METHOD FOR PREPARING A HYDROLYSIS-RESISTANT PRODUCT, THE OBTAINED PRODUCT AND AN ARTICLE CONTAINING THE HYDROLYSIS-RESISTANT PRODUCT

Abstract: The invention relates to a method for preparing a hydrolysis-resistant, mineral product comprising: i) providing an immersion liquid containing at least one silane compound; ii) immersing the mineral product in the immersion liquid; and iii) drying the immersed mineral product, these such that after the steam resistance test the mineral product has substantially retained its structure, and to the mineral, hydrolysis-resistant product which after the steam resistance test has substantially retained its structure, and to an article comprising a matrix material and the mineral, hydrolysis-resistant product dispersed in the matrix material.

Description: METHOD FOR PREPARING A HYDROLYSIS-RESISTANT PRODUCT, THE OBTAINED PRODUCT AND AN ARTICLE CONTAINING THE HYDROLYSIS-RESISTANT PRODUCT The present invention relates to a method for preparing a hydrolysis-resistant, mineral product, to the prepared mineral product and to an article containing the hydrolysis- resistant, mineral product. Mineral products, such as mineral fibres, for instance roc wool fibres, glass fibres and ceramic fibres, and mineral particles such as talc, aluminium trihydrate and mica, have the drawback that as a result of hydrolysis, particularly at increased temperature, these mineral products lose their structure, that is, fibre structure and particle structure. • Due to the reduced hydrolysis or steam resistance such mineral products have a diminished usefulness. The invention has for its object to provide a mineral product having a greatly improved hydrolysis resistance. Understood in this context by hydrolysis resistance is that after the so-called steam resistance test the mineral product has substantially retained its original structure. The steam resistance test comprises exposing the mineral product in an autoclave to steam at a temperature of about 235°C and a pressure of approximately 30 bar for a period of 7 days. It is then determined whether the mineral product has retained its original structure. An indication of structure retention is derived by determining the weight change as a result of the steam resistance test. An increase in weight indicates susceptibility to hydrolysis, while a constant or decreasing weight indicates hydrolysis resistance and therefore structure retention. It has been found from research that the mineral product can be made hydrolysis-resistant by immersing the mineral product in an immersion liquid containing at least one silane compound. This immersion can take place for instance in an immersion bath or by guiding products through a mist, "curtain" or column of the silane compound, optionally dissolved in a solvent. Placing the mineral product in contact with the silane compound in other manner does not result in a hydrolysis-resistant mineral product displaying structure retention after the steam resistance test. The method according to the invention for preparing a hydrolysis-resistant, mineral product is therefore characterized in that the method comprises: i) providing an immersion liquid containing at least one silane compound; ii) immersing the mineral product in the immersion liquid; and iii) drying the immersed mineral product, these such that after the steam resistance test the mineral product has substantially retained its structure. An immersion liquid is generally used which contains a silanol compound, more preferably a silanetriol compound, whereby an optimal improvement of the hydrolysis resistance is obtained. The active silane compound can be added as such to the immersion liquid, but can also occur in situ in the immersion liquid, for instance through hydrolysis. When a silanol compound is used, this silanol compound can be formed in situ from a mono-, di- or trialkoxysilane compound, preferably from a trimethoxy- or triethoxysilane compound. If the hydrolysis-resistant, mineral product is intended for use in an article which contains a matrix with which the mineral product must form a chemical bond, it iε further recommended that the silane compound be provided with a functional group. As functional group the silane compound can be provided with an amino group, an alkylamino group, a vinyl group, a mercapto group, a halogenide group, an acryl group, an (alk)acryl group, a glycidyloxy group, a cyano group and/or a thiocyanate. If the hydrolysis-resistant, mineral product is used in a matrix of rubbery material, it is recommended that the functional group is a vulcanizable group such as an amino group, a vinyl group, an epoxy group, (glycidyloxy group) , a mercapto group, or other sulphur groups. The conditions under which immersion of the mineral product in the immersion liquid takes place must be selected such that the immersed product displays structure retention after the steam resistance test. The type and concentration of the silane compound, the temperature of and treatment time in the immersion liquid must be determined in mutual interdependence. In general the concentration for the silane compound amounts to 0.1-90% by weight, in particular 1-50% by weight and preferably 1-10% by weight. The temperature amounts to between ambient temperature and 90°C, preferably 30-80"C and in general 35-70°C. The treatment time must generally be shorter than 60 minutes and preferably amounts to 1-30 minutes, more preferably 5-20 minutes. The mineral product is preferably a mineral fibre, more preferably a rockwool fibre. Incorporation of such mineral products into other articles make a significant contribution to improvement of the mechanical properties, namely strength, ruggedness and fatigue properties. Another aspect of the present invention relates to the hydrolysis-resistant, mineral product prepared according to the invention and displaying structure retention after the steam resistance test. The invention finally relates to articles containing the matrix material and wherein the mineral, hydrolysis- resistant product according to the invention is dispersed in the matrix material. In the finished product the average fibre length lies generally between 30-5000 μm, in practice between 70-1000 μm. For optimal results for the bending strength the fibre length lies above 100 μm, such as between approximately 110-500 μm. With too great a fibre length dispersion problems occur, depending on the viscosity of the matrix and the dispersion method. This can lead to unhomoge- neouε, anisotropic properties. An example of an article according to the invention has the form of a sealing ring and consists of a vulcanized mixture of rubbery material such as SBR, neoprene, EPR, EPDM, and isoprene rubber. In addition a polyurethane matrix can be applied. The method for preparing a hydrolysis-resistant mineral product, the hydrolysis-resistant mineral product and an article containing the mineral product according to the invention will be further elucidated hereinbelow with reference to a number of embodiments given by way of example. Example 1 20 grams rockwool fibre with a mean length of 2000 μm and a mean diameter of 5 μm are immersed in an immersion liquid on a basis of an aqueous aminosilane hydrolysate (DYNASYLAN 1151 R from Hύls) at a temperature of 45°C and an immersion time of 5 minutes. After immersion the treated mineral fibres are dried and subjected to the steam resistance test. For this purpose 2.5 grams of the fibre are placed in a basket and suspended in an autoclave (diameter 6 cm, length 26 cm) filled with 200ml demineralized water. The autoclave is closed and placed for 7 days in an oven at 235°C. The results are shown in the following table 1. The results in table 1 indicate that, at a concentration of DYNASYLAN 1151 of about 3% and more in the applied immersion conditions, hydrolysis- or steam-resistant mineral fibres are obtained which are also provided with a functional amino group. concentration weight hydrolysis immersion liquid change resistance (%) (% by weight) 0 + 8.2 0.7 + 1.7 1.4 + 0.4 2.0 + 0.2 2.8 + 0.1 +/- 3.5 - 0.82 + 7 - 1.1 14 - 2.8 + 28 - 7.7 + Example 2 Rockwool fibres with a mean length of about 800 μm and a mean diameter of 5 μm are immersed at 45°C and an immersion time of 5 minutes in an immersion bath containing a 5% solu- tion of Arkophob NCS (Hoechst) and 2.5% catalyst. Immersion is performed at a temperature of 45°C and an immersion time of 5 minutes. After drying at 100°C the steam resistance test is performed. The weight of the fibres de¬ creased by 6.2% by weight and the hydrolysis resistance was good. Example 3 Instead of Arkophob NCS use was made of Leomin RWS (Hoechst) in a 2% solution. The weight decrease amounted to - 5.7% by weight and the hydrolysis resistance was good. Example 4 Making use of the same immersion conditions as in exam¬ ple 2, use was made instead of Arkophob NCS of bis(3-tri- ethoxysilylpropyl)-tetrasulphane (Si69; Degussa) in a 10% solution. After the steam resistance test the weight decrease was -2.5% by weight and the treated fibres displayed a good hydrolysis resistance. The fibres were mixed with an elastomer on a basis of SBR rubber and subjected to sulphur vulcanization. The obtained sealing rings had an outstanding steam resistance. *****

Claims: CLAIMS 1. Method for preparing a hydrolysis-resistant, mineral product comprising: i) providing an immersion liquid containing at least one εilane compound; ii) immersing the mineral product in the immersion liquid; and iii) drying the immersed mineral product, these such that after the steam resistance test the mineral product haε substantially retained its structure. 2. Method as claimed in claim 1, wherein the silane compound is a silanol compound. 3. Method aε claimed in claim 1 or 2, wherein the silanol compound is a εilanetriol compound. 4. Method as claimed in claim 2 or 3, wherein the silanol compound iε formed in situ in the immersion liquid. 5. Method as claimed in claim 4, wherein the silanol compound iε formed from a mono-, di- or trialkoxysilane compound. 6. Method as claimed in claims 1-5, wherein the silane compound is provided with a functional group. 7. Method as claimed in claim 6, wherein the functional group compriseε an amino group, an alkylamino group, a vinyl group, a mercapto group, a halogenide group, an acryl group, an (alk)acryl group, a glycidyloxy group and/or a cyano group. 8. Method aε claimed in claim 6 or 7, wherein the functional group iε a vulcanizable group. 9. Method aε claimed in claims 1-8, wherein immersion iε performed at a concentration of the silane compound of 5-50% by weight, a temperature of 30-80°C and a treatment time of 1-30 minuteε. 10. Method aε claimed in clai ε 1-9, wherein the mineral product iε a mineral fibre, preferably a rockwool fibre 11. Mineral, hydrolysis-resistant product prepared as claimed in any of the foregoing claimε 1-10, and which after the steam resiεtance teεt haε εubstantially retained its structure. 12. Mineral product as claimed in claim 11 which is a mineral fibre, in particular a rockwool fibre. 13. Mineral product as claimed in claim 11 or 12 which is prepared as according to claims 6-8. 14. Article comprising a matrix material and a mineral, hydrolysis-resiεtant product as claimed in any of the foregoing claims 11-13 diεpersed in the matrix material. 15. Article aε claimed in claim 14 in the form of a εealing ring with a vulcanized matrix of rubbery material and mineral product aε claimed in claim 13. 16. Article as claimed in claim 14 or 15, wherein the mineral product has a fibre length of 70-1000 μm, more preferably 100-500 μm. *****

Inventors: GHIJZEN CORNELUS JOHANNUS MARI, SIJSTERMANS MARCUS VIRGENIE JA, GHIJZEN, CORNELUS, JOHANNUS, MARIA, SIJSTERMANS, MARCUS, VIRGENIE, JACOBUS
Applicants: GHIJZEN CORNELUS JOHANNUS MARI, LAPINUS FIBRES BV, SIJSTERMANS MARCUS VIRGENIE JA, LAPINUS FIBRES B.V.
Application year: 1993
Main classification: C03C25
IPC codes: C03C25, C04B20, C08J5