NO844922L - ADMINISTRATIVE MIXTURE, SPECIFICALLY FOR MANUFACTURE OF TREE CONSTRUCTIONS, PLATES AND SIMILAR PRODUCTS. - Google Patents

Abstract

The invention relates to a glue mixture specifically for producing glued wood structures. The glue mixture contains a resorcinol-phenol resin as one component. Resorcinol-phenol glues are common knowledge. The main raw materials used for these glues are resorcinol, formaldehyde and phenol. A disadvantage with the use and preparation of resorcinol-phenol glues is, inter alia, the high price of these glues and raw materials and the fact that the raw materials are difficult to obtain. The purpose of the glue mixture of the invention is to remove some of the problems which are associated with the acquisition of the raw materials, in particular resorcinol, and to make possible more advantageous preparation of the glue mixture based on resorcinol-phenol. Some of the resorcinol-phenol used in the glue mixture can be replaced by a mixture prepared from peat, preferably from the humus substance extract prepared from the decomposed part of the peat, or by a mixture prepared from this extract and formaldehyde. The glue mixture of the invention contains 40-90% by weight of resorcinol-phenol resin having a dry substance content of 30-60% by weight and 10-60% by weight of peat-based humus substance extract. This glue mixture is admixed before use with 5-20% by weight of a conventional curing agent, for example formaldehyde. To the humus substance extract of the glue mixture can be added 10-20% by weight of formaldehyde.

Description

The present invention relates to an adhesive mixture

for the production of wooden constructions, wooden panels and other similar products, where one of the components of the adhesive mixture is resorcinol-phenol resin.

Resorcinol-phenol glues are known. The main ingredients in these glues are resorcinol, formaldehyde and phenol. The glue is produced in a reactor where the components are brought under suitable pressure and temperature. The reaction is interrupted at the precondensation stage. If the glue e.g. is to be used for the production of glulam beams or other wooden constructions, the reaction is completed by adding a hardener, e.g. formaldehyde, for the glue.

Disadvantages of the use and production of resorcinol-phenol glues include their high price and that the raw materials are difficult to obtain. The purpose of using the adhesive mixture according to the present invention is to eliminate some of the problems associated with the availability of the raw materials, in particular resorcinol, and to produce a more economical resorcinol-phenol based adhesive.

The invention is characterized by the features that appear

of the following requirements.

The adhesive mixture according to the invention has the following advantages compared to known resorcinol-phenol adhesives. Parts of the resorcinol-phenol resin used in the glue can be replaced by a humus substance extract made from peat, preferably decomposed peat, or by a mixture of the humus substance extract and formaldehyde. Experiments have shown that approx. half of the glue can be replaced with the humus substance extract. The extract is easy to prepare, and thereby also the adhesive mixture according to the invention.

In countries with marshy or swampy areas, peat is always available.

The humus extract can also replace various fillers, e.g. wood flour, which is used in known resorcinol-phenol glues. This extract is significantly cheaper than the resorcinol-phenolic resin. The price ratio is currently approx. 1 : 10. In addition, the adhesive mixture according to the invention provides a strong, weather-resistant adhesive joint that satisfies the requirements in the class for outdoor gluing, which is specified in wooden construction standards and norms in several countries.

Humus extract has not previously been used as an adhesive raw material. The starting material for the humus extract is the decomposed or partially decomposed part of the peat. The structure of the peat layer from the surface of the ground, i.e. from the slightly decomposed top layer, down to the decomposed bottom layer, is shown in table 1 below. The rate of decomposition is measured according to the Hl - H10 scale (humification value).

The proportion of humic matter is greatest in decomposed peat, the application of which the present invention relates to.

Humic substances, especially humic acids, contain polyphenolic compounds, the origin and structure of which are still partly unknown. According to two popular theories, they are formed either a) when lignin decomposes as a result of the action of micro-organisms (the lignin theory) or b) in a microbiological process of carbohydrates and proteins from dead plants (the polyphenol theory). The structure of the polyphenolic compounds resembles the structure of phenolic acid and tannin. Parts of the basic structure are made up of gallic acid, i.e. the same compound that is one of the main components in extracts from kvebracho wood and from bark. In the adhesive mixture according to the invention, formaldehyde reacts with the reactive carbon atom in the 6-position in the gallic acid and forms a polymer of the phenol resin type. In addition to this, the humic acids contain resorcinol, which also forms a polymer with strong bonds with formaldehyde, even at low temperatures.

The main part of the humic substances, i.e. the humic acids, can be separated from the peat by means of an alkaline water solution. It is emphasized that the alkaline water solutions used are weak, 5%, whereby the lignin in the peat is not leached out in the extract, but remains in the solid substance.

The invention will be explained in more detail in the following examples which describe production methods for the humic substance f the extract and the adhesive mixture.

Production of humus substance extract from peat using

of alkaline solution.

When peat is extracted in a weak, 1-5 per cent, aqueous NaOH solution, the weight proportions of the various components are e.g. following:

1 part by weight of dry peat (ground)

10 parts by weight of distilled water

10 parts by weight of NaOH (from the amount of dry peat)

The ingredients are placed in a container where the temperature is raised to 80°C, and the ingredients are continuously mixed. The treatment is carried out for 1 hour. The dry substances are then separated from the extract solution using a centrifugal separator. The dry substances are removed, and the extract solution is recovered and dried, e.g. by drying at a temperature of 50°C. The recovery of the peat extract extracted in this way is approx. 60% of the dry peat weight. 1. Production of humus substance extract-glue mixture.

The humus substance extract is milled in a hammer mill or in a disc refiner where the blade setting is 0.2 mm. The proportions by weight of the components in the adhesive mixture are as follows:

1 part by weight humus substance extract

2 parts by weight of water

A desired amount of the material obtained in this way is added to a specific amount of resorcinol-phenolic resin. 2. Production of humus extract-glue mixture.

The humus extract is finely ground in a hammer mill or a disc refiner in the same way as above. Paraformaldehyde is added to the extract. The weight proportions of the components in the adhesive mixture are as follows:

1 part by weight humus substance extract

10-20 parts by weight of paraformaldehyde, calculated from the extract

weight

2 parts by weight of water

A desired amount of the material obtained in this way

is added to a given amount of resorcinol-phenolic resin.

The preferred proportions of the components in the adhesive mixture according to the invention are the following: 40 - 90% by weight resorcinol-phenol resin, whose dry matter content is 30 - 40% by weight,

10 - 60% by weight humus extract from peat, prepared

e.g. according to the manufacturing methods described above.

A quantity of water, 0-20% by weight, can be added to the mixture to achieve the desired viscosity. Before using the adhesive mixture, a quantity of a hardener, 5 - 20%, is added to it. E.g. formaldehyde can be used as a hardener.

Example 1.

An adhesive mixture according to table 2 was prepared from humus substance f extract and resorcinol-phenol resin. The composition of a corresponding common resorcinol-phenol (RF) adhesive is also given in Table 2.

The adhesive mixture according to the invention was used for

gluing a glulam beam with 6 lamella layers. The glue mixture was distributed using a trowel, and the amount of glue was approx. 300 g/m2, clamping pressure 8 kp/cm2, pressing time 4 hours and temperature 25°C. The dimensions of the ready-made test beam were as follows: length 600 cm, height 190 cm (6 lamellar layers) and width 120 mm. Wood type: spruce. The beam was stored for four days at 65% relative humidity. Test pieces were then sawn for the following tests: 1) The delamination test according to American standard ASTM D 1101-59. In this test, the test piece is wetted and dried twice. The duration of the test is approx. 8 days. 2) The adhesive joint block shear strength test according to American standard ASTM D 905-49.

The results were as follows:

1) The result from the delamination test was 5%.

2) The result from the glue joint block shear strength test was,

as an average of 20 test pieces, 9.29 N/mm2 , and the failure of the wood was 95%.

According to the standard ASTM D 1101-59, the percentage delamination must not exceed 5% after the two-phase test. In the shear strength test according to ASTM D 905-49, according to the regulations in the Nordic countries, the shear strength must be at least 6 N/mm2, and the failure of the wood must be at least 50%. The results obtained thus satisfy the specified conditions.

Example 2.

The mixture of peat extract and resorcinol-phenolic resin glue was tested for adhesion at room temperature. The ingredients in the glue are listed in table 3.

The adhesive mixture U4 was used for gluing a beam

which was made from 33 x 120 mm spruce boards whose length was 550 mm and height was 165 mm (5 lamella layers).

The amount of glue was 400 g/m2, the pressing time 4.5 hours, the pressing pressure 8 kp/cm<2> and the pressing temperature +25°C.

The beam's adhesive joint shear strength was measured according to ASTM-D (the block shear strength). The average shear strength obtained for 20 test pieces was 9.5 N/mm2 , standard deviation 1.6 N/mm2 , and the characteristic shear strength value 6.3 N/mm2 . The strength of the glue joint in glulam beams must be 6.0 N/mm<2>.

The glue mixtures U5, U6 and the common glue RF-30 (V) were used for gluing test pieces according to B.S.

1204. Such test pieces are used in the Nordic approval test for glue for beams. The raw material used was birch. The pressing time at room temperature was 5 hours. The test pieces were tested two days after gluing. The readings for the adhesive joint tensile strengths were as follows (average values for 10 test pieces):

Adhesive mixture U5: 4.4 6 N/mm<2>dry

3.93 N/mm<2> after 6 hours of boiling

Adhesive mixture U6: 4.79N/mm<2>dry

Glue V : 4.78 N/mm<2>dry

Compared to the reference adhesive (RF-30), the adhesive quality of the humus extract adhesive mixture, when tested dry, is good when half of the RF resin is replaced with a mixture of humus extract and water (U6). The requirement according to B.S. 1204 to shear strength for an adhesive joint after 6 hours of boiling is 2.4 N/mm2,

which is easily achieved when the amount of humus extract-water also makes up more than half of the amount of RF resin.

Claims (3)

1. Adhesive mixture, especially for the production of wooden structures, wooden panels and other similar products, where one of the adhesive mixture components are resorcinol-phenol resin, characterized in that the adhesive mixture contains 40 - 90% by weight resorcinol resin, whose solids content is 30 - 60% by weight, and 10 - 60% by weight of humus extract produced from peat, whereby a hardener known per se, such as formaldehyde, is added to the adhesive mixture before use, in an amount of 5 - 20% by weight. 2. Adhesive mixture in accordance with claim 1, characterized in that 10 - 20% by weight of formaldehyde is added to the humus substance extract in the adhesive mixture. 3. Adhesive mixture in accordance with claim 1 or 2, characterized in that a certain amount of water, at most 20% by weight, is added to the adhesive mixture to regulate its viscosity.