HU195241B - Scale-solvent for households - Google Patents

Abstract

Descaling compsns. for domestic use contain 3-10 wt.% hydrochloric acid in aq. soln. as active agent and 0.2-1.0 wt.% urea or thio urea and 0.2-1.5 wt.% hexamethylene-tetramine as stabiliser.

Description

The present invention relates to a household limescale solvent.

Natural waters are known to contain calcium and magnesium salts, including calcium and magnesium bicarbonate. These bicarbonates are unstable compounds and are decomposed by heat and precipitate in the form of calcium and magnesium carbonates (scale). They decompose without heating, even when the water evaporates, and precipitate forms on the water's edge.

Limescale is a serious problem, for example, in households, where it must be removed from household utensils and ceramic bathroom fixtures.

The commercially available home scale lime solvent is a dilute aqueous acid solution which, while soluble in water scale, attacks the metal parts of household equipment and thus damages them.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a limescale solvent which, while dissolving limescale well, does not or only slightly corrode metals.

According to the present invention, this object was solved with a liquid limescale diluent which, in addition to hydrochloric acid 3 to 8% by weight, was used as an inhibitor for the dissolution of lime, 0.1 to 0.5% by weight of urea and 0.2 to 1.0% by weight. containing thiourea and 0.5-1.5% hexamethylenetetramine.

The preparation of the composition according to the invention is illustrated by the following examples.

Example 1

Dissolve 86.34 g in water, 1.00 g hexamethylenetetramine, then 0.40 g thiourea and 0.10 g urea. After dissolution, 12.16 g of a 37 wt% hydrochloric acid solution is added.

Example 2

75.38 g of water was dissolved 1.50 g of hexamethylene tetramine ^10-ene, and then 1.00 g of thiourea and 0.50 g of urea. After dissolution, add

21.62 g of a 37% solution of hydrochloric acid.

The composition according to the invention dissolves the limescale well, but does not attack or, to prolonged contact, only slightly corrode the metals. To confirm this, we performed the following series of experiments.

The same surface area and mass of metal plates placed in a solution prepared as described in Example 1, ²⁰ (iron, copper, aluminum, chromium and nickel) for a period of 6 hours. After this time, the plates were rinsed with water, then with 5% sodium carbonate solution and again with water ^two fifth Then, both sides of the plates were counted for 5 minutes by blowing warm air to constant weight and finally weighed.

for comparison, commercially available Express Limestone Solvent (manufactured by Lacquer Metal Chemistry ISz. Szombathely) containing phosphoric acid as the active ingredient. The weight loss of the metal plates was measured after 6 hours of treatment.

The results obtained are summarized in Table I below:

Table I

Iron Red copper discs Aluminum- Chrome um mass loss Nickel % e% Invention of vízkőol- solvent by 0,017 0,004 0.011 0,007 0,003 A comparison parative agent 0.182 0,120 0.232 0,135 0.113

It can be seen that the composition according to the invention is much less aggressive against metals than the known limescale solvent. This is particularly important for ceramic bathroom fixtures with metal fittings and for descaling of housekeeping vessels θθ. therefore, the composition is well suited for the removal of limescale deposits on household utensils and ceramic sanitary ware, with the exception of enameled metal surfaces, not applicable.

The synergistic effect of urea, thiourea and hexamethylene tetramine in the composition of the present invention is demonstrated by the following series of experiments. In a series of experiments, a combination of hexamethylenetetramine (solution A), thiourea (solution B), urea (solution C), thiourea and hexamethylene tetramine inhibitor (solution D), and a combination of thiourea, urea and hexamethylene tetramine (solution A) Solution E) was compared

-2195241 in hydrochloric acid solution. The metal plates were treated as described above.

Composition of solutions:

Solution A.

5.0% hydrochloric acid

1.0% Hexamethylenetetramine 94.0% Water

Solution B.

5.0% Hydrochloric acid 0.4% Thiourea

94.6% water

Solution C.

5.0% hydrochloric acid

0.1% urea

94.9% water

Solution D.

5.0% hydrochloric acid

1.0% hexamethylene tetramine 0.4% thiourea

93.6% water

Solution E.

5.0% hydrochloric acid

1.0% hexamethylene tetramine 0.4% thiourea 0.1% urea

93.5% water

The results of the experiments are shown in Table II below. are summarized in Table.

II. spreadsheet

Iron Red ^- Aluminum- Chromium Nickel Copper Nickel Plates Weight Loss e%

Solution A. 0.192 0.195 0,160 3,143 0.114 Solution B. 0.185 0,120 0.263 3,115 0,075 Solution C. 0.424 0.352 0.445 3.292 0,253 Solution D. 0.169 0,043 0.103 3,065 0,047 Solution E. 0,017 0,004 0.011 3.007 0,003

The series of experiments demonstrated that the known inhibitors, hexamethylenetetramine, thiourea and urea, when used alone at normal concentrations in hydrochloric acid, do not provide adequate protection (Solution 1A, Solution B, Solution C).

The use of a combination of thiourea and hexamethylene tetramine inhibitors greatly reduced the corrosion of metals (Solution 1D). The combined use of thiourea, hexamethylenetetramine, and urea inhibitors (Solution 1E) resulted in about 45% loss of metal weight. reduced it by an order of magnitude.

This large improvement was achieved by the addition of very small amounts (0.1%) of urea. Such addition of urea concentration in itself virtually showed no effect inhibieiós ⁵⁰ (first solution C). Vízkőoldószerben achieved according to the invention can be attributed to a combination of such materials have good inhibitory ^f synergistic activity.

Claims (1)

Patent Claim Point Household limescale solvent for limescale deposits on iron, copper, aluminum, chromium and nickel surfaces, containing from 3 to 8% by weight of hydrochloric acid, characterized in that it contains from 0.1 to 0.5% by weight of urea, and It contains a mixture of 0.2-1.0% by weight of thiourea and 0.5-1.5% by weight of hexamethylenetetramine.