Insulating product in particular thermal containing a binder based on phenol-formaldehyde resin and method for making same

p0001The invention relates to the field of insulation products, especially thermal or sound, based on mineral wool and an organic binder based on a phenol-formaldehyde resin. It more specifically the reduction of emissions of various pollutants during the manufacture of such mineral wool products includes a first wool manufacturing stage itself by fiber drawing and drawing, and a shaping step in wherein the mineral wool is collected on a receiver member in the form of a sheet. To ensure the cohesion of the web is sprayed onto the wool as it travels towards the receiving member a sizing composition which contains a thermosetting resin. The web thus treated is then subjected to a heat treatment in an oven to cure the resin and obtain a product having the desired properties, such as dimensional stability, mechanical strength, thickness recovery after compression, and homogeneous color.

p0002The sizing compositions are generally in the form of an aqueous composition containing a phenol-formaldehyde resin and additives such as curing catalyst resin, silane adhesion promoter, mineral oil dust ...

p0003So that the composition is capable of being distributed in the most generally by spraying, it is appropriate that the resin is sufficiently water-dilutable. To this end, it is customary to conduct the condensation reaction between formaldehyde and phenol by limiting the degree of condensation of monomers, to prevent the formation of long chains, no hydrophilic which reduce the dilutability. Accordingly, the resin contains a certain proportion of unreacted monomers, in particular formaldehyde, volatility can lead to undesirable emissions of organic compounds into the atmosphere of the plant.

p0004Therefore, it is generally reacted phenol-formaldehyde condensation product with urea which trap free formaldehyde, forming non-volatile condensation products. The presence of urea in the resin also brings a significant economic advantage of its low cost, because it can be introduced in relatively large amounts without significantly affecting the qualities vis-à-vis resin including mechanical properties of the product Finally, by significantly lowering the total cost of the resin.

p0005however it was observed that this solution is not entirely satisfactory as regards air pollution, because the urea-formaldehyde condensation products have proved unstable to heat, so that when using the resin to gluing mineral wool, in which the resin is subjected to temperatures above 100 ° C, the urea-formaldehyde condensation product gives under the effect of heat, urea, formaldehyde and the ammonia, which are released into the atmosphere of the plant.

p0006The present invention aims to make the manufacture less polluting insulating products, particularly as regards ammonia emissions on the production line, without penalizing the cost of production of the insulation product.

p0007The invention is based on the finding that it is possible to significantly reduce the emission of ammonia in the manufacture of an insulating product while using a size that retains a proportion of urea and is therefore a cost competitive.

p0008In this respect the invention relates to an insulating product based on mineral wool bonded with a binder based on a phenol-formaldehyde resin according to claim 1.

p0009According to the invention, first limit the free phenol content by pushing the condensation reaction to a degree sufficient to almost complete consumption of this first minority material. With a F / P ratio greater than 1, but not too high, less than or equal to 3.2, the condensation takes place by forming species of moderately high molecular weight, therefore with a higher formaldehyde consumption than would lead to very long chain phenol-formaldehyde condensates.

p0010Then, once the condensation reaction of the resole complete, captures the remaining formaldehyde molecules present in free form, using urea whose amount can be further reduced as the free formaldehyde resole rate is low.

p0011the proportion of urea in the binder mixture can thus be limited, while maintaining low levels of free volatile organic compounds in the binder. We therefore managed to limit emissions of volatile organic compounds such as phenol and formaldehyde, while reducing the amount of ammonia released on the production line.

p0012To monitor the progress of the resol formation reaction under the conditions required for the invention is measured three characteristic parameters:<ul><li>the rate of phenol and formaldehyde free characterizing the progress of the reaction,</li><li>the dilutability of the neutralized resol that characterizes the length of the formed condensate.</li></ul>

p0013According to the invention, the free phenol content in the resol before addition of urea is less than or equal to 2.5% by weight of phenol relative to the dry weight of resin, to a solids resole of 35 to 45%. Preferably the free phenol content is less than or equal to 2% relative to the dry weight of resin, preferably 1.7% based on the dry weight of resin. It may especially be in the range of 0.5 to 1.7%, eg 0.7 to 1.6% relative to the dry weight of resin.

p0014The free formaldehyde in the resole is less than or equal to 25% by dry weight of resin to a solids resole between 35 and 45. Preferably the level of free formaldehyde is less than or equal to 20% by weight dry resin, preferably to 15.5%, in particular 12%. It may especially be in the range of 2 to 4%.

p0015The dilutability of the resole is the maximum dilution factor of the resol for which we do not observe the formation of a permanent turbidity of the dilution. Is expressed by the dilutability of the water volume, in percent of the volume of resol, which may be added to resole before causing the formation of a permanent turbidity. Thus, a dilutability of 1500% means that can be diluted 10 ml of resin with 15x10 ml of water without the mixture becomes turbid. Generally, and according to the invention, this measurement is done by using for the dilution of the temperate deionized water, that is to say a water at room temperature, of the order of 15 to 25 ° C, generally about 20 ° C (in this temperature range, the dilutability does not vary significantly).

p0016According to the invention, controls the progress of the condensation by measuring the dilutability of the resol neutralized with sulfuric acid. Indeed, it is generally found that the resol synthesized in basic medium has a high dilutability at basic pH (usually pH 9) with a relatively small variation, even when it contains species of very high molecular weight. On the contrary, when the resol is neutralized with sulfuric acid, the dilutability varies significantly decreasing manner when the molecular weight of phenol-formaldehyde condensates increases. May thus follow the growth of undesirable molecular weight compounds.

p0017According to the invention, resols used are therefore characterized by a dilutability of greater than 500 and less than or equal to 1500% in neutralized form by sulfuric acid; preferably, the dilutability is over 500 to 1000% in the neutralized state. By neutralization is meant the addition of a quantity of H₂SO₄ sufficient to react with all the hydroxyl OH^- introduced by the basic catalyst.

p0018Such resole can advantageously be synthesized by reacting phenol and formaldehyde in the presence of a basic catalyst such as sodium hydroxide, at a temperature of the order of 50 to 80 ° C, in particular from 60 to 75 ° C, in particular about 70 ° C, for a period of about 80 to 200 minutes, in particular from 90 to 150 minutes, the period being shorter than the high temperature and / or that the F / P ratio low. In this regard, an F / P ratio is limited to 3.2 to avoid too high reaction times.

p0019The basic catalyst, known per se, especially sodium hydroxide but also potash, lime or baryta, is generally used in an amount corresponding to 6 to 20 mol equivalents of hydroxyl OH^- per 100 moles of initial phenol. The melt condensation step is generally followed by gradual cooling to room temperature.

p0020To prevent unwanted further condensation reaction, is desirable to deactivate the basic catalyst by neutralizing the resole. Neutralization with sulfuric acid is not indicated, as it lowers the dilutability below 1500%, which is usually the threshold guaranteeing good aptitude for carrying out online by spraying.

p0021Thus, the resole used in the invention is advantageously neutralized with at least one acid chosen from boric acid or an equivalent borate (such as ammonium borate, sodium metaborate, sodium tetraborate, polyborate aminoalcohol), the sulfamic acid or an equivalent sulphamate, an amino acid (especially aspartic acid, glutamic acid, aminoacetic ...). These acids have in fact the property of modifying the resole in such a way that its dilutability is higher in the neutralized medium thus obtained than in the medium obtained with sulfuric acid. The neutralization is advantageously carried out until a pH of about 7 to 9.

p0022The neutralization product by one of the aforementioned acids of a resole having features of the invention generally has a greater than 1000% up over 2000% dilutability (it is customary to say that a dilutability greater than 2000% is infinite) just after neutralization, and keeps a dilutability greater than or equal to 1000% after 3 weeks of storage at about 12 ° C with gentle stirring.

p0023Alternatively, the resole may be neutralized with any acid, but in the presence of an emulsifier such as a gum and / or an anionic surfactant, especially guar gum and ghatti, or possibly casein. The acid used may then be chosen from any strong acids known per se, such as sulfuric acid, hydrochloric acid, but boric acid, sulfamic acid (or equivalent salts) or an amino acid .

p0024The preparation of a binder used according to the invention comprises mixing a resol cold as previously described with urea in limited quantity. According to the invention, the mixture comprises 65 to 90 parts by weight of resol (counted in terms of dry weight of the resol) 35 to 10 parts by weight of urea. The mixture comprises at least 65 parts, especially 70 to 85 parts by dry weight of resol per at most 35 parts, especially 15 to 30 parts by weight of urea.

p0025The addition of urea can be done immediately after cooling of the resole, preferably after neutralization, to form a stable premix storage, later used for formulating the sizing, or it may be at the time even of formulating the sizing before a production run. The premix of urea use may however be preferred because it results in fewer emissions of pollutants, including ammonia on the manufacturing line.

p0026Urea is not the only useful compound as formaldehyde scavenger and can particularly further adding ammonium sulphite in an amount of 1 to 20 parts by weight, especially from 1 to 10 parts by weight per 100 parts by weight dry blend of resole + urea. It has been found that ammonium sulfite does not very significantly affect the emission of ammonia, despite the contribution ammonium ion constitutes in the sizing composition. However, it is preferable to limit the ammonium sulphite content to about 1 to 5 parts by weight, especially around 2 parts by weight per 100 parts by weight of dry matter of resin and of urea.

p0027The composition of the sizing may further contain the other customary ingredients, such as:<ul><li>ammonium sulphate as curing catalyst, preferably in an amount of 1 to 5 parts by weight per 100 parts by weight of dry matter of resin and of urea;</li><li>or a silicone;</li><li>or a mineral oil.</li></ul>

p0028Ordinarily, a sizing composition may further comprise ammonia. To minimize the emissions of ammonia gas on the manufacturing line, it is preferable that the gluing is totally free of ammonia. However, it appeared that a lower ammonia content of up to 5 parts by weight of 20% solution per 100 parts by weight of dry resin + urea material allows to stay below the threshold limit for a production in good conditions .

p0029The proportion of sizing in the insulating product is generally of the order of 1 to 12% by weight of dry matter relative to the total weight of mineral wool.

p0030The invention also relates to a sizing composition as described above.

p0031According to another aspect, the invention relates to the use of a sizing composition as described above to reduce ammonia emissions during the manufacture of an insulating product.

p0032According to the invention, one arrives at limit ammonia emissions to less than 10 grams of ammonia per kilogram of mineral wool, in particular less than 8 g / kg, especially at most 5 g / kg.

p0033The invention therefore also relates to a method of manufacturing an insulating product based on mineral wool bonded with a phenol-formaldehyde binder as described above, wherein the cumulative emissions of ammonia to all the manufacturing steps are less 10 grams of ammonia per kilogram of mineral wool.

p0034The invention is illustrated by the following examples.

EXAMPLE 1

p0035a phenol-formaldehyde resin is prepared by charging a stirred reactor that will be maintained throughout the manufacturing cycle, 100 kg of phenol and 241 kg of 37% formaldehyde in aqueous solution and are heated to 45 ° C temperature into the reactor. The molar formaldehyde / phenol ratio is 2.8.

p0036While maintaining the temperature at 45 ° C on a regular basis is introduced over a period of 30 minutes 12.7 kg of sodium hydroxide in 47% aqueous solution, is a weight soda / phenol ratio of 6%, a molar ratio of 14.1%.

p0037Immediately after completion of this addition, the temperature was raised to 70 ° C in 30 minutes, and this temperature is maintained for a period of about 120 minutes. At the end of this time, the dilutability of the resol neutralized with sulfuric acid was 1200%.

p0038then the reactor is cooled and the reaction mixture from 70 ° C to 35 ° C in 35 minutes.

p0039It then adjusts the pH of the reaction medium to 7.2 with sulfamic acid as a 15% aqueous solution (about 88 kg). The operation takes approximately 90 minutes, while cooling the reaction mixture to 20 ° C.

p0040The neutralized resole has a free formaldehyde level of 2.5% by weight of the resole, or 6.8% based on the weight of dry matter of resin and a free phenol content of 0.5% by weight of resole to a solids content of 37%, or 1.4% compared to dry.

p0041The dilutability of the resol neutralized with sulfamic acid was infinite (greater than 2000%) and the rest for a week of storage at 12 ° C with gentle stirring. After three weeks of storage under these conditions, the dilutability is 1000%.

p0042This resin is used to formulate four sizing compositions, three of which to base a premix of resol and of urea, whose formulas are shown in <b>table 1</b> below.

p0043These sizings are employed in a production line for insulating products based on glass wool: the size is diluted to be sprayed onto the glass wool filaments before they are received on a conveyor belt contained in a receiving chamber provided suction means for forcing the glass wool on the carpet. The conveyor belt passes through a shaping area where the glass wool can be compressed vertically and possibly longitudinally, and then routes the shaped mass in a binder crosslinking oven with a temperature of 280 ° C.

p0044The binder content of the product is measured by the loss on ignition of the latter, which here is 4.5% of total product weight.

p0045The gaseous emissions are collected at all points of the production line, in particular in the forming area at the entrance and at the exit from the oven, and one dose of phenol, formaldehyde and ammonia content in these samples. Cumulative emissions over the entire line shown in Table 1 below.

p0046Test 1 shows that adding ammonium sulfite, certainly the level of ammonia emissions rises slightly as a result of the presence of ammonium ions, but the level of free formaldehyde is remarkably low.

p0047An advantageous alternative is to remove ammonia keeping the ammonium sulphite, possibly reduced amount.

p0048Run 2, which uses a resin + urea premix and does not use ammonia, gives very good emission results both as regards formaldehyde as ammonia.

p0049The addition of ammonia in the premix of test 3 reduces the transmission level of formaldehyde, with an emitted ammonia content which remains tolerable.

p0050Finally, the addition of ammonium sulfite in test 4 further reduces the level of formaldehyde emitted, with an emitted ammonia content which also remains tolerable.<tables id="tabl0001" num="0001"><table frame="all"><title><u>TABLE 1</u></title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="28mm" /><colspec colnum="2" colname="col2" colwidth="81mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="15mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><thead><row><entry morerows="1" align="center" valign="top">Example (test)</entry><entry morerows="1" align="center" valign="top">Formulation (Resin / Urea) * / Ammonium Sulfate / 20% ammonia / ammonium sulfite *: (Resin / Urea) brackets if premix</entry><entry namest="col3" nameend="col5" align="center" valign="top">Emissions (g / kg of glass)</entry></row><row><entry align="center" valign="top">phenol free</entry><entry align="center" valign="top">Formalin</entry><entry align="center" valign="top">Ammonia</entry></row></thead><tbody><row><entry align="center">1 (1)</entry><entry>80/20 / 2.5 / 5/5</entry><entry align="center">0.7</entry><entry align="center">0.2</entry><entry align="center">1.2</entry></row><row><entry align="center">1 (2)</entry><entry>(75/25) / 1/0/0</entry><entry align="center">0.6</entry><entry align="center">0.4</entry><entry align="center">1.2</entry></row><row><entry align="center">1 (3)</entry><entry>(75/25/2 20% ammonia) / 2/0/0</entry><entry align="center">0.6</entry><entry align="center">0.3</entry><entry align="center">1.2</entry></row><row><entry align="center">1 (4)</entry><entry>(75/25/2 20% ammonia) / 2/0/2</entry><entry align="center">0.6</entry><entry align="center">0.3</entry><entry align="center">0.9</entry></row><row><entry align="center">2 (1)</entry><entry>(70/30/2 20% ammonia) / 2/3/0</entry><entry align="center">0.4</entry><entry align="center">0.6</entry><entry align="center">1.4</entry></row><row><entry align="center">2 (2)</entry><entry>(70/30/2 20% ammonia) / 2/0/0</entry><entry align="center">0.3</entry><entry align="center">0.6</entry><entry align="center">1.3</entry></row></tbody></tgroup></table></tables>

EXAMPLE 2

p0051a phenol-formaldehyde resin is prepared by charging a stirred reactor that will be maintained throughout the manufacturing cycle, 100 kg of phenol and 276 kg of 37% formaldehyde in aqueous solution and are heated to 45 ° C temperature into the reactor. The molar formaldehyde / phenol ratio is 3.2.

p0052While maintaining the temperature at 45 ° C on a regular basis is introduced over a period of 30 minutes 12.7 kg of sodium hydroxide in 47% aqueous solution, is a weight soda / phenol ratio of 6%, a molar ratio of 14.1%.

p0053Immediately after completion of this addition, the temperature was raised to 70 ° C in 30 minutes, and this temperature is maintained for a period of about 130 minutes. At the end of this time, the dilutability of the resol neutralized with sulfuric acid was 1200%.

p0054then the reactor is cooled and the reaction mixture from 70 ° C to 35 ° C in 35 minutes.

p0055It then adjusts the pH of the reaction medium to 7.3 with sulfamic acid as a 15% aqueous solution (about 88 kg). The operation takes approximately 90 minutes, while cooling the reaction mixture to 20 ° C.

p0056The neutralized resole has a free formaldehyde level of 2.5% and a free phenol content of 0.5% by weight of the resol, for a solids content of 36%.

p0057The dilutability of the resol neutralized with sulfamic acid was 1800% and 1300% passes after three weeks of storage at 12 ° C with gentle stirring.

p0058This resin was used to formulate two sizing compositions based on a premix of resol and of urea, whose formulas are shown in <b>Table 1.</b>

p0059These sizings are used as in Example 1 for the manufacture of insulating products based on glass wool and the results of measurements of gaseous emissions are reported in <b>Table 1.</b>

p0060Test 1 shows that despite the presence of ammonia in the sizing, the level of ammonia emitted remains tolerable, and can easily be reduced if you remove ammonia as shown in partial suppression ammonia in test 2.

p0061The level of formaldehyde and phenol emissions in these two trials are also very satisfactory.