DE3016188A1 - Microbicidal bandage for protecting wood, esp. pole at ground level - comprises polyurethane-polyurea gel contg. rotting inhibitor - Google Patents

Abstract

Bandage with a microbicidal finish for protecting wood consists of a polyurethane-polyurea gel (I), contg. conventional rotting inhibitors. The bandage is used for wooden poles, e.g. telegraph and other poles of pine, fir or spruce wood, which are anchored in the ground, to prevent rotting at ground level. (I) can be produced economically and in reproducible quality. The properties can be optimised to suit the application. In an example, a wooden pole was coated with (I) and then given a protective covering of plastics film or sacking. In the prepn. of (I), 687 (wt.) pts. polyether prepd. from 60 pts. ethylene oxide and 40 pts. propylene oxide, with glycerol as starter (OH no. 28) were heated in 30 min. and stirred 2 h at 120 deg.C with 113 pts. TDI (80% 2,4-, 20% 2,6- isomer), giving a prepolymer with an NCO content of 4.6% and viscosity of 6300 cP at 20 deg.C. 15 pts. prepolymer were stirred into 120 pts. water at +5 deg.C in 3 s. After 80 s, 15g active salt mixt. were added and stirring was continued for 10 s. The mixt. was poured onto polyester fabric, where it set to a gel.

Description

Wood protection bandages

The invention relates to antimicrobial, in particular fungicidal, finished Wood protection bandages for wooden poles.

Wooden masts, such as those used for telephone and electrical free masts made of pine, Fir or spruce wood used are usually anchored in the ground. In the uppermost part of the wooden pole inside the earth, in the oxygen from the air can penetrate, the mast is particularly at risk of being decomposed by rot. It is therefore advisable to take special precautions in this area of the mast against putrefaction.

In DE-PS 975 608, for example, wood protection bandages made from flexible strips or films of high molecular weight organic plastics known to protect the Wood's salt mixtures from alkali fluorides, alkali dichromates, alkali dichromates, alkali arsenates, Contain dinitrophenol and pentachlorophenol.

The plastics used in US Pat. No. 3,974,350 are polyurethane-polyurea gels known, which are used as a carrier for microbicidal active ingredients and for salts can.

There were new microbicidal wood protection bandages based on of a plastic that consist of polyurethane-polyurea gels, the contain the usual active ingredients to protect the wood against rot.

The polyurethane-polyurea gels to be used according to the invention are partially known from DE-OS 2,347,299. They are preserved through implementation of isocyanate group-containing prepolymers made of polyethers with at least 40% of ethylene oxide units such as diamines or polyamines or water as chain extenders in the presence of water and / or alcohols as dispersants, as well as others Additives.

The active ingredients can be used in the polyurethane-polyurea gels To protect the wood against rot, store it easily. The polyurethane-polyurea gels are available inexpensively in a consistently reproducible good quality. By Change in their structure, in particular by varying the type and amount of polyol and the isocyanate, the gel properties can be optimally matched for the active ingredient adapt to necessary requirements. Such gels show a compared to theirs External dimension proportional shrinkage. Because of their primary valence forces Due to the type of cross-linking, they are also extremely dimensionally stable in the heat. Even at temperatures of up to 100 "C, the gel does not flow.

The temperature-stable and easily changeable in their property profile Polyurethane-polyurea gels are obtained by implementing Prepolymers containing isocyanate groups and based on polyethers with ethylene oxide units with diamines or polyamines or water as chain extenders in water and / or Alcohols in the presence of the active ingredients and optionally other additives. Of the The term gel for such materials is intended to refer to their physical properties of the jelly or gelatinous end product as the exact polymer-physical one Structure according to today's views of colloid chemistry about this state reproduce.

The implementation of the individual components with the formation of the gels happens spontaneously. Due to the high speeds of formation, the production the polyurethane-polyurea gels can easily be designed continuously, which is very beneficial for the production of wood protection bandages.

Dispersants for gel formation are both water and alcohols or mixtures of both, so that the gels can also be divided into hydrogels and alcohol gels can be. Both volatile monoalcohols such as Ethanol, isopropanol or butanol in question, as well as low-volatility polyalcohols, such as ethylene glycol, diethylene glycol, glycerin and trimethylol propane.

The production of the polyurethane-polyurea gels can be done in different ways Kind of done. So it is possible to use all components, i.e. the prepolymer, the dispersant, the active ingredient, the chain extender and optionally other additives together at once give. It is advisable to go step by step before.

The active ingredient is used alone or in a mixture with other additives, such as dyes and optionally crosslinking agents such as amines in the dispersant dissolved or emulsified. In parallel with this, an emulsion or solution of the prepolymer is created produced in the dispersant and then both solutions or emulsions approximately stoichiometric proportions mixed together. The mixture is in Molds poured in which the wood protection bandage according to the invention in a period from a few seconds to minutes.

The wood protection bandage is depending on the chain extender used compact or foam-like. If amines are used as chain extenders, if compact gels are obtained, if water is used, the result is because of the conversion of the isocyanate groups with water to form gaseous carbon dioxide foam-like products.

Intensive mixing of the starting components makes the Production of the polyurethane polyurea gels facilitates and the quality of the gels improved.

In the simplest case, the mixing can take place in a zone of increased turbulence, caused by a mechanical stirring device. Better ones Results are obtained using high-speed mixing units, for example of centrifugal homogenizing machines or of agitator mixing chambers known per se commercial polyurethane foaming machines.

Intensive mixing can also be achieved by using Mixing devices of polyurethane Reach foaming machines, in which the mixing takes place by countercurrent reaction.

The prepolymers of polyethers containing at least 40% ethylene oxide and polyisocyanates which still contain free isocyanate groups at the terminal end in a manner known per se by reacting the corresponding polyether with a excess amount of polyisocyanate, i.e. with an NCO / OH ratio greater than 1, preferably 1.5 to 20, particularly preferably 2 to 10, produced.

That used for the production of the wood protection bandages according to the invention Polyurethane-polyurea gel generally has an isocyanate content in the prepolymer from 2 to 20% by weight, preferably from 5 to 10% by weight.

If amines are used as chain extenders, for the formation of the polyurethane-polyurea gels is essentially stoichiometric Amounts of prepolymers and amines required. In the technical implementation of the In the process, however, it is a question of a suitable residence time in the mixing units to achieve, proved to be advantageous, with an excess of the amine component to work, i.e. with an NH2 / NCO ratio greater than 1, preferably of 1 up to 1.2.

If water is used as a chain extender, it can also here the NCO / H20 ratio can be stoichiometrically equivalent. But it is also possible and this is especially true in the manufacture of foamed Gels the case of using significantly more water than for the reaction with the isocyanate groups would be required. It is then even of particular advantage to use the water as a To use dispersants, so that foam-like hydrogels result. In In this case the water has a double function.

On the one hand, it is the reaction component that reacts with the isocyanate groups, on the other hand also the dispersant.

When preparing the gels, the amount of water present is and / or Alcohol variable within wide limits. In relation to the total amount of gel, that can Weight of alcohol and / or water up to 98 wt .-%. By the proportion between polymers and dispersants, however, the properties of the obtained Gels strongly affected. In general, the gels are said to have an increasing polymer content more stable and harder and with decreasing polymer content up to the limit of about 2 % By weight softer and less structurally stable.

If the dispersant is very firmly bound in the gels, it can step out more or less quickly depending on its vapor pressure, whereby the gel body gradually shrinks in proportion to its external dimensions. During this process the active ingredients diffuse out of the gel body and evaporate into the environment.

The shrinkage of the gel makes it a particularly firm concern reached the wood protection bandages on the wooden pole.

The active ingredients contained in the wood protection bandages according to the invention are up to date of the technique. Examples are: Salt mixtures of alkali fluoride chromates and bichromates and arsenates, if appropriate with the addition of organic compounds such as dinitrophenol and pentachlorophenol.

The amount of active ingredient in the gels varies greatly and is dependent on the respective type of active ingredient. In general, however, it is between 2 and 30% by weight, preferably between 10 and 20% by weight.

The polyurethane-polyurea gel containing the active ingredient can on can be applied to the wooden pole in various ways. So it is possible both to apply the gel directly to the wood, such as by pouring or spraying, as well first to provide a carrier layer with the gel, also here about again Pouring, spraying or squeegeeing, and the resulting bandage with the gel side to bring on the wood. The respective outside, that of the air or If soil is exposed, it must also be covered with a film.

About the active ingredients on their backing before and during use to hold on, is expediently still on the polyurethane-polyurea gel a support layer made of textiles, glass fibers or similar materials is attached.

Although it was known from US Pat. No. 3,975,350 that polyurethane-polyurea gels can be used as carriers for microbicidal active ingredients, although from from DE-PS 975 608 it was known that plastic bandages with embedded microbicides Active ingredients as wood Protective bandages can be used It is surprising that the wood protection bandages according to the invention are made from polyurethane-polyurea gels can be used because it has been found that the inclusion of known per se Wood preservatives (e.g. salts) in polyurethane-polyurea gels, compared to known ones Wood protection bandages represent an unexpected improvement in application.

The wood protection bandages according to the invention have their carrier material a material that has "hydromechanical" properties - in contrast to all previously known carrier materials for wood protection salts for use as wood protection bandages.

The discovery of these essential properties results in use from polyurethane-polyurea gels to a surprisingly better introduction and Sustainability of the spread of the effects of the salts in the wood (diffusion).

The bandages according to the invention thus represent a significant advance in bandage technology.

Because a wooden pole draws up to one liter of water from the earth every day can, which he gives together with the adjacent bandage, can cause diffusion of the active ingredient are introduced into the wood. The main advantage of the The use of polyurethane-polyurea gels is that they are used as a carrier material - in contrast to other common carrier materials - hydrophilic are and consequently a faster, more intensive diffusion in addition to the active wood preservatives bring about and ensure (protective depot enrichment in wood and fixation). In the case of the carrier materials used up to now, those stored in the bandages must Due to their hygroscopic properties, active ingredients first initiate diffusion, so that the protective substances can penetrate the wood of the wooden pole to be protected.

Example The wooden pole (1) is made with the active ingredient below described polyurethane-polyurea gel (2) and then covered with a protective layer made of plastic film or sackcloth (3) (following drawing).

Polyurethane gel a) Preparation of the prepolymer 687 parts by weight of a Polyethers based on glycerine with a hydroxyl number of 28 from 60 parts by weight of ethylene oxide and 40 parts by weight of propylene oxide are in a reaction vessel together with 113 parts by weight of toluene diisocyanate (80% 2.4- and 20% 2,6-isomer) heated to 1200C within 30 minutes with stirring. The reaction mixture is stirred at this temperature for a further 2 hours. That The prepolymers obtained have an isocyanate content of 4.6% and a viscosity of 6300 centipoise at 200C.

b) Preparation of the active ingredient gel To 120 parts by weight of water with a temperature of + 50C are 15 parts by weight of the prepolymer described under a) within 3 seconds with mechanical stirring (stirring speed 1200 revolutions / minute) admitted. After a stirring time of 80 seconds, 15 g of an active ingredient-salt mixture are added and mixed intensively in another 10 seconds. The mixture thus obtained is on a polyester fabric is poured, where it solidifies to a gel.

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Claims (2)

Claims 1) Microbicide-equipped wood protection bandage based on of a plastic, characterized in that a polyurethane-polyurea gel used, which contains the usual active ingredients to protect the wood against rot. 2) Use of wood protection bandages made of polyurethane-polyurea gels, which contain the usual active ingredients to protect the wood against rot.