AU2020305490B2

AU2020305490B2 - Rigid urethane foam and method for manufacturing same

Info

Publication number: AU2020305490B2
Application number: AU2020305490A
Authority: AU
Inventors: Kyo Kook Jin; Woo Nyon Kim; Young Kyun Kim; Yeong Beom Lee; Byung Taek Oh; Heung Seok Seo; Young Chul Yang; Ki Ho YIM; Yong Keun Yoon
Original assignee: Korea Gas Corp
Current assignee: Korea Gas Corp
Priority date: 2019-06-26
Filing date: 2020-06-18
Publication date: 2023-02-23
Anticipated expiration: 2040-06-18
Also published as: WO2020262881A1; AU2020305490A1; KR20210001039A; KR102258805B1; CN114026144A; CN114026144B

Abstract

The present invention pertains to: a rigid polyurethane foam containing a 4th generation hydrofluoroolefin (HFO)-based blowing agent and a hydrofluoroether nucleating agent, preferably methoxynonafluorobutane; and a method for manufacturing same. A rigid polyurethane foam containing the above components has reduced cell size, improved mechanical strength, and excellent thermal insulation performance compared to conventional polyurethane foams.

Description

Description Title of Invention RIGID URETHANE FOAM AND METHOD FOR MANUFACRUTING SAME

Technical Field The present invention relates to a rigid polyurethane foam and a method for manufacturing same, and more particularly, to a rigid polyurethane foam having a reduced cell size and thus improved mechanical strength and thermal insulation performance compared to the prior art, by including a nucleating agent and a blowing agent having low Global Warming Potential (GWP) and Ozone Depletion Potential (ODP) of 0, and a method for manufacturing same. Background Art Rigid polyurethane foams having a low thermal conductivity are widely used as insulating materials. Recently, as the demand for storage tanks for transporting liquefied natural gas (LNG) increases, the use of rigid polyurethane foam as an insulating material is steadily increasing, so research on rigid polyurethane foam has been continued. Recently, as environmental regulations have become more severe around the world, there is a trend to prohibit the use of substances with high global warming potential and ozone depletion potential. Among the studies on rigid polyurethane foam, there was an attempt to use a 3 rd generation hydrofluorocarbon (HFC)-based blowing agent and a perfluoroalkane nucleating agent. An insulating material of high-density polyurethane foam with a density of about 115 kg/m 3 was produced by adding perfluoroalkane and a hydrofluorocarbon blowing agent, but it cannot be used after several to more ten years because of environmental regulations. One of the important factors determining physical properties of rigid polyurethane foams is density. This is because the density determines not only the thermal conductivity but also the mechanical strength. At the same density, the more uniform and the smaller the cell size of the polyurethane foam, the lower the thermal conductivity and the better the mechanical strength. Therefore, there is an urgent need for a method of manufacturing a polyurethane foam that has uniform density and small and uniform cell size. The present invention provides a high-density rigid polyurethane foam with a density of about 110 kg/m3 having high mechanical strength and excellent thermal insulation performance compared to conventional polyurethane foams while using a blowing agent having low global warming potential and zero ozone depletion potential.

Detailed Description of the Invention Technical Problem The first problem to be solved by the present invention is to provide a rigid polyurethan foam having a uniform and small cell size, a density maintained constant about 110 kg/m3 , and thus having low thermal conductivity and excellent mechanical properties. The second problem to be solved by the present invention is to provide a method for manufacturing the rigid polyurethane foam as described above. Solution to Problem In order to solve the first problem, the prevent invention provides a rigid urethane foam obtained by urethane reaction of a polyol-containing compound, a hydrofluoroether nucleating agent, an isocyanate group-containing compound, and a blowing agent. In order to solve the second problem, the present invention provides a method for manufacturing a rigid polyurethane foam, comprising: (a) adding a hydrofluoroether nucleating agent to a polyol-containing compound in the presence of a blowing agent and mixing them; (b) stirring the mixture obtained in step (a); and (c) reacting an isocyanate group-containing compound with the stirred mixture obtained in step (b) to obtain a polyurethane. Also provided by the present invention is a method for manufacturing a rigid polyurethane foam, comprising: (a) adding a hydrofluoroether nucleating agent to a polyol-containing compound in the presence of a blowing agent and mixing them; (b) stirring the mixture obtained in step (a) at 1000 to 5000 rpm; and (c) reacting an isocyanate group-containing compound with the stirred mixture obtained in step (b) to obtain a polyurethane

2a

wherein the hydrofluoroether nucleating agent is methoxy nonafluorobutane, wherein the hydrofluoroether nucleating agent is added in an amount of 0.5 wt% to 3 wt% based on the weight of the polyol-containing compound, and wherein the blowing agent is a hydrofluoroolefin (HFO) blowing agent Effect of the Invention The rigid polyurethane foam manufactured according to the present invention contains a blowing agent having low Global Warming Potential and Ozone Depletion Potential of and has a small and uniform cell size, the reduced thermal conductivity and the improved mechanical strength compared to the polyurethane foam commonly used in the prior art, while maintaining the properties of the conventional polyurethane foam. Brief Description of Drawings Fig. 1 is a flowchart showing a method for manufacturing the rigid polyurethane foam according to the present invention. Fig. 2 is a graph of the compressive strength of the rigid polyurethane foams according to Comparative Example 1 and Examples 1 to 4. Fig. 3 is a graph of the shear strength of the rigid polyurethane foams according to Comparative Example 1 and Examples 1 to 4. Fig. 4 is a graph ofthe thermal conductivity of the rigid polyurethane foams according to Comparative Example 1 and Examples 1 to 4. Fig. 5 is a graph ofthe thermal conductivity of the rigid polyurethane foams according to Comparative Example 1, Comparative Example 2 and Example 4 as a function of temperature. Fig. 6 is a graph of the cell size of the rigid polyurethane foams according to Comparative Example 1 and Examples 1 to 4. Fig. 7 is a scanning electron microscope (SEM) photograph of the rigid polyurethane foam to which methoxynonafluorobutane is not added according to Comparative Example 1. Fig. 8 is a SEM photograph of the rigid polyurethane foam to which methoxynonafluorobutane is added according to Example 4.

Best Mode for Carrying out the Invention Hereinafter, a rigid polyurethane foam and a method for manufacturing the same according to an embodiment of the present invention will be described in more detail, but the present invention is not limited to the following embodiments. Those of ordinary skill in the art will be able to implement the present invention in various other aspects without departing from the technical spirit of the present invention. Accordingly, it should be understood that the present invention includes all modifications, equivalents and substitutes falling within the spirit and scope of the present invention.

The polyurethane foam according to the prior art as described above, which contains a perfluoroalkane nucleating agent, a hydrofluorocarbon blowing agent and a dendrimer, has low ozone depletion potential but high global warming potential. Therefore, in the present invention, hydrofluoroether is used instead of perfluoroalkane as a nucleating agent. It is found that the hydrofluoroether used in the present invention has the ozone depletion potential of 0 and the global warming potential of 1/20 to 1/30 that of perfluoroalkane. In the present invention, the hydrofluoroether allows to increase stirring efficiency by reducing the viscosity of the reaction solution and serves as a nucleating agent that increases the nucleation by reducing the surface tension, thereby initially forming dense and uniform polyurethane (nuclei), which results in polyurethane cell growth. In one embodiment, the present invention provides a rigid polyurethane foam comprising a product of the urethane reaction of a polyol-containing compound, a hydrofluoroether nucleating agent, an isocyanate group-containing compound, and a blowing agent. The polyol-containing compound may be polyester polyol or a polyether polyol. More specifically, the polyester polyol may be prepared by polymerizing phthalic anhydride or adipic acid with ethylene oxide, propylene oxide, or a mixture thereof. In addition, the polyether polyol may be prepared by polymerizing ethylene glycol, 1,2-propane glycol, 1,3-propylene glycol, butylene glycol, 1,6 hexanediol, 1,8-octanediol, neopentyl glycol, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, 1,2,3-hexanetriol, butanediol, 1,2,4-butanetriol, trimethylolmethane, pentaerythritol, diethylene glycol, triethylene glycol, polyethylene glycol, tripropylene glycol , polypropylene glycol, dibutylene glycol, polybutylene glycol, sorbitol, sucrose, hydroquinone, resorcinol, catechol, bisphenol, or two or more thereof with ethylene oxide, propylene oxide or a mixture thereof. However, it is not limited to the polyol-containing compounds as described above, but any kind of polyol-containing compound is within the scope of the present invention as long as it can bind to the hydrofluoroether to form a nucleus and then react with the isocyanate group of the isocyanate group containing compound in the process described below, forming polyurethane.

The hydrofluoroether may be methoxy nonafluorobutane, ethoxy nonafluorobutane, or a mixture of methoxy nonafluorobutane and ethoxy nonafluorobutane. The hydrofluoroether is preferably methoxynonafluorobutane. The hydrofluoroether may be contained in an amount of 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1 wt% or more, 1.1 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, 1.5 wt% or more, 1.6 wt% or more, 1.7 wt% or more, 1.8 wt% or more, 1.9 wt% or more based on the weight of the polyol-containing compound. In addition, the hydrofluoroether may be contained in an amount of 3.0 wt% or less, 2.9 wt% or less, 2.8 wt% or less, 2.7 wt% or less, 2.6 wt% or less, 2.5 wt% or less, 2.4 wt% or less, 2.3 wt% or less, 2.2 wt% or less, 2.1 wt% or less, or 2.0 wt% or less based on the weight of the polyol-containing compound. In one embodiment, the hydrofluoroether may be contained in an amount of 0.5 wt% to 3 wt%, based on the weight of the polyol-containing compound, and in a further embodiment, it may be contained in an amount of 0.5 wt% to 2 wt%. If the amount of the hydrofluoroether is less than 0.5 wt% based on the weight of the polyol-containing compound, the effect cannot be sufficiently expected due to the small amount of addition, and if the amount exceeds 3 wt%, the density is significantly reduced and the compressive strength is lowered to deteriorate mechanical properties and the cell size is also increased. Specifically, the isocyanate group-containing compound reacts with the polyol to produce a urethane group, and may be an aliphatic, cycloaliphatic or aromatic polyfunctional isocyanate. This type of polyfunctional isocyanate is known in the art or may be prepared by a method known in the art. The polyfunctional isocyanate may be used in combination. It may have two isocyanate groups ("diisocyanate") or more than two isocyanate groups per molecule. The isocyanate group-containing compound may be selected from dodecane-1,12-diisocyanate; 2-ethyltetramethylene-1,4-diisocyanate; 2 methylpentamethylene-1,5-diisocyanate; tetramethylene-1,4-diisocyanate; hexamethylene-1,6-diisocyanate; cyclohexane-1,3-diisocyanate, cyclohexane 1,4-diisocyanate and mixtures thereof; 1-isocyanato-3,3,5-trimethyl-5 isocyanatomethylcyclohexane; hexahydrotolylene-2,4-diisocyanate, hexahydrotolylene-2,6-diisocyanate and mixtures thereof; dicyclohexanemethane 4,4'-, 2,2'- or 2,4'-diisocyanate and mixtures thereof, but is not limited thereto. The isocyanate group-containing compound may preferably be an aromatic polyfunctional isocyanate, for example it may be at least one selected from the group consisting of monomeric methylene diphenyl diisocyanate (MDI), polymeric MDI which is a combination of monomeric MDI and higher molecular weight polynuclear MDI, and toluene diisocyanate (TDI). The isocyanate group-containing compound may have a ratio (NCO/OH) of isocyanate group (-NCO) moieties and hydroxyl group (-OH) moieties of the polyol-containing compound of from 1 to 2. If the ratio is less than 1, the polyurethane forming reaction may not be completed due to the presence of an excess of polyol, and if the ratio exceeds 2, the polyurethane foam has an excessively high rigidity, so that the polyurethane become fragile. The blowing agent is a substance that promotes cell growth by forming bubbles in the molecule and may be a fourth-generation hydrofluoroolefin (HFO) based blowing agent having low global warming potential and ozone depletion potential of 0. The amount of the blowing agent is not particularly limited and can be adjusted according to the density of the polyurethane foam to be manufactured. In order to obtain a lower density polyurethane foam, the amount of the blowing agent to be added may be increased. In addition, the rigid polyurethane foam according to the present invention may further comprise a commonly used blowing agent in the art. Such additional blowing agents may be preferably those having low thermal conductivity and stable in the atmosphere, such as cyclopentane, chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, distilled water, 1-chloro-3,3,3 trifluoropropene or a mixture thereof. In a further embodiment, the rigid polyurethane foam of the present invention may further comprise additives such as a catalyst, a cell stabilizer, a flame retardant, and a fiber reinforcement. As the catalyst, a metal-based catalyst and an amine-based catalyst may be used. As the metal-based catalyst, lead or tin may be used, and as the amine based catalyst, one or more selected from the group consisting of pentamethyldiethylenetriamine, dimethylcyclohexylamine, tris(3 dimethylamino)propylhexahydrotriamine and triethylenediamine may be used. The cell stabilizer affects the cell structure in the rigid polyurethane foam, and may act to stabilize mixing of reaction raw materials, generate bubbles, stabilize bubbles, and the like. For example, it can increase the surface area of the cell by reducing surface tension to reduce the size of the cell, increase surface elasticity and thus increase foam stability before the cells are broken, and increase surface viscosity, which reduce deformation of the cell structure. As such, in consideration of the cell structure in the rigid polyurethane foam, the type of cell stabilizer may be appropriately selected. The cell stabilizer can be used, for example a silicone-based surfactant, such as, polysiloxane ether with a molecular weight of 1,000 to 10,000 g/mol, preferably a molecular weight of 3,000 to 7,000 g/mol. The cell stabilizer, if present, may be added in an amount of 0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight relative to 100 parts by weight of the polyol-containing compound. The flame retardant is intended to impart flame retardancy to the rigid polyurethane foam. It is not particularly limited, but a halogen-based, phosphorus-based or inorganic flame retardant may be used, for example. Since the rigid polyurethane foam is mostly used where flame retardancy is required, such as building structures and LNG storage tanks, it may be preferable to use a flame retardant. The fiber reinforcement is to further strengthen the mechanical strength of the polyurethane foam, and synthetic fibers such as glass fibers, polyamides, and polyesters, and inorganic fibers such as carbon fibers and ceramic fibers may be used, and a glass fiber mat laminate may be preferred. The fiber reinforcement, if present, may be added in an amount of 5 to 50 parts by weight, preferably 10 to 40 parts by weight relative to 100 parts by weight of the polyol containing compound. When the amount of the fiber reinforcement is less than 5 parts by weight per 100 parts by weight of the polyol-containing compound, the low-temperature shrinkage stability and crack prevention effect are deteriorated, and when it exceeds 50 parts by weight, abnormal foaming and cracking of the foam may occur during polyurethane foaming process. The additives that can be used in the rigid polyurethane foam of the present invention and the amount thereof used are not limited to those exemplified above and can be variously selected as needed. Fig. 1 is a flowchart showing a method for manufacturing the rigid polyurethane foam according to the present invention. Specifically, the method for manufacturing a rigid polyurethane foam may comprise: (a) adding a hydrofluoroether nucleating agent to a polyol-containing compound in the presence of a blowing agent and mixing them (S100); (b) stirring the mixture obtained in step (a) (S200); and (c) reacting an isocyanate group-containing compound with the stirred mixture obtained in step (b) to obtain a polyurethane (S300). The polyol-containing compound in step (a) may be polyester polyol or polyether polyol. More specifically, the polyester polyol may be prepared by polymerizing phthalic anhydride or adipic acid with ethylene oxide, propylene oxide, or a mixture thereof. In addition, the polyether polyol may be prepared by polymerizing ethylene glycol, 1,2-propane glycol, 1,3-propylene glycol, butylene glycol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 2-methyl-1,3 propanediol, glycerol, trimethylolpropane, 1,2,3-hexanetriol, butanediol, 1,2,4 butanetriol, trimethylolmethane, pentaerythritol, diethylene glycol, triethylene glycol, polyethylene glycol, tripropylene glycol , polypropylene glycol, dibutylene glycol, polybutylene glycol, sorbitol, sucrose, hydroquinone, resorcinol, catechol, bisphenol, or two or more thereof with ethylene oxide, propylene oxide or a mixture thereof. However, any kind of polyol-containing compound can be used as long as it can bind to the hydrofluoroether to form a nucleus and then react with the isocyanate group of the isocyanate group-containing compound, forming polyurethane. In step (a), the hydrofluoroether may be methoxy nonafluorobutane, ethoxy nonafluorobutane, or a mixture of methoxy nonafluorobutane and ethoxy nonafluorobutane, preferably methoxynonafluorobutane. The hydrofluoroether may be added in an amount of 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1 wt% or more, 1.1 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, 1.5 wt% or more, 1.6 wt% or more, 1.7 wt% or more, 1.8 wt% or more, 1.9 wt% or more based on the weight of the polyol-containing compound. In addition, the hydrofluoroether may be added in an amount of 3.0 wt% or less, 2.9 wt% or less, 2.8 wt% or less, 2.7 wt% or less, 2.6 wt% or less, 2.5 wt% or less, 2.4 wt% or less, 2.3 wt% or less, 2.2 wt% or less, 2.1 wt% or less, or 2.0 wt% or less based on the weight of the polyol-containing compound. In one embodiment, the hydrofluoroether may be added in an amount of 0.5 wt% to 3 wt%, based on the weight of the polyol-containing compound, and in a further embodiment, it may be added in an amount of 0.5 wt% to 2 wt%. If the amount of the hydrofluoroether is less than 0.5 wt% based on the weight of the polyol-containing compound, the effect cannot be sufficiently expected due to the small amount of addition, and if the amount exceeds 3 wt%, the density is significantly reduced and the compressive strength is lowered to deteriorate mechanical properties and the cell size is also increased. The stirring in step (b) is a process for uniformly mixing the polyol containing compound and the hydrofluoroether nucleating agent. In particular, if additives such as surfactants and catalysts are mixed with the polyol-containing compound in addition to the blowing agent, the stirring process has a technical significance. The stirring may be performed by using a mechanical stirrer so that the hydrofluoroether nucleating agent is interposed between the polyol containing compounds to facilitate the reaction. In one embodiment of the present invention, the stirring speed of the mechanical stirrer may be 1000 to 5000 rpm. The stirring is preferably performed in a two-step method of initially stirring at a low speed, for example, 1500 to 3000 rpm for 3 to 5 minutes, and then stirring at a high speed, for example 3000 to 5000 rpm for 60 to 300 seconds. The stirring speed may have some different optimal numerical ranges for each stirrer. However, it falls within the scope of the present invention as long as the stirring proceeds in the first stage at a low speed and the second stage at a high speed. However, in the case of stirring at a high speed in the initial stage, as the blowing agent evaporates into the air and only a small amount of the blowing agent is left for reaction, it is difficult to obtain a polyurethane foam having desired properties. In addition, if the stirring is performed at a low speed, that is less than 3000 rpm even after the initial stirring, there is a problem that the hydrofluoroether is not sufficiently mixed with the polyol-containing compound. Conversely, when stirring at a high speed more than 5000 rpm, it is difficult to obtain sufficient time to cause a reaction between the hydrofluoroether and the polyol-containing compound. In addition, the mixing of step (a) and stirring of step (b) may be performed at a temperature of 20 to 40 °C. If the temperature is less than the above range, the reaction between the polyol-containing compound and the hydrofluoroether hardly occurs, so that a covalent bond between the polyol-containing compound and the hydrofluoroether is not formed. Conversely, if the temperature exceeds the above range, the hydrofluoroether may be evaporated before the reaction. According to the mixing of step (a) and the stirring process of step (b), a covalent bond between the polyol-containing compound and the hydrofluoroether is formed. In step (c), an isocyanate group-containing compound is added to the stirred mixture obtained in step (b) and then mixed. Here, the -NCO group of the isocyanate group-containing compound reacts with the -OH group of the polyol containing compound to form a urethane group, thereby obtaining a polyurethane foam. In this case, as the isocyanate group-containing compound, substantially the same as described above with respect to the rigid polyurethane foam may be used, and preferably polymeric MDI, monomeric MDI or TDI may be used. The ratio (NCO/OH) of the -NCO moiety of the isocyanate group containing compound and the -OH moiety of the polyol-containing compound may be from 1 to 2. If the ratio is less than 1, the polyurethane forming reaction may not be completed due to the presence of an excess of polyol, and if the ratio exceeds 2, the polyurethane foam has an excessively high rigidity, so that the polyurethane become fragile. The step (c) may be performed at a temperature of 10 to 40 °C. If the temperature is less than the above temperature range, the urethane reaction of polyol with isocyanate does not occur sufficiently. Conversely, if the temperature exceeds the above temperature range, the urethane reaction proceeds too quickly, so that the hydrofluoroether having a low boiling point is evaporated. In one embodiment of the present invention, the reaction for obtaining polyurethane in step (c) may be carried out in the presence of a catalyst. As the catalyst, one or more compounds selected from pentamethyldiethylenetriamine, dimethylcyclohexylamine, tris(3-dimethylamino)propylhexahydrotriamine, and triethylenediamine may be used, for example. The catalyst promotes the urethane reaction of polyol with isocyanate to improve the reaction rate. The steps (a), (b) and (c) for producing the polyurethane foam according to the present invention are shown in the flowchart of Fig. 1.

Mode for Carrying out the Invention Hereinafter, the present invention will be described in detail with reference to examples so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Example 1 Example 1-1: Preparation of polyol compound with methoxynonafluorobutaneadded 100 g of a polyol compound (Anhydride and glycol based polyester-type polyol, AK POL-1001, Aekyung Petrochemical Co.,Ltd. 65g; Pentaerithritol and glycerin based Polyether type polyol, HS480N, KPX Chemicals Co, 30g; Pentaerithritol and glycerin based Polyether type polyol, L3300, BASF, 5g), 2.5 g of a surfactant (Silicone-type surfactant, L6900, Momentive Co.), 0.14 g of an amine-based catalyst (Dimethylcyclohexylamine, PC-8, Air Products and Chemicals, Inc.), 6.2 g of a HFO blowing agent (Trans-1-chloro-3,3,3 trifluoropropene, HFO-1233zd, Honeywell), and 0.5 g (i.e., 0.5 wt%) of methoxynonafluorobutane based on the 100 g of the polyol compound were mixed and the mixture was stirred using a mechanical stirrer at a low speed of 1500 to 3000 rpm for 3 minutes (1st stage stirring) and then at a high speed of 3000 to 5000 rpm for 2 minutes (2nd stage stirring). Example 1-2 100 g of isocyanate (Polymeric 4,4'-diphenylmethane diisocyanate,

M20S, BASF) was added to 100 g of the mixture obtained in Example 1-1 and stirred at 5000 rpm for 60 seconds at room temperature using a mechanical stirrer, followed molding in an open mold to produce a rigid polyurethane foam.

Example 2 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 1.0 g (i.e., 1.0 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Example 3 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 1.5 g (i.e., 1.5 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Example 4 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 2.0 g (i.e., 2.0 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Example 5 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 2.5 g (i.e., 2.5 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Example 6 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 3.0 g (i.e., 3.0 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Comparative Example 1: Preparation of polyol compound with methoxynonafluorobutane not added A rigid polyurethane foam was prepared in the same manner as in

Example 1, except that methoxynonafluorobutane was not added.

Comparative Example 2 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that HFC-245fa, a third-generation blowing agent, was used as the blowing agent.

Reference Example 1 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 0.3 g (i.e., 0.3 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Reference Example 2 A rigid polyurethane foam was prepared in the same manner as in Example 1, except that 3.5 g (i.e., 3.5 wt%) of methoxynonafluorobutane was used based on 100 g of the weight of the polyol compound.

Experimental Example: Changes in physical properties of rigid polyurethane foam according to the addition of methoxynonafluorobutane The compressive strength, shear strength, thermal conductivity and cell size of the rigid polyurethane foams prepared in Examples 1 to 6, Comparative Examples 1 to 2 and Reference Examples 1 to 2 were measured by the following method, and the results are shown in Table 1. Density: ASTM D1622 Compressive strength: ASTM D1621 Shear strength: ASTM D732 Thermal conductivity (R.T.): ISO 8301 Cell Morphology: The sample was destroyed in cryogenic conditions and the surface was coated with platinum and then scanned with a field emission scanning electron microscope (FE-SEM) (Hitachi Model S-4300SE, Tokyo, Japan). The acceleration voltage was 15kV. From the obtained SEM photograph, 50 cells were counted, the cell size was measured and the average was obtained.

[Table 1]

AonofCompressive~hasrnt Thermal methoxynona- strength Shear strength conductivity Cell size fluorobutane (MPa) (MPa) W/mK) (wt%) Comparative 0.0 1.30 0.862 0.0239 221 Example_1 ______ __ ____

Comparative 0.0 1.32 0.863 0.0248 234 Example_2 ______ __ ____

Reference 0.3 1.31 0.863 0.0234 221 Example_1 ______ __ ____

Exame 3.5 1.35 0.879 0.0228 200 Example 1 0.5 1.31 0.863 0.0232 216 Example 2 1.0 1.31 0.864 0.0230 215 Example 3 1.5 1.32 0.867 0.0230 212 Example 4 2.0 1.33 0.870 0.0228 207 Example 5 2.5 1.33 0.874 0.0225 202 Example 6 3.0 1.34 0.882 0.0223 195

From the results in Table 1, it demonstrates that Examples 1 to 6 in which methoxynonafluorobutane was added exhibited high compressive strength and shear strength, low thermal conductivity and small cell size compared to Comparative Examples 1 and 2 in which methoxynonafluorobutane was not added. For example, in Example 4, the compressive strength was increased by 2.3%, the shear strength was increased by 0.92%, the thermal conductivity was decreased by 4.6%, and the cell size was decreased by 6.3%, compared to Comparative Example 1. In addition, in the case of Reference Example 1 in which 0.3 wt% of methoxyplanonafluorobutane was added, there is no significant difference from Example 1 in compressive strength and shear strength, but the thermal conductivity was high and the cell size was increased, thus effect of the addition of the nucleating agent was insignificant. In the case of Reference Example 2 in which 3.5 wt% of methoxynonafluorobutane was added, the shear strength was decreased, the thermal conductivity and the cell size were increased, and the efficiency relative to the amount added is lowered, compared to Example 6.

[Observation of compressive strength]

Fig. 2 is a graph showing the compressive strength of the polyurethane foam of Examples 1 to 4 according to the present invention and Comparative Example 1. Referring to Fig. 2, it can be seen that the compressive strength is maintained or increased depending on addition of methoxynonafluorobutane.

[Observation of shear strength] Fig. 3 is a graph showing the shear strength of the polyurethane foam of Examples 1 to 4 according to the present invention and Comparative Example 1. Referring to Fig. 3, it can be seen that the shear strength is maintained or increased depending on addition of methoxynonafluorobutane.

[Observation of thermal conductivity] Fig. 4 is a graph showingthe thermal conductivity of the polyurethane foam of Examples 1 to 4 according to the present invention and Comparative Example 1. Referring to Fig. 4, it can be seen that Examples 1 to 4 in which methoxynonafluorobutane was added exhibited lower thermal conductivity than Comparative Example in which methoxynonafluorobutane was not added. On the other hand, Table 2 below shows the thermal conductivity as a function of temperature of the polyurethane foams of Example 4, Comparative Example 1 and Comparative Example 2 according to the type of blowing agent and whether or not methoxynonafluorobutane is added, and Fig. 5 is a graph plotting the values of Table 2. Thermal conductivity measurements at cryogenic to room temperature( 160 °C to 20 °C) were performed according to ISO 8302.

[Table 2] Thermal conductivity (W/mK) Temperature(°C) Example 4 Comparative Comparative Example 1 Example 2 -160 0.0157 0.0173 0.0172 -130 0.0171 0.0193 0.0193 -100 0.0174 0.0199 0.0197 -70 0.0187 0.0207 0.0206 -40 0.0191 0.0207 0.0207 -10 0.0204 0.0215 0.0217 20 0.0224 0.0235 0.0244

Referring to Table 2 and Fig. 5, Comparative Example 1 in which the

HFO-based blowing agent was added exhibited lower thermal conductivity at room temperature than Comparative Example 2 in which the HFC-based blowing agent was added. In addition, it can be seen that Example 4 in which the HFO based blowing agent and methoxynonafluorobutane were added according to the present invention exhibits lower thermal conductivity at all temperatures compared to Comparative Example 1 in which HFO-based blowing agent was added but methoxynonafluorobutane was not added, and Comparative Example 2 in which HFC-based blowing agent was added but methoxynonafluorobutane was not added.

[Observation of scanning electron microscope] In order to observe a scanning electron microscope (SEM) photograph, each of specimen of the rigid polyurethane foam according to Comparative Examples 1 and Example 4 were cut into a width of 30 mm, a length of 30 mm, and a height of 30 mm, and the specimen was placed in liquid nitrogen and the cross-section of the cell was measured with a scanning electron microscope. Fig. 6 is a graph of the cell size of the rigid polyurethane foams according to Comparative Example 1 and Examples 1 to 4. Fig. 7 is a scanning electron microscope (SEM) photograph (cell size: 221 pm) of the rigid polyurethane foam of Comparative Example 1. Fig. 8 is a SEM photograph (cell size: 207 pm) of the rigid polyurethane foam of Example 4. Referring to Figs. 7 and 8, it can be seen that the rigid polyurethane foam of Example 4 in which methoxynonafluorobutane was added (Fig. 8) has smaller and uniform cell size than the rigid polyurethane foam of Comparative Example 1 in which methoxynonafluorobutane was not added (Fig. 7). The reduced cell size is considered that because the nuclei generated in a large amount at the beginning of the reaction grow into small and uniform cells through the reaction to form the rigid polyurethane foam, due to the addition of methoxynonafluorobutane. In general, it is known that the smaller the cell size, the better the thermal insulation performance. As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it will be apparent that these specific descriptions are merely preferred embodiments, and the scope of the present invention is not limited thereby. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a rigid polyurethane foam, comprising: (a) adding a hydrofluoroether nucleating agent to a polyol-containing compound in the presence of a blowing agent and mixing them; (b) stirring the mixture obtained in step (a) at 1000 to 5000 rpm; and (c) reacting an isocyanate group-containing compound with the stirred mixture obtained in step (b) to obtain a polyurethane, wherein the hydrofluoroether nucleating agent is methoxy nonafluorobutane, wherein the hydrofluoroether nucleating agent is added in an amount of 0.5 wt% to 3 wt% based on the weight of the polyol-containing compound, and wherein the blowing agent is a hydrofluoroolefin (HFO) blowing agent.

2. The method for manufacturing a rigid polyurethane foam according to claim 1, wherein the polyol-containing compound is polyester polyol or polyether polyol.

3. The method for manufacturing a rigid polyurethane foam according to claim 1 or claim 2, wherein the step (a) and the step (b) are performed at a temperature of 20 to °C.

4. The method for manufacturing a rigid polyurethane foam according to any one of claims 1 to 3, wherein the stirring in step (b) is performed by initially stirring at 1500 to 3000 rpm for 3 to 5 minutes, and then stirring at 3000 to 5000 rpm for 60 to 300 seconds.

5. The method for manufacturing a rigid polyurethane foam according to any one of claims 1 to 4, wherein the isocyanate group-containing compound in step (c) is at least one selected from the group consisting of polymeric methylene diphenyl diisocyanate (MDI), monomeric MDI, and toluene diisocyanate (TDI).

6. The method for manufacturing a rigid polyurethane foam according to any one of claims 1 to 4, wherein the isocyanate group-containing compound has a ratio (NCO/OH) of isocyanate group (-NCO) moieties and hydroxyl group (-OH) moieties of the polyol containing compound of from 1 to 2.

7. The method for manufacturing a rigid polyurethane foam according to any one of claims 1 to 6, wherein the step (c) is performed at a temperature of 10 to 40 °C.

8. The method for manufacturing a rigid polyurethane foam according to any one of claims 1 to 7, wherein the step (c) is performed in the presence of one or more catalysts selected from the group consisting of pentamethyldiethylenetriamine, dimethylcyclohexylamine, tris(3-dimethylamino)propylhexahydrotriamine, and triethylenediamine.

Korea Gas Corporation Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON