SI9111631A - Phenolic resin, process for producing this resin, and resin composition for adhering mineral fibres - Google Patents

Abstract

Phenolic resin. The resin is liquid, contains phenol-formaldehyde, formaldehyde-urea and phenol-formaldehyde-amine condensates and has a free formaldehyde content lower than 3 %, the content being expressed as total weight of liquid, and a water-dilutability at 20 DEG C higher than or equal to 1000 %. In addition, the resin is heat-stable. Application to less contaminating sizing compositions for inorganic fibres; and use of the said fibres sized in this manner for the manufacture of insulating products and of out-of-soil cultivation substrates.

Description

Phenolic resin, process for preparing resin and composition for bonding mineral fibers contained therein

The invention relates to a phenolic resin intended for use in a mineral fiber adhesive composition. This resin is formed by the condensation of phenol, formaldehyde, amine and urea, in the presence of a basic catalyst.

The invention also relates to a specific process for the preparation of this resin and a mineral fiber adhesive composition containing said resin.

It also refers to the use of both bonded mineral fibers, in particular for the manufacture of insulating products as well as products intended as substrates for above-ground culture.

Mineral fiber based products may be formed from fibers obtained by different processes. So e.g. a well-known centrifugal drawing technique can be cited whereby a molten substance is introduced into a centrifuger having a number of small openings, in order to eject against the peripheral wall of the centrifuger under the effect of centrifugal force and to escape through the openings in filamentary form. When they exit the centrifuger, they are stretched and pulled toward the receiving body by means of a gas flow at high speed and temperature to form a web of fibers. In order to ensure the interconnection of the fibers, a composition called a adhesive composition containing a heat-curable resin is sprayed onto the fibers during their passage towards the receiving body. The layers of fibers thus treated are then subjected to a heat treatment in a humid chamber to polycondensate the resin and produce an insulating product having the desired properties, such as dimensional stability, elongation resistance, density recovery after compression, homogeneous color.

Adhesive compositions for mineral fiber spraying comprise a resin which generally occurs in the form of an aqueous composition, and further urea and additives such as silane, mineral oils, ammonia, ammonium sulfate and water.

By resin, the product of condensation of the starting materials in the presence of catalysts is condensed before the heating step in the vapor chamber according to the invention.

The required properties of adhesive compositions depend on the properties of the resin. In particular, the adhesive composition must be easily dusted and be suitable for enveloping and bonding the fibers, while at the same time slightly damaging to the environment.

Therefore, the resin must, above all, be well lasting stable and very dilute with water.

The resin must be stable in particular for at least 8 days at a temperature of 12 to 18 ° C. In fact, it should be stored for several days before being used to form an adhesive composition. The adhesive composition containing the resin and the aforementioned additives is generally prepared immediately before use.

The resin should also be very dilute with water. This dilution property is particularly important because the adhesive composition containing the resin is then suitable for dusting. Generally, dilution is defined as follows: the dilution of a resin with water in the form of an aqueous composition is the volume of deionized water that can be added at a given temperature to the volume unit of that composition before causing a permanent mist.

The water dilution of a resin suitable for use in a dustable adhesive composition should preferably be at least 20 ° C or above 1000% for at least 8 days.

It is further necessary that the resin contains as little unconverted starting products as possible. In reality, the risks of atmospheric pollution are essentially due to the presence of volatile monomers: e.g. the starting products required to produce the resin, e.g. formaldehyde and phenol, which have not been transformed in the reaction or regenerate during the bonding of the fibers or thereafter.

Therefore, in order to obtain adhesive compositions which minimize the content of contaminants, in particular free phenol and free formaldehyde, the resin contains as little residual starting material as possible while maintaining its useful properties.

These purposes, i.e. a stable resin containing little free formaldehyde and phenol, while maintaining the desired properties, in particular good dilution with water, which easily enables mineral sputtering, are inversely contradictory, since the reduction of free phenol and formaldehyde content is generally achieved by increasing the degree of condensation , which in turn results in a decrease in dilution.

It is known to prepare resins useful for mineral fiber adhesive compositions by reacting phenol and formaldehyde in the presence of a basic catalyst. To facilitate the reaction between phenol and formaldehyde and thereby reduce the amount of unreacted phenol, thereby avoiding the risk of contamination, the use of formaldehyde / phenol mole ratios above 1 and the introduction of urea to capture excess formaldehyde are known.

Thus, resins formed from formaldehyde-phenol and urea-formaldehyde condensates.

Thus, as described in EP-A-148 050, a resin in liquid form, obtained by condensation in an alkaline medium of formaldehyde, phenol and urea, with a dilution with water of at least 1000%, and containing by weight, could be obtained of free phenol and free formaldehyde, expressed on an overall weight of liquid less than or equal to 0,5% or. 3%. This resin was obtained with a formaldehyde / phenol mole ratio of 3 to 6. The amount of free phenol and formaldehyde was measured with respect to the total weight of the liquid.

This resin is considered to have satisfactory characteristics for use in mineral fiber adhesive compositions and is a minor contaminant.

If the free phenol content is considered to be quite insignificant, causing minor contamination, then the free formaldehyde content in the resin (about 3%) is still high, and therefore it is sought to further reduce it while retaining those resin properties required for later desirability. use.

Furthermore, the use of a high F / P molar ratio as described in previously cited document EP-A-148 050 allows a significant reduction in the free phenol content, but requires the use of urea for reaction with excess formaldehyde. This results in the formation of a condensation product of urea-formaldehyde, with this product being slightly heat-resistant.

This thermal instability is a disadvantage since the mineral fibers treated with the adhesive composition undergo heat treatment to produce the insulating product.

Indeed, when using a mineral fiber bonding resin subjected to temperatures above 100 ° C during the resin, the condensation product of urea formaldehyde is again under the influence of the heat released by formaldehyde, thus increasing atmospheric pollution.

The subject of the invention is therefore a new resin having satisfactory characteristics for use in a dustable adhesive composition and a minor contaminant, especially with respect to formaldehyde, i.e. a resin containing a small proportion of free formaldehyde and further thermally stable, to avoid formaldehyde regeneration during the use of the resin.

A further object of the invention is a process for the preparation of a resin, in particular a process that allows the use of a lower molar ratio of formaldehyde-phenol by reducing the amount of urea required for reaction with excess formaldehyde.

The subject of the invention is also an adhesive composition containing this resin and its use for bonding mineral fibers for the manufacture of insulating products or substrates for above-ground culture.

The liquid resin of the invention, intended for use in a mineral fiber adhesive composition, contains predominantly condensates of phenol-formaldehyde (P-F), urea formaldehyde (U-F) and phenol-formaldehyde-amine (P-F-A). This resin has a content of free formaldehyde (FL), expressed as a total weight of liquid, of less than or equal to 3%. The resin also has a dilution with water, measured at 20 ° C, at least equal to 1000%. Further, the resin is thermally stable, i.e. contains little or no methyl urea, which is relatively unstable.

In order to evaluate this thermal stability, a resin-containing adhesive composition must be subjected to a test simulating the thermal conditions to which the adhesive composition is exposed when used to produce an insulating product as previously described. The resin is considered to be a thermally stable and insignificant contaminant with formaldehyde when the amount of formaldehyde released in this test is below 4 g of formaldehyde per kg of dry extract of 10% of the adhesive solution. Thermal stability can also be demonstrated by thermogravimetry.

Amin (A) is selected from those that allow a Mannich-type reaction; these are e.g. alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), cyclic amines such as piperidine, piperazine and morpholine.

According to the invention, prior to the reaction of excess free formaldehyde with urea, a reaction in which free formaldehyde and free phenol react with an amine is carried out.

The reaction of the invention is of Mannich type, which generally converts the aldehyde, an organic compound containing active hydrogen atoms, and an amine into a Mannich condensed base. In this case, the aldehyde is formaldehyde and the organic compound is phenol. Amin, however, can be selected from those previously listed. In the invention, the amine reacts with phenol or methylolfenols and formaldehyde, which gives the resulting resin a much more stable structure.

In order to obtain the resin as previously defined, the invention provides a process consisting of reacting phenol and formaldehyde in a molar ratio above 1 in the presence of a basic catalyst, cooling the reaction mixture and reacting excess formaldehyde with urea. The invention is characterized in that, before addition of urea and during cooling, an amine suitable for the Mannich reaction is introduced into the reaction medium.

Phenol and formaldehyde are reacted in greater detail in a molar ratio of 1.8 to 5 until a phenol conversion rate of 93% or greater is achieved, and the reaction mixture is cooled.

The phenol conversion rate is the percentage of phenol involved in the formaldehyde-phenol condensation reaction with respect to 100% of the initial phenol. The condensation reaction of formaldehyde-phenol is stopped by cooling the reaction mixture to a level corresponding to a resin that can still be diluted with water. According to the invention, amine (A) is added before urea is added, either during the cooling of the reaction mixture or in the cold. The amine is added gradually as the reaction with formaldehyde and phenol is exothermic. The addition of an amine may take place from the beginning of cooling of the reaction mixture, or when the mixture is cooled to a temperature between 45 and 20 ° C.

The reaction of the invention between phenol, formaldehyde, methylolfenols and amine allows reducing the amount of free formaldehyde in the reaction medium prior to the addition of urea, thereby obtaining a resin containing a urea-formaldehyde condensate in a smaller amount: hence the greater thermal stability of the resin. The reaction of free formaldehyde with amine, followed by urea, further allows the free formaldehyde content of the final resin to be reduced and even the free formaldehyde content of the resin to be obtained below 0.75% and even below 0.5%.

The addition of the amine of the invention allows for the further reduction of the free phenol content, especially for resins prepared from a high F / P molar ratio.

Indeed, in the known process for preparing a phenolic resin, such as the resin described in pat. published EP-A-148 050, the reaction of the condensation of phenol and formaldehyde (with a F / P molar ratio of 3 to 6) was carried out until a conversion rate above 98% was obtained. The amount of unreacted phenol does not change during the next steps of the preparation process.

The addition of the amine of the invention after the condensation reaction of phenol and formaldehyde enables the fixation of unreacted phenol, which reduces the amount of free phenol. Thus, the free phenol content can be obtained below 0.2%.

The use of the amine of the invention further offers the advantage of reacting phenol and formaldehyde in a F / P molar ratio below 3, however, a resin having the desired properties of water dilution and non-polluting is obtained. Indeed, as the F / P molar ratio decreases, free formaldehyde in the resin decreases and free phenol increases. The addition of the amine of the invention allows one to obtain from a low molar ratio of F / P resins containing such percentages of free phenol as would be obtained only when using high molar ratios.

The resin is prepared in more detail after a temperature cycle, which is schematically divided into three phases: the heating phase, the temperature level maintenance phase, and the cooling phase.

Following this process, phenol and formaldehyde are reacted in the first stage in the presence of a basic catalyst under gradual heating to a temperature between 60 and 75 ° C, preferably about 70 ° C. The F / P molar ratio, as previously indicated, is suitable between

1,8 and 5.

Various basic catalysts such as triethylamine, CaO lime and alkali or alkaline earth metal hydroxides such as sodium and potassium, calcium and barium hydroxides can be used as catalysts.

Regardless of the catalyst selected, the amount of conveniently 6 to 20 moles of OH hydroxyl equivalents per 100 mole of starting phenol is used.

During the second phase (maintaining the temperature level), the temperature of the reaction mixture reached during the heating phase, i.e. 60 to 75 ° C, and preferably 70 ° C, maintained until at least 93% of the phenol conversion step is achieved. The duration of this temperature maintenance phase is preferably at least about 90 minutes.

The third phase is the cooling phase, during which the amine according to the invention is introduced into the reaction mixture by triggering a Mannich reaction, producing the phenolformaldehyde-amine condensate.

An amine may be introduced at the onset of cooling of the reaction mixture. The amine addition is carried out gradually, e.g. per minute in the amount of 0.33 wt. % of the total amount of amine by weight of the resin because the reaction is exothermic.

The amine may also be added at the end of the cooling phase, e.g. at a temperature between 20 and 45 ° C.

The duration of amine addition can vary between 20 and 45 minutes.

The amount of added amine, especially alkarylamine, varies between 5 and 40 wt. % by weight of phenol.

After the formation of the phenol-formaldehyde-amine condensate, the reaction mixture is cooled, if necessary, to reach a temperature of about 20 to 25 ° C and neutralized to stop the condensation reactions.

Generally, the reaction mixture is neutralized by the addition of acid, such as sulfuric acid, sulfamic acid, phosphoric acid and boric acid, in sufficient quantity to keep the pH of the mixture between about 7.0 and 8.5. After neutralization, urea is added to bind unreacted formaldehyde.

According to the invention, the addition of urea is carried out in the cold, i.e., when the temperature of the reaction mixture reaches about 20 to 25 ° C. The amount of urea added varies between 10 and 50 wt. % by weight of the resin expressed in the dry extract.

The addition of urea in the cold in the preparation of the resin is useful because the reaction between formaldehyde and the urea in the cold is slow, which allows us to control the reaction and avoid too rapid condensation, which would lead to a decrease in the dilution of the final resin.

According to another embodiment of the process of the invention, the reaction mixture may be added before or after neutralization of ammonia to trap a portion of free formaldehyde. Hexamethylenetetramine is formed.

Ammonia is added in the form of an aqueous solution in an amount ranging between 0 and 100% of the stoichiometry of the reaction between formaldehyde and ammonia, the amount of formaldehyde calculated from the concentrations at the time of ammonia introduction.

The invention also relates to an adhesive composition intended for coating mineral fibers, in particular glass or stone fibers, whereby the obtained adhered fibers can be used to produce insulating products and substrates for above-ground culture.

The adhesive composition of the invention comprises a resin of the invention, adhesive additives and urea.

As stated previously, the resin of the invention may be characterized by a very low free formaldehyde content, below 2%, with a yield below 0.75%. In this case, the presence of urea in the adhesive composition is no longer necessary, or it is only necessary to set the gel time of the adhesive to avoid any problems of overgrowth.

In the adhesive compositions of the invention containing urea, the proportions of the ingredients, expressed in parts of dry matter, are from 50 to 90 parts of resin and 10 to 50 parts of urea.

Generally, the typical adhesive composition comprises the following additives per 100 parts of resin and urea dry matter:

- 0 to 5 parts of ammonium sulfate, generally 1 to 3;

- 0 to 2 parts of silane, in particular aminosilane;

- 0 to 20 parts of oil, generally 6 to 15;

- 0 to 20 parts of 20% ammonia, generally 3 to 12.

The role of these ingredients is known and is only briefly summarized here: ammonium sulfate is used as a catalyst for polycondensation (in a hot chamber), after dusting the adhesive composition over fibers; silane is a bridging agent between fibers and resin and is also used as an anti-aging agent; oils are dust and hydrophobic agents. Ammonia in the cold acts as a means of delaying polycondensation and further binds free formaldehyde; urea modifies the composition to have an effect on the adhesive overgrowth and reduce contamination.

Aminosilane marketed by Union Carbide under the name Al 100 can be advantageously used as silane. Mineral oil which is marketed by Mobil Oil under the name Mulrex 88 can be used as an oil.

The following non-limiting examples illustrate the invention.

The following examples can be classified according to two variants of the resin preparation process of the invention. In one case, resin production is carried out by introducing an amine in hot; in the second case, the amine is added in the cold.

In both cases, the condensation phase between phenol and formaldehyde takes place as follows:

Formaldehyde and phenol are introduced into the reactor; then, under mechanical stirring, it is heated or cooled to a temperature slightly higher than the melting temperature of the phenol. Mechanical stirring is continued throughout the reaction cycle. The catalyst is introduced in a uniform manner, and then immediately after completion of the introduction, the temperature of the mixture is raised to a value that allows for optimal condensation and soluble resin production. This temperature is maintained until the phenol conversion phase is higher than 93%.

Then, in one case, it is gradually cooled by adding the amine while stirring; in the second case, it is gradually cooled to a temperature between 45 and 20 ° C and the amine is added.

Examples 1 and 2 relate to the production of resins with the addition of an amine during cooling.

EXAMPLE 1

a) Preparation of the resin

To a 2 liter reactor equipped with a stirring system, a condenser, a thermometer and a reagent inlet, 564.66 g of phenol (6 moles) was added to 1217.43 g of formaldehyde (15 moles) in aqueous 37% solution to obtain a molar F / P ratio of 2.5.

The mixture was brought to 45 ° C with stirring, then 56.47 g of soda in an aqueous 50% solution (i.e., 11 moles of OH 'per 100 moles of starting phenol) was uniformly introduced over 30 minutes while maintaining the temperature at 45 ° C.

The temperature is then raised steadily from 45 to 70 ° C for 30 minutes and maintained at 70 ° C for 80 minutes until the conversion rate is 93%.

Then, cool the mixture evenly; diethanolamine (141.16 g, i.e. 25% by weight of phenol) was gradually added over the first 30 minutes. At the end of the amine addition, the temperature is about 60 ° C. During the 15 minutes following the completion of the amine introduction, the temperature of the reaction medium is maintained at 60 ° C because the reaction is exothermic. Then continue to cool the mixture. When the reaction mixture reaches a temperature of about 25 ° C after about 30 minutes, sulfuric acid in 20% solution is added over a period of 60 minutes, reaching a pH of 8.0 to 8.1. Subsequently, grain urea (426.5 g, i.e. 35 wt.% With respect to the total weight of the resin expressed as the dry extract) was added gradually over 60 minutes.

The resin comes in the form of a clear aqueous composition which can be diluted infinitely with water at 20 ° C after more than 8 days. The free phenol content is 0.8% and the free formaldehyde content is below 0.5%.

It can be observed that when comparing this resin with the resin obtained by the process described in pat. publish EP-A-148 050, e.g. with the resin of Example 4, the two resins show slightly different percentages of free phenol (0.5% and 0.8%); this is due to the fact that in one case (in the present invention), the F / P ratio is 2.5, and in the other case (in the sense of the cited patent publication) the F / P ratio is 3.5. Regarding the proportion of free formaldehyde in the resin of Example 4 of the previously cited Pat. posts should be stated as 1.12% and 2000% dilution after more than 8 days.

b) Adhesive composition

The resin obtained previously is used to prepare the adhesive composition without the addition of urea. Adhesive additives are ammonium sulfate and ammonia.

For 100 wt. parts of the resin are ammonium sulphate two parts and ammonia one part.

c) Formation of the final product

When leaving a mineral fiber production plant with known centrifugal drawing, spray the fibers between their exit from the centrifugal plant and receiving them on the collecting body, the adhesive composition previously described, in an amount of 2 to 20 wt. % composition by weight of the final insulation product. The water contained in the composition partially evaporates due to the high temperature. After receiving the fibers on the collecting organ and forming the veil, they are subjected to thermal treatment in a steam chamber at a temperature between 180 and 200 ° C for about 2 minutes, which leads to the polycondensation of the resin.

When used to form the final product, an adhesive composition comprising the resin of the invention formed from condensates of phenol-formaldehyde, formaldehyde-urea and phenol-formaldehyde-amine is subjected to temperatures above 100 ° C. Urea-formaldehyde condensate, which is slightly heat resistant, likes to break down to regenerate formaldehyde.

To evaluate the contamination caused by free formaldehyde that can be released during the treatment of mineral fibers with an adhesive composition, we use a method that simulates the conditions to which the adhesive composition is subjected.

Method for the evaluation of formaldehyde emitted:

100 g of the adhesive composition with 10% dry extract was placed in a steam chamber at 180 ° C for 2 hours and then air-filled in an amount of 11 per minute. The resulting vapors were run into three water-containing rinses to determine the dose of formaldehyde by spectrocolorimetry (chromotropic acid method) and phenol by gas phase chromatography using a device equipped with a flame ionization detector. Sample solutions are used to determine phenol.

The amount of starting formaldehyde is 2.5 g and free phenol is 8.8 g per kg of dry extract of 10% of the adhesive solution.

For information, state that for the standard adhesive (which we will define below), the amounts of formaldehyde that are emitted, respectively. of phenol under the same conditions, 6 oz. Hg.

EXAMPLE 2

In this case, 1003.15 g of formaldehyde (12.4 moles) are reacted in 37% solution of s

377.6 g of phenol (4 moles). Lime (CaO) in an amount of 20.8 g (0.316 mol) is used as a catalyst. Monoethanolamine (75.52 g, i.e. 20 wt% with respect to phenol) was introduced during cooling.

The amount of urea added after neutralization with sulfuric acid to achieve a pH of 8.2 corresponds to 35% by weight with respect to the total weight of the resin expressed in the dry extract.

The resin obtained has an infinite dilution with water, a free phenol content below 0.2% and a free formaldehyde content below 0.5%.

The following example relates to a resin prepared by the addition of a cold amine.

EXAMPLE 3

a) Preparation of the resin

In a reactor equipped in the same manner, 470.55 g of phenol (5 mol) was added to 1420.34 g of formaldehyde in aqueous 37% solution, corresponding to a molar F / P ratio of 3.5. As in Example 1, heat the mixture to about 45 ° C, then add 47.06 g of aqueous, 50% soda solution (i.e. 0.588 moles and 11.76 moles OH 'per 100 moles of starting phenol) over 30 minutes, maintaining the temperature at 45 ° C. The mixture was stirred at 70 ° C for 30 minutes, then maintained at this temperature for about 90 minutes until a phenol conversion rate of 97.5% was reached. The mixture was then cooled gradually to 50 [deg.] C. for 50 minutes. Then 38.76 g of monoethanolamine is added, which corresponds to 8.2 wt.% By weight of phenol. Adding is done gradually over a period of 20 minutes. The reaction mixture was neutralized with a 20% sulfuric acid solution to pH 7.4. Ammonia is then added over a period of about 30 minutes at 20 ° C in 27% solution, in an amount corresponding to 20% stoichiometry for the reaction of formaldehyde with ammonia.

Then, for 60 minutes, 471.2 g of urea was added to the beans, corresponding to 35% by weight, based on the total weight of the resin, expressed as the dry extract.

The resin comes in the form of a clear aqueous composition with infinite dilution with water at 20 ° C after more than 8 days. The free phenol content is below 0.2% and the free formaldehyde content is below 0.75%.

b) Adhesive composition

Thus, as in Example 1, prepare an adhesive composition containing only the resin previously prepared and as adhesive additives 6 parts of ammonium sulfate and 3 parts of ammonia.

The thermal stability of the resin was evaluated as in Example 1.

The amount of formaldehyde recovered in the test is 3 g and phenol 6 g per kg of dry extract of 10% of the adhesive solution.

EXAMPLE 4

Prepare the resin, as in Example 1, starting from formaldehyde and phenol, to have a F / P molar ratio of 2.3. The reaction between formaldehyde and phenol takes place at 70 ° C for 90 minutes. Diethanolamine was added in an amount of 22% by weight, based on the weight of phenol, from the beginning of the cooling of the reaction mixture as indicated in Example 1. No urea was added after neutralization with sulfuric acid.

The resulting mixture has a free phenol content of 1.3% and a free formaldehyde content below 0.5%. The proportion of free phenol higher than in other cases is due to the low F / P ratio. In contrast, because urea was not added, the resin does not contain urea-formaldehyde condensate and is therefore more stable. Urea could be added to the adhesive composition containing this resin to set the gelling time of the adhesive.

Further description relates to the use of mineral fibers adhered to by the invention.

The mineral fibers adhered to the composition of the invention could be used in particular for the manufacture of insulation products as well as for the production of substrates for above-ground cultures.

The advantages of using the adhesive compositions of the invention in these two applications will be demonstrated by the following comparative examples relating to the five compositions Ap A ^ B _p B ₂ and C.

The ingredients Aj and A2 are standard ingredients, like the one mentioned earlier. Both comprise a formaldehyde-phenol-based resin only, in a F / P molar ratio of 2.7 to 4.2, and preferably between 3.0 and 3.5; as well as the usual adhesive additives that we have previously identified: urea, ammonium sulfate, silane, ammonia and, optionally, mineral oil. Therefore, there is no urea additive in the resin production cycle, but only in the final adhesive formulation.

The constituents Bj and B ₂ are of the invention. They comprise a resin with the same composition as in Example 1, with an F / P ratio of 2.5, but with a slightly different urea content, counted for 20 parts of the dry adhesive extract, whereas the total resin counts for Bj 100 parts and 35 in the case of B ₂ . They also include analogue accessories like the previous ones, but nothing extra urea in this case.

Composition C is also, according to the invention, similar in all points to composition B _r Only the F / P ratio, which is 2 here, is modified.

Below we indicate the proportions of each of the ingredients in the parts of the dry adhesive extract:

resin (except urea) urea oil sulfate silan ammonia 70 30 0 1 0.1 6 55 45 9.5 3 0.3 6 B! 80 20 0 1 0.1 6 b ₂ 65 35 9.5 3 0.3 0 C 80 20 0 1 0.1 6

Whether for the manufacture of insulating plates or substrates for cultures, the proportion of phenol and formaldehyde emanating from the fiberglass fiber line is compared when glueing A ₂ and B ₂ between the fiber body (centrifuger) and the receiving body (conveyor) . These measures are carried out at the level of the receiving body, which collects the fibers, usually equipped with suction devices to allow for more efficient collection of the fibers. In the gaseous streams generated by these vacuum cleaners, the quantities of phenol and formaldehyde, expressed in kg per tonne of fiberglass, are evaluated:

phenol formaldehyde:

b ₂

0.36

0.17

1,70

0.17

It is self-evident that the proportions of adhesives / ¾ and B _{2 are} identical with respect to the amount of impregnated glass (about 4.5%, ie the usual proportion for insulating products). Therefore, this shows that the use of the adhesive B ₂ of the invention instead of the standard adhesive enables a significant reduction in the proportion of phenol (53%) and in particular formaldehyde (85%) released on the fiber line at the place where these releases are most preferred.

With an adhesive composition comprising the resin of the invention with an F / P ratio of 2.5, the release rate of phenol and formaldehyde on the bonded fiberglass line is thus 0.17 g per tonne of glass.

We have also evaluated the rate of formaldehyde emission on aboveground substrates based on glued glass and stone fibers when exposed to their conditions of use, ie when impregnated with water, which is used to irrigate plants and provide them with substances necessary for their growth.

First, we specify the method used to simulate these conditions: there are 75 x 70 x 40 mm ³ (210 ml) in the final substrate in the sampling, with the weight of the adhesive in relation to the fibers in this case being about 2.5%, which is the usual share for products of above-ground cultures. These samples should then be soaked in a plastic box and in parallelepiped in the presence of 250 ml of demineralized water. (The dimensions of the box are such that the sample is completely submerged in water). It is recalled that the conditions and duration of irrigation were chosen to best suit the conditions for a standard crop cake saturated in its plastic wrap, to which pepper seedlings are placed 3 days after soaking.

After 3 days of contact in a closed chamber, the whole solution (demineralized water + possible formaldehyde) is recovered by compression and filtration. Then titrate the amount of formaldehyde converted into the aqueous solution with chromotropic acid and express in mg formaldehyde per liter of aqueous solution.

The results of the comparative experiments with the three adhesives Α _χ , Β _χ , C are listed in the table below:

: try formaldehyde formaldehyde (glass) : A ₁ 1.36 0.98 : Nr 0.35 0.53 : C - 0.58

In a completely unexpected way, therefore, it is found that the adhesives of the invention Β _χ and C _x emit much less aldehyde in water than the standard adhesive A ₁ , with a reduction of more than 41% for glass fibers and at least 74% for rock fibers.

Formaldehyde dissolved in too much water with irrigation water nowadays is widely believed to have adverse effects on plant growth. It is therefore particularly convenient to suggest adhesives of the invention that are much less prone to release formaldehyde by hydrolysis into an aqueous medium.

As an example, a resin adhesive composition of the invention with an F / P ratio of 2.5 to allow the rate of release of formaldehyde into glass and stone fiber substrates in the amount of 0.35 mg / l or. 0.53 mg / l irrigation water, ie proportions all below 0.60 mg / l.

Further, it should be noted that although all the resins of the invention may be advantageously used in adhesives for insulating products or above-ground cultures, it seems preferable to avoid catalyzing the polymerization of the barium oxide resin, which subsequently risks plant toxicity.

Claims (29)

PATENT APPLICATIONS 1. Liquid resin containing condensates of phenol-formaldehyde and urea formaldehyde with a free formaldehyde content of less than or equal to 3%, the proportion being expressed in the total weight of the liquid and with a water dilution at 20 ° C of at least 1000%, that it contains, among other things, a phenolformaldehyde-amine condensate. A resin according to claim 1, characterized in that the amine is one that is capable of Mannich reaction. The resin according to claim 2, wherein the amine is alkanolamine. Resin according to claim 3, characterized in that the amine is monoethanolamine or diethanolamine. A resin according to any one of claims 1 to 4, characterized in that the free formaldehyde content is below 0.75%, the free phenol content below 0.2% and infinite dilution. Resin according to one of Claims 1 to 4, characterized in that the free phenol content is below 0.2%, the free formaldehyde content is below 0.5% and the infinite dilution with water. 7. A process for the preparation of a resin containing condensates of phenol-formaldehyde and urea-formaldehyde, comprising a reaction of phenol and formaldehyde in a molar ratio above 1 in the presence of a basic catalyst, cooling the reaction mixture and reacting formaldehyde in excess with urea, to add an amine suitable for the Mannich reaction before the urea is added. Process according to claim 7, characterized in that the phenol and formaldehyde react in a molar ratio between 1.8 and 5. Process according to one of Claims 7 or 8, characterized in that phenol and formaldehyde react in the presence of a basic catalyst in an amount corresponding to 6 to 20 molar equivalents of hydroxyl OH 'per 100 moles of starting phenol at a temperature of 60 to 75 ° C , preferably about 70 ° C, until a phenol conversion rate of 93% or greater is obtained. A process according to any one of claims 7 to 9, characterized in that the amine is alkanolamine. The process of claim 10, wherein the alkanolamine is monoethanolamine or diethanolamine. Process according to one of Claims 7 to 11, characterized in that the amine is added in an amount of 5 to 40% by weight, based on the weight of the phenol. Process according to one of Claims 7 to 12, characterized in that the amine is introduced gradually during the cooling of the reaction mixture. Process according to any one of claims 7 to 12, characterized in that the reaction mixture is cooled to a temperature between 45 and 20 ° C and then the amine is gradually added in the cold. Process according to any one of claims 7 to 14, characterized in that the basic catalyst is lime CaO, hydroxide of sodium, potassium, calcium or barium, or triethylamine. Process according to any one of claims 7 to 15, characterized in that urea is added when the reaction mixture has a temperature of about 25 ° C. Process according to claim 16, characterized in that the amount of urea added is 10 to 50% by weight with respect to the total weight of the resin, expressed as the dry extract. Process according to any one of claims 7 to 17, characterized in that ammonia is added in an amount of from 0 to 100% stoichiometry of the formaldehyde-ammonia reaction, prior to the introduction of urea. Process according to one of Claims 7 to 18, characterized in that the reaction mixture is neutralized before the addition of urea with sulfuric, sulfamic, phosphoric or boric acid. A mineral fiber adhesive composition comprising a phenolic resin according to any one of claims 1 to 6, urea and optionally adhesive additives. 21. Adhesive composition according to claim 20, comprising 50 to 90 parts of resin and 10 to 50 parts of urea, expressed in parts of dry matter. A mineral fiber adhesive composition comprising a phenolic resin according to any one of claims 1 to 6 and optionally adhesive additives. 23. Mineral fibers adhered to an adhesive composition according to any one of claims 20 to 22, characterized in that they are used for the manufacture of insulating products. Mineral fibers adhered to an adhesive composition according to any one of claims 20 to 22, characterized in that they are used to make substrates for above-ground cultures. Mineral fibers according to one of claims 23 or 24, characterized in that they have a very reduced rate of release of phenol and formaldehyde into the atmosphere, especially on the fiber lines. Mineral fibers according to claim 24, characterized in that the substrates formed therefrom have a very reduced rate of release of formaldehyde into the aqueous medium. Insulating products obtained from glued mineral fibers according to claim 23 or 25. 28. Above-ground culture substrates obtained from glued mineral fibers according to one of claims 24, 25 or 26. 29. Overhead culture substrates according to claim 28, characterized in that when the adhesive composition contains a resin according to the invention whose molar ratio between formaldehyde and phenol is equal to 2.5, the rate of release of formaldehyde is below 0.60 mg per liter of aqueous solution. in which said substrate is immersed.