What are the effects of polypropylene masterbatch on the quality of polypropylene fiber? The answer is mainly from the following two aspects:

1. Dispersion of polypropylene masterbatch in polypropylene fiber

The polypropylene fibers with various colors are caused by the uniform dispersion of pigment particles in the polypropylene fibers. The key is that the pigment particles are fully refined and evenly distributed (mixed) in the polypropylene fibers. Refinement and dispersion is to break the agglomerates or agglomerates of pigments to minimize the particles, and the key lies in uniform dispersion. The effect of dispersion affects the brilliance, transparency, luster, fiber strength, elongation, and aging resistance of colored polypropylene fibers. , electronegative rate, etc. are affected.

Generally speaking, the particle size of the pigment dispersed is less than 1um can be used for fibers or ultra-thin films, while more than 5um will lead to dull fiber surface, more than 10um will cause spots and streaks on the fiber surface, and with the increase of particle size The breaking strength and elongation of the fibers continue to decrease. The finer the particle size, the stronger the tinting strength and the better the dispersibility. At the same time, the smaller the particle size, the larger the surface, resulting in an increase in the hiding power.

Since there are three types of pigment particles: primary particles, agglomerates and agglomerates, and general commercial pigment particles are larger than agglomerates (about 75-250um), they must be dispersed. The so-called pigment dispersion is to reunite The process of body crushing and refining.

The dispersion of pigments is first to wet the pigments with a wetting agent and coat them on the surface of the pigments to reduce the cohesion between the pigments and reduce the energy required to break the pigment agglomerates. The free movement of the pigment agglomerates (impact stress) and the shear stress of the surrounding medium break the agglomerate particles. After the pigment is dispersed and refined, the particle size decreases, the surface area increases, and the surface free energy of the pigment also increases, resulting in the instability of the refined pigment. Therefore, further coating treatment is required on the surface of the pigment to reduce the newly formed interface surface. can prevent re-agglomeration, and then the pigment is mixed and dispersed in the melt, that is, the wetted and pulverized pigment is uniformly dispersed and distributed into the material to be colored.

2. Color masterbatch performance and quality requirements

1. Performance requirements of polypropylene masterbatch

Polypropylene is a pure hydrocarbon, and the molecular chain contains tertiary carbon atoms. When heated and exposed to light, the molecules at the tertiary carbon atoms are easily cracked, which deteriorates the quality of polypropylene. Therefore, the masterbatch is required to be produced in high temperature spinning. It is easy to diffuse, does not damage the fiber quality, does not fade the fiber, has excellent light resistance, abrasion resistance, solvent resistance, and can withstand strict spinning drafts.

(1) The pigments used in the heat-resistant color masterbatch are basically required to withstand the temperature in the production process of polypropylene fibers and keep their performance stable. The temperature resistance temperature is generally required to be above 270 to 280 °C.

(2) Pigments for dispersive masterbatches should have excellent dispersibility, and should be uniformly dispersed in the masterbatches, and the dispersants used will not reduce the quality of polypropylene fibers. Otherwise, high-quality dope dyed fibers cannot be produced, and the operation is also unstable, and it is easy to break or produce abnormal fibers when the fibers are drawn.

(3) Brightness Polypropylene dope dyeing has many uses, among which it is used for bed cover base cloth and knitted fabrics, which requires bright colors. Because organic pigments are brighter and brighter, and can be easily colored, organic pigments should be used for the above purposes.

(4) Lightfastness Some pigments have photosensitivity under the action of light, which makes the colored fibers fade and become brittle, and the lightfastness of pigments is basically related to its chemical structure, so pay full attention to the lightfastness of pigments when making masterbatches , When lightfast pigments need to be used, you can consider adding a UV absorber.

(5) The pigment used in the stable color masterbatch should have excellent stability to the colored polypropylene fiber. That is, when the colored fiber polymer is exposed to heat, light or high temperature for a long time, the pigment will not react with the fiber, forming a new chemical group to reduce the performance of the polymer. Therefore, the purest possible pigments should be selected in the masterbatch, without impurities such as iron, copper, lead and other salts, to ensure the excellent physical properties of the colored polypropylene fibers.

(6) Water resistance, dry cleaning resistance, oil resistance, and coloring polypropylene fiber products will inevitably be washed with water or solvent dry cleaning after use and in contact with oil, especially when used in carpets, the colorant used must have Good washing resistance, dry cleaning resistance, oil resistance.

2. Quality requirements of polypropylene masterbatch

The quality index of color masterbatch includes many contents. For example, the appearance size is generally 2㎜×(3～4)㎜, the pigment particle size in the masterbatch is less than 1 um, more than 90%, the melting point, DF value, MI value, heat and weather resistance characteristics, etc. These indicators are the common concerns of color masterbatch factories and polypropylene fiber factories.

(1) Filtration performance

Fiber-grade color masterbatch is used to characterize the quality of color masterbatch. Its value is called DF value. If the value of DF is small, the replacement cycle of filter components during the spinning process is relatively long. Generally, the DF value of polypropylene masterbatch is required to be less than 2.0×105Pa· cm2/g.

(2) Melting point

Polypropylene masterbatch dispersant uses low molecular weight polyethylene wax, so its melting point is between 110 and 120 °C; while pigments generally have a high melting point, which exceeds the spinning temperature of polypropylene fiber, so the color masterbatch has two on the thermal analysis spectrum. Endothermic peak. However, the melting point of the color masterbatch cannot characterize the quality of the color masterbatch. Some enterprise standards stipulate that the melting point is 130-160 °C.

(3) Melt activity index (MI value)

The MI of polypropylene chips is mainly used to characterize its molecular weight, which determines the processing and finished product performance of the chips after they are formed into fibers. The color masterbatch contains pigments, dispersants and carrier low molecular polyethylene wax, so MI cannot be used to express its own molecular weight, and it will change due to different pigments and varieties, so the MI of the color masterbatch is not the color masterbatch. The control index can only be used for reference during spinning. The MI of the selected masterbatch for spinning is slightly larger than that of the original color chip, which is beneficial to the mixing of the two with similar particle sizes. The general requirement is MI value (15-30) g/30min.

(4) Heat resistant masterbatch

The heat resistance index refers to the color masterbatch and polypropylene fiber chips respectively spun at different temperatures in a certain proportion in a period of 5 to 10 minutes to observe the degree of color change. The change of color can be evaluated by a gray sample card or a color sample card for evaluating discoloration. When the total color difference value ⊿E≤3, the temperature is the heat resistance temperature of this color masterbatch, generally requiring a heat resistance of 270-300 ℃, the brilliance change is grade 4.

(5) Weather resistance The weather resistance of pigmented polypropylene is measured with reference to the test method for light fastness of textiles. The results are evaluated by the blue standard for evaluating light fastness. The light fastness is required to be grade 5. 8th grade.

From the above description, it can be concluded that polypropylene masterbatch is closely related to the quality of polypropylene fiber.