CN1297386C - Method for producing two-way stretching polypropylene film for cigarette by pipe soaking method - Google Patents

Abstract

The invention discloses a method for producing a biaxially stretched polypropylene film for cigarettes by using a bubble tube method. The method includes the following steps: mixing polypropylene resin and functional masterbatch according to a specific ratio, and passing through a co-extrusion die on an extruder First extrude the primary tube film, quench the primary tube film, then preheat it in a preheating oven with a temperature of 260°C-400°C, and carry out transverse inflation and longitudinal stretching in an oven with a temperature of 510°C-300°C , the stretching temperature is 135°C-150°C, the longitudinal stretching ratio is 6.5-8.0, and the transverse stretching ratio is 5.0-8.0; air ring cooling, winding, slitting, rewinding, and re-slitting of the bubble film . Compared with the existing flat stretch biaxially oriented polypropylene cigarette film production technology, this production process has the advantages of small equipment footprint and low investment, and the product has high heat shrinkability, which can meet the requirements of cigarette film. Require.

Description

Method for producing biaxially oriented polypropylene cigarette film by bubble tube method

technical field

The invention relates to a method for producing a biaxially stretched polypropylene film for cigarettes by a bubble tube method.

Background technique

The biaxially oriented polypropylene packaging film used for packaging cigarettes has been produced using the "flat stretch biaxially stretched technology", that is, the film is produced by stretching in both vertical and horizontal directions. This production technology requires a large investment in equipment and occupies an area of wide.

The "bubble tube method" production technology, also known as "tube film method", is used in the production of polyethylene heat shrinkable film. The process includes the following steps: mixing raw materials, passing through an extruder in a circular co-extrusion die Extrude the primary tube film, quench the primary tube film to make it crystallize, preheat in the preheating oven, carry out transverse blowing and longitudinal stretching in the stretching oven, cool, wind up, and cut to obtain the finished product . This technology has the advantages of small equipment investment, small modulus of materials used, high flexibility, and high product shrinkage, but this technology has low production speed, small stretching ratio, poor product thickness uniformity, and film thickness fluctuations are often within ±10 % or more, so it cannot be used to produce biaxially oriented polypropylene cigarette film at present.

Due to the harsh technical requirements of the film for cigarettes, if the bubble tube production technology is used to produce the biaxially oriented polypropylene film for cigarettes, the following technical problems must be solved: (1) The thickness fluctuation of the film product is required to be within ±6%. (2) The film should have a suitable shrinkage rate. (3) The rolled product has no wrinkles. (4) The product has a suitable Young's modulus.

Contents of the invention

In view of the above-mentioned problems existing in the production process of the existing biaxially stretched polypropylene cigarette film and the characteristics of the production technology of the bubble tube method, the purpose of the present invention is to provide a method for producing the biaxially stretched polypropylene cigarette film by the bubble tube method According to the production method of the present invention, a biaxially oriented polypropylene film with suitable properties can be produced on the bubble tube process equipment with a small investment, and the film can be used on cigarette packages to obtain satisfactory packaging effects.

In order to make the biaxially oriented polypropylene film produced by the bubble tube method meet the requirements of cigarette packaging film, it is necessary to improve the formula of raw materials, production process conditions and methods in view of the difference between polypropylene raw materials and polyethylene.

The biaxially oriented polypropylene film for cigarettes produced by the bubble tube method of the present invention comprises the following process (the percentages involved in the following product formulations are all percentages by weight):

(1) Blending of polypropylene resin and functional masterbatch, wherein the raw materials used for the surface layer A of the film and their weight content are: 90% to 100% of copolymerized polypropylene, 0% to 10% of anti-adhesive masterbatch; The ingredients and weight content are: homopolypropylene 53%~100%, stiffening masterbatch 0%~35%, smooth masterbatch 0%~7%, antistatic agent 0%~5%; the surface layer C The ingredients and weight content are: copolymerized polypropylene 85%-100%, anti-adhesive masterbatch 0%-15%;

(2) Send the mixed surface layer A, core layer B and surface layer C raw materials to three extruders for extrusion, and then pass through a three-layer co-extrusion die to form a primary tube film, and pass through a sizing mandrel and cooling After water cooling and shaping, it is sent to the oven;

(3) The initial tube film is preheated in a preheating oven with a temperature of 260°C to 430°C, and then inflated and longitudinally stretched in a stretching oven with a temperature of 530°C to 300°C. The stretching temperature of the tube film 135°C-150°C to become a film of predetermined thickness, the longitudinal stretching ratio is 6.5-8.0 times, and the transverse stretching ratio is 5.0-8.0 times;

(4) Air ring cooling is carried out to the film;

(5) There are flannelettes on the stretching driving roller and winding traction roller for stretching and winding;

(6) Immediately cut the rolled film on the slitter, rewind the cut semi-finished product on the rewinder, and then cut it to get the finished product.

The preferred weight content of the above-mentioned surface layer A is 94%-98% of copolymerized polypropylene and 2%-6% of anti-adhesive masterbatch.

The preferred weight content of the above-mentioned core layer B is 72%-79% of homopolypropylene, 18%-25% of stiffening masterbatch, 1%-3% of smoothing masterbatch, and 2%-3% of antistatic agent.

The preferred weight content of the above surface layer C is 96%-99% of polypropylene copolymer and 1%-4% of anti-adhesive masterbatch.

The preferred temperature of the above-mentioned preheating oven (zone 1-4) and stretching oven (zone 5-8) is: zone 1: 300±20°C; zone 2: 330±20°C; zone 3: 360±20°C ℃; Zone 4: 390±20℃; Zone 5: 510±20℃; Zone 6: 460±20℃; Zone 7: 360±20℃; Zone 8: 320±20℃.

In order to improve the winding quality, the winding nip roller can be opened during winding.

In order to ensure smooth roll change, close the winding pinch roller when preparing to change rolls, and open the winding pinch roller after changing.

The process of producing biaxially stretched polypropylene cigarette film by the bubble tube method provided by the present invention, through the screening of raw materials and the improvement of the stretching process and winding method, enables the bubble tube method equipment with small footprint and small equipment investment The biaxially oriented polypropylene film that meets the requirements can be produced, not only can meet the requirements of cigarette packaging, but also has higher heat shrinkage compared with the existing biaxially oriented polypropylene cigarette film produced by the flat drawing method. The property makes the film and the packaged object more intimate, and when used for packaging cigarettes, a better packaging effect can be obtained. Therefore, the process of producing biaxially oriented polypropylene cigarette film for cigarettes by the foam tube method provided by the present invention is compared with the traditional flat-drawing biaxially oriented polypropylene cigarette film technique, and has the characteristics of small footprint and low equipment investment. Moreover, the product has high thermal shrinkage, the thickness fluctuation, shrinkage rate, and Young's modulus of the product are all within the required range, and the product has no wrinkles.

Detailed ways

The production process of the biaxially oriented polypropylene smoking film by the foam tube method of the present invention will be further described below in conjunction with specific examples.

Example 1

The raw materials in this example are that the surface layer A is copolymerized polypropylene, accounting for 90%, anti-adhesive masterbatch, accounting for 10%; the core layer homopolymer polypropylene content is 55%, stiffening The percentage content of the master batch is 35%, and the percentage content of the smooth/antistatic agent master batch is 5%; the material and content of the surface layer C are the same as those of the surface layer A.

The polypropylene raw material and masterbatch are accurately weighed according to the proportion, put into the mixing tank and mixed for 15 minutes, then sent to the storage tank, sent to the extruder through the pipeline and extruded into the primary tube film through the three-layer co-extrusion die. The extruders are: A layer is a φ50 extruder with a screw length-to-diameter ratio of 30:1; B layer is a φ100 extruder with a screw length-to-diameter ratio of 30:1; C layer is a φ50 extruder with a screw length The diameter ratio is 30:1; the extrusion temperature is 180°C to 200°C from Zone 1 to Zone 6 of the A-layer extruder, and the melting temperature of the resin is 190°C; the temperature from Zone 1 to Zone 9 of the B-layer extruder is 210°C ~240°C, the resin melting temperature is 230°C, the temperature in zone 1 to zone 6 of the C-layer extruder is 180°C-200°C, and the resin melting temperature is 190°C. The initial tube film is preheated in the preheating zone of the oven, and the temperatures in zone 1 to zone 4 are 300°C, 335°C, 360°C, and 390°C respectively, and then stretched in the stretching zone of the oven, and the temperatures of each zone in the stretching zone are respectively For: 500°C, 460°C, 360°C, 300°C, the stretching temperature of the tube film is 138°C, the longitudinal stretching ratio is 7.5 times, and the transverse stretching ratio is 6.5 times; The temperature of the ring cooling water is lowered to below 18°C, and then the winding is carried out, and the finished product is cut after slitting and rewinding, and the product is inspected.

The product quality of the biaxially stretched polypropylene cigarette film of gained is serial number Inspection project unit unit test result 1 thickness average value μm 21.9 maximum value μm 22.6 minimum value μm 21.0 2 Tensile Strength portrait MPa 223 horizontal MPa 187 3 elongation at break portrait % 100 horizontal % 106 4 Heat shrinkage portrait % 5.77 horizontal % 11.60 5 Coefficient of friction (static/dynamic) inside / inside 0.15/0.12 outside / outside 0.14/0.12 6 Haze % 1.5 7 Gloss % 90.4 8 Young's modulus portrait N/mm2 3057 horizontal 3187 9 Heat seal strength N/15mm 2.61 10 Static Decay Rate Inside % 2.74(15.82mv) outside % 2.48(15.84mv)

Example 2

The raw materials in this example are that the content of copolymerized polypropylene in surface layer A is 95%, and the percentage content of anti-adhesive masterbatch is 5%; the content of homopolypropylene in core layer B is 78%, and the percentage content of stiffening masterbatch is 18%. %, the percentage content of the smooth masterbatch is 4%; the percentage content of the copolymerized polypropylene in the surface layer C is 85%, and the percentage content of the anti-adhesive masterbatch is 15%.

The polypropylene raw material and masterbatch are accurately weighed according to the proportion, put into the mixing tank and mixed for 15 minutes, then sent to the storage tank, sent to the extruder through the pipeline and extruded into the primary tube film through the three-layer co-extrusion die. The extruders are: A layer is a φ50 extruder with a screw length-to-diameter ratio of 30:1; B layer is a φ100 extruder with a screw length-to-diameter ratio of 30:1; C layer is a φ50 extruder with a screw length The diameter ratio is 30:1. The extrusion temperature is 180°C to 200°C from zone 1 to zone 6 of the A-layer extruder, and the melting temperature of the resin is 190°C; the temperature from zone 1 to zone 9 of the B-layer extruder is 210°C~ 240°C, resin melting temperature 230°C, C-layer extruder zone 1 to zone 6 temperature 180°C-200°C, resin melting temperature 190°C. The initial tube film is preheated in the preheating zone of the oven at a temperature of 290°C, 310°C, 350°C, and 380°C, and then pulled in an oven with a temperature of 510°C, 445°C, 380°C, and 310°C in zones 5 to 8, respectively. Stretching in the stretching zone, the stretching temperature of the tube film is 146°C, the longitudinal stretching ratio is 6.9 times, and the transverse stretching ratio is 5.5 times; the bubble film is cooled by air ring, and the temperature of the fixed air ring cooling water is reduced to 18°C Next, rewinding, slitting, rewinding and slitting to obtain finished products, the products are inspected.

The product quality of the biaxially stretched polypropylene cigarette film of gained is serial number Inspection project unit unit test result 1 thickness average value μm 22.2 maximum value μm 23.2 minimum value μm 21.3 2 Tensile Strength portrait MPa 242 horizontal MPa 223 3 elongation at break portrait % 91 horizontal % 107 4 Heat shrinkage portrait % 8.88 horizontal % 14.26 5 Coefficient of friction (static/dynamic) inside / inside 0.23/0.20 outside / outside 0.23/0.19 6 Haze % 1.6 7 Gloss % 89.3 8 Young's modulus portrait N/ ^mm2 3325 horizontal 3345 9 Heat seal strength N/15mm 2.16 10 Static Decay Rate Inside % 2.22 outside % 1.78

Example 3

The raw materials in this example are that the copolymerized polypropylene content of the surface layer A is 100%; the homopolypropylene weight percentage in the core layer B is 95%, and the stiffening masterbatch weight percentage is 5%; The weight percentage of the copolymerized polypropylene in the surface layer C is 99%, and the weight percentage of the anti-adhesive masterbatch is 1%.

The polypropylene raw material and masterbatch are accurately weighed according to the proportion, put into the mixing tank and mixed for 15 minutes, then sent to the storage tank, and then sent to the extruder through the pipeline to form a tube film through a three-layer co-extrusion die. The extruders are as follows: layer A is a φ50 extruder with a screw length-to-diameter ratio of 30:1; layer B is a φ100 extruder with a screw length-to-diameter ratio of 30:1; layer C is a φ50 extruder with a screw length to diameter The ratio is 30:1; the extrusion temperature is 180°C to 200°C from zone 1 to zone 6 of the extruder of layer A, and the melting temperature of the resin is 190°C; the temperature of zone 1 to zone 9 of the extruder on layer B is 210°C to 240°C, resin melting temperature 230°C, C-layer extruder zone 1 to zone 6 temperature 180°C-200°C, resin melting temperature 190°C. The primary tube film is preheated in the preheating zone of the oven at 320°C, 350°C, 380°C, and 410°C, and then stretched in the stretching zone of the oven. The temperatures in the stretching zone are 530°C, 475°C, 340°C, 335°C, the stretching temperature of the tube film is 149°C, the longitudinal stretching ratio is 8.0 times, and the transverse stretching ratio is 8.0 times; the bubble film is cooled by air ring, and the temperature of the fixed air ring cooling water is reduced to 18°C Next, rewinding, slitting, rewinding and slitting to obtain finished products, the products are inspected.

The product quality of the biaxially stretched polypropylene cigarette film of gained is serial number Inspection project unit unit test result 1 thickness average value μm 22.3 maximum value μm 23.4 minimum value μm 21.6 2 Tensile Strength portrait MPa 227 horizontal MPa 221 3 elongation at break portrait % 100 horizontal % 111 4 Heat shrinkage portrait % 5.65 horizontal % 12.75 5 Coefficient of friction (static/dynamic) inside / inside 0.18/0.16 outside / outside 0.18/0.15 6 Haze % 2.1 7 Gloss % 83.9 8 Young's modulus portrait N/ ^mm2 3047 horizontal 3162 9 Heat seal strength N/15mm 2.80 10 Static Decay Rate Inside % 1.92 outside % 1.41

It can be seen from the product performance that the physical and mechanical properties of the biaxially stretched polypropylene film produced by the production process of the present invention can meet the requirements of cigarette packaging films.

Claims (7)

1. A method for producing biaxially oriented polypropylene cigarette film by a bubble tube method, comprising the following operations successively: (1) The mixing of polypropylene resin and functional masterbatch, wherein the raw materials and weight content of the surface layer A of the film are: copolymerized polypropylene 90%-100%, anti-adhesive masterbatch 0%-10%; The ingredients and weight content are: homopolypropylene 53%-100%, stiffening masterbatch 0%-35%, smooth masterbatch 0%-7%, antistatic agent 0%-5%; the surface layer C The ingredients and weight content are: copolymerized polypropylene 85%-100%, anti-adhesive masterbatch 0%-15%; (2) Send the mixed surface layer A, core layer B and surface layer C raw materials to three extruders for extrusion, and then pass through a three-layer co-extrusion die to form a primary tube film, and pass through a sizing mandrel and cooling After water cooling and shaping, it is sent to the oven; (3) The initial tube film is preheated in a preheating oven with a temperature of 260°C-430°C, and then transversely blown and longitudinally stretched in a stretching oven with a temperature of 530°C-300°C. The stretching temperature of the tube film 135°C-150°C to make it a film of predetermined thickness, with a longitudinal stretching ratio of 6.5-8.0 times and a transverse stretching ratio of 5.0-8.0 times; (4) Air ring cooling is carried out to the film; (5) Winding is carried out on the stretching roller covered with flannelette on the driving roller and the winding roller; (6) Immediately slitting the reeled film on the slitting machine, and rewinding and slitting the semi-finished product on the rewinder after slitting. 2. The method for producing biaxially oriented polypropylene cigarette film by bubble tube method as claimed in claim 1, characterized in that: the weight content of the surface layer A is 94%-98% of copolymerized polypropylene, anti-adhesive masterbatch 2%-6%. 3. The method for producing biaxially oriented polypropylene cigarette film by bubble tube method as claimed in claim 1, characterized in that: the weight content of the core layer B is homopolypropylene 72%-79%, stiffening Masterbatch 18%-25%, smooth masterbatch 1%-3%, antistatic agent 2%-3%. 4. The method for producing biaxially oriented polypropylene cigarette film by bubble tube method according to claim 1, characterized in that: the weight content of the surface layer C is 96%-99% of copolymerized polypropylene, anti-adhesive masterbatch 1%-4%. 5. The method for producing biaxially oriented polypropylene cigarette film by bubble tube method as claimed in claim 1, characterized in that: in step 3, the temperatures in zone 1-4 of the preheating oven are respectively: 300±20°C, 330±20°C, 360±20°C, 390±20°C; the temperatures in zones 5-8 of the stretching oven are: 510±20°C, 460±20°C, 360±20°C, 320±20°C. 6. The method for producing biaxially oriented polypropylene film for cigarettes by the bubble tube method as claimed in claim 1, characterized in that: in step 5, the nip rollers are opened during winding. 7. The method for producing biaxially oriented polypropylene cigarette film by bubble tube method as claimed in claim 1, characterized in that: in step 5, when changing the roll, first close the clamping roller, and open the clamping roll after changing the roll. Roller winding.