Handling additive for silicone elastomer bases

Abstract

A handling additive composition is disclosed. The composition is useful to improve handling of silicone elastomers prepared from polydiorganosiloxanes and silicone elastomers made therewith.

Claims

1. A modified silicone elastomer base composition comprising: I) at least one silicone elastomer base; and II) a handling additive composition comprising: at least one boric acid derivative selected from the group consisting of borinic acids, boronic acids, and mixtures thereof; a silicone polymer; and optionally, a powder.

2. The modified silicone elastomer base composition of claim 1, wherein the boric acid derivative is selected from the group consisting of phenylboronic acid, 4-fluorophenylboronic acid, 3,4-difluorophenylboronic acid, 3,4,5-trifluorophenylboronic acid, n-butylboronic acid, 2-thienylboronic acid, 1,4-phenylenediboronic acid, bis(pentafluorophenyl)borinic acid, diphenylborinic acid, dimesitylborinic acid, Bis(3,4-dimethylphenyl)borinic acid, borinic Acid, B,B-Bis(2,3,4,5,6-pentafluorophenyl), and mixtures thereof.

3. The modified silicone elastomer base composition of claim 1, wherein the silicone polymer is selected from the group consisting of polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, hydroxyfunctional siloxanes, alkoxyfunctional siloxanes, and mixtures thereof.

4. The modified silicone elastomer base composition of claim 1, wherein the powder is present in the handling additive composition and selected from the group consisting of polytetrafluoroethylene, fumed silica, carbon black, carbon nanotubes, multiwalled carbon nanotubes, carbon fibres, graphene, nano diamond, nano clay, graphite, polysaccharide nano compounds, nano cellulose, cellulose nano whiskers, layered silicates, boehmite, hydroxyapatite fillers, reinforcing fibres, nylon, polyethylene, polyamide, glass fibres, and mixtures thereof.

5. The modified silicone elastomer base composition of claim 1, the handling additive composition comprising: 5 to 50 wt. % of the boric acid derivative; 50 to 95 wt. % of the silicone polymer; and 0 to 30 wt. % of the powder.

6. A process for providing the modified silicone elastomer base composition in accordance with claim 1, the process comprising the steps of: (i) providing at least one silicone elastomer base; (ii) adding the handling additive composition to the silicone elastomer base; and (iii) mixing the components of step (ii).

7. The modified silicone elastomer base composition of claim 1, wherein the silicone elastomer base comprises at least one organopolysiloxane having at least 2 silicon-atom bonded alkenyl groups per molecule.

8. The modified silicone elastomer base composition of claim 1, wherein the handling additive composition is present in an amount of from 0.01 wt. % to 10 wt. % of the total weight of the modified silicone elastomer base composition.

9. A curable silicone elastomer stock composition comprising: the modified silicone elastomer base in accordance with claim 1; and a peroxide catalyst or a cure package.

10. The process of claim 6, wherein before step (ii), the process comprises the steps of: 1) providing the boric acid derivative, the silicone polymer, and optionally the powder; and 2) mixing the components to produce the handling additive composition.

11. The process of claim 6, further defined as a process for providing for a silicone elastomer stock composition, the process further comprising the step of: (iv) adding a catalyst or a cure package to the silicone elastomer base before, subsequent to or during step (ii).

12. An article or a composite part cured from the curable silicone elastomer stock composition of claim 9.

13. The article or composite part in accordance with claim 12, selected from the group consisting of thin-walled membranes, switch covers, spark-plug connectors, electrical insulators, single-wire seals, plug connector seals, connector seals and spark plug boots, electric and electronic parts, turbocharge hoses, and rolls in a copying machine.

Description

EXAMPLES

(1) All plasticity measurements are Williams Plasticity measurements in accordance with ASTM D-926-08 unless otherwise indicated. All measurements with regard to Williams plasticity were undertaken on uncatalysed silicone rubber base compositions or modified silicone rubber base compositions containing the handling additive.

(2) Rubber Bases

(3) Rubber base 1—low durometer, (30 Shore A) contains silicone gum, OH-terminated silicone fluid, silica.

(4) Rubber base 2—high durometer (70 Shore A), contains silicone gum, OH-terminated silicone fluid, silica in an increased amount over Rubber base 1.

(5) Rubber base 3: 70 Shore A silicone rubber base for bond strength testing of Turbo charge hose (TCH).

(6) Boric Acid Derivatives

(7) Phenylboronic acid CAS #98-80-6 4-Fluorophenylboronic acid CAS #1765-93-1 3,4-Difluorophenylboronic acid CAS #168267-41-2 3,4,5-Trifluorophenylboronic acid CAS #143418-49-9 n-Butylboronic acid CAS #4426-47-5 Tributyl borate CAS #688-74-4 2-Thienylboronic acid CAS #6165-68-0 1,4-Phenylenediboronic acid CAS #4612-26-4

(8) Unless otherwise indicated, the amounts of bases and handling additives are indicated in % weight and viscosity measurements were taken at 25° C., using Viscosity values given were made using ASTM D 1084-16 Method B (for cup/spindle) for viscosities below 100,000 mPa.Math.s. Viscosities above 100,000 mPa.Math.s viscosity are determined using ASTM D 4287-00(2014) (cone/plate) at a 10 S shear speed unless otherwise indicated.

(9) The handling additive compositions and a comparative handling additive composition were made by mixing the ingredients indicated in Table 1 below, in a kneader mixer. The boric acid derivative was a borinic acid or a boronic acid as identified in the list above.

(10) The handling additive composition may be combined with the rubber base using a two roll mill or kneader mixer.

(11) TABLE-US-00001 TABLE 1 Handling additive Comparative handling composition according additive composition to the invention Ingredient (% wt.) (% wt.) Silicone gum having a 23.80 Mw of approximately 500,000 (GPC) Silicone fluid of 30000 23.80 23.80 mPa .Math. s PTFE powder 23.80 23.80 Silicone fluid of 4.80 4.40 viscosity of 50 mPa .Math. s Boric acid 23.80 — Boric acid derivative — 48.00 Total dosage 100.00 100.00

(12) A reference example and comparative example 1 were prepared. The reference example was 100% of rubber base 1 and Comparative Example 1 comprised 0.2% by weight of the comparative handling additive composition depicted in Table 1 above. Comparative examples 1 and 2 were prepared as indicated in Table 2 below. The Williams Plasticity of the Reference and Comparative 1 base compositions was measured periodically as indicated over a 7 day period in accordance with ASTM D-926-08.

(13) TABLE-US-00002 TABLE 2 Reference Comparative Example 1 example 1 Rubber base 1 100% 99.8% Boric acid None (Blank 0.2% comparative sample) handling additive composition containing boric acid Plasticity (mm/100) Initial 156 169 1 day 157 221 3 days 162 240 7 days 170 244 Plasticity increase? Yes CAS# 10043-35-3

(14) It can be seen that compared to the Reference example, comparative example 1 showed a significant increase in Williams Plasticity due largely to the presence of the boric acid which we are seeking to replace as hereinbefore described. It was also noted that where plasticity results increased, tackiness decreased.

Examples 1 to 6: Boric Acid Derivatives in Rubber Base 1—Low Duro—Table 3

(15) Examples 1 to 6 compare six handling additive compositions (HA), each containing a different boric acid derivative. The handling additive compositions were incorporated into the silicone rubber base 1 in varying amounts, as outlined in Table 2. The selected boric acid derivative chosen for use in each of Examples 1 to 6 is also indicated in Table 2. Again the Williams Plasticity values were determined periodically over a 7 day period in accordance with ASTM D-926-08 as can be seen in Table 3 below.

(16) TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Rubber 99.5% 99.5% 99.5% 99.5% 99.5% 99.01% base 1 (wt. %) Amount of 0.5% 0.5% 0.5% 0.5% 0.5% 0.99% HA (wt. %) Boric acid Phenylboronic 4-Fluorophenylboronic 3,4-Difluorophenylboronic 3,4,5-Trifluorophenylboronic n-Butylboronic Tributyl derivative acid acid acid acid acid borate in HA Plasticity (mm/100) Initial 230 205 225 223 223 235 1 day 218 215 222 202 224 259 3 days 215 226 224 209 220 258 7 days 215 214 217 202 215 255 Plasticity Yes Yes Yes Yes Yes Yes increase vs Reference Example? CAS# 98-80-6 1765-93-1 168267-41-2 143418-49-9 4426-47-5 688-74-4

(17) Williams Plasticity is overall increased when compared to the Reference Example, corresponding to the neat Rubber base 1.

Comparative Examples 2 to 5: Rubber Base 1—Low Duro—Table 4

(18) Comparative examples 2 to 5 review alternative handling additives, which do not increase plasticity, such as pentaerythritol, FKM gum of 25 Mooney Units (MU) viscosity, FKM gum of 10 MU viscosity and PTFE.

(19) TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Comparative example 2 example 3 example 4 example 5 Rubber base 1 99.01% 99.01% 99.01% 99.01% Alternative 0.99% 0.99% 0.99% 0.99% Handling Pentaeryth- 2605 A-100 MP1000 Additive ritol (FKM gum, (FKM gum, (~10 um 25 MU 10 MU PTFE) viscosity) viscosity) Plasticity (mm/100) Initial 156 156 154 1 day 3 days 162 159 7 days 160 160 167 162 Plasticity Almost no Almost no Almost no Almost no increase vs Reference Example?

(20) It can be seen that none of these handling compositions have as good an effect as the examples in accordance with the above.

(21) Reference Example 2 is the Rubber base 2 without any handling additive. Comparative example 6 contains 0.1% of Boric acid. Plasticity is increased over the Comparative example 6.

(22) TABLE-US-00005 TABLE 5 Reference Example 2 Comparative example 6 Rubber base 2 100% 99.9% Boric acid (BA) Blank sample 0.1% Boric acid Plasticity (mm/100) Initial 375 391 1 day 386 743 3 days 396 855 7 days 422 865 Plasticity Yes increase? CAS# 10043-35-3

Examples 7 to 11: Boric Acid Derivatives in Rubber Base 2—High Duro—Table 6

(23) Examples 7 to 11 review 5 different boric acid derivatives used at various amounts in Rubber base 2, as outlined in Table 6.

(24) TABLE-US-00006 TABLE 6 Example 7 Example 8 Example 9 Example 10 Example 11 Rubber 99.8% 99.8% 99.8% 99.8% 99.8% base 2 Boric 0.2% 0.2% 3,4,5- 0.2% n- 0.2% 2- 0.2% 1,4- acid(BA) Phenylboronic Trifluorophenylboronic Butylboronic Thienylboronic Phenylenediboronic alternatives acid acid acid acid acid Plasticity (mm/100) Initial 582 448 612 628 518 1 day 800 750 643 682 748 3 days 812 820 708 708 825 7 days 855 830 765 727 829 Plasticity Yes Yes Yes Yes Yes increase? CAS# 98-80-6 143418-49-9 4426-47-5 6165-68-0 4612-26-4

(25) Plasticity is overall increased when compared to Reference example 2, corresponding to the neat Rubber base 2. Plasticity increase is higher than for Comparative example 8 based on boric acid.

Comparative Examples 7 to 11: Rubber Base 2—High Duro—Table 7

(26) Comparative examples 9 to 11 review alternative handling additives, which do not increase plasticity, such as FKM gum of 25 MU viscosity, FKM gum of 175 MU viscosity, PTFE.

(27) TABLE-US-00007 TABLE 7 Comparative Comparative Comparative example 7 example 8 example 9 Rubber base 2 99.01% 99.01% 99.01% Alternative 0.99% 2605 0.99% 2602-3 0.99% MP 1000 Handling (FKM gum, 25 (FKM gum, 175 (~10 um PTFE) Additive MU viscosity) MU viscosity) Plasticity (mm/100) Initial 375 375 370 1 day 419 387 378 3 days 480 409 415 7 days 545 426 415 Plasticity A little increase Almost no Almost no increase?

Example 12 and Comparative Example 10: Bonding Strength

(28) Example 12 is uses silicone rubber base 3 containing 0.4% phenylboronic acid (from a handling additive composition comprising 48% wt phenylboronic acid among other ingredients), set to bond with a commercial fluorosilicone rubber base. Bonding strength was measured at 0.67 N/mm (HCR/FSR). Test method: Sample prepared in Example 12 and Comparative example 10 were subjected to a 180° peel test using an Inston tensiometer at a crosshead speed of 50 mm/min.

(29) Comparative example 10 uses silicone rubber base 3 containing 0.2% Boric acid (from a comparative handling additive composition comprising 23.8% wt Boric acid among other ingredients), set to bond with a commercial fluorosilicone rubber base. Bonding strength was measured using the same test method as described above at 0.71 N/mm (HCR/FSR).

(30) This test indicates bonding strength is equivalent for the handling additive composition according to the invention, as compared to handling additive composition containing boric acid.