Preparation and use of 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-DIYL) dipropanenitrile

Abstract

A process for preparing 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl) dipropanenitrile is provided. The 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl) dipropanenitrile can be used as an adhesion promoter in a curable polyorganosiloxane composition.

Description

PREPARATION AND USE OF 3,3' 1 ,1 ,3,3MUTRAMETHOXYDISILOXANE- 1 ,3- DIYL)DIPROPANENITRILECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 722,111 filed on November 19, 2024, under 35 U.S.C. §119 (e). U.S. Provisional Patent Application Serial No. 63 / 722,111 is hereby incorporated by reference.FIELD

[0002] A process for preparing a concentrate comprising 3,3'-(l,L3,3-tetramethoxydisiloxane- l,3-diyl)dipropanenitrile is provided. The concentrate is useful as an adhesion promoter in a curable polyorganosiloxane composition.INTRODUCTION

[0003] Cyanoethyltrimethoxysilane (CETMS) is useful as an adhesion promoter in curable polyorganosiloxane compositions, such as room temperature vulcanizable (RTV) polyorganosiloxane sealant compositions. CETMS can be made via hydrosilylation reaction of acrylonitrile with trichlorosilane followed by methoxylation. CETMS can also be made by the hydrosilylation reaction of trimethoxysilane with acrylonitrile. WO2023 / 102314 discloses a process for making CETMS via transesterification of cyanoethyltriethoxy silane (CETES), and provides, “It is desirable to drive the reaction to a high conversion of the ethoxy groups in the CETES to methoxy groups, high purity of CETMS and low amount of Dimer formation.” The transesterification reaction may be performed under conditions that minimize or eliminate the presence of moisture in order to prevent moisture contamination from initiating a side reaction that would take away from CETMS yield.SUMMARY

[0004] A process for preparing a product comprising 3,3'-(l,l,3,3-tetramethoxydisiloxane-L3- diyl)dipropanenitrile is provided. The process comprises dimerization reaction of cyanoethyltrimethoxysilane to form a crude reaction product, and concentrating the crude reaction product to form the concentrate comprising 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyl)dipropanenitrile. The concentrate comprising 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyl)dipropanenitrile is useful as an adhesion promoter in curable polyorganosiloxanecompositions, such as room temperature vulcanizable (RTV) polyorganosiloxane sealant compositions.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a schematic diagram of a wiped film evaporator used in the examples. DETAILED DESCRIPTION

[0006] A dimer of cyanoethyltrimethoxysilane, namely 3,3'-(l,l,3,3-tetramethoxydisiloxane- l,3-diyl)dipropanenitrile, has formula(referred to as“CETMS dimer” or “dimer” herein). The inventors surprisingly found that a concentrate comprising > 80 % of CETMS dimer provides better adhesion promotion than cyanoethyltrimethoxy silane, as shown in the EXAMPLES, below. Therefore, this invention relates to a process for preparing the concentrate comprising > 80 % of CETMS dimer, and using said concentrate as an adhesion promoter.

[0007] The process for preparing the concentrate comprises: 1) mixing under conditions to effect dimerization reaction, starting materials comprising a) cyanoethyltrimethoxysilane with an acid number of 0.01 to 0.06; b) water in an amount of 2% to 8%, based on combined weights of starting materials a), b), c) and d); c) a base catalyst in an amount sufficient to catalyze dimerization of the cyanoethyltrimethoxysilane; and optionally d) a solvent; thereby forming a crude reaction product comprising 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyl)dipropanenitrile, wherein the crude reaction product has acid number of 0 to 0.02; 2) subjecting the crude reaction product to wiped film evaporation at a pressure of 0 mmHg to 4 mmHg, and a temperature of 170 °C to 180 °C, thereby separating the crude reaction productinto a high boiling fraction and a low boiling fraction, wherein the low boiling fraction comprises > 50 weight % to < 80 weight % of 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyl)dipropanenitrile; and 3) subjecting the low boiling fraction to wiped film evaporation at a pressure of 10 mmHg to 15 mmHg, and a temperature of 135 °C to 145 °C, thereby concentrating the low boiling fraction to form the concentrate, wherein the concentrate comprises > 80 weight % to 100 weight % of 3.3'-(1.1.3.3-tetramethoxydisiloxane-l,3- diyljdipropanenitrile.

[0008] Starting material a) in the process is cyanoethyltrimethoxysilane (CETMS), which has CAS No. 2526-62-7. The cyanoethyltrimethoxysilane may be prepared by any convenient means such as reacting acrylonitrile and trichlorosilane (HSiCh) with tri-n-butylamine or platinum as a catalyst to form cyanoethyltrichlorosilane. The cyanoethyltrichlorosilane is then methoxylated by combining the cyanoethyltrichlorosilane and methanol, optionally with solvents and / or other ingredients, to form CETMS. Such processes are exemplified in US Patents US3185719, US4483973. and US5374757; Chinese Patent Application Publication CN111100162A; and German Patent Publication DE10041597. Alternatively, the CETMS may be prepared by any other means such as transesterification of cyanoethyltriethoxysilane as described in PCT Patent Application Publication WO2023102314. CETMS is also commercially available from various sources including Alfa Chemistry of Holbrook, New York, USA and Momentive Performance Materials of New York, USA.

[0009] The CETMS used in step 1) of the process described herein has an acid number of 0.001 to 0.1, alternatively 0.01 to 0.06, as determined by the titration method described below. Alternatively, acid number of the CETMS used in step 1) may be at least 0.01, alternatively at least 0.02, and alternatively at least 0.03; while at the same time the acid number may be up to 0.06, alternatively up to 0.05, and alternatively up to 0.04. Without wishing to be bound by theory, it is thought that the test method for acid number detects hydrolyzable chloride as well as free chloride, and when the CETMS is prepared using a chlorosilane starting material, the acidity in the CETMS may be derived from hydrolyzable chloride, e.g., residual silyl chloride). Alternatively, when the CETMS feedstock does not contain sufficient residual chloride, acid such as HC1 may be added to adjust the acid number of starting material a) > 0.001, alternatively 0.01 to 0.06, and alternatively 0.02 to 0.04 before combining starting material a) with starting material b).

[0010] Starting material b) is water. The water is not generally limited, and may be utilized neat (i.e., absent any carrier vehicles and / or solvents), and / or pure (i.e., free from, or substantially free from, minerals and / or other impurities). For example, the water may be processed or unprocessed prior to use in step 1). Examples of processes that may be used for purifying the water include distilling, filtering, deionizing, and combinations of two or more thereof, such that the water may be deionized, distilled, and / or filtered. Alternatively, the water may be treated by reverse osmosis. Alternatively, the water may be unprocessed (e.g. may be tap water, i.e., provided by a municipal water system or well water, used without further purification). Alternatively, the water may be purified use in step 1). Alternatively, the water may be utilized as a mixture (e.g. solution or suspension) comprising a carrier vehicle and / or solvent, such as any of those listed herein as starting material d). The amount of water is sufficient to form dimer from the CETMS, however, not so much as to cause phase separation and / or gelation during step 1). The amount of water may be 2% to 8% based on combined weights of starting materials a) and b) used in step 1). Alternatively, the amount of water may be at least 2%, alternatively at least 2.5%, alternatively at least 3%, and alternatively at least 4%; while at the same time the amount of water may be up to 8%, alternatively up to 7.5%, alternatively up to 6%, and alternatively up to 5%, on the same basis.

[0011] Starting material c) used in step 1) is a base catalyst. The base catalyst may be sodium methoxide, which has CAS No. 124-41-4. Sodium methoxide is commercially available from various sources including Sigma-Aldrich, Inc. of St. Louis, Missouri, USA and Noah Chemicals of San Antonio, Texas, USA. Alternatively, a different base, such as sodium hydroxide (CAS No. 1310-73-2), potassium hydroxide (CAS No. 1310-58-3), magnesium hydroxide (CAS No. 1309-42-8), potassium methylate (CAS No. 865-33-8), or ammonium hydroxide (CAS No. 1336-21-6) may be used. The amount of the base catalyst depends on various factors including the species of base selected, however, the amount may be 0.005% to 0.05%, based on combined weights of starting materials a), b), c) and d) used in step 1). Alternatively, the amount of base may be at least 0.005%, alternatively at least 0.006%, alternatively at least 0.007%, alternatively at least 0.008%, and alternatively at least 0.009%; while at the same time, the amount of base may be up to 0.05%, alternatively up to 0.04%, alternatively up to 0.03%, alternatively up to 0.02%, and alternatively up to 0.01%, on the same basis.

[0012] Starting material d) is an optional solvent. The solvent may be used to facilitate mixing of starting materials a), b), and c) and / or the solvent may be used for delivery of a starting material such as c) the base catalyst (e.g.. sodium methoxide may be dissolved in the solvent). The solvent may be methanol. Whether the solvent is used and its amount depend on various factors including the selection of base catalyst and solubility thereof in starting materials a) and b). However, when methanol is used to deliver sodium methoxide, the amount of methanol may be 0.02% to 0.2%, based on combined weights of starting materials a), b), c) and d) used in step 1).

[0013] Step 1) of the process described herein may be performed in conventional equipment, such as a jacketed vessel with mixing means, such as an agitator, baffles, or both. Step 1) may be performed for 2 hours to 24 hours at a temperature of 20 °C to 180 °C. Without wishing to be bound by theory, it is thought that CETMS is thermally sensitive, and heating at > 180 °C for extended times may cause CETMS to undergo gelation. Therefore, step 1) may be performed for a time and at a temperature sufficient for dimer to form with no or minimal gelation. For example, step 1) may be performed at a temperature of at least 20 °C, alternatively at least 25 °C, alternatively at least 30 °C, alternatively at least 40 °C, alternatively at least 50 °C, and alternatively at least 60 °C; while at the same time, step 1) may be performed at a temperature up to 180 °C, alternatively up to 100 °C, alternatively up to 90 °C, alternatively up to 80 °C, alternatively up to 70 °C, and alternatively up to 60 °C. Batch time in step 1) may be 2 hours to 24 hours, and the exact time depends on the temperature selected. For example, mixing in step 1) may be performed for up to 24 hours at 20 °C to 25 °C, and alternatively mixing may be performed for less than 24 hours at higher temperature. For example, mixing may be performed for an amount of time that is cut in half for each ten degree increase in temperature, e.g., 6 hours to 8 hours at temperatures of 40 °C to 60 °C.

[0014] The crude reaction product produced in step 1) contains > 20 % to < 50 % of CETMS dimer. The balance of the crude reaction product comprises unreacted CETMS, base catalyst, and solvent, and may further comprise side products and impurities. The crude reaction product is neutral to slightly acidic, i.e., the crude reaction product has an acid number of 0 to 0.02 and a base number of 0, where acid number and base number are measured by the titration method described below. The starting materials and their amounts used in step 1) are selected to produce the neutral to slightly acidic crude reaction product.

[0015] Steps 2) and 3) of the process for preparing the concentrate comprising > 80 % of CETMS dimer are performed in a wiped film evaporator. One wiped film evaporator may be used for both steps 2) and 3), or steps 2) and 3) may be performed in different wiped film evaporators. Wiped film evaporators are known in the art and are commercially available from various vendors including Pope Scientific, Inc. of Saukville, Wisconsin USA; GMM Pfaudler of Mumbai, India; and LCI Corporation of Charlotte, North Carolina, USA.

[0016] Step 2) of the process comprises subjecting the crude reaction product to wiped film evaporation at a pressure of > 0 mmHg to 4 mmHg, and a temperature of 170 °C to 180 °C, thereby separating the crude reaction product into a high boiling fraction and a low boiling fraction, wherein the low boiling fraction comprises > 50 weight % to < 80 weight % of 3,3'- (l,l,3,3-tetramethoxydisiloxane-l,3-diyl)dipropanenitrile. Without wishing to be bound by theory, it is thought that if the temperature in step 2) is too low, then the low boiling fraction will contain < 50 weight % of the dimer, however, if the temperature in step 2) is > 180 °C, the crude reaction product may further polymerize, thereby reducing yield of the dimer and / or causing gelation of the product. Step 2) separates the crude reaction product into a low boiling fraction comprising > 50 weight % to < 80 weight % of 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyljdipropanenitrile and a high boiling fraction. The high boiling fraction may be discarded as waste. The low boiling fraction is then further separated in step 3).

[0017] Step 3) of the process comprises subjecting the low boiling fraction to wiped film evaporation at a pressure of 10 mmHg to 15 mmHg, and a temperature of 135 °C to 145 °C. Without wishing to be bound by theory, it is thought that operating step 3) at lower temperature than step 2) minimizes potential for further polymerization and / or gelation of the concentrate. The concentrate prepared in step 3) comprises > 80 weight % to 100 weight % of 3, 3' -(1, 1,3,3- tetramethoxydisiloxane-l,3-diyl)dipropanenitrile. When the concentrate contains < 100 % of the dimer, the balance to 100% includes unreacted CETMS and optionally side products and impurities, as described above. A lighter fraction is removed in step 3) and comprises unreacted CETMS, which may be recycled in step 1) of the process.

[0018] A schematic diagram of WFE operation is shown in Figure 1. Crude reaction product prepared in step 1) of the process described herein was fed to the WFE (100) with a pump (not shown) through a feed line (101). Volatile materials (110) were collected overhead with a condenser (102). The low boiling fraction produced in step 2) of the process described herein(1 12) was collected as condensate from the internal condenser (103), which was cooled with a chiller (not shown) to 5 °C using 200 fluid from DSC circulating as cooling agent (109). The high boiling fraction (oligomer stream) was flowing down along the internal wall (104) of the WFE (100) and collected in a separate container (not shown). Teflon wiper blades (105) were used to form a film of the crude reaction product on the internal wall (104). Heating elements (106) were used to adjust the temperature.

[0019] When the same WFE is used in step 3), the low boiling fraction (112) may then be fed into the WFE (100) through the feed line (101), and the heating elements (106) were used to adjust the temperature. The resulting concentrate (114), which comprised > 80 weight % to 100 weight % of 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3-diyl)dipropanenitrile, flowed down along the internal wall (104) and was then collected as the product of this process.

[0020] The WFE (100) provides the benefit of high surface area, which allows the separation to occur more efficiently (e.g., as compared to batch distillation or stripping equipment) while avoiding gel formations. Residence time in the WFE is short, thereby minimizing thermal history to which the CETMS dimer is exposed.

[0021] The concentrate prepared in step 3) comprises > 80 weight % to 100 weight % of dimer (and may include CETMS as the balance to 100 % when < 100% of dimer is present). The concentrate may be used as an adhesion promoter in a curable polyorganosiloxane composition, such as a polyorganosiloxane sealant composition or other room temperature vulcanizable (RTV) organopolysiloxane composition (e.g., instead of CETMS). Curable polyorganosiloxane compositions may comprise, for example, a base polymer having reactive groups such as an alkoxy-functional polyorganosiloxane or an acyloxy-functional polyorganosiloxane. In addition to the base polymer, the curable polyorganosiloxane composition may further comprise one or more of a crosslinker, a catalyst, and a filler, which may optionally be surface treated.

[0022] RTV compositions are known in the art, such as those disclosed in US Patents US4483973 to Lucas, et al.; US5962559 to Lucas, et al.; US7550548 to Hatanaka, et al.; US7674871 to Koch, et al.; US Patent Application Publication US20070173597 to Williams, et al.; and PCT Patent Application Publication W02007024792. Alternatively, the CETMS dimer may be added to a commercially available RTV sealant, such as XIAMETER™ SLT-5200 from DSC.EXAMPLES

[0023] The following examples are provided to illustrate the invention to one skilled in the art and are not to be construed so as to limit the scope of the invention set forth in the claims.Starting materials used in these examples are summarized below in Table 1.Table 1 - Starting MaterialsExample 1 - 5% Water, No Catalyst (comparative)

[0024] 950 grams CETMS with acid number of 0.002 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 50 grams of deionized water was added to the flask. The reaction continued at room temperature and atmospheric pressure for 24 hours with mixing. The dimer concentration analyzed by GC was 12.3%. Example 1 shows that when the base catalyst is not included, insufficient amount of dimer forms after 24 hours; the reaction to prepare dimer is much slower than desired.Example 2 - 1% water (Comparative)

[0025] 1000 grams CETMS with acid number of 0.002 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 10 grams of deionized water was added to the flask. 0.303grams of 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure for 24 hours with mixing. The dimer concentration analyzed by GC was 6.7%. Example 2 shows that when the amount of water is too low (1% or less based on combined weights of CETMS, water, base, and solvent), insufficient dimer forms. Example 3 - 2,5% water

[0026] 975 grams CETMS with acid number of 0.04 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 25 grams of deionized water was added to the flask. 0.315 grams of 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature andatmospheric pressure for 24 hours with mixing. The dimer concentration analyzed by GC was 24.3%. Example 3 shows that a crude reaction product with > 20 % dimer can be prepared according to step 1) of the process described herein.Example 4 - 5% water

[0027] 950 grams CETMS with acid number of 0.04 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 50 grams of deionized water was added to the flask. 0.315 grams of 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure for 24 hours with mixing. The dimer concentration analyzed by GC was 21.3%. Example 4 shows that a crude reaction product with > 20 % dimer can be prepared according to step 1 of the process described herein.Example 5 - 5% water, neutral CETMS

[0028] 950 grams CETMS with acid number of 0.002 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 50 grams of deionized water was added to the flask. 0.315 grams of 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure for 24 hours with mixing. The sample contained 22% dimer. Example 5 shows that a crude reaction product with > 20 % dimer can be prepared according to step 1) of the process described herein.Example 6 - 7.5% water

[0029] 925 grams CETMS with acid number of 0.04 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 75 grams of deionized water was added to the flask. 0.315 grams of 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure for 24 hours with mixing. The dimer concentration analyzed by GC was 23.7%. Example 6 shows that a crude reaction product with > 20 % dimer can be prepared according to step 1) of the process described herein.Example 7 - 10% water (Comparative)

[0030] 270 grams CETMS with acid number of 0.04 was charged to a 1-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 30 grams of deionized water was added to the flask. 1.125 grams 25% sodium methoxidemethanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure for 4 hours with mixing. Phase separation was observed. The top phase was mainly methanol and 3-4% dimer by GC. The bottom phase was mainly oligomer with 8-9% dimer. Example 7 shows that when too much base and water are used, the CETMS and its dimer may further polymerize to form oligomer.Example 8 - 15% water (Comparative)

[0031] 85 grams CETMS with acid number of 0.04 was charged to a 1 -liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 15 grams of deionized water was added to the flask. 0.375 grams 25% sodium methoxide methanol solution was added to the mixture. The reaction continued at room temperature and atmospheric pressure with mixing. In less than 2 hours, the mixture turned into gel. No analysis was done with the gel. Example 8 shows that when too much base and water are used, the CETMS may gel such that useful dimer is not present in the reaction product.Example 9 - 5% water

[0032] 950 grams CETMS with acid number of 0.04 was charged to a 2-liter three-neck round bottom flask which was blanketed with nitrogen. The flask was equipped with a magnetic stir bar. 50 grams of deionized water was added to the flask. 0.315 grams of 25% sodium methoxide methanol solution was added to the mixture. The mixture was then heated to 60 °C under atmospheric pressure for up to 2 hours with mixing. The dimer concentration analyzed by GC was 24.3%. Example 9 shows temperature effect on synthesis. Batch time may be reduced by heating (as compared to example 4 at room temperature) and a product with > 20 % dimer can be prepared faster than at RT according to step 1) of the process described herein.Example 10 - Wipe film evaporator (WFE) purification

[0033] A WFE was used to obtain concentrated CETMS dimer. The WFE supplied by PopeScientific Inc. had a 2 inch diameter and was made of glass. A schematic diagram of the WFE operation is shown in Figure 1. Crude reaction product including CETMS dimer was fed to the WFE with a peristaltic pump. Some ultra-low boiling materials were collected overhead with a dry ice condenser. The low boiling fraction (product stream) was collected as condensate from the internal condenser, which was cooled with a chiller to 5 °C using XI AMETER™ PMX-200 fluid from TDCC as cooling agent.

[0034] 433 grams of the crude reaction product from Example 4 (having an acid number of0.02) was fed to the WFE (shown in Figure 1 ) after temperature and vacuum reached the setpoints shown in Table 2 below. The high boiling fraction was wiped down along the glass wall of the WFE with grooved PTFE blades. After separation, the overhead stream collected was 121.2 grams, the low boiling fraction weighed 142.6 grams, and weighed high boiling fraction weighed 158.2 grams. The low boiling fraction from the first pass through the WFE contained 55% CETMS dimer.Table 2. First pass WFE conditions

[0035] The low boiling fraction from the first pass was then fed into the WFE for a second pass to separate CETMS monomer and dimer. 140 grams of the low boiling fraction from the 1stpass was fed to the WFE after the temperature and vacuum reached the setpoints shown in Table 3. After the separation, the overhead stream was 1.8 grams, low boiling fraction weighed 64.9 grams, and high boiling fraction weighed 74.8 grams. The high boiling fraction from the 2ndpass was the concentrate (product) that contained 89.5% CETMS dimer.Table 3. Second pass WFE conditionsExample 11 - Wiped film evaporator purification (comparative)

[0036] Crude reaction product including CETMS dimer from Example 4 (having an acid number of 0.02) was fed to the WFE after temperature and vacuum reached the setpoints shown in Table 4 below. After separation, the low boiling fractions from each condition contained the CETMS dimer levels shown in Table 4.Table 4. WFE Conditions and Resulting CETMS Dimer content after 1stPass

[0037] The CETMS dimer content from the 1stWFE pass under these conditions was low, and a reasonable yield was not obtained. This example demonstrates that operating the wiped film evaporator at a temperature that is too low and a pressure that is too high in the first pass (corresponding to step 2 of the process herein) results in poor yield.Example 12 - Wipe film evaporator purification with basic crude reaction product (comparative)

[0038] The crude reaction product including CETMS dimer prepared in Example 5 (having a base number of 0.15 to 0.19) was processed through the WFE with the same operation conditions described in Example 10. The high boiling fraction gelled in less than 30 minutes after feeding to the WFE. This example shows that crude reaction product that is basic (not neutral to acidic) resulted in gelation in process step 2) under the conditions tested.Example 13 - Wipe film evaporator purification using comparative crude reaction product

[0039] The crude reaction product including CETMS dimer prepared in Example 5 (having a base number of 0.15 to 0.19) was neutralized with 0.1N HC1 in Methanol. The acid number after neutralization was 0.004. The erode was processed through the WFE with the same operation conditions described in Example 10. There was no gelling observed during the process. The low boiling fraction from the 1stpass through the WFE contained 26.8 wt% CETMS dimer. The yield was 17.3% relative to the mass of the crude CETMS dimer fed to the WFE. Due to the low dimer concentration, the low boiling fraction was not further processed. This example shows that when the CETMS starting material used in step 1) had acid number that was too low. acidifying the CETMS starting material with HC1 allowed the process to proceed without gelation, however, yield was lower than the process in which the CETMS starting material as supplied had the acid number described herein.Example 14 - Adhesion Testing

[0040] A sample of the CETMS Dimer prepared in Example 10 and a sample of the CETMS described in Table 1 were each added to a curable polyorganosiloxane sealant composition, which was cured on a fiberglass substrate. The coated substrates were aged for 7 days at room temperature (7d RT) and then immersed in water for 7 days at room temperature (7d RT / 7d water). The results are shown below in Table 5.Table 5. Adhesion test results for sealant prepared using CETMS Dimer and standard CETMS

[0041] In Table 5 above, the indication AF (-) describes a poor adhesion coming from adhesive failure (samples separating easily from the substrates with no peel strength), AF (+) describes a moderate adhesion coming from adhesive failure (sample separating from the substrates with some peel strength). CF (+) describes good adhesion coming from mixed mode failure [mixed with cohesive failure (tear in the elastomer) and adhesive failure]. CF (+) is the most desirable result, and AF (-) is the least desirable result.

[0042] The results in Table 5 showed that adhesion improved when the dimer content of the adhesion promoter increased from 2% to 89.5%. When CETMS (with CETMS dimer content of only 2%), the corresponding cured organopolysiloxane sealant showed poorest adhesion, easily being peeled from fiber glass without force. When the concentrate of this invention, containing CETMS dimer content of 89.5%, the adhesion of the sealant sample improved to a mixed mode failure. After immersion in water for 7 days at room temperature (7d RT / 7d water), the sample made with the concentrate (89.5% dimer) showed better adhesion strength than the control sample, demonstrating that the CETMS dimer unexpectedly provides better adhesion promotion than CETMS.

[0043] The examples above show that a method for improving adhesion of a cured polyorganosiloxane may comprise: adding the concentrate comprising > 80 weight % of CETMS dimer to a curable polyorganosiloxane composition; and curing the composition to form the cured polyorganosiloxane.Test Methods

[0044] Acid numbers and base numbers herein were measured by the following titration method: Take certain amount (30-50 grams) of Bromocresol purple (BCP), the titration color indicator. Add 5-6 grams of test sample to the color indicator, record the weight of the sample. Depending on the acidity of the sample, the sample is titrated with either 0.1 N KOH in methanol (Metrohm Dosimat 876 model) or 0.1 N HC1 in isopropanol (Metrohm Dosimat 775 model). Titration was stopped when the color of the mixture returned to its original color before adding the test sample. The volume of the titrant was recorded in ml. The acid number or base number iscalculated as follows:Acid number = Titration volume in ml / 1000* 0.1 *56.1*1000 / the grams of sample added toBCPBase number = Titration volume in ml / 1000* 0.1 *35.5*1000 / the grams of sample added toBCP

[0045] The GC Method used herein was as follows:Response Factor calculation is as follow:Where:RRFanaiyte.i = Relative response factor for analyte, iAreaanaiyte, i.cs = Peak area of analyte i in the calibration standardAreais iD.es = Peak area of internal standard in the calibration standard manaiyte,i,cs = amount (ug) of analyte i in the calibration standard misTD.cs = amount (ug) of internal standard solution in the calibration standardSample concentration (wt%) of analyte i in the original sample is calculated as follows: 100Where:Canalyte,i = Concentration (wt%) of analyte i in the sampleAreaanaiyte, i.ss = Peak area of analyte i obtained from the analysis of the sample solutionAreaisTD.es = Peak area of internal standard obtained from the analysis of the sample solutionRRFanaiyte.i = Relative response factor for analyte, i misTD.ss = Weight (g) of the internal standard solution added to the sample solutionWss = Weight (g) of the sample test portion added to the sample solutionINDUSTRIAL APPLICABILITY

[0046] The examples above show that the present method provides the benefit of providing CETMS dimer without (or with minimal) degradation that can result in gelation and / or safety concerns that can occur with prolonged heating of CETMS. Furthermore, improved adhesion can be achieved using the CETMS dimer prepared using the method described herein.DEFINITIONS AND USAGE OF TERMS

[0047] The amounts of all starting materials in a composition total 100% by weight. The Summary and the Abstract are hereby incorporated by reference. The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unless otherwise indicated by the context of specification. The singular includes the plural unless otherwise indicated. Each embodiment or alternative presented herein may be combined with any other embodiment or alternative. The term “comprising” and derivatives thereof, such as “comprise” and “comprises” are used herein in their broadest sense to mean and encompass the notions of “including,” “include,” “consist(ing) essentially of,” and “consist(ing) of. The use of “for example,” “e.g. ” “such as,” and “including” to list illustrative examples does not limit to only the listed examples. Thus, “for example” or “such as” means “for example, but not limited to” or “such as, but not limited to” and encompasses other similar or equivalent examples.

[0048] It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, different, special, and / or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0049] Abbreviations used in this application are defined below in Table 5. Table 5 - Abbreviations

Claims

Claims:

1. A process for preparing a concentrate comprising 3,3'-(l,l,3,3-tetramethoxydisiloxane- l,3-diyl)dipropanenitrile, wherein the process comprises:1) mixing under conditions to effect dimerization reaction, starting materials comprising a) cyanoethyltrimethoxysilane with an acid number > 0.001 to 0.06 measured by titration, b) water in an amount of 2 weight % to 8 weight %, based on combined weights starting materials a) and b), c) a base catalyst in an amount sufficient to catalyze dimerization of the cyanoethyltrimethoxysilane, and optionally d) a solvent, thereby forming a crude reaction product comprising 3,3'-(l, 1,3,3- tetramethoxydisiloxane-l,3-diyl)dipropanenitrile, wherein the crude reaction product has acid number of 0 to 0.02;2) subjecting the crude reaction product to wiped film evaporation at a pressure of 0 mmHg to 4 mmHg, and a temperature of 170 °C to 180 °C, thereby separating the crude reaction product into a low boiling fraction comprising > 50 weight % to < 80 weight % of 3, 3' -(1,1, 3,3- tetramethoxydisiloxane-l,3-diyl)dipropanenitrile and a high boiling fraction; and3) subjecting the low boiling fraction to wiped film evaporation at a pressure of 10 mmHg to 15 mmHg, and a temperature of 135 °C to 145 °C, thereby concentrating the low boiling fraction to form the concentrate, which comprises > 80 weight % to 100 weight % of the 3,3’-(l,l,3,3-tetramethoxydisiloxane-l,3-diyl)dipropanenitrile.

2. The process of claim 1, wherein one wiped film evaporator is used in both step 2) and step 3).

3. The process of claim 1 or claim 2, wherein mixing in step 1) is performed for 2 hours to 24 hours at 20 °C to < 180 °C.

4. The process of claim 3. wherein mixing in step 1) is performed for 2 to 12 hours at 40 °C to 80 °C.

5. The process of any one of claims 1 to 4, wherein the base is sodium methoxide.

6. The process of claim 5, wherein d) the solvent is present, and the base is dissolved in d) the solvent.

7. A concentrate comprising > 80 weight % of 3,3'-(l,l,3,3-tetramethoxydisiloxane-l,3- diyl)dipropanenitrile prepared by the process of any one of the preceding claims.

8. Use of the concentrate of claim 7 in as an adhesion promoter in a curable polyorganosiloxane composition.

9. A method for improving adhesion of a cured polyorganosiloxane wherein the method comprises: adding the concentrate of claim 7 to a curable polyorganosiloxane composition; and curing the composition to form the cured polyorganosiloxane.

10. A curable polyorganosiloxane composition comprising:(A) a base polymer comprising a polyorganosiloxane having reactive groups,(B) the concentrate of claim 7, and optionally (C) a crosslinker, optionally (D) a catalyst, and optionally (E) a filler.

11. The composition of claim 10, wherein the base polymer comprises an alkoxyfunctional polyorganosiloxane.

12. The composition of claim 10, wherein the base polymer comprises an acyloxyfunctional polyorganosiloxane.

13. An adhesion promoter comprising > 80 weight % to 100 weight % of 3,3'-( 1 , 1 ,3,3- tetramethoxydisiloxane- 1 ,3-diyl)dipropanenitrile.

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