Polyurethane rigid foam and preparation method thereof

Abstract

The invention discloses a preparation method of polyurethane rigid foam, which comprises the following steps: uniformly mixing a foaming agent and combined polyether under the condition of pressurization according to the following raw materials in parts by weight: 100 parts of combined polyether, 14-32 parts of foaming agent and 130-170 parts of isocyanate, and uniformly mixing the foaming agent with the combined polyether under the condition of pressurization, so as to obtain the polyurethane rigid foam, wherein the foaming agent comprises cyclopentane and trimethylfluorosilane in a mass ratio of (0-12): (2-20); and fully mixing the obtained mixture with isocyanate through a high-pressure foaming machine to prepare the polyurethane high-hardness foam. The strength of the rigid polyurethane foam is improved, the heat conductivity coefficient of the rigid polyurethane foam is reduced, and meanwhile, an existing polyurethane foaming agent which is limited to be gradually stopped and high in cost can be replaced. While the performance of the rigid polyurethane foam is improved, the cost of the rigid polyurethane foam is effectively reduced.

Description

Technical Field

[0001] The invention relates to a polyurethane rigid foam and a preparation method thereof, and particularly relates to a polyurethane rigid foam comprising silicon-based molecules as a polyurethane rigid foam blowing agent. Background Art

[0002] As a polymer material, polyurethane rigid foam is widely used in refrigeration and insulation, building materials, automobiles, refrigerators and many other fields due to its light weight, high strength and low thermal conductivity. The most important raw material in the production process of polyurethane rigid foam is the blowing agent. Except for the pentane series, the polyurethane rigid foam blowing agents currently in use are all carbon-based substances containing fluorine and chlorine elements. Due to the destructive effect of such substances on the atmospheric ozone layer, governments of various countries have long signed the "Montreal Protocol" to restrict the production and use of such products, and China is also one of the signatories.

[0003] After 2008, with the implementation of the Montreal Protocol, chlorofluoroalkanes as polyurethane rigid foam blowing agents have been rapidly developed, and a series of chlorofluoroalkanes 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) have been developed as polyurethane rigid foam blowing agents. We have been looking for a new polyurethane rigid foam blowing agent that meets the requirements.

[0004] The polyurethane rigid foam blowing agent currently used in China is the second-generation chlorofluorocarbon blowing agent HCHC-141b (monochloroethylene), but the production and use of this polyurethane rigid foam blowing agent will be completely banned in 2025. The polyurethane rigid foam blowing agent used in developed countries such as Europe and the United States is the third-generation polyurethane rigid foam blowing agent HFC-245fa and HFC-365mfc, but the second and third generation blowing agents have high GWP (greenhouse effect potential) and cause certain damage to the atmospheric ozone layer, so they are gradually banned. The current mainstream polyurethane rigid foam blowing agents are the fourth-generation blowing agents LBA and OP1100, which are more environmentally friendly than the third-generation polyurethane rigid foam blowing agents, but the product price is expensive. In addition, pentane series products are an important supplement to polyurethane rigid foam blowing agents.

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

[0006] In addition, the prior art discloses the use of water as a polyurethane foaming agent, but due to the hydrogen bonding effect in its structure and its poor solubility in polyether / polyester polyols, it exists in the foaming system in the form of droplets, causing local overreaction and foaming. Using water as a polyurethane foaming agent will form more urea bonds in the polyurethane foam, affecting the strength and thermal insulation properties of the foam material. Summary of the invention

[0007] The present invention is to discover a new type of silicon-based molecule as a polyurethane rigid foam blowing agent, which is used to improve the strength of polyurethane rigid foam and reduce the thermal conductivity of polyurethane rigid foam, and can replace the existing polyurethane foaming agent which is restricted, phased out and expensive. While improving the performance of polyurethane rigid foam, the cost of polyurethane rigid foam is effectively reduced.

[0008] In order to achieve the above purpose, the present invention adopts the following technical scheme:

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

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

[0011] The above-mentioned composite polyether is composed of the following raw materials according to weight fraction: 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%. The polymeric isocyanates that can be used include PM-200, PM-2010 and PM-400 from Yantai Wanhua.

[0013] The polyether polyols of the present invention include the following: polyether polyol A has a hydroxyl value of 380-440 mgKOH / g, and is prepared by an addition reaction between sucrose as an initiator and propylene oxide, such as Wanhua Wanol R8238; polyether polyol B has a hydroxyl value of 200-260 mgKOH / g, and is prepared by an addition reaction between glycerol as an initiator and propylene oxide, such as Wanol S3007; polyether polyol C has a hydroxyl value of 450-600 mgKOH / g, and is prepared by an addition reaction between toluene diamine as an initiator and propylene oxide and ethylene oxide, and the ratio of propylene oxide to ethylene oxide is 90-50:10-50, such as Wanhua Wanol R4040; polyester polyol D has a hydroxyl value of 300-360 mgKOH / g, and is synthesized by condensation polymerization of phthalic anhydride, terephthalic acid and diethylene glycol, such as Wanhua 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 surfactant used in the present invention is a silicon surfactant, such as AK8860 and AK8830 of Nanjing Demeishi Chemical Co., Ltd., B84848 and B8545 of Evonik, etc. These surfactants have strong nucleation effect and good stability, which are conducive to reducing the thermal conductivity of the foam.

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

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

[0017] 1) uniformly mixing a polyether polyol, a surfactant, a catalyst and water to obtain a composite polyether;

[0018] 2) adding trimethylfluorosilane or trimethylfluorosilane and cyclopentane to the combined polyether prepared in step 1, mixing evenly, and foaming to obtain a polyurethane rigid foam.

[0019] The foaming process adopts a foaming machine to mix the combined polyether polyol and isocyanate containing trimethylfluorosilane or a mixed foaming agent of trimethylfluorosilane and cyclopentane, at a temperature of 20±2°C and a pressure of 120±20 bar, and pour it into a mold at a mold temperature of 45±5°C. After curing for 3-6 minutes, demoulding is performed to obtain a polyurethane rigid foam.

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

[0021] 1) The foaming agent used in the present invention has no destructive effect on the ozone layer, ODP=0, and a low GWP value.

[0022] 2) When trimethylfluorosilane is used alone as a foaming agent, trimethylfluorosilane has a low boiling point and good fluidity during the foaming process. The obtained foam has good compression strength and dimensional stability. At the same time, it has a large molecular weight, low gas phase thermal conductivity, and better foam insulation performance.

[0023] 3) When the blowing agents cyclopentane and trimethylfluorosilane are mixed as blowing agents, they can complement each other in terms of performance and cost. Cyclopentane is cheap, has a small molecular weight, and has a strong foaming effect, but the thermal conductivity of the foam is high, and it is extremely flammable, and the process safety requirements are high. By appropriately increasing the amount of toluene diamine polyether C or polyester polyol D, the thermal conductivity of the foam is reduced and the thermal insulation performance is improved. At the same time, due to the low boiling point and good fluidity of trimethylfluorosilane, it can also be used in a faster-reacting foaming formula to obtain a lower thermal conductivity. By optimizing the combination of the components of the polyether polyol, a rigid polyurethane foam that meets different usage requirements can be prepared. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are further described below in conjunction with examples. However, the present invention is not limited to the examples listed, and should also include any other known changes within the scope of the rights claimed by the present invention. The polyether polyol, surfactant, catalyst and water are uniformly mixed, and then mixed with the blowing agent. Finally, the combined polyether containing the blowing agent and isocyanate are mixed in a high-pressure foaming machine to prepare a polyurethane rigid foam.

[0025] The polyether polyol used in the present invention is:

[0026] Polyether polyol A sucrose is used as the initiator, and the hydroxyl value is 430 mgKOH / g;

[0027] Polyether polyol B glycerol is used as the initiator, and the hydroxyl value is 240 mgKOH / g;

[0028] Polyether polyol C toluenediamine is used as the initiator, and the hydroxyl value is 450 mgKOH / g;

[0029] Polyester polyol D is prepared by condensation of phthalic anhydride, terephthalic acid and DEG, and has a hydroxyl value of 315 mgKOH / g.

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

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

[0032] Silicone oil surfactant AK8805, AK8830, Nanjing Meside Co., Ltd.

[0033] Cyclopentane, Jilin Longshan

[0034] Trimethylfluorosilane, Hubei Changxinsheng

[0035] Test Equipment

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

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

[0038] Dimensional stability test: Dongguan Aipei Experimental Instrument Co., Ltd., programmable constant temperature test chamber

[0039] Dimensional test: Mitutoyo Precision Measuring Instruments (Shanghai) Co., Ltd., vernier caliper

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

[0041] Characterization methods

[0042] The foam sample was prepared by using a mold cavity with a length of 200 cm, a width of 20 cm, a thickness of 5 cm, a mold temperature of 45 ± 5 ° C, vertical pouring and foaming, and an overall density of 37 kg / m 3 The foam was taken out after curing in the mold for 6 minutes. After curing at room temperature for 24 hours, the foam was cut into standard size specimens using an electric saw for performance testing.

[0043] The results of polyurethane foam density, compression strength, thermal conductivity, etc. are all measured according to national standards:

[0044] Foam thermal conductivity test is in accordance with the standard: GB / T 10295-2008, the hot and cold plate temperatures are set at 2°C and 18°C

[0045] Foam core density test according to standard: GB / T 6343-2009

[0046] Foam compression strength test according to standard: GB / T 8813-2008

[0047] Foam dimensional stability test according to standard: GB / T 8811-2008

[0048] Table 1

[0049]

[0050]

[0051] Since trimethylfluorosilane has a low boiling point, the foam surface crust is thin and the vapor pressure inside the pores is high. Under the condition of the same overall density, the density and strength of the foam core are greatly improved.

[0052] Trimethylfluorosilane has fast initiation and good fluidity, but slightly more bubble defects. In view of these characteristics, the catalyst was added to adjust the gel time, and the effects of different reactivity on demolding, thermal conductivity and fluidity were studied. The experimental results are shown in Table 2.

[0053] Table 2

[0054]

[0055] From Table 2, it can be concluded that as the gel reaction speed increases, the thermal conductivity becomes lower and lower, but the influence of fluidity is not very obvious. This is because as time increases, the viscosity of the reactants increases more rapidly, making the cell wall more stable, reducing the possibility of bubble merging and bubble breaking. At the same time, due to the rapid solidification of the reactants, the expansion rate of the cells decreases, and the size of the cells is smaller, resulting in a rapid decrease in thermal conductivity. From the results, the faster the reaction speed, the greater the change in thermal conductivity.

Claims

1. A polyurethane rigid foam, comprising various raw material ratios according to weight fraction: combined polyether: foaming agent: isocyanate = 100:14-32:130-170, wherein the foaming agent comprises cyclopentane and trimethylsilylfluoride in a mass ratio of 0-12:2-20.

2. The polyurethane rigid foam according to claim 1, characterized in that The composite polyether is prepared by the following raw materials in weight fractions Composition: polyether polyol: surfactant: catalyst: water = 100: 1.5-4.0: 1.5-4.5: 1-3.

3. The polyurethane rigid foam according to claim 1 or 2, characterized in that: The isocyanate is polymeric MDI (polymethylene polyphenyl polyisocyanate) with an NCO content of 30-32%, such as PM-200, PM-2010 and PM-400 from Wanhua.

4. The polyurethane rigid foam according to claim 2, characterized in that Polyether polyols include the following: Polyether polyol A has a hydroxyl value of 380-440 mgKOH / g, and is obtained by an addition reaction between sucrose and propylene oxide as an initiator, such as Wanhua Wanol R8238; Polyether polyol B has a hydroxyl value of 200-260 mgKOH / g, and is obtained by an addition reaction between glycerol and propylene oxide as an initiator, such as Wanol S3007; the hydroxyl value of polyether polyol C is 450-600 mgKOH / g, and it is prepared by addition reaction of toluenediamine as an initiator with propylene oxide and ethylene oxide, and the ratio of propylene oxide to ethylene oxide is 90-50:10-50, such as Wanhua Wanol R4040; the hydroxyl value of polyester polyol D is 300-360 mgKOH / g, and it is synthesized by condensation of phthalic anhydride, terephthalic acid and diethylene glycol, such as Wanhua Wanthanol WHP-3220; preferably, the amount of 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.

5. The polyurethane rigid foam according to any one of claims 2 to 4, characterized in that: The surfactant is a silicon surfactant, such as AK8860 and AK8830 produced by Nanjing Demeishi Chemical Co., Ltd. and B84848 and B8545 produced by Evonik.

6. The polyurethane rigid foam according to any one of claims 2 to 5, characterized in that: The catalyst is one or more of triethylenediamine, N,N-dimethylcyclohexylamine, pentamethyldiethylenetriamine, hexahydrotriazine and potassium acetate.

7. A method for preparing a rigid polyurethane foam according to any one of claims 1 to 6, comprising the following steps: 1) uniformly mixing a polyether polyol, a surfactant, a catalyst and water to obtain a composite polyether; 2) adding trimethylfluorosilane or trimethylfluorosilane and cyclopentane to the combined polyether prepared in step 1, mixing evenly, and foaming to obtain a polyurethane rigid foam.

8. The preparation method according to claim 7, characterized in that: The foaming process uses a foaming machine to mix the combined polyether polyol and isocyanate of the mixed foaming agent at a temperature of 20±2° C. and a pressure of 120±20 bar, pours the mixture into a mold at a mold temperature of 45±5° C., and then releases the mold after curing for 3-6 minutes to obtain a polyurethane rigid foam.

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