Composition and method for preparing self-collapsing viscoelastic polyurethane foams

Abstract

The polyurethane foam composition comprises the reaction product of an isocyanate component comprising one or more isocyanate compounds and an isocyanate-reactive component comprising 10 wt% to 35 wt% of an ethylene oxide-rich (EO-rich) polyether polyol, 30 wt% to 80 wt% of a propylene oxide-rich (PO-rich) polyether polyol, and 10 wt% to 35 wt% of a polyester polyol based on the reaction product of an aromatic diacid or an alkyl diacid with a polyol having an OH functionality of 2 to 4.

Description

[Technical Field]

[0001] Embodiments relate to self-crushing viscoelastic polyurethane foam compositions, particularly viscoelastic polyurethane foams prepared from polyol blends of one or more polyester polyols and polyether polyols.

[0002] Introduction Viscoelastic polyurethane foam (VE) represents a rapidly growing segment of the polyurethane foam industry. VE foam is characterized, in part, by its slow recovery from compression. These properties distinguish it from high resilience (HR) and "traditional" polyurethane flexible foams, which have much higher resilience and recover almost immediately after compression. VE foam is used in a wide variety of applications, including as memory foam and in sound damping applications to reduce NVH (noise, vibration, and harshness).

[0003] Depending on the application, numerous polyurethane foam properties, such as foam density, thickness, and cell morphology, can be tailored for optimal performance. The preparation of VE foams often utilizes chemical techniques to modify the phase separation of the constituent polymer segments. For example, methods may include using a mixture of polyols of various lengths or crosslinking to reduce the equivalent weight of the soft segments. However, reducing the equivalent weight can also increase the foam's shrinkage rate and reduce the proportion of open cells. To counter these effects, cells can be mechanically opened by crushing, but this requires specialized equipment for additional processing, increasing time and production costs. Summary of the Invention

[0004]

[0009] Embodiments disclosed herein provide a polyurethane foam composition comprising the reaction product of an isocyanate component comprising one or more isocyanate compounds and an isocyanate-reactive component, the isocyanate-reactive component being selected from the group consisting of: 10 wt% to 35 wt% ethylene oxide-rich (EO-rich) polyether polyol, an EO-capped EO / PO polymer containing at least 70 wt% EO, an OH number ranging from 20 mg KOH / g to 50 mg KOH / g, and a primary OH content of at least 40% of total OH groups; 30 wt% to 80 wt% propylene oxide-rich (PO-rich) polyether polyol, an EO-capped EO / PO polymer containing at least 75 wt% PO, an OH number ranging from 20 mg KOH / g to 50 mg KOH / g, and a primary OH content of at least 40% of total OH groups; and a weight percent (wt%) of 10% to 35% of a polyester polyol based on the reaction product of an aromatic diacid or an alkyl diacid with a polyol having an OH functionality of 2 to 4, the polyester polyol having an OH value in the range of 20 mg KOH / g to 100 mg KOH / g. DETAILED DESCRIPTION OF THE INVENTION

[0005] Embodiments relate to self-crushing VE polyurethane foam compositions prepared from polyol blends of one or more polyester polyols and polyether polyols. The VE polyurethane foam compositions disclosed herein are considered "self-crushing" in that the resulting foam does not require a post-formation foam collapse step. Molded articles and foam compositions having high damping coefficients are also disclosed.

[0006] VE polyurethane foam compositions can be prepared by reacting an isocyanate component with an isocyanate-reactive component. The VE polyurethane foam compositions can be molded by transferring the reaction mixture to a closed mold, where the reaction produces a molded polyurethane foam. After removal from the mold, the resulting foam does not require a post-molding foam collapse step and does not exhibit foam shrinkage or collapse after foam expansion.

[0007] Polyol blends can include a mixture of polypropylene oxide-rich (PO-rich) polyether polyols and ethylene oxide-rich (EO-rich) polyether polyols, which modify the blend's mechanical and reactivity properties. In particular, the PO-rich polyether polyols can reduce reactivity within the polyurethane, thereby increasing mechanical performance and resilience. Furthermore, while the EO-rich polyether polyols are introduced to increase reactivity, they also promote phase separation within the polyurethane foam during formation. Phase separation promotes cell connectivity within the foam during formation, thereby increasing air permeability during the foaming process and reducing shrinkage. The special structure of polyester polyols, particularly the natural presence of hard segments in the form of aromatic rings along with carboxyl groups, increases the presence of hard segments in the final polymer, promoting phase separation and raising the glass transition temperature of the final PU polymer. The introduction of polyester polyols results in self-crushing viscoelastic polyurethane foams with good vibration damping properties.

[0008] The resulting polyurethane foam composition may have a high open cell content and damping coefficient without requiring additional crushing to mitigate excessive foam shrinkage. Control of foam properties may include varying the ratio of soft to hard segments in the isocyanate and isocyanate-reactive components, heat treatment, and processing conditions. The polyurethane foam composition may have a foam yield of 40 kg / m or more, as determined by ASTM D-3574-17. 3 ~120kg / m 3 , 40 kg / m 3 ~100kg / m3 , or 50 kg / m 3 ~90kg / m 3 The viscoelastic polyurethane foam composition may have a damping coefficient, as determined by DIN 53426, greater than 0.25, greater than 0.30, or greater than 0.35.

[0009] The viscoelastic polyurethane foam may have an isocyanate index, defined as the molar stoichiometric ratio of isocyanate moieties in the reaction mixture to the number of moles of isocyanate-reactive units (active hydrogens available to react with isocyanate moieties), multiplied by 100. An isocyanate index of 100 means that there is no stoichiometric excess, such that there is 1.0 mole of isocyanate group per 1.0 mole of isocyanate-reactive group multiplied by 100. The isocyanate component may have an isocyanate index ranging from 50 to 120, 60 to 100, or 70 to 90.

[0010] The viscoelastic polyurethane foam compositions disclosed herein may have a multi-layer structure containing polyurethane foam coated on a substrate such as paper, metal, plastic, wood, rubber, cotton fleece, etc. Multi-layer polyurethane foam compositions may also be laminated. Polyurethane foams can be used in applications such as fillers, acoustic applications, and surfaces in automotive interiors, exteriors, and structural components. Examples include automotive applications such as body (frame), hoods, doors, fenders, instrument panels, mirror housings, bumpers, trim, carpeting, etc.

[0011] Viscoelastic polyurethane foams can be made by reacting an isocyanate component with an isocyanate-reactive component containing a polyol blend. The isocyanate component can include at least one compound having an isocyanate group. The isocyanate component can include one or more isocyanates and polyisocyanates having an average of more than 1.0 isocyanate groups per molecule. The isocyanate component can contain moieties that are aliphatic, cycloaliphatic, cycloaliphatic, arylaliphatic, aromatic, and / or derivatives thereof. Examples of compounds suitable for use in the isocyanate component include monomeric methylene diphenyl diisocyanate (MDI), modified MDI, oligomeric MDI, polymeric MDI, toluene 2,4- / 2,6-diisocyanate (TDI), and the like.

[0012] The isocyanates can have an average isocyanate functionality of 1 to 5, 1.5 to 5, 2 to 5, or 3 to 5. The isocyanates can have an isocyanate equivalent weight (EW) ranging from 75 g / eq to 250 g / eq, 80 g / eq to 200 g / eq, or 80 g / eq to 175 g / eq. The isocyanates can have an isocyanate content ranging from 20 wt% to 45 wt%, 25 wt% to 45 wt%, or 25 wt% to 40 wt%, based on the total weight of the isocyanates.

[0013] The isocyanate-reactive component can include a blend of polyols including a polyester polyol and a mixture of an EO-rich polyether polyol and a PO-rich polyether polyol. The isocyanate-reactive component can include a polyol blend containing one or more polyester polyols in a weight percent (wt%) of the blend ranging from 10 wt% to 35 wt%, one or more EO-rich polyether polyols ranging from 10 wt% to 35 wt%, and one or more PO-rich polyether polyols ranging from 30 wt% to 80 wt%.

[0014] The isocyanate-reactive component may include an EO-rich polyether polyol containing an EO-capped copolymer of ethylene oxide / propylene oxide (EO / PO) with at least 70 wt.%, at least 75 wt.%, or at least 80 wt.% EO. The EO-rich polyether polyol may have an average hydroxyl number (OH number or OHv) ranging from 20 mg KOH / g to 50 mg KOH / g, 25 mg KOH / g to 45 mg KOH / g, or 30 mg KOH / g to 40 mg KOH / g, as measured according to ASTM D4274-21. The EO-rich polyether polyol may have a polyol equivalent weight of 1100 to 2800, 1200 to 2500, or 1250 to 2250.

[0015] The EO-rich polyether polyols may have a primary hydroxyl (primary OH) content of at least 40%, at least 50%, at least 70%, or at least 90%, including in the range of 40% to 95%, as determined by ASTM D4273-18. The EO-rich polyether polyols may have a hydroxyl functionality of 3 or greater.

[0016] The isocyanate-reactive component may include a PO-rich polyether polyol containing an EO-capped copolymer of ethylene oxide / propylene oxide (EO / PO) with a weight percent (wt%) of PO of at least 75%, at least 80%, or at least 85%. The PO-rich polyether polyol may have an average hydroxyl number (OH number) ranging from 20 mg KOH / g to 50 mg KOH / g, 25 mg KOH / g to 45 mg KOH / g, or 30 mg KOH / g to 40 mg KOH / g, as measured according to ASTM D4274-21. The PO-rich polyether polyol may have a polyol equivalent weight of 1100 to 2800, 1200 to 2500, or 1250 to 2250.

[0017] The PO-rich polyether polyols may have a primary hydroxyl (primary OH) content of at least 50%, at least 55%, or at least 60%, including a range of 50% to 90%, as determined by ASTM D4273-18. The PO-rich polyether polyols may have a hydroxyl functionality ranging from 3 or greater, including 3 to 7 or 3 to 6.

[0018] The polyester polyols disclosed herein include the reaction product of one or more carboxylic diacids with a polyol having an OH functionality of 2 to 4. Suitable carboxylic acids can include aromatic diacids or anhydrides and C4 to C8 aliphatic diacids. Suitable polyols for forming the polyester include one or more alkylene glycols or polyalkylene glycols having a hydroxy functionality of 2 to 4, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and diethylene glycol. Examples of polyester polyols include polyesters of phthalic anhydride and diethylene glycol, and polyesters of C4 to C8 diacids, such as succinic acid or adipic acid, and diethylene glycol.

[0019] The polyether polyol may have an average hydroxyl number (OH number) ranging from 20 mg KOH / g to 100 mg KOH / g, 25 mg KOH / g to 95 mg KOH / g, or 30 mg KOH / g to 90 mg KOH / g, as measured according to ASTM D4274-21. The polyester polyol may have a polyol equivalent weight of 560 to 2800, 590 to 2300, or 620 to 1900.

[0020] The isocyanate-reactive component may also contain one or more additives including catalysts, blowing agents, surfactants, crosslinkers, plasticizers, fillers, smoke suppressants, fragrances, toughening agents, dyes, colorants, pigments, preservatives, odor maskers, physical blowing agents, chemical blowing agents, flame retardants, internal mold release agents, biocides, antioxidants, UV stabilizers, antistatic agents, thixotropic agents, adhesion promoters, cell openers, and the like.

[0021] The isocyanate-reactive component may comprise one or more catalysts, including amines such as trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, N,N,N',N'-tetramethyl-1,4-butanediamine, N,N-dimethylpiperazine, 1,4-diazabicyclo-2,2,2-octane, bis(2-dimethylaminoethyl)ether, morpholine, pentamethyldiethylenetriamine; and so-called "low-emission" tertiary amine catalysts containing one or more isocyanate-reactive groups, such as N,N-dimethylethanolamine, 1,4-diazabicyclo[2.2.2]octane-2-methanol, N-[2-[2-(dimethylamino)ethoxy]ethyl]-N-methyl-1,3-propanediamine.

[0022] The isocyanate-reactive component may include one or more blowing agents in an amount sufficient to provide the desired foam density. Blowing agents may include water and other aqueous fluids, as well as hydrocarbons such as n-pentane, isopentane, cyclopentane, or related blends, hydrofluorocarbons including hydrofluoroolefins, and the like. The blowing agent may be included in any suitable amount, including, for example, a range of parts per polyol (i.e., isocyanate-reactive component) (pphp) from 1.5 pphp to 6 pphp or from 2 pphp to 5 pphp. [Example]

[0023] The following examples are presented to illustrate embodiments of the present invention, but are not intended to limit its scope. All parts and percentages are by weight unless otherwise indicated. Table 1 lists the materials used in the following examples.

[0024] [Table 1]

[0025] The damping coefficient is measured by vibration experiments according to DIN 53426. During the test, a foam sample (50 mm x 50 mm x 25 mm) is clamped by two aluminum plates (50 mm x 50 mm x 2 mm) and fixed to two accelerometers. The sample is then tested using a vibration sweep at a dominant frequency, which is recorded by the accelerometers. The damping coefficient (η) is obtained from the relative difference response (dB) measured by the accelerometers over the frequency vibration sweep. Specifically, after identifying the peaked response, it is defined as follows: f0: Peak frequency (resonance frequency) f1: The frequency at which the response is 3 dB below the peak, and f1>f0 f2: The frequency at which the response is 3 dB below the peak, f2 <f0である η=(f1-f2) / f0

[0026] Generally, a foam can be defined as viscoelastic if it has a damping coefficient greater than 0.25.

[0027] Example 1: Preparation of polyurethane foam composition In this example, the polyurethane sample formulation was weighed, the components were mixed using a high-speed mixer, and placed in a mold (400 mm x 400 mm x 40 mm) at a temperature ranging from 50°C to 70°C. The reactive mixture was poured into the bottom of the mold itself, and then the mold was sealed. The time required for demolding varied depending on the catalyst and catalyst concentration selected, but all of the inventive examples (IS) and comparative examples (CS) described in this invention were demolded 120 seconds after casting.

[0028] The observation that the specimen is self-collapseable (i.e., no shrinkage occurs) is based on a 65 kg / m 3 This is done by preparing a foam sample at a molded density of 100 psi. After the sample is removed from the mold, shrinkage is calculated by measuring the change in foam thickness. Foam samples in which the foam does not shrink are classified as "self-collapseable."

[0029] Additionally, foam collapse was tested using a foaming experiment conducted in a cup. The sinking of the foam itself from the highest point it reaches during polymerization (maximum height of approximately 20 cm) is recorded. A foam is defined as collapsed if it loses more than 5 cm in height after reaching the highest point. Generally, collapsed foams are not suitable for many applications, including forming molded parts. Results for comparative samples are shown in Table 2, and results for inventive samples are shown in Table 3. Compounds are presented in weight percent unless otherwise indicated.

[0030] [Table 2]

[0031] [Table 3]

[0032] For CS1 and CS2, the absence of polyester polyol resulted in low damping coefficients, even with the addition of EO-rich polyether polyol; i.e., these foams were not viscoelastic. Formulations CS3 and CS4 did not contain EO-rich polyether polyol, and as a result, the damping coefficients remained unacceptably low (these foams were also not viscoelastic), and the samples were not self-collapseable. CS5 is a viscoelastic formulation containing a mixture of EO-rich polyol and PO polyol that exhibits good damping properties, but the absence of polyester polyol results in a foam with unacceptably high shrinkage. CS6 exhibits good damping but unacceptable shrinkage. CS7 is a polyol blend that offers good damping properties but unacceptable shrinkage. CS8 provides another example where the omission of the EO-rich polyol results in shrinkage and poor damping properties (the foam is not viscoelastic).

[0033] In contrast, IS1-IS5 provide a range of polyol blends that meet the desired damping ratio of greater than 0.25 while also having acceptable shrinkage performance.

[0034] While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, which scope is determined by the claims that follow.

Claims

1. 1. A polyurethane foam composition comprising: an isocyanate component comprising one or more isocyanate compounds; Isocyanate-reactive components and wherein the isocyanate-reactive component comprises the reaction product of i) 10 wt% to 35 wt% weight percent (wt%) ethylene oxide-rich (EO-rich) polyether polyol, the EO-rich polyether polyol having an EO-capped EO / PO polymer containing at least 70 wt% EO, an OH number in the range of 20 mg KOH / g to 50 mg KOH / g, and a primary OH content of at least 40% of the total OH groups; ii) 30 wt% to 80 wt% weight percent (wt%) propylene oxide-rich (PO-rich) polyether polyol, the PO-rich polyether polyol having an EO-capped EO / PO polymer containing at least 75 wt% PO, an OH number in the range of 20 mg KOH / g to 50 mg KOH / g, and a primary OH content of at least 50% of the total OH groups; and iii) a weight percent (wt%) of 10 wt% to 35 wt% of a polyester polyol based on the reaction product of an aromatic diacid or an alkyl diacid with a polyol having an OH functionality of 2 to 4, said polyester polyol having an OH number in the range of 20 mg KOH / g to 100 mg KOH / g.

2. 10. The polyurethane foam composition of claim 1, wherein the polyurethane foam has a damping coefficient measured in accordance with DIN 53426 of at least 0.

25.

3. 10. The polyurethane foam composition of claim 1, wherein the one or more isocyanate compounds comprise monomeric methylene diphenyl diisocyanate (MDI), modified MDI, oligomeric MDI, or polymeric MDI.

4. The polyurethane foam has a viscosity of 50 kg / m ３ ~90 kg / m ３ 10. The polyurethane foam composition of claim 1, having a density of

5. The polyurethane foam composition of claim 1 , wherein the isocyanate-reactive component further comprises water as a blowing agent.

6. 10. The polyurethane foam composition of claim 1, wherein the isocyanate-reactive component further comprises an amine catalyst in a weight percent range of from 0.5% to 15% by weight, based on the isocyanate-reactive component.

7. A molded article comprising the polyurethane foam composition of claim 1.

8. 10. A method for preparing the polyurethane foam composition of claim 1, comprising: combining the isocyanate component with the isocyanate-reactive component to form a mixture; processing the mixture in a mold to produce a molded foam article; removing the molded foam article from the mold; and A method comprising:

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