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US-12617915-B2 - Foamable silicone composition and the use thereof

US12617915B2US 12617915 B2US12617915 B2US 12617915B2US-12617915-B2

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.

Inventors

  • Yuanyuan Xu

Assignees

  • WACKER CHEMIE AG

Dates

Publication Date
20260505
Application Date
20210203

Claims (12)

  1. 1 . 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·s at (23±2°) C. before curing measured by Brookfield viscometer using No. 2 spindle at a speed of 10 rpm.
  2. 2 . The composition of claim 1 , 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.
  3. 3 . The composition of claim 1 , wherein component (c) is used in an amount of less than or equal to 15 wt % based on the total weight of the composition.
  4. 4 . The composition of claim 1 , wherein the ratio of the number of moles of Si—H groups provided by component (b) to that of silicon-bonded alkenyl groups provided by component (a) is from 2:1 to 15:1.
  5. 5 . The composition of claim 1 , wherein the ratio of the number of moles of Si—H groups provided by component (b) to that of hydroxyl groups provided by component (c) is from 1:2 to 15:1.
  6. 6 . The composition of claim 1 , wherein component (c1) has a dynamic viscosity of from 10 to 1,000 mPa·s at 25° C.
  7. 7 . The composition of claim 1 , 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·s at 25° C. based on the total weight of component (a).
  8. 8 . The composition of claim 1 , wherein component (b1) has a hydrogen content of from 1.2 wt % to 1.7 wt %.
  9. 9 . The composition of claim 1 , 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·s at 25° C. based on the total weight of component (b2).
  10. 10 . The composition of claim 1 , wherein the composition comprises: (a) 20˜80 wt % of at least one organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms per molecule, (b1) 1˜8 wt % of an organopolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule, (b2) 20˜70 wt % of an organopolysiloxane containing two hydrogen atoms bonded to silicon atoms at both ends of the chain per molecule, (c1) 1˜15 wt % of an organopolysiloxane containing at least one hydroxyl group bonded to silicon atom per molecule, (c2) 0.01˜1 wt % of water, and (d) hydrosilylation catalyst.
  11. 11 . A foam cured from the composition of claim 1 .
  12. 12 . A potting material comprising the composition of claim 1 .

Description

FIELD OF INVENTION The present disclosure relates to a foamable silicone composition and the use thereof. BACKGROUND OF INVENTION Among the incidents of new energy vehicles, fires or explosions caused by lithium-ion batteries have become a major safety concern. One way to reduce or even eliminate such incidents is to use liquid silicone rubbers as potting materials for batteries to improve heat conduction or dissipation so as to protect from fire or explosion. However, liquid silicone rubbers usually have a relatively large specific gravity. Using them as potting materials will increase the weight of battery pack, reducing the specific energy per unit volume, and ultimately affecting the energy density. Liquid foamable silicone rubbers have advantages in reducing the weight of battery pack. However, very few literatures report their application in battery potting. U.S. Pat. No. 4,760,098B describes a viscous liquid composition comprising A-part and B-part wherein the A part is consisting essentially of vinyl terminated siloxane, reactive diluent hydroxyl terminated siloxane, water and catalyst, and B part is consisting essentially of hydrogen siloxane and filler. The viscosity of A-part is from about 30,000 to about 65,000 cps at 32-34° C. and the addition of the B-part makes no significant difference to the viscosity of the foamable mixture. Such viscous liquid composition is not suitable for battery potting. CN106589954A discloses a low-viscosity, flame-retardant, and room temperature-curable silicone composition, comprising α, ω-dihydroxy polydimethylsiloxane with a viscosity of 300 to 5,000 mPa·s as a primary polymer, hydrogen-containing silicone oil and hydroxyl-terminated silicone oil with a viscosity of 60 to 150 mPa·s as a porogenic agent, which cures to a foam with a density of 0.58 to 0.68 g/cm3, and can be used for potting protection of new energy battery modules. A planetary mixer is needed in order to obtain such a foam with desirable characteristics, nevertheless, there still have difficulties in obtaining a foam with uniform porosity and cost for producing such foam is high. U.S. Pat. No. 4,189,545A discloses a composition of another silicone rubber foam comprising vinylpolydimethylsiloxane with a viscosity of 380 cps as a primary polymer, hydrogen-containing silicone oil and water as a porogenic agent in Example 4. Such composition has a short pot life of 45 s and the water is not compatible with siloxanes. Potting materials for batteries are generally required to have a low viscosity due to the requirement of fluidity, and a relatively long pot life facilitating the operation of potting. But preparation of a silicone foam with a low density and uniform porosity from a foamable composition having a relatively low viscosity and long pot life is and has always been a challenge in the art. A low viscosity usually means that bubbles formed from the reaction of Si—H and hydroxyl groups are easy to escape from the foamable composition. A relatively long pot life usually means the reaction between Si—H groups and alkenyl groups starts too slowly to form a network structure to capture the bubbles generated by foaming reaction. As a result, a foam with a higher density is obtained. SUMMARY OF INVENTION In view of the existing problems, the present disclosure provides a foamable silicone composition by using a given ratio of water and silanol as the porogenic agent, well solving the contradiction between the relatively low viscosity and long pot life of the foamable composition and the relatively low density of the derived foam. The first aspect of the present disclosure provides 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,(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. Component (a) The organopolysiloxane (a) as a base polymer is well known. Suitable alkenyl groups bonded to silicon atoms contain from 2 to 6 carbon atoms, for example vinyl, allyl, propenyl, butenyl, hexenyl, preferably vinyl, allyl and propenyl, more preferably vinyl. Organic groups bonded to remaining silicon atoms of organopolysiloxane (a) are each independently selected from monovalent organic groups free of aliphatic unsaturation having from 1 to 20 preferably 1 to 10 carbon atoms, for example, alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, aryl or alkaryl such as phenyl, tolyl, xylyl, mesityl, ethylphenyl, benzyl, naphthyl, a