How to remove the rubber smell on the EPDM window tape?

Recently, many sales elites have been asking about the taste of EPDM. Technical experts believe that EPDM, as a rubber product, has different degrees of special smell, which is very normal. Therefore, when everyone is questioned about the smell of the venue, don't rush to conclusions, but listen carefully. Of course, with the improvement of environmental awareness, reducing rubber products naturally becomes a "necessary" task.

A) who is A)EPDM?

First, let's understand what EPDM is.

Chinese name for EPDM. This name is very vivid, which basically solves the problem of "who is he". EPDM is a terpolymer of ethylene, propylene and a small amount of diene. It has many advantages such as heat aging resistance, weather aging resistance, ozone resistance, chemical medium resistance, water resistance and so on. Because of these advantages, EPDM is widely used in various industries. Our stadium is just his new "customer", and his biggest "customer" at present is the automobile industry.

B) How is ethylene propylene rubber made?

How to synthesize raw rubber from ethylene, propylene and a small amount of diene is a complex process, involving a large number of chemical equations and chemical "bottles". I won't elaborate on it for the time being, but I remember that raw rubber is synthesized by ethylene, propylene and a small amount of diene under the catalysis of a specific catalyst.

What is the size of EPDM? This is similar to our PU, silicone PU plastic playground. Our PU and silicone PU, besides the main raw materials isocyanate and polyether polyol, also have some auxiliary materials with other functions, such as medium and long-chain chlorinated paraffin, powder, anti-ultraviolet agent and so on.

The EPDM compounding agent here is also a similar concept, such as accelerator, vulcanizing agent, inorganic filler, rubber oil and so on.

Everything is ready, so we can say the source of EPDM smell.

C) Where did Wen Jun come from?

A) raw rubber

Just like there are 369 kinds of cosmetics, there are Guerlain, Dior, SK-II, MAC, Lancome and Dabao. EPDM also has three, six and nine grades.

Some manufacturers have relatively old technology, using the traditional Natta-Ziegler process 60 years ago. Due to the low catalytic efficiency, it is necessary to remove the residual catalyst in this process. The removal steps include, but are not limited to, the cooling and washing of catalyst residues, the stripping of solution and the drying of products, but in any case, the raw rubber synthesized by this technology will have a strong smell. However, some manufacturers adopt new metallocene technology, which has high catalytic efficiency, less residual catalyst in the product, no need to remove it, and little smell.

B) filler

The mixing of EPDM also needs fillers, generally carbon black and inorganic fillers. Inorganic filler has a single component, stable performance and is not easy to produce special odor. And the other carbon black, I believe everyone knows how complicated he is, is a troublemaker.

Carbon black consists of 90-99% carbon source, the rest is hydrogen, oxygen and various functional groups composed of them, and a small amount of combined sulfur and other impurities, including sulfur, ash, tar and water. The smell of carbon black is closely related to its synthesis method. The smell of carbon black produced by oil furnace method with heavy oil as raw material is greater than that of natural gas. Because polycyclic aromatic hydrocarbons are adsorbed on the surface of carbon black, but the adsorption is very firm, which is the main source of carbon black odor.

C) rubber oil

Generally speaking, rubber oils for EPDM include high aromatic oil, aromatic oil, naphthenic oil and paraffin-based oil. Generally speaking, the smell of Gaofang sesame oil is much greater than the other two, but it is also the least used one, except for the smell, but also because of its poor yellowing resistance.

D) vulcanization

Vulcanization is another main source of EPDM odor. There are two common vulcanization systems: sulfur and peroxide. Sulfur-vulcanized products are often used in places with low heat resistance requirements, generally less than 120℃, while peroxide-vulcanized products have good heat resistance and can be used in places with higher temperatures, generally less than 150℃.

DCP (dicumyl peroxide) is a common peroxide curing agent, which has good curing properties, but its special smell is serious, and its application scope is greatly limited. Recently, odorless DCP(BIPB-40C) has been widely used. Although the smell of products vulcanized with it is greatly reduced, it still has a slight smell.

E) processing technology

In order to reduce the residual odor in products, more and more manufacturers now adopt special processing technology to reduce and eliminate the residual odor in products. There are two common methods.

Secondary vulcanization technology is a common processing technology for EPDM rubber, and it is even more essential for peroxide vulcanized rubber. It means that the molded vulcanized products can continue in the oven for a certain period of time at a specified high temperature and normal pressure, which can further deepen the vulcanization degree of rubber products, stabilize cross-linking bonds, improve the heat resistance of rubber compound, reduce the content of volatile substances in rubber, and have a significant effect on reducing the odor of products.

The second is water boiling, especially some products that use water as working medium. Because EPDM has good water resistance, it will not adversely affect the product performance. The general process is to soak the product in water and boil it for half an hour, so that satisfactory deodorization effect can be obtained. Therefore, in rainy and humid weather, it will also help to remove the odor of EPDM particles.

Technical experts all know that the odor problem of EPDM is easy to be perceived, which often leads to customer complaints in actual production, but it is not easy to quantitatively study because of the lack of clear definition and testing methods. The most ideal rubber products are tasteless and difficult to achieve for various reasons. However, through the selection of materials and proper processing technology, the odor of the product can still be reduced and the product with little odor can be obtained.

How to reduce the odor problem of EPDM products

abstract

Through the analysis of the odor of commonly used materials in EPDM, it is pointed out that the materials themselves have different odors because of the different varieties and preparation methods of various materials.

◇ EPDM adopts metallocene catalytic technology, and the variety filled with colorless paraffin oil has the least smell.

Carbon black is a kind of natural gas as raw material or inorganic filler (silica) with the least odor.

◇ The smell of peroxide curing agent is the biggest, the smell of sulfur curing system is the smallest, and the smell of comprehensive accelerator is the smallest.

The residual odor in the product can be reduced by secondary vulcanization.

First of all, preface

EPDM is a terpolymer of ethylene, propylene and a small amount of diene. It has excellent heat aging resistance, weather aging resistance, ozone resistance, chemical medium resistance and water resistance, and is widely used in manufacturing various rubber parts in automobile and household appliances industries. Rubber materials are composed of many kinds of materials, and general rubber products have different degrees of special smell. With the enhancement of people's awareness of health and environmental protection, rubber fittings used in many occasions are required to be odorless. This work studies how to reduce and eliminate the special smell of EPDM products.

Second, experimental materials and methods

2. 1 test materials

EPDM K778Z and 2340A langsheng products; EPDM KEP350, a product of South Korea Kumho Company; 3092PM Mitsui Chemistry, Japan; N330 produced by Jiangxi Black Cat Carbon Black Company and N550 natural gas semi-reinforced carbon black produced by Liao Bin Carbon Black Company are produced by Xinjiang Karamay Carbon Black Factory; Spray carbon black, produced by Fushun carbon black factory; Paraffin oil PM-100 produced by Guangzhou Dagang Petroleum Technology Co., Ltd.; Peroxide vulcanizing agent bipb-40p produced by SOVMER Company in Taiwan Province Province; Other additives are general commercial industrial products.

2.2 Evaluation method

Odor evaluation: artificial olfactory comparison was used and evaluated on a scale of 5. The meaning of each score is: 1- not detected; 2 points-slightly stronger, which can be detected by hard sniffing; 3 points-medium strength, which can be directly detected, 4 points-high strength, which can be tolerated; 5 points-great strength, unbearable.

III. Results and discussion

3. 1 Influence of rubber material

Several kinds of EPDM materials of the same brand commonly used in the market were selected, and the odor degree of raw rubber was evaluated by artificial nose smell after unpacking. See table 1 for the results.

Table 1 Odors of different raw rubbers

Rubber brand odor score

K778Z 2

2340A 2

KEP350 3

KEP90 1 4

3092m 1

3072EM 1

From the comparison results, EPDM itself has different degrees of odor, and there is a big gap between EPDM materials from different manufacturers. The 3092M and 3072EM (oil-filled 40phr), known as Mitsui, adopt metallocene catalytic technology, which is almost tasteless;

Lansheng's K778Z and 2340A have a slight smell, and Mianhu's KEP350 has a heavier smell, among which KEP90 1 (oil-filled 100phr) has the heaviest smell. The reason may be that different companies have different manufacturing processes and materials, resulting in different residual organic volatiles in rubber. The traditional Ziegler-Natta catalytic synthesis technology is used in the EPDM of Langsheng and Jinhu Company. Due to the low catalytic efficiency, the residual catalyst needs to be removed [1]. However, the amount of new metallocene catalyst is very small, the catalytic efficiency is very high, and the catalyst residue in the product is very small and does not need to be removed. This production method saves many production steps, including cooling and washing of catalyst residues, stripping of solution and drying of products. The product produced by the new method is colorless transparent body, indicating its high purity [2], so there are few volatile components that produce odor, and the odor is minimal.

KEP90 1 produced by Jinhu Company is filled with ordinary paraffin oil, which is not only strong in smell, but also dark yellow in color. Studies show that EPDM rubber products filled with ordinary paraffin oil are more prone to discoloration under ultraviolet radiation, and their yellowing resistance is not as good as that of products filled with colorless paraffin oil when making light-colored products [3].

3.2 Enhance the influence of filler materials

EPDM materials are mainly carbon black and inorganic fillers. Generally speaking, inorganic fillers, such as silica SD-25, SD-30, etc., are single in composition and stable in performance. On the other hand, carbon black is very complex and needs to be discussed emphatically. Carbon black consists of 90-99% carbon, the rest is hydrogen, oxygen and its various functional groups, and a small amount of bound sulfur and other impurities, including sulfur, ash, tar and water [4]. Due to the different manufacturing processes of carbon black, different brands of carbon black have different smells. Several commonly used carbon black artificial noses were selected to evaluate the odor degree of carbon black. The results are shown in Table 2.

Table 2 Raw materials and preparation methods of different varieties of carbon black

Method for manufacture raw materials with odor fraction of carbon black variety

N330 1 heavy oil furnace process

N550 1 heavy oil furnace process

Xinjiang natural gas semi-reinforcement 1 natural gas furnace method

N990 1 thermal cracking of natural gas

Spraying carbon black 3 is unknown and similar to the oil furnace method.

From the comparison of several kinds of carbon black, except one kind of spray carbon black, other kinds of carbon black are basically tasteless, which shows that the smell of carbon black has a great relationship with raw materials and manufacturing methods. The smell of carbon black produced by oil furnace method with heavy oil as raw material is greater than that of natural gas. Because polycyclic aromatic hydrocarbons are adsorbed on the surface of carbon black, but the adsorption is very firm [4], which may be the source of carbon black odor. The actual test also shows that ordinary carbon black contains a small amount of polycyclic aromatic hydrocarbons, while the content of polycyclic aromatic hydrocarbons in carbon black with natural gas as raw material is very small. The test results are shown in Table 3.

Table 3 Polycyclic Aromatic Hydrocarbons Content in Different Varieties of Carbon Black (ppm)

Total content of polycyclic aromatic hydrocarbons in carbon black variety 16

N330 16.9

N550 23.7

Natural gas semi-reinforced carbon black 10.5438+0

It should be noted that the EU has issued the directive 2005/69/EC, which is aimed at the content of polycyclic aromatic hydrocarbons (PAHs) in products. The smell of rubber products is too strong, and there is a high risk of polycyclic aromatic hydrocarbons (PAHs) in the reaction.

3.3 the influence of softener

Rubber filling oil can be divided into high aromatic oil, aromatic oil, naphthenic oil and paraffin-based oil according to ASTM D2226 standard.

Among them, high aromatic oil and aromatic oil contain high polar compounds, and the compound filled with them has good processability, tensile strength, elongation at break and tearing performance, but the disadvantages are pollution, low elasticity and poor low temperature performance.

Aromatic hydrocarbon content is the most important quality index of oil-extended rubber, which affects the yellowing stability of products: low aromatic hydrocarbon content, slow yellowing speed and high quality. High aromatic oil contains many polycyclic aromatic hydrocarbons (PAHs), so it also has a serious special smell, but this oil is very polar and will not be used for nonpolar EPDM.

Naphthenic oil has low content of asphaltene and polar compounds, good miscibility with rubber and no pollution. The oil-extended rubber prepared from naphthenic oil has stable color and good elasticity, and can be used for EPDM.

Paraffin-based oil has the highest saturated hydrocarbon content and good miscibility with EPDM, so it is widely used in EPDM. Due to the different manufacturing processes, the odor performance of different brands of paraffin oil is different. For example, the odor pairs of various softeners commonly used in EPDM are shown in Table 4:

Table 4 odor comparison of different softeners

Odor score of softener varieties

Paraffin oil 2500 2

Paraffin oil PM- 100 2

Naphthenic oil NM- 100 2

Aromatic oil AM- 18 3

In addition, various resin softeners are often used in rubber. Gumalon resin, petroleum resin, etc. are often much more smelly than the above-mentioned filling oil, which will also aggravate the smell of the final product. Although excellent physical and mechanical properties can be obtained, it is not suitable for use in products with odor requirements.

3.4 Influence of Vulcanization System

EPDM has two common vulcanization systems: sulfur and peroxide. Sulfur sulfide products are often used in places with low heat resistance requirements, generally less than 120℃, while peroxide sulfide products have good heat resistance and can be used in places with high temperature, generally less than 150℃.

DCP (dicumyl peroxide) is a common peroxide curing agent. The vulcanizate has good properties, but its special smell is serious, and its application scope is greatly limited. Recently, it is commonly known as odorless DCP(BIPB-40C), which has been widely used. Although the smell of products vulcanized with it has been greatly reduced, it still has a slight smell. Its odor score is 3, but it still can't reach the odor grade of sulfur vulcanized products, and its score is 2, so it is different when used.

Table 5 Comparison of Odors Produced by Different Vulcanizing Agents

Vulcanizing agent variety odor score

DCP 5

F90 3

Sulfur +TT, m, DM, CZ 2

Sulfur +EP33-75GE 2

3.5 the influence of processing technology

In order to reduce the residual odor in the product, special processing technology can be adopted to reduce and eliminate the residual odor in the product. There are two common methods.

3.5. 1 secondary vulcanization

Secondary vulcanization technology is a common processing technology for EPDM rubber, and it is even more essential for peroxide vulcanized rubber. It means that the molded vulcanized products can continue in the oven for a certain period of time at a specified high temperature and normal pressure, which can further deepen the vulcanization degree of rubber products, stabilize cross-linking bonds, improve the heat resistance of rubber compound, reduce the content of volatile substances in rubber, and have a significant effect on reducing the odor of products. The odor pairs of products with the same formula after primary vulcanization and secondary vulcanization are shown in Table 3, and the technological conditions of secondary vulcanization are: 150℃*3h.

Table 3 odor comparison of products obtained by different vulcanization systems and vulcanization processes

Scoring of primary vulcanization odor and secondary vulcanization odor of vulcanizing agent varieties.

DCP 5 3

BIPB-40C 3 2

Sulfur +TT, m, DM, CZ 2 1

Sulfur +EP33-75GE 2 1

From the actual contrast effect, the odor of the product after secondary vulcanization is reduced, and the odor score of sulfur vulcanization system can be reduced by 1, while the product cured by peroxide has obvious effect, and the odor score can be reduced by 2 points. The reason is that peroxide decomposition temperature is high and time is long. Only with sufficient reaction temperature and time can the decomposition products be fully decomposed and volatilized as much as possible. The longer the secondary vulcanization time, the less odor residue and the more tasteless the product.

Water boiling

For EPDM, boiling can also be used to reduce the residual odor in the product, and the effect is obvious, especially for some products with water as working medium, such as inlet and outlet pipes, which can not only remove odor, but also clean the product. Because EPDM has good water resistance, it will not adversely affect the product performance. The general process is to soak the product in water and boil it for half an hour, so that satisfactory deodorization effect can be obtained. Boiling water method is not suitable for treating products vulcanized by peroxide because of its low temperature.

Fourth, conclusion.

The odor problem of rubber products is easily perceived, which often leads to customer complaints in actual production. However, due to the lack of clear definition and testing methods, it is not easy to conduct quantitative research. Generally, the ideal rubber products are tasteless and difficult to achieve for various reasons. However, through the selection of materials and proper processing technology, the smell of the product can still be reduced, and the product with little smell or even tasteless can be obtained.