WO1983004039A1

WO1983004039A1 - White filler and process for the preparation thereof

Info

Publication number: WO1983004039A1
Application number: PCT/HU1983/000022
Authority: WO
Inventors: Jeno^" MARTON; Keve KARDKOVÁCS
Original assignee: Marton Jenoe; Kardkovacs Keve
Priority date: 1982-05-06
Filing date: 1983-05-06
Publication date: 1983-11-24
Also published as: AU1421483A; HU187695B; AU547958B2; DE3344159T1

Abstract

Aluminium oxide based white filler comprising "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process, being either surface-treated or separated from the particles having a grain size above 5 microns, optionally in admixture with known additives, particularly zinc oxide or sulphur and/or a plasticizer, ageing retarder and/or accelerator. According to the invention there is also provided a process for the preparation of aluminium oxide based white filler which comprises (a) subjecting "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process to surface treatment with a solid or liquid agent; or (b) separating the "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process from the particles having a grain size above 5 microns; and, if desired, admixing the product obtained according to process (a) or (b) with known additives, particularly with zinc oxide, sulphur, and ageing retarder and/or an accelerator, and/or plasticizer. The advantage of the present invention is that the fillers obtained are cheap and when incorporated into rubber or plastics mixtures a significant improvement of the properties (e.g., tensile strength, abrasion, specific electric resistance, etc.) takes place.

Description

White filler and process for the preparation thereof

Technical field

This invention relates to a white filler and a process for the preparation thereof. More particularly, it is concerned with an aluminium oxide baaed white filler and a process for the preparation thereof. The invention also ralates to a rubber or plastics composition including the said white filler, and rubber and plastics products containing the same.

Background art

It is known that various fillers are used in the manufacture of natural or synthetic caoutchouc or plastics products. The so-called black fillers constitute an important group of the said fillers; channel black is the most well-known representative of the black fillers. The use of black fillers is, however, in several cases encountered with difficulties.

In addition to the black fillers an other filler-type - the so-called white fillers - is widespreadly used. These fillers are generally based on oxides or silicates of aluminium, potassium, sodium, barium and magnesium. In German Federal Republic Patent No. 1,071,943 china-clay based fillers are disclosed which have an aluminium oxide/silicic acid ratio of above 0.85 and contain 0.2 - 0.6 % by weight of thiuram disulfide. According to Hungarian patent No . 147,411 white fillers comprising substantially aluminium oxide are prepared by heating at a temperature between 300°C and 750°C aluminium hydroxide precipitated from the sodium-aluminate by means of a separately prepared inoculating material. The drawback of the said process is - as it also appears from the text of the Hungarian patent Ho. 147,411 - that exclusively fillers having a grain size below 0.2 micron meet the requirements of rubber industry.

According to another known process aluminium hydroxide gel prepared by reacting aluminium sulfate with sodium carbonate or by acidifying sodium aluminate is used. The use of the said fillers is accompanied, however, by a number of disadvantages. Thus said fillers are very expensive, their activity is not sufficiently high, in their preparation considerable losses of acid or alkali occur and they may contain contaminations, which may catalyse the ageing of caoutchouc and are therefore very damaging.

Disclosure of the invention

The purpose of the present invention is to provide new fillers which may be prepared by simple methods and overcome the above disadvantages.

According to a feature of the present invention there is provided an aluminium oxide based white filler comprising "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process, being either surface-treated or separated from. the particles having a grain size above 5 microns, optionally in admixture with known additives, particularly zinc oxide or sulphur and/or a plasticizer, ageing retarder and accelerator.

It is known that in the course of the Bayer-type alumina manufacturing process aluminium hydroxide is converted into aluminium oxide in a calcinating oven. The powder leaving the oven is deposited in an electrostatic powder separator in which 70 - 75 % of aluminium oxide to be subjected to electrolysis and 25 - 30% of a powder unsuitable for electrolysis are obtained. The latter - so-called "retour powder" - is re-introduced to an earlier stage of the manufacturing process, namely to the aluminium hydroxide precipitating phase. This has the drawback that the powdery substance is to be dried and calcinated before re-introducing into the cycle and this causes considerable wastes and losses of energy.

It has been found in a surprising manner that by using the said "retour powder" isolated in the electro- statical powder separator and re-introduced to an earlier stage of the manufacturing process, fillers having very preferable properties and suitable for use in rubber and plastics industry can be obtained.

According to a further feature of the present invention there is provided a process for the preparation of aluminium oxide based white filler which comprises a) subjecting "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process to surface treatment with a solid or liquid agent; or. b) separating the "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process from the particles having a grain-size above 5 microns; and, if desired, admixing the product obtained according to process a) or b) with known additives, particularly with zinc oxide, sulfur, an ageing retarder and/or an accelerator and/or a plasticizer. According to a preferred form of realization of the process surface treated "retour powder" is used. According to a still preferable feature of the present invention a "retour powder" is used as starting material which has ignition losses of 3-30 % by weight, a. molecular weight of 110 - 145, a specific weight of 2.5 - 3.0 g/cm³, an aluminium content of 36 - 50 % by weight and a hardness of 4.5 - 6.5 according to the Mosh scale. It is particularly advantageous to use a "retour powder" which has ignition lossess of 6 - 16 % by weight, i. e. α, β, γ-aluminium-oxide-hydrate.

Surface treatment can be carried out with any suitable solid or liquid agent used in rubber or plastics formulations. Thus the following solid or liquid agents are particularly suitable for use in the process of the present invention: stearic acid, an oil - preferably extraction oil or watch-maker's oil -, an organic silanol or silane, diethylene glycol, calcium stearate, dioctyl phthalate, N-phenyl-N^,-isopropyl-p-phenylene diamine, diamino-cyclohexyl-phenylene, phenyl-ρ-naphthyl amide, aldole-α-naphthyl amine, an alkylated phenol, 2-mercapto-benzimidazole or dichloro difluoro methane or a mixture thereof.

According to a particularly preferred embodiment of the present invention a mixture of naphthenic acid and triethanol amine - containing about 10 - 30 % by weight of naphthenic acid - is used in an amount of 0.1 - 10.0 % by weight, related to the weight.of the "retour powder". Surface treatment is carried out at room temperature or under heating. The surface treatment according to the present invention may be carried out by using any equipment or method suitable to the applying of solid or liquid agents to powdery substances. The treatment may be carried out preferably under homogenization. According to another method the liquid agent is applied on the surface of the "retour powder " by means of a nozzle or a sprayer.

According to process b) the "retour powder " is made free of the particles having a grain size above 5 microns. This can be carried out preferably by known methods, e. g. by grinding or sieving. The filler according to the present invention can be used alone (per se) or together with other known fillers.

According to a further feature of the present invention there are provided rubber and plastics articles comprising the fillers hereinbefore disclosed. The fillers according to the present invention may.be used in a wide range of rubber and plastics articles. The following rubber and plastics articles are enumerated by way of illustration only: tyres, technical rubber articles, seals, sole-articles, panels, floors, section bands, formed or moulded pieces, sheets, extruded or pressed tubes, cable coatings, etc. It has been found that the fillers according to the present invention improve the properties of rubbers and plastics to a considerably greater extent than the known fillers. The best results are obtained by using fillers prepared from surface treated "retour powder", but fillers made from "retour powder" made free from the particles having a grain size above 5 microns also gave good results. On adding the fillers of the present invention to rubber articles, tensile strength and hardness are increased to a significant extent and ιbrasion is considerably reduced; these advantages are particularly important in the manufacture of sole-articles and tyre. In addition to natural caoutchouc based rubber, the fillers of the present invention are also suitable. for use in mixtures prepared from artificial rubbers (e. g. nitrile caoutchouc, a mixture of butadiene and styrene, etc.). A further advantage of the filler of the present invention is that in some cases it decreases the necessary amount of expensive accelerators; it has namely been found that the filler of the present invention adsorbs accelerators to a smaller extent than the channel. black or the known white fillers.

On incorporating the fillers of the present invention into PVC nass the tensile strength is decreased to a smaller extent than when using known fillers, while on the other hand - abrasion is reduced and specific electric resistance is increased to a very large extent, even by several orders of magnitude.

The fillers of the present invention are also suitable for use in building industry. When incorporating the fillers of the present invention into plastics -contrary to the known inert fillers used in large amounts, e. g. china clay, calcium carbonate, quartz sand - excellent flame retarding effect is observed. The bound water content of. the filler of the present invention delivers namely at a temperature of about 250°C vapor which damps down the flames. A further advantage of the filler of the present invention resides in the fact that it improves the electric breakdown strength and the leakage current resistance.

According to a preferred embodiment of the present invention there are provided fillers comprising 70 - 99 % by weight of sulphur and 30 - 1 % by weight of surface treated "retour powder". The said products may be prepared either by admixing 70 - 99 % by weight of sulphur with 30 - 1 % by weight of surface treated "retour powder", or by admixing sulphur with "retour powder" and subjecting the homogenized mixture to a surface treatment as disclosed above.

Industrial applicability

The white fillers of the present invention are suitable for use in rubber and plastic industry and also in the building industry.

Modes of carrying out the invention

Further details of the present invention are to be found in the following examples without limiting the scope of protection to the said examples which serve for illustration only.

Example 1 8.5 kg. of "retour powder" (ignition losses: 12.05 %; specific weight: 2.6 g./cm³; aluminium content: 42 %; hardness according to the Mosh scale: 5.0) are admixed with 1 kg. of precipitated silicate in a homogenizer. The mixture thus obtained is surface treated with a mixture of 0.2 kg. of stearic acid, 0.25 kg. of extraction oil, 0.03 kg. of triethanol amine, 0.01 kg. of naphthenic acid and 0.01 kg. of silanol, heated to 72°C. Example 2

9.4 kg. of "retour powder" (ignition losses: 15-45 %; grain size: in 88 % between 1 and 5 microns; specific weight: 2.8 g/cm³, aluminium content: 39 % ; hardness according to the Mosh scale: 4.9) are surface treated in a homogenizer with a liquid mixture of 0.2 kg. of stearic acid, 0.3 kg. of extraction oil and 0.1 kg. of silanol, heated to 72°C. Example 3 One proceeds as described in. Example 2 except that the silanol is replaced by 0.1 kg. of diethylene glycol, triethanol amine or naphthenic acid. Example 4

9.5 kg. of "retour powder" (ignition losses: 8.6 %; grain size: 1 - 20 microns; aluminium content: 43 %; hardness according to the Mosh scale 5.2) are subjected to surface treatment in a homogenizer with a mixture of 0.2 kg. of calcium stearate, 0.3 kg. of dioctyl phthalate and 0.02 kg. of triethanol amine, at 20°C. Example 5

For the purpose of comparison rubber compositions are prepared from the fillers according to the present invention and known fillers (channel black and precipitate silica). The characteristic features and properties are determined after vulcanization by standard methods.

The results obtained are summarized in the following Tables. In Table I the composition of the rubber mixture is disclosed (in parts by weight). Columns I - 17 of Table I relate to the composition of mixtures prepared by using the fillers according to the present invention, while columns 7- 71 show the composition of mixtures containing the known referent fillers. The test results are set forth in Table II.

lt appears from the above data that the tensile strength and hardness of the rubber containing the filler according to the present invention are considerably better than the corresponding properties of rubber having the same composition but comprising known fillers, and simultaneously the abrasion is decreased to a significant extent. According to the said comparative tests the abrasion is reduced by nearly 50 % which is particularly useful in the manufacture of sole-articles and tyres. Example 6

Fillers prepared from the "retour powder" surface treated according to Example 4 is incorporated into hard and soft PVC mixtures having different composition and the properties of the products thus obtained are compared to those of PVC mixtures comprising fillers prepared by conventional methods.

In Table III the composition of the mixtures (in parts by weight) and in Table 17 the measured results are disclosed. Tables III and 17 relate to soft PVC.

It can be seen that the properties of the plastics mixtures prepared by using the fillers according to the present invention are significantly better than those of plastic mixtures comprising known fillers. In addition to a smaller decrease of the tensile strength and a significant reduction of abrasion, it is particularly noteworthy that the specific electric resistance is increased by three or even four orders of magnitude. Example 7

85 parts by weight of sulphur and 10 parts by weight of "retour powder" are homogenized and surface treated with 5 parts by weight of a liquid mixture consisting of oil, fatty acid ester, naphthenic acid and triethanol amine.

Example 8 A homogenized mixture of 60 parts by weight of "retour powder" and 35 parts by weight of China clay are surface treated with 5 parts by weight of a liquid mixture consisting of oil, fatty acid ester, naphthenic acid and triethanol amine.

Claims

What we claim is:

1. Aluminium oxide based white filler comprising "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process, being either surface-treated or separated from the particles having a grain size above 5 microns, optionally in admixture with known additives, particularly zinc oxide or sulphur and/or a plasticizer, ageing retarder and/or accelerator.

2. Filler according to claim 1 comprising a

"retour powder" which has ignition losses of 3 - 30 % by weight, a molecular weight of 110 - 145, a specific weight of 2.5 - 3.0 kg/cm³, an aluminium content of 36 - 50 % by weight and a hardness of 4.5 - 6.5 according to the Mosh scale.

3. Filler according to any of claims 1- 2 comprising a "retour powder" subjected to surface treatment.

4. Filler according to claim 3 comprising "retour powder" surface treated with stearic acid, an oil - preferably extraction oil or watch-maker's oil -, an organic silanol or silane, diethylene glycol, calcium stearate, dioctyl phthalate, U-phenyl-N'-isopropyl-p- phenylene diamine, diamino-cyclohexyl-phenylene, phenyl-β-naphthyl amine, aldole-α-naphthyl amine, an alkylated phenol, 2-mercapto-benzimidazole or dichloro difluoro methane or a mixture thereof.

5. Filler according to claim 4 comprising a "retour powder" surface treated with 0.1 - 10.0 % by weight of a mixture of naphihenic acid and triethanol amine.

6. Filler according to claims 4 - 5 comprising a

"retour powder" surface treated with a mixture of stearic acid, an oil - preferably extraction oil or watch-maker's oil -, an organic silanol or silane, naphthenic acid and triethanol amine.

7. Filler according to any of claims 3 - 6 comprising "retour powder" surface treated with 0.1 - 20 % by weight of a solid or liquid agent.

8. Filler according to claim 1 comprising 70 - 99

% by weight of sulphur and 30 - 1 % by weight of surface treated "retour powder".

9. Process for the preparation of aluminium oxide based with filler which comprises a) subjecting "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process to surface treatment with a solid or liquid agent; or b) separating the "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process from the particles having a grain-size above 5 microns; and, if desired, admixing the product obtained according to process a) or b) with known additives, particularly with zinc oxide, sulphur, an ageing retarder and/or an accelerator and/or a plasticizer.

10. Process according to claim 9 which comprises using a "retour powder" which has ignition losses of 3 - 30 % by weight, a molecular weight of 110 - 145, a specific weight of 2.5 - 3.0 kg/cm², an aluminium content of 36 - 50 % by weight and a hardness of 4.5 - 6.5 according to the Mosh scale.

11. Process according to any of claims 9 - 10 which comprises subjecting "retour powder" to surface treatment.

12. Process according to claim 11 which comprises carying out surface treatment with stearic acid, an oil - preferably extraction oil or watch-maker's oil, an organic silanol or silane, diethylene glycol, calcium stearate, dioctyl phthalate, N-phenyl-N'-isopropyl-p- phenylene diamine, diamino-cyclohexyl-phenylene, phenyl- β-naphthyl amine, aldole-α-naphthyl amine, an alkylated phenol, 2-mercapto-benzimidazole or dichloro difluoro methane or a mixture thereof.

13. Process according to claim 13 which comprises carrying out surfacet treatment with 0.1 - 10.0 % by weight of a mixture of naphthenic acid and triethanol amine.

14. Process according to any of claims 11 - 13 which comprises carrying out surface treatment with a mixture of an oil - preferably extraction oil or watch-maker's oil -, an organic silanol or silane, naphthenic acid and trietahnol amine.

15. Process according to any of claims 11 - 14 which comprises carrying out surface treatment by using 0.1 - 20 % by weight of a solid or liquid agent related to the weight of the "retour powder".

16. Process according to claim 9 which comprises admixing 70 - 99 % by weight of sulphur with 30 - 1 % by weight of surface treated "retour powder", or admixing 70 - 99 % by weight of sulphur with retour powder and subjecting the homogenized mixture to surface treatment according to claim 9.

17. Process according to claim 9 which comprises removing the particles having a grain. size above 5 microns by grinding or sieving.

18. A rubber or plastic composition including white fillers comprising "retour powder" formed in the calcinating oven of the Bayer-type alumina manufacturing process, being either surface treated or separated from the particles having a grain size above 5 microns and optionally known additives, particularly zinc oxide or sulphur or an accelerator and/or an ageing retarder and/or a plasticizer.

19. Rubber and plastic articles, particularly tyres, seals, sole articles, panels, floors, section bands, formed or moulded pieces, sheets, extruded or pressed tubes or cable coatings comprising a filler according to any of claims 1 - 8.