2022.12.01
Processing and Application of Matt Film
Chapter I Application and Feature of Matt Film
1-1 The appearance of the Matt film is like paper, giving people a soft and luxurious feeling. The usage is as follows:
——Direct outer packaging and imitation paper use, including the window of the envelope and oily writing
——Laminated with other materials, such as paper, Metallised film, light-shading film, etc., used for packaging of daily necessities, clothing, cosmetics, small food, etc. and for covering books and periodicals
——Used as adhesive tape base film to make invisible adhesive tape
1-2 The Matt skin layer is not only rough, and the thickness is difficult to accurately characterize, but also the mechanical strength is lower than BOPP layer, so some manufacturers will not include the thickness of this layer in the film thickness.
1-3 The Matt layer has good heat-sealing performance, which shows the high heat-sealing strength and good heat viscosity.
1-4 The wear resistance of Matt film is worse than that of the Plain film.
Chapter II Processing conditions of Matt film
2-1 In order to get a uniform rough surface, a Matt surface, the thickness of the Matt skin layer must be guaranteed. The minimum allowable thickness value has a great association with the die structure. The uniformity of the thickness distribution of the melt flow section in the die and the smooth level of the multi-layer material layer flow state lamination determine the uniformity of the thickness distribution of the Matt material. To ensure that the Matt layer completely covers the BOPP surface, the thickness of the Matt skin layer is recommended as follows:
When the total thickness of the film > 15 μ m, the skin layer thickness is generally between 2.3~2.6 μ m；
When the total thickness of the film is between 12~15 μ m, the skin layer thickness ≥ 2 μ m；
2-2 The Matt layer of the one-side Matt film should be put on the air knife side rather than the chill roll side. The temperature of the cooling roll and water bath can be appropriately higher, such as about 30 ℃.
2-3 We use 80-100 meshes for extrusion filter mesh, and the extrusion temperature is slightly 5~15 ℃ higher than that of general Homopolymer PP. If the feeding section is 210 ℃, other sections are 245 ℃.
2-4 The longitudinal stretching ratio is about 4.8 : 1, the longitudinal stretching temperature is similar to that of random copolymer as the skin layer, such as 125 ℃± 5 ℃ in the drawing zone.
2-5 The formula of Matt film can be divided into three categories:
Packaging and lamination packaging Matt film:
Matt layer(air knife side): Matt masterbatch 100% 2.5μm
Core layer: HOPP 97%+Anti-static masterbatch 3% 13 ~ 15μm
Gloss layer( the side in contact with Chill roll): HOPP 98%+Anti-block masterbatch 2% 0.8μm
Corona treatment is generally on the glossy layer (lamination side). If necessary, the Matt side can also be corona treated, but not flame treated. The resistance of film surface must be less than 1012 Ω.
Invisible adhesive tape Matt film:
Matt layer: Matt masterbatch 100% 2μm
Core layer: HOPP 100% 24μm
Matt layer: Matt masterbatch 100% 2μm
one side corona treatment. In addition, the self-adhesive coating side can also be made into a glossy side.
Paper imitation film:
Matt layer: Matt masterbatch 100% 2μm
Core layer: HOPP 70%+ pearlescent masterbatch 10%+white masterbatch 20% 46 μ m
Matt layer: Matt masterbatch 100% 2μm
In addition, when one of the Matt side is made into a glossy side, a one-side paper imitation film can be made.
Chapter III Control of Matt degree
The Matt degree can be expressed by the surface gloss. The lower the gloss is, the higher the Matt degree is. In most applications, the gloss of the Matt film is required to be high, but there are exceptions. The Matt degree (gloss) is one of the most important indexes of the Matt film.
The following conditions will help to improve the Matt degree:
A. Increase the thickness of the skin layer;
B. Increase the temperature of water bath and chill roll;
C. Moderately increase the stretching ratio.
Chapter IV Control of Defects
The defects of Matt film are mostly silver points. The Matt skin layer breaks to holes, a smooth and glossy core layer appears in the middle of the holes. Such holes are called silver points.
The main causes of silver points are summarized as follows:
——There is dead angle or maldistribution of melt in the extruder and die runner of the production line
——Poor filtering effect, material leakage, etc
——Foreign-matter pollution and moisture caused by the edge trim recycling system and pneumatic conveying system
——The anti-static agent has too high moisture content and too many volatiles
——The thickness of Matt layer is too thin
——Large size gel and other sundries in the Matt layer
——Large size gel and other sundries in the middle layer
Selecting good Matt material can produce the Matt film with the best Matt degree and the least defects with the minimum thickness, and reduce the die precipitation to the minimum.