WO2024129697A1

WO2024129697A1 - High performance polyurethane elastomers

Info

Publication number: WO2024129697A1
Application number: PCT/US2023/083578
Authority: WO
Inventors: Marcin GRIGORIEW
Original assignee: Dow Global Technologies Llc
Priority date: 2022-12-16
Filing date: 2023-12-12
Publication date: 2024-06-20

Abstract

The present disclosure is concerned with a polyurethane elastomer that is a reaction product of (i) of an aminobenzoate diamine chain extender of Formula I: Formula I; (ii) a polyester polyol; (iii) 1,4 butanediol; and (iv) 4,4'-methylene diphenyl diisocyanate.

Description

HIGH PERFORMANCE POLYURETHANE ELASTOMERS

Field of Disclosure

Embodiments of the present disclosure are directed towards elastomers and specifically polyurethane elastomers.

Background

The benchmark technology for high performance polyurethane elastomers is toluene diisocyanate (TDI)/4,4'-Methylenebis(2-chloroaniline), also known as TDI/MbOCA or TDI/MOCA. This composition, however, may be hazardous and brings with its use associated regulatory implications. There are also considerations about the high energy consumption related to the high temperature required to process TDI/MbOCA systems. As a result, customers have tried to switch from TDI/MbOCA to less hazardous and more sustainable MDUGlycol based systems, for the manufacture of elastomers suitable for applications that require high performance polyurethane elastomers that tough and resilient. Such applicants include anvils for cardboard cutting, wheels, rollers and gaskets among other technical articles. However, diphenylmethane diisocyanate (MDI)/Glycol based systems take a long time to cure, which increases demolding times to unsatisfactory levels. MDI technology is also more sensitive to processing conditions like mixing, mixing ratio and temperature. Bubbles or shrinkage marks are also common defects marking MDI technology as more difficult to control in some applications including requiring casting parts in closed or opened moulds like Anvils for cardboard cutting or grading screens.

As a result, there is a need in the art for PU engineering elastomers formulation that can provide improvements in processing and mechanical properties, of value in certain applications, such as anvils for cardboard cutting.

Summary

The present disclosure provides for a process for improvements in PU engineering elastomers formulation that can provide improvements in processing and mechanical properties, of value in certain applications, such as anvils for cardboard cutting, gaskets, wheels, rollers, and other articles that would benefit from the PU engineering elastomers formulations of the present disclosure. Specifically, the present disclosure provides for a multicomponent polyurethane system having an improved curing profile combined with high level mechanical properties and improved aesthetics. Embodiments of the present disclosure introduce an aminobenzoate compound into a polyurethane elastomer reaction mixture that is extended with 1,4- butanediol in a predefined ratio that helps to improve the curing profile while maintaining desirable mechanical properties. Embodiments of the present disclosure also have the potential for processing temperature reduction and a reduction or an eliminating of a high energy consuming post-curing step.

For the various embodiments, the present disclosure provides for a polyurethane elastomer that is a reaction product of (i) 2 to 15 weight percent (wt.%) of an aminobenzoate diamine chain extender of Formula I:

Formula I where n is greater than 2 to less than 4; (ii) 50 to 60 wt.% of a polyester polyol having a Mw of 500 to 4000 g/mol; (iii) 2 to 12 wt.% of 1,4 butanediol; and (iv) 24 to 36 wt. % of 4,4’- methylene diphenyl diisocyanate. For the various embodiments, the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.8: 1 to 2.0:1 (aminobenzoate diamine chain extender : 1,4 butanediol) by weight and where the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%.

Detailed Description

The present disclosure provides for a process for improvements in PU engineering elastomers formulation that can provide improvements in processing and mechanical properties, of value in certain applications, such as anvils for cardboard cutting, gaskets, wheels, rollers and other articles that would benefit from the PU engineering elastomers formulations of the present disclosure. Specifically, the present disclosure provides for a multicomponent polyurethane system having an improved curing profile combined with high level mechanical properties and improved aesthetics. Embodiments of the present disclosure introduce an aminobenzoate compound into a polyurethane elastomer reaction mixture that is extended with 1,4- butanediol in a predefined ratio that helps to improve the curing profile while maintaining desirable mechanical properties. Embodiments of the present disclosure also have the potential for processing temperature reduction and a reduction or an eliminating of a high energy consuming post-curing step. For the various embodiments, the present disclosure provides for a polyurethane elastomer that is a reaction product of (i) 2 to 15 weight percent (wt.%) of an aminobenzoate diamine chain extender of Formula I:

where n is greater than 2 to less than 4; (ii) 50 to 60 wt.% of a polyester polyol having a Mw of 500 to 4000 g/mol; (iii) 2 to 12 wt.% of 1,4 butanediol; and (iv) 24 to 36 wt. % of 4,4’- methylene diphenyl diisocyanate. For the various embodiments, the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.8: 1 to 2.0: 1 (aminobenzoate diamine chain extender : 1,4 butanediol) by weight and where the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%.

(i) Aminobenzoate Diamine Chain Extender

For the various embodiments, the polyurethane elastomer formed via the reaction product with (i) 2 to 15 wt.% of the aminobenzoate diamine chain extender of Formula I:

Formula I where n is greater than 2 to less than 4. For the various embodiments, the polyurethane elastomer can be formed via the reaction product with (i) 5 to 12 wt.% of the aminobenzoate diamine chain extender of Formula I. For the various embodiments, n can also have a range of 3 to 4. Other preferred values for n include a range of 3.3 to 3.7, where a value of 3.5 for n is preferred.

(ii) Polyester Polyol

For the various embodiments, the polyurethane elastomer formed via the reaction product with (ii) 50 to 60 wt.% of a polyester polyol having a Mw of 500 to 4000 g/mol. For the various embodiments, the polyurethane elastomer can be formed via the reaction product with (ii) 53 to 58 wt.% of the polyester polyol. For the various embodiments, the polyester polyol is a polyethylene adipate) polyester polyol. The poly(ethylene adipate) polyester polyol can have the following structure of Formula II:

Formula II where n can be a real number of 2.5 to 25. Preferably, poly(ethylene adipate) polyester polyol has a Mw of 1000 to 3000 g/mol, where 2000 g/mol is a preferred value. The functionality of the poly(ethylene adipate) polyester polyol can be a value of 2.

The poly(ethylene adipate) polyester polyol of the present disclosure can be formed from a polycondensation reaction between monoethylene glycol and adipic acid (dimethyl adipate), as is known in the art.

(iii) 1,4 Butanediol

For the various embodiments, the polyurethane elastomer formed via the reaction product with (iii) 2 to 12 wt.% of 1,4 butanediol. For the various embodiments, the polyurethane elastomer can be formed via the reaction product with (iii) 4 to 9 wt.% of 1,4 butanediol.

(iv) 4,4’-Methylene Diphenyl Diisocyanate

For the various embodiments, the polyurethane elastomer formed via the reaction product with (iv) 24 to 36 wt. % of 4,4’ -methylene diphenyl diisocyanate. For the various embodiments, the polyurethane elastomer can be formed via the reaction product with (iv) 28 to 32 wt. % of 4,4’-methylene diphenyl diisocyanate (4,4’-MDI). For the various embodiments, the 4,4’-MDI can be pure 4,4’-MDI (100 wt.% 4,4’-MDI). Alternatively, the 4,4’-MDI for the present disclosure can also include small amounts of other MDI isomers. For example, suitable 4,4’-MDI for the present disclosure can include 2,4’-MDI up to 2 wt.% (e.g., 98 wt.% 4,4’-MDI and 2 wt.% 2,4’-MDI). Suitable 4,4’-MDI for the present disclosure can also include 2,4’-MDI up to 5 wt.% (e g., 98 wt.% 4,4’-MDI and 5 wt.% 2,4’-MDI).

For the various embodiments, the aminobenzoate diamine chain extender of Formula I can be pre-mixed with the polyethylene adipate) polyester polyol prior to the reaction that forms the polyurethane elastomer. Such a pre-mixing can provide benefits from a processing point of view, which include (a) the pre-mixing helps to reduce freezing temperature of the polyethylene adipate) polyester polyol, which allows the polyurethane elastomer to be formed at a processing temperature that is lower than is typical e.g., the reaction components (i)-(i v) can be processed at 50 °C instead of 70 °C typically required for the poly(ethylene adipate) polyester polyol). As appreciated by one skilled in the art, practical processing temperatures are usually significantly higher than the freezing points to reduce the risk of material freezing at “cold spots” of the dispensing machine and thereby causing a blockage. In addition, premixing the aminobenzoate diamine chain extender of Formula I with the poly(ethylene adipate) polyester polyol prior to the reaction that forms the polyurethane elastomer reduces number of feed lines in the mixing and dispensing system, thereby allowing for the polyurethane elastomer to be formed with a typical three component dispensing machine. In such a three component system, the polyurethane elastomer can be formed by mixing from separate lines (a)-(c): (a) the 1,4-butanediol, (b) the pre-mixed aminobenzoate diamine chain extender of Formula I and the poly(ethylene adipate) polyester polyol; and (c) a polyurethane prepolymer, as provided herein. Other mixing options are available as are known in the art.

Polyurethane Prepolymer

For the various embodiments, prior to forming the reaction product of (i) through (iv) to product the polyurethane elastomer of the present disclosure, the (iv) 4,4’-MDI can first be reacted with (ii) the polyester polyol, as provided herein, to form a polyurethane prepolymer. For the various embodiments, the polyurethane prepolymer is the reaction product of all of the (iv) 4,4’ -MDI used in forming the polyurethane elastomer with (i) through (iv) with less than all of the (ii) polyester polyol used in the reaction to form the polyurethane elastomer. For example, the polyurethane prepolymer can be the reaction product of 100 wt.% of the (iv) 4,4’- methylene diphenyl diisocyanate used in the reaction to form the polyurethane elastomer (e.g., all, 100 wt.%, of the 24 to 36 wt.% of 4,4’-MDI used in forming the polyurethane elastomer with (i) through (iv)) with 90 to 99 wt.% of the (ii) polyester polyol (e.g., less than all of the (ii) polyester polyol used in the reaction to form the polyurethane elastomer with (i) through (iv)) used in the reaction to form the polyurethane elastomer. In this approach, line (b) of the three component system discussed above will include the pre-mixed aminobenzoate diamine chain extender of Formula I and the remainder of the poly(ethylene adipate) polyester polyol not used in forming the polyurethane prepolymer that is being provided in line (c). The present approach also allows for different hardness grades of the resulting polyurethane elastomer to be achieved through adjustment to the wt.% of the (ii) polyester polyol used in forming the polyurethane prepolymer.

In an additional embodiment, it is also possible that prior to forming the reaction product of (i) through (iv) to produce the polyurethane elastomer of the present disclosure, all of the (iv) 4,4’ -MDI used in forming the polyurethane elastomer of the present disclosure is first reacted with all of (ii) the polyester polyol, as provided herein, to form the polyurethane prepolymer. So, for example, the polyurethane prepolymer can be the reaction product of 100 wt.% of the (iv) 4,4’-methylene diphenyl diisocyanate used in the reaction to form the polyurethane elastomer (e.g., all, 100 wt.%, of the 24 to 36 wt.% of 4,4’-MDI used in forming the polyurethane elastomer with (i) through (iv)) with 100 wt.% of the (ii) polyester polyol (e.g., all, 100 wt.%, of the (ii) polyester polyol used in the reaction to form the polyurethane elastomer with (i) through (iv)) used in the reaction to form the polyurethane elastomer. In this approach, line (a) can include the 1,4-butanediol, line (b) can include the aminobenzoate diamine chain extender of Formula I, and line (c) can include the polyurethane prepolymer that includes the reaction product of all of the poly(ethylene adipate) polyester polyol having been pre-reacted with all of the 4,4’ -MDI to form the polyurethane prepolymer.

For the various embodiments, the resulting polyurethane prepolymer discussed herein can have an isocyanate (NCO) group content of 6 to 16 wt.% based on the total weight of the polyurethane prepolymer.

For the various embodiments, the reaction between the (iv) 4,4’-MDI and (ii) the polyester polyol to form the polyurethane prepolymer can take place under vacuum or at atmospheric pressure in a dry nitrogen environment at a temperature of 40 to 80 °C.

As discussed herein the present disclosure provides for a polyurethane elastomer that is a reaction product of (i) 2 to 15 weight percent (wt.%) of an aminobenzoate diamine chain extender of Formula I:

where n is greater than 2 to less than 4; (ii) 50 to 60 wt.% of a polyester polyol having a Mw of 500 to 4000 g/mol; (iii) 2 to 12 wt.% of 1,4 butanediol; and (iv) 24 to 36 wt. % of 4,4’-MDI. For the various embodiments, the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.8: 1 to 2.0:1 (aminobenzoate diamine chain extender : 1,4 butanediol) by weight and where the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%. In an additional embodiment, the present disclosure provides for a polyurethane elastomer that is a reaction product of (i) 5 to 12 wt.% of the aminobenzoate diamine chain extender of Formula I; (ii) 53 to 58 wt.% of the polyester polyol; (iii) 4 to 9 wt.% of 1,4 butanediol; and (iv) 28 to 32 wt. % of 4,4’-MDI, where the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.9:1 to 1.75:1 by weight and where the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%. In another embodiment, the present disclosure provides for a polyurethane elastomer that is a reaction product of (i) 6 to 10 wt.% of the aminobenzoate diamine chain extender of Formula I; (ii) 54 to 57 wt.% of the polyester polyol; (iii) 5.5 to 7 wt.% of 1,4 butanediol; and (iv) 29 to 31 wt. % of 4,4’ -MDI, where the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.95: l to 1.65: 1 by weight and where the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%. For the various embodiments, the polyurethane elastomer is not formed with either toluene diisocyanate or 4,4'-Methylenebis(2-chloroaniline).

Polyurethane Elastomer Reaction

For the various embodiments, reactions to form the polyurethane elastomer of the present disclosure can include the following conditions. Mixing of the components in the reaction to form the polyurethane elastomer can occur in a dynamic polyurethane dispensing machine as are known in the art. Preferably, the dynamic polyurethane dispensing machine is a low pressure dynamic polyurethane dispensing machine as are known in the art. Mixing of the components can occur in the mix head of the polyurethane dispensing machine, where two or more supply lines (e.g., three lines (a)-(c)) containing the components can be mixed prior to dispensing the polyurethane reactive mixture. Dispensing the reactive mixture can be as a spray or can be poured from equipment as is known in the art.

Reaction conditions for forming the polyurethane elastomer of the present disclosure can include preheating each of the components in the reactive system. For example, for a low pressure dispensing machine the processing conditions can include supplying the polyurethane prepolymer, as provided herein, at a temperature of 50 to 70 °C; the aminobenzoate diamine chain extender of Formula I or the mixture of the aminobenzoate diamine chain extender of

Formula I and polyester polyol at a temperature of 50 to 70 °C; and the 1,4 butanediol at a temperature of 30 to 50 °C. The reactions can occur under positive pressure from dry air or nitrogen (0.5 to 1 bar). Mould temperatures can be from 80 to 120 °C. Post-curing times in forming the polyurethane elastomer of the present disclosure can be from 12 to 24 hours at a temperature of 80 to 100 °C. Conditioning of the resulting polyurethane elastomer can be, for example, for seven days at ambient conditions, for example at 23+/-2 °C and 50+/-5% relative humidity.

EXAMPLES The examples below are provided to be illustrative only and are not intended to define or limit the embodiments in any way. In the Inventive Examples (EX) and Comparative Examples (CE), various terms and designations for materials are used including, for instance, the following:

Table 1. Materials

Tests

The following test procedures were used herein.

Hardness was measured according to ISO 868 (unit Shore Hardness A: ShA). Measurements were taken 7 days after post-curing.

Pot Life was measured as the time when the mixed composition was still visually homogenous and had a viscosity low enough to be transferred into the mold. Typically, viscosity threshold is marked as below 20000 mPas as measured by a Brookfield viscometer measured at 23 °C.

Demold Time was measured as the time after which a standard sample (70 mm diameter, 15 - 20 mm height cylinder) could be removed from the mold without causing defects like, for example, permanent distortion, marks or fingerprints. Samples preparation: casting by dispensing machine. All components of the system were delivered from pre-heated tanks of the dispensing machine into the mixing chamber by gear pumps and then mixed composition is transferred into the cup/container in which the curing material is carried and transferred into the mold placed inside the pre-heated oven.

The demold test was used in combination with hardness measurement (e.g., hardness after 20 min. at 100 °C and hardness after 30 min. at 100 °C), to give an indication of the minimum molding time.

Tensile Strength at Break MPa was measured according to ISO 527-Type 5 (2 mm thick specimen).

300% Modulus MPa was measured according to ISO 527.

Angle tear strength was measured according to ISO 34-Pt B, Proc. A.

Elongation at break was measured according to ISO 527.

Compression set (22 hour/70 °C) was measured according to ISO 815-1 (Part 1).

Polyurethane Prepolymer Synthesis

Polyurethane Prepolymer 1

Polyurethane Prepolymer 1 was formed by reacting 4,4’ MDI (36 wt.%, based on the total weight of polyurethane prepolymer 1) with Polyol 1 (64 wt.% based on the total weight of the polyurethane prepolymer 1). The reaction was performed by loading the 4,4’ MDI in a reactor, which was heated to the temperature of 45 °C under inert atmosphere (nitrogen), and then in presence of a small amount of acidifying agent (benzoyl chloride, 200 ppm). Polyol 1 was added progressively to the 4,4’ -MDI under mixing. Polyol 1 was added at a speed that allowed for the removal of the heat generated by the reaction. After completing the addition of Polyol 1, the prepolymer was digested by maintaining the reaction mixture at 70 °C with stirring while monitoring the isocyanate (NCO) content in accordance with the method set forth in ASTM D5155. Prepolymer 1 formation was considered complete when the NCO content reached the target NCO value of 9.45 wt.%, based on the total amount of prepolymer.

Machine Casting

Processing temperatures for the reactants was as follows: Polyurethane Prepolymer 1, 70 °C; Polyol 1, 50 - 70 °C and Chain Extenders (e.g., Chain Extender 1 or Chain Extender 2 each with Chain Extender 3 (BDO)) 30 - 50 °C.

Machine processing using a three component (Polyurethane Prepolymer 1 + Polyol 1 + Chain Extenders) low pressure dispensing machine (Polytec DG 133) equipped with recirculation and mass flow meter for each component. Mixing speed was from 3000 - 5000 rpm; flow rate was from 2 - 5 kg/min. For the Examples (EX) and Comparative Examples (CE) the aminobenzoate chain extender (e.g., Chain Extender 1 or Chain Extender 2) was used in combination with Chain Extender 3 (BDO).

Table 2 shows the impact of changing the weight ratio between the aminobenzoate chain extender and BDO. For example, a weight ratio of the two aminobenzoate chain extenders near 1 :1 helped to increase hardness build up after 20 and 30 minutes. This significantly improved stiffness and reduces demolding time. Further increasing the amount of BDO is undesirable as it leads to slower curing speed hence longer demolding time. Further increasing the amount of aminobenzoate Chain Extender is undesirable as it would negatively impact demolding time. The results of Table 2 are discussed as follows.

CE A is the comparative example only using BDO, demold time is too long. By replacing BDO with aminobenzoate (see other examples in the Table) the demold time is substantially faster. CE B describes the combination of aminobenzoate/BDO that is at too high a ratio, hence resulting in insufficient improvement in demolding and in polymer properties. CE C example is related to larger Mw aminobenzoate (Core Mw of 650 g/mol) which shows good curing profile, longer pot-life and faster hardness build up, but significantly worse mechanical properties especially in terms of Tensile Strength at Break. CE D is related to a combination of larger Mw aminobenzoate (Core Mw of 650 g/mol) with BDO at the same ratio as EX 2. CE D shows the advantage of improved curing profile, but mechanical properties are worse when compared with the EX 1 and EX 2. EX 1 and EX 2 describe the use of aminobenzoate Chain Extender of the present disclosure (n > 2 and < 4), in combination with BDO at the weight ratio of the present disclosure, delivering an improvement of both curing profile and polymer properties. Table 2 below reports the experiments and the results in terms of polymer hardness, pot life, demolding time, and selected mechanical properties. In Table 2, the ratios per 100 parts Polyurethane Prepolymer 1 are determined by stoichiometry and hardness targets: 0.96 (or 1.04 Index) Stoichiometry and 88 - 92 ShA hardness. Table 2

Claims

What is claimed is:

1. A polyurethane elastomer comprising a reaction product of:

(i) 2 to 15 weight percent (wt.%) of an aminobenzoate diamine chain extender of Formula I:

Formula I wherein n is greater than 2 to less than 4;

(ii) 50 to 60 wt.% of a polyester polyol having a Mw of 500 to 4000 g/mol;

(iii) 2 to 12 wt.% of 1,4 butanediol; and

(iv) 24 to 36 wt. % of 4,4’-methylene diphenyl diisocyanate, wherein the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.8: 1 to 2.0: 1 by weight and wherein the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%.

2. The polyurethane elastomer of claim 1, wherein prior to forming the reaction product of (i) through (iv), (iv) is first reacted with (ii) to form a polyurethane prepolymer.

3. The polyurethane elastomer of claim 2, wherein the polyurethane prepolymer is the reaction product of:

100 wt.% of the (iv) 4,4’ -methylene diphenyl diisocyanate used in the reaction to form the polyurethane elastomer; and

90 to 99 wt.% of the (ii) polyester polyol used in the reaction to form the polyurethane elastomer.

4. The polyurethane elastomer of claims 2-3, wherein the polyurethane prepolymer has an isocyanate (NCO) group content of 6 to 16 wt.% based on the total weight of the polyurethane prepolymer.

5. The polyurethane elastomer of any one of claims 1 -4, wherein the polyester polyol is a poly(ethylene adipate) polyester polyol.

6. The polyurethane elastomer of any one of claims 1-4, wherein the polyester polyol is a poly(ethylene adipate) polyester polyol having a Mw of 1000 to 3000 g/mol.

7. The polyurethane elastomer of any one of claims 1-6, wherein for Formula I n is 3 to 4.

8. The polyurethane elastomer of any one of claims 1-6, wherein for Formula I n is 3.5.

9. The polyurethane elastomer of any one of claims 1-7, wherein the polyurethane elastomer is the reaction product of

(i) 5 to 12 wt.% of the aminobenzoate diamine chain extender of Formula I;

(ii) 53 to 58 wt.% of the polyester polyol;

(iii) 4 to 9 wt.% of 1,4 butanediol; and

(iv) 28 to 32 wt. % of 4,4’-methylene diphenyl diisocyanate, wherein the aminobenzoate diamine chain extender has a ratio to the 1,4 butanediol of 0.9: 1 to 1.75: 1 by weight and wherein the wt.% for (i) through (iv) are based on the overall weight of (i) through (iv) and the total weight of (i) through (iv) does not exceed 100%.

10. The polyurethane elastomer of any one of claims 1-9, wherein the polyurethane elastomer is not formed with either toluene diisocyanate or 4,4'-Methylenebis(2-chloroaniline).