How Automotive Interiors and Flexible Polyurethane Foam Industry Reduce VOC Emissions

Technical Paper (Shanghai Xinxing Industry Co., Ltd. 200436)

Summary

The polyurethane industry has developed rapidly in recent decades, and more and more polyurethane products are used in various fields of daily life, including the automotive industry, furniture and other consumer goods. However, with the rapid economic development, people are increasingly demanding for the environment. For the polyurethane industry, the environmental issues include the production and use of links, such as the early use of TDI to gradually transition to the MDI-rich foam, and improve the production environment for production workers. In the links used by consumers, raw materials such as polyether polyols, amine catalysts, silicone surfactants, flame retardants, and antioxidants all determine the performance of the final product, including VOC emissions such as aldehydes and benzenes. And other substances. Low-VOC, low-fogging, low-odor polyurethane products have been increasingly used in the automotive interiors industry. Conventional amine catalysts are currently the focus of attention, while the new generation of amine catalysts can balance the reaction of gels and foams with a wide range of processing technologies. They can meet the low amine emission, low fogging and odor reduction in the polyurethane industry. , including all MDI, TDI/MDI and TDI based formulations.

Introduce

For many years, tertiary amine catalysts are an important part of typical polyurethane foam formulations. Some of the catalysts are biased towards the reaction of water and isocyanate (blowing reaction), while others are biased towards the reaction of polyols with isocyanates (gels). Reactions), depending on the molecular structure of the catalyst itself and its steric hindrance, electronic effects, etc., will all affect its effect.

In high-rebound soft foams, bis(2-dimethylaminoethyl)ether) BDMAEE is used as a conventional hair blowing catalyst. Due to its unique chemical structure, this is a typical highly effective tertiary amine. The catalyst promotes the reaction of water with isocyanate, also known as foaming reaction or early reaction. The vast majority of foam formulations use BDMAEE in combination with triethylenediamine TEDA. TEDA is a commonly used gel catalyst. Currently, there are many catalysts commercially used for the purpose of balancing the effect and the process rate.

The use of such common amine catalysts will continue unless the emission of volatile VOCs from the foam, discoloration, atomization, and odor of the PVC skin is considered. These problems have been greatly improved in silicone oils, polyether polyols, flame retardants, and antioxidants. Especially in the fields of furniture, automotive interiors and other areas, this is a key enabler of this technology improvement. The common tertiary amine catalysts TEDA, BDMAEE clearly have VOC species released in the foam product. In recent years, there have been several ways to reduce the release of amines.

The use of large molecular weight tertiary amine catalysts has three distinct advantages in use: First, the molecules of the catalyst are limited in the combined polyether and cannot diffuse itself, thereby improving the odor, PVC skin discoloration and fogging values; secondly, Due to the large molecular weight catalyst, the low vapor pressure drops the volatility at a certain temperature; a third advantage is that the alternative end of the catalyst not only affects the boiling point or vapor pressure of the catalyst, but also reduces its own toxicity. However, compared with reactive catalysts, the reaction activity is poor, the amount is large, the process tolerance is narrow, and it has a huge impact on the cost. Currently, it is not a mainstream choice.

The result of using a reactive catalyst is to reduce the VOC emission from the foam production and the catalyst in use. Due to the very low toxicity of free amine groups, workers' problems such as bareness, operating environment, atomization and odor are improved at the production and assembly plants during the foam manufacturing process. This article discusses this non-sporadic catalyst that reduces volatiles and odors of VOCs and also reduces catalyst emissions from the foam. Due to the complexity of the PU chemistry, several factors must be considered in an ideal catalyst, such as vapor pressure, amine value, molecular weight, gelling rate, end-capping composition, etc., which have different requirements for different foam and foam grades.

test

The full MDI system and M/T soft molded foam were evaluated in this paper. The catalyst evaluation list is shown in Table 1.

The rise rate of the free foam was used to compare the reactivity of the catalyst formulation. The molded foam is made of 380*380*100mm, and it is demolded with an aluminum mold heated to 50[deg.] C. for 3 to 6 minutes. After demoulding, the foam is mechanically pressed. The TDI foam was treated at 65°C for 30 minutes and physical properties were measured after 7 days.

Table 1: Alternative Catalysts

Ordinary volatile amine catalyst

ALLCHEM A-1 Foaming Catalyst

70% bis (dimethylaminoethyl) ether (BDMAEE) and 30% dipropylene glycol (DPG)

ALLCHEM A-33 Gel Catalyst

33% triethylenediamine (TEDA) and 67% dipropylene glycol (DPG)

Environmentally-friendly non-volatile amine catalysts

ECOCAT E-3201 Foaming Catalyst

Aliphatic secondary amine R2-NH

ECOCAT E-5307 Gel Catalyst

Aliphatic secondary amine R2-NH

New environmentally-friendly non-volatile catalyst - suitable for rapid demolding of molded products

ECOCAT E-7331

Modified aliphatic primary amine R-NH2

ECOCAT E-7341

Modified aliphatic primary amine R-NH2

After at least one week in a closed environment, the properties of the foam were tested and tested at ambient temperature 23°C and relative humidity 50% for at least 24 hours prior to testing. Product density measured according to GB/T6343-2009 method; indentation load measured according to GB/T10807-2006 method; elongation measured according to GB/T6344-2008 method; tear strength measured according to GB/T10808-2006 method; compression set According to GB/T 6669-2008 method

To measure the emission of automotive interior industrial foam, various OEMs have different test methods and standards. For example, Daimler-Benz uses VDA-278:2011; Shanghai Volkswagen uses stainless steel barrel method +VDA278; Shanghai GM uses GMW 15634, GWM 15635. Odor test Volkswagen / Daimler-Benz uses PV3900; Dongfeng Citroen uses D10 5517-E; Shanghai GM uses GMW 3205. Epidermis discoloration test Volkswagen / Daimler-Benz uses PV3937, Dongfeng Citroen uses D10 5496.

Results and discussion

The conventional catalysts such as BDMAEE and TEDA have more VOC emission, atomization and epidermal discoloration, and this view has been recognized. Our research shows that there are good ways to produce foam, and there will be noticeable improvements in alternatives. BDMAEE is considered as a standard blowing catalyst in molding and soft block foam. ALLCHEM's ECOCAT E-3201 acts as a reactive blowing catalyst and has a molecular structure very similar to BDMAEE, but its VOC divergence is relatively low.

ECOCAT E-3201 is a secondary aliphatic amine, which has a relatively large molecular weight, which reduces its volatilization. Compared with A-1, it has fairly close reactivity and catalytic effect. Replacing other catalysts with ECOCAT E-3201 is easy, does not require significant changes to the formulation, and provides good flowability, especially for designing complex molds. In addition BDMAEE (Pure A-1) is considered to be toxic, while ECOCAT E-3201 is non-toxic.

ECOCAT E-3201 is increasingly used as a substitute for BDMAEE.

Substituting TEDA as a gel catalyst has been a challenge until now. TEDA's special structure gives it special catalytic properties. In the polyurethane formulation, which has the most effective catalytic effect, ALLCHEM offers a series of gel catalysts that replace TEDA.

ECOCAT E-5307, E-7331, E-7341 are low vapor pressure, high molecular weight reactive components, especially E-7331 and E-7341. Very low vapor pressure proves their safety and low toxicity. Classified as ordinary chemicals and not regulated.

ECOCAT E-5307 has a secondary amine reactive group (-NH) with a wide process gradient. Compared with A33, its gelling effect is different in the formula with low water content and needs to be increased significantly, but The formula for high water content is similar to that of A33. It can be used as a standard non-volatile gel catalyst for high resiliency cold-moulded foam, Slabstock Foams, semi-rigid, etc. occasion.

ECOCAT E-7331, E-7341 is a modified primary amine product with a primary amine reactive group (-NH2). As can be seen from Table 2, the primary amine reaction rate is 2-5 times faster than the secondary amine group, but does not mean that the amount is much lower than that of ECOCAT E-5307, but it only reflects the change in catalytic efficiency. Compared to primary amine catalysts, secondary amine catalysts have a slower reaction rate, which means slower maturation. Compared to conventional A1 and A33 products, product demoulding will be slower, and the physical properties of foam products will be reduced, especially hygrothermal aging. performance.

ECOCAT E-7331 and E-7341 have better flow properties than E-5307. The extremely high activity promotes the hydroxyl group and isocyanate (late reaction). The curing time is fast, which means that the demoulding time can be shortened, the production efficiency can be improved, and the improvement can be achieved. The effect of the use of a reaction catalyst on the physical properties of the foam article. Excellent flow properties mean that it is suitable for the production of large molded products, such as automotive interiors, high-rebound products such as car seats, automotive headrests, automotive carpets, noise insulation pads on the front, armrests, and self-skinning products such as automobiles. Steering wheel, gear, luggage rack; semi-rigid products such as automobile dashboard, sun visor, etc.

Table 2 Reaction Rate Tables for Different Catalysts

Numbering

Active hydrogen catalyst

Typical structure

Relative reaction rate (uncatalyzed 25°C)

Aliphatic primary amines

R-NH2

100,000

Aliphatic secondary amines

R2-NH

20,000-50,000

Primary hydroxyl

R-CH2-OH

100

ECOCAT E-5307, E-7331, E-7341 have different characteristics of gels, depending on the application and formulation needs, they can be used alone or in combination with two to meet the requirements. These gel catalysts are used in conjunction with the ECOCAT E-3201 foaming catalyst to meet the current demand for reduced VOC emissions. In the study of all-MDI, MDI/TDI, and full TDI molded high resilience foams, we performed the performance of different catalysts on the resulting products.

MDI Molded Foam

Laboratory evaluations of different catalyst mixtures were hand foamed. The amount of catalyst in the formula is different, but it has the same reaction effect. The cut portion was used to test physical properties and VOC emission and fog and epidermal discoloration.

Table 3 shows the results of test formulation reactivity and VOC emission, atomization, and skin discoloration. All increased molecular weight products make it possible to reduce the amount of VOC emission. ECOCAT E-3201, E-5307, E-7331, and E-7341 were not detected when tested by GC/ms. Most of the tests were silicone oils. The atomized portion was most tested from silicone oil and antioxidants. Suppliers of silicone oils and polyols claim that they have greatly reduced the original VOC emissions. Table 3 shows the coloration detection of PVC. ECOCAT E-3201, E-5307, E-7331, and E-7341 all meet the relevant requirements.

Various sporadic tests have demonstrated that the use of several different catalysts in combination or alone is feasible. Several types of reactive catalysts provided by ALLCHEM can be used in combination to meet the low VOC emission requirements of MDI molded foams. This gives The formulator chooses a combination of reactive catalysts to meet the free space required by the formulation and process.

Table 3 MDI-based high-resilience molded foam

raw material

Formula 1

Formula 2

Recipe 3

Polyether/polymer polyols

100

water

3.8

Silicone oil S-3600

0.5

Diethanolamine

1.5

ECOCAT E-3201

0.15

ECOCAT E-5307

0.6

ECOCAT E-7331

1.0

ECOCAT E-7341

0.8

Index (WANNATE 8019)

Process performance Material temperature 25°C

Cream time s

Drawing time s

Stripping time

3 and a half minutes

2 minutes

Dissemination test by VDA278:2011,PV3937

VOC

FOGGING

Skin discoloration

Pass

Color meter

1.8

1.5

1.6

TDI Molded Foam

The reactivity of TM20, TM50 and all MDI is different. The same catalyst is used in the TDI and MDI systems, and the corresponding additions have to be adjusted to balance the blowing and gel rates without the need for excessive modifications. Due to the current regulatory factors of TDI, the more reasonable T/M system is TM50, ie, TDI/MDI=5:5, and the production process performance and the physical properties of foam products are the most reasonable. Table 4 is a study of car seat formulations under the TM50 system.

It can be seen from Table 4 that using ECOCAT E-7331, the E-7341 catalyst has a shorter milking time, a longer drawing time, improved fluidity, accelerated aging time, and faster demolding time, which can meet the demand for rapid demoulding. . This means that when traditional A1, A33 amine catalysts and their derived products are used, the process conditions can be maintained after the transition towards low environmental pollution, low VOC emissions, low fogging, and low odor. Production efficiency will not be reduced as a result, while physical performance can also be maintained.

ECOCAT E-7331, E-7341 is particularly suitable for TM and TDI systems, alone or in combination with other catalysts, such as ECOCAT E-3201 Foam Catalyst and E-5307 Gel Catalyst, to meet different application requirements.

Table 4 TDI-based high-resilience molded foam

raw material

Formula 1

Formula 2

Recipe 3

Polyether/polymer polyols

100

water

3.3

Silicone oil S-3600

0.5

Diethanolamine

1.5

ECOCAT E-3201

0.15

ECOCAT E-5307

0.8

ECOCAT E-7331

1.2

ECOCAT E-7341

1.0

Index (TM50 T/M=5:5)

Process performance material temperature 25 °C

Cream time s

Drawing time s

Stripping time

5 minutes

3 minutes

Dissemination testing by VDA278:2011,PV3937

VOC

FOGGING

Skin discoloration

Pass

Color meter

1.4

1.1

1.3

in conclusion

The automotive interior soft foam molding and large block foam industry faces many problems. Volatile organic compounds can emit odors, toxic VOCs, discoloration of the skin, and fogging. These issues require our attention. However, the use of tertiary amine catalysts in formulations is very small, and the inappropriate selection of tertiary amines and other additives can have a significant effect. Most automotive molded foams and polyether foams are catalyzed by a mixture of TEDA and BDMAEE, and these catalysts have, to some degree, been shown to have a suspicion. We show that it is feasible to replace the catalysts of these substances. They are tertiary amine catalysts that have low sporadic, high molecular weight, and can react.

The ECOCAT E-3201 catalyst is a low emission blowing catalyst that can replace BDMAEE over a wide range of applications. Based on this application, we have a number of E-5307, E-7331, and E-7341 gel catalysts used in conjunction with E-3201 to obtain hair and gel balance requirements. The E-7331, E-7341 catalyst provides a slower initial reaction and a faster maturation time. These new materials open up a vast process window for foam engineers.

With the ALLCHEM ECOCAT series of low-dispersion catalysts and ultra-low atomization silicone oil S-3600, the VOC value and fog value can be improved. This catalyst maintains improved wet-aging of the foam and improves the skin color change of the PVC. These improved catalysts have significantly improved with traditional catalysts based on TEDA and BDMAEE.