Double-layer packaging film, preparation method therefor, and use thereof

Abstract

A double-layer packaging film. The packaging film is a double-layer BOPP film; and both an inner BOPP film and an outer BOPP film are BOPP films prepared by means of a sequential biaxial stretching method in a flat film process. Also disclosed are a preparation method for the double-layer packaging film and a use of the double-layer packaging film as a cigarette pack or carton packaging film.

Description

Double-layer packaging film, preparation method and use thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of tobacco, and particularly relates to a double-layer BOPP film, a preparation method thereof and use of the double-layer BOPP film for cigarette packaging film. BACKGROUND

[0002] Sealing is a packaging process for preventing the exchange of gas, liquid and other substances between the inside and outside of a box, and is one of the main effective measures for effectively preventing mildew. Good sealing of cigarette packaging can not only effectively prevent the loss of cigarette aroma during long-term storage of cigarettes, but also reduce the influence of external temperature and humidity on the moisture content of cigarettes and reduce the risk of mildew of cigarettes, thereby prolonging the storage time of cigarettes. Previous project research shows that after the cigarette product is stored in an open environment for 8 months, the number of microbial colonies of the cigarette product with good sealing degree does not change significantly, and the order of magnitude of the total number of colonies of the product with poor sealing degree increases from 10 3 to 10 5 , and the order of magnitude of xerophilic fungi increases from 101 to 102. Therefore, sealing degree is an important quality index in the cigarette packaging process. At the same time, the sealing performance of a cigarette box is more prominent for the moisture retention performance of a cigarette product under different environmental conditions. This quality requirement is a new requirement of the consumer market, a new topic of consumer market upgrading, and a new field that needs to be improved in the quality control system of cigarettes. There are many factors that affect the moisture retention effect of cigarettes. From the perspective of packaging, under certain conditions, the improvement of factors such as the squareness of the unopened cigarette box, the unit size of the paper material and the BOPP thin material, and the main forming station size of the equipment has a positive effect on improving the cigarette consumption experience. The goal is to improve the squareness and sealing moisture retention of the cigarette box packaging to improve the quality control system of cigarettes.

[0003] BOPP film is colorless, odorless, tasteless, non-toxic, has high tensile strength, impact strength, rigidity, toughness and excellent transparency; its surface energy is relatively low, and needs to be subjected to corona treatment before gluing or printing; after corona treatment, it has good printability and can be printed in multiple colors to obtain a beautiful appearance effect, and therefore can be used as a composite substrate for composite film. Its disadvantages are, for example, easy accumulation of static electricity and poor heat sealing property. In a high-speed production line, BOPP film is prone to static electricity and needs to be installed with a static electricity remover. The technology of BOPP film packaging has become mature, and the application range of the film is also becoming wider and wider, from simple packaging industry to printing, plate making and some special industries, the application of polypropylene film rapidly penetrates into every field of human life.

[0004] BOPP film in the process of making after two-way stretching, so its tensile strength, impact strength outstanding, and high stiffness, high transparency; and the melting point is higher (160 ℃ or more), so it has good resistance to high temperature; BOPP film also has a certain barrier properties, especially for water vapor barrier properties are good; so the material in the packaging industry commonly used printing materials. But BOPP film heat seal poor, can not be used for composite film heat seal layer; and polypropylene glass transition temperature is high, so the low temperature resistance is generally poor; and oxygen barrier is poor. For composite substrate, the thickness is usually about 20 microns, most of the products packaging of low barrier requirements can choose BOPP as a printing composite material.

[0005] Two-way stretching is a technology for subsequent orientation or synchronous orientation of thermoplastic materials. At present, the production process of BOPP film mainly has two types of tubular film method and flat film method, and the double stretching method is divided into step-by-step double stretching and synchronous double stretching. The product obtained by synchronous two-way stretching in flat film method has the advantage of isotropy; but due to the complexity of the equipment, the difficulty of manufacturing and high cost, it has not been well developed. The step-by-step two-way stretching method is adopted by most production enterprises, although the product has some differences in tensile strength, breaking production rate and heat shrinkage rate between longitudinal and transverse directions, but it has little effect on product quality; but it has the advantages of high yield, fast speed, wide range and stable product quality; its process flow is roughly as follows: 1: batching; 2: melting; 3: plasticizing extrusion; 4: filtration; 5: longitudinal stretching; 6: transverse stretching; 7: corona; 8: winding; 9: aging treatment; 10: slitting; 11: finished product. The equipment required by the tubular film method is relatively simple, occupies a small area, has low cost, sees quick results and has moderate yield, so it is welcomed by many production enterprises at the beginning; but due to its low yield and uneven thickness of the film, large heat shrinkage rate, it has developed slowly in recent years.

[0006] The research on the test method of the sealing degree of box packaging has been carried out. The commonly used method for detecting the sealing degree of cigarette small box in the industry is YC / T 140-1998 "Determination of Sealing Degree of Cigarette Small Box by Inflation Method". The standard has been abolished in 2015. The standard method has certain limitations: (1) narrow application scope, the method is only applicable to detecting the sealing degree of small box soft pack cigarette, but for small box hard pack, due to the close contact between the cigarette small box packaging film and the packaging small box, the air flowability is poor, and the principle of inflation method cannot be applied to the detection of the sealing degree of such packaging cigarette; (2) large detection error, for two packs of cigarettes with obvious sealing difference, the detection may show opposite results; (3) detection has blind spots, the method is effective for detecting leakage at both ends, but it is poor for detecting leakage at the pull line or side damage of the packaging cigarette, and it is often difficult to detect; (4) limited guidance for production improvement, the detection result of the method is only the numerical value of the sealing degree, which cannot directly determine the leakage point, and cannot timely guide the improvement and optimization of the production process.

[0007] The commonly used sealing degree detection methods include visual method, talcum powder method, bubble method, sealing performance detector method, differential pressure type air leakage detection method and determination of sealing degree of cigarette small box by inflation method. The visual method, talcum powder method and bubble method are qualitative measurement methods, and the sealing performance detector method, differential pressure type air leakage detection method and determination of sealing degree of cigarette small box by inflation method are quantitative measurement methods. For the quantitative measurement method, the above three quantitative detection methods of packaging sealing degree are not suitable for the determination of the sealing degree of cigarette packaging. For the differential pressure type air leakage detection method, the inflation air pressure is relatively high, and the method is generally suitable for the test of rigid packaging sealing condition. For the sealing performance detector method and the inflation method, the air flow cannot pass through the four edges of the cigarette package, and the method is only suitable for the measurement of the sealing degree of the upper and lower sealing portions of the soft package, and cannot detect the sealing condition of the side of the soft package and the hard package. In addition, the detection methods of packaging sealing degree also include displacement type leakage detection, ultrasonic wave detection, helium mass spectrum leakage detection, new type gas tracer detection and the like. According to the characteristics of the cigarette small box, the methods mainly include volume change method, buoyancy method, water immersion weighing method, negative pressure method, negative pressure water immersion method and negative pressure air pumping method. The negative pressure air pumping method is the most optimal and feasible method in the test of the sealing degree, and has good test repeatability, and the negative pressure water immersion method can realize the positioning of the leakage point of the cigarette small box.

[0008] The moisture content of the tobacco in the cigarette package is generally 12.5% (22 DEG C, relative humidity 60% equilibrium moisture content), the delivery moisture of the cigarette paper is 4.5%, the moisture of the lining paper is 4.0%, the moisture of the frame paper is 6.0%, and the moisture of the carton packaging paper is 5.5%. When the sealing degree stability of the cigarette package is good, the sealing degree reaches the requirement and the humidity is relatively high, the moisture in the tobacco will diffuse to the cigarette paper, the carton packaging paper and the like, and the tobacco, the cigarette paper, the carton packaging paper and the like form a humidity balance system. When the sealing degree stability of the cigarette package is not good, the tobacco, the cigarette paper, the frame paper and the like in the cigarette package are in communication with the external environment for a long time, and when the external environment is too dry or humid, the moisture content of the tobacco, the cigarette paper and the like in the cigarette package will be affected, and then the quality of the cigarette is affected. SUMMARY

[0009] The application provides a double-layer packaging film and a preparation method thereof. The double-layer packaging film is a double-layer BOPP film. The inner-layer BOPP film and the outer-layer BOPP film are both prepared by a step-by-step biaxial stretching method in a flat film method. The double-layer BOPP film has high sealing degree, and is used for cigarette packaging film. The sealing degree of the soft box packaging is not greater than 50 mL under-1.00 kPa. The sealing degree of the hard box packaging is not greater than 10 mL under-8.00 kPa.

[0010] The technical scheme of the application is as follows:

[0011] The first aspect of the present application discloses a double-layer packaging film, which is a double-layer BOPP film; the inner-layer BOPP film and the outer-layer BOPP film are both BOPP films prepared by a step-by-step biaxial stretching method in a flat film method.

[0012] Preferably, the thickness of the inner-layer BOPP film is 15-18 μm, and the inner surface is coated with an activated carbon layer; the film thickness of the outer-layer BOPP film is 18-22 μm.

[0013] Preferably, the double-layer BOPP film has a sealing degree of not more than 50 mL at-1.00 kPa and a sealing degree of not more than 10 mL at-8.00 kPa, as determined by a negative pressure air extraction method.

[0014] Preferably, the folding and heat sealing positions of the inner and outer layers of the BOPP film are the same, and the positions of the tearing heads are the same or different.

[0015] Preferably, the folding and heat sealing positions of the inner and outer layers of the BOPP film are different, and the positions of the tearing heads are different.

[0016] The second aspect of the present application discloses a preparation method of the double-layer packaging film, comprising the following steps:

[0017] (1) heat sealing the inner-layer BOPP film by using a ceramic soldering iron: keeping the temperature of the soldering iron at 340℃±5℃, cutting the BOPP film on line by using a "N" shaped knife, and folding and heat sealing the inner-layer BOPP film according to the shape of the packaged object;

[0018] (2) heat sealing the outer-layer BOPP film by using a ceramic soldering iron: keeping the temperature of the soldering iron at 330℃±5℃, cutting the BOPP film on line by using a "N" shaped knife, and folding and heat sealing the outer-layer BOPP film.

[0019] Preferably, the inner-layer BOPP film and the outer-layer BOPP film are both BOPP films prepared by a step-by-step biaxial stretching method in a flat film method; the thickness of the inner-layer BOPP film is 15-18 μm, and the inner surface is coated with an activated carbon layer; the film thickness of the outer-layer BOPP film is 18-22 μm.

[0020] Preferably, the folding and heat sealing positions of the inner and outer layers of the BOPP film are the same, and the positions of the tearing heads are the same or different.

[0021] Preferably, the folding and heat sealing positions of the inner and outer layers of the BOPP film are different, and the positions of the tearing heads are different.

[0022] The third aspect of the present application discloses the use of the double-layer packaging film as a packaging film for a cigarette box or a cigarette carton.

[0023] The beneficial effects of the present application are:

[0024] 1. The double-layer packaging film of the present application is a double-layer BOPP film; both the inner-layer BOPP film and the outer-layer BOPP film are made of BOPP film prepared by the step-by-step biaxial stretching method in flat film method. The double-layer BOPP film of the present application has higher sealing degree, and is used for cigarette packaging film; the sealing degree of soft-box packaging of cigarettes is not more than 50 mL at -1.00 kPa; and the sealing degree of hard-box packaging is not more than 10 mL at -8.00 kPa.

[0025] 2. In the prior art, the moisture content of tobacco in the cigarette packet is generally 12.5% (equilibrium moisture content, 22℃, relative humidity 60%); while the moisture content of cigarette paper is 4.5%, the moisture content of inner liner paper is 4.0%, and the moisture content of frame paper is 6.0%, and the moisture content of carton packaging paper is 5.5%. The double-layer packaging film of the present application is used for cigarette packaging film, and the sealing stability of the cigarette packet is good, which ensures that the cigarette packet is isolated from the outside world; the moisture in the tobacco in the cigarette packet will diffuse to the cigarette paper, the carton packaging paper, etc., which is a humidity equilibrium system, and the requirements of tobacco packaging are well met. The double-layer packaging film of the present application is used for cigarette packaging film, and the inner surface of the inner-layer BOPP film is preferably coated with an activated carbon layer; the activated carbon can ensure that the moisture content of the tobacco is about 12.5%, and the activated carbon can release moisture when the moisture content is lower than 12.5%, and the activated carbon can release and absorb moisture when the moisture content is higher than 12.5%; that is, the activated carbon can absorb the excess moisture diffused inside, and when the internal moisture decreases, the activated carbon can also diffuse the moisture to the carton packaging paper and the tobacco, so as to maintain the moisture balance in the cigarette packet.

[0026] 3. The double-layer packaging film of the present application is used for cigarette packaging film, and in addition to considering the sealing effect, the consumer can easily tear the packaging film to open the packaging. The folding and heat sealing positions of the inner and outer layer BOPP films are the same, and the positions of the tearing heads are the same, at this time, the tearing effect is the same as that of the single-layer film, but the sealing effect is slightly worse, because the position of the tearing head is the air leakage point; the folding and heat sealing positions of the inner and outer layer BOPP films are the same, but the positions of the tearing heads are different, such as the tearing heads are on the left and right sides, at this time, the packaging needs to be torn twice to be opened, but the sealing effect is better; the folding and heat sealing positions of the inner and outer layer BOPP films are different, and of course the positions of the tearing heads are different, at this time, the packaging needs to be torn twice to be opened (the outer layer packaging is opened first to open the inner layer packaging), but the sealing effect is the best. The double-layer packaging film of the present application is used for cigarette packaging film, and in order to save costs, one of the cigarette box and the cigarette carton can use the double-layer packaging film of the present application; preferably, the cigarette box uses the double-layer packaging film.

[0027] 4, The double-layer packaging film of the present application uses a ceramic type iron to heat seal the inner and outer BOPP films. The iron of the packaging machine of the prior art is generally of cast iron and ceramic types. Since the cast iron type iron is used for a long time under high temperature during the operation of the equipment, the iron plane is prone to concave-convex phenomenon, which can adversely affect the heat sealing tightness of the cigarette film. The ceramic type iron used in the present application can improve the heat sealing tightness of the double-layer packaging film (better sealing degree). In addition, the temperature of the iron for heat sealing the outer BOPP film is about 10℃ lower than that of the iron for heat sealing the inner BOPP film, thereby avoiding damage to the inner BOPP film and ensuring the sealing degree of the cigarette box. DETAILED DESCRIPTION

[0028] The preferred embodiments described herein are used to illustrate and explain the present application, and are not used to limit the present application. Other advantages, objects and features of the present application will be illustrated in the following examples, and will be apparent to those skilled in the art to some extent, or can be taught by the practice of the present application.

[0029] The double-layer packaging film of the present application is a double-layer BOPP film; the inner and outer BOPP films are both BOPP films prepared by the step-by-step biaxial stretching method in the flat film method. The thickness of the inner BOPP film is 15-18 μm, and the thickness of the outer BOPP film is 18-22 μm. The sealing degree of the double-layer BOPP film measured by the negative pressure air extraction method for soft box packaging is not more than 50 mL at -1.00 kPa. The sealing degree of the double-layer BOPP film measured by the negative pressure air extraction method for hard box packaging is not more than 10 mL at -8.00 kPa.

[0030] Example 1: Preparation of double-layer packaging film and packaging of cigarette hard box.

[0031] The inner and outer BOPP films are both BOPP films prepared by the step-by-step biaxial stretching method in the flat film method; the thickness of the inner BOPP film is 18 μm, and the thickness of the outer BOPP film is 22 μm; the inner surface of the inner BOPP film is coated with an activated carbon layer.

[0032] (1) The ceramic type iron is kept at a temperature of 345℃, and an "N" shaped knife is used online to cut the BOPP film, thereby completing the folding and heat sealing of the top, bottom small corner and side surface of the inner BOPP film of the cigarette box;

[0033] (2) The ceramic iron temperature is kept at 335℃, and the "N" shaped knife is used to cut the BOPP film on line to complete the folding and heat sealing of the top, bottom and side of the outer BOPP film of the cigarette carton. The folding and heat sealing position is the same as that of the inner BOPP film, and the tearing head position is the same.

[0034] The sealing degree of the hard box packaging is measured by the negative pressure air extraction method, and the negative pressure is -8.00 kPa, and the result is 8 mL.

[0035] After the cigarette is stored for 6 months, the quality of the cigarette does not change. When smoked, the double-layer BOPP film tearing is basically the same as that of the single-layer film.

[0036] Example 2: Preparation of double-layer packaging film and packaging of cigarette soft box.

[0037] Both the inner and outer BOPP films are prepared by the step-by-step biaxial stretching method in the flat film method. The thickness of the inner BOPP film is 15 μm, and the thickness of the outer BOPP film is 20 μm. The inner surface of the inner BOPP film is coated with an activated carbon layer.

[0038] (1) The ceramic iron temperature is kept at 340℃, and the "N" shaped knife is used to cut the BOPP film on line to complete the folding and heat sealing of the top, bottom and side of the inner BOPP film of the cigarette carton.

[0039] (2) The ceramic iron temperature is kept at 330℃, and the "N" shaped knife is used to cut the BOPP film on line to complete the folding and heat sealing of the top, bottom and side of the outer BOPP film of the cigarette carton. The folding and heat sealing position is the same as that of the inner BOPP film, and the tearing head position is not the same.

[0040] The sealing degree of the hard box packaging is measured by the negative pressure air extraction method, and the negative pressure is -1.00 kPa, and the result is 30 mL.

[0041] After the cigarette is stored for 6 months, the quality of the cigarette does not change. When smoked, the double-layer BOPP film tearing is basically the same as that of the single-layer film.

[0042] Example 3: Preparation of double-layer packaging film and packaging of cigarette hard box, which is the same as example 1. However, the packaging of the cigarette hard box uses ordinary single-layer BOPP film.

[0043] When smoked, the double-layer BOPP film tearing position on the cigarette hard box is the same. After the cigarette is stored for 6 months, the quality of the cigarette does not change.

[0044] Example 4: The same as example 2, except that the folding and heat sealing position is not the same as that of the inner BOPP film, and the tearing head position is not the same.

[0045] The sealing degree of the hard box package was measured by the negative pressure air extraction method, the negative pressure was -1.00 kPa, and the result was 20 mL.

[0046] After the cigarettes were stored for 6 months, the quality of the cigarettes did not change.

[0047] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A dual layer packaging film characterized in that, The packaging film is a double-layer BOPP film; the inner-layer BOPP film and the outer-layer BOPP film are both BOPP films prepared by the step-by-step biaxial stretching method in the flat film method.

2. The dual layer packaging film according to claim 1, wherein, The thickness of the inner-layer BOPP film is 15-18 μm, and the inner surface is coated with an activated carbon layer; the thickness of the outer-layer BOPP film is 18-22 μm.

3. The dual layer packaging film according to claim 1, wherein, The double-layer BOPP film is determined by the negative pressure air extraction method: the sealing degree of the soft-box packaging is not more than 50 mL at-1.00 kPa, and the sealing degree of the hard-box packaging is not more than 10 mL at-8.00 kPa.

4. The dual layer packaging film according to claim 1, wherein, The folding and heat-sealing positions of the inner and outer-layer BOPP films are the same, and the positions of the tearing heads are the same or different.

5. The dual layer packaging film according to claim 1, wherein, The folding and heat-sealing positions of the inner and outer-layer BOPP films are different, and the positions of the tearing heads are different.

6. A process for the production of a double layer packaging film according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) heat-sealing the inner-layer BOPP film by using a ceramic soldering iron: keeping the temperature of the soldering iron at 340±5℃, cutting the BOPP film on line by using a "U" shaped knife, and folding and heat-sealing the inner-layer BOPP film according to the shape of the packaging object; (2) heat-sealing the outer-layer BOPP film by using a ceramic soldering iron: keeping the temperature of the soldering iron at 330±5℃, cutting the BOPP film on line by using a "U" shaped knife, and folding and heat-sealing the outer-layer BOPP film.

7. The production method according to claim 6, wherein The inner-layer BOPP film and the outer-layer BOPP film are both BOPP films prepared by the step-by-step biaxial stretching method in the flat film method; the thickness of the inner-layer BOPP film is 15-18 μm, and the inner surface is coated with an activated carbon layer; the thickness of the outer-layer BOPP film is 18-22 μm.

8. The preparation method according to claim 6, characterized in that, The folding and heat-sealing positions of the inner and outer-layer BOPP films are the same, and the positions of the tearing heads are the same or different.

9. The preparation method according to claim 6, characterized in that, The folding and heat-sealing positions of the inner and outer-layer BOPP films are different, and the positions of the tearing heads are different.

10. Use of the double-layer packaging film according to any one of claims 1-5 as a packaging film for a cigarette box or a cigarette carton.