DK148483B - PROCEDURE FOR THE PREPARATION OF AN Aqueous SOLUTION OF ETHERIFIED MELAMINE FORMALHEAD RESIN - Google Patents

Description

148483

The present invention relates to a process for preparing an aqueous solution of etherified melamine-formaldehyde resins by condensation in alkaline solution of formaldehyde and melamine, followed by an etherification.

Such methods are already known, in particular from German Proposition Writing (DAS) No. 2,005,166. According to this prior process, an alkaline condensation of melamine with formaldehyde is performed in the presence of a polyol. The formaldehyde is used in the form of solid paraformaldehyde. The use of paraformaldehyde presents a considerable disadvantage, since kg of anhydrous formaldehyde in this form is 2 to 3 times higher than in the form of an aqueous solution.

By this prior process etherified tetramethylol melamines which are practically anhydrous or in alcoholic solution are obtained.

In order to better satisfy the requirements of certain applications of etherified melamine-formaldehyde resins, attempts have been made to prepare aqueous solutions of such resins with a long shelf life and low content of free formaldehyde.

Such solutions have now been obtained by the process according to the invention, characterized in that in a first step, the melamine is reacted with formaldehyde by gradual addition with stirring, over 10-15 minutes, of solid melamine to an aqueous solution. which is maintained at a temperature between 60 and 70 ° C, preferably between 63 and 68 ° C, and obtained by mixing: 1) an aqueous solution containing 30-50 wt% and preferably 36 wt% formaldehyde in an amount corresponding to a molar ratio of formaldehyde / melamine of between 5 and 11, preferably between 6.5 and 10, 2) one or more polyols in an amount corresponding to a molar ratio of polyol / melamine of between 3 and 5, preferably between 3.5 and 4 , 0, and 3) triethanolamine in an amount corresponding to a triethanolamine / melamine molar ratio of between 0.2 and 0.6, preferably between 0.3 and 0.4, where the pH value after the melamine addition is between 8.5 and 9.5 and preferably between 8.8 and 9.2, after which the reaction is quenched rapid cooling to a temperature of between 20 and 40 ° C, preferably between 33 and 37 ° C, when there is a cloud point between 40 and 65 ° C, preferably between 45 and 55 ° C, in a second step, etherification takes place during 50-180 minutes, calculated from the beginning of introduction of an acid for neutralization, by decreasing the pH of the reaction mixture from the first step by gradual addition over 25-35 minutes of an acid in pure form or in concentrated aqueous solution, until a pH of between 1.5 and 3.0 is obtained while maintaining the temperature maintained at the end of the first step and at the end of the etherification reaction, the solution obtained is neutralized by the addition of a base which in whole or in part (at least 1/3 mol. mole melamine) consists of triethanolamine, in a third step, matures the solution obtained at the end of the breathed step by holding it for a period of between 2 and 5 hours at a temperature of between 50 and 90 ° C, preferably between 70 and 85 ° C, and in a fourth step, the solution obtained at the end of the third step adds solid urea in an amount between 0.6 and 0.6 moles per mole. moles of melamine used in the first step so as to obtain a final content of free formaldehyde not exceeding 6% by weight.

The resins obtained by the process according to the invention are characterized by a particularly high molar ratio of formaldehyde / melarain, hereinafter referred to as "ratio F / M", a good dilution with water, a shelf life at room temperature of at least 2 months and a content of free formaldehyde less than 6% by weight.

By "dilution with water" is meant the maximum amount of water, expressed in terms of volume and attributed to 100 volumes of the aqueous resin solution which can be added to the latter while being kept under stirring and at a temperature of 25 ° C before cloudiness occurs .

By "shelf life at room temperature" is meant that the aqueous resin solutions, stored after preparation at a temperature of between ca. 15 ° C and approx. 25 ° C, maintains a viscosity measured at 25 ° C below 800 centipoise and a dilution with water of at least 1200.

The limits for the respective values of the two properties given above are adhered to by the aqueous resin solutions in question for a storage period of at least 2 months, which means that it is possible to use them industrially during at least this time.

This use is particularly useful as a binder for fiberglass cloth with other products, so that it all forms a binder for the aforementioned fibers.

The present aqueous resin solutions impart excellent properties to the fiberglass fabric in terms of strength and flexibility.

Compared to the aforementioned prior process, certain differences are set forth below which clearly show the advantages of the process according to the invention.

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Relationship F / M Present Invention IDE Patent Specification __ 2,005,166 "5 to 11 and preferably 2 to 6 show 6.5 to 10 tolerance ratio 3.0 to 5.0 and preferably 0.4 to 1.2 and Iiol / melamine preferably 3.5 to 4.0, preferably ____ 0.7 to 1, - tolerable ratio 0.2 to 0.6 and unspecified triethanolamine / preferably 0.3 to 0.4 in the claims, melamine ____ 0.037 ( Example 3)

Temperature at 60 to -70 ° C and ~ to 80 to 140 ° (3 and alkaline condensers preferably 63 to 68 ° C, preferably 85

to 100 ° C

From the above it appears that the resins in question: - exhibit a greater number of methylol groups per molecule melamine, - is much more etherified with a polyol, for DE-Specification No. 2,005,166 contains indications that, under the alkaline condensation, only a small amount of polyol is used and, on the contrary, to add a substantial amount to the etherification step (more than 6 and in particular 8-20 moles per mole of melamine) of a lower monovalent alcohol, e.g. methanol. Thus, it is quite clear that, by the method of this disclosure, this lower monovalent alcohol is in fact the real etherifying agent and not the polyol.

In the process of the present invention, on the other hand, the polyol is the main etherifying agent, the other hydroxyl compounds present but in very small quantities being triethanolamine and methanol which may be present, but in small amounts, in the aqueous formaldehyde solution. In particular, no other amount of alcohol other than the polyols or initially used is added.

Contains a significant amount of triethanolamine which is attached to the methylol melamines during the etherification step. The presence of these triethanolamine groups in the final resin molecule increases the solubility in water. In contrast, the very low amount of triethanolamine used according to DAS 2.005.166 obviously only serves to obtain the necessary pH value for the alkaline condensation reaction.

The addition of triethanolamine after the etherification, as will be seen below, further increases the dilution of the solution.

In the process of the invention, soot formaldehyde starting material is used, preferably an aqueous solution of 36% by weight, which is commercially available at a more favorable price than the solid paraformaldehyde.

The working conditions of the four steps of the process are described in more detail below.

First step.

The melamine used can be of technical quality, yet it has a melamine content of at least 99 weight and 99 weight of the particles have a diameter of less than 160µ.

In fact, too large particles interfere with the dissolution of the melamine in the reaction medium.

The formaldehyde used must be in aqueous solution at a concentration of 30-50 wt. Preferably, as mentioned, an aqueous solution of 36 wt. Is used, as it is generally available. These solutions should contain no more than 10 weight methanol at most and the content thereof should preferably be less than 1 weight to avoid the presence of methoxy groups in the etherified resin. In fact, in order to increase the dilution with water to the maximum, it is preferred that the etherification is particularly carried out with the polyol and with the triethanolamine.

The ratio F / M should be between 5 and 11 and preferably between 6.5 and 10. Values below 5 will cause a deterioration of the properties, especially of the tensile strength, of the fiberglass cloths. In addition, the resins exhibit a too low dilution with water. Values above 10 for the final aqueous solutions will give low solids content of little industrial interest. The consecutive values 5, 6.5, 10 and 11 for the F / M ratio practically correspond to solids content of 52, 50, 44 and 41%, respectively, if an aqueous solution of 36 wt% is used as a formaldehyde source.

The alkaline condensation reaction is carried out at a pH of between 8.5 and 9.5 and preferably between 8.8 and 9.2. This pH is obtained by adding triethanolamine to the reaction medium.

The amount of triethanolamine should be between 0.2 and 0.6, preferably between 0.3 and 0.4 mol per day. mol of melamine. This ratio is hereinafter referred to as the TEA / M ratio. These amounts are far too large in relation to the amount which allows accurate adjustment of the pH of the reaction medium to the values given. The purpose of this is, as already stated, to impart a good solubility in water to the resins in question.

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The reaction is carried out as follows:

First, the required amounts of aqueous formaldehyde solution, polyol and triethanolamine are mixed and the mixture is heated with stirring to the reaction temperature of between 60 and 70 ° C, preferably between 63 and 68 ° C. At temperatures below 60 ° C, the dissolution of the melamine in the reaction medium takes place too slowly.

The melamine is then added gradually over 10-15 minutes, maintaining the temperature and sustained stirring for a time which usually ranges from 30 to 90 minutes.

The reaction is then quenched by cooling to a temperature of between 20 and 40 ° C and preferably between 33 and 37 ° C.

The reaction is quenched by a rapid cooling at an exact time, which is determined by the reaction mixture's cloud point, which is measured and monitored during the course of the reaction.

This point of cloudiness is characteristic of the degree of condensation obtained by the alkaline condensation. It is measured by continuous sampling of the reaction medium at regular time intervals. . intervals. These samples are cooled with stirring and the temperature at which cloudiness occurs is noted. This temperature, which is rather low at the beginning of the reaction, increases as the reaction proceeds.

Thus, the alkaline condensation reaction is quenched by rapid cooling when the cloud point occurs between 40 and 65 ° C and preferably between 45 and 55 ° C, which, as already stated, usually occurs after a period of 30 to 90 minutes.

If the reaction is interrupted at a cloud point below 40 ° C, the cooled reaction medium exhibits a high viscosity which greatly complicates maintaining its homogeneity upon stirring. Conversely, a cloud point temperature that is above the reaction temperature cannot be exceeded without the reaction medium becoming cloudy at the same temperature as the reaction temperature. However, even in the case where the reaction temperature is 70 ° C, it will be very difficult to measure a cloud point temperature above 65 ° C, as the difference from the reaction temperature is too small.

It should be further noted that reaction temperatures above 70 ° C do not allow the cloud point to be measured and to follow the greater reaction rate at these temperatures.

Second step: etherification.

In this step, the methyl olmelamines obtained in the first step are etherified by the polyol or polyols already introduced into the reaction medium. Conveniently, these polyols are ethylene glycol, diethylene glycol, triethylene glycol, glycerol, sucrose and d-glucose. However, the most preferred diol according to the invention is ethylene glycol due to its price and its availability.

In addition, it should be noted that certain mixtures of polyols are advantageous. According to the invention, it is convenient to use a mixture of ethylene glycol and sucrose. Such a mixture in varying proportions thus makes it possible to control the viscosity of the final resin as sucrose tends to increase it.

As mentioned, the total amount of the polyol (s) to be used must be between 3.0 and 5.0 and preferably between 3.5 and 4.0 moles per mole. mol of melamine. This ratio is hereinafter referred to as P / M ratio. An insufficient amount of polyol greatly reduces the resin dilution with water. On the other hand, an excess of polyol is redundant as it does not increase the dilution anymore.

The acid used to lower the pH of the first stage to the pH of the second stage must be in pure form or in concentrated aqueous solution so that the final dry solids content of the aqueous resin solution is not unnecessarily lowered.

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

As already stated, one immediately cools after the alkaline condensation, and while keeping the obtained temperature constant, the reaction medium is acidified to a pH value which must correspond to the selected temperature. It is then under these conditions of temperature and pH that the etherification reaction is then carried out, these conditions of the invention having to be between the following limits: from 20 ° C for a pH of 1.5 to 40 ° C for a pH of 3.0, or preferably from 33 ° C for a pH of 1.8 to 37 ° C for a pH of 2.2.

The above conditions are generally necessary. In fact, if the etherification is carried out at too high a pH and / or temperature, the resin gets too high a viscosity, and above all, this viscosity increases very quickly upon storage, which in the extreme consequence prevents all use of the resin immediately after manufacture. Conversely, if the pH and / or temperature of the etherification is too low, the viscosity of the resin is too low, and although its dilution with water is extremely good, too low and useless values for the tensile strength are obtained for the fiberglass fabrics.

After the acid addition, after the end of a period that varies as a function of the cloud point temperature, it is found that the reaction medium, which was previously opaque, becomes clear. The etherification reaction is continued for a further time at the same temperature before quenching by neutralization.

In the following, for the etherification step, the terms "cloudy phase" and "clear phase" shall be used for the periods that lie respectively before and after the time when the reaction medium becomes clear.

The following conditions must be observed in the etherification step: the acid is added very regularly and as mentioned over a period of between 25 and 35 minutes and according to the invention preferably. between 28 and 32 minutes in such a way that the temperature is kept practically constant.

It has been found that the total etherification time is constant that a decrease in the addition time of the acid causes a significant increase in the final viscosity of the aqueous resin solution.

On the other hand, the acid has to be added slowly in order for the temperature to be kept constant despite the heat generated in the reaction medium.

Furthermore, according to the invention, it is preferred that the duration of the etherification reaction, from the introduction of the acid to the beginning of the neutralization, be between 50 and 180 minutes for a cloud point temperature of between 40 and 65 ° C, and preferably between 105 and 135 minutes for a cloud point temperature. between 45 and 55 ° C, respectively. These time limits, of course, apply to the previously stated values of pH and temperature.

For the above values for the cloud point, the pH value and the temperature, it is found that the minimum duration of the cloudy phase is 50 minutes from the beginning of the acid addition.

On the other hand, at the above values for the cloud point, pH and temperature, a total etherification time of 180 minutes is exceeded, the viscosity of the resins becomes too high and their dilution with water becomes clearly lower than 1200 , and that immediately after manufacture.

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In addition, these last resins, when stored at the usual temperature, are found to rapidly increase their viscosity and a correspondingly rapid decrease in their dilution with water.

The resins prepared by the process according to the invention have a viscosity measured at 25 ° C of between approx. 30 and approx. 200 cP, i.e. pretty low.

On the other hand, it should be recalled that the minimum shelf life of 2 months for these resins means that their viscosity after the end of this period must not be more than 800 cP and that their dilution with water must not be less than 1200 As is known, the normal aging of the resins helps to increase their viscosity and decrease their dilution with water.

The base used for the neutralization must, as in the first step, be exclusively triethanolamine or at least triethanolamine in an amount of 1/3 mol per liter. mol of melamine. In the latter case, according to the invention, at the end of the etherification reaction, it is convenient to partially neutralize with triethanolamine in an amount of 1/3 mol per liter. mole of melamine and finish the neutralization with a 50% by weight solution of sodium hydroxide.

It has been found that complete neutralization with sodium hydroxide produces resins which are only slightly diluted with water, and at the boundary a precipitate upon neutralization. The purpose of adding this additional amount of triethanolamine is also here to promote the solubility of the resin in water.

In this way, a pH of 7.0-7.5 is obtained, corresponding essentially to neutrality.

Third step.

This maturation step is important as it provides an improvement of two of the properties of fiberglass fabrics which are bonded to a binder made by aqueous solutions of the resins in question.

It has been found that increasing the duration of this maturation step gives a change in the same direction of the bending index of the fiberglass cloths as well as of their tensile strength.

Definition and measurement of the bending index.

60 rectangular specimens of 25 x 5 cm are cut from a fiberglass cloth. On 30 of these samples, the tensile strength is measured and the mean of these measurements is calculated.

148483 10

The other 30 specimens are subjected to folding once, under the following conditions: a 25 cm long, 5 cm wide and 2 mm thick metal plate is provided with two hinges in its center which allow it to be folded into two half plates each of one length of 12.5 cm. Each test piece of tablecloth is placed flat on this plate in a non-folded state, and on the tablecloth two other plates of 12.5 cm x 5 cm are placed. Thus, as the test piece is held in a flat state between the hinged plate and the two half plates, the whole 180 ° around the hinge is completely collapsed. The distance between the two halves of the specimen after folding, the specimen still being held between the plates of the described. . ne way, is 10 mm.

The tensile strength of the 30 specimens that have been folded is measured and the mean of these measurements is determined. The percentage loss in tensile strength is then calculated after folding.

The bending index is a number from 0 to 10, which can be found in the following conversion table:

Percentage loss in tensile strength Bending index after folding_ _ 0-4 10 4-10 9 10-20 8 20-30 7 30-40 6 40-50 5 50-60 4 60-70 3 70-80 2 80-90 1 90- 100 0

During the ripening step, a slight decrease in the percentage content of free formaldehyde in the aqueous resin solution and a gradual increase in its viscosity are observed.

In order not to increase this latter too much to the detriment of the possible storage time by subsequent storage of the resin solution before use, the following conditions must be observed at the ripening step: - the reaction mixture at the end of the second step, after its neutralization, must be heated to a temperature between 50 and 90 And preferably between 70 and 85 ° C without changing its pH value - this temperature must be maintained for a period of between 2 and 5 hours.

Under these conditions, the aqueous resin solution remains diluted with water in at least 12 times its volume.

If the ripening time exceeds 5 hours, for the specified values of the temperature, the resin will have an excessive viscosity. Conversely, interrupting the maturation, still for the same temperature range, before a period of 2 hours, no longer achieves the stated improvement in the flexibility of the fiberglass cloths.

Step 4.

The percentage content of free formaldehyde in the aqueous resin solutions is greater after the ripening step, the greater the ratio of F / M itself at the beginning. This content is on the order of 6-12% or more.

Such free formaldehyde concentrations are disruptive to the use as the emitted vapors irritate the eyes and respiratory tract of the users.

Thus, the main purpose of this 4th step is to reduce the content of free formaldehyde in the aqueous resin solutions to at least 6%. Solutions of such concentrations only emit irritating vapors to the air in amounts tolerable by the users.

However, this step offers two additional advantages: - one consists in increasing the tensile strength of the fiberglass cloth, - the other in that it reduces the viscosity increase rate of aqueous resin solutions upon storage and thus contributes to prolonging the possible duration of this storage.

This fourth and last step, as mentioned, consists in adding the solid urea solution obtained at the end of the third step in an amount between 0.6 and 1.6 moles, with 0.8 being preferably added according to the invention. to 1.2 moles per mol of melamine. This amount depends on the initial ratio of F / M and consequently on the content of the free media of formaldehyde at the end of step 3. This molar ratio of urea to melamine is hereinafter referred to as U / M ratio.

Urea is used in solid form, urea in pearl form, as its endothermic solution in the water in the medium lowers its temperature, and moreover, in order not to decrease the dry matter content of the final product, as an aqueous urea solution would.

The product is then allowed to stand for 12 to 24 hours for natural cooling before storing or using it.

The process according to the invention is further elucidated by the following Examples 1, 2, 3, 4, 7, 10, 11 (partly), 12 (partly), 13 (partly), 14, 15 and 17 (partly), while the other Examples as given are comparative examples. In the examples, the percentages are by weight, the viscosity values are measured at 25 ° C with a Brookfield viscometer, and the dilution values are measured at 25 ° C and expressed in terms of volume per water. 100 volumes of resin,

Example 1

Step I.

Into a 1 liter reaction vessel equipped with a reflux, stirrer and thermometer, 562 g of an aqueous solution containing 36% formaldehyde and 0.5% methanol, 248 g of ethylene glycol and 49.5 g of triethanolamine are introduced. The mixture is then heated with stirring to a temperature of 65 ° C. When this temperature is reached, 126 g of melamine are added over 12 minutes.

The condensation at 65 ° C is continued until a cloudiness point of 50 ° C is reached and the temperature is quickly lowered to 35 ° C.

Step II.

56 g of concentrated sulfuric acid are added regularly and over 30 minutes until a pH of 2 is reached and the etherification is carried out at 35 ° C for 1.5 hours.

Step III.

At the end of the etherification, the pH of the medium is adjusted to 7.2 using 49.5 g of triethanolamine and 50 g of a 50% sodium hydroxide solution.

It is then heated to a temperature of 70 ° C, which is maintained for 5 hours.

Step IV.

At the end of these 5 hours, 48 g of urea is introduced while the resin is cooled and at a temperature of approx. 60 ° C.

The resin obtained has the following properties:

Ratio F / M = 6.75 Ratio P / M = 4 Ratio TEA / M = 0.33 13 148483

Number of moles of triethanolamine added after etherification per mole of melamine: 0.33

Ratio U / M = 0.8 Solids content: 50.1%

Viscosity: 94 cP Free formaldehyde: 1.9%

Clarity: infinite (> 2,000) pH: 7.2

After 2 months of storage: dilution: infinite (> 2,000) viscosity: 160 cP Preparation of the bonding agent.

Starch preparation: An aqueous dispersion of a potato starch modified by treatment with ethylene oxide is prepared which has a concentration of 8% calculated as anhydrous starch. Steam is bubbled through this dispersion until its temperature is 98 ° C. The steam is then continued for 20 minutes and the mixture is allowed to cool. When the temperature has dropped to 25-30 ° C, the starch preparation is ready for use.

110 kg of starch composition is mixed with such an aqueous solution of the above-mentioned melamine-formaldehyde resin which corresponds to a dry matter content of 1.2 kg.

In addition, 1,378 kg of an emulsion having a solids content of 58% of a homopolymeric polyvinyl acetate plasticized by 50% dibutyl phthalate based on the amount of polymer diluted with the same weight of water is weighed.

This diluted emulsion is added to the previous mixture. The whole is homogenized by stirring for 10 minutes to form the concentrated binding agent.

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

Manufacture of fiberglass cloth.

A mat of non-bonded discontinuous glass fibers, hereinafter referred to as "basic cloth", is used. This had to be achieved by regularly distributing on a metal wire mesh conveyor belt discontinuous glass fibers obtained by extraction of steam from molten glass threads flowing out of holes located in the lower portion of a platinum spinning nozzle. These glass fibers have an average diameter of approx. 16 microns. The basic cloth used has a weight of 80 -5 g / m2.

148433 14

The basic cloth is immersed in the form of a continuous belt placed between two metal wire web conveyor belts in the bonding agent prepared above.

Still, in a continuous manner, an excess of bonding agent retained on the base cloth is extracted by means of a saitmen printing box placed under the lower belt. The compression is regulated in the box in such a way that after drying the cloth contains 20% by weight of dry binder, based on the total weight of glass and dry binder.

The bonded and dried ground cloth is then allowed to pass continuously over 2 minutes through an air circulation drying oven heated to 145 ° C.

The following properties are then measured on the finished tablecloth: Tensile strength: 5.5 kg / cm.

Bending index: 7.

Example 2

A melamine-formaldehyde resin is prepared in the same manner as in Example 1, using the following amounts of material:

Formaldehyde, 36% 666 g

Ethylene glycol 248 g

Triethanolamine 49.5 g

Melamine 126 g

Concentrated sulfuric acid 56 g 50% 1 s aqueous solution of NaOH 50 g

Urea 48 g

Triethanolamine 49.5 g

The resin obtained has the following properties:

Ratio F / M: .8.0 Ratio P / M: 4.0 Ratio TEA / M: 0.33

Number of moles of triethanolamine added after etherification rpr. mole melamine: 0.33 Ratio U / M: 0.8 Solids content: 47.8%

Viscosity: 70 cP Free formaldehyde: 4.0%

Clarity: infinite (? 2,000) pH: 7.2

After 2 months of storage: Dilution: Infinite (> 2,000)

viscosity: 130 cP

Using the above resin, a bonding agent is applied which is applied to a base cloth which is then dried in a drying oven in the same manner as described in Example 1.

The following properties are measured on the finished tablecloth:

Tensile strength: 5.6 kg / cm Bending index: 7.

Example 3

A melamine-formaldehyde resin is prepared in the same manner as in Example 1 using the following amounts of material: Formaldehyde, 36% 750 g

Ethylene glycol 248 g

Triethanolamine 49.5 g

Melamine 126 g

Concentrated sulfuric acid 56 g

Triethanolamine 49.5 g 50% aqueous solution of 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 moles of triethanolamine added after etherification per mole melamine: 0.33 Ratio U / M: 0.8 Solids content: 45.6%

Viscosity: 52 cP Free formaldehyde: 5.4%

Clarity: infinite (> 2,000) pH: 7.2

After 2 months of storage: dilution: infinite (> 2,000) viscosity: 100 cP.

Using the above resin, a bonding agent is prepared which is applied to a base cloth treated as described in Example 1.

148483 16 The following properties are measured on the dew obtained:

Tensile strength: 5.9 kg / cm Bending index: 8.

Example 4

A melamine-formaldehyde resin is prepared in the same manner as in Example 1, using the following amounts of material: Formaldehyde, 36% 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 solution of NaOH 40 g

Urea 38.5 g

The properties of this resin are as follows:

Ratio F / M: 10.0 Ratio P / M: 4.0 Ratio ΤΕΔ / Μ: 0.33

Number of moles of triethanolamine added after etherification per molar melamine: 0.33 Ratio U / M: 0.8 Solids content: 43.2%

Viscosity: 44 cP Free formaldehyde: 5.7%

Clarity: infinite (> 2,000) pH: 7.2

After 2 months of storage: dilution: infinite (> 2,000) viscosity: 92 cP.

Using the above resin, a bonding agent is prepared and then a tablecloth is made in the same way as in Example 1. On this tablecloth the following properties are measured: Tensile strength: 6.2 kg / cm Bending index: 7.

By comparing the tensile strength values of the tablecloths obtained in Examples 1, 2, 3 and 4, an increase of this property is found with the increase of the ratio F / M.

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Example No._ Ratio F / M_ Tensile strength of the tabs in kg / cm 1 6.75 5.5 2 8.0 5.6 3 9.0 5.9 4 10.0 6.2

Example 5 (Comparative Example) In a reaction vessel equipped with a powerful stirrer and heating agents, alkaline condensations of formaldehyde and melamine are made at the temperature of 65 ° C using the following amounts of material: ethylene glycol: 248 g (4 moles) of triethylamine: 49.5 g (0.33 mole) of melamine: 126 g (1 mole) of formaldehyde: amounts as given below.

The 36% aqueous formaldehyde solution containing 0.5% methanol is placed in the reaction vessel, then the glycol and triethanolamine are added and heated to the reaction temperature. The melamine is then added over 12 minutes.

With increasing amounts of aqueous formaldehyde solution, the following are found: - F / M ratio: 2.5, even after 3 hours at 65 ° C, the reaction medium remains unclear and by continuing the heating, the resin takes the form of a mass: - ratio F / M: 2.9: after 90 minutes at 65 ° C the reaction mixture is clear. The operations of steps 2, 3 and 4 are continued under the conditions set forth in Example 1. The final resin has a density of 0.

Ratio F / M: 4.0: the reaction medium of the alkaline condensation becomes clear after 50 minutes at 65 ° C. The preparation is completed in the same way as in Example 1. The resin obtained has a water dilution of only 1000.

With this last resin you make a bonding agent and you make a fiberglass cloth according to the requirements of Example 1. The tensile strength of this cloth is only 4.2 kg / cm.

This example shows the disadvantage of a ratio F / M <5.0 which is thus: lack of water dilution for the resins and deterioration of the tensile strength of the fiberglass cloth.

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Example 6 (Comparative Example)

Three resins are prepared under exactly the same conditions as in Example 1, except for the cloudiness point, which is 12 ° C for all the preparations. In addition, the temperature is allowed to vary by the alkaline condensation from one preparation to another. The following results are obtained: Initial preparation: condensation temperature 60 ° C. The condensation time is 45 minutes. The resin obtained has a viscosity of 14 cP and a dilution of over 2000.

Other preparation: condensation temperature 65 ° C. The condensation time is 35 minutes. The resin has a viscosity of 12 cP and a dilution of over 2000.

Third Preparation: Condensation Temperature 70 ° C. The condensation time is 23 minutes. The resin has a viscosity of 11 cP and a dilution of over 2000.

However, after only 15 days of storage, the viscosity of these three resins is increased to such a degree that they have gel consistency.

This example demonstrates the necessity of a sufficiently high value of the cloud point to obtain a shelf life of importance to the resins. It is also noted, when compared with eczema. column 1, the decrease in viscosity resulting from a decrease in cloud point temperature.

Example 7

A melamine-formaldehyde resin is prepared in the same manner as in Example 4, using the following amounts of material: formaldehyde, 36% 666.5 g of ethylene glycol 198.5 g of triethanolamine 39.5 g of melamine 101 g of concentrated sulfuric acid 45 g of triethanolamine 39, 5 g 50% aqueous solution of NaOH 40 g urea 57.5 g

However, the method used differs from the method of Example 4 in that the alkaline condensation is carried on to a cloud point of 62 ° C instead of 50 ° C, the etherification time is 3 hours instead of 2 hours, and the ripening step has a duration of 3 hours at a temperature of 85 ° C

Instead of 5 hours at 70 ° C.

The properties of this resin are the same as for the resin of Example 4, except for the following ratios: U / M: 1.2 dry matter content: 43.3% viscosity: 80 cP free formaldehyde: 4.9% dilution: 1900 after 2 months of storage : dilution: 1400 viscosity: 210 cP.

A bonding agent is prepared using the above resin and is used to make a tablecloth on the same gauge as in Example 1. On this tablecloth the following properties are measured: tensile strength: 6.7 kg / cm bending index: 6.

This example demonstrates the possibility of preparing a resin by the process of the invention by interrupting the alkaline condensation at a cloud point of 62 ° C. It also shows that the bowl should be adjusted to the total duration of the etherification as a function of the value of the cloud point.

Example 8 (Sait Comparison Example)

A resin is prepared entirely according to the instructions given in Example 4, except that for the alkaline condensation only a ratio TEA / M = 0.1 is used instead of 0.33.

The resin obtained has a density of practically 0 (<50) and a viscosity of 275 cP.

This example illustrates well, when compared with Example 4, the disadvantage of using too low a ratio of TEA / M under the alkaline condensation, ie. the important role of the triethanolamine, which consists in giving the resin a good solubility in water and a high dilution with water.

Example 9 (Sait Comparison Example)

A resin is prepared by the procedure of Example 4, however, using the alkaline condensation, sodium hydroxide as the catalyst instead of triethanolamine. The following materials are used: formaldehyde, 36% 666.5 g (8 moles) ethylene glycol 198.5 g (3.2 moles) 50% aqueous solution of NaOH 1 ml melamine 101 g (0.8 moles) concentrated sulfuric acid 10 ml triethanolamine 39.5 g (0.264 mol) 50% aqueous solution of NaOH 7 ml.

The resin obtained after the etherification step and neutralization has a dilution with water of almost 0 (<100). If the product is subjected to maturation by heating under the conditions of Example 4, the resin is converted to a gel.

This example shows, like the previous example 8, the important role played by the triethanolamine introduced in the alkaline condensation step, which is to impart a good solubility in water and good dilution with water, which here has not been obtained with sodium hydroxide. .

Example 10

This example illustrates the use of certain ethylene glycol different polyols in the preparation of the resins of the present invention.

The preparations were carried out entirely under the conditions described in Example 1, except for the nature and amounts of the polyols and except for certain specific details for each polyol as set forth in the table below.

Type and amount of Particular details Results of observation polyols in g moles in preparations ___gene__

Glycerol: 4 mol 3 hours of maturation at Thinness:> 2000

75 ° C (Step III) Viscosity: 90 cP

___Stable 2 months on storage

Diethylene glycol: 4 moles Thickness:> 2000

Viscosity: 94 cP

__Stable 2 months when storing d-glucose: 0.4 Blur point at Fortune level:> 2000

* t / c obtained after we 112 rP

ethylene glycol = 3.0 55 c ligSl mfa when storing triethylene glycol: cloudiness point 47 ° C Clarity:> 2000

4 moles obtained after 120 mM Viscosity: 98 cP

nuts at 65 ° C Stable 2 months when stored (step I) 148483 21

Example 11 (Comparative Examples A and B)

Three preparations of melamine-formaldehyde resins are made with the following amounts of material and by the general procedure of the preceding examples: formaldehyde, 36% 583.3 g (7 moles) of triethanolamine 49.5 g (0.33 moles) of melamine 126 g (1 mole) of concentrated sulfuric acid 56 g of triethanolamine 49.5 g (0.33 mole) of 50% aqueous solution of NaOH 50.0 g of urea 48.0 g (0.8 mole),

The alkaline condensations were carried out at 65 ° C and quenched at a cloudiness of 52 ° C. The etherification process was carried out at pH 2.0 and at a temperature of 30 ° C.

These three preparations are different in terms of the polyols used: __ Preparation A__B__C_

Mixture of Sucrose 342 g 171 g 86 g polyols

Ethylene glycol 0 124 g 186 g

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

After neutralization, the three products were heated (ripening) for 5 hours to 70 ° C. However, during heating, 90 g of water had to be added to resin A due to its thickening.

The properties of the final resins obtained are as follows:

AB C

Ratio F / M 7.0 7.0 7.0 sucrose] _ Q o, 5 o, 25

Mole ratio of melanun - ethylene glycol 2.0 3 n ______ melamine ____'_

Ratio TEA / M 0.33 0.33 0.33

Number of moles of triethanolamih, added - £ - - after etherification, per mol of melamine 0.33 0.33 0.33

Ratio U / M 0.8 0.8 0.8 Solids content in% 57.3 (X) 55.6 54, o

Viscosity in cP 2100 1100 125

Clarity 1800> 2000> 2000 (X) Taking into account the water added during maturation.

This example illustrates the possibility of obtaining resins with viscosities that are very different and can be adjusted at will by changing the relative amounts of sucrose and ethylene glycol. In determining the relative amounts of the two polyols in the three aforementioned resins A, B and C, it has been taken into account that saccharase carrying eight alcohol hydroxyl groups per molecule, must be used in four times smaller quantities than the diol. Finally, it is clear that only a small amount of sucrose can produce resins which are advantageous in ordinary practice, cf. Example C illustrating the invention.

Example 12 and 2 Comparative Examples Three preparations of resin are made according to the method and with the amounts of material given in Example 1, except for the amounts of ethylene glycol.

In a first production, a P / M ratio of only 2.0 is used. During the etherification step, it is found that the resin takes the form of a mass which cannot be solubilized by the addition of water.

In another preparation, a ratio P / M = 2.5 is used. It is not a matter of the resin taking the form of a mass during etherification, but the finished resin has a dilution with water of only 1000.

148483 23

In a third embodiment illustrating the invention, a ratio P / M of 3.0 is used. No difficulties are encountered in the production of the resin which, after completion, exhibits infinite dilution with water (> 2000).

This example demonstrates the need to use a P / M ratio of at least 3.0 to obtain a good water dilution for the resins in question.

Example 13 and a comparative example

Two preparations of resin are made entirely under the conditions described in Example 1, except for the conditions of the pH and the temperature of ether in the icing step.

In a first preparation, the etherification is carried out at pH 4 and at a temperature of 40 ° C. The resin obtained exhibits a normal viscosity and dilution the day after its preparation.

20 days later, however, the viscosity of the resin is increased so much that it is converted to a kind of gel at room temperature.

In another preparation illustrating the invention, the etherification is carried out at pH 1.5 and at a temperature of 20 ° C. The resin, on the day after its manufacture, exhibits a dilution of water greater than 2000 and a viscosity of 15 cP. After 2 months of storage, the dilution with water is still above 2000 and the viscosity is 40 cP.

With this second resin, the preparation of a bonding agent and the preparation of a fiberglass cloth are carried out according to the requirements of Example 1. A tensile strength is measured which is only 4.0 kg / cm for this tablecloth.

When compared with the results set forth in Example 1, the first preparation of the present example shows the adverse consequences that one would get if the etherification step goes beyond the range of the pH value specified herein.

Example 14

Two resins are made entirely according to the requirements of Example 4, except for the duration of the etherification step.

In the first preparation, the total etherification time, including the acid addition, is only 60 minutes for a cloud point of 50 ° C instead of 90 minutes for the same cloud point. The final viscosity of this resin is only 23 cP and its dilution with water is over 2000.

24483 24

With this resin, the preparation of a bonding agent and then the preparation of a fiberglass cloth according to the requirements of Example 1 is carried out.

This fabric measures a tensile strength of only 4.9 kg / cm.

In the second preparation, the etherification is extended to ~ a total duration of 180 minutes for a cloud point still at 50 ° C. The final resin obtained exhibits a viscosity of 285 cP and a water dilution of 1500.

After 2 months of storage, the following values are measured on the resin: dilution: 600 viscosity: 1050 c ?.

- This example, when compared to the results in Example 4, shows the unfortunate consequences it can have when the etherification reaction does not conform to the limits set for its total duration for a given cloud point in accordance with the preferred range as defined in claim 6.

Example 15 i - "A resin is prepared by the method of Example 4 except that 60 g of aqueous 35.5% hydrochloric acid solution is used instead of 45 g of concentrated sulfuric acid.

::; The properties of this resin in addition to the mole ratios of the various reactants that are. in Example 4, the following are: ~ · Solids content 43.3%

Viscosity 35 cP

Free formaldehyde 5.5%

Thinness infinity (> 2000)

Viscosity - .30 cP

After 2 months of storage: dilution: infinite (> 2000) viscosity: 55 cP.

Using this resin, a bonding agent and then a tablecloth are prepared according to the requirements of Example 1. On this tablecloth, measure: - tensile strength: 6.0 kg / cm bend index: 7.

Similar results are obtained by using orthophosphoric acid, nitric acid, formic acid or monochloroacetic acid in the same method and in the same stoichiometric amounts instead of hydrochloric acid.

148433 25

This example shows that these various acids or sulfuric acid can be used without distinction in the process of the present invention.

Example 16 (Seam Comparison Example)

A resin is prepared as per Example 4 except that neutralization to a pH of 7.2, after the etherification, is carried out solely with a 50% aqueous sodium hydroxide solution instead of using 0.33 moles of triethanolamine and then 40 g of aqueous sodium hydroxide solution. During maturation at 70 ° C (Step III), it is found that the resin takes the form of a pulp after 2 hours. This resin can no longer be made soluble by the addition of water.

This example demonstrates the necessity of using at least in part triethanolamine for the neutralization of the resin after the etherification step. Thus, by comparison with Examples 8 and 9, it shows that the triethanolamine plays a significant role in the solubility in water of the resin, not only at stage I (catalyst for the alkaline condensation) but also at the end of stage II (the etherification) during its neutralization.

Example 17 and live sample equation examples

This example shows the improved properties that the (· Step III) maturation imparts to the resins.

Four resins are prepared completely under the conditions of Example 1, except that the etherification temperature is 30 ° C instead of 35 ° C in all the preparations.

Furthermore, the ripening (step III) of these resins is carried out with increasing maturation times from one preparation to another.

With each resin, a bonding agent is prepared and a fiberglass cloth is prepared by proceeding as set forth in Example 1.

148483 26

The results shown in the table below are obtained.

Resin without "Resin with Resin with Resin with any maturation, maturation, maturation ·· a maturation time time of 1 hour of 4 ten time of 5 hours _ more mer____ .. Tensile strength of the fiberglass cloths in kg / cm 4.2 4.6 4.8 4.8 Bending index of the fiberglass cloths 5 6 8

Viscosity in cP of the aqueous resin solutions 41 53 115 245. after manufacture.

These examples, of which the first two are comparative examples, furthermore show the very rapid increase in viscosity after approx. 4 hours of ripening. This is why this operation must be continued for a limited period of time so that the resins remain useful in industrial practice.

Example 18 (Comparative Example)

This example illustrates the improved properties imparted to the resins by the addition of urea after the ripening step.

A resin is prepared completely in accordance with the requirements of Example 4, but no urea is added at the end of manufacture.

Using the resin thus obtained, a bonding agent is prepared and a fiberglass cloth is prepared by walking:. presented as in Example 1.

Compared with the resin of Example 4, the following results are obtained:. 1 .1 · ·. _ 'A ~ ~ - - - _' - -

Resin from eczema- Same resin without pelt 4 Addition of urine __ substance _; __

Free formaldehyde in% 5.7 11.0 ------ f ",! ~ -» - - - - - ---

Glass tensile strength 6.2! 5.7 fiber cloth in kg / cm,

Viscosity after the 44.55 position in cP - ·.

_. - Viscosity 2 months after manufacture 92 185

in cP

Claims (2)

The resins prepared by the process according to the invention are advantageous for bonding thin fiberglass fabrics, especially of a thickness of less than 4 mm, which fabrics impart to good properties in terms of flexibility and tensile strength. A process for preparing an aqueous solution of etherified melamine-formaldehyde resins by condensation in alkaline solution of formaldehyde and melamine, followed by an etherification, characterized in that in a first step, melamine is reacted with formaldehyde by gradual addition with stirring. over 10-15 minutes, of solid melamine to an aqueous solution maintained at a temperature between 60 and 70 ° C, preferably between 63 and 68 ° C, obtained by mixing: 1. an aqueous solution containing 30-50 wt% and preferably 36 wt% formaldehyde in an amount corresponding to a molar ratio of formaldehyde / melamine of between 5 and 11, preferably between 6.5 and 10, 2) one or more polyols in an amount corresponding to a molar ratio of polyol / melamine of between 3 and 5, preferably between 3.5 and 4.0, and 3. triethanolamine in an amount corresponding to a molar ratio of triethanolamine / melamine of between 0.2 and 0.6, preferably between 0.3 and 0.4, the pH value following the melamine addition is between 8.5 and 9.5 and preferably between 8.8 and 9.2, after which the reaction is quenched by rapid cooling to a temperature of between 20 and 40 ° C, preferably between 33 and 37 ° C when a cloud point is between 40 and 65 ° C, preferably between 45 and 55 ° C, in a second step, etherification takes place over 50-180 minutes, from the beginning of introduction of an acid for neutralization, by decreasing the pH of the reaction mixture from the first step by gradual addition over 25-35 minutes of an acid in pure form or in concentrated aqueous solution until a pH of between 1.5 and 3.0, while maintains the temperature maintained at the end of the first step and, at the end of the etherification reaction, neutralizes the solution obtained by adding a base which, in whole or in part (at least 1/3 mol. mole of melamine) consists of triethanolamine,