WO2018167220A1

WO2018167220A1 - Hydroxyl-terminated polyurethane prepolymer and preparation method thereof

Info

Publication number: WO2018167220A1
Application number: PCT/EP2018/056555
Authority: WO
Inventors: Liang Xue; Jianwu GAO; Chenxi Zhang
Original assignee: Covestro Deutschland Ag
Priority date: 2017-03-15
Filing date: 2018-03-15
Publication date: 2018-09-20
Also published as: CN108623771B; CN108623771A

Abstract

The present invention belongs to polyurethane field and relates to hydroxyl-terminated polyurethane prepolymers and use thereof for synthesizing fire retardant polyisocyanurate foam. The hydroxyl-terminated polyurethane prepolymer is the reaction product of the following raw materials: a) one or more polymeric polyols, selected from polyether polyols and polyester polyols; b) one or more phosphates; and c) one or more polyisocyanates. The hydroxyl-terminated polyurethane prepolymer is useful for preparing polyisocyanurate and the resulted polyisocyanurate foam is superior in thermal insulation property, adhesive property, compression strength and dimensional stability, more economic and has excellent fire retardant effect.

Description

Hydroxyl-Terminated Polyurethane Prepolymer and Preparation Method Thereof Technical Field

The present invention belongs to polyurethane field. Specifically, it relates to a hy- droxyl-terminated polyurethane prepolymer, preparation method thereof and use thereof for synthesizing polyisocyanurate foam.

Background Art

Polyurethane foam for spray application has excellent thermal insulation property, moulding property and adhesion with substrates. With the state and the society have more and more requirements for energy conservation and low carbon, polyurethane foam materials for spray application are enjoying increasingly wide applications in the field of building insulation. The Chinese national document No. 65 <Notice on Further Specifying Relevant Requirements for Fire Supervision and Management of External Insulation Materials for Civil Buildings> and document No. 46 the notice of printing and distributing <Interim Provisions on External Insulation Systems for Civil Buildings and Exterior Decorations Fire Protection> have regulated the materials used on the wall to meet the lowest requirement of Rating B2 fire retardancy. Therefore, the key point in developing polyurethane foam for spray application is to increase the fire retardant property thereof and control the cost of high fire retardancy spraying foam.

The patent CN200910186702.2 (CN101724254A) discloses a high efficiency non- halogen fire retardant rigid polyurethane foam and preparation method thereof. The high fire retardancy of this rigid polyurethane foam is achieved by adding inorganic fire retardant, red phosphorus and organic fire retardant, dimethyl methylphosphate (DMMP for abbreviation). This method is capable of producing foam with better fire retardancy, however, the addition of inorganic particles makes it difficult to mix, and the storage stability of the system and dimensional stability of the foam will be adversely affected to some extent after addition of DMMP, limiting its production and use in large scale.

The patent CN201210196201.4 (CN 102719186A) discloses a polyurethane insulation material for spray application obtained by a blowing technique with a system using DMMP as fire retardant. The dimensional stability of the foam prepared by this technique is good, however, the fire retardant rating is low and can merely meet the usage requirement of Rating E in GB8624-2006. The patent CN 103073986 B discloses a high fire retardancy polyurethane foam material for spray application, and preparation method thereof. The foam for spray application has overcome such problems as foam shrinkage, poor dimensional stability and low fire retardancy by introducing a compounded system comprising Br-P composite fire retardant polyether polyol, Mannich polyether polyol and polyester polyol. However, there exist problems for the fire retardant polyether polyol employed such as expensive cost and limited source.

In general, all the methods described in the above patents relate to enhancing fire redardant property mainly through adding significant amounts of various fire retard- ants or Br-P composite fire retardant polyether polyols, which will in turn lead to relatively low mechanical properties, particularly the compression strength of the foam and ultra-high cost of material. Polyurethane foam (PUR) is prepared by the reaction of polyol and isocyanate, and polyisocyanurate foam (PIR) is prepared by trimerization of isocyanate itself to produce polyisocyanurate ring, thus the polyisocyanurate foam is more stable and has good heat resistance, cold resistance, dimensional stability and fire retardancy from the perspective of molecular structure. Compared to PUR, due to the difference in structure, polyisocyanurate foam has high efficiency fire retardancy, good heat resistance and processing properties. However, preparation of the polyisocyanurate foam requires much more excessive amount of isocyanate relative to hydroxyl groups so as to produce polyisocyanurate ring by trimerization of isocyanate itself. The patent CN 105940032 A discloses a fire redardant and insulating polyurethane or carbamate-modified polyisocyanurate foam, which has good foam properties and processing characteristics, and has minimal amount of fire redardant. It is capable of passing DIN4102 test without adding Br-containing fire retardant (providing rating B2), but the ratio of polyisocyanate (component B) and polyether polyol blend (com- ponent A) therein is up to about 1 : 1.6. Since spray machine with a A/B ratio of 1 : 1 is most widely used in the field of polyurethane for spray application, it is obvious that common polyisocyanurate foams cannot be applied by the current polyurethane spray machine. In order to obtain a polyisocyanurate foam for spray application with high isocyanate index under the limitations that A/B ratio is 1 : 1 while the NCO content in the polyisocyanate maintains constant, it is required to reduce hydroxyl value per part by weight of polyol blend. Generally, there exist two methods that may achieve this objective. The first one is to use polyether/polyester polyol with lower hydroxyl value as raw material for the polyol component; the second one is to add significant amount of additive fire retardant to the polyol component to achieve the objective of reducing hydroxyl value. With either method, physical and mechanical properties of the foam will be adversely affected and the polyisocyanurate foam for spray application with isocyanate index of more than 250%, oxygen index of more than 30 and better physi- cal and mechanical properties cannot be practically obtained. The term "isocyanate index" used herein refers to the molar ratio of NCO groups present in the foam formulation relative to reactive hydrogen atoms, given as percentage.

Therefore, there is a need for developing a fire retardant polyisocyanurate foam for spray application which may be prepared by a spray machine with a A/B ratio of 1 : 1 and shows relatively good physical and mechanical properties, as well as relatively high oxygen index.

Summary of the Invention

The technical problem to be solved by the present invention is to provide a fire retardant polyisocyanurate foam for spray application which can be prepared with a spray machine with a A/B ratio of 1 : 1 and shows relatively good physical and mechanical properties, as well as relatively high oxygen index. The above technical problem is solved by the following technical solutions.

According to one aspect of the present invention, there provides a hydroxyl- terminated polyurethane prepolymer, which is the reaction product of the following raw materials:

a) one or more polymeric polyols, selected from polyether polyols and polyester pol- yols;

b) one or more phosphates; and

c) one or more polyisocyanates. According to another aspect of the present invention, there provides a method for preparing the above hydroxyl-terminated polyurethane prepolymer, comprising the following steps:

i) mixing a) one or more polymeric polyols, selected from polyether polyols and polyester polyols, b) one or more phosphates and c) one or more polyisocyanates to give a reaction mixture, and

ii) reacting the reaction mixture to give the hydroxyl-terminated polyurethane prepolymer. According to one aspect of the present invention, there provides a hydroxyl- terminated polyurethane prepolymer, which is the reaction product of the following raw materials:

a) one or more polymeric polyols comprising halogenated polyether polyol; and b) one or more polyisocyanates.

According to another aspect of the present invention, there provides a method for preparing the above hydroxyl-terminated polyurethane prepolymer, comprising the following steps:

i) mixing a) one or more polymeric polyols comprising halogenated polyether polyol and b) one or more polyisocyanates to give a reaction mixture, and

ii) reacting the reaction mixture to give the hydroxyl-terminated polyurethane prepolymer. According to another aspect of the present invention, there provides a polyisocyanu- rate foam, which is obtained by the reaction of the following component A and component B:

Component A, comprising:

a) the above hydroxyl-terminated polyurethane prepolymer;

b) optionally, one or more polymeric polyols;

c) one or more foam stabilizers;

d) one or more catalysts; and

e) one or more blowing agents;

Component B, which is one or more polyisocyanates.

According to another aspect of the present invention, there provides a method for preparing the above polyisocyanurate foam, comprising the following steps:

i) mixing a) the above hydroxyl-terminated polyurethane prepolymer, b) optionally, one or more polymeric polyols, c) one or more foam stabilizers, d) one or more cata- lysts, and e) one or more blowing agents and stirring, to give component A as a uniform mixture;

ii) mixing component B: one or more polyisocyanates with component A to give a reaction mixture; and

iii) reacting the reaction mixture to give the polyisocyanurate foam.

The present invention has prepared a hydroxyl-terminated polyurethane prepolymer with fire retardant elements by adding the fire retardant elements such as halogen and/or phosphorus to raw materials. The hydroxyl-terminated polyurethane prepolymer of the present invention can be used to prepare fire retardant polyisocyanurate foam for spray application with a spray machine with A/B ratio of 1 : 1. The polyisocyanurate foam prepared according to the present invention is superior in thermal insulation property, adhesive property, compression strength and dimensional stability, has a low cost, good fire retardant effect, and is able to achieve a balance between fire retardant property, mechanical property and cost. Detailed Description of the Invention

The embodiments for carrying out the invention are described hereinafter.

b) one or more phosphates; and

c) one or more polyisocyanates.

The polyether polyol has a functionality preferably of 2-8, in particular preferably of 2-4 and a hydroxyl value preferably of 35-800 mg KOH/g, in particular preferably of 35-400 mg KOH/g.

The hydroxyl value may be determined according to DIN EN ISO 53240-2:2007- 1 1.

The polyether polyols are preferably selected from polyether polyols started with saccharides (e.g., glucose, sucrose), pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, ethylenediamine, ethylene glycol, propylene glycol or water. The polyether polyol comprises halogenated polyether polyol and non-halogenated polyether polyol.

The halogenated polyether polyol is a halogen-containing polyether polyol, i.e., the polyether polyol containing halogen and preferably started with saccharide (glucose, sucrose), pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, ethylenediamine, ethylene glycol, propylene glycol or water.

The halogen is selected from CI and Br. Preferably, the halogen is present in the halogenated polyether polyol in an amount of 35-60 wt%, relative to the weight of the halogenated polyether polyol.

The halogenated polyether polyol preferably further contains phosphorus, i.e., it is preferably halogen-phosphorus composite fire retardant polyether polyol.

Preferably, the halogen and phosphorus are present in the halogen-phosphorus composite fire retardant polyether polyol in an amount of 15-40 wt% for the halogen and 1-7 wt% for the phosphorus, respectively, both based on the total weight of the halo- gen-phosphorus composite fire retardant polyether polyol.

The halogen-phosphorus composite fire retardant polyether polyol has a functionality preferably of 2-6, particularly preferably of 2-4 and a hydroxyl value preferably of 200-800 mg KOH/g, particularly preferably of 200-400 mg KOH/g.

The non-halogenated polyether polyol is the polyether polyol free of halogen, i.e., the polyether polyol free of halogen and preferably started with saccharides (glucose, sucrose), pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, eth- ylenediamine, ethylene glycol, propylene glycol or water.

In the present application, when referring to "polyether polyol" without explicitly indicating "halogenated" or "non-halogenated", it intends to include both halogenated polyether polyol and non-halogenated polyether polyol. The polyester polyol is formed by condensation of acid and/or acid anhydride with polyol, with the acid and acid anhydride preferably being selected from o-phthalic acid, m-phthalic acid, p-phthalic acid, adipic acid, glutaric acid and succinic acid and the acid anhydrides of said acids, and the polyol preferably being selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, glycerol, trimethylolpropane, pentaerythritol and sorbitol.

The polyester polyol preferably has a functionality of 2-3 and a hydroxyl value of 200-400 mg KOH/g. The polyester polyol is in particular preferably prepared from terephthalic acid and ethylene glycol as raw materials.

In one embodiment, the polymeric polyol comprises halogenated polyether polyol. In one embodiment, the polymeric polyol comprises halogen-phosphorus composite fire retardant polyether polyol.

In one embodiment, the polymeric polyol is halogenated polyether polyol.

In one embodiment, the polymeric polyol is halogen-phosphorus composite fire retardant polyether polyol.

In one embodiment, the polymeric polyol comprises halogen-phosphorus composite fire retardant polyether polyol and polyester polyol.

In one embodiment, the polymeric polyol comprises halogen-phosphorus composite fire retardant polyether polyol, polyester polyol and non-halogenated polyether polyol. The polymeric polyol is present in the hydroxyl-terminated polyurethane prepolymer in an amount of 1-60 pbw, preferably of 5-55 pbw, and particularly preferably of 10- 55 pbw.

The phosphate is preferably selected from tris(polyoxyalkylene) phosphate, tris(polyoxyalkylene) phosphite, tris(dipropylene glycol)phosphate (commonly known as P430), dimethyl methyl phosphonate (DMMP), dimethyl propyl phospho- nate (DMPP), diethyl ethyl phosphonate (DEEP), triethyl phosphate (TEP), tricresyl phosphate (TPP) etc. Particularly preferable is triethyl phosphate (TEP). The phosphate is present in the hydroxyl-terminated polyurethane prepolymer in an amount of 5-60 pbw, preferably of 10-50 pbw, particularly preferably of 15-40 pbw, and more particularly preferably of 30-40 pbw.

The phosphate can both play a role in fire retarding and reducing viscosity in the pre- sent invention.

The polyisocyanate is preferably selected from 4,4-methylenebis(2,6- diethylphenylisocyanate), tetramethylene 1 ,4-diisocyanate, hexamethylene diisocya- nate (HDI), dodecyl 1 ,2-diisocyanate, cyclobutane- l,3-diisocyanate, cyclohexane- 1,3- diisocyanate, cyclohexane- 1 ,4-diisocyanate, l-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane, hexahydrotoluene-2,4-diisocyanate, hexahydrophenyl- 1,3-diisocyanate, hexahydrophenyl- 1 ,4-diisocyanate, perhydro-diphenylmethane 2,4- diisocyanate, perhydro-diphenylmethane 4,4-diisocyanate, phenylene 1 ,3- diisocyanate, phenylene 1,4-diisocyanate, durene 1,4-diisocyanate, stilbene 1 ,4- diisocyanate, 3,3-dimethyl-4,4-diphenyldiisocyanate, toluene-2,4-diisocyanate (TDI), toluene-2,6-diisocyanate (TDI), diphenylmethane-2,4'-diisocyanate (MDI), diphe- nylmethane-2,2'-diisocyanate (MDI), diphenylmethane-4,4'-diisocyanate (MDI), naphthylene- l,5-diisocyanate (NDI) and isomers thereof, and mixtures thereof. The polyisocyanate is in particular preferably the mixture of 4,4'-, 2,4'- and 2,2'- diphenylmethane diisocyanate, most preferably which has the 2,4'-diphenylmethane diisocyanate content of more than 50% and the NCO content of 33%.

The polyisocyanate is present in the hydroxyl-terminated polyurethane prepolymer in an amount of 5-60 pbw, preferably of 10-50 pbw, and particularly preferably of 15-40 pbw.

The amount of the polyisocyanate may be determined by those skilled in the art according to target hydroxyl value of reaction product, hydroxyl value, type and amount of the polyol used.

ii) reacting the reaction mixture to give the hydroxyl-terminated polyurethane prepolymer.

The mixing in step i) may be carried out as follows: mixing a) one or more polymeric polyols with b) one or more phosphates, and dehydrating at 1 10°C- 130°C and under vacuum to remove moisture therein, then introducing N₂, reducing the temperature to 70-80°C, followed by adding c) one or more polyisocyanates and stirring.

The vacuum pressure is preferably 0.5 mbar to 1 mbar.

The reaction in step ii) is preferably carried out at 70-80°C for 2-3 h. According to one aspect of the present invention, there provides a hydroxyl- terminated polyurethane prepolymer, which is the reaction product of the following raw materials:

a) one or more polymeric polyols, comprising halogenated polyether polyols; and b) one or more polyisocyanates. The halogenated polyether polyol is defined as above.

The halogenated polyether polyol is preferably the halogen-phosphorus composite fire retardant polyether polyol defined as above.

The polyisocyanate is defined as above.

Optionally, the one or more polymeric polyols further comprise the polyester polyol and/or non-halogenated polyether polyol as defined above.

The polymeric polyol is present in the hydroxyl-terminated polyurethane prepolymer in an amount of 1-60 pbw, preferably of 5-55 pbw, and particularly preferably of 10- 55 pbw. The polyisocyanate is present in the hydroxyl-terminated polyurethane prepolymer in an amount of 5-60 pbw, preferably of 10-50 pbw, particularly preferably of 15-40 pbw, and more particularly preferably of 30-40 pbw.

i) mixing a) one or more polymeric polyols, comprising halogenated polyether polyols, and b) one or more polyisocyanates to give a reaction mixture, and

ii) reacting the reaction mixture to give the hydroxyl-terminated polyurethane prepol- ymer.

The mixing in step i) is carried out as follows: dehydrating a) one or more polymeric polyols at 1 10°C- 130°C and under vacuum to remove moisture therein, then introducing N2 , reducing the temperature to 70-80°C, followed by adding b) one or more pol- yisocyanates and stirring.

The vacuum pressure is preferably 0.5 mbar to 1 mbar.

The reaction in step ii) is preferably carried out at 70-80°C for 2-3 h.

According to another aspect of the present invention, there provides a polyisocyanu- rate foam, which is obtained by the reaction of component A and component B:

Component A, comprising:

a) the above hydroxyl-terminated polyurethane prepolymer;

b) optionally, one or more polymeric polyols; c) one or more foam stabilizers;

d) one or more catalysts; and

e) one or more blowing agents;

Component B, which is one or more polyisocyanates.

The hydroxyl-terminated polyurethane prepolymer is present in component A in an amount of 40- 100 pbw, preferably of 50-95 pbw, particularly preferably of 70-95 pbw, and most preferably 70-93 pbw. The polymeric polyol used in component A is selected from the polyether polyols and polyester polyols described for the hydroxyl-terminated polyurethane prepolymer.

The polymeric polyol is used in component A in an amount of 0-40 pbw, preferably of 5-30 pbw, and particularly of 5-20 pbw.

The foam stabilizer used in component A is a material that promotes the formation of regular foam structure during foam forming. Examples that may be mentioned include: polysiloxane-containing foam stabilizers such as siloxane-oxyalkylene copolymers and other organic polysiloxanes, fatty alcohol, oxo alcohol, fatty amine, alkylphenol, dialkylphenol, alkylcresol, alkylresorcinol, naphthol, alkylnaphthol, naphthylamine, aniline, alkylaniline, toluidine, bisphenol A, alkylated bisphenol A, alkoxylated products of polyvinyl alcohol, and alkoxylated products of condensates of formaldehyde and alkylphenol, formaldehyde and dialkylphenol, formaldehyde and alkylcresol, formaldehyde and alkylresorcinol, as well as a mixture of two or more of such foam stabilizers.

The foam stabilizer is present in component A in an amount of 1 -10 pbw, preferably of 1 -5 pbw, and particularly of 1 -3 pbw. Non-limiting examples used as the catalyst in component A include tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, Ν,Ν,Ν',Ν'- tetramethyl diamino diethyl ether, bis(dimethylaminopropyl)urea, N-methylmorpholine or N-ethylmorpholine, N- cyclohexylmorpholine, Ν,Ν,Ν',Ν' -tetramethyl ethylene diamine, Ν,Ν,Ν',Ν'- tetramethyl butanediamine, Ν,Ν,Ν',Ν' -tetramethyl hexane- l,6-diamine, pentamethyl diethylenetriamine, dimethyl piperazine, N-dimethylaminoethyl piperidine, 1 ,2- dimethyl imidazole, l -azabicyclo-[2. 2. 0] octane, l,4-diazabicyclo[2. 2. 2]octane(Dabco), and alkanolamine compounds such as triethanolamine, triisopro- panolamine, N-methyldiethanolamine and N-ethyldiethanolamine, dimethylaminoeth- anol, 2-(N,N-dimethylaminoethoxy)ethanol, Ν,Ν',Ν"- tris(dialkylaminoalkyl)hexahydro-s-triazine such as Ν,Ν',Ν"- tris(dimethylaminopropyl)hexahydro-s-triazine, and triethylenediamine. Metal salts such as ferrous (II) chloride, zinc chloride and lead octoate are also suitable, and tin salts such as tin dioctoate, tin diethyl hexanoate and dibutyltin dilaurate, and particu- larly mixtures of tertiary amines and organic tin salts are preferred. Meanwhile, as usable catalyst for trimerization, potassium acetate and potassium octoate are capable to effectively increase the conversion rate of the trimerization of isocyanates, making foam post-cure better. The catalyst is present in component A in an amount of 1 - 15 pbw, preferably of 1 -10 pbw, and particularly preferably of 3-9 pbw.

The blowing agent used in component A may be selected from those known to be used to prepare polyurethane foam, including chemical and/or physical blowing agents.

The chemical blowing agent refers to compound that produces gaseous product through reacting with isocyanate. Examples of such compounds include water or car- boxylic acids.

The physical blowing agent refers to liquid that is inert to polyisocyanate and has a boiling point of less than 100°C, preferably of less than 50 °C under atmospheric pressure, and which evaporates under the condition of exothermic addition polymerization. Examples of useful physical blowing agent include alkanes such as heptane, hexane, n-pentane and isopentane; cycloalkanes such as cyclopentane and cyclohex- ane; ethers such as furan, dimethyl ether and diethyl ether; ketones such as acetone and methyl ethyl ketone; alkyl carboxylates such as methyl formate, dimethyl oxalate and ethyl acetate; and halogenated hydrocarbons such as dichloromethane, dichloro- fluoromethane, difmoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chlorodifluoroethane, l , l -dichloro-2,2,2-difmoroethane, 2,2-dichloro-2-fluoroethane and heptafluoropropane.

One or more chemical and/or physical blowing agents may be used, or a mixture of such blowing agent and other substituted or unsubstituted hydrocarbon. It is preferred that the blowing agent comprises substituted or unsubstituted hydrocarbon such as alkanes or cycloalkanes.

A mixture of n-pentane and iso-pentane, as well as a mixture of n-butane, isobutane and propane are particularly preferable as blowing agent. The blowing agent is present in component A in an amount of 5-40 pbw, preferably of 10-35 pbw, and particularly preferably of 15-35 pbw.

Suitable polyisocyanate used in component B in the present invention may be those known in the art to be used to prepare rigid polyurethane or carbamate-modified poly- isocyanurate foam, and particularly aromatic polyisocyanates such as diphenylme- thane diisocyanate and oligomers thereof, toluene diisocyanate, 1 ,5-naphthylene diisocyanate and 1 ,4-diisocyanatobenzene, such as diphenylmethane diisocyanates in 2,4'-, 2,2'- and 4,4'-isomers thereof and mixtures thereof, mixtures of diphenylme- thane diisocyanate (MDI) and oligomers thereof (known as "crude product" in the art) or polymeric MDI with an isocyanate functionality of more than 2 (polymethylene polyphenylene polyisocyanate), and toluene diisocyanates in 2,4- to 2,6-isomers thereof and mixtures thereof. Other organic polyisocyanate that may be mentioned include aliphatic diisocyanate such as isophorone diisocyanate, 1 ,6- diisocyanatohexane and 4,4'-diisocyanatodicyclohexylmethane.

During preparation of the polyisocyanurate foam, since a spray machine with a A/B ratio of 1 : 1 is used, the volume of polyisocyanate in component B is required to be the same as that of component A, and the amount of the polyisocyanate in component B can be determined according to the volume of component A.

i) mixing a) the above hydroxyl-terminated polyurethane prepolymer, b) optionally, one or more polymeric polyols, c) one or more foam stabilizers, d) one or more catalysts and e) one or more blowing agents and stirring, to give component A as a uniform mixture;

ii) mixing the above component B with component A to give a reaction mixture; and iii) reacting the reaction mixture to give the polyisocyanurate foam.

Component A and component B are preferably maintained at a temperature of 35- 40°C prior to mixing.

Unless defined otherwise, all the technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains. In the case that the definition of a term in the specification conflicts with that commonly understood by those skilled in the art to which the present invention pertains, the definition described herein controls. The present invention is illustrated through examples hereinafter. However, it is to be understood that the scope of the present invention is not limited to those examples.

Examples

The tests on the following performance parameters are carried out in the present amples:

Heat Conductivity is measured in accordance with DIN-52612-2: 1984-06.

Percentage of Closed Cell Foam is measured in accordance with ASTMD2856-94. Compression strength is measured in accordance with DIN-53421 : 1984-06.

Foam Dimensional Stability is measured in accordance with GB881 1 -1988.

Oxygen Index is measured in accordance with GB/T 2406.2-2009. The following raw materials are used in the examples:

Fire retardant Tris-(2-chlorisopropyl)-phosphate

Foam Stabilizer siloxane-oxyalkylene copolymer surfactant (Niax^® Silicone L- 6920, Momentive Performance Materials Inc.)

Catalyst 1 Potassium acetate in diethylene glycol

Catalyst 2 N,N,N',N",N"-Pentamethyldiethylenetriamine

Catalyst 3 Dibutyltin dilaurate (KOSMOS^® 19, Evonik Specialty Chemicals

Co., Ltd.)

Catalyst 4 N,N',N"-tri(dimethylaminopropyl) hexahydrotriazine (POLY- CAT^® 41, Evonik Specialty Chemicals Co., Ltd.)

Catalyst 5 Dimethylamino-2-ethanol (DABCO^® DMEA, Evonik Specialty

Chemicals Co., Ltd.)

Catalyst 6 amine catalyst (DABCO^® TMR-2, Evonik Specialty Chemicals

Co., Ltd.)

Physical Blowing

Agent 1 , 1 -dichloro- 1 -fluoroethane

Example 1 : Preparation of hydroxyl-terminated polyurethane prepolymer-1

40 g of Br-P composite fire retardant polyether polyol (with a hydroxyl value of 235 mg KOH/g, Saytex RB-79, purchased from Albemarle Corporation, US), 10 g of pol- yester polyol (with a hydroxyl value of 255 mg KOH/g, CF-6245, purchased from Nanjing CSD Chemicals Co., Ltd.), 4 g of non-halogenated polyether polyol (propylene glycol as a starting material, with a functionality of 2, a hydroxyl value of 56 mg KOH/g, DC210, purchased from Shanghai Gaoqiao Petrochemical Co., Ltd, China), 38 g of tri ethyl phosphate were added into three-necked flask equipped with a motor stirrer, mixed with stirring and dehydrated at 120°C and under vacuum to remove moisture present in the raw materials. Then N2 was introduced, and the temperature was decreased to 70°C before 18 g of a mixture of 4,4'-, 2,4'- and 2,2'- diphenylmethane diisocyanate (DESMODUR TP PU0129M from Covestro) was add- ed dropwise and stirred to react for 2.5 h, to give the hydroxyl-terminated polyure- thane prepolymer.

Example 2: Preparation of hydroxyl-terminated polyurethane prepolymer-2

10 g of Br-P composite fire retardant polyether polyol (with a hydroxyl value of 235 mg KOH/g, Saytex RB-79, purchased from Albemarle Corporation, US), 30 g of polyester polyol (formed by polycondensation of o-phthalic acid, with a hydroxyl value of 400 mg KOH/g, a functionality of 2.7, PS-4027, purchased from Jinling Stepan Company), 5 g of non-halogenated polyether polyol (propylene glycol as starting ma- terial, with a functionality of 2, a hydroxyl value of 56 mg KOH/g, DC210, purchased from Shanghai Gaoqiao Petrochemical Co., Ltd, China), 30 g of triethyl phosphate were added into three-necked flask equipped with a motor stirrer, mixed with stirring and dehydrated at 120°C and under vacuum to remove moisture present in the raw materials. Then N2 was introduced, and the temperature was decreased to 70°C before 22 g of a mixture of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate (DESMODUR TP PU0129M from Covestro) was added dropwise and stirred to react for 2.5 h, to give the hydroxyl-terminated polyurethane prepolymer.

Example 3: Preparation of hydroxyl-terminated polyurethane prepolymer-3

34 g of Br-P composite fire retardant polyether polyol (with a hydroxyl value of 235 mg KOH/g, Saytex RB-79, purchased from Albemarle Corporation, US), 10 g of polyester polyol (formed by polycondensation of p-phthalic acid, with a hydroxyl value of 255 mg KOH/g, CF-6245, purchased from Nanjing CSD Chemicals Co., Ltd.), 10 g of halogenated polyether polyol (containing Br and CI, with a hydroxyl value of 330 mg KOH/g, a functionality of 3, IXOL B-251 , purchased from the company SOLVAY, Switzerland), 38 g of triethyl phosphate were added into three-necked flask equipped with a motor stirrer, mixed with stirring and dehydrated at 120°C and under vacuum to remove moisture present in the raw materials. Then N2 was introduced, and the temperature was decreased to 70°C before 22 g of a mixture of 4,4'-, 2,4'- and 2,2'- diphenylmethane diisocyanate (DESMODUR TP PU0129M from Covestro) was added dropwise and stirred to react for 2.5 h, to give the hydroxyl-terminated polyurethane prepolymer.

Example 4: Preparation of hydroxyl-terminated polyurethane prepolymer-4

40 g of Br-P composite fire retardant polyether polyol (with a hydroxyl value of 235 mg KOH/g, Saytex RB-79, purchased from Albemarle Corporation, US), 35 g of triethyl phosphate were added into three-necked flask equipped with a motor stirrer, mixed with stirring and dehydrated at 120°C and under vacuum to remove moisture present in the raw materials. Then N2 was introduced, and the temperature was de- creased to 70°C before 25 g of a mixture of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate (DESMODUR TP PU0129M from Covestro) was added dropwise and stirred to react for 2.5 h, to give the hydroxyl-terminated polyurethane prepolymer.

Table 1 : Raw materials used in Examples 1 -4

Examples 5-8: Preparation of polyisocyanurate foams

The polyisocyanurate foams were prepared according to the formulations in Table 2 using the hydroxyl-terminated polyurethane prepolymers obtained from Examples 1-4. The hydroxyl-terminated polyurethane prepolymer, optional polymeric polyol and foam stabilizer (siloxane-oxyalkylene copolymer surfactant), blowing agent, catalyst, optional fire retardant were mixed and stirred, to give component A as a uniform mixture. Component A was added to the feed tank for component A in the spray machine comprising feed tank for component A and feed tank for component B, transfer pump for component A and transfer pump for component B, proportioning pump for component A and proportioning pump for component B, hose for component A and hose for component B, mixing chamber, with transfer pump for component A were connected to hose for component A via proportioning pump for component A, and transfer pump for component B were connected to hose for component B via proportioning pump for component B, and hose for component A and hose for component B were both connected to the mixing chamber.

Component B: polyisocyanate was added to the feed tank for component B in the spray machine. The proportionality coefficient of proportioning pump A and proportioning pump B was set to 1 : 1. Component A in feed tank for component A in the spray machine was delivered to proportioning pump for component A through transfer pump for component A, and then it was pumped through hose for component A to the mixing chamber of the spray machine by pressurizing proportioning pump for component A; component B in feed tank for component B in the spray machine was delivered to proportioning pump for component B through transfer pump for component B, and then it was pumped through hose for component B to the mixing chamber of the spray machine by pressurizing proportioning pump for component B; component A and com- ponent B were mixed in the mixing chamber with the temperature of proportioning pump for component A and proportioning pump for component B, hose for component A and hose for component B all set to 35^~40 °C.

The mixture was sprayed onto the surface of the workpiece to be sprayed by the high pressure gas delivered to the mixing chamber, thus completing the spray moulding for preparing the polyisocyanurate foam.

Comparative Example 9: Preparation of polyisocyanurate foam

The polyisocyanurate foam was prepared using a high ratio of A/B according to the formulation in Table 2.

The comparative example was carried out referring to example 5-8, with the exception that the hydroxyl-terminated polyurethane prepolymer is absent from component A. Table 2: Raw materials used for preparation of polyisocyanurate foams and properties of the resulted polyisocyanurate foams

It can be seen from Examples 5-8 and Comparative Example 9 that: the isocyanates/polyol blend (B/A) ratio can be brought to 1 : 1 by employing the hydroxyl- terminated polyurethane prepolymer to prepare polyisocyanurate foam and this rigid polyisocyanurate foam has comparable foam physical and fire retardant properties to those from the conventional system with an isocyanates/polyol blend (B/A) ratio of other than 1 : 1 (for example a 1 : 1.36 system). However, the compression strength (parallel and perpendicular) of the polyisocyanurate foams obtained in the Examples 5-8 is improved in view of Comparative Example 9. By employing the hydroxyl- terminated polyurethane prepolymer, foam with the comparable fire retardant property was obtained, while conventional device with A/B ratio of 1 : 1 on the market can be used, thus the complexity and cost were reduced substantially during the practical production and the fire retardant property of the product can be improved.

Although the present invention has been described above regarding the purpose of the present invention, it is to be understood that such a detailed description is merely illustrative. In addition to those that can be defined by claims, various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A hydroxyl-terminated polyurethane prepolymer, which is the reaction product of the following raw materials:

a) one or more polymeric polyols, selected from polyether polyols and polyester polyols; b) one or more phosphates; and

c) one or more polyisocyanates.

2. The hydroxyl-terminated polyurethane prepolymer according to Claim 1 , wherein the polyether polyols are selected from polyether polyols started with saccharides, pentae- rythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, ethylenediamine, ethylene glycol, propylene glycol or water.

3. The hydroxyl-terminated polyurethane prepolymer according to Claim 1 or 2, wherein the polyether polyol has a functionality preferably of 2-8, in particular preferably of 2-4 and a hydroxyl value preferably of 35-800 mg KOH/g, in particular preferably of 35-400 mg KOH/g.

4. The hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 3, wherein the polyester polyol is formed by condensation of acid and/or acid anhy- dride with polyol, with the acid and acid anhydride being selected from o-phthalic acid, m-phthalic acid, p-phthalic acid, adipic acid, glutaric acid and succinic acid and the anhydrides of said acids, and the polyol being selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, glycerol, trimethylolpropane, pentaerythritol and sorbitol.

5. The hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 5, wherein the polyester polyol is that having a functionality of 2-3 and a hydroxyl value of 200-400 mg KOH/g.

6. The hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 5, wherein the phosphate is selected from tris(polyoxyalkylene) phosphate, tris(polyoxyalkylene) phosphite, tris(dipropylene glycol)phosphite, dimethyl methyl phosphonate(DMMP), dimethyl propyl phosphonate(DMPP), diethyl ethyl phospho- nate(DEEP), triethyl phosphate, and tricresyl phosphate(TPP).

7. The polyurethane prepolymer according to any one of Claims 1 to 6, wherein the pol- yisocyanate is selected from 4,4-methylenebis(2,6-diethylphenylisocyanate), tetrameth- ylene 1,4-diisocyanate, hexamethylene diisocyanate(HDI), dodecyl 1 ,2-diisocyanate, cyclobutane- 1 , 3 -diisocyanate, cyclohexane- 1 ,3 -diisocyanate, cyclohexane- 1 ,4- diisocyanate, l -isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, hexahy- drotoluene-2,4-diisocyanate, hexahydrophenyl- 1 ,3 -diisocyanate, hexahydrophenyl- 1,4- diisocyanate, perhydro-diphenylmethane 2,4-diisocyanate, perhydro-diphenylmethane 4,4-diisocyanate, phenylene 1 ,3 -diisocyanate, phenylene 1 ,4-diisocyanate, durene 1,4- diisocyanate, stilbene 1,4-diisocyanate, 3,3-dimethyl-4,4-diphenyldiisocyanate, toluene- 2,4-diisocyanate (TDI), toluene-2,6-diisocyanate (TDI), diphenylmethane-2,4'- diisocyanate (MDI), diphenylmethane-2,2'-diisocyanate (MDI), diphenylmethane-4,4'- diisocyanate (MDI), naphthylene- l ,5-diisocyanate (NDI) and isomers thereof.

8. A hydroxyl-terminated polyurethane prepolymer, which is the reaction product of the following raw materials:

a) one or more polymeric polyols comprising halogenated polyether polyols; and b) one or more polyisocyanates.

9. The hydroxyl-terminated polyurethane prepolymer according to Claim 8, wherein the halogenated polyether polyol is halogen-containing polyether polyol started with saccharides, pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, eth- ylenediamine, ethylene glycol, propylene glycol or water.

10. The hydroxyl-terminated polyurethane prepolymer according to Claim 8 or 9, wherein the halogenated polyether polyol has a functionality preferably of 2-8, in particular preferably of 2-4 and a hydroxyl value preferably of 35-800 mg KOH/g, in particular preferably of 35-400 mg KOH/g.

1 1. The hydroxyl-terminated polyurethane prepolymer according to any of Claims 8 to 10, wherein the polyisocyanate is selected from 4,4-methylenebis(2,6- diethylphenylisocyanate), tetramethylene 1 ,4-diisocyanate, hexamethylene diisocyanate (HDI), dodecyl 1 ,2-diisocyanate, cyclobutane- 1 ,3 -diisocyanate, cyclohexane-1 ,3- diisocyanate, cyclohexane- 1 ,4-diisocyanate, l -isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane, hexahydrotoluene-2,4-diisocyanate, hexahydrophenyl- 1 ,3-diisocyanate, hexahydrophenyl- 1,4-diisocyanate, perhydro-diphenylmethane 2,4- diisocyanate, perhydro-diphenylmethane 4,4-diisocyanate, phenylene 1 ,3 -diisocyanate, phenylene 1,4-diisocyanate, durene 1 ,4-diisocyanate, stilbene 1 ,4-diisocyanate, 3,3- dimethyl-4,4-diphenyldiisocyanate, toluene-2,4-diisocyanate (TDI), toluene-2,6- diisocyanate (TDI), diphenylmethane-2,4'-diisocyanate (MDI), diphenylmethane-2,2'- diisocyanate (MDI), diphenylmethane-4,4'-diisocyanate (MDI), naphthylene- 1,5- diisocyanate (NDI) and isomers thereof.

12. A method for preparing the hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 7 comprising the following steps:

i) mixing a) one or more polymeric polyols, selected from polyether polyols and polyester polyols, b) one or more phosphates and c) one or more polyisocyanates to give a re- action mixture, and

13. The method according to Claim 12, wherein the mixing in step i) is carried out as follows:

mixing a) one or more polymeric polyols, selected from polyether polyols and polyester polyols, and b) one or more phosphates, dehydrating at 1 10°C-130°C and under vacuum to remove moisture therein, then introducing 2 to provide protection, reducing the temperature to 70-80°C, followed by adding c) one or more polyisocyanates and stirring.

14. A method for preparing the hydroxyl-terminated polyurethane prepolymer according to any one of Claims 8 to 1 1 comprising the following steps:

i) mixing a) one or more polymeric polyols comprising halogenated polyether polyols and b) one or more polyisocyanates to give a reaction mixture, and

15. The method according to Claim 14, wherein the mixing in step i) is carried out as follows: dehydrating a) one or more polymeric polyols comprising halogenated polyeth- er polyols at 1 10°C- 130°C and under vacuum to remove moisture therein, then introducing N2 to provide protection, reducing the temperature to 70-80°C, followed by adding b) one or more polyisocyanates and stirring.

16. A polyisocyanurate foam, which is obtained by the reaction of component A and component B:

Component A, comprising:

a) the hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 1 1 ;

b) optionally, one or more polymeric polyols;

c) one or more foam stabilizers;

d) one or more catalysts; and

e) one or more blowing agents;

Component B, which is one or more polyisocyanates.

17. The polyisocyanurate foam according to Claim 16, wherein the polymeric polyol used in the component A is selected from:

halogenated polyether polyols, which are halogen-containing polyether polyols started with saccharides, pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene dia- mine, ethylenediamine, ethylene glycol, propylene glycol or water;

non-halogenated polyether polyols, which are polyether polyols started with saccharides (sorbitol, glucose, sucrose), pentaerythritol, sorbitol, trimethylolpropane, glycerol, toluene diamine, ethylenediamine, ethylene glycol, propylene glycol or water and free of halogen; and

polyester polyols, which are those formed by condensation of acid and/or acid anhydride with polyol, with the acid and acid anhydride being selected from o-phthalic acid , m-phthalic acid, p-phthalic acid, adipic acid, glutaric acid and succinic acid and the anhydrides of said acids, and the polyol being selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, glycerol, trimethylolpro- pane, pentaerythritol and sorbitol.

18. The polyisocyanurate foam according to Claim 17, wherein the polyisocyanate is selected from aromatic polyisocyanates, such as diphenylmethane diisocyanate and oligomers thereof, toluene diisocyanate, 1 ,5 -naphthalene diisocyanate and 1 ,4- diisocyanatobenzene, and aliphatic diisocyanates, such as isophorone diisocyanate, 1 ,6- diisocyanatohexane and 4,4'-diisocyanatodicyclohexylmethane.

19. A method for preparing the polyisocyanurate foam according to any one of Claims 16 to 18 comprising the following steps:

i) mixing a) the hydroxyl-terminated polyurethane prepolymer according to any one of Claims 1 to 1 1, b) optionally, one or more polymeric polyols, c) one or more foam stabilizers, d) one or more catalysts, and e) one or more forming agents and stirring, to give component A as a uniform mixture,

ii) mixing component B: one or more polyisocyanates with component A to give a reac- tion mixture; and

iii) reacting the reaction mixture to give the polyisocyanurate foam.