Instructions for the Preparation Process and Manufacturing Method of Defrosting Heating Element End Sealing Components

A manufacturing process for a defrosting heating element end seal for use in cold storage and refrigerated cabinets operating in extremely humid and low-temperature environments involves polymerizing nitrile rubber, natural rubber, zinc oxide, antioxidants, accelerators, petrolatum, and epoxy resin in a specific weight percentage ratio to form a rubber. The heating element end is then acid-washed, coated with CH3COCH3, CHEMLOK 205, and 220, and pressed together with the synthetic rubber. This invention fundamentally overcomes the weaknesses of traditional defrosting heating elements using ordinary heating elements with rubber sleeves, resulting in poor moisture resistance and freeze protection. It offers advantages such as simple manufacturing process, safety and reliability, heat resistance, freeze resistance, moisture resistance, high insulation, and long service life, solving a major problem for my country's refrigeration industry.

This invention relates to a defrosting heating element and its manufacturing process for use in cold storage and refrigerated cabinets operating in extremely humid and low-temperature environments.

In recent years, with the rapid development of my country's refrigeration industry, severe icing and frosting have become a problem in refrigeration systems of refrigeration equipment, resulting in poor cooling performance and failing to meet the cooling requirements of refrigeration equipment. This affects the full functionality of facilities such as ice storage, cold storage, and refrigerated cabinets. In particular, when the defrosting heating element of imported refrigeration equipment is damaged, the equipment cannot operate normally. Replacing the defrosting heating element with an imported one is expensive and inconvenient. Previously, to solve the problem of icing and frosting in refrigeration equipment, people generally used ordinary heating element ends with rubber sleeves. While this achieved defrosting to some extent, it failed to meet the requirements for moisture resistance, low-temperature resistance, and aging resistance because a gap exists between the rubber sleeve and the heating element. This failed to address issues of moisture resistance, water resistance, and corrosion resistance, resulting in poor performance and a short lifespan.

To address the above shortcomings, the purpose of this invention is to provide a defrosting heating element end seal that is moisture-proof, water-resistant, corrosion-resistant, anti-aging, has good insulation properties, and a long service life, along with its manufacturing process.

The main raw materials for the synthetic rubber of this invention are: nitrile rubber N:41, natural rubber, zinc oxide, antioxidant, accelerator, petrolatum, epoxy resin, etc. The weight percentage proportions of the synthetic rubber formulation of this invention are as follows: Nitrile rubber N: 41: 40-50% Natural rubber #2: 8-15% Zinc oxide: 6-12% Antioxidant A: 0.2-0.5% Accelerator DM: 0.3-0.5% Accelerator CD: 0.1-0.3% Stearic acid: 0.5-1% Calcium carbonate: 10-20% Silica: 8-15% Gumani: 0.5-1.5% Vaseline: 3-5% Epoxy resin: 1-3% The optimal weight percentage ratio of the raw materials is as follows: Nitrile rubber N: 41: 45% Natural rubber #2: 12% Zinc oxide: 8% Antioxidant A: 0.3% Accelerator DM: 0.4% Accelerator CD: 0.2% Stearic acid: 0.8% Calcium carbonate: 15% Silica: 12% Combination ingredients: 1% Vaseline: 4% Epoxy resin: 2% The synthesis process is as follows: First, the epoxy resin is metered and then diluted with a measured amount of warm water and stirred. It is then placed in a pot and steamed until the water is completely evaporated, and then cooled. Next, nitrile rubber, natural rubber, zinc oxide, antioxidant A, accelerator DM, Vaseline, and epoxy resin are polymerized according to the weight percentage formula to form synthetic rubber. The manufacturing process is as follows: The heating element end is acid-washed and cleaned. The heating wire lead is connected to an electric wire. CH3COCH3, CHEMLOK205, and CHEMLOK220 are applied sequentially to the cleaned heating element end and the connection between the lead and the electric wire. After drying, the synthetic rubber is metered and placed into a mold. Simultaneously, the treated heating element end is placed in the center of the mold. A pressure of 100kg-150kg/cm² is applied, and the temperature is raised to 150℃-170℃ for approximately 5 minutes for vulcanization. The vulcanized synthetic rubber of this defrosting heating element, processed with a special technique, exhibits strong adhesion to metal, excellent sealing, high pressure resistance, heat resistance, moisture resistance, freeze resistance, corrosion resistance, resistance to aging, long service life, high insulation, and safe and reliable operation.

The advantages and effects of this invention are as follows:

1. Strong adhesion and excellent sealing effect. This invention uses CH3COCH3, CHELOK205, and CHELOK220 sequentially coated onto the pressed metal part, resulting in excellent adhesion and sealing performance between the metal and the rubber.

2. This synthetic rubber possesses excellent heat resistance, moisture resistance, freeze resistance, and corrosion resistance. It is suitable for operation in humid and low-temperature environments.

III. High voltage resistance and high insulation resistance, with the following specifications: Moisture-state insulation resistance ≥200MΩ～ωMΩ; Insulation resistance after damp heat test ≥5MΩ; Moisture leakage current ≤0.1MA

IV. All technical specifications of this defrosting heating element are similar to those of products manufactured in Russia and the United States, but the price is only one-tenth that of Russian and American heating elements. It replaces the defrosting heating elements in imported equipment, saving the country a significant amount of foreign exchange, completely solving the problem of product upgrades in domestically produced equipment, and solving a major problem for the refrigeration industry.

Figure 1 is a process flow diagram of this invention:

In the diagram: 1. Raw material proportioning and rubber synthesis → 2. Acid washing and sealing of heating element → 3. Coating with CH3COCH3 → 4. CHELOK205 → 5. Coating with CHELOK220 → 6. Synthetic rubber compression molding.

The optimal embodiment of the moisture-proof, freeze-resistant, and defrosting electric heating tube fitting of the present invention is as follows: First, the synthetic rubber is prepared in the following weight percentage proportions: Nitrile rubber N: 41:45% Natural rubber #2: 12% Zinc oxide: 8% Antioxidant A: 0.3% Accelerator DM: 0.4% Accelerator CD: 0.2% Stearic acid: 0.8% Calcium carbonate: 15% White charcoal: 12% Gomani: 1% Vaseline: 4% Epoxy resin: 2% Then, the end of the electric heating tube is acid-washed and sealed, coated with CH3COCH3, CHELOK205, and CHELOK220. Next, the synthetic rubber and the end of the electric heating tube are placed in a mold and pressed into the finished product at a pressure of 100-150 kg/cm², a temperature of 160°C, and a time of 5-6 minutes.