FI62547B - REFERENCE TO A RESOLUTION OF MELAMINE FORMALDEHYDHARTS MED LAONG HAOLLBARHETSTID OCH LAOG HALT FRI FORMALDEHYD FOERFARANDE FOER DESS FRAMSTAELLNING OCH DESS ANVAENDNING FOER IMPREGNERUK AV FIBERP - Google Patents

Description

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France-France (FR) 7513569 (71) Saint-Gobain Industries, 62, Bd Victor-Hugo, 92209 Neuilly sur Seine, France-France (FR) (72) Jean Paul Meunier, Clermont de L'Oise, Jacky Charles Joseph Joachim , Rantigny, Bernard Louis Kafka, Rantigny, France-France (FR) (7U) Berggren Oy Ah (5U) melamine-formaldehyde resins with lord h & llbarhets-tid och läg hait fri formaldehyde, farfarande fess dess framställning och dess användning för impregnering av fiberprodukter

The present invention relates to a long-lasting and low-free formaldehyde-containing aqueous solution of etherified melamine-formaldehyde resin, to a process for its preparation and to its use for impregnating fibrous products.

Methods for preparing such resins are already known, in particular from German Offenlegungsschrift DE-2 005 166. According to this known method, an alkaline condensation of melamine with formaldehyde is carried out in the presence of a polyol. Formaldehyde is used in the form of solid paraformaldehyde. The use of paraform aldehyde has a significant drawback: in this form the price of anhydrous formaldehyde is 2-3 times higher than in the form of an aqueous solution.

According to this known method, etherified tetramethylene melamines are obtained in practically anhydrous or alcoholic solutions.

2 62547

In order to better meet the requirements of certain uses of etherified melamine-formaldehyde resins, efforts have been made to prepare long-lasting and low-free aqueous solutions of these resins.

Accordingly, the invention relates to a process for preparing a solution of etherified melamine-formaldehyde resins by condensing formaldehyde and melamine in an alkaline solution and then etherifying, which process is characterized in that the melamine is initially reacted with formaldehyde for 10 minutes by adding melamine. , in solid form, by mixing with the resulting stirred solution of a solution containing 30-50%, preferably about 36% formaldehyde, in an amount corresponding to a molar ratio of formaldehyde to melamine of 5-11, preferably 6.5-10; an amount of one or more polyols corresponding to a molar ratio of polyol to melamine of 3 to 5, preferably 3.5 to 4.0; triethanolamine in an amount corresponding to a molar ratio of triethanolamine to melamine of 0.2 to 0.6, preferably 0.3 to 0, A, 60 to 70 ° C, preferably 63 to 68 ° C, the pH after the addition of melamine being 8 , 5 and 9.5, preferably between 8.8 and 9.2, and that the reaction is stopped by rapid cooling to a temperature between 20 and 40 ° C, preferably between 33 and 37 ° C, with a cloud point occurring at 40 and 65 ° C, preferably 45 to 55 ^ 0, that in the second step the etherification is carried out by lowering the pH of the reaction mixture obtained from the first step by gradually adding an acid in pure, or concentrated aqueous solution, to a value between 1.5 and 3.0, maintaining the final completion temperature, and at the end of the etherification reaction. the solution is neutralized by adding triethanolamine base until the pH of the solution is neutral, that in the third stage the solution obtained at the end of the second stage is matured by maintaining it at a temperature of between 2 and 5 hours, which is between 50 and 90 ° C, preferably between 70 and 85 ° C, and that in the fourth step the concentration of free formaldehyde in the solution obtained at the end of the third step is reduced so that the final free formaldehyde content does not exceed 6% by weight.

The resins obtained according to the invention are characterized in that they have a molar ratio of formaldehyde to melamine, from which

F

referred to as the "ratio, is particularly high, that they are highly dilutable with water, that they have a shelf life of at least two months at room temperature and that they contain less than 6% free formaldehyde.

By water dilutability is meant the maximum amount of water, expressed in units of volume per 100 units of volume of an aqueous resin solution, which can be added thereto when maintained at 25 ° C with stirring, before turbidity occurs.

The phrase "shelf life at ambient temperature" means the time during which aqueous resin solutions, when stored at a temperature between 15 ° C and 25 ° C, retain their viscosity at 800 cP measured at 25 ° C and a water dilutability of at least 1200.

The values of the above two properties with aqueous solutions of the olive resins which are the subject of the invention remain in storage for at least two months, which corresponds to the possibility of using them in industry at least during this delay.

Industrial use includes, in particular, the use of a binder for glass fiber gauze in combination with other products which together form an adhesive for said fibers.

The present aqueous resin solutions impart excellent tensile strength and flexibility properties to glass fiber gauze.

There are some differences from the above-mentioned known method, which clearly show the advantages achieved by the method according to the invention.

Ratio The present invention DE 2 005 166 5-11 and preferably 2-6 6.5-10

Diol molecules per paddle 3.0-5.0 and preferably 0.4-1.2 and preferably per minimum molecule 3.5-4.0 min 0.7-1.1

Triethanolamine mole- 0.2-0.6 and preferably no mention is made of patent-melamine- mole- 0.3-0.4 in claims, per 0.037 (Example 5)

Alkaline condensation 60-70 ° C and preferably 80-140 ° C and preferred temperature 63-68 ° C min 85-100 ° C

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It can also be seen from the above that the resins according to the invention: - have a higher number of methylol groups per molecule of melamine, and that - they are more strongly etherified with polyol, more than 6 and especially 8-20 molecules per molecule of melamine) a lower monoalcohol, for example methanol. Thus, it appears that in this patent the actual etherification reagent is in fact this lower monoalcohol and not the polyol.

In the process of the present invention, the polyol is instead the main etherifying agent, and the other hydroxylated compounds present, albeit to a much lesser extent, are triethanolamine and methanol, which may be present, change little in aqueous formaldehyde. In particular, no amount of alcohol other than the starting polyol or polyols is added, and - contain a considerable amount of triethanolamine bound to the methylol melamines during the etherification step. The presence of these triethanolamine residues in the final resin molecule increases its water solubility. On the other hand, triethanolamine, which, according to German Publication No. 2,005,166, is used in very small quantities, apparently has no purpose other than to achieve the pH required in the alkaline condensation reaction.

As will be seen below, the addition of triethanolamine after etherification further improves the dilutability of the solution.

According to the invention, about 36% of an aqueous solution, which is commercially available at a lower cost than solid paraformaldehyde, is used as the starting formaldehyde.

The operating conditions of the four steps of the method are explained in more detail below.

5 62547 Phase I The melamine used must be of technical grade, but must contain at least 99% by weight of melamine and 99% by weight of particles with a diameter of less than 160 .mu.m.

Namely, particles that are too large interfere with the dissolution of melamine in the reaction mixture.

The formaldehyde used must be in the form of an aqueous solution having a concentration of 30 to 50% by weight; preferably a 36 # aqueous solution is used because it is widely available. However, the solutions should not contain more than 10% by weight of methanol, and preferably the melamine content should be less than 1% in order to avoid the presence of methoxyl groups in the etherified methoxyl. In order to maximize the dilutability with water, the etherification is in fact preferably carried out primarily with a polyol or triethanolamine.

The F / M ratio should be between 5-11 and preferably between 6.5-10.

If the ratio is less than 5, it degrades the properties, especially the tensile strength of glass fiber buttocks. In addition, the resins then have too poor water dilutability. If the ratio is more than 10, the dry concentrations of the final aqueous solutions remain low and thus industrially uninteresting. The successive values of P / M of 5, 6.5, 10 and 11 correspond essentially to the dry concentrations of 52, 50, 44 and 41 if a 36% aqueous solution is used as the source of formaldehyde.

The alkaline condensation reaction is carried out at a pH between 8.5 and 9 * 5 and preferably between 8.8 and 9 * 2. This pH is obtained by adding triethanolamine to the reaction mixture.

The amount of triethanolamine is between 0.2 and 0.6, preferably between 0.3 and 0.4 molecules per melamine molecule. This quantity is denoted by the following ratio TEA / M. These amounts are much higher than the amount strictly necessary to adjust the reaction pH to the above values. They are used, as has already been said, in order to obtain good water solubility for the resins according to the invention.

The reaction is carried out as follows:

First, the required amounts of an aqueous solution of formaldehyde, polyol and 6 62547 triethanolamine are mixed and this mixture is heated with stirring to a reaction temperature of between 60 and 70 ° C, and preferably between 63 and 68 ° C. At temperatures below 60 ° C, the dissolution of melamine in the reaction mixture is too slow.

The melamine is then added gradually over 10 to 15 minutes, keeping the temperature the same and continuing to stir for a period of time ranging from 30 to 90 minutes.

The reaction is then stopped by cooling to a temperature between 20 ° C and 0 ° C, preferably between 30 ° C and 37 ° C.

The reaction is stopped by rapid cooling at the exact time determined by the cloud point of the reaction mixture, which is measured and monitored during the reaction.

This cloud point is characteristic of the degree of alkaline condensation reached. It is measured by taking successive samples of the reaction mixture at regular intervals. These samples are cooled with stirring and the temperature from which turbidity develops is observed. This temperature, which is quite low at the beginning of the reaction, rises as the reaction proceeds.

Thus, the alkaline condensation reaction is stopped rapidly by cooling when the cloud point occurs between 40-65 ° C and preferably between * t5-55 ° C, which occurs after the above-mentioned reaction time of 30-90 minutes.

If the reaction is stopped at a cloud point below i40 ° C, the viscosity of the cooled reaction mixture is high, which is very detrimental to maintaining its homogeneity by stirring. Conversely, a cloud point temperature higher than the reaction temperature cannot be bypassed without the reaction mixture becoming opaque precisely at the reaction temperature. And even in the case where the reaction temperature is 70 ° C, it is difficult to measure a higher cloud point temperature than 65 ° C because the difference is too small a reaction with respect to the temperature.

It should also be noted that at temperatures above 70 ° C the cloud point cannot be measured and the high reaction rate cannot be monitored at 7 62547 at these temperatures.

Step II: Etherification In this step, the methylol melamines obtained in Step I are etherified with the polyol or polyols already added to the reaction mixture. These polyols can be: ethylene glycols, diethylene glycol, triethylene glycol, glycerol, sucrose, d-glucose. However, due to its price and availability, the primary diol is ethylene glycol.

Some polyol blends are also of interest. Thus, different proportions of mixtures of ethylene glycol and sucrose can be used to control the viscosity of the final resin that sucrose tends to increase.

The total amount of polyol or polyols used should be between 3.0 and 5.0 and preferably between 3.5 and 0.1 molecules per molecule of melamine. This ratio is denoted as P / M in the following. Insufficient amount of polyol reduces too much dilutability of the resin with water.

On the other hand, too much polyol is useless because it does not improve dilutability.

The acid used to lower the pH of Stage I to the value of Stage II should preferably be a pure or concentrated aqueous solution so as not to unnecessarily lower the final dry matter content of the aqueous resin solution.

One of the following acids may be used: sulfuric acid, hydrochloric acid, orthophosphoric acid, nitric acid, formic acid or monochloroacetic acid.

Immediately after the alkaline condensation is cooled, as already mentioned, and keeping the temperature reached constant, the reaction mixture is wafed to a pH which must correspond to the selected temperature. Female s; '. under temperature and pH conditions, etherification reactions are then performed: o.

These conditions must be within the following limits: from 20 ° C at pH 1,5, to 45 ° C at pH 3,0, and preferably from 33 ° C at pH 8 0 62547 1,8, 37 ° C when the pH is 2.2.

The above conditions are absolute. In fact, if the etherification is carried out at too high a pH and / or temperature, the viscosity of the resin is too high and, in addition, this viscosity rises very rapidly during storage, which ultimately completely prevents the use of the resin even immediately after preparation. Conversely, if the pH and / or temperature of the etherification is too low, the viscosity of the resin is low, its water dilutability is quite good, but too low, uninteresting, tensile strength values are obtained for fiberglass gauze.

After the addition of the acid, it is observed that after a varying time, depending on the cloud point, the hitherto opaque reaction mixture becomes clear. The etherification reaction is continued for some time at the same temperature before it is terminated by neutralization.

The periods of time that occur before and after the moment of clarification of the reaction mixture are hereinafter referred to as the opaque phase of etherification and the clear phase, respectively.

The following conditions must be observed during the etherification step: the acid must be poured very regularly and the pouring must take 25-35 minutes and preferably 28-32 minutes.

In fact, it has been found that when the total duration of etherification is constant, the shortening of the acid pouring time significantly increases the final viscosity of the aqueous resin solution.

On the other hand, the acid must be poured slowly in order to keep the temperature constant despite the heat released when the acid is poured into the reaction mixture. The total duration of the etherification, calculated from the start of the acid pouring until neutralization, should be between 50 and 180 minutes when the cloud point is between 40 and 65 ° C, respectively, and preferably between 105 and 135 minutes, with a cloud point between 45 and 55 ° C, respectively. These duration values are, of course, valid for the pH and temperature values defined above.

In fact, the above values of cloud point, pH and temperature state that the minimum duration of the opaque phase is 50 minutes from the start of the acid pouring.

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On the other hand, if at the above-mentioned values of cloud point, pH and temperature, the total duration of etherification exceeds 180 minutes, it is found that the viscosity of the resins becomes too high and their water dilutability is well below 1200, namely immediately after preparation.

With respect to the latter resins, it is further found that when stored at ordinary temperature, their viscosity increases rapidly and their dilutability with water decreases rapidly.

The viscosity of the resins according to the invention immediately after their preparation, measured at 25 ° C, is between about 30 and about 200 centipoise, i.e. quite low.

On the other hand, let us recall that the minimum shelf life of resins, two months, means that after this time their viscosity must not exceed 800 centipoise and that their water dilutability must not be less than 1200. After normal aging, resins tend to increase their viscosity and reduce their viscosity. water dilutability, as is known.

As in the first step, triethanolamine alone is used as the base for the neutralization, or at least 1/3 of the molecule per melamine molecule, the remainder of the neutralizing reagent being 50% NaOH solution.

In fact, it has been found that if neutralization is carried out with sodium hydroxide solution alone, resins are obtained which can be diluted only slightly with water, and in the worst case, precipitation occurs during neutralization. The purpose of this new addition of triethanolamine is, too, to promote the water solubility of the resin.

This achieves a pH between 7 * 0-7.5, which essentially corresponds to neutrality.

Step III This maturing step is important because it provides an improvement in the two properties of glass fiber gauze bonded with a binder made from aqueous solutions of the resins of the invention.

10 62547

In fact, it has been found that prolonging the duration of this maturation step results in the formation in the same direction both in the flexibility index of the glass fiber gauze and in their tensile strength.

Definition and measurement of flexibility index

60 rectangular 25 x 5 cm samples are cut from the glass fiber gauze. Of these 30 samples, the tensile strength is measured and the average of the measurements is calculated.

The other 30 samples are bent one at a time under the following conditions: a metal plate 25 cm long, 5 cm wide and 2 mm thick. It is equipped with two hinges in the middle so that it can be folded into two 12.5 cm long slab halves.

Each gauze sample is placed wide on a lice slab before it is folded, and two other slabs measuring 12.5 cm x 5 cm are placed on top of the gauze. With the specimen thus locked wide between the hinged plate and the two half-plates, the whole combination is folded 180 ° around the hinge. The distance between the halves of the sample after folding, when the sample remains between the tiles at all times, as stated, is 10 mm.

The tensile strength of these 30 bent specimens is measured and the results are averaged. The reduction in tensile strength after bending is then calculated as a%.

The bending index is a number between 0-10, taken from the following correlation table:

Decrease in tensile strength Flexibility index after bending% 0 - M. 10 il - 10 9 10-20 8 20 - 30 7 30-40 6 40 - 50 5 50-60 4 60-70 3 70-80 2 62547

Decrease in tensile strength Flexibility index after bending% 80-90 1 90 - 100 0

During the maturing step, a small decrease in the percentage of free formaldehyde in the aqueous resin solution and a gradual increase in viscosity are observed.

Therefore, in order not to increase the latter too much to the detriment of the possible shelf life of the resin solution before use, the following conditions must be observed during the ripening step, - at the end of stage II after neutralization, heated to 50-90 ° C, preferably 70-85 ° C its pH, - this temperature is maintained for 2-5 hours.

Under these conditions, the aqueous resin solution remains such that it can be diluted with at least 12 times the volume of water.

If the cooking time exceeds five hours at the above-mentioned temperature values, the resin will have too high a viscosity. Conversely, if ripening is interrupted, still under the same temperature conditions before it has lasted for two hours, a considerable improvement in the flexibility of the glass fiber gauze is no longer achieved.

Phase IV

After the maturation step, the higher the initial F / M ratio, the higher the percentage of free formaldehyde in the aqueous resin solutions. These concentrations are in the range of 6-12% or more.

Such concentrations of free formaldehyde are detrimental to the use of resins because the vapors released from them irritate the eyes and respiratory tract of machine operators.

The main purpose of this stage IV is therefore to reduce the free formaldehyde content of the resin solutions to less than 6%. Such concentrations 62547 12 no longer release irritating gases into the air more than workers can tolerate.

However, there are two other advantages to this step: firstly, it improves the tensile strength of the glass fiber gauze; secondly, it reduces the rate of increase in the viscosity of aqueous resin solutions during storage and thus contributes to a possible increase in storage time.

This fourth step comprises adding 0.6-1.6 and preferably 0.8-1.2 molecules per molecule of melamine to the aqueous resin solution, at the final temperature of step III, which amount depends on the initial F / M ratio and thus the free concentration of the reaction mixture. formaldehyde concentration at the end of stage III. This molar ratio of urea to melamine is hereinafter referred to as the U / M ratio.

Urea is used in solid form, as pearl urea, because its endo-thermal dissolution in the water of the reaction mixture lowers the temperature and also so that the dry content of the final product is not reduced as an aqueous solution of urea would.

The product is then left to cool naturally for 12-24 hours before being stored or used.

In the following examples, the percentages given are by weight; viscosity values are measured at 25 ° C with a Brookfield viscometer, dilutability is measured at 25 ° C and is expressed in units of volume of water per 100 units of resin volume.

Example 1 Step I A 1 liter tractor equipped with a reflux condenser, stirrer and thermometer is charged with 562 g of an aqueous solution of 36% formaldehyde and 0.5% methanol, as well as 248 g of ethylene glycol and 49.5 g of triethanolamine. The reaction mixture is then raised to 65 ° C with stirring. When this temperature is reached, 126 g of melamine are added in 12 minutes.

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Condensation at 65 ° C is continued until the cloud point is 50 ° C> then the temperature is rapidly reduced to 35 ° C.

Phase II

56 g of concentrated sulfuric acid are added regularly over 30 minutes until the pH is 2, after which the etherification is continued at 35 ° C for 1 hour and 30 minutes.

Phase III

At the end of the etherification, the pH of the mixture is adjusted to 7.2 with 49.5 g of triethanolamine and 50 g of 50% NaOH solution.

The temperature is then raised to 70 ° C, which is maintained for 5 hours.

Step IV After these 5 hours, 48 g of urea are added as the resin cools to about 60 ° C.

The resin obtained has the following properties: - ratio F / M = 6.75 - ratio P / M = 4 - ratio TEA / M = 0.33 - number of triethanolamine molecules added after etherification per molecule of melamine: 0.33 - ratio U / M = 0 , 8 - dry matter content: 50,1% - viscosity: 4 centipoise - free formaldehyde: 1,9% - dilutability: unlimited O2000) - pH: 7,2 - after two months of storage: dilutability: unlimited (> 2000) - viscosity: l60 cp

Preparation of glue Starch paste: an aqueous dispersion is prepared from potato starch modified by ethylene oxide treatment and having a concentration of 8% calculated as anhydrous starch. Steam is bubbled into this dispersion until its temperature is 98 ° C. The bubbling of steam is then continued for 20 minutes, and allowed to cool. When the temperature has dropped to 62547 14 25 - 30 ° C, the adhesive is ready for use.

110 kg of this adhesive are mixed with an amount of the above-mentioned aqueous solution of melamine-formaldehyde resin corresponding to a dry matter content of 1.2 kg.

On the other hand, 1.378 kg of an emulsion containing 58%, calculated on the dry matter, of homopolymeric polyvinyl acetate plasticized with 50% of the amount of polymer, based on dibutyl phthalate, are weighed and diluted with the same amount of water.

This diluted emulsion is added to the previous mixture. The resulting mixture is homogenized by stirring for 10 minutes and forms a concentrated adhesive.

At the time of use, this concentrated adhesive is diluted with such an amount of water that the final adhesive used has a dry matter content of 2.2%.

Manufacture of glass fiber gauze A mattress consisting of non-glued glass staple fibers, hereinafter referred to as gauze, is used. This mattress is obtained by disintegrating, in the usual manner, on a sheet metal conveyor belt, glass-staple fibers obtained by steam-stretching strands of molten glass flowing from holes in the lower part of a platinum traction plate. The average diameter of these glass fibers is about 16 micrometers. The basis weight of the f-iar blank used is 80 to 5 g / m 2.

The gauze blank is embedded in an adhesive made according to the above in the form of a continuous strip placed between two metal sheet conveyor belts.

Furthermore, the excess adhesive retained by the gauze blank is sucked off by means of a suction box placed continuously below the lower belt. The vacuum box is adjusted in such a way that the gauze after drying contains 20% by weight of dry adhesive, based on the total weight of the glass and the dry adhesive.

The gauze blank is then passed continuously, glued and aspirated to dryness, for 2 minutes in an air recirculation furnace having a temperature of 14525 C.

The following properties are then measured from the finished mat: - tensile strength: 5.5 kg / cm - flexural index: 7

Example 2

According to Example 1, a melamine-formaldehyde resin is prepared using the following amounts: - 36% formaldehyde 666 g - ethylene glycol 248 g - triethanolamine 49.5 g - melamine 126 g - concentrated sulfuric acid 56 g - 50% aqueous NaOH 50 g - urea 48 g - triethanolamine 49.5 g

The characteristics of the resin obtained are as follows: - P / M ratio: 8.0 - P / M ratio: 4.0 - TEA / M ratio: 0.33 - number of triethanolamine molecules added after etherification per molecule of melamine: 0.33 - U / M ratio : 0.8 - dry matter content: 47.8%

- viscosity: 70 cP

- free formaldehyde: 4.0% - dilutability: unlimited (> 2000) - pH: 7.2

After two months of storage: dilutability: unlimited (> 2000)

viscosity: 130 cP

An adhesive is prepared from the above resin, which is impregnated into a gauze blank, which is then dried in an oven as described in Example 1.

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The following properties of the finished gauze are measured: - tensile strength: 5.6 kg / cm - flexibility index: 7

Example 3

The melamine-formaldehyde resin is prepared according to Example 1 using the following amounts: - 36% formaldehyde 750 g - ethylene glycol 248 g - triethanolamine 49.5 g - melamine 126 g - concentrated sulfuric acid 56 g - triethanolamine 49.50 g - 50% aqueous NaOH 50 g - urea 48 g The properties of this resin are as follows: - ratio F / M: 9.0 - ratio P / M: 4 - ratio TEA / M: 0.33 - number of triethanolamines added after etherification per molecule of melamine: 0.33 - ratio U / M: 0.8 - dry matter content: 45.6%

- viscosity: 52 cP

- free formaldehyde: 5.4% - dilutability: unlimited (> 2000) - pH: 7.2

After two months of storage: dilutability: unlimited (> 2000)

viscosity: 100 cP

An adhesive is prepared from the above resin and impregnated into a gauze blank which is treated as described in Example 1.

The following properties of the obtained gauze are measured: 17 62547 - tensile strength: 5.9 kg / cm - flexibility index: 8

Example 4

The melamine-formaldehyde resin is prepared as in Example 1 using the following amounts: - 36% formaldehyde 666.5 g - ethylene glycol 198.5 g - triethanolamine 39.5 g - melamine 101 g - concentrated sulfuric acid 45 g - triethanolamine 39.5 g - 50% Aqueous NaOH 40 g - urea 38.5 g The characteristics of this resin are as follows: - ratio F / M: 10.0 - ratio P / M: 4.0 - ratio TEA / M: 0.33 - molecular weight of triethanolamine added after etherification -min molecule: 0.33 - U / M ratio: 0.8 - dry matter content: 43.2%

- viscosity 44 cP

- free formaldehyde: 5.7% - dilutability: unlimited (> 2000) - pH: 7.2

After two months of storage: dilutability: unlimited (> 2000)

viscosity: 92 cP

An adhesive is prepared from the above resin and then a gauze is prepared according to Example 1. The following properties are measured for this gauze: - tensile strength: 6,2 kg / cm - flexibility index: 7 62547 18

Comparing the tensile strengths of the gauzes obtained in Examples 1, 2, 3 and 4, it is found that this property improves as the F / M ratio increases.

Example No. Ratio F / M Tensile strength of gauze kg / cm 1 6.75 5.5 2 8.0 5.6 3 9.0 5.9 4 10.0 6.2

Example 5

In a reactor equipped with a powerful stirrer and a heating apparatus, alkaline condensations of formaldehyde and melamine are carried out at 65 ° C using the following substances: - ethylene glycol: 248 g (4 moles) - triethanolamine: * 19 * 5 g (0.33 moles) ) - melamine: 126 g (1 mole) - formaldehyde: the amounts indicated below.

A 36% solution of formaldehyde containing 0.5% methanol is placed in the reactor, then glycol and triethanolamine are added and heated to the reaction temperature. Melamine is then added over 12 minutes. With regard to the increasing amounts of aqueous formaldehyde, the following is noted: F / M ratio: 2.5: even after 3 hours at 65 ° C the reaction mixture is still cloudy; continuing the heating results in the resin curing to a mass.

- F / M ratio: 2.9: after 90 minutes at 65 ° C the reaction mixture is clear. The steps corresponding to steps 2, 3 and 4 are carried out under the conditions mentioned in Example 1. The dilutability of the final resin is zero.

- ratio F / M: 4.0: the reaction mixture of the alkaline condensation becomes clear after 50 minutes at 65 ° C. The preparation is terminated according to Example 1. The obtained resin has a water dilutability of only 1000.

An adhesive is prepared from this latter resin and then a fiberglass gauze is prepared according to Example 1. The tensile strength of this gauze 19 62547 is only * J, 2 kg / cm.

This example shows the disadvantages of the ratio F / M <5 * 3, which are as follows: the water dilutability of the resins is lacking and the tensile strength of the glass fiber resin decreases.

Example 6

Three resins are prepared under all conditions of Example 1 except for the cloud point of 12 ° C in all preparations. In addition, the temperature of the alkaline condensation varies from one preparation to another. The following results are obtained: Preparation I: condensation temperature 60 ° C. The condensation time is * 15 minutes. The viscosity of the resin is 1 * 1 cP and the dilutability is more than 2000.

Preparation II: condensation temperature 65 ° C. The condensation time is 35 minutes. The viscosity of the harness is 12 cP and the dilutability is over 2000.

Preparation III: condensation temperature 70 ° C. The condensation time is 23 minutes. The resin has a viscosity of 11 cP and a dilutability of more than 2000.

However, after only 15 days of storage, the viscosity of these resins increases to the extent that they have a gel consistency.

This example demonstrates the need for a sufficiently high cloud point to achieve an interesting shelf life. It should also be noted, by comparison with Example 1, the decrease in impact strength due to the decrease in the cloud point temperature.

Example 7

Prepare the melamine-formaldehyde resin according to Example * 1 using the following substances: - 36% formaldehyde 666.5 g - ethylene glycol 198.5 g - triethanolamine 39> 5 g - melamine 101 g 20 62547 - concentrated sulfuric acid 45 g - triethanolamine 39> 5 g - 50% aqueous NaOH 40 g - urea 57.5 g However, the procedure used differs from that of Example 4 in that the alkaline condensation is continued until the cloud point is 62 ° C instead of 50 ° C, the etherification time is 3 hours 10 minutes instead of 2 hours and that the duration of the ripening phase is 3 hours at 85 ° C instead of 5 hours at 70 ° C.

The properties of this resin are the same as those of the resin of Example 4, except for the following: - U / M ratio: 1.2 - dry matter content: 43.3%

- viscosity: 80 cP

free formaldehyde: 4,9% - dilutability: 1900

After two months of storage: dilutability: 1400

viscosity: 210 cP

An adhesive is prepared from the resin described above and used to make the gauze according to Example 1. The following properties are measured for this gauze: - tensile strength: 6.7 kg / cm - flexibility index: 6 This example shows the possibility of preparing a resin according to the invention by stopping alkaline condensation at a cloud point of 62 ° C. In addition, it indicates that the total duration of etherification must be set according to the value of the cloud point.

Example 8

Prepare the resin according to all the instructions of Example 4, except that the ratio TEA / M = 0.1 is used in alkaline condensation instead of 0.33.

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The resulting resin has a practically zero dilutability (<50) and a viscosity of 275 cP.

This example shows well, compared to Example 4, how detrimental it is to use too low a TEA / M ratio in alkaline condensation, i. the important role of triethanolamine in giving the resin good water solubility and high water dilutability.

Example 9

The resin is otherwise prepared according to Example 4, except that sodium hydroxide is used as the catalyst in the alkaline condensation instead of triethanolamine. The amounts of substances used are as follows: - 36% formaldehyde 666.5 g (8 moles) - ethylene glycol 198.5 g (3.2 moles) - 50% aqueous NaOH solution 1 ml - melamine 101 g (0.8 moles) - concentrated sulfuric acid 10 ml - triethanolamine 39.5 g (0.264 mol) - 50% aqueous NaOH solution 7 ml

The water dilutability of the resin obtained after the etherification step and neutralization is almost zero (<100). If heating by heating is performed under the conditions of Example 4, the resin turns into a gel.

This example, like the previous Example 8, demonstrates the important role of triethanolamine added to the alkaline condensation step, which is to give the resin good water solubility and good water dilutability, which could not be achieved here with sodium hydroxide.

Example 10 This example illustrates the use of certain polyols other than ethylene glycol in the synthesis of the resins of the present invention.

The preparations are carried out under all the conditions of Example 1 except for the type and amounts of polyols and some of the specialties of the polyol, which are shown in the following table.

22 62547

Polyol Types and Manufacturing Results and Findings Quantities in Moles Specialties

Glycerol: 4 moles 3 hours maturation Dilutability:> 2000

At 75 ° C (stage III) viscosity: 90 cP

Stable for 2 months when stored

Diethylene glycol: Dilutability:> 2000

4 moles viscosity: 94 cP

stable when stored for 2 months d-glucose: 0.4 mol Melting point 4γ ° ο Dilutability:> 2000

ethylene glycol: 3.0 achieved JO min viscosity: 112 cP

after 65 ° C stable for 2 months (phase I)

Triethylene glycol: cloud point 47 ° C Dilutability:> 2000

4 moles achieved 120 min viscosity: 98 cP

after storage at 65 ° C for 2 months (phase I)

Example 11

The preparation of 3 melamine-formaldehyde resins is carried out according to the following amounts and the general procedure of the previous examples: - 36% formaldehyde 583.3 g (7 moles) - triethanolamine 49.5 g (0.33 moles) - melamine 126 g (1 mole) - concentrated sulfuric acid 56 g - triethanolamine 49.5 g (0.33 mol) - 50% aqueous NaOH 50.0 g - urea 48.0 g (0.8 mol)

Alkaline condensations are performed at 65 ° C and stopped at a cloud point of 52 ° C. The etherifications are performed at pH 2.0 and 30 ° C.

The three preparations differ in the polyol blend 23 62547 used:

Manufactures ABC

Polyol blend sucrose (sucrose) 342 g 171 g 86 g ethylene glycol 0 124 g 186 g

Resin A was etherified for only 40 minutes because its viscosity was already quite high, resins B and C were etherified for a total of 90 minutes.

After neutralization, the three preparations were heated (maturation) for 5 hours at 70 ° C. However, 95 g of water had to be added to resin A during heating due to its thickening.

The properties of the resins finally obtained are as follows:

ABC

ratio F / M 7.0 7.0 7.0 molecular ratio sucrose 1.0 0.5 0.25 methylamine ethylene glycol 2.0 3.0 melamine ratio TEA / M 0.33 0.33 0.33 triethanol added after etherification -amine molecular weight per molecule of melamine 0.33 0.33 0.33 ratio U / M 0.8 0.8 0.8 dry matter content% 57.3 (X) 55.6 5.0.0 viscosity cP 2100 1100 125 dilutability l800 > 2000> 2000 (X) taking into account the amount of water added during ripening This example shows the possibility of obtaining resins with quite different viscosities and adjustable at will by changing the ratio of sucrose to ethylene glycol. In determining the relative amounts of the two polyols in resins A, B and C, it has been taken into account that sucrose containing 8 alcoholic hydroxyl groups per molecule should be used four times less in a molar amount of 62547 24 than diol. It is finally obvious that even small amounts of sucrose can produce resins of interest in general practice.

Example 12

Three resin preparations are performed using the procedure and amounts of material shown in Example 1, except for the amounts of ethylene glycol.

In the first preparation, P / M = only 2.0 is used. During the etherification step, it is found that the resin hardens to a mass which cannot be made soluble by the addition of water.

The second preparation uses a ratio of P / M = 2.5 · During etherification, there is no curing to a mass, but the dilutability of the finished resin with water is only 1000.

In the third preparation, the ratio P / M = 3.0 is used. There is no difficulty in the preparation of a resin with ready-to-water dilutability at infinity (^ 2000).

This example shows that it is necessary to use a P / M ratio of at least = 3> 0 in order for the resins according to the invention to have good water dilutability.

Example 13

Two resin preparations are carried out under all the conditions of Example 1 except for the pH and temperature of the etherification step.

In the first preparation, the etherification is performed at pH 4 and 40 ° C. The viscosity and dilutability of the obtained resin are normal twenty days after its preparation, however, the viscosity of the resin has increased so much that it turns into a kind of gel at room temperature.

In another preparation, the etherification is performed at pH 1.5 and 20 ° C. After preparation, the resin has a water dilutability of more than 2000 and a viscosity of 15 cP. After two months of storage, its water dilutability is still over 2000, its viscosity is 40 cP.

62547 25 From this second resin, an adhesive is prepared and a fiberglass gauze is prepared according to the instructions of Example 1. Measuring the tensile strength of this gauze gives only 4.0 kg / cm.

Compared to the results of Example 1, this example demonstrates the disadvantages that occur if the etherification step deviates from the range defined in the text of the present patent with respect to pH and temperature values.

Example 1¾

Two resins are prepared according to all other instructions of Example 1 except for the duration of the etherification step.

In the first step, the total duration of the etherification step, including the acid pour time, is only 60 minutes to reach a cloud point of 50 ° C instead of 90 minutes to reach the same cloud point. This resin has a final viscosity of only 23 cP and a water dilutability of more than 2000.

From this, an adhesive and then a fiberglass gauze are prepared according to the instructions of Example 1.

Measurement of the tensile strength of this gauze results in only ^ .9 kg / cm.

In the second preparation, the etherification is continued for a total time of 180 minutes, at which point the cloud point is still 50 ° C. The final resin obtained has a viscosity of 285 cP and a water dilutability of 1500. After two months of storage, the resin is measured - dilutability: 600

- viscosity: 1050 cP

Compared to the results of Example 4, this example shows the disadvantages which occur if the etherification reaction does not respect the limits given for its total duration for a given cloud point.

Example 15

The resin is prepared according to the procedure of Example 4, except that 60 g of an aqueous solution of 35 → 5% hydrochloric acid are used to sensitize 45 g of concentrated sulfuric acid.

The properties of this resin, with the exception of the molar ratios of the various reagents according to Example 4, are as follows: - dry matter content 43.3%

- viscosity 35 cP

- 5.5% free formaldehyde - unlimited dilutability (> 2000)

- viscosity 30 cP

Dilution after two months storage: unlimited (> 2000)

viscosity: 55 cP

An adhesive and then gauze are prepared from this resin according to the instructions of Example 1. The following values are obtained by measuring the gauze: - tensile strength: 6.0 kg / cm - flexibility index: 7

Analogous results are obtained if, according to the same procedure and in the same stoichiometric ratios, orthophosphoric acid, nitric acid, formic acid or monochloroacetic acid are used instead of hydrochloric acid.

This example demonstrates that these various acids or sulfuric acid can be used indifferently in the process of the present invention.

Example 16

The resin is prepared according to all the instructions of Example 4, except that the neutralization after etherification is carried out to pH 7.2 with 50 .mu.l of aqueous sodium hydroxide alone instead of 0.33 mol of triethyleneamine and then 40 g of aqueous sodium hydroxide solution. Upon cooking at 70 ° C (stage III), it is found that the resin hardens to a mass after 2 hours. This resin is not made soluble by the addition of water.

This example shows that it is necessary to use at least part of the triethyleneamine to neutralize the resin after the etherification step. It also shows, compared to Examples 8 and 9, that triethanolamine plays an essential role in the water solubility of the resin not only in stage I (as a catalyst for alkaline condensation) but also in stage II (etherification) in neutralizing the resin.

Example 17 This example demonstrates the improvements in resins achieved by maturation (Step III).

Four resins are prepared in all respects according to Example 1 except that the etherification temperature in all preparations is 30 ° C instead of 35 ° C.

In addition, the maturation of these resins (stage III) is performed using extending durations from one preparation to another.

An adhesive and then a fiberglass gauze are prepared from each resin according to the procedure of Example 1.

The results are shown in the following table:

Resin by Resin by Resin, Resin, maturation time maturation time by maturation with zero maturity is 1 hour ignition time ignition time is 3 hours tia

Strength of fiberglass gauze in kg / cm 4'2 4> 6 4'8

Flexibility index of glass fiber gauze 5 68

The viscosity of the aqueous resin solution was 41 53 115 2 ^ 5

cP

This example further shows that the viscosity increases very rapidly after about 4 hours of maturation. As a result, this supply must be made for a limited period of time in order for the resins to remain usable in industrial practice.

Example 18 This example illustrates the improvements obtained by adding urea to the resins after the maturation step.

62547 28

The resin is prepared according to all the instructions of Example 4 except that no urea is added at the end of the preparation.

From the resin thus obtained, an adhesive and then a fiberglass gauze are prepared according to the procedure of Example 1.

Compared to the resin of Example 4, the following results are obtained:

Resin of Example 4 The same resin without urea addition

Free formaldehyde% 5.7 11.0

Tensile strength of fiberglass gauze kg / cm 6.2 5.7

Viscosity after preparation cP 44 55

Viscosity 2 months after preparation, cP 92 185

The resins obtained according to the invention are advantageous in the bonding of thin glass fiber resins, in particular less than 4 mm thick, to which they give good flexibility and tensile properties.

Claims (12)

62547 29 A process for preparing a solution of etherified melamine-formaldehyde resins by condensing formaldehyde and melamine in an alkaline solution and then etherifying, characterized in that in the first step the melamine is reacted with formaldehyde by adding melamine with stirring over a period of 10 to 15 minutes, to the resulting stirred solution of a solution containing 30-50%, preferably about 36% formaldehyde, in an amount corresponding to a molar ratio of formaldehyde to melamine of 5-11, preferably 6.5-10; an amount of one or more polyols corresponding to a molar ratio of polyol to melamine of 3-5, preferably 3.5-4.0; triethanolamine in an amount corresponding to a molar ratio of triethanolamine to melamine of 0.2 to 0.6, preferably 0.3 to 0.4, 60 to 70 ° C, preferably 63 to 68 ° C, the pH after the addition of melamine being 8, 5 and 9.5, preferably between 8.8 and 9.2, and that the reaction is stopped by rapid cooling to a temperature between 20 and 40 ° C, preferably between 33 and 37 ° C, with a cloud point occurring between 40 and 65 ° C, preferably 45 and Between 55 ° C; that in the second step the etherification is carried out by lowering the pH of the reaction mixture from the first step by gradually adding an acid in pure, or concentrated aqueous solution to between 1.5 and 3.0, maintaining the end temperature of the first step, and neutralizing the solution at the end of the etherification reaction by adding triethanolamine base, The pH is neutral; that in the third stage the solution obtained at the end of the second stage is matured by maintaining it for 2 to 5 hours at a temperature between 50 and 90 ° C, preferably between 70 and 85 ° C, and that in the fourth stage the concentration of free formaldehyde in the solution obtained at the end of the third stage is reduced so that the final free formaldehyde content does not exceed 6% by weight. Process according to Claim 1, characterized in that the polyols used are ethylene glycol, diethylene glycol, triethylene glycol, glycerol, sucrose or d-glucose. 30 62547 Process according to Claim 1, characterized in that ethylene glycol is used as the polyol. Process according to one of Claims 1 to 3, characterized in that a mixture of ethylene glycol and sucrose is used. Process according to one of Claims 1 to 4, characterized in that sulfuric acid or hydrochloric acid is used for the acidification in the second step. Process according to one of Claims 1 to 5, characterized in that the acid is added over a period of between 25 and 35 minutes, preferably between 28 and 32 minutes, in such a way that the temperature is kept substantially constant. Process according to one of Claims 1 to 6, characterized in that the etherification is carried out at a temperature and a pH of between 20 ° C at pH 1.5 and 40 ° C at pH 3, preferably between 33 ° C, at pH 1.8 and 37 ° C at pH 2.2. Process according to Claim 7, characterized in that the duration of the etherification reaction, calculated from the addition of acid to the onset of neutralization, is between 50 and 180 minutes when the cloud point is between 40 and 65 ° C, respectively, and preferably between 105 and 135 minutes when the cloud point is 45 and 55 ° C. Process according to one of Claims 1 to 8, characterized in that, at the end of the etherification reaction, it is partially neutralized with triethanolamine using 1/3 of mole per mole of melamine and the neutralization is terminated with a 50% by weight NaOH solution. Process according to one of Claims 1 to 9, characterized in that, in the fourth step, the reduction in the formaldehyde content is achieved by adding urea in solid form in an amount of between 0.6 and 1.6, preferably between 0.8 and 1.2, moles of starting melamine. depending on the initial amount of formaldehyde. 62547 31 Aqueous solutions of etherified melamine-formaldehyde resin and urea obtained by a process according to any one of claims 1 to 10 and useful for impregnating fibrous products, in particular glass fiber products, characterized in that when their dry content is between 41 and 32% by weight, their formaldehyde / molamine to molar ratio is between 3 and 11, their polyol / melamine molar ratio is between 3 and 3, their urea / melamine molar ratio is between 0.6 and 1.6 and their free formaldehyde content is less than 6%. Aqueous solutions of melamine-formaldehyde resin according to Claim 11, characterized in that they have rested for at least two months at room temperature and after this rest have a viscosity of not more than 800 centipoise and a water dilutability of at least 1200 when measured at 25 ° C: in.