FI109470B - Liquid hardener blend for curing basic phenol-resorcinol-formaldehyde resins - Google Patents

Abstract

A liquid curing agent mixture comprising A) 40 - 85% by weight of a cyclic carbonic acid ester and B) 15 - 60% by weight of paraformaldehyde.

Description

! 109470

This invention relates to liquid hardener blends 5 for cold-gluing wood with phenol-resorcinol-formaldehyde resins, wherein the hardener blend contains A) 40-85% by weight of cyclic carbonic acid ester and B) 15-60% by weight.

The invention further relates to a method of making wood molded bodies 10.

In flat sizing by the cold method using phenol-resorcinol-formaldehyde resins, it is necessary to use curing agents.

It is generally known to use formaldehyde as a curing agent for this purpose, which is usually used either as paraformaldehyde in powder cure or as an aqueous solution of formaldehyde in liquid cure.

For many technical applications, the wood gluing industry is increasingly using liquid hardener-20 systems.

DE-A-2,363,782 describes a process for making hot water-resistant wood raw materials by adding a solution of alkylene · · · nicarbonate and formalin (aqueous formaldehyde) in a phenolic aldehyde resin. In this context, reference is made to difficulties in the use of liquid alkylene carbonates. The processing of such alkylene carbonates into resin solutions results in the formation of gelatinous particles which will be avoided by mixing with aqueous formalin solution 30.

• · ·. BE Patent Publication No. 709,139 likewise relates to the preparation of hot * * * water-resistant wood raw materials using alcali-condensed phenol-aldehyde resins, wherein: during the condensation or use of these resins, carbonates are added to the resin solution. In this case 2 109470 is used! as well as inorganic carbonates, for example alkali metals, or organic carbonates such as propylene carbonate.

EP-A-259 042 describes a process for the preparation of lignocellulosic materials wherein the esters, lactones or organic carbonates are suspended in phenol-formaldehyde resins as curing agents.

EP-A-383 098 discloses hardener blends for pheneno-10 1 -formaldehyde resins obtained by mixing fillers with carbonic esters and optionally paraformaldehyde and having a powdery consistency.

Harmful to hitherto known liquid hardeners is that they lead either to a poor consistency of the adhesive solution or, when used with an aqueous solution of formalin or paraformaldehyde, they produce too high emission values for formaldehyde during curing. In addition, the drying times are usually too short, which causes problems mainly in the preparation. large size glued wood components.

It was an object of the present invention to provide liquid hardener compositions which have advantageous properties with respect to "Formaldehyde I emissions and drying times, and which then meet operational requirements prior to" · everything for building permits in the manufacture of wood form - ".

Accordingly, liquid hardener compositions as initially defined were invented.

30 Cyclic carbonic acid inhibitors · · are used as component A). thighs that are liquid under handling conditions. Suitable compounds include, for example, propylene carbonate, vinylidene carbonate and halogenated cyclic carbonic acid esters. Propylene carbonate is preferably used.

3, 109470

Component A) is used in an amount of 40 to 85% by weight, preferably 45 to 65% by weight, based on the sum of components A) and B).

Paraformaldehyde is used as component B). Both paraformaldehyde having higher degree of polymerization in the range n = 20-40 and paraformaldehyde having low degree of polymerization in the range n-5-15 can be used in such cases. Mixtures thereof may also be used, for example those containing 40-90% by weight. % 10 paraformaldehyde with a high degree of polymerization and 10-60% by weight paraformaldehyde with a low degree of polymerization.

The compositions of the invention may further contain other components such as alumina and / or kernel and nut flour which act as fillers, as well as polyhydric alcohols, for example diethylene glycol or glycerol, to affect storage stability or thixotropic agents such as bentonite or pyrogenic silicic acid. In addition, they may contain natural tanning extracts such as *. there tannins, acacia peel extracts, or kebrazzo.

In addition, the hardener compositions of the invention may further contain carboxylic acids such as benzoic acid, salicylic acid or lactic acid to control reactivity.

The compositions according to the invention may contain these other components preferably in the following amounts in 100 parts by weight of the hardener mixture: - alumina and / or flour in the range of 5 to 28 parts by weight, - ": preferably 30 to 23 parts by weight." alcohols from 8 to 10 parts by weight, preferably from 8.5 to 9.5 parts by weight - thixotropic agents from 0.2 to 5 parts by weight, preferably from 0.4 to 0.5 parts by weight: ·: 35 - antifoaming agents 0.1 to 3 parts by weight, preferably 0.2 to 0.4 parts by weight 4 109470 - natural tanning extracts 3 to 8 parts by weight - organic acids 0.5 to 5.5 parts by weight, preferably 1.4 to 1.8 parts by weight

The hardener compositions of the invention are suitable for curing aqueous resin solutions based on condensation products of phenol, resorcinol and formaldehyde.

Such aqueous resin solutions are known per se and can be prepared by condensation of suburban materials in an alkaline environment. Suitable condensation products can be prepared using phenol, resorcinol and formaldehyde in the following molar ratios: preferably, 0.85 to 1.15 moles of resorcinol and 1 to 1.2 moles of formaldehyde are used per mole of phenol. The condensation takes place in an alkaline environment where 0.05 to 0.3 moles of metal hydroxide are usually used as the base per mole of phenol. Suitable metal hydroxides include alkali and / or alkaline earth hydroxides, preferably sodium hydroxide, potassium hydroxide and calcium hydroxide. The condensation can be carried out at a temperature of 75-100 ° C.

The individual components are condensed with each other so long that the viscosities of the resulting resin solutions are preferably in the range of 500-5000 mPa * s (at a temperature of > 20 ° C), preferably with a solids content of 50-25 70% by weight. results.

* · * 'The solids content can be determined as the solids content by drying the resin sample in a drying oven at 120 ° C for two hours.

The resin solutions may be present after condensation. still alkali contents of 0.6-3.0% by weight, especially I '.. * 0.6-2.0% by weight.

In addition, such resin solutions may further contain from 109470 to 5 to 3.0 to 6.0% by weight of polyhydric alcohols, to 2.0 to 15.0% by weight of nut shells, to 3.0 to 12.0% by weight of cellulose and cellulose derivatives, from 5 to 4.0 to 5.0% by weight of alumina, from 0.2 to 5.0% by weight of thixotroping agents, in each case 100% by weight of a resin solution.

| To these resin solutions are added the liquid hardener compositions of the invention by stirring. In this case, the amount of hardener-10 mixture is preferably selected so that from 12 to 35, preferably from 15 to 25 parts by weight are added per 100 parts by weight of the resin solution.

The hardener compositions of the invention are used primarily for flat gluing of whole wood by the cold process, for example, when gluing wood lamellas to load-bearing board layer boundaries in the glulam industry.

Adhesive solutions prepared with the hardener solutions of the invention are particularly suitable when, within the scope of the building permit, for the bonding of load-bearing wooden structure-parts in accordance with DIN standards 69141 and 53254. requirements, in particular binding rate, layering "*. for missiles, application time of the adhesive solution and free drying time.

* 'Liquid hardener 1 ···· 25 kg of paraformaldehyde with an average degree of polymerization of 30, 23 kg of kaolin, 1.5 kg of salicylic acid and 0.5 kg of bentonite are suspended in 50 kg of propylene carbonate.

Liquid hardener 2 30 was prepared according to hardener 1 but using a paratormaldehyde mixture consisting of paraformaldehyde with an average degree of polymerization of 40 and paraformaldehyde with an average degree of polymerization of 10: 3.

6 109470

Resin solution 1

An aqueous phenol-resorcinol-formaldehyde condensation product was prepared in which the molar ratio of phenol: resorcinol: formaldehyde was 1: 0.85: 1.02 and which further contained 1.6% by weight of sodium hydroxide. The resin solution had a viscosity of 3400 mPa.s (20 ° C) with a solids content of 67.7% by weight.

Resin solution 2

An aqueous phenol-resorcinol-10 formaldehyde condensation product was prepared in which the molar ratio phenol: resorcinol: formaldehyde was 1: 1.21: 1.18 and further contained sodium hydroxide in an amount of 1.48% by weight. The viscosity was 2900 mPa.s (20 ° C) with a solids content of 69.1% by weight.

15 Resin solution 3

An aqueous phenol-resorcinol-formaldehyde condensate was prepared in which the molar ratio phenol: resorcinol: formaldehyde was 1: 0.85: 1.03 and further contained 2.0% by weight of calcium hydroxide. The viscosity of the resin solution was 3,300 mPa.s (20 ° C) of solids content of V; 64.7% by weight.

....: Examples 1-4

General instructions for the preparation of adhesives

In each case, the resin solution in question, containing 25 kg per 100 kg of additional bentonite, | 0.1 kg antifoam, 4.9 kg diethylene glycol, · · "" 9.6 kg coconut shell powder and 4.8 kg kaolin, The compositions of the individual adhesives are shown in the following table.

* · 7 109470

table 1

Adhesive Hardener No. / Quantity Resin Solution No. / Quantity (kg) (kg)

Example 1 1/15 1/100 5 Example 2 1/20 1/100

Example 3 2/25 2/100

Example 4 2/25 3/100

Using glues, beech specimens were manufactured according to DIN Standard 53254 and tested in accordance with DIN Standard 68141 (see Table II). In addition, adhesive properties were evaluated according to DIN standard 68141 and formaldehyde emission according to DIN standard 52368 (see Table III).

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Claims (4)

A liquid hardener blend for curing basic phenolic resorcinol-formaldehyde resins, characterized in that it contains A) 40 to 85% by weight of cyclic carbonic acid ester and B) 15 to 60% by weight of paraformaldehyde. Liquid hardener composition according to Claim 1, characterized in that it further contains 10 'fillers, polyhydric alcohols, thixotropic agents, organic acids or antifoam agents. Use of a liquid hardener mixture according to claim 1 or 2 for curing condensates based on phenol, resorcinol and formaldehyde. 15 Wood-shaped bodies, characterized in that they are obtained by cold-gluing whole wood with phenolic resorcinol-formaldehyde condensates using the liquid hardener mixture according to claim 1 or 2. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • aa ia I 1 · a »<a» a » a »aaa 13 109470