Hydrophilic polymers, articles and methods of making same

The invention relates to the use of novel hydrophilic polymers as coating agents for seawater exposed objects, in particular ship hulls.

It is known per se to produce hydrophilic polymers, in particular crosslinked hydrophilic polymers, and it is also known to produce them in the form of hydrogels in aqueous solution by copolymerization, wherein a predominant amount of a monoester of acrylic acid or methacrylic acid and a bifunctional alcohol, the has a esterifiable hydroxyl group and at least one additional hydrophilic functional group, in aqueous solution with a small amount of a diester of one of these acids and an alcohol having at least two esterifiable hydroxyl groups (see U.S. Patent Nos. 2,976,576 and 3,220,960).

In the previously known procedures, which use the known redox catalysts such as sodium bicarbonate and ammonium persulfate, potassium sulfate, sodium thiosulfate and ammonium persulfate or potassium sulfate, the completion of the polymerization reaction was carried out at temperatures above 0 ° C, and thereby the formation of a prepolymer, preferably in Prevents the formation of a liquid casting syrup which, as such, is dyed, pigmented, can be thickened and otherwise modified in shape and then hardened to produce solid or shaped articles such as rods, plates, tubes and other molded articles or a hard, friable foam.

In addition, only incomplete (namely, up to about 95%) polymerized through in the process known hitherto and also such a polymer, the excessively large amounts of water (more than 30 wt .-% yes even up to 80 wt .-%) to was able to absorb evenly when it was divided in aqueous solutions.

The novel hydrophilic polymers to be used in accordance with the invention which are prepared in an anhydrous state are substantially completely (ie, about 99.5%) fully polymerized and are incapable of absorbing more than about 30% by weight of water if they are evenly divided in aqueous solutions. The polymers to be used according to the invention give coatings which deter barnacles, prevent algae growth, protect against corrosion and promote the gliding of the boats provided therewith.

The hydrophilic polymers to be used in accordance with the present invention can be prepared in an anhydrous system to directly obtain liquid cast syrups in prepolymerized form which can be used for direct in-situ polymerization in the form of coatings. They may contain the usual foaming agents, such as sodium bicarbonate, to obtain hard, friable foams, which can be brought directly into the swollen state or ground directly into powder.

The hydrophilic polymers to be used in the present invention can also be prepared in an anhydrous system so as to be obtained quickly in powder form. Since the hydrophilic polymers to be used in the present invention are prepared in an anhydrous system, they can be directly converted into a powdered foam.

The hydrophilic polymers to be used according to the invention are obtained by polymerization of 100 parts by weight of a water-soluble, polymerisable hydroxyalkyl monoester of a F,. Beta.-unsaturated carboxylic acid, eg acrylic or methacrylic acid containing from 0.05 to 15, preferably from 0.1 to 0.2 parts by weight of a polymerizable diester of one of said olefinic acids, and an alcohol having at least two esterifiable hydroxyl groups in a solvent-free state; in the presence of a polymerization sufficient amount of a free-radical producing vinyl polymerization catalyst. Preferably, the monoester is mixed with the vinyl polymerization catalyst in an anaerobic atmosphere and the mixture is heated to a temperature between room temperature and about 80 ° C until said monomer has become water insoluble. The resulting mixture is then cooled to room temperature and the polymerizable diester is added along with a further amount of said catalyst sufficient to form a liquid casting syrup. The casting syrup can then be suitably dyed and pigmented, and the viscosity of the liquid mass can be increased to the desired value by adding appropriate thickening agents.

The pouring syrup can be cured to obtain the desired coatings. The polymer obtained from the cured casting fluids has good mechanical strength, reversible liquid absorbency, and the ability to retain its shape in a liquid medium and recover it after deformation by elastic recovery.

Prior to the addition of dyes, pigments, thickeners and other additives, the liquid casting syrups are added to an excess amount of water to form a polymer precipitate. The latter is soluble in highly polar organic solvents such as alcohols, glycols and glycol ethers. The precipitated polymer, when dissolved in polar solvents, is used as a polymer solution to form coatings.

The hydrophilic, soluble, thermoplastic polymers to be used according to the invention can also be prepared by suspension polymerization of the monoester, for example hydroxyethyl methacrylate, and of the diester in a non-polar medium, such as a silicone oil or mineral oil. The catalyst-containing monomer mixture is dispersed in the non-polar medium in the form of small droplets, which are then subjected to - 3 -

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Polymerize the formation of finely divided beads or beads. Such beads can be dissolved in polar organic solvents to make coatings. The beads can also be used directly for the production of the coatings. The suspension polymerization is preferably carried out in an oil bath at temperatures in the range of 50 to 150 ° C until the bubbling is completed. The ratio of suspension oil to monomer is preferably about 5: 1 to about 20: 1. The ratios of catalyst to monomer mixture are preferably about 0.05 to 1.0 part per 100 parts of monomers.

The hydrophilic polymers to be used according to the invention - polymerized in the anhydrous state - can be formed in such a way that they firmly adhere to the objects.

The starting materials for the preparation of the polymers to be used according to the invention are hydroxyalkyl esters of a ft-β-unsaturated carboxylic acid, such as 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc. These esters are prepared in an anhydrous system with suitable amounts of a free-radical generating catalyst, such as tert-butyl peroctoate, isopropyl percarbonate, benzoyl peroxide and the like. and mixed with a suitable crosslinking monomer such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, or other polymerizable diesters.

The use of the free radical-providing catalysts is useful in concentrations ranging from 0.05 g to 1 g of catalyst per 100 g of polymerizable hydroxyalkyl ester, the preferred range being between 0.1 and 0.2 per 100 g of starting material.

The mechanical properties imparted to the polymer to be used according to the invention and its ability to retain water as a homogeneous constituent are greatly influenced by the amount of polyfunctional crosslinking agent present. For the polymers to be used according to the invention, concentrations of 0.05 to 15 g of crosslinking agent per 100 g of 2-hydroxyethyl methacrylate have proven to be expedient, the preferred range being between 0.1 and 0.2 g of crosslinking agent per 100 g of polymerizable hydroxyalkyl ester.

The polymerization of the above-mentioned reaction components can be accelerated by heat applications, or it can also by certain selection of the catalyst and the amount thereof, the application of heat cease to exist and yet a rapid polymerization already at room temperature are triggered. In those cases where heat is used for curing, temperatures from about 20 ° C to about 150 ° C have been found to be suitable, with the preferred range being between 40 and 70 ° C.

The properties of the hydrophilic polymer base material can be improved by incorporating in this material a small amount of one or more additives, which may consist of synthetic resins, rosin esters, phenoxy resins, silicone resins, low molecular weight polyisobutylenes, synthetic polymers and prolamins. The new compositions are particularly suitable for the formation of polymer mixtures, which are equipped with new properties and mean an improvement or enhancement of the already existing properties of the hydrophilic polymers.

The mixture is heated or otherwise cured in the absence of compatible, volatile or nonvolatile organic solvents to produce thermosetting polymeric materials having properties superior to the properties of the major constituents of the formulation. The improved properties of these new compositions are improved hardness, improved adhesion, abrasion resistance, resilience and toughness, but of course the improvement need not be limited to these properties. The polymerized material provides coatings with improved machinability and polishability and can also be processed as a molding powder or in admixture with other molding compounds. Property improvements of lesser extent can be achieved by using small amounts of other crosslinking glycol dimethacrylates.

The polymers are used to make thermosetting surface coatings with improved adhesion.

In general, 2-hydroxyethyl methacrylate and the crosslinking monomeric ethylene glycol dimethacrylate are used in an amount of 10 to 50% by weight (more preferably 50% by weight) with 90 to 50% by weight of a technically available coumarone / indene resin type or their phenol-modified modification products in the presence of a free-radical producing catalyst such as tert-butyl peroctoate, isopropyl percarbonate and the like, and heated at temperatures of 40 to 200 ° C for about 30 minutes. In order to increase the compatibility of the components with each other, organic or inorganic solvents are included. Thus, compatible polymers with improved properties in terms of tensile strength, modulus, hardness, thermal conductivity, etc. are formed. The quantitative limits given above are also observed for the additional components of the phenoxy resins and silicone resins type.

The resulting polymers can be obtained, for example, in the form of rods which are suitable for grinding into fine powders. By mixing the reaction components with foaming agents, such as sodium bicarbonate, before curing, the polymer can be obtained in the form of a foam which is easily

No. 306191 can be crushed to a fine powder by means of shearing effectors. The pulverulent polymers are preferably obtained from foams. As stated, amounts of foaming agent of from 1 to 10 g per 100 g of the reaction components are sufficient.

The mechanical properties of the polymers to be used according to the invention are greatly influenced by the proportion of the polyfunctional crosslinking agent which is present. It has been found that concentrations of 0.05 to 15 g per 100 g of 2-hydroxyethyl or hydroxypropyl methacrylate are useful for the polymers to be used according to the invention, the preferred range being 0.1 to 1.0 g of crosslinking agent per 100 g of polymerizable hydroxyalkyl ester is.

The polymerization of the casting solutions can be accelerated by application of heat, or the heat application can be eliminated by properly selecting the catalyst and the amount thereof, and yet rapid polymerization can be initiated at room temperature. In the cases where heat is used for curing, temperatures of about 20 to 150 ° C are maintained, with temperatures of 20 to 100 ° C have been found to be particularly useful and the preferred range between about 40 and 80 ° C. The reaction is advantageously carried out in an inert or anaerobic atmosphere, it being possible for carbon dioxide or nitrogen to serve as protective gas. It is known that the presence of oxygen inhibits the polymerization reaction and then either requires a longer reaction time or has to use higher polymerization temperatures.

The invention is illustrated in the following examples, which, however, merely illustrate the invention, but are not intended to limit it in any way.

Example 1: 2-Hydroxyethyl methacrylate (50 parts by weight) and TiOj (30 parts by weight) are ground in a tube mill with Kieselsteinfiillung to a fine powder (Hegeman value 7 to 8). An additional amount of 2-hydroxyethyl methacrylate (50 parts by weight) is then added together with ethylene glycol dimethacrylate (0.2 parts by weight), cobalt naphthenate, a known drying agent for metal paints or catalyst (0.1% by weight). Parts) and tert-butyl peroctoate (0.4 parts by weight). The resulting viscous syrup is spread on a wooden boat hull and cured at 20 to 35 ° C. The seawater protective coating thus obtained is distinguished in that it can deter barnacles and also prevent algae growth and also protects against prolonged underwater treatment against corrosion.

Example 2: The procedure of Example 1 is repeated but with the modification that the casting syrup is applied to a steel body and cured at 100 ° C in the absence of cobalt naphthenate.

Example 3: The procedure of Example 1 is repeated except that a mixture of isomeric 2-hydroxyisopropyl methacrylates is used in place of hydroxyethyl methacrylate.