CS241640B1 - Powder filling on the base of magnesium hydroxide and nature carbonates - Google Patents

Abstract

The filler powder contains 10 to 9% by weight % by weight of precipitated magnesium hydroxide and 10 to 90% by weight of carbonate calcium or magnesium; up to 2% by weight of hydrophobising agents asb are acids, silanes or titanates. The filler particle size is 20 µm and is achieved by the joint grinding of the two main ones filler components in the presence of hydrophobising agents substances. The filler does not form aggregates and is an excellent flame retardant.

Description

- 1 - 241 640

The present invention relates to powdered fillers based on magnesium hydroxide and natural carbonates for filling plastics.

A great advantage of filled plastics compared to conventional non-filled plastics is the possibility of reducing or even completely suppressing the flammability of these materials without the use of halogen-containing flame retardants which release toxic and co-rosin products during pyrolysis. For filled plastics, such materials can be used as fillers, which release carbon monoxide, water or other volatile substances having an extinguishing effect at temperatures at which pyrolysis polymers are formed by the culprit. Velmiperspective filler for flame retardant composite materials is magnesium hydroxide. Conventional types of magnesium hydroxide, which can be used to fill plastics, are precipitated, crystallizing in brucitic form with crystal sizes usually below 1 m. However, this material does not take the form of separate crystals, but rather forms aggregates ranging from tenths to tens of millimeters. The types of magnesium hydroxides, in the form of separate crystals of micromairS size, i.e. in the optimum size for filler purposes, have only been prepared in the laboratory and cannot be expected to be used in industrial applications for a long time. The disintegration of magnesium hydroxide aggregates to below 20 µm is The usual limit for the use of fillers for plastics has proved to be very difficult due to the large surface area and the considerable electrical power aggregates. In conventional mills, in which fillers are usually prepared (e.g., spherical and vibratory mills), this material may not be disintegrated to the desired fineness or with the addition of a significant amount of grinding additives. For example, in a Molinex - 2 - 241 640 mill, disintegration of aggregates can only be achieved with a large stearic acid additive. as a grinding additive, (wolf than 3% w / w), which is an unacceptable content for plastic filling.

It has now been found that a filler of suitable properties is obtained by co-grinding crystalline magnesium hydroxide with natural carbonate. SUMMARY OF THE INVENTION The present invention relates to a powdered filler based on magnesium hydroxide and natural carbonates with a hydrophobic additive surface comprising 10 to 90% by weight of precipitated magnesium hydroxide and 10 to 90% by weight of calcium carbonate or magnesium carbonate. % by weight of hydrophobic substances such as fatty acids, silanes or titanates having a particle size below about 20 µm achieved by co-grinding the two filler ingredients in the presence of hydrophobic substances.

The pulverulent filler of the present invention is prepared by incorporating magnesium hydroxide in particulate form (aggregates) greater than 50 µm in the mills together with the accompanying grinding material in a weight ratio of 1:10 to 10: 1 and in addition to the grinding additive in an amount of 0.1 to 2% by weight, based on the total grease, wherein the grinder is dolomitic limestone, dolomite or magnesia, and silanes, titanium derivatives, higher fatty acids or mixtures thereof are used as grinding additives. In the preparation phase, the grist may be homogenized in a mill with an active part speed of at least 1 m / s at a pellet time of at least 60 s ^ alternative, 2 & homogeneation takes place in a mode with a mean particle size of accompanying fuel less than 400 µm.

The temperature in the mill is preferably maintained in the range! 60-110 ° C. The polarity of the very finely ground and micronised magnesium hydroxide particles and the calcium, calcium-calcium magnesium and magnesium carbonate particles is such a favorable combination that, by means of a suitable grinding additive, the electric surface of the grist can be substantially passivated. In this way, the reactive tendency of the grist can be reduced in reducing the grit grain in the microfine region, so that the desired granulometric composition of the product can be achieved. The passivation of the electric forces of the grist surfaces is so pronounced that it even results in the overall grinding efficiency, as shown in the examples of comparative grinding experiments. The inclusion of the homogenizer in the process line results in the achievement of the required constant weight ratios in the product and favorably also on the efficiency of grinding, and thus on the energy performance of the product. 3ak is shown in the examples, the efficiency of the grind depends strongly on the input dimensional parameters of the grinding material and the grinding temperature mode.

The following examples illustrate the invention, the percentages of examples being by weight. Example 1

The Molinex laboratory ball mill was blended according to the following table, where the feedstocks were:

CaCO 3, medium grain fraction 3 mm

Mg (0H) o, precipitated product treated to medium grain aggregate 2.5 mmMg CO.-, medium grain 2 mm

Stearin, a commercial mixture of higher fatty acids. The monitored variables are: W - specific energy consumption to achieve a fineness level of 97% of particles smaller than 2o jum d - stearin content dispersion in the product (mean arithmetic deviation) h - changes in Mg (0H) 2 v (intermediate CaC03 Mg (0H) o MgCO3 HSt) JQ dh No. c / cc 'c · m / t · / 0/0/0 t / 0 C' / 0 1 2 5 48 93 51 M 2 1 what 0.37 109 23 3 a) - 51 48 1 1.12 90 19 4 48 51 - 1 0.8 61 15 5 a) b) 48 51 - 1 0.60 57 15) 1 mixture homogenized in a mixer with an active part circumferential velocity of 4.5 m / s and a motion time of 100 sb) CaCO 3 medium grain fraction 93) im 4 months & Polymer · 241 640

At the same time, 50 parts of polypropylene (2% ethylene copolymer characterized by 3 3 melt index 4.5 g / 10 min) and a specific weight of 902 kg. M50 parts of filler - mixture No. 5 (and comparative) were metered into the hopper of the twin-screw mixing extruder. fillers).

The kneading was at 23 ° C, the residence time of the melt in the extruder was 150 seconds. The mixture was extruded as a string and chopped into a granulate from which the test specimens were prepared at a melt temperature of 250 ° C.

As can be seen from the following table, a better kneading (lower consumption of kneading energy), better processing properties (flowability, shrinkage anisotropy) of superior mechanical properties (notch toughness) are compared to a mixture of micronized limestone and precipitated magnesium hydroxide. Compared to the micronized limestone alone, it is a great advantage to achieve flame retardancy, which is characterized by an oxygen number greater than 23:

Sample Filler Acid Number Kneader Flow Rate Aniso- FlangeC% 0o), in spiral tropie duct (kJ.kg “1 (cm) (% length) nat9 (kJ.m ~) A«. 1 L00 46 -5.3 7.0 B CaCO7Mg (0H) 2 J 23.3 1 500 32 -8.0 6.3 C CaCO3 20.5 1 100 46 -5.4 7.1 D Mg (0H) ) 2 25.9 2 200 35 -12.1 3.5 - 5 - Example 2 241 640

The following mixtures were milled on the VM 20 Přerov machine works vibrating mill: mixture CaC0 “Mg (OH) Stearin t Wo d No (%) (%) (%) (° C) (Gj / t) (%) 6 89 10 1 50 0,95 105 7 54 45 1 30 0,91 182 8 54 45 1 90 0,9 93 9 99 - 1 50 1,01 92 where the feedstock corresponds to Example 1) and t represents the product temperature of the mill. Example 3: Milling according to Example No. a of its conditions a), b) CaC0 “Mg (0H) 2 grinding Wo dh No. (%) (%) additive (GO / t) (%) 10 54 45 f ) 0.74 60 13 11 54 45 g) 0.69 64 15 12 48 51 j) 0.59 55 15 where the grinding additives are all dosed at a 1% concentration, with f) aminopropyltriethoxysilane g) ethylndiaminopropyltrimethoxyeilane) triisostearoylisopropyltitanate

The grinding products of mixtures No. 2 to 12 according to Examples 1 to 3 are materials useful as fillers for plastics, by which the flammability of the composites can be suppressed while maintaining very good strength parameters.

The mixed fillers of the previous examples have very favorable fill properties, which not only occur during the handling and storage of fillers, but also in the rheologically very demanding initial phase with polymers.

A great advantage of the fillers according to the invention is their stability by counter-separating their individual components. - 241 - 640

The same procedure as in Example 1 was used, as linear polyethylene, characterized by a flow index of 6.0 g / 10 min and a specific gravity of 961 kg, was used as the polymer. m. The results of the measurement of flammability, processing properties and mechanical properties when using the mixture δ. 12 compared to a mixture prepared by mixing micronized limestone with precipitated Mg (0H) 2 table:

Sample Filler

Acid number (% o2)

Kneaders Infiltration Aniso- Fluid Energy ^ in the tropi · helix (kJ.kg “x) (cm) shrinkage 9 s (% (kJ.m '*) length) δ. 12 23,8

CaCO3 23.8Mg (OH) 2 1.100 1.500 46 32 -10.5 4.5-13.5 4.2

Claims (1)

OBJECT OF THE INVENTION 241 640 Magnesium hydroxide based filler powder and natural carbonates with a surface treated with hydrophobic additives, characterized in that it contains 10 to 90% by weight of magnesium hydroxide and 10 to 90% by weight of calcium or magnesium carbonate and 0.1 up to 2% by weight of hydrophobising agents such as fatty acids, silanes or titanates having a particle size below 20 µm achieved by co-grinding the two main components of the fillers in the presence of hydrophobizing agents ·