Shear process for improving phase stability of recoverable polyol dispersions

Abstract

The phase stability of recoverable polyol dispersions is improved by shearing the dispersions using rotors / stators or other suitable devices. After shearing, the recoverable polyol dispersion has a lower Lumisizer stability index (indicating improved phase stability). The improved storage stability results in easier storage, transportation and use of the recoverable polyol dispersion.

Description

[0001] This invention relates to recyclable polyol dispersions and methods for improving their phase stability.

[0002] Polyurethane can be decomposed into useful polyol products via various chemical dissolution processes. Examples of chemical dissolution processes include hydrolysis, acidolysis, and glycolysis, in which water, carboxylic acid (or equivalently, carboxylic anhydride), and "naïve" polyols are used as reagents, respectively. Chemical dissolution processes typically involve glycolysis as well as hydrolysis and / or acidolysis, which may occur simultaneously, sequentially, or partially simultaneously and partially sequentially. The products of chemical dissolution processes are typically dispersions having a liquid polyol phase and a dispersed phase, the liquid polyol phase comprising "recoverable" polyols, i.e., liquid polyols as products of the decomposition reaction, and the dispersed phase comprising solid oligomer decomposition products in small particulate form. The liquid polyol phase formed in glycolysis processes typically contains naïve polyols in addition to recoverable polyols. The dispersions produced in these chemical dissolution processes have been shown to be used in the preparation of rigid and flexible polyurethane foams.

[0003] The problem with these dispersions is that they are often unstable. Over time, the dispersed solids tend to settle in storage and transport equipment, and even in foam production lines and mixing heads. This leads to various problems, such as inconsistencies in the composition of the dispersion, inconsistencies in foam products made using the dispersion, and equipment contamination. A method for stabilizing dispersions to reduce sedimentation is needed. This solution preferably does not interfere with the polyurethane foaming process utilizing the dispersion, and also preferably does not cause significant adverse effects when the dispersion is used to prepare polyurethane foam.

[0004] The present invention is a method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, the method comprising shearing the initial recyclable polyol dispersion at an average shear rate of at least 5500 / s for a period of time sufficient to produce a stable recyclable polyol dispersion having a Lumisizer instability index of at most 0.55.

[0005] The present invention is also a method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, the method comprising shearing the initial recyclable polyol dispersion at an average shear rate of at least 5500 / s for a period of 0.05 seconds to 10 seconds.

[0006] This invention also relates to a method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, the method comprising providing at least 10 4Under the condition of watts of power per kg of starting recyclable material, the initial recyclable polyol dispersion is sheared in a shearing device for a period of time sufficient to produce a stable recyclable polyol dispersion with a Lumisizer instability index of up to 0.55.

[0007] Surprisingly, it has been found that shear-recoverable polyol dispersions significantly improve their phase stability.

[0008] As used herein, a “recoverable polyol dispersion” is a mixture of (i) liquid polyols and (ii) dispersed particles containing one or more urethane, urea, and / or imide groups, produced in the chemical dissolution of polyurethane and / or polyurea polymers. Liquid polyols include polyols (“recoverable polyols”) regenerated from polyurethane and / or polyurea polymers in a chemical dissolution reaction, and generally also include “virgin” polyols. “Virtual” polyols are polyols added to the chemical dissolution process and do not include polyols produced from the chemical dissolution of polyurethane and / or polyurea polymers or their chemical dissolution. Dispersed particles containing one or more of urethane, urea, and / or imide groups are also materials produced in the chemical dissolution of polyurethane and / or polyurea polymers.

[0009] Liquid polyols may consist of, for example, 10% to 100% by weight, particularly 20% to 60% by weight, of a recyclable polyol and a corresponding 0% to 90% by weight, particularly 40% to 80% by weight, of a virgin polyol. Liquid polyols may include, for example, virgin polyether polyols having a number-average molecular weight (according to gel permeation chromatography according to polystyrene standards) of 400 g / mol to 16,000 g / mol, particularly 400 to 4,000 g / mol, and a hydroxyl functionality of 2 to 8, 2 to 6, or 2 to 4. Recyclable polyols may also include one or more polyether polyols having similar molecular weights and hydroxyl functionalities.

[0010] Alternatively or otherwise, liquid polyols may include short-chain diols and / or short-chain triols having a molecular weight of up to 250 g / mol or up to 150 g / mol, including, for example, one or more of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, trimethylolpropane, triethylolpropane, etc. The short-chain diols and / or short-chain triols may comprise the original material as well as the diols and / or triols formed during a chemical dissolution reaction.

[0011] The dispersed particles may constitute, for example, 1% to 60% of the total weight of the starting recyclable polyol dispersion, preferably 5% to 60% or 10% to 50%. In some embodiments, at least a portion of the dispersed particles contains an imide group. The imide group may be formed, for example, by adding an imide precursor in a chemical dissolution process, as described more fully below. The dispersed particles typically have a particle size of up to 50 μm (D90) (i.e., 90% by volume of the particles have a particle size of 50 μm or less), as measured by laser diffraction, such as according to ASTM E3340. The dispersed particles are insoluble in the liquid polyol and are not grafted or otherwise chemically bonded to the liquid polyol.

[0012] The starting recyclable polyol dispersion has a Lumisizer instability index (or simply "instability index") of at least 0.60. The instability index of the starting recyclable polyol dispersion can be at least 0.65, at least 0.70, or at least 0.75. A lower instability index value indicates higher stability, i.e., less particle settling. The instability index is determined according to ISO 13318-2 (2007) or an equivalent method. The instability index can be determined using a LUMiSizer 6110-77 instrument (LUM GmbH) by centrifuging the material at 4000 rpm for 5 hours. Software packages from the same supplier (SEPView Explorer, LUM GmbH) can be used to calculate the instability index.

[0013] In some embodiments, the starting recyclable polyol dispersion has a hydroxyl value of 20 mg KOH / g to 650 mg KOH / g, particularly 25 mg KOH / g to 500 mg KOH / g (according to ASTM D4274 D); a total basicity of 1 milliequivalent per gram or less, particularly 0.5 milliequivalent per gram or less (ASTM D6979); and an acid value of 20 mg KOH / g or less, particularly 5 mg KOH / g or less (DIN 53402). Stable recyclable polyol dispersions typically have similar hydroxyl and acid values ​​to the starting recyclable polyol dispersion.

[0014] The term "chemical dissolution" or "chemically dissolving decomposition" refers to the decomposition of polyurethane and / or polyurea polymers by chemical means. "Chemical dissolution" includes so-called "glycolysis," in which a polyol reacts with the polyurethane and / or polyurea polymer to decompose it; hydrolysis, in which water is used as the agent for polymer decomposition; acidolysis, in which Brønsted acids, particularly diacids (such as dicarboxylic acids or equivalently, carboxylic anhydrides), are used as decomposition agents; and ammonolysis, in which primary or secondary amine compounds are used as decomposition agents. Chemical dissolution may include multiple decomposition methods among these methods. For example, polyurethane and / or polyurea polymers can be subjected to the following methods to produce a recyclable polyol dispersion: glycolysis and acidolysis, glycolysis and hydrolysis, glycolysis and ammonolysis, glycolysis, acidolysis and hydrolysis, or even glycolysis, acidolysis, ammonolysis and hydrolysis.

[0015] Chemical dissolution processes for producing starting recyclable polyol dispersions are well known. For example, U.S. Patent 2,937,151 describes an alcoholysis (sometimes referred to as "glycolysis") process. U.S. Patent 3,109,824 describes an acidolysis process. U.S. Patent 3,404,103 describes an ammonolysis process. Any of these processes is suitable for producing the starting recyclable polyol dispersions used in this invention.

[0016] Other suitable chemical dissolution processes include the process described in U.S. Patent 5,357,006, in which a monofunctional glycidyl ether is added to the glycolysis process to reduce the amine value of the recyclable polyol dispersion, and the process described in U.S. Patent 5,763,692, in which a cyclic carbonate is added to the glycolysis process to achieve the same effect. It is believed that the monofunctional glycidyl ether and the cyclic carbonate react with the amine groups on the dispersed particles produced by glycolysis to “cover” the chain ends.

[0017] A particularly preferred chemical dissolution process is a glycolysis / acidolysis process, in which a polyurethane and / or polyurea polymer reacts with a polyol and an imide precursor to produce a recyclable polyol dispersion. An example of such a process is described in U.S. Patent 11,124,623. In this process, in a first reaction step, the polyurethane and / or polyurea polymer reacts with an imide precursor and a polyether polyol having a number-average molecular weight (determined by gel permeation chromatography) of 400 g / mol to 6000 g / mol and a hydroxyl functionality of 2 to 4, and then in a second reaction step reacts with a short-chain diol or short-chain triol (with a molecular weight of 250 g / mol or less, preferably 150 g / mol or less) to produce a recyclable polyol dispersion. An "imide precursor" is a material that reacts during the chemical dissolution process to generate imide groups on the dispersed solid particles produced in the chemical dissolution reaction (typically by reaction with a primary amino group). The imide precursor comprises a compound having two or more carboxyl groups, wherein at least one pair of carboxyl groups is located at the 1,2-position relative to each other, and a corresponding carboxylic anhydride. The imide precursor can be, for example, any or more of maleic acid, malic acid, phthalic acid, adipic acid, succinic acid, glutaric acid, dihalophthalic acid and / or tetrahalophthalic acid, trimellitic acid, and their corresponding anhydrides. Imide-containing particles are produced in this process. The reaction temperature in the first step can be in the range of 170 to 210 °C, and the reaction temperature in the second step can be in the range of 180 to 230 °C. Glycolysis / acidolysis is catalyzed by reacting in the presence of a free radical initiator, such as a peroxide compound, a perester compound, or an azo compound.

[0018] The starting polyurethane and / or polyurea polymer is characterized by having urethane groups, urea groups, or both. It may contain other groups formed by the reaction of isocyanates (such as biuret, carbodiimide, ureate esters, isocyanurate esters, etc.). Preferred polyurethane and / or polyurea polymers include polyether chains, particularly homopolymers of 1,2-epoxypropane, homopolymer of ethylene oxide, homopolymer of 1,2-epoxybutane and / or homopolymer of 2,3-epoxybutane, homopolymer of tetrahydrofuran, or copolymers of any two or more of ethylene oxide, 1,2-epoxypropane, 1,2-butene oxide, or 2,3-butene oxide and tetrahydrofuran (e.g., random and / or block copolymers). The polyurethane and / or polyurea polymer can be non-porous, microporous, or porous.

[0019] Preferably, the polyurethane and / or polyurea polymer is or includes post-consumer waste and / or waste polyurethane (such as waste from polyurethane foam manufacturing facilities or facilities that manufacture polyurethane foam into consumer products). Most preferably, the polyurethane and / or polyurea polymer is or includes post-consumer flexible polyurethane foam or waste flexible polyurethane foam. Waste mattresses are a rich source of post-consumer flexible polyurethane foam, which is used to produce recyclable polyol dispersions. Typically, the polyurethane and / or polyurea polymer is chopped into small pieces and chemically dissolved.

[0020] In one aspect of the invention, the initial recyclable polyol dispersion is stabilized by shearing at an average shear rate of at least 5,500 / s. The average shear rate may be at least 10,000 / s or at least 15,000 / s, and may be, for example, at most 100,000 / s, at most 75,000 / s, or at most 50,000 / s. The minimum shear rate during the shearing step is preferably at least 3,000 / s, provided that the average shear rate is at least 5,500 / s. The time during which the initial recyclable polyol dispersion is subjected to the aforementioned shearing conditions may be, for example, at least 0.05 seconds or at least 0.1 seconds, and may be, for example, at most 10 seconds, at most 5 seconds, at most 1 second, or at most 0.5 seconds. More generally, shearing continues at such a shear rate for a period sufficient to produce a stable recyclable polyol dispersion having a Lumisizer instability index of at most 0.55, preferably at most 0.50, or at most 0.45. The shear work (unitless value) performed on the initial recyclable dispersion can be, for example, at least 1200, at least 1500, and can be, for example, up to 50,000, up to 25,000, or up to 12,000. Shearing can be performed in various types of equipment capable of generating the necessary shear, including, for example, rotor / stator types sold by IKA Works, Inc. (Wilmington, Delaware US) and Silverson Machines, Ltd. (Chesham, England); acoustic and ultrasonic mixers, such as Sonolator® (Sonic Corporation, Stratford CT, USA) and the UIP series ultrasonic generators sold by Hielscher Ultrasonics GmbH (Teltow, Germany); grinding equipment, such as bead mills (as described in WO2004 / 020532), etc. Temperatures at or near room temperature (such as 15°C to 35°C) are perfectly suitable, although elevated temperatures, for example, >35°C to 80°C, can be used.

[0021] In another aspect of the invention, when providing at least 10 to the initial recyclable material 4Under the condition of watts of power per kg of starting recyclable material, the starting recyclable polyol dispersion is sheared in a shearing device (such as an ultrasonic generator) for a period of time sufficient to produce a stable recyclable polyol dispersion with a Lumisizer instability index of up to 0.55.

[0022] The shearing step is preferably performed in the absence of fumed silica with a methanol wettability of 10% to 60%. Methanol wettability is measured by weighing 0.2 g of fumed silica and adding it to 20 g of deionized water, then stirring for 1 minute on a high-speed laboratory mixer. The mixture is then visually inspected to see if the fumed silica is uniformly dispersed in the liquid. If so, the methanol wettability is 0. If not, methanol is added incrementally, increasing the proportion of methanol in the methanol / water mixture by 5% by weight each time (i.e., to 5 / 95, 10 / 90, 15 / 85, etc.). After each addition of incremental methanol, the mixture is stirred again on a high-speed laboratory mixer for 1 minute, and then the homogeneity is visually inspected. The minimum weight percentage of methanol that produces a uniform dispersion in this test is the methanol wettability value. The shearing step can be performed in the absence of any type of fumed silica.

[0023] The resulting stable recyclable polyol dispersion is preferably phase stable at 23°C for at least one month, more preferably at least three months, and even more preferably at 50°C for at least one week. Phase stability is evaluated by allowing the sample to stand at a specified temperature for a specified time under static conditions (i.e., without stirring). If no visible precipitation is present at the end of the specified time, the recyclable polyol dispersion is considered phase stable.

[0024] One advantage of this invention is that it achieves a significant improvement in phase stability without significantly increasing viscosity. A decrease in viscosity is often observed after the shearing step. Preferably, this is achieved when using a 25mm parallel plate rheometer with a 1.2mm gap at 25°C and 0.1 seconds. -1 When measured at the shear rate, the viscosity of the stable recyclable polyol dispersion is not greater than the viscosity of the initial recyclable polyol dispersion. More preferably, the viscosity of the stable recyclable polyol dispersion is not greater than 0.85 times, or not greater than 0.75 times, the viscosity of the initial recyclable polyol dispersion. In absolute terms, in some embodiments, the viscosity of the stable recyclable polyol dispersion measured under the above conditions is not greater than 20 Pa. s, not greater than 15 Pa s or not greater than 10 Pa s.

[0025] Stable, recyclable polyol dispersions can be used to prepare various types of polyurethanes, particularly rigid, semi-rigid, and / or flexible polyurethane foams, by reacting with polyisocyanates. Generally, a stable, recyclable polyol dispersion is combined with a polyisocyanate to form a reaction mixture, which is then cured to form polyurethane. Curing is typically spontaneous, even when the stable, recyclable polyol dispersion is combined with the polyisocyanate at approximately room temperature. However, if desired, the curing rate can be adjusted using a catalyst and / or an increased curing temperature. Curing can be performed in a mold; if desired, polyurethane foams can be prepared using a free-flowing foaming process in which the foam formulation is dispensed into an open slot or open box and allowed to rise without vertical constraints. A variety of other components may be present in the reaction mixture, including, for example:

[0026] A) Added polyols (such as polyether and / or polyester polyols) having a hydroxyl value of 375 mg KOH / g or lower and 1 to 8 hydroxyl groups per molecule;

[0027] B) Short-chain polyols having 2 to 4 hydroxyl groups per molecule and hydroxyl values ​​of 376 to 1870;

[0028] C) Amino alcohols, such as diethanolamine, monoethanolamine, and triethanolamine;

[0029] D) Amine-terminated polyethers;

[0030] E) Foaming agents, including chemical foaming agents such as water and various types of physical foaming agents;

[0031] F) Catalysts, including catalysts for the reaction of isocyanate groups with alcohols, catalysts for the reaction of isocyanate groups with water, and isocyanate trimerization catalysts.

[0032] G) Surfactants, including foam-stabilizing surfactants that can be used to prepare polyurethane foams;

[0033] H) Colorants, fillers, and other particles;

[0034] I) Reinforcing fibers;

[0035] J) Preservatives, such as antimicrobial agents, bactericides, and antioxidants;

[0036] K) "Cold-touch" additives, such as encapsulated phase change materials;

[0037] And other additives that can be used to prepare various types of polyurethane.

[0038] For example, suitable methods for preparing various types of polyurethanes are described in U.S. Patents 3,632,707, 4,350,778, 7,704,410, 4,970,243, 5,157,056, 5,582,840, and 6,005,016, as well as U.S. Publication Patent Application 2020 / 0040153. Generally, the stable polyol dispersions of the present invention can be used in the same general manner as conventional polyols having similar hydroxyl functionality and equivalent weight.

[0039] In the following examples, unless otherwise indicated, all portions and percentages are by weight.

[0040] The starting recyclable polyol dispersion (RPD) used in the following example is produced by the chemical dissolution (glycolysis and acidolysis) of polyurethane foam waste according to the general method described in U.S. Patent 11,224,623. The starting RPD has a liquid polyol phase comprising a primary polyol and recyclable polyols produced by the chemical dissolution of the polyurethane foam waste, and dispersed solid particles produced by the chemical dissolution of the polyurethane foam waste. The dispersed solid particles contain imide groups as well as urethane and / or urea groups.

[0041] The initial RPD used in Comparative Sample A and Examples 1-7 contained 13.5% by weight of dispersed particles. Its density was approximately 1100 kg / m³. 3 To prepare comparative sample A, a portion of the initial RPD was heated to 60°C and treated at a flow rate of 50 g / min through a 4” (10.16 cm) IKA process pilot mixer without shearing. Examples 1 to 7 were prepared by treating a portion of the initial RPD at 60°C through the same mixer at the flow rates and rotation speeds shown in Table 3 to produce shear rates and shear work as shown in Table 3.

[0042] The IKA process pilot mixer is equipped with three mixer stages (generators), each with multiple rotor / stator rows and slots of the following dimensions:

[0043]

[0044] The residence time in each row of rotors / stators is calculated by dividing the total slot volume by the flow velocity (in mm). 3 The rotor tip speed is calculated in m / s (unit: m / s). Rotor diameter Rotations per second. The shear rate in each row is calculated by dividing the rotor tip speed by the shear gap. The shear work in each row is calculated as the shear rate. Residence time. The average shear rate is the arithmetic mean of the shear rates in each row. Total shear work is the sum of the shear work in each row.

[0045] In Example 1, the dispersion was fed at a rate of 50 g / min or 759.6 mm. 3 The feed rate is 1174 rpm, or 19.57 revolutions per second, through the rotor / stator mixer. The rotor rotation speed is 1174 rpm, or 19.57 revolutions per second. The shear rate and shear work in each row are as follows:

[0046]

[0047] The minimum, average, and peak shear rates of each of Examples 1-7 were determined in the same manner. The Lumisizer instability index of each of Examples 1-7 (and Comparative Sample A) was determined in accordance with ISO 13318-2 (2007). Furthermore, phase stability was subjectively evaluated by placing the samples in a closed, transparent container and allowing the container to stand at 20-25°C for 3 months. The aged samples were visually inspected for particle settling. The results are shown in Table 3.

[0048]

[0049] The starting RPD used in the comparative sample BD and Example 8 contained 16.8% by weight of dispersed particles. Its density was approximately 1100 kg / m³. 3 To prepare comparative sample B, a portion of the initial RPD was heated to 60°C and pushed through the same rotor / stator mixer at a flow rate of 50 g / min without shearing. Comparative samples C and D, as well as Example 8, were prepared by passing the same initial RPD through the same mixer at 60°C at a flow rate of rotor / stator rotation speed as shown in Table 4.

[0050]

[0051] A 25mm parallel plate rheometer with a 1.2mm gap was used at 25℃ at a speed of 0.1s⁻¹. 1 and 100s -1 The viscosity of certain treated RPDs was measured using shear rate. The results are shown in Table 5.

[0052]

[0053] The particle size of the comparative sample AD and Examples 1-8 were measured using a Beckman Coulter LS 13 320 laser diffraction particle size analyzer. Particle size measurements were performed by first diluting the samples in isopropanol. The D10, D90, D32, and D43 particle sizes are shown in Table 6. The D10 particle size represents 10% by volume of particles having a particle size equal to or smaller than X. The D32 particle size is the Sauter mean diameter; D43 is the De Broukere mean.

[0054]

Claims

1. A method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, the method comprising shearing the initial recyclable polyol dispersion at an average shear rate of at least 5500 / s for a period of time sufficient to produce a stable recyclable polyol dispersion having a Lumisizer instability index of at most 0.

55.

2. A method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, the method comprising shearing the initial recyclable polyol dispersion at an average shear rate of at least 5500 / s for a period of 0.05 seconds to 5 seconds.

3. The method according to claim 1 or 2, wherein the minimum shear rate during the shearing period is at least 3,000 / s.

4. The method according to any of the preceding claims, wherein the average shear rate is from 10,000 / s to 50,000 / s.

5. The method according to any of the preceding claims, wherein the shearing lasts for a period of 0.05 seconds to 5 seconds.

6. The method according to any of the preceding claims, wherein the shearing lasts for a period of 0.1 seconds to 1 second.

7. The method according to any of the preceding claims, wherein the shearing lasts for a period of time sufficient to produce a stable, recyclable polyol dispersion having a Lumisizer instability index of up to 0.

45.

8. The method according to any of the preceding claims, wherein 1,200 to 50,000 shearing operations are performed during the shearing process.

9. The method according to any of the preceding claims, wherein 1,500 to 12,000 shearing operations are performed during the shearing process.

10. The method according to any of the preceding claims, wherein the shearing is performed in the absence of fumed silica with a methanol wettability of 10% to 60%.

11. A method for stabilizing an initial recyclable polyol dispersion having a Lumisizer instability index of at least 0.60, said method comprising providing at least 10 4 The initial recyclable polyol dispersion is sheared in a shearing device under the condition of watts / kg of initial recyclable material for a period of time sufficient to produce a stable recyclable polyol dispersion with a Lumisizer instability index of up to 0.

55.

12. The method according to any preceding claim, wherein the initial recyclable polyol dispersion comprises a continuous liquid phase comprising a recyclable polyol generated by chemical dissolution of a solid polyurethane and / or a polyurethane-urea; and solid particles dispersed in component a), wherein the particles are insoluble in the continuous liquid phase and contain one or more urethane, urea, and / or imide groups, the particles being formed by chemical dissolution of the solid polyurethane and / or the polyurethane-urea.

13. The method of claim 12, wherein the starting recyclable polyol is generated by the following steps: in a first reaction step, reacting a polyurethane and / or polyurea polymer with an imide precursor and a polyether polyol having a number-average molecular weight of 400 g / mol to 6000 g / mol and a hydroxyl functionality of 2 to 4, and then in a second reaction step reacting with a diol or triol having a molecular weight of up to 250 g / mol to produce the starting recyclable polyol dispersion.

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