Polycondensation production of polysiloxanes using co-existing acid / base catalysts

Abstract

The present disclosure provides a process for preparing a polysiloxane, the process being a two-part polycondensation of an alkoxysilane and / or an alkoxysiloxane, the process comprising the steps of: (a) hydrolyzing the alkoxysilane and / or alkoxysiloxane to a hydroxy-functional silane and / or a hydroxy-functional siloxane; and (b) condensing the hydroxyl functional silane and / or hydroxyl functional siloxane to form a polysiloxane polycondensation product; wherein the process is characterized by having both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst present simultaneously during both the hydrolysis step and the condensation step.

Description

Technical Field

[0001] The present invention relates to a method for preparing polysiloxane by a polycondensation reaction involving a hydrolysis reaction and a condensation reaction in the presence of a gel-type heterogeneous acid-base catalyst and a base catalyst.

[0002] introduction

[0003] One route to prepare polysiloxanes is by a two-step polycondensation reaction of alkoxysilanes and / or alkoxysiloxanes. The first step requires hydrolysis of the alkoxysilanes and / or alkoxysiloxanes to form hydroxy-functional silanes and / or siloxanes. The second step requires polycondensation of the hydroxy-functional silanes and / or siloxanes. Acid catalysts and base catalysts can be used to accelerate the reaction rate in the two steps of the polycondensation reaction. The reaction process generally requires the use of an acid catalyst for the hydrolysis step and a base catalyst for the polycondensation step.

[0004] The catalyst can be a "homogeneous" catalyst, which means that the catalyst forms a homogeneous solution with the reaction solution. Alternatively, the catalyst can be a "heterogeneous" catalyst, which means that they are insoluble in the reaction solution and remain in a phase separated from the reactants in the reaction solution. Homogeneous catalysts are often desirable because they are easier to achieve close contact with the reactants in the reaction mixture than heterogeneous catalysts and therefore tend to achieve faster reaction rates. However, heterogeneous catalysts have the desirable property of being easier to separate from the reaction solution after the reaction is completed than homogeneous catalysts. Removal of homogeneous catalysts often requires neutralization to form undesirable salts. Separation of heterogeneous catalysts can be accomplished by, for example, decantation or filtration.

[0005] Acid catalysts and base catalysts are not used simultaneously because they tend to react with each other, thereby destroying their catalytic functionality (neutralization). Thus, a two-step polycondensation reaction may involve multiple steps, including running a hydrolysis reaction with an acid catalyst; neutralizing the acid catalyst to remove the acid catalyst from the hydrolysis reaction mixture; adding a base catalyst for the condensation reaction; and then neutralizing the base catalyst and removing the base catalyst from the polycondensation reaction product.

[0006] It is desirable to identify a way to prepare polysiloxanes starting from alkoxysilanes and / or alkoxysiloxanes by polycondensation using a process that benefits from the rapid reaction rates of a homogeneous catalytic system but uses a heterogeneous catalyst to benefit from the ease and efficiency of catalyst separation when the reaction is complete. In addition, it is desirable to identify a process that allows for the simultaneous presence of both an acid catalyst and a base catalyst in both the hydrolysis reaction and the condensation reaction without the need to remove one catalyst after the hydrolysis reaction and add another catalyst for the condensation reaction. The use of simultaneous catalysts will simplify the two-step polycondensation reaction procedure. Summary of the invention

[0007] The present invention provides a solution to explore ways to prepare polysiloxanes starting from alkoxysilanes and / or alkoxysiloxanes by polycondensation using a process that benefits from the fast reaction rates of a homogeneous catalytic system but uses a heterogeneous catalyst to benefit from the ease and efficiency of catalyst separation when the reaction is complete. Furthermore, the present invention allows the simultaneous presence of both an acid catalyst and a base catalyst in both the hydrolysis reaction and the condensation reaction without the need to remove one catalyst after the hydrolysis reaction and add another catalyst for the condensation reaction. Furthermore, using the present invention, both an acid catalyst and a base catalyst can be used simultaneously without causing material inhibition of the catalytic properties of the acid catalyst and the base catalyst.

[0008] The present invention is the result of the discovery that a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst, such as those commonly used as ion exchange resins, can be present together in a polycondensation reaction solution without neutralizing their acid and base functionalities, and can also effectively catalyze the polycondensation of alkoxysilanes and / or alkoxysiloxanes by hydrolysis and condensation at a rate at least as fast as using a two-step homogeneous catalyst process.

[0009] Surprisingly, it has been found that gel-type heterogeneous catalysts uniquely achieve these results as acid and base catalysts that exist simultaneously in the polycondensation reaction of alkoxysilanes and / or alkoxysiloxanes.For example, macroporous heterogeneous ion exchange resins do not have the same effect, as shown in the following embodiment subsection.Even more surprisingly, the continuous addition of gel-type heterogeneous catalysts is not as good as the use of continuous homogeneous catalytic reaction or gel-type heterogeneous acid and base catalysts while performing (spending longer time and reacting less completely).Therefore, the presence of heterogeneous gel-type heterogeneous acid and base catalysts during the hydrolysis and condensation of alkoxysilanes and / or alkoxysiloxanes simultaneously causes the synergistic performance of whole polycondensation reaction.

[0010] In a first aspect, the present invention is a process for preparing polysiloxanes, wherein the process comprises a two-part polycondensation of an alkoxysilane and / or an alkoxysiloxane, the process comprising the steps of: (a) hydrolyzing the alkoxysilane and / or the alkoxysiloxane to form a hydroxy-functional silane and / or a hydroxy-functional siloxane; and (b) condensing the hydroxy-functional silane and / or the hydroxy-functional siloxane to form a polysiloxane polycondensation product; wherein the process is characterized by having both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst present simultaneously during both the hydrolysis step and the condensation step.

[0011] In a second aspect, the present invention is a composition comprising: (a) a reactant selected from alkoxysilanes and / or alkoxysiloxanes, and / or siloxane polycondensation products of alkoxysilanes and / or alkoxysiloxanes; (b) a gel-type heterogeneous acid catalyst; (c) a gel-type heterogeneous base catalyst; and (d) water.

[0012] The present invention can be used to prepare polysiloxanes from alkoxysilanes and / or alkoxysiloxanes. DETAILED DESCRIPTION

[0013] When a test method number is not used to indicate a date, the test method refers to the most current test method as of the priority date of this document. Reference to a test method includes reference to both the testing association and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to the American Society for Testing and Materials; EN refers to European Standards; DIN refers to the German Institute for Standardization; and ISO refers to the International Organization for Standardization.

[0014] "A plurality" means two or more. "And / or" means "and, or as an alternative, ". All ranges are inclusive unless otherwise indicated. Identification of a material by a trademark or trade name means that the material has the composition sold under that trademark or trade name on the priority date of this document.

[0015] General term "C x-y ″、″C x -C y " and "Cx-Cy" are interchangeable in the context of chemical structures and refer to having from x to y carbon atoms in the chemical structure.

[0016] "Heterogeneous catalyst" refers to a catalyst that is insoluble in the reaction mixture in which it acts as a catalyst and therefore remains in the form of particulates.

[0017] "Homogeneous catalyst" refers to a catalyst that is soluble in the reaction mixture.

[0018] "Gel-type resin" refers to a resin in particle form that, particularly in a non-solvent swollen state, does not contain a pore structure with a pore size greater than that penetrating the surface and extending through the resin particle, wherein the pore structure has a pore size greater than 2 angstroms, typically greater than 1 angstrom, and may not contain a pore structure with a pore size greater than 0.5 angstroms, and may not contain any pore structure that penetrates the surface and extends through the resin particle. Gel-type resins swell significantly (change volume) in polar solvents when absorbing the polar solvents, and typically become translucent when the solvent swells. Gel-type resins are also referred to as microporous resins in the ion exchange field.

[0019] "Gel-type heterogeneous catalyst" refers to a gel-type resin, usually in particulate form, that acts as a heterogeneous catalyst. "Gel-type heterogeneous acid catalyst" is a gel-type resin with acid chemical functional groups that acts as a heterogeneous acid catalyst. "Gel-type heterogeneous base catalyst" is a gel-type resin with base chemical functional groups that acts as a heterogeneous base catalyst.

[0020] "Macroporous resins," also called macroreticular resins, refer to resins in particulate form having a well-defined pore structure extending through the surface and throughout the resin, the pore size of the pore structure typically being greater than 2 angstroms, typically greater than 50 angstroms, and even more typically greater than 100 angstroms, and the pore structure being present regardless of the presence of solvent. Macroporous resins typically have a higher crosslink density than gel-type resins, and therefore do not swell significantly in the presence of polar solvents, and may not swell at all.

[0021] "Macroporous heterogeneous catalyst" refers to a macroporous resin that acts as a heterogeneous catalyst. "Macroporous heterogeneous acid catalyst" is a macroporous resin with acid chemical functional groups that acts as a heterogeneous acid catalyst. "Macroporous heterogeneous base catalyst" is a macroporous resin with base chemical functional groups that acts as a heterogeneous base catalyst.

[0022] "Silane" includes the general formula: R a S Y (4-a) An organosilane, wherein R a Y is hydrogen, alkyl, substituted alkyl, aralkyl, substituted aralkyl, aryl and substituted aryl. Alkyl groups and substituted alkyl groups each independently typically contain one or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, even 7 or more carbon atoms, while typically containing 8 or less and may contain 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, even 2 or less carbon atoms. For "alkoxy-functional silanes", at least one Y is an alkoxy group, and for "hydroxy-functional silanes", at least one Y is a hydroxyl group.

[0023] "Siloxane" refers to a molecule containing at least one siloxane (Si-O-Si) bond. Herein, "siloxane" may be a "polysiloxane" having multiple siloxane bonds or a siloxane having only one siloxane bond. When a siloxane having more than one siloxane bond is intended, the term "polysiloxane" is used. Polysiloxane may have a chain, ring, ladder, or three-dimensional network structure.

[0024] Polysiloxanes contain a plurality of siloxane units linked together by siloxane bonds. Siloxane units can be characterized by the designations M, D, T, or Q. M refers to a polysiloxane having the formula "(CH3)3SiO 1 / 2". D refers to a siloxane unit having the formula "(CH3)2SiO 2 / 2 ". T refers to a siloxane unit having the formula "(CH3)SiO 3 / 2 "Q" refers to a siloxane unit having the formula "SiO 4 / 2 Unless otherwise stated or indicated, the non-oxygen groups bonded to silicon atoms in M, D, and T units are methyl groups. It is worth noting that oxygen atoms with "1 / 2" multiple subscripts indicate that oxygen bridges the designated atom to a second atom, wherein the second atom is also designated with oxygen with "1 / 2" multiple subscripts to form a siloxane bond. For example, ((CH3)3SiO 1 / 2 )(SiO 4 / 2 ) or MQ refers to an M unit bonded to a Q unit, wherein the oxygen atoms are shared between the silicon atom of the M unit and the silicon atom of the Q unit. The 1 / 2 multiple subscript indicates how many oxygen atoms are in this shared bonding configuration with the silicon atom of the siloxane unit.

[0025] Reference to siloxane unit names with the suffix "-type" refers to siloxane units in which any one or more than one methyl group is actually an R group, where R is a group other than methyl, such as hydroxyl, alkoxy, or hydrocarbyl. Hydrocarbyl groups typically contain from one to eight carbon atoms. For example, R can be methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl.

[0026] As a superscript, a siloxane unit may include an indication of a group bonded to the silicon atom in place of an alkyl group. For example, "M H An "M-type" unit is an M-type unit in which one R group is replaced by hydrogen: ((R 1 )2HSiO 1 / 2 ) ″M H " unit refers to an M unit in which a methyl group is replaced by a hydrogen atom ((CH3)2HSiO 1 / 2 ). Ph The unit refers to a T unit in which the methyl group is replaced by a phenyl group.

[0027] The chemical formula names of polysiloxanes using the M, D, T, Q abbreviations generally have a subscript associated with the unit name, which may refer to the average molar ratio of the siloxane unit relative to all siloxane units in the molecule or the average number of associated siloxane units in the molecule. When the subscript associated with a siloxane unit is greater than or equal to one, then the subscript refers to the average number of those siloxane units in the molecule. When the subscript associated with a siloxane unit is less than one, then the subscript refers to the average molar ratio of the siloxane unit relative to the number of moles of all siloxane units in the molecule. The absence of a subscript means that the subscript value is one.

[0028] "OZ" sites refer to the combination of hydroxyl groups and alkoxy groups bonded to a silicon atom. The total number of OZ sites on a molecule or reaction mixture refers to the total number of the combination of hydroxyl groups and alkoxy groups bonded to a silicon atom in the molecule or present in the reaction mixture. The OZ content of a material is reported as a mole percent (mol%) relative to the moles of silicon atoms in the molecule.

[0029] The process of the present invention involves the two-part polycondensation of alkoxysilanes and / or alkoxysiloxanes.

[0030] Alkoxysilanes have the general structure (RO) x R' (4-x) Si; wherein the average value of the subscript x is one or more, 2 or more or even 3 or more, while at the same time 4 or less, 3 or less, or even 2 or less, each R and R' at each occurrence is independently selected from the group consisting of C1-C8 alkyl groups (such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl groups), substituted C1-C8 alkyl groups, aryl groups and substituted aryl groups.

[0031] Alkoxysiloxanes may have one or more siloxane bonds and include one or more alkoxy groups attached to at least one silicon atom. The alkoxy groups are as described for the (RO) groups of alkoxysilanes. Alkoxysiloxanes may be linear, branched, resinous, or any other structure possible for polysiloxanes.

[0032] "Two-part" polycondensation means that the process involves two reactions to achieve the polycondensation: a hydrolysis reaction and a condensation reaction. The hydrolysis reaction and the condensation reaction can occur sequentially or simultaneously. Typically, the alkoxysilane / siloxane undergoes hydrolysis to form a hydroxy-functional silane or a hydroxy-functional siloxane, respectively. The hydroxy-functional silane and / or siloxane then undergoes condensation to form a polysiloxane. Polysiloxanes are the polycondensation products of the two-part polycondensation.

[0033] The method of the present invention is characterized by having both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst present simultaneously during both the hydrolysis step and the condensation step. The method generally involves adding both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst to a reaction mixture containing alkoxysilanes and / or alkoxysiloxanes prior to the hydrolysis reaction step, and maintaining the catalyst in the reaction mixture throughout the condensation reaction step. Preferably, the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst are blended together before being added to the reaction mixture for the hydrolysis reaction, and maintained in the reaction mixture throughout the condensation reaction.

[0034] Surprisingly, the combination of the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst catalyzes both the hydrolysis and condensation reactions to a greater extent than when the gel-type heterogeneous acid catalyst alone is used for hydrolysis and the gel-type heterogeneous base catalyst is added for condensation reaction. The combination of the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst also results in at least as extensive polymerization to form polycondensation products as the more typical sequential use of a homogeneous acid catalyst followed by a homogeneous base catalyst, as demonstrated in the experimental subsection by reacting more "OZ" sites in the reaction mixture and achieving a higher molecular weight and viscosity polycondensation product under the same reaction conditions and the same amount of time. The extent of the polycondensation reaction of the present invention further demonstrates that surprisingly, the combination of the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst is present without neutralizing the acid groups and base groups on the respective catalysts.

[0035] When used in the present method, gel-type heterogeneous acid catalysts and gel-type heterogeneous base catalysts are ideally solvent swollen.Solvent swelling means that their volume has increased due to absorption of solvent.Generally, the solvent is a polar solvent, such as water or preferably alcohol (e.g., ethanol).Solvent swelling gel acts as a more effective catalyst than non-swelling gel, because reactants can more easily penetrate solvent swelling gel than non-swelling gel.It is helpful for reactants to penetrate gel to be exposed to more acid or base functional sites on the gel.Therefore, compared with if the gel-type catalyst is not swollen, more catalytic acid and base sites are available for reactants with solvent swelling gel-type heterogeneous catalysts.By contrast, microporous resin catalysts have a limited pore to allow reactants to penetrate without being swollen by solvent.

[0036] In addition to the alkoxysilane and / or alkoxysiloxane and heterogeneous catalyst described above, the reaction mixture for hydrolysis also comprises water usually. One or more additional solvents are desired to exist, but are not essential. Additional solvents can be selected from, for example, polar solvents, including alcohol (such as ethanol). Additional solvents ideally exist by hydrolysis reaction and condensation reaction.

[0037] The method can be a batch method, a continuous method or a semi-continuous method. In a batch method, all reactants reside in a single reaction vessel from the start of the reaction to the end, and the reaction mixture is usually stirred (or otherwise stirred) to maintain the suspension (slurry) of a heterogeneous catalyst during the whole hydrolysis and condensation reaction to maximize the effective contact with catalyst particles. In a continuous method, reactants flow through one or more reactors continuously when reacting to form a product, and then flow out from the reactor continuously. Semi-continuous methods can adopt many different forms, but relate to batch-like aspects and continuous-like aspects. For example. A kind of semi-continuous method relates to a series of batch reactors, wherein reactants reside in a reactor for a certain period of time, and then flow into another reactor for a certain period of time.

[0038] An example of a continuous process is a fixed bed column process. For example, a reaction mixture comprising an alkoxysilane and / or alkoxysiloxane, water, and optionally a solvent may flow through a column containing a physical mixture of a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst as the stationary phase. Hydrolysis and condensation reactions then occur as the reaction mixture flows through the column and contacts the heterogeneous catalyst.

[0039] Ideally, the method of the present invention is included in the heating reaction mixture during hydrolysis, condensation or hydrolysis and condensation.During the reaction period of the present method, it is usually desirable to have 30 degrees Celsius (℃) or higher, 40 ℃ or higher, 50 ℃ or higher, 60 ℃ or higher, 70 ℃ or higher or even 80 ℃ or higher reaction mixture temperature, meanwhile usually heated to 120 ℃ or lower, 110 ℃ or lower, 100 ℃ or lower, 90 ℃ or lower, even 80 ℃ or lower temperature.Heating can be carried out by applying a thermal source to the reaction mixture.Or, some reactions such as hydrolysis reaction can be exothermic and heating reaction mixture without applying heat separately.In fact, in some cases, it is desirable to adjust the temperature caused by exothermic reaction by cooling or moderating the temperature of reaction mixture in some way (such as by metering into water) to raise the temperature, so that the temperature is maintained in the desired range.

[0040] An ideal way to carry out the method is by utilizing a co-feed / co-stripping procedure during the hydrolysis period. The co-feed / co-stripping procedure can be part of a batch, semi-continuous or even continuous process, but is typically a feature of a batch or semi-continuous process using a single reaction vessel. The byproduct of the hydrolysis reaction is alcohol, which occupies the reactor volume and can inhibit the hydrolysis reaction kinetics. In the co-feed / co-stripping procedure, the catalyst and the hydrolysis reaction mixture of the reactants in the reaction vessel are fully heated to volatilize the alcohol product and remove the volatilized alcohol during the reaction by condensing the volatilized alcohol in a collection vessel. Typically, one or more reactants are fed into the reaction vessel, while the alcohol is volatilized and removed (stripped from the reaction vessel), hence the term "co-feed / co-stripping". The removal of alcohol and the addition of reactants can be continuous or intermittent independently, and primarily occur when alcohol is formed during the hydrolysis period. Once the reaction vessel contains the desired volume, the addition of reactants can be stopped. Once the alcohol has been stripped to the desired level, the stripping procedure (volatization and removal of alcohol) can be stopped. After the reactant feed and the alcohol stripping stop, the reactant can simply reach the desired time to complete the condensation reaction, usually reflux at the same time. If necessary, additional catalyst can be added after stopping the alcohol stripping. For example, this reaction vessel can only contain the catalyst for hydrolysis during the co-feed / co-stripping procedure, and can then add this condensation catalyst when the stripping of alcohol stops. Of course, in the whole hydrolysis and condensation reaction process, hydrolysis catalyst and condensation catalyst can be alternately present in the reaction vessel. The co-feed / co-stripping method can use a combination of homogeneous catalyst, heterogeneous catalyst or homogeneous catalyst and heterogeneous catalyst.

[0041] Removing the alcohol in the co-feed / co-stripping procedure frees up reaction vessel volume. The free reaction vessel volume allows more reactants to be added to the reaction vessel than would be added if the alcohol were retained, and means that more product can be produced in a single reaction vessel than if the alcohol were retained. This is a key benefit of the co-feed / co-stripping procedure—it can allow more polycondensation product to be produced in a given reaction vessel compared to a similar batch process that does not include stripping off the alcohol.

[0042] The desirable feature of the method of the present invention is that the catalyst is easily separated from the reaction mixture and / or the reaction product. In the continuous flow method where the reaction mixture flows through the fixed catalyst, the extrudate from the method is no longer catalyst-free and contains the reaction product. In the intermittent method, the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst are easily separated from the reaction mixture and / or the product, for example, by making the heterogeneous catalyst separate (sedimentation) from the solution and decant the supernatant solution containing the reactants and / or the product or such as in a separating funnel to discharge the catalyst from the supernatant. The gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst can alternatively be separated by filtration. Once separated, the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst can be ideally used again in the method of the present invention, and it is usually not necessary to supplement the acid and base functional sites on the catalyst. The separated catalyst can be rinsed to remove undesirable components before subsequent use.

[0043] An example of a batch method of the present invention comprises the following steps:

[0044] First, a reaction mixture is provided, the reaction mixture comprising: (i) a solvent swollen blend of a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst as a catalyst blend; (ii) a catalyst having the general formula: (RO) x R' (4-x) Si silane; wherein the average value of x is 1 or more, 2 or more, even 3 or more, and at the same time is 4 or less, 3 or less, or even 2 or less; each R and R 'is independently selected from the group consisting of alkyl groups, substituted alkyl groups, aryl groups and substituted aryl groups at each occurrence; and (iii) water. Alkyl groups and substituted alkyl groups independently typically contain one or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, or even 7 or more carbon atoms, and at the same time typically contain 12 or less, 10 or less, 8 or less and may contain 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less carbon atoms. The reaction mixture may contain a solvent such as an alcohol (e.g., ethanol) and other liquid components as a continuous phase. These components can be combined in any order to form a reaction mixture. Some components can be metered in during the reaction of the reactants. For example, water is typically metered in during the hydrolysis rather than added all at once to help regulate the temperature of the reaction mixture and prevent uncontrolled polymerization leading to gelation.

[0045] Second, agitate (for example, stir) reaction mixture, at the same time optionally heat this reaction mixture to set up and maintain the slurry of component.Agitation can start while merging the components of reaction mixture in the first step, or after merging all components of reaction mixture.Ideally, continue to agitate, at the same time allow hydrolysis and condensation reaction to occur in mixture to form product mixture.Ideally, continue to agitate in the whole process, until hydrolysis and condensation reaction both have been carried out to desired degree.

[0046] Third, the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst are separated from the remaining contents of the product mixture. In the widest range of this embodiment, there is no limitation on how to separate the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst from the remaining contents. Examples of how to separate the catalyst include those methods as described above.

[0047] Optionally, the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst may be recycled and used again in another reaction method of the present invention.

[0048] The characteristic feature of the present invention is the presence of both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst throughout the reaction process. Typically, the merging of an acid catalyst and a base catalyst is avoided during the reaction because they tend to react with each other, thereby neutralizing the catalytic acid and base functional groups. However, the present invention is due in part to the discovery that a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst can be combined without neutralizing the catalytic acid and base functional groups, respectively, at least to an extent sufficient to substantially inhibit their catalytic ability in the claimed method. In view of this discovery, the present invention further includes a composition comprising:

[0049] (a) a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst;

[0050] (b) water;

[0051] (c) a reactant selected from alkoxysilanes and / or alkoxysiloxanes; and

[0052] (d) Optionally, a solvent, such as a polar solvent such as ethanol.

[0053] In addition or instead of the reactant selected from alkoxysilanes and / or alkoxysiloxanes, the composition may comprise a siloxane polycondensation reaction product of an alkoxysilane and / or an alkoxysiloxane.

[0054] Example

[0055] Table 1 identifies the materials used in the following Examples (Ex) and Comparative Examples (Comp Ex). The gel-type heterogeneous catalyst was swollen in Solvent 2 prior to use. It is noted that the use of Solvent 1 and Solvent 2 is contemplated to be interchangeable in the methods and procedures described below while producing similar results.

[0056] Table 1

[0057]

[0058]

[0059] AMBERLYST, AMBERTEC and AMBERLITE are trademarks of DDP Specialty Electronic Materials. DUPONT is a trademark of DUPONT Polymers, Inc.

[0060] ** Directly obtained from DUPONT using the material available under the name AMBERLYST 125 or AMBERLYST 131

[0061] Similar results are expected by substituting the AMBERLYST BD20 material.

[0062] The examples and comparative examples were prepared according to the following procedure. The viscosity, weight average molecular weight (Mw), and total OZ content of the resulting products were characterized accordingly using the procedure following the examples and comparative examples. Table 2 provides a general overview of the compositions, reporting the component amounts in grams (g) of each sample and the product characterization of each example and comparative example.

[0063] Comparative Example A - Sequential Acid Then Base Homogeneous Catalyst

[0064] The following components were added to a batch reactor to form a reaction mixture: 190.88 grams (g) of n-octyltriethoxysilane, 12.00 g of solvent 1, 0.65 g of HCL homogeneous acid catalyst, and then 14.18 g of water (fed at a rate of 0.178 ml / min) was fed while mixing at 25° C. at 600 revolutions per minute (RPM) for 80 minutes under a nitrogen blanket atmosphere. During this time, hydrolysis reactions and condensation reactions occurred, producing ethanol as a byproduct. After the water addition was complete, the reaction mixture was heated to 77° C. and refluxed for 2 hours. The reaction mixture was cooled to 25° C. and 0.65 g of homogeneous base catalyst KOH was added to neutralize the HCL homogeneous acid catalyst and make the mixture alkaline. The reaction mixture was heated to 77° C. to reflux for another 2 hours, during which time the reaction product experienced "thickening" and the molecular weight increased. The solution was cooled to 25° C. and 1.4 g of HCL homogeneous acid catalyst was added to neutralize the base. 0.40gCaCO3 neutralizing agent is added to neutralize the acid. At this point, two phases appear in the solution, and a separating funnel is used to separate the two phases. The top phase contains ethanol, and the bottom phase contains the organosilicon resin product (siloxane product). The bottom phase is loaded back into the reactor and heated to 95°C to strip any residual ethanol under atmospheric conditions. Under nitrogen sparge, the solution is heated to 130°C to complete solvent stripping. The residual solvent is collected using a Dean-Stark water trap. The resulting resin is cooled and characterized for viscosity, weight-average molecular weight and OZ content, as Comparative Example A.

[0065] Comparative Example B - Simultaneous Macroporous Heterogeneous Acid and Base Catalysts

[0066] A catalyst premix was prepared by combining 17.64 g of Macroporous Heterogeneous Acid Catalyst 17D and 19.73 g of Macroporous Heterogeneous Base Catalyst A26.

[0067] The following components were added to a batch reactor to form a reaction mixture: 190.58 grams (g) of n-octyltriethoxysilane, 11.71 g of solvent 1, and a catalyst premix. 0.57 g of water was added, followed by 14.18 g of water (fed at a rate of 0.178 ml / min), while mixing at 25 ° C for 80 minutes at 1000 RPM under a nitrogen blanket atmosphere. During this time, hydrolysis and condensation reactions occurred, thereby producing ethanol as a by-product. After the water addition was complete, the reaction mixture was heated to 77 ° C and refluxed for 4 hours. During this time, 0.37 g of water was added. The reaction mixture was cooled to 25 ° C to obtain a turbid mixture. The reaction mixture was vacuum filtered using a Büchner funnel with Fisher Scientific P4 filter paper to remove solid acid and base catalysts. The filtrate was loaded back into the reactor and heated to 95 ° C to strip ethanol under atmospheric conditions. The residual solvent was collected using a Dean-Stark water separator. The solution was heated to 130°C under nitrogen sparge to complete solvent stripping. The resulting resin was cooled and characterized for viscosity, weight average molecular weight and OZ content as Comparative Example B.

[0068] Comparative Example C - Sequential Acid Then Base Gel Type Heterogeneous Catalyst

[0069] 20 g of dry (pre-swollen) material of gel-type heterogeneous acid catalyst BD20 swollen with solvent 2, 11.75 g of solvent 2, 190.79 g of n-octyl triethoxysilane, 585 microliters of water were added to a batch reactor, followed by feeding 14.18 g of water (fed at a rate of 0.178 ml / min), while mixing at 70° C. at 600 revolutions per minute (RPM) for 80 minutes under a nitrogen blanket atmosphere. During this time, hydrolysis and condensation reactions occurred, thereby producing ethanol as a by-product. After the water addition was complete, the reaction mixture was heated to 77° C. and refluxed for 4 hours, while refluxed adding 358 microliters of water. The reaction mixture was cooled to 25° C. and filtered using a Büchner funnel with Fisher Scientific P4 filter paper to remove the gel-type heterogeneous acid catalyst to obtain filtrate 1.

[0070] 20.15g of dry (pre-swollen) material of gel-type heterogeneous base catalyst 550A swollen with solvent 2 and 11.71g of solvent 2 and 177g of filtrate 1 were added to a batch reactor. While mixing at 600RPM under a nitrogen blanket, the mixture was heated to 77°C and refluxed for 21 hours. The solution was cooled and mixing was stopped to obtain a two-phase composition. The entire composition was filtered using a Büchner funnel with Fisher Scientific P4 filter paper to remove the solid catalyst. The filtrate was loaded back into the batch reactor and heated to 95°C to strip ethanol under atmospheric conditions. The residual solvent was collected using a Dean-Stark water separator. It was then heated to 130°C to complete solvent stripping while sparging with nitrogen. The resulting resin was cooled and characterized for viscosity, weight-average molecular weight, and OZ content as Comparative Example C.

[0071] Example 1 - Simultaneous presence of the acid and base gel-type heterogeneous catalyst of Comparative Example C

[0072] A catalyst premix was prepared by combining and physically mixing 20 g of dry (non-swelling) gel-type heterogeneous acid catalyst BD20 and 20 g of dry (non-swelling) material of gel-type heterogeneous base catalyst 550A. The physical mixture was swelled with solvent 2 to obtain a catalyst premix.

[0073] Catalyst premix, 11.69 g of solvent 2, 192.13 g of n-octyltriethoxysilane, 585 microliters of water were added to a batch reactor, followed by feeding 14.18 g of water (fed at a rate of 0.178 ml / min) while mixing at 70° C. at 1000 revolutions per minute (RPM) for 80 minutes under a nitrogen blanket atmosphere. During this time, hydrolysis and condensation reactions occurred, resulting in the production of ethanol byproducts. Once the water addition was complete, the resulting solution was heated to 77° C. and refluxed for 4 hours, then the solution was allowed to cool. It was difficult to filter the solution using a Büchner funnel with Fisher Scientific P4 filter paper, so a small amount of solution was filtered using a polytetrafluoroethylene 0.45 micron syringe filter. The filtered solution was stripped using a rotary evaporator to remove ethanol. Viscosity, weight average molecular weight, and OZ content were characterized as Example 1.

[0074] Example 2 - Simultaneous presence of acid and base gel-type heterogeneous catalyst

[0075] To a batch reactor was added 50 g (dry matter) of a gel-type heterogeneous acid / base blend catalyst that had been pre-rinsed in water, vacuum dried, and then swollen with solvent 2, 11.69 g of solvent 2, 190.41 g of n-octyltriethoxysilane, 585 microliters of water, and then 14.18 g of water (fed at a rate of 0.178 ml / min) while mixing at 70° C. at 600 revolutions per minute (RPM) for 80 minutes under a nitrogen blanket. Throughout the water addition step, 20.39 g of additional solvent 2 was fed. During this time, hydrolysis and condensation reactions occurred, resulting in the production of ethanol byproducts. Once the water addition was complete, the resulting solution was heated to 77° C. and refluxed for 4 hours while 341 microliters of water were added. The resulting solution was cooled. The resulting solution was filtered using a Büchner funnel with Fisher Scientific P4 filter paper to remove the catalyst. The catalyst was rinsed with toluene to extract the final product from the catalyst mixture. The extracted solution was stripped using a rotary evaporator to remove toluene, thereby obtaining Example 2. Viscosity, weight average molecular weight, and OZ content were characterized as Example 2.

[0076] Viscosity

[0077] Use Brookfield viscometer (model LVDV-II+P) and spindle SC4-18, with 6.7 milliliters of sample volume and at 25 ℃ temperature, measure the viscosity of resin. Select spindle, load sample cup, insert the cup into small sample adapter. Connect spindle to instrument. Allow sample to balance at temperature for at least 10 minutes. Start instrument motor and select rotation speed that causes torque range of 10% to 90% and run for three minutes. Collect data about the run and stop motor. Allow sample to stand for two minutes. Repeat twice more, run three times in total. Use average viscosity of three runs as sample viscosity. Report viscosity in milliPascal*second (mPa*s).

[0078] Weight average molecular weight (Mw)

[0079] The weight average molecular weight of the resin sample was determined using gel permeation chromatography (GPC). Agilent Chemstation method 31028B GPC 24-FEB-2012.M was used. The sample was degassed through a membrane. The pump was isocratic, 1 ml / min at 6 to 7 MPa pressure. An automatic sampler was used at 10°C. A 1×5 micron Guard (50mm*7.5mm) and 2x PL gel 5 micron mixed C (300mm*7.5mm) (Fisher Part#50-010-6923) column maintained at 35°C was used. A refractive index detector was used at 35°C. The detector had an automatic valve that sent the material to waste during analysis and was recycled at all other times. Tetrahydrofuran stabilized with 250 parts by weight / million parts by weight of butylated hydroxytoluene (BHT) was the effluent of the system.

[0080] Prepare samples by adding 1000 μL of HPLC grade toluene to 10 μL of sample into a gel chromatography vial. Mix each sample using a vortex mixer. 6 Polystyrene standards were calibrated for Mp analysis, where Mp refers to the molecular weight of the highest peak. A total of 10 polystyrene standards were analyzed in two injections. A logarithmic scale was used to provide >0.999r 2 .

[0081] OZ content

[0082] Use silicon-29 ( 29 The OZ content of the resin was determined by Si) nuclear magnetic resonance (NMR) spectroscopy. NMR spectra were collected using an Agilent 500 MHz DD2 (mi-MR-06) system equipped with a 16 mm silicone-free AutoX probe or on a Varian Inova NMR (mi-MR-04) spectrometer with a proton operating frequency of 400 MHz. Samples were prepared with 0.02 mol chromium (III) acetylacetonate (Cr(acac)3) in deuterated chloroform.

[0083] The OZ content is the sum of the moles of alkoxy groups and hydroxyl groups bonded to silicon atoms, expressed as a percentage relative to the moles of silicon atoms in the molecule. The relative molar concentrations of the functional groups are determined by integrating the peaks corresponding to the different siloxane units (M, D, and T) based on predetermined attributions known in the art. 29 Si NMR spectroscopy determines the OZ content. The OZ content is the sum of the products of the molar concentration of each functional group multiplied by the number of OZ groups associated with each functional group.

[0084] Table 2

[0085]

[0086] *Dry weight (non-solvent swollen weight)

[0087] Comparative Example A serves as a reference for a typical sequential homogeneous catalytic process for producing polycondensation siloxane products. It is expected to achieve similar or better results (equal or higher viscosity, equal or lower OZ content, and equal or higher Mw) than this reference using the same reaction time.

[0088] Comparative Example B illustrates that the simultaneous presence of macroporous heterogeneous acid and base catalysts cannot achieve the desired results of equal or higher viscosity, equal or lower OZ content, and equal or higher Mw relative to Comparative Example A, even at twice the reaction time of Comparative Example A.

[0089] Comparative Example C illustrates that the sequential use of acid then base gel-type heterogeneous catalysts does not achieve the desired results of equal or higher viscosity, equal or lower OZ content, and equal or higher Mw relative to Comparative Example A, even at 6 times the reaction time of Reference Comparative Example A.

[0090] Example 1 uses the same composition as Comparative Example C, except that these catalysts are used simultaneously throughout the process. Surprisingly, the process does achieve the desired results of equal or higher viscosity, equal or lower OZ content, and equal or higher Mw relative to Comparative Example A in the same reaction time.

[0091] Example 2 is a repeat of Example 1, except that a different gel-type heterogeneous catalyst is used simultaneously throughout the process. This process also surprisingly achieves the desired results of equal or higher viscosity, equal or lower OZ content, and equal or higher Mw relative to Comparative Example A in the same reaction time.

Claims

1. A method for preparing polysiloxanes, wherein the method comprises a two-part polycondensation of an alkoxysilane and / or an alkoxysiloxane, the method comprising the following steps: (a) hydrolyzing the alkoxysilane and / or alkoxysiloxane to form hydroxy-functional silane and / or hydroxy-functional siloxane; as well as (b) condensing the hydroxy-functional silane and / or hydroxy-functional siloxane to form a polysiloxane polycondensation product; The process described herein is characterized by having both a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst present simultaneously during both the hydrolysis step and the condensation step. 2 . The method according to claim 1 , wherein the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst are each swollen in a polar solvent.

3. A method according to claim 1 or claim 2, wherein the method is a polycondensation of an alkoxysilane.

4. The method according to claim 3, wherein the alkoxysilane has the general formula: (RO) x R' (4-x) Si; wherein the subscript x is a value in the range of 1 to 4, and each R and R′ at each occurrence is independently selected from the group consisting of a C1-C8 alkyl group, a substituted C1-C8 alkyl group, an aryl group, and a substituted aryl group.

5. A process according to any preceding claim, wherein the polycondensation is carried out in a reaction vessel as a batch reaction or as a continuous flow reaction through a fixed bed reaction column comprising a fixed bed containing a physical mixture of the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst.

6. The method according to any preceding claim, further comprising separating the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst from the reaction product after the reaction is completed.

7. The process according to claim 6, wherein the process comprises filtering and / or settling the heterogeneous catalyst and then decanting the liquid supernatant and / or removing the settled catalyst from the liquid supernatant.

8. The method according to claim 6 or claim 7, wherein the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst are reused in another method of the present invention after separation and without replenishing the acid sites and / or base sites of the catalysts.

9. The method according to claim 1, comprising the steps of: (a) providing a reaction mixture, the reaction mixture comprising: i. a solvent swollen blend of a gel-type heterogeneous acid catalyst and a gel-type heterogeneous base catalyst as a catalyst blend; ii. Silane, said silane having the general formula: (RO) x R' (4-x) Si; wherein x is a value in the range of 1 to 4, each R and R' at each occurrence is independently selected from the group consisting of a C1-C8 alkyl group, a substituted C1-C8 alkyl group, an aryl group, and a substituted aryl group; and iii. Water; (b) mixing the reaction mixture, optionally while heating, to establish and maintain a slurry of the components while allowing hydrolysis and condensation reactions to occur in the reaction mixture to form a product mixture; and (c) separating the gel-type heterogeneous acid catalyst and the gel-type heterogeneous base catalyst from the remainder of the contents of the product mixture.

10. A composition comprising: (a) a reactant selected from alkoxysilanes and / or alkoxysiloxanes, and / or siloxane polycondensation products of alkoxysilanes and / or alkoxysiloxanes; (b) gel-type heterogeneous acid catalysts; (c) a gel-type heterogeneous base catalyst; and (d) Water.

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