CN111875838A

CN111875838A - Preparation method of polyurethane foam

Info

Publication number: CN111875838A
Application number: CN202010724894.4A
Authority: CN
Inventors: 胡远洲; 董洋; 沈保星; 黄立祥
Original assignee: Shanghai Fleetguard Filter Co ltd
Current assignee: Shanghai Fleetguard Filter Co ltd
Priority date: 2020-07-24
Filing date: 2020-07-24
Publication date: 2020-11-03

Abstract

The invention provides a preparation method of polyurethane foam. The preparation method of the polyurethane foam comprises the following steps: (1) mixing and stirring polyether polyol, a foaming agent, a catalyst and a foam stabilizer, introducing gas, and maintaining pressure to obtain a mixture; (2) and (2) mixing the mixture obtained in the step (1) with isocyanate for reaction to obtain polyurethane foam. According to the preparation method of the polyurethane foam, the number of bubble nuclei and the distribution of the bubble nuclei in the solution are controlled, so that the gas adsorption quantity is increased, the gas utilization rate is improved, and the bubbles are uniformly distributed, so that the prepared polyurethane foam has fine and uniform bubbles, low density and excellent mechanical property.

Description

Preparation method of polyurethane foam

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a preparation method of polyurethane foam.

Background

The polyurethane foam has the characteristics of high sound absorption coefficient, small density, high elasticity, easiness in processing, simplicity and convenience in construction and the like, and can be used as a filtering material in air conditioning equipment, a ventilation plate in a building, sound insulation equipment or a sound absorption material in the building. In which attention is increasingly paid as a sound absorbing and noise reducing material. However, at present, polyurethane foam products have the problems of coarse and uneven cells, and on one hand, the products have large brittleness, low toughness and poor performance; on the other hand, the product has high density and high material consumption.

Generally, the current methods for foaming polyurethane foams are: stirring and mixing the polyol, the isocyanate and other auxiliary agents by a glue injection machine for reaction to generate CO₂，CO₂Dissolved in solution, CO as the reaction proceeds₂The amount is increased, the solution is in a saturated state, and CO₂The overflow forms initial bubbles, which are dispersed in the solution, and the subsequently generated gas is adsorbed on the surface of the initial bubbles, which are bubble nuclei. Countless bubbles are formed due to continuous generation and expansion of the bubbles, so that the volume and the surface area of a foam system are increased, the thickness of the bubble walls is reduced, the foam system is unstable, the formed bubbles can continue to expand, or the bubbles are combined, or the bubbles collapse and burst, and the foam is stabilized by a foam stabilizer and control of process conditions.

CN104774316A discloses a polyurethane all-water foaming material and a preparation method thereof, wherein the material consists of a material A and a material B; the material A comprises, by mass, 38-53.5% of polyether, 2-5% of an emulsifier, 3-8% of a high-efficiency flame retardant, 1-2% of a foam stabilizer, 0.5-2% of a strongly foaming reactive catalyst and 40-45% of water; the material B comprises 80-90% of polyisocyanate and 10-20% of flame retardant by mass percent, and is prepared by adding the components of the material A into a reaction vessel to be uniformly mixed, adding the material B under stirring, continuously stirring uniformly, pouring the mixed solution into a mould to be foamed after the mixed solution is stirred to be whitish, and adding a strongly foamed reactive catalyst to foam. However, the number of bubble nuclei is too small during foam molding, and the gas adsorption amount is small, resulting in a problem of low gas utilization rate.

CN109575213A provides a dry foaming polyurethane resin, which is prepared from polyalcohol, chain extender, diphenylmethane diisocyanate and N, N-dimethylformamide. The preparation method of the dry foaming polyurethane resin provided by the invention comprises two methods, wherein the one-step method is to directly mix the preparation raw materials for tackifying and diluting, and the dry foaming polyurethane resin can be obtained by controlling the raw material proportion and the viscosity and solid content of the final system; the two-step method is that firstly, diphenylmethane diisocyanate and polyol are prepolymerized to obtain a prepolymer, and then the dry-process foaming polyurethane resin is obtained through chain extension, and the foaming polyurethane resin obtained through dry-process foaming has thick and uneven foam holes, small quantity and poor economic benefit.

Therefore, the development of a polyurethane foam foaming process which increases the number of bubble nuclei and improves the gas utilization rate is the focus of current research in the field.

Disclosure of Invention

In view of the shortcomings of the prior art, the invention aims to provide a preparation method of polyurethane foam. According to the preparation method of the polyurethane foam, the number of the bubble nuclei and the distribution of the bubble nuclei in the solution are controlled, so that the gas adsorption quantity is increased, the gas utilization rate is improved, and the bubbles are uniformly distributed, so that the prepared polyurethane foam has fine and uniform bubbles, low density and excellent performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a method of preparing a polyurethane foam, comprising the steps of:

(1) mixing and stirring polyether polyol, a foaming agent, a catalyst and a foam stabilizer, introducing gas, and maintaining pressure to obtain a mixture;

(2) and (2) mixing the mixture obtained in the step (1) with isocyanate for reaction to obtain polyurethane foam.

In the invention, polyether polyol, a foaming agent, a catalyst and a foam stabilizer are mixed, gas is introduced into the mixture, and pressure maintaining treatment is carried out on the gas, so that the initial gas is dispersed in the mixture as bubble nuclei, thereby effectively increasing the number of the bubble nuclei; the mixture is stirred to ensure that the cell nuclei are uniformly distributed in the mixture. The preparation method can control the ratio of the total amount of the supersaturated gas to the number of bubble nuclei in the mixture, increase the number of the bubble nuclei, and reduce the number of bubbles obtained by a single bubble nucleus, so that the obtained foam cells are fine and uniform.

Preferably, the mixing and stirring speed in step (1) is 90-110r/min, such as 90r/min, 92r/min, 94r/min, 96r/min, 98r/min, 100r/min, 102r/min, 104r/min, 106r/min, 108r/min, 110 r/min.

The mixing and stirring speed of the invention is 90-110r/min, which is beneficial to the uniform distribution of bubble nuclei in the system, if the speed is too slow, the bubble nuclei can not be uniformly dispersed in the system, and the bubble distribution is nonuniform due to concentration, if the speed is too fast, the material temperature is excessively increased, the reaction speed is accelerated, the fluidity of the material is poor, and the foam density distribution is poor.

Preferably, the time for introducing the gas in the step (1) is more than 200s, for example, 200s, 220s, 240s, 260s, 280s, 300s, 320s, 340s, 380s, 400s, 450s, 500s, etc., preferably 280-320 s.

Preferably, the flow rate of the introduced gas in the step (1) is 300-400L/h, such as 300L/h, 310L/h, 320L/h, 330L/h, 340L/h, 350L/h, 360L/h, 370L/h, 380L/h, 400L/h, and preferably 350L/h.

The invention controls the gas introduction amount by controlling the gas introduction time and flow rate, the initial gases are dispersed in the mixture as bubble nuclei, and finally the number of the bubble nuclei in the solution during foaming is controlled, thereby increasing the gas adsorption amount and improving the gas utilization rate.

Preferably, the humidity of the gas in step (1) is 0.05% or less (sufficiently dry gas is introduced), and may be, for example, 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or the like.

Preferably, the gas in step (1) is air.

Preferably, the pressure of the dwell pressure in step (1) is 1-2bar, and may be, for example, 1bar, 1.1bar, 1.2bar, 1.3bar, 1.4bar, 1.5bar, 1.6bar, 1.7bar, 1.8bar, 1.9bar, 2bar, etc.

In the invention, the number of bubble cores is further ensured to be in a certain range by controlling the pressure of pressure maintaining so as to further ensure that a foam product with fine and uniform foam holes is obtained.

Preferably, the mass ratio of the polyether polyol, the foaming agent, the catalyst and the foam stabilizer in the step (1) is (97-99.5): (0.6-1.0): (0.25-0.5): (0.08-0.11);

wherein "97 to 99.5" may be 97, 97.5, 98, 98.5, 99, 99.5, etc., for example;

wherein "0.6 to 1.0" may be, for example, 0.6, 0.7, 0.8, 0.9, 1.0, etc.;

wherein "0.25 to 0.5" may be, for example, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.;

here, "0.08 to 0.11" may be, for example, 0.08, 0.09, 0.10, 0.11, or the like.

Preferably, the mass ratio of the mixture in the step (1) to the isocyanate in the step (2) is 100 (41-47), and can be 100:41, 100:42, 100:43, 100:44, 100:45, 100:46 and 100: 47.

Preferably, the polyether polyol in step (1) has a functionality of 2 to 4, which may be, for example, 2, 3, 4, and a hydroxyl number of 15 to 120mg KOH/g, which may be, for example, 15mg KOH/g, 20mg KOH/g, 30mg KOH/g, 40mg KOH/g, 50mg KOH/g, 60mg KOH/g, 70mg KOH/g, 80mg KOH/g, 90mg KOH/g, 100mg KOH/g, 110mg KOH/g, 120mg KOH/g, and the like.

Preferably, the polyether polyol in step (1) has a number average molecular weight of 2000-.

Preferably, the blowing agent in step (1) is water.

Preferably, the catalyst in step (1) is stannous octoate.

Preferably, the foam stabilizer in step (1) is silicone oil.

Preferably, the mixture in step (1) further comprises a chain extender.

Preferably, the chain extender is triethanolamine.

Preferably, the chain extender is added in an amount of 0.18 to 0.25% by mass of the total mass of the mixture, and may be, for example, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, etc.

Preferably, the isocyanate in step (2) is diphenylmethane diisocyanate.

Preferably, the temperature of the mixing reaction in the step (2) is 35-65 ℃, for example, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃ and the like, and the time of the mixing reaction is 16-24h, for example, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h and the like.

Preferably, the preparation method of the polyurethane foam comprises the following steps:

(1) mixing and stirring polyether polyol, a foaming agent, a catalyst and a foam stabilizer in a mass ratio of (97-99.5): (0.6-1.0): 0.25-0.5): 0.08-0.11) at a rotating speed of 90-110r/min, introducing gas with the humidity of below 0.05% for 300s at a flow rate of 300-400L/h, and maintaining the pressure, wherein the pressure for maintaining the pressure is 1-2bar, so as to obtain a mixture;

(2) mixing the mixture obtained in the step (1) with the mass ratio of 100 (41-47) with isocyanate, and reacting for 16-24h at 35-65 ℃ to obtain the polyurethane foam.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the preparation method of the polyurethane foam, the number of bubble cores and the distribution of the bubble cores are controlled, so that the gas adsorption quantity is increased, the gas utilization rate is improved, and the bubbles are uniformly distributed, so that the prepared polyurethane foam has fine and uniform cells, low density and excellent performance;

(2) the invention provides polyurethane foams having a foam density of 240-310kg/m³The foam compression strength is 70-110kPa, and the tearing strength is 1.8-2.5 N.mm^-1。

Drawings

FIG. 1 is a sectional view of the polyurethane foam prepared in example 1.

FIG. 2 is a sectional view of the polyurethane foam prepared in example 2.

FIG. 3 is a sectional view of the polyurethane foam prepared in example 3.

FIG. 4 is a sectional view of the polyurethane foam prepared in example 4.

FIG. 5 is a sectional view of the polyurethane foam prepared in example 5.

FIG. 6 is a sectional view of the polyurethane foam prepared in example 6.

FIG. 7 is a sectional view of the polyurethane foam prepared in example 7.

FIG. 8 is a sectional view of the polyurethane foam prepared in example 8.

FIG. 9 is a sectional view of the polyurethane foam prepared in example 9.

FIG. 10 is a sectional view of the polyurethane foam prepared in comparative example 1.

FIG. 11 is a sectional view of the polyurethane foam prepared in comparative example 2.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The sources of the components in the following examples and comparative examples are as follows: polyether polyols were purchased from (manufacturer: hensmei, brand:

YO 40067), isocyanates commercially available from (manufacturer: hensmei, brand:

3209)。

example 1

This example provides a method of preparing a polyurethane foam, comprising the steps of:

(1) mixing and stirring 98.65g of polyether polyol, 0.40g of water, 0.3g of stannous octoate, 0.10g of silicone oil and 0.20g of triethanolamine at the rotating speed of 99r/min, introducing air with the humidity of 0.01% for 300s at the flow rate of 350L/h, and maintaining the pressure, wherein the pressure for maintaining the pressure is 1.5bar, so as to obtain a mixture;

(2) adding 44g of diphenylmethane diisocyanate to the mixture obtained in the step (1), mixing, and reacting at 50 ℃ for 20 hours to obtain polyurethane foam.

FIG. 1 is a sectional view of the polyurethane foam prepared in example 1. As shown in FIG. 1, the polyurethane foam obtained by cutting and observing the foam state formed by the cut surface is found to have good foaming effect, more cells, fine and dense cells and uniform density distribution.

Example 2

(1) mixing and stirring 98.54g of polyether polyol, 0.30g of water, 0.50g of stannous octoate, 0.11g of silicone oil and 0.18g of triethanolamine at the rotating speed of 100r/min, introducing 320s of air with the humidity of 0.02% at the flow rate of 340L/h, and maintaining the pressure, wherein the pressure for maintaining the pressure is 1.2bar, so as to obtain a mixture;

(2) 41g of diphenylmethane diisocyanate was added to the mixture obtained in step (1) and mixed, followed by reaction at 50 ℃ for 20 hours to obtain a polyurethane foam.

FIG. 2 is a sectional view of the polyurethane foam prepared in example 2. As shown in FIG. 2, the polyurethane foam obtained by cutting and observing the foam state formed by the cut surface is found to have good foaming effect, more cells, fine and dense cells and uniform density distribution.

Example 3

(1) mixing and stirring 98.72g of polyether polyol, 0.40g of water, 0.25g of stannous octoate, 0.08g of silicone oil and 0.25g of triethanolamine at a rotating speed of 102r/min, introducing air with the humidity of 0.01% for 280s at a flow rate of 360L/h, and maintaining the pressure, wherein the pressure for maintaining the pressure is 1.3bar, so as to obtain a mixture;

(2) 47g of diphenylmethane diisocyanate was added to the mixture obtained in step (1) and mixed, followed by reaction at 50 ℃ for 24 hours to obtain a polyurethane foam.

FIG. 3 is a sectional view of the polyurethane foam prepared in example 3. As shown in FIG. 3, the polyurethane foam obtained by cutting and observing the foam state formed by the cut surface was found to have a good foaming effect, a large number of cells, fine and dense cells and a uniform density distribution.

Example 4

This example provides a method for producing a polyurethane foam, which is different from example 1 only in that the mixing and stirring speed in step (1) is 80 r/min.

FIG. 4 is a sectional view of the polyurethane foam prepared in example 4. As shown in FIG. 4, the polyurethane foam obtained by cutting and observing the state of the foam formed by cutting the cut surface was found to have a cell density distribution which was not uniform, some having larger cells and some having smaller cells, as compared with the foam obtained in example 1.

Example 5

This example provides a method for producing a polyurethane foam, which is different from example 1 only in that the mixing and stirring speed in step (1) is 120 r/min.

FIG. 5 is a sectional view of the polyurethane foam prepared in example 5. As shown in FIG. 5, the polyurethane foam obtained by cutting and observing the state of the foam formed by cutting the cut surface was found to have a cell density distribution which was not uniform, some having larger cells and some having smaller cells, as compared with the foam obtained in example 1.

Example 6

This example provides a method for preparing a polyurethane foam, which is different from example 1 only in that the time for introducing air in step (1) is 100 seconds.

FIG. 6 is a sectional view of the polyurethane foam prepared in example 6. As shown in FIG. 6, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the polyurethane foam was found to have larger cells and smaller number of cells than the foam obtained in example 1.

Example 7

This example provides a method for preparing polyurethane foam, which is different from example 1 only in that the flow rate of the introduced air in step (1) is 280L/h.

FIG. 7 is a sectional view of the polyurethane foam prepared in example 7. As shown in FIG. 7, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the cut surface was found to have larger cells and smaller number of cells than the foam obtained in example 1.

Example 8

This example provides a process for the preparation of polyurethane foam, differing from example 1 only in that the dwell pressure in step (1) is 0.5 bar.

FIG. 8 is a sectional view of the polyurethane foam prepared in example 8. As shown in FIG. 8, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the polyurethane foam was found to have larger cells and smaller number of cells than the foam obtained in example 1.

Example 9

This example provides a process for the preparation of polyurethane foam, differing from example 1 only in that the dwell pressure in step (1) is 2.5 bar.

FIG. 9 is a sectional view of the polyurethane foam prepared in example 9. As shown in FIG. 9, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the cut surface was found to have larger cells and smaller number of cells than the foam obtained in example 1.

Comparative example 1

This comparative example provides a method of preparing a polyurethane foam comprising the steps of: polyether polyol 98.65g, water 0.40g, stannous octoate 0.3g, silicone oil 0.10g, triethanolamine 0.20g, and diphenylmethane diisocyanate 44g were mixed and reacted at 50 ℃ for 20 hours to obtain polyurethane foam.

FIG. 10 is a sectional view of the polyurethane foam prepared in comparative example 1. As shown in FIG. 10, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the cut surface was found to have coarse and uneven cells and a smaller number of cells than the foam obtained in example 1.

Comparative example 2

This comparative example provides a method of preparing a polyurethane foam comprising the steps of:

(1) mixing and stirring 98.65g of polyether polyol, 0.40g of water, 0.3g of stannous octoate, 0.10g of silicone oil and 0.20g of triethanolamine at the rotating speed of 99r/min, and simultaneously introducing air with the humidity of 0.01% at the flow rate of 350L/h for 300s to obtain a mixture;

FIG. 11 is a sectional view of the polyurethane foam prepared in comparative example 2. As shown in FIG. 11, the polyurethane foam obtained by cutting and observing the foam state formed by cutting the polyurethane foam was found to have larger cells and smaller number of cells than the foam obtained in example 1.

Performance testing

The polyurethane foams prepared in examples 1-9 and comparative examples 1-2 were subjected to a performance test, and the foam density was measured in accordance with GB/T6343-2009 determination of apparent density of foam and rubber; the foam compression strength test is carried out according to the standard GB/T8813-2006, and the foam tear strength test is carried out according to the standard GB/T10808-2006.

The specific test results are shown in table 1:

TABLE 1

Item	Foam Density (kg/m)³)	Compressive strength of foam (kPa)	Tear Strength (N.mm)^-1)
				Example 1	265	95	1.96
Example 2	240	110	1.80
				Example 3	280	88	2.04
Example 4	298	75	2.32
				Example 5	302	73	2.37
Example 6	310	79	2.28
				Example 7	299	83	2.31
Example 8	307	71	2.46
				Example 9	310	74	2.40
Comparative example 1	332	50	2.60
				Comparative example 2	320	60	2.52

As can be seen from the test data in Table 1, the foam density of the polyurethane foam provided by the present invention is 240-310kg/m³The foam compression strength is 70-110kPa, and the tearing strength is 1.8-2.5 N.mm^-1. According to the preparation method of the polyurethane foam, the gas adsorption capacity is increased and the gas utilization rate is improved by controlling the number of the bubbles in the solution, so that the prepared polyurethane foam has fine and uniform cells, low density and excellent mechanical properties.

As can be seen from the comparison between example 1 and examples 4 and 5, when the rotation speed is too low, the bubble nuclei cannot be uniformly dispersed in the system, and are concentrated, so that the foam cells are not uniformly distributed; if the rotating speed is too high, the material temperature is increased too much, the reaction speed is accelerated, the fluidity of the material is poor, and the foam density distribution is poor. As is clear from comparison of example 1 with examples 6 and 7, when the gas flow time and flow rate were too small, the number of cell nuclei was too small, and the cells of the foam were coarse. As can be seen from the comparison between example 1 and examples 8 and 9, when the pressure is too low during the pressure holding, the gas in the mixture overflows too much, the gas dispersed in the mixture is too little, that is, the number of bubble cores is too small, and the foam cells become coarse; too high a pressure during the pressure holding leads to too low a gas flow rate into the mixture, too little gas enters the mixture per unit time, and foam cells become coarse.

From the comparison between example 1 and comparative examples 1 and 2, it is understood that the polyurethane foams obtained without carrying out the gas injection and pressure holding treatment or carrying out the gas injection without carrying out the pressure holding treatment all had the problems of too small number of cells, coarse cells and high foam density, because the number of cell nuclei is too small at the time of foam molding, the gas adsorption amount is small, the gas utilization rate is low, and the amount of cells obtained per cell nucleus may be large, and the cells of the foams obtained therefrom are coarse and uneven and small in number.

The applicant states that the present invention is illustrated by the above examples to the preparation of the polyurethane foam of the present invention, but the present invention is not limited to the above examples, i.e., it does not mean that the present invention must be practiced by relying on the above examples. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A preparation method of polyurethane foam is characterized by comprising the following steps:

2. The method of preparing polyurethane foam according to claim 1, wherein the mixing and stirring in step (1) is performed at a rotation speed of 90 to 110 r/min.

3. The method for producing a polyurethane foam according to claim 1 or 2, wherein the time for introducing the gas in the step (1) is 200s or more, preferably 280s and 320 s;

preferably, the flow rate of the introduced gas in the step (1) is 300-400L/h, preferably 350L/h;

preferably, the humidity of the gas in step (1) is below 0.05%;

preferably, the gas in step (1) is air.

4. The production method of a polyurethane foam according to any one of claims 1 to 3, characterized in that the pressure of the dwell pressure in step (1) is 1 to 2 bar.

5. The production method of a polyurethane foam as claimed in any one of claims 1 to 4, wherein the mass ratio of the polyether polyol, the blowing agent, the catalyst and the foam stabilizer in the step (1) is (97-99.5): (0.6-1.0): (0.25-0.5): (0.08-0.11);

preferably, the mass ratio of the mixture in the step (1) to the isocyanate in the step (2) is 100 (41-47).

6. The process for preparing a polyurethane foam according to any one of claims 1 to 5, wherein the polyether polyol in step (1) has a functionality of 2 to 4 and a hydroxyl value of 15 to 120mg KOH/g;

7. The method of producing a polyurethane foam according to any one of claims 1 to 6, wherein the blowing agent in step (1) is water;

preferably, the catalyst in step (1) is stannous octoate;

preferably, the foam stabilizer in step (1) is silicone oil.

8. The method of producing a polyurethane foam according to any one of claims 1 to 7, wherein the mixture in step (1) further comprises a chain extender;

preferably, the chain extender is triethanolamine;

preferably, the chain extender is added in an amount of 0.18 to 0.25% of the total mass of the mixture.

9. The method of producing a polyurethane foam according to any one of claims 1 to 8, wherein the isocyanate in the step (2) is diphenylmethane diisocyanate;

preferably, the temperature of the mixing reaction in the step (2) is 35-65 ℃, and the time of the mixing reaction is 16-24 h.

10. A process for the preparation of a polyurethane foam as claimed in any one of claims 1 to 9, characterized in that it comprises the following steps: