CH626106A5 - Process for the preparation of a hardener for aminoplastic resin - Google Patents

Description

The present invention relates to a process for the preparation of a hardener for glues and aminoplast binders from acids and anhydrides from effluents resulting from the production of phthalic anhydride by catalytic oxidation of orthoxylene or naphthalene.

It is known according to French certificate of addition No 2200341 to use phthalic acid or anhydride as a hardener for glues and aminoplast binders. However, due to the low solubility in water of these products, it is necessary to use them in solution in a solvent.

In French patent No. 2268047, mono-amides of maleic or fumaric acids are described as hardeners of aminoplast resins. These products have the disadvantage of requiring a complex and expensive implementation.

The hardeners currently most used in these types of resins are most often water-soluble acids or ammonium salts such as chloride, bromide, sulfate, phosphate, oxalate, etc. As a result of their reaction with the labile formalin available in these glues or binders, they provide the acidity necessary for cold or hot hardening.

According to the present invention, there is obtained, very simply and inexpensively, a hardener for aminoplast resin having all the required qualities, by neutralization at a pH between 4.50 and 5.40 of aqueous effluents, the density of which is 30 ° C is adjusted between 1.130 and 1.030, and preferably between 1.050 and 1.110, originating from the manufacture of phthalic anhydride by catalytic oxidation of orthoxylene or naphthalene.

In the manufacture of phthalic anhydride according to the process cited, the effluents come from the slaughter tower or washing tower with water of the gases leaving the synthesis reactor. The acid or anhydride composition of these aqueous effluents is variable and depends on the operation of the manufacturing unit.

In general, the composition of these aqueous effluents, per 100 parts by weight of dry organic matter, is as follows in parts by weight:

Maleic anhydride 43 to 90

Fumaric acid 0 to 3

Citraconic acid 3 to 4.5

Benzoic acid 1 to 4.5

Phthalic anhydride 5.5 to 38

Phthalide 0.5 to 4

The weight of the dry organic materials is determined by steaming 3 g of aqueous effluents at 95 ° C. for 2 h.

It may be necessary to adjust the density of these aqueous effluents by adding water, prior to their neutralization. With a view to their transformation into a hardener for glues and aminoplast binders, these aqueous effluents are neutralized at the pH defined above, preferably:

with ammonia;

by one or more amines of general formula:

r3

in which R1; R2, R3 represent a hydrogen atom or an alkyl radical containing from 1 to 6 carbon atoms and optionally carrying a phenoxy or alkoxy group of 1 to 2 carbon atoms, Rls R2 and / or R3 being identical or different;

or also by a cyclic amine containing 4 or 5 carbon atoms and which may contain in its molecule an oxygen, sulfur and / or nitrogen atom.

As an example of amines, mention may be made of monomethylamine, n-butylamine, dimethylamine, methylhexylamine, trimethylamine, piperidine, pyrrolidine, morpholine.

However, for economic reasons, ammonia remains the most interesting neutralizing agent.

The effluents thus treated can be used as such as hardeners for aminoplast binders and glues; however, it is preferable to filter them in order to remove the solid impurities present in the initial effluents.

These hardeners can be prepared continuously or batchwise. To prepare them continuously, it suffices to add the dilution water and the neutralizing agent, preferably in aqueous solution, in the effluents leaving the water washing tower, at flow rates adjusted so as to obtain a final solution having the density at 30 ° C and the pH essential to the subject of the invention.

According to the batch process, it is for example possible to add, successively or simultaneously, to the effluents, agitated in a reactor provided with a cooling system, the water and the neutralizing agent in sufficient quantities to obtain density at 30 ° C and pH according to the subject of the invention. Generally, the reaction temperature is kept below 60 ° C.

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626106

The hardener solutions thus obtained can be stored during storage. They remain clear up to a temperature close to 0 ° C. At lower temperatures, crystallization occurs, easily absorbed by simple reheating.

For storage convenience, it may be advantageous to recover the hardener in powder form. It suffices in this case to recover the hardener from the treated effluents, by crystallization, by dry evaporation or by any other known means. The powder obtained can be easily returned to an aqueous solution at room temperature and has the same qualities of hardener as the aqueous solution of treated effluents.

The effluent solutions treated under the conditions of the invention are ready for use and are generally used at a rate of 1.5 to 15% by weight relative to the weight of dry matter of the aminoplast resin used. , the dry matter of the aminoplast resin being determined by steaming at 120 ° C. 1 g of commercial aminoplast resin for 2 h.

This type of hardener is particularly suitable for urea / formaldehyde, melamine / formaldehyde, melamine / urea / formaldehyde resins, modified or not, by the addition of phenol in their preparation.

In addition to their excellent qualities as hardener for binders and aminoplast glues, the treated effluents have the enormous advantage of technically recovering the waste water from the production of phthalic anhydride by catalytic oxidation of orthoxylene or naphthalene. Industrially, these waste waters pose a disposal problem; due to the danger of pollution, they cannot be rejected. They are generally destroyed by evaporation and calcination, or else treated chemically or biologically before rejection, which results in loss of product and relatively expensive handling.

The following examples illustrate the subject of the invention.

Example 1:

In 36 kg of aqueous effluents, originating from the production of phthalic anhydride by catalytic oxidation of orthoxylene and having the following composition, per 100 parts by weight of dry organic matter:

Maleic anhydride 77

Citraconic acid 5

Benzoic acid 3

Phthalic anhydride 14

Phthalide 1

101 of water at 50 ° C. are added so as to obtain a density at 30 ° C. of 1.087.

The dry extract of this solution is 29.4% and the pH of 1.15. 8.2 kg of 26% by weight ammonia is then added at 20 ° C. The pH of the solution obtained is 5.

The final solution, after filtration, constitutes the hardener I A.

Example 2:

2 kg of hardener I A of Example 1 are evaporated to dryness under the following conditions: pressure 20 mm of mercury, temperature 70 ° C. 480 g of residue are then obtained which, after grinding, is in the form of a gray powder; this powder is then dissolved in water at 25 "C at a rate of 120 g per 380 g of water. The solution thus obtained has a pH of 4.6 and constitutes the hardener I B.

Example 3:

In 45 kg of aqueous effluents, having a density at 30 ° C of 1.086 and having the following composition, per 100 parts by weight of dry organic matter:

Maleic anhydride 62.7

Citraconic acid 4.1

Benzoic acid 2.4

Phthalic anhydride 30

Phthalide 0.8

7.9 kg of ammonia at 26% by weight are added. The solution obtained, having a pH of 5.1 and a density at 20 ° C of 1.085, constitutes hardener II.

Example 4:

In 36 kg of effluents, having an organic matter composition identical to that of Example 1, 11 of water at 50 ° C. are added. The density of the solution obtained is 1.107 at 30 ° C.

The dry extract of the solution is 36%. Neutralization is then carried out with 7.8 kg of ammonia at 26% by weight and filtration on paper.

The final solution, having a pH of 5, constitutes the hardener III.

Example 5:

The procedure is as in Example 1 with, at the start, 36 kg of effluents of the same organic composition, but replacing 8.3 kg of ammonia at 26% by weight with 9.5 kg of monomethylamine at 40% by weight in water.

The solution obtained, having a pH of 4.6, constitutes the hardener

IV.

Example 6:

The procedure is as in Example 5, but replacing 9.5 kg of monomethylamine with 10.5 kg of morpholine.

The solution obtained, having a pH of 4.6, constitutes the hardener

V.

Example 7:

The procedure is as in Example 6, but replacing 10.5 kg of morpholine with 12.5 kg of diisopropylamine. The final solution having a pH of 4.7 constitutes the hardener VI.

Example 8:

To 100 parts by weight of a commercial melamine / urea / formaldehyde resin, having a dry extract of 65%, 18 parts by weight of a 45% by weight aqueous paraffin emulsion are successively added, 7 parts by weight of hardener IA or VI and 1.8 parts by weight of water. The aqueous paraffin emulsion used is a commercial product prepared from paraffin with a melting point of between 55 ° C. and 80 ° C.

The gel time is then measured at 100 ° C; this being defined as the time measured, from the introduction of 6 g of the previous mixture contained in a test tube, until the start of gelation.

A control sticky mixture is prepared in the same way, by adding to 100 parts by weight of resin 18 parts by weight of a 45% by weight paraffin emulsion, 5.3 parts by weight of a chloride solution. ammonium at 15% by weight, 1 part by weight of concentrated ammonia 22 "B and 2.5 parts by weight of water.

The gel times found with the various hardeners are listed in the table below:

Gel time

(s, 100llC)

Mixture containing hardener I A

68

Mixture containing hardener VI

69

Mixture containing am chloride

monium

70

22 parts by weight of a sticky mixture are sprayed onto 100 parts by weight of wood chips, mixture of poplar and birch at 6% humidity. Shavings are shaped into mat which is then baked at 162 ° C under a pressure of 25 daN / cm2. The compression time is 4 min for a panel thickness of 20 mm, or 12 s / mm.

The panels thus produced are then subjected to the tests of the French standard CTB-H.

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626 106 4

The results obtained, averages of 10 tests, are recorded in the following table:

Mechanical characteristics of the panels

Mixture containing IA hardener

Mixture containing hardener VI

Mixture containing ammonium chloride

Gross thickness (mm)

19.6

19.5

19.6

Density

0.688

0.687

0.688

Dry transverse tensile strength

(kg / cm2)

11.5

11.3

10.8

Resistance to transverse traction after cycle

V313 (kg / cm2)

6.3

6.2

5.2

Swelling with water at 20 ° C after 24 h (%)

2.5

2.7

3

Swelling after V313 cycle (%)

3.6

3.8

4.3

It is noted that the results, obtained with hardeners based on by-products from the production of phthalic anhydride, are clearly superior to those obtained by ammonium chloride, in particular after the V313 cycle.

Example 9:

For each hardener, two sticky mixes are prepared: one, called E, is intended for gluing the outer layers of a particle board; the other, called I, is intended for the inner layer. These sticky mixtures are obtained by adding to 100 parts by weight of a commercial melamine / urea / formalin resin, having a dry extract of 65%, variable amounts, expressed in parts by weight, of paraffin emulsion, water, ammonia, IV or V hardener, or 15% by weight aqueous ammonium chloride solution.

The gelling times are measured.

The compositions of the sticky mixtures and the gel times found are given in the table below:

Hardener IV

Hardener V

Chloride

Sticky mix

ammonium

I

E

I

E

I

E

Melamine / urea / formalin resin

100

100

100

100

100

100

Paraffin emulsion at 45% by weight in water

5

5

5

5

5

5

Ammonia 20% by weight

0

0

0

0

0.3

0.8

Hardener

8

5

8

5

8

5

Water

7

12

7

12

7

12

Gel time (s, 100 ° C)

90

112

84

105

60

83

3-ply particleboard is produced, the outer layers being obtained with fine birch chips, having a humidity of 4%, and the inner layer with coarse chips of a mixture of poplar and birch, having a humidity of 4.8%.

The gluing of the chips is carried out by spraying the chosen sticky mixture, so that the chips, used for the outer layers, contain 14% by weight of dry binder relative to the weight of dry wood and that the chips for the outer layers in contain 12%.

The cake is shaped by superimposing a layer of fine shavings, a layer of coarse shavings and a layer of finely bonded shavings, so that there is 30% in 2 x 15% by weight 40 of fine shavings for 70% by weight of coarse chips and that a panel having a density between 0.670 and 0.720 is obtained after pressing.

The cake is then subjected to a compression of 25 daN / cm2 at 170 ° C for 5 min 30 s.

45 The panels thus produced are then subjected to the tests of French standards CTB-H and NF B 51 262 of September 1972, the latter relating to the tensile strength after the V100 cycle.

The main results obtained, averages of 10 tests, are summarized in the following table:

Mechanical characteristics of the panels

Hardener IV

Hardener V

Ammonium chloride

Gross thickness (mm)

19.59

18.45

18.40

Density

0.692

0.693

0.673

Dry transverse tensile strength

(kg / cm2)

10.8

11.1

9.7

Resistance to transverse traction after cycle

V100 (kg / cm2)

2.1

2.1

1.9

Swelling after V100 cycle (%)

20.5

21

21

Swelling after 24 h in water at 20 "C (%)

6.0

5.9

6.0

Dry bending (kg / cm2)

161

161

134

It can be seen that the panels produced with hardeners IV and V 65 Example 10:

meet the aforementioned standards and have better qualities On 10 mm thick plywood samples, we are mechanical than those made with ammonium chloride as a 180 g / m2 coating of a mixture of 100 parts by weight of hardener resin. melamine / urea / formalin, modified with phenol, such as that described

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626,106

in Example 3 of French Patent No. 2172841 and 3 parts by weight of a hardener solution from Example 1.

The samples are subjected to a pressure of 7 kg / cm2, to

For comparison, the previous operation is repeated, replacing the hardener with 2.1 parts by weight of 2N formic acid. The surface of the plywood obtained appears covered with innumerable small cracks.

Example 11:

The use of the hardener, such as that described in Example 1, improves the kinetics of hardening of the adhesives.

The purpose of this measurement is to predict whether or not the glue will lead to detachments at the press outlet, during veneering or structural bonding, subjected to very high tensions at the level of the assembly of the pieces of wood.

To measure the kinetics of hardening, we proceed as follows:

100 g of commercial urea / formaldehyde resin containing 65% dry matter are introduced into a metal container and heated to 80 ° C. It is then placed in a thermostatic bath at 80 "C and the hardener is added while stirring the glue. As soon as the addition of the hardener is completed, the timer is started and the gelation time of the sticky mixture is measured.

As soon as this mixture is gelled, the measurement of the increase in hardness is immediately carried out, this being defined as being the variation, over time, of the load, placed on the plate of a penetrometer, and necessary so that a rod having a cross-section of 1 mm2 is observed in the hardened resin.

The results reported in the table below are obtained with ammonium chloride, which serves as a comparison.

Hardener

15% by weight ammonium chloride solution

Hardener from Example 1

% in weight

10

5

10

5

Time to

gelling

18

13

9

8

at 80 ° C (s)

Weight (kg)

Time 80 ° C

1 mm after frost

0.6

0.5

0.8

0.8

2 mm after frost

0.8

0.7

1.4

1.2

3 mm after frost

1.0

0.8

1.8

1.3

4 mm after frost

1.2

1.1

2.1

1.5

5 mm after frost

1.5

1.3

2.4

1.7

Example 12:

100 parts by weight of commercial urea / formaldehyde glue,

having a dry matter content of 65%, 40 parts by weight of rye flour, 30 parts by weight of water and 10 parts by 40 weight of hardener IA, III, IB, or comparative are added, the latter consisting of 30 parts by weight of hexamethylenetetramine, 50 parts by weight of urea, 20 parts by weight of ammonium chloride and 100 parts by weight of water. The mixture is homogenized and used for bonding plywood. 45

5-ply plywood panels are produced using okoumé wood sheets at 5% humidity and each of the sticky mixtures defined above.

Gluing is carried out by spreading, using a roller, 200 g of a sticky mixture per square meter of wood film. The 4 outer folds are glued on the inside, the central fold is not glued.

The panel is shaped by superimposing the 5 plies and crossing them so that the fibers of 2 contiguous plies are placed perpendicularly; the assembly is subjected to a compression of 25 daN / cm2, at 110 ° C for 5 min.

The quality of the bonding of the panels thus produced is evaluated, by assigning a score of 0 to 10, depending on the appearance of the detachment with a knife, after immersion of the test pieces for 72 h in water at 20 ° C, or after immersion for 3 h in water at 70 ° C followed by immersion for 21 h in water at 20 ° C (test A 70). Note 0 corresponds to total detachment in the bonding plane and note 10 is assigned when the tearing occurs in the fold of the wood, the glue plane remaining completely covered with wood fibers.

The results, averaged over 10 test pieces, are summarized below:

Sticky mixture comprising the

Comparative

AI hardener

IB hardener

Hardener III

Score after test A 70

3.3

4.3

4.1

4.6

Note after 72 h of immersion in

water at 20 ° C

4.8

5.2

5.1

5.1

These results further demonstrate the superiority of the hardener based on effluents from the synthesis of phthalic anhydride compared to the hardener with ammonium chloride.

Example 13:

The procedure is as in Example 9 with regard to the manufacture of the sticky mixtures E and I. Is added in 100 parts of a commercial urea / formaldehyde resin, having a dry extract of 67.5%, variable amounts of emulsion of paraffin, water, ammonia, hardener II, IB, or a solution of ammonium chloride 65 to 15% by weight in water.

The gel times are measured at 100 ° C.

The compositions of the sticky mixtures and the gel times found are summarized in the table below:

626106

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Hardener II

Hardener I B

Chloride hardener

Sticky mix

ammonium

I

E

I

E

I

E

67.5% urea / formalin resin

100

100

100

100

100

100

Paraffin emulsion 45%

5

5

5

5

5

5

Ammonia 20%

0

0

0

0

0.5

1

Water

5

10

5

10

5

10

Hardener

7

3

7

3

7

3

Gel time at 100 C (s)

70

99

68

95

70

110

The procedure is the same as in Example 9 for the manufacture of particle boards comprising 3 layers, but adopting a sizing rate of 11% instead of 14% for the outer layers and 8% instead of 12 % for the inner layer. The cake, shaped, is subjected to a compression of 25

It is found that the mechanical characteristics of the panels, developed with the hardeners based on effluents from the production of phthalic anhydride, are superior to those of the panels manufactured with ammonium chloride.

Example 14:

To 100 parts of a commercial melamine / formaldehyde resin having a dry matter content of 55%, 1 part of the hardener of Example 1 is added and the mixture is homogenized.

Decorative paper, weighing 110 g / m2, is impregnated with the above mixture until a resin absorption rate of 60% by weight is obtained, then dried until a residual humidity of 5 to 7 is obtained. %, determined by steaming for 5 min at 160 ° C.

This paper, thus treated, is then applied to a particle board and the assembly is subjected to a pressure of 15 kg / cm 2 at 150 ° C for times between 70 and 180 s.

By way of comparison, the same operations are carried out as those described above, but by replacing the catalyst of Example 1 with an equivalent amount of an aqueous solution at 15% by weight of formic acid.

daN / cm2 at 165 ° C for 4 lA min instead of 25 daN / cm2 at 170 ° C for 5 Vi min.

The main mechanical characteristics of the panels thus obtained, averages of 10 tests, are summarized in the following table:

In both cases, glued materials having a perfectly smooth surface are obtained on leaving the press; the crack resistance of these materials is then determined after baking at 85 ° C for 14 h.

The main results are summarized below:

These results further show the superiority of the hardener of Example 1 over the hardener with formic acid.

Mechanical characteristics of the panels

Hardener II

Hardener I b

Ammonium chloride hardener

Gross thickness (mm)

18.73

18.72

18.76

Density

0.657

0.658

0.656

Dry transverse tensile strength

(kg / cm2)

7.9

8.0

7.1

Dry bending (kg / cm2)

135

140

121

Resistance to transverse traction after immersion

sion in water at 40 ° C for 2 Vi h (kg / cm2)

2.4

2.4

2.2

Swelling after 24 h in water at 20 ° C (%)

12.8

12.5

12.6

Swelling after 2 lA h in water at 40 ° C (%)

14.7

14.6

14.7

40

Surface appearance

Surface appearance

85 ° C oven test

with the hardener with the hardener

from example 1

formic acid

/1 C

Pressing time

70 s uncracked

not cracked

90 s uncracked

not cracked

120 s uncracked

slight cracks

150 s uncracked

many cracks

180 s uncracked

many cracks

50

R

Claims (10)

626106 1. Process for preparing a hardener for amino-plast resin, characterized in that the aqueous effluents are neutralized at a pH of between 4.50 and 5.40, the density of which at 30 ° C. is adjusted between 1.130 and 1.030, from the manufacture of phthalic anhydride by catalytic oxidation of orthoxylene or naphthalene. 2. Method according to claim 1, characterized in that the aqueous effluents involved contain per 100 parts by weight of dry organic matter, 43 to 90 parts of maleic anhydride, 0 to 3 parts of fumaric acid, 3 to 7, 5 parts of citraconic acid, 1 to 4.5 parts of benzoic acid, 5.5 to 38 parts of phthalic anhydride and 0.5 to 4 parts of phthalide. 2 3. Method according to one of claims 1 or 2, characterized in that the aqueous effluents involved have at 30 ° C a density between 1.10 and 1.050. 4. Method according to one of claims 1 to 3, characterized in that the neutralization is carried out with ammonia. 5. Method according to one of claims 1 to 3, characterized in that the neutralization is carried out with an amine of formula: / r3 in which R15 R2, R3 represent a hydrogen atom or an alkyl radical containing from 1 to 6 carbon atoms, Rlr R2 and / or R3 being identical or different. 6. Method according to claim 5, characterized in that the alkyl radical of the amine contains phenoxy groups or alkoxy groups containing 1 or 2 carbon atoms. 7. Method according to one of claims 1 to 3, characterized in that the neutralization is carried out by a cyclic amine containing 4 or 5 carbon atoms. 8. Method according to claim 7, characterized in that the cyclic amine contains in its molecule an oxygen, sulfur and / or nitrogen atom. 9. Method according to claim 1, characterized in that the density of the aqueous effluents is first adjusted to a value at 30 ° C of between 1.130 and 1.030, by dilution with water. 10. Use of the product obtained by the process according to claim 1 as hardener, in an amount of 1.5 to 15% by weight relative to the weight of dry matter of the aminoplast resin used.