VII. Reasons for the odor of composite products
In general, there are two reasons for the odor produced by composite products: one is the odor of residual solvents; the other is the odor of extruded polyethylene resin, and the two odors are different.
(I) Odor from residual solvents
1. Residual solvents brought by printed matter The solvent in the gravure ink is generally high boiling point, but not odor, toxic solvent such as butanone, xylene, toluene and butanol. Especially butanone, the residual odor is very strong. Since the pigment particles in the ink are very fine and have a strong adsorption capacity, they have been heated and dried at the time of printing, but due to short time and high speed, they often do not dry completely, especially the printed materials with large inked area and thick ink layer. There are many residual solvents. These residual solvents are brought into the compounding process. After compounding, they are more difficult to run off and will slowly migrate and infiltrate. Among the solvents mentioned above, special attention should be paid to using it in small amounts, but methyl ethyl ketone is preferably not used.
2. Resident agent brought by AC agent
3. Adhesives and solvents used to produce residual solvents
(B) odor produced by the resin
Generally, polyethylene extruded from a T-die is oxidized in a molten state of about 300° C., thereby releasing the odor of the resin.
The amount of residual solvent can be measured by gas chromatograph or gravimetric method. Here is a simple and easy to use weight measurement method:
Remove the baked, uncomposited sample from the outlet of the drying tunnel. The size of the sample is 100×100 mm. Immediately go to the analytical balance and call it the mass. Record it as W1. Then put it in a constant temperature oven at 105°C for 1 hour. After taking it out, cool it to the room temperature in the desiccator and call it its quality. Record it as W2. At this time, W2 must be smaller than W1. This is because the residual solvent is volatile. Then according to the following formula: R=W1-W2/0.10×0.10, R=g/m2, the residual mass per square meter can be calculated. This is a method for measuring the residual content of prints and the residual solvent content of composite products. The amount of residual solvent after compound drying is required to reach below 10mg/m2 in our country, while that in the United States and Japan is below 5mg/m2.
(c) Measures to Control Odor Generation
1. To ensure the dry quality of the product, including drying in printing and drying in compounding. In printing, the slower the vehicle, the less ink is put on, and the faster the solvent is dried, the more thorough the print is; otherwise, it is difficult to dry completely. In compounding, the slower the speed, the thinner the glue, and the lower the amount of glue, the easier it is to dry and dry, and vice versa.
2. A thorough approach is to use water-based inks for printing and composite hot-melt adhesives for pre-coating. No solvents are present and odors and their migration will not occur.
3. For the odor produced by the resin, if possible, the melting temperature of the polyethylene should be reduced as much as possible, or the distance from the T-die to the nip roller should be shortened, so that the odor can be minimized.
VIII. Factors Affecting the Coating Quantity of Pharmaceutical Packaging Aluminium Foil
Printing and coating of aluminum foil for pharmaceutical packaging are performed on a dedicated pharmaceutical packaging coating printer. The device has a multi-color printing function, aluminum foil coating function and drying and retracting roll function. The aluminum foil coating system is a device that coats the substrate with an adhesive or a protective agent. During the coating operation, the adhesive has a mass per unit area of ​​the aluminum foil substrate, and the adhered plastic The fastness of the hard sheet is very much related, so we call the quality of the adhesive coated on the substrate as the amount of coating. If the coating amount is too large, the cost is increased and unnecessary waste is caused. When the coating amount is too small, the bonding quality is affected. Therefore, we analyze the factors affecting the size of the pharmaceutical aluminum foil coating in order to better grasp and control the degree of coating, and accurately achieve the required optimal adhesion.
(a) The effect of the number, depth and shape of the anilox roller on the coating amount
At present, most pharmaceutical aluminum foil coating equipment use an anilox roller coating device, also known as a wire coating method. The anilox roller is composed of a network wall, and the pits on the roller are usually called a net hole, and the high part is called a net wall. The ratio of wall to wall is approximately 1:5. After processing, the anilox roller is coated with a hard chromium layer with a thickness of 0.015-0.020 mm to increase the surface hardness of the anilox roller. The hardness value is HRC62-65. When using an aluminum foil coating device for coating, the construction principle and working state of the anilox roller are generally described as follows: when the adhesive is filled in the cells of the anilox roller, the anilox roller rotates when the cell gap is separated from the stick After the liquid level of the mixture, the liquid at the smooth surface of the roller is scraped off by a scraper, leaving only the liquid that cannot be scraped in the concave netting hole. This liquid adhesive is then brought into contact with the surface of the coated aluminum foil substrate. This contact is achieved by the action of a resilient rubber roller. A portion of the binder solution in the cell site was then transferred to the surface of the aluminum foil substrate. Due to the fluidity of the adhesive, it slowly and automatically flattens on the surface of the foil, turning the original discontinuous fluid into a continuous, uniform layer. A portion of the fluid in the anilox roller cell is transferred to the aluminum foil, while the anilox roller is rotating at the same time, and will be re-immersed in the adhesive liquid after one rotation, and the liquid adhesive will fill the network hole again. . In this way, an anilox roller with a small diameter can continuously and uniformly transfer the adhesive solution to the aluminum foil substrate without interruption, so that the surface of the aluminum foil can be uniformly coated with the adhesive. Obviously, if the network cable in the anilox roller is smaller per inch, the deeper the cable hole, the greater the coating amount; when the number of anilox roller lines is higher, the cell site is shallow, and the filled adhesive volume is small, and the coating volume is small. The amount of cloth is relatively small. The anilox roller has different cell shapes and its coating amount varies.
(b) The relationship between the concentration and density of the binder solution and the coating amount
For the anilox roll that has been made during the production process, the depth of the cell and the number of network wires have been fixed, and the shape of the cell can no longer be changed. Under such conditions, the amount of coating depends on the concentration and density of the binder formulation. The amount of coating refers to how many masses (g) of dry film bonded solid material per square meter of aluminum foil substrate area. Therefore, if the binder solution has a high solid content, the dry film adheres to the aluminum foil substrate to adhere the solid material, resulting in a large amount of coating. From this, it can be seen that the relationship between the coating amount and the depth of the adhesive pocket is “the amount of coating (g/m 2 ) and the depth of the cell (μm) and the concentration of the binder (%), and the density (g/m 3 ) becomes If the depth of the cell depth of the anilox roller is fixed in the actual production operation, the coating weight will have a great relationship with the concentration and density of the binder liquid, ie, the amount of coating will be determined by the concentration of the liquid. After the density is determined, the amount of adhesive applied is determined by the depth of the anilox roller.
(3) The effect of the hardness and pressure of the rubber pressure roller in the coating device on the coating amount
When the depth of the cell, the concentration of the binder, and the density are determined, the coating amount of the screen roller is also affected by the hardness and pressure of the rubber roller in the coating device. The requirement for the rubber roller is that the pressure on both the left and right sides should be uniform, that is, when the rubber roller is manufactured, the compound rubber should be uniform and the vulcanization conditions must be strictly controlled, and the quality at any point is the same. If the rubber roller used is very soft, elastic, and the pressure on the roller is large, the amount of coating is reduced. vice versa. This is because the rubber roller squeezes into the depth of the reticulation cavity under the pressure and pushes the adhesive solution out of the part, so that the amount of adhesive applied is reduced. In practice, the pressure of the rubber roller against the anilox roller is It is suitable to control in the range of 2 to 3 MPa.
(4) The effect of the application of the doctor blade in the coating device on the coating amount.
1. Squeegee pressure The current method of adjusting the blade pressure device in the equipment includes: tension spring pressure regulation, hand wheel pressure regulation, cylinder pressure regulation and pressure hammer pressure regulation. When the coating is applied, the pressure applied by the doctor blade to the anilox roller is small and the pressure is not tight, or there is a mechanical impurity, the blade will be topped up to cause a gap, so that the coating is uneven and the coating amount increases. The factors that affect the squeegee pressure are: different hard and soft blades, different angles between the squeegee and the anilox roller. In actual operation, the hammer adjustment blade is taken as an example, and the blade pressure is generally about 200 to 400 KPa.
2. The angle between the squeegee angle squeegee and the tangent of the anilox roller contact is generally between 15 and 30 degrees. If the angle is too large, the blade is almost against the anilox roller, and the surface of the two anilox rollers is not smooth. When it rotates at high speed, it will cause the elastic blade to vibrate or jump, causing the solution to be bouncing up, causing the coating to The amount of cloth is not uniform, causing a large difference in coating amount. In addition, it is easy to damage the edge due to its large angle.
3. Sharpness of the blade The sharpness of the blade mainly depends on the angle of blade wear and the purity of the solution and the quality of the blade. If it is a new knife, the sharpness of the knife should be able to effectively scrape the adhesive layer on the anilox roller without producing a knife wire, so as to obtain a uniform coating amount, and vice versa, resulting in a large difference in coating amount. .
4. Smoothness of the scraper The smoothness of the scraper is good, and there is no warping deformation, and the coating amount is uniform, otherwise the coating amount varies greatly. The flatness of the scraper depends on how the knife is installed during use. Of course, it may also be related to foreign matters stuck in the holder groove or on the blade or lining. Therefore, the lining should be wiped off when loading the knife, then the new knife should be placed behind the lining, and the knife back screw should be screwed into the slot. When screwing the knife back screw, it should be firstly tightened from the middle of the blade to the middle and back, and then tightened gradually to both sides, and the two sides should be tightened in turn. To prevent blade warping. When the screw is tightened, it should be completed twice or three times. The side should be screwed while clamping the blade and lining with the piece of cloth, and pull it tightly to one side. The knives thus mounted are relatively flat, ensuring that the difference in the amount of coating is within the standard range.
5. The left and right movement of the scraper. The left and right movement of the scraper has an important role in reducing the scraping line, increasing the scraper utilization, and reducing the wear of the anilox roller. Considering from this aspect, the net wall wears less, the net hole is relatively deep, and more liquid is contained, which is favorable for achieving the required coating amount.
(V) Discussion on the optimal coating amount of aluminum foil and adhesive
After the coated aluminum foil is heat-sealed with a polyvinyl chloride (PVC) hard sheet, the degree of adhesion of the two after heat sealing is usually measured by the heat-sealing strength (peeling strength) of the adhesive layer. Is it better to apply the binder as much as possible during the coating process? How much coating can achieve the best adhesion effect? According to physical experiments, the heat seal strength of aluminum foil and PVC is proportional to the coating amount within a certain range, but it is proportional to a certain degree. In most experimental conditions, the coating amount of 3 to 6 g/m2 (dry film) can meet the heat seal strength requirements. If the coating amount (greater than 6g/m2) is increased, the heat seal strength curve tends to be stable, and the change curve thereof is small. Therefore, it is not necessary to increase the coating amount again, which also causes waste and increase costs.
(6) Measuring method of aluminum foil coating amount
First take the same thickness of aluminum foil, the size of a square sample of 100 × 100mm, and said that its quality is W1, and then normal coating on the machine. After coating and drying, remove the sample, weigh the dried mass W2, put it in a constant temperature oven at 105°C for 1 hour, take it out and cool it to room temperature in a desiccator, and finally weigh it completely dry. The mass of the sample was W3, and the coating amount was calculated as follows: coating amount=W3-W1/0.1×0.1 (g/m 2 ).
Nine, the application of flexible printing in flexible packaging
At present, due to the differences in the structure of the printing plate and the ink transfer method used in the flexible packaging printing technology in the world, common printing methods include gravure printing and flexible printing. Gravure printing has been the main method for flexible packaging printing for many years. In recent years, gravure printing has gradually been replaced by flexible printing in flexible packaging printing. Unlike flexo printing, flexo printing has low platemaking cost and short cycle time, and the flexibility of changing prints is much better than gravure printing. The flexible printing and drying system is simple, and the length of drying is also significantly lower than the gravure printing, especially the development of ultra-fine mesh plates and the application of laser technology, the development of sleeve technology, the application of water-based inks and UV inks, making various Post-press processing processes can be machined in-line, making it ideal for flexible packaging prints.
In the packaging printing in the United States in 1996, flexographic prints accounted for more than 70% and grew at a rate of 15% each year. In Italy, 60% of packaging printing uses flexible printing. The current ratio of flexo printing to gravure printing in packaging printing is as follows:
Land
In general, there are two reasons for the odor produced by composite products: one is the odor of residual solvents; the other is the odor of extruded polyethylene resin, and the two odors are different.
(I) Odor from residual solvents
1. Residual solvents brought by printed matter The solvent in the gravure ink is generally high boiling point, but not odor, toxic solvent such as butanone, xylene, toluene and butanol. Especially butanone, the residual odor is very strong. Since the pigment particles in the ink are very fine and have a strong adsorption capacity, they have been heated and dried at the time of printing, but due to short time and high speed, they often do not dry completely, especially the printed materials with large inked area and thick ink layer. There are many residual solvents. These residual solvents are brought into the compounding process. After compounding, they are more difficult to run off and will slowly migrate and infiltrate. Among the solvents mentioned above, special attention should be paid to using it in small amounts, but methyl ethyl ketone is preferably not used.
2. Resident agent brought by AC agent
3. Adhesives and solvents used to produce residual solvents
(B) odor produced by the resin
Generally, polyethylene extruded from a T-die is oxidized in a molten state of about 300° C., thereby releasing the odor of the resin.
The amount of residual solvent can be measured by gas chromatograph or gravimetric method. Here is a simple and easy to use weight measurement method:
Remove the baked, uncomposited sample from the outlet of the drying tunnel. The size of the sample is 100×100 mm. Immediately go to the analytical balance and call it the mass. Record it as W1. Then put it in a constant temperature oven at 105°C for 1 hour. After taking it out, cool it to the room temperature in the desiccator and call it its quality. Record it as W2. At this time, W2 must be smaller than W1. This is because the residual solvent is volatile. Then according to the following formula: R=W1-W2/0.10×0.10, R=g/m2, the residual mass per square meter can be calculated. This is a method for measuring the residual content of prints and the residual solvent content of composite products. The amount of residual solvent after compound drying is required to reach below 10mg/m2 in our country, while that in the United States and Japan is below 5mg/m2.
(c) Measures to Control Odor Generation
1. To ensure the dry quality of the product, including drying in printing and drying in compounding. In printing, the slower the vehicle, the less ink is put on, and the faster the solvent is dried, the more thorough the print is; otherwise, it is difficult to dry completely. In compounding, the slower the speed, the thinner the glue, and the lower the amount of glue, the easier it is to dry and dry, and vice versa.
2. A thorough approach is to use water-based inks for printing and composite hot-melt adhesives for pre-coating. No solvents are present and odors and their migration will not occur.
3. For the odor produced by the resin, if possible, the melting temperature of the polyethylene should be reduced as much as possible, or the distance from the T-die to the nip roller should be shortened, so that the odor can be minimized.
VIII. Factors Affecting the Coating Quantity of Pharmaceutical Packaging Aluminium Foil
Printing and coating of aluminum foil for pharmaceutical packaging are performed on a dedicated pharmaceutical packaging coating printer. The device has a multi-color printing function, aluminum foil coating function and drying and retracting roll function. The aluminum foil coating system is a device that coats the substrate with an adhesive or a protective agent. During the coating operation, the adhesive has a mass per unit area of ​​the aluminum foil substrate, and the adhered plastic The fastness of the hard sheet is very much related, so we call the quality of the adhesive coated on the substrate as the amount of coating. If the coating amount is too large, the cost is increased and unnecessary waste is caused. When the coating amount is too small, the bonding quality is affected. Therefore, we analyze the factors affecting the size of the pharmaceutical aluminum foil coating in order to better grasp and control the degree of coating, and accurately achieve the required optimal adhesion.
(a) The effect of the number, depth and shape of the anilox roller on the coating amount
At present, most pharmaceutical aluminum foil coating equipment use an anilox roller coating device, also known as a wire coating method. The anilox roller is composed of a network wall, and the pits on the roller are usually called a net hole, and the high part is called a net wall. The ratio of wall to wall is approximately 1:5. After processing, the anilox roller is coated with a hard chromium layer with a thickness of 0.015-0.020 mm to increase the surface hardness of the anilox roller. The hardness value is HRC62-65. When using an aluminum foil coating device for coating, the construction principle and working state of the anilox roller are generally described as follows: when the adhesive is filled in the cells of the anilox roller, the anilox roller rotates when the cell gap is separated from the stick After the liquid level of the mixture, the liquid at the smooth surface of the roller is scraped off by a scraper, leaving only the liquid that cannot be scraped in the concave netting hole. This liquid adhesive is then brought into contact with the surface of the coated aluminum foil substrate. This contact is achieved by the action of a resilient rubber roller. A portion of the binder solution in the cell site was then transferred to the surface of the aluminum foil substrate. Due to the fluidity of the adhesive, it slowly and automatically flattens on the surface of the foil, turning the original discontinuous fluid into a continuous, uniform layer. A portion of the fluid in the anilox roller cell is transferred to the aluminum foil, while the anilox roller is rotating at the same time, and will be re-immersed in the adhesive liquid after one rotation, and the liquid adhesive will fill the network hole again. . In this way, an anilox roller with a small diameter can continuously and uniformly transfer the adhesive solution to the aluminum foil substrate without interruption, so that the surface of the aluminum foil can be uniformly coated with the adhesive. Obviously, if the network cable in the anilox roller is smaller per inch, the deeper the cable hole, the greater the coating amount; when the number of anilox roller lines is higher, the cell site is shallow, and the filled adhesive volume is small, and the coating volume is small. The amount of cloth is relatively small. The anilox roller has different cell shapes and its coating amount varies.
(b) The relationship between the concentration and density of the binder solution and the coating amount
For the anilox roll that has been made during the production process, the depth of the cell and the number of network wires have been fixed, and the shape of the cell can no longer be changed. Under such conditions, the amount of coating depends on the concentration and density of the binder formulation. The amount of coating refers to how many masses (g) of dry film bonded solid material per square meter of aluminum foil substrate area. Therefore, if the binder solution has a high solid content, the dry film adheres to the aluminum foil substrate to adhere the solid material, resulting in a large amount of coating. From this, it can be seen that the relationship between the coating amount and the depth of the adhesive pocket is “the amount of coating (g/m 2 ) and the depth of the cell (μm) and the concentration of the binder (%), and the density (g/m 3 ) becomes If the depth of the cell depth of the anilox roller is fixed in the actual production operation, the coating weight will have a great relationship with the concentration and density of the binder liquid, ie, the amount of coating will be determined by the concentration of the liquid. After the density is determined, the amount of adhesive applied is determined by the depth of the anilox roller.
(3) The effect of the hardness and pressure of the rubber pressure roller in the coating device on the coating amount
When the depth of the cell, the concentration of the binder, and the density are determined, the coating amount of the screen roller is also affected by the hardness and pressure of the rubber roller in the coating device. The requirement for the rubber roller is that the pressure on both the left and right sides should be uniform, that is, when the rubber roller is manufactured, the compound rubber should be uniform and the vulcanization conditions must be strictly controlled, and the quality at any point is the same. If the rubber roller used is very soft, elastic, and the pressure on the roller is large, the amount of coating is reduced. vice versa. This is because the rubber roller squeezes into the depth of the reticulation cavity under the pressure and pushes the adhesive solution out of the part, so that the amount of adhesive applied is reduced. In practice, the pressure of the rubber roller against the anilox roller is It is suitable to control in the range of 2 to 3 MPa.
(4) The effect of the application of the doctor blade in the coating device on the coating amount.
1. Squeegee pressure The current method of adjusting the blade pressure device in the equipment includes: tension spring pressure regulation, hand wheel pressure regulation, cylinder pressure regulation and pressure hammer pressure regulation. When the coating is applied, the pressure applied by the doctor blade to the anilox roller is small and the pressure is not tight, or there is a mechanical impurity, the blade will be topped up to cause a gap, so that the coating is uneven and the coating amount increases. The factors that affect the squeegee pressure are: different hard and soft blades, different angles between the squeegee and the anilox roller. In actual operation, the hammer adjustment blade is taken as an example, and the blade pressure is generally about 200 to 400 KPa.
2. The angle between the squeegee angle squeegee and the tangent of the anilox roller contact is generally between 15 and 30 degrees. If the angle is too large, the blade is almost against the anilox roller, and the surface of the two anilox rollers is not smooth. When it rotates at high speed, it will cause the elastic blade to vibrate or jump, causing the solution to be bouncing up, causing the coating to The amount of cloth is not uniform, causing a large difference in coating amount. In addition, it is easy to damage the edge due to its large angle.
3. Sharpness of the blade The sharpness of the blade mainly depends on the angle of blade wear and the purity of the solution and the quality of the blade. If it is a new knife, the sharpness of the knife should be able to effectively scrape the adhesive layer on the anilox roller without producing a knife wire, so as to obtain a uniform coating amount, and vice versa, resulting in a large difference in coating amount. .
4. Smoothness of the scraper The smoothness of the scraper is good, and there is no warping deformation, and the coating amount is uniform, otherwise the coating amount varies greatly. The flatness of the scraper depends on how the knife is installed during use. Of course, it may also be related to foreign matters stuck in the holder groove or on the blade or lining. Therefore, the lining should be wiped off when loading the knife, then the new knife should be placed behind the lining, and the knife back screw should be screwed into the slot. When screwing the knife back screw, it should be firstly tightened from the middle of the blade to the middle and back, and then tightened gradually to both sides, and the two sides should be tightened in turn. To prevent blade warping. When the screw is tightened, it should be completed twice or three times. The side should be screwed while clamping the blade and lining with the piece of cloth, and pull it tightly to one side. The knives thus mounted are relatively flat, ensuring that the difference in the amount of coating is within the standard range.
5. The left and right movement of the scraper. The left and right movement of the scraper has an important role in reducing the scraping line, increasing the scraper utilization, and reducing the wear of the anilox roller. Considering from this aspect, the net wall wears less, the net hole is relatively deep, and more liquid is contained, which is favorable for achieving the required coating amount.
(V) Discussion on the optimal coating amount of aluminum foil and adhesive
After the coated aluminum foil is heat-sealed with a polyvinyl chloride (PVC) hard sheet, the degree of adhesion of the two after heat sealing is usually measured by the heat-sealing strength (peeling strength) of the adhesive layer. Is it better to apply the binder as much as possible during the coating process? How much coating can achieve the best adhesion effect? According to physical experiments, the heat seal strength of aluminum foil and PVC is proportional to the coating amount within a certain range, but it is proportional to a certain degree. In most experimental conditions, the coating amount of 3 to 6 g/m2 (dry film) can meet the heat seal strength requirements. If the coating amount (greater than 6g/m2) is increased, the heat seal strength curve tends to be stable, and the change curve thereof is small. Therefore, it is not necessary to increase the coating amount again, which also causes waste and increase costs.
(6) Measuring method of aluminum foil coating amount
First take the same thickness of aluminum foil, the size of a square sample of 100 × 100mm, and said that its quality is W1, and then normal coating on the machine. After coating and drying, remove the sample, weigh the dried mass W2, put it in a constant temperature oven at 105°C for 1 hour, take it out and cool it to room temperature in a desiccator, and finally weigh it completely dry. The mass of the sample was W3, and the coating amount was calculated as follows: coating amount=W3-W1/0.1×0.1 (g/m 2 ).
Nine, the application of flexible printing in flexible packaging
At present, due to the differences in the structure of the printing plate and the ink transfer method used in the flexible packaging printing technology in the world, common printing methods include gravure printing and flexible printing. Gravure printing has been the main method for flexible packaging printing for many years. In recent years, gravure printing has gradually been replaced by flexible printing in flexible packaging printing. Unlike flexo printing, flexo printing has low platemaking cost and short cycle time, and the flexibility of changing prints is much better than gravure printing. The flexible printing and drying system is simple, and the length of drying is also significantly lower than the gravure printing, especially the development of ultra-fine mesh plates and the application of laser technology, the development of sleeve technology, the application of water-based inks and UV inks, making various Post-press processing processes can be machined in-line, making it ideal for flexible packaging prints.
In the packaging printing in the United States in 1996, flexographic prints accounted for more than 70% and grew at a rate of 15% each year. In Italy, 60% of packaging printing uses flexible printing. The current ratio of flexo printing to gravure printing in packaging printing is as follows:
Land
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