WO2016087366A1

WO2016087366A1 - Free radical polymerizable polyurethane composition

Info

Publication number: WO2016087366A1
Application number: PCT/EP2015/078054
Authority: WO
Inventors: Guobin Sun; Yuan Cheng; Yongming GU; Ian ZHENG; Shuangyin XIAO
Original assignee: Covestro Deutschland Ag; Bayer MAterialScience (China) Company Ltd.
Priority date: 2014-12-01
Filing date: 2015-11-30
Publication date: 2016-06-09
Also published as: CN105778005B; CN105778005A

Abstract

The present invention relates to a free radical polymerizable polyurethane composition comprising a polyurethane having active olefinic bond, and a reactive diluent C), wherein the polyurethane having active olefinic bond is prepared by components including (meth) acrylate, and the polyurethane composition has favorable pot-life, improved heat distortion temperature and lower exothermic peak.

Description

Free Radical Polymerizable Polyurethane Composition

Technical Field

In one aspect, the present invention relates to a free radical polymerizable polyurethane composition comprising a reactive diluent C) and a polyurethane having active olefinic bond. In another aspect, the present application relates to a polyurethane composite material fabricated by the polyurethane composition.

Background Art

Polyurethane composite materials are widely applied in various fields, such as motor vehicle, building, wind turbine blade, and the like for its light weight and high mechanical strength. For example, WO2011069975 discloses a wind turbine blade fabricated by a polyurethane composite material.

Polyurethane composite materials can be produced by various methods, such as infusion, winding, pultrusion, hand lay-up, resin transfer molding, etc. Among these methods, vacuum infusion of polyurethane is a method quite commonly adopted, which generally includes applying a negative pressure in a mold to introduce resin into the mold, infiltrating the reinforcement material, then curing the resin and releasing it from the mold to obtain the composite material. For polyurethane composite materials with large dimension, such as 1.5 Mw wind turbine blade (40 meters), it takes at least 60 minutes to fill the entire mold with resin, while pot-life of polyurethane resin is generally from 10 to 30 minutes, after which viscosity of the polyurethane resin will increase dramatically and result in rapid deterioration of flowability, thus rendering the infusion process unable to proceed.

Under specific conditions, wind turbine blades have to endure high temperature to certain extent, such as direct sunlight in desert area, therefore, polyurethane resin requires certain heat resistance to ensure that there is stable mechanical performance and no distortion, i.e., polyurethane resin requires an adequate heat distortion temperature (HDT).

Another important parameter is exothermic peak temperature during resin curation. Exothermic peak means the maximum temperature that a resin system reaches when temperature increases due to heat generated during the curation. If temperature is too high, it will very likely cause damage to the mold, as well as result in cleavage or other phenomena within the cured resin due to overheat, which is harmful for mechanical and physical properties of the cured resin. The exothermic peak temperature is generally measured as the maximal temperature reached in kernal of resin when 300 grams of liquid resin is cured at room temperature. Generally, a suitable resin system would exhibit an exothermic peak temperature of no greater than 140°C.

Accordingly, there is a need for developing a desirable polyurethane composistion having long pot-life and exhibiting lower shrinkage rate and less exothermicity in curation process, moreover, polyurethane composite material produced thereby will have a higher heat distortion temperature.

Summary of the Invention

In one aspect, this invention provides a free radical polymerizable polyurethane composition comprising a polyurethane having active olefinic bond, and a reactive diluent C), wherein the polyurethane having active olefinic bond is prepared from components including the following:

A) an isocyanate component comprising diphenylmethane diisocyanate or diphenylmethane diisocyanate prepolymer, wherein the diphenylmethane diisocyanate comprises 0-30% by weight of 4,4'-diphenylmethane diisocyanate, or the diphenylmethane diisocyanate prepolymer is prepared by diphenylmethane diisocyanate comprising 0-30% by weight of 4, 4'- diphenylmethane diisocyanate, based on 100% by weight of the isocyanate component;

B) an isocyanate-reactive component comprising:

bl) one or more compounds having the structure of formula (I)

wherein R₁ is selected from a group consisting of H, methyl and ethyl; R2 is selected from a group consisting of C2-C6 alkylene, 2,2-bis(4-phenylene)propane, l,4-bis(methylene)benzene, 1 ,3-bis(methylene)benzene and 1,2- bis(methylene)benzene; and n is an integer selected from 1-6.

In some examples of this invention, the reactive diluent C) is selected from the group consisting of styrene, C1-C10 alkyl acrylate and C1-C10 alkyl methylacrylate.

In some further examples of this invention, component bl) is selected from the group consisting of hydroxyethyl methylacrylate, hydroxypropyl methacrylate, hydroxy lbutyl methacrylate, hydroxylpentyl methacrylate, hydroxylhexyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxylbutyl acrylate, and the combination thereof.

In some further examples of this invention, the polyurethane composition has a pot-life of 60-300 minutes.

In another aspect, this invention provides a polyurethane composite material comprising resin matrix and reinforcing material, wherein the resin matrix is prepared by free radical polymerization of the polyurethane composition described above.

In some examples of this invention, the polyurethane composite material is prepared by a process selected from the group consisting of pultrusion, filament winding, hand lay-up, spray up molding and infusion. Preferably, the polyurethane composite material is prepared by vacuum infusion process.

In some further examples of this invention, the composite material is a polyurethane blade for a wind turbine having a power of at least 1.5Mw.

In yet another aspect, this invention provides a process of preparing polyurethane composite material, including the following step: I) subjecting the active olefinic bond of the free radical polymerizable polyurethane composition to radical polymerization, thus preparing the polyurethane composite material.

In some examples of this invention, the process further includes the following step: II) providing a mold, optionally having reinforcing material arranged therein, and introducing the free radical polymerizable polyurethane composition as described above into the mold, preferably, applying a negative pressure in the mold such that the free radical polymerizable polyurethane composition as described above can be introduced into the mold. Specific embodiments

I. Polyurethane composition

In one aspect, this invention relates to a free radical polymerizable polyurethane composition comprising a polyurethane having active olefinic bond, and a reactive diluent C), wherein the polyurethane having active olefinic bond is prepared from components comprising the following:

A) an isocyanate component including diphenylmethane diisocyanate or diphenylmethane diisocyanate prepolymer, wherein the diphenylmethane diisocyanate comprises 0-30% by weight of 4, 4'-diphenylmethane diisocyanate, the diphenylmethane diisocyanate prepolymer is prepared by diphenylmethane diisocyanate comprising 0-30% by weight of 4, 4'-diphenylmethane diisocyanate, based on 100% by weight of the isocyanate component;

B) an isocyanate-reactive component comprising:

bl) one or more compounds having the structure of formula (I)

The inventors discover that the polyurethane composition exhibits not only improved pot life, allowing the use in preparing big size polyurethane composite materials such as blade for wind turbine having a power of at least 1.5Mw, but also higher heat distortion temperature (HDT), such that the the polyurethane composite materials prepared thereby possess desirable properties.

The term "pot-life" used herein refers to the duration from initiation of free radical polymerization in the polyurethane composition to the point when the viscosity of the composition reaches 600 mPas (25°C).

The term "free radical polymerizable polyurethane composition" means a polyurethane composition which can undergo free radical polymerization reaction. In examples of this invention, the free radical polymerizable polyurethane composition comprises a reactive diluent C) and a polyurethane having active olefinic bond, wherein the reactive diluent C) refers to a diluent that may react with active olefinic bond in said polyurethane through free radical polymerization. The reactive diluent is generally low viscosity small molecule compound having active olefinic bond, including styrenes, acrylates, and methylacrylates.

The term "active olefinic bond" used herein refers to carbon-carbon double bond that can undergo free radical polymerization.

In preferred examples of this invention, the reactive diluent is selected from the group consisting of styrene, Ci-Cio alkyl acrylate and Ci-Cio alkyl methylacrylate. In further preferred examples of this invention, the reactive diluent is selected from the group consisting of styrene, methyl acrylate, ethyl acrylate, methyl methylacrylate and ethyl methylacrylate.

The isocyanate component A) that can be used for the preparation of polyurethane having free radical polymerizable reactive olefinic bond includes diphenylmethane diisocyanate (MDI) or diphenyl methane diisocyanate prepolymer, wherein the diphenylmethane diisocyanate comprises 0-30% by weight of 4,4'-diphenylmethane diisocyanate, or the diphenylmethane diisocyanate prepolymer is prepared by diphenylmethane diisocyanate comprising 0-30% by weight of 4,4'-diphenylmethane diisocyanate, based on 100% by weight of the isocyanate component.

In some examples of this invention, useful isocyanate component A) for preparing polyurethane having reactive olefinic bond comprises diphenylmethane diisocyanate (MDI), wherein the diphenylmethane diisocyanate comprises 0-30% by weight of 4,4'-diphenylmethane diisocyanate. Said diphenylmethane diisocyanate can be obtained by distilling raw MDI, which could be produced by routine process in the art. Distilling raw MDI for producing product with various 4,4^,-diphenylmethane diisocyanate content is already known in the art, for example, as described in Production of Isocyanates by Phosgenation (Handbook of Polyurethane Material, Peilin XU et al. eds, pp 28-38), and Manufacture of Aromatic Diisocyanates (Chemistry and Technology of Isocyanates, Herry Ulrich, pp 285-391), these literatures are incorporated herein by reference in their entirely.

In some examples of this invention, useful isocyanate component A) for preparing polyurethane having reactive olefinic bond includes diphenylmethane diisocyanate prepolymer, wherein the diphenylmethane diisocyanate prepolymer is prepared by diphenylmethane diisocyanate comprising 0-30% by weight of 4,4'- diphenylmethane diisocyanate and polyether polyol or polyester polyol. Said polyether polyol or polyester polyol can be any polyether polyols or polyester polyols that are generally used for the preparation of polyurethane material in the art. In some preferred examples of this invention, the polyether polyol or polyester polyol is preferably a polyol having a molecular weight in the range of 150 to 4000, a functionality of 2 to 6, preferably 2 to 4, and more preferably 2 to 3.

When used in this invention with reference to an organic polyol, functionality and hydroxyl value refer to the average functionality and average hydroxyl value, unless otherwise stated.

In some examples of this invention, the isocyanate component A) may further comprise other organic polyisocyanates, such as aliphatic, alicyclic and aromatic diisocyanate and/or polyisocyanate. Examples for the other organic polyisocyanates which can be used in the present invention include, but are not limited to: 1,4-tetramethylene diisocyanate, 1,5-pentamethylene-diisocyanate, 1,6- hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethyl hexamethylene diisocyanate, bis(4,4'-isocyanato- cyclohexyl)methane or mixtures thereof with other isomers, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI), 1,5-naphthalene diisocyanate, 1,3- and/or 1,4-tetramethylxylylene diisocyanate (TMXDI), 1,3-xylylene diisocyanate (XDI).

In examples of this invention, the isocyanate-reactive component B) useful for preparing polyurethane having active olefinic bond includes one or more compounds bl) having structure shown in Formula (I)

wherein, R₁ is selected from a group consisting of H, methyl and ethyl; R2 is selected from C2-C6 alkylene; and n is an integer selected from 1 to 6.

In preferred examples of this invention, R2 is selected from a group consisiting of ethylene, propylene, butylene, pentylene, 1 -methyl- 1,2-ethylene, 2- methyl-l,2-ethylene, 1 -ethyl- 1,2-ethylene, 2-ethyl- 1,2-ethylene, 1 -methyl- 1,3- propylene, 2-methyl-l,3-propylene, 3-methyl-l,3-propylene, 1 -ethyl- 1,3- propylene, 2-ethyl- 1,3-propylene, 3-ethyl-l,3-propylene, 1 -methyl- 1,4-butylene, 2-methyl-l,4-butylene, 3-methyl- 1,4-butylene and 4-methyl- 1,4-butylene, 2,2- bis(4-phenylene)-propane, 1 ,4-dimethylene-benzene, 1 ,3-dimethylene-benzene and 1,2-dimethylene-benzene.

In preferred examples of this invention, said component bl) is selected from hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxypentyl methacrylate, hydroxyhexyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, or combination thereof.

The compound of Formula (I) can be prepared by routine process in the art, for example, by the esterification reaction between (meth)acrylic anhydride or (meth)acrylic acid, (meth)acryloyl halide and HO-(R20)n-H. Such preparation processes are well known to a person skilled in the art, such as described in Handbook of Raw Material and Adjuvants for Polyurethane (YiJun Liu, published on April 1, 2005) Chapter 3, and Polyurethane Elastomer (HouJun Liu, published in August 2012) Chapter 2, these literatures are incorporated herein by reference in their entirety.

In examples of this invention, the isocyanate-reactive component B) for preparing polyurethane having active olefinic bond may further comprise b2): polyether polyol, polyester polyol, polyether carbonate polyol, or a combination thereof.

The polyether polyol can be prepared by processes known in the art, for example, by reacting an alkylene oxide with an initiator in the presence of a catalyst. Said catalyst is preferably, but not limited to, alkali hydroxide, alkali alkoxide, antimony pentachloride, boron trifluoride diethyl etherate, or a mixture thereof. The alkylene oxide is preferably, but not limited to, tetrahydrofuran, ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide, or a mixture thereof, in particular preferably ethylene oxide and/or propylene oxide. Said initiator is preferably, but not limited to, polyhydroxy compound or polyamine based compound. The polyhydroxy compound is preferably, but not limited to, water, ethylene glycol, 1,2-propanediol, 1,3- propanediol, diethylene glycol, trimethylolpropane, glycerol, bisphenol A, bisphenol S, or a mixture thereof. Said polyamine based compound is preferably, but not limited to, ethylene diamine, propylene diamine, butylene diamine, hexamethylene diamine, diethylenetriamine, tolylenediamine, or mixtures thereof.

The polyether carbonate polyols may also be used in this invention. Said polyether carbonate polyol can be prepared by addition of carbon dioxide and alkylene oxide to starting material containing an active hydrogen in the presence of double metal cyanide catalyst.

The polyester polyols are prepared by reaction between dicarboxylic acid or dicarboxylic anhydride and polyol. The dicarboxylic acid is preferably, but not limited to, C2-C12 aliphatic carboxylic acid, said C2-C12 aliphatic carboxylic acid is preferably, but not limited to, succinic acid, malonic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, lauryl acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, or mixtures thereof. Said dicarboxylic anhydride is preferably, but not limited to, phthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, or mixtures thereof. The polyol reacting with dicarboxylic acid or dicarboxylic anhydride is preferably, but not limited to, ethylene glycol, diethylene glycol, 1 ,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1 ,3-methylpropanediol, 1,4-butanediol, 1,5- pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, glycerol, trimethylolpropane, or mixtures thereof. The polyester polyols further include polyester polyos prepared from lactones. The lactone used for the prepartion of polyester polyol is preferably, but not limited to ε-caprolactone. Preferably, the polyester polyol has a molecular weight in the range of 200 to 3000, and a functionality of 2 to 6, preferablly 2 to 4, more preferably, 2 to 3.

In examples of this invention, the contents of isocyanate component A) and isocyanate-reactive component B) used for preparing the polyurethane having active olefinic bond are configured to give an isocyanate index of 101 - 70, preferably, 101 - 85, and more preferably, 101 - 99.

In examples of this invention, the free radical polymerizable polyurethane composition of the present application further comprises component C): a free radical reaction accelerator. Such a free radical reaction accelerator includes, but is not limited to, peroxide, persulfide, peroxycarbonate, peroxyboric acid, azo compound, or other suitable free radical reaction accelerator that can cause curing of double bond-containing compound, and examples thereof include t-butyl peroxy isopropyl carbonate, t-butyl peroxy-3,5,5-trimethylhexanoate, methyl ethyl ketone peroxide, cumene hydroperoxide. Content of the free radical reaction accelerator is generally 0.1-8% by weight, based on 100% by total weight of the isocyanate-reactive component.

In examples of this invention, the free radical polymerizable polyurethane composition herein may further comprise component D): adjuvant or addtive, which includes but not limited to: filler, internal releasing agent, flame retardant, smoke suppressant, dye, pigment, antistatic agent, antioxidant, UV stabilizer, diluent, defoamer, coupling agent, surface wetting agent, leveling agent, dehydration agent, catalyst, molecular sieve, thixotropic agent, plasticizer, foaming agent, foam stabilizer, foam stablizing agent, free radical reaction inhibitor, or a combination thereof.

II. Polyurethane composite material and method for preparing the same

In another aspect, this invention provides a polyurethane composite material and method for preparing the same, the polyurethane composite material comprises resin matrix and reinforcing material, wherein the resin matrix is prepared by free radical polymerization of the polyurethane composition described above.

In some examples of this invention, the polyurethane composite material is prepared by a process selected from the group consisting of pultrusion, filament winding, hand lay-up, spray up molding and infusion.

In an example of this invention, the polyurethane composite material is prepared by infusion process, and preferably, by vacuum infusion process. A person skilled in the art is clear about the operations involved in polyurethane vacuum infusion process, for example, as described in patent CN 1954995 A, and the full content disclosed therein is incorporated herein by reference.

In the process of infusion under vacuum, one or more core elements are disposed in a mold, and the core element(s) may optionally be covered in part or completely by reinforcing material. Then a negative pressure is applied in the mold to allow infusion of the polyurethane composition into the mold. Before curing, the polyurethane composition fully infiltrates the reinforcing material, while the core element(s) is infiltrated in part or completely by the polyurethane composition. When the polyurethane composition fills the entire mold, the polyurethane composition is cured through free radical addition reaction of the active olefin bonds therein under proper condition, such as UV radiation or heating, thus producing the polyurethane composite material.

In the vacuum infusion process described above, the mold can be a mold generally used in the art, and a person skilled in the art could readily select an appropriate mold according to the desired property and size of the end product.

Using core element(s) in combination with the polyurethane composition and reinforcing material is beneficial for shaping the composite material and reducing the weight of the composite material. In examples of this invention, the reinforcing material is selected from a group consisiting of fiber reinforcing material, carbon nanotube, hard particulate filler, and combinations thereof; and is more preferably, selected from fiber reinforcing material. Weight content of the reinforcing material is 5-95 wt%, preferably 30-85 wt%, based on 100% by total weight of the polyurethane composite material.

There is no requirement on shape and size for the fiber reinforcing material used in this invention. For example, it can be continuous fiber, chopped fiber, fiber web formed by bonding, or fiber fabric.

In some examples of this invention, the fiber reinforcing material is selected from a group consisting of glass fiber, carbon fiber, polyester fiber, natural fiber, aromatic polyamide fiber, nylon fiber, basalt fiber, boron fiber, silicon carbide fiber, asbestos fiber, whisker, metal fiber, and combinations thereof. In preferred examples of this invention, the fiber reinforcing material is selected from glass fiber.

The polyurethane composite material of this invention can use core element routinely used in the art, and the examples thereof include, but not limited to, polystyrene foam, such as COMPAXX® foam; polyester PET foams; polyimide PMI foam; polyvinylchloride foam; metal foam, for example, the metal foam commercially available from Mitsubishi; balsa wood and so on. In one example of this invention, the content of the reinforcing material is preferably 1-90 wt%, particularly preferably 30-85 wt%, in particular, 50-75 wt%, based on 100% by total weight of the polyurethane composite.

The polyurethane composite material of this invention can be wind turbine blade, wind turbine nacelle cover, ship paddle, ship housing, vehicle interior and exterior trim and housing, radar cover, structural material of mechanic equipment, decorative piece and structural part of building and bridge. In a preferred example of this invention, the polyurethane composite material is blade of wind turbine having a power of 750 Kw to 10 Mw, preferably, blade of wind turbine having a power of 1 to 5 Mw.

Examples

This description provided herein on specific examples and processes is illustrative, but not exclusive.

The raw materials used in examples of this invention are described as follows.

Isocyanate A: an isocyanate prepolymer having an NCO group content of 22.8%, wherein the 4,4'-MDI accounts for 86% of the isocyanate component;

Isocyanate B: an isocyanate having an NCO group content of 30.5-32.5%, wherein the 4,4'-MDI accounts for 41.4% of the isocyanate component;

Isocyanate C: an isocyanate having an NCO group content of 33.6%, wherein the 4,4'-MDI accounts for 45% of the isocyanate component;

Isocyanate D: an isocyanate having an NCO group content of 33.6%, wherein the 4,4'-MDI accounts for 100% of the isocyanate component;

ARCOL 1003: having OH value of 280, functionality of 2, viscosity of 70mP.s@25°C, commercially available from Bayer Material Science Ltd.;

Norox MEKP-925H, a free radical reaction accelerator, commercially available from Syrgis;

BYK 066N: a silicone defoamer commercially available from BYK;

H8006: a polymer defoamer commercially available from BMC;

Dabco T-12: an organotin catalyst commercially available from Air

Products.

Examples 1-5: Preparation of polyurethane composition

Example 1 : HPA (100 parts) and styrene (100 parts) were mixed at room temperature, into which 0.1 part of T-12 was added, and then isocyanate A (100 parts) was added dropwise to the above solution with agitation. The reaction substances were further stirred for 5 hours after the addition was completed to completely react all the NCO groups and produce the polyurethane composition.

Example 2: HPA (100 parts) and styrene (100 parts) were mixed at room temperature, into which 0.1 part of T-12 was added, and then isocyanate B (100 parts) was added dropwise to the above solution with agitation. The reaction substances were further stirred for 5 hours after the addition was completed to completely react all the NCO groups and produce the polyurethane composition.

Example 3: 0.1 part of T-12 was mixed into ARCOL 1003 (77 parts) at room temperature, and then isocyanate C (115 parts) was added dropwise to the above solution with agitation. The mixture was further stirred for 5 hours after the addition was completed to completely react ARCOL 1003 and produce the isocyanate prepolymer, which was further mixed with styrene (180 parts). Then HPMA (100 parts) was added dropwise to the above solution, and the substances were further stirred for 5 hours after the addition was completed to completely react all the NCO groups and produce the polyurethane composition.

Example 4: 0.1 part of T-12 was mixed into ARCOL 1003 (77 parts) at room temperature, and then isocyanate C (115 parts) was added dropwise to the above solution with agitation. The mixture was further stirred for 5 hours after the addition was completed to completely react ARCOL 1003 and produce the isocyanate prepolymer, which was further mixed with styrene (180 parts). Then HPA (100 parts) was added dropwise to the above solution, and the substances were further stirred for 5 hours after the addition was completed to completely react all NCO groups and produce the polyurethane composition.

Example 5: 0.1 part of T-12 was mixed into ARCOL 1003 (77 parts) at room temperature, and then isocyanate D (115 parts) was added dropwise to the above solution with agitation. The mixture was further stirred for 5 hours after the addition was completed to completely react ARCOL 1003 and produce the isocyanate prepolymer, which was further mixed with styrene (180 parts). Then HPMA (100 parts) was added dropwise to the above solution, and the substances were further stirred for 5 hours after the addition was completed to completely react all NCO groups and produce the polyurethane composition. This polyurethane composition has a viscosity greater than 3000 mPa-s. Pot-life test Into 100 parts of polyurethane samples produced as indicated above in Examples 1-5, 0.5% of 925H, 0.5% of cobalt naphtenate solution, 0.5% BYK 066N and 0.5% H8006 were added (weight ratios relative to the amount of samples prepared in Examples 1-7). The above resin contents are stirred to homogeneity, vacuumed at room temperature for 5 minutes to remove bubbles in the raw materials, and the viscosity values of the mixture systems were measured periodically. The overall time from the beginning till the point when system viscosity exceeds 600 mPas is taken as the Pot-life.

HPT test

The test was conducted according to standard test DIN EN ISO 75-2.

Exothermic peak temperature test

During the gradual curing process of 300 grams liquid resin

temperature, the maximum kernel temperature in the resin was measured.

Table 1 : Pro erties of the ol urethane com osition

Comparative Examples 6-7

The formulations for resins of Comparative Examples 6-7 are shown in Table 2, and the HDT and Pot-life were measured according to the methods described above.

Table 2: Properties of the ol urethane com osition

As shown in Table 1 and 2, the polyurethane compositions of Examples 1-4 exhibited improved pot-life and HDT as compared to the polyurethane compositions of Comparative Examples 6-7.

Example 8: Preparation of polyurethane composite material

A composite material was produced according to the vacuum infusion process of patent 200610142878.4. One or more core elements were disposed in a mold, and the core elements were covered in part by reinforcing material. Then a negative pressure was applied in the mold to allow infusion of the polyurethane resin into the mold. Before curing, the polyurethane resin fully infiltrated the reinforcing material, while the core elements were infiltrated in part or completely by the polyurethane resin. Heating to have the resin undergo radical polymerization reaction, so that the resin cured to form resin matrix.

Table 3: Pro erties of the ol urethane com osite material

Claims

1. A free radical polymerizable polyurethane composition comprising a polyurethane having active olefinic bond and a reactive diluent C), wherein the polyurethane having active olefinic bond is prepared by components including the following:

A) an isocyanate component comprising diphenylmethane diisocyanate or diphenylmethane diisocyanate prepolymer, wherein the diphenylmethane diisocyanate comprises 4,4'-diphenylmethane diisocyanate at an amount of 0-30 wt% based on 100% by weight of the isocyanate component, and the diphenylmethane diisocyanate prepolymer is prepared from diphenylmethane diisocyanate comprising 4,4'-diphenylmethane diisocyanate at an amount of 0-30 wt% based on 100% by weight of the isocyanate component;

B) an isocyanate-reactive component comprising:

bl) one or more compounds having the structure of Formula (I)

wherein the R₁ is selected from a group consisting of H, methyl and ethyl; the R.2 is selected from a group consisting of C2-C6 alkylene groups, 2,2-bis(4- phenylene)propane, l,4-bis(methylene)benzene, 1 ,3-bis(methylene)benzene and l,2-bis(methylene)benzene; and n is an integer selected from 1-6.

2. The free radical polymerizable polyurethane composition according to claim 1, wherein the reactive diluent C) is selected from the group consisting of styrene, C1-C10 alkyl acrylate and C1-C10 alkyl methylacrylate.

3. The free radical polymerizable polyurethane composition according to claim 1, wherein the component bl) is selected from the group consisting of hydroxyethyl methylacrylate, hydroxypropyl methacrylate, hydroxylbutyl methacrylate, hydroxylpentyl methacrylate, hydroxylhexyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxylbutyl acrylate, and the combination thereof.

4. The free radical polymerizable polyurethane composition according to any one of claims 1-3, wherein the polyurethane composition has a pot-life of 60-300 minutes.

5. A polyurethane composite material comprising resin matrix and reinforcing materials, wherein the resin matrix is prepared by free radical polymerization of the polyurethane composition according to any one of claims 1- 4.

6. The polyurethane composite material according to claim 5, wherein the polyurethane composite material is prepared by a process selected from the group consisting of pultrusion, filament winding, hand lay-up, spray up molding and infusion.

7. The polyurethane composite material according to claim 6, wherein the polyurethane composite material is prepared by a vacuum infusion process.

8. The polyurethane composite material according to claim 7, wherein the composite material is a polyurethane blade of a wind turbine having a power of at least 1.5 Mw.

9. A process of preparing a polyurethane composite material, comprising a step of: I) subjecting the active olefinic bond in the free radical polymerizable polyurethane composition according to any one of claims 1-4 to free radical polymerization to prepare the polyurethane composite material.

10. The process of preparing a polyurethane composite material according to claim 9, further comprising a step of:

II) providing a mold, wherein reinforcing material is optionally disposed within the mold, and introducing the free radical polymerizable polyurethane composition according to any one of claims 1-4 into the mold.

11. The process of preparing a polyurethane composite material according to claim 10, wherein a negative pressure is applied within the mold so that the free radical polymerizable polyurethane composition according to any one of claims 1- 4 is introduced into the mold.