET film preparation technology, specifically to a PET base film for transfer printing and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET) film is widely used as a base film material for various transfer processes such as heat transfer, digital printing, and label printing due to its excellent mechanical strength, dimensional stability, transparency, chemical resistance, and high cost-effectiveness. However, PET macromolecular chains have low polarity and low surface energy, resulting in poor wetting and adhesion to most inks and dyes. Printing on untreated PET film surfaces can lead to problems such as ink layer peeling, poor abrasion resistance, and poor washability. During high-speed heat transfer or prolonged printing, localized high temperatures at the printhead can cause thermal relaxation, deformation, or even softening of ordinary PET base films, affecting printing accuracy and continuity. To improve heat resistance, attempts are often made to increase the crystallinity of PET or add inorganic fillers, but this often leads to decreased film flexibility and increased brittleness. In practical applications, transfer base films often need to bend and stretch along flexible substrates, requiring the base film to possess both good flexibility and elastic recovery capabilities. Summary of the Invention

[0003] The purpose of this invention is to provide a PET base film for transfer printing and its preparation method, which solves the problems of low toughness of PET base film, which cannot stretch and contract with flexible substrate, low surface energy, and poor ink adhesion.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a PET base film for transfer printing specifically includes the following steps:

[0006] Step A1: Mix octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and xylene, and purge with nitrogen. React at 150-200 r / min and 90-95℃ for 3-5 h. Then raise the temperature to 140-145℃ and react for 1-1.5 h to obtain dihydropolysiloxane. Mix dihydropolysiloxane, allyl alcohol, caster catalyst and xylene, and purge with nitrogen. React at 150-200 r / min and 80-85℃ for 6-8 h to obtain modified monomer.

[0007] Step A2: Terephthalic acid, modified monomer, ethylene glycol and antimony trioxide are mixed evenly and reacted at 230-240℃ and 0.3-0.4MPa for 8-10 hours. The temperature is then raised to 250-260℃ and the reaction is carried out at 50-60Pa for 1.5-2 hours to obtain modified PET. Modified PET and N-methylpyrrolidone are mixed and protected with nitrogen gas. The mixture is stirred at 150-200r / min and 180-200℃, and zinc acetylacetone is added. After stirring for 1-1.5 hours, the modifying additive is added, and the reaction is carried out for 3-5 hours to obtain a composite PET solution.

[0008] Step A3: Dissolve sodium bisulfite in deionized water, adjust the pH to 6 to prepare a dropping solution, dissolve 3-methacryloyloxypropyltrimethoxysilane in ethanol, purge with nitrogen for protection, stir and add potassium persulfate and the dropping solution at a speed of 120-150 r / min and a temperature of 60-70℃, react for 3-5 h, then cool to 35-40℃, add deionized water, adjust the pH to 4-5, stir for 40-50 min to obtain the treatment solution;

[0009] Step A4: Coat the composite PET solution onto the substrate and heat it at 90-100℃ for 2-4 hours. Then, heat it to 140-150℃ and heat it under vacuum for 4-6 hours to obtain a composite PET film. Heat the composite PET film at 400-500W and 1m / min for 1 second at a single point and then corona treat it to obtain a pretreated PET film. Immerse the pretreated PET film in the treatment solution and pull it up at a uniform speed of 3-5mm / s. Heat it at 120-130℃ for 20-30 minutes to obtain a PET base film for transfer.

[0010] Furthermore, in step A1, the molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide is 3:1:0.01, the molar ratio of dihydropolysiloxane and allyl alcohol is 1:2, and the amount of caster catalyst is 0.01% of the mass of allyl alcohol.

[0011] Furthermore, the molar ratio of terephthalic acid, modified monomer and ethylene glycol in step A2 is 20:1:19, the molar ratio of terminal carboxyl groups on modified PET to epoxy groups on modified additives is 1:1, and the amount of zinc acetylacetonate is 1% of the mass of modified PET.

[0012] Furthermore, in step A3, the ratio of sodium bisulfite to deionized water in the added solution is 1g:0.7mL, and the ratio of 3-methacryloyloxypropyltrimethoxysilane, ethanol, potassium persulfate, added solution, and deionized water in the treatment solution is 10g:40mL:0.15g:8mL:4mL.

[0013] Furthermore, the modified additive is prepared by the following steps:

[0014] Step B1: Dissolve 3,3'-dithiodipropionic acid in dichloromethane. Stir and add thionyl chloride and N,N-dimethylformamide at a speed of 150-200 r / min and a temperature of 20-25℃ for 12-15 h to obtain intermediate 1. Mix glycerol, triethylamine and dichloromethane. Stir and add intermediate 1 at a speed of 200-300 r / min and a temperature of 3-5℃ for 30-40 min. Then raise the temperature to 20-25℃ and react for 12-15 h. Add allyl alcohol and continue the reaction for 4-6 h to obtain intermediate 2.

[0015] Step B2: Mix intermediate 2, caster catalyst, hydroquinone, and toluene, purge with nitrogen, stir and add dimethylchlorosilane at 120-150 r / min and 0°C, heat to 50-60°C, and react for 6-8 h to obtain the modifier. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran, purge with nitrogen, stir and add hexamethylcyclotrisiloxane at 120-150 r / min and 0°C, heat to 20-25°C, and react for 15-20 h. Then add the modifier and continue the reaction for 1-1.5 h to obtain the modified polysiloxane.

[0016] Step B3: Mix modified polysiloxane, allyl glycidyl ether, caster catalyst and xylene, purge with nitrogen, and react for 6-8 hours at a speed of 200-300 r / min and a temperature of 80-85℃ to obtain the modified additive.

[0017] Furthermore, the molar ratio of 3,3'-dithiodipropionic acid and thionyl chloride in step B1 is 1:2.1, and the molar ratio of glycerol, triethylamine, intermediate 1 and allyl alcohol is n:4n+2:2n+1:n+2, where n is a natural number greater than 4.

[0018] Furthermore, in step B2, the molar ratio of the double bond on intermediate 2 to dimethylchlorosilane is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, the amount of hydroquinone is 0.1% of the mass of intermediate 2, and the molar ratio of the Si-Cl bond on lithium dimethylhydroxysiloxane, hexamethylcyclocyclotrisiloxane, and the modifier is 1:3:1.

[0019] Furthermore, in step B3, the molar ratio of Si-H bonds on the modified polysiloxane to allyl glycidyl ether is 1:1, and the amount of caster catalyst used is 0.01% of the mass of allyl glycidyl ether.

[0020] The beneficial effects of the present invention are as follows: A PET base film for transfer is prepared by corona treatment of a PET composite film to obtain a pretreated PET film, which is then treated with a treatment solution to obtain a PET base film for transfer. The PET composite film is esterified and condensed with terephthalic acid, modified monomers and ethylene glycol to obtain modified PET. The modified PET and modified additives are reacted to react the carboxyl groups on the modified PET and the epoxy groups on the modified additives to obtain a composite PET solution. The composite PET solution is then coated on a substrate and cured at high temperature to obtain a composite PET film.

[0021] The pretreatment solution was prepared by sulfonation of 3-methacryloyloxypropyltrimethoxysilane with sodium bisulfite.

[0022] The modified monomer was prepared by ring-opening polymerization of octamethylcyclotetrasiloxane and then end-capping with tetramethyldisiloxane to obtain dihydropolysiloxane. The dihydropolysiloxane was then reacted with allyl alcohol to react the Si-H bonds on the dihydropolysiloxane with the double bonds on the allyl alcohol to obtain the modified monomer.

[0023] The modified additive is prepared by treating 3,3'-dithiodipropionic acid with thionyl chloride to chlorinate the carboxyl group, yielding intermediate 1. Glycerol is then reacted with intermediate 1, causing the hydroxyl group on glycerol to react with the acyl chloride on intermediate 1, forming a hyperbranched structure. Allyl alcohol is then added, causing the hydroxyl group on allyl alcohol to react with the remaining acyl chloride, yielding intermediate 2. Intermediate 2 is then reacted with dimethylchlorosilane, causing the double bond on intermediate 2 to react with the Si-H bond on dimethylchlorosilane. A modifier is prepared by using lithium dimethylhydrosiloxane as an initiator and hexamethylcyclotrisiloxane as a polymerization monomer to form a polysiloxane with lithium siloxane at one end and Si-H bond at the other end. The modifier is then added to react the Si-Cl bond on the modifier with the lithium siloxane to obtain a modified polysiloxane. The modified polysiloxane is then reacted with allyl glycidyl ether to react the Si-H bond on the modified polysiloxane with the double bond on the allyl glycidyl ether to obtain a modified additive.

[0024] The PET main chain incorporates flexible silicone segments, significantly improving the chain's mobility and elastic recovery, resulting in a soft feel and the ability to stretch and contract synchronously with substrates such as cotton fibers. The flexibility of the silicone segments endows the material with excellent resistance to dynamic fatigue. The hyperbranched disulfide bond structure enhances the toughness of the PET base film through dynamic sacrificial bonds. At the same time, the incorporation of silicone segments ensures that the PET base film does not experience a decrease in stability during long-term high-speed printing. Corona treatment followed by treatment with a processing solution allows for the grafting of sodium sulfonate groups onto the surface, which improves ink adhesion. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: A method for preparing a PET base film for transfer printing, specifically including the following steps:

[0027] Step A1: Octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and xylene are mixed, and under nitrogen protection, the mixture is reacted at 150 r / min and 90 °C for 3 h. The temperature is then raised to 140 °C and reacted for 1 h to obtain dihydropolysiloxane. Dihydropolysiloxane, allyl alcohol, caster catalyst and xylene are mixed, and under nitrogen protection, the mixture is reacted at 150 r / min and 80 °C for 6 h to obtain modified monomer.

[0028] Step A2: Terephthalic acid, modified monomer, ethylene glycol and antimony trioxide are mixed evenly and reacted at 230℃ and 0.3MPa for 8 hours. The temperature is then raised to 250℃ and the reaction is carried out at 50Pa for 1.5 hours to obtain modified PET. Modified PET and N-methylpyrrolidone are mixed and nitrogen gas is introduced for protection. The mixture is stirred at 150r / min and 180℃, and zinc acetylacetone is added. After stirring for 1 hour, the modifying additive is added and the reaction is carried out for 3 hours to obtain composite PET solution.

[0029] Step A3: Dissolve sodium bisulfite in deionized water, adjust the pH to 6 to prepare a dropping solution, dissolve 3-methacryloyloxypropyltrimethoxysilane in ethanol, purge with nitrogen for protection, stir and add potassium persulfate and the dropping solution at 120 r / min and 60℃, react for 3 h, cool to 35℃, add deionized water, adjust the pH to 4, stir for 40 min to prepare the treatment solution;

[0030] Step A4: Coat the composite PET solution onto the substrate, heat it at 90℃ for 2 hours, then heat it to 140℃ and heat it under vacuum for 4 hours to obtain a composite PET film. Treat the composite PET film with a single point for 1 second at a power of 400W and a speed of 1m / min to obtain a pretreated PET film. Immerse the pretreated PET film in the treatment solution and pull it up at a uniform speed of 3mm / s. Heat it at 120℃ for 20 minutes to obtain a PET base film for transfer.

[0031] In step A1, the molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide is 3:1:0.01, the molar ratio of dihydropolysiloxane and allyl alcohol is 1:2, and the amount of caster catalyst is 0.01% of the mass of allyl alcohol.

[0032] The molar ratio of terephthalic acid, modified monomer and ethylene glycol in step A2 is 20:1:19, the molar ratio of terminal carboxyl groups on modified PET to epoxy groups on modified additives is 1:1, and the amount of zinc acetylacetone is 1% of the mass of modified PET.

[0033] In step A3, the ratio of sodium bisulfite to deionized water in the added solution is 1g:0.7mL, and the ratio of 3-methacryloyloxypropyltrimethoxysilane, ethanol, potassium persulfate, added solution, and deionized water in the treatment solution is 10g:40mL:0.15g:8mL:4mL.

[0034] The modified additive is prepared by the following steps:

[0035] Step B1: Dissolve 3,3'-dithiodipropionic acid in dichloromethane. Stir and add thionyl chloride and N,N-dimethylformamide at 150 r / min and 20°C for 12 h to obtain intermediate 1. Mix glycerol, triethylamine and dichloromethane. Stir and add intermediate 1 at 200 r / min and 3°C for 30 min. Then raise the temperature to 20°C and react for 12 h. Add allyl alcohol and continue the reaction for 4 h to obtain intermediate 2.

[0036] Step B2: Intermediate 2, caster catalyst, hydroquinone and toluene are mixed, and nitrogen gas is introduced for protection. Under the conditions of 120 r / min and 0℃, dimethylchlorosilane is added while stirring. The temperature is raised to 50℃ and the reaction is carried out for 6 h to obtain the modifier. Dimethylhydrosilylsilane lithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. Under the conditions of 120 r / min and 0℃, hexamethylcyclotrisiloxane is added while stirring. The temperature is raised to 20℃ and the reaction is carried out for 15 h. Then the modifier is added and the reaction is continued for 1 h to obtain the modified polysiloxane.

[0037] Step B3: Mix modified polysiloxane, allyl glycidyl ether, caster catalyst and xylene, purge with nitrogen, and react for 6 hours at a speed of 200 r / min and a temperature of 80℃ to obtain the modified additive.

[0038] The molar ratio of 3,3'-dithiodipropionic acid and thionyl chloride in step B1 is 1:2.1, and the molar ratio of glycerol, triethylamine, intermediate 1 and allyl alcohol is 5:22:11:7.

[0039] The molar ratio of the double bond on intermediate 2 and dimethylchlorosilane in step B2 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, the amount of hydroquinone is 0.1% of the mass of intermediate 2, and the molar ratio of the Si-Cl bond on lithium dimethylhydroxysiloxane, hexamethylcyclocyclotrisiloxane and the modifier is 1:3:1.

[0040] The molar ratio of Si-H bonds on the modified polysiloxane and allyl glycidyl ether in step B3 is 1:1, and the amount of caster catalyst used is 0.01% of the mass of allyl glycidyl ether.

[0041] Example 2, a method for preparing a PET base film for transfer printing, specifically includes the following steps:

[0042] Step A1: Octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and xylene are mixed, and under nitrogen protection, the mixture is reacted at 150 r / min and 95 °C for 4 h. The temperature is then raised to 140 °C and reacted for 1.3 h to obtain dihydropolysiloxane. Dihydropolysiloxane, allyl alcohol, caster catalyst and xylene are mixed, and under nitrogen protection, the mixture is reacted at 200 r / min and 80 °C for 7 h to obtain modified monomer.

[0043] Step A2: Terephthalic acid, modified monomer, ethylene glycol and antimony trioxide are mixed evenly and reacted at 235℃ and 0.4MPa for 9 hours. The temperature is then raised to 255℃ and the reaction is carried out at 55Pa for 2 hours to obtain modified PET. Modified PET and N-methylpyrrolidone are mixed and nitrogen gas is introduced for protection. The mixture is stirred at 150r / min and 190℃, and zinc acetylacetone is added. After stirring for 1.5 hours, the modifying additive is added and the reaction is carried out for 4 hours to obtain composite PET solution.

[0044] Step A3: Dissolve sodium bisulfite in deionized water, adjust the pH to 6 to prepare a dropping solution, dissolve 3-methacryloyloxypropyltrimethoxysilane in ethanol, purge with nitrogen for protection, stir and add potassium persulfate and the dropping solution at 120 r / min and 65℃, react for 4 h, cool to 38℃, add deionized water, adjust the pH to 5, stir for 45 min to prepare the treatment solution;

[0045] Step A4: Coat the composite PET solution onto the substrate, heat it at 95°C for 3 hours, then heat it to 145°C and heat it under vacuum for 5 hours to obtain a composite PET film. Heat the composite PET film at 450W power and 1m / min speed, treat it at a single point for 1 second, and then corona treat it to obtain a pretreated PET film. Immerse the pretreated PET film in the treatment solution and pull it up at a uniform speed of 4mm / s. Heat it at 125°C for 25 minutes to obtain a PET base film for transfer.

[0046] In step A1, the molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide is 3:1:0.01, the molar ratio of dihydropolysiloxane and allyl alcohol is 1:2, and the amount of caster catalyst is 0.01% of the mass of allyl alcohol.

[0047] The molar ratio of terephthalic acid, modified monomer and ethylene glycol in step A2 is 20:1:19, the molar ratio of terminal carboxyl groups on modified PET to epoxy groups on modified additives is 1:1, and the amount of zinc acetylacetone is 1% of the mass of modified PET.

[0048] In step A3, the ratio of sodium bisulfite to deionized water in the added solution is 1g:0.7mL, and the ratio of 3-methacryloyloxypropyltrimethoxysilane, ethanol, potassium persulfate, added solution, and deionized water in the treatment solution is 10g:40mL:0.15g:8mL:4mL.

[0049] The modified additive is prepared by the following steps:

[0050] Step B1: Dissolve 3,3'-dithiodipropionic acid in dichloromethane. Stir and add thionyl chloride and N,N-dimethylformamide at 150 r / min and 25 °C for 15 h to obtain intermediate 1. Mix glycerol, triethylamine and dichloromethane. Stir and add intermediate 1 at 200 r / min and 4 °C for 35 min. Then raise the temperature to 25 °C and react for 12 h. Add allyl alcohol and continue the reaction for 5 h to obtain intermediate 2.

[0051] Step B2: Intermediate 2, caster catalyst, hydroquinone and toluene are mixed and protected with nitrogen. Under the conditions of 150 r / min and 0°C, dimethylchlorosilane is added and the temperature is raised to 55°C and reacted for 7 h to obtain the modifier. Dimethylhydrosilylsilane and tetrahydrofuran are mixed and protected with nitrogen. Under the conditions of 150 r / min and 0°C, hexamethylcyclotrisiloxane is added and the temperature is raised to 20°C and reacted for 20 h. Then the modifier is added and the reaction is continued for 1 h to obtain the modified polysiloxane.

[0052] Step B3: Mix modified polysiloxane, allyl glycidyl ether, caster catalyst and xylene, purge with nitrogen, and react for 7 h at a speed of 300 r / min and a temperature of 80 °C to obtain the modified additive.

[0053] The molar ratio of 3,3'-dithiodipropionic acid and thionyl chloride in step B1 is 1:2.1, and the molar ratio of glycerol, triethylamine, intermediate 1 and allyl alcohol is 6:26:13:8.

[0054] The molar ratio of the double bond on intermediate 2 and dimethylchlorosilane in step B2 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, the amount of hydroquinone is 0.1% of the mass of intermediate 2, and the molar ratio of the Si-Cl bond on lithium dimethylhydroxysiloxane, hexamethylcyclocyclotrisiloxane and the modifier is 1:3:1.

[0055] The molar ratio of Si-H bonds on the modified polysiloxane and allyl glycidyl ether in step B3 is 1:1, and the amount of caster catalyst used is 0.01% of the mass of allyl glycidyl ether.

[0056] Example 3, a method for preparing a PET base film for transfer printing, specifically includes the following steps:

[0057] Step A1: Octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and xylene are mixed, and nitrogen gas is introduced for protection. The mixture is reacted at 200 r / min and 95 °C for 5 h. The temperature is then increased to 145 °C and the mixture is reacted for 1.5 h to obtain dihydropolysiloxane. Dihydropolysiloxane, allyl alcohol, caster catalyst and xylene are mixed, and nitrogen gas is introduced for protection. The mixture is reacted at 200 r / min and 85 °C for 8 h to obtain modified monomer.

[0058] Step A2: Terephthalic acid, modified monomer, ethylene glycol and antimony trioxide are mixed evenly and reacted at 240℃ and 0.4MPa for 10 hours. The temperature is then raised to 260℃ and the reaction is carried out at 60Pa for 2 hours to obtain modified PET. Modified PET and N-methylpyrrolidone are mixed and nitrogen gas is introduced for protection. The mixture is stirred at 200r / min and 200℃, and zinc acetylacetone is added. After stirring for 1.5 hours, the modifying additive is added and the reaction is carried out for 5 hours to obtain composite PET solution.

[0059] Step A3: Dissolve sodium bisulfite in deionized water, adjust the pH to 6 to prepare a dropping solution, dissolve 3-methacryloyloxypropyltrimethoxysilane in ethanol, purge with nitrogen for protection, stir and add potassium persulfate and the dropping solution at 150 r / min and 70℃, react for 5 h, cool to 40℃, add deionized water, adjust the pH to 5, stir for 50 min to prepare the treatment solution;

[0060] Step A4: Coat the composite PET solution onto the substrate and heat it at 100°C for 4 hours. Then heat it to 150°C and heat it under vacuum for 6 hours to obtain a composite PET film. Heat the composite PET film at 500W and 1m / min for 1 second at a single point and then corona treat it to obtain a pretreated PET film. Immerse the pretreated PET film in the treatment solution and pull it up at a uniform speed of 5mm / s. Heat it at 130°C for 30 minutes to obtain a PET base film for transfer.

[0061] In step A1, the molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane, and tetramethylammonium hydroxide is 3:1:0.01, the molar ratio of dihydropolysiloxane and allyl alcohol is 1:2, and the amount of caster catalyst is 0.01% of the mass of allyl alcohol.

[0062] The molar ratio of terephthalic acid, modified monomer and ethylene glycol in step A2 is 20:1:19, the molar ratio of terminal carboxyl groups on modified PET to epoxy groups on modified additives is 1:1, and the amount of zinc acetylacetone is 1% of the mass of modified PET.

[0063] In step A3, the ratio of sodium bisulfite to deionized water in the added solution is 1g:0.7mL, and the ratio of 3-methacryloyloxypropyltrimethoxysilane, ethanol, potassium persulfate, added solution, and deionized water in the treatment solution is 10g:40mL:0.15g:8mL:4mL.

[0064] The modified additive is prepared by the following steps:

[0065] Step B1: Dissolve 3,3'-dithiodipropionic acid in dichloromethane. Stir and add thionyl chloride and N,N-dimethylformamide at 200 r / min and 25°C for 15 h to obtain intermediate 1. Mix glycerol, triethylamine and dichloromethane. Stir and add intermediate 1 at 300 r / min and 5°C for 40 min. Then raise the temperature to 25°C and react for 15 h. Add allyl alcohol and continue the reaction for 6 h to obtain intermediate 2.

[0066] Step B2: Intermediate 2, caster catalyst, hydroquinone and toluene are mixed, and nitrogen gas is introduced for protection. Under the conditions of 150 r / min and 0℃, dimethylchlorosilane is added while stirring. The temperature is raised to 60℃ and the reaction is carried out for 8 h to obtain the modifier. Dimethylhydrosilylsilane lithium and tetrahydrofuran are mixed, and nitrogen gas is introduced for protection. Under the conditions of 150 r / min and 0℃, hexamethylcyclotrisiloxane is added while stirring. The temperature is raised to 25℃ and the reaction is carried out for 20 h. Then the modifier is added and the reaction is continued for 1.5 h to obtain the modified polysiloxane.

[0067] Step B3: Mix modified polysiloxane, allyl glycidyl ether, caster catalyst and xylene, purge with nitrogen, and react for 8 hours at a speed of 300 r / min and a temperature of 85℃ to obtain the modified additive.

[0068] The molar ratio of 3,3'-dithiodipropionic acid and thionyl chloride in step B1 is 1:2.1, and the molar ratio of glycerol, triethylamine, intermediate 1 and allyl alcohol is 7:30:15:9.

[0069] The molar ratio of the double bond on intermediate 2 and dimethylchlorosilane in step B2 is 1:1, the amount of caster catalyst is 0.01% of the mass of dimethylchlorosilane, the amount of hydroquinone is 0.1% of the mass of intermediate 2, and the molar ratio of the Si-Cl bond on lithium dimethylhydroxysiloxane, hexamethylcyclocyclotrisiloxane and the modifier is 1:3:1.

[0070] The molar ratio of Si-H bonds on the modified polysiloxane and allyl glycidyl ether in step B3 is 1:1, and the amount of caster catalyst used is 0.01% of the mass of allyl glycidyl ether.

[0071] Comparative Example 1: This comparative example did not include any modified monomers compared to Example 1, but the remaining steps were the same.

[0072] Comparative Example 2: This comparative example uses a composite PET film as the PET base film for transfer, while the other steps are the same as in Example 1.

[0073] Comparative Example 3: Compared with Example 1, this comparative example uses succinyl chloride instead of intermediate 1, and the other steps are the same.

[0074] The PET base films prepared in Examples 1-3 and Comparative Examples 1-3 were used to prepare Type 2 samples according to the standard GB / T1040.3-2006. The tensile speed was 50 mm / min, and the tensile strength and elongation at break were tested. The samples were printed on the PET base films prepared in Examples 1-3 and Comparative Examples 1-3 using an inkjet printer. The color fastness to washing was tested according to GB / T5713-2013. The color change was evaluated by using a gray scale for color change and relying on the color difference between the original sample and the sample after fading. The color change grade of the sample was evaluated, which was divided into 5 grades. The larger the value, the better the color fastness to washing. The test results are shown in Table 1 below.

[0075] Table 1

[0076] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (MPa) 61.1 61.8 62.3 66.6 48.7 52.4 Elongation at break % 193 185 181 74 145 214 Color fastness to washing 4-5 4-5 4-5 4 3-4 4-5

[0077] As shown in Table 1, this application has excellent toughness and the ink adheres more easily.

[0078] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a PET base film for transfer printing, characterized in that: Specifically, the steps include the following: Step A1: Mix octamethylcyclotetrasiloxane, tetramethyldisiloxane, tetramethylammonium hydroxide and xylene, and react under nitrogen protection to obtain dihydropolysiloxane. Mix dihydropolysiloxane, allyl alcohol, caster catalyst and xylene, and react under nitrogen protection to obtain modified monomer. Step A2: Terephthalic acid, modified monomer, ethylene glycol and antimony trioxide are mixed evenly and reacted to obtain modified PET. Modified PET and N-methylpyrrolidone are mixed, nitrogen gas is introduced for protection, and zinc acetylacetone is added while stirring. After stirring, modified additives are added and reacted to obtain composite PET solution. Step A3: Dissolve sodium bisulfite in deionized water, adjust the pH to acidic, and prepare a dropping solution. Dissolve 3-methacryloyloxypropyltrimethoxysilane in ethanol, purge with nitrogen for protection, stir, add potassium persulfate and the dropping solution, and react. Add deionized water, stir, and prepare a treatment solution. Step A4: Coat the composite PET solution onto the substrate, heat-treat it to obtain a composite PET film, corona-treat the composite PET film to obtain a pretreated PET film, immerse the pretreated PET film in the treatment solution, pull it up at a uniform speed and heat it to obtain a PET base film for transfer.

2. The method for preparing a PET base film for transfer printing according to claim 1, characterized in that: The molar ratio of octamethylcyclotetrasiloxane, tetramethyldisiloxane and tetramethylammonium hydroxide in step A1 is 3:1:0.01, and the molar ratio of dihydropolysiloxane and allyl alcohol is 1:

2.

3. The method for preparing a PET base film for transfer printing according to claim 1, characterized in that: The molar ratio of terephthalic acid, modified monomer and ethylene glycol in step A2 is 20:1:19, and the molar ratio of terminal carboxyl groups on modified PET to epoxy groups on modified additives is 1:

1.

4. The method for preparing a PET base film for transfer printing according to claim 1, characterized in that: In step A3, the ratio of sodium bisulfite to deionized water in the added solution is 1g:0.7mL, and the ratio of 3-methacryloyloxypropyltrimethoxysilane, ethanol, potassium persulfate, added solution, and deionized water in the treatment solution is 10g:40mL:0.15g:8mL:4mL.

5. The method for preparing a PET base film for transfer printing according to claim 1, characterized in that: The modified additive is prepared by the following steps: Step B1: Dissolve 3,3'-dithiodipropionic acid in dichloromethane, stir and add thionyl chloride and N,N-dimethylformamide to react and obtain intermediate 1. Mix glycerol, triethylamine and dichloromethane, stir and add intermediate 1 to react. After reacting, add allyl alcohol and continue the reaction to obtain intermediate 2. Step B2: Mix intermediate 2, caster catalyst, hydroquinone and toluene, purge with nitrogen for protection, stir and add dimethylchlorosilane, heat and react to obtain the modifier. Mix dimethylhydrosilyl alcohol lithium and tetrahydrofuran, purge with nitrogen for protection, stir and add hexamethylcyclotrisiloxane, heat and react, add the modifier, continue the reaction to obtain modified polysiloxane. Step B3: Mix modified polysiloxane, allyl glycidyl ether, caster catalyst and xylene, purge with nitrogen gas for protection, and react to obtain modified additive.

6. The method for preparing a PET base film for transfer printing according to claim 5, characterized in that: The molar ratio of 3,3'-dithiodipropionic acid and thionyl chloride in step B1 is 1:2.1, and the molar ratio of glycerol, triethylamine, intermediate 1 and allyl alcohol is n:4n+2:2n+1:n+2, where n is a natural number greater than 4.

7. The method for preparing a PET base film for transfer printing according to claim 5, characterized in that: The molar ratio of the double bond and dimethylchlorosilane on intermediate 2 in step B2 is 1:1, and the molar ratio of the Si-Cl bond on lithium dimethylhydroxysilyl alcohol, hexamethylcyclotrisiloxane and the modifier is 1:3:

1.

8. The method for preparing a PET base film for transfer printing according to claim 5, characterized in that: The molar ratio of Si-H bonds on the modified polysiloxane and allyl glycidyl ether in step B3 is 1:

1.

9. A PET base film for transfer printing, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.