NO151667B - STABLE TIKSOTROP DISPERSION CONTAINING A TRIAL CYCLE INFLUORIDE AND USING A MIXTURE CONTAINING THE DISPERSION AS ANTIGROMALING - Google Patents

Description

The present invention relates to compositions containing a dispersed form of a trialkyltin fluoride. More specifically, the invention relates to stable dispersions of trialkyltin fluorides which can be stored for longer periods without any significant increase in viscosity.

A number of trialkyltin fluorides, in particular tri-n-butyltin fluoride, effectively prevent the attachment and growth of creepers and other organisms responsible for fouling submerged surfaces, e.g. hulls of ocean-going ships and piling in quays and other installations that are

set for salt water. The trialkyltin fluorides are therefore useful as a poison in anti-fouling paints. A typical antigro-

paint contains the toxin, one or more pigments and a film-forming polymer. All these components are dissolved or dispersed in an organic solvent, e.g.

xylene or toluene, optionally in combination with a ketone, e.g. 2-butanone.

To date, acceptable agents containing trialkyltin fluorides, which are solids at room temperature, have

were difficult to produce. Dispersions of trialkyltin fluorides in organic solvents show a strong tendency to agglomerate in the form of large particles. These materials cannot therefore be dispersed in coating agents or organic solvents by mixing at high speed. This unusual behavior has been explained by a difference in electronegativity between tin and fluorine.

This difference causes a relatively weak force of attraction between the tin atom on one molecule and the fluorine atom on an adjacent molecule, and results in a structure similar to a linear polymer molecule. Whatever the reason, the agglomeration is undesirable, as it makes it difficult or impossible to produce a usable coating agent where the maximum particle size is 45 µm or less. This degree of fineness cannot

achieved without cumbersome, time-consuming grinding in a grit mill or ball mill. Even after such a grinding operation, there may still be some hard agglomerates in the medium.

These agglomerates must be removed in order to obtain a usable coating agent.

It is therefore a purpose of the invention to provide stable dispersions of trialkyltin fluorides which can be easily dispersed in coating agents without the necessity of painting to achieve the desired particle size.

Surprisingly, it has now been found that the presence of certain inorganic compounds means that trialkyltin fluorides such as e.g. tri-n-butyltin fluoride can be dispersed in a certain class of organic solvents without agglomeration to give stable mixtures. The resulting mixture remains stable for long periods and can be easily incorporated into coatings, including paints.

From JP-PS 7 338 847 it is known to heat tri-n-butyltin fluoride to 40-60°C in a liquid hydrocarbon or halogenated hydrocarbon with a boiling point of 50-200°C. The resulting slurry solidifies if left standing and is therefore not practical for incorporation into antifouling paints. Even after grinding, the resulting particles do not provide a dispersion of sufficient fineness.

The invention is based on a stable, thixotropic dispersion

as stated in claim 1 and use of a mixture as stated in claim 2.

The new feature of the present trialkyl tin fluoride dispersions is that there are relatively small amounts of compounds derived from one of the metallic elements. These compounds stabilize the dispersion by preventing agglomeration of the trialkyltin fluoride particles. The following examples show that not all such compounds are suitable stabilizers, and it is therefore difficult to predict without experimentation which compounds will work.

The liquid medium is also a critical factor when it comes to the stability of the dispersion.

The cationic portion of the compounds which have been found to be effective dispersion stabilizers are derived from one of a number of specific metallic elements and include substances in groups IA, IB, IIA, IIB, IVA, IVB, VA, VIB, VIIB and VIII in the Periodic Table. The anionic part of the molecule is a residue of an inorganic acid, e.g. nitric or silicic acid, or an organic acid, e.g. p-toluenesulfonic acid, phenylphosphonic acid or a carboxylic acid with 2-12 carbon atoms. Representative carboxylic acids include acetic, propionic,

butyric, hexane, heptane, cyclohexane-carboxylic and benzoic acids.

Chlorides of polyvalent metallic elements are also effective dispersion stabilizers. In comparison, a dispersion containing sodium chloride will solidify when allowed to stand. This is also the case with dispersions containing potassium analogues of the sodium compounds mentioned in the present preparation.

Besides the choice of the right inorganic dispersion stabilizer, the choice of organic liquid is also critical for obtaining a non-coagulating dispersion of a trialkyltin fluoride. Suitable organic liquids include aliphatic hydrocarbons and aromatic hydrocarbons with a kauri-butanol number of 96 or less. The kauri-butanol number for a hydrocarbon solvent is equal to the volume in cm (measured at 25°C) of the solvent which will give a certain turbidity when added to 20 g of a standard solution of kauri resin in n-butanol . The test method is published by the American Society for Testing and Materials under the designation ASTM Test No. 01133-61 (new approval given in 1973).

Representative useful liquid hydrocarbons include aliphatic hydrocarbons. These hydrocarbons can be used individually or in commercially available mixtures such as white spirit, petroleum ether and naphtha. The class of aromatic hydrocarbons includes xylene. Toluene has a kauri-butanol number of 105 and is therefore not a suitable medium for the present dispersions. However, it can be used in admixture with aliphatic hydrocarbons. Other useful liquid media include alcohols containing 4-12 carbon atoms, e.g. butanol. Surprisingly, a stable dispersion in n-propanol cannot be produced there.

The trialkyltin fluorides which can be used in the stable dispersions according to the invention have the general formula R^SnF, where R means alkyl with 3-6 carbon atoms. If the dispersion is to be incorporated into a coating material intended for

to prevent fouling with creepers and other organisms on ship hulls and other normally submerged structures, R is preferably n-butyl.

By using the inorganic compounds and liquid organic liquids that are indicated in the preceding description and in the claims, it is possible to distill mixtures containing from approx. 10 percent by weight up to approx. 70% by weight of a tri-alkyl tin fluoride. It has previously not been possible to incorporate more than approx. 40% by weight of a trialkyltin fluoride in a dispersion. The maximum amount of fluoride that can be incorporated will of course vary somewhat depending on the dispersion stabilizer and organic liquid that is chosen.

The physical form of the present dispersions can vary from viscous liquids to semi-solid pastes, depending on the concentration of trialkyltin fluoride. An important advantage of these dispersions is that they exhibit thixotropy and can therefore be easily mixed by stirring with other components that are usually used in paints and other coating agents. These additional components include natural or synthetic film-forming polymers, e.g. rosin and copolymers of vinyl chloride with one or more ethylenically unsaturated monomers such as e.g. vinyl acetate, pigments such as titanium dioxide and iron oxide, viscosity modifiers, special clays such as bentonite, and one or more organic solvents.

Typical antifouling agents that can be prepared using the present dispersed form of trialkyltin fluoride contain 1-20% by weight of the trialkyltin fluoride dispersion containing one or more of the aforementioned salts and organic liquids, 10-50% by weight pigments, typically titanium oxide or zinc oxide alone or in combination with colored pigments such as iron oxide, 10-50 percent by weight of at least one film-forming component which typically comprises vinyl chloride homo- and copolymers, rosin and chlorinated gums such as e.g. polychloroprene, and 20-60 percent by weight of one or more organic solvents, including xylene, cyclohexanone, 2-butanone and mixtures of hydrocarbons commonly referred to as "aliphatic naphtha" or naphtha with a high flash point ("high flash naphtha"). A small amount of viscosity modifying agent, e.g. a betonite clay, is usually incorporated to make the finished coating material thixotropic.

Production of a particularly preferred coating agent is described in one of the following examples.

Incorporating tri-n-butyltin fluoride into a paint recipe has so far been a lengthy and time-consuming operation due to the fluoride's tendency to agglomerate. The resulting paint must usually be ground for several hours in a gravel or sand mill to achieve a fineness of 4-5 on the Hegman N.S. scale that goes from 0 (no paint) to 10 (excellent paint). A value of 4-5

on this scale corresponds to an average particle size of 40-70 pm. Similar problems due to agglomeration are encountered if one attempts to disperse the trialkyltin fluoride in an organic solvent before incorporating it into a paint recipe. Furthermore, once a dispersion with the desired particle size has been obtained, it quickly solidifies into a wax-like solid and therefore cannot be stored for any significant period of time.

The following examples show preferred embodiments of the dispersions according to the invention. In the examples, all parts and percentages are parts by weight or % by weight unless otherwise stated.

Example 1

Dispersions of tri-n-butyltin fluoride were prepared by mixing 60 parts of this compound, 5 parts of the inorganic stabilizer and 35 parts of a mixture containing "64% special naphthalite (a mixture of liquid hydrocarbons containing less than 8% aromatic hydrocarbons ), 12% ethylbenzene, 9% n-butyl acetate, 5% iso-butyl acetate, and 10% n-butanol. The flash point of this mixture is 14.4<0>C; the kauri-butanol number is 36, and the boiling point is in the range 123-145°c. 100 g of the resulting mixture was placed in a cylindrical container with a diameter of 5.1 cm and a height of 11.4 cm. In the same container were also placed 250 g of stainless steel balls with a diameter of 4.7 etc. The container was then sealed and shaken vigorously for 20 min,.after which the contents of the container were emptied onto a large mesh sieve. Dispersions which solidified during the grinding process, and which crumbled when poked with a spatula, were considered unacceptable and was not tested further Acceptable materials were either viscous liquids or homogeneous, cohesive semi-solids that could be forced through the openings in the mesh using a spatula. The materials that passed the mesh were collected and stored under ambient conditions for two days. At the end of the period, they were examined to determine whether any changes in their physical form had taken place. The materials that had solidified and could no longer be stirred with a spatula were considered unacceptable. All of the acceptable materials were thixotropic, semi-solids or viscous liquids which exhibited a considerable reduction in viscosity under the influence of shear forces. Some of the materials appeared to be cohesive solids, but could still be easily stirred with a spatula by hand using very little force.

Inorganic compounds that gave acceptable dispersions included: Sodium p-toluenesulfonate

Calcium di(p-toluenesulfonate)

Sodium phenylphosphonate

Calcium phenylphosphonate

Barium acetate

Strontium acetate

Zirconium acetate

Manganese (II) acetate

Lead acetate

Calcium nitrate

Iron(II) nitrate

Iron (III) nitrate

Zinc nitrate

Sodium silicate

Magnesium chloride

Calcium chloride

Manganese(II) chloride

Iron (II) chloride

Iron(III) chloride

Copper (II) chloride

Tin (II) chloride

Bismuth chloride

Inorganic compounds which did not give acceptable dispersions included: Potassium p-toluenesulfonate

Potassium phenylphosphonate

Potassium acetate

Nickel(II) acetate

Copper (I) acetate

Copper (II) acetate

Cadmium acetate

Potassium nitrate

Barium nitrate

Nickel(Il) nitrate

Magnesium silicate

Chlorides of sodium, potassium and monovalent copper Calcium fluoride

It is believed that an effective stabilizer will interfere with the formation of strong bonds between the fluorine atoms on a molecule and the tin atoms on adjacent molecules. This bond formation is believed to be responsible for the agglomeration that almost always occurs when a trialkyltin fluoride is dispersed in an organic solvent in the absence of one of the inorganic compounds present.

Example 2

The effect of various organic liquids or thinners on the stability of a dispersion containing 60% by weight tri-n-butyltin fluoride, 5% calcium carbonate and 35% of the organic liquid was determined by preparing a dispersion as described in the previous example. The dispersions which could be classified as viscous liquids or cohesive semi-solids after the original grinding operation were stored for one week under ambient conditions and then examined to determine whether the original thixotropic nature had been maintained.

The organic liquids evaluated included a mixture of aromatic hydrocarbons marketed as "Solvesso 150" and having a typical flash point of 63-65°C, VM&P naphtha {a mixture of aliphatic hydrocarbons with a typical flash point of 6, 7°C

in a closed cup (tag closed cup) and a boiling point range of 118-139°c}; white spirit { a mixture of aliphatic hydrocarbons with a typical flash point of 42.2°C (closed cup) and a boiling range of 160-196°C }; ethylbenzene, amyl acetate,

a mixture (A) containing 33.3% VM&P naphtha, 2 8.9% cyclohexane and 37.8% amyl acetate and another mixture (B) containing 34.2% white spirit, 4.4% "Solvesso 150", 12.2% ethylbenzene and 4 9.2% amyl acetate.

The assessment also included cyclohexane, xylene, 2-butanone, n-butyl acetate, isobutyl acetate, n-butanol, ethylene glycol, n-propanol, octanol, "Cellosolve" acetate (ethylene glycol monomethyl ether monoacetate) and toluene. Of the solvents evaluated, two mixtures (A&B), VM&P naphtha, "Solvesso-150", white spirit, xylene, n-butanol and octanol gave acceptable dispersions. Dispersions prepared using the other solvents solidified during a storage period of one week or were too stiff and rubbery for use in a paint recipe.

Example 3

A dispersion containing 60% by weight tri-n-butyltin fluoride (TBTF) prepared as described in example 1 and with calcium chloride as stabilizer was incorporated into a common paint recipe with the following composition:

The solvent used to prepare the dispersions was a mixture containing 64% special naphthalite, 12% ethylbenzene, 9% n-butyl acetate, 5% isobutyl acetate and 10% n-butanol. Special naphthalite is described in example 1.

The amount of tri-n-butyltin fluoride dispersion used corresponded to 12% by weight of the compound in the recipe. The dispersion was mixed together with the other ingredients of the recipe to give a homogeneous mixture.

The paint was scored using a Hegman N.S. gauge to determine the "fineness" of the painted product. Furthermore, a 0.0076 cm thick film was applied to a metal surface using a draw-down blade.

and the structure of the resulting film judged according to the following scale: 1. Rough surface, easily detected by rubbing the hand over the surface of the coating 2. 10-20 observable lumps, evenly distributed on the surface of the paint

3. Some clear lumps

4. Smooth

The results of the paint assessment are shown in the table.

A Hegman fineness of 4 or 5 is considered acceptable.

The film produced using a dispersion containing 0.5% by weight calcium chloride and 60% tri-n-butyltin fluoride was too coarse in consistency to be considered acceptable, but this amount of calcium chloride will be sufficient to stabilize dispersions containing less than 60% of the trialkyltin compound, e.g. about. 50 percent by weight.

Example 4

A typical red paint suitable for use with the present dispersed form of tri-n-butyltin fluoride can be prepared according to the following instructions:

Example 5

A dispersion containing 50% by weight of TBTF prepared as described in Example 1 using calcium chloride as a stabilizer was incorporated into a common paint recipe where the film-forming component was chlorinated rubber.

1- "Benton 27"

2- 64- 65 weight percent chlorine, viscosity = 17-25 oP, measured in a 20 weight percent solution in toluene at 25°C.

The paint was prepared according to the following instructions: 1. Combine bentonite clay and methanol, mix thoroughly and combine with rosin; continue until the mixture is homogeneous. 2. Add solvent (xylene) to the pigments to achieve the desired viscosity during dispersion. 3. Add the pigments in the order given below and disperse to a corresponding paint grade

5 on a Hegman N.S. scale has been achieved:

4. Add the chlorinated rubber slowly while stirring until it is dissolved. 5. Add the TBTF dispersion and mix to achieve a paint grade equivalent to 4-5 on the Hegman N.S. scale.

Claims (2)

1. Stable thixotropic dispersion containing a) 40-70 percent by weight of a trialkyltin fluoride of the formula R^SnF where R means alkyl with 2-12 carbon atoms and b) 20-60 percent by weight of at least one organic liquid with a kauributanol number of 96 or less and selected from alcohols with 4-12 carbon atoms, aliphatic hydrocarbons with 5-12 carbon atoms and aromatic hydrocarbons, characterized in that the dispersion additionally contains c) 0.5-10 percent by weight of a compound selected from 1) lithium and sodium salts of p-toluenesulfonic acid, phenylphosphonic acid and silicic acid, 2) calcium, magnesium, sodium, lithium, iron and zinc salts of nitric acid, 3) salts of p-toluenesulfonic acid or phenylphosphonic acid and magnesium, calcium, strontium or barium, 4) chlorides of metallic elements selected from groups IB, IIA, IIB, IVA, IVB, VA, VIB, VIIB and VIII in the periodic table and 5) lead, manganese(II), zirconium, barium and strontium salts of carboxylic acid with 2-12 carbon atoms. 2. Use of a mixture that is essential in everything consists of 1-20 percent by weight of a dispersion as stated in claim 1, 10-50 percent by weight of at least one pigment, 10-50 percent by weight of at least one film-forming binder selected from vinyl chloride homo- and copolymers, rosin and chlorinated gums, 20 -60 percent by weight of at least one organic solvent and possibly up to 5 percent by weight of a bentonite clay, as an antifouling paint.