Compositions and methods for preparing self-crushable viscoelastic polyurethane foams

Abstract

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

Description

Technical Field

[0001] Embodiments are directed to self-crushable viscoelastic polyurethane foam compositions. Specifically, the viscoelastic polyurethane foam is prepared from a polyol blend of one or more polyester polyols and polyether polyols. Background Art

[0002] Viscoelastic polyurethane (VE) foams represent a rapidly growing segment of the polyurethane foam industry. VE foams are characterized in part by their slow recovery after compression. These properties distinguish VE foams from high resilience (HR) and "conventional" polyurethane flexible foams, which have much greater resilience and recover almost immediately after compression. VE foams are used in a wide range of applications, including as memory foams and in acoustic damping applications for NVH (noise, vibration and harshness) reduction.

[0003] Depending on the application, various polyurethane foam properties can be adjusted to obtain adequate performance, such as foam density, thickness, cell morphology, etc. The preparation of VE foams generally utilizes chemical techniques that change the phase separation of the constituent polymer segments. For example, the method may include crosslinking using a mixture of polyols of different lengths to reduce the equivalent weight of the soft segments. However, a reduction in equivalent weight may also increase the foam shrinkage rate and reduce the fraction of open cells. To offset these effects, the cells can be mechanically opened by crushing, but the additional processing requires specialized equipment and increases time and production costs. Summary of the invention

[0004] Embodiments disclosed herein include polyurethane foam compositions comprising 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, wherein the EO-rich polyether polyol comprises an EO-terminated EO / PO polymer, the EO-terminated EO / PO polymer comprising at least 70 wt % EO, an OH value 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; and 30 wt % to 80 wt % of a propylene oxide-rich (PO-rich) polyether polyol, wherein the PO-rich polyether polyol comprises an EO-terminated EO / PO polymer, the EO-terminated EO / PO polymer comprising at least 75 wt % PO, 20 mg KOH / g to 50 mg KOH / g, and a primary OH content of at least 40% of the total OH groups. KOH / g and a primary OH content of at least 50% of the total OH groups; and a polyester polyol in an amount of 10 wt % to 35 wt %, the polyester polyol being based on the reaction product of an aromatic diacid or an alkyl diacid and a polyol having 2 to 4 OH functionalities, wherein the polyester polyol has an OH value in the range of 20 mg KOH / g to 100 mg KOH / g. DETAILED DESCRIPTION

[0005] Embodiments relate to self-crushable 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 foams produced do not require a post-production foam crushing step. Molded articles and foam compositions having high damping factors are also disclosed.

[0006] The VE polyurethane foam composition can be prepared by reacting an isocyanate component with an isocyanate-reactive component. The VE polyurethane foam composition can be molded by transferring the reaction mixture into a closed mold where it reacts to produce a molded polyurethane foam. After demoulding, the resulting foam does not require a post-foam crushing step and does not exhibit foam shrinkage or collapse after the foam rises.

[0007] The polyol blend may include a mixture of polyether polyols rich in polypropylene oxide (PO) and polyether polyols rich in ethylene oxide (EO), which changes the mechanical properties and reaction characteristics of the blend. Specifically, polyether polyols rich in PO can reduce the reactivity in polyurethane, increase mechanical properties and resilience. In addition, polyether polyols rich in EO are introduced to increase reactivity while also promoting phase separation in the formed polyurethane foam. Phase separation promotes cell connectivity in the formed foam, increases air permeability during the blow molding process, and thus reduces shrinkage. The special structure of polyester polyols, particularly the natural presence of hard segments in the form of aromatic rings together with carboxyl groups, increases the presence of hard segments in the final polymer, promotes phase separation and also increases the glass transition temperature of the final PU polymer. The result of introducing polyester polyols is a self-crushing viscoelastic polyurethane foam with good vibration damping properties.

[0008] The polyurethane foam composition produced can have a high open cell content and damping factor without the need for additional crushing to mitigate excessive foam shrinkage. Control of the foam properties can include varying the ratio of soft segments to hard segments in the isocyanate and isocyanate-reactive components, heat treatment, and processing conditions. The polyurethane foam composition can have a 40 kg / m 3 Up to 120kg / m 3 , 40kg / m 3 Up to 100kg / m 3 or 50kg / m 3 Up to 90kg / m 3 The viscoelastic polyurethane foam composition may have a damping factor as determined by DIN 53426 of greater than 0.25, greater than 0.30, or greater than 0.35.

[0009] The viscoelastic polyurethane foam can have an isocyanate index, which is defined as the molar stoichiometric ratio of isocyanate moieties in the reaction mixture relative 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 there is no stoichiometric excess, such that there are 1.0 mole of isocyanate groups per 1.0 mole of isocyanate-reactive groups, multiplied by 100. The isocyanate component can have an isocyanate index in the range of 50 to 120, 60 to 100, or 70 to 90.

[0010] The viscoelastic polyurethane foam compositions disclosed herein may include a multilayer structure containing a polyurethane foam coated on a substrate such as paper, metal, plastic, wood, rubber, cotton wool, etc. The multilayer polyurethane foam composition may be laminated. The polyurethane foam may 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), hood, doors, fenders, instrument panels, mirror housings, bumpers, trim, carpets, etc.

[0011] Viscoelastic polyurethane foam can be generated by reacting an isocyanate component with an isocyanate reactive component containing a polyol blend. The isocyanate component may include at least one compound with an isocyanate group. The isocyanate component may include one or more isocyanates and a polyisocyanate having an average of more than 1.0 isocyanate group per molecule. The isocyanate component may contain aliphatic, alicyclic, alicyclic, aromatic, aromatic and / or derivatives thereof. Examples of compounds suitable for isocyanate components include monomeric methylene diphenyl diisocyanate (MDI), modified MDI, oligomeric MDI, polymeric MDI, toluene 2,4- / 2,6-diisocyanate (TDI) and the like.

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

[0013] The isocyanate reactive component may comprise a blend of polyols, including a polyester polyol and a mixture of EO-rich and PO-rich polyether polyols. The isocyanate reactive component may comprise a polyol blend, the polyol blend containing, by weight percentage (wt %) of the blend, one or more polyester polyols in the range of 10 wt % to 35 wt %; one or more EO-rich polyether polyols in the range of 10 wt % to 35 wt %; and one or more PO-rich polyether polyols in the range of 30 wt % to 80 wt %.

[0014] The isocyanate reactive component may comprise an EO-rich polyether polyol containing an EO-terminated ethylene oxide / propylene oxide (EO / PO) copolymer containing at least 70 wt%, at least 75 wt%, or at least 80 wt% EO weight percent (wt%). The EO-rich polyether polyol may have an average hydroxyl value (OH value or OHv) in the range of 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 determined 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 polyol may contain a primary hydroxyl (primary OH) content of at least 40%, at least 50%, at least 70%, or at least 90%, including a range of 40% to 95%, as determined by ASTM D4273-18. The EO-rich polyether polyol may have 3 or more hydroxyl functionalities.

[0016] The isocyanate reactive component may include a PO-rich polyether polyol containing an EO-terminated ethylene oxide / propylene oxide (EO / PO) copolymer containing at least 75 wt%, at least 80 wt%, or at least 85 wt% PO weight percent (wt%). The PO-rich polyether polyol may have an average hydroxyl value (OH value) in the range of 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 determined 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 polyol may contain a primary hydroxyl (primary OH) content of at least 50%, at least 55%, or at least 60%, including in the range of 50% to 90%, as determined by ASTM D4273-18. The PO-rich polyether polyol may have 3 or more, including 3 to 7 or 3 to 6 hydroxyl functionalities.

[0018] The polyester polyol disclosed herein includes the reaction product of one or more carboxylic diacids and a polyol having 2 to 4 OH functionalities. Suitable carboxylic acids may include aromatic diacids or anhydrides and C4 to C8 aliphatic diacids. Suitable polyols for forming polyesters include one or more alkylene glycols or polyalkylene glycols having 2 to 4 hydroxyl functionalities, such as ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, etc. 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 polyester polyol may have an average hydroxyl value (OH value) in the range of 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 determined 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, crosslinking agents, plasticizers, fillers, smoke suppressants, fragrances, reinforcing agents, dyes, colorants, pigments, preservatives, odor masking agents, 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 the like; as well as so-called "low-emission" tertiary amine catalysts, which contain 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-malonamide, and the like.

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

[0023] Example

[0024] The following examples are provided to illustrate embodiments of the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, all parts and percentages are by weight. Table 1 lists the materials used in the following examples:

[0025]

[0026]

[0027] The damping factor is measured by vibration experiments according to DIN 53426. During the test, a foam sample (50 mm × 50 mm × 25 mm) is fixed by two aluminum plates (50 mm × 50 mm × 2 mm) and fixed to two accelerometers. The sample is then tested using a frequency-dominated vibration sweep, which is recorded by the accelerometers. The damping factor (η) is obtained from the response (in dB) of the relative difference measured by the accelerometers over the frequency vibration sweep. Specifically, after identifying the response with the peak, it is defined as:

[0028] f0 is the frequency of the peak value (resonance frequency)

[0029] f1 is the frequency of the response 3dB below the peak, where f1>f0

[0030] f2 is the frequency at which the response is 3dB below the peak, where f2 <f0

[0031] η=(f1–f2) / f0

[0032] Generally, when the damping factor is greater than 0.25, the foam can be defined as viscoelastic.

[0033] Example 1: Preparation of polyurethane foam composition

[0034] In this example, the weighed polyurethane sample formulation and components were mixed by a high-speed mixer and placed in a mold (400 mm×400 mm×40 mm) at a temperature ranging from 50° C. to 70° C. The mold was closed after pouring the reaction mixture on the bottom of the mold itself. The demoulding time varied depending on the selected catalyst and catalyst concentration; however, all the inventive examples (IS) and comparative examples (CS) described in the present invention were demoulded after 120 seconds of pouring.

[0035] By 65kg / m 3 Foam samples were prepared at a molded density of 1000 μm to observe samples that were self-crushable (i.e., did not shrink). After the samples were demolded, the shrinkage was calculated by measuring the change in foam thickness. Foam samples that did not shrink were classified as "self-crushable".

[0036] In addition, the collapse of the foam was tested using a foaming experiment performed in a cup. The settling of the foam itself from the highest point reached by the foam during polymerization (maximum height of about 20 cm) was recorded. If the decrease in height after reaching the highest point was higher than 5 cm, the foam was defined as collapsed foam. Generally, collapsed foam is not suitable for many applications, including forming molded parts. The results for the comparative samples are shown in Table 2 and the results for the inventive samples are shown in Table 3. Unless otherwise indicated, the compounds are expressed in wt%.

[0037]

[0038]

[0039] For CS1 and CS2, the absence of polyester polyols results in low damping factors even with the addition of EO-rich polyether polyols: these foams are not viscoelastic. Formulations CS3 and CS4 do not contain EO-rich polyether polyols, with the result that the damping factors remain unacceptably low (these foams are also not viscoelastic) and the samples are not self-crushable. CS5 is a viscoelastic formulation containing a mixture of EO-rich polyols and PO polyols that exhibits good damping properties, however, the lack of polyester polyols results in foams with unacceptably high shrinkage. CS6 exhibits good damping, but exhibits unacceptable shrinkage. CS7 is a polyol blend that provides good damping properties, but provides unacceptable shrinkage. CS8 provides another example where the exclusion of EO-rich polyols exhibits shrinkage and insufficient damping properties (the foam is not viscoelastic).

[0040] In contrast, IS1 to IS5 provide a range of polyol blends that meet the desired damping factor of greater than 0.25 while also having acceptable shrinkage properties.

[0041] While the foregoing is directed to illustrative embodiments, other and further embodiments may be devised without departing from the basic scope of the present invention, which is defined by the claims that follow.

Claims

1. A polyurethane foam composition comprising the reaction product of the following components: an isocyanate component comprising one or more isocyanate compounds, and An isocyanate-reactive component, the isocyanate-reactive component comprising: i) 10 wt% to 35 wt% of an ethylene oxide-rich (EO-rich) polyether polyol, wherein the EO-rich polyether polyol comprises an EO-terminated EO / PO polymer comprising at least 70 wt% EO, an OH value 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% of a propylene oxide-rich (PO-rich) polyether polyol, wherein the PO-rich polyether polyol comprises an EO-terminated EO / PO polymer, wherein the EO-terminated EO / PO polymer comprises at least 75 wt% PO, an OH value in the range of 20 mg KOH / g to 50 mg KOH / g, and the total OH a primary OH content of at least 50% of the groups; and iii) 10 wt % to 35 wt % of a polyester polyol based on the reaction product of an aromatic diacid or an alkyl diacid and a polyol having 2 to 4 OH functionalities, wherein the polyester polyol has a KOH content of 20 mg KOH / g to 100 mg OH value in the range of KOH / g.

2. The polyurethane foam composition according to claim 1, wherein the polyurethane foam has a damping factor measured according to DIN 53426 of at least 0.

25.

3. 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 composition according to claim 1, wherein the polyurethane foam has a relative humidity of 50 kg / m 3 Up to 90kg / m 3 density.

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

6. The polyurethane foam composition of claim 1, wherein the isocyanate reactive component further comprises an amine catalyst in a weight percentage ranging from 0.5 wt% to 15 wt% into the isocyanate reactive component.

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

8. A method for preparing the polyurethane foam composition according to claim 1, the method 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; as well as The molded foam article is demolded.

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