DE2121191A1 - Process for the production of elastomeric polyurethane coatings and coating compositions for carrying out the process - Google Patents

Description

"Process for the production of elastomeric polyurethane coatings and coating compounds for carrying out the process "

Priority: April 29, 1970, V.St.A., Mr. 33 101

In recent times, considerable efforts are being made to develop it Weather and erosion resistant coatings have been undertaken. Helicopter rotor blades, leading edges of Airplanes and radar hoods are e.g. 3. especially that caused by rain, hail, sand and other atmospheric influences exposed to conditional erosion. To protect a subsurface against those caused by various atmospheric influences Many coatings containing reaction products of polyols with isocyanate have been proposed for erosion; cf. e.g. U.S. Patent 2,810,037, U.S. Patent 2,901,467, and U.S. Patent 3,586,962.

Neoprene and various other rubber-based products have also been used to produce the above-mentioned coatings. However, ioinor del- well-known coatings meet the requirements set with him when he is exposed to extreme conditions, lying for a long time and eroding others

10 9 ^ 46/169 6 bath

'Exposed to the effects of the atmosphere' 'i ~ t.

■ Ό *

The object of the invention was therefore to provide a method for the production of polyurethane coverings which .Disadvantages of the known coatings do not have and are characterized by their weather and corrosion resistance. This task, is achieved by the invention,

The invention thus relates to a method for production of elastomeric polyurethane coatings by applying reaction products of polyols with an organic diisocyanate on the substrate and hardening of the applied film, which is characterized by the fact that one is a Pr epo lyra it? or preferably a solution of a prepolymer, which optionally contains usual additives and by reacting

(a) a polytetramethylene ether glycol having an average molecular weight of about 500 to about 700 and

(b) an oxyalkylated triol having an average molecular weight from about 400 to about 1000 in an amount from 0 to 20 weight percent based on the total weight of the oxyalkylated Triols and polytetramethylene ether glycol, with

(c) an amount of an organic diisocyanate such that the ratio of the isocyanate groups of the diisocyanate to the hydroxyl groups of the polytetramethylene ether glycol and the oxyalkylated triol is 1 _? 2: 1 to 1.8: 1, below. Exclusion of moisture is established,

applies to the substrate in an organic solvent and the liassfilra at a moderate temperature in a humid place

108848/1698

Air hardens.

The flexible, Elastonsren polyurethane covers have excellent weather resistance on. This result is particularly surprising, since it was found that from various other glycols, e.g. polypropylene ether glycol, no coatings with the required Combination of flexibility, softness and weather resistance can be produced. It was also surprising and not foreseen that using polytetramethylene ether gljkwl with an average molecular weight of about 500 to about 700 flexible, elastomeric coatings since US Pat. No. 2,830,037 discloses that polytetramethylene ether glycols are used to produce elastonized coatings with a molecular weight of at least 750 must be used.

The prepolymers according to the invention with isoeyanate end groups are preferably made by reacting a polytetramethylene ether glycol or a mixture of a polytetramethylene ether glycol and an oxyalkylated triol with such an amount of one Organic diisocyanates produced that the ratio of the isocyanate groups of the diisocyanate to the hydroxyl groups of the Polytetramethylene ether glycol and the oxyalkylated triol Is 1.4: 1 to 1.6: 1. The ratio of isocyanate groups to hydroxyl groups is a critical factor in Production of the prepolymers according to the invention. Ss was found that at a ratio of isocyanate groups

that of about 1.8: 1
to / liydroxylgruppen / the coating obtained is only slight

109846/1696

Has resistance to erosion. When the ratio of isoeya

• about natgruppen to the hydroxyl groups is less than / 1.2: 1

get sticky, rubbery masses with low strength.

To produce the prepolymers according to the invention, preference is given to a polytetramethylene ether glycol with an average molecular weight of about 600 to about 680 is used.

For the preparation of the prepolymers according to the invention, preference is given to grounding 0 to 15 percent by weight and in particular 8 to 12 percent by weight of an oxyalkylated triol, based on the total weight the oxyalkylated triol and polytetramethylene ether glycol, used. The oxyalkylated triol is preferably an oxypropylated triol, and in particular an oxypropylated one Glycerin used.

The oxyalkylated triol used in the process of the invention is made by reacting a triol with an alkylene oxide (1,2-epoxide) manufactured. As alkylene oxides, e.g. ethylene oxide, propylene oxide, butylene oxide, styrene oxide, glycide, n-hexyloxide, Cyclobutylene oxide, cyclohexylene oxide, epihalohydrins, such as 4,4,4-trichloro-1,2-epoxybutane, and mixtures thereof can be used.

Preference is given to alkylene oxides having 2 to 4 carbon atoms, ζ · Β. Ethylene oxide, propylene oxide and butylene oxide or mixtures thereof are used. *

To prepare the oxyalkylated ones used in the process of the invention Triols can be used as triols, e.g. glycerine, trimethylolpropane, Hexanetriol and mixtures thereof can be used. The oxy-

10 9846/1696

alkylated triols are prepared by known methods by reacting an alkylene oxide with the triol in the presence of a basic catalyst, for example potassium hydroxide. The oxyalkylation is carried out at temperatures of from about 30 to about 200 ⁰ C.

For the preparation of the prepolymers according to the invention, any organic diisocyanate can be used, which is capable of reacting with the aforementioned polyols. These diisocyanates can by the general formula.

?. ("C0) ₂

are represented in which R is a divalent alkylene or Cycloalkylene radical with up to 8 carbon atoms, a divalent arylene radical with 6 to 12 carbon atoms or a divalent alkyl-substituted one Means arylene radical with 7 to 14 carbon atoms.

As alkylene diisocyanates, for example, ethylene, trimethylene, tetramethylene, Pen tarne ethylene, hexamethylene, propylene-1, -2-, butylene-1,2-, butylene-2,3-, butylene-1,3- , Ethyliden- and Butylidenendiisοcyanate can be used. As cycloalkylene diisocyanates, for example, cyclopentylene-1,3-, cyclohexylene-1,4 · and. Cyclohexylene-l ^ -diisocyanate can be used. As arylene diisocyanates, for example, m-phenylene, p-phenylene, 4 »4'-diphenyl and 1,5-naphthylene diisocyanates can be used. As alkyl-substituted arylene diisocyanates, for example 4,4'-diphenylenemethane, 2,4-toluene, 2,6-toluene, 4,4 ⁽ -tolidine and 1,4-xylene diisocyanate, also ring-substituted arylene diisocyanates such as dianisidinedi- 'isoeyanate, Chlordiphenylenendiisoeyanat, A, 4'-Diphenylätherdiisocyanate, mixtures and isomers thereof are used.

109846/1690

"Toluene diisoeyanate is used wisely.

Since the prepolymers according to the invention have free isocyanate end groups and are therefore hardenable by moisture, they are excluded to prevent premature hardening made by moisture. The prepolymers can be produced under nitrogen, for example.

The inventive prepolymer can in the absence of one Solvents are prepared * The prepolymers are preferably prepared in an organic solvent. Examples of solvents that can be used are ethyl acetate, benzene, ethylene glycol monoethyl ether acetate, xylene, toluene, methyl isobutyl ketone, "cyclohexanone" and other alkyl ketones and acetic acid esters or mixtures thereof can be used uses a solvent that forms a low-boiling azeotrope with water. Such solvents are, for example, ethyl acetate or benzene, since their azeotrope with water can easily be removed by distillation. That way will the water is removed from the reaction mixture. When the preparation of the prepolymers is carried out in the absence of a solvent the water is removed from the reaction mixture using suitable devices, e.g. a thin film evaporator. In the preparation of the prepolymer this can various ^ additives are added, e.g. Viscosity, the, stability and the color of the invention Improve prepolymers au. For example, an antioxidant such as 2,6-di-tert-butyl-4-methylphenol can be added to the reaction mixture will. The viscosity is preferably increased by adding

109846/1696

set of a solution of cellulose acetobutyrate in ethylene glycol- ' monoethyl ether acetate regulated. The reaction mixture can be conventional Pigments such as carbon black and titanium dioxide can be added, whereby a coating with a certain color is obtained. the Coatings made by the process of the invention are clear without the addition of a pigment. To produce the inventive Prepolymers are not necessary as catalysts but used.

According to one embodiment of the invention, the polytetramethylene ether glycol and the oxyalkylated triol are mixed with one of the solvents mentioned and optionally with further additives The temperature at which this occurs depends on the type of solvent and the amount of water present. If, for example, ethyl acetate is used to form the azeotrope and the solvent consists of xylene and ethylene glycol monoethyl ether acetate, the solution is generally at about 70 ⁰ C under reflux until all WasBer as an azeotrope of ethyl acetate with v / ater is removed. After removal of water, the solution is cooled to about 10 to about 40 ⁰ C prior to the addition of the organic diisocyanates, up to gel formation during the addition down to a minimum etz. The organic diisocyanate is preferably added to the solution as quickly as possible without stirring.

The addition of the organic diisocyanate generally causes a rise in temperature, since the reaction is exothermic,

109846/1696

The reaction is preferably carried out under atmospheric pressure. Sic but may have been efülirt at each pressure durcL ^ ", animal does not cause undesirable Ilebenreaktionen 'to B02 tying the completion of the reaction the content of free Isoc3 ^r anatgruppen measured in the solution by conventional analytical Jlethoden.

The resulting prepolymer with free isocyanate end groups is stored at an oil temperature below about 30 ⁰ G under nitrogen until it is used for the production of coatings.

The coating compositions according to the invention consist of the above described prepolymers with free isocyanate terminal groups and an organic solvent. If the prepolymer was made in an organic solvent, a straight line is used for Production of coatings obtained suitable coating composition. When the prepolymer is made in the absence of a solvent a solvent is then added to the prepolymer in order to obtain one that is suitable for the production of coatings To obtain coating compound. The prepolymer solution prepared in the presence of an organic solvent can of course ground with further solvents. All solvents mentioned for the preparation of the prepolymer can be used as solvents Solvents can be used. The amount of solvent used is not a critical factor = the prepolymer is therefore mixed with so much solvent that a coating compound obtained that can be used easily and economically

109846/1696

The coating composition according to the invention contains about 40 to about 80 % solids, with pesticides denoting the prepolymer and optionally solid additives.

The coating composition according to the invention hardens in air Humidity because it contains free isocyanate groups that react with the water contained in the air under atmospheric conditions and lead to solidification of the wet film.

The coating composition according to the invention is applied to the substrate by customary methods, for example by brushing, rolling, spraying and dipping. The wet film is then cured in an atmosphere which contains at least about 15 % and preferably about 35 to about 65 % relative humidity. Curing may be carried out at temperatures from room temperature to about 6O ⁰ C.

The wet films according to the invention cure in a satisfactory manner in a short time. To accelerate the curing process , the coating material can be mixed with catalytic amounts of catalysts, for example dibutyltin dilaurate, a 2: 1 mixture of dipropylene glycol with lj ^ -diazobicyclooctane, before it is applied to the substrate

(DABCO-33LV), trimethylpiperazine, tin (II) octoate, triethylenediamine and tetraethylenediamine, added to earth.

The hardening of the wet film in the air due to air humidity is a further critical factor for the production of coatings according to the invention. If the wet film is achieved by adding polyols or hardened by heating to high temperatures,

109846/1696

■ coatings are obtained that do not have the required strength and durability of the coatings according to the invention.

The coating compound according to the invention can on a variety of surfaces, e.g. on metals such as stainless steel, aluminum and various alloys, synthetic resins, such as epoxy and phenolic resins, glass fiber reinforced synthetic resins, Glass, plastics and wood. These substances are superbly protected by the coatings according to the invention.

The coatings according to the invention show without the use of an adhesion promoter good adhesion to the substrate. However, the substrate can also be treated with an adhesion promoter first. As a bonding agent, z.S. Polyvinyl butyral (acid jratailysed) and epoxy resins crosslinked with the aid of amine catalysts be used.

The coatings according to the invention are surprisingly soft and flexible. You are therefore through the. ASIM test standard D 2134 62T characterizes and shows a Sward hardness below 25 in this test. The Sward hardness is determined by a non-destructive test, in which reproducible hardness values are obtained in parts, expressed as a percentage of the hardness of glass. During this test, the number of vibrations of the liormal hardness test device is measured. The novel coatings also pass the test according to ASTM test standard D 522-60 (conical mandrel Elongation Test after at -40 ⁰ C, x 3.175 mm in diameter), which the excellent flexibility of the ER-

109846/1696 IAD original

findun-jsgcrwönt indicating soft coatings.

The coatings according to the invention can also be characterized by their surprising weather and erosion resistance, many of their high erosion resistance, e.g. against sand, peas and hail, they are particularly suitable as coatings e.g. for the front edge of the profile of plug tools, rotor blades of helicopters and kadar hoods. The excellent V / etter- and Srosionsbeständigkeit, which was tested under dynamikchen conditions, the stringent requirements that were placed on such coatings ^{1 is} satisfied or. In the examples below, values are given which demonstrate the excellent weather and erosion resistance of the coatings according to the invention.

Testing of the rain erosion resistance mentioned in the examples is under dynamic conditions according to the USA.-Hilitary test standard KIL-C-7439 3, part 4.3.2.5., In the fit of Performed February 4, 1955. A suitable device, an observation device, is constructed to carry out the test that includes continuous monitoring during the tests permitted. A propeller made of high-strength alloy steel (AISI 4540) is used in the tests. The rain gets through in suitably arranged injection needles simulated.

The test of sand erosion resistance is performed under dynamic Conditions carried out in the same way and using the same device as those used for testing rain erosion resistance is used. The sand is made from storage containers, located at the top of the test device, with the help of inclined Baffles positioned 12.7 mm above the propeller

109846/1696

are brought, finely distributed over the width of the path of the i'feßtkürj.ora.

The destruction side indicated in the test of resistance to rain and sand erosion is the time it takes for penetration of the coating under the conditions described above necessary is.

The examples illustrate the invention. Get parts and percentages based on weight, unless otherwise stated.

example 1

39.48 parts (0.13 hydroxyl equivalents) of polytetramethylene ether glycol with an average molecular weight of about 65 u v / earth in a 5 liter reaction vessel under nitrogen with 27.83 parts of xylene, 9.27 parts of ethylene glycol monoethyl ether acetate, 4.60 parts of methyl isobutyl ketone, 2 50 parts of ethyl acetate and 0.8 part of 2,6-di-tert-butyl-4-diethylene phenol are mixed in. The mixture is then dehydrated by an azeotropic distillation for approximately two hours at about 70 ° C. It is cooled to room temperature 15.51 parts (0.18 isocyanate equivalents) of toluene diisocyanate (80:20 mixture of the 2,4- and 2,6-isomers) are added to the mixture while stirring ! C. laughing close to 8 hours dnc Keaktionsgemisc :; cooled to room temperature, the ratio of isocyanate groups to hydroxyl groups is about 1, ^2. 1: 1.

A streamlined test body made of aluminum (2G24 ~ T3), in the form and size of the USA military test standard HIL-C7439B cnt--

109846/1696

speaks, 2 Iiinuten "at 60 C in 4proscmtige l.'atz onlaviL * ^e and anGchlieosend 15 seconds 50proaentige," is immersed aqueous nitric acid. After this pretreatment, the test specimen is washed and etched several times with distilled oil. the

Coating composition according to the invention produced above is sprayed onto the test specimen in such a way that the dry coating has a thickness of 0.4064 to 0.4572 nm. The] 7assfilm v / ith at the air 14 ^ age at 25, and 50 OE9 C ^c p relative! Cured moisture. The properties of the cured coating are summarized in Table I,

Example

A streamlined specimen made from a glass fiber reinforced Polyester is manufactured, and the USA.-HiIitärprüfncrm KII-P-8OI3 corresponds to the USA military test standard IiIIr-P-15328 3 with polyvinyl butyral (acid catalyzed) treated as a bonding agent. The test specimen treated in this way is then coated with the coating compound described in Example 1 coated so that the dried coating has a thickness of 0.4318 to 0.4826 mm. After the liassfilms for 14 days at 23.89 ° C and 50 # relative humidity is the resistance to erosion of the coating under the conditions given in Table I, 11.4 minutes.

Example 2

Example 1 is a coating compound from the components listed below in the specified Quantities produced:

109846/1696

- 14 components Hen-en

Polytetramethylene Ether Glycol 1,380 parts (Molecular weight 650) (4.45 Hydro :: -: yl'cjuivalente)

XyIöl '1500 parts

Ethylene glycol monoethyl ether acetate 500 parts

Toluene diisocyanate 619 IGiIe

(8O ^- : 20 - mixture of 2,4- (7, H isocyanate equivalents)

and 2,6-isomers)

The coating unmoulding compound obtained, which has a ratio of isocyanate groups to hydroxyl groups of 1.6: 1, is applied by spraying to two streamlined test specimens identical to that used in Example 1, so that the dried coating has a thickness of 0 , 4064 ram has. The left film is cured in air for 14 days at 23.89 ° C and 50 percent relative humidity. The properties of the cured coating are summarized in Table I.

109846/1696

Table I.

Eig ei: s cha f ton gohär tct er P o Iy u r c thEi .ü'b or zu ^ e with ο much \ ■ _. 1 la 2

Sward hardness (ASTI-i test standard 6 - 4

D-2134-62T)

Re.r; energy resistance: 60 11.4 20

? 0.8 mn iiG; - "on / hour; mean
Destruction time, minutes

Sand erosion resistance '5.0 -' 7.5

40.64 mm sand / minute; middle
Destruction time, minutes -

2)

Sand abrasion '> to Durchdringunr 25O -> 250

Required liters of sand / 0.0254 nci coating

Flexibility, conical expansion resistance - accumulation test according to Ilandr el (ASTIi-PrUf-. den 'den standard D-522-GO 3.175 mm diameter, -40 c)

^ Quartz sand (I grain size: 0.105 to 0.149 mm)

² ^ USA.-Bundonormalprüfverfahren ITr. 141-A, Method 1691 using Ottawa sand (grain size: 0.297 to 0.841 mm).

Comparison experiment A

The following experiment shows that the ratio of isocyanate groups to hydroxyl groups in the inventive Coating compounds are critical

Is a factor relating to high rain erosion resistance.

300 parts (0.90 hydroxyl equivalent) of polytetramethylene ether glycol with an average molecular weight of 66O are mixed with about 90 parts of ethylene glycol nonethyl acetate and about 270 parts of xylene. The mixture v / ill be followed by azeotropic distillation at about 80 ⁰ C dewatered. After leaving

109846/1696

cool to room temperature "the mixture is mixed with 156 parts (1.80 isocyanate equivalents) of toluene diisocyanate (80:20 mixture of the 2,4- and 2,6-isomers) while stirring. The ratio of the isocyanate groups to the hydroxyl groups in the above The coating compound obtained is 2: 1.

A streamlined test specimen is treated with the polyvinyl butyral used in Example la as an adhesion promoter. The treated test specimen is then coated with the coating material obtained above by spraying in such a way that the dried coating has a thickness that is essentially the same as that of the coatings of the preceding examples. Before spraying, approximately 0.5 percent of a 2: 1 mixture of dipropylene glycol and 1) 4-diazobicyclooctane is incorporated into the mixture as a catalyst to accelerate the curing process. The Kassfilm is cured for 7 days at 23.89 ⁰ C and 50 percent relative humidity. The cured coating is then subjected to the same test of rain erosion resistance as the coatings of the preceding examples. The coating peeled off the substrate after being exposed to 50.8 mm of rain / hour for 5 hours.

The experiment clearly shows that the ratio of isocyanate groups a critical factor in relation to the hydroxyl groups in the coating compositions according to the invention

represents when the coatings are to have a high level of rain erosion resistance. The coating of the comparison test s A (ratio of isocyanate groups to hydroxyl groups: 2: 1) has a much lower rain erosion resistance than that

109846/1696

coatings according to the invention (ratio of isocyanate groups to the hydroxyl groups at most 1.8:. 1).

Example 3

According to example 1, a coating compound is produced from the components listed below in the specified amounts:

Components

Polytetramethylene ether glycol (molecular weight 650)

Oxypropylated glycerine (molecular weight 600)

Xylene

Ethylene glycol monoethyl ether acetate, methyl isobutyl ketone, ethyl acetate 2,6-di-tert-butyl-4-methylphenol

Toluene diisocyanate (80:20 mixture of 2,4 and 2,6 isomers)

Quantities ^

35.03 parts (.0.113 hydroxyl equivalents)

3.89 file (0.019 riyuroxy equivalents)

27.86 parts 9.25 parts 4.59 parts 2.50 parts 0.80 parts

16.08 parts

(0.185 isocyanate equivalents)

The coating composition obtained in this way with an isocyanate content of about 2.30 fo is applied by spraying to a streamlined test specimen identical to that used in Example 1, so that the dried coating is essentially the same thickness as the coatings of the preceding examples. The ifassfilm 14 days at 23.89 ⁰ C and 50 ^C /> relative humidity is cured. The properties of the hardened coating are summarized in Table II.

109846/1896

Table II Properties of Cured Polyurethane Surfaces

example ., 3

Sward hardness (ASIM test standard D-2134-62T) 9

erosion resistance: 23

50.8 in the rain / hourj mean destruction time, minutes

Sand erosion resistance '7.0

40.64 mm sand / minute \ mean destruction time, minutes

Sand abrasion V for penetration Required liters of sand / 0.0254 mm coating

Flexibility »conical behavior test passed according to mandrel (ASTM test standard D-522-6Oj 3.175 mm diameter, -40 C)

¹ ^ quartz sand (grain size ·. 0.105 "to 0.149-mm)

² 'USA Federal Standard Test Method No. I4I-A, Method I691 using Ottawa sand (grain size: 0.297 to 0.841 mm).

Example4

According to the method of the preceding examples, a Coating compounds · with an isocyanate content

of 3.92 percent from the components listed below produced in the given quantities:

109846/1696

Components . amounts

Polytetrafluoroethylene Ethylene Glycol 936 ropes

(Molecular weight 650) (2.87 hydroxyl equivalents)

- i

Oxypropylated Glycerin 104 parts

(Molecular weight 600). (0.51 hydroxyl equivalents)

Xylene 375 parts

Ethylene glycol monoethyl ether acetate 125 parts

Toluene diisocyanate, 460 parts

(80:20 mixture of the 2.4 and (5.29 isocyanate equivalents) 2,6 isomers)

The coating composition thus obtained

0.2 percent by weight di-

Coating compound butyltin dilaurate catalyst incorporated. This / will Applied to the rotor blades of a HU-I helicopter in such a way that the tracked coating has a thickness of 0.381 to 0.508 mm having. Tor the application of the coating are made of stainless Steel existing rotor blades with polyvinyl butyral (acid-catalyzed) according to the USA military test standard MIL-P-15328 B covered. After the coating has hardened for 7 days in humid air, the helicopter will take 170.4 hours below flown conditions listed: approximately 2 hours of flight time in heavy rain, 15 hours in light rain or Lever, 12 hours in salty air and the rest under normal conditions. After the end of the attempt there is no Detectable erosion of the coating. Slight wear can only be seen at the outer ends of the rotor blades.

Comparative experiment B

r. The experiment shows the surprising effect of the invention Method compared to a known method, the

. ' . 109846/1696

Coating compounds
for the production of 1 with free isocyanate end groups, which are particularly suitable for the production of coatings, a two-stage. Procedure prescribes.

287.9 parts (0.86-hydroxy! Equivalent) polytetramethylene ether- ■ glycol with a molecular weight of about 660 are under nitrogen with 89.3. Parts of ethylene glycol monoethyl ether acetate and 267.8 parts of xylene are mixed. The mixture is then dehydrated by azeotropic distillation at about 80 ⁰ C. After cooling to room temperature, the mixture is stirred with 149.7 parts (1.72 isocyanate equivalents) of toluene diisoeyanate

(80:20 mixture of the 2,4 and 2,6 isomers). These

Mixture is then added with 71.9 parts (0.37 hydroxyl equivalents) oxypropylated glycerol (molecular weight 600) added, a coating compound with a ratio of isocyanate groups to hydroxyl groups of approximately 1.4 ί 1 is obtained.

Approximately 0.5 percent of the curing catalyst used in Comparative Experiment A is incorporated into this mixture. Afterward is a streamlined test body made of aluminum, which with · the polyvinyl butyral used in Example la was treated as an adhesion promoter by spraying so with

Coating compound
the above manufactured / coated that the dried

Coating is essentially the same thickness as the coatings of the

erosion

previous examples · After curing, the rain resistance becomes of the coating as in the previous examples. The destruction of the coating, the 50.8 mm of rain / hour is suspended occurs after 7.2 minutes. The after the loading

109846M696

Known, two-step process achieved coating produced so not the surprisingly high level of RegenerQaion resistance of the coatings according to the invention *

Comparative experiment G

The experiment shows the unexpected effect of the invention Method, compared to a known method which, instead of that used in the method of the invention, is oxyalkylated Triols an aliphatic triol is used.

191.5 ropes (0.57 hydroxyl equivalents) of polytetraraethylene ether glycol with an average molecular weight of 66O are mixed under nitrogen with 47.9 parts (1.07 hydroxyl equivalents) of trimethylolpropane, 90 parts of ethylene glycol monoethyl ether acetate and 270 parts of xylene. The mixture is then dehydrated by azeotropic distillation at about 8O ⁰ C. After cooling to room temperature, the mixture is stirred with

200.6 parts (2.30 hydroxyl equivalents) toluene diisocyanate

(80:20 mixture of the 2,4 and 2,6 isomers). The relationship of the isocyanate groups to the hydroxyl groups of the thus obtained Coating mass is approximately 1.4: 1.

On a streamlined test body made of aluminum, which with the polyvinyl butyral used in example la as adhesion

mass.

has been treated in the middle, the coating prepared above is applied by spraying in such a way that the dried coating is somewhat is the same thickness as the coatings of the previous examples.

Coating compound Before application, the / 0.5 weight percent dee Curing catalyst used in comparative experiment B

109846/1696

incorporated. After hardening, the rain erosion resistance becomes of the coating as * in the previous examples checked "Haoh 1.6 minutes at a hold of 50.8 mi / hour.

Witt the destruction of the coating a « Me according to the invention»

Coatings therefore differ significantly from the known ^ coatings

.Ii äuroij their surprisingly high resistance to erosion, those on using an oxyslkylated triol instead of one aliphatic triols used in the known process are based

Comparative experiment JD

The experiment shows the unpredictable effect of the invention Method, compared with the known methods described in the comparative experiments B and G, which in the comparative experiment B described method differs from Method of the invention in that the coatings after a two-stage Twifahren can be produced · The comparative experiment 0 described method works according to a one-step process and uses instead of the oxyalkylated triol Invention of an oleophilic trial in a ratio of Triol to iolytetramethylene ether glycol of at least 1; 1. Comparative experiment D shows that if the one in j Comparative experiment C used »aliphatic triols by the in .Vergleichsvbrsueh B oxyalkylated triol used so

Preserved side ^ i © htung »do not need the high one!

- Beach Sightseeing]

Rain erosion distance of the trfinduagegeassen / auf-;

10S846 / 1896

Approximately 1. mole (1.80 hydroxyl equivalents) of polytetramethylene ether glycol with a molecular weight of 660 v / earth under nitrogen with approximately 1 UoX (3.05 hydroxyl equivalents) of oxypropylated glycerol with a molecular weight of 600,

ether
180 parts of ethylene glycol monoethylene / acetate and 540 parts of xylene are mixed. The mixture is then dehydrated by azeotropic distillation at about 80 ⁰ C. After cooling to room temperature, the mixture is admixed with 590 parts (6.79 isocyanate equivalents) of toluene diisocyanate (80:20; mixture of the 2,4- and 2,6-isomers). The ratio of the isocyanate groups to the hydroxyl groups in the coating composition thus obtained is 1. * i: 1.

On a streamlined test body made of aluminum, which with

• ι *

the polyvinyl butyral used in example la as adhesion

mass . has been treated in the middle, the coating produced above is

applied by spraying in such a way that the dried coating is about the same as the coatings of the preceding two

* · Coating compound, games. Before the application, the /. 0.5 y » of the hardening catalyst used in Comparative Experiment C was incorporated. After curing, the rain erosion resistance of the coating is tested as in the previous examples. After 2.4 minutes with rain of 50.8 mm / hour, the coating was destroyed.

109846/1696

Claims (8)

Patent claims 1. Process for the manufacture of elastomeric .Polyurethane fiber pulls by applying reaction products of poly oils with an organic diisocyanate on the substrate and Curing of the applied film, characterized in that that a prepolymer or, preferably, a solution of a prepolymer, the optionally customary additives contains and by repositioning (a) a polytetramethylene ether glycol with an average Molecular weight from about 500 to about 700 and (b) an oxyalkylated triol having an average molecular weight from about 400 to about 1000 in an amount of 0 to 20 percent by weight, based on the total weight of the oxyalkylated triol and polytetramethylene ether glycol with. (c) such an amount of an organic diisocyanate that _s the ratio of the isocyanate groups of the diisocyanate to the hydroxyl groups of the polytetraniethylene ether glycol and the oxyalkylated triol is 1.2: 1 to 1.8: 1, is prepared with the exclusion of moisture, in an organic solvent on the substrate and the wet film at a moderate temperature on a more humid one Air hardens. 2. The method according to claim _1, characterized in that a prepolymer using a polytetramethylene ether glycol with an average molecular weight of about $ 00 to about 680 is produced. 109846/1696 3. The method according to claim 1 and 2, characterized in that a prepolymer using 0 to 15 percent by weight, based on the total weight of the oxyalkylated triol and the polytetramethylene ether glycol, an oxyalkylated triol. 4. The method according to claim 1 to 3, characterized in that that one prepolymer using about 8 to about 12 weight percent based on the total weight of the oxyalkylated Triols and polytetramethylene ether glycol, an oxyalkylated trio. 5. The method according to claim 1, 3 and 4, characterized in that that the oxyalkylated triol by oxyalkylating a triol with an alkylene oxide having 2 to 4 carbon atoms or a mixture produces such alkylene oxides. 6. The method according to claim 1, 3, 4 and 5 »characterized in that that the oxyalkylated triol is prepared by oxyalkylating glycerol. 7. The method according to claim 1, 3, 4, 5 and 6, characterized in that that a prepolymer using oxypropylated glycerol with an average molecular weight of about 600 manufactures. 8. The method according to claim 1 to 7, characterized in that a prepolymer using such an amount of diisoeyanate produces that the ratio of the isocyanate groups of the diisocyanate to the hydroxyl groups of the poly.tetra- 109846/1696 methylene ether glycol and the oxyalkylated triol 1.4: 1 up to 1.6: 1 amounts, Method according to claim "1 Ms S, characterized in that a prepolymer using toluene diisocyanate manufactured 10, coating compositions based on polyurethane prepolymers for carrying out the method according to claim 1 to 9, characterized in that the prepolymer by reacting (a) a polytetramethylene ether glycol with an average Molecular weight from about 500 to about 700 and (b) an oxyalkylated triol having an average molecular weight of about ¹ JOO to about 100 p in an amount of 0 to 20 percent by weight, based on the total weight of the oxyalkylated triol and a polytetramethylene ether glycol with (c) such an amount of an organic diisocyanate that the ratio! the isocyanate groups of the diisocyanate to the hydroxyl groups of the polytetramethylene ether glycol and the oxyalkyliejrten triol is 1.2 to 1.8 i 1, below Exclusion of moisture has been established, 109848/1696