DD149182A1 - PREPARATION OF WOODEN MATERIALS WITH VERY LOW FORMALDEHYDE LEAVES - Google Patents

Abstract

The invention relates to a process for the production of wood-based materials with very low formaldehyde release by additions to the wood raw material or to the binder. The aim of the invention was the development of a process that allows the production of wood materials with very low formaldehyde release with reduced economic outlay and extended application options over known solutions. According to the novel process, which is characterized by the addition of formaldehyde-containing condensation products of formaldehybindenden monomers and aldehydes, optionally in conjunction with formaldehybindenden monomers to wood raw material or binder, koenen wood materials can be produced with very low Formaldehydabge with reasonable economic effort in a technically and technologically simple manner ,

Description

-a- 219127

VEB Leuna-Werke: Merseburg

(! Walter Ulbricht Il. DC. Hin. / Ba.

LP 79113

Title of the invention

Production of wood-based materials with very low formaldehyde release

Field of application of the invention

The invention relates to the production of woodworking substance · η with very low formaldehyde release, which by Verleimunr; -Ntsprechender raw materials with condensation product on from urea and / or melamine and / or phenol and formaldehyde, optionally in admixture with another aldehyde produced.

Characteristic of the known technical solutions

It is known that condensation products of formaldehyde with urea or melamine release formaldehyde both during the curing process and after its completion. In particular, the release of formaldehyde from the glued material, which may be caused by residual free or hydrolytically formed formaldehyde, is of extreme importance to the processors and consumers of such materials, as it can lead to health problems. It is furthermore known that the subsequent formaldehyde release from wood-based materials can be achieved by the pre-treatment of the material to be glued. Wood raw materials with an aqueous dispersion

• w 2 ···

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a water-dispersible polymer or wax and a water-compatible agent for binding of pormaldehyde can be reduced by 50-75 % . Despite the considerable advantages of this procedure compared to earlier attempts to reduce the Nachlageglichen formaldehyde release from wood materials turned out to be disadvantageous that, for example, in chipboard production, due to the composition and amount of the additional products, a significant increase in costs occurs. A further disadvantage consists in the fact that the effect of the additional product at its projection is bound to the wood raw material and that the method can thus be used without changing it only for a part of the installations which are normally used for the production of chipboard boards (DE-AS-2 740 207). ·

Object of the invention

The aim of the invention is to produce wood materials with very low formaldehyde release with reduced economic effort and cost extended applicability.

Explanation of the essence of the invention

The object was to develop a process for the production of wood-based materials with very low Pormaldehydabgabe that the cost of material manufacturing does not increase decisively and is universally applicable. This object is achieved by a process for the production of wood materials with very low Pormaldehydabgabe, preferably wood chip boards by gluing appropriate raw materials, preferably wood chips, with condensation products of urea and / or melamine and / or phenol and formaldehyde, optionally in admixture with another aldehyde , prepared v / earth, according to the invention solved by the fact that the wood raw material to be glued or the binder for Pormaldehydaufnähme suitable condensation products au3 formaldehyde-binding monomers, preferably urea,

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Melamine or phenol and aldehydes, preferably formaldehyde, optionally in combination with a formaldehyde-binding monomer.

The condensation products of urea and / or melamine and / or phenol used in the context of the invention for gluing are the usual products used as binders, in particular for the production of wood-based materials, which are commercially available both as aqueous solutions and as powders. For condensates, formaldehyde and urea, the molar ratio of these compounds is usually between 1.2 and 1.7. Even if the condensate contains other constituents, such as Contains melamine, phenol or melamine and phenol or other aldehydes as formaldehyde, the ratio between the carbonyl group and the group responsible for this reaction usually remains in the range that underlies the stated molar ratio of formaldehyde / urea.

The inventive condensation products used for the production of wood materials with very low formaldehyde release from formaldehyde-binding monomers, v / ie z.i3. Urea, melamine or phenol, and formaldehyde or other aldehydes have a reduced ratio between the carbonyl group and the moiety it is capable of reacting with in comparison to the common sizes. e.g. is the molar ratio of urea / formaldehyde condensates, which are used for the production of wood chip boards with very low formaldehyde release, suitably between 1: 0.3 and 1: 1.0. In addition, if the amount of formaldehyde is reduced, strength losses of the chipboard can not be ruled out given otherwise identical bonding conditions. Increasing the formaldehyde content above the stated value would require larger amounts of the condensation product to achieve comparable effects, but these can be reduced by the simultaneous addition of a formaldehyde-binding monomer.

The production of formaldehyde-binding condensation products' takes place differently depending on the starting materials.

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An essential prerequisite for the usability of the condensation products is in addition to the formaldehyde binding their storage stability. The experiments described in the examples were carried out with products which are not commercially available. The formaldehyde-binding condensation products can be added to both the binder and the raw material to be glued. Based on the production of chipboard, this results in the possibility of either adding the condensate to the binder or gluing liquor intended for gluing or to inspect the unembellished chutes. The amount of additive depends on the release of pormaldehyde of the binder used and the size of the desired effect. V / erden eg Spariplattenleime with PESYP-Pormaldehyd value of 0.06 and 0.03 % used as a binder, so to achieve the same Sndwertes the Formaldehydabgabe for the former glue, the larger amount of the inventive additional product is required.

Ausfuehrungsbeispiele

Example 1 (comparative example)

From a commercial Plarnstoff / Pormaldehyd binder is a glue liquor of the composition

Glue 100 kg

Water 25 kg

paraffin emulsion

(40%) 6 kg

15% EH ₄ C1 solution4 kg

prepared and applied in a quantity of 8 % resin, based on atro wood, on jaw cutting edges (length: 15-20 mm, width: 3-5 min, thickness: 0.2-0.4 mm). The glued holes will be under the conditions.

Pressing temperature 16O-65 ° C Pressing pressure 1.5 N / mm

Press time 7 min.

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made into chipboard of 20 mm thickness, which follows the following properties determined by conventional methods

point:

Density g / cm

Bending strength N / mm

Transverse tensile strength V 20 N / mm swelling after 2 h % pormaldehyde release PESYP %

0.610 25.1 0.63 3.3 0.035

Example 2

A urea / pormaldehyde condensate of molar ratio 1: 0.5 is used in the production of chipboard molding example 1. Deviating from Example 1 conditions and the results of the test contains Tab. 1.

Table 1:

% per

Add the atro wood additive

Glue zu (resin) sat2

Density g / cm

Characteristics of particleboard

Bending transverse swelling FESYP-

tightened after 2 h formal

keitp solid-dehyd

N / mm keitp% N / mm

Protrusions 8 2.3 0.611

Plot 8 2.3 0.612

Plot 6.6 2.3 0.614

Example 3

25 3 0 65 3 , 4 25 9 0 64 3 , 5 24 5 O, 60 3

<0.01 <0.01 <0.01

A mixture of 40 Ma. % Glue according to Example 1, 40 Ma. ~% Urea and 20 Ma. ~% Water is used in particle board production according to Example 1 as an additional product. Deviating from Example 1 conditions and the results of the test contains Tab. 2.

Table 2:

% per. ·

Addition of the atro wood characteristic of the chipboard ₍ additional

Glue To- Density Bending- Transverse swelling PESYP (Resin) set g / cnr tighten- after 2h Porm-

strength ₉ . aide-N / mnT kerU hyd /%

Projections 8 2.4 0.607 26.2 0.67 3.1 0.01 Projections 7.4 2.4 0.607 24.9 0.61 3.3 0.01

Example 4

A condensate product of molar ratio 1: 0.7 prepared from phenol and 37% aqueous formaldehyde solution in an alkaline medium is dissolved with urea so that the molar ratio of phenol to urea is 1: 0.5. The product obtained is used in chipboard production according to Example 1 in an amount of 2.2 % per dry span for spraying the chips prior to their gluing. The chipboards produced in this way have the following properties:

Density g / cnr _? 0.604

Bending strength N / mm ₂ 25.2 Transverse tensile strength N / mm 0.62

Swelling after 2 h Ma .-% 3.7

Formaldehyde delivery PESYP Ma. -% 0.01

Example 5

A mixture of 70 Ma. -% of a melamine / pormaldehyde condensation product (56.8% by weight of pesticide) of molar ratio 1: 1.7 and 30 Ma. -% urea is used in chipboard production according to Example 1 as an additive for spraying the chips (3 »3 % per dry chip). The chipboards produced in this way have the following properties:

Density g / cnr ₂ 0.610

Bending strength N / mm _? 25.1

Transverse tensile strength N / mm 0.79

Swelling after 2 h Ma. '-% 3.7

Pormaldehyde release PESYP Ma. -% 0.01

Claims (1)

invention claim 2 f 91 Production of Holzwerkst open with very low formaldehyde 'release, vorzugsv / eise wood chipboard, by gluing appropriate raw materials, preferably wood chips, with condensation products of urea and / or melamine and / or phenol and formaldehyde, optionally mixed with other aldehydes produced be characterized in that to be glued wood raw material or the binder for Formaldehydaufnähme suitable condensation product of formaldehyde-binding monomers, preferably urea, melamine or 'phenol, and aldehydes, preferably formaldehyde, optionally in combination with a formaldehyde-binding monomers, are added.