CS240372B1 - Binders for the production of laminated materials - Google Patents

Abstract

It is used for the production of laminated materials based on phenol-formaldehyde resins. The binder is made of condensate resulting from the purification of 2,6'-xylenol using formaldehyde or paraformaldehyde, or its solution in solvents.

Description

The invention relates to binders for the production of laminated materials.

Binders based on phenol-formaldehyde resins, which are produced by the condensation of phenols with formaldehyde, are used to produce laminated materials.

It has now been discovered that the condensate produced during the purification of 2,6-xylenol is an excellent binder.

The subject of the invention is a binder for the production of laminated materials based on phenol-formaldehyde resins consisting of 20 to 100% by weight mixtures of linear oligomers of condensation products of phenol, cresols, and xylenols with formaldehyde, which are obtained during the purification of 2,6-xylenol using formaldehyde or paraformaldehyde, with a softening point of 50 to 80 °C and up to 80% by weight of alcohols, ketones, esters, aromatics, chlorinated hydrocarbons or mixtures thereof, based on the total weight of the binder.

It is known that the source of 2,6-xylenol is the reaction mixture after methylation of phenol, which contains mainly methylphenols (o-, m- and p-cresols). To a lesser extent, quantitatively insignificant, other products of phenol methylation. Depending on the reaction conditions of phenol methylation, the reaction mixture contains a different ratio of o-cresol and 2,6-xylenol, depending on the requirement whether the main methylation product should be o-cresol or 2,6-xylenol. After distilling off a significant part of the o-cresol, 2,6-xylenol remains in the rest of the reaction mixture as the main and most important component. Of the other methyl derivatives of phenol, individual o-, m- and p-cresols constitute 90 to 95% of the impurities.

From this mixture, 2,6-xylenol was isolated mainly by physical processes such as rectification, crystallization, or fractional crystallization, or a combination of these methods. All of these processes are characterized by being very energy-intensive, lengthy, requiring complex and expensive equipment, and operating with large recycles.

Recently, very advantageous processes for refining crude xylenol by chemical means have been patented. These processes are based on the fact that the by-products accompanying 2,6-xylenol, phenol derivatives having at least one free o-position relative to the phenolic OH group, can be practically removed by heating this mixture with paraformaldehyde, an aqueous solution of formaldehyde or with formaldehyde-releasing substances in the presence of catalysts ensuring the condensation of phenol with formaldehyde predominantly in the o-position.

The condensation reaction product is essentially a linear low-molecular condensate of phenol with formaldehyde, easily melting usually between 50 and 80 °C and soluble in a number of organic solvents, especially in alcohols such as methanol, ethanol, cyclohexanol, cyclic and aliphatic ketones such as ethyl methyl ketone and diethyl ketone, cyclohexanone, esters such as methyl formate, ethyl formate, ethyl4 acetate, methyl acetate, aromatic hydrocarbons such as benzene, toluene, xylene, chlorinated hydrocarbons such as chlorobenzene, chloroform, trichloroethylene and mixtures thereof. The property of this waste product can be advantageously used in the production of laminated materials, especially from paper, fabrics and wood veneers. In addition to advantageous mechanical properties, laminates prepared from this waste material as a binder are characterized by high resistance to moisture, fungi and bacteria. Impregnation with waste condensate can be carried out in the form of a solution, preferably in alcohol, or a melt, for example by spraying, dipping in the melt, or by spraying the precipitated condensate and pressing the individual layers.

Laminates prepared using this condensate as a binder are very resistant both mechanically and weathering-wise. Waste condensate solutions and melt can be colored as desired, using a number of organic dyes and inorganic additives, such as clays. Of course, when using clays, the advantage of transparency of the coating is lost. If we want to use a condensate solution for lamination, it is advantageous to work with higher concentrations of condensate in the solution, i.e. at least 30 to 40% by weight, but solutions with a content of 60 to 80% by weight are optimal for these purposes, taking into account that the solvent must be evaporated before pressing the individual layers. However, it is also possible to process diluted solutions, in which case it is necessary to apply the solution to the sheets several times to obtain a sufficiently high layer.

The great importance of waste utilization lies in the fact that the entire chemical refining of xylenol acquires the character of a waste-free technology. Another advantage of this utilization is that the product can be used either in the form of a powder, melt, or solution, while ethanol can be used as a solvent, the toxicity of which is insignificant. The low melting point of the waste condensate allows for easy processing using powder technology. The high flow index guarantees perfect penetration into the porous materials from which the laminate is made, and thus high mechanical cohesion.

Very advantageous are the methods in which the condensate is applied to the individual sheets to be pressed using a combined technique of painting and immediately spraying the not yet dried coating. This method of application does not require large volumes of solvents and can be used to achieve high layers of condensate more easily without spreading the bonding layer.

The invention will be illustrated by the following examples. The percentages in the examples are by weight.

Example

500 g of 2,6-xylenol were refined by the method described in AO No. 231,085, Example 1.

The xylenol used for refining contained 20.2 percent other methyl derivatives of phenol.

After the described refining process and distillation of pure xylene, the residue was dissolved in 70 grams of ethanol in a 158 g retort. The resulting viscous solution was impregnated with strips of cotton fabric measuring 100 mm x 100 mm at 35 °C and the individual slices were dried at 55 ^° C. The slices were pressed together in 6 pieces at a temperature of 70 to 80 °C, with a pressure of 0.735 MPa, and double spoon-shaped bursting bodies were punched out of the press, which had a width of 6 mm in the narrowest part. The exact height of the bodies was measured before the bursting test for each body separately (Table 1).

The tear test was performed on 10 specimens immediately after fabrication and on 10 specimens after soaking for 10 hours in a 30°C water bath. The measured values are compared with the values obtained when tearing the base material. The results show that lamination significantly increases the strength and is little affected by long-term exposure to water.

T a b l e 1 k a 1

Bursting test result Tensile strength of the specimen

After exposure to water Without soaking

MPa MPa base material laminated material in the form of bodies

Example 2

By the method specified in the author's certificates according to table 2 line 2, dealing with the chemical refining of xylenol, xylenol was refined, which contained 6.4% of other alkylated methyl derivatives of phenol. The residues after refining were used in the form of melts or solutions to produce laminates from various materials. The laminates were produced 25.4 31.3

43.1 45.0 bena test specimens - tear tests. The laminated material and bodies were produced as described in Example 1. The concentration of the prepared solutions is shown in Table 2. In the case that the laminate was produced from a melt, this change is shown in the table. Tear tests were performed according to Example 1. A summary of the results is given in Table 2.

Table 2

Line

Importance

9a

11 12 13

Try*

Refining carried out according to

Distillation residue

Condensate solution for lamination

Method of applying condensate Method of applying condensate Laminated material Tensile strength of laminate MPa

Tensile strength of base material MPa

AO

Example

Weight of xylene g Softening temperature °C Weight of condensate g Solvents g Solvent from melt solution after soaking without soaking

1. 1 2 3 2. 232,834 235,679 232,870 3. 3 13 4 4. 96 96 92.4 5. 72 85 73 6. 16 24 24 7. 160 24 90 8. ethanol ethanol ethanol 9. by soaking acetone (1:1) by spraying benzene (36 : 64) 9a soaking 10. fun. fabric fun. fabric paper 11. 43.1 41.2 6.9 12. 44.1 44.1 8.8 13. 31.3 31.3 3.9 Notes: lj Initial quantity raw xylenols for all tests it was 1000 g. End-

trace were adjusted in the proportion of components used in the cited example of the aforementioned author's certificate.

4 5 6 7 235,607 235,608 236 128 230,842 1 5 7 4 96.2 93.8 93.1 299 69 85 80 77 24 10 5 100 90 100 100 100 toluene (64:36) methanol ethanol ethanol methanol painting + + dusting soaking shopping soaking paper oak foil oak foil paper 6.9 39.2 31.3 5.9 8.8 54.9 40.2 7.8 3.9 27.4 27.4 3.9

2) The softening point was determined using the ring, ball method, described in the monograph by Jiří Helm "Testing of Oil and Its Products" SNTL, Prague 1957, p. 118; according to CSN 65 7060.

3) Average value from 6 measurements (rows 11 and 12).

Claims (1)

SUBJECT Binder for the manufacture of laminated materials based on phenol-formaldehyde resins, characterized in that it consists of 20 to 100% by weight of a mixture of linear oligomers of the condensation products of phenol, cresols and xylenols with formaldehyde, leaving at INVENTION purification of 2,6-xylenol with formaldehyde or paraformaldehyde with a softening point of 50-80 ° C and up to 80% by weight of alcohols, ketones, esters, aromatics, chlorinated hydrocarbons or mixtures thereof, based on the total weight of the binder.