CURABLE SILICONE COMPOSITION WITH A GOOD FLAME RESISTANCE

Abstract

The invention relates to a curable silicone composition comprising (A) a polyorganosiloxane polymer, (B) a cross-linking organosilicon compound having at least 2 silicon-bonded reactive groups, (C) a catalyst capable of promoting the reaction between component (A) and component (B); and (D) from 0.001 to 20%, preferably from 0.01 to 16%, more preferably from 0.05 to 12% of a bentonite, based on the total weight of the other components in the composition; wherein the bentonite is treated with a treatment agent containing at least a quaternary ammonium salt. Furthermore, it is also related to a method of improving the flame resistance of a curable silicone composition as well as a product obtained therefrom.

Claims

1. A curable silicone composition comprising: (A) a polyorganosiloxane polymer containing the siloxane unit represented by the formula (I-1)
R.sup.1.sub.aZ.sub.bSiO.sub.[4-(a+b)]/2  (I-1) in which is independently selected from the group consisting of hydroxyl, alkoxy, alkenyl, and alkynyl groups, Z may be the same or different and represent a monovalent non-reactive hydrocarbon radical having from 1 to 30, optionally from 1 to 12 carbon atoms, optionally selected from alkyl and aryl groups, a is 1, 2 or 3, b is 0, 1 or 2 and the sum of a+b is 1, 2 or 3; (B) a cross-linking organosilicon compound having at least 2 silicon-bonded reactive groups; (C) a catalyst capable of promoting the reaction between component (A) and component (B); and (D) from 0.001 to 20%, optionally from 0.01 to 16%, optionally from 0.05 to 12% of a bentonite, based on the total weight of other components in the composition; wherein bentonite is treated with a treatment agent comprising at least a quaternary ammonium salt.

2. The curable silicone composition according to claim 1, wherein the bentonite is treated with quaternary ammonium salt in an amount of more than 15%, optionally more than 30%, calculated by the ammonium ions and based on the total weight of the treated bentonite.

3. The curable silicone composition according to claim 1, wherein the polyorganosiloxane polymer comprising at least one siloxane unit of formula (I-2): $\begin{array}{cc}{Z}_c^1{\mathrm{SiO}}_{\frac{4-c}{2}}.& \text{(I-2)}\end{array}$ in which: c=0, 1, 2 or 3, Z.sup.1 may be identical or different and represent a monovalent non-reactive hydrocarbon radical having from 1 to 30, optionally from 1 to 12 carbon atoms, optionally selected from alkyl and aryl groups,

4. The curable silicone composition according to claim 1, wherein Z or Z.sup.1 is selected from C.sub.1-C.sub.8 alkyl group and/or C.sub.6-C.sub.20 aryl groups.

5. The curable silicone composition according to claim 1, wherein the polyorganosiloxane polymer comprises alkenyl polysiloxane resin A′ that comprises at least two different siloxane units selected from the group consisting of siloxane units M of formula R.sup.3SiO.sub.1/2, siloxane units D of formula R.sup.2SiO.sub.2/2, siloxane units T of formula RSiO.sub.3/2 and siloxane units Q of formula SiO.sub.4/2, wherein R represents a monovalent hydrocarbon group having from 1 to 20 carbon atoms, and with the proviso that at least one of these siloxane units is the siloxane unit T or Q and at least one of the siloxane units M, D and T comprises an alkenyl group.

6. The curable silicone composition according to claim 1, wherein that the cross-linking organosilicon compound is a monomer, a homopolymer, a copolymer or mixtures thereof which comprises at least one unit of formula R.sup.4.sub.a′R.sup.5.sub.b′SiO.sub.4-a′-b′/2 wherein R.sup.4 is selected from the group consisting of alkyl, aryl, and halogenated alkyl groups having from 1 to about 18 carbon atoms, R.sup.5 is a reactive group selected from the group consisting of hydrogen, hydroxy, and alkoxy, a′ has a value of 0 or 1, b′ has a value of from 2 to 3, and the sum of a′+b′ is 2 or 3.

7. The curable silicone composition according to claim 1, wherein the cross-linking organosilicon compound comprises a hydrogen-containing polysiloxane containing at least two, optionally three or more Si—H groups bonded to the same or different silicon atom(s) per molecule.

8. The curable silicone composition according to claim 7, wherein the hydrogen-containing polysiloxane comprises: (i) at least two siloxyl units and optionally at least three siloxyl units of formula: $\begin{array}{cc}{H}_d{Z}_e^3{\mathrm{SiO}}_{\frac{4-\left(d+e\right)}{2}}& \text{(II-1)}\end{array}$ in which: d=1 or 2 or 3, e=0, 1 or 2 and d+e=1, 2 or 3, Z.sup.3 may be identical or different and represent a monovalent hydrocarbon radical having from 1 to 30, optionally from 1 to 12 carbon atoms, optionally selected from C.sub.1-C.sub.8 alkyl and C.sub.6-C.sub.20 aryl groups, and (ii) optionally at least one siloxane unit of formula: $\begin{array}{cc}{Z}_f^3{\mathrm{SiO}}_{\frac{4-f}{2}}& \text{(II-2)}\end{array}$ in which: f=0, 1, 2 or 3, Z.sup.3 may be identical or different.

9. The curable silicone composition according to claim 1, the quaternary ammonium salt comprises a carbon chain of from 6 to 30, optionally from 10 to 18 carbon atoms.

10. The curable silicone composition according to claim 1, wherein said quaternary ammonium salt includes an alkyl quaternary ammonium salt that comprises an alkyl carbon chain from C.sub.6-C.sub.30, optionally preferable C.sub.10-C.sub.18.

11. The curable silicone composition according to claim 1, wherein the treatment agent further comprises at least one selected from functional organosilane compound containing vinyl, amino, alkyl, methacryloxy and epoxy group; organic titanate coupling agent; octadecanoic acid; and other compounds comprising one or more functional groups.

12. A curable silicone composition according to claim 1, wherein the composition further comprises an adhesive promoter.

13. The curable silicone composition according to claim 12, wherein the adhesive promoter is an organic silicone compound having at least 1 alkenyl group and at least one epoxy and/or trialkoxysilyl group bond to the same or different silicon atom.

14. The curable silicone composition according to claim 1, wherein the total amount of components (A) and (B) is more than 50%, optionally more than 65%, optionally more than 80% and optionally more than 90% by weight, based on a polymer matrix of the composition.

15. The curable silicone composition according to claim 1, wherein the composition comprises silica and/or calcium carbonate optionally in an amount of 1-25% by weight, optionally 5-20% by weight, based on the total weight of the composition.

16. A product comprising a bentonite for improving the flame resistance of a curable silicone composition according to claim 1, wherein the bentonite has been treated with a treatment agent comprising a quaternary ammonium salt and is added in an amount of from 0.001 to 20%, optionally from 0.01 to 16%, optionally from 0.05 to 12%, based on the total weight of other components in the composition.

17. A method of improving flame resistance of a curable silicone composition as defined in claim 1, comprising adding into the composition bentonite, which is treated with a treatment agent comprising a quaternary ammonium salt, in an amount of from 0.001 to 20%, optionally from 0.01 to 16%, optionally from 0.05 to 12%, based on the total weight of other components in the composition

18. A product obtained by curing the curable silicone composition as defined in claim 1 optionally comprising an airbag.

Description

EXAMPLES

[0093] First Part on Coated Fabric Flame Test

[0094] Testing Sample Preparation:

[0095] Knife coating the silicone liquid coating composition on the fabrics and then curing at 160° C. for 2 min

[0096] Fabric: Polyamide 66, 470 dtex, 51*51 (cm)

[0097] Measure of the coat weight: weighing the blank before coating (W1), weighing the coated fabric after curing (W2) and measuring the coated area S. Calculating the weight according to following equation:

CW=(W2−W1)/S,

[0098] unit: gram per square meter

[0099] Test Equipment:

[0100] Testing standard: FMVSS-302

[0101] Test condition: without wire, uncoated side towards fire;

[0102] Raw Materials:

TABLE-US-00001 CAS No. Description Component A1 mixture of MD.sup.ViQ resin and vinyl terminal-polydimethylsiloxane oil with a ratio of about 1:3.35 Component B1 methyl and hydrogen terminated polymethylhydrogensiloxane with SiH content of 0.69 mol/100 g Component C1 Platinum(0)-1,3-divinyl-1,1,3,3-tetra- methyldisiloxane (Pt content: 10 wt %) Garamite 1958 Bentonite treated with 20 wt. % of alkyl quaternary ammonium salt CP-250 Bentonite treated with 45 wt. % of alkyl quaternary ammonium salt CP-27 Bentonite treated with 36 wt. % of alkyl quaternary ammonium salt Precipitated 471-34-1 Calcium Carbonate Non treated 1302-78-9 bentonite Wollastonite Untreated wollastonite, 10 μm Aluminium Al(OH).sub.3 without treatment, 10 μm hydroxide Ferric oxide Fe.sub.2O.sub.3 Component A2; mixture of fumed silica and vinyl terminal-polydimethylsiloxane oil with a ratio of about 1:3.98 Component B2 Methyl terminated polymethyl hydrogensiloxane with 0.415 mol/100 g SiH content Component B3 Hydrogen terminated polymethyl siloxane with SiH content of 0.19 mol/100 g Component A3 mixture of precipitated silica and hydroxygen-terminal-polydimethyl- siloxane oil with a ratio of about 1:4.00 Component B4 68412-37-3 Hydrolyzed tetraethylorthosilicate Component C2 Dibutyltin dilaurate Quatz 14808-60-7 non-treated

Example 1 (Comparative Example 1)

[0103] 75.53 part Component A1 with 14.655 part precipitated calcium carbonate, 5.45 part component B1 and 0.02 part 1-ethynyl-1-cyclohexanol was loaded and mixed in 100 g speed mixer cups under 2000 rpm for 30 sec. Thereafter the promoter 0.75 part Vinyltrimethoxysilane and 1.45 part (3-Glycidyloxypropyl)trimethoxysilane was added into speed mixer and mixed under 2000 rpm for 30 sec, followed by adding 2.1 part Titanium tetrabutanolate and 0.03 part Component C1 and further mixing under 2000 rpm for 30 sec. The prepared mixture of example 1 was tested with regard to the flame resistance and used as a premix for examples 2-6.

Examples 2-8

[0104] Samples of Examples 2-8 were prepared by adding respective fillers i.e. Garamite 1958, CP-250, CP-27, Wollastonite, aluminum hydroxide and ferric oxide in respective amounts as specified in table 1 into the premix according to Example 1 and then mixing in speed mixer under 2000 rpm for 30 sec. The compositions and test results are shown in table 1.

[0105] Comparison Formula (Comp.)

[0106] 75.53 part Component A1 with 14.655 part Non-treated bentonite, 5.45 part component B1 and 0.02 part 1-ethynyl-1-cyclohexanol was loaded and mixed in 100 g speed mixer cups under 2000 rpm for 30 sec. Thereafter the promoter 0.75 part Vinyltrimethoxysilane and 1.45 part (3-Glycidyloxypropyl)trimethoxysilane was added into speed mixer and mixed under 2000 rpm for 30 sec, followed by adding 2.1 part Titanium tetrabutanolate and 0.03 part Component C1 and further mixing under 2000 rpm for 30 sec.

TABLE-US-00002 TABLE 1 Example 1 2 3 4 5 6 7 8 Comp. Premix (g) 100 100 100 100 100 100 100 100 Garamite 1958 (g) 0 2.04 3.09 CP-250 (g) 3 CP-27 (g) 3 Wollastonite (g) 40 Al(OH).sub.3 (g) 40 40 Fe.sub.2O.sub.3 (g) 4.5 Coat weight (gsm) 10 10 10 15 15 17 10 10 10 Average Burn 94.6 60.2 34.2 48.3 71.2 50 31 23 167 rate(mm/min)

[0107] Test Results:

[0108] Example 4-6 can't achieve a low coat weight 10 gsm under same coating condition. Above trials showed that average burn rate less than 40 mm/min can be achieved with only 3% of bentonite, and the low coat weight of about 10 gsm can be achieved by knife coating. As for other fillers, coat weight fails to arrive at a level of less than 15 gsm and even with much higher dosage, it is still hard to achieve average burn rate less than 40 mm/min.

[0109] Testing Sample Preparation:

[0110] Knife coating the silicone liquid coating composition on the fabrics and then curing at 160° C. for 2 min

[0111] Fabric: Polyamide 66, 470 dtex, 46*46 (cm)

[0112] Measure of the coat weight: weighing the blank before coating (W1), weighing the coated fabric after curing (W2) and measuring the coated area S. Calculating the weight according to following equation:

CW=(W2−W1)/S,

unit: gram per square meter

[0113] Test Equipment:

[0114] Testing standard: FMVSS-302

[0115] Test condition: without wire, uncoated side towards fire;

TABLE-US-00003 TABLE 2 Example 1 9 10 12 Premix (g) 100 100 100 100 Garamite 1958 (g) 0 0.25 10 0.25 Al(OH).sub.3 (g) 40 Coat weight (gsm) 10 10 10 12 Average Burn 131 79 88 86 rate(mm/min) Minimum burn 86 58 41 54 rate(mm/min)

[0116] Test Results:

[0117] Examples 9, 10, 12 were also prepared based on the premix as described above with adding various fillers as listed in table 2. They all showed better flame resistance performance on fabrics compared with example 1, and 0.25% dosage of treated Bentonite can improve the performance 40%.

[0118] Second Part on Cured Silicone Elastomer Flame Test

[0119] Testing Sample Preparation:

[0120] Degassing for 2 to 10 min, pouring mixed liquid silicone into the 2 mm thickness Teflon treated metal mold and then curing in the oven at 150° C. for 30 min. Cutting the cured slab into 2 cm width and 15 cm length pieces and placing them under 23±2° C., 50±5% RH for 48 hours.

[0121] Test condition: Each specimen is supported such that its lower end is 10 mm above Bunsen burner tube. Then the specimen is suspended. A blue 20 mm high flame is applied to the center of the lower edge of the specimen for 10 seconds and then removed. As for each formula, five specimens are tested and the individual extinguishing time for each specimen is recorded. t1 is reported as an average of five extinguishing times.

Example 13 (Comparative Example 2)

[0122] 95.27 part component A2, 3.12 part component B2, 1.45 part component B3 and 0.155 part Methylvinylcyclosiloxanes was loaded and mixed in 100 g speed mixer cups under 2000 rpm for 30 sec, followed by adding 0.0182 part component C.sub.1 and further mixing under 2000 rpm for 30 sec. The prepared mixture of Example 13 was tested with regard to the flame resistance and used as a premix for Examples 14-15.

Examples 14-15

[0123] Samples of Examples 14-15 were prepared by adding Garamite 1958 in various amounts as specified in table 2 into the premix according to Example 13 and then mixing in speed mixer under 2000 rpm for 30 sec. The compositions and test results were shown in table 3.

TABLE-US-00004 TABLE 3 Example 13 14 15 Premix (g) 100 100 100 Garamite 1958 (g) 0 0.25 3 SUM (g) 100 100.25 103 t1 (s) 121 51 30

[0124] Test Results:

[0125] Above trials showed that with only 3 parts of bentonite an average t1 less than 50 sec can be achieved.

[0126] Third Part on Cured Silicone Elastomer Flame Test

[0127] Testing Sample Preparation:

[0128] Degassing for 2 to 10 min, pouring mixed liquid silicone into the 2 mm thickness Teflon treated metal mold at room temperature and then curing for 24 hours. Then cutting the cured slab into 2 cm width and 15 cm length pieces and placing them under 23±2° C., 50±5% RH for 48 hours. Test condition: Each specimen is supported such that its lower end is 10 mm above Bunsen burner tube. The specimen is suspended. Then a blue 20 mm high flame is applied to the center of the lower edge of the specimen for 10 seconds and removed. Record the burn time, the burn distance.

Example 16 (Comparative Example 3)

[0129] 58.37 part component A3 with 24.991 part component B4, 12.65 part untreated quartz filler and 0.285 part hydroxygen terminated polydimethylsiloxane oil with 45 mpa.Math.s viscosity was loaded and mixed in 100 g speed mixer cup under 2000 rpm for 30 sec, followed by adding 3.58 part component C.sub.2. The prepared mixture of Example 16 was tested with regard to the flame resistance and used as a premix for Example 17.

Example 17

[0130] Sample of Example 17 was prepared by adding 100 part premix of Example 16 with 3 part Garamite 1958 in 100 g speed mixer cups and then mixing in speed mixer under 2000 rpm for 30 sec. The composition and test results were shown in table 3.

TABLE-US-00005 TABLE 4 Example 16 17 Premix (g) 100 100 Garamite 1958 (g) 0 3 Burn time (s) 180 360 Burn distance (mm) 15 7

[0131] Test Results:

[0132] Only 3 parts of treated bentonite can half the burn distance.