CS249337B1 - Power filler for plastics - Google Patents

Abstract

A fire retarding filler for polyolefins with particle size less than 20 ???m is obtained by calcination of dolomites and/or dolomitic limestones and the subsequent pressure hydration and treatment with a hydrophobizing agent. The filler contains magnesium and calcium hydroxides as a mixture with calcium carbonate. Catalytical impurities from natural raw material are passivated by calcination and composite materials with this filler exhibit good mechanical properties and are nonflammable.

Description

The invention relates to a filler based on calcined dolomite hydrate enabling the production of polyolefins or other organic polymers with reduced flammability.

It is known that by adding high concentrations of inorganic fillers, it is possible to achieve an increase in the modulus of elasticity while maintaining or toughness of the polyolefins, provided the appropriate particle size distribution of the filler is maintained.

The most important industrial inorganic fillers currently include calcium carbonate, both in the form of micronized limestone and in the form of chemically precipitated calcium carbonate. Compositions of polyolefins with calcium carbonate improve some processing and mechanical properties compared to filled polyolefins, but even with high calcium carbonate content, these composite materials remain flammable.

A more recent known flame retardant filler for polyolefins is magnesium hydroxide, which can be used to achieve both flame retardancy and flame retardancy of polyolefins without the formation of fumes and toxic fumes. For many applications, it is also advantageous to use Mg / OH / ₂ with CaCO 3 with different ratios of the two components, which is the subject of АО 241640.

The disadvantage of magnesium hydroxide produced hitherto exclusively by the precipitation of magnesium salts (from seawater from solutions prepared by dissolving magnesium minerals) is mainly the high cost resulting from the expensive production process, often also the lack of purity.

Insufficient purity is the cause of the catalytic activity of the fillers, resulting in faster thermooxidative and photooxidative degradation of polyolefins. In the case of micronised fillers, the reason for their catalytic activity is various transition metal compounds (Cu, Mn, Fe, etc.), which are always present in natural mineral raw materials. In the case of chemically precipitated fillers, these metals are removed by costly processes, but the remaining constituents are present in the form of very reactive salts (chlorides, nitrates, sulphites, sulphates, etc.), whose catalytic effect is particularly pronounced.

SUMMARY OF THE INVENTION The present invention provides a powder filler for plastics, especially polyolefins, based on hydroxides and magnesium and calcium carbonate with particle sizes of up to 20 µm, which is produced by hydrating calcined natural dolomite limestones, calcareous dolomites, dolomites or dolomitic magnesites.

It is a further object of the present invention to provide a process for the production of a powdered filler in which natural dolomitic limestones, calcareous dolomites, dolomites and dolomitic magnesites are calcined at temperatures up to 1,100 ° C and then hydrated with aqueous solutions of anionic or nonionic surfactants.

Dolomitic limestones, calcareous dolomites, dolomites and dolomitic magnesites are defined in CSN 721 210 by a magnesium carbonate content of at least 4,6% by weight in dolomitic limestones.

The filler according to the invention eliminates the above-mentioned drawbacks in combining the advantages resulting from the possibility of simultaneous use of CaCO 2 and Mg / OH / ₂ . The effectiveness of the new filler as a nontoxic flame retardant opens up wide possibilities for heavy-duty applications of polyolefins in a number of fields, such as construction, transportation, electrical engineering, and others.

The filler according to the invention is based on dolomite, calcareous dolomite or dolomitic magnesites or dolomitic limestone, i.e. the starting material contains either an equimolar ratio of MgCO ₃ : CaCO ₃ , an excess of MgCO ₃ or a slight excess of CaCO ₃ . have a decisive influence on the efficiency of the filler as a flame retardant.

The purity of the raw material affects the whiteness of the filler and composite. An essential advantage of the novel filler as compared to mixed fillers of similar composition, but produced by precipitation, is the reduction of the CaO nation, the resulting catalytic activity, without expensive removal of the impurities present. Kalce ^{same the} materials ^d n ^e e ^y m ^longer by ^TP Eq ^Aad Currency ^BC i ^{t h} e ^{pl 75} rotates from 0 to 1 100 ° ^C; lower ^straight and ^p l ^of TE occurs only decomposition MgCO ^ MgO and partial conversion to CaCOj present at higher temperatures there .. MgO CaO. In addition to these major chemical reactions, however, calcination transforms calcination to suppress the catalytically active transition metal salts into inert oxides, i.e. the activity of natural dolomite.

The calcination of dolomite can preferably be carried out in rotary kilns, for reasons of chemical purity it is advisable to use a fuel with a minimum sulfur content, for example natural gas. The calcined and passivated dolomite is subjected to subsequent hydration. Since MgO hydration is much slower than the hydration of CaO, it is advisable to carry out the hydration of the hydrate of ^T nut pressure p ^r i e ^{t h pl} rotates ^{from 150} to ²²⁰ ° C. ^Zh ^ ^d em к that ^the r ^{y l} oic hundred meters ^zest to ^y components are emerging different hydration occurs when the decay spontánímu material to form very small particles. By appropriately conducting the hydration process, it is therefore possible to obtain a product having a particle size distribution that is directly suitable for the purpose, or it is sufficient to sort the product without subsequent grinding. If the fineness requirements of the filler are particularly high, the hydrated product can be dispensed with substantially lower energy requirements prior to sorting than would be the case with the base material. ·

The filler according to the invention may be surface-treated with a mixture of fatty acids, their salts, esters or partial esters of glycerin with fatty acids, optionally other anionic or non-ionic surfactants, which treatment may preferably be carried out directly during the hydration process using solutions or emulsions of these substances in water.

The following examples illustrate the invention, parts and percentages are by weight.

Example 1

Dolomite Dolni Raisin of the following composition was used

MgO. . . . 18.8% CaO. < . . 30.2% ^Fri 2 ° 3 * . . . 0.18 ^SiO 2 · . . 1.10 ^A1 2 ^o 3 · . . . 0.31 Loss annealing 49.41

%%

%%

Dolo ^{T K} and ^{L was C} NOCs ^and n

Using X-ray diffraction analysis OBU ^d after ^{3 h} from. ^L and ^B in oratorio ^and muHové ^p ECI ^{at t} e ^pl OTE 1000 ° C ',, it has been found that the calcined material comprises:

33.1

40.4

22.15

MgO.

CaO.

Thus, CaCO 3 completely decarboxylated MgCO 3 and decarboxylated 70% CaCO 3

Calcined ma ^t eri ^{Al would} l ^hy wired ^and nv ^l £ m aboratorn autoclave ^{EXAMPLE 200C d} OBU 6 hours in the presence of an excess of water containing 0.0% potassium stearate / calculated on kalcinovaý dolomite /. From the resulting suspensions were filtered through a sieve having a mesh diameter 40 ушл separated coarser particles ^No. of twisting ^{and d} b ^y la suspension of ^dp ARENA ^d suc ^h of ^the AA PA dried ^to ESOs 1 hr. At te ^pl OTE 150 ° C. A fine, non-wettable water-free powder was obtained, and a particle size in the range of 1 to 0 µl was detected microscopically. It has been found by DTA that the dry hydrate has the following composition:

24.93 37 4

Mg / OH / ₂ : 38.5%

Ca / OH / ₂ : 41.7 with CaCO ₃ : 19.8 ь

Polypropylene (Mosten 58,412) blends with fillers were kneaded at 220 ° C in a laboratory kneader. Plates of 4 mm thickness were pressed from the material, which were used for the evaluation of flammability by the method of the oxygen number according to ČSN 640 756, and for the evaluation of the yield strength / <T k / and notch toughness / a / according to ČSN 640 612. dolomite / D / and micro-limestone / V / compares the table:

Sample PP /IN D /% / IN /% / CZK /% ° ₂ / k / MPa / _ak /kJ.rn ² / and 60 40 21.9 24.5 5.2 b 50 50 23.3 22.7 5.8 C 40 60 25.1 20.8 6.5 d 60 40 19.6 24.7 5.2 with 50 50 20.5 23.1 6.0 F 40 60 21.7 21.0 7.0 It should be noted that material with an oxygen number greater than 22.5 can be labeled self-flammable. It is clear that the new filler provides practically the same properties as

micronized limestone, however, in addition, a significant reduction in flammability is achieved.

Claims (2)

Powder filler for plastics, in particular polyolefins, based on hydroxides and magnesium and calcium carbonate with a particle size of up to 20 µm, obtainable by hydration of calcined natural dolomotive limestones, calcareous dolomites, dolomites or dolomitic mmannsites in the presence of hydrophilizing substances. 2. The process of claim 1, wherein the natural dolomitic limestone, calcareous dolomites, _r dolomites and dolomitic maanesites are calcined at a temperature of up to 1100 ° C and then hydrated with aqueous solutions of aeeactinic or nonionic surfactants.