NOVAX SF-360 softener replacing methylene chloride in flexible polyurethane foam

Wu Bin
Wan Qihua

OSiC Performance Materials
Urethane Additives

No.1218, Songsheng Road
201600 Shanghai


Flexible polyurethane foam has attracted widespread attention in the industry due to its advantages in hand feeling and comfort, combined with the replacement of methylene chloride. A new environmentally friendly softener ( NOVAX SF-360 ) was applied to the preparation of soft polyurethane foam. The softness effect and foam performance of the foam prepared by the softener were studied. The effects of the softener on the air permeability, cell structure, T-VOC and FOG of the foam were mainly investigated. The effect of the new softener on the molecular structure of the foam was studied by infrared spectroscopy.  The results showed that the new environmentally friendly softeners could effectively increase the softening effect of polyurethane foam and obtain a more open and comfortable foam. The infrared spectrum showed that SF-360 could effectively reduce the content of precipitated urea in the foam and obtain a more flexible soft polyurethane foam.

Key words : polyurethane foam.  Softener. methylene chloride .  Environmental protection  
Soft polyurethane foam  mainly relies on the combination of chemical foaming agent and physical foaming agent to obtain polyurethane porous materials with excellent hand feeling. Water is used as a chemical foaming agent and reacts with isocyanate to release CO2. methylene chloride  is widely used as a physical foaming agent in the preparation of soft polyurethane foam. methylene chloride  has a large gasification heat, which can take sufficient heat in the preparation of soft polyurethane foam and dilute the heat released in the reaction process. After the use of methylene chloride  at the same density, the dosage of chemical foaming agent water decreases, and the content of hard segment in the foam structure decreases, so soft and comfortable soft polyurethane foam can be obtained.  The use of methylene chloride  can bring comfortable soft polyurethane foam and reduce the yellow core risk of polyurethane foam, but there are also environmental protection and safety problems. methylene chloride  itself is toxic, methylene chloride  vapor is strong anesthetic, large inhalation can cause acute poisoning, nasal pain, headache, vomiting and other symptoms.  Chronic poisoning can cause eyeflowers, fatigue, loss of appetite, impaired hematopoietic function, and reduced red blood cells, which are considered as possible carcinogens by the USEPA and the international cancer research institutions. methylene chloride  as a transitional physical foaming agent, ozone depletion potential is greater than zero, still consumes a certain amount of ozone. At the end of 2017, the Ministry of Environmental Protection issued ' 《List of priority control chemicals ( first batch )》 ', methylene chloride  was listed in the list of chemicals, the relevant departments will focus on the main environmental and health risks.

The application of new softener ( SF-360 ) in soft polyurethane foam can completely or partially replace methylene chloride  to obtain soft polyurethane foam, which solves the safety and environmental protection problems caused by methylene chloride . The raw materials used for the preparation of new softener have good biodegradability and good biodegradability, and are green and environmentally friendly softeners.  In this paper, the softening effect and foam energy of the foam prepared by the softener were studied, and the influence of the softener on the porosity and pore structure of the foam was emphatically investigated. The influence of the new softener on the molecular structure of the foam was studied by using an infrared spectrometer.

1 Experimental part

1.1 Main raw materials and equipment
Polyether polyol 5603 (hydroxyl value 56 mgKOH/g), industrial grade, Jiangsu Changhua Polyurethane Co., Ltd.; toluene diisocyanate TDI, industrial grade, Huntsman polyurethane company; foam stabilizer (RETé UF-5880), industrial grade , OSiC Performance Materials.; softener NOVAX SF-360, water content 50%, industrial grade,OSiC Performance Materials; NEXCAT UC-A33, industrial grade, OSiC Performance Materials; NEXCAT UC-A1, industrial grade,OSiC Performance Materials; methylene chloride , analytical grade, Jiangsu Qiangsheng Functional Chemical Co., Ltd.

IKA Electric Mixer, RW20, Guangzhou Yike Laboratory Technology Co., Ltd.; Electronic Platform Scale, JJ1000, Changshu Shuangjie Testing Instrument Factory; Electronic Universal Testing Machine, Model CMT4104, Shenzhen Sansi Material Testing Co., Ltd.; Headspace-Gas Chromatograph, HS-100 GC-2010 plus, Shimadzu (China) Co., Ltd.; foam rebound tester, Shanghai Hengyi Precision Instrument Co., Ltd.

1.2 Test formula and foaming process

The formula of polyurethane foam D32 is shown in Table 1.

Table 1 Polyurethane foam D32 formula

  F-S F-SF-360 F-MC
Component A      
PPG polyol 5603 100 100 100
MC 0 0 4
water 3 2.5 2.56
OSiC RETé UF-5880 0.8 0.8 0.8
OSiC NEXCAT UC-A33 0.1 0.1 0.1
OSiC NEXCAT UC-A1 0.06 0.06 0.06
OSiC NEXCAT UC-T9 0.11 0.11 0.125
OSiC NOVAX SF-360 0 1 0
Component B      
TDI index 105 105 105

Room temperature, material temperature control in 22 ~ 25 °C.  According to the formula in Table 1, the component A was accurately weighed and stirred for 50 s at the speed of 2100 r / min, and then quantitatively poured into the component A, and stirred for 6 s at the speed of 2100 r / min, quickly poured into the mold box. From the end of the inversion of component B, the second meter was used to count the time until the end of the bubble jump and the curing time was 24 hours.

1.3 Physical performance testing  
Density is determined in accordance with GB 6343-1995.  The indentation hardness was measured according to GB / T 10807-2006.  The rebound performance of falling ball was measured according to GB / T 6670 - 2008.  The cell structure was tested by microscopic photography.  T-VOC was determined according to VDA277 standard.

2 Results and discussion

2.1 Effect of Softener on Foam Properties 
As shown in table 1, soft foams F-SF-360 and F-MC are prepared using softener SF-360 and methylene chloride , and soft foams without softener are F-S.  Table 2 data shows that the physical properties of the soft foam without softener and the soft foam with softener are compared. It is found that the indentation hardness of the foam prepared by adding one phr SF-360 decreases by 21.28 % at 65 %, and the indentation hardness of the foam prepared by adding four phr MC decreases by 15.12 %. The addition of one phr SF-360 is better than the use of four phr MC.

Table 2. The influence of different softeners on foam performance

  F-S F-SF-360 F-MC
Density/(Kg/m3) 30.27 29.74 31.06
Hardness 38±1 29±1 34±1
Breathabilty 5 4 5
25%IFD/N 74.77 59.83 65.50
40%IFD/N 85.87 69.22 76.10
65%IFD/N 146.49 115.31 124.34
SAG factor 1.96 1.91 1.90
Ball Rebound/% 47±1 50±1 50±1

Note: Breathability grade 5-total permeability; Breathability grade 4-better breathability; Breathability grade 3-General breathability; Breathability grade 2-Poor breathability; Breathability grade 1-Poor breathability.

2.2 The effect of softener on foam cell structure and air permeability

The fine cell structure can provide a softer and more comfortable hand feeling, so it is necessary to study the effect of softener on the cell structure of polyurethane foam. Fig. 1 shows the cell structure images of polyurethane foam ( F-S ) prepared without softener and polyurethane foam ( F-MC, F-SF-360 ) prepared with softener amplified by 15 times. Compared with the standard F-S foam without softener, the cell structure of polyurethane foam prepared with MC as softener is thicker and the bright spots are reduced significantly, while the cell structure of polyurethane foam prepared with SF-360 is more dense, indicating that the new environmentally friendly softener can improve the cell structure of polyurethane foam, make the cell structure more dense, and provide a more comfortable hand feeling.  The softeners used in soft polyurethane foam mostly use special polyether or special polyols with crosslinking agent and trimer catalyst to make the foam soft. The soft polyurethane foam is prepared at a low isocyanate index, and the permeability of the soft polyurethane foam prepared at a high index is poor. The two new softeners are prepared under the condition of isocyanate index of 105. Figure 1 shows that the bubble bright spots of F-S and F-SF-360 are slightly increased compared with the standard sample. As shown in table 1, F-SF-360 can still ensure good permeability.

Figure 1. Polyurethane foam prepared without softener (F-S) and polyurethane foam prepared with different softeners (F-MC, F-SF-360) magnified 15 times the cell structure picture

2.3 The influence of softener on foam T-VOC
VDA277 is the sum of compounds whose peak area meets certain conditions using HS-GC-FID detector. The acetone content is used to calculate the carbon content, also known as total carbon content ( T-VOC ).  Atomization test ( FOG ), also known as condensed component test, is very necessary for the content of volatile matter in the condensed component of the reaction material and the reasonable control of the generation of volatile matter.  Polyurethane foams contain certain volatile organic compounds , such as alkanes, olefins, aldehydes and ketones, amines, siloxanes and benzene series, which have a great impact on human health.  The T-VOC and FOG results of polyurethane foams ( F-S ) prepared without softeners and polyurethane foams ( F-MC, F-SF-360 ) prepared with different softeners were tested after 24 h. The results showed that the T-VOC and FOG data of foams prepared with MC as softeners were significantly higher, as shown in figure 2. This was because the amount of catalyst needed to increase to stabilize the foam when the foam was prepared with MC, and the large vaporization heat of MC took away too much heat, resulting in the residual of small molecular volatile organic compounds that should have escaped at high temperature in the sponge, resulting in the obvious high T-VOC and FOG of polyurethane foam materials. The T-VOC data of the foam prepared by the environmentally friendly softener is slightly higher than that of the standard sample, because the addition of the softener is mainly to control the rapid precipitation of polyurea and reduce the degree of microphase separation. At this time, the foaming reaction in the process of foam preparation is controlled, and the heat generated is slightly lower than that of the standard sample, resulting in some small molecular volatile organic compounds. However, the FOG data of the foam prepared by the environmentally friendly softener is significantly lower than that of the standard sample, because the softener can capture some condensed volatile substances through hydrogen bonding.

Figure 2. T-VOC and FOG test data of polyurethane foam (F-S) prepared without softener and polyurethane foam (F-MC, F-SF-360) prepared with different softeners after 24 hours

2.4 Infrared spectroscopy study of the effect of softener on foam molecular structure
Many studies have shown that [ 3-4 ] : The free carbonyl infrared absorption peak of polyurethane foam is at 1728 cm-1, the peak at 1710 cm-1 is the carbonyl absorption peak forming hydrogen bond, the peak at 1660 cm-1 is random precipitation polyurea, and the peak at 1640 cm-1 is ordered precipitation polyurea.  Therefore, in this paper, the effect of softener on the molecular structure of foam was studied by infrared spectroscopy, and the relationship between microphase separation and soft hardness of foam was also studied.  The infrared spectra of polyurethane foams ( F-S ) prepared without softeners and polyurethane foams ( F-MC and F-SF-360 ) prepared with different softeners are shown in Fig. 3. There are no obvious absorption peaks at 1710 cm − 1 and 1660 cm − 1 for the tested polyurethane foams, mainly free carbonyl absorption peak at 1728 cm − 1 and ordered precipitation polyurea absorption peak at 1640 cm − 1, indicating that the molecular structure of the foam prepared with this formula presents a relatively ordered microphase separation structure. The polyurethane foam F-S has a strong ordered precipitation polyurea absorption peak, while the absorption peaks of F-MC and F-SF-360 decrease in turn, which is consistent with the physical property data of polyurethane foams in Table 2. The lower the intensity of ordered precipitation polyurea absorption peak is, the more flexible the foam is.  This is because the hard segment of polyurethane foam is combined by hydrogen bonds to form a hard segment, and the soft segment is irregularly wrapped to form a soft segment. The ordered polyurea precipitation is reduced, the degree of microphase separation is improved, the rigidity is enhanced, and the soft and elastic properties are decreased. [5 ].

Figure 3. Infrared spectra of polyurethane foam (F-S) prepared without softener and polyurethane foam (F-MC, F-SF-360) prepared with different softeners

3 Summary

(1) The new environmentally friendly softeners can effectively reduce the indentation hardness of the foam. In the formulation system in the text, SF-360 has a more obvious effect of reducing the indentation hardness of the foam;
(2) When methylene chloride is used as a softening agent, the cell structure of the foam prepared is rougher, while the cell structure of the foam prepared by SF-360 is finer;
(3) For foams prepared with different softeners, after 24 hours, the results of testing the foam T-VOC and FOG showed that the foam T-VOC prepared by methylene chloride  was much higher than the foam T prepared by the new environmentally friendly softener SF-360 -VOC; and the FOG value shows that softener 360 has obvious advantages.
(4) Through the study of infrared spectra of foams prepared by different softeners, it is found that the hard segments of polyurethane foam are combined by hydrogen bonding to form hard segments, and the soft segments are randomly wound to form soft segments. Ordered polyurea precipitation is reduced and microphase separation is achieved. The degree is increased, the rigidity is increased, and the softness and elasticity properties are decreased.

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(3) Zhao Xiaobin, Du Lei, Zhang Xiaoping.Polyurethane structure and microphase separation [ J ].Polyurethane industry : 2001,16,4-8.  
(4) Zhao Peizhong, Wen Qingzhen, Wang Yuansheng and so on.Infrared spectroscopy analysis of hydrogen bond in gradient curing polyurethane urea [ J ].Spectroscopy and spectroscopy.2008,28 : 551-554.  
(5) Tao. Structural regulation, performance and application of polyurethane microphase separation [ D ]. Anhui : Anhui University, 2018, 1 – 154.


Wu Bin
 Born in 1978, Bachelor of Fine Chemicals from East China University of Science and Technology, Master of Economics from Shanghai University of Finance and Economics. In 2000, Wu joined the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, engaged in organic synthesis, participated in and completed the National Natural Science Foundation of China (new drug synthesis) and the National Defense Science and Technology Commission (organic silicon materials). Wu joined GE Toshiba Silicone(later Momentive) in 2004 to work in technical research, project manager, and factory director. In 2010 he joined OSiC and presided over the construction and operation of Songjiang and Zhangjiagang factories. In 2020, Wu began to serve as the principal of the academy of OSiC.

Wan Qihua  

Born in 1987,master of Nanchang University. Wan studied the design, synthesis and application of organic small molecule fluorescent probes in school. He joined OSiC in 2013 as R & D engineer, engaged in the development and application of various additives related to polyurethane flexible foam, including catalysts, surfactants and other functional additives, and special foams development.