CN112693197B - Thermoplastic polyvinyl alcohol film with high barrier property and preparation method thereof - Google Patents
Thermoplastic polyvinyl alcohol film with high barrier property and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a thermoplastic polyvinyl alcohol film with high barrier property and a preparation method thereof, which mainly solve the technical problem that the barrier property of the film is greatly influenced by humidity after the thermoplastic processing of polyvinyl alcohol in the prior art, so that the application range is limited. The thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film has a multilayer assembled thermoplastic polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternating structure, the total nano layer number is at least 20, and the oxygen permeation rate of the film under the same condition is at least 25% lower than the addition theoretical value of two starting materials, so that the problem is well solved, and the film can be used in the industrial production of the thermoplastic polyvinyl alcohol film with high barrier property.
Description
Technical Field
The invention belongs to the field of modification and preparation of high polymer materials, relates to a thermoplastic polyvinyl alcohol composition film with high barrier property and an assembled nano layer alternating structure, and also relates to a method for preparing the thermoplastic polyvinyl alcohol composition film with high barrier property.
Technical Field
Polyvinyl alcohol (PVA) is a polyhydroxy base polymer with excellent comprehensive performance, which can be produced in large scale by petroleum or non-petroleum routes, is usually prepared by polymerization of vinyl acetate and alcoholysis, has excellent chemical corrosion resistance, wear resistance and gas barrier property, and has wide application in the aspects of pesticides, dangerous chemicals packaging, daily necessities, medicines, optical instruments and the like. Compared with the barrier material polyvinylidene chloride (PVDC) which is originally developed, the polymer has the advantages of biological environment protection and degradability. Compared with the barrier resin ethylene-vinyl alcohol copolymer (EVOH), the preparation process is simple, the cost is low, and the mechanical property is better.
The polyvinyl alcohol film is generally produced by adopting a wet method with a polyvinyl alcohol aqueous solution as a raw material, and a wet casting method is mostly adopted in the market at present, but the casting method has long production period, low efficiency and higher cost, and cannot produce a multilayer co-extrusion film of a water-insoluble high polymer material such as polyethylene, so that the application of the water-soluble PVA film in the field of multilayer melt co-extrusion barrier films is limited. Because of these limitations, polyvinyl alcohol can only be dissolved and then coated on the surface of a water-insoluble polymer material for barrier application, but polyvinyl alcohol coated on the surface of other films is easily affected by air humidity to reduce the barrier performance.
Polyvinyl alcohol has a melting point close to the decomposition temperature due to the action of a large number of hydrogen bonds in and between molecules, and does not have thermoplastic processing properties. The thermoplastic modification of polyvinyl alcohol has more research work at home and abroad, mainly comprises a copolymerization method, a blending method, a post-reaction method and a plasticizing method, wherein the plasticizing method is the simplest and most effective, generally adopts single-component or multi-component compounds such as water, glycerol, polyalcohol and oligomers thereof, inorganic salt, alcohol amine and the like as plasticizers, reduces the melting point of the polyvinyl alcohol by a two-step method or a multi-step process method, improves the processing fluidity of the polyvinyl alcohol, and has complicated and complex processes. The polyvinyl alcohol prepared by the method has lower melt strength, poorer fluidity and narrower thermoplastic processing application range, so that low cost and large-scale popularization and application are limited.
US 4952628 discloses a composition of an amorphous polyamide and EVOH, the addition of which can reduce the sensitivity of the polyamide to humidity to a certain extent, thus maintaining good barrier properties. CN107200977 solution-blends EVOH, high-polymer (1500-3000), high-alcoholysis (97-100%) polyvinyl alcohol powder, water, plasticizer, surfactant, oxidant, and tape-casting to obtain the final product with unknown barrier property. And because the PVA with high polymerization degree and high alcoholysis degree is adopted, the thermoplastic processing is difficult, only premixing can be carried out, then the wet tape casting with water as a solvent is used for production, the cost is increased, and the process is complex. There is therefore a need for a polyvinyl alcohol material having high barrier properties while being capable of thermoplastic processing.
Disclosure of Invention
One of the technical problems to be solved by the invention is that the barrier property of the polyvinyl alcohol film in the prior art is sensitive to air humidity, so that the application range is limited, and the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film is provided, and the composition adopted by the film can effectively improve the melt strength of the composition and reduce the viscosity of the composition to be lower than the blending addition theoretical viscosity of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer starting raw materials, so that the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film is more energy-saving in the processing process; the composite film has an unexpected, regular and continuous assembled multilayer nano-layer alternating structure, can effectively reduce the sensitivity to air humidity, reduces the oxygen permeation rate of the composite film under the same condition to be lower than the addition theoretical oxygen permeation rate of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer initial raw material film, and has better performance than the prior similar thermoplastic polyvinyl alcohol film.
The second technical problem to be solved by the invention is to provide a method for preparing a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, wherein the composition film obtained by the method has an unexpected, regular, continuous and multi-layer assembled polyvinyl alcohol 2-dimensional nano-layer and ethylene-vinyl alcohol copolymer 2-dimensional nano-layer alternating structure; the oxygen permeation rate of the composition film obtained by the method under lower humidity (10%) is at least 25% lower than the addition theoretical value of the two starting material films; the oxygen permeation rate at higher humidity (50%) is at least 35% lower than the theoretical addition value for the two starting material films.
The third technical problem to be solved by the invention is to provide an application method of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film corresponding to one of the technical problems.
In order to solve one of the technical problems, the invention adopts the following technical scheme: a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film having a multilayer assembled thermoplastic polyvinyl alcohol 2-dimensional nanolayer alternating with ethylene-vinyl alcohol copolymer 2-dimensional nanolayer structure, the total nanolayer number being at least 20, said composition film having an oxygen permeation rate at the same conditions that is at least 25% lower than the theoretical value of addition of the corresponding thermoplastic polyvinyl alcohol film and ethylene-vinyl alcohol copolymer film.
In the above technical scheme, in the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, the total number of nano layers of the multilayer polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternate structure is at least 60.
In the above technical scheme, in the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, the multilayer polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternate structure is formed by alternately forming a thickness layer with the thickness of more than or equal to 100 nanometers and a thin nano layer with the thickness of less than 100 nanometers.
In the above technical scheme, in the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, the thickness of the thick nano layer in the alternating structure of the thermoplastic polyvinyl alcohol 2-dimensional nano layer and the ethylene-vinyl alcohol copolymer 2-dimensional nano layer is greater than 110 nanometers, and preferably the thickness of the thick nano layer is not greater than 500 nanometers.
In the above technical scheme, in the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, the thickness of the thin nano layer in the thermoplastic polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternate structure is less than 70 nanometers, and preferably the thickness of the thin nano layer is not less than 10 nanometers.
In the above technical scheme, the two starting materials refer to thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer.
In the technical proposal, the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film has a multilayer assembled nano-layer alternating structure, the thickness of the film is not more than 200 mu m, the Young modulus is more than 120MPa, the breaking strength is more than 25MPa, the breaking elongation is more than 180 percent, and the breaking energy is more than>3MJ/m 3 。
In the technical scheme, the composition film preferably comprises the following components in parts by mass:
(1) 51 to 95 parts of thermoplastic polyvinyl alcohol;
(2) 5 to 49 parts of an ethylene-vinyl alcohol copolymer;
(3) 0.1 to 2 parts of functional auxiliary agent.
In the above technical solution, the oxygen permeation rate of the composition film at a lower humidity (10%) is preferably at least 25% lower than the theoretical addition value of the two starting materials; the oxygen permeation rate at higher humidity (50%) is preferably at least 35% lower than the theoretical addition value of the two starting materials.
In the technical scheme, the polymerization degree of the polyvinyl alcohol used in the thermoplastic polyvinyl alcohol is 300-3000, the alcoholysis degree is 90-99 mol%, and the viscosity of the 4% weight fraction concentration aqueous solution is less than or equal to 35.0 mPa.s.
In the above technical scheme, the thermoplastic agent used in the thermoplastic polyvinyl alcohol is at least one selected from ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, glycerol, sorbitol, pentaerythritol, xylitol, polyethylene glycol PEG (number average molecular weight 100-2000), polyethylene glycol/propylene glycol PEPG (number average molecular weight 100-2000), fatty acid esters, glyceric acid, tween. Two, three or more combinations have synergistic effect, and can obtain thermoplastic polyvinyl alcohol with balanced properties, so that the thermoplastic polyvinyl alcohol has good thermoplastic processability, and the service performance of the material can be ensured.
In the above technical scheme, the amount of the thermoplastic agent used in the thermoplastic polyvinyl alcohol is preferably 10 to 30% based on the total mass fraction of the thermoplastic polyvinyl alcohol.
In the above technical scheme, the thermoplastic agent used in the thermoplastic polyvinyl alcohol is more preferably at least one thermoplastic agent with low molecular weight which is selected from the group consisting of thermoplastic agents with low molecular weight less than 100g/mol and at least one thermoplastic agent with high molecular weight which is selected from the group consisting of thermoplastic agents with molecular weight more than or equal to 100g/mol, and the mass ratio of the thermoplastic agent with low molecular weight to the thermoplastic agent with high molecular weight is 5: 95-95: 5.
in the above technical scheme, the ethylene content in the ethylene-vinyl alcohol copolymer is preferably 20 to 50mol%.
In the technical scheme, the functional auxiliary agent comprises a compatilizer, an antioxidant, a light stabilizer, an opening agent, a release agent, pigment, inorganic filler and the like.
In order to solve the second technical problem, the technical scheme adopted by the invention is as follows: a method for preparing a film of a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition according to any one of the above technical solutions, comprising the steps of:
1) Uniformly mixing, extruding and granulating a required amount of polyvinyl alcohol subjected to drying treatment and a required amount of thermoplastic agent in a molten state to obtain the thermoplastic polyvinyl alcohol;
2) Uniformly mixing a required amount of thermoplastic polyvinyl alcohol with a required amount of ethylene-vinyl alcohol copolymer in a molten state, directly adding the melt of the composition into a die through a metering pump, and preparing a film by controlling stretching orientation; or cooling the composition melt, granulating, extruding the composition particles through melting, and controlling the stretching orientation of the composition melt through a die to prepare the film.
In the above technical scheme, the extrusion in the step 1) is preferably continuous melt blending extrusion, and the thermoplastic polyvinyl alcohol is obtained by blending the dried polyvinyl alcohol and the plasticizer according to a required proportion, and then adding the blend into a twin-screw extruder for melting, kneading, extruding and granulating.
In the above technical scheme, the extrusion in the step 1) is more preferably continuous melt blending extrusion, and the polyvinyl alcohol and the plasticizer which are dried are directly added into a twin-screw extruder for melting, kneading, extruding and granulating to obtain the thermoplastic polyvinyl alcohol.
In the above technical scheme, the melt blending method of the thermoplastic polyvinyl alcohol and the ethylene-vinyl alcohol copolymer is preferably a twin-screw continuous extrusion method.
In the above technical scheme, the method preferably comprises the steps of blending thermoplastic polyvinyl alcohol particles and ethylene-vinyl alcohol copolymer according to a required proportion, and then adding the blend into a double-screw extruder for extrusion granulation.
In the above technical scheme, the method preferably comprises the steps of respectively metering thermoplastic polyvinyl alcohol particles and ethylene-vinyl alcohol copolymer into a double-screw extruder according to a required feeding ratio for extrusion granulation.
In the above technical scheme, in the step of preparing the thermoplastic polyvinyl alcohol, the twin-screw extrusion temperature is 140-220 ℃, preferably 180-220 ℃, and the screw rotation speed is 50-500 rpm, preferably 150-300 rpm.
In the above technical scheme, in the step of preparing the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition material, the twin-screw extrusion temperature is 140-220 ℃, preferably 180-220 ℃, and the screw rotation speed is 50-500 rpm, preferably 150-300 rpm.
In the above technical scheme, the method for preparing the film from the thermoplastic polyvinyl alcohol and the ethylene-vinyl alcohol copolymer composition melt is preferably a double-screw blending extrusion film forming method, wherein the thermoplastic polyvinyl alcohol and the ethylene-vinyl alcohol copolymer with required amounts are directly melted and mixed in a double-screw extruder, and are led out by a casting die or a film blowing die to prepare the film.
In the above technical scheme, the method of preparing the blend particles into the film by melt extrusion after cooling and granulating the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition melt is preferably a single-screw extrusion film forming method, and the blend particles are melt extruded by a single-screw extruder and led out by a casting die or a film blowing die to prepare the film.
In order to solve the third technical problem, the technical scheme adopted by the invention is as follows: the use of a film of a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition as described in any one of the above-mentioned technical solutions.
In the above technical scheme, the application is not particularly limited, and for example, the application is not limited to wide application in the aspects of pesticides, hazardous chemical packaging, daily necessities, medicines, optical instruments and the like.
The following materials and preparation methods are briefly described as follows:
1. thermoplastic polyvinyl alcohol
Polyvinyl alcohol is a water-soluble polymer with excellent barrier property, wear resistance and chemical corrosion resistance, is insoluble in organic solvents such as gasoline, benzene, toluene, carbon tetrachloride, acetone, methanol and the like, is slightly soluble in dimethyl sulfoxide, and can be used for manufacturing vinylon synthetic fibers, fabric treatment agents, adhesives, high-strength fibers, optical films and the like.
Polyvinyl alcohol cannot be obtained directly by polymerization of vinyl alcohol monomers because vinyl alcohol monomers are very unstable and undergo spontaneous intermolecular rearrangement to convert acetaldehyde in the normal state. In the prior art, polyvinyl acetate is generally prepared by polymerizing vinyl acetate to obtain polyvinyl acetate, and then alcoholysis of the polyvinyl acetate. The degree of polymerization is an indicator of the molecular size of a polymer, based on the number of repeating units, i.e., the average of the number of repeating units contained in the macromolecular chain of the polymer. The alcoholysis degree refers to the mole ratio of the vinyl alcohol structure in the polyvinyl alcohol obtained after the alcoholysis of the polyvinyl acetate to the total amount of the non-hydrolyzed vinyl acetate. The polyvinyl alcohol used in the thermoplastic polyvinyl alcohol suitable for the present invention has a polymerization degree of 300 to 3000, and the polyvinyl alcohol used in the thermoplastic polyvinyl alcohol suitable for the present invention has an alcoholysis degree of 90 to 99mol%.
The thermoplastic polyvinyl alcohol is high melt strength and high fluidity polyvinyl alcohol obtained by carrying out thermal plasticizing modification on the polyvinyl alcohol in order to improve the processing difficulty and poor melt fluidity of the polyvinyl alcohol caused by the intramolecular and intermolecular forces, and the processing temperature window is widened and the thermoplastic processing performance is obviously improved. The thermoplastic polyvinyl alcohol is obtained by adopting a screw extrusion processing technology, and the polyvinyl alcohol and the plasticizer (10-30% by mass fraction) are mixed according to a proportion and then are introduced into the mixture or are respectively introduced into the mixture to be subjected to melt blending extrusion. The thermoplastic agent is prepared by mixing one, two or more components of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, glycerol, sorbitol, pentaerythritol, xylitol, polyethylene glycol PEG (molecular weight 100-2000), polyethylene glycol/propylene glycol PEPG (molecular weight 100-2000), fatty acid esters, glyceric acid, tween and the like.
2. Ethylene-vinyl alcohol copolymer
Ethylene-vinyl alcohol copolymer (EVOH) is a crystalline polymer having a chain molecular structure, and has both the processability of polyethylene and the high barrier property of vinyl alcohol polymer, but has a high crystallinity, a high melting point, and a temperature close to the decomposition temperature due to the presence of a large amount of hydroxyl groups. The properties are mainly dependent on the mole fraction of comonomer, the gas barrier properties, moisture barrier properties and processability of which vary with the ethylene content, and as the ethylene content increases, the gas barrier properties decrease and the moisture barrier properties improve, making the resin easier to process. In order to ensure stable melt processability and barrier properties, the ethylene content in EVOH is generally kept between 20 and 50mol%, and in addition, the processability, solvent resistance and antistatic property of EVOH are improved, so that the EVOH can be widely applied to the fields of packaging materials, automobile fuel tanks, oxygen-blocking floor heating pipes, textile materials, medical materials and the like.
3. Thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film
The composition (blend) film disclosed by the invention consists of thermoplastic polyvinyl alcohol and an ethylene-vinyl alcohol copolymer, wherein the mass content of the thermoplastic polyvinyl alcohol is 51-95%, and the mass content of the ethylene-vinyl alcohol copolymer is 5-49%. The composition film also comprises 0.1 to 2 mass percent of functional auxiliary agents, wherein the functional auxiliary agents comprise at least one of compatilizer, antioxidant, light stabilizer, opening agent, release agent, pigment, inorganic filler and the like.
The various physicochemical properties of a polymer blend (e.g., melt viscosity, melt index, etc.) are determined primarily by the type and composition ratio of the polymer from which it is made. The type of polymer mainly determines the "compatibility" between the components of the blend, which is a measure of the interaction between different polymers, when the interaction between different polymers is stronger,can be made to be a miscible (miscible) system when they are stably and uniformly mixed on a molecular scale; the interaction between other polymers is weak, and although the polymers are not mutually soluble in the molecular scale, the polymers can be stably and uniformly dispersed in the nanometer scale, and the blend is called a compatible system; other polymers have weak interactions and even when forcedly mixed, they tend to form separate phase regions, and such blends are incompatible (incompatible) systems. Glass transition temperature ("T") of polymer blend g ") information can be used as a simple basis for judging the compatibility between the components [ multicomponent polymer-principle, structure and performance ], by kingdom, 2013, p.20-22 ], if the blend respectively maintains the glass transition temperatures of the raw material components, the compatibility between the components is poor, and when the blend has only one glass transition temperature, the compatibility between the components is good. Under the condition of determining the polymer type, a certain functional relation exists between some physicochemical properties (such as melt viscosity, melt index and the like) of the blend and the composition proportion of the blend (the handbook of plastic engineering, huang Rui, 2000, p.633-637; melt Rheology of Polymer Blends from Melt Flow Index, international Journal of Polymeric Materials,1984,10, p.213-235, one can generally speculate on or even design blends with specific properties.
The theoretical properties of some polymer blends can be generally deduced using the linear addition rule, which can be expressed by the following formula:
P＝c 1 P 1 +c 2 P 2
p is the nature of the blend, c 1 And P 1 Is the concentration and nature of component 1; c 2 And P 2 Is the concentration and nature of component 2. The properties (P) of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition of the invention, such as melt index, oxygen permeation rate, etc., can be calculated as theoretical predicted values using addition rules, i.e., defined as "addition theoretical values", which can be compared with experimentally detected values of melt index, oxygen permeation rate, etc. The concentration of the components may be determined by mass fraction or volume fraction The invention selects the mass fraction to calculate the theoretical value.
A composition film embodying the present invention comprises from 51% to 95% by mass of a thermoplastic polyvinyl alcohol and from 5% to 49% by mass of an ethylene-vinyl alcohol copolymer, characterized in that the composition film has a multilayer assembled 2-dimensional nanolayer of polyvinyl alcohol and 2-dimensional nanolayer of ethylene-vinyl alcohol copolymer alternating structure, the total nanolayer number being at least 20. The multilayer polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternating structure is formed by alternating a thick nano layer with the thickness of more than or equal to 100 nanometers and a thin nano layer with the thickness of less than 100 nanometers. The thickness of the thick nano layer in the multilayer polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternating structure is more than 110 nanometers, and the thickness of the thin nano layer is less than 70 nanometers. The sensitivity of the barrier properties of the ethylene-vinyl alcohol copolymer to air humidity is lower than that of the thermoplastic polyvinyl alcohol, and the 'unexpected' alternating structure of the multilayer nanolayers enables the barrier properties of the composition film to be far better than the addition theoretical value of the two starting materials, and the oxygen permeation rate at low humidity (10%) is at least 25% lower than the addition theoretical value of the two starting materials; the oxygen permeation rate at high humidity (50%) is at least 35% lower than the theoretical addition value of the two starting materials.
4. Process for preparing thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer compositions
The continuous melt preparation method of the invention is a two-step method. In the method for preparing the thermoplastic polyvinyl alcohol, polyvinyl alcohol powder and a thermoplastic agent are mixed according to a proportion and then granulated through a single-screw or double-screw extruder. The other embodiment is that the polyvinyl alcohol powder and the thermoplastic agent are respectively and simultaneously added into a single screw extruder or a double screw extruder according to a certain feeding proportion for granulation. Then, after uniformly mixing the thermoplastic polyvinyl alcohol particles and the ethylene-vinyl alcohol copolymer particles according to a certain proportion, adding the composition particles into a feeding port of a double-screw extruder by a feeding machine according to a certain feeding rate. The feeder may be either a weightless feeder or a volumetric feeder. The other embodiment is that two feeders are adopted to respectively meter thermoplastic polyvinyl alcohol particles and ethylene-vinyl alcohol copolymer particles into a double-screw extruder according to a certain feeding proportion for extrusion granulation.
Extrusion temperatures suitable for the present invention are preferably 140℃to 220℃and more preferably 180℃to 220 ℃. The rotation speed of the extruder is preferably 50rpm to 300rpm, more preferably 150rpm to 300rpm.
Melt blending devices suitable for use in the present invention are a wide variety of devices including mixers, farrel continuous mixers, banbury mixers, single screw extruders, twin screw extruders, multiple screw extruders (more than two screws), reciprocating single screw extruders such as Buss Ko-Kneader, and the like. Preferred methods are continuous melt blending extrusion methods including twin screw extrusion methods. Continuous twin-screw extruders suitable for use in the present invention include twin-screw extruders of different designs, such as ZSK Mcc18 co-rotating parallel twin-screw extruders from Coperion, germany, and the like.
The thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition material prepared by adopting the continuous extrusion blending method disclosed by the invention has a higher melt index than the mixed addition theoretical value of the two starting materials, and the composition film prepared by melt extrusion film blowing processing or casting processing has a lower oxygen permeation rate than the mixed addition theoretical value of the two starting materials under lower and higher humidity, so that the composition film has wide application potential and better technical effect.
5. Method for preparing thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film
The invention discloses a method for preparing a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, which is characterized in that the mass content of thermoplastic polyvinyl alcohol in the composition film is 51-95%, the mass content of ethylene-vinyl alcohol copolymer is 5-49%, and 0.1-2% of functional auxiliary agent, the composition is prepared by the continuous melt extrusion blending method, the melt strength of the composition is at least 40% higher than that of thermoplastic polyvinyl alcohol, and the melt index is at least 50% higher than the addition theoretical value of two starting materials. The composite film of the invention has a multilayer assembled polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternating structure, and consists of a thick nano layer with the thickness of more than or equal to 100 nanometers and a thin nano layer with the thickness of less than 100 nanometers alternately, wherein the total nano layer number is at least 20, the Young modulus is more than 120MPa, the breaking strength is more than 25MPa, the breaking elongation is more than 180 percent, and the breaking energy is more than 100 nanometers>3MJ/m 3 . The oxygen permeation rate at low humidity (10%) is at least 25% lower than the theoretical addition value of the two starting materials; the oxygen permeation rate at high humidity (50%) is at least 35% lower than the theoretical addition value of the two starting materials. In the method, the composition is melted and extruded in a screw extruder, and the melt of the composition passes through a die and is subjected to further controlled orientation stretching to obtain a film with a certain thickness.
The invention discloses a method for preparing a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film, which is a single screw extrusion film forming method. In this process, the pre-prepared composition is fed into a single screw extruder, which is generally divided into three stages over the effective length, the first stage being the conveying section, where the blend is preheated and extruded; the second section is a compression section, the depth of the thread groove is reduced from large to small, and the melt temperature reaches the degree of plasticizing and melting the composition; the third section is a metering section, and the blend melt is conveyed to the film die according to a certain melt flow rate under the rotation of a screw.
One film forming method of the present invention is a cast film forming method. The casting film is cooled by a plurality of stages of cooling rollers to obtain a solidified casting film. The thickness of the casting film is controlled by the melt extrusion speed and the rotation speed of the winding roller, and the above parameters can further control the orientation degree of the casting film. The cast film has a high degree of molecular orientation in the machine or machine direction (Machine Direction, MD) of the film, and thus the tensile strength and young's modulus of the cast film in the MD are high, but the elongation of the film in the machine direction decreases correspondingly with an increase in the degree of orientation. The Direction perpendicular to the machine Direction is the transverse Direction (CD; transverse Direction, TD), the cast film is basically not oriented in the transverse Direction, and the properties of the cast film in the MD and CD are greatly different due to the difference of the orientation degree.
In the film blowing processing method, the blend melt is extruded into a nearly cylindrical hollow film bubble through a circular ring-shaped die, the film bubble is a sealing system which is pre-filled with gas with certain pressure, and the top end of the film bubble is a press roller. The double-layer film at the top is pulled by a series of rollers and then is cut off and rolled up respectively. The thickness of the film is determined by a range of conditions including the rotational speed of the extruder, the speed of the film winding, etc. Films produced by the blown film process have properties in both the machine and transverse directions that are closer to those of cast films due to the orientation.
The extrusion temperature of the composition film is 140℃to 220℃and more preferably 180℃to 220 ℃. The rotation speed of the single screw extruder is preferably 50rpm to 300rpm, more preferably 150rpm to 300rpm.
The invention relates to a method for preparing a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film by a double-screw extrusion film forming method. The process is different from the single screw extruder method, the feeding of the composition is completed by one feeder, the feeder suitable for the invention comprises a weightless feeder or a volumetric feeder, a casting film die or a film blowing die is arranged at the tail end of the double screw extruder, and the film led out from the die is further molded.
Another method of the invention is a one-step method of directly performing twin-screw blending film forming. On a twin-screw extruder equipped with a casting film die or a film blowing die, thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer are added into a feeding area of the twin-screw extruder according to a certain mass ratio, the composition melt after plasticization, melting and blending enters a melt metering pump, and the metering pump can be a gear pump, and the functions of the metering pump are to accurately control the melt flow rate and to add the composition melt into the casting film die or the film blowing die at a certain stable flow rate to prepare a film. The process has the advantages that the granulating process is not needed, the energy consumption can be effectively reduced, the whole process is greener, low-carbon and environment-friendly, and meanwhile, the preparation cost of the film is effectively reduced.
The Young's modulus of the films of the compositions produced is related to the stiffness or stiffness (stinffess) of the films. The Young's modulus of the film is high, so that the rigidity or stiffness of the film is also high, and the film material is not easy to stretch and deform. The elongation at break of a film material is related to the ductility and flexibility of the material, the higher the elongation at break, the greater the deformation the material can withstand during processing and thus the better the toughness. The greater the breaking strength, the better the film's load-bearing properties.
The Young modulus of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film is greater than 120MPa, the breaking strength is greater than 25MPa, and the breaking elongation is greater than 180%. The Young's modulus of the film (the mass ratio of the thermoplastic polyvinyl alcohol to the ethylene-vinyl alcohol copolymer is 70:30-60:40) is more than 200MPa, the breaking strength is more than 30MPa, and the breaking elongation is more than 220%.
The thermoplastic film of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition prepared by adopting the continuous extrusion blending method disclosed by the invention has a melt index higher than the addition theoretical value of two starting materials, and the film utilizes the synergistic performance advantage of the two materials, namely the Young modulus is greater than 120MPa, the breaking strength is greater than 25MPa, the breaking elongation is greater than 180%, and the breaking energy is greater than>3MJ/m 3 The better technical effect is achieved.
The thermoplastic film of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition prepared by adopting the continuous extrusion blending method disclosed by the invention has a multilayer assembled 2-dimensional nano layer of polyvinyl alcohol and 2-dimensional nano layer of ethylene-vinyl alcohol copolymer alternating structure, and consists of a thick nano layer with the thickness of more than or equal to 100 nanometers and a thin nano layer with the thickness of less than 100 nanometers alternately, wherein the total nano layer number is at least 20. The nano lamellar structure refers to a structure in which the lamellar thickness is nano-scale or less than 1 μm, and when the diameter of the polymer material is in the submicron or nanometer range, it has characteristics different from those of a general material, particularly exhibits great superiority in physicochemical properties, making it a functional material with high applicability. The particular structure provides a composition film having an oxygen permeation rate at lower humidity (10%) that is at least 25% lower than the theoretical blending addition of the two starting materials; the oxygen permeation rate at higher humidity (50%) is at least 35% lower than the blending addition theoretical value of the two starting materials, and the application range of the film is widened.
The invention performs performance measurement according to the following method:
melt index (MFR) determination method: according to ISO 1133 standard, lloyd DAVENPORT is adopted TM The MFI-10/230 melt index was measured at 210℃on a cylinder, a weight load of 2.16kg, a die diameter of 2.095mm and a length of 8mm, a preheating time of 4 minutes, automatic sample cutting was performed at a set time interval, and 5 times of sample cutting were averaged to give a measurement result in grams per 10 minutes (g/10 min).
The method for measuring the oxygen barrier property comprises the following steps: test with an OX-TRAN Model 2/22H-type oxygen permeameter from MOCON, USA, resolution 0.02 cc/(m) 2 D) is described. Testing is carried out at 23 ℃ under the conditions of 10% and 50% humidity, and the point is taken for 30min until the oxygen transmittance reaches a stable value.
Film tensile test: the test was performed according to ISO 527-3 using an Instron model 3344 material tester, version 2.31 Bluehill. The film was cut into Type 5 of ISO 527-3 standard in the direction of stretching (MD) and perpendicular to the direction of stretching (CD), and placed in a Blueboard BPS-100CB constant temperature and humidity cabinet (temperature 23 ℃ C., relative humidity 50%) of Shanghai-Heng-Hei scientific instruments Co., ltd for 24 hours. At the time of testing, the initial fixture spacing was 75mm, the test stretching rate was 100mm/min, and each sample was tested at least 5 times, and the average value was taken.
Scanning Electron Microscope (SEM): and observing the section morphology of the film in different directions by adopting a scanning electron microscope (ZEISS Merlin). The film samples were freeze-quenched in liquid nitrogen parallel to the stretching direction (MD) and perpendicular to the stretching direction (CD), and the morphological structure of the samples was observed at a voltage of 1kV and a current of 10 mA.
Wide angle X-ray diffraction scan (WAXD): the crystalline form of the composition film was examined using a Bruker D8 Discovery type X-ray diffractometer. Under the protection of nitrogen, cuK alpha (lambda=0.154 nm) radiation is adopted, the excitation voltage is 50kV, the excitation current is 1000 mu A, the scanning step length is 0.005 DEG, and the scanning range is 8-50 deg.
Haze: the haze of the film is tested by adopting a German BYK haze transparency meter, after the film is started and stabilized for 30min, a sample film is paved on a lens, the film is tested according to a measurement or pedal of an operation interface, different areas of the film are measured for 5 times, and the result is averaged.
Gloss level: the surface glossiness of the film is tested by adopting a German BYK micro-gloss meter, a sample film is tiled on a matched black panel, the meter is pressed on the film, data are tested, and the average value is obtained by carrying out multiple measurements.
Drawings
FIG. 1 shows the relationship between the oxygen permeation rate and the composition of each composition film at a humidity of 10%.
FIG. 2 shows the relationship between the oxygen permeation rate and the composition of each composition film at 50% humidity.
FIG. 3 is a graph showing the relationship between elongation at break and composition of a film of the composition.
FIG. 4 is a graph showing the relationship between the breaking energy and the composition of a film of the composition.
FIG. 5 cross-sectional morphology of a film of the composition after liquid nitrogen quenching parallel to the stretching direction (MD).
FIG. 6 cross-sectional morphology of a film of the composition after liquid nitrogen quenching perpendicular to the direction of stretching (CD).
FIG. 7 shows the relationship between haze and composition of films of the respective compositions.
FIG. 8 is a graph showing the relationship between the gloss and the composition of films of the respective compositions.
The wide angle XRD diffraction results of the films of each composition of fig. 9.
Detailed Description
The present invention is specifically described by the following examples. It is noted that the following examples are given by way of illustration only and are not to be construed as limiting the scope of the invention, as many insubstantial modifications and variations will be apparent to those skilled in the art in light of the above disclosure.
Comparative example 1
As used in the present inventionThe polymerization degree of polyvinyl alcohol (PVA) is about 1000, the alcoholysis degree is 94-96%, polyLab HAAKE by Thermo Fisher technology Co., USA is used TM Rheomer OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, L/D=40) was subjected to thermoplastic and extrusion pelletization. The extruder has 11 sections from a feeding port to a die, and the number of the sections is 1-11, wherein the section 1 only plays a role of feeding and cannot be heated. The powder feeder attached to the extruder was calibrated to feed PVA starting material into the twin screw at a feed rate of 900g/hr. Thermoplastic (glycerin (molecular weight: 92 g/mol) and diethylene glycol (molecular weight: 106 g/mol) are added into a container according to a mass fraction of 90:10, and uniformly mixed to prepare the thermoplastic for use, wherein the thermoplastic is prepared by adding glycerin (molecular weight: 92 g/mol) and diethylene glycol (molecular weight: 106 g/mol) into an extruder through a feed inlet, and the feeding rate is 3mL/min. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is between 56 and 60Nm. The extruder was equipped with a circular die having a diameter of 3mm, and after the bars were extruded from the die and air-cooled, they were cut into cylindrical transparent particles of about 3mm, i.e., thermoplastic polyvinyl alcohol particles, using a granulator. And collecting particles, and packaging for standby.
Comparative example 2
The ethylene-vinyl alcohol copolymer (EVOH) used in the present invention is produced by Cola corporation of Japan, and has an ethylene content of 32mol% and a brand F171B. PolyLab HAAKE from Thermo Fisher technology, inc. of America TM The rheomix OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, l/d=40) was extrusion pelletized. The extruder has 11 sections from a feeding port to a die, and the number of the sections is 1-11, wherein the section 1 only plays a role of feeding and cannot be heated. The extruder was calibrated for feeding EVOH into the twin screw at a feed rate of 850g/hr. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is between 74 and 78Nm. The extruder is provided with a circular die with the diameter of 3mm, and a spline is extruded from the die and is cut into cylinders with the diameter of about 3mm by a granulator after air coolingAnd (3) shaped semitransparent particles. And collecting particles, and packaging for standby.
[ example 1 ]
The EVOH used in the present invention (comparative example 2) was combined with a thermoplastic polyvinyl alcohol (TPVA, comparative example 1) such as PolyLab HAAKE as mentioned above TM Melt blending extrusion granulation is carried out in a Rheomex OS PTW16 co-rotating twin-screw extruder. In section 1 of the extruder, the calibrated feeder was used for feeding EVOH pellets at the following speed: 90g/hr, while the recalibrated powder feeder was used for feeding thermoplastic polyvinyl alcohol TPVA at the rate: 810g/hr. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is between 61 and 65Nm. The extruder was equipped with a circular die having a diameter of 3mm, and after the bars were extruded from the die and air-cooled, they were cut into cylindrical transparent particles of about 3mm by a granulator. And collecting particles, and packaging for standby.
[ example 2 ]
The EVOH used in the present invention (comparative example 2) was combined with a thermoplastic polyvinyl alcohol (TPVA, comparative example 1) such as PolyLab HAAKE as mentioned above TM Melt blending extrusion granulation is carried out in a Rheomex OS PTW16 co-rotating twin-screw extruder. In section 1 of the extruder, the calibrated feeder was used for feeding EVOH pellets at the following speed: 180g/hr, while the recalibrated powder feeder was used for feeding thermoplastic polyvinyl alcohol TPVA at the rate: 720g/hr. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is between 61 and 65Nm. The extruder was equipped with a circular die having a diameter of 3mm, and after the bars were extruded from the die and air-cooled, they were cut into cylindrical transparent particles of about 3mm by a granulator. And collecting particles, and packaging for standby.
[ example 3 ]
The EVOH used in the present invention (comparative example 2) was combined with a thermoplastic polyvinyl alcohol (TPVA, comparative example 1) such as PolyLab HAAKE as mentioned above TM Melt blending extrusion granulation is carried out in a Rheomex OS PTW16 co-rotating twin-screw extruder. In section 1 of the extruder, the calibrated feeder was used for EVThe OH particles were fed at the following rate: 270g/hr, while the recalibrated powder feeder was used for feeding thermoplastic polyvinyl alcohol TPVA at the rate: 630g/hr. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is 63-66Nm. The extruder was equipped with a circular die having a diameter of 3mm, and after the bars were extruded from the die and air-cooled, they were cut into cylindrical transparent particles of about 3mm by a granulator. And collecting particles, and packaging for standby.
[ example 4 ]
The EVOH used in the present invention (comparative example 2) was combined with a thermoplastic polyvinyl alcohol (TPVA, comparative example 1) such as PolyLab HAAKE as mentioned above TM Melt blending extrusion granulation is carried out in a Rheomex OS PTW16 co-rotating twin-screw extruder. In section 1 of the extruder, the calibrated feeder was used for feeding EVOH pellets at the following speed: 360g/hr, while the recalibrated powder feeder was used for feeding thermoplastic polyvinyl alcohol TPVA at the rate: 540g/hr. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 180 ℃,190 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃,200 ℃ and 190 ℃, the screw rotation speed is set at 250rpm, and the torque is between 61 and 65Nm. The extruder was equipped with a circular die having a diameter of 3mm, and after the bars were extruded from the die and air-cooled, they were cut into cylindrical transparent particles of about 3mm by a granulator. And collecting particles, and packaging for standby.
[ example 5 ]
All 6 of the above particles, including comparative examples 1-2 and examples 1-4, HAAKE manufactured in U.S. Thermo Fisher Scientific Inc.) TM Film was prepared by extrusion blown film on a Rheomex OS single screw extruder having a screw diameter of 19mm and an aspect ratio of 25 equipped with a 3:1 standard metering screw, polyLab HAAKE TM OS torque rheometer platform control. The extruder has three heating sections, the temperature from the feed inlet to the outlet is 185 ℃,195 ℃,200 ℃ and the screw rotation speed is 50rpm, the composition melt is extruded into a hollow membrane bubble through a circular ring type mouth die, the double-layer film at the top is pulled by a series of rollers, the double-layer film is rolled after being cooled, and the thickness of the single-layer film is controlled to be 20-23 mu m.
[ example 6 ]
Films of all 6 particles above were subjected to oxygen permeation rate (OTR) testing (10% humidity, 50% humidity respectively) following the procedure described above, and the measured oxygen permeation rate, theoretical oxygen permeation rate and percent difference between the two under the same conditions are shown in tables 1 and 2, and the relationship between oxygen permeation rate and composition is shown in fig. 1 and 2. The lower the oxygen permeation rate, the better the barrier properties of the film.
It can be seen from tables 1 and 2, and figures 1 and 2 that under the same test conditions, the oxygen permeation rate of the composition film was much lower than the theoretical addition value of the two starting materials, i.e., the oxygen barrier properties were unexpected. This is also unusual in polymer blends. The oxygen permeation rate of the composition was about 29% (example 1) to 70% (example 4) below the theoretical blending addition of the two starting materials at 10% humidity; the barrier properties of the films of the compositions were "unexpectedly" improved at 50% humidity by having oxygen permeation rates of the compositions below the theoretical blend addition of the two starting materials of about 37% (example 1) to 73% (example 4). This may be related to the multilayer assembled polyvinyl alcohol 2-dimensional nanolayers and ethylene-vinyl alcohol copolymer 2-dimensional nanolayer alternating structure that the composite film has, when the diameter of the layered structure is in the submicron or nanometer range, producing a characteristic that is distinguished from the linear addition of ordinary materials, and the film takes advantage of the synergistic performance benefits of both materials, producing an "unexpected" high barrier property.
Table 1 measured oxygen permeation rate, theoretical oxygen permeation rate, and percent difference between the two at 10% humidity for each composition film
TABLE 2 measured oxygen permeation rates, theoretical oxygen permeation rates, and percent difference between the two for films of each composition at 50% humidity
[ example 7 ]
The tensile properties of the films of all 6 particles above were measured parallel to the direction of elongation (MD) and perpendicular to the direction of elongation (CD) by the procedure described above, and the results are shown in tables 3 and 4, and FIGS. 3 and 4 are the elongation at break and the energy at break, respectively, as a function of the film composition.
It can be seen from tables 3 and 4 that under the same test conditions, the Young's modulus of the films of the compositions prepared in examples 2 to 4 was greater than 180MPa, the breaking strength was greater than 32MPa, the elongation at break was greater than 220%, the Young's modulus perpendicular to the stretching direction (CD) was greater than 120MPa, the breaking strength was greater than 31MPa, and the elongation at break was greater than 190%, both of which were accompanied by an increase in the content of the ethylene-vinyl alcohol copolymer, the Young's modulus of the films was increased, and the elongation at break was slightly decreased, but still maintained at 190% or more. The elongation at break of the ethylene-vinyl alcohol copolymer is extremely low, 10% of the thermoplastic polyvinyl alcohol, and the energy at break is only about 16% of the thermoplastic polyvinyl alcohol. The composition film is based on thermoplastic polyvinyl alcohol, and after ethylene-vinyl alcohol copolymer with extremely low elongation at break and energy at break is added, the elongation at break of the film can be maintained to be more than 180%, and the energy at break can be maintained >3MJ/m 3 Good performance properties are maintained, which are related to the assembled nano-layered alternating structure formed by the thermoplastic polyvinyl alcohol and the ethylene-vinyl alcohol copolymer. The composite of the nano-scale thermoplastic polyvinyl alcohol and the ethylene-vinyl alcohol copolymer 2-dimensional layered structure enables acting force generated in the stretching process to be absorbed by the inner layer and the interlayer interface, so that the ductility and the flexibility of the film are enhanced, and the composition film still has higher elongation at break and fracture energy after the ethylene-vinyl alcohol polymer with poor toughness is introduced.
The thermoplastic film of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition prepared by the continuous extrusion blending method disclosed by the invention has a 2-dimensional nano-layer alternating structure of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer, and utilizes the synergistic performance advantage of the two raw materials and the unexpected assembled nano-layered alternating structure, and the Young modulusMore than 120MPa, the breaking strength is more than 25MPa, the breaking elongation is more than 180%, and the breaking energy is more than>3MJ/m 3 The better technical effect is achieved.
TABLE 3 tensile Properties (MD) of films of the respective compositions parallel to the stretching direction
TABLE 4 tensile Properties (CD) of films of the compositions perpendicular to the direction of stretching
[ example 8 ]
The above films of all 6 particles were subjected to liquid nitrogen quenching in parallel to the stretching direction (MD) and perpendicular to the stretching direction (CD) according to the procedure described above, and the cross-sectional morphology was observed by a scanning electron microscope, and the results are shown in FIG. 5 and FIG. 6.
As can be seen from fig. 5 and 6, the films prepared in comparative examples 1 and 2 exhibited a flat, single-phase structure in both the MD (fig. 5) and CD (fig. 6), whereas examples 1-4 observed "unexpected" regular layered nano-alternating structures in both the MD and CD (Layered Nano Structure). The cross section of the film can see the bright and dark nano layers, the single layer thickness of the thicker nano layer exceeds 100nm, the average thickness is about 100 to 500nm, and the thicker nano layer is thermoplastic polyvinyl alcohol. The thickness of the thin nano-layer is less than 100nm, and the average thickness is about 10-70 nm. The MD and CD nanolayers of examples 1-3 are nearly the same scale, showing a regular, continuous 2-dimensional nanolayer alternating structure. When the polymer material is in submicron or nanometer range in one direction scale, it has the characteristic different from the common material, especially the physical and chemical property, so that it is one functional material with high application. Such a particular multilayer nanoalternating structure allows the composition film to have a higher oxygen permeation rate (10%) at lower humidity than the two types The blending addition theoretical value of the starting materials is at least 25% lower; the oxygen permeation rate at higher humidity (50%) is at least 35% lower than the blending addition theoretical value of the two starting materials, and the application range of the film is widened. Meanwhile, the special multilayer nanometer alternating structure also ensures that the elongation at break of the film can be maintained to be more than 180 percent after the ethylene-vinyl alcohol copolymer with extremely low elongation at break and energy at break is added into the composition film>3MJ/m 3 Good service performance is maintained.
[ example 9 ]
The haze and gloss of the above films of all 6 particles were measured according to the procedure described above, and the results are shown in FIGS. 7 and 8.
Haze (Haze) is the percentage of the total projected intensity of transmitted light that deviates from the incident light by more than 2.5 degrees, with greater Haze meaning reduced film transparency. As can be seen from fig. 7 and 8, in the examples, the haze of the composition film did not increase at lower EVOH levels (10% and 20%) due to the introduction of the high haze, low gloss ethylene vinyl alcohol copolymer, but was unexpectedly lower than the haze of the thermoplastic polyvinyl alcohol. When the EVOH content is 10-30%, the haze of the composition film is lower than the linear addition theoretical value (dotted line part in the figure) of the two starting material films, which indicates that the transparency of the film is better than expected, and the glossiness of the composition film is also higher than the linear addition theoretical value (dotted line part in the figure) of the two starting material films, which indicates that the glossiness of the film is better than expected, and the application range of the composition film is widened. The use performance of the film is closely related to the structure of the film, and the lower haze and higher glossiness are also specific to the performance of the multilayer nanometer alternating structure of the composition film.
[ example 10 ]
The above films of all 6 particles were subjected to wide angle XRD testing in accordance with the procedure described hereinabove, and the results are shown in FIG. 9.
As can be seen from FIG. 9, the diffraction peaks of the composition film prepared in the examples at 19.5 DEG and 41.5 DEG shift rightwards with the increase of EVOH content, the peak width of 19.5 DEG becomes narrower, the peak width of 41.5 DEG becomes wider, the crystal structure is more perfect, and the interplanar spacing becomes smaller. The peaks of examples 1-3 at around 19.5 deg. coincide with comparative example 1, and there is a characteristic peak at 37.7 deg. consistent with comparative example 1, whereas the peak of example 4 is closer to the peak of comparative example 2 at 19.5 deg., the diffraction peak at 37.7 deg. disappears, and the crystal structure may be changed, which may be related to the multilayer assembled thermoplastic polyvinyl alcohol 2-dimensional nanolaminate and ethylene-vinyl alcohol copolymer 2-dimensional nanolaminate alternating structure formed by the composition.
Claims (9)
1. A thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film having a multilayer assembled thermoplastic polyvinyl alcohol 2-dimensional nanolayer and ethylene-vinyl alcohol copolymer 2-dimensional nanolayer alternating structure with a total nanolayer number of at least 20, said thermoplastic polyvinyl alcohol 2-dimensional nanolayer and ethylene-vinyl alcohol copolymer 2-dimensional nanolayer alternating structure consisting of thick nanolayers having a thickness of greater than or equal to 100 nanometers alternating with thin nanolayers having a thickness of less than 100 nanometers, said composition film having an oxygen permeation rate under the same conditions that is at least 25% lower than the theoretical value of addition of the corresponding thermoplastic polyvinyl alcohol film and ethylene-vinyl alcohol copolymer film; the thermoplastic polyvinyl alcohol in the film is 51 to 95 parts by mass, and the ethylene-vinyl alcohol copolymer is 5 to 49 parts by mass; the thermoplastic agent used in the thermoplastic polyvinyl alcohol is at least one low molecular weight thermoplastic agent with the molecular weight less than 100g/mol and at least one high molecular weight thermoplastic agent with the molecular weight more than or equal to 100g/mol, and the mass ratio of the low molecular weight thermoplastic agent to the high molecular weight thermoplastic agent is 5: 95-95: 5.
2. The film of the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition of claim 1, wherein the total number of nanolayers of the multilayer assembled thermoplastic polyvinyl alcohol 2-dimensional nanolayers alternating with ethylene-vinyl alcohol copolymer 2-dimensional nanolayers is at least 60.
3. The film of a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the thickness of the thick nanolayer in the alternating structure of the thermoplastic polyvinyl alcohol 2-dimensional nanolayer and the ethylene-vinyl alcohol copolymer 2-dimensional nanolayer is greater than 110 nm; the thickness of the thin nano layer in the thermoplastic polyvinyl alcohol 2-dimensional nano layer and ethylene-vinyl alcohol copolymer 2-dimensional nano layer alternating structure is smaller than 70 nanometers.
4. The film of a thermoplastic polyvinyl alcohol-ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the thermoplastic polyvinyl alcohol has a polymerization degree of 300 to 3000, an alcoholysis degree of 90 to 99 mol%, a 4% weight fraction concentration aqueous solution viscosity of 35.0 mPa-s or less, and the thermoplastic agent is at least one selected from the group consisting of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, glycerol, sorbitol, pentaerythritol, xylitol, polyethylene glycol having a number average molecular weight of 100 to 2000, polyethylene glycol/propylene glycol having a number average molecular weight of 100 to 2000, fatty acid esters, glyceric acid, tween, and the thermoplastic agent is used in an amount of 10 to 30% based on the total mass fraction of the thermoplastic polyvinyl alcohol; the ethylene content of the ethylene-vinyl alcohol copolymer is 20-50% in terms of mole fraction.
5. The film of a thermoplastic polyvinyl alcohol-ethylene-vinyl alcohol copolymer composition as claimed in claim 1, wherein the film has a breaking strength of greater than 25 MPa, a breaking elongation of greater than 180% and a breaking energy of greater than>3 MJ/m 3 。
6. The thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film as claimed in claim 1, wherein the oxygen permeation rate of the composition film at low humidity is at least 25% lower than the theoretical addition value of the two starting materials; the rate of oxygen permeation at high humidity is at least 35% lower than the theoretical addition value of the two starting materials; the low humidity is humidity not more than 10%, and the high humidity is humidity not less than 50%.
7. The film of a thermoplastic polyvinyl alcohol-ethylene-vinyl alcohol copolymer composition according to claim 1, wherein the film further comprises 0.1 to 2 parts by mass of a functional auxiliary agent.
8. A method of preparing the thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition film of any one of claims 1-7, comprising the steps of:
1) Uniformly mixing, extruding and granulating a required amount of polyvinyl alcohol subjected to drying treatment and a required amount of thermoplastic agent and optional functional auxiliary agents in a molten state to obtain the thermoplastic polyvinyl alcohol;
2) Uniformly mixing a required amount of thermoplastic polyvinyl alcohol with a required amount of ethylene-vinyl alcohol copolymer in a molten state, adding the melt of the composition into a die through a metering pump, and controlling stretching orientation to prepare the film; or cooling the composition melt, granulating, and performing melt extrusion on the composition particles, and performing die controlled stretching orientation to obtain the film.
9. Use of a film of a thermoplastic polyvinyl alcohol and ethylene-vinyl alcohol copolymer composition as claimed in any one of claims 1 to 7.
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