EP4081594A1

EP4081594A1 - High melt strength polypropylene composition and process for manufacturing thereof

Info

Publication number: EP4081594A1
Application number: EP19957492.2A
Authority: EP
Inventors: Alexey Mikhailovich VOLKOV; Irina Gennadievna RYZHIKOVA
Original assignee: Sibur Holding PJSC
Current assignee: Sibur Holding PJSC
Priority date: 2019-12-27
Filing date: 2019-12-27
Publication date: 2022-11-02
Also published as: WO2021133203A1; EP4081594A4; CN114867782A

Abstract

The present invention relates to a polypropylene composition that is especially suitable for making articles by foaming. The polyethylene composition according to the invention comprises: a random propylene copolymer; a vinyl monomer; a peroxide initiator; an antioxidant and/or a heat stabilizer. Furthermore, the composition may comprise a propylene homopolymer, a polyolefin elastomer, and other additives. The composition is preferably manufactured by pre-blending the first 3 components at a certain temperature and holding time to produce a concentrate, a so-called pre-blend. Blending and processing into a homogeneous melt are carried out in special mixing equipment and an extruder. The technical result of the present invention is to obtain of a high melt strength polypropylene composition by reactive extrusion with melt strength values of between 18 and 43 cN, in combination with improved melt flow indices of the modification products: MFI_230° c/2.16kg ranging from 0.5 to 3.0 g/10 min.

Description

HIGH MELT STRENGTH POLYPROPYLENE COMPOSITION AND PROCESS FOR MANUFACTURING THEREOF

Field of the invention

The present invention relates to high melt strength thermoplastic polymers and/or high melt strength compositions intended for being foamed by any known methods that permit manufacturing high-strength materials for a wide range of applications.

Due to their good functional properties, polypropylene foam materials replaced other foam materials that were actively used before. In particular, polypropylene-based foaming materials have better rigidity, strength and heat resistance than polyethylene, better impact strength than polystyrene, and better chemical stability than polyurethane.

The composition disclosed in the present invention may be used in building and construction, transportation, cable- and pipe-production, in the manufacture of packaging materials and articles with excellent thermal-, acoustic- and waterproof properties, preferably the ones obtained by foaming, and in the form of a film material produced by blowing method or by any other known method .

Prior art

Foaming is one of the simplest processes for manufacturing foam-like and spongiform materials. Specific properties of the materials thus obtained, i.e. light weight, shock-absorbing capacity, high thermal-, acoustic- and waterproof properties, make them advantageous for use thereby extending their fields of application. Conventional polymers for foaming are polyurethanes, polystyrene, epoxy polymers, polyvinyl chloride. However, regardless of some unique properties and various applications in different industries, polypropylene has not found acceptance in foam articles owing to its low strength and melt extensibility.

Several processes are used for making foam materials. One of the basic processes comprises passing a gas mixture (air, nitrogen) through a molten polymer compound to reach a desired foaming level, extruding, and subsequent cooling to room temperature, during which the materials harden in the foamed state. Foam materials made of conventional high linear polypropylene synthesized on Ziegler-Natta catalysts according to the standard industrial technique are distinguished by low capability of maintaining the volume of gas bubbles (pores or cellular structure) and the form of foam during cooling. Maintenance of the volume of bubbles (pores or cellular structure) is affected by such properties of a polymer as melt extensibility (mm/s) and melt strength (MS) (cN). Various approaches are employed in order to improve said properties, i.e. strength and extensibility of the polypropylene melt. All of them are associated with modification of the linear structure of isotactic polypropylene that aims at its substantial branching and/or partial or even full crosslinking.

Nowadays, the following polypropylene-based systems are used to make foam materials:

1. A linear bimodal polypropylene manufactured by multistage polymerization in a reactor or by reacting polypropylene with crosslinking agents; 2. A branched polypropylene manufactured by a peroxide treatment or radiation treatment or by copolymerization of propylene with dienes in the presence of a metallocene catalyst. In terms of branching, the following long chain polypropylene types are distinguished: multi-branched (a), double-stranded (ladder) (b), and short- branch (c) polypropylene, which are represented in Fig. 1. In order to determine a degree of branching of a polymer, the branching index g’ is used, which is defined as [IV]_{branched polymer}/[IV]_{linear polymer} ratio, where [IV]_br is inherent viscosity of a branched polymer and [IV]_lin is inherent viscosity of a linear polyprolylene with a similar molecular weight. A material suitable for making foam must have the index g’ of less than 0.9. The analysis of the prior art allows to identify three main processes for manufacturing high melt strength polypropylene that are used for making articles by foaming: a radiation process, a reactor process, and a post-reactor process.

Radiation processes. Major technical developments in the field of compositions comprising high melt strength polypropylene obtained via the radiation process belong to Total Petrochemical and Montell North America (now a part of LyondellBasel). The process consists of treating a powder or pellets of polypropylene or copolymers thereof by a 5-25 MeV electron beam, holding for a certain period of time that is necessary for having chain fragments migrate to active free radical centres and for forming a branched structure, followed by extrusion with stabilizing additives to deactivate unreacted free radicals. The radiation dose varies from 10 to 120 kGy. This kind of polymer modification is performed in special devices - electron accelerators. The majority of prior art documents describe a process of ionization by radiation that runs in an oxygen-depleted medium or in an inert atmosphere. It is also advisable to extrude polypropylene in an inert gas atmosphere. At the same time, processes have been developed which comprise subjecting bifunctional monomers to radiation in the presence of gases containing double bonds.

According to patent application US20040171712A1 (Braskem SA, 29.12.2000), the modification of polypropylene is activated by high-intensity ionizing radiation in the presence of an atmosphere containing crosslinking promoter gases, such as acetylene, butadiene, butene, etc. This process allows reaching a melt strength of 52 cN.

Patent US6699919B (Total Petr, 20.03.2000) compares polypropylene produced by electron-beam radiation in an inert atmosphere with polypropylene produced in the presence of crosslinking agents. Bismaleimide derivatives, acrylates, silanes, unsaturated acids and anhydrides thereof, nonconjugated dienes, polyisoprenes, styrene, divinylbenzene are used as the crosslinking agents. It has been discovered that introduction of crosslinking agents permits raising polypropylene melt strength from 17 to 45 cN, wherein the radiation dose shrinks from 60 to 15 kGy. The so-obtained polypropylene has the index g’ of 0.7.

The radiation process allows achieving highest melt strength values, although it involves considerable economic expenditures due to the need to use expensive devices - electron accelerators.

Reactor process. Production of high melt strength polypropylene through synthesis in a reactor is described in patent documents owned by Borealis (AT), Exxon Chemical (US), Novolen Technology (DE), Samsung (KR). A distinction can be made between two main trends in production of high melt strength polypropylene by the reactor process: obtainment of bimodal polypropylene during multistage polymerization and polymerization of branched polypropylene on metallocene catalysts.

Patent US6875826B (Borealis Tech, 28.09.1998) suggests a process for preparing polypropylene having high melt strength by two-step polymerization or by copolymerization using different amounts of an agent for adjusting the molecular weight of a polymer. Propylene is polymerized in the presence of a Ziegler-Natta catalyst having decreased chain transfer sensitivity, and a strongly coordinating external donor. The product prepared by this technique exhibits good melt strength, which is a prerequisite for making articles by foaming.

Patent US6225432B (Exxon Chem, 17.08.1999) employs single-site metallocene catalysts for polymerization of propylene so as to achieve high melt strength. The general formula of such a catalyst is Cp_mMR_nX_q, wherein Cp is a cyclopentadienyl ring that may have substituents; M is a transition metal of group IV, V or IV, in particular, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten; R is an alkyl or alkoxy group having 1 to 20 carbon atoms, X is a halogen, and m = 1-3, n = 0-3, q = 0-3. The polymerization yields polypropylene having molecular weight distribution of greater than 4 and the degree of branching g’ of less than 0.95.

Disadvantageous features of the reactor processes for manufacturing high melt strength polypropylene are complexity of technology and additional modification of the product that is required from time to time.

Post-reactor processes. Post-reactor melt modification of polypropylene using crosslinking and/or modifying agents is at present the most widely used technique for the manufacture of high melt strength polypropylene.

Known in the art are patents in the field of post-reactor modification for manufacturing high melt strength polypropylene owned by AkzoNobel, Atofina Research (Total Petrochemical), Borealis AG, Dow Global Technologies.

The post-reactor modification of high melt strength polypropylene is based onmodification of a polypropylene powder or melt with organic peroxides, crosslinking and/or branching agents by means of standard mixing equipment.

US5416169A (JNC, 05.11.1993) discloses a two-step process that combines treatment of a propylene powder in a reactor and in an extruder. In the first step, the polypropylene powder is treated in a reactor in the presence of peroxydicarbonates at a temperature of 135°C for 30 minutes, and then the treated powder is extruded with stabilizers at 230°C.

The process for manufacturing high melt strength polypropylene by the peroxydicarbonate modification of polypropylene was also disclosed in patent US6103833 granted to AkzoNobel (Nld). Borealis AG (AT) in patent US6204348 discloses a continuous solid phase production technique for high melt strength polypropylene by grafting a multifunctional vinyl monomer in the presence of a radical initiator.

A drawback of this technology is that the modification process must be conducted in a heterogeneous phase at a temperature lower than the melting point. If said temperatures are higher, a predominantly linear polymer with slight branching or having no branching at all is generated. Such restrictions make the modification process multi- stage, that include a step of mixing a low-temperature peroxide with polypropylene, a step of gradually heating the mixture from room temperature to 120-150°C, a step of inactivating the free radicals collected. The entire process is carried out in a sealed reaction vessel and only the 3^rd step of the process can be performed by extrusion and can be combined with granulation of the product, which involves a lot of practical difficulties, including in terms of technical equipment. Either liquid peroxydicarbonates or solutions in an inert solvent are used to improve homogeneity of the product, i.e. high melt strength polypropylene.

Patent US6323289B (AkzoNobel (Nld), 19.05.2000) describes an extrusion process of modifying polypropylene with peroxides to improve melt strength at temperatures over 150°C. At present, peroxydicarbonate intended for making high melt strength polypropylene during extrusion is manufactured by AkzoNobel under the tradename Perkadox 24L. When said substance is used, melt strength of polypropylene may be as high as 40 cN at 190°C, although the MFl_{230°C/2.16 kg} of such a product is less 0.7 g/10 min.

Patent application KR2018065303 A (HANWHA Total Petrochemical Co Ltd (KR), 07.12.2016) discloses a high melt strength polypropylene composition and a method of preparing the same, comprising reactive compounding of a mixture melt including from 70 to 90 parts by weight of polypropylene, from 1 to 18 parts by weight of a highly random ethylene-a-olefm linear copolymer, in the presence of from 0.1 to 2.0 parts by weight of peroxidicarbonate. An easily flowable polypropylene composition having a MFl_{230°C/2.16 kg} of greater than 10 g/10 min is intended solely for injection molding of articles with foaming, which substantially limits the field of its practical use.

According to application CN104072874A (Zhang Xishun (CN), 25.03.2013), polypropylene branching is enhanced by adding azodicarbonamide in an amount from 5 to 10 parts by weight and polyethylene in an amount from 10 to 20 parts by weight to a peroxide-modified (from 1.5 to 2.5 parts by weight of dicumyl peroxide) polypropylene composition, thereby solving the problem of its extensibility yet failing to remove poor flowability.

Known in the art are processes for producing high melt strength polypropylene that employ, instead of widely known and available peroxide initiators, organic compounds with azide (N₃) groups that are capable of being thermally decomposed to form free radicals, too. Dow Global Technologies (US) in patent US6800669B (12.12.2001) discloses a technique of producing high-impact propylene copolymers, i.e. high melt strength block copolymers (BC), the technique comprising modifying a melt with azides, preferably polysulfonyl azides that contain at least two polypropylene- reactive -SO₂N₃ groups. The product obtained by said technique exhibits high melt strength values (up to 40 cN), although its disadvantages include reduced flowability and low melt extensibility (up to 23 mm/s).

Recently, Braskem America (US) has offered a more “extensible” formulation of a BC composition modified by sulfonyl azides, comprising from 8 to 25% of ethylene propylene rubber. Nevertheless, the problem of improving flowability of this high impact polypropylene formulation remains unsolved.

One of the shortcomings of “azid” processes for making high melt strength polypropylene is high explosion hazard of organic azides, especially when the content of azide groups is more than 20 wt.%.

Common drawbacks of all known production techniques of high melt strength polypropylene, which use peroxide initiators or other radical initiators, are difficulties in reaching and maintaining a complex of properties of a composition, particularly, melt strength, flowability, and extensibility. A known approach that allows influencing the aforementioned properties of high melt strength polypropylene compositions is use of modifying systems based on mixtures of a radical initiator with a mono- and/or di- and/or polyfunctional vinyl monomer, which permits reducing the concentration of a radical initiator in the system by means of a chain transfer reaction, thereby lowering probability of a competitive side reaction of destruction of polypropylene macrochains.

Reference US5082869A (Ausimont SA (US), 07.03.1991) discloses a polypropylene composition for foam articles produced by a peroxide “dynamic” vulcanization process in the presence of a bifunctional monomer, a furan derivative. The resultant composition consists of from 3 to 75 wt.% of crosslinked polypropylene distributed in non-crosslinked polypropylene in the form of particles having a diameter from 0.5 to 100 pm. When a foaming agent is introduced into the composition, the molding process of a finished product may be combined with the step of dynamic vulcanization.

JP7242762 (03.03.1994), KR101877249 (29.09.2015), WO2017170907 (30.03.2017), WO2018062443 (28.09.2017) are patent documents of Sekisui Chem. that are directed to a process for producing peroxide-crosslinked foams from polypropylene by use of mono- or polyfunctional aromatic vinyl monomers or polyolefin elastomer additives as a coagent. The materials produced by adding foaming agents are intended for lamination or injection molding, or for manufacture of food containers. The main disadvantageous feature of such compositions is that they cannot be recycled due to excessive crosslinking that can hardly be controlled during their synthesis.

Another Japanese company, KANEKA CORPORATION (JP), has used conjugated dienes as coagents when producing polypropylene foam compositions: 1,3- butadiene and isoprene, or a combination thereof with aromatic vinyl monomers: JP2000289082A (07.04.1994), JP2000143856A (09.11.1998), JP03634935B2

(25.03.1997), JP10168214A (13.12.1996), JP10158424A (05.12.1996), JP11035724A (24.07.1997), JP03561078B2 (17.04.1996). In view of high susceptibility of highly active conjugated dienes to crosslinking, control of flowability of final compositions is complicated in these reactive extrusion processes, too. High volatility of diene monomers creates difficulties in terms of technology, as well.

An attempt of solving the above-identified problems is disclosed in a patent issued to Borealis (AT), where diene oligomers applied to a special porous polypropylene are used as coagents. A peroxide available from AkzoNobel under the tradename Trigonox BPIC is introduced into a propylene composition as a concentrate. The melt strength of the composition comprising 9 wt.% of an oligomer reaches 20.1 cN, and extensibility is 250 mm/s.

International application WO2012049690 (Reliance Industries (IN), 11.10.2011) proposes a wide spectrum of coagents for producing high melt strength polypropylene, and also mentions use of phenylenedimaleimide (FDM). It is preferable, however, to use such coagents as triallyl cyanurate, divinylbenzene, and acrylic monomers: trimethylolpropane triacrylate (TMPTA), pentaerythrytol triacrylate, hexadecyl methacrylate, etc. at a concentration ranging from 0.1 to 1.0 wt.%. The non-conjugated system of double bonds of acrylic nature in these monomers probably reduces the contribution of crosslinking processes in favor of branching of macrochains. The growth of melt strength achievable thereby is from 30 to 60% from the initial strength. Moreover, reference US5362808A (BASF (DE), 15.04.2001) teaches using FDM for partial crosslinking of mainly amorphous copolymers of propylene with ethylene and a- olefins. Use of 1,3-bismaleinidbenzene (meta-FDM) in an amount of 0,4 wt.% reduces sagging of a molten web of the aforementioned polymer from 163 to 105 mm, which is circumstantial evidence of crosslinking-branching processes running in the polymer.

Reference CN101418064B (Univ of China (CN), 02.12.2008) suggests a method of producing long-chain, branched polypropylene having high melt strength, in which side processes of polypropylene degradation are controlled by adjusting a ratio of polypropylene, an initiator, a polyfunctional monomer, by changing the time of residence of a mixture of ingredients in an extruder, and by further introducing a monofunctonal styrene monomer and a processing additive, calcium stearate.

In patent CN102432762B (East China university (CN), 02.09.2011), a similar objective is achieved by means of using a three-component mixture of monomers having different functionalities: maleic anhydride, styrene, and isoprene that are fed to a certain zone of an extruder. The melt strength of polypropylene is as high as 24 cN at 190°C.

A somewhat higher melt strength value is obtained in international application WO2012174965 (East China university (CN), 22.06.2011), where linear bifunctional siloxanes, along with diene monomers, styrene, etc., are used as branching agents of polypropylene. The melt strength rises to 24 cN at 190°C.

It is a known approach to reach a balance between melt strength and extensibility to employ a bimodal mixture of polypropylene. Patent US6723795B (Atofina, 08.06.2000) describes a process for producing a bimodal mixture based on isotactic polypropylene by mixing a high molecular weight component (from 55 to 65 wt.%) and a low molecular weight (MW) component (from 45 to 35%) in an extruder in a nitrogen atmosphere at 220°C. The first component has MFl_{230°C/2.16 kg}of less than 0.5 g/ 10 min, while the second component has said MFl_{230°C/2.16 kg} of over 6 g/10 min. The mixture has a dispersion index equal to 8. The resultant composition may be useful for making foams and extruded products, along with fibers, thermoformed articles. Crosslinking agents, for example, allyl methacrylate, divinyl benzene, in combination with a radical initiator may be used to improve characteristics of articles.

A common drawback of peroxide-coagent modifying systems that are utilized in the post-reactor synthesis of high melt strength polypropylene compositions is the necessity of continuous monitoring of the process of destruction and/or crosslinking of polypropylene macrochains. It is an extremely difficult task during the modification, although the balance of main properties of the composition cannot be maintained without such monitoring.

International application WO2013086757 (KANEKA CORPORATION (JP), 23.12.2011) attempts to solve the above-discussed difficulties of the post-reactor synthesis by using a further additive, the so-called organic peroxide decomposition regulator denoted FRS (free radical stabilizator). Various compounds of rare-earth elements (REE) function as the FRS. These additives may be, for example, oxides and carboxylates of REE, as well as their complexes with napthenic and dithiocarbamic acids. As stated in the application, the FRS regulates the destruction and grafting of polypropylene macromolecules and serves to control a polypropylene-initiator-COAG ratio, increase the time for grafting to polypropylene, inhibit the degradation of polypropylene and prolong the lifetime of free radicals. The melt flow index of the resulting products may vary between 0.1 to 50 g/10 min, preferably between 3.2 g/10 min. Glycol diacrylates, TMPTA, pentaerythrytol triacrylate (PETA) are used as the coagents. An apparent deficiency of said engineering solution is the use of expensive, hardly available and unsafe rare-earth compounds.

In terms of the technical essence, the closest to the present invention is the solution described in CN10143468 IB (Changchun institute of applied chemistry (CN), 17.12.2008), in which organosulfur compounds, which are widely applied as fungicides in agriculture, are used as a peroxide decomposition regulator in the post-reactor synthesis. Trimethylopropane triacrylate (TMPTA) is preferred as a coagent. It is disclosed that dithiocarbamates not only reduce intensity of the destruction of polypropylene macrochains but also contribute to raising melt strength of the polymer. The melt strength of modification products ranges from 16 to 36 cN, with the yield strength being between 0.5 to 2.0 g/10 min. A disadvantage of this invention is the reduced flowability and extensibility of products at high melt strength values (MS = 36 cN, MFl_{230°C/2.16 kg} = 0.5/10 min), which may be due to susceptibility of polypropylene modification products to crosslinking when an organosulfur additive is used. Another drawback is the very use of such organosulfur compounds, since they are toxic for the human organism. Moreover, some dithiocarbamates essentially deteriorate organoleptic and sanitary-hygienic properties of modification products thereby restricting considerably their field, in particular, for the manufacture of polypropylene articles that are in contact with food products.

Therefore, the issues of improving efficacy of post-reactor polypropylene modification systems and enhancing quality and balance of main properties of the obtained products having high melt strength remain an urgent challenge.

Summary of the invention

The object of the present invention is to offer the polypropylene composition having high melt strength, which is defining in the manufacture of foam articles by any known process, with improved stability of the foam form and foam homogeneity.

The technical result of the present invention is to obtain of a high melt strength polypropylene composition by reactive extrusion with melt strength values of between 18 and 43 cN, in combination with improved melt flow indices of the modification products: MFl_{230°C/2.16 kg} ranging from 0.5 to 3.0 g/10 min.

A further technical result is the improvement of sanitary-hygienic and organoleptic properties of the product.

In addition to the technical result achievable for melt strength and the other properties listed above, the composition has unique chemical stability and heat resistance.

The composition according to the invention is also characterized by:

- a drawing speed at which the polypropylene filament breaks in the rheometer from 60 to 350 mm/s.

This technical problem is solved and the desired technical result is achieved by using a peroxide modifying system in the form of a concentrate (pre-blend) in the compositions. This concentrate is prepared preferably by dry mixing of a peroxide, advantageously an organic peroxide, a vinyl monomer, advantageously a dimaleimide coagent, and a random propylene-a-olefin copolymer; said polymer is used preferably in the powder form. Thereafter, all components of the concentrate are maintained in contact for a certain time and under certain temperature conditions, the produced polypropylene is added to the main composition, which is followed by melt compounding in suitable equipment.

The inventors have surprisingly found that the preliminary contact and holding of the peroxide and maleimide components of the modifying system under certain conditions, optionally in the presence of a random propylene-a-olefin copolymer, produce essential favorable influence on the subsequent reactive compounding of the polypropylene composition, with an obvious increase in melt strength and with preserving the yield strength and extensibility values. This result is allegedly due to formation of a donor-acceptor complex between the organic peroxide and the maleimide group of the coagent in the modifying system. Probably, in this connection, formation of stable nitroxyl radicals during the processing of a polypropylene melt becomes less complicated, which contributes to certain adjustment of peroxide degradation processes and competing reactions of destruction, branching, and crosslinking of polypropylene macromolecules that are associated with said degradation.

Achievement of the above-listed properties permits obtaining, by foaming, materials based on this composition that have a wide range of applications, starting from heat- and waterproof materials to high-tech packaging.

Brief description of figures

Fig.l Long chain polypropylene types in terms of branching: multi-branched (a), double-stranded (ladder) (b), and short-branch (c) polypropylene.

Detailed description of the invention Abbreviations used herein:

MFI - melt flow index PP - polypropylene MS - melt strength

HMS PP - high melt strength polypropylene cN - centinewton mPa - millipascal MPa - megapascal kGy - kilogray

In accordance with the present invention, claimed is a composition suitable for foaming, which comprises the following components: A. from 30 to 96 wt.% of a random propylene-a-olefin and/or random propylene -

C₄-C₁₀ α-olefin copolymer;

B. from 0.65 to 3 wt.% of a vinyl monomer;

C. from 0.01 to 1.0 wt.% of a peroxide initiator;

D. from 0.02 to 1.0 wt.% of an antioxidant and/or a phosphite termal stabilizer; E. from 0 to 40 wt.% of a propylene homopolymer;

F. from 0 to 25 wt.% of a polyolefin elastomer;

G. from 0 to 20 wt.% of other additives.

In accordance with the next aspect of the present invention, claimed is a composition comprising the following components: A. from 30 to 96 wt.% of a powder or granulated random propylene-ethylene-a- olefin and/or propylene - C₄-C₁₀ α-olefin copolymer having a MFl_{230°C/2.16 kg} from 0.27 to 1.8 g/10 min;

B. from 0.65 to 3 wt.% of dimaleimide;

C. from 0.01. to 1.0 wt.% of a peroxide initiator; D. from 0.02. to 1.0 wt.% of a primary phenolic antioxidant, or a mixture of a phenolic stabilizer and a secondary phosphite stabilizer;

E. from 0 to 40 wt.% (optionally) of a powder or granulated propylene homopolymer having a MFl_{230°C/2.16 kg} of not less than 3 g/ 10 min;

F. from 0 to 25 wt.% (optionally) of a polyolefin elastomer; G. from 0 to 20 wt.% (optionally) of other additives.

A random propylene-ethylene and/or propylene - C₄-C₁₀ α-olefin copolymer having MFl_{230°C/2.16 kg}from 0.27 to 1.8 g/10 min is used as the component A. Examples of engineering grades of the propylene-ethylene and/or propylene - C₄-C₁₀ α-olefin copolymer are: PPR003, PPR007 and PPR015 manufactured at the plant of Tomskneftekhim LLC (Tomsk) owned by Sibur Holiding PJSC. The content of said component varies from 30 to 96 wt.%, preferably from 50 to 96 wt.%, most preferably from 70 to 96 wt.%; An N-containing vinyl monomer, in particular, a bifunctional N-containing vinyl monomer, i.e. dimaleimide, an active functional group of which is a cyclic imide of maleic acid, is used as the component B. Two maleimide groups must be separated by aliphatic and/or aromatic hydrocarbon bridges. The length of hydrocarbon aliphatic radicals may be from C₄ to C₁₂, preferably from C₆ to C₈. Examples of such compounds are hexamethylene dimaleimide manufactured by Nexam Chemical (Sweden) and by Evonik (Germany) under the tradename Nexamit A48, and meta(para)-phenylene dimaleimide manufactured by Shanchai Amino-Chem (China). These monomers are traditionally used together with peroxide as curing agents for rubbers.

Almost any mono-, di- and polyfunctional peroxide compound, which is employed in vulcanization of rubber mixtures and melt processing of hydrocarbon polymers, can be used as the component C, i.e. a peroxide initiator. Examples of the used peroxides may be products marketed under the tradenames Trigonox 301, Luperox DCP, Luperox DI, Luperox DTA, Luperox F, Luperox 101, Luperox 801, etc. Use of cyclic triperoxide methylethylketone, Trigonox 301, is the most preferable. The peroxide concentration in the finished composition is from 0.01 to 1.0 wt.%, preferably from 0.02. to 0.5 wt.%, most preferably from 0.03 to 0.2 wt.%.

As the component D, the composition according to the present invention may contain primary antioxidants, secondary antioxidants, and heat stabilizers or mixtures thereof, etc. Primary antioxidants of the phenolic type, for example, an ester of 3,5-di- tert-butyl-4-hydroxy-phenylpropionic acid and pentaerythritol marketed under the tradename Irganox 1010, secondary antioxidants of the phosphite type, for example tri- (phenyl-2,4-di-tert-butyl)phosphite marketed under the tradename Irgafos 168, and/or heat stabilizers under other tradenames, as well as other types of stabilizers or mixtures of stabilizers marketed under the tradenames Irganox B225, Irganox B215, etc. may be used as such compounds. The content of these additives in the composition may range from 0.02 to 1.0 wt.%, preferably from 0.05 to 0.5 wt.%, most preferably from 0.1 to 0.3 wt.%.

An isotactic propylene homopolymer having MFl_{230°C/2.16 kg} from 3 to 100, preferably from 3 to 50 g/10 min is used as the component E. Examples of engineering grades of polypropylene (homopolymer): PPH030GP, PPH270FF, PPH450GP manufactured by Sibur Holding PJSC. The content of said component varies from 0 to 40 wt.%, preferably from 5 to 20 wt.%;

Engineering grades of random propylene-ethylene copolymers or propylene- ethylene-butene- 1 terpolymers (propylene based copolymers) are used as the component F, i.e. an olefin elastomer. Examples of such copolymers are products manufactured by Exxon Mobil under the Vistamax tradename. A preferable copolymer is a Vistamax 6102 copolymer.

In another embodiment of the invention, ethylene-a-olefin copolymers having 4 to 8 carbon atoms and produced in metallocene catalyst systems are used as the elastomer. An ethylene-octene-1 copolymer is preferable. Said elastomer has a density between 0.855 and 0.890 g/cm³, preferably between 0.857 and 0.885 g/cm³. Also, the elastomer has MFl_{230°C/2.16 kg} in the range from 1 to 30 g/10 min, preferably from 3 to 13 g/10 min, even more preferably from 3 to 7 g/10 min. Examples of such elastomers may be products that are known under the tradenames Engage 8452, Engage 8842, Engage 8137, Exact 8210, etc.

The elastomer F comprises from 0 to 25 wt.%, preferably from 0 to 20 wt.%, most preferably from 5 to 20 wt.% relative to 100 wt.% of the polypropylene composition. It is possible to use mixtures of the two classes of elastomers mentioned above.

As the component G, the proposed composition can further comprise other functional additives, for example, lubricants, processing aids, nucleators, mineral fillers, pigments, etc.

The manufacture of a high melt strength polypropylene composition according to the invention is distinguished by a special process of preliminary preparation of a peroxide modifying concentrate of components (pre-blend), the process comprising subjecting a peroxide initiator (preferably organic), a vinyl monomer as a co-agent (preferably dimaleimide), and a random propylene-a-olefm copolymer (preferably in the powder form) to pre-blending, preferably to dry blending. According to the process of the invention, said concentrate components are maintained in contact under certain temperature and temporal conditions, the produced pre-blend is added to the main polypropylene composition, which is followed by melt compounding in suitable equipment. The components can be blended and the concentrate can be held both at room temperature and at an elevated temperature of 80°C in an air-vented oven, depending on the chemical nature of the peroxide and its thermal stability. Optimal holding time is from 5 to 15 minutes. Longer holding time either does not bring about a further increase in operating efficiency of the modifying system or contributes to deterioration of its performance owing to partial decomposition of the thermally unstable peroxide. This preliminary contact of components of the modifying system and the concentrate substantially rises operating efficiency of the system during reactive melt compounding of the polypropylene composition, with said contact affecting primarily an increase in the melt strength of the end composition and retention of its rheological properties that are expressed by yield strength and extensibility values. The pre-treatment of components of the modifying system allows obtaining the best results when cyclic triperoxide methylethylketone Triganox 301 is held with hexamethylene dimaleimide Nexamit A48 at a Nexamit/Triganox weight ratio from 3:1 to 300:1, preferably from 10:1 to 80:1, more preferably from 20:1 to 50:1, at an optimal holding temperature of the components of between 47 and 53°C. The above-described temperature and temporal pre-treatment of maleimides and peroxides having a different chemical structure brings about a favourable, though somewhat inferior, effect of melt strength improvement of a PP composition. Use of vinyl monomers of other chemical nature, for example, acrylic derivatives, particularly trimethylolpropane triacrylate (TMPTA), etc. does not cause any remarkable changes in operating efficiency of the modifying system. Such specificity of action of the peroxide/dimaleimide coagent might be provided by chemical nature and three-dimensional structure of active functional groups of these compounds.

The finished composition consisting of a dry mixture of the concentrate (pre- blend) with the other ingredients according to the invention can be produced by any known method of melt processing of thermoplastics in any suitable equipment, including single-screw extruders, twin-screw extruders, internal rotary mixing devices, and the like. Preferable equipment is a twin-screw extruder having an L/D ratio of at least 30, preferably at least 35.

The temperature of blending components is traditional for this field and is determined by properties of a specific component of the composition. More particularly, thecomponents are blended at a temperature higher than the melting point of the components and lower than their decomposition temperatures. The blending temperature is preferably between 200 and 260°C, most preferably between 210 and 250°C.

Modes for processing the manufactured composition (compounding) do not differ from standard modes that are used depending on rheological properties. The most preferable method of processing is melt extrusion.

Compositions produced by the process according to the invention are suitable for use as foam materials, starting from heat- and waterproof materials to high-tech packaging.

This invention will be further described in detail with a reference to the examples given below. These examples are given for illustrative purposes and are not intended to limit the scope of the present invention.

Embodiments of the inventionRandom propylene-ethylene copolymer PPR003 in the powder form, having MFl_{230°C/2.16 kg} from 0.3 to 0.5 g/10 min, manufactured by Tomskneftekhim LLC, was used as the component A.

Hexamethylene dimaleimide Nexamit A48 manufactured by Nexan Chemical (Sweden); meta-phenylenedimaleimide (FDM) manufactured by Shanghai Amino- Chem (China); TMPTA manufactured by Evonik (Germany) were used as the component B.

Organic peroxides Triganox 301 manufactured by AkzoNobel (Netherlands), and peroxides Luperox F40 and Luperox 101 manufactured by Arkema (France) were used as the component C.

A blend of a phenolic antioxidant and a phosphite antioxidant Irganox B215 manufactured by BASF, Germany, was used as the component D.

Propylene homopolymers PPH030GP (granules or powder) having MFl_{230°C/2.16 kg} of greater than 3.0 g/10 min, manufactured by Tomskneftekhim LLC; or PPH270GP having a MFl_{230°C/2.16 kg} of 27.0 g/10 min, manufactured by Tomskneftekhim LLC; or PPH450 having a MFl_{230°C/2.16 kg} of 45.0 g/10 min, manufactured by LLC «Neftekhimiya» NRR», were used as the component E.

Amorphous copolymers of propylene with ethylene and butene- 1 (propylene based copolymers) manufactured by Exxon Mobil under the tradenames Vistamax 6102 and Vistamax 6202; amorphous copolymers of ethylene and octene-1 manufactured by Dow Chem under the tradenames Engage 8842, Engage 8137; a hydrogenated copolymer of styrene with butadiene available from North America under the tradename Kraton G 1657 were used as the component F.

The melt flow index was determined at a temperature of 230°C and at a load of 2.16 N in conformity with ASTM D 4101.

Melt strength was measured by means of capillary rheometer Smart Rheo 2000. The melt was pressed through the capillary, fed into a withdrawal device, and was drawn with constant acceleration. As a certain drawing speed was reached, the filament broke. The force at break detected by a strain sensor was considered as the melt strength. The wind-up speed at break, at a rheometer piston speed of 0.30 mm/s, was taken as the melt extensibility. In order to determine polyethylene melt strength, a capillary with a diameter of 2 mm was used, the temperature of the measurements was 210°C.

Examples

Preparation of compositions:

In the preliminary step of preparation of the composition, a concentrate denoted PB-No. and consisting of peroxide, dimaleimide, and a random copolymer powder, was provided, which was maintained under certain temperature and temporal conditions, either at room temperature or in a forced-air oven. Formulations of PB-No. compositions and parameters of their holding are set forth in Table 1.

Thereafter, the resultant concentrate (pre-blend) is mixed manually or by means of any known mixing equipment with the other ingredients of finished polypropylene compositions at room temperature until all the components are blended uniformly. The so-produced charge for performing the step of melt compounding of polypropylene is fed into a funnel, or in a different dosing device of an extruder, preferably a twin-screw one with an L/D ratio of at least 30, more preferably at least 35, and processed into a finished product (granules) by conventional techniques. The maximum melt processing temperature in extrusion equipment is from 200 to 260°C, preferably from 210 to 250°C. Granules of the product are used for further rheology tests.Results of testing the produced polypropylene compositions are given in Tables 2-7, including Examples 1- 65. These examples are given for illustrative purposes and are not intended to limit the scope of the present invention.

Example 1 (comparative)

The polymer material for testing is prepared by melt processing, in a line of a laboratory twin-screw extruder LTE-20-44, of charge consisting of 99.20 wt.% of the random propylene-ethylene copolymer PPR003 powder, 0.65 wt.% of dimaleimide Nexamit A48, 0.05 wt.% of peroxide Trigonox 301, and 0.1 wt.% of antioxidant Irganox B215 at a maximum temperature in roller zones of 230°C and at a speed of rotation of the screws of 250 min^'1.

The obtained material is characterized by an average melt strength (MS) value of 14.1 cN, a maximum MS value of 16.3 cN, and MFl_{230°C/2.16 kg}= 2.23 g/10 min.

Example 2

The polymer material for testing is prepared by melt processing, in a line of a laboratory twin-screw extruder LTE-20-44, of charge consisting of 89.0 wt.% of the random propylene-ethylene copolymer PPR003 powder, 10 wt.% of PB-27 concentrate (pre-blend) (Table 1), and 0.1 wt.% of antioxidant Irganox B215 as a peroxide agent at a maximum temperature in roller zones of 230°C and at a speed of rotation of the screws of 250 min^'1.

The obtained material is characterized by an average melt strength (MS) value of 18.0 cN, a maximum MS value of 19.8 cN, and MFl_{230°C/2.16 kg}= 2.18 g/10 min.

Example 3 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 1 (comparative), save that one of the concentrate (pre-blend) components, a dimaleimide coagent - 1.0 wt.% of Nexamit A48is used.

The obtained material is characterized by an average melt strength (MS) value of 17.5 cN, a maximum MS value of 17.9 cN, and MFl_{230°C/2.16 kg}= 2.10 g/10 min.

Example 4

The polymer material for testing is prepared in a similar manner as in Example 2, save that PB-2 instead of PB-27 is used in an amount of 8.0 wt.%.

The obtained material is characterized by an average melt strength (MS) value of 23.0 cN, a maximum MS value of 24.5 cN, and MFl_{230°C/2.16 kg}= 2.05 g/10 min.

Example 5 (comparative) The polymer material for testing is prepared in a similar manner as in Example 1 (comparative), save that one of the concentrate (pre-blend) components, a dimaleimide coagent -1.25 wt.% of Nexamit A48 is used.

The obtained material is characterized by an average melt strength (MS) value of

20.3 cN, a maximum MS value of 23.6 cN, and MFl_{230°C/2.16 kg}= 1.98 g/10 min.

Example 6

A polymer material for testing is prepared in a similar manner as in Example 4, save that PB-2 is used in an amount of 10.0 wt.%.

The obtained material is characterized by an average melt strength (MS) value of 28.6 cN, a maximum MS value of 33.0 cN, and MFl_{230°C/2.16 kg} = 1.89 g/10 min.

Example 7

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-3 instead of PB-2 is used in the same amount.

29.3 cN, a maximum MS value of 36.0 cN, and MFl_{230°C/2.16 kg}= 1.92 g/10 min.

Example 8

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-4 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 32.9 cN, a maximum MS value of 40.0 cN, and MFl_{230°C/2.16 kg}= 2.07 g/10 min.

Example 9

A polymer material for testing is prepared in a similar manner as in Example 6, save that PB-4 instead of PB-2 is used in the same amount.

31.4 cN, a maximum MS value of 42.0 cN, and MFl_{230°C/2.16 kg} =1.75 g/10 min.

Example 10

A polymer material for testing is prepared in a similar manner as in Example 6, save that PB-5 instead of PB-2 is used in the same amount.

27.5 cN, a maximum MS value of 31.0 cN, and MFl_{230°C/2.16 kg}= 1.73 g/10 min.

Example 11 The polymer material for testing is prepared in a similar manner as in Example 6, save that 5 wt.% of the propylene homopolymer PPH450 powder is additionally introduced into the composition.

30.4 cN, a maximum MS value of 35.5 cN, and MFl_{230°C/2.16 kg} ⁼ 2.02 g/10 min.

Example 12

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-11 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 28.3 cN, a maximum MS value of 32.0 cN, and MFl_{230°C/2.16 kg}= 1-89 g/10 min.

Example 13

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-12 instead of PB-2 is used in the same amount.

29.5 cN, a maximum MS value of 35.0 cN, and MFl_{230°C/2.16 kg} = 1.61 g/10 min.

Example 14

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-13 instead of PB-2 is used in the same amount.

30.2 cN, a maximum MS value of 34.0 cN, and MFl_{230°C/2.16 kg}= 1.73 g/10 min.

Example 15

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-14 instead of PB-2 is used in the same amount.

31.5 cN, a maximum MS value of 37.5 cN, and MFl_{230°C/2.16 kg} = 2.03 g/10 min.

Example 16

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-15 instead of PB-2 is used in the same amount.

31.3 cN, a maximum MS value of 36.5 cN, and MFl_{230°C/2.16 kg}= 1.97 g/10 min.

Example 17 (comparative) A polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 0.1 wt.% of Luperfox F 40 instead of 0.05 wt.% of Trigonox 301 is used as a peroxide agent.

22.2 cN, a maximum MS value of 24.5 cN, and MFl_{230°C/2.16 kg}= 1.92 g/10 min.

Example 18

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-1 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 22.4 cN, a maximum MS value of 25.7 cN, and MFl_{230°C/2.16 kg}= 1.94 g/10 min.

Example 19

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-7 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 22.9 cN, a maximum MS value of 28.0 cN, and MFl_{230°C/2.16 kg}= 1.93 g/10 min.

Example 20

A polymer material for testing is prepared in a similar manner as in Example 6, save that PB-8 instead of PB-2 is used in the same amount.

24.2 cN, a maximum MS value of 30.0 cN, and MFl_{230°C/2.16 kg}= 1.80 g/10 min.

Example 21

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-9 instead of PB-2 is used in the same amount.

25.2 cN, a maximum MS value of 30.0 cN, and MFl_{230°C/2.16 kg}= 1.86 g/10 min.

Example 22

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-10 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 24.0 cN, a maximum MS value of 28.5 cN, and MFl_{230°C/2.16 kg}= 1.81 g/10 min.

Example 23 The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-16 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 22.8 cN, a maximum MS value of 28.0 cN, and MFl_{230°C/2.16 kg}= 1.82 g/10 min.

Example 24 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 0.1 wt.% of Luperfox 101 instead of 0.05 wt.% of Trigonox 301 is used as a peroxide agent.

21.2 cN, a maximum MS value of 23.0 cN, and MFl_{230°C/2.16 kg}= 1.67 g/10 min.

Example 25

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-21 instead of PB-2 is used in the same amount.

24.3 cN, maximum MS value of 25.0 cN, and MFl_{230°C/2.16 kg}= 1.61 g/10 min.

Example 26

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-22 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 21.6 cN, a maximum MS value of 25.5 cN, and MFl_{230°C/2.16 kg}= 1.83 g/10 min.

Example 27

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-23 instead of PB-2 is used in the same amount.

21.3 cN, amaximum MS value of 26.0 cN, and MFl_{230°C/2.16 kg}= 1.78 g/10 min.

Example 28

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-24 instead of PB-2 is used in the same amount.

21.4 cN, amaximum MS value of 25.5 cN, and MFl_{230°C/2.16 kg}= 1.72 g/10 min.

Example 29 The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-25 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 21.8 cN, a maximum MS value of 26.0 cN, and MFl_{230°C/2.16 kg} ⁼ 1.78 g/10 min.

Example 30

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-26 instead of PB-2 is used in the same amount.

21.4 cN, a maximum MS value of 25.0 cN, and MFl_{230°C/2.16 kg}- 1.73 g/10 min.

Example 31 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 1.50 wt.% instead of 1.25 wt.% of Nexamit A48 is used as a dimaleimide coagent, and 0.055 wt.% instead of 0.05 wt.% of Trigonox is dosed as a peroxide agent.

22.5 cN, a maximum MS value of 28.7 cN, and MFl_{230°C/2.16 kg} = 1.23 g/10 min.

Example 32

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-17 instead of PB-2 is used in the same amount.

30.5 cN, a maximum MS value of 40.0 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min.

Example 33

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-17 instead of PB-2 is used in the same amount and 5 wt.% of propylene homopolymer PPH270FF is additionally introduced into the composition.

The obtained material is characterized by an average melt strength (MS) value of 34.0 cN, a maximum MS value of 42.0 cN, and MFl_{230°C/2.16 kg}= 1.15 g/10 min.

Example 34 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 2.0 wt.% instead of 1.25 wt.% of Nexamit A48 is used as a dimaleimide coagent, and 0.07 wt.% instead of 0.05 wt.% of Trigonox 301 is dosed as a peroxide agent. The obtained material is characterized by an average melt strength (MS) value of 26.0 cN, a maximum MS value of 32.0 cN, and MFl_{230°C/2.16 kg}= 1.29 g/10 min.

Example 35

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-18 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 34.0 cN, a maximum MS value of 40.7 cN, and MFl_{230°C/2.16 kg}= 1.27 g/10 min.

Example 36 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 2.5 wt.% instead of 1.25 wt.% of Nexamit A48 is used as a dimaleimide coagent, and 0.075 wt.% instead of 0.05 wt.% of Trigonox 301 is dosed as a peroxide agent.

The obtained material is characterized by an average melt strength (MS) value of 29.1 cN, a maximum MS value of 34.1 cN, and MFl_{230°C/2.16 kg}= 1.19 g/10 min.

Example 37

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-19 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 35.8 cN, a maximum MS value of 41.5 cN, and MFl_{230°C/2.16 kg} = 1.15 g/10 min.

Example 38 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 3.0 wt.% instead of 1.25 wt.% of Nexamit A48 is used as a dimaleimide coagent, and 0.08 wt.% instead of 0.05 wt.% of Trigonox 301 is dosed as a peroxide agent.

The obtained material is characterized by an average melt strength (MS) value of 30.7 cN, a maximum MS value of 35.3 cN, and MFl_{230°C/2.16 kg}= 1.19 g/10 min.

Example 39

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-20 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 36.5 cN, maximum MS value of 42.0 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min.

Example 40 The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-20 instead of PB-2 is used in the same amount, and 5 wt.% of propylene homopolymer PPH270FF is additionally introduced into the composition.

The obtained material is characterized by an average melt strength (MS) value of - 40.0 cN, a maximum MS value of 43.1 cN, and MFl_{230°C/2.16 kg}= 1.17 g/10 min.

Example 41 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that meta-phenylenedimaleimide (FDM) instead of 1.25 wt.% of Nexamit A48 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 18.9 cN, a maximum MS value of 19.7 cN, and MFl_{230°C/2.16 kg}= 1.18 g/10 min.

Example 42

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-28 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 25.7 cN, a maximum MS value of 28.7 cN, and MFl_{230°C/2.16 kg}= 1.15 g/10 min.

Example 43

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-29 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 27.3 cN, a maximum MS value of 30.0 cN, and MFl_{230°C/2.16 kg}= 1.17 g/10 min.

Example 44 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 41 (comparative), save that 2.50 wt.% instead of 1.25 wt.% of FDM is dosed, and 0.075 wt.% instead of 0.05 wt.% of Trigonox 301 is dosed.

The obtained material is characterized by an average melt strength (MS) value of 29.2 cN, a maximum MS value of 32.0 cN, and MFl_{230°C/2.16 kg}= 1.01 g/10 min.

Example 45

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-30 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 32.0 cN, a maximum MS value of 35.0 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min. Example 46 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that 20 wt.% of elastomer Vistamax 6102 is additionally introduced into the composition.

23.7 cN, a maximum MS value of 28.5 cN, and MFl_{230°C/2.16 kg} ⁼ 1.38 g/10 min.

Example 47

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-4 instead of PB-2 is used in the same amount, and 20 wt.% of elastomer Vistamax 6102 is additionally used.

30.4 cN, a maximum MS value of 35.5 cN, and MFl_{230°C/2.16 kg}= 1.33 g/10 min.

Example 48

The polymer material for testing is prepared in a similar manner as in Example 47, save that 10 wt.% instead of 20 wt.% of Vistamax 6102 is used.

The obtained material is characterized by an average melt strength (MS) value of 25.3 cN, a maximum MS value of 30.0 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min.

Example 49 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 47, save that 30 wt.% instead of 20 wt.% of Vistamax 6102 is used.

17.5 cN, a maximum MS value of 20.2 cN, and MFl_{230°C/2.16 kg}= 0.45 g/10 min.

Example 50

The polymer material for testing is prepared in a similar manner as in Example 47, save that Vistamax 6202 instead of Vistamax 6102 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 24.1 cN, a maximum MS value of 28.7 cN, and MFl_{230°C/2.16 kg}= 1.88 g/10 min.

Example 51

The polymer material for testing is prepared in a similar manner as in Example 47, save that Engage 8842 instead of Vistamax 6102 is used in the same amount.

21.7 cN, a maximum MS value of 26.0 cN, and MFl_{230°C/2.16 kg}= 0.56 g/10 min. Example 52

The polymer material for testing is prepared in a similar manner as in Example 47, save that Engage 8137 instead of Vistamax 6102 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 18.0 cN, a maximum MS value of 19.5 cN, and MFl_{230°C/2.16 kg}= 0.75 g/10 min.

Example 53 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 47, save that Kraton G1657 instead of Vistamax 6102 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 13.7 cN, a maximum MS value of 16.5 cN, and MFl_{230°C/2.16 kg} = 1.77 g/10 min.

Example 54

The polymer material for testing is prepared in a similar manner as in Example 47, save that a mixture of 10 wt.% of Vistamax 6102 and 10 wt.% of Engage 8842 instead of 20 wt.% Vistamax 6102 is used. The obtained material is characterized by an average melt strength (MS) value of

18.9 cN, a maximum MS value of 20.5 cN, and MFl_{230°C/2.16 kg} ⁼ 0.89 g/10 min.

Example 55

The polymer material for testing is prepared in a similar manner as in Example 47, save that PB-19 instead of PB-4 is used in the same amount. The obtained material is characterized by an average melt strength (MS) value of

37.4 cN, a maximum MS value of 43.0 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min.

Example 56 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 39, save that 12 wt.% instead of 10 wt.% of PB-20 is used. The obtained material is characterized by an average melt strength (MS) value of

36.7 cN, a maximum MS value of 40.0 cN, and MFl_{230°C/2.16 kg}= 0.85 g/10 min.

Example 57

The polymer material for testing is prepared in a similar manner as in Example 47, save that 7.0 wt.% of the PPH450 powder is additionally dosed in the composition. The obtained material is characterized by an average melt strength (MS) value of

26.3 cN, a maximum MS value of 32.0 cN, and MFl_{230°C/2.16 kg}= 1.47 g/10 min.

Example 58 The polymer material for testing is prepared in a similar manner as in Example 47, save that 10.0 wt.% of the PPH450 powder is additionally dosed in the composition.

The obtained material is characterized by an average melt strength (MS) value of 21.7 cN, a maximum MS value of 25.5 cN, and MFl_{230°C/2.16 kg}= 2.05 g/10 min.

Example 59

The polymer material for testing is prepared in a similar manner as in Example 8, save that 20.0 wt.% of PPH030GP is additionally dosed in the composition.

20.5 cN, a maximum MS value of 24.3 cN, and MFl_{230°C/2.16 kg} = 2.51 g/10 min.

Example 60

The polymer material for testing is prepared in a similar manner as in Example 8, save that 40 wt.% of PPH030GP is additionally dosed in the composition.

The obtained material is characterized by an average melt strength (MS) value of 18.9 cN, a maximum MS value of 21.7 cN, and MFl_{230°C/2.16 kg}= 3.01 g/10 min.

Example 61 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 8, save that 50 wt.% of PPH030GP is additionally dosed in the composition.

14.6 cN, a maximum MS value of 17.5 cN, and MFl_{230°C/2.16 kg}= 5.08 g/10 min.

Example 62 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 5 (comparative), save that TMPTA instead of Nexamit A48 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 17.5 cN, a maximum MS value of 19.8 cN, and MFl_{230°C/2.16 kg}= 0.75 g/10 min.

Example 63 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-31 instead of PB-2 is used in the same amount.

The obtained material is characterized by an average melt strength (MS) value of 17.2 cN, a maximum MS value of 19.5 cN, and MFl_{230°C/2.16 kg}= 0.70 g/10 min.

Example 64 (comparative)

The polymer material for testing is prepared in a similar manner as in Example 6, save that PB-32 instead of PB-2 is used in the same amount. The obtained material is characterized by an average melt strength (MS) value of 17.0 cN, a maximum MS value of 19.1 cN, and MFl_{230°C/2.16 kg}= 0.72 g/10 min.

Example 65 (according to the prototype)

The polymer material for testing is prepared in a similar manner as in Example 62 (comparative), save that 0.1 wt.% of dithiocarbamate tetramethylthiuram disulfide (TMTD) is additionally dosed in the composition.

The obtained material is characterized by an average melt strength (MS) value of 24.7 cN, a maximum MS value of 27.6 cN, and MFl_{230°C/2.16 kg}= 1.05 g/10 min.

Tables 1-4 set out formulations of the concentrate that is preliminarily prepared prior to the step of blending with the basic polymer.

Table 1. Formulations (wt. %) and manufacturing modes of the concentrate (from PB-1 to PB-10).

Table 2. Formulations (wt. %) and manufacturing modes of the concentrate (from PB- 11 to PB-20).

Table 3. Formulations (wt. %) and manufacturing modes of the concentrate (from PB-

5 21 to PB-30).

Table 4. Formulations (wt. %) and manufacturing modes of the concentrate (from PB- 31 to PB-32).

bles 5 to 10 set out formulations of high melt strength polypropylene compositions (Examples 1-11). ble 5. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 1-11.

ble 6. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 12-22.

able 7. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 23-33.

ble 8. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 34-44.

le 9. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 45-55.

able 10. Formulations (wt. %) and properties of the high melt strength polypropylene compositions according to Examples 56-65.

The results of testing high melt strength polypropylene compositions set out in Tables 5-10 give evidence of advantages of the proposed process for manufacturing the same, the process comprising pre-treating concentrates (pre-blend) of active agents of the modifying system under special temperature and temporal conditions, and then in a suspension of a powder of a base polymer of the compositions, i.e. PPR003 random propylene-ethylene copolymer. Examples 2, 4, 6-16, 25-30 and comparative Examples 1, 3, 5, 17, 24 demonstrate influence of nature of a peroxide initiator and temperature-temporal parameters of holding concentrates of mixtures of peroxides with dimaleimide Nexamit A48. Apparently, it is preferable to use a combination of Nexamit A48 with organic peroxide Trigonox 301 under optimal holding conditions of their concentrate PB-4 (50°C, 10 min), see Example 8, including in comparison with the analogues and the prototype, see Examples 62, 63, 64 (comparative) and Example 65 (according to the prototype).

Subsequent Examples 32, 35, 37, 39 and comparative Examples 31, 34, 36, 38 manifest influence of the increase in the dosage of dimaleimide Nexamit A48, within the available range of its variation, on the melt strength growth and on variation of the melt flow index of the manufactured composition. Advantages of the proposed process for manufacturing high melt strength polypropylene compositions can be observed, too. Example 56 (comparative) reveals the behavior of melt strength and melt flow index values of a polypropylene composition when acceptable values of the concentration of dimaleimide Nexamit A48 are exceeded.

Examples 33, 40, 57-60 are indicative of changes in properties of high melt strength polypropylene compositions when medium- and high-index grades of a propylene homopolymer are introduced within the acceptable range of their variation. Example 61 (comparative) shows the degree of degradation of melt strength and melt flow index values of a polypropylene composition when the acceptable range of values of the component E concentration is exceeded.

Examples 42, 43, 45 and comparative Examples 41, 44 demonstrate influence of an aromatic dimaleimide (meta-phenylenedimaleimide (FDM)) on properties of HMS PP compositions under the claimed conditions of dosing and holding of pre-blends on its basis. The level of melt strength and melt flow index values of the compositions is somewhat inferior to similar formulations with Nexamit A48. Examples 47, 48, 50-52, 54, 55 and comparative Example 46 demonstrate the effect of adding polyolefin elastomers on melt strength, extensibility and melt flow index values of polypropylene compositions. Influence of nature and molecular weight of an elastomer on properties of these compositions is evident. Example 49 (comparative) shows degradation of the melt strength and decrease of the melt flow index of a composition when extending beyond the admissible boundaries of variation of the component F content.

Claims

1. A polypropylene composition for foaming, comprising the following components, relative to its total weight:

A. from 30 to 96 wt.% of a random propylene copolymer with one or more a- olefins;

B. from 0.65 to 3 wt.% of a vinyl monomer;

C. from 0.01 to 1.0 wt.% of a peroxide initiator;

D. from 0.02 to 1.0 wt.% of an antioxidant and/or a phosphite heat stabilizer;

E. from 0 to 40 wt.% of a propylene homopolymer;

F. from 0 to 25 wt.% of a polyolefin elastomer;

G. from 0 to 20 wt.% of other additives.

2. The polypropylene composition according to claim 1, wherein the content of the random propylene copolymer with one or more α-olefins, relative to the total weight of the composition, is from 50 to 96 wt.%, preferably from 70 to 96 wt.%.

3. The polypropylene composition according to claims 1 or 2, wherein the content of the peroxide initiator, relative to the total weight of the composition, is from 0.02 to 0.5 wt.%, preferably from 0.03 to 0.2 wt.%.

4. The polypropylene composition according to any of claims 1-3, wherein the content of the antioxidants and/or heat stabilizers, relative to the total weight of the composition, is from 0.05 to 0.5 wt.%, preferably from 0.1 to 0.3 wt.%.

5. The polypropylene composition according to any of claims 1-4, wherein the content of the propylene homopolymer, relative to the total weight of the composition, is from 5 to 20 wt.%.

6. The polypropylene composition according to any of claims 1-5, wherein the content of the polyolefin elastomer, relative to the total weight of the composition, is from 0 to 20 wt.%, preferably from 5 to 20 wt.%.

7. The polypropylene composition according to any of claims 1-6, wherein a C₄- C10 α-olefin or/and ethylene, is used in the random propylene-α-olefin copolymer as the α-olefin.

8. The polypropylene composition according to any of claims 1-7, wherein a N- containing vinyl monomer, preferably a bifunctional N-containing vinyl monomer, more preferably dimaleimide, is used as the vinyl monomer, wherein the dimaleimide preferably contains two maleimide groups, which have aliphatic radicals with the preferable length of the aliphatic radicals being from C₄ to C₁₂, the length of the aliphatic radicals being more preferably from C₆ to C₈.

9. The polypropylene composition according to any of claims 1-8, wherein a compound selected from the group comprising a monofunctional peroxide compound, a difunctional peroxide compound, and a polyfunctional peroxide compound, preferably cyclic triperoxide methylethylketone, is used as the peroxide initiator.

10.) The polypropylene composition according to any of claims 1-9, wherein a compound selected from the group comprising primary antioxidants of the phenolic type and secondary antioxidants of the phosphite type is used as the antioxidants; an ester of 3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid being preferable as the primary antioxidant, tri-(phenyl-2,4-di-tert-butyl)phosphite being preferable as the secondary antioxidant.

11. The polypropylene composition according to any of claims 1-3, wherein the melt flow index MFl_{230°C/2.16 kg} for the propylene homopolymer is from 3 to 100 g/10 min, preferably from 3 to 50 g/ 10 min.

12. The polypropylene composition according to any of claims 1-11, wherein a propylene-α-olefin copolymer, preferably a propylene-ethylene-butene- 1 terpolymer or a random ethylene-propylene copolymer, is used as the polyolefin elastomer.

13. The polypropylene composition according to claim 12, wherein, in the propylene-a-olefin copolymer, the a-olefin contains 4 to 8 carbon atoms.

14. The polypropylene composition according to claim 13, wherein the a-olefin is produced in metallocene catalyst systems.

15. The polypropylene composition according to any of claims 1-14, wherein the MFl_{230°C/2.16 kg} for the polyolefin elastomer is from 1 to 30 g/10 min, preferably from 3 to 7 g/10 min.

16. The polypropylene composition according to any of claims 1-15, wherein the density for the polyolefin elastomer is from 0.855 to 0.890 g/cm³, preferably from 0.857 to 0.885 g/cm³.

17. The polypropylene composition according to any of claims 1-16, wherein the other additives are selected from the group comprising lubricants, processing aids, nucleators, mineral fillers, and pigments.

18. A process for manufacturing a polypropylene composition for foaming, comprising blending and processing into a melt the following components taken in the following amount, relative to the total weight of the composition:

B. from 0.65 to 3 wt.% of a vinyl monomer;

C. from 0.01 to 1.0 wt.% of a peroxide initiator;

D. from 0.02 to 1.0 wt.% of an antioxidant and/or a phosphite heat stabilizer;

E. from 0 to 40 wt.% of a propylene homopolymer;

F. from 0 to 25 wt.% of a polyolefin elastomer;

G. from 0 to 20 wt.% of other additives.

19. The process for manufacturing the polypropylene composition according to claim 18, wherein the composition comprises, relative to its total weight, from 50 to 96 wt.%, preferably from 70 to 96 wt.%, of the random propylene-α-olefin copolymer.

20. The process for manufacturing the polypropylene composition according to claim 18 or claim 19, wherein the composition comprises, relative to its total weight, from 0.02 to 0.5 wt.%, preferably from 0.03 to 0.2 wt.%, of the peroxide initiator.

21. The process for manufacturing the polypropylene composition according to any of claims 18-20, wherein the composition comprises, relative to its total weight, from 0.05 to 0.5 wt.%, preferably from 0.1 to 0.3 wt.%, of the antioxidants and/or heat stabilizers.

22. The process for manufacturing the polypropylene composition according to any of claims 18-21, wherein the composition comprises, relative to its total weight, from 5 to 20 wt.% of the propylene homopolymer.

23. The process for manufacturing the polypropylene composition according to any of claims 18-22, wherein the composition comprises, relative to its total weight, from 0 to 20 wt.%, preferably from 5 to 20 wt.%, of the polyolefin elastomer.

24. The process for manufacturing the polypropylene composition according to any of claims 18-23, wherein, in the composition, a C₄-C₁₀ α-olefin and / or ethylene, is used in the random propylene-α-olefin copolymer as the α-olefin.

26. The process for manufacturing the polypropylene composition according to claim 18, wherein an N-containing vinyl monomer, preferably a bifunctional N- containing vinyl monomer, more preferably dimaleimide, is used as the vinyl monomer in the composition, wherein the dimaleimide is preferably represented by two maleimide groups which contain aliphatic radicals with the preferable length of the aliphatic radicals being from C₄ to C₁₂, the length of the aliphatic radicals being more preferably from C₆ to C₈.

27. The process for manufacturing the polypropylene composition according to any of claims 18-26, wherein a monofunctional peroxide compound is used as the peroxide initiator in the composition.

28. The process for manufacturing the polypropylene composition according to any of claims 18-27, wherein a compound selected from the group comprising a difunctional peroxide compound, a polyfunctional peroxide compound, preferably cyclic triperoxide methylethylketone, is used as the peroxide initiator in the composition.

29. The process for manufacturing the polypropylene composition according to any of claims 18-28, wherein a compound selected from primary antioxidants of the phenolic type and secondary antioxidants of the phosphite type is used as the antioxidants; an ester of 3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid being preferable as the primary antioxidant, tri-(phenyl-2,4-di-tert-butyl)phosphite being preferable as the secondary antioxidant.

30. The process for manufacturing the polypropylene composition according to any of claims 18-29, wherein the MFl_{230°C/2.16 kg} for the propylene homopolymer in the composition is from 3 to 100 g/10 min, preferably from 3 to 50 g/10 min.

31. The process for manufacturing the polypropylene composition according to any of claims 18-30, wherein a compound selected from the group comprising a propylene-ethylene-butene- 1 terpolymer and a random ethylene-propylene copolymer is used as the polyolefin elastomer in the composition.

32. The process for manufacturing the polypropylene composition according to claim 31 , wherein the a-olefin contains 4 to 8 carbon atoms.

33. The process for manufacturing the polypropylene composition according to claim 32, wherein the a-olefin is produced in metallocene catalyst systems.

34. The process for manufacturing the polypropylene composition according to any of claims 18-33, wherein the MFl_{230°C/2.16 kg} for the polyolefin elastomer in the composition is from 1 to 30 g/10 min, preferably from 3 to 7 g/10 min.

35. The process for manufacturing the polypropylene composition according to any of claims 18-34, wherein the density for the polyolefin elastomer in the composition is from 0.855 to 0.890 g/cm³, preferably from 0.857 to 0.885 g/cm³.

36. The process for manufacturing the polypropylene composition according to any of claims 18-35, wherein, in the composition, the other additives are selected from the group comprising lubricants, processing aids, nucleators, mineral fillers, and pigments.

37. The process for manufacturing the polypropylene composition according to any of claims 18-35, wherein a concentrate comprising a random propylene-α-olefin copolymer, a vinyl monomer, and a peroxide initiator is preliminarily prepared.

38. The process for manufacturing the polypropylene composition according to claim 37, wherein the concentrate is prepared by blending a random propylene copolymer, a vinyl monomer, and an organic peroxide, preferably by dry blending.

39. The process for manufacturing the polypropylene composition according to claim 37 or claim 38, wherein the concentrate is held at a temperature and for a period of time.

40. The process for manufacturing the polypropylene composition according to claim 39, wherein the concentrate is held at a temperature of between 28 and 80°C.

41. The process for manufacturing the polypropylene composition according to claim 39, wherein the concentrate is held at a temperature of between 47 and 53°C.

42. The process for manufacturing the polypropylene composition according to any of claims 39-41, wherein the concentrate is held soak for period of time from 5 to 15 min.

43. The process for manufacturing the polypropylene composition according to any of claims 37-41, wherein the organic peroxide to vinyl monomer weight ratio is from 3:1 to 300:1, preferably from 10:1 to 80:1, more preferably from 20:1 to 50:1.

44. The process for manufacturing the polypropylene composition according to any of claims 18-43, wherein all the components are blended and processed into a melt by means of mixing equipment and an extruder.

45. The process for manufacturing the polypropylene composition according to claim 44, wherein the components are blended at a temperature of between 200 and 260°C, preferably between 210 and 250°C.

46. Use of the polypropylene composition according to any of claims 1-17 or the composition manufactured by the process according to any of claims 18-45 as a composition for making articles or materials by foaming.

47. An article manufactured by foaming the composition according to any of claims 1-17 or the composition manufactured by the process according to any of claims 18-45. 48. The article according to claim 47, which is an article selected from a package, a cable, a thermal-insulating and a waterproof material.