CS254218B1 - A method for evaluating the surface properties of a polyolefin powder suitable for preparing concentrated color dispersions - Google Patents

Abstract

The solution relates to a method for evaluating the surface properties of powdered polyolefin suitable for the preparation of concentrated color dispersions intended for dyeing polymers in bulk. The evaluation of the surface properties of powdered polyolefin according to the invention consists in determining the proportion of polypropylene or polyethylene oil (Zo, %) with a viscosity of 50 to 300 mPa.s at 25 °C, which is found in the surface layer after complete wetting of the powdered polyolefin and removal of excess oil by vacuum filtration.

Description

(54) SpOsob evaluation of the surface properties of powdered polyolefin suitable for the preparation of concentrated color dispersions

2

The solution concerns the method of evaluating the surface properties of powdered polyolefin suitable for the preparation of concentrated color dispersions intended for dyeing polymers in mass. The evaluation of the surface properties of the powdered polyolefin according to the invention consists in determining the proportion of polypropylene or polyethylene oil (Z _o .%) with a viscosity of 50 to 300 mPa. s at 25 °C, which is found in the surface layer after complete wetting of the polyolefin powder and removal of excess oil by vacuum filtration.

The invention relates to a method of evaluating the surface properties of powdered polyolefin suitable for the preparation of concentrated color dispersions! intended for dyeing polymers in mass.

In the first) phase of preparation of color concentrated dispersions! (concentrates) with maximum dyeing power, mixing and homogenization of powdered polyolefin and dispersant occurs. The pigment is then added to the mixture and further homogenization of the system follows.

The surface phenomena in the system determining the dispersion mechanism condition the optimal amount of the dispersant (polyoxyethylene glycols and their derivatives) so that the polyolefin powder is perfectly wetted and a surface layer with a thickness of the order of 10 ^B m is formed. In addition, the amount of the dispersant should correspond to 35 to 50 percent of the total weight of the pigment in the mixture. Interrelationships of the components and the character of dlspersion during the homogenization of powder materials and the dispersant was determined by the chemical structure of the components and the surface properties of the polyolefin and the pigment.

The specific surface area of the powdered pigment is determined by the type of pigment and the degree of grinding. The amount of dispersant needed to achieve optimal properties of the color concentrate is determined by the so-called pigment wettability method. Polyolefin powder intended for the production of color concentrates shows considerable unevenness in particle size, surface area, fragmentation and adsorption capacity. The result of this is a different amount of dispersant needed to wet it perfectly and create the required roughness of the surface layer. With a low adsorption capacity, i.e. usually with large parts of powdered PP, there is an excess of dispersant in the system, which then forms flocs that are difficult to disperse with the pigment. On the contrary, with a high adsorption capacity, that is, as a rule, with a very fine powder, it will not be completely wetted by the dispersant. (The amount of dispersant is determined by the concentration of the pigment in the color dispersion. j In both cases, the workability of the mixture during the preparation of color concentrated dispersions and the coloristic properties deteriorate.

Some adsorption methods can be used to evaluate the specific surface area of powdered polypropylene, but they are not used in operational practice due to technical and economic demands. Other suitable simple methods for evaluating the surface properties of powdered polypropylene, apart from sieve analysis, are not developed or used.

The aforementioned shortcomings are eliminated by the method according to the invention, the essence of which is to determine the proportion of polypropylene or polyethylene oil with a viscosity of 50 to 300 m . Well. with (25 °Cj located in the surface layer after perfect wetting of the polypropylene powder and removal of the excess* amount by vacuum filtration. This value (Z _o — oil wettability) expressed in % of the amount of polymer takes into account not only the outer but also the inner surface of the aggregated particles, its fragmentation and adsorption capacity.

The advantage of the method for evaluating the surface properties of powdered polypropylene according to the invention is the simplicity of performing the method, without the need for investment, the technical simplicity enabling the use of the method as an operational method, and a very good correlation of the determined values of Z _o with the processing properties of powdered polypropylene.

The following examples illustrate the subject matter of the invention.

Example 1

Weigh 3 g of powdered polypropylene on preweighing scales into the filter crucible S 1 (content 30 ml). 12 g of polypropylene oil PP K 300 is added to the polypropylene and the mixture is thoroughly mixed for 5 minutes. Then the excess oil is filtered off under vacuum using a water pump. The resulting filter cake is allowed to draw air under vacuum for another 10 minutes. After this time, the weight of the crucible + filter cake is determined as the X value. The filter cake is then removed from the crucible (preferably with a rubber spatula) and the weight of the crucible is determined as the Y value. The PP oil is tempered at 25°C before measurement. We calculate the wettability Z _o from the relationship

The results are in Table 1.

Taboo 1'kal,

Wettability Z _o sample of powdered PP "TATREN"

PP sample \T rr ^Λ , g Y, g And _about , % TATREN HPF 28.7 21.8 127 super soft 28.05 21.3 TATREN HPF 26.0 22.0 32 d < 0.5 mm 25.3 21.4 TATREN HPF 25.6 21.9 23 d > 0.5 mm 25.2 21.5 Example 2 Example 3 Procedure as in the example 1 was established The wettability of the powder was determined wettability of powdered polypropylene after of lyethylene Liten according to the procedure as in example 1, lyethylene oil of viscosity 170 m. Pa. _From = 22%. . with (25 °C). Precision of the method Results: The measurement error expressed in va- TATREN HPF superfine From = 105% by the coefficient (table 2). TATREN HPF d < 0.5 mm From = 30% TATREN HPF d > 0.5 mm From = 21% Table 2 Determination of measurement error Measuring Cups X, g Y, g _From , % 1 1 25.90 21.9 35 2 2 25.20 21.3 30 3 1 25.95 22.0 32 4 2 25.15 21.3 28 5 1 25.95 22.0" 32 6 2 25.55 21.3 41 7 1 26.00 22.0 35 8 2 25.30 21.4 30

Average value Z _o = 32.3

Coefficient of variation in _x — +6.0%

Effect of viscosity on Z _o

The wettability of powdered polypropylene is only slightly dependent on the viscosity of the oil, and therefore also on the temperature, as can be seen from the table. 3. For this reason, it is possible to use commercially produced PP oil or PE oil at normal temperature (25 °C) to determine the wettability Z _o .

Table 3

Effect of viscosity of PP oil on the wettability of powdered polypropylene at 25 °C Fraction of PP oil Viscosity, m.Pa . s Wettability, Z _o , %

1 105 22 2 150 23 3 195 25 4 220 26 5 240 28 6 270 31 7 300 32

Fractions 3 to 5 correspond to the viscosity dispersion of commercially produced PP K 300, which allows its use for determination without correction for viscosity.

Effect of particle size PP and Z _o

Other results tab. 4 show that individual fractions of different PP samples have different wettability, which implies that the particles of powder* PP have very different geometry and surface fragmentation. The wettability value Z _better reflects the surface properties of powdered* polypropylene than mesh analysis and there is no clear relationship between these values.

Table 4

Wettability of powder fractions between sieves Sample PP 1

From, %

400 to 900 mesh/cm ² 45

Z _o , % up to 169 mesh/cm ² 29

The results show that the specification for evaluating the surface properties of powdered polyolefin suitable for the preparation of concentrated color dispersions according to the invention is a suitable method for determining its processing properties and can be used in operational practice due to its simplicity. According to the results, the optimal values of Z _o for powdered PP for the production of color concentrates range from 25 to 50%.

The wettability "Z _o " of powdered PP mainly affects the homogeneity of the powder mixture po400 to 900 Qk/cm ² for PP spit samples 2 3 4

32 68

23 42 lypropylene-pigment-dispersant. Polypropylene powder with wettability values below 25% shows reduced homogeneity when mixed with dispersant and pigment, and remelting creates a large proportion of pigment flocculators, which reduce the workability of the finished polymer and the color strength of the pigment.

At wettability values above 50%, the color concentrate exhibits impaired filterability and also a lower degree of pigment dispersion resulting from the inhomogeneity of the powder mixture.

Claims (1)

SUBJECT Method of evaluating the surface properties of powdered polyolefins suitable for the preparation of concentrated color dispersions intended for coloring polymers in a mass, characterized in that the proportion (Z _o %) of polypropylene or polyethylene is determined OF THE INVENTION oil having a viscosity of 50 to 300 mPa. at 25 [deg.] C. in the surface layer after thoroughly wetting the polyolefin powder and removing the excess amount by vacuum filtration.