SU664971A1 - Method of obtaining modified phenolformaldehyde resin - Google Patents

Description

one

The invention relates to a technique for the production of fast-curing phenol-formaldehyde resins and can be used in the manufacture of press compositions, impregnating materials, foams, adhesives, coatings.

A known method for producing phenol-formaldehyde resins modified with polyisocyanates I.

According to a known method, high polymers are directly modified, which are condensation products of phenol or its derivatives with formaldehyde.

However, this modification method limits the scope of application of the modified resins, since, due to the sensitivity of the polyisocyanates to water and air moisture, the modifier must be added to the polymer immediately before its use. In addition, it is required (the use of "dry polymers and solvents. If these requirements are not met, the polyisocyanates, after reacting with water, turn into inactive, non-modifying loliamines according to the scheme

R - () "+ nH, (NH,)" - fnCO ,.

This circumstance makes the modified polymers unsuitable, for example, in the manufacture of press compositions, impregnation materials, etc.

The aim of the invention is to obtain a fast-hardening modified phenol-formaldehyde resin, which would be insensitive to water and air moisture.

The goal is achieved by co-condensing the phenol, aldehyde and the polyisocyanate by heating. Moreover, the downloaded is the interaction of a polyisocyanate, such as hexamethylene diisocyanate, toluene diisocyanate (with a ratio of isomers of 2.4: 2.6 and 80:20) and others with phenol at a ratio of 1: 2-10, respectively, then the resulting product is condensed with formaldehyde 1.1 - 2.5 mol per 1 mol of fepol at 98-160 ° C.

Formaldehyde can be used both in the form of a 40% aqueous solution (formalin) and in the form of a solid low molecular weight polymer paraforme Due to the fact that the polyisocyanate is in a polymer in a chemically bound state, there is no danger of its deactivation during processing , during storage and transportation. This makes the polymer technology and versatile.

Example 1. A mixture of 16.8 g (0.1 mol) of hexamethylene diisocyanate, 56.4 g (0.6 mol) of phenol and 2.5 ml of trimethylamine is heated at 60 ° C for 2 h, then 21.6 g are added with stirring (0.72 mol) of formaldehyde in the form of an aqueous solution (formalin). By adding caustic alkali, for example KOH (can be NaOH and others), it is adjusted to pH 8.5-9. The temperature of the mixture is raised to 98-100 ° C and heating is continued for 6 hours. Addition of 0.1 n. The HC1 solution is adjusted to pH 6-7. After a clear separation of the reaction mixture into 2 layers, the upper aqueous layer is drained, the lower resin is treated with a sharp lar for 1.5 h and dried with 55–60 ° C in a vacuum-drying cabinet.

Example 2. Do it for example 1, only take formaldehyde in the form of paraform. The temperature of the reaction mixture is raised to 160 ° C and maintained for 3 hours. After the solution becomes clear, the heating is stopped.

Properties of modified phenol formaldehyde resin:

Density, g / cm3,18-1,20

Drop point, ° C 88-110

The viscosity of the 50% aqueous solution in acentone shri 20C, cPz 12-20

Gelation time on

pritch at 150 ° C, s32-40

Phenol content,% 3

Degree of cure

Soxhlet,% 94-96

Warranty period of storage | at 20 ° С, months.9

The properties of the modified resin depend heavily on the ratio of the reactants.

If the minimum amount of phenol is taken to be 1 mol per 1 mol of polyisocyanate, then with any amount of formaldehyde, low molecular weight adducts are obtained, which in the cured state form brittle polymers that have no practical application. If you take the maximum amount of phenol - 10 mol, then for any amount of formaldehyde, the content of urethane coarse relative to the mass of the phenolic nuclei will be so small that the intensifying effect will be small. The curing rate of the resin is determined by the content of methylol groups and Takes a value of 180-210 s when the amount of formaldehyde is 1.5-2.4 mol per 1 mol of phenol and 230-300 s when the amount of formaldehyde is 1.1-1.4 mol per 1 mol of phenol .

The rate of curing of the modified resin obtained when the ratio of ingredients (in moles) of hexamethylene diisocyanate, phenol and formaldehyde is 1: 2:: 2.5--3.2 is 20-25 seconds at 150 ° C, and

at a ratio of 1: 10: 13-18 - / O-80 s at 150 ° C.

Modified phenol formaldehyde resins were used to prepare the press composition and impermeable graphite.

Example 3. A press composition was prepared based on the modified phenol-formaldehyde resin. Use ingredients and technology of preparation of press powder E-2-330-02.

Physicomechanical indicators of press position based on modified phenol-formaldehyde resin.

Density, 4

Destructive stress, kgf / cm:

compression 1400-1800

static bending800

Specific impact viscosity, kgf-cm / cm. 6.5

Brinell hardness,

CGS / MM2 25-30

Martens heat resistance,

° С120

Water absorption for 24 hours,% 0.01-0.03 Benzostoykost for 24 hours, 1% 0.03

Electrical resistivity: superficial. Ohm .. 5-10 volume, Ohm-cm5-10

Dielectric Permeability: at 50 Hz8.0-9.0

at 108 Hz4.0-5.0

Tangent of dielectric loss angle: at 50 Hz0.08

at 108 Hz0.03

Electrical strength, kV / mm 15 Samples are prepared by compression pressing.

Pressing mode: Pressing pressure, kgf / cm 220 Preheating: Temperature, ° С100

Duration, min5

Pressing temperature, C 195 ± 5 Shutting speed,

min / mm

product thickness 0.1

Example 4. Impermeable graphite. Graphite plates of 150X150X10 mm are impregnated with modified phenol-formaldehyde resin and cured at 160 ° C for 50 minutes.

Physico-mechanical properties of impermeable graphite:

Density, g / cm3 1,8

Destructive stress, kgf / cm:

when stretched 240-250

in compression 1100-1200

bending260-320

Specific impact viscosity

kgf cm / cm 6.5

Specific heat

kcal / gf- ° C. 0.25-0.30

Heat transfer coefficient, kcal / mH-° C

Thermal - coefficient of expansion, 1 / ° С

Water absorption, g / dm

Breathability, kgf / cm

Operating temperature ° C

Claims (1)

Invention Formula A method for producing a modified phenol formaldehyde resin comprising condensation of phenol, aldehyde and nitrogen-containing modifier upon heating, characterized in that, in order to obtain a fast-curing resin, polyisocyanates are taken as a nitrogen-containing modifier, first the polyisocyanate is reacted with phenol at a ratio of 1: 2-10, respectively, and the resulting a product with formaldehyde, taken in an amount of 1.1--2.5 mol per 1 mol of phenol at 98-160 C. Sources of information taken into account in the examination 1. US patent number 2349756, 260-57, 1944.