A FOAMABLE SILICONE COMPOSITION AND THE USE THEREOF

Abstract

A foamable silicone composition, includes: (a) at least one organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms per molecule, (b) at least one organopolysiloxane containing at least two hydrogen atoms bonded to silicon atoms per molecule, (c) porogenic agents generating gaseous hydrogen in the presence of component (b) comprising (c1) an organopolysiloxane containing at least one hydroxyl group bonded to silicon atom per molecule and (c2) water, and (d) hydrosilylation catalyst; with the proviso that the ratio of the number of moles of hydroxyl groups provided by component (c2) to that provided by component (c1) is within a range of from 1:5 to 20:1. The composition has a low viscosity and a relatively high pot life, and the foam cured therefrom has a low density, uniform porosity and fine cell structure.

Claims

1-14. (canceled)

15. A foamable silicone composition, comprising: (a) at least one organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms per molecule, (b) at least one organopolysiloxane containing at least two hydrogen atoms bonded to silicon atoms per molecule, comprising: (b1) an organopolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule, and (b2) an organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, (c) porogenic agents generating gaseous hydrogen in the presence of component (b), comprising (c1) an organopolysiloxane containing at least one hydroxyl group bonded to silicon atom per molecule, and (c2) water, and (d) hydrosilylation catalyst; with the proviso that the ratio of the number of moles of hydroxyl groups provided by component (c2) to that provided by component (c1) is within a range of from 1:5 to 20:1, and the composition has a dynamic viscosity of from 200 to 10,000 mPa.Math.s at (232) C. before curing measured by Brookfield viscometer using No. 2 spindle at a speed of 10 rpm.

16. The composition of claim 15, wherein the ratio of the number of moles of hydroxyl groups provided by component (c2) to that provided by component (c1) is within a range of from 1:2 to 10:1.

17. The composition of claim 15, wherein component (c) is used in an amount of less than or equal to 15 wt % based on the total weight of the composition.

18. The composition of claim 15, wherein the ratio of the number of moles of SiH groups provided by component (b) to that of silicon-bonded alkenyl groups provided by component (a) is from 2:1 to 15:1.

19. The composition of claim 15, wherein the ratio of the number of moles of SiH groups provided by component (b) to that of hydroxyl groups provided by component (c) is from 1:2 to 15:1.

20. The composition of claim 15, wherein component (c1) has a dynamic viscosity of from 10 to 1,000 mPa.Math.s at 25 C.

21. The composition of claim 15, wherein component (a) comprises greater than or equal to 80 wt % of organopolysiloxanes containing at least two alkenyl groups bonded to silicon atoms per molecule with a dynamic viscosity of from 10 to 1,000 mPa.Math.s at 25 C. based on the total weight of component (a).

22. The composition of claim 15, wherein component (b1) has a hydrogen content of from 1.2 wt % to 1.7 wt %.

23. The composition of claim 15, wherein component (b2) comprises greater than or equal to 80 wt % of organopolysiloxanes containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule with a dynamic viscosity of from 10 to 2,000 mPa.Math.s at based on the total weight of component (b2).

24. The composition of claim 15, wherein the composition comprises: (a) 2080 wt % of at least one organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms per molecule, (b1) 18 wt % of an organopolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule, (b2) 2070 wt % of an organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule. (c1) 115 wt % of an organopolysiloxane containing at least one hydroxyl group bonded to silicon atom per molecule, (c2) 0.011 wt % of water, and (d) hydrosilylation catalyst.

25. A foam cured from the composition of claim 15.

26. A potting material comprising the composition of claim 15.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0063] The present invention is further illustrated by the following examples, but is not limited to the scope thereof. Any experimental methods with no conditions specified in the following examples are selected according to the conventional methods and conditions, or product specifications.

Determination of Viscosity

[0064] The viscosities of components A and B were measured by Brookfield viscometer using No. 2 spindle at a speed of 10 rpm at room temperature (232) C.

Determination of Pot Life

[0065] Pot life refers to the window of time that the mixture of components A and B is able to be used once they are mixed. The wording able to be used means such a state that the mixture of components A and B is still a slurry with good fluidity and has not begun to solidify. The pot life of the present disclosure was determined at (232) C. and 5010% relative humidity.

Determination of Foam Density

[0066] It was conducted according to standard GB/T 6343-2009.

Porosity Condition

[0067] Cross-section of the foam was visually observed with regard to uniformity of pores across the entire cross-sectional areas. When existence of localized excessively large pores or nonexistence of localized pores was observed in the cross section, uniformity of pores was evaluated as inhomogeneous. When there was no such excessively large pores and pores were uniformly found in the cross-section, uniformity of pores was evaluated as uniform.

Cell Size

[0068] The central portion of the cross-section of the foam was observed under an electron microscope. When more than or equal to 90% of the cells were observed to have a maximum diameter of less than or equal to 1 mm, the size of cells was evaluated as a fine cell, otherwise it was evaluated as a coarse cell.

[0069] Details of the raw materials used in the Examples and Comparative Examples are as follows. [0070] a1: dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of about 20,000 mPa.Math.s at 25 C. and a vinyl content of 0.042 mmol/g, supplied by Wacker Chemicals. [0071] a2: dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of about 500 mPa.Math.s at 25 C. and a vinyl content of 0.17 mmol/g, supplied by Wacker Chemicals. [0072] a3: dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of about 200 mPa.Math.s at 25 C. and a vinyl content of 0.26 mmol/g, supplied by Wacker Chemicals. [0073] a4: polydimethylsiloxane having multiple vinyls, with a dynamic viscosity of mPa.Math.s at 25 C. and a vinyl content of 0.24 mmol/g, supplied by Wacker Chemicals. [0074] b1: polydimethylsiloxane having multiple hydrogen atoms, with a dynamic viscosity of about 20 mPa.Math.s at 25 C. and a hydrogen content of 16.3 mmol/g, supplied by Wacker Chemicals. [0075] b2: dimethylhydrosiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of about 1,000 mPa.Math.s at 25 C. and a hydrogen content of 0.12 mmol/g, supplied by Wacker Chemicals. [0076] c1: dimethylhydroxylsiloxy-terminated polydimethylsiloxane, with a hydroxyl content of 1.2 wt %, supplied by Wacker Chemicals. [0077] c2: water-based emulsion of polydimethylsiloxane, with a dynamic viscosity of 5,00010,000 mPa.Math.s at 25 C. and a hydroxyl content of 59.9 wt %, supplied by Wacker Chemicals. [0078] d: platinum-based catalyst, WACKER CATALYST EP, supplied by Wacker Chemicals. [0079] e: inhibitor, WACKER INHIBITOR PT 88, supplied by Wacker Chemicals. [0080] f: vinyl MQ resin, with a molar ratio of M units to Q units of 0.7:1 and a vinyl content of 0.78 mmol/g, supplied by Wacker Chemicals. [0081] g: trimethylsiloxy-terminated polydimethylsiloxane with a dynamic viscosity of about 100 mPa.Math.s at 25 C., supplied by Wacker Chemicals. [0082] h: color paste, ELASTOSIL COLOR PASTE FL BLACK RAL 9005 F, supplied by Wacker Chemicals.

Examples 1-3 and Comparative Examples 1-2

[0083] According to the formulas in Table 1, the ingredients in each Component A and Component B were mixed well respectively. Then Component A and B were mixed respectively and the obtained mixture was cured at room temperature for 60 min to give a silicone foam.

[0084] Table 2 shows pot life of the compositions, foam density, porosity condition and cell size of the foams obtained in each example and comparative example. Foams of Examples 1-3 have a low density, uniform porosity and fine cell structure by using water and hydroxy-terminated polydimethylsiloxane as the porogenic agent. Foam of Comparative Example 1 has a higher density by using hydroxy-terminated polydimethylsiloxane only as the porogenic agent. Foam of Comparative Example 2 has a higher density, inhomogeneous porosity and coarse cell structure by using water only as the porogenic agent.

TABLE-US-00001 TABLE 1 Ingredients (parts by Example Example Example Comparative Comparative weight) 1 2 3 Example 1 Example 2 Component a1 7.48 7.48 7.48 7.48 7.48 A a2 70.00 70.00 70.00 70.00 70.00 a3 19.44 19.44 19.44 19.44 19.44 c1 6.95 5.99 8.21 33.00 / c2 0.54 0.56 0.51 / 0.69 d 0.40 0.40 0.40 0.40 0.40 f 5.53 5.53 5.53 5.53 5.53 g / / / / 6.80 viscosity 1,000 1,000 900 750 1,100 (mPa .Math. s) Component a4 11 11 11 11 11 B b1 6.78 6.78 6.78 6.78 6.78 b2 83.40 83.40 83.40 83.40 83.40 e 0.1 0.1 0.1 0.1 0.1 h 0.4 0.4 0.4 0.4 0.4 viscosity 1,000 1,000 1,000 1,000 1,000 (mPa .Math. s) SiH/SiVi* (molar ratio) 4.52 4.52 4.52 4.52 4.52 SiH/OH (molar ratio) 4.53 4.53 4.56 4.51 4.50 OH from ingredient c2/ 3.72 4.48 2.98 / / OH from ingredient c1 (molar ratio) *Number of moles of SiVi is calculated based on the SiVi groups in ingredients a1-a4 and f.

TABLE-US-00002 TABLE 2 Compar- Compar- Exam- Exam- Exam- ative ative ple 1 ple 2 ple 3 Example 1 Example 2 Pot life 120 120 120 120 140 (s) Foam 0.55 0.55 0.55 0.70 0.65 density (g/cm.sup.3) Porosity uniform uniform uniform uniform inhomogeneous condition Cell size fine cell fine cell fine cell fine cell coarse cell