DE2206696A1 - Glue admixture - preventing formaldehyde release, consisting of molecular associations contg amide, imine or amine component - Google Patents

Abstract

Glue admixture, esp. in storage-stable form, for diminishing any subsequent HCHO release from chipboard manufactured by using glues based on HCHO-contg. condensates, contains at least one molecular cpd., one component of which is an aliphatic cpd. contg. an amido-, thioamido-, imino-, or primary, sec. or tert. amino gp., pref. urea, thiourea or hexamethylene tetramine; while the second component of molecular cpd. may be a cpd. contg. an alcoholic OH gp. or a metal salt. Admixture contains sufficient liquid, esp. water to ensure flowable consistency and is weakly alkaline, pref. having pH 7-8.5. It may also contain latent hardeners and/or accelerators and/or fungicides and/or materials for improving adhesive powers. Admixture pref. contains: (a) urea/protein glue (esp. from hides), (b) urea/NaCl, (c) thiourea/Na thiocyanate, (d) hexamethylene tetramine MgCl2.6H2O and advantageously Ca lignin sulphonate, ammonia water and water.

Description

³⁰²⁶ Admixture of glue

The invention relates to an admixture of glue, preferably in the form of a storable glue additive, for reduction the subsequent elimination of formaldehyde using glues based on formaldehyde-containing Condensates of manufactured chipboard or the like.

Formaldehyde-containing condensates used as wood glue are urea-formaldehyde condensates and melamine-formaldehyde condensates or phenolic or cresol resin glues are common. It are hardenable synthetic resin glues.

For the production of wood-based materials such as chipboard or plywood, binders based on Amino or phenolic plastic resins are used.

The chipboard or the like produced using the aforementioned glues have the disadvantage, however, that they release formaldehyde, especially in warm and humid weather, which is due to the irritation of this Connection can lead to significant annoyance.

In order to reduce this subsequent release of formaldehyde, which occurs after the glue has hardened, is with glues based on urea-formaldehyde, it has already been proposed to add formaldehyde-binding substances to the glues or Part of the wood chips in the manufacture of chipboard

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to be treated with such materials before gluing.

In a known process for the production of condensation products from urea or thiourea and formaldehyde becomes the products after the condensation, however before curing, ammonia was added as a formaldehyde-binding compound.

However, the amounts of formaldehyde-binding substances that can be added to the glues are very limited because by adding these substances, the setting speed of the wood glue is reduced. It has also been shown that by using glues which contain ammonia or other formaldehyde-binding compounds, the Strength properties of the chipboard, in particular the transverse tensile strength, are considerably impaired.

A deterioration in the mechanical properties also occurs when the formaldehyde-binding compound not added to the glue, but rather the wood-based material is treated with it before gluing, quite apart from that that this procedure is cumbersome and time consuming.

To avoid the first-mentioned disadvantages in particular, when adding glue of the type mentioned at the beginning provided according to the invention that it contains at least one molecular compound, one component of which is a

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Amido, thioamido, imino or primary, secondary or tertiary amino group-containing aliphatic compound.

Molecular compounds are generally understood to mean compounds which are composed of two components (usually in a molar ratio 1: 1 or in other integer molar ratios, e.g. 1: 2 or the like). Each of the the two components forming the molecular compound is one in itself according to the rules of chemical valence theory saturated, stable compound, STAAB "Introduction to Theoretical Organic Chemistry, 1962". See also RÖMPP "Chemielexikon", according to which molecular compounds are stoichiometric largely defined assemblies (associations) of molecules in the gaseous, liquid or solid state are caused by van der Waals forces (also dipole orientation, Hydrogen bonds and the like) are brought about and the main valences are neither dissolved when they arise still to be formed.

The novel admixture can be added to the glue at any suitable point in time if it is designed as a storable additive be added before hardening, expediently shortly before gluing the wood-based material. But it can Glue may also be added during its production or the glue additive can initially be dry Wood particles are added and only then the glue

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be added or the like.

It turned out that, if desired, relatively large amounts of the novel admixture can be mixed with the glue, preferably 5-25% by weight based on the solid substance of the glue and the admixture.

The new admixture generally improves the strength values (flexural strength, transverse tensile strength) considerable and can reduce the swelling in thickness considerably. Both are extremely desirable. It therefore succeeds With the new admixture, not only can the subsequent leakage of formaldehyde be considerably reduced, but there are also the properties of the glued wood-based materials in question, in particular the properties of Chipboard, much improved.

Particularly good results are obtained when the second component of the molecular compound has an alcoholic hydroxyl group having compound or a metal salt.

The metal salts in the molecular compounds are preferably zinc chloride, magnesium chloride, ammonium bicarbonate, Alkali thiocyanates (preferably ammonium or sodium thiocyanates), sodium chloride, chromium (III) sulfate, iron (III) chloride or calcium nitrate.

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Among the compounds containing alcoholic hydroxyl groups, aliphatic alcohols, in particular Diols or triols, preferably ethylene glycol, diethylene glycol, Glycerine, trimethylolpropane, hexanetriol, 1,2-propanediol, 1,3-propanediol, 1,4-butylene glycol or polyols, preferably Erythritol or sorbitol or grape sugar proved to be particularly beneficial.

These represent a component of the molecular compound In many cases, polyhydric alcohols can also advantageously be esterified with dicarboxylic acids, the dicarboxylic acids are in deficit. Preferred dicarboxylic acids are adipic acid, phthalic acid or maleic acid,

Among those components of the molecular compound which carry amido groups, urea and melamine have emerged as proved particularly advantageous.

Among the compounds bearing a thioamido group is preferably thiourea is used.

Furthermore, the use of hexamethylenetetramine has proven itself proved to be the component of the molecular compound having a tertiary amino group.

In addition to the compounds mentioned, can be used as amido or primary, secondary or tertiary amino groups Compounds with advantage ammonium hydroxide, melamine,

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Phenyl urea, cyanamide, dicyandiamide, guanidine, 1-cyano-guanidine or diaminotriazines, expediently guanamines or aminodiazines, expediently aminopyrimidines / those according to the invention Admixtures may be included.

The admixture according to the invention preferably contains a sufficient amount of a suitable liquid, water is particularly useful in order to have a liquid or at least flowable consistency. Instead of water however, the additive can also contain alcohols, esters or the like, preferably polar liquids.

In order to avoid premature hardening of the glue, the additive is advisable to be weakly alkaline. In general its pH can advantageously be adjusted to about 7-8.5.

Of course, the additive can also contain one or more additives, such as latent hardeners, accelerators, fungicidal substances or substances to improve stickiness, such as lignosulphonic acid salts, starch glues (e.g. dextrin, potato starch, aqueous dispersions of plastic resins or the like). The lignosulphonic acid salts are those which arise during cellulose production or which are formed by salting Calcium, magnesium and sodium salts of lignosulfonic acid are preferred. The additive contains glue as a fungicidal substance Advantageously, sodium pentachlorophenol, chlorocresol or hexachlorocyclohexane. The salts of lignin sulfonic acid

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are preferably thickened to a solids content of 50-58% by weight.

A glue admixture has proven to be particularly advantageous proven, which contains a mixture of the following molecular compounds:

a) Urea Z protein glue (preferably hide glue),

b) urea-sodium chloride,

c) thiourea-sodium thiocyanate,

d) hexamethylenetetramine-magnesium chloride hexahydrate.

This admixture can expediently also contain calcium lignosulfonic acid, ammonia water, water, barium hydroxide octahydrate and sodium pentachlorophenol. Such additives can of course also be used with others Molecular compounds or mixtures of other molecular compounds may be expedient. . - -.

When using the admixtures according to the invention produced chipboard or the like, the release of formaldehyde is reduced to a minimum. There aren't any Changes in the manufacture of the chipboard / plywood panels or the like required.

Among the molecular compounds which can be used for the preparation of the admixtures according to the invention are with the following compounds with regard to formaldehyde absorption and improvement of the mechanical properties of the finished chipboard or barrier

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wood panels have achieved particularly good results:

1 mole of thiourea, 1 mole of sodium thiocyanate 1 mol of thiourea, 1 mol of sodium chloride, 1 mol of urea, 1 mol of sodium thiocyanate

1 mole of urea, 1 mole of sodium chloride

2 moles of urea, 1 mole of zinc chloride

2 mol of urea, 1 mol of magnesium chloride, 2 mol of urea, 1 mol of grape sugar 2 mol urea, 1 mol glycerol, 2 mol urea, 1 mol erythritol, 2 mol urea, 1 mol sorbitol 2 mol thiourea, 1 mol zinc chloride, 4 mol urea, 1 mol calcium nitrate 4 mol urea, 1 mol glycerol 6 mol urea, 1 mol iron (III) chloride 6 mol urea, chromium (III) sulfate Hexamethylene, aldehydes (Pfeiffer, p. 305) 2 mol urea, 1 mol ethylene glycol 2 mol of urea, 1 mol of trimethylolpropane, 2 mol of thiourea, 1 mol of diethylene glycol 2 moles of thiourea, 1 mole of hexanediol

In general, mixtures of two or more molecular compounds for the inventive Glue admixtures are provided. But at least in many cases a single molecular compound can also be used can be used.

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The admixtures according to the invention can be supplied in powder form, with the molecular compounds under Certain circumstances do not have to have formed, but may only be formed by adding water or the like. However, the admixtures are expediently in liquid form, preferably as an aqueous solution or slurry added to the glue with a solids content of preferably 20-40% by weight. The addition of glue must be in each Case, whether in solid or liquid form, brought together or mixed with the glue before it hardens will.

In many cases it can also expediently be used molecular compounds which are also latent at the same time Hardeners are effective. The following molecular compounds can preferably be provided here: thiourea / sodium chlorine id, urea / oxalic acid, urea / sodium rhodanide.

The admixture according to the invention also has the advantage, among other things, that, with a liquid consistency, if desired, A very high solids content can be obtained, for example 80-90% by weight. She also has an excellent one Shelf life. The additive according to the invention is expediently brought into such a liquid consistency that can be atomized at room temperature.

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If the second component of a molecular compound is protein glue, then the other component can advantageously be urea, Thiourea or a metal salt, especially sodium thiocyanate, Be magnesium chloride or zinc chloride. Contains when using urea or thiourea then both components of the molecular compound nitrogen. The following are preferred as protein glues: hide glue, Leather glue, bone glue, gelatin.

In the following exemplary embodiments, the production of some particularly advantageous, storable glue additives described. These additives also increase the strength values of the chipboard or the like produced and reduce their swelling in thickness.

Example A.

First, the following are four different molecular compounds produced at room temperature:

a) In 1000 parts by weight of water there are 200 Parts by weight of urea are dissolved and then 200 parts by weight are ground Hide glue entered. After about 2-3 hours the hide glue is also loosened;

b) 120 parts by weight of urea and 116 parts by weight of sodium chloride are dissolved in 200 parts by weight of water;

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c) In 200 parts by weight of water there are 76 parts by weight of thiourea and 81 parts by weight Dissolved sodium thiocyanate;

d) In 200 parts by weight of water, 74 parts by weight of hexamethylenetetramine and 102 parts by weight of magnesium chloride · 6 dissolved water.

These four separately prepared aqueous solutions of molecular compounds are then intimately mixed with one another and another 150 parts by weight of water are added and 1 part by weight of sodium pentachlorophenol is added. Become yourself of this mixture, 500 parts by weight of calcium lignosulfonate (solids content 50% by weight), 50 parts by weight Ammonia water with a density of 0.9 and 3 parts by weight of barium hydroxide octahydrate added and stirred well » The mixture obtained has a pH of 8 and a solids content of about 35% by weight. This glue additive obtained in this way is referred to below as the addition Ά. Its ability was tested for that contained in chipboard free forraaldehyde content and strength properties and to influence the thickness swelling of the chipboard.

For this purpose, two pairs of plates were used made of the following glue batches:

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Addition Two "zero plates" (comparison plates) without / and with un-

buffered hardener (15 parts by weight NH ₄ Cl / 35 _{parts by weight H 2} O) and the following
Glue base: 100 parts by weight of liquid glue 10 parts by weight of hardener solution

Two chipboards with the following glue: 100 parts by weight of liquid glue, 10 parts by weight of hardener solution, 20 Parts by weight of the additive according to the invention A.

A urea resin glue was used as glue, which is below the trade name Kauritleim 385 is manufactured and sold by the company BASF. The glue batches were calculated so that for the top layers of the chipboard a resin content of 11%, for the middle layers of 7% became. The pressing temperature was a uniform 150 ° C. The test conditions to which the two zero plates and the other two plates were subjected, were identical.

First of all, the chipboard, which cannot be submerged from the outside, was used after 5 days of storage in a normal climate, trimmed and placed in the test specimens for the comparative measurement of formaldehyde elimination divided up. The elimination of formaldehyde was determined by the microdiffusion method according to L. Plath, in which the free formaldehyde was determined by a colorimetric method at 30 ° C. For formaldehyde determination Representative samples were taken from the plates in the form of chips. The measurement of formaldehyde elimination

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took place once after 6 days of air conditioning, in one Repetition after 12 days of air conditioning. The response time has been used to increase the measurement accuracy from 18 to 42 Hours increased.

The measured values are compiled in the following table:

plates Raw
density
kg / m ³ Thickness
swelling
in % Bend
firm
ability ₂
kp / cm iuer-
: ug-
: estig-
teit ₂
: p / cm Formaldehyde
after 6
Days ydabgabe
after 12
Days without
glue
additive 619 15.6 228 6.5 138 96.3 with
glue
additive 600 12.0 254 7.5 45.5 38.0

The table clearly shows that there was a considerable reduction (67%) in the elimination of formaldehyde. Of the Thickness swell value was reduced by approx. 20%. The flexural and transverse tensile strength increased by over 10%.

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Example B.

First of all, the following molecular compounds were produced as separate, aqueous solutions:

a) 150 parts by weight of urea were dissolved in 750 parts by weight of water and this Solution then 150 parts by weight of leather glue added. After 2-3 hours the leather glue had also loosened, so that the solution obtained was ready to use.

b) 120 parts by weight of urea and 126 parts by weight of zinc chloride were dissolved in 200 parts by weight of water.

c) 84 parts by weight of dicyandiamide and 102 parts by weight of magnesium chloride × 6 water were dissolved in 200 parts by weight of water.

These batches were then mixed well with one another and 40 parts by weight of ammonia water were specified for the mixture obtained. Weight 0.91, 327 parts by weight of water, 1 part by weight of sodium pentachlorophenol, 3 parts by weight of barium hydroxide octahydrate were added.

The mixture obtained is a storable glue additive according to the invention.

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Example C

Initially, three different solutions of molecular compounds were made manufactured:

a) 240 parts by weight of urea and 406 parts by weight of magnesium chloride · 6 water were dissolved in 400 parts by weight of water.

b) In 200 parts by weight of water were 76 parts by weight Dissolved thiourea and 58 parts by weight of sodium chloride.

c) In 200 parts by weight of water were 120 parts by weight Dissolved urea and 30 parts by weight of glycerol.

Another approach was then made in which 200 parts by weight of an aqueous dispersion of a copolymer of butyl acrylate and vinyl acetate 1: 1 (solids content approx. 50% by weight) with 4 Ge * parts by weight of ammonia water (specific weight 0.91) were mixed.

You bring these four approaches together and mix well. Then 10 parts by weight of ammonia water are added (specific weight 0.91) and 380 parts by weight of water added «

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A glue additive according to the invention is then present / which has a solids content of approx. 35% by weight.

The use of the glue additives according to examples A, B and C will be explained in more detail using examples.

example 1

100 parts by weight of a wood glue based on a urea-formaldehyde polycondensate (molar ratio 1: 1.6), which contains 66.5% solids in aqueous solution, are mixed with 20 parts by weight of an aqueous solution built up ^{according to Example A.} 10 parts by weight of an aqueous solution containing 3.0 parts by weight of ammonium chloride and 7 parts by weight of a 50% strength paraffin emulsion are added to this mixture.

These binder mixtures are used to glue wood chips, with such amounts of binder being used that 8 parts by weight of resin (dry weight) are used for 100 parts by weight of chips.

The chips coated with binder are converted to chipboard 16 mm thick ^{at a temperature of 150 ° C.}

2 presses. The pressing time was 2 minutes at 25 Kp / cm and 5

2
Min. At 10 Kp / cm pressure.

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Example 2

100 parts by weight of a wood glue based on a phenol-foraldehyde polycondensate (molar ratio 1/2) , which contains 48% solids (40% polycondensate and 8% sodium hydroxide) in aqueous solution, is mixed with 21 parts by weight of a solution prepared according to Example B. is constructed.

The plate is finished in a known manner. Example 3

This example is similar to example 2), but contains as aqueous additional solution one which is composed according to example C.

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Claims (11)

3026 - 18 - P atent Claims 1. Admixture of glue, preferably in the form of a storable glue additive, to reduce the subsequent elimination of formaldehyde made using glues based on formaldehyde-containing condensates Chipboard or the like, thereby characterized in that it contains at least one molecular compound, one component of which is a Amido, thioamido, imino or aliphatic compound having primary, secondary or tertiary amino groups 1st. 2. admixture according to claim l _f, characterized in that the second component of the molecular compound is a compound containing alcoholic hydroxyl groups. 3. Admixture according to claim 1, characterized in that the second component is a metal salt. 4. admixture according to one of claims 1-3, characterized in that that the compound having an amido group is urea. 5. admixture according to one of claims 1-3, characterized in that that the compound having a thioamido group is thiourea. - 19 309833/1002 6. admixture according to one of claims 1-3, characterized in that that the compound having an imino group is hexamethylenetetramine. 7. admixture according to one of the preceding claims, characterized in that it is one to achieve a flowable consistency contains sufficient amount of a liquid, preferably water. 8. admixture according to one of the preceding claims, characterized in that it is weakly alkaline. 9. admixture according to claim 8, characterized in that its pH is about 7-8.5. 10. admixture according to one of the preceding claims, characterized in that they are latent additives Contains hardeners and / or accelerators and / or fungicidal substances and / or substances to improve stickiness. 11. Admixture according to one of the preceding claims, characterized in that it is a mixture of the following Molecular compounds contains: a) urea / protein glue (preferably hide glue), b) urea / sodium chloride, c) thiourea / sodium thiocyanate, d) hexamethylenetetramine / magnesium chloride hexahydrate, that it preferably also contains calcium lignosulfonate, ammonia water and water. 309833/1002 OPJGSNAL INSPECTED