DE2043440C3 - Use of an aminoplastic wood glue as cold-hardening wood glue - Google Patents

Description

The patent 20 20 481 relates to a novel curable aminoplastiscnes binder for wood gluing based on a condensate of 1 mol of melamine or a mixture of at least 15 mol% melamine and up to 85 mol% urea, 1.7 to 3.0 mol Formaldehyde and 0.05 to 0.2 mole of a phenol, which is characterized in that 1 mole of melamine and / or urea and 14 to 2.5 moles of formaldehyde in aqueous solution are added in a manner known per se up to a water compatibility of 0 , 5 to 10 condensed and the condensate at a pH of 7.5 to 10 and at 45 to 100 ⁰ C with 0.05 to 0.2 mol of a phenol, optionally up to 0.5 mol of formaldehyde and optionally up to converts to 0.5 mol of melamine until the aqueous solution - measured at a solids content of about 60% and at 20 ⁰ C - reaches a viscosity of 300 to 2000 cP.

The present invention relates to a further embodiment of the invention according to the main patent.

It was found that the novel wood glue according to the main patent is not only suitable for weatherproof hot gluing, but also for joint-filling and boiling and weather-resistant cold gluing, Especially suitable for the field of timber engineering if you have a special Hardening agent used.

The invention relates to the use of an aqueous, aminoplastic Ho'zlcime containing 40 to 70% solids, which, according to patent 20 20 481, has been obtained by mixing 1 mol of melamine and / or urea and 1.5 to 2, 5 mol of formaldehyde prepared a suitably concentrated aqueous condensate solution with a water tolerance of 0.5 to 10 and the solution at a pH of 74 to 10 and at 45 to 100 ° C with 0.05 to 0.2 mol of a phenol, if necessary has reacted up to 0.5 mol of formaldehyde and optionally up to 0.5 mol of melamine until the aqueous solution - measured at a solids content of 63% and at 20 ^° C. - reached a viscosity of 300 to 2000 cP, in conjunction with formic acid as a hardener and, if necessary, the usual additives as cold-curing wood glue.

To further improve the joint-filling properties, the wood glue can also be used Extenders, particularly useful for. B. Coconut shell flour contain.

It is already known from German patent 8 75 568 that melamine, phenol and formaldehyde ") can be condensed with one another, producing wood glues. The glues obtained according to the aforementioned German patent contain a relatively large amount of phenol, for example about 0.5 Moles per mole of melamine. However, usable wood glues are apparently only obtained by subjecting the condensed resin solutions to spray drying and thus processing them into pulverulent, re-dissolvable glues generally not mixed condensates, but mixtures of condensates, ie phenolic and aminoplastic binder components present next to one another.
Otherwise, the task is to make wood glue for

2 () weatherproof bonds, as aqueous solutions are stable and are suitable for cold gluing, through the teaching of the aforementioned German patent unsolved. As the example described there shows, the bond strength leaves one with the relevant

2 '. Resin produced gluing after a relatively short time under the influence of moisture after.

Also the use of acids or substances that can release acids (such as ammonium chloride) as

i <> hardener for aminoplastic binders is in itself known. However ha! Surprisingly, among many common technical acids examined as Only formic acid is sufficiently suitable as hardening agent for the present special wood glue

j ^r i proved when the wood glue should be used for the weatherproof cold glue; As cold glue for weatherproof gluing in timber engineering, only so-called resorcinol glue have come into question because of the considerable demands on the glue quality. The invention accordingly closes a clear and tangible gap here.

The ready-to-use, resin and hardener containing glue can in a known manner Bringing glue solution and hardener together -

4 ^r i also this optionally in the form of a dilute solution - can be obtained. It is particularly advantageous to use the glue with the hardener after the mixing-in process - in contrast to the well-known prepainting process. In the mixing process, the glue is mixed with the hardener and immediately afterwards - ie within the pot life - the glue is glued using the hardening mixture. Since this process belongs to the state of the art, no protection is sought for the special implementation of the gluing process and this is not described further.

However, it is advisable to use the following mixing ratios for glue, hardener and, if applicable to adhere to the extender: to 100 parts of the im

bo main patent described, about a solids content from 58 to 63% glue solution are z. B. 1 to 8 parts of formic acid, the z. B. in 30 to 85% aqueous solution is present, and optionally 10 to 20 parts of the extender used. You then get for

b5 the submixing process open times, e.g. B. between 30 to 300 minutes, which are precisely adapted to the respective task in suitable preliminary tests can. Except for the coconut shell flour already mentioned

Wood flour, hardened and ground phenoplasts or aminoplasts can be used as an extender, if necessary cereal or legume flours are also used in small percentages.

In addition, depending on the task, z. B. the use of suitable wood preservatives such as fungicides or insecticides, characterizing dyes, thickeners and the like are possible.

The percentages given in the following examples relate - as in the preceding ι ο genen description - on the weight.

example 1

For every 1 kg of a 59% strength aqueous solution of a glue resin according to patent 20 20 481, the melamine, π Urea, phenol and formaldehyde in the molar ratio (1: 3.2: 0.6: 10) (resin I) or 1: 1.8: C, 4: 7.2 (resin II) Contains condensed and condensed up to a viscosity of 60OcP, are 0.15 kg each Coconut shell flour, as it is currently available under the trade name 2 "Vavanite" and 30 g each mixed with a 34% aqueous solution of formic acid and used for gluing. The open and closed waiting time is then between 10 and 75 minutes. r>

Spruce and beech boards measuring 30 × 14 × 0.5 cm were glued together as test specimens while maintaining a 1 mm thick glue joint. The test for bond strength and Holzausriß carried out according to the provisions of DIN 53 254 in the dry state, after 96stündigem Water at 20 ⁰ C and the test for resistance to boiling according to the standard provision AW 100 of DIN 68 705. The results are shown in Table I, wherein each reported reading was determined as the average of 30 samples.

Table 1

Cold gluing of beech boards with thick ones Glued joint (1 mm) - open lying time 30 minutes at 4 « 24 C -

Glue contained 1 kg of resin 1 30 g of 34% formic acid and 200 g of coconut shell flour. The specified As described above, numerical values are mean values from 30 individual measurements.

Table 2

Cold gluing of boards with a thick glue joint (1 mm) - open lying time 15 minutes at 20C-

beech Spruce Dry tear value, kp / cm ² 80.90 63.20 wood chipping in% 86 94 Tear value after 96 ^{h soaking} 64.00 48.10 at 20 C, kp / cm ² Wood chipping in% 77 92 Tear value according to AW 100 53.40 43.07 (Cook change test), kp / cm ² Wood chipping in% 72 84

Example 3

As described above, 1 kg of resin I, 200 g of coconut shell flour and 30 g of hardener were used to create a glue attached and for gluing spruce beds with narrow lee joint (0.1 mm) used. The open lying time was varied and the bond strength of the Gluing as well as the wood tear, which is a measure of the relative strength of wood and glue joint, determined. The result is shown in Table 3.

Table 3

Spruce boards with a thin glue line (0.1 mm), cold glueing at 20 C / 65% rel. Humidity and staggered open lying time

Lay time

(Minutes)

strength

Wood tear

(kp / crn ² ) (%)

Resin 1

Resin Π

Tear value (bond strength) 75.80
dry, kp / cm ²

Wood chipping in% 87

Tear value after 96 h soaking 58.11
at 20 C

Wood chipping in% 99

Tear value according to AW 100 50.85

(Cook change test)

Wood trim in% 77

₄ - dry 77.63

76
67.05

98

55.25 ₉₆ i 'watering

55

The table shows, among other things, that the degree of condensation of the wood glue according to patent 20 20 481 plays a certain role in the process according to the invention. Particularly recommended as cold glue are z. B. glues, the degree of condensation is characterized by a viscosity of the 59% solution of from 500 to 80OcP at 20 ⁰ C.

Example 2

Comparative gluing tests were carried out with the resin I described in more detail in Example 1 on two different types of wood. The one used

60 cooking change test (AW 100)

15th
30th
45
60
75
average

15th
30th
45
60
75
average

15th
30th
45
60
75
average

37.83 37.50 33.00 35.83 26.33

34.09

25.00 33.33 26.50 28.83 21.66

27.06

31.00 33.75 24.87 24.62 18.25 26.49

100 100 100 100 100

100

100 93 23

100 53

55 100 83 68 95 80

Claims (1)

Claim: Use of an aqueous, aminoplastic wood glue with a solids content of 40 to 70%, which has been obtained according to patent 20 20 481 in that one mole of melamine and / or Urea and 14 to 2.5 moles of formaldehyde are an appropriately concentrated aqueous condensate solution a water tolerance of 0.5 to 10 and the solution at a pH of 74 to 10 and at 45 to 100 ° C with 0.05 to 0.2 mol each of a phenol, optionally up to 0.5 mol of formaldehyde and optionally up to 0.5 mol Melamine has reacted until the aqueous solution - measured at a solids content of 63% and at 20 ° C - reached a viscosity of 300 to 200OcP, in conjunction with formic acid as Harder and, if necessary, the usual additives than cold-curing wood glue.