Amorphous copolyester material for heat shrink film as well as preparation method and application of amorphous copolyester material

Abstract

The invention belongs to the field of copolyester materials, and particularly relates to an amorphous copolyester material for a heat shrink film as well as a preparation method and application of the amorphous copolyester material for the heat shrink film, and the amorphous copolyester material for the heat shrink film comprises the following raw materials in parts by weight: 35-45 parts of modified copolyester, 2-4 parts of a flame retardant, 1-3 parts of a lubricant and 0.5-1 part of an antioxidant. The amorphous copolyester material for the heat shrinkage film prepared by the invention is high in heat shrinkage rate, easy to process and excellent in mechanical property.

Description

Technical Field

[0001] The invention belongs to the field of copolyester materials, and in particular relates to a non-crystalline copolyester material for a heat shrinkable film and a preparation method and application thereof. Background Art

[0002] Heat shrink film is a kind of packaging film that generates shrinkage force after being heated to wrap the items and protect them. Due to its advantages such as good heat shrinkage, sealing, moisture resistance, and lightness, it has a large market size in the packaging industry. At present, the main material commonly used for heat shrink film on the market is PVC, but the light stability of PVC film is poor. A large amount of plasticizer needs to be added during processing. It cannot be recycled and can only be incinerated after use. Toxic gases will be produced during the combustion process, polluting the environment. At present, some regions have banned its use in the field of food packaging. Copolyester materials have the advantages of good recyclability, non-toxicity, good heat resistance and high strength, and are gradually favored in the packaging field. However, due to the good crystallinity of ordinary copolyesters, it is not easy to be processed into heat shrink films. Therefore, non-crystalline copolyester materials have gradually been studied by relevant personnel.

[0003] Patent CN103483784B discloses a flame-retardant PET heat shrink film. By adding environmentally friendly flame retardants and additives to PET resin, a flame-retardant heat shrink film with high tensile strength and strong shrinkage performance is prepared. The film is suitable for the outer packaging of electronic products to prevent the spontaneous combustion of electronic products due to heat and prevent the occurrence of fire. The heat shrink film prepared by the invention requires the addition of plasticizers, which may be detrimental to people's health and cannot be used for food packaging.

[0004] Patent CN105283506B discloses a composition for forming a heat shrinkable film comprising polyethylene terephthalate resin and a copolymer polyester resin, which has excellent shrinkage even under low temperature conditions. The heat shrinkable film prepared according to the composition is suitable for different occasions and requires adjustment of the content of the polyester resin, which is not easy to process.

[0005] Therefore, there is an urgent need for a non-crystalline copolyester material for heat shrinkable film that does not contain plasticizers, has a high heat shrinkage rate, and is easy to process. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a non-crystalline copolyester material for shrinkage film which has high heat shrinkage rate, is easy to process and has excellent mechanical properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a non-crystalline copolyester material for heat shrinkable film, which comprises the following raw materials by weight: 35-45 parts of modified copolyester, 11-14 parts of modified starch, 2-4 parts of flame retardant, 1-3 parts of lubricant, and 0.5-1 part of antioxidant.

[0009] In some embodiments, the method for preparing the modified copolyester comprises the following steps:

[0010] 1) The copolymer, terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol and neopentyl glycol are mixed and beaten for 35-45 minutes to obtain a slurry, and the slurry is sent to the first reaction kettle for reaction. The temperature in the kettle is controlled at 245-255° C., and the temperature at the top of the tower is controlled at 95-110° C. After the slurry is transported, the temperature in the kettle is maintained at 70-95° C., and the reaction is carried out for 11-13 hours to obtain a reaction liquid material 1;

[0011] 2) nitrogen is introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then a catalyst and a heat stabilizer are added and stirred for 10-20 minutes, and the temperature is controlled at 245-250° C. to obtain reaction liquid 2;

[0012] 3) The reaction liquid 2 in the second reactor is introduced into nitrogen and pressed into the third reactor. When the temperature reaches 260-265°C, the pressure in the reactor is pumped down to -0.1KPa~1KPa within 45-60min under stirring. The temperature in the reactor is controlled at 280-295°C. The reaction is carried out for 1-2h. The vacuum jet pump is turned on. The pressure in the reactor reaches 40-90Pa. The reaction time is 210-270min. The power value of the slurry stirring motor is set. When the power value is reached, the stirring is stopped. The material is discharged, pelletized and dried to obtain the modified copolyester.

[0013] In some embodiments, the mass ratio of the copolymer, terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol, and neopentyl glycol is (0.1-0.15):1:(0.15-0.25):(0.1-0.2):(0.1-0.3).

[0014] Conventional polyester materials are crystalline materials. They have the characteristics of few molecular segments in the amorphous region, high melting point and strong rigidity, and are not suitable for processing heat shrinkable films. They are often copolymerized to become non-crystalline before they can be used for processing heat shrinkable films. The present invention prepares a copolymer for copolymerization to destroy the regularity of the molecules and slow down the crystallization rate. The obtained modified copolyester has easy processing, high heat shrinkage rate and maintains good mechanical properties.

[0015] In some embodiments, the method for preparing the copolymer comprises the following steps:

[0016] (1) adding dodecenylsuccinic acid, acrylic acid and an initiator into a reaction vessel, reacting at 60-70° C., controlling the number average molecular weight to be 300-400, and obtaining a polymer;

[0017] (2) Add the polymer obtained in step (1), (4-hydroxyphenyl)phosphonic acid and tetraisopropyl titanate to dimethyl sulfoxide, react at 70-80° C. for 1-2 hours, and dry to obtain a copolymer.

[0018] Preferably, the mass ratio of the polymer to (4-hydroxyphenyl)phosphonic acid is (1.8-2.3):1.

[0019] In order to improve the crystallinity of polyester, isophthalic acid and diethylene glycol are generally added to disrupt the regularity of the molecular structure to slow down the crystallinity of polyester, but isophthalic acid cannot make polyester reach a non-crystalline state, and diethylene glycol is easily decomposed during processing. The present invention utilizes dodecenylsuccinic acid and acrylic acid to react with (4-hydroxyphenyl)phosphonic acid to obtain a copolymer with a new structure. The copolyester obtained by copolymerizing the homemade copolymer can reach a non-crystalline state and has good mechanical properties and flame retardancy. The possible reason is that the copolymerization of dodecenylsuccinic acid and acrylic acid destroys the original regular structure of the polyester and reduces its crystallinity. At the same time, the molecular weight of the polymer is controlled to make it easier to react with (4-hydroxyphenyl)phosphonic acid. In addition, the mass ratio of the polymer and (4-hydroxyphenyl)phosphonic acid is controlled so that the hydroxyl group on the (4-hydroxyphenyl)phosphonic acid can react with an indefinite position carboxyl group on the polymer, further improving the non-crystalline characteristics of the copolyester. In addition, due to the presence of benzene rings and phosphorus atoms in the copolymer, the mechanical properties and flame retardancy of the copolyester are also further improved.

[0020] In some embodiments, the method for preparing the modified starch comprises the following steps:

[0021] 1) adding aconitic acid and an initiator into ethanol, reacting at 65-75° C., controlling the number average molecular weight to be 100-200, and drying to obtain polyaconitic acid;

[0022] 2) Add polyaconitic acid, starch and tetraisopropyl titanate into dimethyl sulfoxide, and react at 70-80° C. for 0.5-1 h to obtain modified starch.

[0023] Preferably, the mass ratio of polyaconitic acid to starch is 1:(1-1.3).

[0024] Copolyester heat shrinkable film used in food packaging sometimes requires a higher hiding rate and often needs to add a large amount of fillers with whitening effect. Titanium dioxide is often added as a filler. On the one hand, it is expensive, and on the other hand, it degrades slowly, which may cause metal ions in soil and water to exceed the standard and damage the environment. The applicant adds starch as a filler. Starch is cheap and easy to obtain and has a certain whitening effect. However, the starch surface contains a large number of hydroxyl groups and has poor compatibility with modified copolyesters. Directly adding it to the modified copolyester may deteriorate the mechanical properties of the prepared copolyester heat shrinkable film, and it is easy to crack during the film forming process and difficult to process.

[0025] The applicant uses aconitic acid containing multiple carboxyl groups to modify starch, but aconitic acid contains double bonds that are easily oxidized, and the distribution of carboxyl groups is relatively "loose". The copolyester heat shrink film obtained by directly modifying starch is easy to age. The present invention self-polymerizes aconitic acid to obtain polyaconitic acid. The copolyester heat shrink film prepared by modified starch has high hiding power and mechanical properties. On the one hand, the possible reason is that the modified starch has a large number of ester groups, which increases the compatibility with the copolyester and improves the mechanical properties of the copolyester; on the other hand, it may be due to the presence of acidic groups in the copolymer. Under acidic conditions, the copolyester may cause part of the copolyester to decompose during high-temperature extrusion, and the molecular weight decreases, thereby causing the toughness of the obtained heat shrink film to decrease. The modified starch still retains a certain number of active hydroxyl groups, and under acidic conditions, it cross-links with the broken copolyester. At the same time, the mass ratio of polyaconitic acid to starch is limited, and the reinforcing effect on the copolyester will not be reduced due to too few cross-linking sites with the copolyester, nor will the movement of the copolyester chain segments be restricted due to excessive cross-linking, resulting in a decrease in the heat shrinkage rate, thereby further improving the mechanical properties of the heat shrink film.

[0026] In some embodiments, the flame retardant is one or more of triphenyl phosphate, aluminum hydroxide, decabromodiphenyl ether, brominated epoxy resin, and ammonium polyphosphate.

[0027] In some embodiments, the lubricant is one or more of polyethylene wax, calcium stearate, paraffin, and butyl stearate.

[0028] In some embodiments, the antioxidant is one or more of hindered phenols, hindered amines, and phosphites.

[0029] Preferably, the antioxidant is a hindered phenol antioxidant.

[0030] The second aspect of the present invention provides a method for preparing a non-crystalline copolyester material for a heat shrinkable film, comprising the following steps:

[0031] S1. Mix the modified copolyester, modified starch, flame retardant, lubricant and antioxidant, add them into a mixer, and mix for 10-30 minutes to obtain a premix;

[0032] S2. The premix obtained in step S1 is put into a twin-screw extruder and extruded from a die head. The extrusion temperature is controlled at 210-220° C. The extruded melt is attached to the surface of a casting roll for cooling. The surface temperature of the casting roll is 40-50° C. to obtain a non-crystalline copolyester material for a heat shrinkable film.

[0033] A third aspect of the present invention provides an application of a non-crystalline copolyester material for a heat shrinkable film, wherein the non-crystalline copolyester material for a heat shrinkable film is used for food packaging.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention obtains a non-crystalline copolyester material by copolymerizing a self-made copolymer and adding modified starch. The non-crystalline copolyester material has a high heat shrinkage rate and is easy to process while maintaining good mechanical properties.

[0036] 2. The copolyester obtained by copolymerizing the self-made copolymer of dodecenylsuccinic acid, acrylic acid and (4-hydroxyphenyl)phosphonic acid in the present invention can reach a non-crystalline state and at the same time have good mechanical properties and flame retardancy.

[0037] 3. The present invention uses polyaconitic acid obtained by self-polymerization of aconitic acid to modify starch, thereby increasing the compatibility of the modified starch with the copolyester and improving the mechanical properties of the copolyester. On the other hand, the modified starch can be cross-linked with the broken copolyester, while limiting the mass ratio of polyaconitic acid to starch, further improving the mechanical properties of the heat shrinkable film. DETAILED DESCRIPTION

[0038] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples and comparative examples are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0039] In order to facilitate those skilled in the art to implement the present invention, some raw materials and manufacturers of the embodiments and comparative examples are described as follows: the compounds and related reagents used in the present invention can be purchased from the market, among which corn starch was purchased from Shandong Xinshunjie Chemical Technology Co., Ltd.

[0040] Preparation Example 1

[0041] The preparation method of copolymer-1 comprises the following steps:

[0042] (1) 29 g of dodecenylsuccinic acid, 7.2 g of acrylic acid and 0.3 g of dicumyl peroxide were added to a reaction vessel and reacted at 65° C. to obtain a polymer with a number average molecular weight of 361;

[0043] (2) 21 g of the polymer obtained in step (1), 10 g of (4-hydroxyphenyl)phosphonic acid and 0.015 g of tetraisopropyl titanate were added to 100 g of dimethyl sulfoxide, reacted at 75° C. for 1.5 h, and dried to obtain copolymer-1.

[0044] Preparation Example 2

[0045] The preparation method of copolymer-2 comprises the following steps:

[0046] (1) 29 g of dodecenylsuccinic acid, 7.2 g of acrylic acid and 0.3 g of dicumyl peroxide were added to a reaction vessel and reacted at 65° C. to obtain a polymer with a number average molecular weight of 358;

[0047] (2) 28 g of the polymer obtained in step (1), 20 g of (4-hydroxyphenyl)phosphonic acid and 0.015 g of tetraisopropyl titanate were added to 100 g of dimethyl sulfoxide, reacted at 75° C. for 1.5 h, and dried to obtain copolymer-2.

[0048] Preparation Example 3

[0049] The preparation method of modified copolyester-1 comprises the following steps:

[0050] 1) 130 g of copolymer-1, 1000 g of terephthalic acid, 200 g of ethylene glycol, 150 g of 1,4-cyclohexanedimethanol, and 200 g of neopentyl glycol were mixed and slurried for 40 min to obtain a slurry, and the slurry was sent to the first reactor through a screw slurry delivery pump for reaction, the temperature in the reactor was controlled at 250° C., and the tower top temperature was controlled at 100° C. After the slurry delivery was completed, the temperature in the reactor was maintained at 80° C., and the reaction was carried out for 12 h to obtain a reaction liquid 1;

[0051] 2) nitrogen was introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then 0.6 g of antimony trioxide and 0.6 g of trimethyl phosphite were added and stirred for 15 minutes, and the temperature was controlled at 250° C. to obtain reaction liquid 2;

[0052] 3) The reaction liquid 2 in the second reactor was introduced into nitrogen and pressed into the third reactor. When the temperature reached 260°C, the pressure in the reactor was reduced to 1 KPa within 50 minutes under stirring. The temperature in the reactor was controlled at 285°C. The reaction was carried out for 1.5 hours. The vacuum jet pump was turned on, the pressure in the reactor reached 70 Pa, the reaction time was 250 minutes, and the power of the slurry stirring motor was set to 20 KW. After reaching the value, stirring was stopped, the material was discharged, pelletized underwater, and dried to obtain modified copolyester-1.

[0053] Preparation Example 4

[0054] The preparation method of modified copolyester-2 comprises the following steps:

[0055] 1) 180 g of copolymer-1, 1000 g of terephthalic acid, 200 g of ethylene glycol, 150 g of 1,4-cyclohexanedimethanol, and 200 g of neopentyl glycol were mixed and slurried for 40 min to obtain a slurry, and the slurry was sent to the first reactor through a screw slurry delivery pump for reaction, the temperature in the reactor was controlled at 250° C., and the tower top temperature was controlled at 100° C. After the slurry delivery was completed, the temperature in the reactor was maintained at 80° C., and the reaction was carried out for 12 h to obtain a reaction liquid 1;

[0056] 2) nitrogen was introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then 0.6 g of antimony trioxide and 0.6 g of trimethyl phosphite were added and stirred for 15 minutes, and the temperature was controlled at 250° C. to obtain reaction liquid 2;

[0057] 3) The reaction liquid 2 in the second reactor is pressurized into the third reactor by nitrogen. When the temperature reaches 260°C, the pressure in the reactor is reduced to 1KPa within 50 minutes under stirring. The temperature in the reactor is controlled at 285°C. The reaction is carried out for 1.5 hours. The vacuum jet pump is turned on. The pressure in the reactor reaches 70Pa. The reaction time is 250 minutes. The power of the slurry stirring motor is set to 20KW. After reaching the value, the stirring is stopped, the material is discharged, pelletized underwater, and dried to obtain modified copolyester-2.

[0058] Preparation Example 5

[0059] The preparation method of modified copolyester-3 comprises the following steps:

[0060] 1) 130 g of copolymer-2, 1000 g of terephthalic acid, 200 g of ethylene glycol, 150 g of 1,4-cyclohexanedimethanol, and 200 g of neopentyl glycol were mixed and slurried for 40 min to obtain a slurry, and the slurry was sent to the first reactor through a screw slurry delivery pump for reaction, the temperature in the reactor was controlled at 250° C., and the tower top temperature was controlled at 100° C. After the slurry delivery was completed, the temperature in the reactor was maintained at 80° C., and the reaction was carried out for 12 h to obtain a reaction liquid 1;

[0061] 2) nitrogen was introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then 0.6 g of antimony trioxide and 0.6 g of trimethyl phosphite were added and stirred for 15 minutes, and the temperature was controlled at 250° C. to obtain reaction liquid 2;

[0062] 3) The reaction liquid 2 in the second reactor is pressurized into the third reactor by nitrogen. When the temperature reaches 260°C, the pressure in the reactor is reduced to 1KPa within 50 minutes under stirring. The temperature in the reactor is controlled at 285°C. The reaction is carried out for 1.5 hours. The vacuum jet pump is turned on. The pressure in the reactor reaches 70Pa. The reaction time is 250 minutes. The power of the slurry stirring motor is set to 20KW. After reaching the value, the stirring is stopped, the material is discharged, pelletized underwater, and dried to obtain modified copolyester-3.

[0063] Preparation Example 6

[0064] The method for preparing copolyester comprises the following steps:

[0065] 1) 130 g of isophthalic acid, 1000 g of terephthalic acid, 200 g of ethylene glycol, 150 g of 1,4-cyclohexanedimethanol, and 200 g of neopentyl glycol were mixed and slurried for 40 min to obtain a slurry, and the slurry was sent to the first reactor through a screw slurry delivery pump for reaction, the temperature in the reactor was controlled at 250° C., and the tower top temperature was controlled at 100° C. After the slurry delivery was completed, the temperature in the reactor was maintained at 80° C., and the reaction was carried out for 12 h to obtain a reaction liquid material 1;

[0066] 2) nitrogen was introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then 0.6 g of antimony trioxide and 0.6 g of trimethyl phosphite were added and stirred for 15 minutes, and the temperature was controlled at 250° C. to obtain reaction liquid 2;

[0067] 3) The reaction liquid 2 in the second reactor is pressurized into the third reactor by nitrogen. When the temperature reaches 260°C, the pressure in the reactor is reduced to 1KPa within 50 minutes under stirring. The temperature in the reactor is controlled at 285°C. The reaction is carried out for 1.5 hours. The vacuum jet pump is turned on. The pressure in the reactor reaches 70Pa. The reaction time is 250 minutes. The power of the slurry stirring motor is set to 20KW. After reaching the value, the stirring is stopped, the material is discharged, pelletized underwater, and dried to obtain the copolyester.

[0068] Preparation Example 7

[0069] The preparation method of modified starch-1 comprises the following steps:

[0070] 1) 17.4 g of aconitic acid and 0.1 g of diisopropylbenzene peroxide were added to 300 g of anhydrous ethanol, reacted at 70° C., the number average molecular weight was controlled to be 156, and dried to obtain polyaconitic acid;

[0071] 2) 10 g of polyaconitic acid, 12 g of corn starch, and 0.01 g of tetraisopropyl titanate were added to 500 g of dimethyl sulfoxide, and reacted at 75° C. for 1 h to obtain modified starch-1.

[0072] Preparation Example 8

[0073] The preparation method of modified starch-2 comprises the following steps:

[0074] 1) 17.4 g of aconitic acid and 0.1 g of dicumyl peroxide were added to 300 g of anhydrous ethanol, reacted at 70° C., the number average molecular weight was controlled to be 161, and dried to obtain polyaconitic acid;

[0075] 2) 10 g of polyaconitic acid, 7 g of corn starch, and 0.01 g of tetraisopropyl titanate were added to 500 g of dimethyl sulfoxide, and reacted at 75° C. for 1 h to obtain modified starch-2.

[0076] Example 1

[0077] A non-crystalline copolyester material for a heat shrinkable film comprises the following raw materials, measured by weight: 140 parts of modified copolyester, 113 parts of modified starch, 3 parts of aluminum hydroxide, 2 parts of butyl stearate, and 10100.8 parts of an antioxidant.

[0078] The method for preparing the non-crystalline copolyester material for the heat shrinkable film of this embodiment comprises the following steps:

[0079] S1, after mixing modified copolyester-1, modified starch-1, aluminum hydroxide, butyl stearate and antioxidant 1010, add them into a mixer and mix for 20 minutes to obtain a premix;

[0080] S2. The premix obtained in step S1 is put into a twin-screw extruder and extruded from a die head. The extrusion temperature is controlled at 215° C. The extruded melt is attached to the surface of a casting roll for cooling. The surface temperature of the casting roll is 45° C. to obtain a non-crystalline copolyester material for a heat shrinkable film.

[0081] Example 2

[0082] A non-crystalline copolyester material for a heat shrinkable film comprises the following raw materials, measured by weight: 135 parts of modified copolyester, 111 parts of modified starch, 2 parts of aluminum hydroxide, 1 part of butyl stearate, and 10100.5 parts of an antioxidant.

[0083] The method for preparing the non-crystalline copolyester material for the heat shrinkable film of this embodiment comprises the following steps:

[0084] S1, after mixing modified copolyester-1, modified starch-1, aluminum hydroxide, butyl stearate and antioxidant 1010, add them into a mixer and mix for 10 minutes to obtain a premix;

[0085] S2. The premix obtained in step S1 is put into a twin-screw extruder and extruded from a die head. The extrusion temperature is controlled at 220° C. The extruded melt is attached to the surface of a casting roll for cooling. The surface temperature of the casting roll is 40° C. to obtain a non-crystalline copolyester material for a heat shrinkable film.

[0086] Example 3

[0087] A non-crystalline copolyester material for a heat shrinkable film comprises the following raw materials, measured by weight: 145 parts of modified copolyester, 114 parts of modified starch, 4 parts of aluminum hydroxide, 3 parts of butyl stearate, and 10101 parts of an antioxidant.

[0088] The method for preparing the non-crystalline copolyester material for the heat shrinkable film of this embodiment comprises the following steps:

[0089] S1, after mixing modified copolyester-1, modified starch-1, aluminum hydroxide, butyl stearate and antioxidant 1010, add them into a mixer and mix for 30 minutes to obtain a premix;

[0090] S2. The premix obtained in step S1 is put into a twin-screw extruder and extruded from a die head. The extrusion temperature is controlled at 210° C. The extruded melt is attached to the surface of a casting roll for cooling. The surface temperature of the casting roll is 50° C., and a non-crystalline copolyester material for a heat shrinkable film is obtained.

[0091] Example 4

[0092] A non-crystalline copolyester material for heat shrinkable film and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified copolyester-1 is replaced by the modified copolyester-2 in equal amounts.

[0093] Example 5

[0094] A non-crystalline copolyester material for heat shrinkable film and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified copolyester-1 is replaced by the modified copolyester-3 in equal amounts.

[0095] Example 6

[0096] A non-crystalline copolyester material for heat shrinkable film and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the modified starch-1 is replaced by modified starch-2 in equal amounts.

[0097] Comparative Example 1

[0098] A non-crystalline copolyester material for heat shrinkable film and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified copolyester-1 is replaced by copolyester in equal amounts.

[0099] Comparative Example 2

[0100] A non-crystalline copolyester material for heat shrinkable film and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified starch-1 is replaced by corn starch.

[0101] Performance Testing

[0102] The mechanical properties of the non-crystalline copolyester material for the heat shrinkable film obtained in the above-mentioned embodiments and comparative examples were tested, and the copolyester material obtained in each embodiment and comparative example was subjected to biaxial stretching, heat setting, thickness measurement, edge trimming and winding to obtain a heat shrinkable film, and the heat shrinkage rate, tear resistance and flame retardancy were tested, wherein the biaxial stretching temperature was 90°C, the heat setting temperature was 130°C, and the film thickness was 35μm.

[0103] (1) Mechanical properties: The tensile strength of non-crystalline copolyester materials was measured according to GB / T1040.2-2006.

[0104] (2) Heat shrinkage test: The heat shrinkable film was baked in an oven at 150°C for 30 min under tension-free conditions. The distance between the calibration points before and after heating was measured, and the longitudinal (MD) shrinkage and transverse (TD) shrinkage were calculated according to the following formulas.

[0105] Thermal shrinkage % = ((L0-L) / L0) × 100%

[0106] L0: The distance of the calibration point before baking

[0107] L: The distance between the calibration points after baking at 150℃ for 30min

[0108] (3) Tear resistance: The tear strength of a heat shrinkable film obtained from a non-crystalline copolyester material was measured in accordance with JIS K7128-3:1998.

[0109] (4) Flame retardancy: Passed the UL-94 grade test according to GB / T2406.2-2009 standard.

[0110] The test results are shown in Table 1:

[0111] Table 1

[0112]

[0113] It can be seen from the data in Table 1 that the non-crystalline copolyester materials for heat shrinkable films in Examples 1-3 of the present invention have good mechanical properties, tear resistance and flame retardant properties. From the comparison between Example 4 and Example 1, it can be seen that after changing the mass of copolymer-1, the mechanical properties of the copolyester material may be reduced due to excessive non-crystalline properties; from the comparison between Example 5 and Example 1, it can be seen that the use of modified copolyester-3 may cause the mechanical properties, heat shrinkage properties and tear resistance of the copolyester material to deteriorate due to the increase in the amount of polymer; from the comparison between Example 1 and Example 6, it can be seen that the change in the ratio of polyaconitic acid to corn starch in modified starch-2 may lead to a reduction in the cross-linking endpoints of the copolyester during the processing process, and the mechanical properties, heat shrinkage rate and tear resistance are all reduced; from the comparison between Comparative Example 1 and Example 1, it can be seen that the copolyester material obtained by using isophthalic acid has low non-crystallization, resulting in a decrease in various properties; from the comparison between Comparative Example 2 and Example 1, it can be seen that the addition of unmodified corn starch has poor various properties of the copolyester material.

[0114] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A non-crystalline copolyester material for heat shrinkable film, characterized in that: The raw materials are as follows, calculated by weight: 35-45 parts of modified copolyester, 11-14 parts of modified starch, 2-4 parts of flame retardant, 1-3 parts of lubricant and 0.5-1 parts of antioxidant.

2. The non-crystalline copolyester material for heat shrinkable film according to claim 1, characterized in that: The preparation method of the modified copolyester comprises the following steps: 1) The copolymer, terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol and neopentyl glycol are mixed and beaten for 35-45 minutes to obtain a slurry, and the slurry is sent to the first reaction kettle for reaction. The temperature in the kettle is controlled at 245-255° C., and the temperature at the top of the tower is controlled at 95-110° C. After the slurry is transported, the temperature in the kettle is maintained at 70-95° C., and the reaction is carried out for 11-13 hours to obtain a reaction liquid material 1; 2) nitrogen is introduced into the reaction liquid 1 in the first reaction kettle and pressed into the second reaction kettle, and then a catalyst and a heat stabilizer are added and stirred for 10-20 minutes, and the temperature is controlled at 245-250° C. to obtain reaction liquid 2; 3) The reaction liquid material 2 in the second reactor is introduced into nitrogen and pressed into the third reactor. When the temperature reaches 260-265°C, the pressure in the reactor is pumped down to -0.1Kpa~1Kpa within 45-60min under stirring. The temperature in the reactor is controlled at 280-295°C. The reaction is carried out for 1-2h. The vacuum jet pump is turned on. The pressure in the reactor reaches 40-90Pa. The reaction time is 210-270min. The power value of the slurry stirring motor is set. When the power value is reached, the stirring is stopped. The material is discharged, pelletized and dried to obtain the modified copolyester.

3. The non-crystalline copolyester material for heat shrinkable film according to claim 2, characterized in that: The mass ratio of the copolymer, terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol and neopentyl glycol is (0.1-0.15):1:(0.15-0.25):(0.1-0.2):(0.1-0.3).

4. The non-crystalline copolyester material for heat shrinkable film according to claim 2 or 3, characterized in that: The preparation method of the copolymer comprises the following steps: (1) adding dodecenylsuccinic acid, acrylic acid and an initiator into a reaction vessel, reacting at 60-70° C., controlling the number average molecular weight to be 300-400, to obtain a polymer; (2) Add the polymer obtained in step (1), (4-hydroxyphenyl)phosphonic acid and tetraisopropyl titanate to dimethyl sulfoxide, react at 70-80° C. for 1-2 hours, and dry to obtain a copolymer.

5. The non-crystalline copolyester material for heat shrinkable film according to claim 1, characterized in that: The preparation method of the modified starch comprises the following steps: 1) adding aconitic acid and an initiator into ethanol, reacting at 65-75° C., controlling the number average molecular weight to be 100-200, and drying to obtain polyaconitic acid; 2) Add polyaconitic acid, starch and tetraisopropyl titanate into dimethyl sulfoxide, and react at 70-80° C. for 1-2 hours to obtain modified starch.

6. The non-crystalline copolyester material for heat shrinkable film according to claim 1, characterized in that: The flame retardant is one or more of triphenyl phosphate, aluminum hydroxide, decabromodiphenyl ether, brominated epoxy resin, and ammonium polyphosphate.

7. The non-crystalline copolyester material for heat shrinkable film according to claim 1, characterized in that: The lubricant is one or more of polyethylene wax, calcium stearate, paraffin wax and butyl stearate.

8. The non-crystalline copolyester material for heat shrinkable film according to claim 1, characterized in that: The antioxidant is one or more of hindered phenols, hindered amines and phosphites.

9. A method for preparing the non-crystalline copolyester material for heat shrinkable film according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Mix the modified copolyester, modified starch, flame retardant, lubricant and antioxidant, add them into a mixer, and mix for 10-30 minutes to obtain a premix; S2. The premix obtained in step S1 is put into a twin-screw extruder and extruded from a die head. The extrusion temperature is controlled at 210-220° C. The extruded melt is attached to the surface of a casting roll for cooling. The surface temperature of the casting roll is 40-50° C. to obtain a non-crystalline copolyester material for a heat shrinkable film.

10. Use of the non-crystalline copolyester material for heat shrinkable film according to any one of claims 1 to 8 or the non-crystalline copolyester material for heat shrinkable film obtained by the preparation method of the non-crystalline copolyester material for heat shrinkable film according to claim 9, characterized in that: The non-crystalline copolyester material for the heat shrinkable film is used for food packaging.

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