Polyurethane foams with adjustable porosity over wide range

Abstract

The invention relates to a method for producing a polyurethane foam, comprising reacting a polyisocyanate with a polyether polyol component a) in the presence of a blowing agent, the polyether polyol component a) comprising: a1) a first polyether polyol having a molecular weight of from 300 g / mol to 1,500 g / mol, a hydroxyl number of from 100 mg KOH / g to 650 mg KOH / g, and a propylene oxide content of higher than 50% by weight, and a2) a second polyether polyol having a molecular weight of from 300 g / mol to 1,500 g / mol, a hydroxyl number of from 100 mg KOH / g to 650 mg KOH / g, and a propylene oxide content of higher than 50% by weight; and a2) a second polyether polyol having a molecular weight of from 500 g / mol to 1,700 g / mol, a hydroxyl value of from 50 mg KOH / g to 650 mg KOH / g, an ethylene oxide content of greater than 30% by weight, a propylene oxide content of less than 50% by weight, and a primary hydroxyl content of less than 40%.

Description

Technical Field

[0001] The present invention relates to a method for preparing polyurethane foam, a polyether polyol composition, a polyurethane foam obtainable by the method, and a shaped article comprising the polyurethane foam. Background Art

[0002] Polyurethane foams, particularly flexible polyurethane foams, have been widely used in a variety of industrial and consumer applications. For some applications, flexible polyurethane foams may have a relatively low porosity, while for many other applications, the foam should have a relatively high porosity.

[0003] One class of flexible polyurethane foams is known as viscoelastic (VE) or "memory" foams. Viscoelastic foams exhibit a time-delayed response to applied stress (compression). They have low resilience and are slow to recover when compressed. These properties are generally associated with the glass transition temperature (Tg) of the polyurethane. Viscoelasticity is generally exhibited when the polymer has a Tg at or near the use temperature, which for many applications is room temperature.

[0004] Like most polyurethane foams, VE polyurethane foams can be prepared by the reaction of a polyether polyol component with a polyisocyanate in the presence of a blowing agent. The blowing agent is typically water or a mixture of water and another material. VE formulations are generally characterized by the selection of the polyether polyol component and the amount of water in the formulation. The primary polyether polyol used in these formulations may have a functionality of about 3 hydroxyl groups per molecule and a molecular weight in the range of 400-1,500. The polyol is primarily the primary determinant of the Tg of the polyurethane foam, although other factors such as water content and isocyanate index also play an important role.

[0005] Typically, VE polyurethane foams are prepared at a low isocyanate index (100 times the molar ratio of -NCO groups to NCO-reactive groups in the reaction mixture). Typically, the isocyanate index is at most about 120, or even at most about 100 or at most about 90.

[0006] Typically, VE polyurethane foams have low air flow characteristics, typically less than about 1.0 standard cubic feet per minute (scfm) (28.2 liters / minute) at room temperature (22°C) and atmospheric pressure (1 atm), and therefore promote sweating when used as comfort foams (e.g., bedding, seating, and other cushioning pads). Low air flow also results in low heat and moisture transfer out of the foam, resulting in increased temperature and increased moisture content in the foam. The result of the increased temperature is higher resilience and reduced viscoelastic characteristics. The combination of heat and moisture results in accelerated fatigue of the foam. In addition, if the foam air flow is low enough, the foam can shrink during the manufacturing process.

[0007] Polyurethane foam can be prepared by reacting a polyether polyol and a polyisocyanate in the presence of a blowing agent. It is known that the foam porosity can be changed by reducing or increasing the amount of a so-called "cell opener", which is a property of the foam porosity resulting from the efficiency of the opening of the cells during the foam preparation process. The "cell opener" can be a polyether polyol having a relatively high ethylene oxide (EO) content, a relatively high molecular weight, and a relatively low hydroxyl (OH) value. WO2019086655 discloses the use of such open-cell polyether polyols, specifically "Caradol SA36-02". According to Table 6 of the WO2019086655, by increasing the amount of the polyol when preparing viscoelastic polyurethane foam, the porosity is also increased from 8 l / min (in an amount of 2 pbw = parts by weight) to 28 l / min (in an amount of 8 pbw).

[0008] It would be advantageous to prepare polyurethane foams, in particular viscoelastic (VE) polyurethane foams, in such a way that, depending on the specific foam application and the corresponding specific foam porosity required, the foam porosity can be varied (adjusted) within a wide range (e.g. 5 l / min to 200 l / min), preferably while still retaining the viscoelastic properties in the case of VE polyurethane foams.

[0009] However, polyurethane foams, in particular VE polyurethane foams, having such adjustable foam porosity as described above should still meet other desired foam properties, such as foam stability during foam production. In particular, foam instability may manifest itself as so-called foam "sinking" and / or relatively low foam height (low foam rise) and / or even foam cracking or collapse. Sinking refers to a phenomenon in which, after reaching a certain height, the foam height decreases. The disadvantage of such sinking is that the final foam density distribution is uneven and / or the final foam height is relatively low.

[0010] An object of the present invention is to provide a process for preparing polyurethane foams, in particular viscoelastic (VE) polyurethane foams, by reacting a polyisocyanate and a polyether polyol in the presence of a blowing agent, which foams have one or more of the above-mentioned desired properties and advantages, including both foam stability and adjustability of the foam porosity, that is, the porosity is varied within a wide porosity range while still maintaining foam stability.

[0011] In addition, it may be an object of the present invention to reduce the compression set and / or increase the porosity of the polyurethane foam prepared in the above method. In addition, it may be an object of the present invention to use only relatively small amounts of different alcohols, including polyether polyols and monools, to achieve one or more of the above objects. The latter has the advantage of requiring fewer tanks, feed lines, pumps, etc., which, besides being cheaper, may also reduce any risk of cross contamination. Summary of the invention

[0012] Surprisingly, it has been found that the above objects can be achieved by combining a first polyether polyol having a relatively low molecular weight, a relatively high hydroxyl number and a propylene oxide content of more than 50% by weight with a different second polyether polyol also having a relatively low molecular weight and a relatively high hydroxyl number and also having an ethylene oxide content of more than 30% by weight, a propylene oxide content of less than 50% by weight and a primary hydroxyl content of less than 40%.

[0013] The present invention therefore relates to a process for preparing a polyurethane foam, which comprises reacting a polyisocyanate with a polyether polyol component a) in the presence of a blowing agent, wherein the polyether polyol component a) comprises:

[0014] a1) a first polyether polyol having a molecular weight of 300 g / mol to 1,500 g / mol, a hydroxyl value of 100 mg KOH / g to 650 mg KOH / g, and a propylene oxide content of more than 50 wt %; and

[0015] a2) a second polyether polyol having a molecular weight of 500 to 1,700 g / mol, a hydroxyl value of 50 to 650 mg KOH / g, an ethylene oxide content of more than 30% by weight, a propylene oxide content of less than 50% by weight, and a primary hydroxyl content of less than 40%.

[0016] The present invention also relates to a composition comprising the first polyether polyol and the second polyether polyol as described above.

[0017] Furthermore, the present invention relates to a polyurethane foam obtainable by the above-mentioned method for preparing a polyurethane foam, and a shaped article comprising the polyurethane foam obtained or obtainable by the method. DETAILED DESCRIPTION

[0018] Although the methods and compositions of the present invention may be described as "comprising," "containing," or "including" one or more of the various steps or components, respectively, they may also "consist essentially of" or "consist of" the various steps or components, respectively.

[0019] In the context of the present invention, where the composition comprises two or more components, these components are selected in a total amount not exceeding 100% by weight.

[0020] Where upper and lower limits are cited for a property, a range of values ​​defined by the combination of any of the upper limits with any of the lower limits is also implied.

[0021] The term "molecular weight" (or "MW") is used herein to refer to number average molecular weight, unless otherwise stated or the context requires otherwise. The number average molecular weight of a polyol can be measured by gel permeation chromatography (GPC) or vapor pressure osmometry (VPO).

[0022] The term "hydroxyl (OH) value" or "hydroxyl (OH) value" used herein refers to the number of milligrams of potassium hydroxide equivalent to the hydroxyl content in one gram of polyol determined by wet titration. Therefore, the OH value or value is expressed in mg KOH / g.

[0023] As used herein, the term "equivalent weight" (or "EW") refers to the weight of the polyol per reactive site. The equivalent weight is 56,100 divided by the hydroxyl number of the polyol.

[0024] The term "functionality" or "hydroxyl (OH) functionality" of a polyol refers to the number of hydroxyl groups per molecule of the polyol. The nominal functionality (or "Fn") of a polyol is the same as the nominal functionality of its starting compound (initiator). Unless otherwise indicated, functionality refers to the actual average functionality, which may be lower than the nominal functionality and is determined by dividing the number average molecular weight of the polyol by the equivalent weight of the polyol.

[0025] As used herein, the term "primary hydroxyl content" (or "PHC") refers to the relative proportion (in %) of primary hydroxyl groups in a polyether polyol based on the total number of hydroxyl groups including primary and secondary hydroxyl groups.

[0026] The terms "ethylene oxide content" and "propylene oxide content" in relation to polyether polyols refer to those portions of the polyol derived from ethylene oxide and propylene oxide, respectively. The contents may also be referred to as ethylene oxide content and propylene oxide content, respectively. Furthermore, the contents are herein based on the total alkylene oxide weight.

[0027] The method of the present invention is a method for preparing polyurethane foam, which comprises reacting a polyisocyanate with a polyether polyol component a) in the presence of a blowing agent, wherein the polyether polyol component a) comprises: a1) a first polyether polyol and a2) a second polyether polyol.

[0028] In the present invention, the polyether polyol component a) comprises two or more polyether polyols, including the above-mentioned first polyether polyol and the second polyether polyol and the optional third polyether polyol mentioned below, which are prepared by ring-opening polymerization of alkylene oxide in the presence of an initiator and a catalyst having multiple active hydrogen atoms. The catalyst can be an alkaline catalyst, such as potassium hydroxide (KOH), or a composite metal cyanide complex catalyst, the latter catalyst is also commonly referred to as a double metal cyanide (DMC) catalyst. One or more initiators can be used to prepare the polyether polyol. Suitable initiators include polyfunctional alcohols, typically containing 2 to 6 hydroxyl groups. Examples of such alcohols include glycols, glycerol, pentaerythritol, trimethylolpropane, triethanolamine, sorbitol and mannitol. Advantageously, monopropylene glycol (MPG), glycerol or a combination of the two can be used as an initiator.

[0029] In the present invention, two or more polyether polyols in the above-mentioned polyether polyol component a) comprise polyether polyols containing ether bonds (or ether units). In addition, the polyether polyol may additionally contain ester bonds (or ester units) and / or carbonate bonds (or carbonate units). Preferably, the polyether polyol does not contain ester bonds (or ester units). In addition, preferably, the polyether polyol does not contain carbonate bonds (or carbonate units). Further, the polyether polyol may be composed of ether bonds.

[0030] In the present invention, the first polyether polyol and the second polyether polyol are different from each other and should meet the following requirements:

[0031] a1) a first polyether polyol having a molecular weight of 300 g / mol to 1,500 g / mol, a hydroxyl value of 100 mg KOH / g to 650 mg KOH / g, and a propylene oxide content of more than 50 wt %; and

[0032] a2) a second polyether polyol having a molecular weight of 500 to 1,700 g / mol, a hydroxyl value of 50 to 650 mg KOH / g, an ethylene oxide content of more than 30% by weight, a propylene oxide content of less than 50% by weight, and a primary hydroxyl content of less than 40%.

[0033] The first polyether polyol and the second polyether polyol are further described below.

[0034] The first polyether polyol has a molecular weight of 300 g / mol to 1,500 g / mol. The molecular weight of the first polyether polyol is at least 300 g / mol, and may be at least 400 g / mol, or at least 500 g / mol, or at least 550 g / mol, or at least 600 g / mol. In addition, the molecular weight of the first polyether polyol is at most 1,500 g / mol, and may be at most 1,250 g / mol, or at most 1,000 g / mol, or at most 900 g / mol, or at most 800 g / mol.

[0035] In addition, the first polyether polyol has a hydroxyl value of 100 mg KOH / g to 650 mg KOH / g. The hydroxyl value of the first polyether polyol is at least 100 mg KOH / g, more preferably at least 150 mg KOH / g, more preferably at least 190 mg KOH / g, and most preferably at least 220 mg KOH / g. In addition, the hydroxyl value of the first polyether polyol is at most 650 mg KOH / g, more preferably at most 500 mg KOH / g, more preferably at most 400 mg KOH / g, and most preferably at most 300 mg KOH / g.

[0036] Furthermore, the first polyether polyol has a propylene oxide content of greater than 50% by weight.The first polyether polyol comprises a polyether chain having a propylene oxide content (greater than 50% by weight), an optional butylene oxide content and an optional ethylene oxide content.

[0037] Preferably, the propylene oxide content of the first polyether polyol is at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%, most preferably at least 99 wt%. In addition, preferably, the propylene oxide content of the first polyether polyol is at most 100 wt%.

[0038] The ethylene oxide content of the first polyether polyol can be 0 wt % or at least 3 wt % or at least 5 wt % or at least 10 wt % or at least 12 wt % or at least 15 wt %. In addition, the ethylene oxide content of the first polyether polyol can be less than 30 wt % or at most 25 wt % or at most 20 wt % or at most 15 wt % or at most 12 wt %.

[0039] The polyether chain of the first polyether polyol may comprise no ethylene oxide content but may comprise only propylene oxide and / or butylene oxide content, suitably only propylene oxide content.

[0040] In addition, the first polyether polyol may contain primary hydroxyl groups. The primary hydroxyl content of the first polyether polyol may be 0% or at least 1% or at least 3% or at least 5%. In addition, the primary hydroxyl content of the first polyether polyol may be at most 15% or at most 10% or at most 5%.

[0041] Furthermore, the first polyether polyol may have a functionality of 2 to 6, preferably 2 to 4, more preferably 2.5 to 3.5, and most preferably 2.7 to 3.3.

[0042] The second polyether polyol has a molecular weight of 500 g / mol to 1,700 g / mol. The molecular weight of the second polyether polyol is at least 500 g / mol and may be at least 700 g / mol or at least 800 g / mol or at least 850 g / mol or at least 900 g / mol. In addition, the molecular weight of the second polyether polyol is at most 1,700 g / mol, and may be at most 1,500 g / mol or at most 1,300 g / mol or at most 1,200 g / mol or at most 1,100 g / mol.

[0043] In addition, the second polyether polyol has a hydroxyl value of 50 mg KOH / g to 650 mg KOH / g. The hydroxyl value of the second polyether polyol is at least 50 mg KOH / g, more preferably at least 90 mg KOH / g, more preferably higher than 90 mg KOH / g, more preferably at least 100 mg KOH / g, more preferably at least 120 mg KOH / g, most preferably at least 140 mg KOH / g. In addition, the hydroxyl value of the second polyether polyol is at most 650 mg KOH / g, more preferably at most 450 mg KOH / g, more preferably at most 300 mg KOH / g, more preferably at most 250 mg KOH / g, most preferably at most 200 mg KOH / g.

[0044] Furthermore, the second polyether polyol has an ethylene oxide content of more than 30% by weight and a propylene oxide content of less than 50% by weight. The second polyether polyol comprises a polyether chain containing an ethylene oxide content (greater than 30% by weight), a propylene oxide content (less than 50% by weight) and optionally a butylene oxide content, suitably only an ethylene oxide content and a propylene oxide content.

[0045] Preferably, the ethylene oxide content of the second polyether polyol is at least 50 wt%, more preferably at least 60 wt%, more preferably at least 70 wt%, more preferably at least 75 wt%, more preferably greater than 75 wt%, more preferably at least 77 wt%, most preferably at least 80 wt%. In addition, preferably, the ethylene oxide content of the second polyether polyol is at most 99 wt%, more preferably at most 95 wt%, more preferably at most 90 wt%, more preferably at most 87 wt%, most preferably at most 85 wt%.

[0046] Preferably, the propylene oxide content of the second polyether polyol is at least 1 wt %, more preferably at least 5 wt %, more preferably at least 10 wt %, more preferably at least 13 wt %, most preferably at least 15 wt %. In addition, preferably, the propylene oxide content of the second polyether polyol is at most 50 wt %, more preferably at most 40 wt %, more preferably at most 30 wt %, more preferably at most 25 wt %, most preferably at most 20 wt %.

[0047] Furthermore, preferably, the second polyether polyol has a weight ratio of ethylene oxide to propylene oxide of at least 1: 1, more preferably at least 2: 1, more preferably at least 3: 1, more preferably at least 3.5: 1, more preferably at least 4: 1, and most preferably at least 4.5: 1. Furthermore, preferably, the second polyether polyol has a weight ratio of ethylene oxide to propylene oxide of at most 20: 1, more preferably at most 15: 1, more preferably at most 10: 1, more preferably at most 7: 1, more preferably at most 6: 1, and most preferably at most 5: 1.

[0048] In addition, the second polyether polyol comprises primary hydroxyl groups. The second polyether polyol has a primary hydroxyl content of less than 40%. Preferably, the primary hydroxyl content of the second polyether polyol is at least 1%, more preferably at least 5%, more preferably at least 10%, more preferably at least 14%, most preferably at least 17%. In addition, preferably, the primary hydroxyl content of the second polyether polyol is at most 35%, more preferably at most 30%, more preferably at most 25%, more preferably at most 23%, most preferably at most 21%.

[0049] Furthermore, the second polyether polyol may have a functionality of 2 to 6, preferably 2 to 4, more preferably 2.5 to 3.5, and most preferably 2.7 to 3.3.

[0050] Preferably, when preparing the second polyether polyol having both ethylene oxide content and propylene oxide content, only ethylene oxide is added in an initial step to react with the initiator, followed by the addition of only propylene oxide in a further step. This produces a second polyether polyol having an ethylene oxide midblock and propylene oxide endblocks, which may also be referred to as "PO-capped". Thus, such polyether polyols have a relatively low primary hydroxyl content which may be within the above range.

[0051] In the present invention, the weight ratio of the first polyether polyol to the second polyether polyol can be advantageously within a wide range. As demonstrated in the examples below, the present invention makes it possible to change the porosity of the polyurethane foam within a wide range by using the second polyether polyol in combination with the first polyether polyol, simply by changing the relative amount of the second polyether polyol relative to the amount of the first polyether polyol, without experiencing any foam sinking.

[0052] Thus, the weight ratio of the first polyether polyol to the second polyether polyol may advantageously be within a wide range and may be from 0.01: 1 to 100: 1. The weight ratio may be at least 0.01: 1 or at least 0.05: 1 or at least 0.1: 1 or at least 0.3: 1 or at least 0.5: 1 or at least 0.9: 1 or at least 1.5: 1. Furthermore, the weight ratio may be at most 100: 1 or at most 70: 1 or at most 50: 1 or at most 40: 1 or at most 30: 1 or at most 20: 1 or at most 10: 1 or at most 5: 1.

[0053] Furthermore, preferably, in the polyurethane foam preparation method of the present invention, in addition to the first polyether polyol and the second polyether polyol added for reacting with the polyisocyanate, no monool is added. Monool is an alcohol containing one hydroxyl group, while polyol is an alcohol containing two or more hydroxyl groups.

[0054] Furthermore, in the present invention, the polyether polyol component a) may further comprise a3) a third polyether polyol which is different from each of the first polyether polyol and the second polyether polyol and has a molecular weight of 2,000 to 12,000 g / mol, a hydroxyl value of 10 to 90 mg KOH / g, and a propylene oxide content of more than 50 wt %.

[0055] The third polyether polyol has a molecular weight of 2,000 g / mol to 12,000 g / mol. The molecular weight of the third polyether polyol is at least 2,000 g / mol and may be at least 2,300 g / mol or at least 2,500 g / mol or at least 2,700 g / mol. In addition, the molecular weight of the third polyether polyol is at most 12,000 g / mol and may be at most 8,000 g / mol or at most 5,000 g / mol or at most 4,000 g / mol or at most 3,500 g / mol or at most 3,000 g / mol.

[0056] In addition, the third polyether polyol has a hydroxyl value of 10 mg KOH / g to 90 mg KOH / g. The hydroxyl value of the third polyether polyol is at least 10 mg KOH / g, more preferably at least 30 mg KOH / g, more preferably at least 40 mg KOH / g, and most preferably at least 50 mg KOH / g. In addition, the hydroxyl value of the third polyether polyol is at most 90 mg KOH / g, more preferably at most 80 mg KOH / g, more preferably at most 70 mg KOH / g, and most preferably at most 65 mg KOH / g.

[0057] Furthermore, the third polyether polyol has a propylene oxide content of greater than 50 wt.%. The third polyether polyol comprises a polyether chain containing a propylene oxide content (greater than 50 wt. %), an optional butylene oxide content and an optional ethylene oxide content, suitably only an ethylene oxide content, more suitably only a propylene oxide content and an ethylene oxide content.

[0058] Preferably, the propylene oxide content of the third polyether polyol is at least 50 wt %, more preferably at least 70 wt %, more preferably at least 80 wt %, more preferably at least 85 wt %, most preferably at least 90 wt %. In addition, preferably, the propylene oxide content of the third polyether polyol is at most 100 wt %, more preferably at most 98 wt %, more preferably at most 96 wt %, most preferably at most 94 wt %.

[0059] Preferably, the ethylene oxide content of the third polyether polyol is at least 0 wt %, more preferably at least 2 wt %, more preferably at least 4 wt %, most preferably at least 6 wt %. In addition, preferably, the ethylene oxide content of the third polyether polyol is at most 50 wt %, more preferably at most 30 wt %, more preferably at most 20 wt %, more preferably at most 15 wt %, most preferably at most 10 wt %.

[0060] In addition, the third polyether polyol may contain primary hydroxyl groups. The primary hydroxyl content of the third polyether polyol may be 0% or at least 3% or at least 6% or at least 8%. In addition, the primary hydroxyl content of the third polyether polyol may be at most 25% or at most 20% or at most 15%.

[0061] Furthermore, the third polyether polyol may have a functionality of 2 to 6, preferably 2 to 4, more preferably 2.5 to 3.5, and most preferably 2.7 to 3.3.

[0062] The third polyether polyol can be part of a polymer polyol. That is, one or more polymers can be dispersed in the third polyether polyol. In particular, a solid polymer can be dispersed in the polyol to form a "polymer polyol". The base polyol of such a polymer polyol can generally have the characteristics of the third polyether polyol described above. Therefore, generally, a polymer polyol is a dispersion of a solid polymer in a liquid polyol. Such systems are well known in the art and are generally prepared by polymerizing one or more ethylenically unsaturated monomers in the presence of a free radical catalyst.

[0063] Examples of such polymer polyol systems and methods for their preparation are disclosed in, for example, EP 076491 A2, EP 0343907 A2 and EP 0495551 A2. It is also known that polyurea or polyurethane polymers can be used as dispersing polymers in polymer polyols instead of polymers based on ethylenically unsaturated monomers.

[0064] The polymer dispersed in the base polyol can in principle be any such polymer known to be suitable for this purpose. Therefore, suitable polymers include polymers based on ethylenically unsaturated monomers, in particular polymers of vinyl aromatics such as styrene, α-methylstyrene, methylstyrene and various other alkyl-substituted styrenes. Among them, styrene is preferably used. Vinyl aromatic monomers can be used alone or in combination with other ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile, vinylidene chloride, various acrylates and conjugated dienes such as 1,3-butadiene and isoprene. However, preferred polymers are polystyrene and styrene-acrylonitrile (SAN) copolymers. Another class of suitable polymers are polyureas and polyurethane polymers. Specifically, the condensation products of primary amines or polyol amines with aromatic diisocyanates are very useful in this regard. A suitable polymer is the condensation product of triethanolamine and toluene diisocyanate (TDI).

[0065] In the context of the present invention, the polyether polyol component a) additionally comprises the above-mentioned third polyether polyol, and the weight ratio of the third polyether polyol to the combination of the first polyether polyol and the second polyether polyol can be from 0.01: 1 to 10: 1. The weight ratio can be at least 0.01: 1 or at least 0.05: 1 or at least 0.1: 1 or at least 0.15: 1 or at least 0.2: 1. In addition, the weight ratio can be at most 50: 1 or at most 20: 1 or at most 10: 1 or at most 5: 1 or at most 1: 1 or at most 0.7: 1 or at most 0.5: 1 or at most 0.3: 1.

[0066] In the case of using a combination of a first polyether polyol, a second polyether polyol and a third polyether polyol as described above, the polyether polyol component a) may comprise 40 to 90 wt % (more suitably 60 to 85 wt %) of the first and second polyether polyols combined, and 10 to 60 wt % (more suitably 15 to 40 wt %) of the third polyether polyol.

[0067] The present invention also relates to a composition comprising the first polyether polyol and the second polyether polyol as described above. The above-discussed embodiments and preferences related to the first polyether polyol and the second polyether polyol used in the polyurethane foam preparation method of the present invention are also applicable to the first polyether polyol and the second polyether polyol contained in the composition.

[0068] In the process, the polyether polyol component a) is reacted with a polyisocyanate in the presence of a blowing agent.

[0069] The polyisocyanate may comprise an aromatic polyisocyanate or an aliphatic polyisocyanate, with aromatic polyisocyanates being preferred.

[0070] The aromatic polyisocyanate may, for example, include toluene diisocyanate (TDI) or polymeric TDI, xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenylmethane diisocyanate (MDI) or polymeric MDI (i.e., polymethylene polyphenyl isocyanate) or modified products thereof. Preferably, the aromatic polyisocyanate includes toluene diisocyanate (TDI), i.e., non-polymeric TDI. TDI may be a mixture of 80% by weight 2,4-TDI and 20% by weight 2,6-TDI, which is sold as "TDI-80".

[0071] Furthermore, the aliphatic polyisocyanate may include, for example, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate or isophorone diisocyanate, or modified products thereof.

[0072] In addition, the polyisocyanate may comprise any mixture of two or more of the above polyisocyanates. For example, the polyisocyanate may comprise a mixture of TDI and MDI, particularly a mixture wherein the weight ratio of TDI:MDI is from 10:90 to 90:10.

[0073] In the present invention, the blowing agent may include a chemical blowing agent and / or a physical (non-chemical) blowing agent. In this specification, a "chemical blowing agent" refers to a blowing agent that can provide a foaming effect only after chemically reacting with another compound. In the case where the blowing agent includes a chemical blowing agent, the chemical blowing agent preferably includes water. Water reacts with the isocyanate groups of the polyisocyanate, thereby releasing carbon dioxide, which causes foaming to occur.

[0074] However, other suitable blowing agents may additionally or alternatively be used, such as acetone, gaseous or liquid carbon dioxide, halogenated hydrocarbons, aliphatic alkanes and cycloaliphatic alkanes.

[0075] Due to the ozone depletion effect of fully chlorinated fluorinated alkanes (CFCs), it is generally not preferred to use this type of blowing agent, but they can be used within the scope of the present invention. Halogenated alkanes in which at least one hydrogen atom is not replaced by a halogen atom (including the so-called HCFCs) have no or less ozone depletion effect and are therefore preferred halogenated hydrocarbons for physically blown foams. One suitable HCFC-type blowing agent is 1-chloro-1,1-difluoroethane. Another halogenated alkane of this type suitable for use as a blowing agent is dichloromethane.

[0076] The above-mentioned foaming agents may be used alone or in admixture of two or more.

[0077] The amount of blowing agent is determined by the desired density of the polyurethane foam to be prepared. For example, a relatively low density can be obtained by using a relatively high amount of blowing agent, and vice versa. A skilled person can easily determine the amount of blowing agent (physical and / or chemical blowing agent) required to obtain a desired foam density.

[0078] In the present invention, water may be used as a blowing agent in an amount of at least 0.1 parts by weight (pphp) per hundred parts by weight of polyol, or at least 0.5 pphp, or at least 1 pphp. In addition, in the present invention, water may be used as a blowing agent in an amount of up to 10 parts by weight (pphp) per hundred parts by weight of polyol, or up to 5 pphp, or up to 3 pphp, or up to 2 pphp.

[0079] In the case of halogenated hydrocarbons, aliphatic alkanes and alicyclic alkanes, the amount of blowing agent may be 1 to 50 parts per hundred parts by weight of polyol (pphp), suitably 1 to 30 pphp, more suitably 1 to 20 pphp.

[0080] Furthermore, preferably, the polyurethane foam to be prepared in the present method is a flexible polyurethane foam. Furthermore, the flexible polyurethane foam is suitably a block foam. In the present specification, "block foam" refers to a foam made by applying the free rise (unconstrained rise) of foam.

[0081] In the present invention, the isocyanate index (or NCO index) may be relatively low, which is particularly desirable when viscoelastic (VE) properties are desired for the resulting foam. The isocyanate index may be at most 120, more suitably at most 110, more suitably at most 100, and most suitably at most 90. In addition, the isocyanate index is preferably above 60 and may be at least 70 or at least 80.

[0082] In this specification, the "isocyanate index" is calculated as 100 times the molar ratio of -NCO groups (isocyanate groups) to NCO-reactive groups in the reaction mixture. In other words, the isocyanate index is defined as: [(actual amount of isocyanate) / (theoretical amount of isocyanate)]*100, where the "theoretical amount of isocyanate" is equal to 1 equivalent of isocyanate (NCO) groups per 1 equivalent of isocyanate-reactive groups.

[0083] Such "isocyanate-reactive groups" as mentioned above include, for example, OH groups from the polyether polyol component a) and from any water that may be used as blowing agent. Isocyanate groups also react with water.

[0084] Further, preferably, the polyurethane foam to be prepared in the present method has a relatively low resilience. Resilience is a measure of the surface elasticity of the foam and can be related to comfort or "feel". Resilience is usually measured by dropping a steel ball onto the foam and measuring the height of the ball rebound. This test is generally referred to as the "ball rebound test". A suitable ball rebound test method is the "ASTM D3574-Test H" method. In the present invention, the polyurethane foam can have a resilience lower than 40%, suitably lower than 35%, more suitably lower than 30%, and most suitably the resilience is at most 25% or at most 20% or at most 15%. In addition, the resilience can be at least 1% or at least 2%. The resilience of the polyurethane foam in the present invention can be measured by Test H from the above-mentioned ASTM D3574 method.

[0085] In addition, other components may also be present during the polyurethane preparation process of the present invention, such as one or more polyurethane catalysts, surfactants and / or crosslinking agents.

[0086] Polyurethane catalysts are known in the art and include many different compounds. For the purposes of the present invention, suitable catalysts include tin-based, lead-based or titanium-based catalysts, preferably tin-based catalysts, such as tin salts and dialkyltin salts of carboxylic acids. Specific examples are stannous octoate, stannous oleate, dibutyltin dilaurate, dibutyltin acetate and dibutyltin diacetate. Other suitable catalysts are tertiary amines, such as bis(2,2'-dimethylamino)ethyl ether, trimethylamine, triethylamine, triethylenediamine and dimethylethanolamine (DMEA). Examples of commercially available tertiary amine catalysts are those sold under the trade names Niax, Tegoamin and Dabco (all trademarks). The catalyst is typically used in an amount of 0.01 to 2.0 parts by weight (php) per one hundred parts by weight of polyether polyol. The preferred amount of the catalyst is 0.05php to 1.0php.

[0087] The use of foam stabilizers (surfactants) is well known. Silicone surfactants are most commonly used as foam stabilizers in polyurethane production. A variety of such silicone surfactants are commercially available. Typically, such foam stabilizers are used in an amount of 0.01 to 5.0 parts by weight per hundred parts by weight of polyether polyol (pphp). The preferred amount of stabilizer is 0.25 pphp to 2.0 pphp, more preferably 0.75 pphp to 1.5 pphp.

[0088] The use of crosslinking agents in the production of polyurethane foams is also well known. It is known that polyfunctional diolamines can be used for this purpose. The most commonly used polyfunctional diolamine that can also be used to prepare polyurethane foams, especially flexible polyurethane foams, is diethanolamine, usually abbreviated as DEOA. The crosslinking agent can be applied in an amount of up to 2 parts by weight per hundred parts by weight of polyol (pphp), but most suitably an amount in the range of 0.01 pphp to 0.5 pphp is applied.

[0089] In addition, in the polyurethane preparation method of the present invention, other well-known auxiliary agents such as colorants, flame retardants and fillers can also be used.

[0090] The method of the present invention may involve combining polyisocyanates, polyether polyol component a), blowing agents, catalysts, and optional surfactants, crosslinking agents, flame retardants, colorants, and / or fillers in any suitable manner to obtain polyurethane foam. For example, the method may include mixing polyether polyol component a), blowing agents, catalysts, and any other optional components other than polyisocyanates, and then adding polyisocyanates.

[0091] Furthermore, the method of the invention may comprise forming the foam into a shaped article before it has fully cured. Suitably, forming the foam may comprise pouring a liquid mixture containing all components into a mould before gelling is complete.

[0092] The present invention also relates to a polyurethane foam obtainable by the above method, and a shaped article comprising the polyurethane foam obtainable by the above method or a polyurethane foam obtainable by the above method.

[0093] The present invention is further illustrated by the following examples.

[0094] Example

[0095] 1. Experimental Procedure

[0096] The materials (polyether polyol, polyisocyanate and other components) used in the polyurethane foam experiments are shown in Table 1 below.

[0097] Table 1

[0098]

[0099] DMC = double metal cyanide; KOH = potassium hydroxide; EO = ethylene oxide; PO = propylene oxide; EO content and PO content based on the total alkylene oxide weight; MW = molecular weight; PHC = primary hydroxyl content

[0100] In the polyurethane foam experiment, the non-polyisocyanate components were mixed in a high-speed mixer at about 2,500 rpm for 50 seconds. The polyisocyanate component was then added and the mixture was stirred for about 5 seconds before being poured into a box measuring 30 cm*20 cm*15 cm to form the polyurethane foam. The full rise time was measured. The full rise time is the time period between the time the polyisocyanate is added and the time the maximum height is reached.

[0101] Furthermore, the following properties of the foams thus obtained were measured:

[0102] 1) Density according to ASTM D3574-Test A, where the sample size is 100*100*50mm 3 And 2 samples / foam.

[0103] 2) Porosity according to ASTM D3574-Test G using an "IDM" foam porosity tester, where a 50*50*25 mm 3 The foam sample is placed in a vacuum chamber cavity and a specified automatic constant air pressure differential is applied (125 Pa). The air volume reading is recorded in liters / minute.

[0104] 3) According to ASTM D3574-Test M recovery time, where 100*100*50mm 3 Foam sample. Measure the recovery time (RT) to 1N.

[0105] 4) Resilience test according to ASTM D3574-H, where the sample size is 100*100*50mm 3 and 2 samples / foam. This involves dropping a 16mm diameter steel ball onto the sample and measuring the percentage height at which the ball rebounds.

[0106] 2. Polyurethane foam experiment

[0107] Polyurethane foams were prepared according to the formulations shown in Table 2 below, which also shows foam properties such as full rise time, foam sink (yes / no), density, porosity, recovery time (RT), and resilience.

[0108] As can be seen from Table 1, polyol A, polyol B and polyol C correspond to the first polyether polyol, the second polyether polyol and the third polyether polyol related to the present invention, respectively.

[0109] In addition, the difference between polyol D and polyol B is that the molecular weight of polyol B is relatively low and the OH value is relatively high, while the molecular weight of polyol D is relatively high and the OH value is relatively low. In addition, polyol B is PO-terminated (mainly having secondary hydroxyl groups from PO at the ends of the polyether chains), resulting in relatively low primary hydroxyl content (PHC). On the contrary, polyol D is EO-terminated (mainly having primary hydroxyl groups from EO at the ends of the polyether chains), resulting in relatively high PHC. However, what is common to polyol B and polyol D is that both are prepared by the ring-opening polymerization of propylene oxide and ethylene oxide in the presence of KOH catalyst and glycerol, and both have relatively high EO content and relatively low PO content. Polyol D is the same polyol as the polyether polyol referred to as "Caradol SA36-02" in WO2019086655 discussed above.

[0110] Experiment 1 is a reference experiment, in which only polyol A and polyol C were used without polyol B or polyol D. As can be seen from Table 2, the foam obtained in Experiment 1 did not sink and had a porosity of 6 l / min. Experiments 2 to 6 are comparative experiments, in which polyol D was used in addition to polyol A and polyol C. By increasing the amount of polyol D, the porosity of the foam can be increased from 9 l / min (Experiment 2: 2 pbw polyol D) to 39 l / min (Experiment 5: 15 pbw polyol D). However, it is unfavorable that it is impossible to further increase the porosity without the resulting foam sinking. Because in Experiment 6, in which 20 pbw polyol D was used, the foam experienced sinking, which shows that the foam stability is low at high amounts of polyol D (i.e., 20 pbw and above).

[0111] In Experiments 7 to 15 according to the present invention, Polyol B was used instead of Polyol D used in Experiments 2 to 6. Surprisingly and advantageously, the use of Polyol B also increased the porosity of the foam. However, unlike the foam in Experiment 5 using 20 pbw of Polyol D, the foams in Experiments 7 to 15 did not experience any sinking at any of the tested amounts of Polyol B (varying in a wide range from 2 pbw to 60 pbw). This indicates that the foam stability is high at both low and high amounts of Polyol B.

[0112] Thus, surprisingly and advantageously, the present invention makes it possible to vary the porosity of the polyurethane foam within a wide range, without experiencing any foam sinking, simply by varying the amount of the second polyol, when the second polyol (e.g., polyol B) is used in combination with the first polyether polyol (e.g., polyol A) described above. Thus, the present invention has a wide range of applicability (high adjustability), since, depending on the specific foam application and the corresponding specific foam porosity desired, the relative amount of the second polyol relative to the first polyol is simply increased or decreased without any foam sinking.

[0113] Table 2

[0114]

[0115]

[0116] pbw = parts by weight

[0117] 1) Experiment 1 is a reference experiment and Experiments 2 to 6 are comparative experiments (not according to the present invention); Experiments 7 to 15 are experiments according to the present invention.

Claims

1. A method for preparing a polyurethane foam, the method comprising reacting a polyisocyanate with a polyether polyol component a) in the presence of a blowing agent, wherein the polyether polyol component a) comprises: a1) a first polyether polyol having a molecular weight of 300 g / mol to 1,500 g / mol, a hydroxyl value of 100 mg KOH / g to 650 mg KOH / g, and a propylene oxide content of more than 50 wt %; and a2) a second polyether polyol having a molecular weight of 500 to 1,700 g / mol, a hydroxyl value of 50 to 650 mg KOH / g, an ethylene oxide content of more than 30% by weight, a propylene oxide content of less than 50% by weight, and a primary hydroxyl content of less than 40%.

2. The method of claim 1, wherein the first polyether polyol has an ethylene oxide content of less than 30 wt%.

3. The method of claim 1 or 2, wherein the first polyether polyol has a primary hydroxyl content of at most 15%.

4. The method according to any one of the preceding claims, wherein the second polyether polyol has a hydroxyl value of 100 mg KOH / g to 650 mg KOH / g.

5. The method according to any one of the preceding claims, wherein the weight ratio of the first polyether polyol to the second polyether polyol is from 0.01:1 to 100:

1.

6. The process according to any one of the preceding claims, wherein the polyether polyol component a) further comprises: a3) a third polyether polyol having a molecular weight of 2,000 to 12,000 g / mol, a hydroxyl value of 10 to 90 mg KOH / g, and a propylene oxide content of more than 50 wt %. 7 . The method of claim 6 , wherein a weight ratio of the third polyether polyol to a combination of the first polyether polyol and the second polyether polyol is from 0.01:1 to 10:

1. 8 . A composition comprising the first polyether polyol and the second polyether polyol according to any one of claims 1 to 5 .

9. A polyurethane foam obtainable by the method according to any one of claims 1 to 7. 10 . A shaped article comprising the polyurethane foam obtained by the method according to any one of claims 1 to 7 or the polyurethane foam according to claim 9 .

Images