CN107745509B - Preparation method of multilayer co-extrusion two-way stretching composite film - Google Patents
Preparation method of multilayer co-extrusion two-way stretching composite film Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/023—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
- B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
- B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/04—Polymers of ethylene
- B29K2023/06—PE, i.e. polyethylene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2007/00—Flat articles, e.g. films or sheets
- B29L2007/002—Panels; Plates; Sheets
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Abstract
The invention relates to a preparation method of a multilayer co-extrusion two-way stretching composite film, which is prepared by adopting a mode of combining tube film method synchronous stretching and flat film method two-step stretching, aiming at the composite film, firstly, a co-extrusion tube film method forming process is adopted to synchronously carry out first melting stretching on the longitudinal direction and the transverse direction of an extruded film bubble to obtain a tubular film, and then, the tubular film is flatly folded to obtain a double-layer film or a single-layer film, wherein under the flatly folded state, when the temperature of the material of the inner layer of the extruded film bubble reaches or is lower than the glass transition temperature of the material, the double-layer film is obtained, and when the temperature of the material of the inner layer of the extruded film bubble is higher than the melting point of the material; and then, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily performing non-melting stretching on the double-layer membrane or the single-layer membrane by a flat membrane stretching method, and finally performing post-treatment on the double-layer membrane or the single-layer membrane to obtain the biaxially oriented composite membrane.
Description
Technical Field
The invention relates to a preparation method of a multilayer co-extrusion two-way stretching composite film.
Background
Synchronous stretching by a tube membrane method and biaxial stretching by a flat membrane method are two common biaxial stretching plastic film production processes, and the two production processes have the advantages and the disadvantages respectively.
And when the tubular film bubble is formed by blowing in the synchronous stretching of the tubular film method, the longitudinal and transverse biaxial stretching of the film is completed. The principle of the method is that a tube is extruded, then the tube is cooled by a water bath, and between a first pair of nip rollers and a second pair of nip rollers, transverse stretching is formed by properly adjusting the air pressure state in the bubble, and longitudinal stretching is achieved by adjusting the speed difference between the first pair of nip rollers and the second pair of nip rollers. The stretched film produced by the tube film stretching method has uniform properties, but the resin has the problems of low shrinkage rate, uneven thickness, incapability of accurately controlling the temperature and the stretching ratio and low heat sealing temperature and has bonding problems.
Biaxial stretching by the flat film method is to make a sheet or a thick film from a melt or a solution of a high molecular polymer by a long and narrow head, then stretch the sheet or the thick film in two perpendicular directions (longitudinal direction and transverse direction) simultaneously or step by step in a special stretching machine at a certain temperature and a set speed, and then form a film by proper cooling or heat treatment or special processing (corona, etc.). The process can balance the longitudinal and transverse mechanical properties of the film uniformly, and can also intentionally produce films with different longitudinal and transverse properties. The two-way stretching by the flat film method comprises a synchronous stretching method and a two-step stretching method, the film produced by the synchronous stretching method has uniform performance and is non-contact stretching, but the production equipment has complex mechanical structure, low flexibility and low production speed; the film produced by the two-step stretching method has excellent flexibility, uniform and good thickness, low shrinkage rate and unbalanced properties.
Disclosure of Invention
The invention aims to provide a preparation method of a multilayer co-extrusion biaxially oriented composite film.
In order to achieve the purpose, the first technical scheme adopted by the invention is as follows: a preparation method of a multilayer co-extrusion two-way stretching composite film is innovative in that:
the composite film contains a main stretching layer, the main stretching layer is made of PET, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first synchronous melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a single-point or multi-point stretching mode, the stretching ratio is 2 ~ 4.5.5, and the stretching temperature is between the glass transition temperature and the melting temperature of the main stretching layer and is close to the glass transition temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
In order to achieve the purpose, the invention adopts a second technical scheme that: a preparation method of a multilayer co-extrusion two-way stretching composite film is innovative in that:
the composite film contains a main stretching layer, the main stretching layer is made of PE, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion pipe film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the viscous flow temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the first synchronous melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120℃ on the basis of the stretching temperature
Thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the thermal deformation temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a single-point or multi-point stretching mode, the stretching ratio is 2 ~ 6, and the stretching temperature is between the thermal deformation temperature and the viscous flow temperature of the main stretching layer and is close to the thermal deformation temperature;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the second longitudinal stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the second longitudinal stretching temperature.
In order to achieve the above object, the third technical solution adopted by the present invention is: a preparation method of a multilayer co-extrusion two-way stretching composite film is innovative in that:
the composite film contains a main stretching layer, the main stretching layer is made of PP, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first synchronous melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the thermal deformation temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a multipoint stretching mode, the stretching ratio is 2 ~ 8, and the stretching temperature is between the thermal deformation temperature and the melting temperature of the main stretching layer and is close to the thermal deformation temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
In order to achieve the above object, the fourth technical solution adopted by the present invention is: a preparation method of a multilayer co-extrusion two-way stretching composite film is innovative in that:
the composite film contains a main stretching layer, the main stretching layer is made of PA, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first synchronous melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the adhesive layer is lower than the crystallization temperature of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a multipoint stretching mode, the stretching ratio is 2 ~ 5, and the stretching temperature is lower than the crystallization temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
The relevant content in the above technical solution is explained as follows:
in the scheme, the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film.
In the above scheme, the pretreatment functions are: after stretching by a tube membrane method, thermal stress is generated in the double-layer membrane or single-layer membrane structure due to the existence of a temperature gradient, and the thermal stress formed by a temperature difference generated in the thickness direction of the membrane is called thickness stress. This thermal stress must be removed before the flat film is biaxially stretched before the second non-melt stretching can be performed.
In the above scheme, the post-treatment functions as: the stretching condition of the longitudinal second non-melt stretching of the composite film is mainly based on the material property and the thickness of the main stretching layer, so that the conformational internal stress of the composite film structure due to different polymerization forms under the same stretching condition exists in the composite film structure, and the conformational internal stress of the composite film structure after the flat film is stretched in the two directions is eliminated through post-treatment.
In the above scheme, the longitudinal stretching includes single-point stretching and multi-point stretching, wherein: when the slab heated to the rubber-like state is stretched by two rolls of different rotation speeds, it is called single-point stretching; the ratio of the linear speeds of the two roll surfaces is the draw ratio, generally between 1 and 9, when the draw ratio is divided into several rolls with different rotation speeds, called multi-point drawing, which are sequentially increased, and the total draw ratio is the ratio of the rotation speed of the last draw roll (or chill roll) to the rotation speed of the first draw roll (or preheat roll). In the above scheme, the "glass transition temperature" refers to the temperature at which an amorphous or semi-crystalline polymer begins to transition from a glassy state to a high elastic state, and is the lowest temperature at which the macromolecular segments of the amorphous polymer move freely, and is the inherent property of the amorphous polymer material, and is generally represented by Tg. Above this temperature, the high polymer exhibits elasticity; below this temperature, the high polymer exhibits brittleness.
In the above embodiment, the "heat distortion temperature" refers to a temperature corresponding to a temperature at which a polymer material or a polymer is heated at a constant rate by applying a constant load thereto and reaches a predetermined distortion.
In the above scheme, the "viscous flow temperature" or softening temperature refers to the onset temperature of the transition of the amorphous polymer from the high-elastic state to the viscous state, generally denoted as Tf.
In the scheme, the brittle temperature is the lowest temperature at which forced high-elastic deformation can occur when the glass state is detected; generally denoted by Tb
In the above embodiment, the "melting temperature" is the melting point of the crystalline polymer, i.e., the temperature at which the crystalline polymer melts, and is generally represented by Tm.
In the above embodiment, the "crystallization temperature" is a temperature at which the crystalline polymer starts to crystallize, and is generally represented by Tc. In the above embodiment, the "maximum crystallization rate temperature" is a temperature at which an optimum growth rate for crystallization occurs, and in general, crystallization is possible between the glass transition temperature Tg and the melting temperature Tm, the optimum growth rate for crystallization is in a range between the glass transition temperature Tg and the melting temperature Tm, and the maximum crystallization rate temperature is in the vicinity of 0.8 Tm.
In the above scheme, the "reduced diameter" refers to: the film formed by the blow molding method is folded by taking the circumference of a die head as a unit, the length after folding is the folding diameter, the folding diameter = pi d/2, and d is the diameter of a film forming die.
In the above scheme, the term "close" means: taking the median of the two temperatures, when the stretching temperature lies between the median and one of the temperatures, the stretching temperature is considered to be close to this temperature.
In the above embodiment, the "melt-drawing" means drawing in a state where the "dew point" of the bubble is close to the melting point; the "non-melt stretching" means stretching in a high elastic state (non-melt state) of the film; the dew point is also called frost line and refers to a boundary line of plastic from viscous state to high elastic state. When the dew point temperature is higher than the viscous flow temperature, the film is blown in a liquid state, the film is only thinned by blowing, and molecules are not subjected to stretching orientation; when the dew point approaches the viscous flow temperature, the film is blown up in the solid state, causing the molecules to orient laterally.
The working principle and the advantages of the invention are as follows: the preparation method is implemented by combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, carrying out primary fusion stretching on the longitudinal direction and the transverse direction through synchronous tube film stretching by adopting a co-extrusion tube film method forming process to obtain a tubular film bubble, then flatly folding the tubular film bubble to obtain a double-layer film or a single-layer film, then carrying out pretreatment on the double-layer film or the single-layer film, simultaneously carrying out longitudinal secondary non-fusion stretching on the double-layer film or the single-layer film by using a flat film stretching method, and finally carrying out post-treatment on the double-layer film or the single-layer film to obtain the biaxially oriented composite film. The multilayer co-extrusion biaxial stretching composite film with uniform thickness and controllable shrinkage rate is prepared.
Detailed Description
The invention is further described below with reference to the following examples:
the first embodiment is as follows:
a preparation method of a multi-layer co-extrusion two-way stretching composite film comprises a main stretching layer, wherein the main stretching layer is made of PET, and the thickness of the main stretching layer accounts for 38% of the total thickness of the composite film.
Aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous stretching multiplying power in the co-extrusion tube film method forming process is 4, the stretching temperature is 265 ℃, wherein the glass transition temperature of the main stretching layer material is 69 ℃, and the melting point temperature is 270 ℃.
Secondly, the pretreatment is to perform stress relief annealing treatment on the double-layer membrane or the single-layer membrane obtained after the first melting and stretching, and the pretreatment temperature is 240 ℃. The pretreatment temperature is reduced by 25 ℃ based on the first melt-stretching temperature.
Thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the adhesive layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer.
Fourthly, the longitudinal second non-melting stretching adopts a single-point stretching mode, the stretching magnification is 3, the stretching temperature is 86 ℃, and the temperature is between the glass transition temperature and the melting temperature of the main stretching layer and is close to the glass transition temperature of the main stretching layer.
Fifthly, the post-treatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after longitudinal second non-melting stretching, the post-treatment temperature is 106 ℃, and the annealing temperature is increased by 20 ℃ on the basis of the longitudinal second non-melting stretching temperature.
Example two:
a preparation method of a multi-layer co-extrusion two-way stretching composite film comprises a main stretching layer, wherein the main stretching layer is made of PE, and the thickness of the main stretching layer accounts for 50% of the total thickness of the composite film.
Aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, in the co-extrusion tube film method forming process, the synchronous stretching multiplying power is 16, the stretching temperature is 140 ℃, wherein the thermal deformation temperature of PE is 85 ℃, and the viscous flow temperature is 140 ℃.
Secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first melting and stretching, and the annealing temperature is 120 ℃. The pretreatment temperature is reduced by 20 ℃ based on the first melt-stretching temperature.
Thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the thermal deformation temperature of the adhesive layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer.
Fourthly, the longitudinal second non-melting stretching adopts a two-point stretching mode, the stretching ratio is 5, the first point stretching temperature is 100 ℃ ~ 105 ℃, the second point stretching temperature is 105 ℃ ~ 110 ℃, and the temperature is between the thermal deformation temperature and the viscous flow temperature of the main stretching layer and is close to the thermal deformation temperature.
Fifthly, the post-treatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after longitudinal second non-melting stretching, wherein the post-treatment temperature is 140 ℃, and is increased by 30 ℃ on the basis of the longitudinal second non-melting stretching second point stretching temperature.
Example three:
a preparation method of a multi-layer co-extrusion two-way stretching composite film comprises a main stretching layer, wherein the main stretching layer is made of PP (polypropylene), and the thickness of the main stretching layer accounts for 45% of the total thickness of the composite film.
Aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, in the co-extrusion tube film method forming process, the synchronous stretching multiplying power is 8, the stretching temperature is 180 ℃, the thermal deformation temperature of the PP (polypropylene) of the main stretching layer material is 93 ℃, and the melting temperature is 185 ℃.
Secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first melting and stretching, and the pretreatment temperature is 157 ℃ which is reduced by 23 ℃ on the basis of the stretching temperature.
Thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the adhesive layer is lower than the thermal deformation temperature of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer.
Fourthly, the longitudinal second non-melting stretching adopts a two-point stretching mode, the stretching ratio is 5.5, the first point stretching temperature is 100 ℃ ~ 110 ℃, the second point stretching temperature is 110 ℃ ~ 126 ℃, and the temperature is between the thermal deformation temperature and the melting temperature of the main stretching layer and is close to the thermal deformation temperature of the main stretching layer.
Fifthly, the post-treatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the longitudinal second non-melting stretching, the post-treatment temperature is 167 ℃, and the post-treatment temperature is increased by 41 ℃ on the basis of the longitudinal second non-melting stretching temperature.
Example four:
a preparation method of a multi-layer co-extrusion two-way stretching composite film comprises a main stretching layer, wherein the main stretching layer is made of PA, and the thickness of the main stretching layer accounts for 30% of the total thickness of the composite film.
Aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; secondly, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, and finally post-treating the double-layer membrane or the single-layer membrane to obtain a two-way stretching composite film; wherein, the technological parameters and requirements are as follows:
firstly, in the co-extrusion tube film method forming process, the synchronous stretching ratio is 3, the stretching temperature is 230 ℃, the crystallization starting temperature of the main stretching layer material PA is 85 ℃, the maximum crystallization speed temperature is 168 ℃, and the melting temperature is 220 ℃.
Secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after the first melting and stretching, and the pretreatment temperature is 180 ℃ which is reduced by 50 ℃ on the basis of the stretching temperature.
Thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the adhesive layer is higher than the embrittlement temperature of the main stretching layer.
Fourthly, the longitudinal second non-melting stretching adopts a two-point stretching mode, the stretching ratio is 3, the first point stretching temperature is 65 ~ 70 ℃, and the second point stretching temperature is 70 ~ 80 ℃ (lower than the crystallization temperature of the main stretching layer).
Fifthly, the post-treatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after longitudinal second non-melting stretching, the post-treatment temperature is 180 ℃, and the post-treatment temperature is increased by 100 ℃ on the basis of the longitudinal second non-melting stretching second point stretching temperature.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (5)
1. A preparation method of a multilayer co-extrusion two-way stretching composite film is characterized by comprising the following steps:
the composite film contains a main stretching layer, the main stretching layer is made of PET, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; then, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, wherein the longitudinally and secondarily stretching in a non-melting way is longitudinal stretching, and finally, post-treating the double-layer membrane or the single-layer membrane to obtain a biaxially oriented composite membrane; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after synchronous first melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a single-point or multi-point stretching mode, the stretching ratio is 2 ~ 4.5.5, and the stretching temperature is between the glass transition temperature and the melting temperature of the main stretching layer and is close to the glass transition temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
2. A preparation method of a multilayer co-extrusion two-way stretching composite film is characterized by comprising the following steps:
the composite film contains a main stretching layer, the main stretching layer is made of PE, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; then, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, wherein the longitudinally and secondarily stretching in a non-melting way is longitudinal stretching, and finally, post-treating the double-layer membrane or the single-layer membrane to obtain a biaxially oriented composite membrane; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion pipe film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the viscous flow temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after synchronous first melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120℃ on the basis of the stretching temperature
Thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the thermal deformation temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a single-point or multi-point stretching mode, the stretching ratio is 2 ~ 6, and the stretching temperature is between the thermal deformation temperature and the viscous flow temperature of the main stretching layer and is close to the thermal deformation temperature;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the second longitudinal stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the second longitudinal stretching temperature.
3. A preparation method of a multilayer co-extrusion two-way stretching composite film is characterized by comprising the following steps:
the composite film contains a main stretching layer, the main stretching layer is made of PP, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; then, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, wherein the longitudinally and secondarily stretching in a non-melting way is longitudinal stretching, and finally, post-treating the double-layer membrane or the single-layer membrane to obtain a biaxially oriented composite membrane; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after synchronous first melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, a bonding layer is arranged between the main stretching layer and the adjacent layer, and the thermal deformation temperature of the bonding layer is lower than that of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a multipoint stretching mode, the stretching ratio is 2 ~ 8, and the stretching temperature is between the thermal deformation temperature and the melting temperature of the main stretching layer and is close to the thermal deformation temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
4. A preparation method of a multilayer co-extrusion two-way stretching composite film is characterized by comprising the following steps:
the composite film contains a main stretching layer, the main stretching layer is made of PA, and the thickness of the main stretching layer accounts for at least 30% of the total thickness of the composite film;
aiming at the composite film, the composite film is prepared by adopting a mode of combining the synchronous stretching of a tubular film method and the two-step stretching of a flat film method, and specifically comprises the following steps: firstly, synchronously performing first-time melting and stretching on the longitudinal direction and the transverse direction of an extruded bubble by adopting a co-extrusion tube membrane method forming process to obtain a tubular film, and then flatly folding the tubular film to obtain a double-layer membrane or a single-layer membrane, wherein in a flatly folded state, when the temperature of an inner layer material of the extruded bubble reaches or is lower than the glass transition temperature of the material, the double-layer membrane is obtained, and when the temperature of the inner layer material of the extruded bubble is higher than the melting point of the material, the single-layer membrane is obtained; then, pre-treating the double-layer membrane or the single-layer membrane, longitudinally and secondarily stretching the double-layer membrane or the single-layer membrane in a non-melting way by a flat membrane stretching method, wherein the longitudinally and secondarily stretching in a non-melting way is longitudinal stretching, and finally, post-treating the double-layer membrane or the single-layer membrane to obtain a biaxially oriented composite membrane; wherein, the technological parameters and requirements are as follows:
firstly, the synchronous first melting and stretching multiplying power in the co-extrusion tube film method forming process is 4 ~ 16, and the synchronous first melting and stretching temperature is +/-0 ~ 10 ℃ on the basis of the melting temperature of the main stretching layer material;
secondly, the pretreatment is to perform stress relief treatment on the double-layer membrane or the single-layer membrane obtained after synchronous first melting and stretching, and the pretreatment temperature is reduced by 20 ~ 120 ℃ on the basis of the stretching temperature;
thirdly, an adhesive layer is arranged between the main stretching layer and the adjacent layer, and the glass transition temperature of the adhesive layer is lower than the crystallization temperature of the main stretching layer and is higher than the embrittlement temperature of the main stretching layer;
fourthly, the longitudinal second non-melting stretching adopts a multipoint stretching mode, the stretching ratio is 2 ~ 5, and the stretching temperature is lower than the crystallization temperature of the main stretching layer;
fifthly, the post-treatment is to perform stress relief treatment on the double-layer film or single-layer film obtained after the longitudinal second non-melting stretching, and the post-treatment temperature is increased by 20 ~ 140 ℃ on the basis of the longitudinal second non-melting stretching temperature.
5. The method for preparing the multilayer coextruded biaxially oriented laminated film according to claim 1, 2, 3 or 4, wherein the thickness of the primary stretched layer is 30 ~ 60% of the total thickness of the laminated film.
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