A processing technology of PP coated paper container

Abstract

The present application discloses a processing technology for a PP coated paper container, which belongs to the field of coated paper forming technology, including the steps of PP coated paper production, container wall and container bottom production, and container initial forming; the container wall is subjected to heating treatment and surface treatment on the edges to be overlapped before lamination, and the heating includes preheating, hot air blowing, and heat preservation. The surface treatment of the side edges of the base paper includes hot embossing, ultrasonic roughening, and corona treatment, and the surface treatment of the side edges of the coating includes corona treatment, chlorine plasma treatment, and oxygen plasma treatment. Before the hot-pressing lamination of the coated paper roll, the present application preheats the edges to be overlapped to reach the softening and melting temperature of the PE component in the coating layer, so that the molecular chains are curled, affecting the surface roughness and improving the hydrophilicity, and enhancing the adhesive properties; after heating, the surface treatment is performed to increase the effective adhesion area of ​​the base paper surface, and change the surface activity, polarity, and hydrophilicity of the film to further improve the adhesive properties.

Description

Technical Field

[0001] The present application relates to the field of laminated paper forming technology, and in particular to a processing technology for a PP laminated paper container. Background Art

[0002] Laminated paper is a new type of composite release paper material that is formed by laminating a film layer with base paper through a laminating process. Laminated paper includes plastic release paper and plastic-free release paper. Laminated paper used in the food and medical fields mainly refers to plastic laminated paper. Its laminating process generally uses PE, PP or PLA melts, which are coated on the surface of the base paper through a casting machine to form an oil-proof, waterproof and heat-sealed laminated layer.

[0003] Laminated paper containers refer to container products made by cutting and hot-gluing laminated paper raw materials, such as instant noodle buckets, paper cups, disposable bowls / plates, etc. In addition to cutting, the bonding process of laminated paper containers generally adopts two methods: adhesive bonding and adhesive-free bonding. Adhesive bonding needs to consider the adhesive's adhesion, component safety, and solvent volatilization after bonding. The solvent volatilization problem after bonding refers to the problem that the solvent component of the adhesive volatilizes during the drying process, which is easy to produce a large number of bubbles, causing the adhesive layer to be susceptible to moisture and leakage, and failing to achieve sealed packaging.

[0004] Therefore, adhesive-free bonding is a green and environmentally friendly production trend for thermal bonding forming of laminated paper containers. It mainly uses the principle that the laminated layer can penetrate and bond to the base paper layer after secondary melting under hot pressing conditions. However, since the laminated layer often has a very high flatness and low surface polarity, under the existing hot pressing bonding conditions, the adhesion between the laminated layer and the base paper layer is often low, resulting in poor thermal stability of the overlapping part of the two, which leaks rapidly when loaded with hot water. Summary of the invention

[0005] In order to improve the problem of low adhesion of the overlapping portion between the laminated layer and the base paper layer in the thermal bonding molding process of the laminated paper container, the present application provides a processing technology for a PP laminated paper container.

[0006] The specific technical solutions adopted are as follows:

[0007] A processing technology for a PP coated paper container comprises the following steps:

[0008] Step 1: PP coated paper production: PP coating is performed on base paper to obtain PP coated paper;

[0009] The raw material PP used for laminating mainly includes the following components by weight: 100 parts of PP, 15-25 parts of LDPE, 4-8 parts of PE-g-MAH, 0.2-0.5 parts of HSt, 2-4 parts of titanate coupling agent, and 2-4 parts of antioxidant;

[0010] Step 2, making container wall and container bottom: die-cutting the obtained PP coated paper to obtain container wall paper and container bottom; heating the edge of the container wall paper to be overlapped to the softening temperature of LDPE in the raw material PP and heat-insulating treatment, and then rolling it to obtain the container wall;

[0011] Step 3: Initial forming of the container: insert the container bottom into the container wall, heat and bond them to obtain a PP coated paper container.

[0012] By adopting the above technical solution, the edges to be overlapped on both sides are heated before rolling, so that the surface characteristics of the coating side are changed, thereby improving the bonding performance.

[0013] It should be noted that the heating bonding in step three refers to: placing the container wall in a heating mold, applying glue around the container bottom, and bonding it to the container wall at high temperature, and still using the container molding equipment and process in the prior art, such as the "Paper cup bottom bonding equipment and paper cup processing equipment" proposed in patent publication number CN110936658A. The glue used is Mingchuang 5080B coating glue with a viscosity of 20000±2000cps. This application only improves the glue-free bonding process of the container wall, and the improvement of the container bottom lacks relevant equipment support and needs further research and development.

[0014] It should be noted that this application uses FC9413L of Singapore TPC, a common commodity that falls within the composition range, as the PP laminating raw material for comparative tests, which contains the main components LDPE and PE-g-MAH, which are the basic components of PP laminating materials, and the remaining components are all based on the film-forming properties and performance requirements after film formation. The composition range is obtained to prove that the laminating process of this application has wide applicability and market potential. This application analyzes the commodity for reverse development and obtains a more preferred formula. Preliminary tests show that the softening point, melting point and adhesion of the laminating side of the laminating paper obtained by using the formula raw materials within the above range are close to those of FC9413L. After testing, the melting point of the raw material PP laminating is 146-151°C, so the temperature of hot pressing laminating should exceed 155°C; after testing, the melting point and softening point of the LDPE component in the raw material PP are both within the range of 115-123°C, so the temperature for changing the surface properties of the laminating side by heating also needs to reach this temperature range.

[0015] Preferably, the antioxidant includes at least one of BASF Irganox MD 1024, ADEKA AO-60, STAB 8T and Albemarle AT-1135; and the titanate coupling agent includes at least one of TMC-102, TMC-201, TMC-101 and TMC-311w.

[0016] By adopting the above technical solution, the antioxidant is mainly used to improve the free radical resistance, heat resistance and anti-aging performance of the coating layer; in addition, HSt as a toughening agent can also be replaced by other ingredients: at least one of metal soap toughening agents, aliphatic amide toughening agents, fatty acid toughening agents or fatty acid ester toughening agents. Metal soap toughening agents include zinc stearate, calcium stearate or magnesium stearate, etc.; aliphatic amides include EBS, oleic acid amide, etc.; fatty acids include stearic acid and hydroxystearic acid; fatty acid esters are exemplified by PETS, glyceryl monostearate, glyceryl polystearate, etc.

[0017] Preferably, the heating treatment of the edge to be overlapped in step 2 specifically includes the following steps:

[0018] 1) Preheating: Place the PP coated paper with the base paper side at the bottom and the coated side at the top. Preheat the lower side of the base paper on both sides through an electric heating plate. Control the temperature of the electric heating plate at 60-80°C for 1-2 minutes.

[0019] 2) Hot air blowing: Blow hot air on the top of one side of the laminated paper, and use a thick plate to cover the rest of the surface of the PP laminated paper. The hot air temperature is gradually increased from 60℃ to 120±5℃ at a heating rate of 5-10℃ / min. Keep the hot air blowing continuously and evenly on the surface of the laminated side edge. The hot air blowing flow rate is 0.05-0.15m / s;

[0020] 3) Insulation: quickly adjust the electric heating plates under the sides of the base paper to 100±5℃, and keep the sides of the base paper warm for 5-10 minutes;

[0021] 4) Hot pressing: Place the PP coated paper on the roll core mold so that the coated side edge on one side in step 2) covers the base paper side edge on the other side, and hot press for 5-8 seconds at 165±10°C to form the container wall.

[0022] By adopting the above technical solution, the temperature of the electric heating plate in step 1) is 60-80°C, which is to facilitate subsequent temperature control. Too high or too low a temperature will affect the temperature control of subsequent steps 2) and 3);

[0023] In step 2), the blowing temperature of the hot air is 120±5°C, which is the melting point and softening point of LDPE in the PP coated paper. By preheating, heating and heat preservation before hot pressing, the surface temperature of the coating side edge is adjusted to this temperature range. Microscopically, the LDPE region in the polymer film reaches a viscous flow state in advance, causing a sudden change in the van der Waals force between each phase region (including the crystallization region), thereby causing the curling and stretching of the molecular chain to change, thereby affecting the film morphology. Macroscopically, under the influence of the surface tension at the interface between the film and the paper, wrinkles are caused on the film surface. The wrinkles are evenly distributed by heat preservation, and the change in the roughness of the film surface affects the surface contact angle and activity, further affecting the bonding performance of the film and the paper during thermal bonding.

[0024] In step 3), the temperature of the electric heating plate is 100±5°C, which is the film surface temperature measured by infrared. The heating temperature of the electric heating plate is difficult to control and needs to be controlled under the above conditions. The surface temperature of the electric heating plate shall not exceed 105°C. Due to the large temperature control error, the temperature of the electric heating plate is set within the range of 95-100°C in actual operation. This point is emphasized to remind relevant technical personnel; in step 4), the hot pressing of 5-8s is also the basic time of the existing hot pressing and laminating process. If it is too short, the degree of melting of the coating layer is insufficient. If it is too long, the coating layer is easily squeezed out under the action of hot pressing, resulting in a thinner thickness of the laminating layer; the hot pressing and laminating temperature of 165±10°C refers to the temperature of the hot pressing head, which exceeds the coating temperature of 155±5°C of the PP coating material. After the side edge of the coating is laminated with the side edge of the base paper, the coating layer melts and penetrates into the base paper layer. The interface effect between the two depends on the activity (including physical activity and chemical activity) of the two laminating surfaces, so it is necessary to perform surface treatment on it.

[0025] Preferably, the PP coated paper obtained in step 1 can be a single coated paper in which only one side of the base paper is coated with a coating layer, or can be a double coated paper in which both sides of the base paper are coated with a coating layer.

[0026] By adopting the above technical solution, single-laminated paper is used to hold hot foods, and double-laminated paper is used to hold cold foods. Our factory's production line mainly uses single-laminated paper, so the following mainly improves the laminating process of the overlapping part of the single-laminated paper.

[0027] Preferably, the edge to be overlapped includes a coated side edge on one side and a base paper side edge on the other side, and the edge to be overlapped is subjected to surface treatment during the heating process.

[0028] By adopting the above technical solution, the surface treatment of the edge to be overlapped is specifically carried out after the heat preservation process in step 3), and the heating device (electric heating plate or hot air nozzle) is temporarily removed during the treatment.

[0029] Preferably, the surface treatment of the side edge of the base paper includes at least one of hot embossing, ultrasonic roughening or corona treatment.

[0030] By adopting the above technical solution, the container wall paper is placed flat on the conveyor belt with the coated side facing upward, the upper surface is flattened by a steel plate and one side of the coated side edge is exposed, and the base paper side is facing downward and the other side of the base paper side edge is exposed, that is, the upper surface of the coated side edge is processed, and the bottom surface of the base paper side edge is processed.

[0031] Preferably, the hot embossing uses a polishing plate with the same size as the side edge of the base paper, which is attached to the bottom surface of the side edge of the base paper. The plate surface temperature is controlled at 80-100°C to perform hot stamping and embossing on the bottom surface to form grid-like folds.

[0032] By adopting the above technical solution, the hot pressing pressure needs to be determined according to the thickness and material of the base paper. The hot pressing pressure should not exceed 1.5Mpa to avoid damaging the internal fiber structure of the base paper.

[0033] Preferably, the ultrasonic roughening uses a grinding plate with the same size as the side edge of the base paper, which is attached to the bottom surface of the side edge of the base paper, and uses an ultrasonic vibration source to ultrasonically grind and polish the bottom surface.

[0034] By adopting the above technical solution, the powder adhering to the bottom surface should be cleaned after grinding to avoid affecting the adhesion.

[0035] Preferably, the corona treatment uses needle-shaped electrodes evenly arranged just below the side edges of the base paper and applied with a positive voltage. When the voltage rises to a certain value, the luminous part extending from the needle tip will touch the steel plate attached above and be divided into many linear luminous parts, all of which are in a state of continuous flashing. These luminous parts are plasma, which has a cleaning and activation effect on the surface of the base paper.

[0036] By adopting the above technical solution, a BXS-08 intelligent corona machine is used, the output power range of the corona machine is 2-70kW, the frequency adjustment range is 10-25kHz, and the processing voltage range is between 10000-20000V. The corona treatment of this application adopts 20 groups of electrodes distributed in strips, and is directly facing the midline position of the side edge of the base paper, and the voltage is gradually adjusted to 15±1kV, and the treatment is 1-2min. The corona plasma causes a free radical reaction on the plastic surface to cause the polymer to cross-link, the surface becomes rough and increases its wetting to polar solvents. These plasmas enter the surface of the printed body through electric shock and penetration to destroy its molecular structure, thereby oxidizing and polarizing the treated surface molecules, activating the surface, and increasing the adhesion ability of the printed surface.

[0037] Preferably, the surface treatment of the side edge of the coating includes at least one of corona treatment, chlorine plasma treatment or oxygen plasma treatment.

[0038] By adopting the above technical solution, when undergoing multi-stage processing, an assembly line mechanism can be used, that is, the die-cut container wall paper is placed on the conveyor belt, and through holes are opened on the conveyor belt to expose the edges to be overlapped on both sides, and a steel plate can be used to press the upper surface to expose only one side of the coated side edge. The coated side edge on one side is successively subjected to hot air blowing, corona treatment, chlorine plasma treatment or oxygen plasma treatment, and the base paper side edge on the other side is successively subjected to electric heating plate, hot embossing, ultrasonic roughening or corona treatment, and finally curled by the mold, and the upper roll is subjected to hot pressing and laminating.

[0039] Preferably, plasma surface treatment: uses a radio frequency generator to emit excitation energy at a relatively high voltage to produce a characteristic glow discharge phenomenon, so that the gas substance passing through generates many excited electrons, ions and atoms, and a cover is made to surround the side edge of the coating, and the excited gas is used to bombard the surface of the coating layer, so that the surface chemical groups change or form new groups or generate free radicals, generate deposition, and achieve the purpose of chemical modification and physical modification of the polymer surface, and generate polarity;

[0040] The chlorine plasma is produced by using an ICP-98C plasma etcher, and the production conditions are: ICP power 300-700W, more preferably 500W, DC bias 100-300V, more preferably 200V, gas Cl2 / He, flow rate 32sccm / 8sccm; the generated chlorine plasma is discharged into the cover body, and the upper surface of the side edge of the coating is treated for 1-2min;

[0041] By adopting the above technical solution, XPS surface detection shows that the surface of the coating side has obvious polyvinyl chloride and polyvinylidene chloride and a large number of active Cl· free radicals, but no quantitative analysis has been done yet. In addition to changing the surface polarity, the non-crystallized polyvinyl chloride and polyvinylidene chloride also have a higher bonding strength with the base paper than the PP and PE components.

[0042] Oxygen plasma is produced by ICP-98C plasma etcher, and the production conditions are: ICP power 400-800W, more preferably 600W, DC bias 150-350V, more preferably 250V, gas O2 / He, flow rate 30sccm / 5sccm;

[0043] By adopting the above technical solution, the generated oxygen plasma can be discharged into the cover body, and the upper surface of the side edge of the coating is treated for 1-2 minutes. XPS surface detection shows that there are a large number of active O·, HO· and carbonyl radicals, which remove and cover some Cl-based components, but no quantitative analysis has been done yet. The surface hydrophilicity is greatly improved, the contact angle is reduced, and thus the adhesion is improved.

[0044] In summary, the present application includes at least one of the following beneficial technical effects:

[0045] 1. In the present application, the edges to be overlapped are first heated before the laminated paper rolls are hot-pressed and laminated, which specifically includes preheating, hot air blowing and heat preservation processes, and reaches the softening and melting temperature of the PE component in the laminated layer, so that the molecular chains are curled and the surface tension of the film is changed, thereby affecting the surface roughness and improving the hydrophilicity, thereby enhancing the bonding performance.

[0046] 2. The present application secondly performs surface treatment on the overlapped edges after heating, and treats the coated side edges and the base paper side edges respectively. The surface treatment of the base paper side edges includes hot embossing, ultrasonic roughening and corona treatment, and the surface treatment of the coated side edges includes corona treatment, chlorine plasma treatment and oxygen plasma treatment. The surface treatment of the base paper side edges is mainly to increase the effective adhesion area of ​​the base paper side surface, and the surface treatment of the coated side edges is to change the surface activity, polarity and hydrophilicity of the membrane, thereby greatly improving the adhesion performance. DETAILED DESCRIPTION

[0047] The present application is further described in detail below in conjunction with specific preparation examples, embodiments and comparative tests.

[0048] Preparation Example 1:

[0049] The raw material PP used for laminating mainly includes the following components: 100Kg of PP, 15Kg of LDPE, 8Kg of PE-g-MAH, 0.5Kg of HSt, 2Kg of TMC-102 titanate coupling agent, 4Kg of BASF Irganox MD 1024 antioxidant. The above components are mixed and granulated, and then coated on the base paper through a laminating machine. The temperature of the laminating machine is controlled at 270-280℃, the laminating thickness is 2.5mm, and the laminating paper is obtained after cooling with a cold water wall at 10-20℃. The melting point and softening point of the LDPE component are detected by DSC to be 117-119℃, and the melting point of the PP laminating is 148-150℃.

[0050] Preparation Example 2:

[0051] The raw material PP used for laminating mainly includes the following components in parts by weight: 100Kg of PP, 25Kg of LDPE, 4Kg of PE-g-MAH, 0.2Kg of HSt, 4Kg of TMC-201 titanate coupling agent, and 2Kg of ADEKA AO-60 antioxidant; the above components are mixed and granulated, and then coated on the base paper through a laminating machine. The temperature of the laminating machine is controlled at 270-280℃, the laminating thickness is 2.5mm, and the laminating paper is obtained after being cooled by a cold water wall at 10-20℃. The melting point and softening point of the LDPE component are both found to be 116-117℃, and the melting point of the PP laminating is 146-147℃.

[0052] Preparation Example 3:

[0053] The raw material PP used for laminating mainly includes the following components in parts by weight: 100Kg of PP, 20Kg of LDPE, 6Kg of PE-g-MAH, 0.4Kg of HSt, 3Kg of TMC-311w titanate coupling agent, and 3Kg of Albemarle AT-1135 antioxidant; the above components are mixed and granulated, and then coated on the base paper through a laminating machine. The temperature of the laminating machine is controlled at 270-280°C, the laminating thickness is 2.5mm, and the laminating paper is obtained by cooling with a cold water wall at 10-20°C. The melting point and softening point of the LDPE component are both found to be 117-120°C, and the melting point of the PP laminating is 147-148°C.

[0054] Preparation Example 4:

[0055] The raw material PP used for laminating mainly includes the following components in parts by weight: 100Kg of PP, 22Kg of LDPE, 5Kg of PE-g-MAH, 0.3Kg of HSt, 3Kg of TMC-101 titanate coupling agent, and 3Kg of STAB 8T antioxidant; the above components are mixed and granulated, and then coated on the base paper through a laminating machine, the temperature of the laminating machine is controlled to be 270-280°C, the laminating thickness is 2.5mm, and the laminating paper is obtained by cooling with a cold water wall at 10-20°C. The melting point and softening point of the LDPE component are 120-123°C and the melting point of the PP laminating is 150-151°C as detected by DSC.

[0056] Preparation Example 5:

[0057] The commonly used commodity FC9413L from Singapore TPC was used as the PP coating raw material for the comparative test. The FC9413L particles were coated on the base paper by a coating machine. The temperature of the coating machine was controlled at 270-280℃, the coating thickness was 2.5mm, and the coated paper was obtained by cooling with a cold water wall at 10-20℃. The melting point and softening point of the LDPE component were found to be 119-123℃ by DSC detection, and the melting point of the PP coating was 147-150℃.

[0058] Example 1

[0059] A processing technology for a PP coated paper container comprises the following steps:

[0060] Step 1, PP coated paper production: using the PP coated paper obtained in Preparation Example 1;

[0061] Step 2: Making container wall and container bottom: die-cutting the obtained PP coated paper to obtain container wall paper and container bottom; heating the edge of the container wall paper to be overlapped, and then rolling it to obtain the container wall;

[0062] An assembly line mechanism can be used, that is, the die-cut container wall paper is placed on the conveyor belt with the coated side facing upward, and a through hole is opened on the conveyor belt to expose the edges to be overlapped on both sides. A steel plate can be used to press the upper surface with only one side of the coated side exposed. The specific processing process of the container wall paper in step 2 is as follows:

[0063] 1) Preheating: Preheat the sides of the base paper through the electric heating plate, control the temperature of the electric heating plate to 60°C, and continue for 2 minutes;

[0064] 2) Hot air blowing: Blow hot air on the top of one side of the coating. The hot air temperature is gradually increased from 60℃ to 125℃ at a heating rate of 5℃ / min. Keep the hot air blowing continuously and evenly on the surface of the coating side. The hot air blowing flow rate is 0.05m / s.

[0065] 3) Insulation: quickly adjust the electric heating plates under the sides of the base paper to 105°C, and keep the sides of the base paper warm for 5 minutes;

[0066] 4) Surface treatment: Move the container wall paper so that the coated side edge on one side is sequentially subjected to corona treatment, chlorine plasma treatment and oxygen plasma treatment, and the base paper side edge on the other side is sequentially subjected to hot embossing, ultrasonic roughening and corona treatment;

[0067] The corona treatment uses a BXS-08 intelligent corona machine with an output power range of 2-70kW, a frequency adjustment range of 10-25kHz, and a treatment voltage range of 10000-20000V. 20 groups of electrodes distributed in strips are used to face the midline of the coating side or the base paper side, and the voltage is gradually adjusted to 15±1kV for 1-2 minutes.

[0068] The chlorine plasma was produced by ICP-98C plasma etcher, and the production conditions were: ICP power 500W, DC bias voltage 200V, gas Cl2 / He, flow rate 32sccm / 8sccm; the generated chlorine plasma was discharged into the cover body surrounding the side edge of the coating, and the upper surface of the side edge of the coating was treated for 2 minutes;

[0069] Oxygen plasma was produced by ICP-98C plasma etcher, and the production conditions were: ICP power 600W, DC bias voltage 250V, gas O2 / He, flow rate 30sccm / 5sccm; the generated oxygen plasma was discharged into the cover body surrounding the side edge of the coating, and the upper surface of the side edge of the coating was treated for 2min;

[0070] The hot embossing uses a grinding plate with the same size as the side edge of the base paper, which is attached to the bottom surface of the side edge of the base paper. The plate surface temperature is controlled at 100°C to perform hot stamping and embossing on the bottom surface to form grid-like folds.

[0071] Ultrasonic roughening uses a grinding plate with the same size as the side edge of one side of the base paper, which is attached to the bottom surface of the side edge of the base paper, and uses an ultrasonic vibration source to ultrasonically grind and polish the bottom surface.

[0072] 5) Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, put on a roll core mold, and hot pressed and laminatd so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressed at 175°C for 5s to form the container wall.

[0073] Step 3: Initial forming of the container: The top and bottom openings of the container wall are curled outward, and the container bottom is inserted into the container wall, heated and bonded to obtain a PP coated paper container.

[0074] In this embodiment, the base paper side edges and the coated side edges to be overlapped on both sides of the container wall paper are heated and subjected to multi-level surface treatment respectively, so that the surface properties of the two are changed before lamination, thereby improving the adhesion.

[0075] Example 2

[0076] The steps are the same as those in Example 1, except that the PP coated paper obtained in Preparation Example 2 is used.

[0077] Example 3

[0078] The steps are the same as those in Example 1, except that the PP coated paper obtained in Preparation Example 3 is used.

[0079] Example 4

[0080] The steps are the same as those in Example 1, except that the PP coated paper obtained in Preparation Example 4 is used.

[0081] Example 5

[0082] The steps are the same as those in Example 1, except that the coating raw material PP of Preparation Example 5 is used.

[0083] Embodiment 6:

[0084] The steps are basically the same as those in Example 1, except that the specific processing process of the container wall paper in step 2 is as follows:

[0085] 1) Preheating: Preheat the sides of the base paper through the electric heating plate, control the temperature of the electric heating plate to 80°C for 1 minute;

[0086] 2) Hot air blowing: Blow hot air on the top of one side of the coating. The hot air temperature is gradually increased from 60℃ to 115℃ at a heating rate of 10℃ / min. Keep the hot air blowing continuously and evenly on the surface of the coating side. The hot air blowing flow rate is 0.15m / s.

[0087] 3) Insulation: quickly adjust the electric heating plates under the sides of the base paper to 95°C, and keep the sides of the base paper warm for 8 minutes;

[0088] 4) Surface treatment: Move the container wall paper, so that the coated side edge on one side is sequentially subjected to corona treatment, chlorine plasma treatment and oxygen plasma treatment, and the base paper side edge on the other side is sequentially subjected to hot embossing, ultrasonic roughening and corona treatment; the corona treatment lasts for 1 minute, the chlorine plasma treatment lasts for 1 minute, and the oxygen plasma treatment lasts for 1 minute. The temperature of the hot embossed board surface is 80°C.

[0089] 5) Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, put on a roll core mold, and hot pressed and laminatd so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressed at 155°C for 8s to form the container wall.

[0090] Embodiment 7:

[0091] The steps are basically the same as those in Example 1, except that the specific processing process of the container wall paper in step 2 is as follows:

[0092] 1) Preheating: Preheat the sides of the base paper through the electric heating plate, control the temperature of the electric heating plate to 70°C, and last for 1.5 minutes;

[0093] 2) Hot air blowing: Blow hot air on the top of one side of the coating. The hot air temperature is gradually increased from 60℃ to 120℃ at a heating rate of 8℃ / min. Keep the hot air blowing continuously and evenly on the surface of the coating side. The hot air blowing flow rate is 0.10m / s.

[0094] 3) Insulation: quickly adjust the electric heating plates under the sides of the base paper to 105°C, and keep the sides of the base paper warm for 10 minutes;

[0095] 4) Surface treatment: Move the container wall paper, so that the coated side edge on one side is sequentially subjected to corona treatment, chlorine plasma treatment and oxygen plasma treatment, and the base paper side edge on the other side is sequentially subjected to hot embossing, ultrasonic roughening and corona treatment; the corona treatment is 1.5 minutes, the chlorine plasma treatment is 1.5 minutes, the oxygen plasma treatment is 1.5 minutes, and the hot embossing board surface temperature is 90°C;

[0096] 5) Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, placed on a roll core mold, and hot pressed and laminatd so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressed at 165° C. for 7 seconds to form the container wall.

[0097] Comparative Example 1:

[0098] The steps are basically the same as those in Example 1, except that the hot air blowing temperature on the side edge of the coating in the container wall paper in step 2 is 130° C. If the temperature is too high, there will be obvious bulging after bonding, indicating that the molecular chain melt curling range is too large, resulting in extremely uneven surface of the coating side.

[0099] Comparative Example 2:

[0100] The steps are basically the same as those in Example 1, except that the hot air blowing temperature on the coating side of the container wall paper in step 2 is 110° C. The temperature is too low, and the coating side surface is basically unchanged, indicating that the molecular chain is basically not melt-curled, resulting in a surface similar to that without heating treatment.

[0101] Comparative Example 3:

[0102] The steps are basically the same as those in Example 1, except that the oxygen plasma treatment time of the coating side edge of the container wall paper in step 2 is 3 minutes. If the treatment time is too long, the surface will have slight discoloration and odor.

[0103] Comparative Example 4:

[0104] The steps are basically the same as those in Example 1, except that the oxygen plasma treatment time of the coating side of the container wall paper in step 2 is 30 seconds. If the treatment time is too short, there are fewer surfactant particles, and there is no obvious carbonyl peak after XPS qualitative detection.

[0105] Embodiment 8:

[0106] The steps are basically the same as those in Example 1, except that in step 2, the coated side edge of the container wall paper is not treated with oxygen plasma.

[0107] Comparative Example 5:

[0108] The steps are basically the same as those in Example 4, except that the chlorine plasma treatment time of the coated side edge of the container wall paper in step 2 is 3 minutes. If the treatment time is too long, the surface will have slight discoloration and odor.

[0109] Comparative Example 6:

[0110] The steps are basically the same as those in Example 4, except that the chlorine plasma treatment time of the coated side edge of the container wall paper in step 2 is 30 seconds. The treatment time is too short, the surface active particles are less, and there is no obvious polyvinyl chloride peak after XPS qualitative detection.

[0111] Embodiment 9:

[0112] The steps are basically the same as those in Example 4, except that in step 2, the coated side edge of the container wall paper is not treated with chlorine plasma and oxygen plasma.

[0113] Comparative Example 7:

[0114] The steps are basically the same as those in Example 9, except that the corona treatment time of the coated side edge of the container wall paper in step 2 is 3 minutes. If the treatment time is too long, the surface will have slight discoloration and odor.

[0115] Comparative Example 8:

[0116] The steps are basically the same as those in Example 9, except that the corona treatment time of the coated side edge of the container wall paper in step 2 is 30 seconds. The treatment time is too short, and the polarity is basically unchanged.

[0117] Embodiment 10:

[0118] The steps are basically the same as those in Example 9, except that in step 2, the coated side edge of the container wall paper is not subjected to any surface treatment.

[0119] Embodiment 11:

[0120] The steps are basically the same as those in Example 10, except that in step 2, the side edges of the base paper of the container wall paper are not subjected to corona treatment.

[0121] Embodiment 12:

[0122] The steps are basically the same as those in Example 11, except that in step 2, the side edges of the base paper of the container wall paper are not subjected to ultrasonic roughening and corona treatment.

[0123] Embodiment 13:

[0124] The steps are basically the same as those in Example 12, except that in step 2, the side edges of the base paper of the container wall paper are not subjected to any surface treatment.

[0125] Comparative Example 9:

[0126] The steps are basically the same as those in Example 13, except that the processing of the container wall paper in step 2 includes the following process:

[0127] 1) Preheating: Preheat the sides of the base paper through the electric heating plate, control the temperature of the electric heating plate to 60°C, and continue for 2 minutes;

[0128] 2) Hot air blowing: Blow hot air on the top of one side of the coating. The hot air temperature is gradually increased from 60℃ to 125℃ at a heating rate of 5℃ / min. Keep the hot air blowing continuously and evenly on the surface of the coating side. The hot air blowing flow rate is 0.05m / s.

[0129] 3) Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, and then put on a roll core mold for hot pressing and laminating, so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressing is performed at 175°C for 5 seconds to form the container wall.

[0130] Comparative Example 10:

[0131] The steps are basically the same as those in Example 13, except that the processing of the container wall paper in step 2 includes the following process:

[0132] 1) Preheating: Preheat the sides of the base paper through the electric heating plate, control the temperature of the electric heating plate to 60°C, and continue for 2 minutes;

[0133] 2) Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, and then put on a roll core mold for hot pressing and laminating, so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressing is performed at 175° C. for 5 seconds to form the container wall.

[0134] Comparative Example 11:

[0135] The steps are basically the same as those in Example 13, except that the processing of the container wall paper in step 2 includes the following process:

[0136] Hot pressing and laminating: The container wall-shaped paper is rolled through a mold, put on a roll core mold, and hot pressing and laminating is performed so that the coating side edge on one side in step 2) covers the base paper side edge on the other side, and hot pressing is performed at 175°C for 5 seconds to form the container wall.

[0137] Performance testing includes:

[0138] 1) XPS surface energy spectrum qualitative analysis, instrument model: Thermo Fisher Scientific K-Alpha XPS detection instrument, after the obtained coating side edge is quenched, it is cut into samples with a specification size of 1×1×0.5cm, placed in the sample analysis chamber in the envelope, and whether there are corresponding activated particles after the coating side surface activation treatment;

[0139] 2) Surface characteristics: After the coating side is heated or activated, the contact angle of deionized water is tested immediately after quenching. The JC2000C1 contact angle meter is used. The droplet is 1 μL of deionized water. The height method is used to measure θ. The surface with θ>90° is hydrophilic, so as to measure the hydrophilicity and polarity of the coating side surface.

[0140] 3) Adhesion strength and mechanical property test: After the container wall is formed, the long overlapping edges are obtained by laser cutting, and a 180° peel strength test is performed using a HE-BL-2000N 180-degree peel strength tester. The test standard is in accordance with GB / T2792-2014 "Test method for peel strength of adhesive tapes"; the overlapping edges are subjected to a tensile test in both length and width directions in accordance with standard ISO 1924 / 2-1985 "Determination of tensile strength of paper and paperboard - Constant rate of tension method".

[0141] 4) Water resistance test: After the container is formed, fill it with 100℃ boiling water. After 30 minutes, check whether there is water inside the overlapping edges. After 60 minutes, check whether the container is leaking.

[0142] Data analysis is shown in Table 1 below:

[0143] Table 1. Performance test of the overlapping edges of various container products in this application

[0144]

[0145]

[0146] It should be noted that the contact angle, 180° peel force and tensile test in Table 1 are the average values ​​of the values ​​obtained from at least 3 tests. The degree of leakage is as follows: container damage > large leakage > obvious leakage > trace leakage.

[0147] I. Comparing Examples 1-5, when the PE softening point and the PP melting point fall within the heating range designed in this application, within a certain PE content range, the change in formula makes the contact angle, adhesion performance and mechanical properties fall within a certain range, indicating that the self-made coated PP material of this application is not much different from the existing products, can be used in mass production, and can be applied to the improved adhesion process proposed in this application.

[0148] II. Comparing Example 1 with Examples 6 and 7, within a certain range, as the oxygen plasma treatment time increases, the surface contact angle decreases slightly and the hydrophilicity increases, indicating that the number of hydrophilic groups on the membrane surface increases, but hydrophilicity is not the only determining factor of the adhesion performance; as the activation time increases, the longer the activated particles react, the greater the depth of the membrane surface modification, which in turn affects the mechanical properties of the coating side. In the 180° peel test, the thickness of the modified layer increases, which easily produces stratification between the polymerized surface layer and the internal PP secondary structure, thereby reducing the peel force, so it is necessary to control the time of each activation reaction.

[0149] III. Comparing Example 1 with Comparative Examples 1 and 2, when the temperature is lower than 110°C, since the melting point of the PE phase is not reached, the subsequent surface activation treatment is performed on the non-softened and melted film surface, and the resulting surface roughness is relatively small, which directly affects the substantial increase in the contact angle; when the temperature reaches above 130°C, in addition to the complete melting of the PE phase, the compatibilizer PE-g-MAH is also completely melted, resulting in large and extremely uneven wrinkles on the film surface. Although the tested contact angle is reduced, due to the poor uniformity, there are a large number of bulges during bonding, resulting in a significant reduction in the peeling force and mechanical properties, and liquid seepage begins after being soaked in boiling water for about 10 minutes.

[0150] IV. Comparing Example 1 with Comparative Example 3, Comparative Example 4 and Example 8, the treatment time is too long, and the surface has slight discoloration and odor. Although the hydrophilicity is improved, as analyzed in I, too long activation time is easy to cause stratification between the surface and the interior of the polymer, resulting in reduced peeling force; when the oxygen plasma treatment time is too short, there are fewer surface active particles, and there is no obvious carbonyl peak after XPS qualitative detection, and its surface contact angle is greatly increased, so that the performance of Comparative Example 4 and Example 8 without oxygen plasma treatment is similar; Example 8 has not been subjected to oxygen plasma, and the surface is a modified layer treated with chlorine, and there is no hydrophilic group, resulting in a higher contact angle.

[0151] V. Comparing Example 8 with Comparative Example 5, Comparative Example 6 and Example 9, the chlorine plasma treatment time is too long, the surface has slight discoloration and odor, the surface PE and PP are modified more obviously, a large amount of PVC and PVDC are gathered on the surface, and the hydrophilicity is greatly reduced. As analyzed in I, too long activation time is easy to cause stratification between the polymer surface and the interior, resulting in reduced peeling force; when the chlorine plasma treatment time is too short, there are fewer surface active particles, and there is no obvious active Cl peak after XPS qualitative detection, and its surface hydrophilicity is improved, so that the performance of Comparative Example 6 and Example 9 without chlorine plasma treatment is similar; Example 9 is not treated with chlorine plasma, and the surface is corona treated, the polarity is temporarily changed, and its hydrophilicity is higher than that of the surface treated with chlorine plasma, and the high voltage alternating current generates static electricity on the film surface, so that the surface activity is higher, but the high-energy particles generated by the corona treatment are unevenly distributed, and the viscosity is lower when directly used for lamination, which is more inclined to physical activation effect, so Example 1 uses it as the first step of the lamination side.

[0152] VI. Comparing Example 9 with Comparative Example 7, Comparative Example 8 and Example 10, the corona treatment time is too long, the surface has obvious burnt smell and discoloration, and although the hydrophilicity is greatly reduced, it seriously affects the mechanical properties and peeling force of the film; when the corona treatment time is too short, the surface polarity does not change significantly, so that the performance of Comparative Example 8 and Example 10 without corona treatment is similar; Example 10 is not corona treated, and the polarity is obviously unchanged. Although the surface roughness changes after heating, it still shows obvious water-absorbing properties, resulting in a significant reduction in adhesion.

[0153] VII. Comparative Examples 10-13, the surface of the coating side is not treated. As the treatment of the base paper side decreases, the adhesive properties decrease successively, and the mechanical properties decrease slightly.

[0154] VIII. Comparing Example 13 with Comparative Examples 9-11, Comparative Example 9 lacks a heat preservation process, resulting in the failure of the curling of the molecular chains caused by heating and melting to continue, while Comparative Example 10 does not have the step of heating and melting with hot air at all, so the bonding performance is greatly reduced; Comparative Example 11 is the performance of direct hot pressing bonding in the prior art, and the bonding performance is greatly reduced. After the container is immersed in boiling water for 5 minutes, a large amount of liquid seeps and is destroyed. Therefore, the coated paper containers in the prior art all need to be coated with glue, which obviously does not meet the original requirements of the research and development of this application.

[0155] The above are only preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Since the processes and control parameters of each process in the present application are relatively comprehensive, the amount of cross-tests for selecting and screening combinations is relatively large. All test schemes made by equivalent changes made according to the structure, shape, and principle of the present application and other test schemes of similar heating or surface treatment combinations should be included in the protection scope of the present application.

Claims

1. A processing technology for PP coated paper container, characterized by: The following steps are involved: Step 1: PP coated paper production: PP coating is performed on base paper to obtain PP coated paper; The raw material PP used in the coating mainly includes the following components in parts by weight: 100 parts of PP, 15-25 parts of LDPE, 4-8 parts of PE-g-MAH, 0.2-0.5 parts of HSt, 2-4 parts of titanate coupling agent, and 2-4 parts of antioxidant; Step 2, making container wall and container bottom: die-cutting the obtained PP coated paper to obtain container wall paper and container bottom; heating the edge of the container wall paper to be overlapped to the softening temperature of LDPE in the raw material PP and heat-insulating treatment, and then rolling it to obtain the container wall; Step 3: Initial forming of the container: insert the container bottom into the container wall, heat and bond them to obtain a PP coated paper container; The heating treatment of the edge to be overlapped in step 2 specifically includes the following steps: 1) Preheating: Place the PP coated paper with the base paper side at the bottom and the coated side at the top. Preheat the lower side of the base paper on both sides through an electric heating plate. Control the temperature of the electric heating plate at 60-80℃ for 1-2 minutes. 2) Hot air blowing: Blow hot air on the top of one side of the laminated paper, and use a thick plate to cover the rest of the surface of the PP laminated paper. The hot air temperature is gradually increased from 60℃ to 120±5℃ at a heating rate of 5-10℃ / min. Keep the hot air blowing continuously and evenly on the surface of the laminated side edge. The hot air blowing flow rate is 0.05-0.15m / s; 3) Insulation: quickly adjust the electric heating plates under the sides of the base paper to 100±5℃, and keep the sides of the base paper warm for 5-10 minutes; 4) Hot pressing: Place the PP coated paper on the roll core mold so that the coated side edge on one side in step 2) covers the base paper side edge on the other side, and hot press at 165±10℃ for 5-8s to form the container wall.

2. The processing technology of a PP coated paper container according to claim 1, characterized in that: The antioxidant includes at least one of BASF Irganox MD 1024, ADEKA AO-60, STAB 8T, and Albemarle AT-1135; the titanate coupling agent includes at least one of TMC-102, TMC-201, TMC-101, and TMC-311w.

3. The processing technology of a PP coated paper container according to claim 1, characterized in that: The edge to be overlapped includes a coating side edge on one side and a base paper side edge on the other side, and the edge to be overlapped is subjected to surface treatment during the heating process.

4. The processing technology of a PP coated paper container according to claim 3, characterized in that: The surface treatment of the side edge of the base paper includes at least one of hot embossing, ultrasonic roughening and corona treatment.

5. The processing technology of a PP coated paper container according to claim 4, characterized in that: The hot embossing uses a polishing plate with the same size as the side edge of the base paper, which is attached to the bottom surface of the side edge of the base paper. The plate surface temperature is controlled at 80-100°C to perform hot stamping and embossing on the bottom surface to form grid-like folds.

6. The processing technology of a PP coated paper container according to claim 4, characterized in that: The ultrasonic roughening adopts a grinding plate with the same size as the side edge of the base paper, which is attached to the bottom surface of the side edge of the base paper, and uses an ultrasonic vibration source to perform ultrasonic grinding and polishing on the bottom surface.

7. The processing technology of a PP coated paper container according to claim 4, characterized in that: The corona treatment uses 20 groups of electrodes distributed in strips and facing the center line of the side edge of the base paper, and gradually adjusts the voltage to 15±1 kV for 1-2 minutes.

8. The processing technology of a PP coated paper container according to claim 3, characterized in that: The surface treatment of the side edge of the coating includes at least one of corona treatment, chlorine plasma treatment and oxygen plasma treatment.

9. The processing technology of a PP coated paper container according to claim 8, characterized in that: The chlorine plasma treatment refers to discharging chlorine plasma into a cover body surrounding the side edges of the coating, and treating the upper surface of the side edges of the coating for 1-2 minutes; the oxygen plasma treatment refers to discharging oxygen plasma into a cover body surrounding the side edges of the coating, and treating the upper surface of the side edges of the coating for 1-2 minutes.

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