AU704287B2 - A flexible polyurethane foam - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT :Name of Applicant: IMPERIAL CHEMICAL INDUSTRIES PLC '"Actual Inventor(s): Dirk Gerber; Johan Derluyn; Eric Huygens Address for Service: CALLINAN LAWRIE, 711 High Street, Kew, 3101, Victoria, Australia S* Invention Title: "A FLEXIBLE POLYURETHANE FOAM" The following statement is a full description of this invention, including the best method of performing it known to me:- So 24/98LP9743 CS.

I i~a~ A flexible polyurethane foam The present invention is concerned with flexible polyurethane foams.

Preparation of known flexible polyurethane foams has been disclosed extensively; see e.g. EP--22617, EP--10850, EP-296449, EP-392788, EP- 111121, EP-344551 and EP-555721.

EP-392788 discloses the preparation of flexible foams from MDIbased prepolymers having a rather low NCO value and from an isocyanatereactive composition comprising relatively high amounts of water.

EP-111121 describes the preparation of flexible polyurethane foam from 1) a prepolymer based on diphenylmethane diisocyanate (MDI) and optionally polymeric MDI and a polyol having 5-30% of oxyethylene groups, the prepolymer having an NCO content of 12-30% by weight, 2) polymeric MDI if the above prepolymer is made from MDI, 3) a polyol, having a low EO content, and 4) a blowing agent.

EP-344551 discloses a process for preparing a flexible foam from a prepolymer having an NCO value of 15-30% by weight which is made from a polyol having a hydroxyl functionality of at least 4.

EP-555721 discloses the preparation of flexible foams from a polyisocyanate prepolymer, water and a mixture of a polyol having a low 20 oxyethylene content and a polyol having a high oxyethylene content.

Surprisingly it has now been found that the properties of foams and their preparation may further be improved. The foams according to the invention Sshow a very high resilience, a very low compression set and a very low hysteresis and are stable (reduced shrinkage); the process for making the foams is characterised by good processing.

Therefore the present invention is concerned with a flexible Spolyurethane foam having a resilience of at least 60%, (ISO/DIS 8307); a hysteresis loss of at most 20% (ISO 3386/1); a compression set core/dry and humid of at most 5% (ISO 1856) and a compression hardness, 40% of kPa (ISO 3386/1).

The flexible foam of the invention preferably has a core density of kg/ 13 (ISO/DIS 845), a resilence of at least 65%, a hysteresis loss of at most and a compression hardness, 40% of 2.5-5 kPa.

24 '),9P9743.SP' 2 W- -3- Preferably the flexible polyurethane foam of the invention is prepared by reacting 1. a polyisocyanate composition, having an NCO value of by weight comprising a) 70-90 parts by weight of an isocyanate prepolymer having an NCO value of 5-15% by weight prepared by reacting an excessive amount of an organic polyisocyanate and a polyol having an average nominal hydroxyl functionality of 2-3, a number average equivalent weight of 1000-3000 and an oxyethylene content of 5-25% by weight, preferably the oxyethylene units being at the end of tne polymer chain; b) 10-30 parts by weight of a polyisocyanate having an NCO value of 30-33% by weight; and 2. a polyol composition in an amount of 30-150, preferably 100, parts by weight per 100 parts by weight of the above polyisocyanate composition, said polyol composition comprising a) 70-90, preferably 70-85 parts by weight of a polyoxyethylenepolyoxypropylene pLlyol having an average nominal hydroxyl functionality of 2-3, a number average equivalent weight of 1000-3000, preferably 1000-2000, and an oxyethylene content of 5-25% by weight, preferably the oxyethylene units 20 being at the end of the polymer chain; b) 5-25, preferably 10-25, parts by weight of a polyether polyol having an average nominal hydroxyl functionality of 2-8, a number average molecular weight of 200-3000 and an oxyethylene content of at least preferably of 100, by weight based or, the total oxyalkylene content; c) 2-8 parts by weight of water; the amount of 2a), 2b) and 2c) together being 100 parts by weight; and optionally d) additives; at an isocyanate-index of 40-100.

Preferably, the polyisocyanate used for making the isocyanate prepolymer is selected from 4,4'-diphenylmethane diisocyanate, isomeric 241981 P9743 SI'S.3 mixtures of and 2,4'-diphenylmethane diisocyanate, uretonimine and/or carbodiimide modified diphenylmethane diisocyanate having an NCO content of at least 25% by weight and urthane modified diphenylmethane diisocyanate having an NCO content of at least 25% by weight.

For preparing the foams ingredients la and 1b may be premixed or brought into contact with the isocyanate-reactive ingredients independently.

Likewise ingredients 2a-d may be premixed or not. Preferably the ingredients la and 1b are premixed, as well as ingredients 2a-d.

The process is suitable to make moulded flexible foams as well as slabstock flexible foams and prefera-' y is conducted at an isocyanate-index of 70-90.

In the context of the present invention the following terms have the following meaning: 1) isocyanate index or NCO index or index: the ratio of NCO-groups over isocyanate-reactive hydrogen atoms present in a formulation, given as a percentage: FNCO]xl00 [active hydrogen] In other words the NCO-index expresses the percentage of isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.

It should be observed that the isocyanate index as used herein is Sconsidered from the point of view of the actual foaming process involving the isocyanate ingredient and the isocyanate-reactive ingredients. Any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including such isocyanate-derivatives referred to in the art as quasi or semi- *prepolymers and prepolymers) or any active hydrogens reacted with isocyanate to produce modified polyoli or polyamines, are not taken into account in the calculation of the isocyanate index. Only the free isocyanate groups and the free 2!4.98LP9743.SP1 .4

M

isocyanate-reactive hydrogens (including those of the water, if used) present at the actual foaming stage are taken into account.

2) The expression "isocyanate-reactive hydrogen atoms" as used herein for the purpose of calculating the isocyanate index refers to the total of hydroxyl and amine hydrogen atoms present in the reactive compositions in the form of polyols, polyamines and/or water; this means that for the purpose of calculating the isocyanate index at the actual foaming process one hydroxyl group is considered to comprise one reactive hydrogen, one primary amine group is considered to comprise one reactive hydrogen and one water molecule is considered to comprise two active hydrogens.

3) Reaction system a combination of components wherein the polyisocyanate components are kept in a container separate from the isonyanatereactive components.

4) The expression "polyurethane foam" as used herein generally refers to cellular products as obtained by reacting polyisocyanates with isocyanate-reactive hydrogen containing compounds with water as reactive foaming agent (involving a reaction of water with isocyanate groups yielding urea linkages and carbon dioxide and producing polyurea-urethane foams).

5) The term "average nominal hydroxyl functionality" is used herein to indicate the number average functionality (number of hydroxyl groups per molecule) of the polyol composition on the assumption that this is the number average functionality (number of active hydrogen atoms per molecule) of the initiator(s) used in their preparation although in practice it will often be somewhat less because of some terminal unsaturation.

Ingredient la and its preparation has been described in EP-392788.

~Organic polyisocyanates for making ingredient la) may be selected from aliphatic, cycloaliphatic and araliphatic polyisocyanates, especially diisocyanates, like hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1, 4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and m- 2 4IIIl"7.1 SlPl -6and p- tetramethylxylylene diisocyanate, and in particular aromatic polyisocyanates like tolylene diisocyanates (TDI), phenylene diisocyanates and most preferably polymethylene polyphenylene polyisocyanates having an isocyanate functionality of 2 or more.

The polymethylene polyphenylene polyisocyanates may be selected from diphenylmethane diisocyanate, which includes 4,4'-MDI and isomeric mixtures of 4,4'-MDI, 2,4'-MDI and less than 10% by weight of 2,2'-MDI, crude MDI, polymeric MDI and modified variants of these polymethylene polyphenylene polyisocyanates containing carbodiimide, uretonimine, isocyanurate, urethane, allophanate, urea or biuret groups. Preferred polymethylene polyphenylene polyisocyanates are pure 4,4'-MDI, isomeric mixtures with 2,4'-MDI, uretonimine and/or carbodiimide modified MDI having an NCO content of at least 25% by weight and urethane modified MDI (obtained by reacting excess MDI and a low molecular weight polyol, MW at most 999 preferably) having an NCO content of at least 25% by weight.

Mixtures of MDI with up to 25% by weight of other polyisocyanates mentioned above may be used if desired.

i. The polyisocyanate may contain dispersed urea particles and/or urethane particles prepared in a conventional way, e.g. by adding a minor 20 amount of an isophorone diamine to the polyisocyanate. Most preferred MDI are isomeric mixtures containing less than 5% of 2,2'-MDI, 5-60% of 2,4'-MDI, the remainder being 4,4'-MDI.

Polyether polyols for making ingredient 1 a) preferably are selected from products obtained by the polymerisation of propylene oxide in the presence of polyfunctional initiators followed by the polymerisation of ethylene oxide.

S Suitable initiator compounds contain a plurality of active hydrogen atoms and include water, butanediol, ethylene glycol, propylene glycol, diethylene glycol, te triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexane dimethanol, glycerol, trimethylolpropane and 1,2,6- 2,4 (11P9741 WSl .h -1 hexanetriol. Mixtures of initiators may be used.

Other polyols which may be used comprise dispersions or solutions of addition or condensation polymers in polyols of the types described above. Such modified polyols, often referred to as "polymer polyols" have been fully described in the prior art and include products obtained by the in situ polymerisation of one or more vinyl monomers, for example styrene and/or acrylonitrile, in the above polyether polyols, or by the in situ reaction between a polyisocyanate and an amino- and/or hydroxy-functional compound, such as triethanolamine, in the above polyol.

Polyoxyalkylene polyols containing from 5 to 50% of dispersed polymer are particularly useful. Particle sizes of the dispersed polymer of less than 50 microns are preferred.

During the last years several methods have been described to prepare polyether polyols having a low level of unsaturation. These developments have made it possible to use polyether polyols at the higher end of the molecular weight range since such polyols can now be prepared with an acceptably low level of unsaturation. According to the present invention polyols having a low level of unsaturation may be used as well. In particular such high molecular weight polyols having a low level of unsaturation may be used for preparing 20 flexible foams having a high ball rebound.

Ingredient 1b preferably is a polymeric MDI having an isocyunatefunctionality of 2.5-2.9. Such polymeric MDI's have been described widely; see

S.

e.g. the ICI Polyurethanes Book by George Woods, 2nd edition, 1990, page 12.

Ingredient 2a may be selected from the polyols mentioned before for preparing ingredient la.

Ingredient 2b may be selected from polyols containing 2-8 and S S.

preferably 2-6 hydroxy groups prepard by oxyalkylating an initiator which may be selected from ethanolamine, diethanolamine, triethanolamine, 24 91)S I9741 SI'[ .7 ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, toluene diamine, diethyl toluene diamine, cyclohexane diamine, phenylene diamine, diphenylmethane diamine, an alkylated diphenylmethane diamine and ethylene diamine using ethylene oxide and optionally another alkylene oxide like propylene oxide. Such polyols and their preparation are widely known in the art.

The additives which optionally are used may be selected from, amongst others, chain extenders, cross-linkers, formation of urea and urethane enhancing catalysts like tertiary amines and tin compounds, surfactants, stabilises, flame retardants, fillers and anti-oxidants.

The process may be used to make slab-stock or moulded flexible foams. Moulding may be conducted with (preferably to at most 500C) and without heating the mould. The foams in generaly have a core density of 25-80, preferably 40-80, kg/m 3 (ISO/DIS 845) and may be used as cushioning material in furniture, car-seats and mattresses.

The present invention is illustrated by the following example.

Example A polyisocyanate composition was made by mixing 80 parts by weight (pbw) of prepolymer 1, 20 pbw of polymeric MDI and 0.7 pbw of SH210.

A polyol composition was made by mixing 2.5 pbw of water, 40 pbw of polyol 1, 10 pbw of a glycerol initiated polyoxyethylene polyol of MW1200, 0.35 pbw of D8154, 0.3 pbw of triethanolamine and 0.3 pbw of DMAPA.

A moulded flexible foam was prepared by allowing the above compositions to react in a mould (Krauss Maffei 2K RIMSTAR 40/20 mould temperature 45 0 After demoulding a foam was obtained having a core density of 62 kg/m 3 (ISO/DIS 845); compression set, 50%- core/dry and humid (100% humidity at 50 0 C) of 2% and 3% (ISO 1856); compression hardness, 40% of 24 X[lPW4 SI MI.X I-L-~I I -9- 2 5 i* kPa (ISO 3386/1), a resilience of 70% (ISO/DIS 8307) and a hysteresis loss of 12% (ISO 3386/1).

The polyisocyanate composition and the polyol composition were easily processable.

Prepolymer 1: The reaction product of MDI (10% 2,4'-MDI and 90% 4,4'- MDI) and a 6000 MW EO/PO polyol with nominal functionality of 3 and 15% w EO (all tipp). NCO value of prepolymer is 6.8% w.

Polymeric MDI: NCO value 30.7% by weight; isocyanate functionality 2.7.

SH210: silicone surfactant from OSi Specialties.

Polyol 1: 4500 MW EO/PO polyol with nominal functionality of 3 and w EO (all tipp).

D8154: amine catalyst from Air Products.

DMAPA: dimethylaminopropylamine, catalyst.

COMPARATIVE EXAMPLES An experiment equivalent to example 4 of EP-555721 was conducted: Experiment 1 A polyol blend was made from 90 pbw of a polyol 1 (OH value 28 mg KOH/g; EO= 15% w all tip; initiator glycerol); 10 pbw of anothe, polyol (OH value 42 mg KOH/g; EO=75% w random; initiator is trimethylol propane); 2.5 pbw of water; 0.80 pbw of D33 LV catalyst from Air Products; 0.30 pbw of dimethylethanolamine; 0.80 pbw of dimethylaminopropylamine; 0.50 pbw of B4113, a surfactant from Goldschmidt and 1.00 pbw of triethanolamine. 100 pbw of this blend was reacted with 44.5 pbw of a polymeric MDI (78% w diisocyanate; the diisocyanate fraction contains 26% w of 2,4'-MDI; NCO content 32.6%w).

The foam obtained had open cells and was subjected to physical testing measuring the physical properties.

24 94 1''43 S ILB C -7 l)l~a;P An experiment equivalent to example 6 of EP-111121 was conducted: Experiement 2: A polyol blend was made from 91 pbw of polyol 1; 2.60 pbw of water; 0.19 pbw of Niax A99 from Union Carbide; 0.57 pbw of D33 LV; 1.00 pbw of 1,4 butanediol; 0.30 of B 4690 a surfactant from Goldschmidt and 4.34 pbw of Arcton 11. 100 pbw of this blend was reacted with 69 pbw of a polyisocyanate. The polyisocyanate was prepared by reacting 100 pbw of MDI w of 2,4'-MDI) with 41 pbw of an EO/PO polyol (OH value 41 mg KOH/g; EO= 14%w random; glycerol initiated); then 60 pbw of polymeric MDI was added (NCO 30.7% w and isocyanate functionality was th rinal NCO value was 25.2%w. The foam obtained showed shrinkage and was subjected to the same tests as above. The results were as follows; the values claimed are given as well.

Experiment 2 Experiment 1 Claimed S. Invention Density kg/m 3 ISO/DIS 845 46.3 53.8 25-80 5 Resilience ISO/DIS 8307 52 59 CLD 40% kPa ISO 3386/1 5.9 4.4 Hyst. Loss ISO 3386/1 26 18 Comp Set 50% dry ISO 1856 7.6 4.0 50% humid ISO 1856 12.4 5,1 SWhere the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification, they are to be interpreted as specifying the presence of the stated features, integers, steps or components referred to, but not to preclude the presence or addition of one or more other feature, integer, step, component or group thereof.

This Application is a divisional Application of Australian Patent Application No. 26725/95, the disclosure therein is incorporated herein by way of reference.

2 4 t81 P9743 SPI',i

Claims (3)

1. A flexible polyurethane foam having a resilience of at least (ISO/DIS 8307); a hysteresis loss of at most 20% (ISO 3386/1); a compression set core/dry and humid of at most 5% (ISO 1856) and a compression hardness, 40% of 1-5 kPa (ISO 3386/1).

2. Flexible foam according to claim 1, having a core density of

25-80 kg/m 3 (ISO/DIS 845). 3. Flexible foam according to claim 1 or claim 2 having a resilience of at least 65%, a hysteresis loss of at most 15% and a compression hardness, 40% of 2.5-5 kPa. 4. Flexible foam according to any one of claims 1 to 3 prepared by reacting a polyisocyanate composition, having an NCO value of by weight and comprising a) 70-90 parts by weight of an isocynate prepolymer having an NCO value of 5-15% by weight prepared by reacting an excessive Samount of an organic polyisocyanate and a polyol having an average nominal hydroxyl functionality of 2-3, a number average equivalent weight of 1000-3000 and an oxyethylene content of 5-25% by weight; b) 10-30 parts by weight of a polyisocyanate having an NCO value of 30-33% by weight; and a polyol composition in an amount of 30-150 parts by weight per 100 parts by weight of the above polyisocyanate composition, said polyol composition comprising a) 70-90 parts by weight of a polyoxyethylene- polyoxypropylene polyol having an average nominal hydroxyl functionality of 2-3, a number average equivalent weight of 1000-3000 and an oxyethylene content of 5-25% by weight; b) 5-25 parts by weight of a polyether polyol having an 124 s[ JNI743 'I .I 12- average nominal hydroxyl functionality of 2-8, a number average molecular weight of 200-3000 and an oxyethylene content of at least 80% by weight based on the total oxyalkylene content; c) 2-8 parts by weight of water; the amount of 2a), 2b) and 2c) together being 100 parts by weight; and optionally d) additives; at an isocyanate-index of 40-'i 0. Flexible foam according to claim 4, wherein the polyisocyanate used for making the isocyanate prepolymer is selected from 4,4'- diphenylmethane diisocyanate, isomeric mixtures of and 2,4'- diphenylmethane diisocyanate, uretonimine and/or carbodiimide modified diphenylmethane diisocyanate having an NCO content of at least 25% by weight and urethane modified diphenylmethane diisocyanate having an NCO content of at least 25% by weight. 6. Flexible foam according to claim 4 or claim 5, wherein polyol 2b has an oxyethylene content of 100% by weight. 7. Flexible foam according to any one of claims 4 to 6, wherein the amount of polyol 2b is 10-25 parts by weight. 8. Flexible foam according to any one of claims 4 to 7, wherein the amount of the polyol composition is 30-100 parts by weight. 9. Flexible foam according to any one of claims 4 to 8, wherein the index is 70-90. Flexible foam, substantially as herein described with reference to the Example but excluding the comparative Examples. DATED this 2nd day of April, 1998. IMPERIAL CHEMICAL INDUSTRIES PLC By their Patent Attorneys: CALLINAN LAWRIE 24.,981.P9743 Sl.l 12 I L. ~-CII ABSTRACT A flexible polyurethane foam having a resilience of at least (ISO/DIS 8307); a hysteresis loss of at most 20% (ISO 3386/1); a compression set core/dry and humid of at most 5% (ISO 1856) and a compression hardness, of 1-5 kPa (ISO 3386/1). The flexible foam of the invention preferably has a core density of 25-80 kg/m 3 (ISO/DIS 845), a resilience of at least 65%, a hysteresis loss of at most 15% and v compression hardness, 40% of 2.5-5 kPa. Z4 14 1K74A AI IIII