The monomer is pure 4, 4apos; mDI adhesive prepolymers

Abstract

The present disclosure relates to a solvent-free, NCO-terminated prepolymer comprising the reaction product of (1) a pure, unmodified 4, 4 'MDI, (2) a silane coupling agent capable of grafting to a urethane prepolymer, and (3) a polyol. The present disclosure also relates to a solvent-free NCO-terminated prepolymer that is synthesized by (1) first mixing a polyol and a silane coupling agent that can be grafted to a urethane prepolymer, then (2) adding pure 4, 4 'MDI, (3) reacting the composition at a temperature, and (4) cooling the product. Finally, the present disclosure relates to a method of synthesizing an NCO-terminated prepolymer comprising (1) first mixing a polyol and a silane coupling agent capable of grafting to a urethane prepolymer, (2) adding pure 4, 4 'MDI, (3) reacting the composition at a temperature, (4) cooling the product. Also disclosed is an adhesive comprising the disclosed prepolymer and an OH-terminated prepolymer.

Description

Technical Field

[0001] The present disclosure relates to NCO-terminated prepolymers and methods of producing NCO-terminated prepolymers. More specifically, the present disclosure relates to solvent-free NCO-terminated prepolymers comprising pure, unmodified 4,4'MDI. The disclosed prepolymers can be used to make adhesives. Background Art

[0002] Adhesives can be based on the chemistry of polyurethanes and are divided into two main categories: solvent-based and solvent-free. Adhesives can be synthesized from NCO-based components and OH-based components. Solvent-free NCO-based components can be synthesized by reacting monomeric MDI with polyether and / or polyester polyols to produce NCO-terminated prepolymers.

[0003] Typically, NCO-terminated prepolymers are synthesized with an excess of isocyanate. Thus, at the end of the reaction, unreacted diphenylmethane diisocyanate (MDI) dilutes the synthesized prepolymer. If 4,4′MDI is used, the prepolymer is unstable. The inherent symmetry of 4,4′MDI promotes the formation of dimers, especially at about 25° C. These dimers tend to separate from the phase after production, causing the prepolymer to become turbid.

[0004] Likewise, 4,4′MDI is the most reactive MDI isomer found in nature. Therefore, the final prepolymer is often difficult to handle after production.

[0005] One existing solution to this problem involves partially modifying 4,4′MDI to carbodiimides and uretonimines. When the desired plateau level is reached, a toxic reagent such as SnCl is added. 2 to terminate the conversion. The presence of these agents can prevent the use of adhesives in food packaging applications. Likewise, modified 4,4′ MDI remains largely difficult to handle and extremely reactive.

[0006] The second existing solution involves producing a 50:50 composition of 4,4'MDI and 2,4'MDI. The addition of 2,4'MDI reduces reactivity and increases ease of handling while preventing dimer formation. However, 2,4'MDI contains 2,2'MDI which is extremely undesirable for food product applications and can cause problems passing PAA testing. Various methods have been developed to remove 2,2'MDI from 2,4'MDI, but all methods increase the cost and complexity of prepolymer production.

[0007] Therefore, a process for producing NCO-terminated prepolymers from pure 4,4'MDI which avoids the production of dimers and the subsequent phase separation is desired. Summary of the invention

[0008] The present disclosure relates to a solvent-free NCO-terminated prepolymer, which comprises the reaction product of the following substances: (1) pure unmodified 4,4'MDI, (2) a silane coupling agent capable of being grafted to a urethane prepolymer, and (3) a polyol. The present disclosure also relates to a solvent-free NCO-terminated prepolymer, which is synthesized by the following steps: (1) first mixing a polyol and a silane coupling agent capable of being grafted to a urethane prepolymer, then (2) adding pure 4,4'MDI, (3) reacting the composition at a certain temperature, and (4) cooling the product. Finally, the present disclosure relates to a method for synthesizing an NCO-terminated prepolymer, which comprises: (1) first mixing a polyol and a silane coupling agent capable of being grafted to a urethane prepolymer, (2) adding pure 4,4'MDI, (3) reacting the composition at a certain temperature, and (4) cooling the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a picture of CE1 prepolymer.

[0010] Figure 2 This is a picture of CE2 prepolymer.

[0011] Figure 3 This is a picture of IE1 prepolymer.

[0012] Figure 4 This is a picture of IE2 prepolymer.

[0013] Figure 5 is a graph showing the viscosity of a reference sample, a comparative sample and two experimental samples as a function of time at 40° C. This value is usually referred to as the pot life. DETAILED DESCRIPTION

[0014] As used herein, the term "prepolymer" means a monomer or monomer system that is reacted to an intermediate state and is capable of further polymerization. The terms "prepolymer" and "polymer precursor" are used interchangeably herein.

[0015] As used herein, a "polyol" is a compound having two or more hydroxyl groups. A polyol having exactly two hydroxyl groups is a "diol" and a polyol having exactly three hydroxyl groups is a "triol."

[0016] As used herein, the term "polymer" means a polymeric compound prepared by polymerizing monomers or prepolymers of the same or different types. The generic term polymer thus encompasses the term homopolymer (used to refer to polymers prepared from only one type of monomer) and the term copolymer or interpolymer. Trace impurities (e.g., catalyst residues) may be incorporated into and / or within the polymer. The polymer may be a single polymer, a polymer blend, or a polymer mixture, including a mixture of polymers formed in situ during polymerization.

[0017] As used herein, the term "polyolefin" refers to a polymer that comprises, in polymerized form, a majority amount of an olefin monomer (eg, ethylene or propylene) (based on the weight of the polymer) and optionally may contain one or more comonomers.

[0018] As used herein, the term "polyethylene" refers to a polymer comprising a major amount (>50 mol%) of units derived from ethylene monomers.

[0019] As used herein, the term "unmodified 4,4' diphenylmethane diisocyanate" or "unmodified 4,4' MDI" means 4,4' MDI that has not been partially or completely converted to a carbodiimide, uretonimine, or any other chemical entity in an attempt to prevent dimerization.

[0020] As used herein, the term "at a temperature" means bringing a composition to a certain temperature and maintaining the composition at that temperature until completion of some process is completed.

[0021] As used herein, the term "pure" when used to describe 4,4' diphenylmethane diisocyanate or 4,4' MDI means 4,4' diphenylmethane diisocyanate containing no more than 2 weight percent 2,4' diphenylmethane diisocyanate based on the weight of 4,4' MDI.

[0022] Numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit, and include the lower limit and the upper limit. For ranges containing exact values ​​(e.g., ranges from 1 or 2 or 3 to 5 or 6 or 7), any sub-ranges between any two exact values ​​are included (e.g., the above ranges 1 to 7 include sub-ranges of 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6, etc.).

[0023] The term "composition" refers to a mixture of materials comprising the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0024] The terms "comprising," "including," "having," and derivatives thereof are not intended to exclude the presence of any additional components, steps, or procedures, whether or not specifically disclosed. For the avoidance of any doubt, all compositions claimed through use of the term "comprising" may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term "consisting essentially of excludes from the scope of any subsequently recited component, step, or procedure, except those that are not essential to operability. The term "consisting of excludes any ingredient, step, or procedure not specifically recited or listed.

[0025] A solvent-free NCO-terminated prepolymer is disclosed which is composed of the reaction product of (1) pure, unmodified 4,4′ diphenylmethane diisocyanate, (2) a silane coupling agent capable of grafting to a urethane prepolymer, and (3) a polyol. Without wishing to be bound by theory, it is believed that the addition of the silane coupling agent capable of grafting to the urethane prepolymer stabilizes the 4,4′ MDI and reduces the reactivity to a point where dimers are not formed and the resulting prepolymer is clear rather than turbid.

[0026] Silane coupling agents are well known as adhesion promoters between organic and inorganic substrates. Typically, in a silane coupling agent, a silicon atom is bonded to both an organic functional group and a hydrolyzable group. The organic functional group is grafted to the organic substrate, and the hydrolyzable group is bonded to the inorganic substrate. Silane coupling agents can generally be considered to have the structure shown in Structure 1:

[0027]

[0028] Structure 1 :

[0029] And has long been used as an adhesion promoter. It has been unexpectedly found that silane coupling agents capable of grafting to urethane prepolymers can act as 4,4′MDI stabilizers and performance modifiers. The selected silane coupling agents can be those commonly used with thermosetting urethanes. The selected silane coupling agent can be an amine or alkanolamine functional silane. The selected silane coupling agent can be grafted to the urethane prepolymer. The selected silane coupling agent can include structure 1, wherein R is an amino, epoxy, carboxyl, isocyanate, anhydride or urethane group. The silane coupling agent capable of grafting to the urethane prepolymer can include (3-aminopropyl) triethoxysilane.

[0030] The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 0.100% by weight based on the weight of the pure unmodified 4,4′ diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 0.500% by weight based on the weight of the pure unmodified 4,4′ diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 1.00% by weight based on the weight of the pure unmodified 4,4′ diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 1.50% by weight, based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 2.00% by weight, based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 2.50% by weight, based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 3.00 wt % based on the weight of the pure unmodified 4,4′ diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition. The silane coupling agent capable of being grafted to the urethane prepolymer may account for more than 3.50 wt % based on the weight of the pure unmodified 4,4′ diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition.

[0031] Based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition, the silane coupling agent capable of being grafted to the urethane prepolymer may account for between .100 wt% and 1.50 wt%. All individual values ​​and subranges are included and disclosed. For example, based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition, the silane coupling agent capable of being grafted to the urethane prepolymer may account for between .500 wt% and 1.30 wt%. Based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition, the silane coupling agent capable of being grafted to the urethane prepolymer may account for between 1.50 wt% and 4.50 wt%. All individual values ​​and subranges are included and disclosed. For example, based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of grafting to the urethane prepolymer and the polyol composition, the silane coupling agent capable of grafting to the urethane prepolymer can account for between 2.00 wt% and 4.00 wt%.

[0032] Any pure, unmodified 4,4′-diphenylmethane diisocyanate may be used. Suitable commercial sources include those available from DOW TM ISONATE obtained by chemical TM 125MDR Pure MDI. Pure unmodified 4,4'MDI may contain up to 2% by weight of 2,4'MDI. Pure unmodified 4,4'MDI may contain up to 1% by weight of 2,4'MDI. Pure unmodified 4,4'MDI may contain up to 0.5% by weight of 2,4'MDI. Pure unmodified 4,4'MDI may contain up to 0.0% by weight of 2,4'MDI.

[0033] Based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition, the 4,4' MDI may comprise 0.100 wt% to 90.0 wt%. All individual values ​​and subranges are included and disclosed. For example, based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition, the 4,4' MDI may comprise 40.0 wt% to 50.0 wt%.

[0034] Any polyol can be used, including but not limited to polyether polyols, polyester polyols, polybutadiene polyols, polycarbonate polyols, bio-based polyols and polyacrylate polyols. Based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, a silane coupling agent capable of being grafted to a urethane prepolymer, and a polyol composition, the polyol can account for 0.100 wt % to 90.0 wt %. All individual values ​​and subranges are included and disclosed. For example, based on the weight of pure unmodified 4,4' diphenylmethane diisocyanate, a silane coupling agent capable of being grafted to a urethane prepolymer, and a polyol composition, the polyol can account for 40.0 wt % to 50.0 wt %.

[0035] If it is desired to reduce the final viscosity of the prepolymer, isomeric MDI isocyanate or modified MDI isocyanate can be added after the reaction. Isomeric MDI suitable for use in the present disclosure includes but is not limited to ISONATE TM OP 50 Pure MDI. Modified MDI suitable for use in the present disclosure include, but are not limited to, ISONATE TM M143. Isomeric or modified MDI isocyanates do not participate in the reaction and are only added after the reaction. Isomeric or modified MDI isocyanates do not participate in the prepolymer synthesis. Therefore, their use is not required and can be replaced with an equal amount of ISONATE TM 125MDR Pure MDI instead.

[0036] If PAA testing for food contact applications is of concern, up to 7 wt% ISONATE may be used. TM OP 50 Pure MDI. Even if PAA testing for food contact applications is not a concern, using no more than 10 wt% is advisable. Based on the weight of pure unmodified 4,4′ diphenylmethane diisocyanate, silane coupling agent capable of grafting to urethane prepolymers, and polyol composition, ISONATE TM OP 50 Pure MDI may account for less than 7.01% by weight. Based on the weight of pure unmodified 4,4′ diphenylmethane diisocyanate, a silane coupling agent capable of being grafted to a urethane prepolymer, and a polyol composition, ISONATE TM OP 50 Pure MDI may account for less than 10.1% by weight. Based on the weight of pure unmodified 4,4′ diphenylmethane diisocyanate, silane coupling agent capable of being grafted to the urethane prepolymer, and polyol composition, ISONATE TMOP 50 Pure MDI may comprise 0.000 wt % to 10.0 wt %. All individual values ​​are included and disclosed. For example, based on the weight of pure unmodified 4,4′ diphenylmethane diisocyanate, silane coupling agent capable of being grafted to the urethane prepolymer, and polyol composition, ISONATE TM OP 50 Pure MDI may comprise 0.000 wt % to 7.00 wt %.

[0037] The solvent-free NCO-terminated prepolymer can be synthesized by first mixing a polyol and a silane coupling agent capable of being grafted to a urethane prepolymer. Then pure unmodified 4,4′ diphenylmethane diisocyanate is added. The composition is reacted at a certain temperature and the product is cooled. This is called a reverse feed synthesis route. The MDI, polyol, and silane coupling agent capable of being grafted to a urethane prepolymer used are as described above.

[0038] This is in contrast to the direct feed route of the prior art where the isocyanate is loaded first and then all the polyols are added. If the silane coupling agent is added during the synthesis following this route, a white material can be observed to come out of phase almost as the silane coupling agent is added. This is true if the silane coupling agent is added with all the polyols at the beginning of the reaction (direct feed) or if the silane coupling agent is added after all the polyols have been added and reacted with the MDI to the desired NCO% (referred to as direct feed 1). The white material is likely the pure modified diisocyanate terminated with the silane coupling agent.

[0039] The solvent-free NCO-terminated prepolymer can be synthesized by loading the liquefied polyol into a reaction flask equipped with an agitator, reflux condenser, thermometer and heating jacket. Once the polyol is mixed, the silane coupling agent is added and mixed into the composition. When the mixing of the silane coupling agent is complete, the liquefied pure 4,4' unmodified MDI is added. Once the liquefied pure 4,4' unmodified MDI is mixed, the composition is reacted at a certain temperature. Once the reaction is complete, the modified MDI or isomeric MDI (if necessary) is added, the composition is cooled, and the contents of the flask are discharged.

[0040] The solvent-free NCO-terminated prepolymer can be synthesized by first mixing a polyol and a silane coupling agent capable of being grafted to a urethane prepolymer. Then pure unmodified 4,4′ diphenylmethane diisocyanate is added. It is disclosed that the composition is reacted at a certain temperature and the product is cooled. This is called a reverse feed synthesis route. The MDI, polyol and silane coupling agent capable of being grafted to the urethane prepolymer used are as described above.

[0041] The solvent-free NCO-terminated prepolymer can be synthesized by loading the liquefied polyol into a reaction flask equipped with an agitator, reflux condenser, thermometer and heating jacket. Once the polyol is mixed, the silane coupling agent is added and mixed into the composition. When the mixing of the silane coupling agent is complete, the liquefied pure 4,4' unmodified MDI is added. Once the liquefied pure 4,4' unmodified MDI is mixed, the composition is reacted at a certain temperature. Once the reaction is complete, the modified MDI or isomeric MDI (if necessary) is added, the composition is cooled, and the contents of the flask are discharged.

[0042] A method for synthesizing an NCO-terminated prepolymer is disclosed, the method comprising first mixing a polyol and a silane coupling agent capable of being grafted to a urethane prepolymer, then adding pure unmodified 4,4′ diphenylmethane diisocyanate, reacting the composition at a certain temperature, and cooling the product. The MDI, polyol, and silane coupling agent capable of being grafted to the urethane prepolymer used are as described above. The method is called a reverse feed synthesis route.

[0043] The method of synthesizing an NCO-terminated prepolymer may include loading a liquefied polyol into a reaction flask equipped with an agitator, a reflux condenser, a thermometer, and a heating jacket. The polyols are mixed. Once the polyols are mixed, a silane coupling agent is added and mixed into the composition. When the mixing of the silane coupling agent is complete, liquefied pure 4,4' unmodified MDI is added. Once the pure 4,4' unmodified MDI is added, the composition is mixed. Once the liquefied pure 4,4' unmodified MDI is mixed, the composition is reacted at a certain temperature under stirring. If necessary, modified MDI or isomeric MDI is added. The composition is cooled and the contents of the flask are discharged.

[0044] Adhesives composed of 1 wt % to 99 wt % of the solvent-free NCO-terminated prepolymer of the present disclosure and 1 wt % to 99 wt % of an OH-terminated prepolymer can be produced. The production of adhesives from NCO-terminated prepolymers and OH-terminated prepolymers is well known in the art and is described in Blackley, “ Emulsion polymerization Polymerization "(Wiley,1975); H.Warson," The Applications of Synthetic Resin Latex Synthetic Resin Emulsions) ”, Chapter 2 (Ernest Benn Ltd., London 1972); discussed in U.S. patent application US2008 / 0176996.

[0045] The prepolymers produced separately are contacted with each other and mixed together to produce an adhesive. This mixing can be carried out at any suitable time during the process of forming the adhesive composition and applying the adhesive to the substrate, such as before, during or as a result of the application process. This mixing can be carried out using a suitable conventional mixer (such as an electric, pneumatic or other powered mechanical mixer).

[0046] Example

[0047] Table 1: Materials

[0048]

[0049]

[0050] Table 2: Preparation of experimental samples and inventive samples

[0051]

[0052] Direct Feed, Direct Feed 1 and Reverse Feed refer to the synthesis methods explained in the Detailed Description.

[0053] Production of Comparative Sample 1 (CE1)

[0054] 1100 g of ISONATE, which had been preheated and liquefied at 50°C, TM 125MDR Pure MDI was loaded into a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The temperature was set to 55°C and the system was placed under stirring. 775 g of Bester TM 127 was heated in an oven at 50°C and then mixed with 225g of Bester TM 104 (also heated in an oven at 50°C before addition) and 225g of castor oil were loaded. After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed for 2 hours and 30 minutes with stirring, after which the NCO% was checked to be within specification via volumetric titration. While continuing to stir, the reaction flask was cooled to 60°C and 175g of ISONATE TM OP 50 Pure MDI. After mixing for 35 minutes at 60°C, the final NCO% was checked again via volumetric titration and the temperature was lowered to 45°C before draining the contents of the reaction flask.

[0055] Production of Comparative Sample 2 (ce2)

[0056] 775 g of BESTER which had been preheated and liquefied at 50°C TM BESTER 127 and 225g TM104 was loaded with 225 g of castor oil at 40°C in a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The sample was then mixed for 35 minutes. 1100 g of ISONATE TM 125MDR Pure MDI was heated and liquefied in an oven at 50°C and loaded into a reaction flask. After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed for 3 hours with stirring, after which the NCO% was checked to be within specification via volumetric titration. While continuing to stir, the reaction flask was cooled to 60°C and 175 g of ISONATE TM OP 50 Pure MDI. After mixing for 35 minutes at 60°C, the final NCO% was checked again via volumetric titration and the temperature was lowered to 45°C before draining the contents of the reaction flask.

[0057] Production of Comparative Sample 3 (CE3)

[0058] 1100 g of ISONATE, which had been preheated and liquefied at 50°C, TM 125MDR Pure MDI was loaded into a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The temperature was set to 55°C and the system was placed under stirring. 750 g of Bester TM 127 was heated in an oven at 50°C and then loaded, followed by 200g of Bester TM 104 (also heated in an oven at 50°C before addition), 200 g of castor oil and 75 g of SILQUEST TM A-1100 (the white material quickly leaves the phase). After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed for 3 hours with stirring, after which the NCO% was checked to be within specification via volumetric titration. While continuing to stir, the reaction flask was cooled to 60°C and 175 g of ISONATE TM OP 50 Pure MDI. The temperature was then lowered to 45°C and the contents of the reaction flask were discharged.

[0059] Production of Comparative Sample 4 (CE4)

[0060] 1100 g of ISONATE, which had been preheated and liquefied at 50°C, TM 125MDR Pure MDI was loaded into a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The temperature was set to 55°C and the system was placed under stirring. 750 g of Bester TM 127 was heated in an oven at 50°C and then loaded, followed by 200g of BesterTM 104 (also heated in an oven at 50°C before addition) and 225g of castor oil. After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed with stirring for 2 hours and 30 minutes, after which the NCO% was checked by volumetric titration to be within specification. While continuing to stir, the reaction flask was cooled to 60°C and 75g of Silquest A-1100 was subsequently added (at which point the white material rapidly dephased). The temperature was then set back to 85°C and the composition was kept at that temperature with stirring for 60 minutes. While continuing to stir, the reaction flask was cooled to 60°C and 175g of ISONATE TM OP 50 Pure MDI. The temperature was then lowered to 45°C and the contents of the reaction flask were discharged.

[0061] Production of Invention Sample 1 (IE1)

[0062] 762.5 g of BESTER TM BESTER of 127 and 218.8g TM 104 was loaded with 218.8 g of castor oil at 40°C under stirring in a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The sample was then mixed for 35 minutes. Then 25 g of SILQUEST TM A-1100 was loaded at 40°C under stirring and the sample was mixed for 55 minutes. 1100 g of ISONATE TM 125MDR Pure MDI was heated and liquefied in an oven at 50°C and loaded into a reaction flask. After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed for 3 hours with stirring, after which the NCO% was checked to be within specification via volumetric titration. While continuing to stir, the reaction flask was cooled to 60°C and 175 g of ISONATE TM OP 50 Pure MDI. After mixing for 35 minutes at 60°C, the final NCO% was checked again via volumetric titration and the temperature was lowered to 45°C before draining the contents of the reaction flask.

[0063] Production of Invention Sample 2 (IE2)

[0064] 750 g of BESTER which had been preheated and liquefied at 50°C TM BESTER 127 and 200g TM 104 was loaded with 200 g of castor oil at 40°C under stirring in a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket. The sample was then mixed for 35 minutes. Then 75 g of SILQUEST TMA-1100 was loaded at 40°C under stirring and the sample was mixed for 55 minutes. 1100 g of ISONATE TM 125MDR Pure MDI was heated and liquefied in an oven at 50°C and loaded into a reaction flask. After the last addition, the temperature was set to 85°C and the reaction was allowed to proceed for 3 hours with stirring, after which the NCO% was checked to be within specification via volumetric titration. While continuing to stir, the reaction flask was cooled to 60°C and 175 g of ISONATE TM OP 50 Pure MDI. After mixing for 35 minutes at 60°C, the final NCO% was checked again via volumetric titration and the temperature was lowered to 45°C before draining the contents of the reaction flask.

[0065] Experimental Production of OH-Terminated Prepolymers

[0066] 2225g of VORANOL TM CP 775 POLYOL was charged into a reaction flask equipped with a stirrer, reflux condenser, thermometer and heating jacket at 55°C under stirring and mixed for 60 minutes. 275 g of ISONATE TM 125MDR PureMDI was preheated and liquefied in an oven at 50°C and then loaded into a reaction flask. The temperature was then set to 60°C for 10 minutes. It was then raised to 85°C. The reaction was stirred for 2 hours and then the NCO% was confirmed to be 0 by volumetric titration. While continuing to stir, the reaction flask was then cooled to 40°C and the contents were then discharged.

[0067] Table 3: Properties of the samples of the present invention and the comparative samples

[0068]

[0069] Figure 1 and Figure 2 The turbid samples produced using CE1 and CE2 are shown. Figure 3 and Figure 4 Clear samples are shown produced when IE1 and IE2 were used. This, combined with the data in Table 3 above, indicates that stable NCO terminated prepolymers based on monomeric, pure, unmodified 4,4'MDI can be obtained when a silane coupling agent is used during prepolymer synthesis.

[0070] Table 4: Evolution of the residence time at 40 °C

[0071]

[0072]

[0073] Retention time test procedure

[0074] In a typical experiment, the selected adhesive system was premixed at room temperature for 1 minute according to the mixing ratio in Table 3. Subsequently, 20 grams of the mixed adhesive was placed in a HT-2DB-100 aluminum cuvette, and the cuvette was placed in a Brookfield DV-III programmable rheometer and adjusted to 40° C. The rheometer monitored the increase in viscosity over time using an SC4-28 spindle at a speed of 100 rpm until 95% torque was reached, then 40 rpm until 95% torque was reached, and finally 10 rpm until 95% torque was reached.

[0075] Table 5: Machine life cleaning test

[0076]

[0077]

[0078] Machine Life Cleaning Test Procedure

[0079] In a typical experiment, the selected adhesive system was premixed at room temperature for 1 minute according to the mixing ratio in Table 5 and then deposited on the fixed cylinder of a Nordmeccanica Duplex SL 1-Shot solventless laminator pre-set to 40°C. Typically, 20g of each mixed adhesive system to be tested was placed on the cylinder. Before the test began, each individual sample was placed on a separately marked point. The system was placed for 60 minutes, after which the visual appearance and whitening of all systems were checked, while the viscosity increase was checked by contacting the adhesive system while wearing rubber gloves. Any adhesive system that was almost completely hardened after 60 minutes was tried to be cleaned with ethyl acetate. If cleaning is possible within 2 minutes, the machine life is rated as 60 minutes. If cleaning takes more than 2 minutes, the machine life is rated as 45 minutes. If cleaning with ethyl acetate is impossible, a special cleaning product is used and the machine life is rated as 45 minutes. All adhesive systems that still need to be hardened after 60 minutes are placed on the cylinder for another 30 minutes, after which the same steps are performed on all adhesive systems that feel almost completely hardened. This 30 minute waiting and testing procedure was repeated until all samples felt almost completely hardened.

Claims

1. A solvent-free NCO-terminated prepolymer, the solvent-free NCO-terminated prepolymer comprising the reaction product of: a. Pure unmodified 4,4'-diphenylmethane diisocyanate b. Silane coupling agent capable of grafting to urethane prepolymer c. Polyols.

2. The solvent-free NCO-terminated prepolymer according to claim 1, wherein the solvent-free NCO-terminated prepolymer is stable and non-dimeric, and wherein a minimum amount of pure modified diisocyanate terminated by a silane coupling agent is produced, so that the synthesized solvent-free NCO-terminated prepolymer is transparent in liquid form.

3. The solvent-free NCO-terminated prepolymer of claim 1, wherein the silane coupling agent capable of being grafted to the urethane prepolymer accounts for greater than 0.1 wt% based on the weight of the pure unmodified 4,4'-diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer and the polyol composition.

4. The solvent-free NCO-terminated prepolymer according to any preceding claim, wherein the silane coupling agent capable of grafting to the urethane prepolymer has the following structure, and wherein R is an amino, epoxy, carboxyl, isocyanate, anhydride or urethane group:

5. The solvent-free NCO-terminated prepolymer according to any preceding claim, wherein the silane coupling agent capable of grafting to the urethane prepolymer is (3-aminopropyl)triethoxysilane.

6. The solvent-free NCO-terminated prepolymer according to any preceding claim, wherein the NCO-terminated prepolymer is not the reaction product of a composition containing more than 2 weight percent of 2,4' diphenylmethane diisocyanate based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, a silane coupling agent capable of grafting to a urethane prepolymer, and a polyol composition.

7. A solvent-free NCO-terminated prepolymer, wherein the solvent-free NCO-terminated prepolymer is synthesized by the following steps: a. First mix the polyol and the silane coupling agent that can be grafted to the urethane prepolymer b. Then add pure unmodified 4,4' diphenylmethane diisocyanate c. allowing the composition to react at a certain temperature d. Cool the product.

8. The solvent-free NCO-terminated prepolymer of claim 7, wherein the silane coupling agent capable of being grafted to the urethane prepolymer accounts for greater than 0.1 wt% based on the weight of the pure unmodified 4,4'-diphenylmethane diisocyanate, the silane coupling agent capable of being grafted to the urethane prepolymer, and the polyol composition.

9. The solvent-free NCO-terminated prepolymer according to claims 7 to 8, wherein the silane coupling agent capable of being grafted to the urethane prepolymer has the following structure, and wherein R is an amino, epoxy, carboxyl, isocyanate, anhydride or urethane group:

10. The solvent-free NCO-terminated prepolymer according to claims 7 to 9, wherein the silane coupling agent capable of grafting to the urethane prepolymer is (3-aminopropyl)triethoxysilane.

11. The solvent-free NCO-terminated prepolymer according to claims 7 to 10, wherein the solvent-free NCO-terminated prepolymer is not the reaction product of a composition containing more than 2 wt% of 2,4'-diphenylmethane diisocyanate based on the weight of the pure unmodified 4,4'-diphenylmethane diisocyanate, a silane coupling agent capable of grafting to a urethane prepolymer, and a polyol composition.

12. A method for synthesizing an NCO-terminated prepolymer, the method comprising: a. First mix the polyol and the silane coupling agent that can be grafted to the urethane prepolymer b. Then add pure unmodified 4,4' diphenylmethane diisocyanate c. allowing the composition to react at a certain temperature d. Cool the product.

13. The method of claim 12, wherein the silane coupling agent capable of grafting to the urethane prepolymer comprises greater than 0.1 wt% based on the weight of the pure unmodified 4,4'-diphenylmethane diisocyanate, the silane coupling agent capable of grafting to the urethane prepolymer and the polyol composition.

14. The method according to claims 12 to 13, wherein the silane coupling agent capable of being grafted to the urethane prepolymer has the following structure, and wherein R is an amino, epoxy, carboxyl, isocyanate, anhydride or urethane group:

15. The method according to claims 12 to 14, wherein the silane coupling agent is (3-aminopropyl)triethoxysilane.

16. The method of claims 12 to 15, wherein the NCO terminated prepolymer is not the reaction product of a composition containing more than 2 weight percent 2,4' diphenylmethane diisocyanate based on the weight of the pure unmodified 4,4' diphenylmethane diisocyanate, a silane coupling agent capable of grafting to a urethane prepolymer, and a polyol composition.

17. An adhesive comprising the reaction product of: a. 1% to 99% by weight of a solvent-free NCO-terminated prepolymer according to claim, based on the weight of the reaction mixture, and b. 1 to 99 wt. % of OH-terminated prepolymer, based on the weight of the reaction mixture.

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