NZ622889B2 - Process for making a polyurethane foam - Google Patents

Abstract

Process for making a foam suitable as plant growth medium by reacting a polyisocyanate, a polyether polyol mixture and water at an isocyanate index of 90-150 wherein the polyol mixture used comprises at least 2 polyols and wherein the polyol mixture comprises less than 50 % by weight oxyethylene calculated on the weight of the polyol mixture. The polyurethane foam may be prepared from a polyisocyanate comprising diphenylmethane diisocyanate (MDI) and homologues thereof having an isocyanate functionality 5 of 3 or more wherein the amount of diisocyanate calculated on the total amount of the diisocyanates and the homologues is in the range of 20-80% or 25-70% by weight. culated on the weight of the polyol mixture. The polyurethane foam may be prepared from a polyisocyanate comprising diphenylmethane diisocyanate (MDI) and homologues thereof having an isocyanate functionality 5 of 3 or more wherein the amount of diisocyanate calculated on the total amount of the diisocyanates and the homologues is in the range of 20-80% or 25-70% by weight.

Description

/071162 PROCESS FOR MAKING A POLYURETHANE FOAM.

The present invention relates to a process for making a polyurethane foam, to a plant growth medium comprising such a foam and to the use of such a foam as plant growth medium.

Plant growth media comprising ethane foams are known.

US 3798836 discloses a water insoluble open celled foamed polyurethane matrix haVing dispersed therein thermoplastic particles.

US 3889417 makes a hydrophilic foam by reacting a prepolymer with a high amount of water. This foam may be used in horticultural ations. The water index applied is 1300-78000. A similar process has been disclosed in W0 96/16099 wherein no special guidance as to the nate index and the water index has been given; in the examples the water index was more than 1700 and the isocyanate index was less than 6. The prepolymers used are made from polyols haVing a molecular weight of at least 1000.

US 8 discloses a substrate for cultivating plants which substrate is a low density (18 kg/m3) hydrophilic polyurethane foam made by reacting a polyisocyanate and a polyol at a low NCO index, the polyol haVing an hydroxyl value of 900-1800 and the polyisocyanate being a toluene diisocyanate (TDI) type polyisocyanate.

US 5155931 uses a foam as plant mat, which foam is made by reacting an c isocyanate, which ably is TDI, and a polyol at an NCO-index of 90-120.

US 6479433 discloses a horticultural growing medium made by reacting a prepolymer and water in the presence of a selected filler material.

US 2005/0131095 discloses a process for making polyurethane foams at an NCO-index of . No special attention has been given to the water index; in the examples the NCO-index was n 85-106 and the water index varied between 93-120. However in this process the polyol mixture used has an overall high ylene content % by weight) and no polyol having a medium oxyethylene content (< 50 % by weight). The obtained foams as illustrated in the examples are flexible foams having a resilience of at least 60% and a compression load tion at 40 % (CLD) below 10 kPa.

WO2011/042284 describes flexible polyurethane foams for use as plant substrates.

These foams have a density of 25-70 kg/m3, a compression load deflection at 40 % (CLD) of 5-15 kPa and a volume increase at water saturation of at most 25 %. These foams are made at a low isocyanate index of 20-70 and at a high water index of 200-400 which means that there is a huge competition between the isocyanate ve components in the ation to react with the available isocyanate components which may lead to frothing (of the draining water) when the foam is used as substrate material.

The above described polyurethane foams could be further improved in particular ing water uptake and retention characteristics (further characterized as pF0 and pF1 values), foam stability and swelling at 100 % water saturation together with a high compression load deflection at low density, the prevention of frothing and the prevention of growth inhibition in particular of young plants (seedlings).

Surprisingly, we have found that all above mentioned ed side effects (e.g. frothing, growth inhibition,…) can be avoided by using a polyurethane foam fabricated at an isocyanate index in the range of 90 up to 150 in combination with a specific selection of isocyanates and polyether polyols.

Furthermore the foams according to the invention show excellent hardness which makes them in ular very suitable for example for green roof and landscaping applications.

Furthermore the foams according to the invention show excellent water ion characteristics and low swelling at 100% water saturation which makes them very suitable for use as plant growth ate for the promotion of seed germination and seedling growth.

Therefore the present invention is concerned with a plant growth medium made of a polyurethane foam and prepared from a polyisocyanate comprising diphenylmethane diisocyanate (MDI) and homologues thereof having an isocyanate functionality of 3 or more wherein the amount of diisocyanate calculated on the total amount of the yanates and the homologues is in the range of 20-80% or 25-70% by weight and having a resilience (measured according to ISO 8307) of at most 40%, a compression load deflection (CLD) at 40% (measured according to ISO ) of at least 16 kPa, a free-rise core y (measured according to ISO 845) of at least 20 kg/m3 and a volume increase at water saturation of at most 25%.

The polyurethane foam according to the invention preferably has a CLD which is at least 20 kPa and more preferably at least 25 kPa, a density which is 20 up to 50 kg/m3, a resilience which is at most 30% and a volume increase at water saturation of at most 20%.

The polyurethane foam according to the invention has in particular good water absorption e) and water retention. Water uptake and in particular water retention of a polyurethane foam can be measured by determination of pF values and may be visualized by means of a water retention curve which is a plot of measured tric water content retained in the foam on the Y-axis versus applied under pressure on the X-axis (see Figure 2A).

The polyurethane foam according to the invention preferably has a pF0 value of at least 70%, preferably at least 80%, more preferably at least 90% wherein the pF0 value is ed after subjecting a water ted foam sample having dimensions of 100 x 120 x 75 mm to a pressure of 0 cm H2O column for 30 minutes.

The polyurethane foam according to the invention may have a pF1 value in the range of % up to 90% wherein the pF1 value is measured after subjecting a water saturated foam sample of 100 x 120 x 75 mm to a re of -10 cm H2O column for 24 hours.

The polyurethane foam according to the invention suitable for g seedlings preferably has a pF1 value of at least 50%, more preferably at least 60% and most preferably at least 70% wherein the pF1 value is measured after subjecting a water saturated foam sample of 100 x 120 x 75 mm to a pressure of -10 cm H20 column for 24 hours.

A foam according to the invention having pF1 values in the range of 50% up to more than 75% is ideally suitable as plant growth medium for growing seedlings. The plant growth media according to the invention suitable for growing seedlings may be in the form of individual containers, also referred to as cultivating gation) blocks 2 and illustrated in Figure 1A. Said cultivating blocks 2 may be placed on a larger plant growth medium according to the invention and which may be in the form of a slab 1. The combination of a plant growth system in which several cultivating blocks 2 are placed onto a slab 1 as rated in Figure 1B is known and is in particular suitable for ating vegetables, fruit, flowers, etc in ouses. Cultivating (propagation) blocks according to the invention preferably have a pF1 values in the range of 50% up to more than 75% while larger plant growth medium (slabs) according to the invention preferably have a pF1 values in the range of 10% up to 50%. Figure 2A illustrates red pF characteristics for slabs and propagation blocks.

Furthermore the t invention is concerned with a process for making a polyurethane foam.

The process disclosed in the present ion can be used to fabricate the above mentioned plant growth media made of polyurethane foam.

The process according to the present invention comprises reacting at an isocyanate index of 90-150: — a polyisocyanate comprising diphenylmethane diisocyanate (MDI) and homologues thereof having an isocyanate functionality of 3 or more wherein the amount of diisocyanate calculated on the total amount of the diisocyanates and the homologues is 20-80 % by weight, preferably 25-70 % by weight and — a first polyoxyethylene polyoxypropylene polyol having an average nominal hydroxy functionality of 2-6, an average lar weight of 2000-12000, an oxyethylene content of more than 50 % weight calculated on the weight of this polyol, and — a second polyoxyethylene polyoxypropylene polyol having an average nominal hydroxy functionality of 2-6, an average molecular weight of 2000-6000, an oxyethylene content of 20-45% by weight calculated on the weight of this polyol, — a water content of 2-7 pbw, and wherein the weight ratio of the first and the second polyol used is ranging from 60:40 to :80.

Foams and processes for making ethane foams have been widely disclosed.

However the foams and processes according to the present invention have not been disclosed. The foams of the present invention are unique since they combine good water retention properties with excellent foam characteristics such as stability, hardness and limited foam ng at 100% water saturation.

The foams of the present invention are very suitable for use as plant growth medium since they have good wetting, water retention and water e ties.

The polyisocyanates used to make the polyisocyanate lymer) are known in the art.

They are widely called polymeric or crude MDI and es of polymeric or crude MDI and MDI.

Polymeric or crude MDI comprise MDI and homologues having an isocyanate functionality of 3 or more and are well known in the art. They are made by the phosgenation of a mixture of polyamines obtained by the acid condensation of aniline and formaldehyde.

The manufacture of both the polyamine mixtures and the polyisocyanate mixtures is well known. The condensation of aniline with formaldehyde in the presence of strong acids such as hydrochloric acid gives a reaction t containing diaminodiphenylmethane together with polymethylene polyphenylene polyamines of higher fiJnctionality, the e composition ing in known manner inter alia on the aniline/formaldehyde 2012/071162 ratio. The polyisocyanates are made by phosgenation of the polyamine es and the s proportions of es, triamines and higher polyamines give rise to related proportions of diisocyanates, triisocyanates and higher polyisocyanates. The relative proportions of diisocyanate, triisocyanate and higher polyisocyanates in such crude or polymeric MDI compositions determine the average fianctionality of the compositions, that is the average number of isocyanate groups per molecule. By varying the proportions of starting materials, the average functionality of the polyisocyanate compositions can be varied from little more than 2 to 3 or even . In ce, however, the average isocyanate functionality preferably ranges from 2.3-2.8. The NCO value of these polymeric or crude MDIs is at least 30% by weight. The polymeric or crude MDI contain diphenylmethane diisocyanate, the remainder being polymethylene polyphenylene polyisocyanates of fianctionality greater than two. If desired this polymeric or crude MDI may be mixed with MDI provided the polyisocyanate has the ed amount of diisocyanates and homologues having an isocyanate functionality of 3 or more.

The polyisocyanate used in the process according to the invention comprises 20-80%, preferably 25-70%, more preferably 25-55 % by weight of MDI and 80-20%, preferably 75-30% and more preferably 75-45 % by weight of homologues ofMDI, the homologues having an isocyanate functionality of 3 or more, wherein both amounts are calculated on the total amount of polyisocyanate.

For example such polyisocyanates may be made by mixing in appropriate ve amounts SUPRASEC® MPR (ex Huntsman), a 4,4’-diphenylmethane diisocyanate and EC® 2185 (ex Huntsman), a polymeric MDI having an NCO value of 30.7% by weight comprising about 37.7% by weight of diisocyanate. Mixtures of SUPRASEC® 2185 and SUPRASEC® MI 20 (obtainable ex Huntsman), containing about 80 parts by weight of 4,4’-MDI and about 20 parts by weight of 2,4’-MDI and less than 2 parts by weight of 2,2’-MDI may also be used.

Use of a ocyanate having a functionality of 3 and more is beneficial in order to fabricate a polyurethane foam for use as plant growth substrate having high pF1 values (pF1 values > 50%) because isocyanates having functionality of 3 and more lead to foams with relatively more closed pores (cell membranes) and have hence better water retention properties.

Prepolymers made of above mentioned polyisocyanates may be used. The prepolymer preferably has an NCO-value of 10-30 % by weight and is made by ng a polyisocyanate comprising 20-80 % (preferably 25-55%) by weight of ylmethane diisocyanate (MDI) and 80-20 % (preferably 75-45%) by weight of homologues of this diisocyanate, the gues having an isocyanate functionality of 3 or more, the amounts both calculated on the amount of polyisocyanate, and a polyol having an average molecular weight of 0 and an average nominal hydroxyl functionality of 2-6.

Polyols suitable for use in the polyisocyanate prepolymer have an average molecular weight of 62-7000 and an average nominal hydroxyl fianctionality of 2-6. Examples include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, glycerol, triethanolamine, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, sorbitol, polyoxyethylene s, polyoxypropylene polyols, yethylene polyoxypropylene polyols and mixtures thereof Preferred are polyols obtained by the polymerization of ne oxide and optionally propylene oxide in the presence, where necessary, of polyfiJnctional initiators.

Suitable initiator nds contain a plurality of active hydrogen atoms and include water, butanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, ylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexane- anol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol and sorbitol.

Mixtures of initiators and/or cyclic oxides may be used. The polyoxyethylenepolyoxypropylene polyols are obtained by the simultaneous or sequential addition of ethylene and propylene oxides to initiators as fully described in the prior art. Random copolymers, block copolymers and combinations thereof may be used. red ones are those having at least part and preferably all of the oxyethylene groups at the end of the polymer chain d or tipped). Mixtures of the said polyols may be used as well.

Preferred polyols suitable for use in the polyisocyanate prepolymer are polyoxyethylene polyols and polyoxyethylene polyoxypropylene polyols having an average nominal hydroxyl fianctionality of 2-4 and most preferably of 3, an average molecular weight of 250-1000 and an oxyethylene content of at least 50 % by weight, calculated on the weight of the polyol. Such polyols are commercially available. An example is Polyol 3380 ex Perstorp.

Also according to the invention part of polyol 1 and/or polyol 2 may be prereacted with all or part of the isocyanate. Part of polyol 1 and/or 2 may hence be used to make a polyisocyanate prepolymer composition. Therefore, a suitable prepolymer may be made by first reacting the polyisocyanate according to the invention with at least part of the first and/or second polyol.

The polyisocyanate prepolymers according to the invention are made in known manner by combining and mixing the polyisocyanate and the polyol and allowing them to react.

The polyisocyanate and the polyol ratio is such that after the reaction a ymer is obtained having an NCO-value of 10-30 % by weight. If desired a st may be used which enhances the formation of urethane .

Preferably polyisocyanate prepolymers are used to make the foam according to the invention. Use ofprepolymers may be beneficial towards formation of cross links in the polyurethane foam and a harder foam may be obtained in that case.

Polyols which may be used as first and second polyol e products ed by the polymerisation of ethylene oxide and propylene oxide in the presence, where necessary, of polyfunctional initiators. Suitable initiator compounds contain a plurality of active hydrogen atoms and include water, butanediol, ethylene glycol, propylene , diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexane dimethanol, glycerol, trimethylolpropane, l,2,6-hexanetriol, rythritol and sorbitol. Mixtures of initiators may be used as well. The polyoxyethylene-polyoxypropylene polyols are obtained by the simultaneous or tial addition of ne and propylene oxides to initiators as fully described in the prior art. Random mers, block copolymers and combinations thereof may be used having the indicated amount of oxyethylene groups.

The first her polyol used in the process for making the foam according to the invention has an e nominal hydroxy filnctionality of 2-6, an average lar weight of 2000-12000 and an oxyethylene content of more than 50 % weight calculated on the weight ofthis polyol.

According to some embodiments, the first polyether polyol used in the process for making the foam according to the invention ably has an average l hydroxy functionality of 2-4 and more preferably of 3, an average molecular weight of 2000-8000 and more preferably of 3000-6000 and an oxyethylene t of more than 60% by weight calculated on the weight of this polyol.

According to some embodiments the unsaturation content of the first polyether polyol may be at most 0.03 meq/g, preferably at most 0.02 meq/g more preferably at most 0.01 meq/g.

The second polyether polyol used in the process for making the foam according to the invention has an average nominal hydroxy filnctionality of 2-6, an average molecular weight of 2000-6000 and an oxyethylene content of 20-45% by weight calculated on the weight ofthis polyol.

According to some embodiments, the second polyether polyol used in the process for making the foam according to the invention preferably has an average l hydroxy functionality of 2-4 and more preferably of 3, an average molecular weight of 2000-4000 and an oxyethylene content of 20-35 % by weight and more preferably of 25-30 % by weight calculated on the total weight of this polyol.

According to some embodiments the oxyethylene groups in the first and second polyol are randomly distributed.

According to some embodiments the unsaturation content of the second polyether polyol may be at most 0.03 meq/g, preferably at most 0.02 meq/g, more preferably at most 0.01 meq/g.

According to some ments the weight ratio of the first polyol to the second polyol used in the process for making the foam according to the invention is ranging from 60:40 to 20:80, preferably ranging from 49:51 to 30:70.

According to some ments the weight ratio of the second polyether polyol used is preferably at least 50% calculated on the total weight of the first and second polyether polyol or in other words the weight ratio of the first and the second polyol used is ranging from 49:51 to 20:80, more preferably ranging from 49:51 to 30:70.

The total ylene content is preferably lower than 50 % by weight calculated on the total weight of the first and second polyether.

According to some embodiments the first and second polyether polyol may be first mixed to form a stable dispersion of polyether polyols before adding them to the polyisocyanate ition.

The average weight ratio of the oxyethylene t in the stable dispersion of polyether polyols is preferably less than 50 % calculated on the weight ofthe dispersion.

The first and second polyether polyols are known in the art and/or commercially ble.

Examples ofthe first type of polyether polyols are Daltocel® F442, F444 and F555, all ex Huntsman and having an oxyethylene t of more than 60 % by weight. An example of the second type of polyether polyol is Jeffol® G11-56 ex Huntsman. Daltocel and Jeffol are trademarks of the Huntsman Corporation or an Affiliate thereof which has been registered in one or more but not all countries.

According to some embodiments, the process for making the foam according to the present ion is performed at an isocyanate index of 95-120, more preferably at an isocyanate index of100-110.

Further isocyanate-reactive chain extenders and/or cross-linkers having an average molecular weight of 60-1999 may be added. es of such nds are butanediol, ethylene , propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexane dimethanol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, sorbitol and polyoxyethylene polyols, polyoxypropylene polyols, polyoxyethylene polyoxypropylene polyols and mixtures thereof having an average molecular weight of about 200, 600 and 1000 and mixtures of such compounds. The amount used of these chain extenders and/or cross- s is up to 20 and preferably up to 10 pbw per 100 pbw of the above polyether polyol mixture having an average molecular weight of 2000 and more.

Water may be added to the reaction in such an amount that the isocyanate index is in the range of 90-150 (preferably 95-120, more preferably 100-110). The amount of water (water content) used in the process according to the invention is preferably in the range of 2-7 pbw and more ably in the range of 3.5-6 pbw.

Further a catalyst may be used which enhances the formation of urethane groups.

Preferably it is used in an amount of 0.1 — 2% by weight (on all isocyanate reactive ingredients). Such catalysts are generally known in the art. Examples are amine catalysts, like triethylenediamine, N,N-dimethylethanolamine, bis (N,N-dimethylaminoethyl)ether, imethylaminoethoxy)-ethanol, N,N,N’-trimethyl-N’-hydroxyethylbisaminoethyl- ether, N-(3-dimethylaminopropyl)-N,N-diisopropanolamine, iethylpiperazine and 1-(bis(3-dimethyl-aminopropyl)aminopropanol and organometallic compounds like stannous octoate and dibutyltin ate. Mixtures of catalysts may be used as well.

Optionally the foams may be made in the presence of additives and aries used in the polyurethanes art, like fire retardants, surfactants, other blowing agents, smoke- surpressants, colouring agents, carbon black, anti-microbial agents, anti-oxidants, mould release agents, fillers and fertilizers.

The foams are made by combining and mixing all ingredients and allowing the reaction to take place. The foams may be made according to a free rise process, a moulding process, a slabstock s, a lamination s or a spray process. When the foams are made in a mould, an overpack of at most 100 %, preferably at most 50% is used.

When using a moulding process, the foams may show an advantageous morphology: when two pieces of the same foam are placed upon each other, both saturated with water, then the lower piece will absorb less of the water from the upper foam than a prior art foam made without this overpack.

The ingredients may be fed ndently to the mixing head of a foaming machine.

Preferably the isocyanate reactive ingredients are premixed, ally together with the ves and auxiliaries used in the polyurethanes art, before they are mixed with the polyisocyanate.

The foams ed by the process of the present invention have an overall free-rise core density of at least 20 kg/m3 and preferably of 20-50 kg/m3 a resilience of at most 40 % and preferably at most 30 % and a volume increase at water saturation of at most 25 % and preferably at most 20 %.

The foams obtained by the process of the present invention preferably have a compression load deflection (CLD) at 40 % which is at least 16 kPa, more ably more than 20 kPa.

The foams obtained by the process of the present invention may have a compression load deflection (CLD) at 40 % up to 200 kPa.

The foams ed by the process of the present invention fiirther have a water absorption, a level of air flow and cell openness which makes them in particular suitable for use as plant growth medium.

The foams obtained by the process of the present ion may be used in greenhouses for cultivating flowers, fruit, vegetables and other suitable vegetation as well as for cultivating le vegetation on green walls and greenroofs and other applications related to water economy management for plants.

For use in green houses the foam of the present invention may be r complemented by a drip irrigation system to which additional nutrients can be ed.

For use in greenroofs and landscape coverage the foam of the present invention may be further complemented by a waterproof system based on pure polyurea (e.g. Tecnocoat P- 2049).

For use in greenroofs the foams obtained by the present invention may improve the isolation of the covering of a building. An onal layer of thermal insulation may further improve the energy efficiency and may reduce the costs of heating and refrigeration up to 5 %.

Furthermore the use of the foam of the present invention in greenroofs, green walls and landscape coverage may reduce the acoustic contamination thanks to the muffling of the sound and it will diminish the number of "hard" surfaces available for the reverberation of the sound.

The hydrophilic ate foam of the present ion is characterized by the ability to very efficient manage and retain water. The foam may be used in various thicknesses and profiles to meet the end user final requirements.

The main advantages of the foam of the present invention compared to existing plant vating) substrates are: 0 The foam of the present invention can hold up to 30 times its weight in water with limited swelling (< 25%). 0 The foam of the t invention has water retention characteristics which are comparable to natural plant growth media such as soil. 0 The foam of the t invention can drain sufficiently the overload of water while more than 65% of the water is retained in the foam. 0 The foam of the present invention is easy to handle and install (various thicknesses and profiles can be configured in order to meet the end user final requirements). 0 Due to its light weight (20-50 kg/m3), the foam of the present invention is ideally le for greenroofs on older buildings with weak structural properties. 0 The use of the foam of the present invention may improve building insulation and hence reduce heating and cooling costs by up to 5%.

In the context ofthe present application 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: lOO (%). [active hydrogen] In other words the NCO-index expresses the percentage of nate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive en used in a formulation.

It should be observed that the isocyanate index as used herein is considered from the point of View of the actual foaming process involving the isocyanate ingredient and the isocyanate-reactive ients used in that reaction step. Only the free isocyanate groups and the free isocyanate-reactive hydrogens (including those of the water) present at the actual foaming stage are taken into t.

Water index is the ratio lOOY/X (%) wherein Y is the amount of water in grams actually used in a ation and X is the total amount of water in grams theoretically needed in the same formulation so as to obtain an isocyanate index of 100. 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 t 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 s one yl group is considered to comprise one reactive hydrogen and one water molecule is considered to comprise two active hydrogens. 3) The sion “polyurethane foams” as used herein generally refers to cellular products as obtained by reacting polyisocyanates with isocyanate-reactive hydrogen containing compounds, using foaming agents, and in particular includes cellular products obtained with water as reactive foaming agent (involving a reaction of water with isocyanate groups yielding urea linkages and carbon dioxide and producing polyureapolyurethane foams). 4) The term “nominal yl functionality” or “nominal functionality” or “hydroxyl functionality” is used herein to indicate the functionality (number ofhydroxyl groups per le) of the polyol composition on the assumption that this is the fianctionality r 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. The term “equivalent weight” refers to the molecular weight per isocyanate reactive hydrogen atom in the molecule.

) The word “average” refers to “number average”. 6) Density is measured on foam samples made under atmospheric conditions without use of auxiliary blowing agents and according to ISO 845. 7) Hardness CLD: compression load deflection at 40 % measured according to ISO 3386/1 with the proviso that the hardness is measured on dry and non-crushed samples during the first cycle. 8) Foam swelling AV is the volume increase of foam samples at 100 % water saturation, in %: V1 _V2 AV: x 100(%) wherein V2 is the volume of the foam without water intake and V1 is the volume of the foam at maximal water tion both at 23 °C and 50 % relative humidity. In order to determine V1, the foam is immersed in water for 24h at ambient pressure and 23 °C. 9) Resilience is measured according to ISO 8307 with the provisio that the resilience is measured on dry and ushed samples.

) Water retention values are measured in this invention by means of pF values. In the context of the invention pF values correspond to water volumes retained in the foam after immersing a foam sample in water for a predefined period to e a water ted foam sample and then ting the water saturated foam to different under pressures for a predefined . In a pF curve the measured volumetric water content retained in the foam is plotted on the Y-axis, against the applied under pressure on the (negative) X-axis.

On the pF curve a pFo value corresponds to a volume of water retained in a water saturated foam sample after subjecting said foam sample for a predefined period to a pressure of 0 cm H20 column. On the pF curve a pF1 value corresponds to a volume of water retained in a water saturated foam sample after subjecting said foam sample for a predefined period to a pressure of -10 cm H20 column. On the pF curve a pF1_5 value corresponds to a volume of water retained in a water saturated foam sample after subjecting said foam sample for a predefined period to a pressure of -32 cm H20 . pFo and pF1 values taken fiom the pF curve are le to calculate the water retention and hence availability of water in a polyurethane foam. pFo and pF1 are fiirther defined pFo = x 100(%) pF1= ”1 x 100(%) wherein Vf is the initial volume (in ml) of a (dry) foam sample, Vu is the water uptake (meaning the volume of water retained in a water saturated foam sample after subjecting said foam sample for a ined period to a pressure of 0 cm H20 column) in ml of the foam sample when saturated with water and VH is the volume ofthe water retained in ml after subjecting the water saturated foam sample to a pressure of -10 cm H20 column for a predefined period.

Vf, Vu and VH are determined as follows: a foam sample is cut to obtain indicated dimensions such as 100x120x75 mm or 0x60 mm (length x width x height).

Hence Vf of the sample is 900ml or 720 ml. The dry weight of the foam sample is determined at 105 CC. Then the foam sample is immersed for a predefined period of 6 hours at atmospheric re and 23 °C in a water bath in such a way that 1 cm of the sample in the height direction extends above the water surface.

Then the sample is immersed completely in the water bath for 18 hours at atmospheric re and 23 oC. Subsequently the sample is placed on a sieve with a mesh of 0.5-1 cm at the same pressure and ature and allowed to release water for 30 minutes.

Finally the weight of the foam sample (containing the remaining water) is determined again and Vu is calculated, assuming a density of the H20 of l kg/dm3.

W0 60779 Then the water saturated sample is placed for 24 h in a closed environment at 23 CC and a sub-atmospheric pressure is applied to the bottom surface of the sample (for example to a pressure of -10 cm H2O column measured from the half height of the foam sample in order to measure pF1).

Finally the weight of the sample is determined again and the volume VH of water retained in the sample is ated (assuming a water density of 1 kg/dm3).

A device which may be used to measure pF values and suitable to create a sub- atrnospheric nment on the bottom surface of the sample is a so-called Sandbox obtainable from the Dutch firm Eijkelkamp (www.eijkelkamp.com) and is used for pF- determinations.

Calculation of the water content on volume basis is also described in ISO 11274 for soil samples after subjecting the soil samples to a metric pressure (see section 5.5) and can also be d to ate the water content in the foam samples of the present invention.

The metric pressure refers here to the applied under pressure in cm H2O column. 11)Water buffer capacity (WBC, %) may be defined as pFO- pF1_5 (also referred to in prior art as (Do - (1332), wherein pF0= CDo: x100(%) and pF1.5— CD32 —_ _ Vrilj x100(%) and wherein Vf is the initial volume (in ml) of a (dry) foam sample, Vu is the water uptake (in ml) of the foam sample when saturated with water and VH5 is the volume of the water retained after subjecting the water saturated foam sample to a re of -32 cm H2O column for a predefined period in ml. Vf, Vu and VH5 are determined as described in 10) 12) The unsaturation of the polyol mixture which is used in the process according to the present ion, expressed in meq/g (milli-equivalents of rated groups per gram of polyol), is determined by ISO 17710.

The invention is further illustrated with the ing examples.

Examples 1-8 Foams were made by allowing the ted formulations to react under free rise conditions (except example 6 which compares moulded versus free rise samples).

Following ingredients are used: Polyisocyanate 1: a prepolymer having an NCO value of 26.82 % by weight, prepared by reacting 93 pbw of Suprasec® 2185 ex Huntsman and 7 pbw of Perstorp’s P3380 a trimethylolpropane initiated polyoxyethylene polyol having an OH value of 382 mg KOH/g. This prepolymer is in particular very suitable for the production of substrate foam with a pF1 value of >70 % for use in propagation . ocyanate 2 is a prepolymer obtained by reacting 54 pbw of Suprasec® 2185 and 36 pbw Suprasec® MPR and 10 pbw of Polyol 3380 (a yethylene triol ex Perstorp having an OH value of 382 mg KOH/g) and having an NCO value of about 25.9 % by weight. This prepolymer is in particular very suitable for the production of substrate foam with a pF1 value in the range of 10 - 60 % for use in cultivation mats. ocyanate 3 is Suprasec® 2185 ex Huntsman (no prepolymer).

Polyisocyanate 4 is a prepolymer obtained by reacting 30 pbw of4,4’MDI and 70 pbw of a triol initiated polyoxyethylene having random oxyethylene and oxypropylene residues with 75% by weight oxyethylene content. The prepolymer having an NCO value of about 7.85 % by weight.

Polyol l: Daltocel® F555, a polyether polyol ex Huntsman having an OH value of about 28 mg KOH/g, an oxyethylene content of about 77 % by weight (on polyol). Polyol l is suitable for use as the first polyether polyol as referred to in this invention.

Polyol 2: Jeffol® G ll-56 (also similar to commercial available Daltocel® F450, a her polyol ex an), a polyoxyethylene polyoxypropylene polyol having an OH value of about 56 mg KOH/g, an oxyethylene content in the range 25-30 % by weight (on polyol) and an average molecular weight of about 3000. Polyol 2 is suitable for use as the second polyether polyol as referred to in this invention.

Polyol 3: Daltocel® F442, a polyether polyol ex Huntsman having a nominal filnctionality of 3, an OH value of about 42 mg KOH/g and comprising oxyethylene and oxypropylene groups, the amount of oxyethylene groups being about 75 % by weight (on polyol).

Polyol 3 is suitable for use as the first polyether polyol as referred to in this invention.

Polyol 4: Daltocel® F489, a polyether polyol ex an having a nominal filnctionality of 3, an OH value of about 28 mg KOH/g and comprising oxyethylene and oxypropylene , the amount of oxyethylene groups being about 27.5 % by weight (on polyol). st 1: Jeffcat® DPA ex Huntsman Catalyst 2: Jeffcat® ZF-10, ex Huntsman.

Surfactant l: Tegostab® B8724LF, ex Evonik Surfactant 2: Dabco® DC198, ex Air Products Suprasec, el, Jeffol and Jeffcat are trademarks of the Huntsman Corporation or an Affiliate thereofwhich have been registered in one or more but not all countries.

The foams were ted to physical tests in order to determine the density, the resilience, the hardness (CLD), the dimensional foam stability or swelling (AV), water retention values (pFo, pF0_7, pF1, pF1_5, pF2). The water retention values are measured on non-crushed foam samples having dimensions 100x120x75 mm unless otherwise indicated.

Amounts in the formulations are always given in parts by weight (pbw).

Example 1: Comparison with state of the art plant substrate foams made ofpolyurethane and fabricated at low isocyanate index In Table l foams l and 2 are state of the art plant substrate foams made of polyurethane and fabricated at low isocyanate index. Foams l and 2 are hence comparative examples, Foams 3 and 4 are ing to the invention. Foam l was first d before performing pF measurements in order to open the cells in the foam (otherwise the foam is too closed and will not absorb water), foams 2, 3 and 4 do not need to be crushed hand.

Example 2: Water Retention values In Table 2 foams 5 and 6 are state of the art plant substrate foams made of polyurethane and fabricated at low isocyanate index. Rockwool is a commercial ble plant growth substrate based on mineral fibers. Rockwool, Foams 5 and 6 are hence comparative examples, foams 7 and 8 are according to the invention and are produced on a low pressure dispensing machine. Foam 5 (comparable to prior art foam 1 in example 1) was first crushed before performing pF ements in order to open the cells in the foam (otherwise the foam is too closed and will not absorb water).

Figure 2B illustrates the pF curve for the plant substrates ed to in Table 2.

The pF values are measured on s having dimensions 100x100x60 mm (length x width x height). For foam 5 the pF data in Figure 2B are originating from crushed samples.

Example 3: Effect of polyether polyol ratios and composition used to fabricate the ethane foams according to the invention In Table 3 foams 9-17 are foams made of polyurethane and fabricated using the reactive ingredients ing to the invention but at different ratios of polyisocyanate ve ingredients (polyether polyols). Foams 10, 11, 12, 13 and 14 are produced using the formulations (ratios) according to the invention, foams 9, 15, 16 and 17 are produced using different ratios and are hence comparative examples. Foam 9 has a too low pFo value and hence no good water retention for plant growth, foams 16 and 17 collapsed and foam 15 had a more coarse cell structure.

Example 4: Effect of water t in process used to fabricate the polyurethane foams according to the invention In Table 4 all foams are ated according to the invention using the same isocyanate composition and at an identical isocyanate index of 110. Foams 18, 20 and 22 are foams made with 5.5 pbw water and foams 19, 21 and 23 are foams made with 6.5 pbw water.

Foams fabricated using a higher amount ofwater lead to foams haVing less ng.

Example 5: Effect of isocyanate composition in process used to fabricate the polyurethane foams according to the invention In Table 5 all foams are fabricated according to the invention using the same polyether polyol composition but with a different isocyanate composition. Foams 24, 25, 27 and 28 are foams made using a polyisocyanate prepolymer. Foams 26 and 29 are foams made with a polyisocyanate composition which is not a prepolymer. Foams fabricated using a prepolymer isocyanate have a higher hardness. Foams made using a prepolymer isocyanate ition are better for fabricating plant growth media for ngs due to their better water retention capability (pF1 values).

Example 6: Effect of moulding during the fabrication of the polyurethane foams according to the ion In Table 6 all foams are fabricated using the same formulations (according to the invention). The amount of overpack was 0% (no moulding, free rise process), 30%, 45% and 55%.

Example 7: Typical formulation used to fabricate the foams according to the invention and suitable as plant growth media In Table 7 typical formulations are shown which are suitable for fabricating the foams according to the invention. Foams 34-39 have all very good water ion values and are very suitable for use as plant growth media. The high pF1 value (pF1> 50%) makes these foams in particular suitable for growing seedlings (high demand of water). The foams in Table 7 are produced on a large scale low pressure dispensing e (which could result in a slightly more “open cell” foam compared to hand-mixed lab-scale foams).

Example 8: growth results er seeds were allowed to grow in comparative foam 1 as well as in foams 7 and 8 which are according to the invention (see Table 2 for formulations). After 21 days the plants were cut off above the substrate foam and then the weight of the plants was determined (see Table 8). Foams according to the ion give plants with significant increased plant weight compared to plants grown on comparative foam 1. v M89: 860m 0-5893 v. - fimo - R 8 - - fi S - N - OS OS a: # 8.2 3.2 ww - Q 2 3 - m 002 m 628:an 860m @5893 fimo - - R 8 - - fi S - N - 2: 2: 3: R 3.0m 3.2 a - Q 8 - ON - E - can N :55 £88m 860m - - oofi - - - - - - - - om 0 Q: N? E 1m E 0% - ww - ms - im - Sm - q% - 2: 28393 860m 2-35% - Twm - - - 3 Man 00 No.0 mmd - E mm 3a :8 52 ma: Mad m: E we“ S wwm E 3% E 3% 2 Mam 0% 2: 93 g 0 Ea «be J a EE 2an Bag Bag Bag GE augmeo-aoq g g 6 Ea 6 in g g g J “N v a a 3% Ea Ea 259 259 Mace “8:28 augmeo-=o= g g g Anna 6252059 Bangooflbom Bangooflbom Bangooflbom fig get: Amie 8?”: g g g J “N g g - - @8388 ; “N a: ov “8:35 Ho 298an fi N m v Egonfism Egonfism E3 wave 8: 6235 6250 “8530-8: 6228 “8530-8: 6230 6235 PE PE 638 6&3 6&8 638 €38 €38 9235 Sagoé doaemom 5580 3 555 So a A A >< gagging 5% éfifi?§=§% ”Eva :3 :3 5% Anna augmeoeoqflm Pa 83 83 3035 2808 Snow NEN>O ONO: h.

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Claims (1)

The Claims defining the invention are as follows:

1. A plant growth medium made of a polyurethane foam and prepared from a polyisocyanate comprising diphenylmethane diisocyanate (MDI) and 5 homologues f having an isocyanate functionality of 3 or more wherein the amount of diisocyanate calculated on the total amount of the diisocyanates and the homologues is in the range of 20-80% or 25-70% by weight and having a resilience (measured according to ISO 8307) of at most 40%, a compression load deflection (CLD) at 40% red according to ISO 10