TECHNICAL FIELD

The present invention relates to a two-component polyurethane composition used for preparing vapor barrier in the building with low indoor temperature, which comprises component A comprising (b) polyol, comprising at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms, (c) chain extender, (d) catalyst, (e) water scavenger, and (f) optionally crosslinker, defoamer, and/or other auxiliaries and additives, and component B comprising (a) at least one polyisocyanate. The present invention also relates to the method of preparing vapor barrier in the building with low indoor temperature by the two-component polyurethane composition mentioned above, and the use of the two-component polyurethane composition mentioned above for decreasing vapor permeation in the building with low indoor temperature.

BACKGROUND

In modern food industry, low indoor temperature buildings, such as cold storage warehouses, are widely used to preserve foods for extended periods. In the construction of such buildings with low indoor temperature, it is required that the thermal insulation layer should have excellent heat preservation and water resistance, so as to prevent the rise of the indoor temperature and the spoilage of the foods due to moisture. Nevertheless, a lot of cold storage warehouses are facing the problems of increasing energy consumption and increasing maintenance cost after 5-10 years of operation. The reason for this includes damage of the thermal insulation layer and penetration of vapor into the wall of the cold storage warehouse. Dewing and frosting have been found inside the thermal insulation layers of these cold storage warehouses, and some of the thermal insulation layers have even been soaked in moisture. Therefore, means for moist proof and vapor barrier have been contemplated and incorporated into the wall of the cold storage warehouses.

CN107903803A discloses a two-component polyurethane coating for vapor barrier, in which component A comprises isocyanates and polyether polyols, and component B comprises fluorine-containing acrylate resin, polyether polyols, catalyst, chain extender, defoamer, dispersant, fillers, and other additives. According to CN107903803A, the main technical means for preventing vapor include the fluorine- containing acrylate resin, the barrier filler, the dispersant and the defoamer, so as to obtain vapor barrier effect.

CN109810623A discloses a coating for vapor barrier in cold storage warehouses, comprising the raw materials of polyether polyols, isocyanates, plasticizer, catalyst, stabilizer, and solvents. The coating is not two-component composition but is prepared by sequential addition of each component.

CN109177391A discloses a film for water proof and vapor barrier in cold storage warehouse construction, comprising water-proof film made of aluminum-plated polyester film and polypropylene filament non-woven fabrics and polyurethane adhesive II. Said polyurethane adhesive II is a two-component composition, comprising polymeric MDI (pMDI), polyether polyols, CaCOs powder, water, cyclohexylamine, and aqueous ethyl acetate solution. In the water proof and vapor barrier film of CN 109177391 A, the vapor barrier effect is obtained mainly through the water-proof film made of aluminum-plated polyester film and polypropylene filament non-woven fabrics.

Despite the above achievements, the water prevention and vapor barrier effects of the cold storage warehouses are still not satisfactory, and it is still needed in this technical field to provide vapor barrier with improved performance in buildings with low indoor temperature.

SUMMARY OF THE PRESENT INVENTION

One object of the present invention is to provide a polyurethane composition used for preparing vapor barrier in the building with low indoor temperature, which exhibits improved effect in decreasing water vapor penetrating and permeating into the thermal insulation layer of buildings with low indoor temperature, such as cold storage warehouses. This object is fulfilled by a two-component polyurethane composition for preparing vapor barrier, which comprises component A comprising

(b) polyol, comprising at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms,

(c) chain extender,

(d) catalyst,

(e) water scavenger, and

(f) optionally crosslinker, defoamer, and/or other auxiliaries and additives, and component B comprising

(a) at least one polyisocyanate.

The two-component polyurethane composition as described above can be used for preparing vapor barrier by mixing the two components A and B together and curing the thus formed mixture. Preferably, the mixing of components A and B is accomplished by spraying.

In an embodiment, the component (a) polyisocyanate is selected from the group consisting of tri-, tetra-, penta-, hexa-, hepta- and/or octamethylene diisocyanate, 2- methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1 ,4-diisocyanate, hexamethylene 1 ,6-diisocyanate (HDI), pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, trimethylhexamethylene 1 ,6-diisocyanate, isophorone diisocyanate (IPDI), 1 ,4- and/or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4- diisocyanate, 1 -methylcyclohexane 2,4- and/or 2, 6-diisocyanate, methylene dicyclohexyl 4,4'-, 2,4'- and/or 2, 2'-diisocyanate (H12MDI), naphthylene 1,5- diisocyanate (NDI), tolylene 2,4- and/or 2, 6-diisocyanate (TDI), 3,3’-dimethyl-4,4’- diisocyanatodiphenyl (TODI), p-phenylene diisocyanate (PDI), diphenylethane 4,4’- diisocyanate (EDI), dimethyl diphenyl 3,3'-diisocyanate, diphenylethane 1,2- diisocyanate and/or diphenylmethane diisocyanates (MDI), including diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate, the mixtures of monomeric diphenylmethane diisocyanates with diphenylmethane diisocyanate homologs having at least two rings (polymeric MDI)., and mixtures of two or more of these isocyanates.

In an embodiment, the component (b) polyol comprises at least one natural oil polyol having at least one, preferably more than one, more preferably three aliphatic chains having 12 to 30 carbon atoms, preferably 16 to 26 carbon atoms, more preferably 18 to 24 carbon atoms.

In a further embodiment, the component (c) chain extender is a substance having two hydrogen atoms reactive toward isocyanates and having a molar mass which is smaller than 500 g/mol, preferably from 60 to 400 g/mol. Preferably, the chain extender is a diol.

In an embodiment, the component (d) catalyst is selected from amines and organic metal compounds, used either alone or in combination. Preferably, the catalyst is an organo-bismuth compound.

In an embodiment, the component (e) water scavenger is selected from epoxy resins and aluminosilicates.

In a further embodiment, the component (f) includes crosslinkers, defoamers, fillers, surfactants, colorants, pigments, flame retardants, stabilizers, viscosity reducers, and substances having fungistatic and bacteriostatic action.

In a further embodiment, the two-component polyurethane composition of the present invention has a solid content of 98 wt% or above, preferably 99 wt% or above, or more preferably 99.5 wt% or above, measured according to GB/T 16777-2008.

In an embodiment, the component A and component B are mixed in a weight ratio of 1:1-1.3, more preferably 1:1-1.2,.

The present invention also relates to a method for preparing vapor barrier from the two-component polyurethane composition defined above, including the steps of mixing component A and component B in the two-component polyurethane composition together and curing the thus formed mixture.

The present invention further relates to the use of the two-component polyurethane composition defined above for decreasing vapor permeation in the building with low indoor temperature, such as in cold storage warehouses.

Compared with conventional polyurethane compositions, the two-component polyurethane composition of the present invention can be applied conveniently by, for example, spraying without the facilitation of organic solvent, and the vapor barrier prepared thereby has reduced vapor permeability and improved binding strength with the substrate. The vapor barrier may impart the cold storage warehouses with improved water proofing and heat preservation effect.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the invention belongs. As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.

As used herein, the articles "a" and "an" refer to one or to more than one (i.e. , to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

As used herein, the term "about" is understood to refer to a range of numbers that a person of skill in the art would consider equivalent to the recited value in the context of achieving the same function or result.

As used herein, the term “additives" refers to additives included in a formulated system to enhance physical or chemical properties thereof and to provide a desired result. Such additives include, but are not limited to, dyes, pigments, toughening agents, impact modifiers, rheology modifiers, plasticizing agents, thixotropic agents, natural or synthetic rubbers, filler agents, reinforcing agents, thickening agents, inhibitors, fluorescence or other markers, thermal degradation reducers, thermal resistance conferring agents, surfactants, wetting agents, defoaming agents, dispersants, flow or slip aids, biocides, and stabilizers.

Unless otherwise identified, all percentages (%) are “percent by weight".

The radical definitions or elucidations given above in general terms or within areas of preference apply to the end products and correspondingly to the starting materials and intermediates. These radical definitions can be combined with one another as desired, i.e., including combinations between the general definition and/or the respective ranges of preference and/or the embodiments. All the embodiments and the preferred embodiments disclosed herein can be combined as desired, which are also regarded as being covered within the scope of the present invention.

Unless otherwise identified, the temperature refers to room temperature and the pressure refers to ambient pressure.

Unless otherwise identified, the solvent refers to all organic and inorganic solvents known to the persons skilled in the art and does not include any type of monomer molecular.

The present invention is directed to a two-component polyurethane composition for preparing vapor barrier in buildings with low indoor temperature, which comprises component A comprising

(b) polyol, comprising at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms,

(c) chain extender,

(d) catalyst,

(e) water scavenger, and

(f) optionally crosslinker, defoamer, and/or other auxiliaries and additives, and component B comprising

(a) at least one polyisocyanate.

(a) Polyisocyanate

The polyisocyanates (a) used in the polyurethane composition according to the invention comprise all polyisocyanates known for the production of polyurethanes. These comprise the aliphatic, cycloaliphatic and aromatic divalent or polyvalent isocyanates known from the prior art and any desired mixtures thereof. Aliphatic diisocyanates used are customary aliphatic and/or cycloaliphatic diisocyanates, for example tri-, tetra-, penta-, hexa-, hepta- and/or octamethylene diisocyanate, 2- methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1 ,4-diisocyanate, hexamethylene 1 ,6-diisocyanate (HDI), pentamethylene 1,5-diisocyanate, butylene 1 ,4-diisocyanate, trimethylhexamethylene 1,6-diisocyanate, 1-isocyanato-3,3,5- trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and/or 1 ,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4-diisocyanate, 1- methylcyclohexane 2,4- and/or 2, 6-diisocyanate, methylene dicyclohexyl 4,4'-, 2,4'- and/or 2,2'-diisocyanate (H12MDI). Suitable aromatic diisocyanates are especially naphthylene 1,5-diisocyanate (NDI), tolylene 2,4- and/or 2, 6-diisocyanate (TDI), 3,3’- dimethyl-4,4’-diisocyanatodiphenyl (TODI), p-phenylene diisocyanate (PDI), diphenylethane 4,4’-diisocyanate (EDI), dimethyl diphenyl 3,3'-diisocyanate, diphenylethane 1 ,2-diisocyanate and/or diphenylmethane diisocyanates (MDI), including diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate, the mixtures of monomeric diphenylmethane diisocyanates with diphenylmethane diisocyanate homologs having at least two rings (polymeric MDI).

Polyisocyanates (a) preferably used herein are the aromatic polyisocyanates which are readily obtainable in industry, particularly preferably mixtures of diphenylmethane diisocyanates (MDI) and of polyphenyl polymethylene polyisocyanates.

The polyisocyanates (a) may also be employed in the form of polyisocyanate prepolymers. These polyisocyanate prepolymers are obtainable by reacting an excess of the above-described polyisocyanates (component (a)) with polymeric compounds having isocyanate-reactive groups and/or chain extenders for example at temperatures of 20°C to 100°C, preferably at about 80°C, to afford the isocyanate prepolymer.

Polymeric compounds having isocyanate-reactive groups and chain extenders are known to those skilled in the art and described for example in “Kunststoffhandbuch [Plastics Handbook], volume 7, Polyurethane [Polyurethanes]”, Carl Hanser Verlag, 3rd edition 1993, chapter 3.1.

In a preferred embodiment, the polyisocyanate (a) is polymeric diphenylmethane diisocyanate (pMDI).

(b) Polyol Component (b) polyol used here preferably have a number average molecular weight in the range from 400 to 15 000 g/mol, preferably 500 and 12 000 g/mol, more preferably from 500 to 6 000 g/mol, in particular from 500 to 3 000 g/mol, and of average functionality from 2 to 8, preferably from 2 to 6, more preferably from 2 to 4. Useful compounds under this heading may thus be selected from the group of polyether polyols, polyester polyols, polycarbonate polyols, polycaprolactone polyols, or mixtures thereof, and are preferably polyether polyols. Polyether polyols are for example prepared from epoxies, such as propylene oxide and/or ethylene oxide, or from tetrahydrofuran with active-hydrogen starter compounds, such as aliphatic alcohols, phenols, amines, carboxylic acids, esters, water or natural-based compounds, such as sucrose, sorbitol or mannitol, by using a catalyst. Suitable catalysts here include basic catalysts or double metal cyanide catalysts as described for example in PCT/EP2005/010124, EP 90444 or WO 05/090440.

In the present invention, the polyol (b) comprises at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms. Preferably, the polyol (b) comprises at least one natural oil polyol having at least one, preferably more than one, more preferably three aliphatic chains having 12 to 30 carbon atoms, preferably 16 to 26 carbon atoms, more preferably 18 to 24 carbon atoms. In the context of the present invention, examples of suitable natural oil polyol include castor oil, hydrogenated castor oil, soybean oil polyols, palm oil polyols, rosin-based polyols, hydroxyl-modified fatty acid esters based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid, and derivatives thereof. By the term “derivatives”, these include alkoxylates, transesterification products, products of ozonolyis/reduction, products of ozonolyis/glycolysis, products of hydroformylation/reduction, products of epoxidation/ring-opening to the carbon-carbon double bonds, or other hydroxylcontaining products of those oils and esters. Preference here is given to using castor oil and its reaction products with alkylene oxides or ketone-formaldehyde resins. Such compounds are for example available from BASF under the designation Sovermol® 750. As known in the art, castor oil contains as its main constituent triglycerides of ricinoleic acid, which contains hydroxyl group in its carbon chain. Polyether polyol based on castor oil is obtained by using castor oil as starting material with ethylene oxide and/or propylene oxide.

In certain embodiments, polyol (b) may further comprise at least one polyether polyol, other than natural oil polyols mentioned above, which is started with amine, ester and/or alcohol having one or more aliphatic chains having at least 6 carbon atoms. The amine, ester and/or alcohol defined here are referred to as starter compounds. Suitable starter compounds used for the polyether polyol in the present invention comprise amine, ester and/or alcohol having at least one C6-C30 aliphatic chain, preferably C6-C20 aliphatic chain. Said aliphatic chain can be saturated or unsaturated, possibly comprising one or more alkenyl or alkynyl groups. Moreover, functional groups, such as hydroxyl, can be attached to the carbon atoms in the aliphatic chain. Examples of the starter compounds include octadecyl amine, stearyl alcohol, sucrose, and sorbitol. In a preferred embodiment, the polyether polyol has a functionality of larger than 5.

The polyether polyols that can be used in the present invention are produced by known processes. By way of example, they can be produced via anionic polymerization using alkali metal hydroxides, e.g. sodium hydroxide or potassium hydroxide, or using alkali metal alcoholates, e.g., sodium methanolate, sodium ethanolate or potassium ethanolate, or potassium isopropanolate, as catalysts, and with addition of at least one C6-C30 aliphatic alcohol, ester and/or amine starter molecule which has from 2 to 8, preferably from 2 to 6, reactive hydrogen atoms as stated above, or via cationic polymerization using Lewis acids, such as antimony pentachloride, boron fluoride etherate, etc., or bleaching earth, as catalysts. Polyether polyols can likewise be produced via double-metal-cyanide catalysis, from one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene moiety. It is also possible to use tertiary amines as catalyst, an example being triethylamine, tributylamine, trimethylamine, dimethylethanolamine, imidazole, or dimethylcyclohexylamine. It is also possible, for specific intended uses, to incorporate monofunctional starters into the structure of the polyether. The polyether polyols can be used individually or in the form of a mixture. Examples of suitable alkylene oxides are tetrahydrofuran, propylene 1,3-oxide, butylene 1,2- or 2,3-oxide, styrene oxide, ethylene oxide and propylene 1,2-oxide, and preferably ethylene oxide and propylene 1,2-oxide. The alkylene oxides can be used individually, in alternating succession, or in the form of a mixture.

In an embodiment of the present invention, the polyol (b) is present in an amount of 50% to 95% by weight, preferably 60% to 92% by weight, and more preferably 70% to 90% by weight, based on the total weight of component A in the composition. In further embodiment of the present invention, the at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms accounts for 40% to 100% by weight, preferably 60% to 90% by weight of the polyol (b). Particularly, the polyol (b) comprises castor oil solely as the at least one natural oil polyol having one or more aliphatic chains having at least 12 carbon atoms.

(c) Chain extender

Component (c) chain extenders that can be used are substances having a molar mass which is preferably smaller than 500 g/mol, particularly preferably from 60 to 400 g/mol, wherein the chain extenders have two hydrogen atoms reactive toward isocyanates. These can be used individually or preferably in the form of a mixture. It is preferable to use diols having molecular weights smaller than 400 g/mol, particularly from 60 to 400 g/mol, and in particular from 60 to 350 g/mol. Examples of those that can be used are aliphatic, cycloaliphatic, and/or araliphatic diols having from 2 to 14, preferably from 2 to 10, carbon atoms, e.g. ethylene glycol, 1,3-propanediol, 1,4- butanediol, 1,6-hexanediol, 1,10-decanediol, and bis(2-hydroxyethyl)hydroquinone, 1,2-, 1,3-, and 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, and low-molecular-weight hydroxylated polyalkylene oxides based on ethylene oxide and/or on propylene 1,2-oxide, and on the abovementioned diols, as starter molecules. It is particularly preferable to use, low-molecular-weight hydroxylated polyalkylene oxides based on ethylene oxide and/or on propylene 1,2- oxide, particularly preferably on ethylene.

The proportion of chain extender (c), based on the weight of component A, is preferably from 1 to 25% by weight, particularly preferably from 3 to 20% by weight, and in particular from 5 to 15% by weight.

(d) Catalyst

Component (d) catalysts greatly accelerate the reaction of the component (b) and chain extender (c) with the polyisocyanates (a). The catalysts (d) preferably comprise amine-based catalysts and/or organic metal compounds.

Typical catalysts employable for production of polyurethanes include for example amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- and N- cyclohexylmorpholine, N , N , N ' , N'-tetramethylethylenediamine, N , N , N ' , N tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1- azabicyclo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine and dimethylethanolamine. Likewise contemplated are organic metal compounds, preferably organic biemuth compounds, especially bismuth carboxylates, such as bismuth(lll) neodecanoate, bismuth 2-ethylhexanoate and bismuth octanoate, or mixtures thereof. The organic metal compounds may be used either alone or preferably in combination with strongly basic amines.

Amine-based catalysts have at least one, preferably 1 to 8 and particularly preferably 1 to 2 groups reactive toward isocyanates, such as primary amine groups, secondary amine groups, hydroxyl groups, amides or urea groups, preferably primary amine groups, secondary amine groups, hydroxyl groups. Amine-based amine catalysts are mostly used for production of low-emission polyurethanes especially employed in automobile interiors. Such catalysts are known and described for example in EP1888664. These comprise compounds which, in addition to the isocyanate-reactive group(s), preferably comprise one or more tertiary amino groups. At least one of the tertiary amino groups in the incorporable catalysts preferably bears at least two aliphatic hydrocarbon radicals, preferably having 1 to 10 carbon atoms per radical, particularly preferably having 1 to 6 carbon atoms per radical. It is particularly preferable when the tertiary amino groups bear two radicals independently selected from methyl and ethyl radical plus a further organic radical. Examples of amine-based catalysts that may be used are bis(dimethylaminopropyl)urea, bis(N,N- dimethylaminoethoxyethyl) carbamate, dimethylaminopropylurea, N,N,N-trimethyl-N- hydroxyethylbis(aminopropylether), N,N,N-trimethyl-N- hydroxyethylbis(aminoethylether), diethylethanolamine, bis(N,N-dimethyl-3- aminopropyl)amine, dimethylaminopropylamine, 3-dimethylaminopropyl-N,N- dimethylpropane-1 ,3-diamine, dimethyl-2-(2-aminoethoxyethanol), (1 ,3- bis(dimethylamino)propan-2-ol), N,N-bis(3-dimethylaminopropyl)-N-isopropanolamine, bis(dimethylaminopropyl)-2-hydroxyethylamine, N,N,N-trimethyl-N-(3-aminopropyl)- bis(aminoethylether), 1 ,4-diazabicyclo[2.2.2]octane-2-methanol and 3- dimethylaminoisopropyl diisopropanolamine or mixtures thereof.

Catalysts (d) may be employed for example in a content of 0.005 to 5 wt%, preferably 0.01 to 3 wt%, more preferably 0.1-2 wt%, based on the total weight of the component A. In a particularly preferred embodiment, the component (d) catalyst employed is organo-bismuth catalyst.

(e) Water scavenger

The component (e) water scavengers are substances that can remove water, steam, moisture, and/or vapor from the composition and/or the ambient environment where the composition is stored or used. These include, for example, epoxy resins and/or aluminosilicates. Possible aluminosilicates are selected from the group of the sodium aluminosilicates, potassium aluminosilicates, calcium silicates, caesium aluminosilicates, barium aluminosilicates, magnesium aluminosilicates, strontium aluminosilicates, sodium aluminophosphates, potassium aluminophosphates, calcium aluminophosphates, and mixtures thereof. It is particularly preferable to use T-paste as the water scavenger.

The number-average particle size of the water scavenger is preferably not greater than 200 pm, more preferably not greater than 150 pm, and in particular not greater than 100 pm. The pore width of the water scavenger of the invention is preferably from 2 to 5 A.

The amount of the water scavenger here is preferably greater than 0.5 wt%, particularly preferably in the range from 1 to 10 parts by weight, more preferably in the range of 2-8 wt%, based on the total weight of the component A.

(f) Crosslinker, defoamer and/or other auxiliaries and additives The two-component polyurethane composition according to the present invention may optionally further comprise crosslinkers, defoamers and/or other auxiliaries and additives. The component (f), if present, is in an amount of 0.5-30% by weight, preferably 1-20% by weight, and more preferably 1.5-10% by weight, based on the total weight of the component A.

Crosslinkers are molecules having more than two isocyanate-reactive hydrogens. Preference is given to using triols and/or triamines having molecular weights below 300 g/mol, more preferably in the range from 62 g/mol to below 300 g/mol and especially in the range from 62 g/mol to 250 g/mol. Suitable crosslinkers are, for example, aliphatic, cycloaliphatic and/or araliphatic or aromatic triamines and triols having 2 to 14, preferably 2 to 10 carbon atoms, such as 1,2,4-, 1,3,5- trihydroxycyclohexane, glycerol and trimethylolpropane, diethanolamines, triethanolamines, and low molecular weight hydroxyl-containing polyalkylene oxides based on ethylene oxide and/or 1 ,2-propylene oxide and the aforementioned diols and/or triols as starter molecules. Particular preference for use as crosslinkers is given to low molecular weight hydroxyl-containing polyalkylene oxides based on ethylene oxide and/or 1,2-propylene oxide, more preferably 1 ,2-propylene, and trifunctional starters, especially glycerol and trimethylolpropane. When crosslinkers are used, the proportion of crosslinkers will typically be in the range from 1 to 12 wt%, preferably from 2 to 8 wt%, based on the total weight of the component A.

Defoamers used preferably comprise silicone-based foam stabilizers. The foam stabilizers used can also comprise siloxane-polyoxyalkylene copolymers, organopolysiloxanes, ethoxylated fatty alcohols, and alkylphenols, and castor oil esters and, respectively, ricinoleic esters. Other auxiliaries and additives that can be used comprise fillers, surfactants, dyes, pigments, flame retardants, stabilizers, viscosity reducers, and substances having fungistatic and bacteriostatic action.

The stabilizers used with respect to aging and weathering effects mostly comprise antioxidants. By way of example, these can be sterically hindered phenols, HALS stabilizers (hindered amine light stabilizer), triazines, benzophenones, and benzotriazoles.

Examples of surfactants that can be used are compounds which serve to promote homogenization of the starting materials and ensure phase stability of the polyol component over prolonged periods. These are, optionally, also suitable for regulating cell structure. Mention may be made by way of example of emulsifiers, such as the sodium salts of castor oil sulfates, or of fatty acids, and also salts of fatty acids with amines, e.g. diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate, salts of sulfonic acids, e.g. the alkali metal or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers, such as siloxane-oxalkylene copolymers and other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oils, castor oil esters and, respectively, ricinoleic esters, Turkey red oil, and peanut oil, and cell regulators, such as paraffins, fatty alcohols, and dimethylpolysiloxanes. Other suitable compounds for improving emulsifying effects, or cell structure, and/or for stabilizing the foam are oligomeric polyacrylates having polyoxyalkylene and fluoroalkane radicals as pendent groups.

The amounts usually used of the surfactants, based on the total weights of the component A, are usually from 0.01 to 5% by weight.

Fillers that can be added, in particular reinforcing fillers, comprise the materials known per se which are conventional organic and inorganic fillers, reinforcing agents, and weighting agents. In detail, examples that may be mentioned are: inorganic fillers, e.g., silicatic minerals, for example phyllosilicates, such as antigorite, serpentine, hornblendes, amphiboles, chrysotile, zeolites, talc; metal oxides, e.g. kaolin, aluminum oxides, aluminum silicate, titanium oxides, and iron oxides, metal salts, e.g. chalk, barite, and inorganic pigments, such as cadmium sulfide, zinc sulfide, and also glass particles. Examples of organic fillers that can be used are: carbon black, melamine, collophony, cyclopentadienyl resins, and polymer-modified polyoxyalkene polyols.

Flame retardants used include flame retardants which comprise expandable graphite and which comprise oligomeric organophosphorus flame retardant. Expandable graphite is well known. This comprises one or more expandable materials, so that considerable expansion takes place under the conditions present in a fire. Expandable graphite is produced by known processes. The usual method here begins by modifying graphite with oxidants, such as nitrates, chromates, or peroxides, or via electrolysis, in order to open the crystal layers, and nitrates or sulfates are then intercalated into the graphite, and can bring about expansion under given conditions. The oligomeric organophosphorus flame retardant preferably comprises no less than 5% by weight of phosphorus content, with the presence of at least 3 phosphate ester units in preferred embodiments. “Phosphorus ester units” here comprise phosphate ester units and phosphonate ester units. The oligomeric organophosphorus flame retardants of the invention therefore comprise structures having pure phosphonate units, having pure phosphate units, and also having phosphonate units and phosphate units.

It is possible to use one or more arbitrary flame retardant(s) usually used, alongside the oligomeric organophosphorus flame retardants and expandable graphite, for polyurethanes. These comprise halogen-substituted phosphates, such as tricresyl phosphate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(1 ,3- dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, and tetrakis(2- chloroethyl) ethylene diphosphate, and/or inorganic flame retardants, such as red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate, and calcium sulfate, and/or cyanuric acid derivatives, e.g., melamine. It is preferable that the flame retardants comprise no compounds having halogen groups.

Further information concerning the mode of use and of action of the abovementioned auxiliaries and additives, and also further examples, are given by way of example in "Kunststoffhandbuch, Band 7, Polyurethane" [“Plastics handbook, volume 7, Polyurethanes”], Carl Hanser Verlag, 3rd edition 1993, chapter 3.4.

The two-component polyurethane composition of the present invention can be obtained by using polyisocyanate (a) as component B and simply mixing components (b) to (f) as component A, and kept them separately. These components are stable under ambient pressure and room temperature, and can be formulated into ready-use form before application. In the two-component polyurethane composition, the weight ratio of component A and component B is preferably in the range of 1 :1-1.3, more preferably in the range of 1:1-1.2. In an embodiment, the two-component polyurethane composition of the present invention may have a solid content of 98 wt% or above, preferably 99 wt% or above, and more preferably 99.5 wt% or above, measured according to GB/T 16777-2008. That is to say, organic solvent is not required in the two-component polyurethane composition. In an embodiment, the two-component polyurethane composition of the present invention comprises no organic solvent.

The present invention also relates to a method for preparing vapor barrier in building with low indoor temperature, including the steps of mixing component A and component B in the abovementioned two-component polyurethane composition together and curing the thus formed mixture. The vapor barrier prepared from the two- component polyurethane composition is typically formed between the substrate layer and the thermal insulation layer in constructing the building with low indoor temperature, such as cold storage houses. The mixing of the component A and component B is preferably accomplished by spraying. In spray coating, the component A and component B can be sprayed by a spraying apparatus with two separate nozzles under elevated pressure onto the substrate layer of the cold storage warehouse in certain weight ratio, preferably in weight ratio of 1:1-1.3, more preferably 1:1-1.2, and the thus formed mixture is cured on the substrate layer. The pressure for the spraying can be 1000 psi or above, or 1300 psi or above, or 1500 psi or above. The curing of the sprayed mixture can be accomplished within, for example, 0.5-8 h, preferably 1-4 h, more preferably 1-2 h. In an embodiment, the component A and component B are sprayed in the form of powders, and upon mixing, these components begin to react with each other immediately and are cured within a short period. Even in a solid content of 98 wt%, 99 wt% or above, the component A and component B can be sprayed conveniently, and no organic solvent is required to add into the mixture, which makes the two-component polyurethane composition of the present invention eco-friendly and safe to the users.

In an embodiment, the vapor barrier can be prepared by the two-component polyurethane composition as described above in one step. Here “in one step” is to be understood as meaning that the components for preparing the vapor barrier, i.e., components (a) to (e) and, if present, (f) are all mixed together immediately before commencement of the reaction and the reaction is subsequently carried on to obtain a cured polyurethane material without the admixture of further compounds and especially without admixture of further compounds comprising isocyanate-reactive groups. The isocyanate index during production of the polyurethane coating is from 90 to 130, preferably from 95 to 120, and more preferably 100-110. For the purposes of the present invention, this isocyanate index is the stoichiometric ratio of isocyanate groups to groups reactive toward isocyanate, multiplied by 100. Groups reactive toward isocyanate here are any of the groups which are present in the reaction mixture and reactive toward isocyanate.

Once cured, the polyurethane vapor barrier formed from the two-component polyurethane composition of the present invention acquires excellent physical properties. The thus formed polyurethane vapor barrier may have a high binding strength of, for example, 2.9 MPa or above, preferably 3.0 MPa or above, and more preferably 3.3 MPa or above, as determined according to GB/T 16777-2008. The polyurethane vapor barrier forms strong binding with the substrate layer, and improves the integral strength of the wall in the building with low indoor temperature. Moreover, the polyurethane vapor barrier imparts the substrate layer and the thermal insulation layer with substantially reduced vapor permeability. The polyurethane vapor barrier formed from the two-component polyurethane composition of the present invention may have a vapor permeability of 10 g/( m ² .24h) or below, preferably 2.5 g/(m ² .24h) or below, more preferably 1.8 g/(m ² .24h) or below, still more preferably 1.6 g/(m ² .24h) or below at the thickness of about 0.5 to 3 mm. It is understood that for the same composition, vapor permeability of a barrier with a greater thickness is smaller than that of a barrier with a smaller thickness. The vapor permeability is determined according to GB/T 17146-2015 at the temperature of 23±0.5 °C. Thus, even if the thermal insulation layer of the cold storage warehouse is damaged to some extent and vapor penetrates the thermal insulation layer, the polyurethane vapor barrier located between the thermal insulation layer and the substrate layer can effectively impede entry of vapor into the inner space of the cold storage warehouse. Thus, the present invention also relates to the use of the two-component polyurethane composition according to the present invention for producing vapor barrier in the building with indoor temperature lower than 18 °C. Here, the indoor temperature is preferably lower than 15 °C, more preferably lower than 10 °C, still more preferably lower than 6 °C.

The two-component polyurethane composition of the present invention, by comprising certain type of at least one polyether polyol in component A together with other components, can prepare vapor barrier which strongly binds to the substrate layer and effectively reduces vapor permeability in buildings with low indoor temperature, such as cold storage warehouse.

The present invention will now be described with reference to Examples (EX) and Comparative Example (CEX), which are not intended to limit the present invention.

The following materials were used:

Isocyanate: Polymeric MDI, commercially available from BASF as Lupranate M20s, with a functionality of approximately 2.7 and an NCO content of 31.5%.

Polyol 1 : castor oil, commercially available from BASF, with OH number of 163 mg KOH/g, and a functionality of about 2.7. Castor oil is a mixture of triglycerides characterized by about 90 wt% of triglyceride of ricinoleic acid.

Polyol 2: TAE-202 from EnHou Polymer Chemical Ind. Co., Ltd., polyether polyol started with C18 alkyl amine, with OH number of 314 mg KOH/g, average molecular weight of 357 g/mol, and a functionality of 2.

Polyol 3: NJ4502 from Jurong Ningwu New Material Co., Ltd., polyether polyol started with sorbitol, with OH number of 450±20 mg KOH/g, and a functionality of 5.2.

Glycerin: commercially from SinoPharm Jiangsu Co. Ltd.

DEOA: Diethanolamine, commercially available from BASF.

MEG: Ethylene glycol commercially available from BASF.

Dabco® DC193: water soluble silicon oil defoamer from Evonik.

T-Paste: a sodium aluminosilicate of the zeolite A type in oil from UOP, used as water scavenger.

E-100: Diethyl toluenediamine available from Albemarle Corporation.

Coscat™ 83: Organo-bismuth catalyst from Vertellus.

Reactint® X96: reactive colorant from Milliken.

Measurement Methods:

Binding strength was determined according to GB/T 16777-2008 (Test methods for building waterproofing coatings).

Vapor permeability was determined according to GB/T 17146-2015 (Test methods for water vapor transmission properties of building materials and products) at the temperature of 23±0.5 °C.

Solid content is measured according to GB/T 16777-2008 (Test methods for building waterproofing coatings).

Reaction time was determined according to GB/T 23446-2009 (Spray polyurea waterproofing coating).

Example 1 :

64.5 parts by weight of polyol 1 , 15 parts by weight of polyol 3, 10 parts of DEOA, 5 parts by weight of MEG, 0.1 part by weight of DC193, 4 parts by weight of T-paste, 1 part by weight of E-100, 0.3 parts by weight of Coscat 83, and 0.1 part by weight of X96 were mixed thoroughly to give a component A. 120 parts of pMDI was used as component B. Component A and component B were stored in two separate barrels in a reactor H-40 from GRACO. To produce the polyurethane coating, component A and component B were sprayed by the spraying machine from two separate nozzles simultaneously onto a 30cmx30cm cement plate. Upon spraying, the mixture began to cure, and after 5 minutes of curing, a homogeneous polyurethane coating was formed on the cement plate. The thickness of the coating was about 0.5 to 1 mm.

Example 2:

The same procedure was repeated as that of Example 1 , except that 44.5 parts by weight of polyol 1, 15 parts of polyol 2, 25 parts by weight of polyol 3, 10 parts of DEOA, 0.1 part by weight of DC193, 4 parts by weight of T-paste, 1 part by weight of E-100, 0.3 parts by weight of Coscat 83, and 0.1 part by weight of X96 were mixed thoroughly to give a component A.

Comparative examples 1 and 2:

The same procedures were repeated as that of Example 1, except that the formulations were different and as given in Table 1.

For the measurement, samples of the polyurethane coating were formed by the two- component polyurethane systems in the examples and comparative examples according to GB/T 16777-2008, and tested for the binding strength and vapor permeability according to the measurement methods stated above. The polyurethane coating had a thickness of 0.5mm to 3 mm. The composition of each sample was summarized in the following table 1 and the testing results were summarized in the following table 2 and table 3. In table 2, the permeability value for a specific film was given along with the thickness of the film. For the same thickness, a film with a lower permeability value shows a strong impermeability of water vapor. For the same permeability value, a film with a less thickness shows a strong impermeability of water vapor. Table 1: Composition of the polyurethane coatings produced in examples and comparative examples Table 2: Testing results of the samples

Table 3: Reaction time of the examples and comparative examples

It can be seen from the above table 2 that all the samples in the examples resulted in polyurethane coatings with impermeable vapor barrier. Nevertheless, the sample prepared from the composition used in example 1 exhibited the highest binding strength and the lowest vapor permeability among all the samples. Without bonding to any theory, it is believed that the significantly reduced vapor permeability of example 1 results from the use of highest amount of castor oil in these examples, which has three aliphatic C18 chains. In contrast, the sample prepared in comparative example 2, without the addition of castor oil, exhibited significantly higher vapor permeability, which makes it unsuitable for use as vapor barrier in cold storage warehouse. Moreover, comparative example 1, including no chain extender but using glycerin, resulted in sample with high vapor permeability and high tendency to delaminate due to the poor compatibility of glycerin with other components. Moreover, example 1 comprised T-paste as water scavenger, which reduced the content of free water through absorption or other mechanisms. As known in the art, water in the polyurethane system may react with isocyanates and cause the sample foaming to some extent, deteriorating the vapor permeability resistance of the sample.

The structures, materials, compositions, and methods described herein are intended to be representative examples of the invention, and it will be understood that the scope of the invention is not limited by the scope of the examples. Those skilled in the art will recognize that the invention may be practiced with variations on the disclosed structures, materials, compositions and methods, and such variations are regarded as within the ambit of the invention. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.