CS199141B1 - Inorganic Powder Fillers · - Google Patents

Abstract

Inorganic powder fillers for polyolefins based on natural aluminosilicates such as kaolin calcined at a temperature of 200 to 800 °C and with a particle size of up to 50 μm are modified with cations of the first and second groups of the periodic system before impregnation with aminosilane coupling agents so that at least half of the surface protonic centers are bound to the cation. The modification prevents decomposition of the aminosilane and foaming of the extruded string of filled polyolefin.

Description

The present invention relates to alumino-bilayer filler organic polymers enabling thermoplastic processing of non-degradable products.

The constantly increasing need for plastics and the limited availability of basic petrochemical raw materials have led to the development of new materials, so-called composites, with a high proportion of inorganic fillers. Another factor supporting the development of these materials was the observed improvement in some of their mechanical properties, achieved by the addition of reinforcing fillers, which made it possible to extend the applicability of composites, particularly in the field of construction materials.

Natural alumosilicates are among the most attractive fillers. They are readily available and have a stiffening effect over a wide range of particle sizes. In mixing these. however, the undesirable surface reactivity manifested by the formation of liquid and gaseous degradation products, together with changes in the structure of the polymer matrix, leading to deterioration in performance, even when agents improving the adhesion of the polymer matrix to the filler, are adversely affected. such as strong .. - ',.

The surface reactivity of natural aluminum silicates is conditioned by the presence of an octahedrally coordinated aluminum atom in its structure and by a configuration vortex or by a less regular arrangement of their layered structure, which in addition to octahedrons also consists of silicon tetrahedrons. This, in particular in the case of the so-called three-layer minerals, can lead to a charge imbalance of the crystal lattice surface supported by

- isomorphic exchange of central (Al, Si) atoms with lower bond atoms

- fracture defects resulting in charge on fracture and fissure edges and surfaces

- ionization of surface functional groups' Si-OH.

From the chemical reactivity point of view, such a surface is characterized as acidic and by systematic study it was found that the acid centers of the surface aluminum silicates are of two kinds according to their manifestation: protonic (Sráhetedov) and aprotic (Lewia). Their frequency, polydispersity, strength and ratio depend under normal conditions on the particle size, crystalline structure and composition (i.e., the ratio of AlgO ^SiOg).

It is believed that protonic ether is represented by surface chemisorbed water molecules and those surface OH groups that are capable of ionizing in a given environment to form a proton (e.g., Si-OH in an alkaline environment). Aprotic centers are made up of coordinated unsaturated aluminum and silicon atoms and are converted into protonic centers by water. Therefore, under normal conditions, aprotic centers cannot exist. Likewise, protonic centers are neutralized by water, so that the natural alumosilicates formed by weathering and hydrolytic decomposition of igneous rocks are only slightly acidic or neutral in aqueous solutions. Its acidic nature only becomes apparent when they are entertained by neutralizing branches of water, when in some cases they reach the acidity of the strong m-mineral acids. These jojioh properties have long been used in catalyzing the cracking of hydrocarbons.

In order to increase the adhesion of the surface of the inorganic filler to the organic polymer matrix, resulting in an improvement in some of the useful properties of the composite, fasteners have been successfully used, the typical representatives of which are organosilicon compounds. two diverse functional groups in its molecule that allow interaction with both the surface

X fillers, both with polymer matrix. In the case of silanes, these are silicon-linked alkoxy- or γ-groups which, after hydrolysis, yield silanol -OH groups reacting with the surface groups of the filler. Coupling with the organic polymer matrix is then facilitated by epoxy, vinyl, ester, carboxyl or amine groups which are bonded to the silicon atom through a shorter or longer hydrocarbon chain.

The interaction of the nylon functional groups of the coupling agent with the surface of the filler tends to be catalyzed by azo-base, whereas the reaction with the polymer matrix is most often of a free-radical nature with deliberately induced initiation by classical initiators.

The end result is then the formation of a bonding agent on the surface of the filler particles, giving them an organophilic character, improving their adhesion and dispersibility in the polymer matrix and hydrophobicity.At the same time they facilitate easy localization of energy, concentrating under mechanical stress of the zxa composite surface and causing defects. and cracks in the material.

Kaolin is a typical representative of a natural aluminum-aluminum filler, which has a long tradition in many industries, whether as a pigment, filler or extender. Its essential component (60 to 95%) is the double-layered kaolinite mineral, but the wider use of cablin in polymer composites has so far been limited by its surface reactivity, exhibiting, especially at elevated temperatures, the typical effects of both a proton donor and an electron acceptor catalyst.

The most attractive for the preparation of composites are mass-produced polymers, in particular polyolefins, in which the addition of a filler can achieve a significant improvement in the mehanogenic properties. However, alumosilicates cause significant degradation of the polymer matrix at processing temperatures (180 DEG-280 DEG C.), which results in undesired foaming of the extruded string even with the use of known fasteners.

Additives limiting thermal and thermo-oxidative degradation also interact with the reactive filler surface, therefore the question of surface modification appears to be a complex problem whose prior solution has not ensured reproducible and technologically feasible achievement of the necessary thermal stability of alumosilicate composite processing temperatures without significant degradation. and optionally other additives used.

It has now been found that 1 such a superficial reactive filler, such as kaolin, can be modified by a suitable process such that:

- was applicable in organic polymer matrix to high filler: matrix ratios}

- even at a filler: matrix ratio of 1: 1, no gaseous and other degradation products were formed to an undesirable extent during processing up to 280 ° C)

- the passive surface of the particles has been pierced in such a way that a sufficient number of functional groups are required to interact with the coupling agent,

-reactive surface of the filler did not cause undesirable reaction with grafting or thickening initiator before preparation of granulates at normal or slightly elevated temperatures)

- did not show reactive surface of the filler. The interaction with the stabilizing ingredients and thus did not cause its concentration to fall below the effective level}

the passivated surface of the filler exhibited reduced hydrophilicity, thereby limiting the hydrolytic effect of water in the composite, exhibiting limited shelf life or reduced utility properties of the product.

The present invention provides inorganic powdered fillers based on natural alumosilicates, such as kaolin, calibrated at 200-800 ° C and particle size, up to 50 µm, wherein at least half of the surface protonic acid centers are bound to cations of the first groups of the lithium, sodium, potassium, rubidium or other groups of the periodic system such as beryllium, magnesium, calcium, strontium, barium, zinc and cadmium.

The absolute number of protonic centers is not unambiguously definable in terms of existing knowledge. Information about the number of protonic centers is always a function of the method and conditions used. In general, protonic and aprotic acidity is discussed, without any evidence of their relationship to the structure of alumosilicates. For the purposes of the present invention, we consider the surface protonic centers to be those which are active in the protolytiocyte-induced deamination reaction of an aliphatic amine chemisorbed onto the surface of alumosilicates. According to this method, the value representing the sum of the proteolithiocyte active centers is expressed by the size of the area defined by the deamination curve in the conductivity-temperature coordinates, and any change thereof observed under any other condition represents a change in the protolytic reactivity.

It is known that the surface reactivity of alumosilicates, namely kaolin, is mainly due to the peripheral and fractional edges and crystal surfaces of the elementary particles, where the centers of chemical reactivity are concentrated. In poorly crystalline kaolins, active centers also appear on basal surfaces, where defects in the crystalline lattice. The causes of the surface acidity of kaolinite must therefore be sought in its structure.

. Elementary layers cannot end in incomplete constraints. The atom of the terminal tetrahedron terminates in the - OH group. The charge imbalance of the boundary coupling atom O between the central Si and Al atoms is compensated by a hydrated proton. Normally, the entire surface is filled with water which, depending on the nature of the sorption given by the force field of the crystal lattice, forms a mono- to multi-layer.

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The heating of such a system leads to a gradual exit of the neutralizing layers of water, revealing (exposing) the protonic centers, which may be the surface and the closest and therefore the most polarized water molecule. Aprotic centers may appear only after the sorbed water has exited, but this process is complicated by the onset of diffusion and controlled dehydroxylation of the surface and later structural groups -OH, when kaolinite prev. ? · Is based on metakaoiinite. Therefore, the strength, distribution, nature, number and ratio of acid centers for a given material is a function of temperature and Sass.

When studying the surface reactivity of kaolin observed by non-radical decomposition of cumorohydroperoxide in anhydrous medium or by protonic deamination of aliphatic amines as a function of temperature, it was shown that protonic acidity correlates with temperatures releasing individual sorbed water groups, increasing relative protonic acidity surface induced by ionizability of surface hydrogen atoms *

We have also found that by replacing surface reactive protons with another electrophilic particle, more strongly bound, less readily ionizable and hydrophilic, more stable, the protonic acid manifestation can be significantly reduced without blocking the surface groups that need to be retained for interaction with the linker, most commonly a siliceous agent.

The substitution of the most difficultly available and acidic acid proton of the linking oxygen atom is achieved by controlled calcination, which removes sterically shielding surface hydroxyl groups at the peripheral Al atom from as low as 200 ° C.

Both inorganic and organic salts or oxides capable of providing sterically and coupling-compatible cations can be used as substitution agents, provided that the ion-liberated anions, if not washed or otherwise removed, provide with the replaced protons the appropriate acid which must not disrupt the alumosilicate crystal lattice or otherwise interfere with this grid. Otherwise, it is expedient to bind or otherwise eliminate the resulting acid. ·

Salts having neutral or slightly different pH values in aqueous solutions, such as, for example, halides, carbonates, bicarbonates, sulfates, sulfites, simstates, nitrates or phosphates of alkali and caustic earth metals, are most preferred. Among the organic compounds, the corresponding alcoholates, salts of mono- and multifunctional acids, hydroxy acids, amino acids, and possibly metal salts of sugars.

The three- and multi-anionic cations are not suitable for its anomalous and adverse behavior on both the surfaces and lattice of aluminosilicates and in composites where they may induce undesirable degradaonies and other side reactions, especially in the presence of atmospheric oxygen and moisture *

In general, the choice of a suitable cation is controlled by:

- the radius of the non-hydrated ion,

-fire, ·

- hydration energy.

The larger the first two parameters and the smaller the third, the stronger the interaction of each. A thionate with a surface.

Thus, a surface treatment process for aluminosilicates such as kaolin must be such that the prepared composite exhibits better or at least the same meo-hanoic properties as a composite with a non-passivated filler, but which always exhibits concomitant degradation phenomena at processing temperatures.

The following examples illustrate the invention but do not limit it. Parts and percentages given in the examples are by weight unless otherwise indicated.

Example 1

100 g of kaolin from Chlumčany, fired 90 min. at 650 ° C, ground and sorted to the desired granulometry, i.e. 50 µm, having a pH of 5.25 (according to ASTM D-1957) after calcination, was stirred in 250 ml of 1 N aqueous CaCl 2 · H 2 O for 1 hour and po 18'hod. standing decanted. After adding 300 ml of distilled water, the suspension was 15 min. stirred and decanted again after the aqueous phase was separated. Washing of the excess salt was repeated 7 more times, when the detection of O1 'and by AgNO4 was visually virtually unnoticeable in the filtrate. The decanted kaolin was dried in a hot air oven at 120 ° C for 12 hours. 10 g of the treated kaolin were stirred for 1 hour and 20 ml of ethanol-water 9 * 1 containing 0.1 g of 7-aminepropyltriethoxysilane and then dried at 115 ° C to constant weight. 200 mg of the thus impregnated sample was subjected to thermal stress by heating in el. furnaces with linear temperature increase of 6 ° / min. in a stream of argon (20 ml / min.) Detection of the released ammonia was performed with a conductivity cell located in a flow apparatus at a constant flow rate of deionized water of 1 ml / min. The start of the decamination reaction of this sample, indicated by the increase in conductivity, only occurred when the temperature reached 250 ° C, while an untreated sample of the same callainized kaolin showed the start of the decamination reaction even when the temperature reached 150 to 160 ° C. The area delimited by the declination curve in the conductivity-temperature coordinate record showed a value of 40 area% compared to the β area obtained under the same conditions, but with kaolin that was not treated with Ca ⁺⁺ ions.

Example 2

500 g of kaolin, calibrated, milled and graded as in Example 1, were stirred for 2 hours with 1 liter of a 1N aqueous HgClg solution and after standing for 24 hours washed with distilled water on a separating laboratory centrifuge until reaction to Cl 'disappeared. After drying in an oven at 115 ° C to constant weight, 100 g of the treated sample were impregnated with 1 g of γ-aminopropyl-triethoxysilane, applied to the filler in 200 ml of ethanol-water 9: 1 with stirring in a glass rotary evaporator for 1 hour. followed by withdrawing the liquid phase under a water pump vacuum and drying the sample at 110 ° C to constant weight. Thermal analysis performed as in Example 1 indicated the onset of deamination of the reaction in the temperature range of 245 to 250 ° C. The area under the deamination curve was 42 area% compared to untreated kaolin.

Example 3

500 g of kaolin as in Example 1 were treated with 1 liter of 0.5 N aqueous ZnSO4 solution. Cue ^{0 and} P ° agitation and 48 hours of standing, the filler was washed to whisk the laboratory centrifuge until the reaction to SG ^ ² 'disappeared and dried at 120 ° C to const. Scales. After aminopropylsilane impregnation as in Example 2, an onset of ammonia evolution was observed in the temperature range 235 to 250 ° C by thermal analysis as in Example 1. The area under the deamination curve was 45 area% compared to untreated kaolin.

Example 4

250 g of kaolin as in Example 1 were treated with 500 ml of a 1 N aqueous solution of AlCl ₂ · 6h ₂ O according to the procedure of Example 2, including drying. 10 g of the treated filler was impregnated with 1% aminopropylsilane as in Example 1 and the sample was subjected to thermal analysis in the same manner. The onset of deamination of the reaction was observed up to 200 ° C, but followed by a sharp increase, indicating the maximum decomposition of amlnosilane as early as 250 ° C. The area under the deamination curve was 95 area% compared to untreated kaolin.

Example 5

As described in Example 1, kaolin was impregnated with various cations. The salt used and the onset temperature of the deamination reaction are shown in Table 1:

Impregnating salt Start of deamination reaction ° C IN Area under deamination curve% cheeks 180 50 NaCl 190 50 KC1 200 40.. RbCl 180 45 ^CsC1 2 200 48 ^SrC1 2 ²¹⁰ 43 BaClg 220 42 CdCl ₂ 210 49

EXAMPLE 6 g of kaolin from Chlorate, calibrated at 650 DEG C. with a specific sorbent of n-butylamine T..10-5 mol / g, were impregnated in 10 ml of an alcoholic solution of CaCl2 · HgO and then dried in a hot air oven at 125 DEG C. for 2 hours. hours. The kaolin so treated was impregnated with an aminosilane as in Example 1 and the onset temperature of the deamination reaction was measured. The dependence of the onset of deamination reaction on the added amount of calcium chloride is shown in the table

Table

Addition of CaClg.HHgO mg ' ²

Onset of deamination reaction ° C

150

150 160 ¹⁸⁰

200

Area under deamination curve%

100 ALIGN!

100 ALIGN!

Β

Object of the invention

Claims (1)

Object of the invention. · I, Inorganic powdered fillers based on natural aluminosilicates such as kaolin, calibrated at 200-800 ° C with particle size up to 50 µm, characterized in that at least half of the surface protonative acid centers are bound to cations of the first group of the periodic system HtMnm, sodium, potassium, rubidium or the other groups of the Periodic Table, beryllium, magnesium, calcium, strontium, barium, zinc and cadmium.