Resol resin stabilized by a urea derivative

Abstract

The present invention relates to an amine resole resin stabilized by a solubilizing agent selected from among certain urea derivatives, to a sizing composition prepared from said resin, to a process for manufacturing a fiber-based insulation product, in particular based on mineral wool, using said sizing composition, as well as to a thermal insulation and / or soundproofing product obtained by said manufacturing process.

Description

[0001] Resol resin stabilized by a urea derivative

[0002] The present invention relates to an amino resol resin stabilized by a solubilizing agent chosen from certain urea derivatives, as well as a sizing composition prepared from this resin, a method for manufacturing a fiber-based insulation product, in particular based on mineral wool, using this sizing composition, as well as a thermal and / or acoustic insulating product obtained by this manufacturing method.

[0003] BACKGROUND OF THE INVENTION

[0004] The manufacture of mineral wool insulation products generally includes a step of manufacturing the wool itself, which can be implemented by different processes, for example according to the known technique of internal or external centrifugal fiberization. Internal centrifugation consists of introducing the molten mineral material (glass or rock) into a centrifugal device comprising a multitude of small orifices, the material being projected towards the peripheral wall of the device under the action of centrifugal force and escaping in the form of filaments. External centrifugation methods, which are more suitable for rock wool, typically use a cascade of centrifuge wheels fed with molten material to be fiberized by a distribution device, as described for example in applications EP 0465310 or EP 0439385.At the outlet of the centrifugal device, the filaments are stretched and carried towards a receiving organ by a gas current having a high temperature and speed, to form a sheet of fibers (or mineral wool).

[0005] To ensure the assembly of the fibers together and to allow the sheet to have cohesion, a sizing composition in the form of an aqueous solution containing a thermosetting resin is sprayed onto the fibers, on the path from the outlet of the centrifugal device to the receiving member. The sheet of fibers coated with the sizing is then subjected to a heat treatment, at a temperature generally higher than 100°C, or even 200°C, in order to carry out the polycondensation of the resin and thus form a binder intended to ensure the cohesion of the fibers together and to give the insulating product thus obtained the desired properties, in particular dimensional stability, tensile strength, thickness recovery after compression and a uniform color.

[0006] The gluing compositions are prepared shortly before use by diluting the concentrated thermosetting resin with water and adding various commonly used additives (coupling agents, anti-dust additives, hydrophobic agents, catalysts).

[0007] Concentrated thermosetting resins must be stable during storage, i.e. they must retain their ability to be diluted with water for as long as possible when preparing the sizing composition. A concentrated thermosetting resin is generally considered to be stable when, after a storage period of at least 14 days at a temperature between 12 and 18 °C, it retains a dilutability of at least 1000% (the addition of 9 volumes of water to 1 volume of resin gives a clear solution, free from permanent cloudiness).

[0008] Furthermore, from a regulatory point of view, it is necessary that the resin be considered non-polluting, that is to say that it contains and generates during its use as few compounds as possible that could harm human health or the environment.

[0009] The most commonly used thermosetting resins are phenolic resins belonging to the resol family. In addition to their good crosslinking ability under the aforementioned thermal conditions, these resins are soluble in water, have a good affinity for mineral fibers, particularly glass, and are relatively inexpensive.

[0010] Resol resins are obtained in a basic medium by reacting phenol with formaldehyde. They contain numerous methylol functions carried by an aromatic ring, which constitute the crosslinking sites by dehydration / release of formalin. This reaction is generally not complete, so that the resulting resin remains dilutable. These resins are therefore essentially composed of phenol / formaldehyde (PF) condensates, residual phenolic compounds, and residual formaldehyde. Residual phenolic compounds present toxicity problems. To resolve these, an excess of formaldehyde is traditionally used, the formaldehyde / phenol molar ratio being typically between 2 and 4, each phenol molecule being potentially able to react with three formaldehyde molecules.

[0011] The resin obtained therefore contains a significant quantity of residual formaldehyde, which certainly contributes to the stability of the resin but itself poses regulatory problems.

[0012] To reduce the amount of residual formaldehyde without negatively affecting the storage stability of the resins, it was initially proposed in EP 0 148 050 to add urea during resin formation, thus leading to the production of a phenol-formaldehyde-urea resin and additional by-products, namely mono-, di- and trimethylolurea, as well as urea-formaldehyde condensates. However, these condensates are thermally unstable in an acidic medium, i.e. in the sizing composition, so that they tend to release formaldehyde during its curing. They also negatively affect the dilutability of the resin.

[0013] A few years ago, the Applicant proposed improved resol resins, hereinafter referred to interchangeably as “amino resols” or “amino phenolic resins”, which are stable during storage and essentially free of urea-formaldehyde (UF) condensates.

[0014] These amino phenolic resins are water-soluble resins stable at acid pH, even at very acid pH between 1 and 2. This good stability is obtained thanks to an additional reaction step which consists of reacting the resols consisting essentially of phenol / formaldehyde condensates, phenol and formaldehyde with an amine, preferably a monoalkanolamine, and in particular monoethanolamine, or an amino acid, preferably glycine.

[0015] This alkanolamine reacts according to the Mannich reaction with phenol / formaldehyde condensates (PF) and with residual phenol and formaldehyde to form phenol / formaldehyde / amine condensates (PFA). At the end of the reaction, the reaction mixture can be acidified without causing polymerization at room temperature. These amine resols are described in applications WO2008 / 043960 and WO2008 / 043961 and are further distinguished by the fact that they are free from urea-formaldehyde condensates.

[0016] The Applicant has however observed that an oligomer of phenol and formaldehyde formed during the synthesis of the phenolic resin, namely bis-4-diphenyltetramethylol, is found in the stabilized resol resin and leads to the formation of a precipitate in the pipes transporting the sizing composition and in the storage tank for this composition. This phenomenon requires maintenance of the production line which generates unacceptable costs. It has therefore been envisaged to add to the aminated phenolic resin, after reaction with the monoalkanolamine, cooling of the reaction mixture and acidification, up to 25% by weight, preferably between 10% and 20% by weight of urea, these quantities being expressed relative to the total dry weight of the aminated resol. The urea then serves mainly as a solubilizing agent and also makes it possible to reduce the cost of the sizing compositions and products obtained.Aminated phenolic resins, in aqueous solution stabilized by urea (solubilizing agent), have been used for more than ten years by the Applicant for the manufacture of insulation products based on mineral or organic fibers which release very small quantities of formaldehyde during production and during use.

[0017] The only drawback of these resins is that ammonia (NH3), a thermal degradation product of urea, is formed during the thermal curing stage at the production site and also, in some applications, during use. However, some regulations are very strict regarding ammonia emissions from insulation products, particularly those allowing for Ml certification in Scandinavian countries.

[0018] To counter this phenomenon, it has been suggested to add to the sizing formulation a co-solvent comprising a water-soluble aromatic polyol such as resorcinol (W02022 / 003289), possibly in combination with a small amount of urea.

[0019] After much research, it appeared to the Applicant that certain formaldehyde traps described in WO2009 / 136105 made it possible to avoid the precipitation of bis-4-diphenyltetramethylol, without negatively affecting the dilutability of the resin obtained, nor causing significant emission of ammonia during the processing of the latter, whether during the curing of the binder or during the use of the final product (such as an insulator).

[0020] In WO2009 / 136105, formaldehyde scavengers such as ethylene urea are added at the time of formulation of the sizing composition and not immediately after synthesis of the resin. Furthermore, the Applicant has demonstrated that bis-4-diphenyltetramethylol is not solubilized by most of the formaldehyde scavengers cited in WO2009 / 136105.

[0021] SUMMARY OF THE INVENTION

[0022] It has been observed that certain urea derivatives, including ethylene urea, constitute excellent co-solvents, in that they:

[0023] - are capable of stabilizing an aqueous solution of phenol-formaldehyde amino resin at least as effectively as urea, in that the composition retains a dilutability greater than 1000% and an absence of precipitate for at least 14 days, - release virtually no ammonia when subjected to the curing temperatures of resol resins, i.e. temperatures typically between 180 and 230°C,

[0024] - are not classified as carcinogenic, mutagenic or toxic for reproduction (CMR) chemical agents, and

[0025] - are available at an acceptable price for industrial exploitation.

[0026] The present invention therefore relates to a stabilized resol resin comprising:

[0027] (a) water,

[0028] (b) an amino phenolic resin, and

[0029] (c) a urea derivative of formula (I):

[0030] R3R4-N-CO-N-R1R2 (I) where:

[0031] Ri denotes a hydrogen atom or a linear or branched C1-Cg alkyl group,

[0032] R2 denotes a hydrogen atom or a linear or branched C1-C8 alkyl group, or forms, with R4 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle

[0033] R3 denotes a hydrogen atom, a linear or branched C1-C8 alkyl group or a linear or branched C1-C8 hydroxyalkyl group,

[0034] R4 denotes a linear or branched C1-C6 alkyl group or a linear or branched C1-C6 hydroxyalkyl group or forms, with R2 and the nitrogen atoms to which they are attached, a 5 or 6-membered heterocycle, the stabilized resol resin having a dry matter content of between 40 and 70% by weight.

[0035] It also relates to a sizing composition, prepared by diluting the stabilized resol resin and adding common additives. This sizing composition therefore comprises (dilution) water, the stabilized resol resin defined above, and one or more additives chosen from coupling agents, oils, hydrophobic agents and accelerators of the hardening reaction and contains from 0 to 5% by weight of urea, relative to the dry weight of the sizing composition.

[0036] The invention further relates to the use of the stabilized resol resin defined above for the preparation of a sizing composition. It also relates to a process for stabilizing an amino resol resin, comprising the addition to the resin, within one minute to 12 hours, preferably one minute to 2 hours following its synthesis and its cooling to less than 30°C, of ​​at least one urea derivative as defined above. The addition is preferably carried out in the reactor where the resin is located at the end of the synthesis.

[0037] Finally, it relates to a process for manufacturing an insulating product based on mineral or organic fibers, comprising:

[0038] - the application of the sizing composition to mineral or organic fibers, preferably mineral fibers, and

[0039] - heating the fibers sized with the sizing composition so as to evaporate the volatile phase of the sizing composition and to achieve thermal hardening of the non-volatile residue, or packaging the mineral or organic fibers sized with the sizing composition, for storage and / or transport, as well as an insulating product obtained by this process, in which the organic or mineral fibers are bound together by an insoluble and infusible binder obtained by hardening the ingredients of the sizing composition.

[0040] DETAILED DESCRIPTION

[0041] Throughout the description of the present invention, it is appropriate to differentiate between:

[0042] - amino phenolic resin, obtained by condensation of phenol, formaldehyde and amine in a basic medium and which is free from urea-formaldehyde (UF) condensates,

[0043] - the stabilized resol resin which contains the amino phenolic resin, water, and the solubilizing agent according to the invention, and

[0044] - the sizing composition prepared by diluting the stabilized resol resin and adding known additives.

[0045] Stabilized resol resin is therefore the concentrated resin, resulting from synthesis, which will be stored, transported, marketed and used as a thermosetting component for the preparation of the sizing composition.

[0046] The stabilized resol resin advantageously contains

[0047] - from 75 to 99% by weight, preferably from 80 to 97% by weight, in particular from 90 to 97% by weight, of amino phenolic resin, and

[0048] - from 1 to 25% by weight, preferably from 3 to 20% by weight, in particular 3 to 10% by weight of a urea derivative of formula (I), these percentages being relative to the total dry weight of the stabilized resol resin.

[0049] In the case of ethylene urea, for example, it is preferable to use a weight ratio of 6 to 10%, better, 7 to 9%. In the case of l-(2-hydroxyethyl)-2-imidazolidinone (or H El ), it is advantageous to use a weight ratio of 1 to 5%, preferably 2 to 4%.

[0050] The dry matter content of the stabilized resol resin is between 40 and 70% by weight, preferably between 45 and 65% by weight and in particular between 50 and 60% by weight.

[0051] The term "a urea derivative of formula (I)" used to describe the solubilizing agent encompasses both the compounds used alone and mixtures of two or more of these compounds.

[0052] The resin also contains small amounts of salt resulting from the neutralization of the catalyst (strong base such as NaOH or KOH) by an acid, for example sulfamic acid, at the end of the resin synthesis.

[0053] The adjective "stabilized" relating to the resol resin means in the present invention that the resin remains for at least 14 days of conservation from its synthesis, at a temperature of 12 to 18 °C, in the sense that it is in the form of a clear solution, free from precipitate, and that it retains during this period a dilutability in water of at least 1000%.

[0054] The solubilizing agent used in the present invention to at least partially replace urea, used until now, is chosen from urea derivatives of formula (I) which are preferably not part of the carcinogenic, mutagenic or toxic for reproduction (CMR) chemical compounds. The list of CMR chemical compounds is that which appears in Annex VI of EC Regulation No 1272 / 2008.

[0055] In general, these derivatives are soluble in the amino resol resin, i.e. they have a solubility in the resin at 12°C greater than 30 g / L, preferably greater than 50 / L-

[0056] The urea derivatives used according to the invention correspond to formula (I):

[0057] R3R4-N-CO-N-R1R2 (I) where:

[0058] Ri denotes a hydrogen atom or a linear or branched C1-Cg alkyl group,

[0059] R2 denotes a hydrogen atom or a linear or branched C1-Cg alkyl group, or forms, with R4 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle R3 denotes a hydrogen atom, a linear or branched C1-Cg alkyl group or a linear or branched C1-Cg hydroxyalkyl group,

[0060] R4 denotes a linear or branched C1-C8 alkyl group or a linear or branched C1-C8 hydroxyalkyl group or forms, together with R2 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle.

[0061] According to a preferred embodiment:

[0062] Ri denotes a hydrogen atom or a linear or branched C1-C4 alkyl group, preferably hydrogen, methyl or ethyl,

[0063] R2 denotes a hydrogen atom or a linear or branched C1-C4 alkyl group, or forms, with R4 and the nitrogen atoms to which they are attached, a 5 or 6-membered heterocycle, preferably hydrogen, methyl, ethyl or forms, with R4 and the nitrogen atoms to which they are attached, an imidazolidine ring.

[0064] R3 denotes a hydrogen atom, a linear or branched C1-C4 alkyl group or a linear or branched C1-C4 hydroxyalkyl group, preferably hydrogen, methyl, ethyl, hydroxymethyl or hydroxyethyl,

[0065] R4 denotes a linear or branched C1-C4 alkyl group or forms, with R2 and the nitrogen atoms to which they are attached, a 5 or 6-membered heterocycle, preferably methyl, ethyl or forms, with R2 and the nitrogen atoms to which they are attached, an imidazolidine ring.

[0066] More preferably, the urea derivative of formula (I) is such that each of the linear or branched C1-C6 alkyl groups is a methyl group and / or R1 = H.

[0067] Examples of urea derivatives of formula (I) are: ethylene urea, 2-hydroxyethyl urea, dimethyl urea, methyl urea, trimethylene urea, l-(2-hydroxyethyl)-2-imidazolidinone, l,3-dimethyl-2-imidazolidinone and mixtures thereof. It is preferred to use ethylene urea, dimethyl urea or l-(2-hydroxyethyl)-2-imidazolidinone, more preferably l-(2-hydroxyethyl)-2-imidazolidinone (or HEI).

[0068] The addition of urea to the resol resin is in principle superfluous and the stabilized resol resin of the present invention is therefore preferably free of urea.

[0069] For cost reasons, it may be useful to add urea to the resol resin to be stabilized. In this case, a small amount of urea should be chosen to ensure the absence of significant ammonia (NH3) emissions during the thermal curing stage of the binder and during use of the manufactured insulation product. This addition can be made before or after the addition of the solubilizing agent, or simultaneously, but must be made after the end of the synthesis of the amino phenolic resin consisting essentially of PF and PFA condensates, i.e. after cooling and neutralization of the reaction solution. It is indeed advisable to avoid the formation of urea-formaldehyde condensates during the synthesis of the resin.

[0070] When both urea and a solubilizer according to the invention are used, the resin advantageously contains at most 10% by weight, for example from 0.5 to 10% by weight, in particular at most 5% by weight, for example 1 to 5% by weight of urea, based on the total dry weight of the stabilized resol resin (amine phenolic resin + solubilizer + urea).

[0071] The phenolic resin used in the present invention contains basic (protonable) amine functions and is stable in an acidic medium.

[0072] These amine-functional phenolic resins are known and their preparation is described in detail in the Applicant's applications WO2008 / 043960 and WO2008 / 043961. They consist essentially of phenol / formaldehyde (PF) and phenol / formaldehyde / amine (PFA) condensates and are distinguished in particular by the absence of urea-formaldehyde (UF) condensates. As explained in the introduction, these urea-formaldehyde condensates are present in significant quantities in many other phenolic resins of the prior art and have insufficient thermal stability, releasing formaldehyde and ammonia by thermal decomposition.

[0073] The stabilized resol resin of the present invention advantageously has a pH of between 1.0 and 6.5, preferably between 1.5 and 5.5, more preferably between 1.6 and 5.0.

[0074] Sizing compositions prepared by diluting stabilized resol resin with water generally have a less acidic pH than resol resins, typically between 3 and 7, particularly between 3.5 and 6.5, which is advantageous for preventing corrosion of insulation product manufacturing facilities. The dilution water used for preparing sizing compositions from stabilized resol resin may come in part from recycled wash water from insulation product manufacturing facilities.

[0075] The sizing composition of the present application therefore contains water, a stabilized resol resin and one or more additives, commonly used in the field of mineral wool-based insulating products.

[0076] These additives are chosen, inter alia, from coupling agents, in particular functional silanes such as aminosilanes or epoxysilanes, oils, in particular mineral oils, hydrophobic agents such as reactive or non-reactive polyorganosiloxanes (silicones), and curing reaction accelerators (catalysts). In addition, the sizing composition may contain from 0 to 5% by weight of urea. Preferably, it is free of urea.

[0077] At the time of application to the fibers, the sizing composition preferably has a dry matter content of between 2 and 25% by weight, preferably between 3 and 15% by weight. It therefore contains from 75 to 98% by weight, in particular from 85 to 97% by weight of water.

[0078] The sizing composition is applied in an amount such that the content of insoluble and infusible binder in the final product obtained after thermal curing is between 2% and 20% by weight, preferably between 3% and 15% by weight, in particular between 4 and 12% by weight.

[0079] The present invention also relates to a method for manufacturing an insulating product based on mineral or organic fibers. This method comprises the following successive steps:

[0080] - the application of a sizing composition according to the invention to mineral or organic fibers, preferably mineral fibers, and

[0081] - heating the fibers sized with the sizing composition so as to evaporate the volatile phase of the sizing composition and to achieve thermal hardening of the non-volatile residue, or packaging the mineral or organic fibers sized with the sizing composition, for storage and / or transport.

[0082] Mineral fibers are advantageously chosen from mineral wool fibers, in particular glass or rock wool.

[0083] When the insulation product is a mineral wool-based product, the sizing composition is sprayed onto the mineral fibers at the outlet of the centrifugation device (fiberizing) and before the mineral fibers are collected on the receiving member (forming) in the form of a sheet of fibers which is then treated in an oven at a temperature allowing the crosslinking of the reactive ingredients and the formation of an infusible binder (cooking). This crosslinking / thermal curing step is carried out by heating to a temperature greater than or equal to 180°C, preferably between 190°C and 220°C, for a period of between 20 seconds and 300 seconds, preferably between 30 and 250 seconds.When the insulation product is a product based on organic fibers, such as fibers of plant origin, for example cellulosic fibers, or of animal origin, for example wool, the cooking temperature is generally lower than that used for cooking products based on mineral fibers in order to protect the organic fibers from possible thermal degradation. Cooking temperatures are for example between 120 and 200 °C. The cooking time is generally between one minute and several tens of minutes, for example between 5 and 50 minutes, preferably between 5 and 30 minutes, in particular between 5 and 15 minutes.

[0084] In the process of the present invention, the cooking of the mineral or organic fibers can be carried out immediately after application of the sizing composition to the fibers and collection of the sized fibers on a conveyor belt, for example by passing through a thermostatically controlled oven at the desired cooking temperature.

[0085] The method of the present application also covers an embodiment where the sized fiber mat is not immediately cooked but is conditioned, for example partially dried, cut, compressed, shaped and packaged, for a cooking step separate from the step of manufacturing the sized fiber mat.

[0086] The packaging material must be chosen so as to allow the storage and / or transport of these intermediate products (fibers coated with an uncured binder) for an additional process step, carried out later or in a different location, and comprising the thermal curing of the sizing composition, possibly after forming the intermediate product, for example in a mold.

[0087] The packaging material is preferably plastic film.

[0088] EXAMPLES

[0089] Synthesis of unstabilized resol resin

[0090] In a 2-litre reactor topped with a condenser and equipped with a stirring system, 380 g of phenol (4 moles), 313 g of paraformaldehyde, used as a source of formaldehyde (10 moles), and 367 g of water (paraformaldehyde / phenol molar ratio equal to 2.5) are introduced and the mixture is heated to 45°C with stirring.

[0091] 53.2 g of a 50% sodium hydroxide solution (7% by weight relative to the phenol) are then added regularly over a period of 30 minutes, then the temperature is gradually raised to 70°C over 30 minutes and maintained for 80 minutes.

[0092] Then, the temperature is gradually reduced over a period of 30 minutes to 60°C while simultaneously adding 71.5 g of monoethanolamine (1.17 moles) to the reaction mixture in a regular manner. The temperature is maintained at 60°C for 15 minutes, the mixture is cooled to about 35°C in 30 minutes and solid sulfamic acid is added over one hour until the pH is equal to 5.0. A 15% sulfamic acid solution is then used to lower the pH to 4.5. The solids content of the liquid resin is adjusted to 58% by weight with water if necessary.

[0093] The resulting resol resin has the appearance of a transparent yellow-orange liquid: it has a free formaldehyde content of less than or equal to 0.2%, preferably 0.1%, a free phenol content of less than or equal to 1%, preferably 0.5% (these contents being expressed relative to the total weight of liquid) and a dilutability greater than 2000%. It is called unstabilized resol resin.

[0094] Preparation of stabilized resol resins

[0095] The unstabilized resol resin is divided into several batches immediately after preparation and a stabilizing agent to be tested is added to each batch in an amount equal to x parts by weight per 80 parts of dry weight of resin (see Table 1). Stir at room temperature until completely dissolved, so as to obtain so-called "stabilized" resol resins.

[0096] Dilutability

[0097] The dilutability over time (or water tolerance) of the different resol resins is assessed as follows: 10 mL of the resin is poured into a 250 mL Erlenmeyer flask. 10 mL of water is added, stirred, and checked for cloudiness. When the solution remains clear after 30 seconds, another 10 mL of water is added, stirred, and the solution is again assessed for clarity. This cycle is repeated until permanent cloudiness appears. Dilutability is calculated as follows:

[0098] Dilutability = (number of additions + 1) x 100

[0099] The resin is considered to have a dilutability of 2000% and to be infinitely dilutable when 10 mL of water has been added 19 times without the appearance of cloudiness.

[0100] Crystallization stability

[0101] To assess the crystallization stability of resol resins, 20 mL of resin is poured into a glass pillbox and stored at 3°C, checking at regular intervals for the appearance or absence of crystals. A qualitative analysis is performed to compare the amount of precipitate and its formation kinetics with those obtained for a reference consisting of a resin stabilized with 15 parts urea. The smaller the amount and the slower the kinetics, the higher the number of + assigned to the sample. Similarly, the larger the amount of precipitate and the faster the kinetics, the higher the number of - assigned to the sample.

[0102] Free formaldehyde level

[0103] The free formaldehyde content of resol resins is also assessed to verify the ability of the stabilizing agent to react with residual formaldehyde (formaldehyde trapping agent function).

[0104] To do this, take approximately 1 g of resol resin into a 100 mL graduated flask and note the mass m taken. Fill with distilled water up to the mark. The free formalin content is determined using a LANGE DR6000 colorimeter equipped with an LCK 325 formalin quantification kit, following the supplier's recommendations.

[0105] The measurement is carried out on 1 mL of the sample taken from the preparation flask. The result A obtained by the colorimeter is given in mg / L. The free formaldehyde level is calculated as follows:

[0106] % free formaldehyde = (A x 0.l) / m x 100

[0107] The free formaldehyde level is given as a % of the sample, expressed as ± 0.01%. Any result below 0.01% is noted as < 0.01%.

[0108] Ammonia emissions

[0109] Finally, the ammonia emissions during the curing of the different resol resins are evaluated by carrying out laboratory pollution simulations. A resol resin solution corresponding to 1 g of dry matter, previously diluted to a dry matter content of 30%, is introduced into a flat-bottomed glass flask with a capacity of 1 L. The inlet of a plunger is connected to the flat-bottomed flask so as to sweep the surface of the sample with an air flow of 1 L / min. The assembly is placed in a ventilated oven at 120°C for 15 minutes, then the temperature is raised to 215°C for one hour. The outlet of the plunger is connected to three bubblers arranged in series outside the oven, each containing 100 mL of a 0.02 N sulfuric acid solution. The contents of the bubblers are analyzed by ion chromatography to quantify the amount of ammonia trapped after each temperature step. Two measurements are taken for each of the batches tested.

[0110] The measurement results are summarized in Table 1 below for all substances tested as stabilizing agents, potential candidates for replacing urea, as well as for urea which serves as a reference and for various formaldehyde scavengers described in W02009 / 136105.

[0111] [Table 1]

[0112] Among the organic compounds evaluated, only the urea derivatives according to the invention have a stabilizing power for the resol resin at least equal to, or even greater than, that of urea: a dilutability greater than 1000% and stabilization upon crystallization over an equivalent or longer period are in fact observed, at a rate of urea derivative less than or equal to the quantity of urea used.

[0113] When comparing these compounds with urea, it is also found that ammonia emissions are significantly reduced.

[0114] Furthermore, the precipitate formed in the presence of urea and urea derivatives according to the invention was analyzed, following the methods described by B. Méchin et al. in Eur. Polym. J. Vol.

[0115] 22, No. 2, pp. 115-124 (1986) and Eur. Polym. J. Vol. 20, No. 4, pp. 333-341 (1984). The precipitate was subjected to HPLC analysis using a chromatograph that was either equipped with a UV detector at 280 nm or coupled to a mass spectrometer (m / z = 319) in negative scanning. The chromatograms obtained were compared with that of a sample of bis-4-diphenyltetramethylol obtained by preparative chromatography (control).It was thus possible to confirm that the precipitate observed in the case of urea (comparative sample) and 1-(2-hydroxyethyl)-2-imidazolidinone at 4% by weight (sample according to the invention) corresponded to bis-4-diphenyltetramethylol, insofar as the chromatograms obtained in UV were superimposable on that of the control and the chromatograms obtained in mass spectrometry of the sample according to the invention and of the comparative sample (having specifically extracted the 319 ion) presented a peak identical to that of the control and at the same retention time as on the chromatogram obtained in UV.

Claims

CLAIMS 1. Stabilized resol resin comprising - water, - an amino phenolic resin and - a urea derivative of formula (I): R3R4-N-CO-N-R1R2 (I) where: Ri denotes a hydrogen atom or a linear or branched C1-Cg alkyl group, R2 denotes a hydrogen atom or a linear or branched C1-C8 alkyl group, or forms, with R4 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle R3 denotes a hydrogen atom, a linear or branched C1-C8 alkyl group or a linear or branched C1-C8 hydroxyalkyl group, R4 denotes a linear or branched C1-C8 alkyl group or a linear or branched C1-C8 hydroxyalkyl group or forms, with R2 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle, the stabilized resol resin having a dry matter content of between 40 and 70% by weight.

2. Stabilized resol resin according to claim 1, characterized in that it contains: - from 75 to 99% by weight, preferably from 80 to 97% by weight, in particular from 90 to 97% by weight, of amino phenolic resin, - from 1 to 25% by weight, preferably from 3 to 20% by weight, in particular from 3 to 10% by weight of a urea derivative of formula (I), these percentages being relative to the total dry weight of the stabilized resol resin.

3. Stabilized resol resin according to claim 1 or 2, characterized in that the urea derivative of formula (I) is such that: Ri denotes a hydrogen atom or a linear or branched C1-C4 alkyl group, preferably hydrogen, methyl or ethyl, R2 denotes a hydrogen atom or a linear or branched C1-C4 alkyl group, or forms, with R4 and the nitrogen atoms to which they are attached, a 5- or 6-membered heterocycle, of preferably hydrogen, methyl, ethyl or forms, with F and the nitrogen atoms to which they are attached, an imidazolidine ring. R3 denotes a hydrogen atom, a linear or branched C1-C4 alkyl group or a linear or branched C1-C4 hydroxyalkyl group, preferably hydrogen, methyl, ethyl, hydroxymethyl or hydroxyethyl, R4 denotes a linear or branched C1-C4 alkyl group or forms, with R2 and the nitrogen atoms to which they are attached, a 5 or 6-membered heterocycle, preferably methyl, ethyl or forms, with R2 and the nitrogen atoms to which they are attached, an imidazolidine ring.

4. Stabilized resol resin according to any one of claims 1 to 3, characterized in that the urea derivative of formula (I) is chosen from the group consisting of: ethylene urea, 2-hydroxyethyl urea, dimethylurea, methylurea, trimethylene urea, l-(2-hydroxyethyl)-2-imidazolidinone, l,3-dimethyl-2-imidazolidinone and mixtures thereof, preferably ethylene urea, dimethylurea or l-(2-hydroxyethyl)-2-imidazolidinone.

5. Stabilized resol resin according to any one of the preceding claims, characterized in that it is free from urea.

6. Stabilized resol resin according to any one of the preceding claims, characterized in that the amino phenolic resin consists essentially of phenol-formaldehyde condensates and phenol-formaldehyde-amine condensates.

7. Sizing composition comprising water, a stabilized resol resin according to any one of the preceding claims and one or more additives chosen from coupling agents, oils, hydrophobic agents and accelerators of the curing reaction, characterized in that it comprises from 0 to 5% by weight of urea, relative to the dry weight of the sizing composition, preferably it is free of urea.

8. Sizing composition according to claim 7, characterized in that it contains from 75 to 98% by weight of water.

9. A method of stabilizing an amino resol resin, comprising adding to the resin, in a delay of one minute to 12 hours, preferably one minute to 2 hours following its synthesis and its cooling to less than 30°C, of ​​at least one urea derivative as defined in any one of claims 1, 3 or 4.

10. Use of the stabilized resol resin according to any one of claims 1 to 6 for the preparation of a sizing composition.

11. Method for manufacturing an insulating product based on mineral or organic fibers, comprising: - the application of a sizing composition according to any one of claims 7 to 8 to mineral or organic fibers, preferably mineral fibers, and - heating the fibers sized with the sizing composition so as to evaporate the volatile phase of the sizing composition and to achieve thermal hardening of the non-volatile residue, or packaging the mineral or organic fibers sized with the sizing composition, for storage and / or transport.

12. Method according to claim 11, characterized in that the mineral fibers are chosen from mineral wool fibers, in particular glass or rock wool.

13. Insulating product based on organic or mineral fibers, obtained by the process according to any one of claims 11 and 12.

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