Precoating in preparation of composite flexible packaging film, hot melt adhesive for BOPP film as raw material, can simplify the production process (
No JiaoGong period)
, need to use heating stick to BOPP pre-coating film heated to proper temperature can directly with the rest of the base material compound, eliminated the pollution caused by JiaoGong section.
The worth pointing out is that the use of BOPP pre-coating film coating technology of preparation, before coating coating material, the first thing to corona treatment was carried out on the base material.
Because unprocessed substrate surface activity is low, and the coating resin bond is small, the late formation of the composite film peel strength will be low.
BOPP corona processing can form a certain depression, increase the surface roughness, oxidation at the same time a certain amount of hydroxyl, carboxyl and carbonyl polar groups, to improve the peel strength of composite membranes.
Moreover after corona treatment will be great extent improve the gas barrier property of composite membrane.
Because after corona treatment surface can form many active point, the combination of these active points and coating layer closely, almost no gap between the precoat and BOPP.
BOPP precoating specular membrane products use points a, BOPP precoating specular membrane with EVA (
Colloid for hot melt glue)
, in use is associated with draping quality of colloid heat melt, flow ping.
The key to grasp well in the operating temperature, pressure, speed of three key parameters, the rule is: in the guarantee colloid under the premise of fully melting on the surface and the production speed when the temperature and pressure to increase relatively.
2, the amount of ink in print, different versions of completely different, the same version also has certain change, and pre-coating film colloid quantitative is fixed, as a result of ink in printing when most of the mixture is the solvent, the solvent most of colloid and base membrane has a role in melt up, so the print in the effect of the solvent residue control is important to the whole effect of the quality control is a link.
three and many use of solvent-based glue coated (
Manufacturers often appear after draping products binding foaming phenomenon, some even though no blisters but can not bend stamping, the reason and the use of coated technology and colloid is directly related to print before they can have a certain effect of solvent residue, and the type of coated coating the glue is not completely volatile solvent after baked road, residual amount is larger, so the draping within products after double solvent is more, from the adhesive solid content analysis, the type of coated coating the solid content of only 5-7 grams per square meter, and difficult to control, and pre-coating film colloid content in more than 10 grams per square meter, which is why solvent the coating effect of the causes of blister products more easily.
Bopp production process and superiority of precoating specular membrane two-way stretching method is a kind of plastic forming method of technical requirements are very high, in addition to the processing needs to have the good performance of equipment, more important is to require production personnel to be able to deeply know the performance of the PP and the influence of processing conditions on the properties of product, to solve the problems existing in the production in time.
Bopp precoating specular membrane is important in the field of packaging products, have qualitative light, transparent, non-toxic, low moisture, air permeability, high mechanical strength, widely used in food, medicine, daily light industrial products such as packaging, cigarette, and used as a composite film base material, have the laudatory title of 'packing the queen'.
at present BOPP touch membrane film production methods mainly include tube membrane membrane method of peace.
Tube membrane is a two-way stretching method in one step.
Flat film method is divided into two-way step stretched and two-step stretch two methods.
Tube membrane method has some advantages such as simple equipment, less investment, covers an area of small, material loss, simple operation, etc.
but due to the low production efficiency, the product thickness tolerance big disadvantages, such as almost no development since the 1980 s, is now only used in the production of BOPP special varieties, such as heat shrinkable film.
Two-way step stretching the product of the legal system to balance performance, little in the process of tensile rupture, but because of its complicated equipment, manufacturing difficulty, the price is expensive, edge material loss, more difficult to restricted problems such as high speed, the product thickness, at present has not been large-scale use.
Step and two-way stretching method mature equipment, high efficiency, suitable for mass production, is used by most enterprises.
industrialized production of BOPP touch membrane film with the main components of the main ingredient is PP.
PP is a kind of typical stereoregular polymers, according to the hydrocarbon molecules on either side of the plane distribution, can be divided into isotactic PP, syndiotactic PP and PP random.
Isotactic PP and syndiotactic PP with different crystalline structure of isotactic PP with all other nuclear crystallization in the form of three-dimensional growth and syndiotactic PP mainly by all other nuclear way of two-dimensional crystal, formed the appearance size irregular small chip, and due to the molecular structure of syndiotactic PP neat degree is low, making syndiotactic PP has lower crystallization rate and crystallinity.
study indicates that the larger the isotactic degree, the faster the crystallization rate, film product yield strength and surface hardness will increase obviously, and the random internal lubricant and PP in polymer and polymer orientation and contribute to the improvement of the optical properties of thin films.
at present, the BOPP film is a great variety of thin film, tactility performance difference is very big, also the main cause of this situation is to use different raw materials and production process.
Practice has proved that only the isotactic PP mass fraction of 95%
The mass fraction of 97%, random PP for 3%
5% of the PP is only suitable for production of BOPP pre-coating film, and melt flow rate of 2 - is generally selected
4 g / 10 min of PP.
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