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WO2025181065A1 - Film à haute résistance aux intempéries - Google Patents

Film à haute résistance aux intempéries

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Publication number
WO2025181065A1
WO2025181065A1 PCT/EP2025/055013 EP2025055013W WO2025181065A1 WO 2025181065 A1 WO2025181065 A1 WO 2025181065A1 EP 2025055013 W EP2025055013 W EP 2025055013W WO 2025181065 A1 WO2025181065 A1 WO 2025181065A1
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WO
WIPO (PCT)
Prior art keywords
range
low density
density polyethylene
modified low
film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/055013
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English (en)
Inventor
Gerd Mannebach
Andre-Armand Finette
Juergen MOHRBUTTER
Christof Justus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Basell Polyolefine GmbH
Original Assignee
Basell Polyolefine GmbH
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Filing date
Publication date
Application filed by Basell Polyolefine GmbH filed Critical Basell Polyolefine GmbH
Publication of WO2025181065A1 publication Critical patent/WO2025181065A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/02—Ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2400/00—Characteristics for processes of polymerization
    • C08F2400/04—High pressure, i.e. P > 50 MPa, 500 bars or 7250 psi

Definitions

  • the present disclosure refers to a propylene controlled branched low density polyethylene, for use e.g., for film applications, such as agricultural films, greenhouse films, or scattering films with improved weathering resistance, increased lifetime, comprising a propylene controlled low density polyethylene which has been obtained by a radical initiated propylene controlled process to obtain a branched low density polyethylene with low density.
  • Polyethylene a widely used commercial polymer, can be prepared by different processes, such as polymerization in the presence of free-radical initiators at elevated pressures.
  • Low density polyethylene can be obtained by different processes varying dependent on the process in mechanical und structural properties. Which is valuable when it comes to different applications, e.g. LDPE's flexible and versatile nature is highly appreciated for some well known applications including the use for plastic bags, in food packaging, or medical packaging, besides industrial wraps and the use in films, e.g. agricultural films. So, typical agricultural films are made of blends on LDPE, or LDPE and LLDPE and at least an UV stabilizer.
  • the density of the polyethylene should be high, which means that reduction of density is unfavorable.
  • adding UV stabilizers are mostly required, to extend lifecycle of the agricultural films due to the exposure to challenging weather conditions, like sun, UV radiation, wind, snow and the like.
  • UV light and the other weathering conditions deteriorate the structure of the polyethylene applied in agricultural films through a process known as photodegradation.
  • UV radiation contains high-energy photons interacting with the polymer chains in LDPE. This interaction leads to the breaking of chemical bonds, causing the material to weaken, become brittle, and lose its mechanical strength overtime. Additionally, exposure to environmental factors like moisture, temperature variations, and atmospheric pollutants, further accelerates the degradation process. This combined effect of UV light and weathering conditions ultimately leads to the deterioration of polyethylene, e.g. LDPE derived agricultural films.
  • extension of lifetime is directly connected to an environmental friendly production of vegetables and plants, and helps to benefit for economic reasons and also helps to save energy and resources resulting in eco-friendly agriculture as it helps to reduce carbon dioxide emission and prevent PE waste.
  • a modified low density polyethylene comprising low density polyethylene with high weathering resistance and increased lifetime obtained by a polymerization process using propylene as modifier, whit high resistance and resilience against exposure to UV radiation, wind and weather conditions. It has been found that the use of propylene as chain transfer agent in the polymerization process described further herein, increases the weathering resistance and/or lifetime of the polymer.
  • a modified low density polyethylene grade is disclosed, comprising low density polyethylene with high weathering resistance, obtained by a polymerization process using propylene as modifier.
  • Figure 1 shows the influence of different modifiers on the weathering resistance and/or lifetime of the disclosed modified low density polyethylene and also the relatively poor UV stability of all the other samples comprising UV-stabilizers or without an UV-stabilizer, already known from the state of the art. It is shown that after 500 hours under the testing conditions the samples Comp. Ex. 2 one with and the other without Irganox 1010, the material has lost more than 80% of the elongation properties, whereas the disclosed non-polar modified low density polyethylene grade, grades Comp. Ex. 1 and Comp. Ex. 2 remain still more than 50% of their elongation properties. After 1000 hours under testing conditions all samples have lost almost all of their mechanical resistance, but also the propionaldehyde modified Comp. Ex. 3 samples are significant worse compared to the Example comprising the modified low density polyethylene disclosed herein.
  • FIG. 1 shows the influence on mechanical film properties of artificial weathering conditions according to ISO 527 and ISO 4892-2 before and after weathering of before (0 h), after 500 h and after 1000 h of exposure time under artificial weathering resistance, for the elongation at break in MD [%] for all samples Comp. Ex. 1-3 also the Example.
  • Figure 3 shows the I R spectra of the test samples Comp. Ex. 2 and the Example before exposure to artificial weathering conditions.
  • Figure 4 shows the IR spectra after exposure for 500 hours to artificial weathering conditions. Changes in the IR - spectra the come along with the variations in the mechanical properties, where the carbonyl band becomes more pronounced with increasing weathering time. The IR spectra for Comp. Ex. 2 and the Example is almost similar, but the CO-band is more pronounced.
  • Figure 5 shows a IR spectra for the disclosed low density polyethylene grade after 0, 500 and 1000 hours of artificial weathering.
  • the increase in the carbonyl band for the Example, the modified low density polyethylene shows the time-dependent transmittance decrease of the CO- band at a wavelength of 1720-1680 cm' 1 , compared to other low density polyethylene grades the present modified polyethylene grade shows the exceptional weathering resistance and an extended lifetime even after 1000 hours under testing conditions.
  • Figure 6 shows the temperature-depending reactor profile of the radical polymerization process to produce the modified low density polyethylene.
  • a modified low density polyethylene having a high weathering resistance and/or extended and/or increased lifetime, obtained by a polymerization process using propylene as modifier in a reactor, which can be a tubular reactor. It has been surprisingly found that using propylene instead of propionaldehyde increases the weathering resistance and/or extends the lifetime of the polymer significantly.
  • the obtained modified low density polyethylene shows not only good optical and mechanical properties, besides high gloss and less haze, but also increased lifetime and exceptional weathering resistance, good draw down, wherein the production itself is also highly cost efficient.
  • the modified low density polyethylene has a density of 0.917 to 0.926 g/cm 3 , preferably 0.919 to 0.924 g/cm 3 , preferably 0.920 to 0.922 g/cm 3 , a Mw of 300,000 to 400,000 g/mol measured by GPC-LS, preferably 350,000 g/mol, an amount of short chain branches (SCB) of 18 to 22 -CH3 1/1000C measured by IR, preferably 19 to 21 , and a MFR of 0.15 g/10 min to 0.35 g/10 min (2.16 kg/190°C, ISO 1133), preferably 0.18 g/10 min to 0.30 g/10 min, preferably 0.20 g/10 min to 0.28 g/10 min, preferably 0.22 g/10 min.
  • SCB short chain branches
  • the disclosed material is therefore suitable for use as agricultural film and or greenhouse film, or scattering film and shows compared to other agricultural films improved mechanical properties, increased lifetime and extraordinary weathering resistance although one would have expected the opposite as the density is lower.
  • the disclosed modified low density polyethylene disclosed herein has preferably an MFR (2.16 kg/190°C) of from 0.1 to 1 g/10 min, preferably 0.13 to 0.5 g/10 min, preferably 0.15 to 0.35 g/10 min, preferably 0.18 g/10 min to 0.30 g/10 min, preferably 0.20 g/10 min to 0.28 g/10 min, preferably 0.22 g/10 min, according to ISO 1133, according to ASTM D1238.
  • the disclosed modified low density polyethylene shows an MFRw (10 kg/190°C), which is in the range from 1 to 15 g/10 min, preferably from 2 to 10 g/10 min, preferably from 3 to 7 g/10 min, preferably from 3.5 to 5 g/10 min, preferably 3.7 to 4 g/10 min according to ISO 1133, according to ASTM D1238.
  • the modified low density polyethylene can be used for agricultural and/or greenhouse film, and/or scattering film applications, although the density is lower than that of comparable LDPE known from the state of the art (without propylene used in the process).
  • the film application shows that comprising the modified low density polyethylene results in longer and increased lifetime and exceptional good weathering resistance tested under artificial weathering conditions of at least 500 hours, preferably 1000 hours. So the films can be used longer than other films already known in the state of the art, and even can be reused for several seasons.
  • films comprising the disclosed propylene controlled modified low density polyethylene helps to save costs, also to avoid more plastic waste as it can be seen as a sustainable film, as it reduces carbon dioxide emission, and leads to establish a “greener” more eco-friendly and more sustainable agricultural business.
  • the term “sustainable” means, that the production and use of the material and the use of the films comprising the low density polyethylene as described herein is environmentally friendly and resource-efficient, aiming to minimize negative impacts on the environment. It may also imply that the LDPE films are recyclable.
  • the term “greener” as per definition means, that the production and use of this material are environmentally friendly than conventional alternatives. This may involve aspects such as a lower ecological footprint, the use of renewable resources, or improved recycling capabilities. It aims to reduce environmental impacts and represents a more sustainable option compared to traditional alternatives.
  • the disclosed modified low density polyethylene shows exceptional mechanical properties and high processability due to its molecular structure and molecular weight distribution, which is influenced and determined by the process conditions such as temperature, pressure, content of ethylene and also propylene present in the reactor during the radical polymerization.
  • a so called chain transfer agent or modifier as it is also called is applied and used.
  • the chain transfer agent terminates the growing polymer by transferring a hydrogen or other atom to the growing chain, which leads in the production of a new radical which then reinitiates the polymerization.
  • propylene and propionaldehyde can be used as modifiers to obtain low density polyethylene.
  • These modifiers show a significantly different behavior and lead to different products with different mechanical properties, different molecular structures, crystallinity, and density, besides different processing behavior resulting in different weathering resistance, lifetime, and UV stability used for film applications.
  • a high weathering resistance indicates that such conditions can be endured without or less significant degradation or loss of properties in relation to the starting conditions.
  • polar propionaldehyde leads to a low density polyethylene , with unsatisfying weathering resistance (please see comparative examples 1 , 2 and 3 discussed in the following).
  • the polar modified LDPE shows insufficient weathering resistance when exposed to artificial weathering conditions, in form of a film sample, due to the loss of almost all mechanical properties, e.g., elongation at break, or tensile strength (Table 4, Table 5 or Table 6), just like other comparative films known in the state of the art.
  • the films lose all their mechanical properties and show a significant decrease in elongation at break tests after being exposed to artificial weathering conditions ( Figure 1 and 3, showing the IR Spectra after 0, 500 and 1000 hours under artificial weathering conditions).
  • Figure 2 shows the IR - spectra of the disclosed modified low density polyethylene, compared to the samples known from the state of the art. All samples were obtained by radical polymerization processes, while Comp. Ex. 1 and the Example comprising modified LDPE were processed with propylene as modifier, and for obtaining Comp. Ex. 2 and 3 propionaldehyde as chain transfer agent was used.
  • test samples wherein propionaldehyde is used
  • propionaldehyde is used
  • all test samples are heavily damaged by the applied artificial weathering and completely destructed after 1000 h of testing, which can be tested by an increase of the CO- band.
  • modified low density polyethylene which shows the best weathering resistance of all test materials.
  • the modified polyethylene film shows high weathering resistance which is measured via IR spectra over time by the increase in the carbonyl band which is at 1710-1680 cm 1 ( Figure 3), and indicates the thermal and oxidative damage of the polyethylene.
  • UV light, sunlight, and normal weather can cause degradation of LDPE; especially of agricultural films made from low density polyethylene (LDPE) through a process called photodegradation.
  • LDPE low density polyethylene
  • photodegradation When LDPE is exposed to UV radiation from the sun, the energy from the UV light promotes the breakage of chemical bonds in the polymer chain. This leads to a weakening of the material's structure, resulting in a loss of mechanical properties like strength and flexibility.
  • oxygen in the air and other environmental factors can contribute to the degradation PE-process.
  • Oxygen molecules can interact with free radicals formed during photodegradation, accelerating the degradation process. So, even when no propionaldehyde is used and propylene serves as modifier, carbonyl groups can be formed. Even when there are no initial carbonyl groups e g., derived from propionaldehyde, the interaction of the formed radicals induced by UV light and environmental factor, with the low density polyethylene in combination with oxygen due to aging processes.
  • SCB short chain branching
  • the initial carbonyl-content is so low, that there is no need to add UV stabilizers, and even without the lifetime of the modified low density polyethylene used for e.g., agricultural films comprising the disclosed LDPE is increased and the test results (please see Table 6, Example) are exceptionally good.
  • Film applications comprising the disclosed propylene controlled modified low density polyethylene, are more resilient to external climate conditions, such as temperature (artificial weathering conditions according to ISO 4892-2, method A and black-standard temperature of 65°C to evaluate the weather resistance of the samples, performed under 65°C), or solar irradiation, UV radiation, UV intensity, global energy, weathering conditions, rain, snow, wind, storm, and also to mechanical stress, when the films are applied to greenhouses or fields etc. leading to a longer period of use.
  • external climate conditions such as temperature (artificial weathering conditions according to ISO 4892-2, method A and black-standard temperature of 65°C to evaluate the weather resistance of the samples, performed under 65°C), or solar irradiation, UV radiation, UV intensity, global energy, weathering conditions, rain, snow, wind, storm, and also to mechanical stress, when the films are applied to greenhouses or fields etc. leading to a longer period of use.
  • propylene instead of propionaldehyde prevents to have a further source of carbonyl groups in the polymer.
  • the amount of initial carbonyl-g roups via using propionaldehyde is extremely low, it has a great influence on the weather resistance of LDPE blown films for the use in agricultural film applications as greenhouse films and scattering films. It is known that all aliphatic CO- groups absorb UV in the region of 300 nm and that the concentration of these groups accelerates the degradation of polyethylene chains.
  • aliphatic ketones degrade under UV- light by chain scissions after either Norrish type I or Norrish type II mechanism. These scissions create free radicals which then react with oxygen or other polymer chains causing a decrease in polymer length and thus cause the decrease of mechanical properties.
  • the "weathering resistance" of low density polyethylene with respect to the IR spectrum carbonyl band in the region of 300 nm refers to the material's ability to withstand the detrimental effects of environmental factors such as UV radiation, moisture, and temperature fluctuations, which tend to degrade the structural integrity and performance of the material overtime.
  • a well-developed weathering resistance indicates that the LDPE material exhibits increased resistance to the degrading effects of these environmental factors, leading to an extended lifespan and enhanced functionality of the product.
  • the modified low density polyethylene shows high UV stability without adding an UV stabilizer.
  • the non-additivated low density polyethylene (LDPE) film exhibits good tear strength and toughness, and offers good flexibility and processability, and a higher weathering resistance, compared to the comparative examples 1 , 2 and 4.
  • the modified low density polyethylene does not comprise any UV stabilizers, not comprising any UV stabilizers, its UV stability is higher compared to other polyethylene films and grades produced with propylene as modifier in a comparable pressure process (Comp. Ex. 3). Due to the different structure of the low density polyethylene, having higher amounts of short chain branches, the density is lower, and the mechanical properties and processability is improved. TEST RESULTS
  • the disclosed low density polyethylene shows high values after testing for 0 h at elongation at break [%] in (MD) in the range of 510 to 550, preferably 515 to 540, preferably 520 to 535, more preferably 525 to 530, still more preferably 528.
  • the disclosed low density polyethylene shows high values after testing for 0 h at tensile strength at break [MPa] in (MD) in the range of 22 to 27, preferably 23 to 26, preferably 24 to 25, still more preferably 24.8.
  • the disclosed low density polyethylene shows high values after testing for 0 h at elongation at break [%] in (TD) in the range of 620 to 660, preferably 625 to 650, more preferably 630 to 640, still more preferably 637.
  • the disclosed low density polyethylene shows high values after testing for 0 h at tensile strength at break [MPa] in (TD) in the range of 22 to 27, preferably 21 to 26, 22 to 25, more preferably 23 to 24, still more preferably 24.1 .
  • the modified low density polyethylene shows high values for the elongation at break [%] in (MD) after testing for 500 h under artificial weathering conditions being greater than 300 %, preferably in the range of 320 to 380, preferably 330 to 370, preferably 340 to 360, more preferably 350 to 355, still more preferably 357, compared to the initial starting value.
  • the modified low density polyethylene shows high values after testing for 500 h under artificial weathering conditions at tensile strength at break [MPa] in (MD) being greater than 10, preferably in the range of 8 to 15, preferably 9 to 13, more preferably 10 to 12, still more preferably 11 , compared to the initial starting value.
  • the modified low density polyethylene shows high values after testing for 500 h under artificial weathering conditions at elongation at break [%] in (TD) being greater than 300 %, preferably in the range of 280 to 350, preferably 300 to 340, preferably 310 to 330, more preferably 315 to 325, still more preferably 320, compared to the initial starting value.
  • the disclosed low density polyethylene shows high values after testing for 500 h under artificial weathering conditions at tensile strength at break [MPa] in (TD) greater than 10, preferably in the range of 7 to 15, preferably 8 to 14, preferably 9 to 13, more preferably 10 to 12, still more preferably 11 , compared to the initial starting value.
  • the disclosed low density polyethylene shows high values after testing for 1000 h under artificial weathering conditions at elongation at break [%] in (MD) greater than 11 % in the range of 16 to 25, preferably 16.5 to 24, preferably 17 to 23, preferably 17.5 to 22, more preferably 18 to 21 , more preferably 18.5 to 20, still more preferably 19, compared to the initial starting value.
  • the modified low density polyethylene shows high values after testing for 1000 h under artificial weathering resistance at tensile strength at break [MPa] in (MD) greater than 9, preferably in the range of 8 to 16, preferably 9 to 14, 10 to 13, more preferably 11 to 12, still more preferably 11 .6, compared to the initial starting value.
  • the disclosed low density polyethylene shows high values after testing for 1000 h at elongation at break [%] in (TD) in the range of 5 to 14, preferably 6 to 12, preferably 7 to 11 , more preferably 8 to 10, still more preferably 9, compared to the initial starting value.
  • the disclosed low density polyethylene shows high values after testing for 1000 h under artificial weathering conditions at tensile strength at break [MPa] in (TD) greater than 7, preferably in the range of 4 to 12, preferably 5 to 11 , preferably 6 to 10, more preferably 7 to 8, still more preferably 7.6, compared to the initial starting value.
  • the polyethylene film comprises at least one additive chosen from the following group, e.g., one or more of kaolin, hindered amine light stabilizer (HALS) and heavy metals are used to stabilize LDPE films.
  • HALS hindered amine light stabilizer
  • heavy metals are used to stabilize LDPE films.
  • Low density polyethylene is produced exclusively by high pressure free radical polymerization.
  • High pressure and high temperature conditions, together with the monomers and a chain transfer agent result in numerous competing side reactions such as branching and premature chain termination. Therefore product properties are only controlled via concentration, temperature, pressure, vinyl monomers and co-monomers, e.g., polar vinyl acetate and methacrylic acid and the chain transfer agents.
  • the modified low density polyethylene was obtained using a polymerization process to produce a polyethylene film using a Lupotech T process.
  • the molecular weight of the obtained modified low density polyethylene can be varied.
  • the modified low density polyethylene In one embodiment, the molecular weight Mw of the low density polyethylene ranges from 300.000 to 400.000 g/mol, preferably 350,000 g/mol measured by GPC-LS.
  • the density of the low density polyethylene tends to increase, differing also in a more broader or narrower molecular weight distribution when different reaction conditions such as a higher or lower pressure is applied besides a certain number of short chain branches (SCB) of 18 to 22 -CH 3 1/1000C by IR.
  • SCB short chain branches
  • the conditions for producing the modified low density polyethylene are a) a pressure of 2300 bar b) a starting temperature in zone 1 of 170 °C, c) a maximum temperature in zones 1 to 4 of 300 °C, d) a propylene dosing of 8 kg/t of resulting product, e) at a conversion rate of 26.4 %, f) and a reactor cooling water of 160 to 180 °C.
  • both homopolymers and copolymers can be obtained.
  • the polymer disclosed is to be understood as homopolymer, when the propylene is only used as chain transfer agent, but also as copolymer, when the propylene is added to the primary chains, resulting in short chain branches, or even long chain branches when so called backbiting reactions occur.
  • the disclosed low density polyethylene may also be understood as both, a homo- and a copolymer, and blends therefrom. So, the use of propylene influences also significantly the MFR of the obtained homo- and/or copolymer. Therefore, besides ethylene and propylene and optionally one or more comonomers are used in the process, such as ethylene, propylene, butene, hexene, heptene and/or octene.
  • low density polyethylene includes polyethylene homopolymers and copolymers, using comonomers as defined above. So, a low density polyethylene is a versatile thermoplastic polymer characterized by its molecular structure. As a homopolymer it is composed solely of ethylene monomers, or as a copolymer, where ethylene is copolymerized with amounts of other monomers, e.g., propylene, or butene, hexene, heptene, or octene.
  • the polyethylene film, used as reference for testing etc. is obtained by an extrusion process.
  • the extrusion process comprises the following steps and process conditions to prepare a 100 pm film using an Alpine sing HS 50 S-30.
  • the 100 pm film was produced according to the following standard operating conditions: the Alpine Extruder HS 50 S-30, was applied using a barrier screw, a BFC 4-16, with a die diameter of 120 mm and die gap width of 1 .0 mm.
  • As air cooling ring a HK 300/ML was used, with a freeze height of 0.3 m, BUR 2.5.
  • the disclosed modified low density polyethylene can be used to produce an agricultural film, a greenhouse film, or a scattering film comprising the polyethylene film.
  • the films are produced via blow film extrusion and film extrusion processes.
  • Optical properties of the films, comprising the modified low density polyethylene are measured with standard methods, gloss according to ASTM D 2457, and haze according to ASTM D 1003. And gloss and haze are measured and given in table 3.
  • the disclosed modified low density polyethylene is used for producing films, e.g. single or for production of multilayer films.
  • Article comprising the modified low density polyethylene according to any one of the preceding claims.
  • Producing agricultural films using the modified low density polyethylene is preferred.
  • Such films include scattering film applications, wherein the scattering film has a function of adjusting temperature, light, humidity, and diffuse scattering.
  • weathering resistance means and refers to the ability to withstand the effects of exposure to outdoor weather conditions, or artificial weathering conditions, over time. Furthermore, it can be understood, that it also means, that the material is exposed to sunlight, moisture, temperature variations, and other environmental factors. A high weathering resistance indicates that such conditions can be endured without or less significant degradation or loss of properties in relation to the starting conditions.
  • the exposure to artificial weathering conditions showed according to ISO 4892-2 (method A under black standard temperature of 65 °C),
  • deterioration of the polyethylene means also, a loss in mechanical properties, which is caused by sun, UV radiation, temperature, climate conditions such as rain, snow wind storm etc., compared to the state of the art (according to ISO 4892-2).
  • the term “improved lifetime” refers to an extended or enhanced lifetime of low density polyethylene compared to standard samples comprising LDPE, obtained by using propylene or propionaldehyde as chain transfer agent.
  • LDPE refers to a low density polymer containing a copolymer of ethylene and one or more a-olefins polymerized in the presence of one or more single-site catalysts, such as one or more Ziegler-Natta catalysts, one or more metallocene catalysts, and combinations thereof.
  • single-site catalysts such as one or more Ziegler-Natta catalysts, one or more metallocene catalysts, and combinations thereof.
  • Such LDPE can have density within the range from a low 0.917 g/cm 3 to a high of 0.935 g/cm 3 .
  • the term “LDPE composition” refers to a composition containing a LDPE polymer.
  • the LDPE polymer composition can be in any form. Some examples include: the form of a reactor grade (e g., granules or resin) containing the LDPE polymer; the form of a molten or at least partially molten composition containing the LDPE polymer and one or more additives undergoing or about to be undergoing the process of finishing (such as in the process of compounding extrusion), which is may be referred to as a pre; in the form of a finished LDPE polymer product such as LDPE polymer pellets containing the LDPE and any additives (such as PPA); or in the form of a finished LDPE product such as LDPE resin undergoing the process of mixing (e.g., via coextrusion, melt blending, or other processing) with additives, such as in the case of LDPE being extruded to form blown film, cast film or other polymer-containing
  • photodegradation is UV light, sunlight, and normal weather can cause degradation of LDPE; especially of agricultural films made from low density polyethylene (LDPE).
  • Photodegradation of polyethylene refers further to the process by which the polyethylene in general, undergoes degradation and breakdown due to exposure to light, especially sunlight. This exposure can lead to chemical and physical changes in the polyethylene structure, causing it to lose some of its original properties. UV radiation is a common trigger for the photodegradation of polyethylene, and this process can result in the formation of smaller molecular fragments and, eventually, impact the materials performance.
  • modified low density polyethylene can be seen as homopolymer and also as copolymer.
  • the propylene can act as chain transfer agent and can also be incorporated into the PE-chain.
  • at least one monomer differing from ethylene such as butene, hexene, heptane or octene can be additionally applied in the production process and incorporated into the polyethylene.
  • ageing stability is to be understood as the resisting to external and internal degradation influences on the structure of polyethylene resulting in loss of structure and properties.
  • Short chain branches of 18 to 25 -CH3 1/1000C, preferably in the range of 19 to 23 -CH3 1/1000C are measured by IR. The determination is carried out in accordance with ASTM D 6248-98.
  • a common set-up for preparing polyethylene comprises a polymerization reactor, which can be a tubular reactor or a combination of such reactors, and additional equipment.
  • a set of two compressors usually a set of two compressors, a primary compressor and a secondary, or hyper, compressor, is used.
  • a set-up for high-pressure polymerization normally further includes apparatuses like extruders and granulators for pelletizing the resulting polymer.
  • such a set-up generally also comprises means for feeding monomers and comonomers, free-radical initiators, modifiers or other substances at one or more positions to the polymerization reaction.
  • Table 1 Test materials and samples.
  • Comp. Ex. 1 The density of Comp. Ex. 1 , and of modified low density polyethylene are quite similar, whereas the density for Comp. Ex. 3 is significantly higher, which results in a higher melting temperature measured via DSC and a higher elastic modulus measured on the blown films in TD.
  • the MFR 2 values are also quite similar for all products but the differences in the MFR 10 values indicates a higher degree in long chain branching of the Comp. Ex. 1, which can be related to differences in the polymerization process between the present herein described and other processed known from the art.
  • a comparison of the film properties shows the advantages of Comp. Ex. 2 in comparison with the other grades. Due to the higher density of Comp. Ex. 2 this grade offers the best optical film properties, the best yield strength and the highest stiffness. Furthermore attention should be paid to the relative good dart drop performance of Comp. Ex. 2 even if the Example of the disclosed LDPE is the benchmark in dart drop test amongst the test grade.
  • the inventive LDPE preferably Mw in the range of 300.000 to 400.000 g/mol, preferably in the range of 330,000 to 350,000 g/mol measured by GPC-LS.
  • Table 2 The following tables summarize the measured results at the LDPE pellets and the film as source material.
  • Table 4 Table shows test results after 0 hours of artificial weathering.
  • Table 5 Table shows test results after 500 hours of artificial weathering.
  • Table 6 Table shows test results after 1000 hours of artificial weathering.
  • Table 6 shows the test results after 1000 hours of artificial weathering conditions. It was not possible to run every test with the examples. Surprisingly, the performance of the disclosed modified low density polyethylene grade (please compare the date for the disclosed Example) exceeds the examples known from the state of the art.
  • Table 8 Film properties after exposure to weathering conditions.

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Abstract

La présente divulgation concerne un polyéthylène basse densité modifié pouvant être dérivé d'un procédé de polymérisation radicalaire à l'aide de propylène en tant que modificateur, qui peut être utilisé pour un film agricole ou un film de serre, ou un film de diffusion sans ajouter de stabilisants UV comprenant une résistance aux intempéries améliorée, une durée de vie accrue obtenue par un procédé, qui est traité dans un réacteur tubulaire. La durée de vie, la résistance aux intempéries et la stabilité vis-à-vis de la lumière UV sont augmentées par rapport à d'autres grades de polyéthylène basse densité bien connus.
PCT/EP2025/055013 2024-02-29 2025-02-25 Film à haute résistance aux intempéries Pending WO2025181065A1 (fr)

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EP24160709 2024-02-29

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