CN101378902A - Multilayer thermoshrinkable films - Google Patents
Multilayer thermoshrinkable films Download PDFInfo
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- CN101378902A CN101378902A CNA2007800042939A CN200780004293A CN101378902A CN 101378902 A CN101378902 A CN 101378902A CN A2007800042939 A CNA2007800042939 A CN A2007800042939A CN 200780004293 A CN200780004293 A CN 200780004293A CN 101378902 A CN101378902 A CN 101378902A
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Abstract
A multilayer thermoshrinkable film and a process for manufacturing the same are described. The film is particularly suitable for packaging applications, in particular as a packaging thermoshrinkable hood for enclosing an item or a secondary packaging essentially consisting of polyethylene. The multilayer thermoshrinkable film of the invention comprises: a) at least one first film layer comprising a linear ethylene copolymer having a density of 0.920 to 0.950 g/cm<3>; b) at least one second film layer comprising a first copolymer of propylene with ethylene and/or at least one CH2=CHR1 a-olefins, where R1 is a hydrocarbon radical having 2-10 carbon atoms; and c) at least one third film layer comprising a linear ethylene copolymer having a density of 0.920 to 0.950 g/cm<3>; wherein said at least one first film layer is arranged between said at least one second film layer and at least one third film layer. The multilayer thermoshrinkable film, which has improved shrinkage and seal properties, may be advantageously produced by means of standard symmetrical film extrusion plants.
Description
Technical field
The present invention relates to multilayer film, particularly based on poly multilayer heat shrinkable film.More particularly, the present invention relates to multilayer heat shrinkable film, it comprises that at least one comprises polyvinyl first rete and at least one second rete, wherein first rete is given described multilayer film heat shrinkability characteristic, and second rete is used for contacting with object to be wrapped, and also can be not adhered thereto when object to be wrapped is made by ethene polymers basically.
In this specification and following claim, unless opposite indication, term " polymer " are arranged " be used to indicate homopolymers, promptly comprise polymer derived from the repeated monomer unit of same monomer species; And copolymer, promptly comprise polymer derived from the repeated monomer unit of at least two kinds of different monomers species, number according to used different monomers species refers to bipolymer, terpolymer etc. in this case, and described copolymer is for example block polymer, atactic polymer and alternating polymer.
The invention still further relates to the method for making above-mentioned film.
Multilayer heat shrinkable film of the present invention is especially suitable for use as level package (primarypackaging), promptly as unique packaging film of parcel object or a plurality of objects, the perhaps object that has been wrapped up by level package as parcel or the secondary package (secondarypackaging) of a plurality of objects.
The invention still further relates to the purposes of this class multilayer heat shrinkable film as packaging film, particularly with this area be commonly referred to " not fusing shrink wrapping cover (non-fusion shrink hood) " (promptly being not bonded to encasement) based on poly object or packing, based on the purposes of the packaging film of poly form membrane.Based on poly object or packing is respectively object and the packing of being made (promptly comprising polyethylene as solvent) basically by polyethylene.
In this specification and following claim; term " encasement (hood) " is used for the tubular film that indication has first open end and passes through second end of sealing (sealing) sealing; this tubular film is used to overlap and installs to object (for example load of palletize (palletizedload)) to be protected or parcel, and shrinks around this object by conducting heat.
Prior art
Heat-shrinkable film is made by the mixture of polymer or multiple polymers, can shrink when it is exposed to uniform temperature, is restricted if perhaps shrink, and then produces shrink tension in film.This class film is widely used in protecting dissimilar objects, and goods for example a large amount of and in heaps, but these goods independent packagings are perhaps with the packaged of the goods (stacked goods) that piles up.
According to the type of film manufacturing method, mainly contain two class heat-shrinkable films, i.e. blowing (blown) shrink film and orientation (oriented) shrink film.
The blowing shrink film is made by the film-forming method that froths (blow bubble film process) usually, and the directional retraction film is usually by two and the preparation of uniaxial orientation method, comprises that double bubble process (doublebubble method), amphiorentation method (biorientedmethod), band shape bubble (tape bubble), trapped bubble (trapped bubble) or tentering (tenter framing) method of carrying out the vertical and horizontal orientation simultaneously make.
Ground known in this field, the manufacturing of heat-shrinkable film can be extruded realization via the extrusion die of flat board or tubular form by the polymer that will be heated to (or a little higher than) its flowing temperature (flow point) or melting temperature usually.
After extruding the back quench cooled, extrudate is heated to once more the orientation temperature scope of described polymer.Different according to the polymer that can make described film and polymeric blends, the orientation temperature scope of given film also can change.Yet common described orientation temperature scope can be decided to be the fusing point that is higher than room temperature and is lower than film.
Based on poly heat-shrinkable film is known.The heat-shrinkable film of being made by low density polyethylene (LDPE) (LDPE) or LLDPE (LLDPE) also is known.LLDPE mainly is used in the directional retraction film.Because it is in the balance contraction level of machine direction and horizontal direction and the good shrinkage character aspect the low processing shrinkage temperature, LDPE is used in the blowing shrink film.Simultaneously known ground mixes LLDPE with LDPE (as the mixed with little amount component), improve the tensility in the film blowing process, improves sealing characteristics, and is minimized in the pore-forming tendency in the thermal contraction process.
Based on poly multilayer heat shrinkable film, particularly comprise first rete that comprises LLDPE, with the heat-shrinkable film of second, third rete also be well known in the art, wherein said second and the tertiary membrane layer comprise and be applicable to give described film sealing or optical characteristics and be applicable to and prevent that described film the time is bonded to together polymeric blends in work.Give inotropic first rete of described film and be generally internal layer, and described second and the 3rd layer be generally outer, one of them is used for contacting with object to be wrapped, and another skin is used to be exposed to external environment condition.
When object to be packaged itself is made of polyethylene substantially, for example under situation based on poly container, in the time of perhaps in object to be packaged has been wrapped in based on poly level package film, in the heating steps of packaging process, be used separately as may the adhering to inconveniently or even be sealed on described polyethylene object or the polyethylene packaging film of level package film or secondary package film based on poly heat-shrinkable film.
Adhere to problem on the object to be wrapped for fear of film, also developed based on poly multilayer film, skin wherein is provided except polyethylene layer, described skin or provide anti-adhesion (antiblocking) additive is perhaps made by polypropylene or ethylene/propene copolymer (EPC).
European patent application EP-A-0 586 160 and EP-A-0 595 252 have described the example based on poly multilayer film of prior art.
EP-A-0 586 160 has described and has comprised central core and outer field heat shrinkable multilayer film, wherein central core is made by LLDPE, and skin can be by the mixture of EPC and polybutene (PB), the perhaps mixture of polypropylene (PP) or ethylene/propene copolymer (EPC) and propene/but-1-ene copolymer (PBC), or PBC makes.It is said that using the main purpose of PBC at skin is in order to obtain good lap seal characteristic.
EP-A-0 595 252 discloses and has comprised shrinkage layer of being made by LLDPE and outer field three layers of heat-shrinkable film of being made by polypropylene or EPC, wherein in described shrinkage layer, added hydrocarbon resin, polyethylene or additives such as polypropylene wax, VLDPE, in described skin, also added identical additive such as hydrogenation.
Other examples of heat shrinkable multilayer film have been provided in the United States Patent (USP) 4 532 189.This patent has been described and has been comprised central core and outer field three layers or five tunics, described central core comprises LLDPE or linear density polyethylene (LMDPE), and also optional EPC, ethylene (EVA) or the low density polyethylene (LDPE) (LDPE) of comprising, described skin comprises EPC, and also optional Noblen (PP), LLDPE or the LMDPE of comprising.Also be provided with the intermediate layer between central core and skin, and this class intermediate layer is by EVA, perhaps the mixture of LLDPE or LMDPE and ionomer resin is made.
Yet the film of this class prior art has many shortcomings, and these shortcomings are all relevant with the person's character of the composition of different layers basically.First shortcoming is found in when two skins are made by EPC and/or PP, described film can only be under high relatively temperature heat seal because the skin of this composition can not be realized sufficient sealing when low temperature.Second shortcoming is obtained contractive effect deficiency.The 3rd shortcoming is found in and can causes the rete of gained film to take place undesirable layer based on poly central core and connection based on (being between the relatively poor material of compatibility own) between polyacrylic two skins separating.
Provided in the International Application No. WO 97/22475 and comprised the outer field multilayer heat shrinkable film of making by EPC, its disclose comprise at least one deck comprise the layer of polyolefin composition and at least one deck to comprise density be 0.88-0.945g/cm
3Linear ethylene copolymer the layer multilayer heat shrinkable film, described polyolefin composition comprises the propylene copolymer with predetermined degree of crystallinity.More specifically, it is the trilamellar membrane of 0.19 μ m that WO97/22475 discloses thickness, it comprises center shrinkage layer and skin, this center shrinkage layer is made by the propylene that comprises ethene/butene-1 copolymer of 85% and 15% and the trimeric polymeric compositions of ethene and 1-butylene, and described skin is made by the polyolefin composition that comprises propylene/1-butene/ethylene trimer thing.
If not opposite indication, in this specification and following claim, all percentages all are weight percentage.
On the one hand, WO 97/22475 disclosed film is not suitable for making the shrink wrapping cover, because wherein disclosed film prepares by double bubble process, promptly be used for making the method for only extremely thin film by main design, the thickness of this film does not meet the requirement that the shrink wrapping cover is used.
In addition, described pair of foam method method must be carried out on the production line of the heating and cooling device that comprises main blown film production line and add, because investment and cost of serving, this makes that whole production line is unaccommodated economically.
On the other hand, the shrinkage deficiency of WO 97/22475 disclosed film all comprises propylene copolymer (this is unaccommodated economically) in two skins, and the foam stability that demonstrates in film blowing step (bubble stability) deficiency.
Known ground, the blowing heat-shrinkable film for preparing by the film forming method that froths is applicable to manufacturing shrink wrapping cover.Use for this class, in case described encasement cover install on the object to be wrapped, by the object behind the suit is introduced in the heated oven, perhaps by using thermal stress along described film encasement mobile gas or electrically heated framework.Be delivered to the result of described film as heat, shrink process, (frozen) mechanical stress of freezing is relaxed, and the size of the described film of result reduces.In this way, described object is closely kept or is protected, and avoids the ectocine such as rainwater, dust pollution, finger mark etc.Contraction process during encasement is produced has been described in for example US 3 673 703, US 3 727 324, US 3 744146, US 5 471 818, EP 0 252 527, EP 0 375 850, EP 0 649 791, GB 2 014534.
Because its good shrinkage character, more general based on LDPE as the standard heat-shrinkable blown film of key component, but also being based on poly the time when object to be wrapped, the LDPE encasement may adhere on this object.
Adhere to problem on the object to be wrapped for fear of encasement, US 3 933 244 has instructed the heat-shrinkable LDPE film encasement of using anti-stick company additive agent modified, and purpose is to reduce described encasement and the contact area that is wrapped in an object in the polyethylene film.Yet, adhere in this way and can only reduce to a certain degree, and can not be eliminated.
Selectively, described film can be to comprise the outer field multilayer film of non-adhesive, and this skin is used for contacting with the polyethylene object, thereby avoids any contact the between described polyethylene shrinkage layer and the described polyethylene object.Usually by under shrinkage temperature, having skin lower or that do not have an affinity to obtain described non-adhesive, this low or not have affinity be because the physical incompatibility between outermost resin and the polyethylene to polyethylene.Yet because described skin has lower to polyethylene shrink film or not adhesion, this can cause sealing the stress induced separation of generation.Therefore, need provide the compatibility layer between described non-adhesive skin and described polyethylene shrinkage layer, this compatibility layer is commonly referred to tack coat (tie layer).In this case, described polyethylene shrinkage layer is by two-layer at least additional rete and the separated theca externa of object to be wrapped, and this two-layer extra play is outer at least non-adhesive layer and intermediate adhesive layer.For the production cost of minimum membrane, the outer field thickness of intermediate adhesive layer and non-adhesive all is set at low as much as possible.Therefore, with respect to intermediate adhesive layer and both thickness of non-adhesive skin, the outer layer polyethylene shrinkage layer has the thickness that accounts for leading (prevailing) usually, thereby produces asymmetric film.Such asymmetrical membrane structure needs asymmetric blown film extruding production line, and this production line is necessary for this purpose specialized designs.The custom-designed blown film extruding production line of this class is by first extruder and auxiliary (additional) second and the 3rd extruder formation, first extruder is used to extrude the polyethylene shrinkage layer with leading thickness, and the second and the 3rd extruder is respectively applied for and extrudes described intermediate adhesive layer and non-adhesive skin, and this two-layer thickness is all less than the thickness of polyethylene shrinkage layer.
European application EP-A1-1 332 868 has provided the example by multilayer heat shrinkable film blown film extrusion molding preparation, that be used to cannot not produce stickingly encasement.More specifically, EP-A-1 332 868 discloses and has comprised the polyethylene shrinkage layer with leading thickness, the outer field film of non-adhesive that comprises the intermediate adhesive layer of LLDPE and propylene copolymer or vinyl acetate copolymer and comprise one or more propylene copolymers.
Summary of the invention
In sum, the present patent application people has been known provides multilayer heat shrinkable film, be applicable to that particularly preparation does not fuse the demand of shrink wrapping cover, this heat-shrinkable film has the shrinkage and the sealing of improvement, cohesive between the adjacent layer that improves, but can not adhere on possible lower floor's level package film, perhaps adhere to substantially on lower floor's object of making by polyethylene, can produce in flexible and simple mode by the standard film extrusion equipment simultaneously.
In other words, the technical problem that the present invention relates to provides multilayer heat shrinkable film, and do not fuse the shrink wrapping cover by what it was made, it goes up processing at any conventional film extrusion equipment (for example standard symmetric membrane blowing production line) easily, can be in low shrinkage temperature (being generally 110 ℃ to 180 ℃) thermal contraction down, can be at heat seal under the low seal temperature, and in case also can be not adhered thereto when being retracted on the object to be wrapped.
The applicant has found to improve the shrinkage and the sealing intensity of the multilayer heat shrinkable film that comprises at least one first, second and tertiary membrane layer, the mode of avoiding undesirable interlayer to separate simultaneously, this mode is that all to have at least a density be 0.920 to arrive 0.950g/cm at least two adjacent film layers of imagination in described at least three retes (promptly be used for the skin that contact with environment, and be arranged at the internal layer between the latter and the skin that is used to contact object to be wrapped)
3, i.e. linear polyethylene in the scope of LLDPE (LLMDPE) and linear density polyethylene (LMDPE) substantially.
Avoid any bonding phenomenon between described heat-shrinkable film and the object to be wrapped simultaneously in order to ensure the suitable sealing function of described film, also imagine the rete that is used for contacting according to the present invention and comprise specific propylene copolymer with object to be wrapped.
Therefore, the present invention relates to multilayer heat shrinkable film, wherein at least two adjacent layers (above-mentioned ground floor and the 3rd layer) comprise linear ethylene copolymer, particularly ethene with have the linear copolymer of the alpha-olefin of 3-12 carbon atom, and one deck (the above-mentioned second layer) comprises specific propylene copolymer at least.
In other words, solved above-mentioned technical problem by multilayer heat shrinkable film, this multilayer is received heat-shrinkable film and is comprised:
A) it is 0.920 to 0.950g/cm that at least one first rete, this rete comprise density
3Linear ethylene copolymer;
B) at least one second rete, this rete comprise propylene and ethene and/or one or more and plant CH
2=CHR
1First copolymer of alpha-olefin, wherein R
1For having the alkyl of 2-10 carbon atom;
C) it is 0.920 to 0.950g/cm that at least one tertiary membrane layer, this rete comprise density
3Linear ethylene copolymer;
Wherein said at least one first rete is arranged between described at least one second rete and described at least one tertiary membrane layer.
For the purpose of this specification and following claim, unless opposite indication is arranged, in all cases, the numerical value of all expression content, quantity, percentage or the like all is interpreted as being modified by term " about ".Simultaneously, any scope includes the optional combination of disclosed maximum point and smallest point, and comprises optional intermediate range therebetween, and these scopes may specifically be enumerated also in this article and may not enumerate.
More specifically; in case use described film; preferably as being applicable to protection object (or set of a plurality of objects) packaging film not affected by environment; when more preferably conduct does not fuse the shrink wrapping cover; described first rete is used to constitute its internal contraction layer; be that described layer has been given described multilayer film heat shrinkability characteristic substantially; and the described second layer is used to constitute the layer of sealing object to be wrapped; promptly this layer is used for contacting with this class object substantially; and described tertiary membrane layer is used to constitute the interface with external environment condition, by the protected influence that is not subjected to this external environment condition of its described object.
Based on described tertiary membrane layer comprise with described first rete in the fact of identical linear tetrafluoroethylene polymer, be density 0.920 to 0.950g/cm based on this polymer especially
3The fact of linear ethylene copolymer, the shrinkage that may advantageously be improved with respect to each tunic that comprises the single rete that comprises linear ethylene copolymer.In other words, provide two aforementioned adjacent LLDPE that comprise hereinafter further definition and/or first rete and second rete of LMDPE, be considered to obtain the inotropic improvement of above-mentioned film.
More specifically, film of the present invention can be exposed to uniform temperature, particularly during 110 ℃ to 180 ℃ relatively low temperature, shrinks.
Film of the present invention can also be exposed to uniform temperature, during particularly relatively low temperature, and the performance sealing function.
In addition, all to comprise density be 0.920 to 0.950g/cm for described first rete and tertiary membrane layer
3The proposition of linear ethylene copolymer, advantageously make the foam stability that in film blowing process, obtains improvement.
Further advantage is, based on above-mentioned membrane structure, particularly be arranged between described at least one second film and described at least one tertiary membrane and (promptly be positioned at the center of described film based on described first rete (promptly giving the layer of described multilayer film heat shrinkability characteristic substantially), be clipped in two intermediate layers between the outside rete) the fact, even when described ground floor has when accounting for leading thickness with respect to described second and third layer, described film still can have basic symmetrical structure, and this general better illustrates with reference to the preferred embodiment of film of the present invention hereinafter.Therefore, film of the present invention can be advantageously has on the standard symmetry blowing production line of balanced configuration according to the production of film blowing extrusion method, thereby avoids the demand to custom-designed extrusion equipment.
In this specification and following claim, standard " symmetrical blowing production line " refers to be applicable to the blowing production line of producing conventional multilayer symmetry blown film.This production line comprises at least three extruders that are connected in parallel to each other and are provided with, wherein Zhong Jian extruder is used to form intermediate layer (preferably have and account for leading thickness), and other extruders that are arranged on the side and have a same size for extruder in the middle of first are respectively applied for second and the tertiary membrane layer.
By this way, may advantageously produce film of the present invention by conventional extrusion-blown modling equipment with balanced configuration.
(promptly be used for constituting sealing object to be wrapped based on described second rete, thereby the rete that will contact) comprises the fact that can not adhere to the propylene copolymer on the polyethylene with this object, advantageously when described object make by polyethylene substantially or and then when being wrapped in the polyethylene film, described second rete can not adhere on the described object yet.In this way, multilayer heat shrinkable film of the present invention can be advantageously used in the packing by the object that constitutes based on poly material, perhaps is wrapped in the packing by the object in the level package of forming based on poly material.
In addition, multilayer heat shrinkable film of the present invention comprises propylene copolymer in a skin (being described second rete), and it is more convenient economically with respect to having two outer field films that comprise propylene copolymer in the prior art to make film of the present invention.
The propylene copolymer of second rete has sufficient adhesiveness to the ethylene copolymer of first rete, thereby can not observe a layer segregation phenomenon between these retes.Therefore, needn't provide the above reference tack coat that argumentation of the prior art is described.
The copolymer of described at least one first rete and at least one tertiary membrane layer is that density is 0.920 to 0.950g/cm
3Linear ethylene copolymer, thereby comprise that LLDPE (LMDPE), linear density polyethylene (LMDPE) and density are higher than 0.940g/cm
3Linear copolymer (it is commonly referred to high density polyethylene (HDPE) (LHDPE)).
In this specification and following claim, term LLDPE, LMDPE and LHDPE are used to indicate a class mainly to comprise the polymer of ethene and the linear copolymer of the alpha-olefin with 3-12 carbon atom.
With according to the free radical polymerisation process preparation of under high pressure (about 1500-3000 crust), carrying out, highly cladodification conventional low, in or the high density polyethylene (HDPE) molecule different, the molecule of LLDPE, LMDPE and LHDPE copolymer obtains according to the catalytic polymerization that carries out in low pressure (promptly being lower than 50 crust), and, therefore be called as " linearity " because to comprise long Polyethylene Chain and comonomer side chain branch or cross-linked structure less relatively.
Preferably, above-mentioned ethene linear copolymer mainly comprises one or more CH
2=CHR alpha-olefin, wherein R is the alkyl with 1-10 carbon atom, for example propylene, 1-butylene, 1-amylene, 1-hexene, 4-methyl-1-pentene and 1-octene, preferably 1-butylene, 1-hexene and 1-octene, more preferably 1-butylene.
Preferably, according to the range (thereby depending primarily on the catalyst that is used to prepare this copolymer) of molecular weight of copolymer distribution and the density of copolymer, above-mentioned ethene linear copolymer comprises one or more CH of 20mol% at the most
2=CHR alpha-olefin, it is preferably selected from above-mentioned group, more preferably 2-20mol%.
Preferably, the density of above-mentioned linear ethylene copolymer is 0.920 to 0.940g/cm
3
In this preferred density scope, film of the present invention has advantageously possessed enough rigidity (stiffness).
More preferably, described linear ethylene copolymer has 0.927 to 0.943g/cm
3Density, further preferred, described linear ethylene copolymer has 0.930 to 0.940g/cm
3Density.
Advantageously, wherein the density of the linear ethylene copolymer film that is positioned at this preferable range has the mechanical performance of enhancing, particularly aspect creep resistance, anti-tearing autgmentability, puncture resistance and impact resistance, and particularly aspect its improved balance.In addition, in this preferred density value, advantageously obtain the further improvement of rigidity, this advantageously feasible thickness that can reduce film.
According to the preferred embodiments of the invention, the linear ethylene copolymer of first rete and tertiary membrane layer has the MFR (190/2.16) that is lower than the 5.0g/10 branch, and more preferably less than 3.0g/10min, and more a step preferably is lower than 1.0g/10min.
In this specification and following claim, term " MFR " refers to " melt flow rate (MFR) ".This melt flow rate (MFR) MFR (190/2.16) records under the load of 2.16kg at 190 ℃ according to ISO1133.
Based on above-mentioned preferred melt flow rate value, described linear ethylene copolymer is particularly advantageous in the rheological property aspect mobile, thereby has extrudability easily, kept particularly foam stability of machinability simultaneously, thereby made film of the present invention to produce by the film blow moulding.In addition, in above-mentioned preferred L FR scope, can advantageously can obtain in machine direction (machine direction) and the heat shrinkable multilayer film that laterally all has the shrinkage of balance, thereby further improve the shrinkage character of heat shrinkable multilayer film of the present invention.
More preferably, the MFR of described linear ethylene copolymer (190/2.16) is lower than 0.8g/10min, further preferably is lower than 0.5g/10min, more particularly is lower than 0.3g/10min, and especially more particularly is lower than 0.25g/10min.
Particularly preferred MFR (190/2.16) scope is 0.05-1.0g/10min, more preferably 0.05-0.8g/10min, further preferred 0.05-0.3g/10min, and further preferred 0.1-0.25g/10min.
Preferably, the linear ethylene copolymer of first rete and tertiary membrane layer has the MFR (190/21.6) that is lower than 21.0g/10min, more preferably less than 14.0g/10min, and further preferably 10.0g/10min is to 14.0g/10min, and particularly 11.0g/10min is to 14.0g/10min.
In this case, this melt flow rate (MFR) MFR (190/21.6) records under the load of 21.6kg at 190 ℃ according to ISO1133.
According to the preferred embodiment of multilayer heat shrinkable film of the present invention, described first rete does not contain vinyl acetate copolymer substantially, and vinyl acetate copolymer content is lower than the 1wt% of the described first rete gross weight especially.
Preferably, removing described density is 0.920-0.950g/cm
3And more preferably outside the linear ethylene copolymer of density in above-mentioned most preferred range, the propylene copolymer that provides in described second rete also is provided described first rete, i.e. propylene and ethene and/or one or more CH
2=CHR
1The copolymer of alpha-olefin, wherein R
1It is alkyl with 2-10 carbon atom.
By this method, advantageously between described first rete and second rete, obtain improved adhesiveness.
This class propylene copolymer that randomly provides in described first rete preferably provides with the amount of the 10wt% that is lower than the described first rete gross weight, and more preferably content is 0.5-5wt%, and more preferably content is 0.5-3wt%.
Randomly the propylene copolymer that provides in described first rete can have following at the described preferred feature of second rete, although preferred embodiment described below mainly is to describe by the feature of further qualification second rete, the consideration that propylene copolymer is done all is effective for propylene copolymer that provides in second rete and the propylene copolymer that randomly provides in first rete.
Preferably, described second rete comprises first propylene copolymer that contains the propylene that is higher than 70% weight.
In this way, advantageously avoid any bonding between multilayer film of the present invention and the object to be wrapped fully, particularly make by polyethylene substantially when described object, perhaps by the time based on poly level package film parcel.
Preferably, described second rete comprises first propylene copolymer, and this propylene copolymer is propylene and one or more C
4-C
10The random copolymer of alpha-olefin, or propylene and one or more C
4-C
10The mixture with different random copolymers of forming of alpha-olefin, described copolymer or copolymer mixture comprise the alpha-olefin unit of 4-14% weight.
According to selectable embodiment of the present invention, described second rete comprises first propylene copolymer, the insoluble part of the dimethylbenzene of this propylene copolymer surpasses 80%, preferably surpasses 85%, the temperature of maximum melting peak is higher than 120 ℃, and crystalline content (crystallinity content) makes that the percentage of melted material is higher than 10% in the time of 90 ℃.
In order to measure the xylene soluble part, with polymer and the 250cm of 2.5g
3Dimethylbenzene introduce and to be equipped with in the glass flask of refrigerator and magnetic stirrer.In 30 minutes, temperature is increased to boiling point up to solvent.The settled solution that will obtain in this way subsequently keeps refluxing and stirring 30 minutes.Flask with sealing kept in ice-water bath 30 minutes subsequently, and kept 30 minutes in 25 ℃ water bath with thermostatic control.Leaching formed solid on the filter paper fast.With 100cm
3The filtrate impouring aluminium vessel of weighing in advance in, it flows down on heating plate at nitrogen and heats, and desolvates thereby remove by evaporation.Subsequently this container is remained in 80 ℃ the vacuum drying oven, up to constant weight.
Use method described below, measure maximum melting peak and crystalline content to fixed temperature by differential scanning calorimetry (DSC).
Preferably, the degree of crystallinity that had of described first propylene copolymer makes that the percentage of melted material surpasses 15% in the time of 90 ℃; More preferably described degree of crystallinity makes that the percentage of melted material surpasses 20% in the time of 100 ℃, and the percentage of melted material surpasses 30% in the time of 110 ℃.
Preferably, so first propylene copolymer comprises the unit, the particularly unit of the derived from propylene of 80-94% weight of the derived from propylene that surpasses 70% weight usually, the units derived from ethylene of 1-5% weight, and 5-15% weight derived from CH
2=CHR
1The unit of alpha-olefin.
According to the preferred embodiments of the invention, the MFR (230/2.16) of first propylene copolymer that provides in described at least one second rete is lower than 10g/10min, more preferably be included in the scope of 0.2-8.5g/10min, further be preferably 0.5-1.0g/10min.
For purpose of the present invention, term " MFR (230/2.16) " refers to according to ISO1133 230 ℃ of polyacrylic " melt flow rate (MFR)s " that record under the load of 2.16kg.
Preferably, described second rete also comprises propylene and ethene and/or at least a CH
2=CHR
1Second copolymer of alpha-olefin, wherein R
1It is alkyl with 2-10 carbon atom.When described comonomer was ethene, described copolymer preferably comprised the units derived from ethylene of 1-5% weight.In this case, described second rete preferably comprises the propylene of 40-80 weight portion and first copolymer of ethene, and second copolymer of the propylene of 20-60 weight portion and ethene.
According to the preferred embodiments of the invention, the MFR (230/2.16) of second propylene copolymer that provides in described at least one second rete is lower than 10g/10min, more preferably be included in the scope of 4-8g/10min, and further preferably be contained in the scope of 4-6g/10min.
The composition that comprises above-mentioned first and second propylene copolymers can prepare by two kinds of components of molten condition are mixed, and for example homogenizes in the mixer of ability having height, perhaps selectively directly in extruder.The composition that comprises these first and second propylene copolymers preferably directly prepares by the synthetic method of using sequential polymerization, described polymerization comprises at least two stages, wherein, in each stage, make propylene and ethene and/or at least a and/or at least a CH by optional order
2=CHR
1Alpha-olefine polymerizing, wherein R
1Be alkyl, thereby obtain the first above-mentioned copolymer and second copolymer with 2-10 carbon atom.
As exemplary example, described method can comprise two stages, wherein makes ethene and propylene polymerization in the phase I, thereby obtains second copolymer of propylene and ethene, it contains the units derived from ethylene of 1-5% weight, and makes ethene, propylene and CH in second stage
2=CHR
1Alpha-olefine polymerizing, thus obtain first copolymer, it contains the unit of the derived from propylene of 80-94% weight, the units derived from ethylene of 1-5% weight and 5-15% weight derived from CH
2=CHR
1The unit of alpha-olefin.
Described CH
2=CHR
1Alpha-olefin is selected from 1-butylene, 1-amylene, 1-hexene, 4-methyl-1-pentene and 1-octene usually, preferred 1-butylene.
According to the preferred embodiments of the invention, described second rete comprises composition, and said composition comprises propylene and ethene and/or one or more CH
2=CHR
1First copolymer of alpha-olefin, wherein R
1Be alkyl with 2-10 carbon atom, optional second copolymer that comprises propylene and ethene, it preferably contains the units derived from ethylene of 1-5% weight, and density is 0.920 to 0.950g/cm
3Linear ethylene copolymer.In this way, further strengthen adhesiveness between described first and second retes.
Preferably, described second rete comprises hemicrystalline polyolefin composition, and said composition comprises:
A) propylene of 20-60% and C
4-C
10The random copolymer of alpha-olefin, it contains the C of 1-10% weight
4-C
10Alpha-olefin; And
B) propylene of 40-80% and C
4-C
10The random copolymer of alpha-olefin, it contains the C of 15-40% weight
4-C
10Alpha-olefin.
Advantageously, the fusing point of this based composition is 135 ℃ to 150 ℃, and the part that dissolves in dimethylbenzene in the time of 25 ℃ is lower than 20%, is usually less than 16%, and the heat seal temperature is 90-105 ℃.
More preferably, described second rete comprises semicrystalline polyolefin composition, and said composition comprises hemicrystalline polyolefin composition, and it comprises the random copolymer of three kinds of propylene, that is:
A) 25-40%, propylene and at least a C that is selected from of preferred 28-38%
4-C
10The random copolymer of the comonomer of alpha-olefin, it comprises the repetitive derived from described comonomer of 2-10% weight;
B) 25-40%, propylene and at least a C that is selected from of preferred 26-36%
4-C
10The random copolymer of the comonomer of alpha-olefin, it comprises the repetitive derived from described comonomer of 10-20% weight; And
C) 25-40%, propylene and at least a C that is selected from of preferred 28-38%
4-C
10The random copolymer of the comonomer of alpha-olefin, it comprises the repetitive derived from described comonomer of 6-12% weight, wherein derived from the total amount (for described composition) of the repetitive of described comonomer more than or equal to 6%, and represent separately copolymer a), b) and c) in the percentage and in all the other two kinds of copolymers each of described repetitive content in each copolymer all inequality, be at least 1 unit (unit), preferred 1.5 units with each this difference of repetitive percentage in all the other two kinds of copolymers.
Usually, the sealing initiation temperature of described preferred composition is 110 ℃ to 120 ℃, and the VICAT value that records according to the ISO306 method is generally 115-140 ℃, and the heat distortion temperature value is 65-75 ℃.
According to other preferred embodiments of the present invention, described second rete comprises the polyolefin composition of crystallization, and it comprises:
A) 20-60%, the propylene of preferred 25-45% weight and the random copolymer of ethene, it contains 1-5%, the ethene of preferred 2-5% weight; And
B) 40-80%, the propylene of preferred 55-75% weight and ethene and one or more C
4-C
8The random copolymer of alpha-olefin, ethylene contents are 1-5%, preferred 2-5% weight, C
4-C
8The content of alpha-olefin is 6-15%, preferred 6-12% weight,
Ethylene total content in the wherein said composition is 1-5%, and the C in the described composition
4-C
8The alpha-olefin total content is 2.4-12%.
Advantageously, the fusing point of this class preferred composition is 126-147 ℃, and sealing initiation temperature is 90-114 ℃, and the part that dissolves in n-hexane 50 ℃ the time is lower than 5.5%.
Be suspended in the excessive hexane by membrane sample, in excessive hexane, in autoclave, keep measuring in 2 hours the part that dissolves in n-hexane in 50 ℃ with the composition to be analyzed of 100 micron thickness.Make the hexane evaporation subsequently, and the dry residue of weighing.
According to other preferred embodiments of the present invention, described second rete comprises the propylene copolymer compositions of crystallization, and it comprises:
A) one or more of 20-80% are selected from following propylene copolymer: the propylene/ethylene copolymer that (a1) contains 1-7% ethene; (a2) propylene and one or more C
4-C
8The copolymer of alpha-olefin, it contains the described C of 2-10%
4-C
8Alpha-olefin; (a3) propylene and ethene and one or more C
4-C
8The copolymer of alpha-olefin, it contains the ethene of 0.5-4.5% and the C of 2-6%
4-C
8Alpha-olefin, condition are ethene and the C in (a3)
4-C
8The total content of alpha-olefin is less than or equal to 6.5%; With
B) one or more of 20-80% are selected from following propylene copolymer: (b1) propylene and one or more C
4-C
8The copolymer of alpha-olefin contains the C of 10-30%
4-C
8Alpha-olefin; (b2) propylene and ethene and one or more C
4-C
8The copolymer of alpha-olefin contains the ethene of 1-7% and the C of 6-15%
4-C
8Alpha-olefin.
This preferred compositions advantageously has low sealing initiation temperature, be usually less than 100 ℃, the part that dissolves in organic solvent or the extraction of available organic solvent of low content, in n-hexane, be less than or equal to 5% weight when in dimethylbenzene, being less than or equal to 20% weight and 50 ℃ in the time of common 25 ℃, and low-down turbidity (haze values), be usually less than 0.5-1%.
Preferably, the melt flow rate (MFR) MFR of this class preferred composition (230/2.16) value is 2-15g/10min, and through after the degraded, the same composition that comprises aforementioned proportion a) and b) MFR (230/2.16) value of precursor composition be 0.3-5g/10min, preferred 0.5-3g/10min, and the MFR of final composition (230/2.16) is 2-20 to the ratio of the MFR (230/2.16) of precursor composition, preferred 3-15.
Based on this preferable feature, this embodiment utilizes this composition to form second rete, it advantageously has low sealing initiation temperature, be usually less than 100 ℃, the part that dissolves in organic solvent or the extraction of available organic solvent with low content, usually in dimethylbenzene less than equaling 20% weight, and low-down turbidity is usually less than 0.5-1%.
According to another preferred embodiment of the present invention, described second rete comprises composition, and said composition contains:
A) 15-60%, preferred 20-60%, the more preferably propylene of 20-50% and C
4-C
8The copolymer of alpha-olefin, it contains and surpasses 10%, preferred 11% or higher, but is lower than 14%, more preferably the described C of 13-13.5% at the most
4-C
8Alpha-olefin;
(b) 40-85%, preferred 40-80%, the more preferably propylene of 50-80% and C
4-C
8The copolymer of alpha-olefin contains 14-30%, preferred 14.5-25%, the more preferably described C of 14.5-22%
4-C
8Alpha-olefin, and the optional ethene that contains 0.5-3%, condition is the C in the prolylene polymer composition
4-C
8The total amount of alpha-olefin is higher than 10%.
Advantageously, this based composition has low sealing initiation temperature, is usually less than 100 ℃, the part that dissolves in organic solvent or the extraction of available organic solvent with low content, usually in dimethylbenzene less than equaling 20% weight, and low-down turbidity is usually less than 0.5-1%.
The melt temperature of described preferred composition is generally 125-140 ℃.
The comonomer of above-mentioned copolymer can be identical or different, is preferably selected from 1-butylene, 1-amylene, 1-hexene, 4-methyl-1-pentene and 1-octene, more preferably the 1-butylene.
According to the preferred embodiments of the invention, above-mentioned second rete also comprises linear ethylene copolymer, and it preferably has 0.915 to 0.950g/cm
3Density, more preferably 0.920 to 0.950g/cm
3, further preferred 0.927 to 0.943g/cm
3, preferred especially 0.930 to 0.940g/cm
3
Advantageously, described second rete has the adhesiveness of improvement to first rete.
According to an alternative embodiment of the present invention, all to comprise density be 0.920 to 0.950g/cm for described at least one first film and described at least one tertiary membrane layer
3Linear ethylene copolymer, but described at least one first rete comprises the linear ethylene copolymer that density is lower than described at least one tertiary membrane layer density.Selectively, all to comprise density be 0.920-0.950g/cm for described at least one first film and described at least one tertiary membrane layer
3Linear ethylene copolymer, but described at least one first rete comprises the linear ethylene copolymer that density is higher than described at least one tertiary membrane layer density.Preferably, to comprise density be 0.930-0.950g/cm to described at least one first rete
3Linear ethylene copolymer, be 0.920-0.943g/cm3 and described at least one tertiary membrane layer comprises density, 0.927-0.943g/cm more preferably
3Linear ethylene copolymer, be lower than the density of the linear ethylene copolymer of described at least one first rete.
According to an alternative embodiment of the present invention, described at least one tertiary membrane layer can comprise and is selected from the polymer that is provided at the polymer in described first and second retes, condition is when described tertiary membrane layer comprises above-mentioned first propylene copolymer, and the density of described linear ethylene copolymer is 0.930 to 0.940g/cm
3Particularly, according to preferred embodiment, described heat-shrinkable film comprises that at least one contains density is 0.930 to 0.940g/cm
3First rete of linear ethylene copolymer; At least one contains propylene and ethene and/or one or more CH
2=CHR
1Second rete of first copolymer of alpha-olefin, wherein R
1Be the alkyl of 2-10 carbon atom, and described first copolymer contains the propylene that surpasses 70% weight; And at least one comprises the tertiary membrane layer of this class first propylene copolymer, and wherein said at least one first rete is arranged between described at least one second film and at least one tertiary membrane.
When the density of described linear ethylene copolymer is positioned at this scope, can advantageously prepare with respect to (subtracting thick by the use less dense, downgauging) the multilayer film thickness that ethylene copolymer obtains reduces, but realizes the multilayer film of effective seal effect simultaneously under temperature lower for the seal temperature that shows with respect to more highdensity ethylene copolymer.
According to the preferred embodiments of the invention, it is 0.920 to 0.950g/cm that described first rete comprises density
3Linear ethylene copolymer, and described tertiary membrane layer comprises polymer composition, said composition comprises that density is 0.920 to 0.950g/cm
3Linear ethylene copolymer, and contain propylene and ethene and/or one or more CH that surpasses 70% weight acrylamide
2=CHR
1The copolymer of alpha-olefin, wherein R
1Alkyl for 2-10 carbon atom.
What limit in the claims 1 has above-mentioned feature a) to c) film can advantageously to be processed into thickness be that 25-160 μ m reaches higher any film.Preferably, the thickness of described film is between 40 and 140 μ m, more preferably between 60 and 120 μ m.
According to the preferred embodiments of the invention, described heat shrinkable multilayer film comprises at least one first rete with first thickness, and this first thickness accounts for leading (promptly higher) with respect to the thickness of described at least one second rete and the thickness of described at least one tertiary membrane layer.
In this way, commercially available co-extruded films blowing production line can be advantageously used in preparation multilayer heat shrinkable film of the present invention, described production line is widely used in numerous films and extrudes application, and comprises extruder and at least two auxiliary extruders that are arranged on this first middle extruder side in the middle of first.
Different layers can be different with respect to the content of described film gross weight.
Preferably, the thickness of described first rete constitutes at least 33% of described film gross thickness, and more preferably at least 40%, further preferably at least 50%.
Preferably, described at least one first rete have described relatively second and the tertiary membrane layer in each rete account for leading thickness, and the thickness of described at least one second rete is preferably basic identical with the thickness of described tertiary membrane layer.More specifically, described second rete and tertiary membrane layer preferably make by the sidepiece extruder with same size, and this size is less than the size of the middle extruder that is used to prepare described first rete.
According to embodiment preferred, the thickness of described second rete preferably is set to low as far as possible, preferably is lower than 15 μ m, thereby production cost is minimized.
According to selectable embodiment, the thickness of described at least one second rete also can be different from the thickness of described tertiary membrane layer.Therefore, for example, the thickness of described at least one second rete can be lower than the thickness of described tertiary membrane layer.In this way, can make the amount of used propylene copolymer minimum expediently, and then make the production cost minimum of above-mentioned film.
Preferably, the thickness of described second rete is different from the thickness of described tertiary membrane layer, but difference is no more than 60%, more preferably no more than 50%, further preferably is no more than 40%.
Preferably, the thickness of described second rete is lower than 25% of multilayer heat shrinkable film gross thickness of the present invention, and more preferably 20%, further preferred 15%.
Preferably, film of the present invention comprises aforesaid three layers.According to other preferred embodiments of the present invention, also can expect to comprise and surpass three layers film.For example, the preferred embodiment of multilayer heat shrinkable film of the present invention can comprise 5 layers, promptly except that above-mentioned first, second and tertiary membrane layer (wherein said first rete is arranged between described second rete and the described tertiary membrane layer), also comprise two mainly based on poly additional layer, they be clipped in respectively described first rete and described second and and described tertiary membrane layer between.Described first rete preferably all has with respect in other four retes each and accounts for leading thickness.
According to second aspect, the present invention relates to produce the method for above-mentioned multilayer heat shrinkable film, described method comprises the steps:
-make above-mentioned linear ethylene copolymer and above-mentioned first propylene copolymer, reach the randomly above-mentioned second propylene copolymer fusion;
-with described linear ethylene copolymer, above-mentioned first propylene copolymer,,, thereby obtain comprising the tubular film of above-mentioned first, second and the 3rd layer by the ring mould coextrusion randomly with the described second optional propylene copolymer; And
-described tubular film is collapsed to described multilayer film.
Heat shrinkable multilayer film of the present invention can use method well known in the art to prepare expediently, for example froth into embrane method, the polymers compositions that will constitute each layer according to this method is extruded the preparation tubular film, the wherein said mould of extruding by having annular opening carries out, thereby has the shape of tubulose when the polymer of fusion leaves mould.By between pipe internal pressure and pipe external pressure, forming pressure differential, described melt polymerization property management is expanded keep tubulose simultaneously.A kind of method for optimizing that forms pressure differential is to use the source of the gas of blowing in pipe.In the time of in air is blown into pipe, makes and move that pipe stretches and expansion by being higher than the outer atmospheric air pressure inside of pipe.
Make its cooling when moving up subsequently, along with the melt polymer material pipe.By ventilation ring (air ring), blow cooling blast by outer surface and can quicken this cooling procedure around described pipe.Along with described melt polymer material cooling, it is transformed into solid polymer membrane through phase transformation.Molten polymer membrane crystallization and the point that becomes solid are defined as frost line (frost line) or crystallization line, thereby it has divided the boundary between melted material and the solidification material.Surpass this frost line, then the distortion of described pipe can be ignored, and described pipe only is made of monophase materials (polymer that solidifies).
Advantageously, as previously mentioned, multilayer heat shrinkable film of the present invention has improved foam stability, shows as the foam that forms in the blowing process and axially and radially all has regular shape.In other words, described foam has on the one hand at the frost line that axially keeps settling position, has constant diameter on the other hand.Based on these features, advantageously has constant thickness by the film of described foam preparation.
According on the other hand, the present invention relates to above-mentioned multilayer heat shrinkable film as the packing heat-shrinkable film that is used to wrap up object or the set of a plurality of object, the purposes of the heat-shrinkable film of the form that particularly " do not fuse the shrink wrapping cover ".If described object, in fact can not observed bonding or adhesion substantially by making based on poly material between described film and described object.
In addition, the present invention relates to the purposes of above-mentioned multilayer heat shrinkable film as secondary package, described secondary package is used to wrap up the level package that is made of polyethylene substantially.
Detailed description of preferred embodiments
By following examples the present invention has been carried out further instruction.
Measure every character of reporting among the described embodiment by the following method.
Polymer is formed: by
13The FTIS (FTIR) of C-NMR calibration detects the percentage by weight of each monomer.
Be insoluble to the part of dimethylbenzene: stir with the 2g polymer dissolution at 250cm
3, in 135 ℃ the dimethylbenzene.After 20 minutes, allow gained solution cool off under stirring, reach 25 ℃ up to temperature.After 30 minutes, by filtering to isolate the insoluble polymer of precipitation.From described solution, remove solvent by evaporation in nitrogen stream, and with residue 80 ℃ of vacuum drying to constant weight.In this way, calculate the polymer percentage in the dimethylbenzene that dissolves in 25 ℃, thereby determine the percentage of insoluble polymer.
Measure melt temperature according to ISO 3146.
Measure density according to ISO 1183.
To measuring acrylic polymers and polyvinyl melt flow rate (MFR) respectively at 230 ℃ and 190 ℃ under the fixed load.Melt flow rate (MFR) (MFR) is under given weight, and respectively when the temperature of 230 ℃ and 190 ℃, what calibrate to that the testing equipment of ISO 1133 extruded in 10 minutes is the amount of polymers of unit with the gram.Particularly, measure melt flow rate (MFR) according to the following condition that provides:
Melt flow rate (MFR) MFR (190/2.16): ISO1133:2005 (E), condition D.
Melt flow rate (MFR) MFR (190/21.6): ISO1133:2005 (E), condition G.
Melt flow rate (MFR) MFR (230/2.16): ISO1133:2005 (E), condition M.
Measure shrinkage character according to ISO 14616.
Table 1 has shown the polymer of the film that is used to prepare each embodiment, i.e. the propylene copolymer represented of the ethylene copolymer represented of A and B, composition and character thereof.
Table 1
| Character | A | B |
| C 2(% weight) | 95 | 4 |
| C 3(% weight) | - | 90 |
| C 4(% weight) | - | 6 |
| C 6(% weight) | 5 | - |
| Density g/cm 3 | 0.937 | 0.900 |
| MFR(190/2.16)g/10min | 0.10 | - |
| MFR(190/21.6)g/10min | 13.0 | - |
| MFR(230/2.16)g/10min | - | 0.9 |
| Melt temperature ℃ | 124 | 133 |
The preparation of film: general process
Prepare trilamellar membrane by the film blow moiding method, this method comprises the steps:
-every kind of polymer feed that will be used to form layer is given extruder separately;
-extrude three layers of tubular film by ring mould, die head temperature (head termperature) is 200-240 ℃;
-with this tubular film expansion (expanding)
-by the source of the gas that air is blown in the described tubular film, make this film remain tubulose simultaneously described pipe inflation by between pipe internal pressure and pipe external pressure, forming pressure reduction;
-blow cooling blast by ventilation ring around the outer surface of described tubular film.
Embodiment 1
As mentioned above, on conventional Macchi film blowing pilot-plant, prepared trilamellar membrane.Concrete extruding with the blow molding operation condition is as shown in table 2.
The trilamellar membrane of embodiment 1 is by constituting with the lower part:
-by first rete that linear medium density ethylene copolymer A constitutes, this copolymer A contains the unit derived from the 1-hexene of the units derived from ethylene and 5% weight of 95% weight, and has the character shown in the table 1;
-by second rete that propylene/1-butene/ethylene trimer thing B constitutes, this trimer B contains the unit of the derived from propylene of 90% weight, 6% weight derived from the unit of 1-butylene and the units derived from ethylene of 4% weight, and have the character shown in the table 1.In addition, this highest trimeric melting peak is at 137 ℃, and degree of crystallinity makes that when being 25.5%, 110 ℃ when the percentage of melted material is 16.5%, 100 ℃ in the time of 90 ℃ be 36.8%, and the insoluble part of its dimethylbenzene surpasses 94.5%;
-tertiary membrane the layer that constitutes by above-mentioned ethylene copolymer A.
Described first rete be arranged on described second and the tertiary membrane layer between.
Obtain the thick film of 80 μ m as mentioned above.In percentage, described first rete accounts for 60%, and described second rete accounts for 15%, and described tertiary membrane layer accounts for 25%.
In table 2, according to the layer that forms by each extruder, with the described extruder of 3,1 and 2 indications: thus the film blowing pilot-plant that is used to make described trilamellar membrane by be used to form above-mentioned first rete first in the middle of extruder 1 and be arranged on extruder 1 side in the middle of described first, be respectively applied for two the auxiliary extruders 2 and 3 that form above-mentioned second rete and tertiary membrane layer and constitute.
The character of gained heat-shrinkable trilamellar membrane is as shown in table 3.
Table 2
Embodiment 2
Operate as described in example 1 above, make trilamellar membrane.Extrude and the actual conditions of blow molding operation identical with shown in the table 2, unique difference is the charging of extruder 2.More specifically, the trilamellar membrane of embodiment 2 is by constituting with the lower part:
-first rete formed by copolymer A;
-second rete formed by the copolymer A of the copolymer B of 80% weight and 20%; And
-tertiary membrane the layer formed by copolymer A.
Described first rete be arranged on described second and the tertiary membrane layer between.
Described in the conventional method of the film production that is used for carrying out according to the film blow moiding method, and under the identical extrusion condition shown in the table 2, operate, making the thick film of 80 μ m, wherein said first rete accounts for 60%, and described second rete accounts for 15%, and described tertiary membrane layer accounts for 25%.
The character of gained heat-shrinkable trilamellar membrane is as shown in table 3.
Embodiment 3
Operate as described in example 1 above, make trilamellar membrane.Extrude and the actual conditions of blow molding operation identical with shown in the table 2, unique difference is the charging of extruder 1 and 2.
More specifically, the trilamellar membrane of embodiment 3 is by constituting with the lower part:
-first rete formed by the copolymer B of the copolymer A of 85% weight and 15% weight;
-second rete formed by the copolymer A of the copolymer B of 80% weight and 20% weight; And
-tertiary membrane the layer formed by copolymer A.
Described first rete be arranged on described second and the tertiary membrane layer between.
Described in the conventional method of the film production that is used for carrying out, and under the identical extrusion condition shown in the table 2, operate, make the thick film of 80 μ m according to the film blow moiding method.Wherein said first rete accounts for 60%, and described second rete accounts for 15%, and described tertiary membrane layer accounts for 25%.
The character of gained heat-shrinkable trilamellar membrane is as shown in table 3.
Embodiment 4
Operate as described in example 1 above, make trilamellar membrane.Except that blow-up ratio equals 3.4, extrude and the actual conditions of blow molding operation identical with described in the embodiment 3.
The composition of the trilamellar membrane of embodiment 4 is identical with the trilamellar membrane of embodiment 3.
The shrinkage character of gained heat-shrinkable trilamellar membrane is as shown in table 3.
More specifically, table 3 has shown the characteristic of heat-shrinkable trilamellar membrane on machine direction (MD) and horizontal (TD) of embodiment 1-4.
Tested in the machine direction (MD) and the horizontal shrinkage character of (TD) according to the method for standard ISO 14616, this test is undertaken by the film of embodiment 1-4 is placed the scheduled time in the baking oven of predetermined temperature.The residing pinch condition of sample is: the heating period is 20s, and the baking oven design temperature is 220 ℃.
Table 3
| Embodiment | Temperature (℃) | F r/mm 2(N/mm 2) | F c/mm 2(N/mm 2) | R (％) |
| 1 | MD 154 TD 159 | 0.13 0.1 | 1.72 0.84 | 57 3 |
| 2 | MD 156 TD 161 | 0.12 0.13 | 1.87 0.87 | 56 4 |
| 3 | MD 152 TD 155 | 0.11 0.07 | 1.82 1.04 | 58 6 |
| 4 | MD 146 TD 154 | 0.07 0.05 | 1.90 1.42 | 48 14 |
Temperature shown in the table 3 refers in machine direction (MD) and horizontal (TD) temperature of detecting at the baking oven place of sealing.
F
rBe convergent force, i.e. the shown force that spendes when described film reaches uniform temperature, this temperature is corresponding to the temperature that causes this stress when producing.High film shrinks less relevant with this power.This little power and high the contraction make described film be retracted in the load lightly.In heating process, detect this power.
F
cBe (contracting) power of dwindling, the power that promptly described film demonstrates in cooling procedure.This power has been guaranteed the tight parcel to described load much larger than described convergent force.
R is a shrinkage ratio, and promptly when sample is elevated to shrinkage temperature, the reduction degree of sample length is expressed as the percentage of initial sample length.This is a kind of tolerance of film retraction (retraction) in the cooling procedure.
As mentioned above, the film that on film blowing pilot-plant, has prepared embodiment 1-4.Result shown in the table 3 shows: if with blow-up ratio be set at that conventional film blowing production equipment is allowed, than the higher value of institute's measured value in the foregoing description, for example about 4-5, can expect the described power of dwindling of further raising, and further improve described film in horizontal shrinkage character.
Also according to standard A STM D 882 methods analysts the sealing characteristics of heat-shrinkable trilamellar membrane of embodiment 1-4.Determine described sealing characteristics by drawing the width (broadness) that seals curve and measure this plateau: the maximal seal strength when having measured different temperatures in this way.Use RDM HSE-3 heat sealer, place 10 samples that 15mm is wide therein, this sample is from the 42X10cm preparing diaphragm in the MD cutting.After under 23 ℃ and 50% relative humidity, regulating (conditioning) 24h, sealing is tested.Air-proof condition is as follows:
-sealing the time: 1.2s
-sealing load: 6 crust
-unit loads (cell load): 100N
-peeling rate: 500mm/min
-seal temperature is 100-160 ℃, each 10 ℃ at interval.
The result is as shown in table 4.
Table 4
| Temperature, ℃ | 100 | 110 | 120 | 130 | 140 | 150 | 160 |
| Maximal seal strength, N-embodiment 1 | 0.14 | 0.63 | 12.54 | 9.79 | 10.39 | 9.47 | 7.30 |
| Maximal seal strength, N-embodiment 2 | 0.34 | 5.91 | 15.21 | 10.54 | 12.79 | 13.81 | 12.06 |
| Maximal seal strength, N-embodiment 3 | 0.37 | 5.71 | 19.79 | 14.38 | 14.32 | 17.96 | 14.91 |
| Maximal seal strength, N-embodiment 4 | 0.35 | 7.13 | 20.27 | 14.02 | 15.53 | 16.89 | 17.53 |
In 120-160 ℃ of seal temperature scope, observe the sealing intensity of raising.
Carried out similar sealing test on the film of correspondence, first rete and tertiary membrane layer are by density 0.920g/cm in described film
3, MFR (190/2.16) is for the conventional LDPE of 0.25g/10min makes, and second rete is made by as above described in embodiments of the present invention propylene copolymer B.Observe and between first rete that LDPE makes and second rete made by propylene copolymer, layer occurs and separate.
Film of the present invention has plurality of advantages with respect to the non-fusion shrink wrapping cover film of the film of prior art, particularly prior art. Except contraction and the sealing characteristics that improves, and without any outside the layer segregation phenomenon, film of the present invention also can advantageously be made by the standard film extrusion equipment.
Claims (10)
1. multilayer heat shrinkable film comprises:
A) it is 0.920 to 0.950g/cm that at least one first rete, this rete comprise density
3Linear ethylene copolymer;
B) at least one second rete, this rete comprise propylene and ethene and/or at least a CH
2=CHR
1First copolymer of alpha-olefin, wherein R
1For having the alkyl of 2-10 carbon atom; With
C) it is 0.920 to 0.950g/cm that at least one tertiary membrane layer, this rete comprise density
3Linear ethylene copolymer;
Wherein said at least one first rete is arranged between described at least one second rete and described at least one tertiary membrane layer.
2. film according to claim 1, the density of wherein said linear ethylene copolymer are 0.920-0.940g/cm
3
3. film according to claim 1 and 2, the MFR of wherein said linear ethylene copolymer (190/2.16) is lower than 1g/10min.
4. according to the described film of arbitrary claim among the claim 1-3, wherein said linear ethylene copolymer comprises at least a CH of 20mol% at the most
2=CHR alpha-olefin, wherein R is the alkyl of 1-10 carbon atom.
5. according to the described film of arbitrary claim among the claim 1-4, wherein said first rete also comprises propylene and ethene and/or at least a CH
2=CHR
1Second copolymer of alpha-olefin, wherein R1 is the alkyl with 2-10 carbon atom.
6. according to the described film of arbitrary claim among the claim 1-5, it is 0.915-0.950g/cm that wherein said second rete also comprises density
3Linear ethylene copolymer.
7. according to the described film of arbitrary claim among the claim 1-6, wherein said at least one first, second and the tertiary membrane layer have first, second and the 3rd thickness respectively, described first thickness all accounts for leading with respect in the described second and the 3rd thickness each.
8. the method for the described multilayer heat shrinkable film of arbitrary claim comprises the steps: among the production claim 1-7
-make described linear ethylene copolymer and described first propylene copolymer, reach the randomly described second propylene copolymer fusion;
-coextrusion that comprises annular die head production line is provided;
-with the linear ethylene copolymer of described fusion, described first propylene copolymer,,, thereby obtain the multilayer tubular film by described annular die head coextrusion randomly with the described second optional propylene copolymer; And
-described multilayer tubular film is collapsed to described multilayer film.
Among the claim 1-7 the described multilayer heat shrinkable film of arbitrary claim as the purposes that is used to wrap up based on the heat-shrinkable encasement of the packing of poly object.
Among the claim 1-7 the described multilayer heat shrinkable film of arbitrary claim as the purposes that is used to wrap up based on the encasement of the secondary package of poly level package.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP06002144 | 2006-02-02 | ||
| EP06002144.1 | 2006-02-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN101378902A true CN101378902A (en) | 2009-03-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2007800042939A Pending CN101378902A (en) | 2006-02-02 | 2007-01-09 | Multilayer thermoshrinkable films |
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| Country | Link |
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| CN (1) | CN101378902A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103331969A (en) * | 2013-06-09 | 2013-10-02 | 南通环球塑料工程有限公司 | Multi-layer co-extruded two-way stretching poultry meat packaging shrink film and preparation method thereof |
| CN107225830A (en) * | 2017-06-23 | 2017-10-03 | 江南大学 | A kind of slim heavy packaging low temperature heat shrink films and preparation method thereof |
| CN109435400A (en) * | 2018-11-26 | 2019-03-08 | 付进 | A kind of multi-layer co-extrusion packaging film and preparation method thereof with papery feel |
| CN110435127A (en) * | 2019-08-13 | 2019-11-12 | 苏州鼎政电子科技有限公司 | High temperature resistant PET protection film production technology |
-
2007
- 2007-01-09 CN CNA2007800042939A patent/CN101378902A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103331969A (en) * | 2013-06-09 | 2013-10-02 | 南通环球塑料工程有限公司 | Multi-layer co-extruded two-way stretching poultry meat packaging shrink film and preparation method thereof |
| CN103331969B (en) * | 2013-06-09 | 2017-02-15 | 南通环球塑料工程有限公司 | Multi-layer co-extruded two-way stretching poultry meat packaging shrink film and preparation method thereof |
| CN107225830A (en) * | 2017-06-23 | 2017-10-03 | 江南大学 | A kind of slim heavy packaging low temperature heat shrink films and preparation method thereof |
| CN107225830B (en) * | 2017-06-23 | 2019-03-26 | 江南大学 | Slim heavy packaging low temperature heat shrink films of one kind and preparation method thereof |
| CN109435400A (en) * | 2018-11-26 | 2019-03-08 | 付进 | A kind of multi-layer co-extrusion packaging film and preparation method thereof with papery feel |
| CN110435127A (en) * | 2019-08-13 | 2019-11-12 | 苏州鼎政电子科技有限公司 | High temperature resistant PET protection film production technology |
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