CN109181066B - High-resilience polyethylene filling particle, application and processing method thereof - Google Patents
High-resilience polyethylene filling particle, application and processing method thereof Download PDFInfo
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Abstract
The invention discloses a high-resilience polyethylene filling particle, application and a processing method, belonging to the field of high polymer materials, wherein the particle diameter of the high-resilience polyethylene filling particle is 0.1-10 mm, the shape of the particle is flocculent, the compression permanent deformation of the high-resilience polyethylene filling particle is less than 20% under the conditions of 70 ℃ of temperature, 50% of compression ratio and 22 hours of compression time, and the bulk density of the high-resilience polyethylene filling particle is less than 0.1g/cm in a natural state3. The preparation method comprises a cross-linking foaming step, a foaming material primary crushing step and a low-temperature crushing step after primary crushing. The invention also provides a method for preparing the high-resilience polyethylene filling particles. The invention forms the method for preparing the high-resilience, low-density and flocculent polyethylene particles by simultaneously matching the crushing process and the crosslinking process and matching with specific process parameters, and the polyethylene particles in the form can replace the existing cotton and polyurethane foaming materials and be used as fillers of household articles and toys.
Description
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to high-resilience polyethylene filling particles, application and a processing method thereof.
Background
At present, the fillers of household articles and toys are mainly cotton, polyurethane foam, synthetic fibers and other materials. The materials are generally high in specific density and strong in hydrophilicity, and some materials are weak in resilience or easy to agglomerate, for example, cotton and fiber materials are easy to agglomerate, and the defects that the use comfort of terminal products is poor, pollution is easy, peculiar smell is remained and the like are easily caused.
Polyethylene is a nonpolar material, has stable chemical properties, is a polymer material which is most widely applied at present, and has a great amount of applications in the daily life fields of food, packaging, buildings and the like. But has the following disadvantages: the creep resistance under natural conditions is poor and is not suitable as a shape-retaining filler. In addition, since polyethylene resin has a relatively high specific density compared to cotton and polyurethane foam materials, polyethylene materials are rarely used as a filler.
Therefore, it is required to develop a polyethylene filling material and a method for preparing the polyethylene filling material so as to be capable of replacing the cotton or polyurethane foam filling material.
Disclosure of Invention
In view of the above defects or improvement needs of the prior art, the present invention provides a high resilience polyethylene filling particle, application and a processing method thereof, and the object is to form a method for preparing high resilience, low density and flocculent polyethylene particles by simultaneously matching a crushing process and a crosslinking process and matching specific process parameters, wherein the polyethylene particles in the form can replace the existing cotton and polyurethane foaming materials and be used as fillers for household articles and toys.
To achieve the above objects, according to one aspect of the present invention, there is provided a high resilience polyethylene infill particle having a particle size of 0.1mm to 10mm, a flocculent morphology having a compression set of less than 20% at a temperature of 70 ℃, a compression time of 22 hours and a 50% compression ratio, and a natural bulk density of less than 0.1g/cm3。
Furthermore, the preparation method comprises a cross-linking foaming step, a foaming material primary crushing step and a low-temperature crushing stage after primary crushing.
According to a second aspect of the present invention there is also provided the use of filled particles of high resilience polyethylene as described above as a filler to replace cotton and foamed polyurethane in household goods and toys. For example, for the preparation of filling materials for doll bodies, for the preparation of cushions and cushions.
According to a third aspect of the present invention, there is also provided a process for the preparation of high resilience polyethylene filled microparticles as described above, comprising the steps of, in order:
s1: a crosslinking foaming step, which is to mix polyethylene with a chemical foaming agent, then carry out chemical crosslinking or irradiation crosslinking, heat and foam,
s2: a primary crushing step of the foaming material, wherein the temperature of the primary crushing is set to be-30-40 ℃,
s3: a low-temperature crushing step, wherein the temperature of the low-temperature crushing is set to be-200 ℃ to-160 ℃.
Further, in step S2, the primary crushing step is performed using one or more of a rotary knife crusher or a double-shaft shredder.
Further, in step S3, cryogenic pulverization is performed using one or more of a rotary knife pulverizer, a biaxial shredder, and a grinder.
Further, the crosslinking agent for chemical crosslinking in step S1 is selected from cumene hydroperoxide, tert-butyl peroxide and tert-butyl cumene hydroperoxide.
Further, the irradiation crosslinking is carried out by using an electron accelerator or by using gamma rays.
Further, the irradiation dose is generally 50Mrad to 70Mrad, and preferably 60 Mrad.
Further, in step S1, a low density polyethylene resin is selected as a raw material.
In general, the above technical solutions contemplated by the present invention can achieve the following beneficial effects compared with the prior art:
the invention adopts a crosslinking foaming technology, so that the polyethylene material is light in weight and has good rebound resilience and creep resistance. The polyethylene material after cross-linking foaming is crushed to ensure that the crushed particles reach certain fineness, the particle size of the particles is between 10mm and 0.1mm, the microcosmic appearance of the particles is irregular flocculent continuous bodies (the flocculent continuous bodies refer to granular or small blocky bodies in a cotton-like shape), and the polyethylene material can be used as a filling material with light weight, moisture resistance and high cleanness, and the polyethylene material has the effects after three processes of cross-linking, foaming and crushing.
The polyethylene particles prepared by the process conditions have good shape retention capacity, and the compression set is less than 20% under the conditions of 70 ℃, 22 hours and 50% compression ratio; the macroscopic bulk density is less than 0.1g/cm3The material can replace the existing cotton and the existing foamed polyurethane as the filler of household articles and toys.
Drawings
Fig. 1 is an electronic scanning picture of high resilience polyethylene particles obtained by the preparation in example 1 of the present invention at a magnification of 100 times.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention adopts a cross-linking foaming technology (the cross-linking foaming comprises chemical cross-linking foaming and irradiation cross-linking foaming), and the polyethylene material is light in weight and has good rebound resilience and creep resistance by controlling the design and parameters of the foaming process. Furthermore, the polyethylene material after cross-linking foaming is crushed, the crushed particles have unique shape and performance through the control and design of the crushing process, and the crushed particles reach certain fineness (or called particle size) through the comprehensive foaming process and crushing process, so that the polyethylene material can be used as a filling material with light weight, moisture resistance, high cleanness and high resilience.
It should be noted that the polyethylene material or the polyethylene porous material is easily deformed by strong shearing action during the pulverizing process, and is difficult to be processed into fine particles. Even if the low-temperature technology is adopted, the temperature of the crushing environment is reduced to the embrittlement temperature of the polyethylene, the instantaneous shearing force in the crushing process is large, and the porous structure formed by the foaming process of the polyethylene particles can be damaged, and the structure is a main factor for ensuring the low bulk density of the material. Therefore, the design of the comminution process is of great importance to ensure the properties of the end product.
In more detail, in the step of crosslinking and foaming the polyethylene, the purpose of foaming the polyethylene is to form a porous structure by a foaming expansion process, and the structure can greatly reduce the density of the material. More specifically, the purpose of crosslinking is three-fold:
firstly, in the foaming process, crosslinked structure is the prerequisite that improves material foaming ratio, because the foaming process goes on under the high temperature condition, and the temperature is set for between the softening temperature and the melting temperature of material usually, and polyethylene is the higher linear polymer of degree of crystallinity, and melt strength is lower under the high temperature condition, is unfavorable for the foaming, through the cross-linking modification back, linear molecular structure to network structure transition, and then has strengthened the melt strength of polymer, is favorable to lasting foaming to reach higher magnification.
And secondly, the material has good low-temperature resilience through crosslinking, so that deformation is avoided in the subsequent crushing process, a complex flocculent particle structure is formed, and the aim of light weight is fulfilled.
And thirdly, the cross-linked structure can enable the material to have good creep resistance, and the material is one of the basic properties of the material.
The cross-linking foaming technology used in the invention is divided into two types according to the difference of the process and the equipment:
the first is chemical crosslinking foaming: different from the existing chemical crosslinking foaming technology, the invention adopts a secondary crosslinking method. The process is as follows:
firstly, mixing and granulating polyethylene resin (LDPE), an AC foaming agent, a first crosslinking agent (the half-life temperature of 1 minute is below 180 ℃), a second crosslinking agent (the half-life temperature of 1 minute is above 190 ℃) and other auxiliary agents according to a certain proportion.
Then, the mixture of the granules is extruded into a coiled material by an extruder, and the coiled material is foamed in a high-temperature foaming furnace, wherein the foaming temperature is controlled below 180 ℃, and under the temperature and the processing conditions, the first cross-linking agent generates free radical decomposition to initiate a polymer system and generate cross-linking reaction. Under the temperature condition, the second cross-linking agent is decomposed slowly and is relatively stable in the system
And then, the foamed coiled material passes through a high-temperature foaming furnace again, the temperature of the second furnace is controlled to be more than 190 ℃, and under the temperature and the process condition, the second cross-linking agent is decomposed at a higher speed, so that the cross-linking reaction of the polymer system is initiated again. The traction tension in the process is required to be as small as possible, and the traction tensile stress value is required to be less than 5KPa according to different widths and thicknesses.
Finally, the material after the secondary crosslinking reaction has high foaming multiplying power and high crosslinking degree. It should be noted that, the secondary crosslinking process is adopted to improve the crosslinking degree in two steps, rather than improving the crosslinking degree to the final target in one step, such a process design has certain ingenuity, because the too high crosslinking degree of the material reduces the foamability in the foaming stage, so that the foaming ratio of the material is reduced, and the requirement of light weight cannot be met.
The second cross-linking foaming method is irradiation cross-linking foaming, which is also used for the purpose of high foaming and high cross-linking degree, the invention adopts a secondary irradiation method, and the process is as follows:
firstly, polyethylene resin (LDPE), AC foaming agent and other auxiliary agents are mixed and granulated according to a certain proportion.
The pelletized mixture is then extruded by an extruder into a first roll.
And then, carrying out first irradiation crosslinking on the first coiled material by a continuous irradiation (the irradiation source is an electron accelerator or a metal isotope radioactive source) device to obtain a second coiled material.
And then, foaming the second coiled material through a high-temperature foaming furnace to obtain a foamed coiled material.
And finally, passing the foamed coiled material through a continuous irradiation device again to obtain a final coiled material.
The process is similar to a chemical crosslinking method, the first step of crosslinking is to increase the melt strength of the polyethylene in the foaming process and improve the foamability of the material; the second step of crosslinking is to increase the crosslinking degree of the foaming material, so that the material has good shape retention capacity and low-temperature resilience, and meets the requirement of low-temperature crushing.
In the preliminary crushing step, as the foamed finished product is a continuous coiled material or sheet with larger volume and a closed pore structure, the low-temperature crushing is directly carried out to be not beneficial to cooling treatment, so the preliminary crushing is carried out before the low-temperature crushing. The particle size of the pulverized material is controlled to be 100mm or less, preferably 12mm or less.
In the low-temperature crushing step, the primarily crushed material is sent to a crusher set with low-temperature control, the low-temperature medium adopted by the invention is liquid nitrogen, the temperature reduction and the crushing are carried out synchronously, and the discharge particle size is controlled by a sieve plate. Experiments show that the particle shape maintaining effect obtained by crushing is the best in the temperature range of minus 160 +/-5 ℃. The temperature is too high, the particles obtained by crushing are slender, are difficult to pass through the pore passages of the sieve plate and are not beneficial to screening selection; the temperature is too low, the bulk density of the particles obtained by crushing is low, and the production cost of the low-temperature control process is greatly increased.
In order to illustrate the process and product of the present invention in more detail, further details are provided below with reference to specific examples.
Example 1
The first step is as follows: adding 100 parts by weight of low-density polyethylene resin, 25 parts by weight of azodicarbonamide foaming agent, 5 parts by weight of cumyl peroxide, 5 parts by weight of tert-butyl peroxide, 3 parts by weight of talcum powder, 2 parts by weight of zinc stearate, 2 parts by weight of polyethylene wax and 2 parts by weight of antioxidant into an internal mixer for fully internal mixing at the internal mixing temperature of 130 ℃, and then discharging into a two-stage mixing granulator for mixing granulation.
The second step is that: discharging the mixed particles into a single-screw extruder, and extruding into coiled materials, wherein the temperature control range of the single-screw extruder is 90-110 ℃.
The third step: continuously placing the coiled material into a high-temperature foaming furnace for foaming, wherein the foaming temperature is controlled to be 170-180 ℃, and the foaming time is 5 minutes. A foamed web was obtained.
The fourth step: and (3) putting the foamed coiled material into a high-temperature foaming furnace again, controlling the heating temperature to be 195-205 ℃ and the foaming time to be 8 minutes, thus obtaining the high-resilience polyethylene foamed coil.
The fifth step: and (3) putting the high-resilience polyethylene foamed roll into a rotary cutter pulverizer to perform primary pulverization, and controlling the diameter of fragments to be smaller than 100 mm.
And a sixth step: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 10 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the particle diameter is less than 10mm, and the macroscopic bulk density under the natural state is 0.03g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent.
Example 2
The first step is as follows: adding 100 parts by weight of low-density polyethylene resin, 15 parts by weight of azodicarbonamide foaming agent, 5 parts by weight of cumyl peroxide, 5 parts by weight of tert-butyl cumyl peroxide, 3 parts by weight of talcum powder, 2 parts by weight of zinc stearate, 2 parts by weight of polyethylene wax and 2 parts by weight of antioxidant into an internal mixer for fully internal mixing, wherein the internal mixing temperature is 130 ℃, and then discharging into a two-stage mixing granulator for mixing granulation.
The second step is that: discharging the mixed particles into a single-screw extruder, and extruding into coiled materials, wherein the temperature control range of the single-screw extruder is 90-110 ℃.
The third step: continuously placing the coiled material into a high-temperature foaming furnace for foaming, wherein the foaming temperature is controlled to be 170-180 ℃, and the foaming time is 5 minutes. A foamed web was obtained.
The fourth step: and (3) putting the foamed coiled material into a high-temperature foaming furnace again, controlling the heating temperature to be 195-205 ℃ and the foaming time to be 10 minutes, thus obtaining the high-resilience polyethylene foamed coil.
The fifth step: and (3) putting the high-resilience polyethylene foamed roll into a rotary cutter pulverizer to perform primary pulverization, and controlling the diameter of fragments to be less than 10 mm.
And a sixth step: putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 0.1 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the grain diameter is less than 0.1mm, the bulk density is 0.1g/cm3, the compression permanent deformation at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent deformation at 23 ℃ is less than or equal to 10 percent.
Example 3
The first step is as follows: adding 100 parts by weight of low-density polyethylene resin, 10 parts by weight of azodicarbonamide foaming agent, 3 parts by weight of talcum powder, 2 parts by weight of zinc stearate, 2 parts by weight of polyethylene wax and 2 parts by weight of antioxidant into an internal mixer for fully internal mixing at the internal mixing temperature of 130 ℃, and then discharging the mixture into a two-stage mixing granulator for mixing granulation to prepare foaming master batches, wherein the working temperature of the two-stage mixing granulator is 100 ℃.
The second step is that: adding 60 parts by weight of low-density polyethylene resin, 60 parts by weight of ethylene-vinyl acetate copolymer, 2 parts by weight of polyethylene wax, 0.5 part by weight of antioxidant and 0.4 part by weight of trimethylolpropane trimethacrylate into the prepared foaming master batch, adding the mixture into a high-speed mixer, mixing for 3-5 minutes at normal temperature, then discharging the mixture into a single-screw extruder, and extruding the mixture into sheets, wherein the working temperature of the single-screw extruder is 100 ℃.
The third step: the extruded sheet was cross-linked by irradiation with an electron accelerator at a dose of 20 Mrad.
The fourth step: and (3) feeding the sheet subjected to radiation crosslinking into a high-temperature foaming furnace for foaming, wherein the temperature of the foaming furnace is 200 ℃. And (5) preparing the foaming coiled material.
The fifth step: and (3) carrying out radiation crosslinking on the polyethylene foamed roll by using an electron accelerator again, wherein the radiation dose is 60 Mrad. And obtaining the high-resilience polyethylene foamed roll.
And a sixth step: and (3) putting the high-resilience polyethylene foamed roll into a rotary cutter pulverizer to perform primary pulverization, and controlling the diameter of fragments to be less than 10 mm.
The seventh step: putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 0.1 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the particle diameter is less than 0.1mm, and the bulk density is 0.1g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent.
Example 4
The first step is as follows: adding 100 parts by weight of low-density polyethylene resin, 15 parts by weight of azodicarbonamide foaming agent, 1 part by weight of talcum powder, 3 parts by weight of zinc stearate and other auxiliary agents into an internal mixer for fully internal mixing at the internal mixing temperature of 130 ℃, and then discharging the mixture into a two-stage mixing granulator for mixing and granulating to prepare foaming master batches, wherein the working temperature of the two-stage mixing granulator is 100 ℃.
The second step is that: adding 60 parts by weight of low-density polyethylene resin, 60 parts by weight of ethylene-vinyl acetate copolymer, 2 parts by weight of polyethylene wax, 0.5 part by weight of antioxidant and 0.4 part by weight of trimethylolpropane trimethacrylate into the prepared foaming master batch, adding the mixture into a high-speed mixer, mixing for 3-5 minutes at normal temperature, then discharging the mixture into a single-screw extruder, and extruding the mixture into sheets, wherein the working temperature of the single-screw extruder is 100 ℃.
The third step: the extruded sheet was cross-linked by irradiation with gamma rays (cobalt source) at a dose of 20 Mrad.
The fourth step: and (3) feeding the sheet subjected to radiation crosslinking into a high-temperature foaming furnace for foaming, wherein the temperature of the foaming furnace is 200 ℃. And (5) preparing the foaming coiled material.
The fifth step: the polyethylene foam rolls were again radiation crosslinked with gamma rays (cobalt source) at an irradiation dose of 60 Mrad. Obtaining the high-resilience polyethylene foamed roll
And a sixth step: and (3) putting the high-resilience polyethylene foamed roll into a rotary cutter pulverizer to perform primary pulverization, and controlling the diameter of fragments to be less than 10 mm.
The seventh step: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 1 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the particle diameter is less than 1mm, and the bulk density is 0.05g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent.
Example 5
S1: a crosslinking foaming step, namely mixing polyethylene with a chemical foaming agent, then performing irradiation crosslinking, and heating for foaming, wherein the crosslinking foaming step specifically comprises the following steps:
adding the low-density polyethylene resin, the foaming agent, the talcum powder, the zinc stearate and other auxiliary agents into an internal mixer for fully mixing at the mixing temperature of 130 ℃, and then discharging into a mixing granulator for mixing granulation to prepare the foaming master batch.
Adding the prepared foaming master batch and another part of low-density polyethylene resin, ethylene-vinyl acetate copolymer, polyethylene wax, antioxidant, trimethylolpropane and trimethacrylate into a high-speed mixer, mixing for 3-5 minutes at normal temperature, then discharging into an extruder, and extruding into sheets, wherein the working temperature of the extruder is 100 ℃.
The extruded sheet was cross-linked by irradiation with gamma rays (cobalt source) at a dose of 20 Mrad.
And (3) feeding the sheet subjected to radiation crosslinking into a high-temperature foaming furnace for foaming, wherein the temperature of the foaming furnace is 200 ℃, and preparing the foamed coiled material.
The polyethylene foam rolls were again radiation crosslinked with gamma rays (cobalt source) at an irradiation dose of 60 Mrad. And obtaining the high-resilience polyethylene foamed roll.
S2: and a primary crushing step of the foaming material, wherein the temperature of the primary crushing is set at 40 ℃, and the primary crushing step is executed by adopting a rotary cutter crusher, and the diameter of the fragments is controlled to be less than 10 mm.
S3: putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-200 ℃, and controlling the aperture of a sieve plate to be 1 mm. The obtained product is the high-elasticity polyethylene particles.
The high-resilience polyethylene filling particle prepared in the embodiment of the invention has the particle diameter of 1mm, the morphology of the particle is flocculent, the compression permanent deformation of the high-resilience polyethylene filling particle is less than 12% under the conditions that the temperature is 70 ℃, the xx time is 22 hours and the 50% compression ratio, and the bulk density of the high-resilience polyethylene filling particle is 0.08g/cm in a natural state3. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
Example 6
S1: a crosslinking foaming step, namely mixing polyethylene with a chemical foaming agent, then performing irradiation crosslinking, and heating for foaming, wherein the crosslinking foaming step specifically comprises the following steps:
adding the low-density polyethylene resin, the foaming agent, the talcum powder, the zinc stearate and other auxiliary agents into an internal mixer for fully mixing at the mixing temperature of 130 ℃, and then discharging into a mixing granulator for mixing granulation to prepare the foaming master batch.
Adding the prepared foaming master batch and another part of low-density polyethylene resin, ethylene-vinyl acetate copolymer, polyethylene wax, antioxidant, trimethylolpropane and trimethacrylate into a high-speed mixer, mixing for 3-5 minutes at normal temperature, then discharging into an extruder, and extruding into sheets, wherein the working temperature of the extruder is 100 ℃.
The extruded sheet was cross-linked by irradiation with gamma rays (cobalt source) at a dose of 20 Mrad.
And (3) feeding the sheet subjected to radiation crosslinking into a high-temperature foaming furnace for foaming, wherein the temperature of the foaming furnace is 200 ℃, and preparing the foamed coiled material.
The polyethylene foam rolls were again radiation crosslinked with gamma rays (cobalt source) at an irradiation dose of 60 Mrad. And obtaining the high-resilience polyethylene foamed roll.
S2: and a primary crushing step of the foaming material, wherein the temperature of the primary crushing is set at 5 ℃, and the primary crushing step is executed by adopting a rotary cutter crusher, and the diameter of the fragments is controlled to be less than 10 mm.
S3: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 1 mm. The obtained product is the high-elasticity polyethylene particles.
The high-resilience polyethylene filling particle prepared in the embodiment of the invention has the particle diameter of 0.5mm, the shape of the particle is flocculent, the compression permanent deformation of the high-resilience polyethylene filling particle is less than 19 percent under the conditions that the temperature is 70 ℃, the xx time is 22 hours and the 50 percent compression ratio is 50 percent, and the bulk density of the high-resilience polyethylene filling particle is 0.03g/cm in a natural state3. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
Example 7
S1: a crosslinking foaming step, namely mixing polyethylene with a chemical foaming agent, then performing irradiation crosslinking, and heating for foaming, wherein the crosslinking foaming step specifically comprises the following steps:
adding the low-density polyethylene resin, the foaming agent, the talcum powder, the zinc stearate and other auxiliary agents into an internal mixer for fully mixing at the mixing temperature of 130 ℃, and then discharging into a mixing granulator for mixing granulation to prepare the foaming master batch.
Adding the prepared foaming master batch and another part of low-density polyethylene resin, ethylene-vinyl acetate copolymer, polyethylene wax, antioxidant, trimethylolpropane and trimethacrylate into a high-speed mixer, mixing for 3-5 minutes at normal temperature, then discharging into an extruder, and extruding into sheets, wherein the working temperature of the extruder is 100 ℃.
The extruded sheet was cross-linked by irradiation with gamma rays (cobalt source) at a dose of 50 Mrad.
And (3) feeding the sheet subjected to radiation crosslinking into a high-temperature foaming furnace for foaming, wherein the temperature of the foaming furnace is 200 ℃, and preparing the foamed coiled material.
The polyethylene foam rolls were again radiation crosslinked with gamma rays (cobalt source) at a radiation dose of 70 Mrad. And obtaining the high-resilience polyethylene foamed roll.
S2: a primary crushing step of the foaming material, wherein the temperature of the primary crushing is set to be-30 ℃, a double-shaft shredder is adopted to execute the primary crushing step, and the diameter of the fragments is controlled to be less than 10 mm.
S3: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-190 ℃, and controlling the aperture of a sieve plate to be 2 mm. The obtained product is the high-elasticity polyethylene particles.
The high-resilience polyethylene filling particle prepared in the embodiment of the invention has the particle diameter of 2mm, the morphology of the particle is flocculent, the compression permanent deformation of the high-resilience polyethylene filling particle is less than 18 percent under the conditions that the temperature is 70 ℃, the xx time is 22 hours and the 50 percent compression ratio is higher, and the bulk density of the high-resilience polyethylene filling particle is 0.09g/cm in a natural state3. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
Example 8
S1: and a crosslinking foaming step, namely mixing the polyethylene with a chemical foaming agent, then carrying out chemical crosslinking or irradiation crosslinking, and then heating for foaming, specifically:
adding low-density polyethylene resin, azodicarbonamide foaming agent, cumyl peroxide (as chemical cross-linking agent), tert-butyl cumyl peroxide (as chemical cross-linking agent), talcum powder, zinc stearate, polyethylene wax and antioxidant into an internal mixer, fully mixing at 130 deg.C,
then the mixture is discharged into a two-stage mixing granulator for mixing granulation. Discharging the mixed particles into a single-screw extruder, and extruding into coiled materials, wherein the temperature control range of the single-screw extruder is 90-110 ℃. Continuously placing the coiled material into a high-temperature foaming furnace for foaming, wherein the foaming temperature is controlled to be 170-180 ℃, and the foaming time is 5 minutes. A foamed web was obtained. And (3) putting the foamed coiled material into a high-temperature foaming furnace again, controlling the heating temperature to be 195-205 ℃ and the foaming time to be 10 minutes, thus obtaining the high-resilience polyethylene foamed coil.
S2: a step of primary crushing of the foaming material, which is to put the high-resilience polyethylene foaming roll into a rotary cutter crusher for primary crushing, control the diameter of the fragments to be less than 10mm, set the temperature of the primary crushing at-25 ℃,
s3: putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-160 ℃, and controlling the aperture of a sieve plate to be 0.1 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the particle diameter is less than 0.1mm, and the bulk density is 0.1g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
Example 9
S1: and a crosslinking foaming step, namely mixing the polyethylene with a chemical foaming agent, then carrying out chemical crosslinking or irradiation crosslinking, and then heating for foaming, specifically:
adding low-density polyethylene resin, azodicarbonamide foaming agent, cumyl oxide (as chemical cross-linking agent), tert-butyl cumyl peroxide (as chemical cross-linking agent), talcum powder, zinc stearate, polyethylene wax and antioxidant into an internal mixer, fully mixing at 130 deg.C,
then the mixture is discharged into a two-stage mixing granulator for mixing granulation. Discharging the mixed particles into a single-screw extruder, and extruding into coiled materials, wherein the temperature control range of the single-screw extruder is 90-110 ℃. Continuously placing the coiled material into a high-temperature foaming furnace for foaming, wherein the foaming temperature is controlled to be 170-180 ℃, and the foaming time is 5 minutes. A foamed web was obtained. And (3) putting the foamed coiled material into a high-temperature foaming furnace again, controlling the heating temperature to be 195-205 ℃ and the foaming time to be 10 minutes, thus obtaining the high-resilience polyethylene foamed coil.
S2: a step of primary crushing of the foaming material, which is to put the high-resilience polyethylene foaming roll into a rotary cutter crusher for primary crushing, control the diameter of the fragments to be less than 10mm, set the temperature of the primary crushing at 20 ℃,
s3: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-180 ℃, and controlling the aperture of a sieve plate to be 6 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the particle diameter is less than 6mm, and the bulk density is 0.02g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
Example 10
S1: and a crosslinking foaming step, namely mixing the polyethylene with a chemical foaming agent, then carrying out chemical crosslinking or irradiation crosslinking, and then heating for foaming, specifically:
adding low-density polyethylene resin, azodicarbonamide foaming agent, tert-butyl peroxide (as chemical cross-linking agent), tert-butyl cumyl peroxide (as chemical cross-linking agent), talcum powder, zinc stearate, polyethylene wax and antioxidant into an internal mixer, fully mixing at 130 deg.C,
then the mixture is discharged into a two-stage mixing granulator for mixing granulation. Discharging the mixed particles into a single-screw extruder, and extruding into coiled materials, wherein the temperature control range of the single-screw extruder is 90-110 ℃. Continuously placing the coiled material into a high-temperature foaming furnace for foaming, wherein the foaming temperature is controlled to be 170-180 ℃, and the foaming time is 5 minutes. A foamed web was obtained. And (3) putting the foamed coiled material into a high-temperature foaming furnace again, controlling the heating temperature to be 195-205 ℃ and the foaming time to be 10 minutes, thus obtaining the high-resilience polyethylene foamed coil.
S2: a step of primary crushing of the foaming material, which is to put the high-resilience polyethylene foaming roll into a rotary cutter crusher for primary crushing, control the diameter of the fragments to be less than 1mm, set the temperature of the primary crushing at minus 10 ℃,
s3: and putting the primarily crushed fragments into a low-temperature crushing system, controlling the temperature in a crushing cavity to be-195 ℃, and controlling the aperture of a sieve plate to be 0.9 mm. The obtained product is the high-elasticity polyethylene particles.
In this example, the properties of the polyethylene particles are: the grain diameter is less than 0.9mm, and the bulk density is 0.09g/cm3The compression permanent set at 70 ℃ is less than or equal to 20 percent (75 percent compression, 22 hours) and the compression permanent set at 23 ℃ is less than or equal to 10 percent. The product is applied to household articles and toys as a filler for replacing cotton and foamed polyurethane, and has good deformation resistance, and is not easy to absorb moisture and mildew.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A method for preparing high-resilience polyethylene filling particles is characterized by sequentially comprising the following steps:
s1: and a crosslinking foaming step, namely improving the crosslinking degree to a final target by adopting secondary crosslinking, and specifically comprises the following steps:
firstly, mixing and granulating polyethylene resin, a chemical foaming agent, a first cross-linking agent with the half-life temperature of less than 180 ℃ in 1 minute, a second cross-linking agent with the half-life temperature of more than 190 ℃ in 1 minute and other auxiliary agents, extruding the granulated mixture into a coiled material by an extruder, and then foaming in a high-temperature foaming furnace, wherein the foaming step is as follows: firstly, controlling the foaming temperature below 180 ℃ to enable a first cross-linking agent to initiate a cross-linking reaction, and then controlling the furnace temperature above 190 ℃ to enable a second cross-linking agent to initiate a cross-linking reaction;
alternatively, the first and second electrodes may be,
after polyethylene is mixed with a chemical foaming agent, firstly, irradiating for crosslinking, heating for foaming, and then, irradiating for crosslinking;
s2: a primary crushing step of the foaming material, wherein the temperature of the primary crushing is set to be-30-40 ℃;
s3: and a low-temperature crushing step, wherein the temperature of the low-temperature crushing is set to be-200 ℃ to-160 ℃.
2. The method for preparing high resilience polyethylene infill particles according to claim 1, wherein in step S2, the primary pulverization step is performed using one or both of a rotary cutter pulverizer and a biaxial shredder.
3. The method for preparing high resilience polyethylene infill particles according to claim 2, wherein in step S3, cryogenic pulverization is performed using one or more of a rotary knife pulverizer, a twin screw shredder, and a grinder.
4. A method for preparing high resilience polyethylene filled particles according to claim 1, wherein the irradiation crosslinking is performed by an electron accelerator or by gamma rays.
5. The method for preparing filled high resilience polyethylene particles according to claim 4, wherein the irradiation dose is 50 Mrad-70 Mrad.
6. The method for preparing high resilience polyethylene infill particles according to claim 5, wherein in step S1, a low density polyethylene resin is selected as a raw material.
7. The high resilience polyethylene filled particles prepared by the method according to any one of claims 1 to 6, wherein the high resilience polyethylene is filled with the particlesThe particle size of the particles is 0.1 mm-10 mm, the particles are flocculent, the compression permanent deformation of the high-resilience polyethylene filling particles is less than 20% under the conditions of 70 ℃ of temperature, 50% of compression ratio and 22 hours of compression time, and the bulk density of the high-resilience polyethylene filling particles is less than 0.1g/cm in a natural state3。
8. Use of the high resilience polyethylene filled particles according to claim 7 as a filler to replace cotton and foamed polyurethane in household goods and toys.
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| CN1235966C (en) * | 2002-08-15 | 2006-01-11 | 三井化学株式会社 | composition and its use |
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| CN102816363A (en) * | 2011-06-07 | 2012-12-12 | 东莞市宏恩塑胶制品有限公司 | High-resilience flame-retarding antistatic foamed polyethylene material |
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| CN102690459A (en) * | 2012-04-27 | 2012-09-26 | 华东理工大学 | High-resilience chemical crosslinked polyethylene foam material and preparation method thereof |
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| CN106977760A (en) * | 2017-04-20 | 2017-07-25 | 苏州固德新材科技有限公司 | Super soft high resilience resin foamed material and preparation method thereof |
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| CN107814972A (en) * | 2017-11-06 | 2018-03-20 | 佛山佛塑科技集团股份有限公司 | A kind of secondary irradiation treatment method of foamed plastics |
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