What are the processing and applications of matt film?

1. The uses and characteristics of matting film

1-1 The matte film looks like paper, giving people a soft and luxurious feeling. The uses are as follows:

——Direct outer packaging and imitation paper use, including being used as a letter window and oily writing

——Combined with other materials, such as paper, aluminized film, light-shielding film, etc., used for daily necessities, clothing,

Packaging of cosmetics, snacks, etc. and used as cover for books and periodicals

——Used as base material for adhesive tape to make invisible adhesive tape

1-2 The matte surface layer is not only rough and uneven, and its thickness is difficult to accurately characterize, but its mechanical strength is lower than that of the BOPP layer, so some manufacturers do not include the thickness of this layer into the film thickness.

1-3 The matting layer has good heat sealability, which is characterized by high heat sealing strength and good hot adhesion.

1-4 The wear resistance of matt film is worse than that of bright film.

2. Processing conditions of matt film

2-1 In order to obtain a uniform rough surface, that is, a matte surface, the thickness of the matte surface must be guaranteed. The minimum allowable thickness value is closely related to the die structure, the uniformity of the thickness distribution of the melt flow section in the die and the laminar flow of multi-layer materials. The state recombination stationary level determines the uniformity of the thickness distribution of the matting material. In order to ensure that the matte layer completely covers the BOPP surface, the thickness of the matte surface layer is recommended as follows:

When the total thickness of the film is greater than 15μm, the surface thickness is generally 2.3 ~ 2.6μm;

When the total film thickness is 12~15μm, the surface layer thickness is ≥2μm.

2-2 The matte surface of the single-sided matte film should be placed on the air knife surface instead of the chilling roller surface. The temperature of the cooling roller and water tank can be appropriately higher, such as around 30°C.

2-3 The extrusion filter uses 80 to 100 molybdenum, and the extrusion temperature is slightly higher than that of general homopolymer PP by 5~15°C. For example, the feeding section is 210℃ and other sections are 245℃.

2-4 The longitudinal stretching ratio is about 4.8:1, and the longitudinal stretching temperature is similar to that of random copolymer as the surface layer, such as 125℃±5℃ in the stretching zone.

2-5 Matting film formulas can be divided into three categories:

Matt film for packaging and composite packaging:

Matting layer (air knife surface): Matting masterbatch 100% 2.5μm

Core layer: HOPP 97% + antistatic masterbatch 3% 13 ~ 15μm

Bright layer (cooling roller surface): HOPP 98% + opening masterbatch 2% 0.8μm

Corona treatment is generally done on the bright layer (composite surface). The matte surface can also be corona treated if necessary, but flame treatment cannot be performed. The film surface resistance must be less than 1012 Ω.

Invisible adhesive tape matt film:

Matting layer: Matting masterbatch 100% 2μm

Core layer: HOPP 100% 24μm

Matting layer: Matting masterbatch 100% 2μm

Single sided corona treatment. In addition, the self-adhesive surface can also be made into a glossy surface.

Imitation paper film:

Matting layer: Matting masterbatch 100% 2μm

Core layer: HOPP 70%+ pearlescent masterbatch 10%+ white masterbatch 20% 46μm

Matting layer: Matting masterbatch 100% 2μm

In addition, when one of the matte surfaces is made into a glossy surface, a single-sided paper-like film can be produced.

3. Control of extinction

The extinction degree can be expressed by the surface gloss. The lower the glossiness, the higher the extinction degree. Most applications require the matt film to have a higher extinction degree, but there are exceptions. Matting (gloss) is one of the most important indicators of matting film.

The following conditions contribute to the improvement of extinction:

A. Increase surface thickness;

B． Increase the temperature of the water bath and cold roller;

C． Moderately increase the stretch ratio.

4. Defect control

Most of the defects that appear on the matt film are silver spots. The matte surface layer is broken to produce holes, and a smooth and bright core layer appears in the middle of the holes. Such holes are called silver spots.

The main causes of silver spots are summarized as follows:

——The extruder and die runner of the production line have dead corners or the melt is unevenly distributed

——Poor filtration effect, material leakage, etc.

——The edge material recovery system and pneumatic conveying system bring foreign matter pollution and moisture

——The antistatic agent contains too much moisture and too many volatiles

——The thickness of the matting layer is too thin

——There are large-sized gel objects and other debris in the matting layer

——There are large gels and other debris in the middle layer

Selecting a good matting material can produce a matting film with the best matting degree and the fewest defects at the smallest thickness, and minimize the die precipitates.