DE3542719A1 - POWDERED FILLER FOR ORGANIC POLYMERS, METHOD FOR THE PRODUCTION THEREOF AND FILLED COMPOSITE MATERIALS THEREFOR - Google Patents

Description

CHEMOPETROL koncernova iicelovä organizace Vyzkumny iistav macromolecular! chemistry

Brno, CSSR

Powdered filler for organic Polymers, processes for their production and composite materials filled with them

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

It is known that it is possible by the addition of high concentrations of inorganic fillers in polyolefins an increase in the modulus of elasticity with a simultaneous increase Retention, if necessary, to achieve an increase in toughness, provided that the particle size distribution is suitable of the filler is complied with.

One of the most important industrial inorganic fillers is currently calcium carbonate / on the one hand in the form of micro-milled limestone / on the other hand in the form of chemically precipitated calcium carbonate. In the case of mixtures of polyolefins with calcium carbonate, a comparison is achieved with unfilled polyolefins an improvement in some processing and mechanical properties; even with a high content of calcium carbonate, however, these mixtures remain flammable.

A more recent known filler / which acts as a retarder of burning polyolefins / is magnesium hydroxide / by using it you get self-extinguishing and non-flammable properties of polyolefins without formation of smoke and toxic products.

The disadvantage of magnesium hydroxide / that has so far only been due to the precipitation of magnesium salts (from seawater or from solutions obtained by dissolving magnesium-containing minerals) is / is primarily the high price / caused by the expensive manufacturing process becomes / and often also an insufficient degree of purity.

The insufficient degree of purity is the cause of a catalytic activity of the fillers / which are in a faster thermo-oxidative and photo-oxidative degradation of the polyolefins. In the case of micromilled fillers the cause of the catalytic activity are various transition metals (Cu / Mn / Fe and others) / those in natural mineral raw materials are always present. In the case of chemically precipitated fillers, these metals are

comfortably eliminated by costly procedures / the remaining However, shares are present in the form of extremely reactive salts (chlorides / nitrates / sulfites / sulfates, etc.) / whose catalytic influence is particularly strong.

Another disadvantage of the precipitated magnesium hydroxide is the tendency to form aggregates / what is their mixing made difficult with the plastic. For a good homogenization of the composite material it is necessary / large Apply shear forces.

One of the processes / that make it possible / homogenization To simplify the magnesium hydroxide with the plastic / is the use of mixtures of magnesium hydroxide with calcium carbonate in different proportions of the components according to the Czechoslovak patent application PV 754-84. The micro-milled calcium carbonate destroys the aggregates of the magnesium hydroxide microcrystals / and the mixed filler is then lightly mixed with the plastic homogenized.

The elemental analysis of such a mixed filler has a similar ratio of the individual components as a hydrated dolomite or a dolomitic limestone / with the difference / that these hydrates / which were prepared by known processes / only a small proportion contained in carbonates.

The previously known processes for hydrating burned dolomites are mainly aimed at applications in magnesia mortars / in which the presence of Ca (OH) ₅ / which forms the main component / is necessary. That's why it happens at

35427

the production of dolomitic lime mostly to an overburning of the magnesium oxide; because the firing temperature depends on the operating conditions for burning calcium oxide. Magnesium oxide burned in this way can very difficult to get hydrated.

If a dolomite is used at lower temperatures, e.g. B. 800 ° C, a so-called half-burnt dolomite is formed, which contains magnesium oxide in addition to undecomposed calcium carbonate and z. B. is used for water treatment. According to HU-PS 13 564 (July 28, 1977), the hydration of a semi-burnt dolomite is achieved through the addition of various Activators (e.g. calcium chloride, triethanolamine, fatty acids). A favorable influence of various Salts (such as calcium chloride) act to accelerate the hydration of magnesium oxide and dolomitic lime earlier Kaminskas ("Z. neorg. chim." 1J3, 3144 (1973)) described.

Even if the described process produces a dolomite hydrate with a large surface area and a small diameter of the individual particles, after drying the hydrates produced in this way, solid aggregates are formed which cannot be dispersed in polymer melts and which are used as fillers affect the mechanical properties of the organic polymers unfavorably. It is therefore necessary that the individual particles become hydrophobic during the hydration process, with the formation of a homogeneous protective layer on the individual particles. A necessary condition for the magnesium hydroxide, which ^{releases water above 340 °} C., as an effective retarder of burning

ORIGINAL INSPECTED

works / is the perfect, homogeneous dispersion of the individual filler particles.

The invention is based on the object / a powdered filler for organic polymers of a hydrate of calcined dolomite with improved dispersibility in organic polymer melts and to specify a method for its manufacture.

The subject of the invention / with which this object is achieved / is a powdery filler for organic polymers / in particular polyolefins, based on hydroxides and carbonates of magnesium and calcium with a particle size up to 20 μπί / marked by hydration Calcined natural dolomitic limestones, calcareous dolomites / dolomites or dolomitic magnesites is made in the presence of hydrophobizing substances.

The invention also relates to a method for producing such a powdery filler / with the characteristic / that natural dolomitic limestones, calcareous dolomites / dolomites or dolomitic magnesites are ^{calcined at temperatures up to 1100 °} C. and then hydrated with solutions of anionic or non-ionic surfactants .

The preferred surfactants are ammonium salts of fatty acids with 12 to 20 carbon atoms or mixtures Fatty acid salts with esters of fatty acids with at least two free alcohol groups are used.

Finally, the invention relates to composite materials based on polyolefins and a powdery one Filler according to the invention.

Dolomitic limestones / calcareous dolomites / dolomites and dolomitic magnesites are natural raw materials / which are defined by the content of magnesium carbonate. This is lowest in dolomitic limestones / in which the proportion of MgCO- is at least 4 _; 6% by weight / while it is 22/9% by weight in the calcareous Dolomites / 41/2% by weight in the dolomites and up to 45/7% by weight in the case of dolomitic magnesites.

The filler produced according to the invention from these natural raw materials eliminates the mentioned deficiencies while combining the advantages / which result from the possibility of the simultaneous use of CaCO and Mg (HO) ₅ .

The manufacture of the new filler is relatively simple and inexpensive; because none of the components will produced by felling from solutions. The effectiveness of the new filler as a non-toxic retarder of the Burning opens wide opportunities for high-volume applications of polyolefins in a number of industries /

as in construction, transport / electrical engineering, etc.

The filler according to the invention is based on dolomite or dolomitic magnesites or dolomitic limestones from / d. H. the starting raw material contains either one equimolecular ratio of MgCO_: CaCO_ or one Excess of MgCO- or a slight excess of CaCO-. It is clear / that the composition of the starting raw material a decisive influence on the effectiveness of the

Will have filler as a retarder of burning. The degree of purity of the raw material influences the degree of whiteness the filler and the composite. An essential one Advantage of the new filler compared to filler mixtures of a similar composition, which, however, through Cases are made, there is a reduction in the final catalytic activity without costly disposal of the impurities present.

The calcination of the dolomite can be carried out at temperatures from 750 to 1100 ^° C .; At lower temperatures there is only a decomposition of MgCO- to MgO and a partial conversion of the CaCO- to CaO ₇ that is present. At higher temperatures, MgO.CaO is formed. In addition to these most important chemical reactions, however, the active salts of the transition metals are converted into inert oxides during calcination, ie the calcination suppresses the catalytic activity of the natural dolomite. The calcination of the dolomite can advantageously be carried out in rotary furnaces; because of the preservation of the chemical purity, it is advisable to use a fuel with a minimal sulfur content, e.g. B. natural gas to use. The calcined and passivated dolomite is then subjected to hydration. Since the hydration of MgO is much slower than the hydration of CaO, it is advisable to carry out the hydration pressure in hydrators at temperatures of 150 to 220 ⁰ C. In view of the fact that the crystal lattices of the resulting compounds are different, hydration leads to spontaneous disintegration of the material with the formation of very small particles. Through suitable

Controlling the process of hydration one can therefore obtain a product with such a particle size distribution / that it can be used directly for the given purpose / or a sifting of the product without subsequent grinding enough. If the requirements for the fineness of the filler are / can be particularly high, the hydrated product be ground before the sighting with far lower energetic demands than when grinding the basic raw material.

The filler according to the invention can surface with fatty acids / their salts / esters or partial esters of glycerine are treated with fatty acids / possibly other anionic or non-ionic surfactants / with this treatment advantageously directly during hydration using solutions or emulsions these substances can be carried out in water.

A suitable means of surface treatment must be as follows Satisfy conditions:

1) It must be soluble in water.

2) It must form a hydrophobic film on the surface of the filler.

3) Neither the thermo-oxidative nor the photo-oxidative Reduce the stability of the filled polyolefins.

Regarding 1) The treatment agent must form a true or micellar solution in an aqueous medium. With regard to condition 2) it must be noted / that micellar

Solutions of such substances are used / which contain a hydrophobic chain in addition to a hydrophilic functional group.

The hydrophilic functional groups can have an ionic or non-ionic character. Ionic functional groups form salts of (organic) carboxylic acids R-COO X / in which the cation X can contain either an ion of an alkali metal (Na / K) or ammonium (NH.).

The use of ammonium salts of organic acids is particularly suitable in view of the fact that ammonia occurs during chemisorption on the basic surface of the filler is released / which escapes when the filler is hydrated. The reverse remains the case when using metal salts Ions of these metals are sorbed on the surface of the filler / which is undesirable.

Ethylene oxide or ethylene glycol telomers serve as examples of non-ionic functional groups. To achieve a required solubility in water, it is necessary / that the hydrophilic functional group has at least 10 ethylene oxide units contains.

Regarding 2) So that the surface of the filler has a hydrophobic character / it is necessary / that the hydrophobic part of the agent for treating the filler contains a sufficient number of hydrophobic units. If this group is formed by hydrocarbons, the number of carbon atoms in the chain must be at least 12. That means / that of the fatty acids / which are obtained from natural vegetable or animal fats / the following acids can be used / and that individually

or in any mixture: lauric acid ( ^c -i 2 ^Η 24 ⁰ ? ^ 'acid (C ₁₄ H ₂₈ O ₂ ), palmitic acid ( ^C ₁₆ H 0), ^stearic acid (CH 0), arachidic acid (C ₂₀ H ₄₀ O- ), Behenic acid (C ₂₂ H ₄₄ O ₉ ), oleic acid (C, _O H_.O _n ), linoleic acid (C ₁₀ H _0n O _n ) and erucic acid

JLo J4 Z Io OZ Z

(C _n -H ₄₄ O _n ). The last three mentioned are examples of unsaturated acids whose double bonds can advantageously be used to form chemical bonds between the filler and the polyolefins, which in composite materials has a beneficial effect in reducing creep. Instead of natural fatty acids, synthetic acids with a straight or branched chain can also be used if they contain at least 12 carbon atoms.

Re 3) The salts of the transition metals (Fe, Mn, Cu, Cr, Ti) act as catalysts for the thermo- and photo-oxidative degradation of polyolefins. Even if very pure raw materials are used to make the dolomitic filler (as in Example 2) and a pure polyolefin is used to make composite materials, one can see a complete absence of transition metals in both the filler and the polymer, wherever residues of the polymerization catalysts are present are not guarantee. It is known that only those compounds of these metals are catalytically active in which the transition metal is in the lower valence state and in such a form that active complexes can be formed with atmospheric oxygen (see: Zahradniikova A., Vesely K .: " Chemicky prumysl "32, 533 (1982); Lufiak S., Lederer P., Stopka F., Veprek-SiMka J .:" Coll. Czech. Chem. Commun. "46, 2455 (1981); Vesely K., Petrüj J. and Zahradnickovä A,: "28th IUPAC Microsymposium", Prague 8-11 July 1985).

The fatty acids react with the oxides that are present Transition metals with the formation of catalytically active salts, which not only cause the oxidation of the polyolefins themselves / but also the phenolic antioxidants used catalyze / which not only leads to significant deterioration the stability of the composite materials / but also leads to undesirable discoloration / which leads through Oxidation products of the phenolic antioxidants is caused. It was found / that the oxidation stability can be improved significantly by adding compounds can form stable complexes with the transition metals. That is why it is cheap / next to the ammonium salt a fatty acid / that works as an emulsifier / an ester of a fatty acid with a polyhydric alcohol / in which at least two OH groups remain free / to be added. Examples of suitable esters are: glycerine monostearate / Pentaerythritol distearate / sorbitol monostearate. The listed esters can easily be added to aqueous emulsifier solutions / z. B. ammonium salts of fatty acids / are dispersed. The amount of the aqueous solution or emulsion of the treatment agent / that fully or partially calcined for hydration Dolomite is used / can be very different. It is beneficial to use only a small excess (approx. 50 mol%) of water over the amount stoichiometrically necessary for hydration. In this case it runs the hydration "dry" / d. H. the heat of hydration of MgO (34/3 kJ / mol) or CaO (64.9 kJ / mol) is sufficient Evaporation of the excess water from / and a powder with good pouring properties is obtained directly / that is not more needs to be dried.

The specific optimal amount of water for hydration

is therefore dependent on the composition of the raw material / the degree of its calcination and the technical solution the hydration process.

The essence of the invention is explained in more detail by the following examples, where parts and percentages in the examples are based on weight refer to units.

example 1

It became a dolomite "Dolni Ro'z'inka" with the following combination setting used:

MgO . 18.8% CaO .... . 30.2% . 0.18% SiO ₂ . 1.10% AJl λ ν. / Α · · · »· . 0.31% Loss on ignition. .49.41%

The dolomite was calcined in a laboratory muffle furnace at a temperature of 1000 ^° C. for 3 hours. By means of X-ray diffractometric analysis (RDA) it was determined

that the calcined material contains:

MgO 34.1%

CaO 40.4%

CaCO ₃ 25.5%

Therefore, the complete decarboxylation of MgCO ₃ and the decarboxylation of 74% CaCO- took place.

The calcined material was placed in a laboratory autoclave at 200 ⁰ C for 6 hours in the presence of excess water and 0/4% potassium stearate (calculated on the calcined dolomite) hydrated. From the resulting suspension, the large particles by filtering through a sieve having a mesh width of 40 μΐη separated / and the resulting suspension was evaporated to dryness and dried for 1 hour at 150 ⁰ C. A fine / pourable / non-wettable powder was obtained / and microscopically a particle size in the range from 1 to 4 μm was determined. By means of RDA it was found / that the dry hydrate has the following composition:

Mg (OH) ₂ : 38.5% Ca (OH) ₂ : 41.7% CaCO ₃ : 19.8%

In a laboratory kneader, a mixture of polypropylene ( "musts 58.412") was kneaded with fillers at a temperature of 220 ⁰ C. Plates with a thickness of 4 mm were pressed from the material, which were used on the one hand to evaluate the flammability according to the method of the oxygen number (LOI) according to ASTM D 2863 / on the other hand to evaluate the flow limit (cr'k) and the notched impact strength (a,)

ic

according to DIN 53 453 were used.

The properties of treated dolomite (D) and micro-milled limestone (V) filled polypropylene are compared in the following table:

Sample PP D V LOI CTk a,

(%) (%) (%) (% O ₂ ) (MPa) (kJ.m ~ ² )

a 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 e 50 - 50 20.5 23.1 6.0 f 40 - 60 21.7 21.0 7.0

It must be noted that a material with an oxygen number of over 22.5 can be described as self-extinguishing. It is clear that the new filler is practical gives the same properties as micromilled limestone, but also gives a significant degradation the flammability is achieved.

Example 2

A "Varin" dolomite with the following composition was used:

MgO 21.19%

CaO 31.19%

O ₃ 0.22%

Fe ₃ O ₃ 0.044%

Loss on ignition .... rest.

The dolomite was left in a laboratory muffle furnace for 3 hours calcined at a temperature of 850 ° C. Using X-ray diffractometric Analysis found the calcined material to contain:

MgO 29.2%

CaO 7.7%

CaCO ₃ 63.1%

To 100 g of calcined material, 25 g of an aqueous solution containing 4% ammonium stearate was added. Carry the stirring a moist lumpy product, which was placed in a laboratory stirred autoclave and heated therein for a period of 2 hours at a temperature of 120 ⁰ C was formed. After opening the autoclave, a dry, pourable, hydrophobic hydrate was obtained, in which the following composition was determined by means of RDA:

Mg (OH) ₂ . . 36.6%

Ca (OH) ₂ 8.8%

CaCO ₃ 54.6%

A fraction containing particles separated from over 10 μΐη, and the fine fraction was used as a filler in the following mixtures with various polyolefins, which are kneaded in the "Plasticorder Brabender "at 220-230 ° C and from which test specimens were prepared by pressing at 230 ° C. The table shows an overview of the mixtures produced and their properties:

Table: Properties of composite materials

polymer filler additive Enamel Enamel
^index 49 N LOI
(% O ₂ ) Bend
module <rk
(MPa) ^a k
(kJ.nT ² ) I. (GPa) I-
CD
ι PP 40 CaSt 2 0.38 1.30 21.8 2.53 24.5 2.9 I. PP 40 GM 2 0.35 1.47 21.7 2.41 22.8 5.0 PP 60 GM 2 24.5 15.6 2.0 IPE 40 GM 2 0.05 0.36 22.0 18.1 18.8 rPE 40 GM 2 0.08 0.50 22.0 11.4 8.5

Explanations: PP = polypropylene "MOSTEN 55212" - manufacturer CHZ Litvinov IPE = linear polyethylene "LITEN FB 29" - manufacturer CHZ Litvinov rPE = branched polyethylene "BRALEN RB 03-23" - manufacturer Slovnaft Bratislava

CaSt = calcium stearate GM = glycerine monostearate

GJ

cn ISJ

OD

Claims (5)

1. Powdered filler for organic polymers / especially polyolefins, based on hydroxides and carbonates of magnesium and calcium with a particle size of up to 20 μπί / characterized / that it is calcined by hydration of natural dolomitic Limestones / calcareous dolomites / dolomites or dolomitic magnesites in the presence of hydrophobing agents Fabric is made. 2. A method for producing a powdery filler according to claim 1 / characterized / that natural dolomitic limestones / calcareous dolomites / dolomites or dolomitic magnesites are ^{calcined at temperatures up to 1100 0} C and then hydrated with solutions of anionic or non-ionic surfactants. 3. The method according to claim 2,
characterized/ 233-S10663-T / Wa that ammonium salts of fatty acids having 12 to 20 carbon atoms are used as surfactants. 4. The method according to claim 2 and 3 / characterized / that as surfactants, mixtures of fatty acid salts with esters of fatty acids with at least two free alcohol groups be used. 5. Composite materials based on polyolefins and a powdered filler according to claim 1.