Growth substrate

Abstract

The present invention relates to a growth substrate formed of man-made vitreous fibres bonded with a binder, wherein the growth substrate further comprises a non-ionic wetting agent, wherein the non-ionic wetting agent is one or more compounds of formula (I).

Description

[0001] GROWTH SUBSTRATE

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a growth substrate, the use of the growth substrate as a growth substrate for growing plants, or for propagating seeds, seedlings, or cuttings, a method of growing plants or propagating seeds, seedlings, or cuttings, and a method of manufacturing the growth substrate.

[0004] BACKGROUND

[0005] It has been known for many years to grow plants in growth substrates formed from man-made vitreous fibres (MMVF). MMVF products for this purpose, which are provided as a coherent plug, block or slab, generally include a binder, usually an organic binder, in order to provide structural integrity to the product. This allows the growth substrate product to retain its structure during water irrigation. However, MMVF products which are to be used as growth substrates must have a capacity to take up and hold water, which is routinely supplied by an irrigation system to the growth substrate product, and must also have re-wetting properties. Accordingly, it has been well known for many years to include a wetting agent in MMVF products which are to be used as growth substrates.

[0006] One class of wetting agents known for use in growth substrates are anionic wetting agents. For example, W02008 / 009467 discloses the use of an anionic wetting agent such as linear alkyl benzene sulphonate (LAS) in a growth substrate product. Alkyl ether sulphate (AES) wetting agents are also known for use in growth substrate products, as disclosed in WO2015 / 181323.

[0007] Anionic wetting agents such as LAS and AES have been successfully used commercially in growth substrate products. However, there are drawbacks to using anionic wetting agents such as LAS and AES in growth substrates. For example, there is a tendency for the wetting agents to be extracted from the growth substrate during irrigation, causing foaming of the irrigation water. These wetting agents also do not provide the growth substrates with satisfactory ageing properties, meaning that initial wetting of the growth substrate after storage is more difficult and takes longer.

[0008] Non-ionic wetting agents are also known, and these can minimise the issues associated with foaming and ageing properties. For example, EP1278410 discloses the use of a non-ionic fatty acid polyglycol ester wetting agent with a low degree of ethoxylation, such as Rewopal E070, in a growth substrate product. However, the water characteristics of growth substrates with these wetting agents could be improved. In particular, the water retention properties are not as good as with anionic wetting agents such as AES.

[0009] EP3275307 discloses the use of low molecular weight polyethylene glycols, such as PEG600, as wetting agents in a mineral fibre plant growth substrate. Similarly, WO 92 / 04824 discloses the use of low molecular weight polyalkylene glycols as a tenside to provide a mineral fibre plant growing medium with water-absorbing properties. For example, the polyalkylene glycol may be a polyethylene glycol with a molecular weight of from 200 to 1000. However, these known low molecular weight polyalkylene glycol wetting agents do not provide growth substrates with satisfactory water characteristics. In particular, the water uptake rate of the growth substrates is too low.

[0010] There is therefore a need for an improved wetting agent for MMVF growth substrates that minimises issues associated with foaming and ageing, while providing excellent water uptake and retention characteristics.

[0011] SUMMARY OF INVENTION

[0012] According to a first aspect of the invention, there is provided a growth substrate formed of man-made vitreous fibres bonded with a binder, wherein the growth substrate further comprises a non-ionic wetting agent, wherein the non-ionic wetting agent is one or more compounds of formula (I): wherein R1and R2are each independently H or a substituent; wherein each R3is independently H, methyl, or ethyl; wherein each R4is independently H, methyl, or ethyl; wherein at least one of R3and R4in each repeat unit is H; wherein the average value of n is at least 30, and wherein the amount of the non-ionic wetting agent is at least 0.01 wt.% by weight of the total solids content of the binder.

[0013] The present invention is based on the surprising discovery that polyalkylene glycol compounds of formula (I) with a high degree of alkoxylation (i.e. an average value of n of at least 30) are advantageous for use as non-ionic wetting agents in MMVF growth substrates.

[0014] In particular, it has surprisingly been found that compounds of formula (I) with an average value of n of at least 30 provide MMVF growth substrates with a higher water uptake rate compared to compounds of formula (I) with a lower average value of n that are known for use as wetting agents. Rapid water absorption by growth substrates is advantageous because it facilitates easy wetting of the substrates and leads to increased output on wetting lines.

[0015] It has also been found that the compounds of formula (I) according to the invention do not suffer from the same ageing issues associated with some known wetting agents. In particular, the compounds of formula (I) allow rapid wetting of growth substrates even after the growth substrates have been stored for a long period of time, which enhances product reliability and shelf life. The compounds of formula (I) according to the invention also provide growth substrates with excellent water retention characteristics, including a good water distribution over the height of the growth substrates. This provides a good medium for the growth of plants and allows the manufacture of growth substrates of greater height.

[0016] It has also been found that the compounds of formula (I) according to the invention may minimise foaming issues that have been seen with known wetting agents.

[0017] According to a second aspect of the invention, there is provided the use of a growth substrate according to the first aspect of the invention as a growth substrate for growing plants, or for propagating seeds, seedlings, or cuttings.

[0018] According to a third aspect of the invention, there is provided a method of growing plants or propagating seeds, seedlings, or cuttings, the method comprising: a) providing a growth substrate according to the first aspect of the invention; b) positioning one or more plants, seeds, seedlings, or cuttings for growth in the growth substrate; and c) irrigating the growth substrate.

[0019] According to a fourth aspect of the invention, there is provided a method of manufacturing the growth substrate according to the first aspect of the invention, comprising the steps of: a) providing man-made vitreous fibres; b) applying the binder to the man-made vitreous fibres; c) applying the non-ionic wetting agent to the man-made vitreous fibres; and d) collecting and consolidating the man-made vitreous fibres. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a graph showing the amount of water taken up by grit bar samples over time for polyethylene glycol (PEG) wetting agents with a variety of molecular weights.

[0021] Figure 2 is a graph showing the amount of water taken up by grit bar samples over time for phenol ethoxylate wetting agents with a variety of molecular weights.

[0022] Figure 3 is a graph showing the amount of water taken up by grit bar samples over time for various wetting agents.

[0023] Figures 4 and 5 are graphs showing the water content of grit bar samples over time when suction pressures of -16hPa (WC-16) and -21 hPa (WC-21) were applied for various wetting agents.

[0024] Figures 6 to 9 are graphs showing the water content of grit bar samples over time when suction pressures of 21hPa (WC-21) were applied for various wetting agents in different amounts.

[0025] Figure 10 is a graph showing the sinking time of MMVF growth substrates for different storage times and for a variety of wetting agents.

[0026] Figure 11 is a graph showing the water retention characteristics of MMVF growth substrates with different wetting agents before flushing the growth substrates with water.

[0027] Figure 12 is a graph showing the water retention characteristics of MMVF growth substrates with different wetting agents after flushing the growth substrates with water three times.

[0028] Figure 13 is a graph showing the water distribution in MMVF growth substrates with different wetting agents before flushing the growth substrates with water. Figure 14 is a graph showing the water distribution in MMVF growth substrates with different wetting agents after flushing the growth substrates with water three times.

[0029] DETAILED DESCRIPTION

[0030] The present invention relates to a growth substrate formed of man-made vitreous fibres (MMVF).

[0031] The growth substrate is in the form of a coherent mass. That is, the growth substrate is generally a coherent matrix of man-made vitreous fibres, which has been produced as such, but can also be formed by granulating a slab of mineral wool and consolidating the granulated material.

[0032] The MMVF can be any of the conventional types used for the formation of known MMVF growth substrates. For example, the MMVF may be glass wool, slag wool, or stone wool, preferably stone wool.

[0033] Stone wool generally has a content of iron oxide of at least 3% and a content of alkaline earth metals (calcium oxide and magnesium oxide) from 10 to 40%, along with the other usual oxide constituents of mineral wool. The other oxides usually present are silica; alumina; alkali metals (sodium oxide and potassium oxide) which are usually present in low amounts; and can also include titania and other minor oxides.

[0034] Fibre diameter is often in the range of 2 to 10 microns, in particular 3 to 8 microns, as conventional.

[0035] The growth substrate preferably comprises at least 90 wt. % man-made vitreous fibres by weight of the total solids content of the growth substrate. An advantage of having such an amount of fibres present in the growth substrate is that there are sufficient pores formed between the fibres to allow the growth substrate to hold water and nutrients for the plant, whilst maintaining the ability for roots of the plants to permeate the growth substrate. The remaining solid content is made up primarily of binder and wetting agent, as will be discussed in more detail below.

[0036] The growth substrate may have an average density of from 30 to 150 kg / m3, preferably 30 to 100 kg / m3, more preferably 40 to 90 kg / m3.

[0037] The growth substrate may have a volume in the range 3 to 86,400 cm3, preferably 5 to 30,000 cm3, more preferably 8 to 20,000 cm3.

[0038] The growth substrate may be in the form of a product conventionally known as a plug, or in the form of a product conventionally known as a block, or in the form of a product conventionally known as a slab.

[0039] The growth substrate may have dimensions conventional for the product type commonly known as a plug. Thus, the growth substrate may have a height from 20 to 35 mm, often 25 to 28 mm, and a length and width in the range 15 to 25 mm, often around 20 mm. In this case the growth substrate is often substantially cylindrical with the end surfaces of the cylinder forming the top and bottom surfaces of the growth substrate.

[0040] The volume of the growth substrate in the form of a plug is preferably not more than 150 cm3. In general, the volume of the growth substrate in the form of a plug is in the range 3 to 150 cm3and preferably not more than 100 cm3, more preferably not more than 80 cm3, more preferably not more than 75 cm3, most preferably not more than 70 cm3. The minimum distance between the top and bottom surfaces of a plug is preferably less than 60 mm, more preferably less than 50 mm and most preferably less than 40 mm.

[0041] Another embodiment of a plug has a height from 30 to 50 mm, often around 40 mm and a length and width in the range 20 to 40 mm, often around 30 mm. The growth substrate in this case is often of cuboid form. In this first case the volume of the growth substrate is often not more than 50 cm3, preferably not more than 40 cm3. Alternatively, the growth substrate may be of the type of plug described as the first MMVF growth substrate in our publication WO2010 / 003677. In this case the volume of the growth substrate is most preferably in the range of from 10 to 40 cm3.

[0042] The growth substrate may have dimensions conventional for the product type commonly known as a block. Thus, the growth substrate may have a height from

[0043] 4 to 20 cm, often 6 to 15 cm, and a length and width in the range 4 to 30 cm, often 10 to 20 cm. In this case the growth substrate is often substantially cuboidal. The volume of the growth substrate in the form of a block is preferably in the range 64 to 8000 cm3.

[0044] The growth substrate may have dimensions conventional for the product type commonly known as a slab. Thus, the growth substrate may have a height from

[0045] 5 to 15 cm, often 7.5 to 12.5 cm, a width in the range of 5 to 30 cm, often 12 to 24 cm, and a length in the range 30 to 240 cm, often 40 to 200 cm. In this case the growth substrate is often substantially cuboidal. The volume of the growth substrate in the form of a slab is preferably in the range 750 to 86,400 cm3.

[0046] The height of the growth substrate is the vertical height of the growth substrate when positioned as intended to be used and is thus the distance between the top surface and the bottom surface. The top surface is the surface that faces upwardly when the growth substrate is positioned as intended to be used and the bottom surface is the surface that faces downwardly (and on which the growth substrate rests) when the growth substrate is positioned as intended to be used.

[0047] In general, the growth substrate may be of any appropriate shape including cylindrical, cuboidal and cubic. Usually, the top and bottom surfaces are substantially planar.

[0048] The man-made vitreous fibres (MMVF) in the growth substrate of the invention are bonded with a binder. The binder is usually an organic binder, which is generally heat-curable. The growth substrate is therefore preferably a coherent matrix of MMVF connected by cured binder. The binder can be an organic hydrophobic binder, and in particular it can be a conventional heat-curable (thermosetting) hydrophobic binder of the type which has been used for many years in MMVF growth substrates (and other MMVF-based products). This has the advantage of convenience and economy. Thus, the binder may be a phenol formaldehyde (PF) resin or urea formaldehyde resin, preferably a phenol urea formaldehyde (PUF) resin.

[0049] Alternatively, the binder may be a sugar-based binder comprising a mixture of phenol urea formaldehyde (PUF) resin and dextrose. The dextrose can be present in an amount of up to 60 wt. % dextrose.

[0050] In a further embodiment, the sugar-based binder may be a formaldehyde-free binder, such as disclosed in WO 2012 / 028650. Prior to curing, such binders may comprise; a) a sugar component, b) a reaction product of a polycarboxylic acid component and an alkanolamine component, wherein the binder prior to curing contains at least 42% by weight of the sugar component based on the total weight (dry matter) of the binder components, preferably wherein the binder prior to curing contains 46 to 64% by weight of the sugar component based on the total weight (dry matter) of the binder components.

[0051] The binder may alternatively be other known formaldehyde-free sugar-based binders, such as those disclosed in WO2013179323 and WO2016102444. For example, the binder may be a formaldehyde-free aqueous binding composition comprising: at least one monosaccharide, ammonium sulfamate or alkali or alkaline earth metal sulfamate, ammonium hydroxide, and / or an organic or inorganic ammonium salt.

[0052] Alternatively, the binder may be an aqueous binder composition comprising: a component (i) in form of one or more carbohydrates; a component (ii) in form of one or more compounds selected from sulfamic acid, derivative of sulfamic acid or any salt thereof.

[0053] Formaldehyde-free binder compositions are particularly beneficial to plant growth, and especially plant propagation, as plants are sensitive to high concentrations of formaldehyde, which can have a detrimental effect on plant growth.

[0054] The binder may alternatively be a formaldehyde-free protein-based binder as described in WO2017 / 194722 or WO2022 / 175310. Such binders may comprise:

[0055] - at least one phenol and / or quinone containing compound;

[0056] - at least one protein.

[0057] The binder may alternatively be a lignin or lignosulfonate binder as disclosed in WO2021 197631 , WO2022 / 144110, WO2021 / 197661 , or W02020 / 070338. For example, the binder may be a cured aqueous binder composition, wherein the aqueous binder composition prior to curing comprises:

[0058] - a component (i) in the form of one or more oxidized lignins;

[0059] - a component (ii) in the form of one or more cross-linkers;

[0060] - a component (iii) in the form of one or more plasticizers.

[0061] Alternatively, the binder may be a cured aqueous binder composition, wherein the aqueous binder composition prior to curing comprises:

[0062] - a component (i) in form of one or more lignosulfonate lignins having a carboxylic acid group content of 0.03 to 1 .4 mmol / g, based on the dry weight of the lignosulfonate lignins, and

[0063] - a component (ii) in form of one or more cross-linkers.

[0064] The binder can be itself hydrophilic. A hydrophilic binder does not require the use of as much wetting agent as a hydrophobic binder. A wetting agent can nevertheless be used to increase the hydrophilicity of a hydrophilic binder in a similar manner to its action in combination with a hydrophobic binder. This means that the MMVF substrate will absorb a higher volume of water than if the wetting agent is not present. Any hydrophilic binder can be used, for example the binder disclosed in WO2012 / 028650.

[0065] In one aspect of the invention, the binder may not comprise lignin or lignosulfonate (e.g. the binder may not be a lignin or lignosulfonate binder, such as the binders discussed above).

[0066] The amount of the binder present in the growth substrate of the invention may be in the range of from 0.1 to 10 wt. % by weight of the total solids content of the growth substrate, preferably in the range of from 0.5 to 5.0 wt. %, more preferably in the range of from 1 .5 to 5.0 wt. %.

[0067] In addition to the binder, the growth substrate of the invention further comprises a non-ionic wetting agent, which is one or more compounds of formula (I):

[0068] The compounds of formula (I) contain a polyalkylene glycol chain formed from the following repeat unit:

[0069] The number of repeat units in the polyalkylene glycol chain is represented by the number “n”. As the skilled person would appreciate, compounds of formula (I) typically comprise molecules with a distribution of chain lengths. It is therefore common to define the compound in terms of the average value of n, otherwise known as the average degree of alkoxylation. In the compounds of formula (I) used in the present invention, the average value of n is at least 30. It is thought that the relatively high number of alkylene oxide repeat units is responsible for the improved water uptake characteristics of the growth substrates of the invention. In particular, it is believed that the increased number of hydrophilic oxygen atoms in the compounds of formula (I) causes water to be taken up faster by the growth substrate.

[0070] Increasing the average value of n further increases the water uptake rate of the growth substrate. The average value of n is therefore preferably at least 40, more preferably at least 45, even more preferably at least 55, even more preferably at least 65, even more preferably at least 80, even more preferably at least 90, even more preferably at least 100, most preferably at least 110.

[0071] However, if the average value of n is too high, there is a risk of crystallisation of the compound of formula (I), which could lead to slower wetting of the growth substrate. Furthermore, the increased viscosity of the compound may make processing more difficult. It is therefore preferred that the average value of n is no more than 800, more preferably no more than 600, even more preferably no more than 460, even more preferably no more than 300, even more preferably no more than 230, even more preferably no more than 200, even more preferably no more than 185, even more preferably no more than 160, most preferably no more than 140.

[0072] The average value of n may therefore be in the range of from 30 to 800, preferably in the range of from 40 to 600, more preferably in the range of from 45 to 460, even more preferably in the range of from 55 to 300, even more preferably in the range of from 65 to 230, even more preferably in the range of from 80 to 200, even more preferably in the range of from 90 to 185, even more preferably in the range of from 100 to 160, most preferably in the range of from 110 to 140.

[0073] In the compounds of formula (I), each R3is independently H, methyl, or ethyl, and each R4is independently H, methyl, or ethyl. However, at least one of R3and R4in each repeat unit is H. In other words, if R3in a particular repeat unit is methyl or ethyl then R4in that repeat unit is H. Similarly, if R4in a particular repeat unit is methyl or ethyl then R3in that repeat unit is H.

[0074] The polyalkylene glycol chain in the compounds of formula (I) is therefore formed from polyethylene glycol, polypropylene glycol, polybutylene glycol, or a copolymer thereof.

[0075] Preferably, each R3is independently H or methyl, and each R4is independently H or methyl (with at least one of R3and R4in each repeat unit being H). In which case, the polyalkylene glycol chain in the compounds of formula (I) is formed from polyethylene glycol, polypropylene glycol, or a copolymer of polyethylene glycol and polypropylene glycol.

[0076] The copolymer of polyethylene glycol and polypropylene glycol may be a random copolymer or a block copolymer. The block copolymer may comprise any suitable number of blocks of ethylene oxide and propylene oxide units. As an example, the compound of formula (I) may have the following formula: wherein x+y = n

[0077] As another example, the compound of formula (I) may have the following formula: wherein x+y+z=n.

[0078] As another example, the compound of formula (I) may have the following formula: wherein x+y+z=n.

[0079] Most preferably, R3and R4are H in all repeat units. In which case, the compound of formula (I) is as follows:

[0080] The ends of the polyalkylene glycol chain in the compounds of formula (I) according to the invention may be substituted or unsubstituted. R1and R2are therefore each independently H or a substituent.

[0081] Any suitable substituents may be present on the ends of the polyalkylene glycol chain. For example, R1and R2may each independently be selected from the group consisting of: H, RA, -C(O)RA, and Ce-C aryl optionally substituted with one or more RA, wherein each RAis independently C1-C20 alkyl, C2-C20 alkenyl, or C2-C20 alkynyl, wherein each C1-C20 alkyl, C2-C20 alkenyl, and C2-C20 alkynyl group is optionally substituted, for example with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH.

[0082] Preferably, the compounds of formula (I) are not amphiphilic wetting agents (i.e. R1and R2are not large hydrophobic groups), which helps minimise foaming issues seen with known amphiphilic wetting agents.

[0083] Preferably, R1and R2are therefore each independently selected from the group consisting of H, RA, -C(O)RA, and phenyl, wherein each RAis independently Ci-C6alkyl, C2-C6 alkenyl, or C2-Ce alkynyl, wherein each Ci-Ce alkyl, C2-C6 alkenyl, and C2-C6 alkynyl group is optionally substituted, for example with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH.

[0084] More preferably, R1and R2are each independently selected from the group consisting of: H, C1-C4 alkyl, and phenyl, wherein the C1-C4 alkyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH.

[0085] Even more preferably, R1and R2are each independently selected from the group consisting of: H, C1-C2 alkyl, and phenyl, where the C1-C2 alkyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH.

[0086] Even more preferably, R1and R2are each independently H or phenyl, most preferably H.

[0087] R1is preferably H or phenyl, most preferably H.

[0088] R2is preferably H.

[0089] In a particularly preferred aspect of the invention, the non-ionic wetting agent is one or more of the following compounds:

[0090] Polyethylene glycol Phenol ethoxylate

[0091] Particularly preferred polyethylene glycols for use in the present invention have a molecular weight in the range of from 2000 to 35000 g / mol, preferably 4000 to 20000 g / mol, more preferably 4000 to 10000 g / mol, even more preferably 4000 to 8000 g / mol, even more preferably 5000 to 7000 g / mol, most preferably about 6000 g / mol.

[0092] Particularly preferred phenol ethoxylates for use in the present invention have a molecular weight in the range of from 1500 to 10000 g / mol, preferably 3000 to 7000 g / mol, more preferably 4000 to 6000 g / mol, most preferably about 5000 g / mol. Phenol ethoxylate shows particularly good compatibility with PUF binders which helps achieve good water characteristics. In one embodiment, the non-ionic wetting agent is therefore phenol ethoxylate (Ri is phenyl; and R2is H) and the binder is a phenol urea formaldehyde (PUF) resin.

[0093] As used herein, the term “molecular weight” refers to the number average molecular weight (Mn).

[0094] For compounds of formula (I) that contain free hydroxyl groups (i.e. when R1and / or R2is H), the molecular weight can be determined from the hydroxyl value (OH number) of the compound. The hydroxyl value of the compound can be determined in accordance with the standard test method set out in DIN53240.

[0095] For compounds of formula (I) containing two free hydroxyl groups (e.g. R1and R2are H, such as in polyethylene glycol), the molecular weight can be calculated from the OH number using the following formula:

[0096] For compounds of formula (I) containing one free hydroxyl group (e.g. one of R1and R2is H, such as in phenol ethoxylate), the molecular weight can be calculated from the OH number using the following formula:

[0097] For compounds of formula (I) that do not contain free hydroxyl groups (e.g. R1and R2are not H), the molecular weight can be determined by other standard methods such as1H-NMR, Gel Permeation Chromatography (GPC), or Mass Spectrometry. The average value of “n” in the compounds of formula (I) can be determined from the molecular weight of the compound, as the skilled person would understand. The molecular weight of the repeating unit and the molecular weight of the substituents attached to the ends of the repeating unit is first calculated based on the formula of the compound. The average value of n can then be calculated as follows:

[0098] Mn— molecular weight of substituents average value of n = - - - - - ; - - - molecular weight of repeating unit

[0099] Taking polyethylene glycol as an example, the repeating unit is (CH2CH2O)nand the substituents attached to the ends of the repeating unit are -OH and -H. The repeating unit has a molecular weight of 44 g / mol (12 + 2 + 12 + 2 + 16) and the substituents have a molecular weight of 18 g / mol (16 + 1 + 1). The average value of n for polyethylene glycol with a molecular weight of 6000 g / mol, for example, can therefore be calculated as:

[0100] 6000 - 18 average value of n = - — - = approx 136

[0101] The amount of the non-ionic wetting agent may be at least 0.01 wt. % by weight of the total solids content of the binder, preferably at least 0.05 wt. %, more preferably at least 0.10 wt. %, most preferably at least 0.5 wt. % (such as at least 1.0 wt. % or at least 2.0 wt. %).

[0102] The amount of the non-ionic wetting agent may be no more than 10 wt. % by weight of the total solids content of the binder, preferably no more than 5.0 wt. %, more preferably no more than 4.0 wt. %, most preferably no more than 3.0 wt. %.

[0103] The amount of the non-ionic wetting agent may therefore be in the range of from 0.01 to 10 wt. % by weight of the total solids content of the binder, preferably in the range of from 0.05 to 5.0 wt. %, more preferably in the range of from 0.10 to 4.0 wt. %, most preferably in the range of from 0.5 to 3.0 wt. % (such as from 1 .0 to 3.0 wt. % or from 2.0 to 3.0 wt. %). Known wetting agents tend to be used in relatively high amounts in order to provide satisfactory water uptake characteristics, but this tends to negatively affect the water retention characteristics. A benefit of the non-ionic wetting agent of the present invention is that it provides excellent water uptake characteristics even when used in relatively low amounts. The non-ionic wetting agent of the present invention may therefore be used in relatively low amounts and achieve good water uptake and retention characteristics simultaneously.

[0104] The growth substrate may comprise any other wetting agents in addition to the non-ionic wetting agent of the invention.

[0105] The growth substrate may also comprise a further compound of formula (I) but with a low average value of n (such as PEG400 or PEG600).

[0106] The growth substrate of the invention may also contain other types of conventional additives in addition to the binder and wetting agent(s), for instance salts such as ammonium sulphate and adhesion promoters such as silanes.

[0107] Use of the growth substrate

[0108] The present invention also provides the use of a growth substrate according to the invention as a growth substrate for growing plants, or for propagating seeds, seedlings, or cuttings.

[0109] Method of growing plants or propagating seeds, seedlings, or cuttings

[0110] The present invention also provides a method of growing plants or propagating seeds, seedlings, or cuttings. The method comprises: a) providing a growth substrate according to the invention; b) positioning one or more plants, seeds, seedlings, or cuttings for growth in the growth substrate; and c) irrigating the growth substrate.

[0111] Irrigation in step c) may occur by direct irrigation of the growth substrate, that is, water is supplied directly to the growth substrate, such as by a wetting line, tidal flooding, a dripper, sprinkler or other irrigation system.

[0112] Method of Manufacture

[0113] The present invention also provides a method of manufacturing the growth substrate of the invention. The method comprises the steps of: a) providing man-made vitreous fibres; b) applying the binder to the man-made vitreous fibres; c) applying the non-ionic wetting agent to the man-made vitreous fibres; and d) collecting and consolidating the man-made vitreous fibres.

[0114] The man-made vitreous fibres (MMF) may be provided in step a) in any suitable manner. For example, the MMVF may be made by any of the methods known to those skilled in the art for the production of MMVF growth substrates. In general, a mineral charge is provided, which is melted in a furnace to form a mineral melt. The melt is then formed into fibres by means of rotational fiberisation such as internal centrifugal fiberisation e.g. using a spinning cup or external centrifuging e.g. using a cascade spinner, to form a cloud of fibres.

[0115] In step b), the binder is usually applied to the man-made vitreous fibres by spraying the man-made vitreous fibres with the binder. For example, the man-made vitreous fibres may be sprayed with a solution of the binder components in finely divided / atomised form.

[0116] In step c), the non-ionic wetting agent is also generally applied by spraying the man-made vitreous fibres with the non-ionic wetting agent. For example, the man-made vitreous fibres may be sprayed with a solution or dispersion of the non-ionic wetting agent in finely divided / atomised form.

[0117] The non-ionic wetting agent and the binder may be applied to the man-made vitreous fibres simultaneously or separately. Preferably, steps b) and c) occur simultaneously. The binder and the non-ionic wetting agent may be sprayed simultaneously from separate spraying devices. Alternatively, the binder and the non-ionic wetting agent may be mixed and sprayed from the same spraying device. An advantage of the binder and the non-ionic wetting agent being sprayed substantially simultaneously is that the man-made vitreous fibres receive a consistent amount of both the binder and the non-ionic wetting agent.

[0118] As discussed above, the binder is usually a curable binder. In which case, the method of manufacturing the growth substrate of the invention may further comprise the step of: e) curing the binder.

[0119] Curing is normally conducted by passing the consolidated fibres from step d) through a curing oven. Curing is normally conducted at a temperature of around 200 °C or greater, often at least 220 °C, for instance in the range of from 220 to 290 °C, or in the range of from 220 to 275 °C. Examples of curing temperatures are 225, 240, and 250 °C.

[0120] EXAMPLES

[0121] Example 1

[0122] Laboratory evaluations were conducted using grit bar samples. The grit (stone wool shot) was washed and sieved to a particle size of 200-500 pm, mixed with a formulation containing phenol urea formaldehyde (PUF) binder and a wetting agent, and then cured at 200°C. The cured grit bars measured 10mm x 25mm x 55mm. The amount of the wetting agent used was 2.5 wt.% by weight of the total solids content of the PUF binder.

[0123] The water uptake characteristics of the grit bar samples was then measured for a variety of different wetting agents. The sorption measurements were performed on a Sigma701 tensiometer, using room temperature tap water as a probe liquid. The immersion depth was set to 0.5 mm, the function “zero balance at target” was turned off, and sample interval was set to 0 s for measurements under 30 minutes and adjusted accordingly for longer measurements. The probe setting “rectangular plate” was chosen, with dimensions of 10 x 25 mm. Samples were hung from the tensiometer balance by use of a suitable clamp. All measurements were performed at room temperature and had a duration of at least 15 minutes. The results of the sorption measurements were fitted using the least-square method with an empirical equation that describes the mass increase in time: m(t) = m0+ (mt- m0) ■ (1 - e(~))

[0124] Where m0is the mass of water absorbed when the sample first comes into contact with water and mtis the ‘total’ amount of water absorbed by the sample (in grams), and t and T represent the time and the time constant (in seconds), respectively. Using this equation the water absorption rate of the measured samples can be compared objectively. The time constant, defined in the equation, is the time required for the sample to get 1-1 / e (which is approximately 0.63) closer to the final value during the water uptake process. In this specific case, the final value (which is asymptotic) equals (mt-m0). With each successive T, the sample will get 63% closer to the final value. Therefore, T can be considered as a measure of the water uptake rate - the smaller the value of T, the faster the water uptake. The reported time constants are averages from the fits of multiple measurements, with each sorption measurement performed at least twice on two samples from the same batch. Grit bar samples were made with polyethylene glycol as the wetting agent. The water uptake characteristics of the grit bar samples are summarised in Table 1 below and depicted in Figure 1 , for various molecular weights of the polyethylene glycol. Polyethylene Glycol

[0125] Table 1 : Water uptake characteristics for PEG wetting agents

[0126] The results in Table 1 show that increasing the molecular weight of polyethylene glycol decreases the value of T and therefore provides the grit bar sample with an increased water uptake rate. This can also be clearly seen from the graph in Figure 1 , which shows that the amount of water taken up by the grit bars increases faster as the molecular weight of polyethylene glycol increases. The molecular weight of polyethylene glycol is determined by the number of ethylene oxide repeat units in the compound, i.e. the average value of “n” in the formula above. The results in Table 1 and Figure 1 show that polyethylene glycol with a low average value of n (such as PEG400, PEG600, and PEG1000) provides a low water uptake rate. However, polyethylene glycol with an average value of n of at least 30 provides much improved water uptake rates making these compounds more effective wetting agents for MMVF growth substrates.

[0127] A similar trend was observed when phenol ethoxylate was used as the wetting agent. As can be seen from Table 2 below and Figure 2, the water uptake rate increases as the molecular weight of phenol ethoxylate increases. Phenol ethoxylate with a low average value of n (e.g. PLU1) provides a low water uptake rate. However, phenol ethoxylate with an average value of n of at least 30 provides much improved water uptake rates and therefore these compounds are more effective wetting agents for MMVF growth substrates.

[0128] Phenol ethoxylate

[0129] Table 2: Water uptake characteristics for phenol ethoxylate wetting agents

[0130] For comparison, two known wetting agents that are used commercially in MMVF growth substrates were also tested, in particular a non-ionic ethoxylated fatty acid (EFA) and an alkyl ethoxylated sulfate (AES).

[0131] The EFA tested was oleic acid polyethoxylate with the following structure:

[0132] The EFA is therefore a compound of formula (I) disclosed herein, but the average value of “n” is very low (around 9) and therefore it is not a wetting agent according to the invention.

[0133] The alkyl ethoxylated sulfate (AES) tested has the following structure:

[0134] The water uptake characteristics of grit bar samples with the EFA or AES wetting agent are summarised in Table 3 below.

[0135] Table 3: Water uptake characteristics - known commercially used wetting agents

[0136] By comparing the results in Table 3 with those in Tables 1 and 2, it can be seen that polyethylene glycol and phenol ethoxylate with an average value of “n” of at least 30 provide comparable or better water uptake rates compared to the EFA and AES wetting agents. For example, Figure 3 shows that PEG6000 and PLU3 provide a higher water uptake rate compared to both the EFA and AES wetting agents.

[0137] Conclusion

[0138] The data discussed above demonstrates that compounds of formula (I) according to the invention in which the average value of n is at least 30 provide higher water uptake rates compared to comparative compounds of formula (I) with a lower average value of n. Furthermore, the compounds of formula (I) according to the invention provide comparable or even better water uptake rates compared to known wetting agents that are used commercially in MMVF growth substrates.

[0139] Example 2

[0140] The experiments in Example 1 were repeated to investigate the effect of the amount of the wetting agent on the water uptake characteristics. The results are summarised in Table 4 below.

[0141] Table 4: Water uptake characteristics for different amounts of wetting agents

[0142] The results in Table 4 show that increasing the amount of each wetting agent increases the water uptake rate. However, PEG6000 and PLU3 provide a higher water uptake rate compared to the AES and EFA wetting agents when used in equivalent amounts. Furthermore, PEG6000 and PLU3 provide a high water uptake rate even when used in low amounts. For example, the water uptake rate for PEG6000 and PLU3 when used in an amount of 0.5 wt. % is already higher than the water uptake rate for AES when used in an amount of 4.0 wt. % (which is the concentration at which the AES wetting agent is typically used commercially). Conclusion

[0143] These results demonstrate that compounds of formula (I) according to the invention which have an average value of n of at least 30 provide high water uptake rates even when used in low amounts, which are much improved compared to known commercially used wetting agents for MMVF growth substrates.

[0144] Example 3

[0145] The water retention characteristics of grit bar samples made in the same way as those in Examples 1 and 2 were assessed using a sandbox in accordance with test method M170, RHP (European knowledge centre for growing media), Product Certification Scheme RHP 2020. The grit bar samples were submerged in water and then placed on the sandbox while a suction pressure of -16hPa (WC-16) or -21 hPa (WC-21) was applied. The water content of the grit bar samples was measured over time, by weighing the samples and comparing the weight to the dry weight of the samples.

[0146] Figures 4 and 5 show the results for the grit bar samples comprising 2.5 wt. % of the wetting agents (by weight of the total solids content of the PUF binder). It can be seen from Figures 4 and 5 that grit bars comprising polyethylene glycol or phenol ethoxylate as the wetting agent retain a higher water content compared to the grit bars comprising the AES or EFA wetting agents.

[0147] Figures 6 to 9 show the effect of varying the amount of the wetting agents on the water retention properties of the grit bar samples. In general, increasing the amount of all of the wetting agents leads to a decrease in the water content retained in the grit bar samples. However, the polyethylene glycol and phenol ethoxylate wetting agents still provide improved water retention properties compared to the AES and EFA wetting agents when used in equivalent amounts or even when used in higher amounts. Conclusion

[0148] These results show that compounds of formula (I) according to the invention provide excellent water retention characteristics, that are improved compared to known commercially used wetting agents for MMVF growth substrates.

[0149] Example 4

[0150] Growth substrates were produced in the form of a block of stone wool fibres bonded with a binder. The growth substrates had a density of 75 kg / m3and contained 2.4 wt. % PUF binder by weight of the total solids content of the growth substrate. Growth substrates were produced with either 2.5 wt. % PEG6000, 2.5 wt. % PLU3, 4.0 wt. % AES, or 12.5 wt. % EFA as the wetting agent. The amounts of the wetting agents are by weight of the total solids content of the binder.

[0151] The growth substrates were stored under ambient conditions and then the sinking time of the growth substrates was measured to evaluate the water uptake characteristics. The sinking time was measured as detailed below in accordance with test method M172, RHP (European knowledge centre for growing media), Product Certification Scheme RHP 2020.

[0152] A sample of each growth substrate was prepared with a length of 10 cm, a width of 10 cm, and a height of 6.5 cm. A water tank was filled with tap water at a temperature of 20 °C. The sample was placed just above the surface of the water and allowed to sink. The sinking time was measured as the time from when the sample first comes into contact with the water until the sample is completely submerged.

[0153] The results are depicted in Figure 10, which shows the sinking time of the growth substrates for different storage times measured in days.

[0154] As can be seen from Figure 10, the growth substrates comprising PEG6000 or PLU3 as the wetting agent have a lower sinking time than the growth substrates comprising the AES or EFA wetting agents, even though the PEG6000 and PLU3 wetting agents were used in lower amounts. A lower sinking time indicates that the growth substrate takes up water faster.

[0155] Furthermore, it can be seen from Figure 10 that the sinking time of the growth substrate comprising the AES wetting agent increases as the growth substrate is stored for longer. This means that the initial wetting of the growth substrate takes longer after the growth substrate has been stored. In contrast, growth substrates comprising PEG6000 and PLU3 still exhibit rapid water absorption even after the growth substrates have been stored for a long period of time.

[0156] Conclusion

[0157] These results demonstrate that compounds of formula (I) according to the invention provide MMVF growth substrates with rapid water absorption, which is much improved compared to known commercially used wetting agents. Rapid water absorption by growth substrates is advantageous as it facilitates easy wetting of the substrates and leads to increased output of wetting lines.

[0158] Furthermore, the compounds of formula (I) according to the invention provide rapid wetting of growth substrates even after the growth substrates have been stored for a long period of time, which enhances product reliability and shelf life. The growth substrates of the invention do not therefore suffer from the ageing issues associated with known wetting agents such as AES.

[0159] Example 5

[0160] The water retention characteristics of the growth substrate samples from Example 4 were assessed using a sand box in accordance with test method M170, RHP (European knowledge centre for growing media), Product Certification Scheme RHP 2020. The water content of the samples was measured under various conditions as detailed below. The water content of the samples was determined at each stage by weighing the samples and comparing the weight to the dry weight of the samples. Initial saturation the water content of the samples was measured after first submerging the samples in water.

[0161] Saturation the samples were submerged in water and then placed on the sandbox without any suction pressure applied. The water content of the samples was measured once stable.

[0162] WC-10 the samples were submerged in water and then placed on the sandbox while a suction pressure of -1 OhPa was applied. The water content of the samples was measured once stable.

[0163] WC-16 the samples were submerged in water and then placed on the sandbox while a suction pressure of -16hPa was applied. The water content of the samples was measured once stable. the samples were submerged in water and then placed on the sandbox while a suction pressure of -21 hPa was applied. The water content of the samples was measured once stable.

[0164] Resaturation the samples were submerged in water and then placed on the sandbox. The water content of the samples was reduced to 50% under pressure.

[0165] The samples were placed in a layer of 0.5 cm of water and the water content of the samples was measured once stable.

[0166] The water distribution over the height of the samples was also assessed. The samples were submerged in water and then placed on the sandbox. The water content of the samples was reduced to 50% under pressure. The water content of the samples was then measured at the top, middle, and bottom of the samples using Grodan GroSens.

[0167] The measurements discussed above were taken before the growth substrates were flushed with water as well as after the growth substrates were flushed with water three times. The results are depicted in figures 11 to 14. The results in Figures 11 and 12 show that the growth substrates comprising PEG6000 and PLU3 retain a high water content at all stages of the testing. The growth substrates also maintain a fairly homogeneous water distribution over the height of the products, as shown in Figures 13 and 14.

[0168] In general, the water retention characteristics of the growth substrates comprising PEG6000 and PLU3 are similar to the results for the AES wetting agent and outperform the results for the EFA wetting agent. For example, the growth substrates comprising PEG6000 and PLU3 retain a high water content when suction pressures are applied, whereas the water content of the growth substrate comprising the EFA wetting agent is more significantly reduced.

[0169] The water retention properties of the growth substrates comprising PEG6000 and PLU3 are also more stable after flushing with water compared to the AES and EFA wetting agents. It is assumed that the EFA wetting agent is partially removed during flushing, resulting in a lower water content. For the AES wetting agent, it is assumed that stable air bubbles in the substrate will be formed during flushing, again resulting in a lower water content. However, these issues were not seen for PEG6000 and PLU3, but instead the water content was fairly stable after flushing. The growth substrates of the invention will therefore exhibit stable and reliable water retention characteristics in use during flushing or irrigation.

[0170] Conclusion

[0171] These results demonstrate that the compounds of formula (I) according to the invention provide MMVF growth substrates with excellent water retention characteristics that are comparable to or even better than known commercially used wetting agents. The compounds of formula (I) according to the invention provide growth substrates with a good water distribution over the height of the growth substrates, which is important for providing a good medium for the growth of plants and also allows the manufacture of thicker growth substrates. EMBODIMENTS

[0172] 1. A growth substrate formed of man-made vitreous fibres bonded with a binder, wherein the growth substrate further comprises a non-ionic wetting agent, wherein the non-ionic wetting agent is one or more compounds of formula (I): wherein R1and R2are each independently H or a substituent; wherein each R3is independently H, methyl, or ethyl; wherein each R4is independently H, methyl, or ethyl; wherein at least one of R3and R4in each repeat unit is H; and wherein the average value of n is at least 30.

[0173] 2. The growth substrate of embodiment 1 , wherein the average value of n is at least 40, preferably at least 45, more preferably at least 55, even more preferably at least 65, even more preferably at least 80, even more preferably at least 90, even more preferably at least 100, most preferably at least 110.

[0174] 3. The growth substrate of embodiment 1 or 2, wherein the average value of n is no more than 800, preferably no more than 600, more preferably no more than 460, even more preferably no more than 300, even more preferably no more than 230, even more preferably no more than 200, even more preferably no more than 185, even more preferably no more than 160, most preferably no more than

[0175] 140.

[0176] 4. The growth substrate of any preceding embodiment, wherein each R3is independently H or methyl, and each R4is independently H or methyl, preferably R3and R4are H. 5. The growth substrate of any preceding embodiment, wherein R1and R2are each independently selected from the group consisting of: H, RA, -C(O)RA, and Ce-C aryl optionally substituted with one or more RA, wherein each RAis independently C1-C20 alkyl, C2-C20 alkenyl, or C2-C20 alkynyl, and wherein each C1-C20 alkyl, C2-C20 alkenyl, and C2-C20 alkynyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH; preferably R1and R2are each independently selected from the group consisting of: H, C1-C4 alkyl, and phenyl, wherein the C1-C4 alkyl group is optionally substituted with one or more substituents independently selected from epoxy -NH2, -COOH, and -SH; more preferably R1and R2are each independently selected from the group consisting of: H, C1-C2 alkyl, and phenyl, where the C1-C2 alkyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH; even more preferably R1and R2are each independently H or phenyl, most preferably H.

[0177] 6. The growth substrate of any preceding embodiment, wherein R1is H or phenyl, most preferably H.

[0178] 7. The growth substrate of any preceding embodiment, wherein R2is H.

[0179] 8. The growth substrate of any preceding embodiment, wherein the non-ionic wetting agent is one or more of the following compounds:

[0180] 9. The growth substrate of any preceding embodiment, wherein the amount of the non-ionic wetting agent is in the range of from 0.01 to 10 wt. % by weight of the total solids content of the binder, preferably in the range of from 0.05 to 5.0 wt. %, more preferably in the range of from 0.10 to 4.0 wt. %, most preferably in the range of from 0.5 to 3.0 wt. %. 10. The growth substrate of any preceding embodiment, wherein the growth substate comprises at least 90 wt. % man-made vitreous fibres by weight of the total solids content of the growth substrate.

[0181] 11. The growth substrate of any preceding embodiment, wherein the binder is a phenol formaldehyde resin or a urea formaldehyde resin, preferably a phenol urea formaldehyde resin.

[0182] 12. The growth substrate according to any preceding embodiment, wherein the growth substrate has an average density of from 30 to 150 kg / m3, preferably 30 to 100 kg / m3, more preferably 40 to 90 kg / m3.

[0183] 13. Use of a growth substrate according to any preceding embodiment as a growth substrate for growing plants, or for propagating seeds, seedlings, or cuttings.

[0184] 14. A method of growing plants or propagating seeds, seedlings, or cuttings, the method comprising: a) providing a growth substrate according to any of embodiments 1 to 12; b) positioning one or more plants, seeds, seedlings, or cuttings for growth in the growth substrate; and c) irrigating the growth substrate.

[0185] 15. A method of manufacturing the growth substrate according to any of embodiments 1 to 12, comprising the steps of: a) providing man-made vitreous fibres; b) applying the binder to the man-made vitreous fibres; c) applying the non-ionic wetting agent to the man-made vitreous fibres; and d) collecting and consolidating the man-made vitreous fibres.

Claims

CLAIMS1. A growth substrate formed of man-made vitreous fibres bonded with a binder, wherein the growth substrate further comprises a non-ionic wetting agent, wherein the non-ionic wetting agent is one or more compounds of formula (I):wherein R1and R2are each independently H or a substituent; wherein each R3is independently H, methyl, or ethyl; wherein each R4is independently H, methyl, or ethyl; wherein at least one of R3and R4in each repeat unit is H; wherein the average value of n is at least 30, and wherein the amount of the non-ionic wetting agent is at least 0.01 wt.% by weight of the total solids content of the binder.

2. The growth substrate of claim 1 , wherein the average value of n is at least 40, preferably at least 45, more preferably at least 55, even more preferably at least 65, even more preferably at least 80, even more preferably at least 90, even more preferably at least 100, most preferably at least 110.

3. The growth substrate of claim 1 or 2, wherein the average value of n is no more than 800, preferably no more than 600, more preferably no more than 460, even more preferably no more than 300, even more preferably no more than 230, even more preferably no more than 200, even more preferably no more than 185, even more preferably no more than 160, most preferably no more than 140.

4. The growth substrate of any preceding claim, wherein each R3is independently H or methyl, and each R4is independently H or methyl, preferably R3and R4are H.

5. The growth substrate of any preceding claim, wherein R1and R2are each independently selected from the group consisting of: H, RA, -C(O)RA, and Ce-C aryl optionally substituted with one or more RA, wherein each RAis independently C1-C20 alkyl, C2-C20 alkenyl, or C2-C20 alkynyl, and wherein each C1-C20 alkyl, C2-C20 alkenyl, and C2-C20 alkynyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH; preferably R1and R2are each independently selected from the group consisting of: H, C1-C4 alkyl, and phenyl, wherein the C1-C4 alkyl group is optionally substituted with one or more substituents independently selected from epoxy -NH2, -COOH, and -SH; more preferably R1and R2are each independently selected from the group consisting of: H, C1-C2 alkyl, and phenyl, where the C1-C2 alkyl group is optionally substituted with one or more substituents independently selected from epoxy, -NH2, -COOH, and -SH; even more preferably R1and R2are each independently H or phenyl, most preferably H.

6. The growth substrate of any preceding claim, wherein R1is H or phenyl, most preferably H.

7. The growth substrate of any preceding claim, wherein R2is H.

8. The growth substrate of any preceding claim, wherein the non-ionic wetting agent is one or more of the following compounds:

9. The growth substrate of any preceding claim, wherein the amount of the non-ionic wetting agent is in the range of from 0.01 to 10 wt. % by weight of the total solids content of the binder, preferably in the range of from 0.05 to 5.0 wt. %,more preferably in the range of from 0.10 to 4.0 wt. %, most preferably in the range of from 0.5 to 3.0 wt. %.

10. The growth substrate of any preceding claim, wherein the growth substate comprises at least 90 wt. % man-made vitreous fibres by weight of the total solids content of the growth substrate.

11. The growth substrate of any preceding claim, wherein the binder is a phenol formaldehyde resin or a urea formaldehyde resin, preferably a phenol urea formaldehyde resin.

12. The growth substrate according to any preceding claim, wherein the growth substrate has an average density of from 30 to 150 kg / m3, preferably 30 to 100 kg / m3, more preferably 40 to 90 kg / m3.

13. Use of a growth substrate according to any preceding claim as a growth substrate for growing plants, or for propagating seeds, seedlings, or cuttings.

14. A method of growing plants or propagating seeds, seedlings, or cuttings, the method comprising: a) providing a growth substrate according to any of claims 1 to 12; b) positioning one or more plants, seeds, seedlings, or cuttings for growth in the growth substrate; and c) irrigating the growth substrate.

15. A method of manufacturing the growth substrate according to any of claims 1 to 12, comprising the steps of: a) providing man-made vitreous fibres; b) applying the binder to the man-made vitreous fibres; c) applying the non-ionic wetting agent to the man-made vitreous fibres; andd) collecting and consolidating the man-made vitreous fibres.

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