JPS5833105B2 - How to coat the substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing foils, textile coverings and laminates from polyurethane and polyurethaneurea powders by knife coating and screening methods.

Coating and laminating the sheets can be accomplished in a variety of ways using a variety of materials.

Conventional methods used for this purpose in the textile industry include, for example, knife painting, padding, spraying and calendering.

For technical reasons, it is often necessary to use coatings and laminates that can be applied in liquid form during the process.

Exceptions to this rule include, for example, the flame lamination of calendered polyurethane foams commonly used in the rubber industry or the application of polymer powders to various sheet materials by thermal sealing.

It is known to utilize materials such as polyurethane powders to line carpets using coating knives or as floor coverings in automobile construction.

However, aside from these exceptions, coating and lamination techniques rely on the use of products within suitable viscosity ranges that can be applied by industrial glue coating or spraying methods.

For example, when a thermoplastic polymer is applied, for example by the so-called roller melting method, the desired hardness can be adjusted by heating it above its melting point.

However, one disadvantage of this method is that the polymer is held at elevated temperatures for long periods of time and is simultaneously subjected to large mechanical stresses.

Not all polymers can withstand such harsh conditions.

As well as over a wide range of temperatures, the precision (the so-called convexity) of the rollers used for roller melting must be a constant standard, especially for extremely thin layers of polymers, e.g. When used at 4 og/m, it is difficult to satisfy in practice.

A widely used method in practice involves dissolving the polymer in an organic solvent and then applying the resulting solution by spreading or spraying.

The inherent advantages and disadvantages of both these methods are well known in the art.

The concentration of solids in the spreading or spraying solution is
Particularly in the case of high-quality products based on polyurethane, they are relatively low, and in spread coating or lamination processes they therefore contain relatively high amounts of solvent.

For ecological and economic reasons, it is necessary to recover the evaporated solvents and solvent mixtures and recycle them, preferably in purified form, after careful rectification.

Furthermore, the operations necessary to dissolve, sifter or otherwise process the paste are very time consuming and require the use of considerable equipment.

Increasingly, aqueous emulsions or dispersions can be used for coating and lamination processes.

Methods of this kind are particularly interesting because they are physiologically and ecologically harmless.

Their main disadvantage, however, is that very few emulsions or dispersions of synthetic polymers are stable when frozen.

In contrast to frozen solutions of polyurethane dissolved in organic solvents, for example, frozen aqueous emulsions or suspensions are often unusable even when they are thawed.

Aqueous suspensions of polymer particles, on the other hand, are stable in the frozen state.

In reality these suspensions are unstable dispersions.

The polymer particles can be recovered in solid form from the suspension by decanting and then careful drying.

These solid substances can be reconverted into aqueous suspensions or pastes, if necessary, by redispersing them in water, optionally with the addition of additives such as thickeners, fillers or inorganic pigments. .

One disadvantage of using an aqueous paste, however, is that it requires considerably more energy to evaporate the water, even more than would be required if an organic solution was used.

There is therefore great interest in the coatings industry to find methods that can be operated in a dry manner, ie without the use of any solvents or dispersants.

As mentioned above, dry powders can be used in exceptional cases, for example to heat seal carpet backings or textiles.

Belgian Patent No. 770,420 describes the application of polyurethane powders by a modified electrostatic powder spraying method.

Apart from the fact that this requires very specific and complex mechanical techniques, it can also be used to apply powders with very specific electrical properties, including current resistances of over 1014 ohms/cm. Not too much.

The knife painting method is described in ordinary terms in Belgian patent no. 664.
It is described in No. 168.

However, the powder according to Belgian Patent No. 664168
When applied using a coating knife, they can only form thick coatings and are therefore obtained in a form that cannot be universally used.

There is therefore a gap in technical knowledge regarding coating sheets and laminated sheets, which has given rise to a desire to develop coating methods that do not have the above-mentioned drawbacks.

Some kind of dry polyurethane powder is produced in a normal coating factory.
It has been found that it can be applied by conventional spread coating and screening methods.

In contrast to that described in Belgian Patent No. 770,420, electrostatic powder spraying methods (ESP) can be used for the application of these powders, but this is not necessary.

The present invention provides coatings, either homogeneous or inhomogeneous, uniform or irregular, varying in weight per unit area from 109/rrl to almost any desired thickness according to its particular criteria. It differs from Belgian Patent No. 664168 in that it clearly states that the powder must be selected in order to obtain a

It is clear that the solid particles must meet strict requirements, in particular with regard to their surface properties and melting properties.

The diameter of the particles should be in the range 5-200μ, preferably 8-150μ.

The particles should have a smooth surface and be approximately spherical in shape from the beginning so that they can be easily diffused and flushed.

The melt properties of the polymer are particularly important.

The best way to characterize the product used according to the method of the invention is by plotting an intrinsic melt index (IMI) curve.

To measure the intrinsic melt index, which does not change over time, a synthetic resin melt heated to a predetermined temperature is extruded at a predetermined pressure through a passage (nozzle) with a predetermined ratio of diameter and length. -6
It is measured by measuring the extruded volume, which is used as a measurement standard for melt index similar to 5T.

When the melt index is measured by varying the preheating time in this way, the intrinsic melt index is 1.
Obtained by extrapolating to = 0 (assuming that the relationship between time and melt index is always a straight line)
.

This intrinsic melt index is constant for a given material regardless of the preheating time.

This melt index is independent of time, so if the material can be heated to the test temperature in 0 minutes, how much material will be extruded under the given test conditions after a preheat time of 0 minutes? This shows that.

The test equipment used here was an HKV2000 viscometer [Ruchenlodenw
ald) (West Germany) Getfeld ((Jtt-fe
rt) company].

The nozzle of this device had a conical inlet with a length of 15 lobes, a diameter of 1.05 mm, and an opening angle of 60°C.

The pressure on the melt was 177, Ok p /crA.

If measurements of the melt index, which does not vary over time, are made at various temperatures but otherwise under the same conditions, and the obtained values are plotted on a graph, will the resulting graph be a straight line with a characteristic slope? Or it becomes a curve.

Melting point or melting range of 110 to 250°C, preferably 1
It has been found that it is suitable for coating and lamination to use polyurethane powders in the range 10-190°C.

Moreover, the IMI curve resembles the rising part of the parabolic line,
As shown in Figure 1, 5 to 50°C, preferably 10
Within the temperature range ~40°C the IMI curve is 2 per 10 minutes.
g to 50 g per 10 minutes.

Powders with melting properties represented by curve 1 could not be used in the process of the invention, whereas curves 2 and 3 were obtained by testing polyurethane powders that could be used in accordance with the invention. (Example 1 and Example 3 products).

Polyurethanes or polyurethaneureas suitable for use according to the invention further have an ionic group content in the range of 1 to 15 meq/100 g and a current resistance of 1010
Must be within the range of ~1014 ohms/am.

Therefore, the present invention provides a method for coating a substrate with polyurethane or polyurethaneurea, which (a) has a smooth spheroidal surface, (b) has an average diameter within the range of 5 to 200 μ; (c)
The ionic group content is within the range of 1 to 15 milliequivalents per 100 g, (b) the current resistance is within the range of 1010 to 1014 ohm/cm, and (e) the IMI curve in the temperature range of 110 to 250°C. The shape resembles the ascending part of a parabola, so that the IMI values vary within the range of 2 g per 10 minutes to 350 g per 10 minutes within the temperature interval 5-50°C.

characterized in that the powdered polyurethane or polyurethane urea is applied dry to the substrate and then sintered and/or melted by the action of heat and optionally also calendered. A method of coating a substrate with polyurethane or polyurethane urea.

The polyurethane and polyurethaneurea powders used according to the method of the invention are prepared by combining NCO prepolymers (containing ionic groups) with primary amines and/or secondary amines (containing aliphatically bonded amino groups) and/or dicarboxylic acid dihydrazides. It can be produced by reacting with water in the presence of water.

The NH/NGO ratio in the chain extension reaction is preferably 0.
．． It is within the range of 1 to 0.95, particularly 0.25 to 0.85.

The content of ionic groups contained in the NGO prepolymer ranges from 1 to 15 milliequivalents, preferably from 2 to 10 milliequivalents per 101 of the product.
Calculated to have the desired ionic group content of milliequivalents.

The powder is preferably prepared by first preparing a solution of the prepolymer containing both isocyanate and ionic groups in an organic solvent, combining this solution with an aqueous solution of the chain extender, and finally removing the organic solvent, preferably by distillation. can get.

By using this method, the powder used according to the method of the invention is obtained in the form of a precipitating dispersion.

A particular advantage of this embodiment of the process is that a high speed stirrer is not required for full heat, and the NGO prepolymer can be simply mixed with the chain extender using a low speed stirrer.

The above prepolymers containing both free incyanato groups and ionic groups are known compounds for the preparation of emulsifier-free polyurethane dispersions.

Average molecular weight: 300-25,000, preferably 800-1
5000 especially types of NC within the range of 2000 to 7000
Preference is given to using O prepolymers.

The properties of the insect repellent polyurethane urea powder can be varied as desired over a wide range by suitable means.

This applies in particular to hardness and particle size.

A first possibility to influence the properties of the powder lies in controlling the structure of the ionic prepolymers containing incyanato groups.

This can be achieved by known methods (see Belgian Patents No. 653,223 and No. 730,543) using the starting materials described in the above-mentioned patent specifications.

In addition to these compounds, compounds containing amino groups such as French Patent Nos. 1361810 and 1300
The compounds described in DE 981, DE 1122254 and US Pat. No. 2,888,439 can also be used as high molecular weight substances containing reactive hydrogen atoms.

The particle size is determined primarily by the ionic group content of the prepolymer.

The hardness of the particles is determined primarily by the chemistry of the polyisocyanate or compound with reactive hydrogen atoms used to make the NGO prepolymer.

If these polyisocyanates or compounds with reactive hydrogen atoms are limited to those with low molecular weights of up to about 500, hard polyurethanes are obtained;
Exclusive use of high molecular weight compounds with molecular weights up to
A soft product is obtained.

Mixtures can be used in any proportion between these extremes.

Since the formation of the prepolymer is carried out in a relatively large excess of isocyanate using a molar ratio of NCO groups to reactive hydrogen atoms in the range from 4 to 1.1, preferably from 2 to 1.4, Since the molecular weight of the prepolymer is not very high, the NCO prepolymer used for powder production does not have to have a strictly linear structure, although it is preferably linear with two fat-bonded isocyanate end groups.

These powders are preferably prepared by reacting a solution of the prepolymer with an aqueous solution or dispersion of the chain extender.

However, in some cases a chain extender dissolved in an organic solvent can be added while the dispersion is being formed.

The polyurethane powder used according to the invention can be used in accordance with Belgian patents Nos. 653,223 and 7305, in order to obtain polyurethane dispersions which are, in principle, free of emulsifiers.
It can be produced by the conventional method described in the specification of No. 43.

Suitable chain extenders are in particular primary and/or secondary amines containing amino groups of fatty bonds and dicarboxylic acid bis-hydrazides (in the case of the latter chain extenders, NG
It is believed that it is primarily the amino groups in the β-position relative to the carbonyl groups that react with the O prepolymer, and thus the dicarboxylic acid bis-hydrazide can be considered a difunctional chain extender in the first vicinity). .

Suitable diamines are especially those having a molecular weight below 250, such as ethylenediamine, propylene-1,2-diamine, N-methyl-propylenediamine, butylenediamine, hexamethylenediamine, piperazine, 2-methylbiperazine, dimethylpiperazine, N,N '-Dimethyl-ethylenediamine, N,N'-diethyl-diethylenediamine, N,N'-diisopropyl-ethylenediamine, N,N'-dimethyl-propylene-1,2-diamine, N,N'-diisopropyl-propylene-1
,Z-cyamine, N,N'-bis(hydroxyethyl)
Ethylenediamine, N-hydroxyethyl-ethylenediamine, N-hydroxypropyl-ethylenediamine,
N,N'-bis(hydroxypropyl)-ethylenediamine, N,N'-dimethyl-hexamethylenediamine,
Propylene-1,3-diamine, γ,γ′-bis(aminopropyl)sulfide, γ,γ′-bis(aminopropyl)-methylamine, N,N-bis(γ-aminopropyl)-aniline and N, Nbis(γ-aminopropyl)-m-toluidine.

Ether diamines, ester diamines and cyanoethylated diols or diamines formed by hydrogenation of difunctional dihydroxy polyesters or dihydroxy-polyethers are also suitable chain extenders.

The diamines are used in the form of their salts, for example carbonates or acetates.

Salt formation can be carried out only partially, for example to increase solubility.

Formation of salts at primary amino groups results in decreased reactivity.

The dicarboxylic acid bis-hydrazide used is, for example, a low molecular weight dicarboxylic acid having a molecular weight of 250 or less;
For example, bis-hydrazides of carbonic acid, oxalic acid, succinic acid, adipic acid, phthalic acid, terephthalic acid and tetrahydrophthalic acid are suitable.

Difunctional polyesters with carboxylic acid-hydracite end groups can also be used.

Solvents suitable for the production of the products used in the process of the invention are in particular compounds which are miscible with water and have a boiling point below 100°C, such as acetone, methyl ethyl ketone,
Tetrahydrofuran and ethyl acetate.

Water-immiscible solvents can also be used provided the reactants are stirred sufficiently to ensure vigorous stirring.

Solvents with a boiling point of 100°C or higher, such as toluene,
Chlorbenzene, dimethylformamide or dimethyl sulfoxide can also be added, but the removal of these solvents from the product of the process of the invention requires considerably greater effort.

The polyurethane powder used according to the method of the invention is preferably produced as follows.

i.e., from a dihydroxyl compound (having a molecular weight of 500 to 5000), a diisocyanate, and optionally a chain extender, using an excess of diisocyanate to ionicize so that the adduct contains a weight ratio of 1 to 4 parts NCO groups. NG
The O prepolymer is plated in a conventional manner.

In addition, the NCO prepolymers contain 1 to 15 milliequivalents of quaternary nitrogen atoms, carboxylate groups or sulfonate groups per 100 g.

A solution of ionic NCO prepolymer dissolved in acetone at a weight ratio of 30 to 90 (viscosity at 50°C 30 to 800)
0 cp) is mixed with an aqueous solution of an aliphatic diamine containing primary and/or secondary amino groups.

The acetone is then distilled off and the polyurethaneurea powder is obtained in the form of an aqueous precipitated dispersion.

The product of this process can be obtained in pure form by just one filtration.

It can be redispersed in water whenever required, but it is preferred to apply the dry powder by dry knife coating or screening.

To initiate the chain extension reaction, an aqueous solution may be added to the acetone solution with stirring or vice versa.

This mixing method is preferably carried out in a continuous working device, for example by pumping the two solutions into a mixing tank.

In the simplest case, the mixing vessel is equipped with a stirrer and an overflow port from which the aqueous acetone dispersion flows into the distillation apparatus.

The dispersion temperature is in the range of 20-60°C, preferably 35-55°C.

The amount of water required for dispersion and in which the diamine is dissolved is 0.8 to 3 times, preferably 1 to 2 times, the amount of ionic NCO prepolymer.

For continuous mixing at high production rates, it is preferred to use high-speed stirring equipment or mixers capable of generating high shear forces.

Apparatus suitable for this purpose include, for example, high- or low-pressure mixing chambers with mixing screws, in particular multi-screws, built-in mixers, countercurrent mixers or ultrasonic dispersers,
All of these are well known in the art.

When using the above equipment, it is recommended to work with solutions in the 70-90 part range or, if the prepolymer has sufficient fluidity, to work without full-heat solvents. is preferred.

The properties of the polyurethane powder initially obtained as a suspension can be varied as desired not only by the chemical composition of the polyisocyanate prepolymer but also by the conditions under which the dispersion is carried out.

The most important factors are the nature and amount of the chain extender, the amount of water,
The nature and amount of the organic solvent, the pH and the reaction temperature can vary from O'C to the boiling point of the organic solvent, and elevated pressures can also be used if desired.

Another important factor is the method used to mix the water and organic phases, i.e. whether these two phases are introduced at about the same time, for example into a continuously operated mixing device, or whether the organic phase is mixed with water or not. whether it is added to the phase or vice versa.

However, it must be reiterated that suitable products can also be obtained by simple means, for example by pouring the aqueous phase into the organic phase with stirring using a conventional stirrer.

During or after mixing the two phases, the organic solvent is removed by distillation.

The finished powder is obtained by one sieve from the resulting aqueous polyurethane dispersion.

The polyurethane powder is applied by conventional doctor coating methods, i.e. fixed doctor coating equipment, e.g. floating knife coating equipment,
Application can be made using rubber blanket coating equipment and especially doctor roll coating and roll coating machines or reverse roll coating machines.

Surprisingly, polyurethane powders with the necessary properties for use in the process of the invention can only be used for paste-like mixtures that can otherwise be expanded coated industrially. It has been found that the method allows for doctor coating in the dry state.

The powder is very fine and easily pourable and therefore can be used without any additives or additional milling.
To measure the flow rate according to the EGUSSA method, it is best to pass through the finest nozzle of a series of glass nozzles.

Further improvements can be obtained, if desired, by adding small amounts of magnesium stearate and other conventional lubricants.

The amount added can be within the range of 0.1 to 5 parts based on the total solids content.

It is surprisingly easy to pour these powders even when the residual moisture content of the powders is in the range of 0.5 to 5.0 parts by adsorption.

This residual water content is even more desirable since these small amounts of water have the effect of plasticizing the synthetic resin and slightly lowering the melting point of the product.

Both direct coatings and preferably countercoatings can be obtained by the method of the invention.

The countercoating is preferably carried out using a siliconized rubber separation support or a conventional separation paper, but more preferably a steel strip.

The thickness of the coating obtained is in the range of 10 to several 100 g/m.

Powders applied by coating or screening are immediately exposed to heat, for example in the infrared range, and when heated rapidly to a temperature above their melting point they melt to form a homogeneous foil.

If, on the other hand, the dry powder applied to the support is only heated gradually and to its melting point, the resulting layer, hereinafter referred to as frit, has a macroporous structure.

The coating can be colored in various ways, preferably by mixing the polyurethane powder with powdered pigments or fillers such as carbon black, titanium dioxide, aluminum bronze, iron pigments or cadmium pigments before application.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Polyurethane powder (average diameter 43μ, melting point 145 °C
A current resistance of 5×10” ohms/crnA% IMI value curve 2) of FIG. 1 is produced.

1. Polyurethane powder is applied to the paper to be separated by knife painting.
oog/m” thickness and then exposed to a temperature of 140° C. in a 12-tread-long nozzle duct, through which it is passed at a speed of 1.5 m.

A tough resilient frit is formed that can be easily separated from the support and processed without the use of any other support.

Example 2 A frit produced according to Example 1 is coated with a second coating of the same powder (thickness 60.!i27 m) and then passed through a duct at 170° C. as described in Example 1.

A homogeneous, transparent foil is obtained, which has a total thickness of 16
0.9/m, offering high tensile strength and good elasticity.

Example 3 Powder described in Example 11 of Belgian Patent No. 800 185 (melting point 165°C, average diameter of spherical particles 61μ,
Current resistance 1011 ohm/crn, IMI value Curve 3) in Figure 1 was applied to the steel belt using knife coating, and the thickness was 0.
．． A 3 mm layer is produced which is then melted in a nozzle duct at a temperature of 175° C. to form a foil.

During the second coating operation, apply the powder described in Example 1 to a thickness of 0.3
m rudder and then brought to a temperature of 145° C. and sintered to form a frit that adheres to the previously made foil.

These two layers can no longer be separated by mechanical methods without destruction.

The foils formed according to Examples 1-3 can be adhered to one or more sides of any suitable support material such as cotton cloth, polyester cloth, and nonwoven fibrous fabric by conventional wet lamination methods.

For example, polyurethane solutions or dispersions or other adhesives can also be used for wet lamination.

In addition, lamination can also be carried out by a heat sealing method using thermoplastic resin powder.

Example 4 A porous foil produced according to Example 1 was coated with a layer of polyurethane powder from Example 1 (80 g/m
(applied to a thickness of ) and exposed to a temperature of 145°C.

While still in a plastic state, the powder is also laminated under pressure to a noodle fluff (80 g/m).

When cooled, the laminate bonds tightly and can withstand more than 1,000,000 bends in a Bally bendometer.

Example 5 Polyurethane powder IoOg described in Example 1 and titanium dioxide 1
0 g and added to a siliconized separation runner by roller coating method.

The layer is exposed to a temperature of 160° C. in the duct described in Example 1.

A white, coherent foil is obtained which is mechanically stable after cooling.

Example 6 (a) 100 g of the polyurethane powder described in Example 1 and 5 g of carbon black are mixed.

(o) 100 g of the polyurethane powder described in Example 1 and 2 g of aluminum bronze are mixed.

(c) 100 g of the polyurethane powder described in Example 1 and 5 g of cadmium red pigment are mixed.

Mixtures (a), (b) and (c) are applied to the steel belt from three different nozzles arranged to distribute the solids and located across the width of the support.

As the belt passes through the gap in the knife applicator, the layer of applied mixture is then worked up, causing the mixture to mix irregularly in the border zone.

After cooling and separation from the steel belt, a mechanically stable foil is obtained with a color effect in the form of diagonal lines that become thinner at the boundaries.

Although the thickness of the layer becomes the same by passing through the gap in the paint machine, components (a), (→ and ←) mix at the boundaries of each zone, giving an overall uniform appearance. However, each pattern is formed locally within it.

Example 7 The powder mixture prepared according to Example 6 is applied as described in Example 6, with the exception that the applied powder is not all spread evenly.

The resulting foil not only has the color effect of the product described in Example 6, but also has an irregular pattern on the surface resembling an irregular flat raised pattern.

Example 8 Preparation of polyurethane powder 950 g of dehydrated polyester of butanediol/adipic acid having an average molecular weight of 2190, 1669 g of hexane-1,6-diisocyanate and 8.8 g of N-methyl-jetanolamine are reacted at 100° C. for 1 hour to form a prepolymer. Manufacture.

Dimethyl sulfate 6.8cc and acetone total 1280. !
Add li' to this prepolymer.

A prepolymer 5ofb acetone solution with an NGO content of 1.23 is obtained.

757 parts of this prepolymer were mixed with 189 parts of propylene-1,2-diamine-normal aqueous solution and 568 g of water,
A polyurethaneurea suspension is obtained.

After removing the acetone by distillation, filtering once, washing and drying, a polyurethaneurea powder having a melting point of 168-174°C is obtained.

This powder consists of spherical particles with an average diameter of 60 μm and a current resistance of 10 12 Ohm A/crrL.

This powder is applied to a steel belt to a thickness of 1oo9/m, which is heated to 200'C and sintered to form a foil.

A second coating of polyurethane powder as described in Example 3 (60 g/m
) is applied to this foil.

A belt with this material on top is passed through a 1.5 m long infrared beam at a speed of 1.5 m/min.

The infrared region has a total power of 24 kW over its entire length and is designed such that the surface temperature measured on the separation support is 200°C.

After passing through the infrared range, the foil is immediately laminated to the knitted fabric of the noodles.

The application of the foil is controlled such that the spacing is such that width of the spacing=fabric thickness 10 layer thickness-0.1 degrees.

The backside coating removed from the steel belt has excellent properties.

Example 9 The polyurethane powder according to Example 3, consisting of spherical particles with a diameter of 25 μ, having a melting point of 165° C. and a current resistance of 1011 ohms/cfrL, was applied to a steel belt by means of a screen (application thickness s o g/m), and then 8, it passes the infrared region.

In a second operation, a thin layer (4
0 g/m) is applied to the resulting homogeneous foil.

The coating is sintered to form a frit and, while still plastic, laminated to a nonwoven web of polyester/polyamide fibers.

Excellent adhesives are obtained with this method. Example 10 The polyurethane powder described in Example 1 was applied to Momen Boblin material at a thickness of about 1009/m", and suddenly 18/m" was applied in the infrared range.
Heat to 0-200°C (see Example 8) and then allow to cool immediately.

Next, it is calendered at 110° C. under a pressure of 7 tons.

A directly coated fabric with a smooth surface is obtained.

Example 11 The polyurethane powder described in Example 3 is applied to a steel belt by knife coating to a thickness of approximately 1609/m and sintered in a conventional manner.

While the material is cooling and still in a plastic state,
Place a noodle mesh cloth on top of it.

A second coating consisting of the polyurethane powder described in Example 1 is then applied by knife painting to a thickness of approximately 150 g/m.

The coating is also sintered in the infrared range, cooled and calendered.

A stable foil that does not sag is obtained, which can be used, for example, as a conveyor belt.

Example 12 The polyurethane powder described in Example 5 was applied to a steel belt and sintered in a conventional manner.

While still plastic, it is passed under a conditioning device consisting of a doctor knife and a doctor roller with a replaceable surface.

The adjustment device is adjusted to be 0.01 to 0.05 mm lower than the combined layer thickness of steel belt and sintered powder.

The melt is homogeneously distributed and conditioned in this way.

Example 13 The polyurethane powder described in Example 3 is applied to a steel belt at room temperature by knife painting.

Sintering and melting of the powder is not carried out by direct heat transfer, as in example 1 (nozzle duct) or example 8 (infrared range), but by first heating the steel belt with hot air and then melting the powder. This is done by an indirect heating method consisting of heating to the sintering point and then melting by transfer of heat from the steel belt.

The above-mentioned examples are described for explaining the present invention and are not intended to limit the present invention in any way.

Thus, for example, a person skilled in the art could easily use other types of heating ducts or fittings instead of the nozzle duct.

Similarly, the indirect heating method described in Example 13 uses, but is not limited to, using a steel belt as the heat transfer medium or heated air as the energy button.

[Brief explanation of the drawing]

The figure is a diagram showing the melting properties of polyurethane powders described in the Examples herein.

Claims (1)

[Scope of Claims] 1. A method of coating a substrate with polyurethane or polyurethaneurea, which (a) has a smooth spheroidal surface, (b) has an average diameter within the range of 5 to 200μ, and (h) has a smooth spheroidal surface; )
ionic group content is within the range of 1 to 15 milliequivalents per 100 g, (b) current resistance is within the range of 1010 to 1014 ohm/cm, and (e) IMI curve in the temperature range of 110 to 250'C. is similar in shape to the ascending part of the animal line, so that the IMI value varies within the range of 2 g per 10 minutes to 50 g per 10 minutes within the temperature interval 5-50°C. characterized in that the powdered polyurethane or paryurethane urea is applied dry to the substrate and then sintered and/or melted by the action of heat and optionally also calendered. A method of coating a substrate with polyurethane or polyurethane urea.