A method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process.

Abstract

This invention discloses a method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process. The polyurethane flexible foam contains a composition of TDI monomer and phenyl triisocyanate in its raw materials; the phenyl triisocyanate accounts for 0.1-5 wt% of the TDI monomer and phenyl triisocyanate composition. This invention can reduce the release of isocyanate-containing volatile substances during the foaming process of polyurethane flexible foam by adjusting the phenyl triisocyanate content in TDI.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology, specifically relating to a method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process. Background Technology

[0002] Polyurethane flexible foam typically has an open-cell structure. It generally possesses properties such as low density, good elastic recovery, sound absorption, breathability, and thermal insulation, and is mainly used as furniture cushioning material, vehicle seat cushioning material, and various soft padding laminate composite materials. In both industrial and civilian applications, flexible foam is also used as a filter material, sound insulation material, shock absorption material, decorative material, packaging material, and thermal insulation material. Due to its excellent performance, polyurethane flexible foam is widely used in many fields such as furniture, automobiles, medical, sports, packaging, construction, electronics, and industry, bringing convenience and comfort to people's lives and work.

[0003] Toluene diisocyanate is classified as a highly toxic chemical, but it has a significant irritant effect on the eyes and respiratory mucous membranes and can cause allergic asthma. According to the safety data sheet, the time-weighted average (TWA) tolerance for toluene diisocyanate is 0.1 mg / m³. 3 The short-term exposure limit (STEL) is 0.2 mg / m³. 3 .

[0004] Given the increasingly standardized requirements of occupational health regulations, almost no research has addressed the control of isocyanate volatilization during the polyurethane flexible foam foaming process from the raw material end. CN106496499A utilizes low-monomer residue and low-volatility polymeric polyols and polyether-modified isocyanates to reduce foam odor. Simultaneously, a combined catalyst that reduces polyurethane foam odor is employed, avoiding the release of traditional amine catalysts, thus reducing system odor and improving production efficiency. CN111471142B provides a method for preparing modified polymeric polyols. This method uses small-molecule polyols with a functionality of 4-8 as initiators, propylene oxide as the polymerizing monomer, and reacts under the action of a catalyst. The resulting base polyether is then graft-copolymerized with styrene and acrylonitrile to obtain the modified polymeric polyol. This modified polymeric polyol exhibits high reactivity and low VOC release. Adding it to other raw materials for polyurethane flexible foams can not only directly reduce VOC release but also reduce production costs by minimizing the amount of catalysts and fillers used in the polymerization reaction, or even eliminating the need for fillers altogether, effectively reducing odor during the preparation or storage of polyurethane flexible foams. Existing inventions can only control the volatilization of isocyanates during the polyurethane flexible foaming process through modification, which is costly and has a certain impact on the foaming process.

[0005] Therefore, in response to the current problems and development trends in the industry, there is an urgent need to develop a method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process, so as to achieve the goal of reducing isocyanate release during the foaming process by simply adjusting the composition of the TDI component raw material. Summary of the Invention

[0006] To achieve the above objectives, this invention provides a method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process. This method allows for the preparation of polyurethane flexible foam with low isocyanate volatilization during the foaming process by adjusting the content of phenyl triisocyanate in TDI (toluene diisocyanate) under the same formulation system. This achieves the goal of reducing isocyanate release during the foaming process by simply adjusting the composition of the TDI component. The technical solution adopted by this invention is as follows:

[0007] A method for preparing polyurethane flexible foam, wherein the raw materials used in the method comprise an isocyanate composition of TDI monomer and phenyl triisocyanate; wherein the phenyl triisocyanate accounts for 0.1-5 wt%, preferably 2-4 wt%, and the remainder is TDI monomer; wherein the phenyl triisocyanate comprises methyl phenyl triisocyanate and / or 1,3,5-phenyl triisocyanate; preferably, the molar ratio of methyl phenyl triisocyanate to 1,3,5-phenyl triisocyanate is 1:10-10:1, preferably 2:1-3:1.

[0008] The inventors discovered in experiments that introducing phenyl triisocyanate during the preparation of TDI adducts resulted in lower NCO functional group reactivity of phenyl triisocyanate during polyurethane flexible foam foaming compared to NCO functional group reactivity on TDI. The gel reaction preferentially consumed TDI monomer, which effectively reduced the residual TDI monomer after polyurethane flexible foam foaming, ultimately reducing the release of isocyanate during the foaming process.

[0009] In one embodiment of the present invention, the amount of raw materials used in the method is as follows:

[0010] 100 parts by weight of polyether polyol;

[0011] Amine catalyst: 0.1-0.8 parts by weight; preferably 0.2-0.5 parts by weight;

[0012] Organometallic catalyst, 0.1-0.25 parts by weight: preferably 0.1-0.2 parts by weight;

[0013] The foaming agent is used in an amount of 0.1-1.2 parts by weight, preferably 0.2-0.6 parts by weight;

[0014] Water 2-4.2 parts by weight, preferably 2-2.8 parts by weight;

[0015] The isocyanate composition has an isocyanate index of 1.05-1.2, preferably 1.08-1.15, in parts by weight.

[0016] In one embodiment of the present invention, the method includes the following steps:

[0017] S1: Amine catalyst, organometallic catalyst, foam stabilizer, water and polyether polyol premixed as component A;

[0018] S2: Isocyanate composition as component B;

[0019] S3: Component A and component B are mixed and foamed.

[0020] In one embodiment of the present invention, the polyether polyol in S1 is a polyether polyol with a number average molecular weight of 2000-8000, preferably a polyether polyol with a molecular weight of 3000-5000. The above-mentioned polyether polyol is a commonly used polyether polyol in the art.

[0021] In one embodiment of the present invention, the tertiary amine catalyst S1 is preferably bis(dimethylaminoethyl) ether and / or triethylenediamine. The above-mentioned tertiary amine catalyst is a commonly used tertiary amine catalyst in the art.

[0022] In one embodiment of the present invention, the organometallic catalyst S1 is preferably stannous octoate and / or dibutyltin dimethylsiloxane. The above-mentioned organometallic catalysts are commonly used in the art.

[0023] In one embodiment of the present invention, the foam stabilizer in S1 is selected from silicone-based surfactants and / or fluorocarbon-based surfactants, preferably silicone-based surfactants. The aforementioned foam stabilizer is a commonly used foam stabilizer in the art.

[0024] In one embodiment of the present invention, the premixing temperature in S1 is 20-30°C.

[0025] In this invention, the flexible foam mixing and foaming process is well known in the art.

[0026] Another object of the present invention is to provide an isocyanate composition.

[0027] An isocyanate composition, wherein the composition is the composition used in the above method, the isocyanate composition comprising an isocyanate composition of TDI monomer and phenyl triisocyanate; wherein the phenyl triisocyanate accounts for 0.1-5 wt%, preferably 2-4 wt%, and the remainder is TDI monomer; wherein the phenyl triisocyanate comprises methyl phenyl triisocyanate and / or 1,3,5-phenyl triisocyanate; preferably, the molar ratio of methyl phenyl triisocyanate to 1,3,5-phenyl triisocyanate is 1:10-10:1, preferably 2:1-3:1.

[0028] Another object of the present invention is to provide a use of an isocyanate composition.

[0029] Use of an isocyanate composition, wherein the composition is the composition used in the above method, or the composition described above, wherein the composition is used to prepare polyurethane flexible foam with low isocyanate volatilization during the foaming process.

[0030] Another object of the present invention is to provide a polyurethane flexible foam.

[0031] A polyurethane flexible foam, wherein the flexible foam is prepared using the composition described above as a raw material, or using the composition described above as a raw material.

[0032] Through experiments, the inventors further discovered that the refined TDI from the TDI refining tower, after being processed by distillation, can yield TDI with varying phenyl triisocyanate contents, which can be directly used to prepare polyurethane flexible foam with low isocyanate volatilization during the foaming process. In existing technologies, the refined TDI from the TDI refining tower contains a small amount of phenyl triisocyanate. The presence of such substances reduces the purity of the refined TDI product, affecting its application in certain fields requiring high raw material activity. Therefore, during TDI production, multiple distillation purification methods or separation and incineration are used to reduce the phenyl triisocyanate content in the TDI product. This invention proposes a diversified development direction for TDI products regarding the utilization of phenyl triisocyanate.

[0033] Another object of the present invention is to provide a method for preparing an isocyanate composition.

[0034] A method for preparing an isocyanate composition, wherein the composition is the composition used in the above method, or is the composition described above, wherein the composition is obtained by directly mixing TDI with phenyl triisocyanate, or by introducing phenyl triisocyanate through the phenyl triisocyanate inherent in the TDI monomer. There are no specific limitations on the preparation method described in this invention.

[0035] In one embodiment of the present invention, the step of introducing phenyl triisocyanate through the phenyl triisocyanate naturally present in the TDI monomer is as follows: the TDI is processed by a distillation separation process to obtain the target TDI containing phenyl triisocyanate; preferably, the step is as follows: the TDI collected from the TDI purification tower is processed by a distillation separation process to obtain the target TDI containing phenyl triisocyanate.

[0036] In one embodiment of the present invention, the conditions for distillation separation in the preparation method are: pressure 1-10 kPaA, preferably 4-5 kPaA, and temperature 110-160°C, preferably 143-148°C.

[0037] In one embodiment of the present invention, the preparation method involves distillation and purification using a plate column or a structured packed column. The aforementioned separation equipment is commonly used in the art for distillation separation.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The present invention provides a method for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process, which can effectively reduce the release of isocyanate during the foaming process of polyurethane flexible foam.

[0040] (2) This invention provides a method for the resource utilization of phenyl triisocyanate in refined TDI. Detailed Implementation

[0041] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0042] The main raw material sources involved in the various embodiments and comparative examples of this invention are as follows; unless otherwise specified, all raw materials were obtained from ordinary commercial channels:

[0043] Organotin catalyst, stannous octoate (T9), Guangzhou Yourun Synthetic Materials Co., Ltd.;

[0044] Organotin catalyst, dibutyltin disilicate (T12), Guangzhou Yourun Synthetic Materials Co., Ltd.;

[0045] Organosilicon foam stabilizer, L-580, Momentive Advanced Materials, USA;

[0046] Organosilicon foam stabilizer, L-570, Momentive Advanced Materials, USA;

[0047] TDI-80, Wanhua Chemical Group Co., Ltd.;

[0048] Polyether polyol, F3156D, Wanhua Chemical Group Co., Ltd.;

[0049] Polyether polyol, F3135, Wanhua Chemical Group Co., Ltd.;

[0050] Toluene diisocyanate, TDI-80, Wanhua Chemical Group Co., Ltd.;

[0051] TDI containing high levels of phenyl triisocyanate, obtained from the side of the TDI refining tower, with a phenyl triisocyanate content of 50% (methyl phenyl triisocyanate: 1,3,5-phenyl triisocyanate = 2:1), Wanhua Chemical Group Co., Ltd.

[0052] Tertiary amine catalyst, bis(dimethylaminoethyl) ether, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0053] Tertiary amine catalyst, triethylenediamine, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0055] Composition of the TDI monomer and phenyl triisocyanate composition: analyzed by Agilent 7890B gas chromatograph.

[0056] Method for testing isocyanate gas release during flexible foam preparation:

[0057] Based on 100g of polyether polyol, the isocyanate index was controlled between 1.05 and 1.2. All materials were rapidly mixed evenly and then quickly poured into a 30cm × 30cm × 30cm wooden square mold for free foaming. Under windless conditions, the highest isocyanate concentration and the isocyanate concentration at 1m above the mold during the soft foaming process were measured. The isocyanate vapor content was determined using a Honeywell SPM Flex Gas Monitor detector.

[0058] Physical property testing methods for flexible foam products:

[0059] The SL-SLH-500 foam plastic drop ball rebound tester from High-speed Rail Testing Instruments Co., Ltd. was used.

[0060]

Example 1

[0061] TDI collected from the TDI refining column was further purified by distillation to obtain a composition of TDI monomer and phenyl triisocyanate. The distillation conditions were: separation and purification via a plate column at 110°C and 1 kPaA. Gas chromatography analysis of the TDI monomer and phenyl triisocyanate composition revealed the following mass percentage composition: 0.2 wt% phenyl triisocyanate (methyl phenyl triisocyanate: 1,3,5-phenyl triisocyanate = 10:1) and 99.8 wt% TDI.

[0062] The steps for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process are as follows:

[0063] 1) Accurately weigh 0.2g stannous octoate, 0.1g triethylenediamine, 0.1g bis(dimethylaminoethyl) ether, 0.1g L-580 and 4g deionized water and premix them with 100g F3156D to obtain component A.

[0064] 2) Measure 52.6g of the composition of TDI monomer and phenyl triisocyanate (component B) into component A, stir at high speed, and quickly pour into a 30cm×30cm×30cm wooden square mold for free foaming. After curing at room temperature for 24 hours, demold to obtain a polyurethane flexible foam material sample.

[0065]

Example 2

[0066] TDI and TDI-80, containing high levels of phenyl triisocyanate, were blended from the TDI refining tower side. The composition of the TDI monomer and phenyl triisocyanate was analyzed by gas chromatography, and the mass percentage composition was: 5 wt% phenyl triisocyanate (methyl phenyl triisocyanate: 1,3,5-phenyl triisocyanate = 2:1), and 95 wt% TDI.

[0067] The steps for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process are as follows:

[0068] 1) Accurately weigh 0.18g dibutyltin disterol silicate, 0.1g triethylenediamine, 1.2g L-570 and 2g deionized water and premix them with 100g F3156D to obtain component A.

[0069] 2) Measure 29.37g of the mixture of TDI-80 and 3.26g of TDI containing high phenyl triisocyanate (component B) into component A, stir at high speed, and quickly pour into a 30cm×30cm×30cm wooden square mold for free foaming. After curing at room temperature for 24 hours, demold to obtain a polyurethane flexible foam material sample.

[0070]

Example 3

[0071] TDI was purified by distillation to obtain a composition of TDI monomer and phenyl triisocyanate. The distillation conditions were: temperature 160℃ and pressure 10 kPaA, using a plate column for separation and purification. Gas chromatography analysis of the TDI monomer and phenyl triisocyanate composition showed the following mass percentage composition: 4.6 wt% phenyl triisocyanate (methyl phenyl triisocyanate: 1,3,5-phenyl triisocyanate = 1:10) and 95.4 wt% TDI.

[0072] The steps for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process are as follows:

[0073] 1) Accurately weigh 0.25g dibutyltin disterite, 0.8g bis(dimethylaminoethyl) ether, 1g L-580 and 4.2g deionized water and premix them with 100g F3135 to obtain component A.

[0074] 2) Measure 33.13g of the composition of TDI monomer and phenyl triisocyanate (component B) into component A, stir at high speed, and quickly pour into a 30cm×30cm×30cm wooden square box mold for free foaming. After curing at room temperature for 24 hours, demold to obtain a polyurethane flexible foam material sample.

[0075]

Example 4

[0076] TDI collected from the TDI refining column was further purified by distillation to obtain a composition of TDI monomer and phenyl triisocyanate. The distillation conditions were: temperature 134℃ and pressure 4.7 kPaA, using a plate column for separation and purification. Gas chromatography analysis of the TDI monomer and phenyl triisocyanate composition revealed the following mass percentage composition: 0.6 wt% phenyl triisocyanate (methyl phenyl triisocyanate: 1,3,5-phenyl triisocyanate = 1:5), and 99.4 wt% TDI.

[0077] The steps for preparing polyurethane flexible foam with low isocyanate volatilization during the foaming process are as follows:

[0078] 1) Accurately weigh 0.1g dibutyltin disterol silicate, 0.1g triethylenediamine, 0.06g bis(dimethylaminoethyl) ether, 1g L-580 and 4.2g deionized water and premix them with 100g F3135 to obtain component A.

[0079] 2) Measure 33.2g of the composition of TDI monomer and phenyl triisocyanate (component B) into component A, stir at high speed, and quickly pour into a 30cm×30cm×30cm wooden square mold for free foaming. After curing at room temperature for 24 hours, demold to obtain a polyurethane flexible foam material sample.

[0080] Comparative Example 1

[0081] Compared with Example 1, the only difference is that only TDI monomers are used, and TDI containing 1,3,5-phenyl triisocyanate is not used.

[0082] The rest is the same as in Example 1.

[0083] Comparative Example 2

[0084] Compared with Example 3, the only difference is that an isocyanate composition with methyl phenyl triisocyanate and 1,3,5-phenyl triisocyanate contents not within the specified range is used, with phenyl triisocyanate content of 5.2 wt%.

[0085] The rest is the same as in Example 3.

[0086] The viscosity, free monomer, and xylene tolerance of the adducts prepared in each embodiment and comparative example were tested. The test results are shown in Table 1 below:

[0087] Table 1. Results of physical property tests on adduct products

[0088]

[0089] The results of the highest isocyanate concentration after foaming and the isocyanate concentration after 10 minutes of foaming in Table 1 show that, using the polyurethane flexible foam preparation method mentioned in this invention, polyurethane flexible foam with low isocyanate release during the foaming process can be obtained by adjusting the phenyl triisocyanate content in TDI. This indicates that distilling TDI and increasing the content of phenyl triisocyanates within a certain range can significantly reduce the release of toxic isocyanate vapors during the foaming process of polyurethane flexible foam. In Comparative Example 2, although the release of toxic isocyanate vapors during the foaming process was reduced when using TDI with a phenyl triisocyanate content exceeding the range specified in the instructions, the resilience performance of the polyurethane flexible foam decreased significantly, which is very detrimental to the basic properties of the polyurethane flexible foam.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing polyurethane flexible foam, characterized in that, The method uses an isocyanate composition containing TDI monomer and phenyl triisocyanate as raw materials. In the isocyanate composition, the proportion of phenyl triisocyanate is 0.1-5 wt%, preferably 2-4 wt%, and the remainder is TDI monomer; The phenyl triisocyanate comprises methyl phenyl triisocyanate and / or 1,3,5-phenyl triisocyanate; Preferably, the molar ratio of methylphenyl triisocyanate to 1,3,5-phenyl triisocyanate is 1:10-10:1, more preferably 2:1-3:

1.

2. The method according to claim 1, characterized in that, The raw material usage amounts used in the method are as follows: 100 parts by weight of polyether polyol; Amine catalyst: 0.1-0.8 parts by weight; preferably 0.2-0.5 parts by weight; Organometallic catalyst, 0.1-0.25 parts by weight: preferably 0.1-0.2 parts by weight; The foaming agent is used in an amount of 0.1-1.2 parts by weight, preferably 0.2-0.6 parts by weight; Water 2-4.2 parts by weight, preferably 2-2.8 parts by weight; The isocyanate composition has an isocyanate index of 1.05-1.2, preferably 1.08-1.15, in parts by weight.

3. The method according to claim 1 or 2, characterized in that, The method includes the following steps: S1: Amine catalyst, organometallic catalyst, foam stabilizer, water and polyether polyol premixed as component A; S2: Isocyanate composition as component B; S3: Component A and component B are mixed and foamed.

4. The method according to any one of claims 1-3, characterized in that, The polyether polyol mentioned in S1 is a polyether polyol with a number average molecular weight of 2000-8000, preferably a polyether polyol with a molecular weight of 3000-5000. And / or, the tertiary amine catalyst of S1, preferably in bis(dimethylaminoethyl) ether and / or triethylenediamine; And / or, the organometallic catalyst described in S1 is preferably stannous octoate and / or dibutyltin dibutylsilicate; And / or, the foam stabilizer in S1 is selected from silicone surfactants and / or fluorocarbon surfactants, preferably silicone surfactants; And / or, the premixing temperature in S1 is 20-30℃.

5. An isocyanate composition, said composition being the composition used in the method of any one of claims 1-4, characterized in that, The isocyanate composition comprises an isocyanate composition of TDI monomer and phenyl triisocyanate; In the isocyanate composition, the proportion of phenyl triisocyanate is 0.1-5 wt%, preferably 2-4 wt%, and the remainder is TDI monomer; The phenyl triisocyanate comprises methyl phenyl triisocyanate and / or 1,3,5-phenyl triisocyanate; Preferably, the molar ratio of methylphenyl triisocyanate to 1,3,5-phenyl triisocyanate is 1:10-10:1, more preferably 2:1-3:

1.

6. Use of an isocyanate composition, wherein the composition is the composition used in the method of any one of claims 1-4, or the composition of claim 5, wherein the composition is used to prepare polyurethane flexible foam with low isocyanate volatilization during the foaming process.

7. A polyurethane flexible foam, wherein the flexible foam is made from a composition prepared by any one of claims 1-4, or from a composition of claim 5.

8. A method for preparing an isocyanate composition, wherein the composition is the composition used in the method of any one of claims 1-4, or the composition of claim 5, characterized in that, The composition is obtained by directly mixing TDI with phenyl triisocyanate, or by introducing phenyl triisocyanate through the phenyl triisocyanate contained in the TDI monomer.

9. The preparation method according to claim 8, characterized in that, The step of introducing phenyl triisocyanate through the phenyl triisocyanate naturally present in TDI monomer is as follows: TDI is processed by a distillation separation process to obtain the target TDI containing phenyl triisocyanate; preferably, the step is as follows: TDI collected from the TDI purification tower is processed by a distillation separation process to obtain the target TDI containing phenyl triisocyanate.

10. The preparation method according to claim 8 or 9, characterized in that, In the preparation method, the conditions for distillation separation are: pressure 1-10 kPaA, preferably 4-5 kPaA, and temperature 110-160℃, preferably 143-148℃. And / or, the preparation method involves distillation and purification using a plate column or a structured packed column.

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