CN112194834B - High-temperature-shrinkage-resistant polyethylene foam sheet and preparation method thereof - Google Patents
High-temperature-shrinkage-resistant polyethylene foam sheet and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
- C08J9/10—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing nitrogen, the blowing agent being a compound containing a nitrogen-to-nitrogen bond
- C08J9/102—Azo-compounds
- C08J9/103—Azodicarbonamide
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/246—Intercrosslinking of at least two polymers
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/28—Treatment by wave energy or particle radiation
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/04—N2 releasing, ex azodicarbonamide or nitroso compound
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/04—Homopolymers or copolymers of ethene
- C08J2323/06—Polyethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2423/04—Homopolymers or copolymers of ethene
- C08J2423/06—Polyethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2423/04—Homopolymers or copolymers of ethene
- C08J2423/08—Copolymers of ethene
Abstract
The invention discloses a high-temperature-shrinkage-resistant polyethylene foam sheet, which is characterized in that the polyolefin foam composition comprises HDPE and LDPE or a composition of LDPE and LLDPE; when the foaming sheet is prepared, the traction speed of the foaming sheet entering the high-temperature foaming area after the softening stage is the first traction speed, the traction speed of the foaming sheet entering the cooling shaping area after the high-temperature foaming area is the second traction speed, and the ratio of the second speed to the first speed to the ratio of the expansion ratio of the foaming material relative to the volume of the original material is in the range of 0.65-0.8. The invention also provides a preparation method of the high-temperature-shrinkage-resistant polyethylene foam sheet. The foaming sheet material has stronger temperature resistance, hardness, tensile strength, rigidity and creep property, and has the functions of buffering, heat insulation, water resistance and sound insulation under the conditions of high temperature environment and higher requirement on dimensional accuracy.
Description
Technical Field
The invention belongs to the technical field of polyethylene foaming, and particularly relates to a high-temperature shrinkage-resistant polyethylene foaming sheet and a preparation method thereof.
Background
The LDPE has low cost, environment protection, easy processing and forming, wide foaming multiplying power range and is commonly used for heat preservation and shock absorption of air-conditioning pipelines, water and heat insulation of floors, buffering and sound insulation of the interiors of automobiles, sealing and water prevention in electronic products and the like. Polyethylene foam materials are mostly foamed with LDPE as matrix resin and composite part reinforced, modified or other purpose materials. LDPE has excellent processability and foamability due to long chain branching structure, relatively high melt strength and rheological property, and has wide application in polyethylene foamed products. However, the LDPE foaming preparation has the defects of low strength and poor toughness, and in some application fields, particularly, the use of products is seriously affected due to large dimensional change caused by high temperature or external force pulling and the like.
The crystallinity, the temperature resistance, the hardness, the tensile strength, the rigidity, the creep property and the like of the high-density polyethylene HDPE are all superior to those of LDPE. However, the use of HDPE is affected in terms of processing by the characteristic of high viscosity during melt processing and low melt strength during foaming, which are important reasons for limiting the large-scale use of HDPE for foaming, due to the linear molecular chain structure of HDPE.
Meanwhile, in the processing technology of polyolefin foam sheets, a common continuous foaming mode is to foam the extruded and crosslinked sheets through vertical heating foaming or horizontal heating, the acting force of the crosslinked sheets along the traction direction enters a foaming area with set temperature to soften and start foaming, the crosslinked sheets can show obvious volume change under the actions of heating softening and decomposition expansion of a foaming agent, and the mismatch of the volume change rate and the traction speed is an important cause for shrinkage of the polyethylene foam sheets after being heated in the MD direction.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a high-temperature-shrinkage-resistant polyethylene foam sheet and a preparation method thereof, wherein the polyethylene foam sheet has stronger temperature resistance, hardness, tensile strength, rigidity and creep property, and has the functions of buffering, heat insulation, water resistance and sound insulation under the conditions of high temperature environment and higher requirements on dimensional accuracy.
In order to achieve the above object, according to one aspect of the present invention, there is provided a high temperature shrinkage-resistant polyethylene foamed sheet, characterized in that the polyolefin foamed composition comprises HDPE, and further comprises LDPE or a combination of LDPE and LLDPE, wherein the HDPE is 40% or more by weight;
when the foaming sheet is prepared, the traction speed of the foaming sheet entering the high-temperature foaming area after the softening stage is the first traction speed, the traction speed of the foaming sheet entering the cooling shaping area after the high-temperature foaming area is the second traction speed, the ratio of the second speed to the first speed to the value of the expansion ratio of the foaming material relative to the volume of the original material is defined as a foaming tension correction coefficient K, and the range of the foaming tension correction coefficient K is 0.65-0.8.
That is, the expansion tension correction coefficient
The tension of the sheet in the foaming process is set to be X=b/a, a is the traction speed of the sheet entering a high-temperature foaming area after the sheet passes through a softening stage, and b is the traction speed of the sheet entering a cooling shaping area after the sheet exits the high-temperature foaming area; a is the expansion ratio of the foam material relative to the volume of the original material. />
Further, the HDPE and LDPE ratios comprise ratios by weight of 45:55, 55:45, 65:35, 75:25, 85:15, 95:5, and any other HDPE ratios above 40%; and wherein the LDPE is not limited to a low density polyethylene, and may include a combination of linear low density polyethylene and low density polyethylene in any ratio.
Further, the high density polyethylene HDPE has a shear viscosity of 800 to 1500pa x s measured at 20rad/s and 200 to 500pa x s measured at 100rad/s using a torque rheometer.
Further, the density of the high-density polyethylene HDPE is 0.930-0.960 g/cm based on the ASTM D1505 standard test 3 Melt index based on ASTMD1238 standard is 0.1g/10 min-8 g/10min.
Further, the LDPE has a density of 0.91-0.93 g/cm based on ASTM D1505 standard 3 The melt index based on ASTM D1238 standard ranges from 0.4 to 6g/10min.
Further, the polyolefin foam composition comprises the following components: 100 parts of a high-density polyethylene HDPE and low-density polyethylene composition, 0-3 parts of an additive and 2.5-15 parts of a foaming agent.
Further, the blowing agent is preferably azodicarbonamide (AC blowing agent), the average particle size of the AC blowing agent and its particle size distribution span are key factors affecting its decomposition temperature and decomposition rate, since the melting point of high density polyethylene is generally over 125 ℃, the melt processing temperature is also generally higher than the melting point temperature, and AC blowing agent with lower particle size can decompose in advance during the melt processing, severely affecting product quality and processing. The AC blowing agent of the present invention preferably has a particle size D50 in the range of 12 to 25 μm, and the relative particle size distribution span should be less than 1.5; the particle size distribution span of the present invention is defined as: span= (D90-D10)/D50.
Further, the additive is selected from any compatible additive which does not affect foaming, including but not limited to one or more of carbon black, white carbon black, boron nitride, aluminum oxide, talcum powder, diatomite, zirconium phosphate, montmorillonite, activated clay, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, kaolin, silicon oxide, glass powder or fly ash; the above additives should not contain components that affect the cross-linking foaming of the resin and the particle size should be less than 8 μm to avoid affecting the rupture of the cells of the product.
According to another aspect of the present invention, there is provided a method for producing a high temperature shrinkage-resistant polyethylene foamed sheet, wherein the foamed sheet is produced such that, when it is subjected to a softening stage, the drawing speed at which it starts to enter the high temperature foaming region is a first drawing speed, and the drawing speed at which it exits the high temperature foaming region into the cooling and shaping region is a second drawing speed, and the ratio of the second speed to the first speed to the ratio of the expansion ratio of the foamed material to the volume of the original material is in the range of 0.65 to 0.8.
The method specifically comprises the following steps:
s1, mixing polyolefin foaming compositions according to a set proportion;
s2, adding the polyolefin foaming composition into a kneader for mixing, wherein the set temperature is higher than the melting point of HDPE, the surface of the polyolefin foaming composition is free from obvious granular particles until the particles are completely melted, the pressure for kneading and mixing is set between 5 and 10MPa, and the mixing time is 5 to 20 minutes;
s3, granulating the melt after mixing to obtain a particle composition; the granulating mode includes, but is not limited to, single screw extrusion granulating, twin screw extrusion granulating or open mill bracing granulating;
s4, adding the particle composition into a double-screw extruder for extrusion molding to form a sheet, wherein the temperature of a molding die is set above the melting point of HDPE; the sheet thickness in this step was set to d1
S5, carrying out electron irradiation crosslinking on the formed sheet, wherein the electron irradiation crosslinking is used for improving the melt strength of the sheet in a high-temperature melting state, and setting the energy and the dosage required by the electron irradiation crosslinking ensures that the gel content of the sheet reaches 20-69% so as to meet the melt strength required by foaming of the sheet; wherein the determination of gel content is in accordance with ASTM D2765-2011;
s6, performing high-temperature foaming on the sheet subjected to irradiation crosslinking, and performing horizontal furnace foaming or vertical furnace foaming.
In general, polyethylene foam materials undergo three stages when foaming at high temperature: the method comprises a sheet preheating stage, a sheet foaming stage, and a sheet cooling and shaping stage. The temperature of the sheet in the preheating stage is generally set to be higher than the melting point of the resin but lower than the decomposition temperature of the foaming agent, the purpose of this stage being to soften the sheet by preheating so as to satisfy the preparation for foaming the sheet; the temperature in the foaming stage is higher than the decomposition temperature of the foaming agent, and is generally set at 190-230 ℃, and the temperature of the foaming sheet in the foaming stage is set at least 190-225 ℃ according to the melt strength of the sheet at high temperature and the catalyst part of the foaming agent; the purpose of the cooling and shaping stage is to cool and shape the foamed sheet.
In step S6, when the sheet is foamed in a horizontal furnace or a vertical furnace foaming furnace, the sheet starts to enter a traction speed a of a high-temperature foaming area after a softening stage, and enters a traction speed b of cooling and shaping in the high-temperature foaming area.
In the field of polyethylene cross-linked foaming, the expansion ratio of the foam material relative to the volume of the original material is generally referred to as the expansion ratio A
The foaming region can be defined as three parts according to the decomposition characteristics of the AC foaming agent and the corresponding series of changes of the polyethylene cross-linked foaming material in the foaming region: the foaming section 1 is a stage of further heating the sheet material subjected to the preheating stage to the rapid decomposition temperature of the AC foaming agent; the foaming section 2 is the rapid decomposition of the AC foaming agent and the rapid expansion of the crosslinked sheet; the foaming section 3 is the continuous slow decomposition of the AC foaming agent after passing through the severe decomposition section of the AC foaming agent, and the volume change of the sheet is small at the stage.
Factors that have a greater influence on the drawing speeds a and b during foaming include the thickness Z of the product 1 And the expansion ratio of the foaming of the product. For the sheet entering the foaming section 1 just after the sheet preheating stage, the surface temperature and the internal temperature of the sheet are not consistent and do not reach the decomposition temperature of the AC foaming agent, because the foaming furnace is generally used for heating the crosslinked sheet at two sides, the heat conduction rate is calculated according to the Fourier heat transfer formula
(Z 1 The thickness of the cross-linked sheet to be foamed is lambda, the heat conductivity coefficient of the cross-linked sheet to be foamed, S is the heat conduction area, the outer surface temperature and the central temperature of the cross-linked sheet to be foamed are respectively in T, and the thickness Z 1 The larger the crosslinked sheet, the longer it takes to warm up to the decomposition temperature of the AC blowing agent, and the lower the traction speed a should be set. The foaming section 2 is the region where the cross-linked foaming sheet generates the largest volume change, and the traction speed b needs to be set to match the rapid expansion of the volume so as to avoid production instability and quality problems caused by serious deformation of the high-temperature softening sheet. The foaming section 3 had slight but less pronounced changes in sheet volume.
In the actual foaming process, due to the deviation of the crosslinking degree and the furnace temperature of the crosslinked foaming sheet, the range of the optimal sheet feeding traction speed a based on the combination of theory and practical experience is 1.4x10 -3 /Z 1 ～1.8×10 -3 /Z 1 Thickness Z of crosslinked sheet to be foamed to which the present invention is applied 1 The range is 0.2 mm-1.8 mm, and the corresponding traction speed a ranges from 0.78m/min to 9m/min。
Further, the invention defines a foam tension correction factor K for guiding the drawing speed into and out of the foaming zone during the actual foaming process, the drawing speed correction factor
Wherein A is the expansion ratio. Because the structure of different foaming furnaces is different and the stability of the temperature is inconsistent in the actual process, the optimal range of the foaming tension correction coefficient K defined by the invention is 0.65-0.8. The corresponding traction speed b ranges from 0.73m/min to 24.2m/min. />
According to a series of production test data, the expansion rate of the sheet in the foaming area can be well matched with the speed of drawing the foaming sheet out of the foaming area by defining the foaming tension correction coefficient K to be at least greater than 0.65. When K is less than 0.65, the foam material cannot be fully spread in the foaming area, and the foam material softened at high temperature can be stuck together or serious folds can appear, so that the product quality is affected. However, when K is more than 1, the tensile tension of the foam material is larger, so that the stress of the foam sheet under the condition of high-temperature softening is overlarge, the polyethylene foam sheet is subjected to larger plastic deformation, and the foam sheet with lower strength can be broken.
When the foaming sheet material reenters the environment with higher temperature (for example, 80 ℃ and 100 ℃) and the thermal movement of molecules is increased, the dimensional shrinkage of the foaming sheet material in the MD direction is especially increased, and the expansion of the cross-linked sheet material in the foaming process can be well matched with the traction speed by the foaming tension correction coefficient defined by the invention, so that the plastic deformation caused by the tension mismatch in the foaming process is reduced.
In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:
(1) The expansion rate of the foaming area of the polyethylene foaming sheet material can be well matched with the speed of pulling the foaming sheet material out of the foaming area, so that the dimensional shrinkage rate of the polyethylene foaming sheet material in the MD direction is lower than 0.7% at 80 ℃ and lower than 2% at 100 ℃ based on ISO2796 test, and the polyethylene foaming sheet material has strong heat resistance, hardness, tensile strength, rigidity and creep property, and has the functions of buffering, heat insulation, water resistance and sound insulation under the conditions of high temperature environment and high requirements on dimensional accuracy.
(2) According to the preparation method of the high-temperature-shrinkage-resistant polyethylene foam sheet, proper raw materials and proportions are selected, the mixing temperature, time and pressure are optimized, proper energy and dosage required by irradiation crosslinking are selected to meet the melt strength required by sheet foaming, and proper foaming temperature is set according to different stages of high-temperature foaming, so that the preparation method can be adapted to the material.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Example 1
In the polyolefin foaming composition, 40 parts by weight of High Density Polyethylene (HDPE), 60 parts by weight of Low Density Polyethylene (LDPE) and 2.5 parts by weight of foaming agent, wherein the HDPE has a shear viscosity of 850Pa x s measured at a rotating speed of 20rad/s, a shear viscosity of 315Pa x s measured at a rotating speed of 100rad/s, a HDPE density of 0.94g/cm3, a melt index of 4.23g/10min, an LDEP density of 0.923g/cm3, a melt index of 1.6g/10min, a particle size D50 of 20 mu m, a particle size distribution span of 1.1, and a thickness Z of a crosslinked foaming semi-finished sheet to be foamed 1 Is 0.2mm.
The preparation method comprises the following steps:
step 1: mixing the materials according to the proportion;
step 2: adding the prepared materials into a kneader for mixing, setting the temperature to 140 ℃ until the particles are completely melted, setting the pressure of kneading and mixing to be 5-10 MPa and the mixing time to be 5-20 min, wherein no obvious granular particles are arranged on the surface of the particles.
Step 3: granulating the melt after mixing; the granulating mode is double-screw extrusion granulating.
Step 4: the pellet composition was fed into a twin screw extruder and extruded into a sheet having a thickness of 0.6mm, and the temperature of the molding die was 135 ℃.
Step 5: and (3) carrying out electron irradiation crosslinking on the formed sheet obtained in the step (4).
Step 6: and (3) performing high-temperature foaming on the sheet subjected to irradiation crosslinking, wherein the foaming modes comprise horizontal furnace foaming and vertical furnace foaming, the traction speed a is set to 9m/min, the tension X is set to 1.103, and the foaming tension correction coefficient K is set to 0.65.
Example 2:
the difference between this embodiment and embodiment 1 is that:
in the polyolefin foaming composition, 65 parts by mass of high-density polyethylene (HDPE), 35 parts by mass of low-density polyethylene (LDPE), 6 parts by weight of foaming agent and 3 parts by weight of additive, wherein the HDPE has a shear viscosity of 1000 Pa/s measured at a rotating speed of 20rad/s, 370 Pa/s measured at a rotating speed of 100rad/s, 0.96g/cm3, 9.8g/10min of melt index, 0.91g/cm3 of LDEP density, 5.4g/10min of melt index, 14 mu m of particle size D50 of foaming agent, 0.8 of particle size distribution span, talcum powder, diatomite and 2 mu m of particle size, and the thickness Z of a cross-linked foaming semi-finished product to be foamed is measured 1 The traction speed a was set to 2.8m/min, the tension X was set to 1.551, and the expansion tension correction coefficient K was set to 0.72 at 0.5 mm.
The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Example 3:
the difference between this embodiment and embodiment 1 is that:
in the polyolefin foaming composition, 95 parts by mass of high-density polyethylene (HDPE), 5 parts by mass of low-density polyethylene (LDPE), 15 parts by weight of foaming agent and the additive is1.5 parts by weight, wherein the HDPE has a shear viscosity of 900 Pa/s measured at a rotational speed of 20rad/s, a shear viscosity of 315 Pa/s measured at a rotational speed of 100rad/s, a HDPE density of 0.95g/cm3, a melt index of 6.3g/10min, an LDEP density of 0.92g/cm3, a melt index of 3.6g/10min, a blowing agent particle size D50 of 18 μm, a particle size distribution span of 0.5, the additive is talc, a particle size of 4 μm, a thickness Z of the crosslinked foamed semifinished sheet to be foamed 1 The traction speed a was set to 0.78m/min, the tension X was set to 2.275, and the expansion tension correction coefficient K was set to 0.8 at 1.8 mm.
The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Example 4:
the difference between this embodiment and embodiment 1 is that:
in the polyolefin foaming composition, 55 parts by mass of High Density Polyethylene (HDPE), 25 parts by mass of Low Density Polyethylene (LDPE), 20 parts by mass of Linear Low Density Polyethylene (LLDPE), 6 parts by weight of foaming agent, 1.5 parts by weight of additive, wherein the HDPE has a shear viscosity of 1500Pa x s measured at a rotation speed of 20rad/s, 470Pa x s measured at a rotation speed of 100rad/s, a HDPE density of 0.93g/cm3, a melt index of 0.5g/10min, an LDEP density of 0.928g/cm3, a melt index of 0.7g/10min, a particle size D50 of 25 mu m, a particle size distribution span of 1.4, the additive is white carbon black, boron nitride, a particle size of 7 mu m, a cross-linked foaming semi-finished sheet thickness Z to be foamed 1 The traction speed a was set to 1.7m/min, the tension X was set to 1.4, and the foam tension correction factor K was 0.65.
The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Comparative example 1:
the difference between this embodiment and embodiment 1 is that:
25 parts by mass of High Density Polyethylene (HDPE) and 75 parts by mass of Low Density Polyethylene (LDPE). The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Comparative example 2:
the difference between this embodiment and embodiment 1 is that:
the HDPE has a shear viscosity of 750pa x s measured at 20rad/s and 170pa x s measured at 100rad/s using a torque rheometer. The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Comparative example 3:
the difference between this embodiment and embodiment 1 is that:
HDPE density is 0.97g/cm3 and LDEP density is 0.9g/cm3. The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Comparative example 4:
the difference between this embodiment and embodiment 1 is that:
the tension X was set to 2.844 and the foam tension correction coefficient K was set to 1. The rest is substantially the same as in embodiment 1, and will not be described in detail here.
Comparative example 5:
the difference between this embodiment and embodiment 1 is that:
the tension X was set to 1.706, and the expansion tension correction coefficient K was set to 0.6. The rest is substantially the same as in embodiment 1, and will not be described in detail here.
The results of each example and comparative example are compared as follows:
it will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. The polyethylene foam sheet resistant to high temperature shrinkage is characterized by comprising HDPE and LDPE or a combination of LDPE and LLDPE, wherein the HDPE accounts for more than 40% by weight;
when the foaming sheet is prepared, the traction speed of the foaming sheet entering a high-temperature foaming area after the softening stage is a first traction speed, the traction speed of the foaming sheet entering a cooling shaping area after the high-temperature foaming area is a second traction speed, and the ratio of the second traction speed to the first traction speed to the ratio of the expansion ratio of the foaming material relative to the volume of the original material is in the range of 0.65-0.8;
the range of the first traction speed is 0.78-9 m/min, and the range of the second traction speed is 0.73-24.2 m/min;
the shear viscosity of the HDPE measured at the rotating speed of 20rad/s is 800-1500 Pa s, and the shear viscosity measured at the rotating speed of 100rad/s is 200-500 Pa s;
the polyethylene foam sheet comprises the following components:
100 parts of a composition of high-density polyethylene HDPE and low-density polyethylene LDPE, 0-3 parts of an additive and 2.5-15 parts of a foaming agent; or 100 parts of a composition of high-density polyethylene HDPE, low-density polyethylene LDPE and linear low-density polyethylene LLDPE, 0-3 parts of an additive and 2.5-15 parts of a foaming agent;
the particle size of the additive is required to be less than 8 mu m.
2. The high temperature shrinkage resistant polyethylene foam sheet according to claim 1, wherein the polyethylene foam sheet has a dimensional shrinkage in MD at 80 ℃ of less than 0.7% and a dimensional shrinkage in MD at 100 ℃ of less than 2% based on ISO2796 test.
3. The heat shrinkage resistant polyethylene foam sheet according to claim 1 or 2, wherein the HDPE has a density of 0.930-0.960 g/cm as measured by ASTM D1505 standard 3 The melt index based on the ASTM D1238 standard is 0.1g/10min to 8g/10min.
4. The high temperature shrinkage resistant polyethylene foam sheet according to claim 1 or 2, wherein the LDPE has a test density of 0.91-0.93 g/cm based on ASTM D1505 standard 3 The melt index based on ASTM D1238 standard is in the range of 0.4 to 6g/10min.
5. The high-temperature shrinkage-resistant polyethylene foam sheet according to claim 1 or 2, wherein the foaming agent is an azodicarbonamide foaming agent with a particle size D50 ranging from 12 to 25 μm and a relative particle size distribution span of less than 1.5.
6. The high temperature shrinkage resistant polyethylene foam sheet according to claim 1 or 2, wherein the additive comprises one or more of carbon black, white carbon black, boron nitride, aluminum oxide, talc, diatomaceous earth, zirconium phosphate, montmorillonite, activated clay, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, kaolin, silica, glass powder, or fly ash.
7. A method for producing a heat shrinkage resistant polyethylene foamed sheet according to any one of claims 1 to 6, wherein the foamed sheet is produced at a first drawing speed at which the foamed sheet starts to enter the high-temperature foamed region through the softening stage, and at a second drawing speed at which the foamed region enters the cooling shaping region, wherein the ratio of the second drawing speed to the first drawing speed is in a range of 0.65 to 0.8 relative to the ratio of the expansion ratio of the foamed material to the volume of the raw material, which is open cubic.
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| CN116102809A (en) * | 2023-01-31 | 2023-05-12 | 江苏大毛牛新材料有限公司 | Ultra-light water material and preparation method thereof |
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