Low-residue ultralow-temperature heat-sealing paper-plastic composite film and preparation method thereof

Abstract

The invention belongs to the technical field of packaging, and particularly relates to a low-residue ultralow-temperature heat-sealing paper-plastic composite film and a preparation method thereof. The composite film is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealing CPP film, the paper layer is connected with the BOPP printing film by coating first solvent type glue, and the low-temperature heat-sealing CPP film is connected with the paper layer by coating second solvent type glue; the low-temperature heat-sealing CPP film is composed of a composite layer, a middle layer and a heat-sealing layer, and the composite layer is connected with the paper layer. The prepared paper-plastic composite film is low in solvent residue and not prone to layering.

Description

Technical Field

[0001] The invention relates to the technical field of packaging, in particular to a low-residue ultra-low temperature heat-sealed paper-plastic composite film and a preparation method thereof. Background Art

[0002] In plastic flexible packaging, paper-plastic composite films are widely used. They are used in some flexible packaging products that require good stiffness, such as common melon seed bags and nut bags, and in some product packaging that requires easy tearing but not high barrier properties, such as sugar bags and fast food tableware packaging.

[0003] Although paper-plastic composite film has advantages such as high stiffness and easy tearing, if solvent glue is used for composite during production, the paper will absorb the solvent and the residual solvent will be greater than 5mg / m 2 , resulting in excessive residues, making it difficult to meet the national standard residue requirements for food packaging. When the composite film is heat-sealed, if the paper is placed in the middle layer, due to the poor thermal conductivity of the paper and the heat-sealing temperature required for the inner heat-sealing film is 100°C or above, the temperature of the outer layer will exceed 100°C, causing the moisture in the paper to vaporize and not be released, thereby generating bubbles and causing the composite film to delaminate. Therefore, paper-plastic composite films are prone to the disadvantages of excessive residues and heat-sealing delamination.

[0004] At present, the solution to the problem of excessive residue is to use water-glue lamination. However, if the paper is placed in the outer layer, the water in the water-glue will enter the paper, causing the paper to become warped and uneven. If the paper is placed in the middle layer, the water will enter the paper, resulting in a high water content in the paper. When heat-sealed at high temperature, the water vaporizes and causes the paper to delaminate. The solution to heat-sealing delamination is to laminate all the paper in the outer layer, which can be exhausted instantly without destroying the composite strength and causing delamination. However, if the paper is placed in the outer layer, the stiffness of the composite film will be greatly reduced, and the printability and water resistance will be poor. Therefore, the use of these two measures limits the composite process and film material structure of the paper-plastic composite film. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a low-residue ultra-low temperature heat-sealed paper-plastic composite film and a preparation method thereof. The low-residue ultra-low temperature heat-sealed paper-plastic composite film has low solvent residue and is not easy to delaminate.

[0006] In order to achieve one of the purposes of the present invention, the present invention adopts the following technical solutions:

[0007] A low-residue ultra-low-temperature heat-sealing paper-plastic composite film, which is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealing CPP film, wherein the paper layer is connected to the BOPP printing film by coating a first solvent-based glue, and the low-temperature heat-sealing CPP film is connected to the paper layer by coating a second solvent-based glue; the low-temperature heat-sealing CPP film consists of a composite layer, an intermediate layer and a heat-sealing layer, and the composite layer is connected to the paper layer.

[0008] Preferably, after coating the first solvent-based glue and coating the second solvent-based glue, the glue is dried using a guide roller nozzle air suspension circulating wind desolventization technology.

[0009] Preferably, the composite layer and the middle layer are each composed of 100 parts by mass of homopolymer polypropylene resin, and the heat sealing layer is composed of 45-55 parts by mass of copolymer polypropylene resin, 40-50 parts by mass of elastomer, 2 parts by mass of antiblocking agent and 3 parts by mass of slip agent.

[0010] Preferably, the first solvent-based glue is applied by flexographic gluing, and the undried glue coating amount is 6-8g / m 2 , solvent content is 3.3-4.4g / m 2 The second solvent-based glue is applied by anilox roller gravure, and the undried glue coating amount is 8-12g / m 2 , containing solvent in the range of 5.6-8.4g / m 2 .

[0011] Preferably, the brands of the first solvent-based glue and the second solvent-based glue are both LA2880 produced by Henkel.

[0012] Preferably, the brand of homopolymer polypropylene resin is HD601CF produced by Borouge; the brand of copolymer polypropylene resin is 7410XCP produced by Basel; the brand of Dow is ENGAGE8200; the brand of antiblocking agent is PPAB-5 produced by Yintai; the brand of slip agent is SLPP-7 produced by Beijing Yalun.

[0013] Preferably, the thickness of the low-temperature heat-sealing CPP film is 20-50 μm; the thickness of the composite layer is 10-15% of the thickness of the low-temperature heat-sealing CPP film, the thickness of the intermediate layer is 60-70% of the thickness of the low-temperature heat-sealing CPP film, and the thickness of the heat-sealing layer is 15-20% of the thickness of the low-temperature heat-sealing CPP film.

[0014] Preferably, the thickness of the BOPP printed film is 18 μm.

[0015] Preferably, the square grammage of the paper layer is 40 g.

[0016] In order to achieve one of the purposes of the present invention, the present invention provides a method for preparing a low-residue ultra-low temperature heat-sealed paper-plastic composite film, the specific steps of which are as follows:

[0017] S1. Apply a first solvent-based glue on the ink surface of the BOPP printing film with a flexographic plate, and laminate the coated BOPP printing film with the paper layer after it dries, thus completing the first lamination;

[0018] S2. A low-temperature heat-sealing CPP film is obtained through a casting process, and then a second solvent-based glue is flexographically coated on the composite surface of the low-temperature heat-sealing CPP film. After drying, it is laminated with the first laminated paper layer to complete the second lamination to obtain a low-residue ultra-low-temperature heat-sealing paper-plastic composite film.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The present invention adopts widely used solvent glue to solve the problem of excessive solvent residue through process innovation; adopts low-temperature heat sealing formula design of heat sealing film to solve the problem of heat damage to the bonding strength of the composite film, thereby achieving the lamination of paper in the middle layer of the composite film and expanding the composite film.

[0021] 2) The present invention adopts solvent-based glue compounding, high-concentration glue, low glue application amount, and air suspension exhaust technology of guide roller nozzle, which can quickly volatilize the solvent and reduce solvent residue.

[0022] 3) The paper of the present invention is arranged between two films, and a low-temperature heat-sealed CPP film is used. By lowering the heat-sealing temperature of the composite film, the thermal stratification of the bonding surface of the paper and the film caused by high-temperature heat sealing is avoided, which not only solves the stratification problem of the paper-plastic composite film, but also improves the stiffness of the composite film.

[0023] 4) Use solvent-based glue for compounding, use 45% high-concentration glue, use four-roller flexographic gluing method to apply glue, and use exhaust technology to quickly evaporate the solvent to reduce the solvent residue, which can make the composite film residue at 4mg / m 2 Within.

[0024] 5) The low-temperature heat-sealing CPP designed by the present invention can reduce the heat-sealing temperature of the composite film from 185°C to 135°C for packaging equipment. The actual sealing temperature required for the inner layer is 85°C, which greatly reduces the heat-sealing temperature. Therefore, the moisture in the paper cannot be vaporized, thereby not destroying the bonding strength between the paper and the film.

[0025] 6) Borouge's homopolymer polypropylene resin is used as the raw material resin for the composite layer and the intermediate layer. The resin has a Vicat softening point of 154°C, a melting point of 164°C, and good heat-resistance deformation. It can support the CPP film without deformation when the composite film is heat-sealed, making the heat-sealed area smooth and beautiful. The heat-sealing layer uses Basel's copolymer polypropylene resin and Dow elastomer blended. The Vicat softening point of the blended resin after film formation is less than 70°C, the melting point is less than 95°C, and the film heat-sealing temperature is 85°C. The heat-sealing layer also adds an opening agent from Yintai Company, which contains a high-efficiency anti-adhesion masterbatch of 5% high-purity zeolite. Its function is to produce protrusions or ridges on the surface of the film so that air can enter between the rolled films without vacuum adhesion. The heat-sealing layer also adds a slip agent, the active ingredient of which is erucic acid amide. After the film is made, it can be precipitated on the heat-sealing surface of the film to reduce the friction between the film and the contact roller or mold, so that the film can flow smoothly, which can meet the requirements of high-speed packaging.

[0026] 7) Use 18 micron matte BOPP produced by Yongxin New Materials Company for inner printing, and flexographically coat solvent-based glue on the ink surface of the printed film. The selected glue concentration is high (the solvent accounts for a small proportion) and the coating amount is small, so that the undried glue solvent applied is small and easy to dry. After drying, the coated printed film is compounded with 40g of paper produced by Zhejiang Xianhe Paper Industry to complete the first layer. The composite layer of the 30 micron low-temperature heat-sealed CPP film produced by the present invention is coated with glue, and the gluing and drying processes are the same. After drying, it is compounded with the paper surface of the first film to complete the second layer.

[0027] 8) The use of solvent-based glue for compounding, 45% high-concentration glue, four-roller flexographic gluing, and exhaust technology for rapid solvent evaporation greatly reduce the solvent residue, which can make the composite film residue at 4mg / m 2 Within; during the second layer, the low-temperature heat-sealed CPP cannot reduce the solvent residue by increasing the drying temperature. The present invention adopts the guide roller nozzle air suspension circulating wind desolventization technology. The air suspension + guide roller nozzle can increase the effective action area of ​​the hot air, reduce the solvent residue, and use a lower temperature drying to reduce the film stretching; the composite film prepared by the flexographic gluing process has good gloss and a smooth glue layer, which is different from the concave and convex gluing surface of the anilox roller. Therefore, the glue layer can be made thinner, thereby obtaining the minimum glue amount and further reducing the solvent residue. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the composite film is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealed CPP film, the paper layer is connected to the BOPP printing film by coating a first solvent-based glue, and the low-temperature heat-sealed CPP film is connected to the paper layer by coating a second solvent-based glue; the low-temperature heat-sealed CPP film is composed of a composite layer, an intermediate layer and a heat-sealing layer, and the composite layer is connected to the paper layer. The composite layer and the intermediate layer are both composed of 100 parts by mass of homopolymer polypropylene resin, and the heat-sealing layer is composed of 50 parts by mass of copolymer polypropylene resin, 45 parts by mass of elastomer, 2 parts by mass of opening agent and 3 parts by mass of slip agent. After coating the first solvent-based glue and the second solvent-based glue, the glue is dried by using a guide roller nozzle air suspension circulating wind desolventization technology.

[0031] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the specific steps are as follows:

[0032] S1. The first solvent-based glue is applied to the ink side of the 18-micron matte BOPP printing film produced by Yongxin New Materials Company. The undried glue coating is 6g / m 2 , where the amount of solvent is 3.3g / m 2 ; After the glued BOPP printed film is dried, it is laminated with the paper to complete the lamination;

[0033] S2, a low-temperature heat-sealing CPP film is obtained by a casting process, and then a second solvent-based glue is coated on the composite surface of the low-temperature heat-sealing CPP film, and the undried glue coating amount is 8g / m 2 , containing solvent at 5.6g / m 2 After drying, it is compounded with a laminated paper layer to complete the second lamination to obtain a paper-plastic composite film 1.

[0034] Example 2

[0035] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the composite film is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealed CPP film, the paper layer is connected to the BOPP printing film by coating a first solvent-based glue, and the low-temperature heat-sealed CPP film is connected to the paper layer by coating a second solvent-based glue; the low-temperature heat-sealed CPP film is composed of a composite layer, an intermediate layer and a heat-sealing layer, and the composite layer is connected to the paper layer. The composite layer and the intermediate layer are both composed of 100 parts by mass of homopolymer polypropylene resin, and the heat-sealing layer is composed of 55 parts by mass of copolymer polypropylene resin, 40 parts by mass of elastomer, 2 parts by mass of opening agent and 3 parts by mass of slip agent. After coating the first solvent-based glue and the second solvent-based glue, the glue is dried by using a guide roller nozzle air suspension circulating wind desolventization technology.

[0036] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the specific steps are as follows:

[0037] S1. The first solvent-based glue is applied to the ink side of the 18-micron matte BOPP printing film produced by Yongxin New Materials Company. The undried glue coating is 7g / m 2 , containing solvent at 4g / m 2 ; After the glued BOPP printed film is dried, it is laminated with the paper to complete the lamination;

[0038] S2, a low-temperature heat-sealing CPP film is obtained by a casting process, and then a second solvent-based glue is coated on the composite surface of the low-temperature heat-sealing CPP film, and the undried glue coating amount is 10g / m 2 , containing solvent at 6.5g / m 2 After drying, it is compounded with a laminated paper layer to complete the second lamination to obtain a paper-plastic composite film 2.

[0039] Example 3

[0040] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the composite film is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealed CPP film, the paper layer is connected to the BOPP printing film by coating a first solvent-based glue, and the low-temperature heat-sealed CPP film is connected to the paper layer by coating a second solvent-based glue; the low-temperature heat-sealed CPP film is composed of a composite layer, an intermediate layer and a heat-sealing layer, and the composite layer is connected to the paper layer. The composite layer and the intermediate layer are both composed of 100 parts by mass of homopolymer polypropylene resin, and the heat-sealing layer is composed of 45 parts by mass of copolymer polypropylene resin, 50 parts by mass of elastomer, 2 parts by mass of opening agent and 3 parts by mass of slip agent. After coating the first solvent-based glue and the second solvent-based glue, the glue is dried by using a guide roller nozzle air suspension circulating wind desolventization technology.

[0041] A low-residue ultra-low temperature heat-sealed paper-plastic composite film, the specific steps are as follows:

[0042] S1. The first solvent-based glue is applied to the ink side of the 18-micron matte BOPP printing film produced by Yongxin New Materials Company. The undried glue coating is 8g / m 2 , containing solvent at 4.4g / m 2 ; After the glued BOPP printed film is dried, it is laminated with the paper to complete the lamination;

[0043] S2, a low-temperature heat-sealing CPP film is obtained by a casting process, and then a second solvent-based glue is coated on the composite surface of the low-temperature heat-sealing CPP film, and the undried glue coating amount is 8g / m 2 , containing solvent at 4.4g / m 2 After drying, it is compounded with a laminated paper layer to complete the second lamination to obtain a paper-plastic composite film 3.

[0044] Comparative Example 1

[0045] Paper-plastic composite film 4: Solvent glue was used to composite matte BOPP printing and 40g paper, and then aqueous glue was coated on the paper surface and composited with composite-grade CPP film to obtain paper-plastic composite film 4.

[0046] Comparative Example 2

[0047] Paper-plastic composite film 5: The matte BOPP printing and 40g paper were compounded with water-based glue, and then the water-based glue was coated on the paper surface and compounded with the composite-grade CPP film to obtain paper-plastic composite film 5.

[0048] In the above examples 1-3, the brand of the homopolymer polypropylene resin is HD601CF produced by Borouge; the brand of the copolymer polypropylene resin is 7410XCP produced by Basel; the brand of the Dow is ENGAGE8200; the brand of the antiblocking agent is PPAB-5 produced by Yintai; the brand of the slip agent is SLPP-7 produced by Beijing Yalun. The specific particle properties are shown in Table 1 below:

[0049] Table 1 Performance of different particles

[0050]

[0051] In Examples 1-3, the casting process parameters of the low temperature heat-sealed CPP film are shown in Table 2 below:

[0052] Table 2 Casting process parameters

[0053]

[0054] The performance of the paper-plastic composite film 2 prepared in Example 2 and the paper-plastic composite films 4-5 of Comparative Examples 1-2 were tested respectively, and the results are shown in Table 3 below:

[0055] Table 3 Paper-plastic composite film performance test

[0056] Test items Example 2 Comparative Example 1 Comparative Example 2 <![CDATA[Residual solvent mg / m 2 > 3.2 11.7 4.1 Heat sealing temperature℃ 95 130 125 TD heat seal strength N / 15mm 7.8 7.3 6.9 Heat resistance 180℃, 0.5s No bubbles No bubbles There are bubbles

[0057] It can be seen from Table 3 above that the paper-plastic composite film prepared in Example 2 has the lowest solvent residue and the highest heat sealing strength, and there are no bubbles in the heat sealing area. By using ultra-low temperature heat sealing CPP in the inner layer, the heat sealing temperature is lower than 100° C., so that the moisture originally contained in the paper is not vaporized, and the paper does not produce bubble stratification.

Claims

1. A low-residue ultra-low temperature heat-sealing paper-plastic composite film, characterized in that: The composite film is formed by sequentially connecting a BOPP printing film, a paper layer and a low-temperature heat-sealing CPP film; the paper layer is connected to the BOPP printing film by coating a first solvent-based glue, and the low-temperature heat-sealing CPP film is connected to the paper layer by coating a second solvent-based glue; the low-temperature heat-sealing CPP film consists of a composite layer, an intermediate layer and a heat-sealing layer, and the composite layer is connected to the paper layer.

2. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: After coating the first solvent-based glue and coating the second solvent-based glue, the glue is dried by using a guide roller nozzle air suspension circulating wind desolventization technology.

3. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: The composite layer and the middle layer are both composed of 100 parts by weight of homopolymer polypropylene resin, and the heat-sealing layer is composed of 45-55 parts by weight of copolymer polypropylene resin, 40-50 parts by weight of elastomer, 2 parts by weight of anti-blocking agent and 3 parts by weight of lubricant.

4. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: The first solvent-based glue is applied by flexographic glue, and the undried glue coating amount is 6-8g / m 2 , solvent content is 3.3-4.4g / m 2 The second solvent-based glue is applied by anilox roller gravure, and the undried glue coating amount is 8-12g / m 2 , containing solvent in the range of 5.6-8.4g / m 2 .

5. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: The brands of the first solvent-based glue and the second solvent-based glue are both LA2880 produced by Henkel.

6. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 3, characterized in that: The brand of the homopolymer polypropylene resin is HD601CF produced by Borouge; the brand of the copolymer polypropylene resin is 7410XCP produced by Basel; the brand of the Dow is ENGAGE8200; the brand of the antiblocking agent is PPAB-5 produced by Yintai; the brand of the slip agent is SLPP-7 produced by Beijing Aaron.

7. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 3, characterized in that: The thickness of the low temperature heat seal CPP film is 20-50 μm; the thickness of the composite layer is 10-15% of the thickness of the low temperature heat seal CPP film, the thickness of the middle layer is 60-70% of the thickness of the low temperature heat seal CPP film, and the thickness of the heat seal layer is 15-20% of the thickness of the low temperature heat seal CPP film.

8. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: The thickness of the BOPP printed film is 18 μm.

9. The low-residue ultra-low temperature heat-sealing paper-plastic composite film according to claim 1, characterized in that: The square grammage of the paper layer is 40 g.

10. A method for preparing a low-residue ultra-low temperature heat-sealing paper-plastic composite film according to any one of claims 1 to 9, characterized in that: The specific steps are as follows: S1. Apply a first solvent-based glue on the ink surface of the BOPP printing film with a flexographic plate, and laminate the coated BOPP printing film with the paper layer after it dries, thus completing the first lamination; S2. A low-temperature heat-sealing CPP film is obtained through a casting process, and then a second solvent-based glue is flexographically coated on the composite surface of the low-temperature heat-sealing CPP film. After drying, it is laminated with the first laminated paper layer to complete the second lamination to obtain a low-residue ultra-low-temperature heat-sealing paper-plastic composite film.

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