NZ206859A

NZ206859A - Formaldehyde binder for boards prepared from lignocellulosic materials

Info

Publication number: NZ206859A
Application number: NZ206859A
Authority: NZ
Inventors: E V Markessini
Original assignee: Enigma Nv
Priority date: 1983-02-07
Filing date: 1984-01-17
Publication date: 1986-09-10
Also published as: GB8401225D0; PL144282B1; PT78066B; PT78066A; HUT34048A; DK165184B; DD232018A5; NO169848B; IL70844A0; FR2540506B1; AU570028B2; SE8400509L; DK45184D0; GB2136008A; DE3403136C2; IL70844A; CA1225630A; IT8447647A0; DK165184C; MY8700455A

Description

New Zealand Paient Spedficaiion for Paient Number £06859 2 068 59 No.: Date: Priority Date(s) Complete Specification Filed: Class: f:?.?. .. to ...

Publication Date: P.O. Journal, No ft 0 SEP (986 ; MO DBAWSII6S NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION A FORMALDEHYDE BINDER X/We, ENIGMA N.V., a Dutch company, of Handelskade 8, Curasao (Netherlands Antilles), / hereby declare the invention for which i / we pray that a patent may be granted to j&$/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by 2®) - lor 2 ©68 A Formaldehyde Binder Boards such as particleboard, chipboard and the like are prepared from lignocellulosic materials using adhesives. The preferred adhesives (or glues) are 10 based on formaldehyde, such as urea-formaldehyde, me- lamine-formaldehyde, phenol-formaldehyde and resorcinol-formaldehyde resins or mixtures thereof. It is a well-known fact that boards prepared using these adhesives have a formaldehyde odour which is both harmful and un-15 pleasant. Formaldehyde is emitted both during the production of such boards and during their storage and final use.

Many methods of avoiding the emission of formaldehyde have been proposed, but all of them are either 20 ineffective or reduce the properties of the boards or require complicated application procedures. Some of these procedures involve spraying or spread coating the warm boards coming out of the press with various solutions, such as solutions of urea and/or ammonia or of ammonium 25 salts. Generally, these types of methods are not desirable for industrial application because they require additional process steps and anyway are not very efficient.

Other methods involve the use of very complica-30 ted mixtures of a large number of components, some of which are natural glues. These products also are not very efficient. One handicap thereof is the fact that the properties of natural products are not constant. 206859 Another way of reducing the content of free formaldehyde involves the use of an aqueous suspension of urea prills coated with a special wax. This method, too, requires a separate feeding line, because the product is not 5 added to the adhesive formulation itself.

An object of the present invention is to provide a formaldehyde binder which effectively reduces the formaldehyde odour without reducing the properties of .the board, without changing the reactivity of the 10 adhesive formulations and without requiring any additional steps in the production of particleboard, plywood or blockboard.

The invention provides a formaldehyde binder when for use in boards prepared from lignocellulosic ma-15 terials using adhesives based on formaldehyde, which comprises a solution of (a) at least one organic hydroxy compound with the exception of monohydric aliphatic alcohols and (b) at least one amide in water. The formaldehyde binder can also contain (c) an organic compound which acts as a solvent for (a) and (b) and also reacts with formaldehyde and/or (d) an inorganic compound soluble in water. The organic compound (c) is preferably a monohydric aliphatic alcohol. The inorganic com-25 pound (d) is preferably a halide salt. Even if the individual components are not soluble in water, they may dissolve in water if a mixture thereof is heated in water to 70 °C.

Preferably the organic hydroxy compounds [cora-30 ponent (a)] are soluble in water or in C1_4 monohydric aliphatic alcohols. Examples of such preferred hydroxy compounds -are the dihydric, trihydric and pentahydric alcohols containing up to 6 carbon atoms, the monosaccharides containing up to 6 carbon atoms, the di- f* is 206859 saccharides containing up to 12 carbon atoms and the polysaccharides having an Ostwald viscosity up to 200 mPas at 25 °C and a concentration corresponding to 37 % refraction. Other examples of preferred hydroxy compounds are the 5 aromatic alcohols and phenols, which preferably are used alone or in combination with one or more of the above-mentioned dihydric, trihydric and/or pentahydric alcohols and/ or monosaccharides, disaccharides and/or polysaccharides. The phenols and aromatic alcohols can be monohydric or 10 polyhydric phenols and monohydric or polyhydric aromatic alcohols containing one benzene ring.

Specific examples of suitable organic hydroxy compounds are monoethyleneglycol, diethyleneglycol, 15 glycerine, pentaerythritol, fructose, mannose, sorbitol, dextrose, sucrose, maltose, lactose, dextrin, phenol, resorcinol, hydroquinone and the like.

Preferably the amides [component (b)] used in the formaldehyde binder of the invention are likewise soluble 20 in water or in monohydric aliphatic alcohols. Parti cularly preferred are the aliphatic amides containing up • to 6 carbon atoms and the aromatic amides containing one benzene ring.

Suitable examples of amides are urea, thiourea, formamide, acetamide, .benzamide, oxamide, succinamide, malonamide and the like.

If desired, to enhance solubility, the formaldehyde 30 binder of the invention can additionally contain additives '^2) [component (c)] which are C1_4 monohydric aliphatic alco hols such as methanol, ethanol, isopropanol and the like.

A cheaper and more efficient formaldehyde binder * - i, - 206859 is obtained if 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, are added.

The ratio of organic hydroxy compound [component (a) and component (c), if present] and inorganic compound [component (d), if present] to amide [component (b)] 1 is preferably 10:100 to 400:100, particularly 10:100 to 10 200:100, by weight. The formaldehyde binder of the invention can be added to the usual glue formulations in quantities varying from 1 to 10 %3 preferably 3 to 7 %, of form-—> aldehyde binder solids, based on the weight of the liquid resin containing 65 % by weight of resin solids.

. The formaldehyde binder of 'the invention may contain 20 to 80 % by weight, preferably 50 to 70 % by weight, of the active ingredients [components (a) and (b) and components (c) and/or (d), if present]. The water con-20 tent of the formaldehyde binder depends on the solubility of the active ingredients and the amount of water which can be tolerated in the glue formulations.

The formaldehyde binder of the invention can be 25 produced by simply adding the active ingredients and water to a mixer and mixing until the active ingredients are dissolved. This can be done at room temperature or at an elevated temperature up to 70 °C.

The formaldehyde binder of the invention may be used whenever boards are prepared from lignocellulosic materials using adhesives based on formaldehyde, such as urea-formaldehyde, melamine-formaldehyde, phenol-formaldehyde or resorcinol-formaldehyde resins or mix- tures thereof.

When using the formaldehyde binder of the invention, it is possible to produce boards actually containing 5 less than 10 mg of free formaldehyde per 100 g , of the dry board, as determined by the F.E.S..Y.P. (Federation Euro-i p£enne des Syndicats des Fabricants de Panneaux de Par-;ticules) perforator method No. EN 120.

I The amount of the free formaldehyde reduction 'depends on many factors and, therefore, can vary widely. If the emission of free formaldehyde is high (higher than 50 mg of formaldehyde per 100 grams of dry board), the reduction can be as high as up to 60 to 85 %. If the emission 15 of free formaldehyde is relatively low, i.e. 20 to 50 mg of free formaldehyde per 100 g of the dry board, the maximum reduction is usually 50 to 60 %. The amount of reduction obtained also depends on the amount of formaldehyde binder used: The more formaldehyde binder is 20 used, the lower is the amount of free formaldehyde.

When the active ingredients of the formaldehyde binder are used in combination with each other, the free formaldehyde reduction is surprisingly much higher than 25 the sum of the effects of the separate components, and they have no adverse effect on the reactivity of the glue formulation or the properties of the boards.

G The following examples illustrate the invention. Parts and percents are by weight. 2 068 59 Example 1 In this example the organic compound containing hydroxyl groups is glycerine and the amide is urea. Here, there is illustrated the synergistic toes' haviour of these two compounds. Various glue formulations are prepared and each is used subsequently in order to produce particleboard.

The control does not include any of the 10 components of the formaldehyde binder according to the invention. Sample 1 includes both glycerine and urea, sample 2 includes only glycerine and sample 3 includes only urea.

It is noticed from the tables reported here below that glycerine when used on its own (sample 2) is a very efficient formaldehyde binder, but urea (sample 3) gives a poorer formaldehyde reduction and lower mechanical values and water resistance, however, 20 when urea is used in combination with glycerine (sample 1), it gives values that are equivalent to those of glycerine on its own.

We may therefore use a cheaper and less 25 efficient product (urea) and make it react as effec-tively as a more expensive and more efficient product (glycerine). The efficiency refers to formaldehyde absorbing capacities as well as to maintaining good mechanical properties and water resistance without 30 changing the reactivity of the glue formulation and without the need to introduce any special apparatus for its use.

Formaldehyde reduction actually is in this 2 068 n /~S O"' case 46 %.

The formulations of the various samples ■ used are as follows: 1 parts by 2 parts by 3 parts by weight weight weight Glycerine (100 %) 270 590 - Urea (100 %) 320 - 590 Water 410 1000 410 1000 410 1000 % solids 59 59 59 The glue formulations used are as follows: Control grams 1 grams 2 3 grams grams Urea-formalde hyde resin 65 % ' 3077 3077 3077 3077 (Molar ratio F:U 1.27=1) Hardener 400 400 400 400 (Ammonium chloride *) Paraffin emulsion 50 % 250 250 250 250 Ammonia 25° Baume :.

Sample 1 - 308 Sample 2 Sample 3 Water 268 - 308 308 Total 4000 4040 404-0 404 0 Gel time in sees. 68 68 71 62 Single-layer boards are prepared in the laboratory by spraying each of these formulations onto kgs wood chips. Boards are pressed at 10, and 9 and 8 sees./mm. The thickness of the boards is 17.3 nuns.

The temperature of the press is 200 °C and the pressure 2 is 35 kg/cm . The dimensions of the boards produced are 40 x 56 cms.

The results obtained are reported in the 10 following table and are average values.

Control 1 2 3 Density (kg/m^) 683 66 9 663 657 2 Bending strength (N/mm ) 19. 9 18. 1 17 • 3 16 .3 2 Tensile strength (N/imn ) 0. 73 0. 72 0 .71 0 .63 2 hr. thickness swelling ( .%) 5. 2 4. 9 4 -5 .4 24 hr. thickness swelling ( 1—1 in tjs. 4 49. 9 47 .4 53 .1 Free formaldehyde . 8 8. 8 • 7 11 • 7 (mg/100 g dry board) Example 2 This is another example illustrating the synergistic behaviour of glycerine and urea in reducing the free formaldehyde of particleboards while main-25 taining the mechanical properties of the boards and the water resistance as well.

The control does not include any of the components of the formaldehyde binder according to the 30 invention,! Sample 1 contains both components of the formaldehyde binder according to the invention and sample 2 contains only one of the two components (the most efficient of the two components).

It is noticed here again that only sample 1 gives free formaldehyde that is below 10 mg/100 g. dry board (which is the desir ed level for El class) and is the only one to have absolutely equivalent mechanical properties and water resistance. Formaldehyde reduction actually is 34 %.

The formulations of the various samples used are as follows: 1 2 parts by weight parts by weight Glycerine (100 %) 2.28 128 Urea (100 %) 424 - Water 448 872 % solids 1000 55.2 1000 12.8 The glue formulations used are as follows Control 1 grams grams Urea formaldehyde resin 65 % (Molar ratio F:U = 1.27:1) Hardener (Ammonium chloride %) Paraffin emulsion 50 % Ammonia 25° Baume Sample 1 Sample 2 Water Total Gel time in sees. 3077 400 250 5 268 4000 66 3077 400 250 5 268 4000 67 2 grams 3077 400 250 - 5 268 4000 69 Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 kgs wood chips. Boards are pressed at 10, 9 and 8 sees./mm. The thickness of the boards is 17-3 mms. The temperature of the press is 200 °C and the pressure 2 is 35 kg/cm . The dimensions of the boards produced are 40 x 56 cms.

The results obtained are reported in the following table and are average values.

Control 1 2 Density (kg/m^) 685 684 687 O Bending strength (N/mm ) . 7 . 6 19. 4 2 Tensile strength (N/mm ) 0. 7^ 0. 73 0. 67 2 hr. thickness swelling (*) 11. 0 7- 9 8. 6 2 4 hr. absorption (#) 23. 23- 2 23. 7 Free formaldehyde 14. 3 9. 12. 3 (mg/100 g dry board) Example 3 This example illustrates the efficiency of mono-ethyleneglycol together with urea as a formaldehyde binder.

Two formulations are prepared: the control without any of the ingredients of the formaldehyde binder according to the invention and sample 1 which includes both monoethyleneglycol and urea.

Boards are produced from these two glue formulations and it is proved here, too, that with the formaldehyde binder according to our invention we obtain with a urea-formaldehyde resin that gives V 59 f ) normally boards classified as E 2 (control), boards classified as E 1 (sample 1).

The formaldehyde reduction is in this case 37 %.

The formulation of sample 1 used is as follows Sample 1 parts by weight Monoethyleneglycol 100 % J>60 Urea 100 % 365 Water 275 1000 % solids 72.5 The glue formulations used are as follows: • Control 1 grams grams Urea formaldehyde resin 65 % 3077 3077 (Molar ratio F:U = 1.27:1) Hardener 400 400 (Ammonium chloride 15 %) Paraffin emulsion 50 % 250 250 Ammonia 25° Baume 5 5 Sample 1 - 268 Water 268 Total 4000 4000 Gel time in sees. 66 60 Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 legs wood chips. Boards are pressed at 10, 9 and 2 068 n 8 sees./mm. The thickness of the boards is 17-3 rams.

The temperature of the press is 200 °C and the pressure 2 is 35 kg/cm 40 x 56 mms. 2 is 35 kg/cm . The dimensions of the boards produced are The results obtained are reported in the following table and are average values.

Control 1 Density (kg/m ) 685 684 O Bending strength (N/mm ) 20.7 20.2 ^ Tensile strength (N/mxn^) 0.74 0.74 —'' 2 hr. thickness swelling (%) 11.0 8.6 24 hr. absorption (%) 23-5 22.6 Free formaldehyde , 14.3 9.0 (mg/100 g dry board) Example 4 - In this example we are illustrating the 20 synergistic behaviour of monoethyleneglycol and urea.

Boards are prepared from three different formulations: the control wherein no ingredients of the formaldehyde binder according to the invention 25 are used, sample 1 wherein both ingredients wJ of the formaldehyde binder of the present invention are used and sample 2 wherein only one ingredient is used.

It is obvious from the results obtained and 30 reported here in below that sample 1 containing both ingredients is much more effective than sample 2 containing only one ingredient (the most efficient of the two ingredients). 2 068 The formaldehyde reduction obtained in this case is 32 %.

The formulations of the various samples used 5 are as follows: o Monoethyleneglycol 100 10 Urea 100 % Water % solids 1 -2 parts by weight parts by weight, 230 580 ° -420 420 1000 58 1000 58 The glue formulations are as follows: o Control 1 grams grams Urea formaldehyde . 3077 3077 resin 65 % (Molar ratio F:U = 1.27:1) Hardener 400 400 (Ammonium chloride 15 %) Paraffin emulsion 50 % 250 250 Ammonia 25° Baume 5 5 Sample 1 - 268 Sample 2 - Water 268 - Total 4000 4000 Gel time in sees. 70 71 2 • grams 3077 400 250 5 268 4000 76 Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 kgs wood chips. Boards are pressed at 10, 9 and _ in _ 206859 8 sees./mm. The thickness of the boards is 17-3 mms. The temperature of the press is 200 °C and the pressure is 35 kg/cm . The dimensions of the boards produced are 40 x 56 mms.

The results obtained are reported in the following table' and are average values.

Control 1 2 Density (kg/m^) 688 688 687 Bending strength (N/mm ) 17 .6 17- 6 17- 2 Tensile strength (N/mm ) 0 .55 0. 60 0. 56 2 hr. thickness swelling ( :%) 6 • 7 4. 9 4. 7 24 hr. absorption {%) .1 . 1 19.

Free formaldehyde (mg/100 g dry board) .0 . 3 12. 3 Example 5 In this example the use of a resin of diffe-20 rent molar ratio is illustrated as well as various levels of addition .of the formaldehyde binder itself.

The formaldehyde binder used has the following formulation: Glycerine 100 % Urea 100 % Water % solids parts by weight 270 318 412 1000 -58.8 The glue formulations used in the various samples are as follows: 2 ©68 • m - 15 Control 1 2 3 grams. grams grams gram Urea formaldehyde resin 65 % 3077 3077 3077 3077 (Molar ratio F:U = 1.4:1) Hardener 293 380 380 380 (Ammonium chloride 15 %) Paraffin emulsion 50 % 250 250 250 250 Ammonia 25° Baume Formaldehyde binder - 154 215 375 Water 375 134 73 - Total 4000 4000 4000 4087 Gel time in sees. 73 73 72 75 Single-layer boards are prepared in the 15 laboratory by spraying each of these formulations onto 25 kgs wood chips. Boards are pressed at 10, 9 and 8 sees./mm. The thickness of the boards is 17*3 mms. The temperature of the press is 200 °C and the pressure is 35 kg/cm . The dimensions of the boards produced 20 are 40 x 56 cms.

Control 1 2. 3 3 Density (kg/m ) 680 687 685 688 0 Bending strength (N/mm ) 22. 0 22 • 5 22. 3 21 .6 p Tensile strength (N/mm .) 0. 61 0 .63 0. 66 0 .64 2 hr. thickness swelling (,%) . 1 9 • 3 8. 8 9 • 5 24 hr. thickness swelling {%) . 6 21 .8 21. 0 21 .5 Free formaldehyde 22. 2 13 .0 . 1 9 .5 (mg/100 g dry board) It is noticed that the mechanical properties 206^3® and water resistance of' the boards are equivalent and the formaldehyde reduction is 4l % in case of sample 1, 55 % in case of sample 2 and 57 % in case of sample 3- Example 6 In this example six different types of poly-alcohols are illustrated, two different types of amides, one additive and a variation in the ratio of alcohol to amide covering a range from 57*5/100 to 385/100.

The various types of formaldehyde binder used are as follows: <u O 1 2 3 Dextrose 230 - - Diethyleneglycol Monoethyleneglycol - ' - 260 Glycerine • - .. - - Sucrose - - - Sorbitol - - - Methanol - - 200 Urea 400 300 - Thiourea - ■ - 170 Water 370 370 370 Total 1000 1000 1000 % solids 63 63 63 Weight ratio of alcohol/amide 57.5/100 110/100 270/11 o 3 4 6 - tm 110 500 - - 140 - - 140 80 130 350 330 370 370 370 1000 1000 1000 63 63 63 385/100 80/100 91/100 m All above-mentioned figures are in parts by weight.

The glue formulations used in the various 5 samples are as follows: 2 068 59 o o Urea-formaldehyde resin 65 % (Molar ratio F:U = 1.27:1) Hardener (Ammonium chloride 15 % solution) Paraffin emulsion 50 % Ammonia 25° Baum^ Formaldehyde binder Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Water Total .

Gel time in sees.

Control 1 grams grams 3077 3077 400 500 . 250 250 5 307 268 .4000 4134 65 66 O o 3 2 3 4 5 6 grams grams grams grams grams 3077 3077 3077 3077 3077 500 500 500 500 500 250 250 250 250 250 307 307 307 307 \o 307 - - . i i 4134 4134 4134 4134 4134 j 65 67 *66 62 69 o Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 kgs wood chips. Boards are pressed at 103 9 and 8 sees./mm. The thickness of the boards is 17-3 mms. The temperature of the press is 200 °C and the pressure 2 is 35 kg/cm . The dimensions of the boards produced are 40 x 56 cms.

The results obtained are reported in the following table and are average values. (. 0 Control 1 Density (kg/m^) 688 689 2 Bending strength (N/mm ) 19.6 19-5 Tensile strength (N/mm^) 0.71 . O.69 2 hr. thickness swelling (5?) 7.0 6.5 24 hr. thickness swelling (%) 19.7 19.3 Free formaldehyde lb.1 8.9 (mg/100 g dry board) Formaldehyde reduction % - 45 o 0 23456 687 685 690 685 692 18.3 19.5 20.1 19.3 19.4 0.67 0.73 0.7^ 0.72 0.70 .0 5.5 6.1 . 6.5 6.2 .0 19.8 19-5 20.1 19-9 8.6 11.0 9.0 9.8 8.5 47 32 44 39 ^7 .JJ. 2 £ The above-mentioned results prove that all samples used have values equivalent to the control and that the formaldehyde reduction is of the order of 32 to 47 %.

Example 7 In this example three different types of organic compounds containing hydroxyl groups are exemplified by means of dextrin, phenol and resor-cinol.

One monohydric alcohol acting as an additive other than methanol is also illustrated, namely ethyl alcohol.

The various types of formaldehyde binder used are as follows: W o 1 2 3 4 Monethyleneglycol Dextrin Phenol Resorcinol 230 140 130 .130 Methanol - 140 130 130 Ethanol 80 - - - Urea 350 350 370 . 370 Water 340 370 370 370 1000 1000 1000 1000 % solids 66 63 63 63 All above-mentioned figures are in parts by weight. The formaldehyde binder samples are used in this example to substitute a part of the resin used. 2 063 59.

The glue formulations actually used are as follows: 400 Urea formaldehyde resin (Molar ratio F:U = 1.27:1) Hardener (Ammonium chloride 10 15 % solution) Paraffin emulsion 50 % 250 Ammonia 25° Baum^ 5 Formaldehyde binder Sample 1 15 Sample 2 Sample 3 Sample 4 Water 268 Total Gel time in sees.

Control 1 2 grams grams grams 3077 2770 2770 4000 65 500 400 250 ' 250 307 307 3827 64 3727 62 3 grams 2770 450 4 grams 2770 400 250 250 307 3777 63 307 3727 63 o Single-layer boards are prepared in the laboratory by spraying each of these formulations onto kgs wood chips. Boards are pressed at 10, 9 and 8 sees./mm. The thickness of the boards is 17-3 mms.

The temperature of the press is 200 °C and the pressure 2 is 35 kg/cm . The dimensions of the boards pressed are 40 x 56 cms.

Density (kg/m^). 2 Bending strength (N/mm ) p Tensile strength (N/mm ) 2 hr. thickness swelling {%) 24 hr. thickness swelling (50 Free formaldehyde (mg/100 g dry board) Formaldehyde reduction (%) Control 702 20.1 0.75 7.1 20.3 13.1 698 695 705 710 19-5 19.7 .0 .8 0.70 0.75 0.73 0.72 6.8 6.5 6.3 6.6. 21.5 21.3 21.8 21.3 9.6 9.2 8.2 27 30 37 24 n - -25 " The above-mentioned results prove that all samples have values that are equivalent to the control sample that contains no formaldehyde binder even though the latter substitutes an equivalent amount of urea-5 formaldehyde resin in the formulation. The formaldehyde reduction varies in this example from 24 to 37 %. .

Example 8 In this example one type of formaldehyde 10 binder is used and the resin is based on phenolize lamine -urea formaldehyde resin.

The formaldehyde binder used has the following formulation: parts by weight Monoethyleneglycol 300 Urea 330 Water 370 1000 The glue formulations used are as follows: Control j ■' grams grams 25 Phenol-melamine-urea-formal- dehyde resin 63 % 56OO 5600 Hardener (solution in water •of 15.5 % ammonium chloride) 840 840 Paraffin emulsion 50 % 150 150 Formaldehyde binder - 560 Total 6590 7150 Gel time in sees. 73 79 206850 Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 kgs wood chips. Boards are pressed at 10, 9 and 8 sees./mm. The thickness of the boards is 17-3 mms. 5 The temperature of the press is 200 °C and the pressure is 35 kg/cm2 . The dimensions of the boards produced are 40 x 56 cms.

Control 1 3 Density (kg/m ) 705 695 2 Bending strength (N/mm ) 26 .2 . 9 2 Tensile strength (N/mm ) 0 -.27 0, 26 Tensile strength V100 (N/mm^) 2 .7 2. 6 2 hr. thickness swelling (%) 7 .1 6. 2 2M hr. thickness swelling (%) 12 .0 11. 3 Free formaldehyde (mg/100 g dry board) 12 .8 7 Formaldehyde reduction (%) - 45 The above-mentioned results prove that the formaldehyde binder according to the present invention 25 can be used also for phenol-melamine-urea-formaldehyde resins reducing considerably the free formaldehyde emission without adversely affecting the properties of the boards. 206859 Example 9 In this example the formaldehyde binder used includes an inorganic compound [component (d)]3 illustrated in this case by sodium chloride.

The formaldehyde binder used has the following formulation: Parts by weight Monoethyleneglycol 100 % 270 Urea 100 % 318 Sodium chloride 100 % 50 Water . 362 • Total % solids 1000 63.8 o Urea-formaldehyde resin (Molar ratio F:U=1.27:1) Hardener 25 (Ammonium chloride 15 % solution) Paraffin emulsion 50 % Ammonia 25° Baum£ Formaldehyde binder Water Total Gel time in sees. 4000 65 grams 2770 The glue formulations used in the various samples are as follows: 20 Control 1 grams 3077 400 250 5 268 450 250 307

Claims

a 10 68 5 9 - 28 - Single-layer boards are prepared in the laboratory by spraying each of these formulations onto 25 kg wood chips. Boards are pressed at 10, 9 and 8 secs/mm. The thickness of the boards is 17• 3 nuns. The temperature of the press is 2 200 °C and the pressure is 35 kg/cm . The dimensions of the boards pressed are 40 x 56 cms. The results obtained are reported in the following table and are average values. Control 1 Density (kg/m^) 695 699 2 Bending strength (N/mm ) 19*9 19.5 Tensile strength (N/mm^) 0.71 0.73 15 2 hr. thickness swelling (%") 7.0 6.6 24 hr. thickness swelling (%) 20.5 20.8 Free formaldehyde (mg/100 g dry board) 17 9.5 Formaldehyde reduction (5?) - 44 20 The results prove that the sample including the formaldehyde binder gives values that are equivalent to the control sample in spite of the fact that the formaldehyde binder substitutes a part of the urea-formaldehyde, resin in 25 the formulation. The formaldehyde reduction is 44 %. 30 ^ B n - 29 - what//we claim is: -M- 10

1) A formaldehyde binder when for use in boards prepared from lignocellulosic materials using adhesives based on formaldehyde, which comprises a solution of (a) at least one organic hydroxy compound with the exception of C1_4 monohydric aliphatic'*alcohols and (b) at least one amide in water.

2) The formaldehyde binder of claim 1 which, in addition, contains (c) an organic compound which acts as a solvent for (a) and (b) and also reacts with formaldehyde. 15

3) The formaldehyde binder of claim 2 wherein (c) is a aliphatic monohydric alcohol.

4) The formaldehyde binder of any one of claims 1 to 3 which, in addition, contains (d) an inorganic compound 20 soluble in water.

5) The formaldehyde binder of claim 4 wherein (d) is a water-soluble halide salt. 25

6) The formaldehyde binder of claim 5 wherein (d) is a water-soluble halide of an alkali metal or an alkaline earth metal.

7) The formaldehyde binder of claim 6 wherein (d) is 30 sodium chloride, potassium chloride or calcium chloride.

8) The formaldehyde binder of any one of claims 1 to 7 wherein component (a) is soluble in water or in a monohydric aliphatic alcohol. - 30 - 206850

9) The'formaldehyde binder of claim 8. wherein component (a) is selected from dihydric, trihydric and pentahydric alcohols containing up to 6 carbon atoms, monosaccharides containing up to 6 carbon atoms, di-5 saccharides containing up to 12 carbon atoms and polysaccharides having an Ostwald viscosity up to 200 mPas at 25 °C and a concentration corresponding to 37% refraction,

'10) The formaldehyde binder o-f claim 8, wherein 10 component (a) is selected from aromatic alcohols and phenols.

^ 11) The formaldehyde binder of claim 10, wherein component (a) is selected from monohydric and poly-15 hydric aromatic alcohols containing one benzene ring and monohydric and polyhydric phenols. \

12) The formaldehyde binder of any one of claims 1 to 11 wherein component (b) is soluble in water or in a 20 C2_4 monohydric aliphatic alcohol.

13) The formaldehyde binder of claim 12, wherein component (b) is selected from aliphatic amides containing up to 6 carbon atoms and aromatic amides containing 25 one benzene ring. O

14) The formaldehyde binder of any one of claims 1 to 13, characterized in that the ratio by weight of component (a) plus components (c) and (d), if present/ to 30 component (b) is 10:100 to 400:100.

15) The formaldehyde binder of any one of claims 1 to 14, characterized in that it contains 20 to 80 % by weight of the active ingredients. - 31 - 206859

16) The formaldehyde binder as claimed in claim 1 substantially as hereinbefore described in any of theExamples.

17) .A process for preparing the formaldehyde binder as claimed in claim 1, wherein (a) at least one organic hydroxy compound .with the exception of monohydric aliphatic alcohols-, (b) at least one amide and '(c) optionally at least one organic cpmpound which acts as a solvent for (a) and (b) and also reacts with formaldehyde and (d) optionally an inorganic compound soluble in water and water are mixed at a temperature from room temperature to 70°C. *

18) A process as claimed in claim 17 wherein (c) is a C1_^ monohydric aliphatic alcohol.

19) A process as claimed in claim 17 or 18 wherein (d) is a water-soluble halide salt.

20) A process as claimed in claim 19 wherein (d) is a water-soluble halide of an alkali metal or an alkaline earth metal.

21) A process as claimed in claim 20 wherein (d) is sodium chloride, potassium chloride or calcium chloride.

22) A process according to any one of claims 17 to 21 wherein component (a) is soluble in water or in a monohydric aliphatic alcohol.

23) A process according to claim 22, wherein component (a) is selected from dihydric, trihydric and - 32 - 206859 pentahydric alcohols containing up to 6 carbon atoms, monosaccharides containing up .to 6 carbon atoms, di- . saccharides containing up to 12 carbon atoms and polysaccharides having an Ostwald viscosity up to 200 mPas at 25 °C and a concentration corresponding to 37% refraction.

24) A process according to claim 22, wherein component (a) is selected from aromatic alcohols and phenols. .

25) A process according to claim 24, wherein component (a) is selected from monohydric and poly-hy-dric aromatic alcohols containing one benzene ring and monohydric and polyhydric phenols.

26) A process according to any one of claims 17 to 25* wherein component (b) is soluble in water or in monohydric aliphatic alcohols.

27) A process according to claim. 26wherein com- • ponent (b) is selected from aliphatic amides containing up to 6 carbon atoms and aromatic amides containing one benzene ring.

28) A process according to any one of claims 17 to 273 characterized in that the ratio by weight of component (a) plus components (c) and (dj, if present, to component (b) is 10:100 to 400:100.

29) A process according to any one of claims 17 to 28, characterized in that the formaldehyde binder contains 20 to 80 % by weight of the active ingredients.

3'0) A process for preparing boards from lignocel-lulosic materials using an adhesive based an formaldehyde, - 33 - 2 OGg 59' wherein a formaldehyde binder according to any one of claims 1 to 16 is added to the adhesive.

31) A process as claimed in claim 30 substantially 5 as hereinbefore described in the Examples.

32) Boards when produced by a process as claimed in claim 30 or claim 31. n 10 bated THK I DKr OF a. j. par PER 15 Q /* L a. £ % V* P