NEW MODIFIED SILICON OIL FOR LOW TEMPERATURE CURE DIE CASTING LUBRICANTS

Abstract

The present invention relates to a mixture of polyalkylsiloxanes that cure at temperatures of about 170 C. while being unreactive under ambient conditions during storage or transport and which are obtained through a hydrosilylation reaction wherein a mixture of ethylenically unsaturated olefins consisting of 1-100% of one or more polyene(s), and 0-99 mol % of monounsaturated olefins with 6 to 15 carbon atoms is reacted with an amount of one or more polyalkylhydrosiloxanes in the presence of a hydrosilylation catalyst. Furthermore, the present invention relates to water-based compositions suitable for use in metal casting processes as a mold release agent comprising a mixture of polyalkylsiloxanes of the invention and a non-ionic surfactant. In addition, the present invention relates to the use of the polyalkylsiloxanes and mixtures of polyalkylsiloxanes as defined herein.

Claims

1. A mixture of polyalkylsiloxanes obtained through a hydrosilylation reaction wherein a mixture of ethylenically unsaturated olefins consisting of: a) 1-100 mol % of one or more polyene(s) having one terminal double bond, which is either monosubstituted or geminal disubstituted, and one or more tri- or tetrasubstituted double bond(s); and b) 0-99 mol % of monounsaturated olefins with 6 to 15 carbon atoms; is reacted with an amount of one or more polyalkylhydrosiloxanes in the presence of a hydrosilylation catalyst while each polyalkylhydrosiloxane comprises a repeating unit according to the general structure (I): ##STR00007## with n indicating the number of repeating units being in a range of from 5 to 10,000; with the residue R.sup.1 being selected from linear or branched alkyl groups with less than 6 carbon atoms.

2. The mixture of polyalkylsiloxanes according to claim 1, wherein said terminal double bond and said one or more tri- or tetrasubstituted double bond(s) are non-conjugated.

3. The mixture of polyalkylsiloxanes according to claim 1, wherein said polyene(s) comprise terpenes.

4. The mixture of polyalkylsiloxanes according to claim 3, wherein said terpenes comprise (R)-limonene, (S)-limonene or a mixture thereof.

5. The mixture of polyalkylsiloxanes according to claim 1, wherein the amount of polyalkylhydrosiloxanes equals at least 60% of a stoichiometric amount and not more than the stoichiometric amount.

6. The mixture of polyalkylsiloxanes according to claim 1, wherein the polyalkylhydrosiloxanes are at least partially selected from polymethylhydrosiloxanes.

7. The mixture of polyalkylsiloxanes according to claim 1, wherein at least 80 mol % of the repeating units according to the general structure (I) have a residue R.sup.1 being a methyl group.

8. The mixture of polyalkylsiloxanes according to claim 1, wherein at least 80 mol % of the monounsaturated olefins with 6 to 15 carbon atoms are selected from -olefins.

9. The mixture of polyalkylsiloxanes according to claim 1, wherein the hydrosilylation catalyst is a platinum catalyst.

10. The mixture of polyalkylsiloxanes according to claim 1, obtained in a hydrosilylation reaction run at a temperature in a range of from 80 to 170 C. for a time sufficient to yield a mixture of polyalkylsiloxanes that contains not more than 10 mol % Si-H bonds.

11. The mixture of polyalkylsiloxanes according to claim 1, wherein an inert liquid vehicle that acts as a solvent for the one or more polyalkylhydrosiloxanes and/or the mixture of ethylenically unsaturated olefins is present in an amount of less than 20 wt.-%; and/or the mixture of polyalkylsiloxanes is an oil.

12. A water-based die casting release agent composition comprising: a) 1-50 wt.-% of the mixture of polyalkylsiloxanes according to claim 1, b) 1-15 wt-% of a non-ionic surfactant having a HLB value of at least 8, and c) 0-30 wt.-% of waxes, mineral oils, natural oils and/or synthetic oils.

13. The water-based die casting release agent composition according to claim 12, wherein: i) the non-ionic surfactant is a mixture of polysorbate 85 and ethoxylated tridecyl alcohol; ii) the water-based composition is an oil-in-water emulsion; and/or iii) the waxes are polyethylenes and/or polypropylenes which are insoluble in water, are malleable at 20 C. and melt above 45 C.

14. A polyalkylsiloxane comprising repeating units according to general structure (II): ##STR00008## wherein n indicates the number of repeating units comprised in the polyalkylsiloxane, wherein n is an integer of 5 to 10,000 and residue R.sup.1 is selected from the group consisting of linear or branched alkyl groups with less than 6 carbon atoms, wherein a) in 1-100% of the repeating units, R.sup.2 is selected from the group consisting of linear or branched or cyclic alkenyl groups, obtained by the addition of a Si-H bond across the terminal double bond of a polyene having one terminal double bond, which is either mono- or geminal disubstituted, and one or more tri- or tetrasubstituted double bond(s), in a hydrosilylation reaction; b) in 0-99% of the repeating units, R.sup.2 is selected from the group consisting of linear or branched alkyl groups with 6 to 15 carbon atoms; and c) in 0-10% of the repeating units, R.sup.2 is H.

15. The polyalkylsiloxane according to claim 14, wherein the polyalkylsiloxane has a kinematic viscosity of 100 to 20000 mPa.Math.s at 25 C.

16. The polyalkylsiloxane according to claim 14, wherein i) in the repeating units b), R.sup.2 is selected from the group consisting of linear or branched alkyl groups with 6 to 14 carbon atoms; ii) repeating units a) make up 10-30% of the repeating units, R.sup.2; iii) repeating units b) make up 70-90% of the repeating units R.sup.2; iv) the repeating units a) have a ratio to the repeating units b) in a range of from 1:10 to 1:1; v) the polyalkylsiloxane is an oil; and/or vi) residue R.sup.1 of each repeating unit according to general structure (II) is a methyl group.

17. A water-based die casting release agent composition comprising: a) 1-50 wt.-% of the polyalkylsiloxane according to claim 14, b) 1-15 wt.-% of a non-ionic surfactant having a HLB value of at least 8, and c) 0-30 wt.-% of waxes, mineral oils, natural oils and/or synthetic oils.

18. Use of polyalkylsiloxanes as a mold release agent in a metal casting process, wherein the polyalkylsiloxanes are: i) the polyalkylsiloxanes according to claim 14; and/or ii) polyalkylsiloxanes comprising a repeating unit according to the following general structure (II): ##STR00009## wherein n indicates the number of repeating units being in a range of from 5 to 10,000; wherein for each repeating unit the residue R.sup.1 is independently selected from linear alkyl groups with less than 6 carbon atoms; and wherein for each repeating unit the residue R.sup.2 is independently selected from (a) hydrogen or (b) linear or branched alkyl groups having 6 to 15 carbon atoms or (c) a linear or branched or cyclic alkenyl group, obtained by the addition of a Si-H bond across the terminal double bond of a polyene having one terminal double bond, which is either monosubstituted or geminal disubstituted, and one or more tri- or tetrasubstituted double bond(s), in a hydrosilylation reaction, while the fraction of repeating units with a residue R.sup.2 being hydrogen is less than 0.1, being an alkenyl residue, is in a range of from 0.01-1.0, and being a linear or branched alkyl group having 6 to 15 carbon atoms is in a range of from 0-0.99.

19. The use according to claim 18, option ii), wherein: a) the fraction of repeating units according to the general structure (II) with R.sup.2 being a linear or branched alkyl group having 6 to 15 carbon atoms is at least 0.7 and not greater than 0.9; and/or b) the fraction of repeating units according to the general structure (II) with the R.sup.2 being an alkenyl group, is at least 0.10 and not greater than 0.30.

20. A method of lubricating a die for use in a die casting process comprising: 1) applying a die casting release agent comprising the mixture of polyalkylsiloxanes according to claim 1 to a die; 2) curing the die casting release agent on the die at temperatures in a range of at least 170 C. and up to about 190 C. to form a solid film.

Description

EXAMPLES

Example 1

[0102] To a mixture of polymethylhydrosiloxane with the average formula (CH.sub.3).sub.3SiO(CH.sub.3HSiO).sub.25Si(CH.sub.3).sub.3 (80 g, 1.205 mol free Si-H) and 1-dodecene (15.41 g, 0.092 mol) was added 4 ppm of a H.sub.2PtCl.sub.6 solution in isopropanol (0.145 mL, 17.1 mg/mL). The mixture was heated to 80 C. resulting in an exotherm heating the mixture to 140 C. 1-dodecene (138.7 g, 0.82 mol) was added at such a rate to keep the temperature 140-150 C. Subsequently, limonene (31.2 g, 0.23 mol) was added dropwise. After complete addition the mixture was heated at 150 C. for 1.5 hours. FTIR analysis showed <5% SiH. The viscosity of the product was 1500 mPa.Math.s.

[0103] A 10 m layer of the prepared silicon oil was applied on a steel plate followed by heating of the plate for 2 minutes at temperatures between 160 and 230 C. under aerobic conditions. Film formation was observed for the new low curing silicon oil and compared to state of the art silicon oils. Formation of a polymeric film on the metal surface was observed at temperatures of 170 C. and higher for the silicon oil of the invention. All other tested silicon oils (prior art silicon oils) showed film formation at temperatures of 225 C. and higher.

[0104] Mixtures of the silicon oil with light petroleum distillates in weight ratios of 10:1 to 1:3 afforded very low viscous oils with identical curing temperatures compared to the pure oil. These low viscous oils allow application of pure oils on the die by state of the art oil spraying equipment used in the pressure die casting industry.

[0105] Thermogravimetric analysis of the silicon oils showed a decomposition temperature of the low curing silicon oil which was identical or slightly better compared to regular silicon oil. The material was fully decomposed above 520 C.