阅读说明：本技术 偶联剂 (Coupling agent ) 是由 A·努米拉-帕卡里内 T·桑德霍尔姆 H·K·塔赫瓦奈内 V·波利亚科娃 于 2019-01-30 设计创作，主要内容包括：本发明提供了一种多峰线性低密度聚乙烯(LLDPE),其已与酸性接枝剂接枝以形成接枝LLDPE(g-LLDPE),其中所述LLDPE是乙烯与至少一种α-烯烃共聚单体的共聚物,并且其中所述LLDPE的MFR<Sub>2</Sub>为0.05至50g/10min,优选为0.05至10g/10min。(The present invention provides a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, and wherein the MFR of said LLDPE 2 Is 0.05 to 50g/10min, preferably 0.05 to 10g/10 min.)

1. A multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, and wherein said LLDPE has an MFR of from 0.05 to 50g/10min, preferably from 0.05 to 10g/10min₂。

2. LLDPE as claimed in claim 1, wherein said LLDPE has a density of 915 to 950kg/m³Preferably 918 to 940kg/m³。

3. LLDPE as claimed in claim 1 or 2, wherein the MFR of said LLDPE₂From 0.05 to < 1g/10min, preferably from 0.06 to 0.9g/10min, more preferably from 0.07 to 0.8g/10min, for example from 0.08 to 0.6g/10 min.

4. LLDPE as claimed in any one of claims 1 to 3, wherein said LLDPE has a zero shear melt viscosity of η₀(measured according to ISO 6721-1 and-10 at a frequency of 0.05rad/s and 190 ℃) of 10000Pa s to 70000Pa s, preferably 15000Pa s to 60000Pa s.

5. An LLDPE as claimed in any one of claims 1 to 4, wherein said LLDPE is produced in situ in a multistage polymerisation process.

6. An LLDPE as claimed in any one of claims 1 to 5, wherein said LLDPE is bimodal.

7. The LLDPE as claimed in any one of claims 1 to 6, wherein said at least one α -olefin comonomer is C₄-C₈- α olefin, preferably 1-butene or 1-hexene.

8. An LLDPE as claimed in any one of claims 1 to 7, wherein said LLDPE is produced using a Ziegler-Natta catalyst.

9. An LLDPE as claimed in any one of claims 1 to 8, wherein said LLDPE comprises:

i) a low molecular weight fraction which is a homopolymer of ethylene or a copolymer of ethylene and at least one alpha-olefin comonomer, and

ii) a high molecular weight fraction which is a copolymer of ethylene and at least one alpha-olefin comonomer, wherein the comonomer content in the high molecular weight fraction ii) is the same or higher than the comonomer content in the low molecular weight fraction i).

10. An LLDPE as claimed in any one of claims 1 to 9 wherein the LLDPE is grafted with maleic anhydride.

11. An LLDPE as claimed in any one of claims 1 to 10 wherein the g-LLDPE is used to compatibilize a composite comprising at least one non-polar polymer and at least one material that is incompatible with the non-polar polymer.

12. A coupling agent comprising a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, and wherein said LLDPE has an MFR of from 0.05 to 50g/10min₂Wherein the LLDPE is the sole polymeric component of the coupling agent.

13. Use of a g-LLDPE as defined in any one of claims 1 to 11 as a coupling agent, preferably wherein said LLDPE is the sole polymer component in said coupling agent.

14. Use according to claim 13, wherein the coupling agent is used in a composite, preferably a composite comprising a non-polar polymer and at least one component incompatible with the non-polar polymer.

15. A composite material comprising a coupling agent, wherein the coupling agent comprises, preferably consists of, a g-LLDPE as defined in any one of claims 1 to 11.

16. The composite of claim 15, further comprising a non-polar polymer and at least one component incompatible with the non-polar polymer.

17. A process for producing a grafted LLDPE comprising:

a. an LLDPE as defined in any one of claims 1 to 11 is produced by a process comprising the steps of:

(i) homopolymerizing ethylene or copolymerizing ethylene and at least one alpha-olefin comonomer in a first polymerization stage in the presence of a ziegler-natta catalyst to produce a first ethylene homopolymer or copolymer;

(ii) (ii) copolymerizing ethylene with at least one alpha-olefin comonomer in a second polymerization stage in the presence of the first ethylene homo-or copolymer and the same ziegler-natta catalyst as in step (i) to produce the LLDPE comprising the first ethylene homo-or copolymer and a second ethylene copolymer;

wherein the comonomer content in the second ethylene copolymer is the same or higher, preferably higher, than the comonomer content in the first ethylene homopolymer or copolymer; and

wherein the first polymerization stage can be carried out by one or two polymerization steps, preferably by one step in a loop reactor, while the second polymerization stage is carried out in a gas phase reactor; and

b. the LLDPE obtained from the polymerization reactor is grafted with an acidic grafting agent, preferably maleic anhydride.

18. The method of claim 17, wherein the first ethylene homopolymer or copolymer has 920 to 980kg/m³And/or a melt flow rate MFR of at least 10g/10min₂。

Technical Field

The present invention relates to a novel coupling agent, in particular a coupling agent for multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent. The invention further relates to a composite material comprising said coupling agent and to the use of a multimodal grafted LLDPE (g-LLDPE) as coupling agent in a composite material.

Background

A composite material is a material that comprises two or more component materials that typically have completely different physical and/or chemical properties. When combined together, these component materials result in a new material that has different properties than the individual components and in some applications tends to provide particular advantages. For example, the composite material may be stronger, stiffer, softer, lighter, heavier, or have other desirable properties when compared to the individual components. Concrete is perhaps one of the best known composite materials, but plastics provide countless other examples and are widely used in a variety of end uses, including aerospace components (tails, wings, fuselages, propellers), boat and twin-screw boat hulls, bicycle frames, racing car bodies, fishing rods, water storage tanks, swimming pool panels, baseball batons, solar panels, spacecraft, mufflers, packaging materials, and pipes and fittings for a variety of uses (e.g., transportation of drinking water, fire fighting, irrigation, sea water, desalinated water, chemical and industrial waste, and sewage).

However, due to the different properties of the individual components in the composite, they tend to remain separate and distinct in the final structure. This incompatibility between the components means that the final material may suffer from poor properties, such as poor mechanical properties, e.g. poor impact strength. To address this problem to some extent, a coupling agent is typically added to the material. These coupling agents are compounds that are capable of improving the interfacial properties between different components (e.g. different polymeric materials and fillers), i.e. they provide bonding, e.g. chemical or physical, between the different components, helping to provide a more homogeneous material.

Many coupling agents are known and commercially available. It will be appreciated that the appropriate coupling agent is selected based on the components of the particular composite material. Known coupling agents include organosilanes, organotitanates, fatty acid esters and functionalized polyolefins.

In the plastics industry, functionalized polyolefins are gaining increasing attention as potential coupling agents. Polyolefins containing polar or reactive groups may be prepared by grafting polar monomers (e.g., maleic anhydride) onto the polyolefin. The polyolefin used for grafting is generally a monomodal polyolefin. Various grafting techniques are well known to those skilled in the art, including solution grafting using peroxide initiation, solid state grafting using peroxide or radiation initiation, and reactive extrusion in a twin screw extruder, typically using peroxide initiation. Alternatively, polyolefins containing polar or reactive groups may be prepared by copolymerizing at least one olefin monomer with at least one polar monomer (e.g., maleic anhydride). These polyolefins having reactive groups are effective as a transition bridge between polar and non-polar components which are commonly used in plastic materials, especially those used for food packaging. For example, ethylene vinyl alcohol (EVOH) and Polyamide (PA) are commonly used to provide attractive properties to packaging. Furthermore, EVOH acts as an oxygen barrier, while PA provides good mechanical and barrier properties. However, these polar polymers are completely incompatible with polyolefins, which tend to form the matrix polymer of the packaging material. The coupling agent acts to improve the compatibility of the components, resulting in a more homogeneous material.

Coupling agents may also be used as tie-layer materials or components thereof in multi-layer products (e.g., laminates) where, although the requirements for tie-layer materials are generally more stringent, there is still a need to improve the adhesion of layers of different properties, since properties such as softness and uniform branch distribution are important.

The use of MAH (maleic anhydride) grafted polyethylene or polypropylene compositions as tie-layer materials is well known. WO 99/37730 discloses an adhesive composition comprising an ethylene copolymer component and 2 to 35 wt% of a grafted metallocene polyethylene. WO 03/046101 is another example and describes an adhesive polymer composition comprising a blend of an elastomeric ethylene copolymer with a non-elastomeric polyethylene, wherein at least one of the components has been grafted with an acid grafting agent.

The possibility of recycling plastic articles, in particular articles for plastic packaging and multilayer plastic packaging articles made of or comprising composite materials, is an important requirement. To prepare the composite, a coupling agent is required to mix the incompatible ingredients with each other. In general, it is desirable to not deteriorate the properties of the composite material by using a coupling agent. WO 2017/207221 discloses a laminate structure which provides oxygen barrier properties and which can be recycled. In the tie layer of the multilayer structure, commercially available tie polymers are used, including graft copolymers of ethylene with polar comonomers (such as organic acids and organic acid derivatives).

However, recently, composite materials are important not only in being recyclable but also in having improved properties. It is desirable to use a coupling agent to improve the quality and performance of the recyclate. Commercially available binders include the dow RETAIN polymer modifier. These are olefin polymers that have been designed to be reactive, with ultra-low viscosity, and in particular, to have good haze. However, to date, no coupling agent has been designed that improves the stiffness-toughness balance of the material as a whole. Furthermore, it would be desirable to find a coupling agent that has a wide range of applications, i.e., is suitable for use with a variety of different types of ingredients in a composite material.

The inventors have surprisingly found that the coupling agent of the present invention comprising a multimodal LLDPE which has been grafted with an acidic grafting agent has the necessary balance of properties. The multimodal LLDPE to be grafted can have a high viscosity, have a multimodal branch distribution and have a relatively high stiffness. These properties are essentially unchanged during the grafting process. Commercially available MAH-graft compounds based on PE generally have very low viscosity. The material of the present invention also offers the advantage that it is a single LLDPE that has been grafted, i.e. the polymer to be grafted does not need to be blended with other polymers before grafting. An example of a single multimodal LLDPE used according to the invention is a reactor-made polymer, i.e. a polymer obtained directly from a polymerisation reactor without further blending with other polymers prior to grafting. However, as is well known in the art, antioxidants may be added to the polymer. Typically, commercially available coupling agents comprise several components in which the polymer mixture has been grafted. The use of a single LLDPE (e.g., a reactor-made LLDPE) helps to achieve a homogeneous graft polymer of consistent quality, and thus a more homogeneous composite. The additional blending step with other polymers can easily lead to non-uniformity of the grafted material. Naturally, such blending also results in additional work steps, and it is desirable to avoid these steps from both an ease and cost perspective.

It is therefore an object of the present invention to provide an improved coupling agent which not only provides uniform chemical bonding, but also enhances the mechanical properties of the composite material and does not hinder its recyclability. A coupling agent was sought that could be used with a variety of different components in a composite material. Thus, the novel coupling agents should ideally make it possible or even possible to recycle the components to be used in the composite. In particular, a coupling agent that can be directly produced is desired. It is best to observe improvement in many of these factors.

Disclosure of Invention

Accordingly, in a first aspect, the present invention provides a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer and said LLDPE has an MFR of from 0.05 to 50g/10min, preferably from 0.05 to 10g/10min₂。

In a second aspect, the present invention provides the use of a g-LLDPE as defined herein as a coupling agent, preferably wherein said g-LLDPE is the sole polymer component of the coupling agent.

Typically, coupling agents are applied in the composite material.

In a third aspect, the present invention provides a coupling agent comprising a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, wherein said LLDPE has an MFR of from 0.05 to 50g/10min₂Wherein the LLDPE is the sole polymeric component of the coupling agent.

In a fourth aspect, the present invention provides a composite material comprising a coupling agent, wherein the coupling agent comprises g-LLDPE as defined herein, preferably the coupling agent consists of g-LLDPE as defined herein.

In a fifth aspect, the present invention provides a process for producing a grafted LLDPE, the process comprising:

a. the LLDPE as defined herein is produced by a process comprising the steps of:

(i) homopolymerizing ethylene or copolymerizing ethylene and at least one alpha-olefin comonomer in a first polymerization stage in the presence of a ziegler-natta catalyst to produce a first ethylene homopolymer or copolymer;

(ii) (ii) copolymerizing ethylene with at least one alpha-olefin comonomer in a second polymerization stage in the presence of the first ethylene homo-or copolymer and the same ziegler-natta catalyst as in step (i) to produce said LLDPE comprising the first ethylene homo-or copolymer and a second ethylene copolymer;

wherein the comonomer content in the second ethylene copolymer is the same as or higher than the comonomer content in the first ethylene homo-or copolymer, preferably higher than the comonomer content in the first ethylene homo-or copolymer; and

wherein the first polymerization stage can be carried out by one or two polymerization steps, preferably by one step in a loop reactor, while the second polymerization stage is carried out in a gas phase reactor; and

b. the LLDPE obtained from the polymerization reactor is grafted with an acidic grafting agent, preferably maleic anhydride.

Definition of

The term molecular weight as used herein refers to weight average molecular weight (Mw) unless otherwise specified.

All MFR values determined according to ISO 1133 at 190 ℃, under a load of 2.16kg, 5.0kg or 21.6kg, are marked MFR respectively₂、MFR₅And MFR_21.6。

The term "reactor-made polymer" as used herein refers to a polymer obtained directly from a polymerization reactor. It will be understood as having the desired multimodality without any additional blending with other polymers. Thus, the term "reactor-made multimodal LLDPE" is used herein to refer to LLDPE that is obtained directly from a multi-stage polymerization reactor configuration and has the desired multimodal properties. Thus, multimodality in such polymers is achieved by the configuration of a multistage polymerization.

Multimodal LLDPE as used herein refers to LLDPE that is multimodal with respect to molecular weight and/or comonomer distribution as described below.

"grafted LLDPE" means an LLDPE that has been grafted with an acidic grafting agent. It will be appreciated by those skilled in the art that during grafting, the acidic grafting agent is chemically bonded (typically by at least one covalent bond) to the LLDPE. Thus, "grafted LLDPE" includes LLDPE and an acidic grafting agent chemically bonded to each other (e.g., consisting of LLDPE and an acidic grafting agent chemically bonded to each other).

Detailed Description

The present invention relates to a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, and wherein said LLDPE has an MFR of from 0.05 to 50g/10min₂。

The grafted LLDPE will be referred to herein as "g-LLDPE". The LLDPE prior to grafting is referred to herein as "LLDPE".

The g-LLDPE may also be referred to as a "coupling agent" as described herein. Accordingly, the present invention relates to a multimodal linear low density polyethylene (LLD)PE) which is a copolymer of ethylene and at least one α -olefin comonomer having an MFR of 0.05 to 50g/10min₂And has been grafted with an acidic grafting agent.

In a particular aspect, the present invention relates to a coupling agent comprising a multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE), wherein said LLDPE is a copolymer of ethylene and at least one α -olefin comonomer, wherein said LLDPE has an MFR of 0.05 to 50g/10min₂Wherein the LLDPE is the sole polymeric component of the coupling agent.

Thus, the multimodal Linear Low Density Polyethylene (LLDPE) which has been grafted with an acidic grafting agent to form a grafted LLDPE (g-LLDPE) can be used, inter alia, for example, for compatibilizing (acting as a compatibilizer) a composite comprising at least one non-polar polymer and at least one material which is incompatible with the non-polar polymer, in particular, for example, polymer recyclates and/or polymer recyclates from a multilayer film comprising at least one material which is incompatible with the non-polar polymer and/or comprising inorganic components which are incompatible with the non-polar polymer.

LLDPE can be produced in a multistage polymerization process using ziegler-natta catalysts.

LLDPE

The LLDPE of the invention is "multimodal". Thus, by definition, it comprises at least two parts. LLDPE comprising at least two polyethylene fractions having different (weight average) molecular weights and preferably also different comonomer contents, usually as a result of production under different polymerisation conditions, is said to be "multimodal". The form of the molecular weight distribution curve, i.e. the plot of polymer weight percent versus molecular weight change for a multimodal polymer (e.g. LLDPE), will show more than two maxima or will generally be significantly broadened compared to the curves for the individual fractions. For example, if the polymer is produced in a sequential multistage process using reactors connected in series and using different conditions in each reactor, the polymer fractions produced in the different reactors will each have their own molecular weight distribution and weight average molecular weight. When the molecular weight distribution curve of such a polymer is recorded, the individual curves from these fractions typically together form a broadened molecular weight distribution curve for the overall resulting polymer product.

The prefix "multi" represents the number of different polymer moieties present in the polymer. Thus, for example, multimodal polymers include so-called "bimodal" polymers consisting of two fractions. Preferably, the LLDPE is bimodal, i.e. consists of two fractions.

The multimodal LLDPE polymers of the invention have preferably a molecular weight of 915 to 950kg/m³More preferably 918 to 940kg/m³More preferably in the range of 920 to 935kg/m³In the range of (1), even more preferably from 921 to 930kg/m³In particular 922 to 926kg/m³Density in the range of (ISO 1183).

MFR of multimodal LLDPE₂From 0.05 to 50g/10min, preferably from 0.05 to 20g/10min, more preferably from 0.05 to 10g/10min, for example from 0.1 to 5g/10min or even more preferably from 0.05 to < 1g/10min, further preferably from 0.06 to 0.9g/10min, further preferably from 0.07 to 0.8g/10min, further preferably from 0.08 to 0.6g/10 min. In general, MFR₂Less than 5g/10min, in particular less than 3g/10min, and therefore preferably from 0.05 to 3g/10min or from 0.1 to 2.5g/10min, or in some embodiments from 0.2 to 2g/10min (ISO 1133, 190 ℃/min, 2.16kg load).

MFR of multimodal LLDPE₅Preferably from 0.1 to 20g/10min, preferably from 0.1 to 10g/10min, for example from 0.2 to 8g/10min, in particular from 0.2 to 6g/10min (ISO 1133, 190 ℃/min, 5.0kg load).

MFR of multimodal LLDPE₂₁Preferably from 5 to 150g/10min, preferably from 10 to 100g/10min, for example from 15 to 70g/10min (ISO 1133, 190 ℃/min, 21.6kg load).

The multimodal LLDPE used in the invention is preferably a bimodal LLDPE. FRR (i.e. ratio MFR) of bimodal LLDPE₂₁/MFR₅) Preferably 10 to 100, preferably 12 to 70, for example 15 to 30.

Typically, when a reactor-made multimodal polymer having the above-defined FRR is used to produce a monolayer film, the film will be very hazy (hazy). The haze (haze) measured according to ASTM D1003 for a 40 micron blown film produced from a W/H extruder with an L/D of 30, die 200x1,2mm, BUR 3:1, FLH 2DD is preferably greater than 30%, more preferably greater than 50%, even up to 70%; where BUR is the blow-up ratio, FLH is the frost line height (frost line height), DD is the draw down.

The multimodal LLDPE used in the invention desirably has a low xylene soluble fraction (XS). Thus, XS may be less than 25 wt%, preferably less than 20 wt%.

In addition, the LLDPE had a zero shear melt viscosity of η₀(measured according to ISO 6721-1 and-10 at a frequency of 0.05rad/s and 190 ℃) preferably from 10000Pa s to 70000Pa s, preferably from 15000Pa s to 60000Pa s.

Suitable multimodal LLDPEs have a melting point (measured by DSC according to ISO 11357-1) of typically below 130 ℃, preferably from 120 to 130 ℃, more preferably from below 120 to 128 ℃.

The multimodal LLDPE according to the invention is a copolymer of ethylene and at least one alpha-olefin comonomer. Preferably, at least one alpha-olefin comonomer has 4 to 8C atoms, more preferably 4 to 6C atoms. The most preferred comonomer is selected from 1-butene and 1-hexene or mixtures thereof.

Typically, the LLDPE comprises:

i) a Low Molecular Weight (LMW) moiety which is an ethylene homopolymer or ethylene and at least one α -olefin comonomer (e.g., C)₄-C₈α -olefin comonomer), and

ii) a High Molecular Weight (HMW) fraction of ethylene with at least one α -olefin comonomer (e.g., C)₄-C₈α -olefin comonomer), wherein the comonomer content in the high molecular weight fraction ii) is the same or higher than the comonomer content in the low molecular weight fraction i).

As used herein, the expression "ethylene homopolymer" refers to a polyethylene which essentially comprises, i.e. at least 97 wt%, preferably at least 99 wt%, more preferably at least 99.5 wt%, most preferably at least 99.8 wt% of ethylene.

As mentioned above, multimodal LLDPE consists of at least two fractions. Preferably, the LLDPE consists of a Low Molecular Weight (LMW) fraction and a High Molecular Weight (HMW) fraction as described above. In a preferred embodiment of the invention, the LLDPE consists of two fractions, wherein both fractions are ethylene copolymers with comonomers as described above.

The HMW fraction may comprise at least one comonomer which is the same as the comonomer used in the LMW fraction. Both fractions may be copolymers of ethylene with the same comonomer (e.g., ethylene with 1-butene or ethylene with 1-hexene). It will be appreciated, however, that if both parts contain the same comonomer, the parts are not identical and their (weight average) molecular weights and preferably comonomer contents will also be different.

The LMW fraction and HMW fraction may also comprise different comonomers. In embodiments where the comonomer in the LMW fraction is different from the comonomer in the HMW fraction, preferred combinations of comonomers include (LMW/HMW) 1-butene/1-hexene and 1-hexene/1-butene.

It was therefore concluded that the multimodal LLDPE of the invention can be a copolymer of ethylene with only one type of alpha-olefin comonomer or a copolymer (i.e. a terpolymer) of ethylene with two different alpha-olefin comonomers. In this case, one or both of the LMW fraction and HMW fraction may comprise two or more different copolymers, e.g., 1-butene and 1-hexene. Another possibility is a combination of a polyethylene homopolymer LMW fraction and a HMW fraction comprising ethylene and two comonomers, preferably 1-butene and 1-hexene. Thus, the HMW fraction is a terpolymer.

In a particularly preferred embodiment, the LLDPE is a bimodal LLDPE comprising a LMW fraction and a HMW fraction, both of which are ethylene/1-butene copolymers of different molecular weights and wherein the comonomer content in the higher molecular weight fraction is higher than the comonomer content in the lower molecular weight fraction.

The comonomer content present in the multimodal LLDPE as a whole is preferably from 1 to 30 wt%, more preferably from 1 to 20 wt%, even more preferably from 2 to 15 wt%, for example from 3 to 10 wt%, relative to the total weight of the LLDPE as a whole.

LMW part

The lower molecular weight fraction of the multimodal LLDPE preferably has an MFR of at least 10g/10min, preferably at least 100g/10min, more preferably from 110 to 3000g/10min, e.g.from 110 to 500g/10min, especially from 200 to 400g/10min₂。

The density of the low molecular weight fraction may be 920 to 980kg/m³Preferably 940 to 970kg/m³More preferably from 945 to 965kg/m³。

The amount of LMW fraction generally constitutes from 25 to 55 wt%, preferably from 35 to 52 wt%, more preferably from 40 to 50 wt%, for example from 41 to 48 wt%, relative to the total weight of the LLDPE as a whole.

The lower molecular weight component may be an ethylene homopolymer (i.e. where ethylene is the only monomer present), but is preferably an ethylene copolymer of ethylene with at least one alpha-olefin comonomer, particularly where only one comonomer is present. In particular, the copolymer of the LMW moiety is a copolymer of ethylene and 1-butene.

The comonomer content in the LMW fraction is usually kept at most at the same level as the comonomer content in the HMW fraction, preferably lower than the comonomer content in the HMW fraction. In the LMW fraction, comonomer contents of less than 10 wt% are suitable, preferably less than 7 wt%.

HMW fraction

The high molecular weight fraction should have a lower MFR than the lower molecular weight fraction₂(i.e., higher Molecular Weight (MW) and lower density.

The high molecular weight fraction should have an MFR of preferably less than 1g/10min, more preferably less than 0.5g/10min, in particular less than 0.2g/10min₂。

MFR of HMW fraction₂₁It should preferably be less than 20g/10min, more preferably less than 10g/10min, e.g. less than 8g/10 min.

The HMW fraction should have less than 915kg/m³E.g. less than 913kg/m³Preferably less than 912kg/m³In particular less than 910kg/m³The density of (c). It is also preferred that the density of the HMW fraction is greater than 890kg/m³. Ideally, the density should be 895 to 912kg/m³Within the range of (1). It should be noted that it is not possible to measure the properties of the HMW fraction directly when it is prepared in the second step of the multistage polymerization. However, the density, MFR, of the HMW fraction₂Etc. can be calculated based on the properties of the final polymer as described in the description of the production process.

The high molecular weight fraction generally constitutes from 45% to 75% by weight, preferably from 48% to 65% by weight, more preferably from 50% to 60% by weight, for example from 52% to 59% by weight, relative to the total weight of the LLDPE as a whole.

The high molecular weight fraction is an ethylene copolymer, particularly a bipolymer (i.e., where only one comonomer is present) or terpolymer (having two comonomers). The comonomer in the HMW fraction is an alpha-olefin, preferably 1-butene.

The amount of comonomer present in the HMW is at least the same as the amount of comonomer present in the LMW fraction. Preferably, the comonomer content in the HMW fraction is higher than the comonomer content in the LMW fraction to obtain the desired bimodal comonomer content distribution. In the HMW fraction, comonomer contents of less than 15 wt%, for example less than 12 wt%, are suitable.

It should be noted that during the formation of the HMW component in the second stage of the multi-stage process, the amount of comonomer in the HMW component cannot be directly measured, but can be calculated based on the amount of LMW component present and the amount of final polymer and knowledge of the split (split). Production split refers to the portion of polymer produced in each step of a multistage polymerization.

Other Components of multimodal LLDPE

The multimodal LLDPE of the invention can consist of a LMW fraction and a HMW fraction as defined herein. Alternatively, the multimodal LLDPE may comprise further polymer components in addition to the LMW fraction and the HMW fraction. For example, the polymer may comprise up to 10 wt% of a polyethylene prepolymer (as is well known in the art, obtainable from a prepolymerization step). In the case of such a prepolymer, the prepolymer component may be contained in one of the LMW fraction and the HMW fraction as defined above, preferably in the LMW fraction. It is well known that for LLDPE, the amount of all polymer components adds up to 100%.

It will be appreciated that the LLDPE may also contain conventional polymer additives, which may be added thereto (e.g. during the pelletization step). Such additives are well known to those skilled in the art.

Polymerisation reaction

The multimodal LLDPE polymer according to the invention can be prepared by in-situ blending in a multistage polymerisation process comprising at least two polymerisation stages. Such polymers are referred to herein as "reactor made" polymers. The term "reactor-made polymer" as used herein refers to a polymer obtained directly from a polymerization reactor. It will be understood as having the desired multimodality without any additional blending with other polymers. Thus, the term "reactor-made multimodal LLDPE" is used herein to refer to LLDPE that is obtained directly from a multistage polymerization reactor configuration and has the desired multimodal properties.

In all embodiments of the present invention, preferably the multimodal LLDPE is a single polymer prepared by in situ blending in a multistage polymerisation process. Multimodality in such polymers is achieved by a multistage polymerization configuration. It is to be understood that such polymers are distinct from polymer blends in which two or more components are mixed, prepared in separate polymerization processes.

Thus, the process for producing the LLDPE of the invention may comprise more than two polymerization stages or zones, wherein the terms "stage" and "zone" have the same meaning in the present application. Typically, the low molecular weight ethylene polymer component is produced in a first polymerization zone and the high molecular weight ethylene copolymer component is produced in a second polymerization zone. The first polymeric region and the second polymeric region may be connected in any order, i.e., the first polymeric region may precede the second polymeric region, or the second polymeric region may precede the first polymeric region, or the polymeric regions may be connected in parallel. However, it is preferred to operate the polymerization zone in a cascade mode. The polymerization zone may be operated under slurry, solution or gas phase conditions or a combination thereof. Suitable processes comprising slurry and gas phase cascaded polymerization stages are disclosed, for example, in WO-A-92/12182 and WO-A-96/18662.

It is generally preferred to remove the reactants of a preceding polymerisation stage from the polymer before introducing the polymer into a subsequent polymerisation stage. This operation is preferably carried out when the polymer is transferred from one polymerization stage to another. Suitable processes are disclosed, for example, in EP-A-1415999 and WO-A-00/26258.

The LLDPE of the present invention is generally produced in the presence of a suitable Ziegler-Natta catalyst known to those skilled in the art.

A prepolymerization step may be carried out before the actual polymerization step. The purpose of the prepolymerization is to polymerize small amounts of polymer onto the catalyst at low temperatures and/or low monomer concentrations. By prepolymerization, it is possible to improve the properties of the catalyst in the actual polymerization and/or to modify the properties of the final polymer. The prepolymerization step can be carried out in slurry or in gas phase. Preferably, the prepolymerization is carried out in a slurry.

A preferred multistage process for the production of LLDPE for use according to the present invention comprises at least one loop reactor and at least one gas phase reactor, for example from Borealis A/S, Denmark (known asTechniques) and described in the patent literature (for example in EP 0887379, WO 92/12182, WO 2004/000899, WO 2004/111095 or WO 00/68315). It is also possible to use more than two polymerization stages, for example more than one slurry reactor and/or more than one gas phase reactor. A preferred multistage polymerization configuration comprises two slurry (loop) reactors and one gas phase reactor.

In one example of this process, in a first step, ethylene is polymerized in a loop reactor in the liquid phase in an inert low boiling hydrocarbon medium. The polymerized reaction mixture is then withdrawn from the loop reactor and at least a major part of the inert low boiling hydrocarbons is separated from the polymer. The polymer is then transferred in a second or further step to one or more gas-phase reactors in which the polymerization is continued in the presence of gaseous ethylene.

At least a portion of the LLDPE of the invention is an ethylene copolymer, as described above, in which ethylene is polymerized with at least one alpha-olefin comonomer. Furthermore, it is preferred that if the polyethylene is produced according to the above described multistage process, the LMW fraction is produced in the loop reactor and the HMW fraction is produced in the gas phase reactor. The high molecular weight fraction and the low molecular weight fraction are homogeneously mixed during the polymerization using a multistage process.

Thus, in another embodiment, the present invention relates to a process for producing a grafted LLDPE, which process comprises:

b. the LLDPE as defined herein is produced in a process comprising the following steps:

(i) homopolymerizing ethylene or copolymerizing ethylene and at least one alpha-olefin comonomer in a first polymerization stage in the presence of a ziegler-natta catalyst to produce a first ethylene homopolymer or copolymer;

(ii) (ii) copolymerizing ethylene with at least one alpha-olefin comonomer in a second polymerization stage in the presence of the first ethylene homo-or copolymer and the same Ziegler-Natta catalyst as in step (i) to produce said LLDPE comprising the first ethylene homo-or copolymer and a second ethylene copolymer,

wherein the comonomer content in the second ethylene copolymer is the same or higher, preferably higher, than the comonomer content in the first ethylene homopolymer or copolymer, and

wherein the first polymerization stage can be carried out by one or two polymerization steps, preferably by one step in a loop reactor, while the second polymerization stage is carried out in a gas phase reactor; and

c. the LLDPE obtained from the polymerization reactor is grafted with an acidic grafting agent, preferably maleic anhydride.

In this process, the first ethylene homopolymer or copolymer preferably has a weight fraction of 920 to 980kg/m³And/or a melt flow rate MFR of at least 10g/10min₂。

The properties of multimodal polyethylene can be adjusted by varying the ratio of the low molecular weight fraction to the high molecular weight fraction in the multimodal polyethylene (production split). Preferably, the LLDPE comprises 35 wt% to 55 wt%, preferably 41 wt% to 48 wt%, of the LMW fraction and 45 wt% to 65 wt%, preferably 52 wt% to 59 wt%, of the HMW fraction.

Another possibility for preparing the multimodal LLDPE of the invention is to polymerize the two fractions in a one-stage polymerization process using two different ziegler-natta polymerization catalysts. Preferably, however, the LLDPE of the invention is produced in a multistage process using the same ziegler-natta catalyst in all polymerisation stages. Typically, the catalyst is fed to the first reactor, which may also be a prepolymerization reactor.

Preferably, the multimodal LLDPE of the invention is produced by a process employing slurry polymerization in a loop reactor followed by gas phase polymerization in a gas phase reactor.

The conditions used in such a process are well known. For slurry reactors, the reaction temperature will typically be in the range of 60 to 110 ℃ (e.g., 85-110 ℃), the reactor pressure will typically be in the range of 5 to 80bar (e.g., 50-65bar), and the residence time will typically be in the range of 0.3 to 5 hours (e.g., 0.5 to 2 hours). The diluent used is generally an aliphatic hydrocarbon having a boiling point in the range from-70 to +100 ℃. In such a reactor, the polymerization can be carried out under supercritical conditions, if desired. Slurry polymerization may also be carried out in bulk when the reaction medium is formed from the monomers being polymerized, however, for ethylene polymerization, the diluent is preferably an inert aliphatic hydrocarbon.

For gas phase reactors, the reaction temperature used will typically be in the range of 60 to 115 ℃ (e.g., 70 to 110 ℃), the reactor pressure will typically be in the range of 10 to 25bar, and the residence time will typically be in the range of 1 to 8 hours. The gases used are generally non-reactive gases, such as nitrogen or low boiling hydrocarbons (e.g. propane), and monomers such as ethylene.

Preferably, the low molecular weight fraction is produced in a continuously operated loop reactor, wherein ethylene is polymerized optionally in the presence of comonomers, a ziegler natta polymerization catalyst and a conventional cocatalyst, i.e. a compound of a group 13 metal, such as an alkyl aluminium compound, and a chain transfer agent, e.g. hydrogen. The diluent is generally an inert aliphatic hydrocarbon, preferably isobutane or propane. The high molecular weight fraction can then be formed in the gas phase reactor using the same catalyst.

When the HMW fraction is prepared in the second step of a multistage polymerisation, it is not possible to measure its properties directly. However, for the above polymerization process of the present invention, the Kim McAuley's equations can be used to calculate the density, MFR, of the HMW fraction₂And the like. Thus, density and MFR₂Both are available using k.k.mcauley and j.f.mcgregor: on-line Inference of Polymer Properties in commercial polyethylene reactors (Online interference of Polymer Properties in an Industrial polyethylene Reactor), AIChE Journal, 6.1991, volume 37, No. 6, page 825-. The density is calculated according to equation 37 of McAuley, where the final density and the density after the first reactor are known. MFR₂Is calculated according to McAuley's equation 25, where the MFR after the first reactor₂And final MFR₂Are known.

If the multimodal LLDPE used is a recycled material, this material comes from recycled post-consumer waste and post-industrial waste, which have been re-pelletized.

Catalyst and process for preparing same

Ziegler-Natta (ZN) type polyolefin catalysts are well known in the art for the production of olefin polymers, such as ethylene (co) polymers. Generally, the catalyst comprises at least one catalyst component formed from a compound of a transition metal of groups 4 to 6 of the periodic table (IUPAC, nomenclature of inorganic chemistry, 1989), a compound of a metal of groups 1 to 3 of the periodic table (IUPAC), optionally a compound of group 13 of the periodic table (IUPAC), optionally an internal organic compound (e.g. internal electron donor). ZN catalysts may also comprise other catalyst components, for example, a cocatalyst and optionally external additives.

Suitable Ziegler-Natta catalysts preferably comprise a magnesium compound, an aluminium compound and a titanium compound supported on a particulate support.

The particulate support may be an inorganic oxide support, for example silica, alumina, titania, silica-alumina, silica-titania or based on MgCl₂The vector of (1). Preferably, the support is silica or based on MgCl₂The vector of (1).

The average particle size of the silica support is generally from 5 to 100. mu.m. However, it has been found that particular advantages can be achieved if the support has an average particle diameter of from 10 to 30 μm, preferably from 15 to 25 μm, or from 18 to 25 μm. Alternatively, the average particle diameter of the carrier may be 30 to 80 μm, preferably 30 to 50 μm.

The magnesium compound may be the reaction product of a magnesium dialkyl with an alcohol. The alcohol is a linear or branched aliphatic monohydric alcohol. Preferably, the alcohol has 6 to 16 carbon atoms. Branched alcohols are particularly preferred, and one example of a preferred alcohol is 2-ethyl-1-hexanol. The magnesium dialkyl may be any compound of magnesium bonded to two alkyl groups, which may be the same or different. An example of a preferred magnesium dialkyl is butyl octyl magnesium.

The aluminium compound may be a chlorine-containing aluminium alkyl. Particularly preferred compounds are alkylaluminum dichlorides and alkylaluminum sesquichlorides.

The compound of a transition metal of groups 4 to 6 is preferably a titanium compound or a vanadium compound, more preferably a halogen-containing titanium compound, and most preferably a chlorine-containing titanium compound. A particularly preferred titanium compound is titanium tetrachloride.

The catalyst may be prepared by sequentially contacting the support with the above compounds as described in EP 688794 or WO 99/51646. Alternatively, it may be prepared by first preparing the components as a solution and then contacting the solution with the carrier, as described in WO 01/55230.

Another group of suitable Ziegler-Natta catalysts comprises a titanium compound and a magnesium halide compound as support. Thus, the catalyst comprises a titanium compound and optionally a group 13 compound (e.g., an aluminum compound) on a magnesium dihalide (e.g., magnesium dichloride). Such catalysts are disclosed, for example, in WO 2005/118655, EP 810235, WO2014/096296 and WO 2016/097193.

According to the present invention multimodal LLDPE is preferably produced using a silica supported ziegler-natta catalyst as described in EP 688794, EP 835887 or WO 99/51646.

Typical internal organic compounds (e.g. internal electron donors, if used) are selected from ethers, esters, amines, ketones, alcohols, anhydrides or nitriles or mixtures thereof, preferably from ethers and esters, most preferably from ethers of 2 to 20 carbon atoms, especially saturated or unsaturated ethers of monocyclic, bicyclic or polycyclic rings containing 3 to 6 ring atoms.

Ziegler-Natta catalysts are typically used with a co-catalyst. Suitable cocatalysts are compounds of group 13 metals, usually alkyl compounds of group 13, especially alkyl aluminum compounds, wherein the alkyl group contains from 1 to 16 carbon atoms. These compounds include trialkylaluminum compounds (e.g., trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum and tri-n-octylaluminum), alkylaluminum halides (e.g., ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, dimethylaluminum chloride, etc.). Particularly preferred cocatalysts are trialkylaluminums, with triethylaluminum, trimethylaluminum and triisobutylaluminum being particularly useful.

The amount of cocatalyst used depends on the particular catalyst and cocatalyst. Typically, triethylaluminum is used in an amount such that the molar ratio of aluminum to transition metal (e.g., Al/Ti) is from 1 to 1000, preferably from 3 to 100, and especially from about 5 to about 30, mol/mol.

Grafting

The multimodal LLDPE of the invention has been grafted with an acidic grafting agent to produce a grafted LLDPE (g-LLDPE). Such a grafted LLDPE can be used as a coupling agent. As acidic grafting agent, any such agent known to the person skilled in the art to be suitable for this purpose can be used. Preferably, the acidic grafting agent is an unsaturated carboxylic acid or derivative thereof, for example, anhydrides, esters and salts (metallic or non-metallic). Preferably, the unsaturated group is conjugated with a carboxyl group. Examples of such grafting agents include acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, citraconic acid, itaconic acid, crotonic acid and anhydrides, metal salts, ester amides or imides thereof. The preferred grafting agent is maleic acid or a derivative thereof (e.g., maleic anhydride), with maleic anhydride being most preferred.

Grafting can be carried out by any method known in the art, for example grafting in a solvent-free melt or in a solution or dispersion or in a fluidized bed. Preferably, the grafting is carried out, for example, in a heated extruder or mixer, for example, grafting is described in US3236917, US 4639495, US 4950541 or US 5194509. Grafting is preferably carried out in a twin-screw extruder, as described, for example, in US 4950541.

The grafting can be carried out in the presence or absence of a free radical initiator, but is preferably carried out in the presence of a free radical initiator (e.g., an organic peroxide, an organic perester, or an organic hydroperoxide).

The amount of the acidic grafting agent added to the LLDPE before grafting is preferably 0.01 to 3.0 parts by weight, more preferably 0.03 to 1.5 parts by weight, relative to the total weight of the LLDPE and grafting agent combined.

Composite material

According to the invention, the g-LLDPE of the invention can be used as coupling agent in composites. Accordingly, the present invention also relates to a composite comprising a g-LLDPE as defined herein as coupling agent. Preferably, the coupling agent consists of the g-LLDPE of the present invention. As used herein, the term "composite material" is intended to encompass any material comprising two or more component materials having substantially different physical or chemical properties, preferably finely divided (finely divided) and mixed with each other. For the avoidance of doubt, in the sense of the present invention, a "composite material" may preferably comprise, for example, more than just a multi-layer arrangement of different materials. It will be appreciated that these two or more component materials are complementary to the g-LLDPE of the present invention.

Typically, the composite material of the present invention will comprise at least one non-polar polymer. Typically, the non-polar polymer is a polyolefin of linear or cyclic monomers having from 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms, especially polyethylene or polypropylene, or copolymers thereof with ethylene or alpha-olefins of from 3 to 8 carbon atoms. An exemplary composite material is one in which the non-polar polymer is polyethylene, such as LLDPE. Any suitable LLDPE may be employed. The LLDPE may be the same or different from the LLDPE used to prepare the g-LLDPE (coupling agent) of the present invention. The non-polar polymer may constitute a substantial portion of the composite material by weight, and may then be referred to as a matrix material or matrix material. However, the amount of non-polar polymer may also constitute a minority of the composite material by weight.

The other components of the composite are generally materials that are incompatible with the non-polar polymer. Such materials may be more than one polymer, usually polar, or they may be another type of material, such as inorganic, synthetic or organic fillers, pigments, other additives or mixtures thereof. Exemplary polar polymers include ethylene vinyl alcohol (EVOH) and Polyamide (PA). The filler includes spherical filler or plate-like filler or fibrous filler. Examples of fillers may include stone powder, talc, glass fibres, carbon carbonate, wollastonite, wool or cellulose fibres or cotton fabrics. Typical examples of pigments are carbon black and TiO₂。

As noted above, the type and amount of ingredients in the composite material can vary widely depending on the needs of the end application. However, the fraction of ingredients that are incompatible with the non-polar polymer and comprise polar polymer, filler, pigment and/or any other ingredient or mixture thereof may be from 0.1 to 80 wt% of the composite. Thus, the non-polar polymer and the coupling agent may together comprise 20 wt% to 99.9 wt% of the composite.

The amount of coupling agent is highly dependent on the amount of non-polar polymer and the amount of ingredients that are incompatible with the non-polar polymer. In addition, the nature of the incompatible ingredients affects the amount of coupling agent. The amount of coupling agent present in the composite material generally ranges from 1 wt% to 20 wt%, for example from 3 wt% to 15 wt%, relative to the total weight of the composite material as a whole.

Illustrative, non-limiting examples of composites using the coupling agent of the invention may comprise, as incompatible ingredients, from 0.1 to 30% by weight of EVOH and/or from 0.2 to 35% by weight of PA and/or from 1 to 70% by weight of filler, from 1 to 20% by weight (for example, from 3 to 15% by weight) of the coupling agent of the invention (g-LLDPE), the remainder being non-polar polyolefins, with the% by weight being relative to the total weight of the composite.

It will be appreciated that the composite material of the invention may contain, in addition to the above components, small amounts, preferably up to 4 wt%, of conventional additives. For example, the antioxidant in the composite may be present in an amount of up to 10,000ppm, more preferably up to 5,000ppm, most preferably up to 3,000 ppm.

The composites of the present invention may be prepared by any method known in the art, but they are typically prepared by mixing the various components.

Applications of

According to the invention, multimodal, preferably bimodal, LLDPE is used as coupling agent in grafted form (g-LLDPE).

Ideally, the g-LLDPE is the sole polymeric component of the coupling agent.

As discussed, it is particularly preferred if the grafted LLDPE of the present invention (i.e.the g-LLDPE as defined herein) is used as a coupling agent in a composite. Viewed from a further aspect therefore the invention provides the use of a g-LLDPE as defined herein as a coupling agent in a composite. The composite material may be any suitable material as defined herein.

Potential end uses for the composite material in which the coupling agent of the invention may be used include various articles such as pipes, waste water systems, conduits, decking (e.g., WPC (wood plastic composite) for decking), shipping containers, pallets, shipping containers, siding, ceilings, garden furniture, garnitures, fences and utility poles.