Single-component moisture curable silane sealant plasticized with hydrolysable polyether monosilanes

Abstract

Moisture-curable resin compositions include a mixture of one or more polysilylated of ethers and one or more polyether monosilanes. The polyether monosilanes have one hydrolysable silane group per molecule, and the hydrolysable silane group has at least two hydrolysable substituents. The polyether monosilane is an effective plasticizer and viscosity reducer. Despite the presence of the polyether monosilane, the resins compositions cure to form cured sealants having useful tensile and elongation properties.

Claims

1. A moisture-curable resin composition comprising a) at least one liquid silane-terminated polyether having a number average molecular weight of at least 8000 and at least two hydrolysable silane groups per molecule; and b) 50 to 90 mole percent, based on the total number of moles of components a) and b), of at least one liquid polyether monosilane compound having a polyether segment having a number average molecular weight of 500 to 2500 daltons and exactly one di- or trifunctional hydrolysable silane group per molecule; and c) at least one silanol catalyst, wherein the blend of components a) and b) contains 5 to 35 mole-% of one or more component a) materials that have at least three hydrolysable silane groups per molecule, the average functionality of components a) and b) is 2.24 to 4 hydrolysable substituents per molecule.

2. The moisture-curable resin composition of claim 1, wherein the blend of components a) and b) has an average of at least 1.12 hydrolysable silane groups per molecule.

3. The moisture-curable resin composition of claim 1, wherein the blend of components a) and b) has an average of 1.35 to 2 hydrolysable silane groups per molecule.

4. The moisture-curable resin composition of claim 1, which contains 20 to 50 percent of component b), based on the combined weights of components a) and b).

5. The moisture-curable resin composition of claim 1 wherein the hydrolysable silane group of the liquid polyether monosilane is a difunctional hydrolysable silane group.

6. The moisture-curable resin composition of claim 5, wherein the hydrolysable silane group of the liquid polyether monosilane is a dialkoxysilane group.

7. The moisture-curable resin composition of claim 1 wherein the liquid polyether monosilane has at least one hydroxyl group.

8. The moisture-curable resin composition of claim 1, wherein the liquid polyether monosilane compound formed in a reaction of a polyether having one terminal carbon-carbon double bond with a silane hydride having two or three hydrolysable substituents.

9. The moisture-curable resin composition of claim 1, wherein the silane-terminated polyether is a urethane group-containing polysilylated polyether that is free of urea groups.

10. The moisture-curable resin composition of claim 9, wherein the urethane-group-containing polysilylated polyether is made in a process wherein a polyether monol having terminal ethylenic unsaturation is hydrosilylated by reaction of the ethylenic unsaturation with a silyl hydride that has one or more hydrolysable substituents, and the resulting hydrosilylated polyether monol is coupled in one step by reaction with a polyisocyanate or in two steps by capping the alcohol group with a polyisocyanate and then coupling the resulting isocyanate-capped monosilylated polyether with a polyol.

11. The moisture-curable resin composition of claim 1 wherein component a) includes one or more compounds represented by the structure (I): ##STR00004## where A is either H or has the structure (II): ##STR00005## k is a number from 0 to 4, m and n are independently numbers from 0 to 3, the values of x and y are numbers such that the compound has a molecular weight of 4000 to 20,000, R.sub.1, R.sub.2, R.sub.10 and R.sub.11 are independently straight chain or branched alkyl groups having 1 to 4 carbon atoms, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.8 and R.sub.9 are independently hydrogen or straight chain or branched alkyl groups having 1 to 4 carbon atoms, and R.sub.7 is aliphatic, cycloaliphatic, bis-benzylic and/or aromatic and has 2 to 20 carbon atoms.

12. The moisture-curable resin composition of claim 1, which further comprises at least one mineral filler and at least one adhesion promoter.

13. The moisture-curable resin composition of claim 1, which contains no more than 1 weight percent of a fugitive plasticizer.

14. A moisture-curable sealant composition comprising the moisture-curable resin composition of claim 1 and at least one silanol catalyst.

Description

EXAMPLES 1-3 AND COMPARATIVE SAMPLE A

(1) Comparative Sample A is prepared by mixing 0.5 parts of dibutyltindi(acetylacetone) into 100 parts of Polysilylated Polyether B using a high-speed mixer.

(2) Polysilylated Polyether B and the Polyether Monosilane are mixed at an 80/20 weight ratio. A portion of the mixture is taken for viscosity measurement. Example 1 is prepared by adding 0.5 weight-percent dibutyltindi(acetoacetone) to another portion of the mixture. Example 2 is prepared by adding 1.0 weight-percent dibutyltindi(acetoacetone) to still another portion of the mixture.

(3) Polysilylated Polyether B and the Polyether Monosilane are mixed at an 60/40 weight ratio. A portion of the mixture is taken for viscosity measurement. Example 3 is prepared by adding 0.5 weight-percent dibutyltindi(acetoacetone) to another portion of the mixture.

(4) The room temperature viscosity of each of Examples 1-3 and Comparative Sample A is measured by a rheometer with cone and plate geometry in oscillation mode at a constant shear rate of 1 sec.sup.1.

(5) In each case, curing time is measured by casting a 2.95 mil (75 m) film on a glass substrate from about 1 mL of the material. The film is cured at room temperature under ambient humidity for one week. Tack-free time of the film is measured according to ASTM D-5895 using a BYK drying time recorder. 0.05+/0.005 g of catalyst is mixed with 9.95 g of the resin components on a speed-mixer. A 75 mil (1.9 mm) film is then formed on a glass substrate using 1 mL of the sample. Tack-free time of the thin film is recorded with BYK drying time recorder set at 0-12 hrs.

(6) Mechanical properties are measured according to ASTM D-1708 on thin films of the cured material. Films are prepared by casting a 25 mil (635 m) film onto a polypropylene substrate and curing at room temperature and ambient humidity for one week. Dogbone samples for analysis are cut from the cured films.

(7) Results of the testing of Examples 1-3 and Comparative Sample A are as indicated in Table 1.

(8) TABLE-US-00001 TABLE 1 Comp. Designation Sample A* Ex. 1 Ex. 2 Ex. 3 Polyether Monosilane, wt-% 0 20 20 40 Polyether Monosilane, mole-% 0 76.2 76.2 86.8 Polysilylated Polyether B, mole-% 100 23.8 23.8 13.2 Average # of Hydrolysable Silyl 3 1.6 1.6 1.3 Groups per molecule.sup.1 Average Resin Functionality.sup.2 6 3.2 3.2 2.6 Amount of Catalyst, % 0.5% 0.5% 1% 0.5% Viscosity, Pa .Math. s 10.4 5.9 5.9 2.2 Curing Time 2.75 hr 4.8 hr 2.5 hr >12 hours Tensile Strength, psi (kPa) 143.2 (987) 67.4 (465) 81.3 (561) 40.8 (281) Elongation at Break, % 206 212 234 486 Tensile stress at 100% 78.9 (544) 37.0 (255) 42.0 (290) 8.8 (61) elongation, psi (kPa) *Not an example of the invention. .sup.1Average number of hydrolysable silane groups per molecule in the mixture of the Polyether Monosilane and Polysilylated Polyether. .sup.2Average number of hydrolysable substituents per molecule in the mixture of Polyether Monosilane and Polysilylated Polyether.

(9) The Polyether Monosilane is an effective plasticizer, as evidenced by the reduction in viscosity of Examples 1-3 compared to Comparative Sample A, and the increased elongation and reduced tensile strength of the cured adhesive. The presence of the Polyether Monosilane tends to slow the rate of cure; however, this is easily compensated for by increasing the catalyst level slightly, as seen by comparing the curing times of Example 2 with Example 1 and Comparative Sample A.

EXAMPLES 4-7 AND COMPARATIVE SAMPLES B AND C

(10) Examples 4-7 and Comparative Samples B and C are made from the following general formulation:

(11) TABLE-US-00002 Ingredient Parts by Weight Polysilylated Polyether A 20 Calcium Carbonate 55 Plasticizer Type and amount varies Titanium Dioxide 2.4 UV absorber 0.4 Vinyl silane moisture scavenger 0.8 Amino silane adhesion promoter 0.7 Dibutyltin diacetylacetonate Varies

(12) The plasticizer type and amount, and the amount of catalyst, are as indicated in Table 2.

(13) In each case, all ingredients except catalyst are mixed, and viscosity is measured. Then, the indicated amount of catalyst is added and curing time and mechanical properties measured as described before.

(14) TABLE-US-00003 TABLE 2 Comp. Comp. Samp. Samp. Designation Ex. 4 Ex. 5 B* C* Ex. 6 Ex. 7 Plasticizer Type PEM.sup.1 PEM DINP.sup.2 DINP PEM PEM Plasticizer Amount, 20.45 20.45 20.45 20.45 10.22 10.22 wt.-% Amount of Catalyst, 0.25 0.75 0.20 0.60 0.20 0.60 wt-% Polyether Monosilane, 93 93 0 0 86.5 86.5 mole-% Polysilylated Polyether 7 7 100 100 13.5 13.5 A, mole-% Average # of 1.14 1.14 3 3 1.27 1.27 Hydrolysable Silyl Groups per molecule.sup.3 Approx. Resin 2.28 2.28 6 6 2.54 2.54 Functionality.sup.4 Viscosity, cps 92 ND 37 ND 213 ND Curing Time >11 hr 8-10 hr 7.5 hr 2.5 hr 10 hr 4 hr Tensile Strength, psi 52.8 (368) 40.7 (284) 133 (929) 153 (1069) 126 (880) 130 (908) (kPa) Elongation at Break, % 727 670 301 358 440 466 Tensile stress at 100% 11.7 (82) 8.3 (58) 94.7 (661) 89.6 (626) 93.1 (650) 82.8 (578) elongation, psi (kPa) *Not an example of the invention. .sup.1PEMPolyether Monosilane. .sup.2DINP-diisononylphthalate. .sup.3Average number of hydrolysable silane groups per molecule in the mixture of the Polyether Monosilane and Polysilylated Polyether. .sup.4Average number of hydrolysable substituents per molecule in the mixture of Polyether Monosilane and Polysilylated Polyether.

(15) As shown by the data in Table 2, the Polyether Monosilane is a highly effective plasticizer. When present at the 20% level, its use leads to a large reduction in tensile strength and a large increase in elongation, compared to when an equal amount of diisononyl phthalate is used (as in Comparative Samples B and C). The reduction in tensile strength and increase in elongation are evidence of plasticization. Examples 6 and 7, when compared with Comparative Samples B and C, demonstrate that 10% of the polyether monosilane plasticizes very similarly to 20% of diisononylphthalate. As with Examples 1-3, a small increase in catalyst level is needed to obtain curing times equivalent to those of the Comparative Samples.

EXAMPLE 8 AND COMPARATIVE SAMPLE D

(16) A mixture of polysilylated polyethers and a polyether silane is prepared as follows:

(17) An 800 molecular weight polyether monol having a terminal allylic group is silylated with HSiCH.sub.3(OCH.sub.3).sub.2 in the presence of a platinum catalyst. The resulting monosilylated polyether monol is capped by reaction with toluene diisocyanate. The isocyanate-capped material thus obtained is reacted with a mixture of a monol, a diol and a triol formed by alkoxylating a mixture of 55.7 mole-% of a monol initiator, 36.6 mole-% of a diol initiator and 7.7 mole-% of a triol initiator to a hydroxyl equivalent weight of 1533.

(18) The resulting mixture contains about 37 weight percent (55.7 mole-%) of polyether monosilanes and 63 weight percent of polysilylated polyethers. The mixture contains 7.7 mole-% of polysilylated polyethers that contain 3 hydrolysable silane groups. The average number of hydrolysable silane groups per molecule is about 1.5.

(19) The viscosity of the mixture is measured as described in Example 1. The mixture is separated into portions. Into one portion (Example 8A), 0.5 weight-% of dibutyl tin diacetylacetonate catalyst is mixed in. 1 weight-% of the catalyst is mixed into the other portion to make Example 8B. Each sample is cured and curing time and tensile properties are measured as described in Example 1. Results are as indicated in Table 3. For comparison, typical values achieved by curing a mixture of 0.5 weight-% of the catalyst in Polysilylated Polyether C are indicated.

(20) TABLE-US-00004 TABLE 3 Comp. Designation Ex. 8A Ex. 8B Sample D Polyether monosilane, mole-% 55.7 55.7 0 Polyether monosilane, wt-% 37 37 0 Trisilylated polyethers, wt-% 8 8 0 Trisilylated polyethers, mole-% 7.7 7.7 0 Average # of Hydrolysable Silyl Groups per 1.52 1.52 2 molecule.sup.1 Average resin functionality.sup.2 3.04 3.04 4 Viscosity (Pa .Math. s) 3.0 3.0 15-25 Curing Time, hr 6.5 3.5 3-5 Tensile Strength, psi (kPa) 53 (370) 56 (391) 50-85 (350-600) Elongation, % 276 286 275-450 Tens. stress @100% elongation, psi (kPa) 22.5 (157) 21.0 (147) 20-30 (140-210) .sup.1Average number of hydrolysable silane groups per molecule in the mixture of the Polyether Monosilane and Polysilylated Polyether. .sup.2Average number of hydrolysable substituents per molecule in the mixture of Polyether Monosilane and Polysilylated Polyether.

(21) As the data in Table 3 shows, the resin mixture of the invention has a large viscosity advantage over Polysilylated Polyether C and cures to give very comparable properties.

(22) Two other portions of the resin mixture are combined with a particulate calcium carbonate. In each case, 1% by weight of dibutyltin diacetylacetonate is added based on the combined weight of resin mixture and calcium carbonate, to form formulated sealant Example 8C and 8D. Portions of each of Examples 8C and 8D are cured as in previous examples, and tensile properties are measured as before. Results are as indicated in Table 4.

(23) TABLE-US-00005 TABLE 4 Designation Ex. 8C Ex. 8D % Filler 55 70 Tensile str., psi (kPa) 166 (1160) 164 (1146) Elongation, % 517 428 Tens. Stress % 100% 66 (461) 93 (650) elongation, psi (kPa)

EXAMPLE 9

(24) A mixture of polysilylated polyethers and a polyether monosilane is prepared as follows:

(25) An 800 molecular weight polyether monol having a terminal allylic group is silylated with HSiCH.sub.3(OCH.sub.3).sub.2 in the presence of a platinum catalyst. The resulting monosilylated polyether monol is capped by reaction with toluene diisocyanate. The isocyanate-capped material thus obtained is reacted with a mixture of a monol, a diol and a triol formed by alkoxylating a mixture of 72.3 mole-% of a monol initiator, 13.2 mole-% of a diol initiator and 14.4 mole-% of a triol initiator to a hydroxyl equivalent weight of 1533.

(26) The resulting mixture contains about 34 weight percent (72.3 mole-%) of polyether monosilanes and 66 weight percent of polysilylated polyethers. The mixture contains about 13.5 mole-% of polysilylated polyethers that contain 3 hydrolysable silane groups. The average number of hydrolysable silane groups per molecule is about 1.3 and the average functionality is about 2.6.