DE1653266A1 - Process for the production of wood-based materials and plywood panels with high resistance to hot water, which contain alkali-condensed phenol-aldehyde resins as binding or gluing agents - Google Patents

Description

BHEINPREUSSEN Homberg, March 5th, 1970

SHARED COMPANY? E 67 001 / Sweden

for mining and chemistry
4102 Homberg / lfdrh.
Baumstrasse 31

Process for the production of wood-based materials and plywood panels with high hot water resistance, the alkaline condensed phenol-aldehyde resins as binding or gluing agents

contain.

The invention relates to a method for the production of woodwork materials and plywood panels with high hot water resistance, which condensed alkaline as a binding or gluing agent Contain phenol-aldehyde resins.

Have phenolic resin-bonded wood-based materials and plywood panels Compared to other types of wood-based materials and plywood boards bound by carbamide resins, for example, it is a remarkable one Resistance to hot water. Since this hot water resistance, which is determined by the transverse tensile strength 2 hours of boiling in hot water can be measured, in many cases as a measure of the weather resistance of the plates or Is considered briquettes, there is great interest in the production of wood-based materials and plywood panels with high Hot water resistance, this resistance for reasons of economy after the shortest possible pressing time, corresponding to a low compression factor, is to be achieved. In addition, the compressed materials, for example as chipboard, pressed wood, laminated wood, laminated panels or plywood panels, versatile use in industry especially the construction industry, find, also the highest possible bending and

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Documents (Art 7 SI Paragraph 2 No. I Clause 3 of the Amendment ”. V. 4.9.19.

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Have transverse tensile strengths and the lowest possible swelling in cold water.

It is already known to use wood-based materials and plywood panels bonded with phenolic resin by gluing or impregnating wood flour, Wood chips, wood veneers, wood papers or other wood products with alkaline phenol-aldehyde condensation products and hot pressing of the glued or impregnated parts or to produce masses, including pre-drying or surface spraying of, for example, the pressing preformed fleeces can precede.

The phenol-aldehyde resins used as binders, which are, for example, condensation products of formaldehyde and phenol, resorcinol, phenol-sulfur compounds or alkylphenols can act, are mostly in the form of their alkaline, aqueous, alcoholic for processing reasons or aqueous-alcoholic solutions.

It has also been suggested the properties, especially the rate of hardening, of these binders to improve manufactured wood-based materials by adding carbonates of the elements of the first three groups of the periodic table.

Surprisingly, it has now been found that, under otherwise comparable conditions, wood-based materials with even further improved properties can be obtained if alkali-condensed phenol-aldehyde resins with an aldehyde-phenol molar ratio of at least 1.6: 1 are used as binding or gluing agents Viscosity at a solids content of about 48% of over 200 cP, measured in the Höppler viscometer at 20 ⁰ C, an alkali hydroxide content of 0.05 to 2 mol and a content of free phenol of less than 6 % , where 0.01 - 1 mole of alkylene carbonate is added. The alkylene carbonate used is preferably propylene carbonate. It is best to add the alkylene carbonates to the phenolic resin after

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densation, preferably before or during the gluing of the Add wooden parts.

If the aldehyde-phenol molar ratio is below 1.6: 1, then one does not have satisfactory physical-technical properties of the wood-based materials, because of the hardening speed is too low.

A sufficiently high degree of condensation of the phenolic resins is also essential for the properties. At a solids content of 4-8%, the phenolic resin solution should have a viscosity of at least about 200 cP, corresponding to about 50 seconds in the 4 mm DIN cup at 20 ° C.

Larger amounts of free phenol and formaldehyde in the phenolic resin solution are not beneficial. The content of free phenol soIL less than 6%, if possible less than 1%,

Particularly advantageous when processing phenolic resin binders it is when the alkylene carbonates are only shortly before gluing mixed in or separated from the binder in the form of their solutions sprayed onto the wood, pieces of wood or wood shavings will. This avoids that the phenolic resin solutions used as binders are already used as a result of the addition of the carbonate age too much during the time it takes to process them. In addition, the addition of the carbonate shortly before processing also has the great advantage that the middle and Cover layers, e.g. in the manufacture of chipboard panels, Mix in different amounts of hardener and thereby compensate for the different hardening times of the individual layers crooked.

The benefits of adding alkylene carbonates as hardeners to the Phenolic resins versus the addition of carbonates of the elements of the first three groups of the periodic table are:

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1) Shorter setting times, thus faster hardening and shorter longer pressing times of wood materials,

2) Increased flexural strength of wood-based materials.

3) Increased transverse tensile strength of wood-based materials, especially

• _m

after 2 hours of cooking.

4) The hardener does not crystallize out.

5) Reduced blooming of the alkali salts.

The method according to the invention will be explained in more detail using the following example.

example

94.1 g of phenol (1 mol), 254.6 ml of a 30% formalin solution (2.55 mol CH ₂ O) and 28.9 ml of 33 # sodium hydroxide solution (0.325 mol NaOH) are placed in a glass flask Stir mixed and heated to 90 ° C within 40 minutes. A further 28.9 ml of 33 # sodium hydroxide solution are then added. It is left to 60 minutes at 90 ⁰ O react distilled 70 ml of water and condenses to a "r viscosity of about 60 sec., Measured in a 4 mm-DIN cup at 20 C. Subsequently, the strength about 48 # Resin solution divided into several samples and mixed with the hardeners listed in the table.

Chipboard panels are produced with these phenolic resin solutions. For this purpose, wood chips are dried to a moisture content of about 6% and sprayed with 9 parts by weight of phenolic resin per 100 parts by weight of wood in a mixing device. The glued wood chips are then scattered to form chipboards and pressed in a hydraulic press at a temperature of 165 G and a pressure of about 20 kp / cm to form chipboard panels with a density of about 0 ^ 7.

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The chipboard panels obtained have those listed in the table Properties on.

From this it is clear that the propylene carbonate in comparison to. Potassium carbonate causes a shorter gel time and thus a shorter hardening or pressing time. The ones with propylene carbonate hardened phenolic resin-bonded chipboard panels are also characterized by particularly high flexural and transverse tensile strengths, Above all, however, through significantly improved transverse tensile strengths after cooking, as the values in the table show.

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lamella

Hardener additive to 100 g without hardener - 4 g 50%. 4 g 50%.

Phenolic resin solution in g additive KoCO ^ solution propylene carbon

⁷ natural solution

Pesticide ± n _n % approx. 48 approx. 48 approx. 48

(1 g / 2 h / 120 ° C)

Viscosity in 4 mm DIU 63 sec. 58 sec. 117 sec.

__ mug at 20 C

ο """ ■

<° Weight at 20 ⁰ C 1.22 1.25 1.23

o> gel time at 10O ⁰ C 27.3 Hin. 17.3 min. 8.1 min.

# * Hard time at 110 ⁰ C 106 sec. 93 sec. 78 sec.

ο ___—

Set time at 130 ⁰ C 45 sec. 42 sec. 35 sec.

Press temperature in ⁰ C. 165 ° 165 ° 165 °

PreS factor in min./mm 0.4 0.4 0.4

Weight approx. 0.70 0.69 0.69. __

Flexural strength in kp / cm ² 219 516 347 'gj

Transverse tensile strength "4.6, 7.4 8.9

Transverse tensile strength "1.5 2.1 3.1"

after Y 100 '

Claims (2)

Claims 1) Process for the production of wood-based materials and plywood panels with high resistance to hot water, using alkaline condensed phenol-aldehyde resins as binding or gluing agents with an aldehyde-phenol molar ratio of at least 1.6: 1, a viscosity with a solids content of about 48 % of about 200 cP, measured in a Hoppler viscometer at 20 ⁰ C, a Alkalxhydroxidgehalt from 0.05 to 2 mol and a content of free phenol of less than 6% included, characterized in that diesaiPhenolharzei0,01 is added to 1 mol Alkylenkarbonat . 2) Method according to claim 1, characterized in that that the alkylene carbonate used is preferably fropylene carbonate. 109886 / U07 __ INSFECTEO