BG106498A - Biaxially oriented polypropylene tobacco film heat shrinkable - Google Patents

Abstract

Biaxially oriented polypropylene tobacco film heat shrinkable consists of three layers featuring isotactic and syndiotactic metallocene polypropylene mixture and antistatic masterbatch in the core layer and the terpolymer and sliding masterbatch in the two outer heat sealable layers. The way of production of the biaxially oriented polypropylene heat shrinkable tobacco film features higher orientation ratios in the machine orientation, or transversal orientation and reduced temperatures in stabilizing zones in the width orientation. 10 claims

Description

BIAXIALALLY ORIENTED POLYPROPYLENE THERMO-SHOCKING

CIGARETT FILM

Field of application

The invention relates to a heat shrinkable biaxially oriented polypropylene cigarette film for packing cigarette cases and cigarette cartons. It belongs to the film-packed products.

BACKGROUND OF THE INVENTION

Shrinkable films have a good ability to shrink at a certain temperature, which is used in the packaging of various types of goods. The packaging devices are provided with heating parts to allow the film in which the product is placed to shrink. The final packaging is fully adapted to the shape of a product, resulting in its good, aesthetic appearance.

Outside of many mono- or multilayer shrink films of different chemical composition, used mainly for packaging applications, polyolefin films, which are well protected by patents, account for a large proportion. Among them are, for example, the protected by EP 885121 and WO 9825765 two-layer heat-shrinkable polyolefin film composed of a low density polyethylene layer A and a mixed layer B consisting of at least 73 to 95% by weight ethylene copolymer with alpha-olefin CH ₂ = CHR = CHR = CHR = CHR wherein R is an alkyl radical having 1-10 carbon atoms and 60-98% by weight propylene. The copolymer is characterized by an insoluble xylene fraction of more than 70% by weight. Multilayer polyethylene film is protected in EP 72983 and WO 729831. The intermediate layer consists of a mixture of specific linear low density polyethylene, and the inner and outer layers are composed mainly of specified high pressure polyethylene, alpha-olefin-ethylene copolymer and linoleic copolymer. .

A mixture of surfactant in at least two layers can be added, resulting in excellent anti-war effect. The multilayer film is also protected in EP 681914, which is an improved thermally shrinkable biaxially oriented film suitable for vacuum food packaging. Enhanced shrink films according to EP 662989 are intended for mixtures or compositions containing exact combinations of polyethylene with a "narrow, unambiguous" melting point and polyethylene with a higher melting point (at least 10 °). Similarly, WO 9512490 protects laminated polyethylene heat shrink film and EP 562496 is a biaxially oriented multilayer film suitable for poultry wrapping. Another single or multi-layer ethylene-based film has a very good combination of physical properties and machinability and is characterized by higher shrinkage and puncture resistance (EP 374783). The target property, shrinkage, can be achieved by a number of production methods, the choice of which is subject to the distinctive qualities of the films developed by the application. Most important of these is the temperature at which the film shrinks. The wrapping of cigarette cases and cartons requires the application of such brand films in which shrinkage occurs at relatively low temperatures.

This low temperature shrinkage occurs in films containing certain additives supporting this shrinkage and / or in films oriented to conditions allowing shrinkage at low temperatures. The additives act as modifiers acting on the crystallinity of the polypropylene core, e.g. the process of crystallization of the core layer, and thus affect the final properties of the finished film. Suitable additives may be hydrocarbon resins, the disadvantage of which is migration at the time of end-use, nucleotide agents used to form a beta-type polypropylene, tact polypropylene, ethylene-propylene copolymer, and the like. Orientation at lower temperatures is affected, which causes problems in film production because of the greater effort required to achieve orientation. The shrinkage levels achieved need not be sufficient.

This disadvantage is eliminated based on the solution of EP 865913, according to which the biaxially oriented thermally shrinkable polyolefin film consists of a polypropylene based resin with microscopic cavities created while the resulting film is oriented by melt extrusion through a nozzle and subsequent cooling of the film during production. consisting of beta-type polypropylene. The film shrinkage is 10% in at least one direction (at 130 ° C, 10 min). According to the cited invention, the film may consist of a resin based on micro-cavity polypropylene, however it may often contain one or more other layers having a specific characteristic property, e.g. ability to seal heat, gloss, etc. These layers are mainly made of polyolefins. They are obtained by extrusion or co-extrusion of the corresponding molten polymers through the nozzle opening to the required layer (or layers), which is cooled and then gradually oriented biaxially, first in length, in the direction of the machine at a temperature of from 70 to 110 ° C. , most preferably from 80 to 95 ° C, with an orientation ratio ranging from at least 3: 1 to 3.5: 1 to 8: 1, and then at latitude, but at temperatures lower than commonly used for transverse orientation . The required temperatures are below 160 ° C to 155 ° C, most preferably between 140 - 152 ° C. The orientation ratio is 3: 1 to 10: 1.

Recently, metallocene isotactic and syndiotactic polypropylene can be obtained using new metallocene catalysts. Due to their specific properties, these new metallocene polymers have different applications in the packaging industry and in packaging films and have new useful properties.

Currently used biaxially oriented polypropylene

* M tobacco packaging films obtained by standard methods (eg low orientation at the beginning and high orientation at the end, eg 1.05 to 5.3) have a shrinkage of 3.0 to 5.0% (at 135 ° C and at least 7 min drying time). The shrinkage parameter depends on the polypropylene used (mainly the value of its active part) and also on the technological conditions of production. The shrinkage of the cigarette packing film directly affects the quality of the finished packing of the cigarette box, mainly the quality requirements of the good visible appearance of the packaged cigarette box. The requirement is that the film is sufficiently stretched around the entire box and does not form unwanted creases. The application of a heat shrinkable tobacco wrapping film covered by this invention eliminates these drawbacks and thus improves the packaging of cigarette cases.

The quality of the packing of the cigarette boxes, mainly the quality requirements for a good visible appearance of the packaged box, can be achieved by the appropriate size of the film, properly fed to the cigarette box, appropriate mechanical properties and inelasticity of the material. A very good parameter to evaluate (used by tobacco film converters) is the measurement of the tightness of multi-layer biaxially oriented polypropylene films used for packing on cigarette cases.

SUMMARY OF THE INVENTION>

SUMMARY OF THE INVENTION A heat shrinkable bi-axially oriented polypropylene cigarette film consisting of three layers, wherein the core layer is composed of an isotactic and syndiotactic metallocene polypropylene and an antistatic starting mixture and of two seals which can be sealed and sealed starting mixtures providing sliding and antistatic properties. The content of syndiotactic metallocene polypropylene is in the range of 1.0 to 5.0% by weight. Both outer heat sealable seals are either of the same composition, A-B-A, three-layer type without corona treatment, or of different composition, A-B-C, three-layer type with one treatment corona discharge on side C. In this type of film, the effective additive for sliding on the outside A is silicone oil and on the outside C - erucamide. The biaxially oriented, heat sealable polypropylene cigarette film achieves 6.0 to 11.0% machine shrinkage and cross direction at 135 ° C. The method of producing a biaxially oriented heat-sealed cigarette film for cigarettes according to these characteristics is performed at high machine orientation ratios or transverse orientations and reduced temperature in the width-stabilizing zones. The length orientation is 6.0 to 8.0 times depending on the final shrinkage requirement. In width orientation, the film is pre-air-dried to 165 - 178 ° C and then gradually oriented 8.0 to 10.0 times wide at 160 - 165 ° C air temperature. The temperature in the stabilization zones is lowered to 145 ° C and lower, depending on the operational stability of production.

The biaxially oriented, heat-sealed, polypropylene cigarette film is manufactured in accordance with this invention in such a way that mixtures of the raw materials for the core layer and the two upper layers are plasticized by heating in a screw extruder to a melting point of approximately 265 ° C. After the melt is filtered from the main extruder and two additional co-working extruders, the resulting co-extrudate is discharged through the flat nozzle opening heated to 260 ° C. The melt from the nozzle is cast and cooled on a 32 ° C cooling roller. On the other hand, the melt is cooled with 22 ° C water in a cooling bath. These melt cooling conditions provide the required structure of the thick film before it enters the part of the orientation machine (MDO).

The thick film is heated on heating rolls at 125-135 ° C in the orientation of the machine (so that the thick film does not stick to the surface of the rolls, which would damage the terpolymer layer). The heated thick film is oriented along the length of the orientation rollers (different roll speeds). The ultimate degree of contraction depends on the degree of orientation achieved. To achieve the required contractility of the finished film, min 6.0 -11.0% (in the oven at 135 ° C and 7 min), the two-stage machine orientation of the thick film is most appropriate. The ratio of orientation to length is 6 x

1.1 to 6 x 1.3. The resulting value is 6.6 to 7.8 times the length orientation. The use of syndiotactic polypropylene in the mixture is more appropriate than the use of other modifiers, since the electrical drive effort in MDO is less. After leaving the MDO, the film is drawn with a width orientation chain (TDO). The film is heated to 172 ° C with hot air in the TDO preheat zones and followed 8 - 10 times in width by gradually increasing the chain distance at 165 ° C. In TDO stabilization zones, it is necessary to lower the temperature to 145 ° C (or lower, if production reliability allows it) and to increase the chain distance of the TDO outputs as far as the width of the rollers beyond the TDO outlet and in the winding part the machine allows it.

The final film intended for single-sided printing may be corona-coated on the coiling part of the machine. Films are obtained with a thickness of 14 to 40 μιτι (usually 16, 20, 21 µm). One of the target parameters is film contractility or dimensional stability. The sample of the film is measured with a Hirlinger line at marked points (because of measurement accuracy) before insertion into the oven and after removal. The change in dimensions is measured in the longitudinal and transverse directions. The conditions in the dryer are as follows:

temperature 135 ° C, 7 min drying time. The compressibility values of the cigarette film obtained according to this invention vary from 6.0 to 11.0% depending on the orientation ratio. (Cigarette films obtained in this manner were used to achieve a shrinkage of 3.0 to 5.0%). A cigarette film with such shrinkage values can pack a cigarette box or a cardboard box perfectly, which improves its visual quality.

The cigarette film obtained by said technological process can be illustrated by the following examples in which temperatures in a separate technological part of the production line may vary in plus / minus tolerances compared to the temperatures specified in individual examples depending on the production temperature line, performance and main isotactic polypropylene used.

Examples of carrying out the invention

Example 1

A standard system line is used to produce the film. The mixture of crude materials for the production of AB-A-type film is as follows: the core layer B is made of 98.6874% by weight isotactic polypropylene, 1.0% by weight syndiotactic metallocene polypropylene and 0.3126% by weight antistatic starting material, the composition of which is 0.0700 wt% glycerol monostearate, 0.2300% alkyl (C ₁₂ -C ₁₈ ) bis (2-hydroxyethyl) amine, 0.0072 wt% bis- [3 glycol ester , 3-bis- (4'-hydroxy-3-tert-butyl-phenyl) butanoic acid], 0.0027% by weight of tris (2,4-di-tert-butyl-phenyl) phosphite and two identical heat-sealable surfaces terpolymer layers, produced and 99.4115 wt.% of terpolymer (C ₂ C ₃ C _4), 0.5489 wt.% of silicone oil, 0.0275 wt.% calcium stearate, 0.0088 wt.% tris (2,4-di- tert-butyl-phenyl) phosphite and 0.033 wt% bis- [3,3-bis- (4'-hydroxy-3-tert-butyl-phenyl) butanoic acid] glycol ester plasticized by heating in a screw extruder to a melting point of about 265 ° C. After the melt is filtered from the main extruder and from two additional co-working extruders, the final co-extrudate is extruded through the flat nozzle opening heated to 260 ° C. The melt from the nozzle is cast and cooled on a 32 ° C cooling roller. On the other hand, the melt is cooled with water to a temperature of 22 ° C in a cooling bath. On MDO heating rolls, the thick film is heated to 125-135 ° C (so that the thick film cannot stick to the surface of the rolls, which could damage the terpolymer layer). The heated thick film is oriented along the orientation rollers (different roll speeds). The final shrinkage value depends on the orientation achieved. In order to achieve the required shrinkage value, min 6.0 to 11.0% (in the oven at 135 ° C and 7 min), a two-stage orientation along the thick film is most appropriate. The found orientation ratio is 6 x 1.1 to 6 x 1.3. The resulting value of the longitudinal MD orientation is 6.6 to 7.8 times. The use of syndiotactic polypropylene in the mixture is particularly advantageous compared to other modifiers, since a lower electrical actuation effort in MDO is required for longitudinal orientation, thus increased. After leaving the MDO, the film is drawn with a width orientation chain (TDO). The film is heated to approximately 172 ° C with hot air in TDO preheating zones and followed 8 - 10 times in width by gradually increasing the chain distance at 165 ° C. In TDO stabilization zones, a temperature reduction of up to 145 ° C (or lower, if production reliability allows it) is required, similar to the increase of the chain distance in TDO production, if the roll width beyond the TDO outlet and in the winding part of the machine allows it.

Finished films are obtained with a thickness ranging from 14-40 [mu] m (typically 16, 20 and 21 μίτι). The shrinkage of the cigarette film obtained according to this example is a minimum of 6%.

Example 2

For plasticization in an auger extruder for the production of A-B-A type film, the mixture of crude materials is as follows: the core layer B is composed of a different ratio of isotactic and syndiotactic polypropylene, from that in Example 1, i. of 97.6874% by weight isotactic polypropylene and 2.0% by weight syndiotactic metallocene polypropylene, maintaining the content of the antistatic starting mixture and the manufacturing process as in Example 1, similar to two identical, surface-sealed thermally polymer layers in agreement with Example 1. The shrinkage values are from 6.0 to 11.0%, depending on the actual orientation ratio.

Example 3

For plasticization in a screw extruder for the production of A-B-A type film, the mixture of crude materials is as follows: the core layer B is composed of a different ratio of isotactic and syndiotactic polypropylene, from that in Examples 1 and 2, i. . from 96.6874% by weight isotactic polypropylene and 3.0% by weight syndiotactic metallocene polypropylene, from 0.0700% by weight glycerol stearate, 0.2300% by weight alkyl (C ₁₂ C ₁₈ ) bis (2-hydroxy-ethyl) ) amine, 0.0072% by weight glycolic ester of bis- [3,3-bis (4'-hydroxy-3-tert-butyl-phenyl) butanoic acid], 0.0027% by weight of tris (2,4 -di-tert-butyl-phenyl) phosphite and two identical surface sealable thermal terpolymer layers identical to Example 1. The procedure for film production is similar to Example 1. Upon reaching the obtained orientation values of 6.6 - 7 , 8 times, the values of contractility by 6,0 - 11,0%, depending on the actual terms of orientation.

Example 4

For plasticization in the screw extruder for the production of

A-B-A type of film, the mixture of raw materials is as follows: the core layer B is composed of a different ratio of ejected and syndactate polypropylene, from that in Examples 1, 2 and 3, i. from 95.6874% by weight isotactic polypropylene and 4.0% by weight syndiotactic metallocene polypropylene, from 0.0700% by weight glycerol stearate, 0.2300% by weight alkyl (C ₁₂ C ₁₈ ) bis (2-hydroxy-ethyl) ) amine, 0.0072% by weight glycolic ester of bis- [3,3-bis (4'-hydroxy-3-tert-butyl-phenyl) butanoic acid], 0.0027% by weight of tris (2,4 -di-tert-butyl-phenyl) phosphite, but the two identical surface sealed thermal terpolymer layers are in accordance with Example 1. The process for producing the film is similar to Example 1. Upon reaching the resulting orientation values of 6, 6 - 7.8 times, the shrinkage values net are 6,0 - 11,0%, depending on the actual terms of orientation.

Example 5

For plasticization in an auger extruder for the production of A-B-A type film, the mixture of crude materials is as follows: the core layer B is composed of a different ratio of isotactic and syndiotactic polypropylene than that of Examples 1 to 4, i. from 94.6874% by weight isotactic polypropylene and 5.0% by weight syndiotactic metallocene polypropylene, from 0.0700% by weight glycerol stearate, 0.2300% by weight alkyl (C ₁₂ C ₁₈ ) bis (2-hydroxy-ethyl) ) amine, 0.0072% by weight glycolic ester of bis- [3,3-bis (4'-hydroxy-3-tert-butyl-phenyl) butanoic acid], 0.0027% by weight of tris (2,4 -di-tert-butyl-phenyl) phosphite, but the two identical surface sealed thermal terpolymer layers are in accordance with Example 1. The process for producing the film is similar to Example 1. Upon reaching the resulting orientation values of 6, 6 - 7,8 times, the values of shrink net are 6.0 - 11.0%, depending on the actual orientation ratio.

Example 6

For plasticization in the screw extruder for the production of

A-B-C type film, the mixture of crude materials is as follows: the core layer B and the surface terpolymer A layer are composed of the materials specified in Example 1 of this invention. The second outer thermally copolymer C outer sealant consists of 99.4115 wt% terpolymer (C ₂ C ₃ C ₄ ), 0.5489 wt% erucamide, 0.0275 wt% calcium stearate, 0.0088 wt%. % tris (2,4-di-tert-butyl-phenyl) phosphite and 0.0033 wt% bis- [3,3-bis- (4'-hydroxy-3-tert-butylphenyl) butane glycol ester acid]. This layer is coated with an application printing crown. The procedure for producing the film is similar to Example 1. The finished film is intended for single-sided printing and is corona discharged in the coiling section. The shrinkage values range from 6.0 to 11.0%, depending on the actual orientation ratio.

Example 7

For plasticization in an auger extruder for the production of A-B-C type film, the mixture of crude materials is as follows: the core layer B and the surface terpolymer A layer are composed of the materials specified in Example 2 of this invention. The second outer thermally copolymer C outer seal is composed of the materials specified in Example 6, the manufacturing process including corona discharge treatment is similar to that of Example 2

6. Shrinkage values range from 6.0 to 11.0%, depending on the actual orientation ratio.

Example 8

For plasticization in an auger extruder for the production of A-B-C type film, the mixture of crude materials is as follows: the core layer B and the surface terpolymer A layer are composed of the materials specified in Example 3 of this invention. The second outer thermally copolymer C outer sealant consists of the materials specified in Example 6, the manufacturing process

including corona discharge treatment is similar to that of Example

6. Shrinkage values range from 6.0 to 11.0%, depending on the actual orientation ratio.

Example 9

For plasticization in a screw extruder for the production of A-B-C type film, the mixture of crude materials is as follows: the core layer B and the surface terpolymer A layer are composed of the materials specified in Example 4 of this invention. The second outer thermally copolymer C outer seal is made up of the materials specified in Example 6, the manufacturing procedure including corona discharge treatment is similar to that of Example

6. Shrinkage values range from 6.0 to 11.0%, depending on the actual orientation ratio.

Example 10

For plasticization in an auger extruder for the production of A-B-C type film, the mixture of crude materials is as follows: the core layer B and the surface terpolymer A layer are composed of the materials specified in Example 5 of this invention. The second outer thermally copolymer C outer seal is composed of the materials specified in Example 6, the manufacturing procedure including corona discharge treatment is similar to that of Example 6. The shrinkage values range from 6.0 to 11.0%, depending on the actual orientation attitude.

Industrial application of the invention

This new cigarette film has been sufficiently treated with antistatic and sliding additives, making it suitable for the use of high-speed packing machines with a packing rate of up to 600 boxes / min.

Claims (10)

Patent Claims 1. A heat shrinkable biaxially oriented polypropylene cigarette film comprising three layers, characterized by an isotactic and syndiotactic metallocene polypropylene mixture and an antistatic base mixture in the core layer, and a terpolymer and sliding base mixture in two outer layers. A heat shrinkable biaxially oriented cigarette polypropylene film according to claim 1, characterized by an isotactic and syndiotactic metallocene polypropylene mixture in the core layer having a content of syndiotactic metallocene polypropylene in the core from 1.0 to 5.0% by weight. A heat shrinkable bi-axially oriented polypropylene cigarette film according to claims 1 and 2, characterized by the same composition of the two outer, heat-sealed, AB-A three-layer film without surface corona treatment. A heat shrinkable biaxially oriented polypropylene cigarette film according to claims 1 and 2, characterized by a different composition of the two outer, heat-sealed, AB-C three-layer film with a coronal surface-treated side C. A heat shrinkable biaxially oriented polypropylene cigarette film according to claim 4, characterized by an effective sliding additive in the outer layer A, silicone oil and an effective sliding additive in the outer layer C, erucamide. 6. A heat shrinkable biaxially oriented polypropylene cigarette film according to claims 1 to 5, characterized by a film shrinkage of 6.0 to 11.0% in the longitudinal and transverse directions at defined measurement conditions of 135 ° C and a time of 7 min. 7. A method of producing a heat shrinkable biaxially oriented polypropylene cigarette film according to claims 1-6, characterized by higher orientation ratios in machine orientation or transverse orientation and reduced temperatures in the stabilization zones in width orientation. A method of producing a heat shrinkable bi-axially oriented polypropylene cigarette film according to claim 7, characterized by 6-8 times the longitudinal orientation depending on the required shrinkage value. A method of producing a heat shrinkable biaxially oriented polypropylene cigarette film according to claim 7, characterized by a width orientation with preheated warm air having a temperature of 165 - 178 ° C and subsequent orientation 8-10 times at 160-165 ° C. . A method of producing a heat shrinkable biaxially oriented polypropylene cigarette film according to claims 7 and 9, characterized by a reduced temperature in the stabilization zones of 145 ° C and lower, depending on the operating stability of the production.