CN114316546A - Preparation method of biodegradable packaging film and biodegradable packaging film - Google Patents
Preparation method of biodegradable packaging film and biodegradable packaging film Download PDFInfo
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Abstract
The invention relates to the technical field of packaging films, and particularly provides a preparation method of a biodegradable packaging film, wherein modified polylactic acid and modified polysiloxane are mixed according to the weight ratio of 1 (0.05-0.4), and are uniformly melted and mixed, and the mixture is subjected to tape casting to form a film, shaping, stretching and irradiation crosslinking to obtain the packaging film; the structural general formula of the modified polylactic acid is as follows: h (OCHCH)3CO)cO(SiOMe2)a(SiOMeVi)b(COCH3CHO)cH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, 500c is less than or equal to 5000, Me is methyl, and Vi is vinyl; modification ofThe polysiloxane has the general structural formula: r1Me2SiO(SiOMeR2)e(SiOMeR3)f(SiOMe2)gSiMe2R1Wherein e is more than or equal to 0 and less than or equal to 30, f is more than or equal to 0 and less than or equal to 10, g is more than or equal to 20 and less than or equal to 1000, R1Is C1-C18 alkyl, C1-C18 substituted alkyl, vinyl and hydroxyl, R2Is C1-C12 alkyl or substituted alkyl or phenyl, R3Is gamma- (meth) acryloyloxypropyl. The packaging film disclosed by the invention has better toughness and high puncture strength, and has small influence on the tensile strength.
Description
Technical Field
The invention belongs to the technical field of packaging films, and relates to a preparation method of a biodegradable packaging film and the biodegradable packaging film.
Background
The existing packaging film is difficult to degrade, and has serious influence on the environment. Various biodegradable packaging films have been developed, but the mechanical properties of the product are not sufficient to reach the level of the existing non-degradable packaging films.
Polylactic acid is a completely biodegradable polymer material and has great potential when being applied to packaging films. However, polylactic acid is mainly brittle, and therefore, the toughening modification is the most important modification direction, but the toughness is improved and the tensile strength is greatly affected, resulting in insufficient tensile strength.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a preparation method of a biodegradable packaging film.
The invention also provides a biodegradable packaging film.
The technical scheme of the invention is as follows:
a preparation method of a biodegradable packaging film comprises the steps of mixing modified polylactic acid and modified polysiloxane according to a weight ratio of 1 (0.05-0.4), uniformly melting and mixing, carrying out tape casting to form a film, shaping, stretching, and carrying out irradiation crosslinking to obtain the packaging film;
the structural general formula of the modified polylactic acid is as follows: h (OCHCH)3CO)cO(SiOMe2)a(SiOMeVi)b(COCH3CHO)cH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, 500c is less than or equal to 5000, Me is methyl, and Vi is vinyl;
the structural general formula of the modified polysiloxane is as follows: r1Me2SiO(SiOMeR2)e(SiOMeR3)f(SiOMe2)gSiMe2R1Wherein e is more than or equal to 0 and less than or equal to 30, f is more than or equal to 0 and less than or equal to 10, g is more than or equal to 20 and less than or equal to 1000, R1Is C1-C18 alkyl, C1-C18 substituted alkyl, vinyl or hydroxyl, R2Is C1-C12 alkyl or substituted alkyl or phenyl, R3Is gamma- (meth) acryloyloxypropyl.
Preferably, the modified polylactic acid is prepared by the following method,
mixing an initiator, a lactide monomer and a catalyst, and heating for ring-opening polymerization;
dissolving the ring-opening polymerization product in an organic solvent, and then adding a precipitation solvent for precipitation to obtain the modified polylactic acid.
The structural general formula of the initiator is HO (SiOMe)2)a(SiOMeVi)bH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, Me is methyl, and Vi is vinyl.
More preferably, the catalyst is selected from at least one of stannous octoate, dibutyltin dilaurate, dibutyltin bis (dodecylthio) and dibutyltin diacetate.
Preferably, the weight ratio of the modified polylactic acid to the modified polysiloxane is 1 (0.1-0.3).
Preferably, the stretching is unidirectional stretching, and the stretching magnification is 3 to 6 times.
More preferably, the stretching is biaxial stretching, and the stretching magnification is 3 to 6 times in the transverse direction and 3 to 6 times in the longitudinal direction.
Preferably, at least one of a processing aid and an antioxidant is further added in the mixing step.
More preferably, the processing aid is one or more selected from stearic acid, polyethylene wax, silicone wax, zinc stearate, magnesium stearate, calcium stearate and erucamide.
Preferably, the irradiation intensity of the irradiation crosslinking is 0.3-2 KGy.
A biodegradable packaging film obtained by the production method according to any one of the above embodiments.
In the invention, terminal hydroxyl polysiloxane with a side chain containing vinyl is used as an initiator in the ring-opening polymerization of polylactic acid, so that the modified polylactic acid of the ABA type block copolymer is obtained, the flexibility of the polylactic acid is improved, and the vinyl is introduced into the side chain of the modified polylactic acid. However, the polysiloxane has high molecular chain flexibility, so that the tensile property of the modified polylactic acid is obviously reduced. According to the invention, the modified polylactic acid and the modified polysiloxane are compounded, the flexibility of the modified polylactic acid is further improved by utilizing the flexibility of the modified polysiloxane, and meanwhile, carbon-carbon double bonds on the modified polysiloxane structure can be subjected to free radical polymerization with carbon-carbon double bonds on the side chain of the modified polylactic acid, and a cross-linked structure is formed. Therefore, the modified polylactic acid and the modified polysiloxane are combined and subjected to a crosslinking reaction to form the packaging film, so that the toughness of the obtained packaging film is improved and the good tensile property is maintained on the basis of maintaining the biodegradability of the polylactic acid.
The invention has the beneficial effects that:
(1) the invention adopts the hydroxyl-terminated polysiloxane with a side chain containing vinyl as an initiator to prepare the modified polylactic acid, and the modified polylactic acid is combined with the modified polysiloxane with a terminal group or a side chain having carbon-carbon unsaturated double bonds to generate a crosslinking reaction, so that the obtained packaging film has better toughness and tensile property.
(2) Polysiloxane has better flame retardant property, so that the flame retardant property of polylactic acid can be improved by the packaging film provided by the invention.
(3) The hydroxyl-terminated polysiloxane is adopted as an initiator to modify polylactic acid and is added, and the polysiloxane can reduce the surface energy of the packaging film.
(4) The invention adopts two modified polysiloxanes with larger molecular weight difference, the cross-linking density areas of the formed cross-linking structure are distributed differently, and the modified polysiloxanes have the function of dispersing stress, and can further improve the toughness of the film.
Detailed Description
The technical solution of the present invention is further illustrated and described by the following detailed description.
The invention provides a preparation method of a biodegradable packaging film, which comprises the steps of mixing modified polylactic acid and modified polysiloxane according to the weight ratio of 1 (0.05-0.4), melting and mixing uniformly, casting to form a film, shaping, stretching, irradiating and crosslinking to obtain the packaging film;
the structural general formula of the modified polylactic acid is as follows: h (OCHCH)3CO)cO(SiOMe2)a(SiOMeVi)b(COCH3CHO)cH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, 500c is less than or equal to 5000, Me is methyl, and Vi is vinyl;
the structural general formula of the modified polysiloxane is as follows: r1Me2SiO(SiOMeR2)e(SiOMeR3)f(SiOMe2)gSiMe2R1Wherein e is more than or equal to 0 and less than or equal to 30, f is more than or equal to 0 and less than or equal to 10, g is more than or equal to 20 and less than or equal to 1000, R1Is C1-C18 alkyl, C1-C18 substituted alkyl, vinyl or hydroxyl, R2Is C1-C12 alkyl or substituted alkyl or phenyl, R3Is gamma- (meth) acryloyloxypropyl.
According to the invention, on one hand, the modified polysiloxane can improve the flexibility of the modified polylactic acid when being physically blended with the modified polylactic acid by utilizing the flexibility of the modified polysiloxane, on the other hand, the vinyl group of the terminal group or the carbon-carbon double bond of the side chain of the modified polysiloxane can generate radical crosslinking reaction with the carbon-carbon double bond in the modified polylactic acid to form chemical mixing, so that the toughness of the modified polylactic acid is further improved, and the tensile property of the polylactic acid can be better maintained due to the existence of a crosslinking structure.
When R is1When the vinyl group is used, f can be within the range of 0-5; when R is1When the other group is not a vinyl group, f may be in the range of 2. ltoreq. f.ltoreq.10. In the present invention, R3The structure of the film mainly achieves the purpose of crosslinking with the side chain of the modified polylactic acid, and meanwhile, due to the ester bond, the film can have better interaction with the polylactic acid, thereby being beneficial to improving the mechanical property of the packaging film.
In the present invention, the modified polysiloxane may be prepared from the corresponding blocking agents, such as R1For the vinyl group, a tetramethyldivinyldisiloxane, or R1For methyl, the blocking agent can be hexamethyldisiloxane, which is obtained by ring-opening reaction with corresponding cyclic or dialkoxysilanes such as octamethylcyclotetrasiloxane, tetramethyltetraphenylcyclotetrasiloxane, 3-chloropropylmethyldialkoxysilane, gamma- (meth) acryloxypropylmethyldimethoxysilane in the presence of an acidic catalyst (such as concentrated sulfuric acid) or a basic catalyst (tetramethylammonium hydroxide or potassium hydroxide) followed by removal of the low boilers.
In the invention, the modified polysiloxane can be composed of two modified polysiloxanes with the average relative molecular mass difference of more than 2000, so that a cross-linking structure with the cross-linking density difference can be formed, namely, the cross-linking density of a part of regions in the cross-linking structure is relatively large, and the cross-linking density of a part of regions is relatively small, thereby being beneficial to dispersing stress, further improving the toughness of the packaging film, namely, the film has better puncture resistance.
In a preferred embodiment of the present invention, the modified polylactic acid is prepared by a method comprising,
mixing an initiator, a lactide monomer and a catalyst, and heating for ring-opening polymerization;
dissolving the ring-opening polymerization product in an organic solvent, and then adding a precipitation solvent for precipitation to obtain the modified polylactic acid.
The structural general formula of the initiator is HO (SiOMe)2)a(SiOMeVi)bH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, Me is methyl, and Vi is vinyl.
The initiator is vinyl hydroxyl silicone oil, and can be prepared by reacting vinyl ring bodies (such as trimethyl trivinyl cyclotrisiloxane) and methyl ring bodies (such as hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane) in the presence of a catalyst (acid or alkali) and taking water as a molecular weight regulator and a blocking agent.
The molecular weight of the modified polylactic acid can be set according to the molar weight ratio of the lactide monomer to the initiator.
In the invention, the temperature of ring-opening polymerization is 115-160 ℃, and the more preferable reaction temperature is 120-155 ℃; the reaction system is in a micro negative pressure state, such as the pressure of the reaction system is 30-70kPa, and the pressure of the reaction system is more preferably 45-55 kPa; or the reaction system can be in an inert atmosphere, and the inert gas can be nitrogen, helium and the like; the ring-opening polymerization time is 2 to 6 hours, and the ring-opening time is more preferably 3 to 4 hours.
In the present invention, the ring-opening polymerization product may be dissolved in an organic solvent commonly used for dissolving polylactic acid, including dichloromethane, chloroform, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and the like, and may be used alone or in combination. The precipitation solvent used in the precipitation is also commonly used in the preparation of polylactic acid, and comprises ethanol, methanol, diethyl ether, petroleum ether, n-heptane, cyclohexane, n-hexane and the like, and can be used alone or in a mixture. The volume of the precipitation solvent may be 8 to 20 times the volume of the organic solvent used for dissolution. The number of times of precipitation can be set as desired, and may be 1 time, 2 times, or 3 times.
In a more preferred embodiment of the present invention, the catalyst is a catalyst commonly used in the preparation of polylactic acid by lactide ring-opening polymerization, and the amount of the catalyst is also a conventional means without any particular limitation, but the more commonly used catalyst is at least one of stannous octoate, dibutyltin dilaurate, dibutyltin didodecylsulfate and dibutyltin diacetate.
In a preferred embodiment of the present invention, the modified polylactic acid and the modified polysiloxane are present in a weight ratio of 1 (0.1-0.3). If the weight of the modified polysiloxane is too small, a better toughening effect cannot be achieved; if the weight of the modified polysiloxane is too large, the resulting film is too soft and is inferior in both tensile strength and toughness. In a more preferred embodiment of the present invention, the modified polylactic acid and the modified polysiloxane are present in a weight ratio of 1 (0.12-0.25), specifically, 1:0.12, 1:0.15, 1:0.18, 1:0.2, 1:0.22 or 1: 0.25.
In a preferred embodiment of the present invention, the stretching is uniaxial stretching with a stretching magnification of 3 to 6 times. Specifically, the stretch ratio may be 3 times, 4 times, 5 times, or 6 times.
In a more preferred embodiment of the present invention, the stretching is biaxial stretching with a stretching magnification of 3 to 6 times in the transverse direction and 3 to 6 times in the longitudinal direction. Specifically, the transverse stretching magnification may be 3 times, and the longitudinal stretching magnification may be 6 times; the transverse stretching magnification can be 4 times, and the longitudinal stretching magnification can be 4 times; the transverse stretching magnification may be 3 times, and the longitudinal stretching magnification may be 3 times; the transverse stretching magnification can be 3 times, and the longitudinal stretching magnification can be 4 times; the stretching magnification in the transverse direction may be 4 times, and the stretching magnification in the longitudinal direction may be 4 times.
In the invention, before stretching, the casting film is preheated at the temperature of 50-90 ℃ for 10-20 seconds and then stretched. The drawing speed may be 30-70mm/s and the temperature 60-80 ℃.
In a preferred embodiment of the present invention, at least one of a processing aid and an antioxidant is further added in the mixing step.
In a more preferred embodiment of the present invention, the processing aid is selected from one or more of stearic acid, polyethylene wax, silicone wax, zinc stearate, magnesium stearate, calcium stearate and erucamide. The processing aid can be used in an amount of 0.5 to 2% by weight based on the weight of the modified polylactic acid and the modified polysiloxane.
In the present invention, the antioxidant is not particularly limited, and antioxidants conventionally applicable to various plastics and rubbers can be applied to the present invention, including antioxidant 1010, antioxidant 1076, and the like.
The packaging film of the present invention may be incorporated with fillers as desired. The added weight of the filler can be 1-30% of the weight of the modified polylactic acid. The filler can be one or a mixture of inorganic filler or organic filler, and the size of the filler is micrometer grade. The inorganic filler can be talcum powder, wollastonite, glass fiber, solid glass microsphere, hollow glass microsphere, calcium carbonate, titanium pigment, kaolin and the like. The organic filler can be nylon fiber, polyethylene fiber, polypropylene fiber, polyethylene micropowder, polytetrafluoroethylene micropowder, etc.
According to the requirements, the invention can also add some pigments, and the inorganic pigment and the organic pigment can be both, or the color master batch formed by the inorganic pigment or the organic pigment. The added weight of the pigment can be 0.1-2% of the weight of the modified polylactic acid.
In the invention, the uniform melting and mixing can be carried out in an extruder at the temperature of 170-; the temperature of an extruder during the casting film formation is 180-220 ℃, the film thickness of the casting film formation can be set according to the film thickness and the stretching ratio of the packaging film, and the range can be 100-1000 mu m; the setting temperature can be 80-130 deg.C, and the setting time can be 5-7 s.
In a preferred embodiment of the present invention, the irradiation intensity of the irradiation cross-linking is 0.3-2 KGy.
In another aspect, the present invention provides a biodegradable packaging film, which is prepared by the preparation method according to any one of the above embodiments.
The packaging film of the present invention can be applied to various packaging occasions, such as agricultural films, and has good degradation performance.
The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts described in the following examples are parts by weight.
Preparation example 1
Initiator: HO (SiOMe)2)47.2(SiOMeVi)3.3H, Me and Vi are as described above;
mixing lactide monomer and the initiator according to the molar ratio of 1200:1, adding stannous octoate accounting for 2 percent of the weight of the lactide monomer, mixing, controlling the pressure of a reaction system at 50-60kPa, and heating to 120-125 ℃ for ring-opening polymerization for 4 hours;
dissolving the ring-opening polymerization product in chloroform of 3 times of the weight of the ring-opening polymerization product, adding the ring-opening polymerization product into ethanol of 10 times of the volume of the chloroform for precipitation, and drying to obtain modified polylactic acid, which is marked as R-1.
Preparation example 2
Initiator: HO (SiOMe)2)62.5(SiOMeVi)5.8H, Me and Vi are as described above;
mixing lactide monomer and the initiator according to a molar ratio of 1500:1, adding stannous octoate accounting for 2 percent of the weight of the lactide monomer, mixing, controlling the pressure of a reaction system at 50-60kPa, and heating to 125-130 ℃ for ring-opening polymerization for 3.5 hours;
dissolving the ring-opening polymerization product in 3 times of chloroform, adding into methanol with the volume of 10 times of that of the chloroform for precipitation, and drying to obtain the modified polylactic acid, which is marked as R-2.
Preparation example 3
Initiator: HO (SiOMe)2)106.2(SiOMeVi)7.1H, Me and Vi are as described above;
mixing lactide monomer and the initiator according to the molar ratio of 1300:1, adding stannous octoate accounting for 2 percent of the weight of the lactide monomer, mixing, controlling the pressure of a reaction system at 50-60kPa, and heating to 120-125 ℃ for ring-opening polymerization for 4.5 hours;
dissolving the ring-opening polymerization product in dichloromethane with the weight 3 times that of the ring-opening polymerization product, adding the ring-opening polymerization product into methanol with the volume 8 times that of the dichloromethane for precipitation for 2 times, and drying to obtain modified polylactic acid, which is recorded as R-3.
Example 1
Modified polysiloxane: me3SiO(SiOMeR2)12.6(SiOMeR3)4.1(SiOMe2)73.8SiMe3，R2Is phenyl, R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-1 in preparation example 1 and 12 parts of modified polysiloxane into an extruder, heating to 170 ℃ and 210 ℃, uniformly melting and mixing, extruding at 205 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at the temperature of 60 ℃ for 15 seconds, biaxially stretching the cast film at the temperature of 70 ℃ at the stretching rate of 60mm/s at the stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 0.8KGy to obtain the packaging film.
Example 2
The modified polysiloxane in example 1 was changed from 12 parts to 20 parts, and the rest of the procedure was kept unchanged.
Example 3
Modified polysiloxane: me3SiO(SiOMeR2)14.2(SiOMeR3)7.7(SiOMe2)69.2SiMe3，R2Is phenyl, R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-1 in preparation example 1 and 20 parts of modified polysiloxane into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 205 ℃, and casting to form a film with the thickness of about 450 mu m; the cast film is preheated at 60 ℃ for 15 seconds and 70 ℃, stretched at the stretching rate of 60mm/s in a bidirectional stretching way, the stretching magnification is 4 multiplied by 4, and then the cast film is irradiated and crosslinked under the irradiation intensity of 0.8KGy, so that the packaging film is obtained.
Example 4
Modified polysiloxane: ViMe2SiO(SiOMeR2)17.2(SiOMeR3)1.2(SiOMe2)113.5SiMe2Vi，R2Is propyl, R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-2 in preparation example 2, 15 parts of modified polysiloxane and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 210 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at 70 ℃ for 12 seconds, stretching the cast film at 65 ℃ in a biaxial manner at a stretching rate of 65mm/s with a stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 1.0KGy to obtain the packaging film.
Example 5
The modified polysiloxane in example 4 was changed from 15 parts to 20 parts, and the rest of the procedure was kept unchanged.
Example 6
The modified polysiloxane of example 4 was changed from 15 parts to 25 parts, and the remaining steps were kept unchanged.
Example 7
Modified polysiloxane 1: ViMe2SiO(SiOMeR2)17.2(SiOMeR3)1.2(SiOMe2)113.5SiMe2Vi，R2Is propyl, R3Is gamma- (meth) acryloyloxypropyl.
Modified polysiloxane 2: ViMe2SiO(SiOMeR2)20.7(SiOMeR3)1.5(SiOMe2)170.3SiMe2Vi，R2Is propyl, R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-2 in preparation example 2, 10 parts of modified polysiloxane 1, 5 parts of modified polysiloxane 2 and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 210 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at 70 ℃ for 12 seconds, stretching the cast film at 65 ℃ in a biaxial manner at a stretching rate of 65mm/s with a stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 1.0KGy to obtain the packaging film.
Example 8
Modified polysiloxane 1: ViMe2SiO(SiOMeR2)17.2(SiOMeR3)1.2(SiOMe2)113.5SiMe2Vi，R2Is propyl, R3Is gamma- (meth) acryloyloxypropyl.
Modified polysiloxane 2: ViMe2SiO(SiOMeR2)18.5(SiOMeR3)1.6(SiOMe2)260.9SiMe2Vi，R2Is propyl, R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-2 in preparation example 2, 15 parts of modified polysiloxane 1, 5 parts of modified polysiloxane 2 and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 210 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at 70 ℃ for 12 seconds, stretching the cast film at 65 ℃ in a biaxial manner at a stretching rate of 65mm/s with a stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 1.0KGy to obtain the packaging film.
Example 9
Modified polysiloxane: ViMe2SiO(SiOMeR3)6.2(SiOMe2)247.2SiMe2Vi，R3Is gamma- (meth) acryloyloxypropyl.
Adding 100 parts of modified polylactic acid R-3 in preparation example 3, 12 parts of modified polysiloxane and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 200 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at 70 ℃ for 12 seconds, biaxially stretching the cast film at 70 ℃ at a stretching rate of 65mm/s at a stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 1.3KGy to obtain the packaging film.
Example 10
The modified polysiloxane of example 9 was changed from 12 parts to 18 parts, and the rest of the procedure was kept unchanged.
Example 11
In example 9, the modified polysiloxane was changed from 12 parts to 25 parts, and the rest of the procedure was kept unchanged.
Example 12
Modified polysiloxane 1: ViMe2SiO(SiOMeR3)6.2(SiOMe2)247.2SiMe2Vi，R3Is gamma- (meth) acryloyloxypropyl.
Modified polysiloxane 2: ViMe2SiO(SiOMeR3)5.9(SiOMe2)511.7SiMe2Vi，R3Is gamma- (meth) acryloyloxypropyl。
Adding 100 parts of modified polylactic acid R-3 in preparation example 3, 14 parts of modified polysiloxane 1, 4 parts of modified polysiloxane 2 and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 200 ℃, and casting to form a film with the thickness of about 450 mu m; preheating the cast film at 70 ℃ for 12 seconds, biaxially stretching the cast film at 70 ℃ at a stretching rate of 65mm/s at a stretching ratio of 4 multiplied by 4, and then irradiating and crosslinking the cast film under the irradiation intensity of 1.3KGy to obtain the packaging film.
Comparative example 1
In example 4, the crosslinking is carried out without irradiation, the remaining steps remaining unchanged.
Comparative example 2
In example 7, the crosslinking is carried out without irradiation, the remaining steps remaining unchanged.
Comparative example 3
In example 8, the crosslinking is carried out without irradiation, the remaining steps remaining unchanged.
Comparative example 4
In example 10, the crosslinking is carried out without irradiation, the remaining steps remaining unchanged.
Comparative example 5
Adding 100 parts of modified polylactic acid R-2 in preparation example 2 and 1 part of zinc stearate into an extruder, heating to 170-210 ℃, melting and mixing uniformly, extruding at 210 ℃, and casting to form a film, wherein the film thickness is about 450 mu m; the cast film was preheated at 70 ℃ for 12 seconds, stretched at 65 ℃ at a stretching rate of 65mm/s in both directions at a stretching ratio of 4X 4 to obtain a packaging film.
Performance testing
The results of the performance tests are shown in table 1.
Table 1 results of performance testing
Therefore, as shown in the data result of table 1, the packaging film of the present invention adopts the vinyl hydroxy silicone oil as the initiator to modify the polylactic acid, introduces carbon-carbon double bonds into the side chain or the end group of the modified polysiloxane, mixes the modified polylactic acid and the modified polysiloxane, extrudes the mixture to form a film by tape casting, stretches the film, and then performs irradiation crosslinking, so as to significantly improve the toughness of the polylactic acid and maintain the tensile strength as much as possible. As can be seen from the comparison of the data in example 4 and example 7, example 5 and example 8, and example 10 and example 12, the modified polysiloxane of the present invention was formulated with two polysiloxanes having different molecular weights, and the obtained film had better puncture resistance and less influence on tensile strength.
The foregoing has shown and described the fundamental principles, principal features and advantages of the invention. It should be understood by those skilled in the art that the present invention is not limited by the foregoing embodiments, which are merely preferred embodiments of the present invention, and the scope of the present invention should not be limited thereby, and that equivalent changes and modifications made within the scope of the present invention and the specification should be covered thereby. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. A preparation method of a biodegradable packaging film is characterized in that modified polylactic acid and modified polysiloxane are mixed according to the weight ratio of 1 (0.05-0.4), and the mixture is melted and mixed uniformly, cast into a film, shaped, stretched and irradiated for crosslinking to obtain the packaging film;
the structural general formula of the modified polylactic acid is as follows: h (OCHCH)3CO)cO(SiOMe2)a(SiOMeVi)b(COCH3CHO)cH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, 500c is less than or equal to 5000, Me is methyl, and Vi is vinyl;
the structural general formula of the modified polysiloxane is as follows: r1Me2SiO(SiOMeR2)e(SiOMeR3)f(SiOMe2)gSiMe2R1Wherein e is more than or equal to 0 and less than or equal to 30, f is more than or equal to 0 and less than or equal to 10, g is more than or equal to 20 and less than or equal to 1000, R1Is C1-C18 alkyl, C1-C18 substituted alkyl, vinyl or hydroxyl, R2Is C1-C12 alkyl or substituted alkyl or phenyl, R3Is gamma- (meth) acryloyloxypropyl.
2. The production method according to claim 1, wherein the modified polylactic acid is produced by the method comprising,
mixing an initiator, a lactide monomer and a catalyst, and heating for ring-opening polymerization;
dissolving the ring-opening polymerization product in an organic solvent, and then adding a precipitation solvent for precipitation to obtain the modified polylactic acid.
The structural general formula of the initiator is HO (SiOMe)2)a(SiOMeVi)bH, wherein a is more than or equal to 5 and less than or equal to 200, b is more than or equal to 2 and less than or equal to 10, Me is methyl, and Vi is vinyl.
3. The production method according to claim 2, wherein the catalyst is at least one selected from the group consisting of stannous octoate, dibutyltin dilaurate, dibutyltin dilauryl sulfide and dibutyltin diacetate.
4. The production method according to claim 1, wherein the modified polylactic acid and the modified polysiloxane are present in a weight ratio of 1 (0.1-0.3).
5. The production method according to claim 1, wherein the stretching is unidirectional stretching with a stretching magnification of 3 to 6 times.
6. The production method according to claim 5, wherein the stretching is bidirectional stretching with a stretching ratio of 3 to 6 times in the transverse direction and 3 to 6 times in the longitudinal direction.
7. The method of claim 1, further comprising at least one of a processing aid and an antioxidant.
8. The preparation method according to claim 7, wherein the processing aid is one or more selected from stearic acid, polyethylene wax, silicone wax, zinc stearate, magnesium stearate, calcium stearate and erucamide.
9. The method according to claim 1, wherein the irradiation cross-linking has an irradiation intensity of 0.3 to 2 KGy.
10. A biodegradable packaging film, characterized by being obtained by the production method according to any one of claims 1 to 9.
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| CN106977726A (en) * | 2017-04-18 | 2017-07-25 | 长春工业大学 | A kind of methylvinyl-polysiloxane biodegradable polyesters block copolymer |
| CN111363327A (en) * | 2020-05-07 | 2020-07-03 | 青岛森丽达包装有限公司 | High-strength polylactic acid packaging bag and preparation method thereof |
| CN111961348A (en) * | 2020-08-27 | 2020-11-20 | 内蒙古农业大学 | Polylactic acid copolymer film with siloxane side chain, preparation method thereof and application thereof in fruit and vegetable fresh keeping |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106977726A (en) * | 2017-04-18 | 2017-07-25 | 长春工业大学 | A kind of methylvinyl-polysiloxane biodegradable polyesters block copolymer |
| CN111363327A (en) * | 2020-05-07 | 2020-07-03 | 青岛森丽达包装有限公司 | High-strength polylactic acid packaging bag and preparation method thereof |
| CN111961348A (en) * | 2020-08-27 | 2020-11-20 | 内蒙古农业大学 | Polylactic acid copolymer film with siloxane side chain, preparation method thereof and application thereof in fruit and vegetable fresh keeping |
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| "复合包装材料成为肉类保鲜发展趋势" * |
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