AU2013100053A4 - Second generation hybrid silane modified polymers of low viscosity for low toxicity RTV sealants and adhesives - Google Patents

Abstract

Provisional patent September 2012V1 Embodiments of the innovation are shown that allow the significant reduction of alkoxysilane modified or terminated polymer composition viscosity where the high viscosity of silyated polyether due to hydrogen bonding of urethane groups made with isocyanato silane reaction are mostly eliminated with some small chemical additions that block the process. These added chemicals have further benefits of inhibiting reactivity and producing more stable compositions. Sealants are disclosed that use these improved polymers, are very stable in storage, and a process for preparing such sealant is also provided.

Description

Wolantech Patent Application dated Sept 2012 Second generation Hybrid silane modified polymers of low viscosity for low toxicity RTV sealants and adhesives. Cross References to Related Applications This patent application claims the benefit of IP Australia provisional application 2012903059 and fully incorporated here by reference. Foreign Patent references 6,265,517 6/2001 Stuart J.T. 524/589 003187 Al 01/2012 Vykaranan K. et al US7115696 B2 10/2006 Roesler R.R. et al US2011/0257324A1 10/2011 Ziche W. et al US2010/0204384A1 12/2010 Huang M.W. et al 528/28 Field of the Invention The present invention is a development of the silyl modified compositions of alkoxysilane cross linkable or end capped polyether and alkoxysilane modified polyurethane polymers where one or more urethane group is present. The hydrogen bonding of these urethane groups increases the viscosity of the high viscosity high molecular weight DMC based polyether capped and reacted with isocyanato silanes, with and without chain extension. This hydrogen bonding across polymer chains results in high viscosity polymers, and can be reduced substantially for polymers suitable for use in sealant and adhesive Manufacturing.

Background of the invention The development of moisture curable alkoxysilane terminated polyether and polyurethane polymers to replace standard isocyanate capped polyurethane prepolymers in one component RTV moisture curing compositions have in the last 25 years shown they are alternate lower toxicity polymers to replace older technology polyurethane prepolymers with the benefits of better physical properties such as UV resistance, adhesion to certain substrates with no primers and a marked reduction in bubbling of sealant when curing. There has been almost complete replacement of the older PU sealants in some markets such as the aftermarket windscreen sealant segment where the first generation alkoxysilane capped difunctional polymers which do not have a urethane group present have replaced the traditional TDI based PU sealant to a large extent .The advantages of good UV resistance of these silane modified polyether polymers has been very significant which is mainly the lack of aromatic molecules in the chain. The issues with high tin content catalysis, moisture sensitivity over time and high monol polyether content of these first generation polymers have limited the replacement of PU prepolymer and silicone based sealants and adhesives in other sealant markets such as the higher volume construction and adhesive markets. An alternate polymer design was introduced where a NCO terminated polyurethane prepolymer was capped with secondary amino propyl trimethoxy silanes of various types, which did shown the benefits of faster crosslinking of the trimethoxy silane, lower tin content requirement for curing the alkoxysilane, and the significant benefits of low monol DMC process in high molecular weight polyether's. This type of polymer design allowed the use of high DIDP plasticizer content as used with standard PU prepolymers, produced sealants and adhesives with good elastic recovery and low tin catalyst content. These systems are a good alternate to PU prepolymers. However the huge disadvantage was and still is the high polymer viscosity due to the formation of urea groups when these secondary amino alkoxysilane end cappers are used. Viscosity is in the range of 75000 Mpas to 150000 Mpas, with the need to use plasticizer contents of at least 20 percent in the prepolymer to make the prepolymer pourable at 20 to 30 degree Celsius temperatures. Drums of these polymers are impossible to empty satisfactorily without heating in colder climates. The alternate moisture curable alkoxysilane polymers with lower polymer viscosity than the above amino silane based polymers now commonly developed are using high molecular weight low monol polyether polyols where the hydroxyl end group is end capped with isocyanato silanes. Here the viscosity is due to the long chain of the base polyether, which can be a result of some chain extension using a diisocyanate molecule , and also the hydrogen bonding by the urethane group formed when the isocyanato silane NCO reactive group reacts with the hydroxyl group. The commonly known polymers viscosities using this design are currently in the range of 30000 to 75000 Mpas depending on the average molecular weight of the base polyether or polyurethane which start at 12000 MW and can be built up to 30000 MW. The high viscosities of the alkoxysilane capped polyether using isocyanato silanes above the base viscosity of the polyether chain are due to the hydrogen bonding between adjacent polymer chains when urethane groups are formed in the reaction of the hydroxyl groups and the isocyanate of the isocyanato alcoxysilane . The urethane group has one double bonded oxygen atom attached to a carbon atom, and adjacent to the carbon atom is a nitrogen atom with a hydrogen atom. The electrostatic hydrogen bonding is developed between the double bonded oxygen atom referred to as carbamate and the hydrogen attached to a nitrogen atom in an adjacent polymer chain to form the known hydrostatic bond and this interchain bond increases the polymer viscosity. Standard methods to reduce this hydrogen bond viscosity increase in polyurethane prepolymers have been to add solvents like Xylene , and plasticizers like DIDP. The viscosity increase depends on the polymer design and the number or urethane groups. To replace standard TDI and MDI based polyurethane prepolymers in polyurethane , silicone and other sealant market polymers, or the existing adhesive markets we need to give formulators and their Factories a safer low toxicity, lower viscosity moisture curable alkoxysilane polymer and a method where they are able to manufacture sealants in a very similar process to what is currently used. They need stable lower viscosity alkoxysilane capped prepolymers or resins , moisture scavengers they can add, and cure inhibitors so they are able to formulate products that are able to be manufactured in equipment that is currently used for high volume PU sealant production. They also need to be able to replace current proven PU sealant formulations with less development and advantages in physical properties such as UV exposure resistance. The replacement of the tin based DBTDL catalyst by less environmentally problematic catalysts is also needed. The moisture content of currently used calcium carbonate and other mineral or synthetic mineral fillers and reinforcing fillers such as the Precipitated calcium carbonate products of rhombic shape is handled in many ways, as the aim of producing single pack room temperature curing, RTV compositions, requires low levels of residual moisture content, and additives that prevent premature cure in cartridges or the normal packaging used in all these sealant and adhesive markets. SUMMARY OF THE INVENTION We have now developed a new generation of alcoxysilane terminated polymers which have the low tin catalyst requirement of trimethoxy terminated polymers, with lower viscosities in the range of 5000 to 30000 Mpas. We also disclose our discovery of an addition of commonly available moisture scavenger chemical ,that is able to give the formulator the ability to have a sealant open time from 15 minutes to 1.0 hours. This allows the formulation of a cheaper sealant with properties that are close to current PU formulations and allow the applicators a safer low toxicity product with minimal difference in application methods. DETAILED DESCRIPTION OF THE INVENTION The polymers are composed of a backbone of polyurethane, polyether, polyester, polyacrylate and can be any polymer of linear or cross linked composition with free reactive hydroxyl groups available for reaction. The design of the backbone is chosen to give the required hardness, tensile and elongation properties when reacting hydroxyl group with a trifunctional or difunctional Isocyanato silane to produce the alcoxysilane capped polymer. These can be commonly known gamma and beta and alpha silanes. This use of isocyanato silanes is well documented and there are many patent references, and depending on the content of the carbamate groups added, results in viscosities that are 50% to 200% higher than the starting DMC process low monol polyether chains, which are the preferred embodiment of this invention. Double Metal Cyanide (DMC) catalyst polyether based polymers result in sealants with excellent physical properties as shown in example formulation. It has been found that these silane terminated polyether's are stable but do need to have a moisture scavenger and reaction retarder added at some stage so that the Customer is able to manufacture sealants using various fillers such as calcium carbonates that have up to 500 ppm moisture present, even after some drying process for these fillers. The common moisture scavengers used are the vinyl silanes, various faster carbamate silanes as well as the Family of moisture scavengers used by polyurethane formulations which include the oxyzoladine derivatives.

It has been found surprisingly that a small amount of vinyl silane and methanol added together to the capped polymer where isocyanato silanes has been used, has a dramatic effect on the viscosity of a trimethoxy or methyl dimethoxy amount silane capped polyether or polyurethane composition, where the hydrogen bonding generated across adjacent urethane groups is reduced by up to 90 %, with preferred amounts of only 0.5% vinyl silane and 0.5% methanol added to the polymer after the reactions are completed and the polymer is cooled to below 40 degree C. The total polymer viscosity reduction is in the order of 30 to 60% depending on the design and composition. The amount needed depends on the number of urethane bonds present in the polymer chain . It has also been discovered that the addition of the small amount of vinyl silane and methanol to the polymer results in improved stability of the polymer when drums are opened during manufacturing with commonly used manufacturing equipment. When combined with a sealant manufacturing process where residual moisture is reduced with heating under vacuum, these additives combined do help reduce moisture content with the benefit of the methanol aiding residual moisture elimination from the fillers used by azeotropic distillation process. It is well known that methanol reduces the reaction rate of alkoxysilanes but needs to be used at low levels as methanol is toxic to humans in large quantities and should not be used at level above 1% where it also has an effect on the flammability of the polymer. It is common in PU sealant formulation practice in one part RTV sealants and adhesives to use the very toxic paratoluenesulphonicisocyanate, known as PTSI , the fast moisture scavenger to reduce moisture content as the reaction is faster than the isocyanate containing polymer NCO groups. To date the sealant formulators using trimethoxy silane terminated polyether polymers have not had these options, as the known faster carbamate silanes do dry the powders but also crosslink the polymer chains if the moisture content is not known and excess is added. There is also a need for the new technology trifunctional alkoxysilane resins to have a similar additive, and we have found that the oxyzoldines are a suitable moisture scavenging additive for the trimethoxy polymers with preference given to addition of Zoldine MS-PLUS moisture scavenger from the Angus Chemical Company, a Dow subsidiary. The additive can be incorporated into the resin or added during compounding at small levels to scavenge residual moisture, which is the preferred embodiment. With these combinations of additives and reaction retarders, we are able to offer the sealant formulators a unique low viscosity polymer and a production method and some flexibility in formulating that has the advantage of manufacturing RTV sealants and adhesives of lower toxicity and the ability to control curing rates in a similar method as currently used with the PU sealants commonly made. Below we demonstrate some aspects of the invention without restricting it. EXAMPLES The invention is described by reference to the specific examples for the purpose of illustration , and it is to be understood that numerous options will be apparent to those skilled in the art, and are considered to be within the scope of this invention. Test methods Hardness ASTM D2240 Tensile strength ASTM D412 Elongation ASTM D412 Trimethoxy silane capped Hybrid Polymer A. In a standard large glass laboratory flask with good stirring, 5000 grams of approx 3.0% monol content, DMC catalyst process polyether Diols were blended to achieve an OH value 10 . These diols were dried and reacted under Nitrogen at 40 degree C, with 37.0 grams HDI and monitored with FTIR until NCO was less than 5 % to chain extend the polyether to approx 25000 MW average. The remaining OH groups were then reacted in a second step with 95 grams of 3-isocyanatopropyl-trimethoxy silane(95% purity) until the reaction showed low residual NCO by FTIR. The second reaction was approx 3 hours at 75 Centigrade using well known PU catalyst at low levels. The above resin was cooled in the laboratory flask to 40 degree C and addition of 25 grams of vinyl silane and 25 grams of anhydrous methanol was made and mixing was continued. A very immediate reduction in viscosity is apparent and the viscosity reduced to 30000 at 25 degree C after cooling and packaged in 1 litre metal sample container. The viscosity of the above composition with no addition of methanol or vinyl silane is of the order of 70000 Mpas at 25 degree C . Any residual NCO group from the isocyanato silane reacts with the methanol immediately producing a carbamate silane, and this is shown by FTIR absence of any peak at 2242 cm-1. Open time before skinning of this polymer when mixed with 1% DBTDL is approx 50 minutes at 25 C and 50% humidity in laboratory glass dish. Shore A hardness is approx 22 to 25 after 7 days cure. The trimethoxy alcoxysilane terminated polymer also cures with all of the Tin metal containing catalysts such as DBTDL, DOTL , and the tin diketonate catalysts such as the Dow Chemical manufactured Metatin 740. The addition of secondary amino silane adhesion promoter such as Shinetsu KBM603 at the 1% level combined with 1% DBTL increases the reaction rate and at 25C and 50% humidity the open time of a resin sample using DBTDL and a secondary amino adhesion promoter is 8 minutes The use of the synergy DBTDL and secondary amino silane which are used for adhesion allows for very low levels of tin catalyst content to produce a 1 part RTV sealant or adhesive. Trimethoxy silane capped Hybrid polymer A2. Polymer variant A2 is polymer A with the addition of 15 grams of Zoldine MS-Plus by a Manufacturer as an addition prior to manufacture where he has limited powder drying facilities and wishes to also chemically dry the powders used in the sealant. The moisture scavenger additive needs to be calculated or measured as there is also possibility of moisture in the plasticizer, and this can be reduced in a number of ways, one of which is demonstrated here. SEALANT FORMULATION WITH HYBRID POLYMER A2 In a standard 5 litre laboratory planetary mixer, with nitrogen, vacuum and small press we were able to produce some sealant samples from Hybrid polymer A2, where the manufacturer did not have good powder drying facilities and wished to continue with this method. The calcium carbonate moisture levels were measured at about 1000 PPM. The mixer contents were heated and vacuum was applied to aid moisture removal. The additional vinyl silane was added to the DIDP plasticizer and mixing was started, and then Zoldine MS Plus was added as necessary in the resin addition, so moisture scavenger was present when the calcium carbonate was incorporated into resin and plasticizer. The base formulation is in parts, was adjusted for the mixer used and is a softer construction sealant style composition. Hybrid resin A2 100 parts DIDP plasticizer 80 parts Vinyl silane 1 parts PCC Takehara 100 parts GCC omyacarb 2T 100 parts T102 Paint grade 50 parts Amino KBM603 2 parts DBTDL catalyst 1 part Tinuivin B75 3 parts Aerosil R202 10 parts The mechanical properties of the above construction type joint sealant using Hybrid polymer A2 composition and packed into aluminium lined soft tube packaging, after 7 days cure is shown below. Tack free time 54 minutes Viscosity Mpas 1,200,000 Slump mm 0.0 (customer specific test) VOC 1.50 percent loss SG g/cm3 1.44 Tensile at break 1.55 n/mm2 Elongation % 630 at break Hardness Shore A 32 Adhesion to concrete 95 % cohesive after 30 days Cartridge stability > 9.0 months in aluminium lined hermetic cardboard cartridge While the major embodiments of the invention are illustrated and described herein, it is not intended that these illustrate all possible uses of the invention, rather the example describes how the next generation of low viscosity hybrid polymers can be used to produce less toxic and commercially viable RTV compositions suitable as an alternate to current NCO containing polyurethane sealants and adhesives that often also contain some residual free TDI monomer and xylene solvent. The examples show sealant properties close to commercial PU sealants based on TDI isocyanate prepolymers. The polyether used are blended to achieve a target OH value and consistent tensile properties and shore A hardness of sealants are very dependent on polyether number average molecular weight, the resulting OH value and polymer design. Resins or polymers with mixtures of diols and triols result in enhanced properties as is well known in the art of Polyurethane technology.

Claims (11)

1.An innovation that discloses it is the Hydrogen bonding between adjacent urethane groups that increases in a large part the viscosity of silane terminated polyether polymer compositions by electrostatic bonding of adjacent chains via the carbamate and hydrogen atoms joined to the nitrogen atom.

2. A method of manufacture of a silane terminated polymer where the urethane bonding is reduced by the addition of vinyl silane and methanol at the same time at level of up to 1 percent each and reducing the polymer viscosity by blocking the hydrogen bonds across chains by substitution of another molecule .

3. A polymer composition where the Double metal cyanide catalyst based polyether has a number average molecular weight from 6000 to 18000 and an unsaturation or monol level that is below 5%.

4. A polymer composition where the primary polyether can be chain extended fully or partially by difunctional Isocyanate molecules with hexamethylene diisocyanate and isophorone diisocyanate being preferred.

5. A polymer composition where the capping isocyanato silane is comprised of an isocyanato propyl trimethoxy silane and also isocyanato propyl methyl dimethoxy silane.

6. A method where the addition of the vinyl silane and methanol inhibit the alkoxysilane reaction with moisture forming silanol groups and results in a stable clear polymer with shelf life in Closed drums of at least 12 months.

7. A method of polymer composition where the resin additives provide adequate cure open time of the resin alone up to 1 hour when 1% DBTDL catalyst is added in a 25 C and 50% Relative humidity environment.

8. A method where the addition of methanol to the silane terminated polymer at levels of up to 1 percent inhibits the reactivity of the polymer for use in Manufacturing where low moisture level is present in the used filler powders such as PCC or GCC and and needs to be eliminated for sealant and adhesive stability .

9. The disclosure of azeotropic distillation process with the methanol addition that aids removal of low residual moisture in Calcium carbonate and other fillers.

10. The methanol addition can be fully removed during the manufacturing process with vacuum and some heat, where the Manufacturer wishes to have no methanol present in the final sealant or adhesive.

11. A fast moisture scavenger that can be added to the sealant or adhesive during the compounding or manufacturing process to eliminate moisture from compositions using trimethoxy silane terminated polymers. 9. A sealant manufacturing process where the polymer and plasticizer mixture contain enough fast moisture scavenger additive to enable drying of powders in one step in the manufacturing and mixing process and enables continuing stability of the sealants or adhesives produced.