JP2004285319A - Rigid polyurethane foam composition and low-temperature insulator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rigid polyurethane foam composition exhibiting excellent heat-insulating properties and mechanical characteristics which is obtained by using a hydrofluorocarbon blowing agent having no ozone-depletion potential, a specific isocyanate and a specific polyether, and to provide a low-temperature insulator. <P>SOLUTION: The rigid polyurethane foam composition is obtained using a polymeric 4,4'-diphenylmethane diisocyanate as the isocyanate, a polyol mixture as the polyether comprising polyether polyols obtained by addition-polymerization of propylene oxide and ethylene oxide to (a) sorbitol, (b) pentaerythritol and (c) sucrose, respectively, (d) a polyester polyol obtained by addition-polymerization of propylene oxide and ethylene oxide to phthalic anhydride, and (e) a polyether polyol obtained by addition-polymerization of ethylene oxide and propylene oxide to glycerine having a bromine-substituent, and the hydrofluorocarbon as the blowing agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention, by using a hydrofluorocarbon (hydrofluorocarbon (HFC)) based blowing agent having no ozone depleting ability as a blowing agent, is environmentally friendly, has excellent heat insulating performance, and has improved mechanical properties such as high compressive strength. The present invention relates to a rigid polyurethane foam composition and a cold insulator using the composition.

  Generally, a rigid polyurethane foam is produced by using a diisocyanate and a polyol as raw materials and foaming with a foaming agent such as water, chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, carbon dioxide, or cyclopentane.

  As diisocyanates, toluene diisocyanate (Tluene diisocyanate; TDI) and 4,4′-diphenylmethane diisocyanate are known. In particular, in the case of rigid polyurethane foam, polymer type 4,4 ′ having an average functional group of 2.7 or more is used. -Diphenylmethane diisocyanate is mainly used.

  As the polyol, a polyether-based polyol and a polyester-based polyol are used. Polyether polyols are advantageous in that they have low viscosity, are easy to process, have stable hydrolysis, and are low in cost, and are particularly widely used. Polyester-based polyols are excellent in heat stability and tensile strength, are excellent in oil resistance and the like, but have a drawback of poor hydrolysis resistance. Therefore, at present 90% or more of polyurethane production uses polyether-based polyols, and polyester-based polyols are used for special purposes.

  Physical properties of rigid polyurethane foams can generally be expressed as a function of density. Since the thermal conductivity decreases as the density of the polyurethane foam decreases, the heat insulating performance improves, but the mechanical properties such as the compressive strength decrease as the density decreases. Therefore, although it is extremely difficult to develop a rigid polyurethane foam having excellent heat insulation performance and mechanical properties, it is a property that is necessarily required in ultra-low temperature insulation materials for liquefied natural gas storage tanks or ultra-low temperature pipe covers, general-purpose heat insulation materials, and the like. .

Methods of improving the mechanical properties of the polyurethane foam include a method of increasing the density of the polyurethane foam and a method of using a filler such as glass fiber or carbon fiber.
However, both methods have a problem that the thermal conductivity of the foam is increased, and as a result, the heat insulating performance is reduced.

  Decreased insulation performance has a particularly detrimental effect, especially when polyurethane foam is used as a cryogenic insulation. Therefore, a method of increasing mechanical strength without reducing such heat insulation performance is expected.

Generally, water, a carboxylic acid, a fluorocarbon-based blowing agent or an inert gas such as carbon dioxide or air is used as a blowing agent in a polyurethane foam.
In the past, chlorofluorocarbons with low thermal conductivity and stable in the atmosphere were widely used, but recently chlorofluorocarbons have caused environmental destruction, so hydrochlorofluorocarbons, cyclohexane, water, hydrochlorofluorocarbons, hydrochlorofluorocarbons, Alternative blowing agents such as fluorocarbons have been used. In particular, hydrofluorocarbons have low thermal conductivity, do not easily diffuse into the air from inside the polyurethane foam, maintain long-term insulation performance, and have attracted much interest as a next-generation foaming agent without ozone destruction ability I have.
Therefore, as an alternative to CFC-11 or CFC-12, HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane) or HCFC-141b (1,1-dichloro-1-fluoroethane) Besides, HFC-134a (1,1,1,2-tetrafluoroethane), HFC-152a (1,1-difluoroethane) and HFC-365mfc (1,3-pentafluorobutane) having no ozone depleting ability ), HF-245fa (1,3-pentafluoropropane) and the like have also attracted attention.

In addition, a foaming agent, a catalyst, a flame retardant, a chain extender, and the like are further used for producing a polyurethane foam.
Furthermore, low molecular weight diols or diamines are used as chain extenders or crosslinking agents for the purpose of increasing the mechanical strength of the polyurethane foam.
As the catalyst, tin (tin) type and amine type are used.

Since polyurethane has low flame retardancy, a flame retardant may be further added. Flame retardants are classified into reactive flame retardants and additive flame retardants, and are broadly classified into halogen-based flame retardants, phosphorus-based flame retardants, and inorganic flame retardants.
In addition, when small and uniform cells are generated during foam formation by foaming, since the cells have an advantageous effect on heat insulation performance and mechanical properties, a silicon-based surfactant is added as a cell stabilizer. are doing.

  Accordingly, the present invention has been made in order to solve such a technical demand, and an object of the present invention is to use an HFC-based blowing agent, which is a cleaning alternative blowing agent having no ozone depleting ability, to provide a very economical method. Another object of the present invention is to provide a rigid polyurethane foam composition having excellent environmental properties and excellent heat insulation properties and mechanical properties even at ordinary temperature and ultra-low temperature, and a cold insulator using the composition.

  In order to achieve the above object, the present invention provides a method of adding a polymer type 4,4′-diphenylmethane diisocyanate (MDI) and (a) sorbitol to propylene oxide and ethylene oxide. 20 to 60% by weight of a polyether polyol polymerized by polymerization, (b) 10 to 40% by weight of a polyether polyol polymerized by adding propylene oxide and ethylene oxide to pentaerythritol, and (c) propylene oxidation to sucrose 10 to 30% by weight of a polyether polyol polymerized by adding a product and ethylene oxide, and 5 to 20% by weight of (d) a polyester polyol polymerized by adding propylene oxide and ethylene oxide to phthalic anhydride % And (e) polymerization by adding ethylene oxide and propylene oxide to glycerin substituted with bromo group The polyol mixture consisting of 1 to 20% by weight of the polyether polyol is adjusted so that the NCO / OH ratio is in the range of 1.0 to 2.0, and 1,3-pentafluoro is used as a hydrofluorocarbon foaming agent. A rigid polyurethane foam composition containing butane, 1,3-pentafluoropropane or a mixture thereof, and a cold insulator using the composition are provided.

  That is, high-molecular 4,4′-diphenylmethane diisocyanate is used as a diisocyanate, and three types of polyether polyols having a hydroxyl value of 200 to 650, one type of polyester type polyol and one type of bromo type polyol are mixed. By using this, it is possible to produce a polyurethane foam having excellent heat insulating performance and mechanical properties.

  According to the present invention, while using a hydrofluorocarbon compound having no ozone depleting ability, it exhibits excellent mechanical strength such as being able to suppress the occurrence of cracks while maintaining excellent heat insulating properties inherent to polyurethane foam. Can be. In addition, using the polyurethane foam composition of the present invention, an environmentally friendly cold insulator excellent in heat insulating properties and mechanical properties can be produced by a known production method.

The mixed polyol component used in the present invention comprises (a) 20 to 60% by weight of a polyether polyol obtained by adding propylene oxide and ethylene oxide to sorbitol and polymerizing the same. (B) 10 to 40% by weight of a polyether polyol obtained by adding propylene oxide and ethylene oxide to pentaerythritol and polymerizing (c) sucrose with propylene oxide and ethylene oxide 10 to 30% by weight of a polyether polyol polymerized by adding propylene oxide and ethylene oxide to (d) phthalic anhydride, and 5 to 20% by weight of a polyester polyol polymerized by adding And (e) a polymer obtained by adding ethylene oxide and propylene oxide to glycerine substituted with a bromo group and polymerizing the glycerine. 1 to 20% by weight of a polyester polyol.
The average OH value of the mixed polyol component is 380-510.
In the present invention, the NCO / OH ratio between the polymer type 4,4′-diphenylmethane diisocyanate and the mixed polyol is preferably 1.0 to 2.0.

  The polyols used in the present invention are glycerin, pentaerythritol, sorbitol, and sucrose based polyols, respectively. These have 3, 4, 6, and 8 functional groups capable of reacting depending on their structures, respectively, and form a linear bond or a cross-linking upon reaction with an isocyanate. This shows a great difference in the physical properties of the produced polyurethane foam. For example, the compressive strength of a glycerin-based polyol and a sorbitol-based polyol have a difference of 10% or more. In the present invention, the content of each polyol is adjusted and optimized by comprehensively considering the reaction time, viscosity, and physical properties of the product required for the cold insulator synthesis reaction. The reason for using a polyol having a bromo group substituted is that the flame retardancy is increased. In the case of a low density, when a polyol having a bromo group substituted is not used, the produced heat insulating material does not have the desired flame retardancy. A group-substituted polyol was used.

The polyurethane foam composition of the present invention further includes a blowing agent, a catalyst, and other additives in addition to the diisocyanate and the polyol.
As the foaming agent, HFC-365mfc (1,3-pentafluorobutane) or HFC-245fa (1,3-pentafluoropropane) was used individually or as a mixture. Compared to the case, there is almost no deterioration in physical properties, and there is no problem even when mixed and used. Therefore, the mixing ratio of HFC-245fa and HFC-365mfc can be set to 0 to 100%. If necessary, use water as an auxiliary blowing agent. It is preferable to use 3 to 35 parts by weight of the organic blowing agent with respect to 100 parts by weight of the polyol component. Further, the water as the auxiliary foaming agent is preferably 0 to 7 parts by weight based on 100 parts by weight of the polyol component.

In this case, the density of the prepared polyurethane foam has a 30~140kg / ^{m 3,} by appropriately adjusting the amount of blowing agent, of less than 30kg / ^{m 3} low density foam or 140 kg / ^{m 3} or more high Density foam can be manufactured.
In particular, the HFC-365mfc and HFC-245fa facilitate the production of polyurethane foam due to low evaporation temperature, and impart excellent heat insulating performance to polyurethane foam by having low thermal conductivity.

  Water is used as an auxiliary blowing agent to release carbon dioxide while reacting with diisocyanate to form urea. The released carbon dioxide is used for foaming the polyurethane foam. The heat of reaction between water and diisocyanate is also used for vaporizing HFC-365mfc and HFC-245fa. If the amount of water used exceeds 7 parts by weight based on 100 parts by weight of the polyol component, excessive heat of reaction may cause scorch in the polyurethane foam to be produced, and excessive carbon dioxide may be contained in the polyurethane foam. And the thermal conductivity also increases.

  The polyurethane foam of the present invention can be obtained by reacting a mixed polyol component and an isocyanate component as basic raw materials in the presence of a foaming agent, a reaction catalyst, a foam stabilizer and other additives. That is, a rigid polyurethane foam is produced by mixing and reacting a resin stock solution containing a polyol component, a foaming agent, a reaction catalyst, a foam stabilizer, and other additives with an isocyanate component.

  As a reaction catalyst used in the present invention, an amine-based catalyst can be used as a typical catalyst used for obtaining a polyurethane foam. In particular, in the present invention, three kinds of catalysts such as pentamethyldiethylenetriamine, dimethylcycloamine, and tris (3-dimethylamino) propylhexahydrotriamine are used alone or in combination. These catalysts are preferably used in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the polyol component. When a reaction catalyst is not used, the reaction rate may be reduced and the physical properties may be reduced due to the incomplete completion of the rigid polyurethane foam forming reaction. Further, even if it is used in excess of 2.0 parts by weight, the effect on the improvement of the reaction rate or the increase in physical properties is insignificant.

  The foam stabilizer used in the present invention is a polysiloxane ether as a silicone surfactant. During the production of the polyurethane foam, the foaming agent vaporized by the heat of the reaction foams the polyurethane-bonded reactant while forming cells. At this time, the air bubbles solidify and become large due to the internal pressure, but in this case, the heat insulation performance and the mechanical strength are reduced. At this time, when a silicon-based surfactant is used, the surfactant supplies an electric charge to the surface of the foamed cells to provide an electrostatic repulsion between these cells, and a polyurethane having cells of small and uniform size. Forms can be manufactured. The amount of the foam stabilizer used is preferably from 0 to 2.0 parts by weight based on 100 parts by weight of the polyol component. At this time, if the amount of the foam stabilizer exceeds 2.0 parts by weight, the compressive strength and load resistance of the polyurethane foam decrease, which is not preferable.

  Further, in the present invention, a flame retardant may be added to enhance the flame retardancy of the polyurethane foam. As the flame retardant of the present invention, for example, a phosphorus-based flame retardant such as tricresyl phosphate is used. When a flame retardant is used, its amount is preferably 5 to 15 parts by weight based on 100 parts by weight of the mixed polyol component. At this time, if the amount of the flame retardant used is less than 5 parts by weight, satisfactory flame retardancy is not ensured, and even if it exceeds 15 parts by weight, an additional increase in flame retardancy is insignificant. In addition, the productivity of the polyurethane foam decreases, which is not preferable.

Further, a crosslinking agent may be used in order to reinforce the strength of the polyurethane foam of the present invention and to shorten the curing time.
In addition, a filler, an antioxidant, a stabilizer such as an ultraviolet absorber, a coloring agent, and the like used in the urethane chemistry field can be added as necessary.

The polyurethane foam can be manufactured by a one-shot method, a prepolymer method, a spray method, and various other well-known methods depending on the method of reacting the raw materials. Among these, the one-shot method is a method in which all the raw materials such as an isocyanate component and a polyol component are simultaneously charged and reacted. The one-shot method has an advantage that the operation is simple and easy, but since the reaction occurs at one time, it is relatively difficult to adjust the reaction rate, and a large amount of reaction heat is generated, and cracks are generated inside the foam. There is a disadvantage that there is a possibility. In contrast, the prepolymer method is a method in which a part of a polyol component is reacted in advance with an isocyanate component, and then another raw material is further reacted. Therefore, this prepolymer method has the advantage that the reaction heat is high while the reaction occurs relatively slowly, the rate of increase in the viscosity of the foam due to the reaction is low, and even complicated structures are filled to every corner. There is a disadvantage in that the manufacturing stage is prolonged and the cost is increased. Therefore, in the present invention, it is preferable to use the one-shot method in consideration of workability, productivity, and cost. However, the polyols and additives are appropriately adjusted so that scorch and cracks inside the foam do not occur due to a large amount of heat generated when the reaction occurs at one time.
As the foaming device, a high-pressure or low-pressure foaming device generally used in the polyurethane industry can be used.

The present invention is specifically described by the following examples.
(Example 1)
35.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to pentaerythritol, 25.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to sucrose, and propylene to phthalic anhydride A mixed polyol component composed of 10.0 g of a polyol polymerized by adding an oxide and ethylene oxide, and 30.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to sorbitol and glycerin, respectively. 2.0 g of polysiloxane ether, 0.3 g of pentamethyldiethylenetriamine as a catalyst, 0.8 g of dimethylcycloamine and 0.3 g of tris (3-dimethylamino) propylhexahydrotriamine, and 10.3 g of tricresyl phosphate as a flame retardant. 0g and water 0.4g, HFC-365m A resin foam solution was prepared by adding 8.0 g of fc, and then 140.0 g of 4,4-diphenylmethane diisocyanate was mixed and reacted and foamed to produce a polyurethane foam.
Table 1 shows the methods for measuring the physical properties of the polyurethane foam for a heat insulating material of the present invention obtained in Example 1, and the results.

  The closed cell rate affects physical properties such as thermal conductivity, water vapor transmission rate, and moisture absorption rate of the polyurethane foam. Also, the closed cell rate can be a simple and quick measure of polyurethane foam quality control. The closed cell rate of ordinary polyurethane is about 90%, which indicates that the polyurethane foam produced in this example has a very high closed cell rate.

The microstructure of the polyurethane foam produced in this example was observed using an electron microscope. In the polyurethane foam, the foam is generated while small cells are formed by foaming. As shown in FIG. 1, it can be seen that the polyurethane foam of this example has small and uniform cells.
(Example 2)

25.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to pentaerythritol, 45.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to sucrose, and propylene oxide to glycerin 13.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to phthalic anhydride; and 14.0 g of a polyol polymerized by adding propylene oxide and ethylene oxide to phthalic anhydride, and glycerin substituted with a bromo group. To a mixed polyol component consisting of 4 g of a polyether polyol polymerized by adding propylene oxide, 2.0 g of a polysiloxane ether, 0.4 g of pentamethyldiethylenetriamine as a catalyst, 0.8 g of dimethylcyclohexylamine, and phosphorus as a flame retardant 3.0 g of tricresyl acid, 1.1 g of water, and HF The resin stock solution was adjusted by adding -365Mfc26.5G, by mixing 4,4-diphenylmethane diisocyanate 160.0g herein, by reacting foam was prepared rigid polyurethane foam.
Table 2 shows the physical properties of the polyurethane foam for a heat insulating material of the present invention obtained in Example 2.

（実施例３）

(Example 3)

A rigid polyurethane foam was produced in the same manner as in Example 2, except that 22.0 g of HFC-245fa was added instead of HFC-365mfc as a foaming agent and foaming was performed. After curing for one week, the surface was removed and various physical properties were measured.
Table 3 shows the physical properties of the polyurethane foam for a heat insulating material of the present invention obtained in Example 3.

1 is an electron micrograph showing a microstructure of a rigid polyurethane foam of the present invention produced using HFC-365mfc as a foaming agent.

Claims (8)

  Polymer type 4,4'-diphenylmethane diisocyanate, (a) 20-60% by weight of polyether polyol polymerized by adding propylene oxide and ethylene oxide to sorbitol, (b) propylene oxide in pentaerythritol 10 to 40% by weight of a polyether polyol polymerized by adding propylene oxide and ethylene oxide to (c) sucrose, and 10 to 30% by weight of a polyether polyol polymerized by adding (D) 5 to 20% by weight of a polyester polyol obtained by adding propylene oxide and ethylene oxide to phthalic anhydride and polymerizing it; and (e) adding propylene oxide and propylene oxide to glycerin substituted with a bromo group. Of polyol comprising 1 to 20% by weight of polyether polyol polymerized by adding So that the NCO / OH ratio is in the range of 1.0 to 2.0, and contains 1,3-pentafluorobutane, 1,3-pentafluoropropane or a mixture thereof as the hydrofluorocarbon-based blowing agent A rigid polyurethane foam composition, characterized in that:   The composition according to claim 1, wherein the polyol mixture has an average OH value of 380 to 510, and the diisocyanate has an average NCO% of 29 to 32.   The composition according to claim 1, further comprising 3 to 35 parts by weight of a hydrofluorocarbon-based blowing agent per 100 parts by weight of the polyol mixture.   The composition according to any one of claims 1 to 3, further comprising 5 to 30 parts by weight of a phosphorus-based flame retardant per 100 parts by weight of the polyol mixture.   The composition according to any one of claims 1 to 3, further comprising 0.1 to 2.0 parts by weight of an amine catalyst per 100 parts by weight of the polyol mixture.   The composition according to any one of claims 1 to 3, further comprising 0 to 2.0 parts by weight of a polysiloxane ether as a surfactant per 100 parts by weight of the polyol mixture.   The composition according to claim 3, further comprising water as an auxiliary blowing agent. A cold insulator using the polyurethane foam composition according to claim 1.

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