RU1790579C - Method of increasing water resistance of phenol-formaldehyde plastic foam - Google Patents

Abstract

SUMMARY OF THE INVENTION: A coating comprising synthetic rubber rubber latex and phenolic foam waste powder in a percentage of 80-82: 18-20, respectively, is applied to the foam surface. 1 tab.

Description

The invention relates to the production of foams intended for the manufacture of building products and structures used as thermal insulation for underground heat pipes.

Currently in construction for thermal insulation, cheap phenol-formaldehyde foams are used. However, phenol-formaldehyde foams are openly cellular materials (up to 95

- 98% of the surface of open pores), which causes their high water absorption and reduces the service life due to the penetration of water from the environment into the foam. Therefore, typically phenol-formaldehyde foams are made with coatings.

A known method of obtaining a moisture-resistant phenol-formaldehyde foam by coating (welding)

- plastic film. The use of a plastic film slightly increases the water resistance and durability of the foam, g:

The known method has a number of serious disadvantages: it requires preliminary heating of the film to 50-60 ° C; coating is carried out manually, which makes it impossible to produce a high-quality waterproofing layer, especially for large-sized products.

The closest in technical essence and the achieved result to the present invention is (2) a method for producing a water-resistant phenol-formaldehyde foam by applying a polymer composition of the following composition to the surface of the foam, wt.%:

VI

che oe

VI

Yu

with

Resole phenol-formaldehyde resin

80 - 82

Condensation Product of Sulfofenolurea with Formaldehyde and Phosphoric Acid 18-20 However, the water-resistant phenol-formaldehyde foam obtained by the known aid has a number of the following disadvantages:

low degree of water resistance and short service life (durability) due to the porous coating that has formed, resulting in a partial displacement of air from the intercellular space during the preparation of the foam;

rigid (inelastic) structure of polyformeldehyde polystyrene ograni-. there are the possibilities of exploitation, polystyrene, for example, for insulation of underground heat pipelines;

emission of toxic substances into the atmosphere during operation (phenol-formaldehyde resins, condensation products - phenol);

low processability of coating due to the speed of curing of the polymer composition.

The aim of the invention is to reduce water absorption and increase the service life of the foam.

The goal is achieved in that in the claimed method for producing a water-resistant phenol-formaldehyde foam, by applying a polymer composition to its surface followed by its 6-hardening, according to the invention, a polymer composition of the following composition is applied, wt.%:

Latex80 - 82 Wastes of phenol-formaldehyde ... foam. 18-20 The use of phenol-formaldehyde foam for coating latex with waste makes it possible to reduce water absorption and increase the service life of the foam by allowing deep penetration of the coating composition into the foam space, displacing residual air, bonding the active foam groups to the coating composition and uniform distribution of the coating over foam surface.

For coating the foam surface, synthetic latex of the SKS-65 GP state standard specification 10564-75 or BS-50 state standard specification 15080 (styrene-butadiene) grade manufactured by the domestic industry was used.

In order to obtain comparative data and substantiate the essence of the invention, 5 examples of preparation of the coating composition of the invention were carried out.

PRI me R 1. To 80 g (80 wt.%) Of latex was added 18 g (18 wt.%) Of phenol-formaldehyde foam waste (pieces, fragments of an exploited foam) pre-crushed to powder. The mixture was stirred for 10 minutes.

Under conditions analogous to Example 1, the coating mixture was prepared in Examples 2-5 with varying proportions of the components, moreover, in Examples 1-3, the ratio of the components of the foam coating mixture was within the protected range, and in 4-5 they went beyond these limits.

At the same time, a coating mixture was prepared from a known composition, taken as a prototype.

The resulting protective coatings were applied to the foam samples at a temperature of 18 - 20 ° C without preheating using a mechanical feed.

Consumption of the coating composition with a thickness of 200 microns - 400 g per 1 m.

Then, the foam samples were kept at a temperature of 18–20 ° С for 4 hours. After exposure (curing of the coating), the samples were tested for water absorption and moisture absorption (service life - aging).

For this, the foam samples were weighed and kept in water for 960 hours (40 days) at 19–20 ° С. Then, the foam samples were taken out and water absorption was determined by the difference in weight.

In order to check the service life of the obtained phenol-formaldehyde foam, aging acceleration tests were carried out in the following two modes;

I mode. Coated foam samples were frozen for 16 hours to -25 ° C and immersed in water for 2 hours. Then, the foam samples were removed from the water and tested for moisture absorption.

Then, the coated foam samples were heated for 7-8 hours to + 50 ° С, after which they were immersed in water for 2 hours. The foam samples were removed from the water and tested for moisture absorption.

II mode: The temperature of the foam samples was raised over 24 hours to + 60 ° С at a humidity of 100%, then the temperature was reduced for 5 hours to -40 ° С, then it was kept for 16 hours at room temperature and tested for moisture absorption.

Similarly tested samples of foam coated with a prototype.

The number of cycles for each regimen was taken up to 40, and testing of samples was carried out after 1.10. 20, 30,40 cycles.

The test results of the foam samples are shown in the table.

As can be seen from the above examples and the data of the table, the coated foam made by the claimed method has higher quality indicators compared to the foam, which is made by the known method taken as the prototype: water absorption decreased by 7.7% ; the service life was increased due to a decrease in moisture absorption by 7.6% in the regimen and by 6.5% in the II regimen.

The content of latex in the coating composition is less than 80 wt.% And phenol-formaldehyde foam waste is more than 21 wt.%

(see Example 4), it is impossible to obtain a protective coating with the required parameters (water absorption, moisture absorption).

An increase in the amount of latex content of 83 wt.% In the coating composition and phenol-formaldehyde foam waste of 17 wt.% Does not provide good adhesion to the foam surface of the coating mixture.

which significantly increases water absorption and moisture absorption.

The use of the claimed invention provides, in comparison with the known invention, taken as a prototype

The following technical and socially useful advantages: reduction of water absorption by 7.7%; increase in the service life of the foam by reducing moisture absorption by 7.6% in mode I and by 6.5%

by mode II; waste management; reducing the cost of foam.

Claims (1)

SUMMARY OF THE INVENTION A method for producing a water-resistant phenol-formaldehyde foam by applying a polymer composition to its surface followed by curing, characterized in that, in order to reduce water absorption and increase the service life, experimental studies of coated foam samples obtained by the proposed method in comparison with the prototype for a foam, as a polymer composition, use a composition containing synthetic styrene rubber or styrene butadiene rubber latex and phenol-formaldehyde foam waste powder in a percentage ratio of 80 - 82: 18 - 20, respectively. Table continuation