PP Injection Parts

Polypropylene resin is one of the four general-purpose thermoplastic resins (polyethylene, polyvinyl chloride, polypropylene, and polystyrene). It is produced by polymerizing propylene as raw material and ethylene as comonomer. The main products of Zhongwei Precision Machinery Co., Ltd. are nylon products, plastic products, ABS series, rubber products, etc. Types of injection molding materials that can be processed: polyethylene (PE), polypropylene (PP), nylon (PA, PA6, PA66), polyoxymethylene (POM), ABS, polyurethane (TPU), polyphenylene sulfide (PPS), polystyrene Carbonate (PC), Polyetheretherketone (PEEK), etc.

Product Description

1. Implementation standards: the company strictly implements ISO9001, ISO14001, IATF16949, VDA6.3 certification, and products have passed ROHS, FDA EU certification, etc.

2. Product material standards: ISO, GB, ASTM, SAE, EN, DIN, BS, AMS, JIS, ASME, DMS, TOCT, GB

3. Main processes: plastic injection molding, metal insert injection molding, investment casting, die-casting aluminum,

4. Available materials for injection molding:

Processable nylon products, plastic products, ABS series; injection molding material types: polyethylene (PE), polypropylene (PP), nylon (PA, PA6, PA66), polyoxymethylene (POM), ABS, polyurethane (TPU), poly Phenyl sulfide (PPS), polycarbonate (PC), polyether ether ketone (PEEK) and 3D printing can be customized according to customer requirements.

Production Process

Polypropylene resin is one of the four general-purpose thermoplastic resins (polyethylene, polyvinyl chloride, polypropylene, polystyrene). It is produced by polymerization with propylene as raw material and ethylene as comonomer. The process methods used in the production of polypropylene in the world are mainly divided into the following categories according to categories: solvent method, solution method, liquid phase bulk method (including liquid phase and gas phase combination) and gas phase bulk method. The characteristics of each process are introduced as follows:

• Solvent polymerization

Solvent method (also known as slurry method or slurry method, slurry method) is the earliest polypropylene production process. However, due to the deashing and solvent recovery processes, the process is long and complicated. Since the 1980s, the solvent method has become stagnant and gradually replaced by the liquid bulk method.

Process features:

(1) The propylene monomer is dissolved in an inert liquid-phase solvent (such as hexane), and the solvent is polymerized under the action of a catalyst, and the polymer is suspended in the solvent in a solid state of particle delivery, and a tank-type stirring reactor is used;

(2) There are deashing and solvent recovery processes, the process is long and complicated, the equipment investment is large, and the energy consumption is high. But the production is easy to control and the product quality is good;

(3) Separating polypropylene particles by centrifugal filtration, then boiling, drying and extrusion granulation.

• Solution polymerization

Process features:

(1) Using high-boiling straight-chain hydrocarbons as solvents, operating at a temperature higher than the melting point of polypropylene, all the obtained polymers are dissolved in the solvent and are homogeneously distributed;

(2) Evaporate and remove the solvent by high temperature stripping method to obtain molten polypropylene, and then extrude and granulate to obtain pellet products;

(3) The only manufacturer is Kodak in the United States.

• Liquid bulk method

The liquid-phase gas-phase combined type, liquid-phase bulk polypropylene production process is a new process developed in the middle and late stages of polypropylene production. The production process comes seven years after polypropylene industrial production began in 1957.

Using the liquid phase bulk method to produce polypropylene is to directly disperse the catalyst in the liquid phase propylene without adding any other solvent to the reaction system to carry out the propylene liquid phase bulk polymerization reaction. The polymer is continuously precipitated from the liquid phase propylene and suspended in the liquid phase propylene in the form of fine particles. As the reaction time increases, the concentration of polymer particles in the liquid phase propylene increases. When the propylene conversion rate reaches a certain level, the unpolymerized propylene monomer is recovered by flash evaporation to obtain a powdered polypropylene product. This is a relatively simple and advanced industrial production method of polypropylene. The liquid bulk method represents the new technology and new level of polypropylene production in the 1980s.

Process features:

(1) No solvent is added in the system, propylene monomer is polymerized in liquid phase in the tank reactor in liquid phase, and ethylene and propylene are copolymerized in gas phase in the fluidized bed reactor;

(2) Simple process, less equipment, less investment, low power consumption and production cost;

(3) The homopolymerization adopts a tank-type stirred reactor (Hypol process) or a loop reactor (Spheripol process), and both random copolymerization and block copolymerization are carried out in a stirred fluidized bed.

A typical representative of the liquid bulk method is the Spherizone liquid bulk method of BASELL. Spherizone is a gas-phase recycling technology that uses Ziegler-Natta catalysts to produce polymers that maintain toughness and processability while maintaining high crystallinity, stiffness, and greater homogeneity. It produces highly uniform multimonomer resins or bimodal homopolymers in a single reactor. The Spherizone loop reaction has two intercommunicating zones, with different zones functioning as the gas-phase and liquid-phase loop reactors of other processes. These two regions can produce resins with different relative molecular mass or monomer composition distributions, expanding the range of properties of polypropylene.

The core equipment of this process is MZCR (multi-zone circulating reactor system) reactor R230 system. The reactor consists of a riser and a descender. In the riser, the polymer is blown upward by the reaction gas to form fluidization, and sent to the upper part of the downcomer to pass through the cyclone separator, and the powder is collected in the downcomer. The reaction gas is circulated by a centrifugal compressor through an external line, and the heat of reaction is removed by means of a circulator cooler on the external circulation line. Reactor product is discharged through a valve installed in the lower part of the downcomer. After the discharged powder is degassed at high pressure and low pressure, when producing homopolymer and random copolymer, it is directly steamed and dried to obtain powder product. When producing impact products, the powder after high pressure degassing is discharged into the gas phase fluidized bed reactor. The reactor still uses the Spheripol II gas phase reactor system. The copolymerization reactor is a vertical cylindrical vessel, the upper and lower parts are spherical heads, the lower part is a fluidized bed, the main material is stainless steel, and the inner surface is polished.

The current single-line maximum production capacity of this process has reached 450,000 tons/year. MZCR (Multi-Zone Circulation Reactor) impact copolymers with an ethylene content of up to 22% (rubber content greater than 40%) can also produce terpolymers containing ethylene and 1-butene.

• Gas phase bulk method

Process features:

(1) No solvent is introduced into the system, and the propylene monomer is polymerized in gas phase in the reactor in a gas phase state;

(2) The process is short, the equipment is small, the production is safe, and the production cost is low

(3) The polymerization reactor has fluidized bed, vertical stirring bed and horizontal stirring bed.

A typical representative of the gas phase bulk method is the DOW Chemical Company Unipol gas phase process. The Unipol gas-phase polypropylene process is a gas-phase fluidized-bed polypropylene process developed by United Carbon Corporation (UCCP) and Shell in the 1980s. Polypropylene production and success. The process adopts a high-efficiency catalyst system, the main catalyst is a high-efficiency carrier catalyst, and the co-catalyst is triethylaluminum and an electron donor.

The UNIPOL process is simple, flexible, economical and safe; the process produces a full range of products including homopolymers, random copolymers and impact copolymers with very little equipment, and can be used in larger Operating conditions are adjusted within the operating range to maintain uniform product performance. Because the number of equipment used is small, the maintenance workload is small, and the reliability of the device is improved. Due to the limitation of the reaction kinetics of the fluidized bed itself, and the low operating pressure reduces the storage of materials in the system, the process is safer to operate than other processes, and there is no danger of equipment overpressure in the event of an accident out of control.

The process has no liquid waste discharge and very little hydrocarbon emissions to the atmosphere, so the impact on the environment is very small, making it easier to meet stringent environmental, health and safety specifications than other processes. Another notable feature of this process is that it can be operated in a supercondensed state, the so-called supercondensed state gas-phase fluidized bed process (SCM). This technology can increase the existing production capacity by 200% by increasing the proportion of liquid phase in the reactor to 45%. Since the liquid content is not the basic factor for the instability of the fluidized bed and the formation of polymer agglomerates, the key operating variables of this technology are the density of the expanded bed and the ratio of expanded bulk density to settled bulk density. Since the operation in the supercondensed state can remove the reaction heat most effectively, it can increase the production capacity of the reactor by more than 2 times without increasing the volume of the reactor, and the investment saving is very considerable. Impact copolymer products with ethylene content up to 17% (rubber content greater than 30%) impact copolymer products.

The core equipment of the process is a gas-phase fluidized bed reactor, a circulating gas compressor, a circulating gas cooler and an extrusion granulation unit. The fluidized bed reactor is a hollow vessel with an enlarged section at the top and a distributor at the bottom. The operating pressure of the first reactor is 3.5 MPaG and the temperature is 67 °C. The operating pressure of the second reactor is 2.1 MPaG and the temperature is 70 °C. ; The circulating air compressor is a single-stage, constant speed, centrifugal compressor.

Post Injection Molding Process

1. Processing equipment: CNC, WEDM, lathe, milling machine, drilling machine, grinder, etc.;

2. Surface treatment: For some products that require subsequent processing, we can provide surface treatment services to achieve the special purpose of customers. At present, we can provide degreasing, polishing, electroplating (gold, silver, nickel, tin, galvanized, etc.), anodizing, electrophoresis and other surface treatment services for precision parts.

Moulds and Inspection Fixtures

1. Mold service life: usually semi-permanent. (except for lost foam)

2. Mold delivery time: 10-25 days, (according to product structure and product size).

3. Tooling and mold maintenance: Zhongwei is responsible for precision parts.

Quality Control

1. Quality control: the defective rate is less than 0.1%.

2. Samples and trial run will be 100% inspected during production and before shipment, sample inspection for mass production according to ISDO standards or customer requirements

3. Testing equipment: automated visual inspection equipment can carry out 100% inspection of products, spectrum analyzer, golden elephant analyzer, three-coordinate measuring machine, hardness testing equipment, tensile testing machine.