Formaldehyde binder

Formaldehyde-binding composition, its preparation and use Formaldehyde-binding composition, preparation and use

Boards such as particle board, plywood, bundle board and the like are made of 1-part materials using binders. Preferred binders (or adhesives) are based on formaldehyde, such as urea formaldehyde, melamine formaldehyde, phenol formaldehyde and resorcinol resins, or mixtures thereof. It is well known that sheets made using these adhesives contain formaldehyde odor, which is both harmful and unpleasant. Formaldehyde is removed both during the manufacture of these sheets and during their storage and use.

Many methods have been proposed to avoid formaldehyde emissions, but all of them are either inefficient or degrade the properties of the sheets or require complex applications. Some of these methods, which have been known for more than 10 years, require the spraying or application of various solutions to the hot plates coming from the press, in which case solutions of urea and / or ammonia or ammonium salts are involved. In general, these types of methods are not advantageous in industrial use because they require additional processing steps and, in the long run, their effectiveness is limited.

Other methods require the use of highly complex mixtures of many ingredients, with some substances being natural adhesives. These products are also not very effective. One of their disadvantages is that the properties of natural products are not unchanged.

Another way to reduce the free formaldehyde content is to use an aqueous suspension of special wax coated urea pieces. This method also requires a separate

8736?

feed channel because the product is not added to the adhesive product itself.

An effective formaldehyde-binding composition for reducing free formaldehyde in sheets and factory halls is described in British Patent Application Publication No. 2,136,008 A. This publication discloses a formaldehyde-binding composition for use as an adhesive in the form of

(a) at least one organic hydroxy compound other than C 1-4 monohydric aliphatic alcohols and (b) at least one amide in water. This formaldehyde may further contain (c) an organic compound which acts as a solvent for (a) and (b) and also reacts with formaldehyde and / or (d) a water-soluble inorganic compound.

The organic compound (c) is preferably a C 1-4 aliphatic monohydric alcohol and the inorganic compound (d) is preferably a water-soluble halide salt.

The above formaldehyde-binding composition effectively reduces free formaldehyde in the sheets without deteriorating the properties of the sheet, without altering the reactivity of the adhesive products and without requiring any additional steps in the manufacture of particle board, plywood or plywood, while reducing free formaldehyde in the manufacturing process.

The above formaldehyde binding composition is very effective when used with adhesives rich in formaldehyde compared to other ingredients such as urea, melamine, phenol or resorcinol to give more than 50 mg of free formaldehyde per 100 g of dry board. The reduction in this case is up to 60-85% of free formaldehyde. When using low formaldehyde dip resins with a free formaldehyde emission of between 20 and 50 mg of free formaldehyde per 100 g of dry sheet, the maximum reduction is usually 50 to 60%. No readings are given for low formaldehyde resins that give less than 20 mg of free formaldehyde per 100 g of dry sheet.

In recent years, there have been significant developments in resins that provide low emissions of free formaldehyde.

is to obtain is all English008 A form which in addition is free formaldehyde

It is an object of the present invention to provide a formaldehyde-binding composition which has the advantages of an aldehyde-binding composition and is very effective even at very low emissions.

In this case, a new formaldehyde-binding composition has been developed which can be used with resins which give less than 20 mg of free formaldehyde per 100 g of dry board, whereby this binder completely eliminates the free formaldehyde released by the resins (the boards still release some free formaldehyde but wood itself). .

In the case of resins which give more than 20 mg of free formaldehyde per 100 g of dry sheet, the formaldehyde-binding composition according to the invention eliminates up to 60-85% of the free formaldehyde.

The invention relates to a formaldehyde-binding composition which is an aqueous solution comprising (a) at least one organic hydroxy compound selected from dihydric and trihydric alcohols containing up to 20 carbon atoms, pentaerythritol, sorbitol, monosac8736 having up to 6 carbon atoms?

carides, disaccharides having up to 12 carbon atoms and mixtures thereof, and (b) at least one amide, and optionally (c) an organic compound which acts as a solvent for (a) and (b) and also reacts with formaldehyde, and / or (d) a water-soluble inorganic compound characterized in that the composition is that the composition further comprises (x) 0.01 to 5.00% by weight of ammonia or an ammonium salt of a weak acid or a mixture thereof and (y) 0.01 to 5.00% by weight of a strong acid or a strong acid releasing agent or a a mixture wherein the weight ratio of components (a) and (c) and (d), if present, to component (b) is from 20: 100 to 400: 100.

The amount of ammonium salt of ammonia and / or weak acid or mixtures thereof is 0.01 to 5.00% by weight, preferably 0.03 to 3.00% by weight (calculated as 100% product) based on the total amount of formaldehyde-binding composition and the strong acid and and / or the amount of strong acid releasing agent or mixtures thereof is likewise 0.01 to 5.00% by weight, preferably 0.03 to 3.00% by weight (calculated as 100% by weight) based on the total amount of formaldehyde-binding composition.

Specific examples of suitable organic hydroxy compounds include monoethylene glycol, diethylene glycol, polyethylene glycols, glycerol, pentaerythritol, fructose, mannose, sorbitol, dextrose, sucrose, maltose, lactose, and the like.

The amides [component (b)] used in the formaldehyde-binding composition of the invention are also preferably soluble in water or lower monohydric aliphatic alcohols. Particularly preferred are aliphatic amides containing up to 6 carbon atoms35

87369 m i. ^a and a t. dreams of atfi set amides. containing one benthic ring.

Suitable examples of amides include urea, thiourea, formamide, acetamide, benzamide, oxamide, succinamide, malonamide, guanidine, biuret, dicyandiamide and the like.

To improve solubility, the formal dehyde-binding composition of the invention may, if desired, further contain additives [component (c)] which act as solvents for components (a) and (b) and also react with formaldehyde and are preferably lower monohydric aliphatic alcohols such as methanol, ethanol , isopropanol and the like.

A cheaper and more effective formaldehyde-binding composition is obtained by adding inorganic compounds [component (d)], which are preferably halide salts, more preferably halides of alkali metals or alkaline earth metals, such as sodium chloride, potassium chloride and calcium chloride.

Examples of weak acid ammonium salts that may be present in the formaldehyde-binding composition of the invention include ammonium carbonate, ammonium bicarbonate, ammonium sulfamate, ammonium acetate, ammonium carbamate, and the like.

Examples of strong acids and / or strong acid releasing agents which may be present in the formaldehyde-binding composition of the invention include hydrochloric acid or ammonium chloride, ammonium sulfate, sulfuric acid, formic acid or ammonium formate and others.

• 35 Ratio of organic hydroxy compound [component (a) and component (c), if present]] and inorganic compound [component (d), if present] to amide [component ⁶ 87362 (b)] is preferably 10: 100 to 400: 100, especially

10: 100 to 200: 100 by weight. The formaldehyde-binding composition of the invention may be added to conventional adhesive preparations in amounts ranging from 1 to 10%, preferably 3 to 7% of the solid formaldehyde-binding composition based on the weight of the liquid resin containing 65% by weight of solid resin.

The formaldehyde-binding composition according to the invention may contain from 20 to 85% by weight, preferably from 50 to 75% by weight, of active ingredients [components (a) and (b) and components (c) and / or (d), if present, and ammonia and / or weak acid ammonium salts and strong acids and / or strong acid releasing agents]. The water content of the formaldehyde-binding composition depends on the solubility of the active ingredients and the amount of water that can be allowed in the adhesive preparations. Even when the individual components are insoluble in water, they can be dissolved in water by heating their mixture in water to 70oC.

The formaldehyde-binding composition of the invention can be prepared simply by adding the active ingredients and water to the mixer and stirring until the active ingredients are dissolved. This can be done at room temperature or even at an elevated temperature of about 70oC.

When the active ingredients of the formaldehyde-binding composition of the invention are used in combination with each other, the reduction in free formaldehyde is surprisingly much greater than the sum of the effects of the individual ingredients and has no detrimental effect on the reactivity or sheet properties of the adhesive.

It is well known in the art that ammonia reacts with formaldehyde, thus significantly reducing the free formaldehyde of the resulting sheets. However, it is also known in the art that it is not possible to add ammonia to the adhesive mixture in such a way as to substantially reduce the free formaldehyde, since at the same time it deteriorates the properties of the obtained sheets and requires longer pressing times. This is due, on the one hand, to a considerable retardation of the reactivity and also to the fact that the free formaldehyde present is chemically bound, thus further reducing the curing of the resin, which can be achieved under similar conditions. For this reason, ammonia was added for several years after the plates were removed from the press, requiring time-consuming treatments and expensive and complex equipment, and had the significant disadvantage of not reducing free formaldehyde in the manufacturing facilities.

It was really surprising to find that by adding ammonia and / or an ammonium salt of weak acids and / or mixtures thereof in the form of a formaldehyde according to the invention [i.e. a combination of a strong acid and / or a strong acid releasing agent or mixtures thereof and components (a) and (b) ) and / or (d)] sheets were released into the adhesive mixture itself which release less free formaldehyde even when when low formaldehyde adhesives are used and sheets are formed which release less than 20 mg of free formaldehyde per 100 g of dry sheet and that the properties of the sheets do not deteriorate, the reactivity of the adhesive products does not change and no additional steps are required in patent application for a formaldehyde binding composition disclosed in 2,136,008 A. This latter advantage is very important for the health of those working in sheet metal factories.

The formaldehyde-binding composition of the invention is not added to the adhesive preparation in addition to all its other conventional ingredients, but replaces part of the adhesive resin. Therefore, the formaldehyde-binding composition of the invention is very economical. It can be used with all kinds of formaldehyde-based adhesives and even special resins of type E 1 (resins giving about 10 mg of free formaldehyde per 100 g of dry board), in which case it further reduces the free formaldehyde to about 5 mg per 100 g of dry board (the amount of formaldehyde released by the wood itself).

The following examples illustrate the invention, which is of course not limited to the values ​​shown in the examples. Parts and percentages are parts and percentages by weight.

Example 1

In this example, plates were prepared in the laboratory.

Four sets of plates were prepared. The first set was made with a glue preparation that did not contain a formaldehyde binding composition and was called a blank. The second series was prepared using a formaldehyde-binding composition (Preparation 1) according to British Patent Application Publication No. 2,136,008 A without the addition of ammonium and / or an ammonium salt of weak acids and together with a strong acid and / or a strong acid releasing agent.

The third and fourth series were prepared using the formaldehyde binding composition of the present invention (Preparations 2 and 3). It can be seen that the reduction in free formaldehyde is much greater with preparations 2 and 3 than with preparation 1.

The formaldehyde-binding compositions were as follows (expressed as parts by weight with all ingredients calculated as 100% solid):

3

Glycerol Urea

Sodium chloride Ammonia Ammon and water Water

IN TOTAL

200 200 200 250 250

100 100 , 65 5

250

100

1,98 6

442,02

1.000

450 443^35

1.000 1.000

In the following tables, the formaldehyde-binding composition is abbreviated Fsk

The adhesive preparations used were as follows (expressed as weight):

<td></td><td>Aihi o</td><td> 1</td><td> 2</td><td> 3</td>

<td>Urea-formaldehyde</td><td> 3080</td><td> 2864</td><td> 2864</td><td> 2864</td>

<td>65% (molar ratio F: U = 1</td><td> ,27:1)</td><td></td><td></td><td></td>

<td>Curing agent</td><td> 400</td><td> 400</td><td> 400</td><td> 400</td>

<td>(Ammonium chloride 15%)</td><td></td><td></td><td></td><td></td>

<td>Paraffin emulsion 50%</td><td> 210</td><td> 210</td><td> 210</td><td> 210</td>

<td>Fsk 1</td><td> -</td><td> 216</td><td> -</td><td> -</td>

<td>Fsk 2</td><td> -</td><td> -</td><td> 216</td><td> -</td>

<td>F. s. k 3</td><td> -</td><td> -</td><td> -</td><td> 216</td>

<td>Water</td><td> 310</td><td> 310</td><td> 310</td><td> 310</td>

<td>Single-layer boards</td><td>prepared</td><td colspan="2">1aboratoriossa</td><td>showe</td>

by weaving each of these preparations into 25 kg of wood chips. The plates were pressed at speeds of 10.9 and 8 sec./mm. The thickness of the plates was 17.3 mm. The temperature of the press was 200 ° C and the pressure was 35 kg / cm 2. The dimensions of the prepared plates were 40x56 cm.

The results obtained are shown in the following table and are the averages of the corresponding properties.

<td></td><td>Aihi o</td><td> 1</td><td> 2</td><td> 3</td>

<td>Density (kg / m³)</td><td> 702</td><td> 705</td><td> 700</td><td> 705</td>

<td>Flexural strength (N / mm²)</td><td> 20,0</td><td> 19,5</td><td> 19,3</td><td> 19,5</td>

<td>Internal bond strength (N / mm²)</td><td> 0,69</td><td> 0,65</td><td> 0,63</td><td> 0,60</td>

<td>2 hour thickness swelling (%)</td><td> 7,1</td><td> 7,2</td><td> 7,5</td><td> 8,0</td>

<td>24 hour thick swelling (%)</td><td> 20,9</td><td> 21,3</td><td> 22,8</td><td> 23,5</td>

<td>Free formaldehyde</td><td> 14,4</td><td> 8,0</td><td> 6,4</td><td> 4,0</td>

<td>(mg / 100 g dry plate)</td><td></td><td></td><td></td><td></td>

<td>% Reduction in formaldehyde</td><td> -</td><td> 44,4</td><td> 55,6</td><td> 72,2</td>

<td>The results presented show that</td><td colspan="2">that though</td><td colspan="2">used</td>

<td>ureaformaldehyde resin gives</td><td>1evyjä,</td><td>with</td><td colspan="2">is low</td>

free formaldehyde value, ie less than 20 mg per 100 g dry sheet (actual value 14.4 mg per 100 g dry sheet), the reduction achieved with the formaldehyde-binding composition according to the invention is much higher (up to 72.2%) than previously known ( English Patent Application Publication No. 2,136,008 A) achieved with a formaldehyde-binding composition of 44.4%.

Example 2

In this example, the sheets were manufactured industrially in a Bison mono-Etage type plant. A triple sheet was made; for this reason, two different adhesive preparations, interior and surface preparations, were prepared for each plate.

The plates were made in two sets. A first set of adhesive preparations was prepared which did not contain any formaldehyde binding composition (preform); a second set was prepared using the formaldehyde binding composition of the invention (Sample 1).

The formaldehyde binding composition used was as follows:

Ethylene glycol: 200

Urea: 260

Methanol: 50

Sodium chloride: 50

Ammonium bicarbonate: 7.6

Ammonium chloride: 6

Water: 426.4

All of the above chemicals are calculated as 10% solids and amounts are given by weight.

The adhesive preparations used were as follows:

<td rowspan="2"></td><td colspan="2">The blank</td><td colspan="2">Sample 1</td>

<td>Interior kg</td><td>Surface kg</td><td>Interior kg</td><td>Surface kg</td>

<td>Urea-formaldehyde</td><td></td><td></td><td></td><td></td>

<td>65% (molar ratio F: U = 1.15: 1)</td><td> 338</td><td> 383</td><td> 314</td><td> 356</td>

<td>Hardener (ammonium chloride</td><td></td><td></td><td></td><td></td>

<td> 15 %)</td><td> 50</td><td> 5</td><td> 50</td><td> 5</td>

<td>Paraffin emulsion</td><td> 15</td><td> 10</td><td> 15</td><td> 10</td>

<td>F. s. k</td><td> -</td><td> -</td><td> 24</td><td> 27</td>

<td>Water</td><td> 17</td><td>1Q2.</td><td> 17.</td><td> 102</td>

<td>In total</td><td> 420</td><td> 500</td><td> 420</td><td> 500</td>

Three-layer boards were manufactured industrially by spraying the interior product on 275 kg of wood chips and the surface product on 200 kg of wood fibers. The plates were pressed at a speed of 7.5 sec / mm. The thickness of the plates was 17 mm. The press temperature was 200oC and the pressure was 35 kg / cm².

The results obtained are shown in the following table. The plates were tested after sandpaper grinding.

<td>Density (kg / m 2)</td><td>Aihi o 675</td><td>Sample 1 688</td>

<td>Flexural strength (N / mm²)</td><td> 16,1</td><td> 15,8</td>

<td>Internal bond strength (N / mm²)</td><td> 0,76</td><td> 0,78</td>

<td>2 hour thick swelling (%)</td><td> 7,0</td><td> 7,7</td>

<td>Free formaldehyde</td><td> 6 , 6</td><td> 3,0</td>

<td>mg / 100 g dry plate)</td><td></td><td></td>

<td>% Reduction in formaldehyde</td><td> -</td><td> 54,5</td>

Free formaldehyde was reduced in Sample 1 to the extent that the resin itself no longer released any formaldehyde. Formaldehyde emissions are as low as 3.0 mg / 100 g dry sheet; such amounts are released by the tree itself.

Example 3

In this example, plates were prepared in the laboratory.

The plates were made in two sets. The first set was a blank and was prepared with an adhesive formulation without any formaldehyde binding composition. The second set was prepared using the following formaldehyde binding composition of the invention:

Parts by weight

Polyethylene glycol 200 (Hoechst): 200

Urea: 250

N Atri chlorides: 100

Ammonia: 1.65

Ammonium chloride: 5

Water: 443.35

All ingredients in the above preparations are calculated as 100% solid. The adhesive preparations used were as follows:

<td></td><td>Aihi o</td><td>Sample 1</td>

<td></td><td>g</td><td>g</td>

<td>Ureaformaldehyde resin 65%</td><td> 3080</td><td> 2772</td>

<td>(molar ratio F: U = 1.7: 1)</td><td></td><td></td>

<td>Hardener (ammonium chloride 15%)</td><td> 400</td><td> 400</td>

<td>Paraffin emulsion 50%</td><td> 210</td><td> 210</td>

<td>Fs .k</td><td> -</td><td> 308</td>

<td>Water</td><td> 310</td><td> „310...</td>

<td>In total</td><td> 4000</td><td> 4000</td>

Single-layer boards were prepared in the laboratory by weaving each of these preparations into wood chips, was 25 kg. The plates were pressed at a speed of 8 sec / mm. the thickness was 17.3 mm. The temperature of the press was 200oC and the pressure was 35 kg / cm². The dimensions of the prepared plates were 40x56 cm.

showered it

Record jen and

The results obtained are shown in the following table:

Blank Sample 1

Density (kg / m3) 710 700

Flexural strength (N / mm2) 19.6 19.0

Internal bond strength (N / mm2) 0.76 0.75 hour thickness swelling (%) 6.2 7.8

24 hourly thickness swelling (%)

Free formaldehyde 53.1 28.3 (mg / 100 g dry plate)

% Reduction in formaldehyde - 46.7

This example proves that essentially also those di which, in principle, have di while all the others in 1ukemi.

It is possible to reduce the resin-free formaldehyde-free formaldehyde properties to remain the same