IE81159B1

IE81159B1 - Phenolic resin process for preparing the resin and composition for sizing mineral fibres containing this resin

Info

Publication number: IE81159B1
Application number: IE257891A
Authority: IE
Inventors: Serge Tetart; David Segal
Original assignee: Saint Gobain Isover
Priority date: 1990-10-12
Filing date: 1991-07-23
Publication date: 2000-05-03
Also published as: FR2667865A1; HU913230D0; SI9111631A; NO912944D0; DK0480778T3; HUT61787A; MX9101505A; FI914806A; FR2667865B1; YU163191A; NO912944L; AU638859B2; AU8164691A; ES2101732T3; KR920008097A; HU211021B; TR26094A; EP0480778A3; NO300222B1; BR9104285A

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 THE RESIN AND COMPOSITION FOR ςτζτΜπ MINERAL FIBRES CONTAINING THIS RESIN varvouiUN FOR SIZING The invention relates to a phenolic resin intended to be used in a sizing composition for mineral fibres. This resin results from the condensation of phenol, formaldehyde, amine and urea in the presence of a basic catalyst.

The invention further relates to a specific process for preparing this resin and to the composition for sizing mineral fibres containing the said resin.

It also relates to the use of mineral fibres sized in this way, in particular for manufacturing products for insulation as well as for products to 1-5 be used as substrates for soil-free culture.

Mineral-fibre based products may be formed from fibres obtained by various processes. There can be cited, for example, the known technique of drawing by centrifugation in which the molten material is introduced into a centrifuge comprising a large number of small openings, is projected under the effect of centrifugal force towards the peripheral wall of the centrifuge and is discharged therefrom via the openings in the form of filaments. When leaving the centrifuge, these filaments are drawn out and carried along towards a receiving member by a gas stream flowing at high velocity and 1 59 having a high temperature, to form a layer of fibres there. In order to assemble the fibres with respect to one another, there is sprayed onto the fibres as they pass to the receiving member a so5 called sizing composition which contains a thermosetting resin. The layer of fibres treated in this manner is then subjected to a heat treatment in an oven to polycondense the resin and obtain an insulation product having the desired properties, such as dimensional stability, resistance to traction, thickness recovery after compression and a uniform colour.

Sizing compositions which have to be sprayed onto the mineral fibres contain a resin which is generally in the form of an agueous composition and, in addition, urea and additives such as silane, mineral oils, ammonia, ammonium sulphate and water.

What is understood by resin according to the invention is the product resulting from the condensation of the initial reagents in the presence of a catalyst before any stage involving curing in an oven.

The properties sought-after for sizing compositions depend on the properties of the resin. A sizing composition should above all be easily sprayable as well as having good coating and fibre-bonding properties, and at the same time it should not be highly pollutant.

For this purpose, the resin should in particular have good stability over time and high dilutability in water.

The resin must be stable in particular for at least 8 days at 12-18° C. In fact, it should be possible to store the resin for several days before it is used to form the sizing composition. The sizing composition containing the resin and the above-mentioned additives is generally prepared at the moment of use.

Furthermore, the resin should be highly dilutable in water. The concept of dilutability is particularly important since the sizing composition containing the resin is then suitable for spraying. Dilutability is generally defined as follows: the dilutability in water of a resin in the form of an aqueous composition is the volume of deionised water which, at a given temperature, may be added to the volume unit of this composition before causing permanent breakdown to occur.

The dilutability in water of a resin suitable for use in a sprayable sizing composition must preferably be equal to or greater than 1000% at 20°C for at least 8 days.

It is further necessary for the resin to be as free as possible of unconverted starting materials. The risks of atmospheric pollution are essentially due to the presence of volatile monomers: for example these are the starting materials required for obtaining the resin, for example formaldehyde and phenol which are not converted during the reaction or are regenerated when the fibres are sized or subsequently.

Consequently, in order to obtain sizing compositions with which the content of pollutants, in particular free phenol and free formaldehyde, is as low as possible, the resin must have the lowest possible content of residual starting materials, whilst retaining its useful qualities.

The aims, i.e. a stable resin containing little free formaldehyde and free phenol, whilst retaining the desired properties, in particular high dilutability in water which enables it to be sprayed easily onto mineral fibres, are -in opposition to one another since the reduction in the content of free phenol and free formaldehyde is generally achieved by increasing the degree of condensation, which results in a reduction in dilutability.

It is known to prepare resins which can be used for mineral fibre sizing compositions by reacting phenol and formaldehyde in the presence of a basic catalyst. To encourage the reaction between the phenol and the formaldehyde and thus reduce the amount of non-reacted phenol and avoid the risks of pollution, it is known to use formaldehyde/ phenol molar ratios which are greater than 1, and to introduce urea in order to take up the excess formaldehyde.

In this way resins formed from condensates of phenol-formaldehyde and urea-formaldehyde are obtained.

Thus, as is described in European Patent Application EP-A-148 050 it has been possible to obtain a resin in liquid form resulting from the condensation in an alkaline medium of formaldehyde, phenol and urea, having dilutability in water of at least 1000% and a content of free phenol and free formaldehyde, expressed as total liquid weight, of less than or equal to 0.5 % and 3% respectively. This resin is obtained with a formaldehyde/phenol molar ratio of between 3 and 6. The content of free phenol and free formaldehyde is measured in relation to the total liquid weight.

This resin is considered as having properties suitable for it to be used in mineral fibre sizing compositions and as not being highly pollutant.

Although the free phenol content may be considered as sufficiently low and causing little pollution, the content of free formaldehyde in the resin (approximately 3%) is still high and attempts are therefore made to reduce it even further whilst retaining the properties of the resin necessary for its subsequent desired use.

In addition, the use of a high F/P molar ratio, as described in above-mentioned EP-A-148 050, enables the content of free phenol to be reduced considerably but requires urea to be used in order to react with the excess formaldehyde. This results in the formation of a urea-formaldehyde condensation product which is not very stable on heating.

This thermal instability is a disadvantage since the mineral fibres treated with the sizing composition are subjected to a heat treatment in order to obtain an insulating product.

When the resin is used to size mineral fibres during which process the resin is subjected to temperatures above 100° C, under the effect of the heat the urea-formaldehyde condensation product releases formaldehyde which is given off and thus increases atmospheric pollution.

The aim of the invention is thus to obtain a new resin which has satisfactory characteristics for its use in a sprayable sizing composition and which is not highly pollutant, in particular as regards formaldehyde, i.e. a resin which has a low free formaldehyde content and, in addition, is stable on heating in order to avoid the regeneration of formaldehyde when the resin is being used.

A further aim of the invention is a process for preparing the resin, in particular a process enabling a lower formaldehyde/phenol molar ratio to be used so as to reduce the amount of urea required for the reaction with the excess formaldehyde.

A further subject of the invention is a sizing composition containing the said resin and its use for sizing mineral fibres in order to form insulation products or substrates for soil-free culture.

The liquid resin according to the invention, to be used in a sizing composition for mineral fibres, basically comprises condensates of phenol formaldehyde (P-F), urea formaldehyde (D-F) and phenol formaldehyde amine (P-F-A). This resin has a free formaldehyde content (FL), expressed as total liquid weight, which is less than or equal to 3%. It also has a dilutability in water, measured at 20° C, of at least 1000%. The resin is 15 furthermore thermally stable, i.e. the resin contains little or no methylolurea which is relatively unstable.

In order to assess this heat stability, a sizing composition containing the resin is subjected to a test simulating the heat conditions to which a sizing composition is subjected when used to manufacture an insulating product as described above. It is considered that the resin is heat stable and not highly pollutant as regards formaldehyde if the amount of formaldehyde released during this test is less than 4 g of formaldehyde per kilogram of dry extract of a 10% sizing solution. Heat stability may thus be demonstrated by thermogravimetry.

The amine (A) is selected from the group enabling a Mannich-type reaction to be performed; these are for example alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), cyclic amines such as piperidine, piperazine or morpholine.

In accordance with the invention, the reaction between the excess free formaldehyde and urea is preceded by a reaction of the free formaldehyde and free phenol with an amine.

The reaction according to the invention is of the Mannich type which in a general manner converts an aldehyde, an organic compound containing active hydrogen atoms and an amine, into a Mannich base by condensation. In this case, the aldehyde is formaldehyde and the organic compound is phenol.

The amine may be selected from those mentioned above for example. In the invention the amine reacts with phenol or methylolphenols and formaldehyde which gives the resin obtained a far more stable structure.

In order to obtain a resin as defined above, the invention proposes a process which consists in reacting phenol and formaldehyde in a molar ratio of more than 1 in the presence of a basic catalyst, cooling the reaction mixture and reacting the excess formaldehyde with urea. The invention is characterised in that an amine suitable for performing the Mannich reaction is introduced into the reaction medium before the urea is added and during the cooling process.

More particularly, phenol and formaldehyde are made to react in a molar ratio between 1.8 and 5 until a phenol conversion rate which is equal to or greater than 93% is obtained, and the cooling of the reaction mixture is begun.

The phenol conversion rate is the percentage of phenol which participated in the phenolformaldehyde condensation reaction relative to 100% of the initial phenol. The phenolformaldehyde condensation reaction is stopped by cooling the reaction mixture at a stage corresponding to a resin which is still dilutable in water.

In accordance with the invention, the amine (A) is added before the urea, either during the cooling phase of the reaction mixture or when it is cold. The amine is added gradually since the reaction with formaldehyde and phenol is exothermic. The amine may be added at the beginning of the cooling phase of the reaction mixture or when the mixture has been cooled to a temperature between 45° and 20°C.

The reaction according to the invention between phenol, formaldehyde, the methylolphenols and the 10 amine enables the amount of free formaldehyde in the reaction medium to be reduced before the urea is added and, consequently, a resin comprising a smaller quantity of urea-formol condensate to be obtained: this therefore results in the resin having greater heat stability. The reaction of free formaldehyde with the amine then with urea enables the free formaldehyde content of the final resin to be reduced even further and even a free formaldehyde content of the resin of less than 0.75%, and even less than 0.5%, to be attained.

The addition of an amine according to the invention also enables the free phenol content to be reduced even further, in particular for resins prepared on the basis of a high F/P molar ratio.

Indeed, in a known process for preparing a phenolic resin, such as the resin described in patent EP-A-148 050, the condensation reaction between phenol and formaldehyde (with an F/P molar ratio between 3 and 6) occurs until a conversion rate of greater than 98% is obtained; during the subsequent stages of the preparative process the amount of unreacted phenol does not vary.

The addition of an amine according to the invention, after the condensation reaction between phenol and formaldehyde, enables the non-reacted phenol to be fixed, which decreases the amount of free phenol. Free phenol contents of less than 0.2% may therefore be attained.

The use of an amine in accordance with the invention has the further advantage of being able to cause the phenol and formaldehyde to react in an F/P molar ratio of less than 3, whilst obtaining a resin which has the desired properties of being dilutable in water and not pollutant.

When the F/P molar ratio is reduced, the free formaldehyde in the resin decreases but the free phenol increases. The addition of amine, in accordance with the invention, enables resins having percentages of free phenol which could only be obtained using high molar ratios to be obtained on the basis of a low F/P molar ratio.

More particularly, the resin is prepared according to a temperature cycle which is divided schematically into three phases: a heating phase, a constant temperature stage and a cooling phase.

In accordance with this process, phenol and formaldehyde are reacted during a first stage in the presence of a basic catalyst by heating gradually to a temperature between 60° and 75° C and preferably to approximately 70° C. As indicated above, the F/P molar ratio is advantageously between 1.8 and 5.

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

Irrespective of the catalyst selected, the amount used is advantageously from 6 to 20 moles of hydroxyl equivalent OH- per 100 moles of the initial phenol.

During the second phase (constant temperature stage), the temperature of the reaction mixture reached during the heating phase, i.e. 60° to 75° C and preferably 70° C, is maintained until a phenol conversion rate of at least 93% is obtained. The duration of this constant temperature stage is preferably approximately 90 minutes maximum.

The third phase is a cooling phase during which, in accordance with the invention, the amine is introduced into the reaction mixture such that the Mannich reaction is triggered and produces the phenol-formaldehyde-amine condensate.

The amine may be introduced at the very beginning of the cooling of the reaction mixture. The amine is added progressively, for example' at a rate of 0.33 weight percent per minute of the total amount of amine in relation to the mass of the resin since the reaction is exothermic.

The amine may also be added at the end of the cooling phase, for example between 20° C and 45° C.

The amount of time during which the amine is added 20 may vary between 20 and 45 minutes.

The amount of amine, in particular alkanolamine, added varies between 5 and 40 weight percent relative to the weight of phenol.

When the phenol-formaldehyde-amine condensate has been formed, the reaction mixture is cooled if necessary in order that its temperature reaches approximately 20-25° C, and it is neutralised in order to check condensation reactions.

Generally, the reaction mixture is neutralised by adding an acid, such as sulphuric acid, sulphamic acid, phosphoric acid, boric acid, in an amount sufficient for the pH of the mixture to be between approximately 7,0 and 8.5. After neutralisation, urea is added to fix the non-reacted formaldehyde.

In accordance with the invention, urea is added in the cold state, i.e. when the temperature of the reaction mixture has reached approximately 2015 25°C. The amount of urea added varies from 10 to 50 weight percent in relation to the weight of resin expressed as dry extract.

The addition of urea in the cold state when the resin is being prepared is advantageous since the reaction between formaldehyde and urea, when cold, is slow, which enables the reaction to be controlled and condensation which is too advanced and would lead to a reduction in the dilutability of the final resin to be avoided.

In accordance with a further variant of the process according to the invention ammonia may be added to the reaction mixture before or after neutralisation in order to take up some of the free formaldehyde. Hexamethylenetetra-amine is formed.

Ammonia is added in the form of an aqueous solution at a rate of between 0 and 100% of the stoichiometric amount required by the 10 formaldehyde-ammonia reaction, the amount of formaldehyde being calculated on the basis of the concentrations at the moment when the ammonia is introduced.

The invention also relates to a sizing composition for coating mineral fibres, in particular glass or rock fibres, as well as the sized fibres obtained which can be used to manufacture insulating products and substrates for soil-free culture.

A sizing composition according to the invention comprises the resin according to the invention, sizing additives and urea.

As indicated above, the resin according to the invention may have the property of having a very low free formaldehyde content, of less than 2% and advantageously less than 0.75%. In this case, it is no longer necessary for urea to be present in the sizing composition or its presence is necessary merely to adjust the gel time of the size in order to avoid any problems of pregelling.

In the sizing compositions according to the invention containing urea, the proportions of the components are from 50 to 90 parts of resin and from 10 to 50 parts of urea, expressed as parts of dry matter.

In general terms, a typical sizing composition comprises the following additives per 100 parts of dry matter of resin and urea: - 0 to 5 parts of ammonium sulphate, generally 1 to 3 parts; - 0 to 2 parts of silane, in particular an aminosilane; - 0 to 20 parts of oil, generally 6 to 15 parts; - 0 to 20 parts of 20% ammonia, generally 3 to 12 parts.

The role of these ingredients is known and will only be recalled briefly here: ammonium sulphate is used as a polycondensation catalyst (in the 25 oven in the hot state) after the sizing composition has been sprayed onto the fibres; silane is an agent which bridges the fibres and the resin and also acts as an anti-ageing agent? the oils are anti-dust and hydrophobic agents. In the cold state, ammonia acts as a polycondensation retarding agent and also fixes the free formaldehyde; the urea modifies the composition so as to affect the pregelling of the sizing process and reduce pollution.

A silane which may advantageously be used is aminosilane marketed by the Union Carbide company under the name A1100. Mineral oil marketed by the Mobil Oil company under the name Mulrex 88 may be used as the oil.

The following non-limiting examples illustrate the invention.

The following examples may be classified according to two variants of the process for obtaining the resin according to the invention. In one case the 2θ resins are produced by introducing the amine in the hot state, in the other case the amine is added cold.

In both cases the first condensation stage between the phenol and formaldehyde occurs as follows: Formaldehyde and phenol are introduced into a reactor; then, whilst being stirred mechanically, the mixture is heated or cooled until a temperature slightly higher than the melting temperature of phenol is reached. Mechanical stirring is continued for the entire duration of the reaction cycle. The catalyst is introduced steadily then, immediately after it has all been added, the temperature of the mixture is increased to a value enabling optimum condensation and a dilutable resin to be obtained. This temperature is maintained until the phenol conversion rate is greater than 93%.

Subsequently, in one case, the mixture is gradually cooled and the amine added whilst being stirred; in the other case, the mixture is cooled progressively to a temperature between 45° C and 20° C and the amine is then added.

Examples 1 and 2 relate to the manufacture of resins with the addition of amine during the cooling phase.

EXAMPLE 1 a) Preparation of the resin In a 2-litre reactor equipped with a stirring system, a condenser, a thermometer and a reagent inlet 564.66 g of phenol (6 moles) are added to 1217.43 g of formaldehyde (15 moles) in a 37% aqueous solution, providing an F/P molar ratio of 2.5.

The mixture is brought to 45° C whilst being stirred, then 56.47 g of sodium hydroxide in a 50% aqueous solution (i.e. 11 moles OH' per 100 moles of initial phenol) are added steadily over a period of 30 minutes whilst the temperature is maintained at 45°C.

The temperature is then increased steadily from 45°C to 70° C over a period of 30 minutes and it is maintained at 70° C for 80 minutes until the phenol conversion rate is 93%.

Then the steady cooling of the mixture is started; during the first 30 minutes diethanolamine (141.16 g i.e. 25 weight percent relative to the weight of phenol) is gradually added. When the amine has been added, the temperature is approximately 60° C. During the 15 minutes following the end of the amine introduction phase the temperature of the reaction medium is maintained at 60° C since the reaction is exothermic. Then the cooling of the mixture is continued. When the temperature of the reaction mixture reaches approximately 25° C, after approximately 30 minutes, a 20% solution of sulphuric acid is added for 60 minutes so as to reach a pH of 8.0 - 8.1. Granules of urea are then added progressively (426.5 g i.e. 35 weight percent relative to the total weight of the resin expressed as dry extract) over 60 minutes.

The resin is in the form of a clear aqueous composition having an infinite degree of dilutability in water at 20° C after more than 8 days. The free phenol content is 0.8% and the free formaldehyde content is less than 0.5%.

It may be noted that, if this resin is compared with a resin obtained according to the process described in EF-A-148 050, for example, the resin in example 4, these two resins have slightly different free phenol contents (0.5% and 0.8%); this is due to the fact that in one case (that of the present invention), the F/P ratio is 2.5 and in the other case (that of the patent) the F/P ratio is 3.5. The free formaldehyde content of the resin of example 4 of the cited patent is 1.12% and the dilutability 2000% after more than 8 days. b) Sizing composition The resin obtained previously is used to prepare a sizing composition without the addition of urea. The sizing additives are ammonium sulphate and ammonia. parts ammonium sulphate and 1 part ammonia are used per 100 parts by weight of resin. c) Formation of the finished product; At the outlet of a known device for manufacturing mineral fibres by the centrifugal drawing process there is sprayed onto the fibres, between their discharge from the centrifuge device and their reception on a collector member, the abovedescribed sizing composition at a rate of 2 to 20 weight percent of the sizing composition relative to the weight of the finished insulating product. The water present in the composition is partially evaporated owing to the high temperature. When the fibres have been received on the collector member and a mat has formed, they are subjected to a heat treatment in an oven at a temperature between 180 and 200° C for approximately 2 minutes, which causes the resin to polycondense.

When it is being used to form the finished product, the sizing composition comprising the resin according to the invention, constituted byphenol -formaldehyde, urea-formaldehyde and phenolformaldehyde-amine condensates, is subjected to temperatures greater than 100° C. As the ureaformaldehyde condensate is not very stable in heat, it tends to decompose and regenerate formaldehyde.

A method simulating the conditions to which the sizing composition is subjected is used to evaluate the degree of pollution attributable to the free formaldehyde which may be released when the mineral fibres are being treated with the sizing composition.

Method of evaluating formaldehyde vapour: 100 g of the sizing composition with 10% dry extract are placed in an oven at 180° C for 2 hours and it is swept with air at a rate of 1 litre per minute. The vapour released is introduced into three bubble-through devices containing water, and the formaldehyde is determined by colour spectrometry (chromo trophic acid method) and the phenol is determined by gas phase chromatography using an apparatus fitted with a flame ionisation sensor. Reference solutions are used to determine the phenol.

The amount of formaldehyde released is 2.5 g, that of free phenol is 8.8 g, per kilogram of dry extract of a 10% sizing solution.

By way of indication, for a standard size (to be defined below), the respective amounts of formaldehyde and phenol released under the same conditions increases to 6 and 11 g.

Example 2 In this example 1003.15 of formaldehyde (12.4 moles) in a 37% solution are reacted with 377.6 g (4 moles) of phenol. Lime (CaO) is used in an amount of 20.8 g (0.316 mole) as catalyst. During the cooling phase, monoethanolamine (75.52 g i.e. weight percent relative to phenol) is introduced.

The amount of urea added after neutralisation with sulphuric acid to reach a pH of 8.2 is 35 weight percent relative to the total weight of the resin expressed as dry extract.

The resin obtained has infinite dilutability in water, a free phenol content of less than 0.2% and a free formaldehyde content of less than 0.5%.

The following example relates to a resin prepared by adding amine in the cold state.

Example 3 a) Preparation of the resin In a reactor having the same equipment 470.55 g of phenol (5 moles) are added to 1420.34 g of formaldehyde in a 37% aqueous solution, corresponding to an F/P molar ratio of 3.5. As in example 1, the mixture is heated to approximately 45° C then 47.06 g of a 50% aqueous solution of soda (i.e. 0.588 mole and 11.76 moles of OH per 100 moles of initial phenol) are added over a period of 30 minutes while the temperature is maintained at 45° C. The mixture is heated to 70° over 30 minutes, then it is maintained at this temperature for approximately 90 minutes until a phenol conversion rate of 97.5% is obtained. The mixture is then gradually cooled to 25° C over 50 minutes. 38.76 g of monoethanolamine, corresponding to 8.2 weight percent relative to the weight of phenol, are then added; the monoethanolamine is added gradually over 20 minutes. The reaction mixture is neutralised with a 20% sulphuric acid solution until the pH reaches 7.4. Ammonia as a 27% solution is then added at 20° C over approximately 30 minutes in an amount corresponding to 20% of the stoichiometric amount required by the formaldehyde-ammonia reaction.

Subsequently 471.2 g of urea in granules, corresponding to 35 weight percent relative to the total weight of resin expressed as dry extract, are added over a period of 60 minutes.

The resin is in the form of a clear aqueous composition having infinite dilutability in water at 20°C after more than 8 days. The free phenol content is less than 0.2% and the free formaldehyde content is less than 0.75%. b) Sizing composition As in example 1, a sizing composition containing only the resin prepared previously and 6 parts of ammonium sulphate and 3 parts of ammonia as sizing additives is prepared.

The thermal stability of the resin is evaluated as in example 1.

The amount of formaldehyde regenerated during the test is 3 g and that of phenol 6 g per kilogram of dry extract of the 10% sizing solution.

Example 4 A resin is prepared as in example 1 from formaldehyde and phenol in order to attain an F/P molar ratio of 2.3. The reaction between the formaldehyde and the phenol occurs at 70° C over 90 minutes. Diethanolamine is added at a rate of 22 weight percent relative to the weight of phenol at the very beginning of the cooling phase of the reaction mixture, as indicated in example 1. No urea is added when the mixture has been neutralised with sulphuric acid.

The resin obtained has a free phenol content of 1.3% and a free formaldehyde content of less than 0.5%. The free phenol content which is higher than in the other examples is due o the low F/P ratio. In contrast, as no urea is added, the resin does not contain any urea-formaldehyde condensate and is therefore more stable. Urea may be added to the sizing composition containing this resin to adjust the gelling time of the size.

The remainder of the description relates to applications of mineral fibres sized according to the invention.

Mineral fibres sized with a sizing composition according to the invention may be used in particular to form insulating products but they may be used equally well to form soil-free culture substrates .

The advantages connected with the use of sizing compositions according to the invention in both these areas of application will be demonstrated using the comparative examples given below and relating to five compositions A,, A£, Blz B2, and C.

Compositions Ax and A2 are standard compositions like that mentioned above. They both comprise a resin based solely on formaldehyde and phenol in an F/P molar ratio between 2.7 and 4.2 and preferably between 3.0 and 3.5, as well as the conventional sizing additives mentioned above: urea, ammonium sulphate, silane, ammonia and optionally a mineral oil. Urea is thus not added during the resin production cycle but only during the final formulation of the size.

Compositions Bi and B2 are in accordance with the invention. They comprise a resin having a composition identical to example 1 above with an F/P ratio of 2.5 but with a slightly different proportion of urea, corresponding to 20 parts of dry extract of size whereas the finished resin amounts to 100 parts in the case of B1 and 35 parts in the case of B2. They also comprise additives similar to the preceding additives, however with no additional urea in this case.

Composition C is also in accordance with the invention and similar to composition Bx in all respects. Only the F/P ratio, which is 2 in this case, is modified.

The table below indicates the proportions, as parts of dry extract of the sizes, for each of the constituents of the sizes: Resin Urea Oil Sulphate Silane Ammonia (without urea)A1 70 30 0 1 0.1 6 55 45 9.5 3 0.3 6 Bl 80 20 0 1 0.1 6 b2 65 35 9.5 3 0.3 0 c 80 20 0 1 0.1 6 Irrespective of whether the production of insulating panels or of culture substrates is concerned, the amounts of phenol and formaldehyde released in a glass fibre centrifuging/fibredrawing line when sizes Ag and B2 are sprayed between the fibre-drawing member (the centrifuge) and the receiving member (the conveyor belt) were compared. These measurements are taken at the receiving member collecting the fibres, usually provided with suction means to enable the fibres to be collected more efficiently. It is in the gaseous currents created by these suction devices that the amounts of phenol and formaldehyde, expressed in kilograms per tonne of glass fibre, are measured: i 1 I i phenol formaldehyde j ί 1 ! 0.36 1.70 ! ί b2 0.17 0.17 ! It will be appreciated that the proportions of sizes Ag and B2 in relation to the amount of glass impregnated are identical (approximately 4.5%, i.e. a conventional amount for insulating products) . This thus shows that using a B2 size according to the invention instead of a standard Aj size permits a substantial reduction in the amount of phenol (by 53%) and in particular in the amount of formaldehyde (by 85%) released on the fibre-drawing line at the place most likely to encourage these products to be released.

With a sizing composition containing a resin according to the invention with an F/P ratio of 2.5, quantities of phenol and formaldehyde released in the sized glass fibre line of 0.17 g per tonne of glass are obtained.

The content of formaldehyde released by the soilfree substrates based on sized glass and rock fibres has also been assessed when these are in their conditions of use, i.e. when they are impregnated with water which irrigates the plants and provides them with the substances necessary for their growth.

The method used to simulate these conditions will first be described: it consists in taking 75 x 70 x 40 mm3 (210 ml) samples from the final substrate, the mass proportion of the size in relation to the fibres in this case being approximately 2.5%, the usual amount for products for soil-free culture. These samples are then left to soak in a parallelepipedal plastics box in the presence of 250 ml of demineralised water. (The dimensions of the box are such that the sample is completelysaturated with water).

It should be noted that the conditions and duration of soaking have been selected such that they correspond as well as possible to the conditions of a standard culture cake, saturated in its plastics casing on which the pepper seedling is placed after three days of soaking.

After three days of contact in a closed box the solution (demineralised water and optionally formaldehyde) is totally recovered by pressure and filtration. Then the amount of formaldehyde which has passed into solution, in the water is determined with chromotrophic acid and expressed in mg of formaldehyde per litre of aqueous solution.

The comparative test results with the three sizes At, Bx and C are shown in the table below: 1 1 formaldehyde formaldehyde * tests (rock) (glass) ί A, 1.36 0.98 J : Bi 0.35 0.53 J ! C — 0.58 j In a quite unexpected manner, it is thus observed that sizes Bx and Cx according to the invention release far less formaldehyde into the water than does the standard size Αχ, the reduction being more than 41% in the case of glass fibres and at least 74% in the case of rock fibres.

It would now appear to be established that formaldehyde dissolved in too large an amount in the irrigation water may have unfortunate consequences for the growth of plants. It is thus particularly advantageous to propose sizes according to the invention which are far less likely than other sizes to release formaldehyde by hydrolysis in a aqueous medium.

By way of indication it is thus shown that a sizing composition containing a resin according to the invention with an F/P ratio of 2.5 enables formaldehyde release rates to be obtained for glass fibre and rock fibre culture substrates of 0.35 mg/1 and 0.53 mg/1 of immersion water, respectively, i.e. rates which in both cases are less than 0.60 mg/1.

It is further specified that although all the resins according to the invention may be used advantageously in sizes for insulating products or products for soil-free culture, it would appear preferable to avoid catalysing the polymerisation of the resin with barium oxide which might well subsequently be toxic to plants.

Claims

1.8 and 5.

1. Liquid resin containing phenolformaldehyde and urea-formaldehyde condensates having a free formaldehyde content which is less than or equal to 3%, the content being expressed as a total liquid weight, and having dilutability in water at 20 °C of at least 1000%, characterised in that it also contains a phenol-formaldehydeamine condensate that is to improve the stability, especially the thermal stability, of the resin, the amine being capable of reacting in accordance with the Mannich reaction. 2.5, the amount of formaldehyde released is less than 0.60 mg per litre of aqueous solution for the immersion of the said substrate. 29. Liquid resin according to Claim 1, substantially as herein described in the Examples. 30. A process for preparing a resin according to Claim 6,

2. Resin according to Claim 1, characterised in that the amine is an alkanolamine.

3. Resin according to Claim 2, characterised in that the amine is monoethanolamine or diethanolamine.

4. Resin according to any one of Claims 1 to 3, characterised in that it has a free formaldehyde content of less than 0.75%, a free phenol content of less than 0.2% and infinite dilutability. 5. Substantially as described in the Examples. 31. Sizing composition for mineral fibres according to Claim 19 or 21, or mineral fibres according to Claim 22 or 23 or insulating products according to Claim 26, or 5 10 to 50 parts of urea expressed as parts of dry material. 21. Sizing composition for mineral fibres comprising a phenolic resin according to any one of Claims 1 to 5 and optionally sizing additives. IO 22. Mineral fibres sized with the sizing composition according to any one of Claims 19 to 21, characterised in that they are used to manufacture insulating products. 23. Mineral fibres sized with the sizing 15 composition according to any one of Claims 19 to 21, characterised in that they are used to manufacture soil-free culture substrates. 24. Mineral fibres according to either Claim 22 or Claim 23, characterised in that the amount 20 of phenol and formaldehyde released into the atmosphere is very low, in particular in a fibredrawing line. 25. Mineral fibres according to Claim 23, characterised in that the amount of formaldehyde released in an aqueous medium from the substrates formed from the fibres is very low. 5 26. Insulating products obtained from mineral fibres sized according to Claim 22 or 24. 27. Substrates for soil-free culture obtained from mineral fibres sized according to any one of Claims 23, 24 and 25. 10 28. Substrates for soil-free culture according to Claim 27, characterised in that when the sizing composition contains a resin according to the invention, of which the molar ratio of formaldehyde with respect to that of phenol is 5 15. process according to any one of Claims 6 to 14, characterised in that the addition of the urea is started when the reaction mixture is at a temperature of approximately 25°C. 16. Process according to Claim 15, 10 characterised in that the amount of urea added is from 10 to 50 weight percent relative to the total weight of the resin expressed as dry extract. 17. Process according to any one of Claims 5 to 16, characterised in that ammonia is added in 15 an amount of from 0 to 100% of the stoichiometric amount required by the formaldehyde-ammonia reaction before the urea is introduced. 18. Process according to any one of Claims 6 to 17, characterised in that before urea is added the reaction mixture is neutralised with sulphuric, sulphamic, phosphoric or boric acid. 19. Sizing composition for mineral fibres comprising a phenolic resin according to any one of Claims 1 to 5, urea and optionally sizing additives. 20. Sizing composition according to Claim 19, comprising from 50 to 90 parts of resin and from 5 alkanolamine. 10. Process according to Claim 9, characterised in that the alkanolamine is monoethanolamine or diethanolamine. 11. Process according to any one of claims 6 10 to 10, characterised in that the amine is added in an amount of from 5 to 40 weight percent relative to the weight of the phenol. 12. Process according to any one of Claims 6 to 11, characterised in that the amine is 15 gradually added whilst the reaction mixture is being cooled. 13. Process according to any one of Claims 6 to 11, characterised in that the reaction mixture is cooled to a temperature between 45°C and 20°C 20 then the amine is gradually added in the cold state. 14. Process according to any one of Claims 6 to 13, characterised in that the basic catalyst is lime CaO, sodium, potassium, calcium or barium hydroxide or triethylamine.

5. Resin according to any one of Claims 1 to 4, characterised in that it has a free phenol content of less than 0.2%, a free formaldehyde content of less than 0.5% and infinite dilutability in water.

6. ' Process for preparing a resin containing phenol-formaldehyde and urea-formaldehyde condensates, consisting in reacting formaldehyde and phenol in a molar ratio F/P greater than 1 in the presence of a basic catalyst, cooling the reaction mixture and reacting the excess formaldehyde with urea, characterised in that an amine suitable for the Mannich reaction is added to the reaction medium before the urea is added.

7. Process according to Claim 5, characterised in that the phenol and the formaldehyde are reacted in a molar ratio between

8. Process according to either Claim 6 or Claim 7, characterised in that the phenol and the formaldehyde are reacted in the presence of a basic catalyst in an amount corresponding to 6 to 20 moles of hydroxide equivalents OH per 100 moles of initial phenol at a temperature between 60°C and 75 °C and preferably at approximately 70 °C until a phenol conversion rate which is equal to or greater than 93% is obtained.

9. Process according to any one of Claims 6 to 8, characterised in that the amine is an

10. Substrates according to Claim 27 or 28, substantially as herein described.