A method for preparing PE stretch film with strong stretchability

Abstract

The present invention discloses a method for preparing a PE wrapping film with strong stretchability. The method for preparing a PE wrapping film with strong stretchability comprises the following steps: step (1): heating PE plastic particles, adding a xanthene photosensitizer, stirring the mixture evenly, placing the mixture in a melt extruder, extruding it into a flat film, cooling and shaping it to obtain a PE composite film layer; step (2): placing a non-isocyanate polyurethane resin in a melt extruder, extruding it into a flat film under high temperature and high pressure conditions, cooling and shaping it to obtain a non-isocyanate polyurethane resin layer, uniformly coating a layer of environmentally friendly adhesive on both sides thereof, and then pressing the PE composite film layer on both sides of the non-isocyanate polyurethane resin film, curing, cooling, and obtaining a PE wrapping film with strong stretchability. The obtained PE wrapping film has excellent stretchability, environmental protection and thermal stability, wherein the elongation rate is as high as 473.66%.

Description

Technical Field

[0001] The invention belongs to the technical field of PE stretch films, and in particular relates to a method for preparing a PE stretch film with strong stretchability. Background Art

[0002] PE stretch film is a widely used packaging material and has a wide range of applications in various fields. Traditional PE stretch film has limitations in use due to its lack of strong tensile properties. When dealing with complex packaging needs, it is prone to tearing or deformation and cannot meet high-quality packaging requirements. At the same time, due to its poor biodegradability and difficulty in decomposition, it is easy to cause environmental pollution. With the improvement of environmental awareness, the environmental friendliness of PE stretch film needs to be improved.

[0003] Patent CN 213769772 U discloses a PE wrapping film with stretch resistance. The PE film is provided with at least two layers, and a carbon fiber layer is fixedly connected between the two PE film layers. The top view of the carbon fiber layer presents a grid-like structure, and the diagonal lines of the structure are respectively arranged in the horizontal and vertical directions. The PE film and the carbon fiber layer are adhered by a glue layer. This invention ensures its stretch resistance in both the horizontal and vertical directions by arranging the PE film into two layers, and fixing the carbon fiber layer in a grid-like structure between the two layers of PE film by a glue layer, thereby improving the stretch resistance effect. However, the tensile performance and environmental protection performance of the PE wrapping film obtained by this method still have room for improvement. Summary of the invention

[0004] The object of the present invention is to provide a PE stretch film with strong stretchability and a preparation method thereof, so as to solve the technical problems of poor stretchability and environmental protection performance of PE stretch film in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing a PE stretch film having strong stretchability, comprising the following steps:

[0007] Step (1): heating PE plastic particles, adding a xanthene photosensitizer, stirring the mixture evenly, placing the mixture in a melt extruder, extruding the mixture into a flat film under high pressure, and cooling and shaping the mixture to obtain a PE composite film layer;

[0008] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, extruding the non-isocyanate polyurethane resin into a flat film under high temperature and high pressure conditions, cooling and shaping to obtain a non-isocyanate polyurethane resin layer, uniformly coating a layer of environmentally friendly adhesive on both sides of the non-isocyanate polyurethane resin film, and then laminating a PE composite film layer on both sides of the non-isocyanate polyurethane resin film, curing, and cooling to obtain a PE wrapping film with strong stretchability.

[0009] Preferably, the method for preparing the xanthene photosensitizer comprises the following steps:

[0010] Q1: Phenothiazine, 2-bromo-5-iodotoluene, cuprous iodide and sodium tert-butoxide were added to a reaction flask, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, heated to reflux, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0011] Q2: The intermediate product 1 is dissolved in anhydrous tetrahydrofuran, cooled under nitrogen protection, then n-butyl lithium is added, stirred, and then 4,4'-diaminobenzophenone is added, the temperature is increased, stirred, and after the reaction is completed, acidification, stirring, dilution, extraction, drying, and purification are performed to obtain an xanthene photosensitizer.

[0012] In the above process, phenothiazine and 4,4'-diaminobenzophenone are connected through a phenyl linker to obtain a xanthene photosensitizer that can absorb wavelengths from far infrared to near infrared. The synthesis process is as follows:

[0013]

[0014] The results of mass spectrometry analysis are: m / z: 485.19 (100.0%), 486.20 (34.9%), 487.20 (6.2%), 487.19 (4.9%), 486.19 (1.9%), 488.19 (1.6%). The obtained xanthene photosensitizer can absorb light energy and convert it into chemical energy. The energy conversion causes the photosensitizer molecules to be excited, generating free radicals or excited molecules with strong chemical activity, which can attack the molecular chain of PE materials. The molecular weight after the attack is easily broken, triggering a chain reaction, making the PE material degradable.

[0015] Preferably, the molar ratio of phenothiazine, 2-bromo-5-iodotoluene, cuprous iodide and sodium tert-butoxide in Q1 is (8-12):(10-12):(0.1-0.3):(18-22), the heating temperature is 120-140°C, and the reflux time is 14-18h.

[0016] Preferably, the molar ratio of the intermediate product 1, n-butyl lithium and 4,4'-diaminobenzophenone in Q2 is (0.8-1.0): (0.8-1.0): (0.2-0.4), the cooling temperature is -70--80°C, the stirring time is 1-2h, the heating temperature is 27-30°C, the stirring time is 4-6h, 3mol / L hydrochloric acid is used for acidification, the stirring time is 30-50min, it is diluted with distilled water, extracted with dichloromethane, and dried with anhydrous sodium sulfate.

[0017] Preferably, in step (1), the mass ratio of PE plastic particles to xanthene photosensitizer is (25-43):(1-3), the heating temperature is 150-170°C, the stirring time is 2-4h, and the pressure is 1-3MPa.

[0018] Preferably, the method for preparing the non-isocyanate polyurethane resin comprises the following steps:

[0019] S1: adding hexamethylenediamine and p-toluenesulfonic acid into a two-necked flask, heating for sulfonation, then adding L-glutamic acid, introducing nitrogen, heating for reaction, placing under vacuum pressure for reaction, and cooling to room temperature after the reaction is completed to obtain a polyamine;

[0020] S2: Add propylene carbonate and polyamine into a two-necked flask, heat and react under nitrogen protection, and after the reaction, recrystallize and dry to obtain urethane polyol;

[0021] S3: placing the urethane polyol in a two-necked flask and performing a heating treatment, then adding succinic acid and p-toluenesulfonic acid, heating for reaction under nitrogen protection, then raising the temperature for reaction under vacuum pressure, cooling after the reaction is completed, and obtaining a non-isocyanate polyurethane resin.

[0022] In the above process, hexamethylenediamine and L-glutamic acid are used to generate polyamine, which reacts with propylene carbonate to generate urethane polyol, and urethane polyol and succinic acid are reacted by acid polycondensation to obtain non-isocyanate polyurethane resin. The synthesis process is as follows:

[0023]

[0024] Non-isocyanate polyurethane resin has a high molecular weight and regular structure, which can form a more solid and uniform molecular chain network. The network structure is not easy to break when subjected to external force and has strong tensile strength; the peptide bonds it contains have high bond energy, which enables it to maintain stability in a wide temperature range, and the electron cloud distribution of the peptide bonds gives it certain acid and alkali resistance and redox resistance; the carbon-oxygen bonds in the ester groups it contains have high bond energy. Using non-isocyanate polyurethane resin as the middle layer of PE stretch film can effectively improve the tensile properties and thermal stability of PE stretch film.

[0025] Preferably, in S1, the purity of hexamethylenediamine is 98.5%, the heating temperature is 80-90°C, the sulfonation time is 30-40min, the purity of L-glutamic acid is 98%, the heating temperature is 150-170°C, the reaction time is 20-30min, the vacuum pressure is -0.05MPa, the reaction time is 6-8h, and the molar ratio of L-glutamic acid to hexamethylenediamine is 1:(0.9-1.1).

[0026] Preferably, in S2, the purity of propylene carbonate is 98%, the molar ratio of propylene carbonate to polyamine is 1:(0.8-1.2), the heating temperature is 120-130°C, the reaction time is 4-5h, the drying temperature is 50-60°C, and the drying time is 24-26h; in S3, the molar ratio of urethane polyol to succinic acid is 1:(0.93-1.01), the heating temperature is 90-100°C, the heating temperature under nitrogen protection is 160-180°C, the reaction time is 4-6h, the vacuum pressure is -0.08MPa, the heating temperature is 220-230°C, the reaction time is 20-24h, and the temperature is cooled to 26-30°C.

[0027] Preferably, the method for preparing the environmentally friendly adhesive comprises the following steps:

[0028] P1: Dissolve 10-13g soy protein and 10-15g whey protein in 80-100mL distilled water, adjust the solution pH to 8-10 with 1mol / L ammonia water, heat and stir at 50-70℃ for 2-4h to obtain a protein solution;

[0029] P2: Add 3-6 g urea and 0.1-0.3 g protease to the protein solution, stir at 35-38°C for 3-5 hours to obtain an environmentally friendly adhesive.

[0030] The modified protein molecular chains can form a more stable and dense network structure, which is not easy to break when subjected to external forces and exhibits excellent adhesive properties. Since no toxic or harmful chemicals are added during the entire production process and the main component of the adhesive is natural protein, it can be biodegraded after use, further reducing pollution to the environment.

[0031] Preferably, in step (2), the high temperature is 170-180°C, the high pressure is 1-2MPa, the curing temperature is 60-70°C, and the curing time is 2-3h.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. The present invention first prepares a xanthene photosensitizer and adds it to a PE material to improve the degradation performance of the PE material. Subsequently, a non-isocyanate polyurethane resin with strong tensile strength and excellent thermal stability is prepared. The environmentally friendly adhesive obtained by modifying the protein is used to adhere the PE film layer and the non-isocyanate polyurethane resin layer, so that the obtained PE wrapping film has excellent tensile properties, thermal stability and environmental protection.

[0034] 2. In the present invention, hexamethylenediamine, L-glutamic acid, propylene carbonate and succinic acid are used as raw materials to obtain a non-isocyanate polyurethane resin with strong stretchability and environmental protection through a condensation reaction. The high molecular weight and regular structure of the non-isocyanate polyurethane resin enable the molecular chains to form a strong and uniform network, thereby improving the tensile properties. The presence of peptide bonds and ester groups can also improve the thermal stability of the non-isocyanate polyurethane resin. Adding the non-isocyanate polyurethane resin into a layered form and into a PE film can effectively improve the tensile strength and thermal stability of the PE wrapping film.

[0035] 3. In the present invention, phenothiazine, 2-bromo-5-iodotoluene and 4,4'-diaminobenzophenone are used as raw materials to synthesize xanthene photosensitizers. The photosensitizers generate free radicals under light conditions, which trigger the breakage of the molecular chains of PE materials and oxidative degradation reactions. The free radicals attack the carbon-carbon bonds of the PE materials, causing the molecular chains to gradually break into low molecular weight fragments, accelerating the degradation process. Adding the photosensitizers to PE materials can improve the degradation performance of PE wrapping films and reduce environmental pollution. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment discloses a method for preparing an environmentally friendly adhesive, comprising the following steps:

[0039] P1: 11.5 g of soy protein and 12.5 g of whey protein were dissolved in 100 mL of distilled water, the pH of the solution was adjusted to 9 with 1 mol / L ammonia water, and the protein solution was obtained after heating and stirring at 70°C for 2 h;

[0040] P2: 5 g urea and 0.2 g protease were added to the protein solution and stirred at 35 °C for 3 h to obtain an environmentally friendly adhesive.

[0041] Example 2

[0042] This embodiment discloses a method for preparing a xanthene photosensitizer, comprising the following steps:

[0043] Q1: 1.837 g of phenothiazine, 1.55 mL of 2-bromo-5-iodotoluene, 0.031 g of cuprous iodide and 1.837 g of sodium tert-butoxide were added to a reaction bottle, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, and the mixture was heated to reflux at 120°C for 16 h, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0044] Q2: 0.29 g of intermediate product 1 was dissolved in anhydrous tetrahydrofuran and cooled under nitrogen protection at -78°C. Subsequently, 0.065 mL of n-butyl lithium was added and stirred for 1 h. Then, 0.75 g of 4,4'-diaminobenzophenone was added and the temperature was raised to 30°C and stirred for 4 h. After the reaction was completed, 3 mol / L hydrochloric acid was used for acidification and stirred for 30 min. The mixture was diluted with distilled water, extracted with dichloromethane, dried with anhydrous sodium sulfate, and purified to obtain an xanthene photosensitizer.

[0045] This embodiment discloses a method for preparing a non-isocyanate polyurethane resin, comprising the following steps:

[0046] S1: 0.147 g of hexamethylenediamine with a purity of 98.5% and p-toluenesulfonic acid were added to a two-necked flask, sulfonated at 80°C for 40 min, then 0.113 g of L-glutamic acid with a purity of 98% was added, nitrogen was introduced, heated at 170°C for reaction for 20 min, and then placed under a vacuum pressure of -0.05 MPa for reaction for 8 h. After the reaction was completed, it was cooled to room temperature to obtain a polyamine;

[0047] S2: 0.114 g of propylene carbonate with a purity of 98% and 0.301 g of polyamine were added to a two-necked flask, and reacted at 120° C. for 5 h under nitrogen protection. After the reaction, the mixture was recrystallized and dried at 60° C. for 24 h to obtain urethane polyol;

[0048] S3: Place 0.635 g of urethane polyol in a two-necked flask, heat to 90°C, then add 0.115 g of succinic acid and p-toluenesulfonic acid, react at 180°C for 4 hours under nitrogen protection, then heat to 220°C under a vacuum pressure of -0.08 MPa and react for 24 hours. After the reaction is completed, cool to 28°C to obtain a non-isocyanate polyurethane resin.

[0049] This embodiment discloses a method for preparing a PE stretch film with strong stretchability, comprising the following steps:

[0050] Step (1): 34 g of PE plastic particles are heated to 150° C., 2 g of xanthene photosensitizer is added, and the mixture is placed in a melt extruder after stirring for 4 h. Under a pressure of 2 MPa, the mixture is extruded into a flat film, and cooled and shaped to obtain a PE composite film layer;

[0051] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, and extruding the non-isocyanate polyurethane resin into a flat film at 180° C. and 2 MPa. After cooling and shaping, a non-isocyanate polyurethane resin layer is obtained. A layer of environmentally friendly adhesive is evenly coated on both sides of the non-isocyanate polyurethane resin film. Subsequently, a PE composite film layer is laminated on both sides of the non-isocyanate polyurethane resin film, cured at 70° C. for 2 hours, and cooled to obtain a PE wrapping film with strong stretchability.

[0052] Example 3

[0053] This embodiment discloses a method for preparing a xanthene photosensitizer, comprising the following steps:

[0054] Q1: 1.602 g of phenothiazine, 1.44 mL of 2-bromo-5-iodotoluene, 0.023 g of cuprous iodide and 1.745 g of sodium tert-butoxide were added to a reaction bottle, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, and the mixture was heated to reflux at 120°C for 16 h, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0055] Q2: 0.28 g of intermediate product 1 was dissolved in anhydrous tetrahydrofuran and cooled under nitrogen protection at -78°C. Subsequently, 0.07 mL of n-butyl lithium was added and stirred for 1 h. Then, 0.67 g of 4,4'-diaminobenzophenone was added and the temperature was raised to 30°C and stirred for 4 h. After the reaction was completed, 3 mol / L hydrochloric acid was used for acidification and stirred for 30 min. The mixture was diluted with distilled water, extracted with dichloromethane, dried with anhydrous sodium sulfate, and purified to obtain an xanthene photosensitizer.

[0056] This embodiment discloses a method for preparing a non-isocyanate polyurethane resin, comprising the following steps:

[0057] S1: 0.147 g of hexamethylenediamine with a purity of 98.5% and p-toluenesulfonic acid were added to a two-necked flask, sulfonated at 80°C for 40 min, then 0.105 g of L-glutamic acid with a purity of 98% was added, nitrogen was introduced, heated at 170°C for 20 min, and then placed under a vacuum pressure of -0.05 MPa for 8 h. After the reaction was completed, it was cooled to room temperature to obtain a polyamine;

[0058] S2: 0.114 g of propylene carbonate with a purity of 98% and 0.287 g of polyamine were added to a two-necked flask, and reacted at 120° C. for 5 h under nitrogen protection. After the reaction, the mixture was recrystallized and dried at 60° C. for 24 h to obtain urethane polyol;

[0059] S3: Place 0.635 g of urethane polyol in a two-necked flask, heat to 90°C, then add 0.110 g of succinic acid and p-toluenesulfonic acid, react at 180°C for 4 hours under nitrogen protection, then heat to 220°C under a vacuum pressure of -0.08 MPa and react for 24 hours. After the reaction is completed, cool to 28°C to obtain a non-isocyanate polyurethane resin.

[0060] This embodiment discloses a method for preparing a PE stretch film with strong stretchability, comprising the following steps:

[0061] Step (1): 38 g of PE plastic particles are heated to 150° C., 1.5 g of anthracene photosensitizer is added, and the mixture is stirred for 4 h. The mixture is placed in a melt extruder, and the mixture is extruded into a flat film under a pressure of 2 MPa, and cooled and shaped to obtain a PE composite film layer;

[0062] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, and extruding the non-isocyanate polyurethane resin into a flat film at 180° C. and 2 MPa. After cooling and shaping, a non-isocyanate polyurethane resin layer is obtained. A layer of environmentally friendly adhesive is evenly coated on both sides of the non-isocyanate polyurethane resin film. Subsequently, a PE composite film layer is laminated on both sides of the non-isocyanate polyurethane resin film, cured at 70° C. for 2 hours, and cooled to obtain a PE wrapping film with strong stretchability.

[0063] Example 4

[0064] This embodiment discloses a method for preparing a xanthene photosensitizer, comprising the following steps:

[0065] Q1: 2.113 g of phenothiazine, 1.46 mL of 2-bromo-5-iodotoluene, 0.041 g of cuprous iodide and 1.943 g of sodium tert-butoxide were added to a reaction bottle, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, and the mixture was heated to reflux at 120°C for 16 h, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0066] Q2: 0.32 g of intermediate product 1 was dissolved in anhydrous tetrahydrofuran and cooled under nitrogen protection at -78°C. Subsequently, 0.074 mL of n-butyl lithium was added and stirred for 1 h. Then, 0.50 g of 4,4'-diaminobenzophenone was added and the temperature was raised to 30°C and stirred for 4 h. After the reaction was completed, 3 mol / L hydrochloric acid was used for acidification and stirred for 30 min. The mixture was diluted with distilled water, extracted with dichloromethane, dried with anhydrous sodium sulfate, and purified to obtain an xanthene photosensitizer.

[0067] This embodiment discloses a method for preparing a non-isocyanate polyurethane resin, comprising the following steps:

[0068] S1: 0.147 g of hexamethylenediamine with a purity of 98.5% and p-toluenesulfonic acid were added to a two-necked flask, sulfonated at 80°C for 40 min, then 0.119 g of L-glutamic acid with a purity of 98% was added, nitrogen was introduced, heated at 170°C for 20 min, and then placed under a vacuum pressure of -0.05 MPa for 8 h. After the reaction was completed, it was cooled to room temperature to obtain a polyamine;

[0069] S2: 0.114 g of propylene carbonate with a purity of 98% and 0.359 g of polyamine were added to a two-necked flask, and reacted at 120° C. for 5 h under nitrogen protection. After the reaction, the mixture was recrystallized and dried at 60° C. for 24 h to obtain urethane polyol;

[0070] S3: Place 0.635 g of urethane polyol in a two-necked flask, heat to 90°C, then add 0.119 g of succinic acid and p-toluenesulfonic acid, react at 180°C for 4 hours under nitrogen protection, then heat to 220°C under a vacuum pressure of -0.08 MPa and react for 24 hours. After the reaction is completed, cool to 28°C to obtain a non-isocyanate polyurethane resin.

[0071] This embodiment discloses a method for preparing a PE stretch film with strong stretchability, comprising the following steps:

[0072] Step (1): 30 g of PE plastic particles are heated to 150° C., 2.5 g of xanthene photosensitizer is added, and the mixture is stirred for 4 h. The mixture is placed in a melt extruder, and the mixture is extruded into a flat film under a pressure of 2 MPa, and cooled and shaped to obtain a PE composite film layer;

[0073] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, and extruding the non-isocyanate polyurethane resin into a flat film at 180° C. and 2 MPa. After cooling and shaping, a non-isocyanate polyurethane resin layer is obtained. A layer of environmentally friendly adhesive is evenly coated on both sides of the non-isocyanate polyurethane resin film. Subsequently, a PE composite film layer is laminated on both sides of the non-isocyanate polyurethane resin film, cured at 70° C. for 2 hours, and cooled to obtain a PE wrapping film with strong stretchability.

[0074] Example 5

[0075] This embodiment discloses a method for preparing a xanthene photosensitizer, comprising the following steps:

[0076] Q1: 1.973 g of phenothiazine, 1.66 mL of 2-bromo-5-iodotoluene, 0.025 g of cuprous iodide and 2.108 g of sodium tert-butoxide were added to a reaction bottle, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, and the mixture was heated to reflux at 120°C for 16 h, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0077] Q2: 0.31 g of intermediate product 1 was dissolved in anhydrous tetrahydrofuran and cooled under nitrogen protection at -78°C. Subsequently, 0.068 mL of n-butyl lithium was added and stirred for 1 h. Then, 0.81 g of 4,4'-diaminobenzophenone was added and the temperature was raised to 30°C and stirred for 4 h. After the reaction was completed, 3 mol / L hydrochloric acid was used for acidification and stirred for 30 min. The mixture was diluted with distilled water, extracted with dichloromethane, dried with anhydrous sodium sulfate, and purified to obtain an oxygen-anthene photosensitizer.

[0078] This embodiment discloses a method for preparing a non-isocyanate polyurethane resin, comprising the following steps:

[0079] S1: 0.147 g of hexamethylenediamine with a purity of 98.5% and p-toluenesulfonic acid were added to a two-necked flask, sulfonated at 80°C for 40 min, then 0.120 g of L-glutamic acid with a purity of 98% was added, nitrogen was introduced, heated at 170°C for 20 min, and then placed under a vacuum pressure of -0.05 MPa for 8 h. After the reaction was completed, it was cooled to room temperature to obtain a polyamine;

[0080] S2: 0.114 g of propylene carbonate with a purity of 98% and 0.403 g of polyamine were added to a two-necked flask, and reacted at 120° C. for 5 h under nitrogen protection. After the reaction, the mixture was recrystallized and dried at 60° C. for 24 h to obtain urethane polyol;

[0081] S3: Place 0.635 g of urethane polyol in a two-necked flask, heat to 90°C, then add 0.114 g of succinic acid and p-toluenesulfonic acid, react at 180°C for 4 hours under nitrogen protection, then heat to 220°C under a vacuum pressure of -0.08 MPa and react for 24 hours. After the reaction is completed, cool to 28°C to obtain a non-isocyanate polyurethane resin.

[0082] This embodiment discloses a method for preparing a PE stretch film with strong stretchability, comprising the following steps:

[0083] Step (1): 42 g of PE plastic particles are heated to 150° C., 3 g of xanthene photosensitizer is added, and the mixture is stirred for 4 h. The mixture is placed in a melt extruder, and the mixture is extruded into a flat film under a pressure of 2 MPa, and cooled and shaped to obtain a PE composite film layer;

[0084] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, and extruding the non-isocyanate polyurethane resin into a flat film at 180° C. and 2 MPa. After cooling and shaping, a non-isocyanate polyurethane resin layer is obtained. A layer of environmentally friendly adhesive is evenly coated on both sides of the non-isocyanate polyurethane resin film. Subsequently, a PE composite film layer is laminated on both sides of the non-isocyanate polyurethane resin film, cured at 70° C. for 2 hours, and cooled to obtain a PE wrapping film with strong stretchability.

[0085] Example 6

[0086] This embodiment discloses a method for preparing a xanthene photosensitizer, comprising the following steps:

[0087] Q1: 2.007 g of phenothiazine, 1.50 mL of 2-bromo-5-iodotoluene, 0.055 g of cuprous iodide and 2.015 g of sodium tert-butoxide were added to a reaction bottle, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, and the mixture was heated to reflux at 120°C for 16 h, cooled, extracted, concentrated, ground and purified to obtain intermediate 1;

[0088] Q2: 0.30 g of intermediate product 1 was dissolved in anhydrous tetrahydrofuran and cooled under nitrogen protection at -78°C. Subsequently, 0.063 mL of n-butyl lithium was added and stirred for 1 h. Then, 0.48 g of 4,4'-diaminobenzophenone was added and the temperature was raised to 30°C and stirred for 4 h. After the reaction was completed, 3 mol / L hydrochloric acid was used for acidification and stirred for 30 min. The mixture was diluted with distilled water, extracted with dichloromethane, dried with anhydrous sodium sulfate, and purified to obtain an oxygen-anthene photosensitizer.

[0089] This embodiment discloses a method for preparing a non-isocyanate polyurethane resin, comprising the following steps:

[0090] S1: 0.147 g of hexamethylenediamine with a purity of 98.5% and p-toluenesulfonic acid were added to a two-necked flask, sulfonated at 80°C for 40 min, then 0.125 g of L-glutamic acid with a purity of 98% was added, nitrogen was introduced, heated at 170°C for reaction for 20 min, and then placed under a vacuum pressure of -0.05 MPa for reaction for 8 h. After the reaction was completed, it was cooled to room temperature to obtain a polyamine;

[0091] S2: 0.114 g of propylene carbonate with a purity of 98% and 0.373 g of polyamine were added to a two-necked flask, and reacted at 120° C. for 5 h under nitrogen protection. After the reaction, the mixture was recrystallized and dried at 60° C. for 24 h to obtain urethane polyol;

[0092] S3: Place 0.635 g of urethane polyol in a two-necked flask, heat to 90°C, then add 0.117 g of succinic acid and p-toluenesulfonic acid, react at 180°C for 4 hours under nitrogen protection, then heat to 220°C under a vacuum pressure of -0.08 MPa and react for 24 hours. After the reaction is completed, cool to 28°C to obtain a non-isocyanate polyurethane resin.

[0093] This embodiment discloses a method for preparing a PE stretch film with strong stretchability, comprising the following steps:

[0094] Step (1): 26 g of PE plastic particles are heated to 150° C., 1 g of a xanthene photosensitizer is added, and the mixture is stirred for 4 h. The mixture is placed in a melt extruder, and the mixture is extruded into a flat film under a pressure of 2 MPa, and cooled and shaped to obtain a PE composite film layer;

[0095] Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, and extruding the non-isocyanate polyurethane resin into a flat film at 180° C. and 2 MPa. After cooling and shaping, a non-isocyanate polyurethane resin layer is obtained. A layer of environmentally friendly adhesive is evenly coated on both sides of the non-isocyanate polyurethane resin film. Subsequently, a PE composite film layer is laminated on both sides of the non-isocyanate polyurethane resin film, cured at 70° C. for 2 hours, and cooled to obtain a PE wrapping film with strong stretchability.

[0096] Comparative Example 1

[0097] Comparative Example 1 Compared with Example 1, in the process of preparing the non-isocyanate polyurethane resin in Comparative Example 1, no succinic acid was added, and other conditions remained unchanged.

[0098] Comparative Example 2

[0099] Comparative Example 2 Compared with Example 1, in the process of preparing the xanthene photosensitizer in Comparative Example 2, 4,4'-diaminobenzophenone was not added, and other conditions remained unchanged.

[0100] Experimental example

[0101] The properties of the PE stretch films prepared in Examples 2-6 and Comparative Examples 1-2 were tested.

[0102] 1. Tensile performance test

[0103] The tensile properties of the samples were measured according to GB 13022-91, and the results are shown in Table 1:

[0104] Table 1

[0105] project Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Elongation / % 473.66 464.12 456.98 461.37 450.53 360.22 338.57

[0106] From the test results in Table 1, it can be seen that the PE wrapping film with strong stretchability prepared in Examples 2-6 of the present invention has excellent stretching rate. From the comparison between Comparative Example 1 and Examples 2-6, it can be seen that adding succinic acid can effectively improve the stretching rate of the PE wrapping film.

[0107] 2. Degradability Test

[0108] The obtained samples were cut into strips and placed under light conditions. The humidity in the environment was controlled to be 50-55% and the temperature was 40-45°C. The samples were placed for 20 days. The mass of the samples before and after the test was weighed and the mass reduction rate was calculated. The test results are shown in Table 2:

[0109] Table 2

[0110]

[0111]

[0112] From the test results in Table 2, it can be seen that the PE wrapping film with strong stretchability prepared in Examples 2-6 of the present invention has excellent degradability. From the comparison between Comparative Example 2 and Examples 2-6, it can be seen that the addition of 4,4'-diaminobenzophenone can improve the degradability of the PE wrapping film.

[0113] 3. Thermal stability performance test

[0114] The obtained samples were placed in an electric constant temperature blast drying oven (DHC-9053A, Nanjing Dongmai Technology Instrument Co., Ltd.) and tested for thermal stability at 80°C. The changes in elongation before and after the experiment were measured. The test results are shown in Table 3:

[0115] Table 3

[0116] project Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Change rate / % 3.5 4.1 4.8 5.3 5.7 10.4 6.9

[0117] From the test results in Table 3, it can be seen that the PE wrapping film with strong stretchability prepared in Examples 2-6 of the present invention has excellent thermal stability. From the comparison between Comparative Example 1 and Examples 2-6, it can be seen that adding succinic acid can improve the thermal stability of the PE wrapping film.

[0118] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0119] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a PE stretch film with strong stretchability, characterized in that: The following steps are involved: Step (1): heating PE plastic particles, adding a xanthene photosensitizer, stirring the mixture evenly, placing the mixture in a melt extruder, extruding the mixture into a flat film under high pressure, and cooling and shaping the mixture to obtain a PE composite film layer; Step (2): placing a non-isocyanate polyurethane resin in a melt extruder, extruding the non-isocyanate polyurethane resin into a flat film under high temperature and high pressure conditions, cooling and shaping to obtain a non-isocyanate polyurethane resin layer, uniformly coating a layer of environmentally friendly adhesive on both sides of the non-isocyanate polyurethane resin film, and then laminating a PE composite film layer on both sides of the non-isocyanate polyurethane resin film, curing, and cooling to obtain a PE wrapping film with strong stretchability; The preparation method of the xanthene photosensitizer comprises the following steps: Q1: Phenothiazine, 2-bromo-5-iodotoluene, cuprous iodide and sodium tert-butoxide were added to a reaction flask, 1,4-dioxane was injected under nitrogen protection, and then 1,2-diaminocyclohexane was added, heated to reflux, cooled, extracted, concentrated, ground and purified to obtain intermediate 1; Q2: The intermediate product 1 is dissolved in anhydrous tetrahydrofuran, cooled under nitrogen protection, then n-butyl lithium is added, stirred, and then 4,4'-diaminobenzophenone is added, the temperature is increased, stirred, and after the reaction is completed, acidification, stirring, dilution, extraction, drying, and purification are performed to obtain a xanthene photosensitizer; The preparation method of the non-isocyanate polyurethane resin comprises the following steps: S1: adding hexamethylenediamine and p-toluenesulfonic acid into a two-necked flask, heating for sulfonation, then adding L-glutamic acid, introducing nitrogen, heating for reaction, placing under vacuum pressure for reaction, and cooling to room temperature after the reaction is completed to obtain a polyamine; S2: Add propylene carbonate and polyamine into a two-necked flask, heat and react under nitrogen protection, and after the reaction, recrystallize and dry to obtain urethane polyol; S3: placing the urethane polyol in a two-necked flask and performing a heating treatment, then adding succinic acid and p-toluenesulfonic acid, heating for reaction under nitrogen protection, then raising the temperature for reaction under vacuum pressure, cooling after the reaction is completed, and obtaining a non-isocyanate polyurethane resin.

2. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: The molar ratio of phenothiazine, 2-bromo-5-iodotoluene, cuprous iodide and sodium tert-butoxide in Q1 is (8-12):(10-12):(0.1-0.3):(18-22), the heating temperature is 120-140° C., and the reflux time is 14-18 h.

3. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: The molar ratio of the intermediate product 1, n-butyl lithium and 4,4'-diaminobenzophenone in Q2 is (0.8-1.0): (0.8-1.0): (0.2-0.4), the cooling temperature is -70--80°C, the stirring time is 1-2h, the heating temperature is 27-30°C, the stirring time is 4-6h, 3mol / L hydrochloric acid is used for acidification, the stirring time is 30-50min, it is diluted with distilled water, extracted with dichloromethane, and dried with anhydrous sodium sulfate.

4. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: In the step (1), the mass ratio of PE plastic particles to xanthene photosensitizer is (25-43): (1-3), the heating temperature is 150-170° C., the stirring time is 2-4 h, and the pressure is 1-3 MPa.

5. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: In the S1, the purity of hexamethylenediamine is 98.5%, the heating temperature is 80-90°C, the sulfonation time is 30-40min, the purity of L-glutamic acid is 98%, the heating temperature is 150-170°C, the reaction time is 20-30min, the vacuum pressure is -0.05MPa, the reaction time is 6-8h, and the molar ratio of L-glutamic acid to hexamethylenediamine is 1:(0.9-1.1).

6. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: In the S2, the purity of propylene carbonate is 98%, the molar ratio of propylene carbonate to polyamine is 1:(0.8-1.2), the heating temperature is 120-130°C, the reaction time is 4-5h, the drying temperature is 50-60°C, and the drying time is 24-26h; in the S3, the molar ratio of urethane polyol to succinic acid is 1:(0.93-1.01), the heating temperature is 90-100°C, the heating temperature under nitrogen protection is 160-180°C, the reaction time is 4-6h, the vacuum pressure is -0.08MPa, the heating temperature is 220-230°C, the reaction time is 20-24h, and the temperature is cooled to 26-30°C.

7. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: The preparation method of the environmentally friendly adhesive comprises the following steps: P1: Dissolve 10-13g soy protein and 10-15g whey protein in 80-100mL distilled water, adjust the solution pH to 8-10 with 1mol / L ammonia water, heat and stir at 50-70℃ for 2-4h to obtain a protein solution; P2: Add 3-6 g urea and 0.1-0.3 g protease to the protein solution, stir at 35-38°C for 3-5 hours to obtain an environmentally friendly adhesive.

8. The method for preparing a PE stretch film with strong stretchability according to claim 1, characterized in that: In the step (2), the high temperature is 170-180° C., the high pressure is 1-2 MPa, the curing temperature is 60-70° C., and the curing time is 2-3 hours.

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