A polyurethane rigid foam and a method for producing the same

Abstract

The application discloses a polyurethane rigid foam preparation method, and various raw materials are proportioned according to weight fractions as follows: combined polyether: foaming agent: isocyanate = 100: 14-32: 130-170, wherein the foaming agent comprises cyclopentane and trimethylfluorosilane in a mass ratio of 0-12:2-20; the foaming agent is uniformly mixed with the combined polyether under pressure; and the obtained mixture is fully mixed with isocyanate by a high-pressure foaming machine to prepare polyurethane high-rigid foam. The polyurethane rigid foam has improved strength and reduced thermal conductivity, and can replace existing polyurethane foaming agents which are gradually stopped using due to restrictions and are expensive. While the performance of the polyurethane rigid foam is improved, the cost of the polyurethane rigid foam is effectively reduced.

Description

Technical Field

[0001] This invention relates to a rigid polyurethane foam and its preparation method, and specifically to a rigid polyurethane foam containing silicon-based molecules as a rigid polyurethane foam blowing agent. Background Technology

[0002] Rigid polyurethane foam, as a polymer material, is widely used in many fields such as refrigeration insulation, building materials, automobiles, and refrigerators due to its light weight, high strength, and low thermal conductivity. The most important raw material in the production process of rigid polyurethane foam is the foaming agent. Currently, the foaming agents used in rigid polyurethane foam, apart from pentane series, are all carbon-based substances containing fluorine and chlorine elements. Because of the destructive effect of these substances on the atmospheric ozone layer, governments around the world have long signed the Montreal Protocol to restrict the production and use of such products; China is also a signatory country.

[0003] Following the implementation of the Montreal Protocol in 2008, the use of chlorofluorocarbons (CFCs) as blowing agents for rigid polyurethane foams rapidly evolved, leading to the development of a series of CFCs such as HFC-245fa (1,1,1,3,3-pentafluoropropane), HFC-365mfc (1,1,1,3,3-pentafluorobutane), LBA (monochlorotrifluoropropane), and OP1100 (1,1,1,4,4,4-hexafluoro-2-butene). A new, suitable CFC blowing agent for rigid polyurethane foams has been continuously sought.

[0004] Currently, the second-generation chlorofluorocarbon (CFC) blowing agent still used in China is HCHC-141b (dichlorofluoroethane), but its production and use will be completely banned by 2025. Developed countries in Europe and America use third-generation blowing agents HFC-245fa and HFC-365mfc, but both second and third-generation blowing agents have high GWP (global warming potential) and cause some damage to the ozone layer, thus they are being phased out. The mainstream rigid polyurethane foam blowing agents are now the fourth-generation LBA and OP1100, which are more environmentally friendly than third-generation agents, but are expensive. In addition, pentane series products serve as an important supplement to rigid polyurethane foam blowing agents.

[0005] Existing technologies disclose the use of carbon dioxide (CO2) as a polyurethane blowing agent, but due to its poor solubility in raw materials MDI and polyether / polyester polyols and the escape of CO2 gas, it cannot be uniformly dispersed in the foaming composition.

[0006] Furthermore, existing technologies disclose the use of water as a polyurethane blowing agent. However, due to the hydrogen bonding in its structure and its poor solubility in polyether / polyester polyols, water exists in the foaming system as microdroplets, causing localized overreaction and foaming. Using water as a polyurethane blowing agent will result in the formation of more urea bonds in the polyurethane foam, affecting the strength and thermal insulation performance of the foam material. Summary of the Invention

[0007] The present invention relates to the discovery of a novel silicon-based molecule as a blowing agent for rigid polyurethane foam, which improves the strength of rigid polyurethane foam, reduces its thermal conductivity, and can replace existing polyurethane blowing agents that are restricted from use and are expensive. This effectively reduces the cost of rigid polyurethane foam while enhancing its performance.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A rigid polyurethane foam, comprising various raw materials in the following weight fraction ratio: polyether: blowing agent: isocyanate = 100:14-32:130-170, wherein the blowing agent comprises cyclopentane and trimethylfluorosilane in a mass ratio of 0-12:2-20.

[0010] The mass ratio of cyclopentane in the foaming agent is, for example, 0, 1, 3, 5, 7, 9, or 11, and the mass ratio of trimethylfluorosilane is, for example, 2, 4, 6, 8, 10, 12, 14, 16, or 18. The mass ratio includes any combination of the above masses.

[0011] The above-mentioned polyether composition is composed of the following raw materials in weight fractions: polyether polyol: surfactant: catalyst: water = 100: 1.5-4.0: 1.5-4.5: 1-3.

[0012] The isocyanate is polymeric MDI (polymethylene polyphenyl polyisocyanate) with an NCO content of 30-32%. Suitable polymeric isocyanates include PM-200, PM-2010, and PM-400 from Yantai Wanhua.

[0013] The polyether polyols of this invention include the following: Polyether polyol A with a hydroxyl value of 380-440 mgKOH / g is prepared by an addition reaction of sucrose with propylene oxide, for example, Wanol R8238; Polyether polyol B with a hydroxyl value of 200-260 mgKOH / g is prepared by an addition reaction of glycerol with propylene oxide, for example, Wanol S3007; Polyether polyol C with a hydroxyl value of 450-600 mgKOH / g is prepared by an addition reaction of toluene diamine with propylene oxide and ethylene oxide, wherein the ratio of propylene oxide to ethylene oxide is 90-50:10-50, for example, Wanol. R4040; Polyester polyol D has a hydroxyl value of 300-360 mg KOH / g, and is obtained by condensation polymerization of phthalic anhydride and terephthalic acid with diethylene glycol, such as Wanthanol WHP-3220; The amount of each polyether polyol is 30-50 parts of polyether polyol A, 5-15 parts of polyether polyol B, 10-45 parts of polyether polyol C, and 0-15 parts of polyester polyol D.

[0014] The surfactants used in this invention are silicone surfactants, such as AK8860 and AK8830 from Nanjing Demeishichuang Chemical Co., Ltd., and B84848 and B8545 from Evonik. These surfactants have strong nucleation properties and good stability, which helps to reduce the thermal conductivity of the foam.

[0015] The catalyst used in this invention is one or more of triethylenediamine, N,N-dimethylcyclohexylamine, pentamethyldivinyltriamine, hexahydrotriazine, and potassium acetate.

[0016] On the other hand, the present invention provides a method for preparing rigid polyurethane foam, the method comprising the following steps:

[0017] 1) Mix polyether polyol, surfactant, catalyst and water evenly to obtain composite polyether;

[0018] 2) Add trimethylfluorosilane or trimethylfluorosilane and cyclopentane to the polyether combination prepared in step 1, mix evenly, and foam to obtain rigid polyurethane foam.

[0019] The foaming process involves using a foaming machine to mix the above-mentioned combination polyether polyol and isocyanate containing trimethylfluorosilane or a mixture of trimethylfluorosilane and cyclopentane as foaming agents, controlling the temperature at 20±2℃ and the pressure at 120±20 bar, and pouring it into a mold at a temperature of 45±5℃. After curing for 3-6 minutes, the mixture is demolded to obtain rigid polyurethane foam.

[0020] The rigid polyurethane foam prepared by this invention has the following advantages:

[0021] 1) The foaming agent used in this invention has no ozone-depleting effect, ODP=0, and low GWP value.

[0022] 2) When trimethylfluorosilane is used alone as a foaming agent, its low boiling point results in good fluidity during the foaming process, leading to good compressive strength and dimensional stability of the resulting foam. At the same time, its large molecular weight and low gas phase thermal conductivity result in better foam insulation performance.

[0023] 3) When using a mixture of cyclopentane and trimethylfluorosilane as blowing agents, their performance and cost can complement each other. Cyclopentane is inexpensive, has a small molecular weight, and strong foaming effect, but the foam has a high thermal conductivity and is extremely flammable, requiring high process safety. By appropriately increasing the amount of toluene diamine polyether C or polyester polyol D, the thermal conductivity of the foam can be reduced, improving its insulation performance. Meanwhile, due to its low boiling point and good fluidity, trimethylfluorosilane can also be used in faster-reacting foaming formulations to obtain even lower thermal conductivity. Optimizing the combination of polyether polyol components can produce rigid polyurethane foams that meet different application requirements. Detailed implementation method:

[0024] The embodiments of the present invention are further illustrated below with reference to examples. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention. Polyether polyol, surfactant, catalyst and water are mixed evenly, and then mixed evenly with a foaming agent. Finally, the polyether combination containing the foaming agent and isocyanate are mixed in a high-pressure foaming machine to prepare rigid polyurethane foam.

[0025] The polyether polyol used in this invention is:

[0026] Polyether polyol A sucrose was used as the initiator, with a hydroxyl value of 430 mg KOH / g;

[0027] Polyether polyol B glycerol was used as the initiator, with a hydroxyl value of 240 mg KOH / g;

[0028] Polyether polyol C toluene diamine was used as the initiator, with a hydroxyl value of 450 mg KOH / g;

[0029] It is prepared by condensation of polyester polyol D, phthalic anhydride and terephthalic acid with DEG, and has a hydroxyl value of 315 mg KOH / g.

[0030] Polyether polyols, polyester polyols, PM200, Wanhua Chemical Co., Ltd.;

[0031] N,N'-Dimethylcyclohexylamine (DMCHA), pentamethyldiethyltriamine (PMDETA), hexahydrotriazine, silicone oil surfactants B8545 and B84848, Evonik Specialty Chemicals (Shanghai) Co., Ltd.

[0032] Silicone oil surfactants AK8805 and AK8830, Nanjing Meiside Co., Ltd.

[0033] Cyclopentane, Jilin Chemical Longshan

[0034] Trimethylfluorosilane, Hubei Changxinsheng

[0035] Testing instruments

[0036] Compression strength test: ZwickRoell Z005 universal testing machine

[0037] Thermal conductivity test: EKO Corporation, HC-074-200 thermal conductivity meter

[0038] Dimensional stability testing: Dongguan Aipei Experimental Instrument Co., Ltd., Programmable Constant Temperature Test Chamber

[0039] Size testing: Mitutoyo Precision Measuring Instruments (Shanghai) Co., Ltd., Vernier calipers

[0040] Quality testing: Mettler Toledo Instruments (Shanghai) Co., Ltd., ML3002 / 02 electronic balance

[0041] Characterization methods

[0042] The foam sample was prepared using a mold cavity with dimensions of 200cm in length, 20cm in width, and 5cm in thickness. The mold temperature was 45±5℃. Vertical pouring was used for foaming, and the overall density was 37kg / m³. 3 After the foam has cured in the mold for 6 minutes, it is removed and cured at room temperature for 24 hours. Then, the foam is cut into standard-sized samples using an electric saw for performance testing.

[0043] The polyurethane foam density, compressive strength, thermal conductivity, and other parameters were all measured according to national standards.

[0044] The thermal conductivity of the foam was tested according to standard GB / T 10295-2008, with the hot and cold plate temperatures set at 2℃ and 18℃.

[0045] The foam core density test shall be conducted in accordance with the standard: GB / T 6343-2009

[0046] The foam compressive strength test shall be conducted in accordance with the standard: GB / T 8813-2008

[0047] Foam dimensional stability testing was conducted according to standard GB / T 8811-2008.

[0048] Table 1

[0049]

[0050]

[0051] Because trimethylfluorosilane has a low boiling point, it forms a thin skin on the foam surface and a high vapor pressure inside the cells. Under the same overall density, the density and strength of the foam core are greatly improved.

[0052] Trimethylfluorosilane has a fast emulsification rate and good fluidity, but it has a slightly higher number of bubble defects. To address these characteristics, a catalyst was added to adjust the gelation time. The effects of different reactivity on demolding, thermal conductivity, and fluidity were investigated. The experimental results are shown in Table 2.

[0053] Table 2

[0054]

[0055] Table 2 shows that as the gelation reaction rate increases, the thermal conductivity decreases, while the effect on flowability is not significant. This is because the viscosity of the reactants increases more rapidly over time, making the cell walls more stable and reducing the possibility of cell coalescence and breakage. Simultaneously, the rapid solidification of the reactants reduces the cell expansion rate, resulting in smaller cell sizes and a rapid decrease in thermal conductivity. The results indicate that the faster the reaction rate, the greater the change in thermal conductivity.

Claims

1. A rigid polyurethane foam, comprising the following raw materials in the following weight percentages: polyether: blowing agent: isocyanate = 100:14-32:130-170, wherein the blowing agent comprises cyclopentane and trimethylfluorosilane in a mass ratio of 0-12:2-20, and the polyether is composed of the following raw materials in the following weight percentages: polyether polyol: surfactant: catalyst: water = 100:1.5-4.0:1.5-4.5:1-3.

2. The rigid polyurethane foam as described in claim 1, characterized in that, The isocyanate is polymeric MDI with an NCO content of 30-32%.

3. The rigid polyurethane foam as described in claim 2, characterized in that, The isocyanate is selected from Wanhua's PM-200, PM-2010 and PM-400.

4. The rigid polyurethane foam as described in claim 1, characterized in that, Polyether polyols include the following: Polyether polyol A has a hydroxyl value of 380-440 mg KOH / g, and is prepared by addition reaction of sucrose with propylene oxide as an initiator; Polyether polyol B has a hydroxyl value of 200-260 mg KOH / g, and is prepared by addition reaction of glycerol with propylene oxide as an initiator; Polyether polyol C has a hydroxyl value of 450-600 mg KOH / g, and is prepared by addition reaction of toluene diamine with propylene oxide and ethylene oxide as an initiator, with a propylene oxide to ethylene oxide ratio of 90-50:10-50; Polyester polyol D has a hydroxyl value of 300-360 mg KOH / g, and is obtained by condensation polymerization of phthalic anhydride and terephthalic acid with diethylene glycol; The amount of polyether polyol used is 30-50 parts of polyether polyol A, 5-15 parts of polyether polyol B, 10-45 parts of polyether polyol C, and 0-15 parts of polyester polyol D.

5. The rigid polyurethane foam as described in claim 1, characterized in that, Polyether polyols include the following types: Polyether polyol A is Wanol R8238; Polyether polyol B is Wanol S3007; Polyether polyol C is Wanol R4040; Polyester polyol D is Wanthanol WHP-3220.

6. The rigid polyurethane foam as described in claim 1, characterized in that, The surfactant is a silicone-based surfactant.

7. The rigid polyurethane foam as described in claim 6, characterized in that, The surfactants are AK8860 and AK8830 from Nanjing Demeishichuang Chemical Co., Ltd., and B8545 from Evonik.

8. The rigid polyurethane foam as described in claim 1, characterized in that, The catalyst is one or more of triethylenediamine, N,N-dimethylcyclohexylamine, pentamethyldivinyltriamine, hexahydrotriazine, and potassium acetate.

9. The method for preparing rigid polyurethane foam according to any one of claims 1-8, wherein the method comprises the following steps: 1) Mix polyether polyol, surfactant, catalyst and water evenly to obtain composite polyether; 2) Add trimethylfluorosilane or trimethylfluorosilane and cyclopentane to the polyether combination prepared in step 1, mix evenly, and foam to obtain rigid polyurethane foam.

10. The preparation method according to claim 9, characterized in that, The foaming process involves mixing a combination of polyether polyol and isocyanate with a foaming agent using a foaming machine at a temperature controlled at 20±2℃ and a pressure of 120±20 bar. The mixture is then poured into a mold at a temperature of 45±5℃ and cured for 3-6 minutes before demolding to obtain rigid polyurethane foam.

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