Field of the invention

The present invention relates to easily flowable polypropylene compositions, a process for manufacturing the same, and polymer articles made of such compositions that have a complex of properties, such as high impact strength, transparency, and low shrinkage. The propylene composition manufactured according to the claimed process is intended for use in 3d-printing by a Fused Deposition Modelling (FDM) method and is capable of replacing compositions based on an acrylonitrile butadiene styrene (ABS) resin, polylactide (PLA), high-impact polystyrene (HIPS), and the like in making articles of a complex shape, having improved appearance, high impact resistance, and reduced haze. Moreover, the claimed composition is suitable for moulding thin-walled articles, reservoirs for liquid and bulk materials, and for laminating various surfaces.

Prior art

One of the most important technological properties for polymer materials that are used both in injection moulding and in 3d-printing by fused deposition modelling is decreased shrinkage that prevents various defects from occurrence, particularly, distortion, especially of thick-walled and three-dimensional articles when cooling them.

Polymer materials that are the most widely used in 3d-printing by fused deposition modelling are the ABS resin and polylactide (PLA), which have a shrinkage of not greater than 0.8 and 0.3%, respectively. Owing to its high crystallinity, isotactic polypropylene has a shrinkage from 1.5 to 2.5%, which stands in the way of its use in 3d-printing by fused deposition modelling.

A crucial requirement to a composition for 3d-printing by fused deposition modelling is high interlaminar adhesion that inhibits delamination of an article during printing and produces a direct influence on shape homogeneity of the article. What is also important for articles produced via 3d-printing is article’s appearance that can be visually assessed, in particular, on the basis of such surface effects of the article as decreased haze, glance, surface smoothness. The most widespread materials in the market of 3d-printing by fused deposition modelling are, particularly, the polylactide (PLA) and ABS resin. However, all these materials have major disadvantages for being used in 3d-printing. Specifically, PLA’s deficiencies are low humidity and chemical resistance, a low glass transition temperature, which considerably limit fields of application of articles made from PLA. The ABS resin is characterized by moderate resistance to chemical reagents and solvents, unsatisfactory appearance of a finished article, and is environmentally unfriendly due to the presence of highly toxic monomers, such as styrene and acrylonitrile, that are released from ABS resin articles at elevated operation temperatures and can cause irritation of mucosae and intoxication. All the disadvantages listed above limit considerably the applications of said resin, in particular, it is not recommended to use the ABS resin for manufacturing food containers and tableware, especially for storage of hot food, or children’s toys. Thus, development of a polypropylene (PP) composition that is devoid of the aforementioned disadvantages of the PLA and ABS resin is a vital task and, in addition, polypropylene is one of inexpensive polymers produced on an industrial scale.

Prior art reference CN 104592626 (06.05.2015), [1], discloses polypropylene compositions for use in 3d-printing by fused deposition modelling; in particular, proposed is a polypropylene (PP) composition for 3d-printing with decreased shrinkage and distortion, comprising: A) from 60 to 94 wt.% of an isotactic polypropylene having a melt flow index (MFI230 _/ 2 _. 16) ranging from 0.5 to 60 g/10 min; B) from 5 to 20 wt.% of an elastomer, advantageously an ethylene-octene elastomer, having a melt flow index (MFI190 _/ 2 _. 16) ranging from 0.5 to 50 g/10 min; C) from 0 to 20 wt.%, preferably from 10 to 20 wt.% of a disperse mineral filler, such as talc, barium sulfate, and the like; D) from 0.1 to 0.3 wt.% of a nucleating agent, and E) optionally other additives, such as antioxidants, lubricants, dyes.

Application CN 106674736 (17.05.2017), [2], discloses a formulation of a polypropylene composition for 3d-printing, comprising: A) from 70 to 98 wt.% of polypropylene; B) from 1 to 20 wt.% of an elastomer, advantageously, an ethylene-acryl elastomer; C) from 0 to 10 wt.% of a mineral filler; D) from 0.2 to 5 wt.% of other additives. In addition to a polar ethylene-acryl elastomer, the composition comprises from 0.1 to 0.5 wt.% of a b- nucleator . From the viewpoint of 3d-printing, shortcomings of the two variants of compositions according to references [1], [2] discussed above are: a high haze level, even in the absence of mineral fillers, because the elastomers used therein, both ethylene-octene ones, and, even more so, ethylene-acryl ones, are restrictedly compatible with polypropylene due to essential differences in physical and optical density of these elastomers and polypropylene.

Furthermore, the high content of polypropylene (at least 70 wt.%) in these compositions, in the absence of mineral fillers, does not permit achieving the desired shrinkage level of the material, in particular, values of below 1.5%.

Further known in the art (EP 2338657, 29.06.201 1, [3]) are high transparent polypropylene compositions; particularly, disclosed is a polypropylene composition with an improved balance between impact strength and transparency, intended for being used as a film material or for thin-walled molded articles applied for packaging and storage of frozen products. The total content of the ethylene-octene elastomer and a linear ethylene copolymer in the known polypropylene composition is from 6 to 45 wt.%, which gives a shrinkage interval of the material of from 0.8 to 1.5% or more. This does not allow successfully using this material in 3d-printing by fused deposition modelling.

International application WO 2017182209, 26.10.2017, [4], is the closest to the present invention in terms of technical essence. Said application discloses novel reactor synthesis techniques and formulations of propylene-ethylene copolymers, propylene- ethylene-butene- 1 or hexene- 1 terpolymers for using such compositions to produce articles by 3d-printing. A melt flow index (MFI230 _/ 2 _. 10) of such propylene copolymers varies between 1 and 20 g/10 min. A soluble amorphous fraction in these propylene copolymers comprises 30 wt.% thereby providing high interlaminar adhesion during 3d- printing by fused deposition modelling. Nevertheless, this level of content of soluble fractions does not guarantee the required shrinkage parameters of a material, which at best are in the range from 0.9 to 1.0%. Propylene-ethylene-butene- 1 terpolymers are commercially available; consider, for example, a similar composition available from LyondellBasell under the tradename Adsyl 5C30F and exhibiting a mold shrinkage of 0.9% after 2 hours and 1.0% after 24 hours, with the melt flow index (MFI230/2.16) being 5.5 g/10 min. As follows from the prior art references [1] to [4], the major problem of the proposed solutions remains unattainability of an optimal complex of basic characteristics of polypropylene compositions that are used for making articles by 3d- printing, including satisfactory physical and mechanical properties, a low haze level and low shrinkage values.

There is therefore a need to provide a polypropylene composition that, while maintaining a desired shrinkage level, particularly not greater than 0.8%, has high transparency and optimal physical and mechanical properties. Hence, it is an object of the present invention to providea composition with an improved complex of said properties.

Figures illustrating the present invention

Figure shows appearance of a sample made of a polypropylene (PP) composition by 3d-printing.

Brief summary of the invention

The problem underlying the present invention is the provision of a high melt flow polypropylene composition, wherein articles made of the composition are characterized by a low shrinkage level, which, in its turn, prevents such defects as distortion, and have improved optical and physical-mechanical properties, which allows using such composition not only for molded articles, but also for articles made by the fused deposition modelling method of 3d-printing.

The technical result of the present invention is a decrease in mold shrinkage of an article made of a polypropylene composition and maintenance of decreased haze. Specifically, the mold shrinkage of such composition is reduced to the range between 0.6 and 0.8% after holding a finished article for 24 hours. Haze of 1 mm of molded articles simultaneously remains below 35%.

At the same time, the invention provides the melt flow index (MFI230/2 16) of the composition at above 10 g/10 min, which is crucial for ensuring high manufacturability of articles produced from polypropylene compositions.

A further technical result consists of improvement of performance characteristics, in particular, thermal and chemical resistance, as well as physical and mechanical properties, especially tensile strength, modulus of elasticity, and impact strength, that constitute structural strength of polypropylene articles in comparison with the identical characteristics of articles produced from the known materials, PLA and ABS resins.

The aforementioned technical result is achievable by using at least three polymer components with a certain combination of properties in the composition:

A) a crystalline isotactic propylene homopolymer, characterized by an increased melt flow index to ensure high performance and improve quality of the surface of articles during 3d-printing;

B) an elastomeric copolymer of ethylene and an a-olefln comprising 4 to 10 carbon atoms, wherein the elastomer is characterized by a certain range of density and melt flow so as to provide good compatibility of composition components and ensure required shrinkage and transparency of articles; and

C) a thermoplastic polymer based on a copolymer of ethylene with an a-olefm comprising 3 to 10 carbon atoms, wherein the polymer is characterized by a certain range of density and melt flow so as to ensure the required level of optical, physical- mechanical, and thermophysical characteristics of the produced composition.

Furthermore, if necessary, a nucleating agent and/or other additives (antioxidants, thermostabilizers, lubricants, dyes, pigments and other additives) are optionally used to improve transparency of articles made of the composition; introduction of such additives does not adversely affect shrinkage, as well as the complex of optical, physical-mechanical, and thermophysical properties. At that, the nucleating agent is employed in compositions, wherein the content of the crystalline isotactic propylene homopolymer is at least 50 wt.%, particularly, in compositions, wherein the content of the crystalline isotactic propylene homopolymer is in the range from 50 to 55 wt.%.

Detailed description of the invention

The composition for making articles according to the present invention comprises the following components, relative to its total weight:

A) from 40 to 55 wt.% of a crystalline isotactic propylene homopolymer;

B) from 13 to 28 wt.% of an elastomeric ethylene-a-olefm copolymer comprising 4 to 10 carbon atoms;

C) from 27 to 32 wt.% of one or more random thermoplastic ethylene-a-olefm copolymers comprising 3 to 10 carbon atoms; D) not more than 0.5 wt.% of a nucleating agent and/or other additives.

Propylene having a density of at least 0.895 g/cm ³ , preferably at least 0.900 g/cm ³ , is used as the crystalline isotactic propylene homopolymer (A) during the preparation of the composition. A melt flow index (MFI230/2 _. 16) of said crystalline isotactic propylene homopolymer ranges from 25 to 50 g/10 min, preferably from 27 to 45 g/10 min.

Examples of the crystalline isotactic propylene homopolymer (A) include any engineering grades, in particular, products marketed under the tradenames PPH250GP, PPH270GP, PPH350GP, PPH450GP (manufactured by Tomskneftekhim OOO, Tobolsk-Polimer OOO, Poliom OOO, Neftekhimiya NPO), and Balen 01270 manufactured by Ufaorgsintez OAO, PP1300R manufactured by Nizhnekamskneftekhim, and commercially available analogues thereof.

The content of said crystalline isotactic polypropylene, relative to the total weight of the composition, is from 40 to 55 wt.%, preferably from 45 to 55 wt.%, most preferably from 50 to 55 wt.%.

A copolymer of ethylene with an a-olefln comprising 4 to 10 carbon atoms is used as the elastomer (B). Preferred as the elastomer (B) is a copolymer of ethylene with octene-1. Use of an elastomer of exactly this nature, specifically a copolymer of ethylene with octene-1, contributes to haze reduction and influences physical and mechanical properties, in particular, impact strength and modulus of elasticity of articles made of this composition.

Meanwhile, it is important to use an elastomeric ethylene-a-olefm copolymer, having a density from 0.855 to 0.890 g/cm ³ , preferably from 0.857 to 0.880 g/cm ³ , and a melt flow index (MFI230/2.16) in the range from 1 to 30 g/10 min.

The authors of the present invention have surprisingly discovered that use of elastomeric ethylene-a-olefm copolymers having a density in the range from 0.855 to 0.885 g/cm ³ causes a substantially greater decrease in shrinkage and improvement of optical properties (haze) of the produced polypropylene composition in contrast to carbon-chain hydrocarbon aliphatic elastomers of a different nature, such as a terpolymer of ethylene, propylene and nonconjugated diene (EPDM), or mainly amorphous copolymers of propylene with ethylene and/or butene- 1. Examples of the used elastomers (B) include, but are not limited to, products marketed, particularly, under the tradenames Engage 8452, Engage 8842, Engage 8137, Engage 8200, Exact 8210, Lucene 670.

The content of the elastomer (B), relative to the total weight of the composition, is from 13 to 28 wt.%, preferably from 15 to 25 wt.%, most preferably from 15 to 23 wt.%.

One or more random thermoplastic ethylene-a-olefm copolymers having 3 to 10 carbon atoms are used as the component (C) in the composition. Density of said ethylene copolymer is from 0.910 to 0.927 g/cm ³ , preferably from 0.915 to 0.925 g/cm ³ .

Therefore, any basic grades of a commercial linear low-density polyethylene denoted LLDPE that meet the aforementioned requirements may be used as the component (C).

A polyethylene obtained by anionic coordinate random copolymerization of ethylene with a-olefins comprising 4 to 10 carbon atoms at a low pressure in the presence of Ziegler-Natta catalyst systems or metallocene catalyst systems according to conventional industrial techniques is used as the LLDPE.

The LLDPE used in the composition is characterized by a melt flow index (MFl230 _° c _/ 2 _.i 6 _kg ) in the range from 1 to 10, preferably from 2 to 10, most preferably from 2 to 8 g/10 min.

Copolymers of ethylene with an a-olefm comprising 3 to 10 carbon atoms are used as the LLDPE according to the present invention. Specifically, employed is an a- olefin selected from the group consisting of butene- 1, hexene- 1 , and octene-1. It is the most advantageously to use a copolymer of ethylene with octene-1. The content of the a-olefm comonomer in the LLDPE is from 2.5 to 8 wt.%, preferably from 3 to 6 wt.%, most preferably from 3.5 to 5 wt.%.

Any known LLDPE tradenames or a mixture thereof, for example, XP 9400, XP 9200, 3306WC4, PE 5118Q, UF414C4, 3840, SABIC LLDPE 318B, SABIC LLDPE 6318 BE, SABIC LLDPE R500035, and the like may be used as the LLDPE.

The content of the component (C) in the composition, relative to the total weight of the composition, is from 27 to 32 wt.%, preferably from 27 to 31 wt.%, most preferably from 28 to 30 wt.%. It is important to note that, in order to achieve the best technical result, contents of the components (B) and (C) are varied within the claimed ranges so that the following requirements are met: the density of a mixture of the elastomer (B) and the thermoplastic copolymer (C) is close to or equal to the density of the isotactic propylene homopolymer (A), i.e. the density of (B+C) must be at least 0.995, preferably at least 0.997 of the density of the propylene homopolymer (A) and not greater than 1.007, preferably not greater than 1.005 of the density of the propylene homopolymer (A).

If necessary, a nucleating agent and/or other additives are optionally used to improve transparency of articles made from the composition, the introduction of which does not adversely affect shrinkage and the complex of optical, physical-mechanical, and thermophysical properties. A nucleating agent is employed in compositions, where the crystalline isotactic propylene homopolymer is comprised in the amount of at least 50 wt.%, i.e. in compositions, where the amount of crystalline isotactic propylene homopolymer is in the range from 50 to 55 wt.%.

A nucleating agent and/or other additives are used in an amount of not greater than 0.5 wt.%, preferably up to 0.3 wt.%. It is preferable to use an organic nucleating agent. A mixture of nucleating agents may be used.

The most preferable nucleating agents are dibenzylidene sorbitol derivatives that may also be known as“brighteners”. In particular, 3,4-dimethyldibenzylidene sorbitol, bis(4-propylbenzylidene) propyl sorbitol, or a mixture thereof are used as the nucleating agent. Examples of said nucleating agents are products marketed under the tradenames Millad 3988, Millad 8000.

The composition of the present invention may also optionally include further additives other than nucleating agents, for example, antioxidants, thermostabilizers, stabilizers, mixtures thereof, lubricants, processing additives, pigments, dyes. Exemplary antioxidants are 2,6-di-tert-butyl-p-cresol, tetrakis-[methylene-3-(3,5-di-t- butyl-4-hydroxyphenyl)propionate]methane, and an ester of 3,5-di-tert-butyl-4- hydroxy-phenylpropionic acid and pentaerythritol marketed under the tradename Irganox 1010.

Exemplary thermostabilizers and light stabilizers are tri-(phenyl-2,4-di-tert- butyl)phosphite marketed under the tradename Irgafos 168, and/or similar thermostabilizers of other tradenames, as well as light stabilizers of the sterically hindered amine type and composite mixtures of stabilizers under such tradenames as Irganox B225, Irganox B215, and analogues thereof.

The composition according to the present invention is obtained by blending all components using the known thermoplastic blending techniques, for example, extrusion, or blending in mixers of various types. Internal mixers with blades or rotors, single-screw extruders, counter-rotating or co-rotating twin-screw extruders may be used.

In accordance with the present invention, the composition is manufactured by blending the components followed by melt compounding the resulting mixture by means of prior art equipment, for example, mixing equipment (Banbury mixers, Brabender mixers), single-screw extruders, twin-screw extruders, and similar mixers. Blending is preferably performed in mixing equipment, while the further compounding of the resultant blend is carried out in an extruder. Meanwhile, what is understood under the compounding in the present invention is an engineering process of blending polymers and additives so as to obtain a composition with homogeneously mixed components.

More precisely, the process according to the present invention comprises blending the components taken in the following amounts, relative to the total weight of the composition:

A) from 40 to 55 wt.% of a crystalline isotactic propylene homopolymer;

B) from 13 to 28 wt.% of an elastomeric copolymer of ethylene and a- olefmcomprising 4 to 10 carbon atoms;

C) from 27 to 32 wt.% of one or more random thermoplastic copolymers of ethylene and a-olefincomprising 3 to 10 carbon atoms;

D) not more than 0.5 wt.% of a nucleating agent

to produce a blend of components (A), (B), (C) and optionally (D), and subsequently subjecting said blend to melt compounding.

At that, the polymer components (A), (B), and (C) are preferably used in a granular form.

When using nucleating agents and/or other additives in the composition, it is advantageous: - to blend the components taken in the following amounts, relative to the total weight: A) from 40 to 55 wt.% of a crystalline isotactic propylene homopolymer; B) from 13 to 28 wt.% of an elastomeric copolymer of ethylene and a-olefm comprising 4 to 10 carbon atoms; C) from 27 to 32 wt.% of one or more random thermoplastic copolymers of ethylene and a-olefm comprising 3 to 10 carbon atoms to obtain a blend of polymer components;

- to introduce lubricants into the so-obtained blend of polymer components;

- to mix the so-obtained blend of lubricant-treated polymer components with a nucleating agent and/or other additives, and then subject said blend to melt compounding.

It is preferable to introduce lubricants into the resultant blend of polymer components followed by mixing said blend for at least 1 to 2 minutes before feeding a nucleating agent and/or other additives for more homogeneous distribution of the same in the final composition.

Lubricants are employed to facilitate the production of the composition, especially its extrusion. Examples of lubricants include, but are not limited to, stearamides, oleamides, erucinamides, calcium stearate, zinc stearate, aluminium stearate, magnesium stearate, polyethylene wax, petrolatum oil.

The amount of the lubricant is preferably from 0.1 to 0.5 wt.%, more preferably 0.2 wt.%.

Blending of the components is preferably performed in mixing equipment for a period of time from 1 to 20 minutes, preferably from 2 to 10 minutes, at a temperature from 10 to 50°C, preferably from 20 to 40°C. The so-obtained blend is subjected to melt compounding, preferably in an extruder, at a temperature from 190 to 240°C, preferably from 200 to 230°C.

The compositions of the present invention are preferably used to manufacture polymer articles through 3d-printing by fused deposition modelling. It is also admissible to manufacture articles from the claimed composition by injection moulding.

The present invention also relates to use of the claimed composition for making articles through 3d-printing by fused deposition modelling or through injection moulding, a filament for making articles produced using the claimed composition, as well as to articles made from the claimed composition through 3d-printing by fused deposition modelling or through injection moulding. This invention will be 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 disclosure.

Examples of carrying out the invention

Test methods

A melt flow rate at 230°C and at a load of 2.16 kg is measured in conformity with ASTM D 1238-04C.

Samples for physical and mechanical tests are made by injection moulding in conformity with ASTM D 4101.

Moulding modes on an Engel Victory 200/50 moulding machine:

- volume moulded per shot - 31 cm ³ ;

- transition point - 3.5 cm ³ ;

- temperature per zones - 230-230-225-220°C;

- mould temperature - 35°C;

- dosing rate - 0.06 m/s;

- injection rate - 100 c Vs;

- injection pressure - 800 bar;

- dynamic pressure - 50 bar;

- backup pressure - 400 bar;

- holding time - 20 s;

- cooling time - 30 s.

Notched Izod impact strength at 23°C and minus 10°C is determined in conformity with ASTM D 256 (Method A).

Mold shrinkage is determined in conformity with ASTM D 955, Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics.

Haze for 1- and 2-mm thick samples is measured in conformity with ASTM

D1003.

Tensile yield strength and strain at yield are determined in conformity with ASTM D 638.

A modulus of elasticity in flexure is determined in conformity with ASTM D 790, Test Method: Three-Point Bending, testing rate: 1.3 mm/min.

Components used in the examples: Compounds used as the crystalline isotactic propylene homopolymer (A) are:

PPH270GP manufactured by Tomskneftekhim OOO (MFl230/2 _{. i} 6= 27 g/10 min);

PPH350GP manufactured by Tomskneftekhim OOO (MFl230 _/ 2.i6= 35 g/10 min);

PPH450GP manufactured by Neftekhimiya OOO (MFl _{230/2. i6} )=45 g/10 in).

Compounds used as the elastomer (B) are:

Engage 8452, Engage 8842, Engage 8137, Engage 8200 - a copolymer of ethylene and octene manufactured by Dow Chemical;

Lucene 670 - a copolymer of ethylene and octene manufactured by LG Chim (Korea),

Royalene 593 - an ethylene-propylene-diene terpolymer manufactured by Lion Copolymer (USA);

Vistamax 6202 - a propylene-ethylene-butene- 1 terpolymer manufactured by Exxon Mobil.

Compounds used as the thermoplastic ethylene-a-olefm copolymer (C) are:

Daelim XP 9200, 9400 - a metallocene linear low-density polyethylene manufactured by Daelim (South Korea);

LDPE158020 - a low-density polyethylene manufactured by Tomskneftekhim

OOO.

And the compound used as the nucleating agent is Millad 8000 - a brightener manufactured by Milliken.

Example 1

A blend according to the formulation of the composition given in Table 1 is prepared in a mixer with blades. Such ratio of the elastomer component (B) to the thermoplastic polymer (C) is selected that the density of the blend (B+C) is -0.900 g/cm ³ . The polymer components are then blended for a period of time from 2 to 10 minutes at room temperature. The resultant blend is processed in an LTE-20-44 twin- screw extruder at a maximum temperature in roller zones of 230°C and at a speed of rotation of the screw of 250 min ¹ . The granulate prepared in this extruder line is then used to determine MFI230 _/ 2 16 values and to obtain samples for subsequent physical- mechanical and optical-physical tests by injection moulding.

Results of all tests of the obtained composition are summarized in Table 1. Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 10.0 g/10 min; haze of 1 mm of a surface is 20.1%; mold shrinkage after holding an article for 2 hours is 0.6%; mold shrinkage after holding an article for 24 hours is 0.6%; tensile yield strength is 15.5 MPa (moulding) and 14.0 MPa (3d-printing); the modulus of elasticity in flexure is 450 MPa (moulding) and 380 MPa (3d-printing).

A part of the granulate is used to produce a filament (d=1.75±0.05 mm) in a single-screw laboratory extruder at a maximum temperature in roller zones of 220°C and at a speed of rotation of the screw of 40-60 min ¹ . The filament is used to produce samples of PP compositions in the form of dumb-bells and bars of a standard size to determine major physical and mechanical characteristics for the purposes of comparison with data obtained on moulding samples. Samples are 3d-printed on a Picasso Designer X-Pro printer at a nozzle temperature of 220°C, a table temperature of 120°C, a chamber temperature of 50°C, and at a layer thickness of 0.2 mm. Appearance of a standard size dumb-bell sample is shown in the Figure.

Example 2

The composition according to Example 1 is provided, save that 50 wt.% instead of 40 wt.% of the PPH270GP crystalline isotactic polypropylene is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 10.9 g/10 min; haze of 1 mm of a surface is 23.5%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.7%; tensile yield strength is 18.1 MPa (moulding) and 16.0 MPa (3d-printing); the modulus of elasticity in flexure is 560 MPa (moulding) and 480 MPa (3d-printing).

Example 3

The composition according to Example 1 is provided, save that 55 wt.% instead of 40 wt.% of the PPFI270GP crystalline isotactic polypropylene is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 1 1.5 g/10 min; haze of 1 mm of a surface is 27.1%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.8%; tensile yield strength is 20.5 MPa; the modulus of elasticity in flexure is 750 MPa.

Example 4 (comparative)

The composition according to Example 1 is provided, save that 35 wt.% instead of 40 wt.% of the PPH270GP crystalline isotactic polypropylene is used. Key properties of the resultant composition are: the melt flow index (MFI230 _/ 2 _. 16) is 8.9 g/10 min; haze of 1 mm of a surface is 29.1%; mold shrinkage after holding an article for 2 hours is 0.8%; mold shrinkage after holding an article for 24 hours is 0.8%; tensile yield strength is 13.8 MPa; the modulus of elasticity in flexure is 390 MPa.

Example 5 (comparative)

The composition according to Example 1 is provided, save that 70 wt.% instead of 40 wt.% of the PPH270GP crystalline isotactic polypropylene is used.

Key properties of the resultant composition are: the melt flow index (MFI230 _/ 2 _. 16) is 14.6 g/10 min; haze of 1 mm of a surface is 38.3%; mold shrinkage after holding an article for 2 hours is 1.2%; mold shrinkage after holding an article for 24 hours is 1.3%; tensile yield strength is 25.3 MPa; the modulus of elasticity in flexure is 890 MPa.

Example 6 (comparative)

The composition according to Example 1 is provided, save that a blend of two polymer components PP-Engage 8452 instead of a triple blend of polymer components PP-Engage 8452- Daelim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 12.3 g/10 min; haze of 1 mm of a surface is 68.4%; mold shrinkage after holding an article for 2 hours is 0.8%; mold shrinkage after holding an article for 24 hours is 0.9%; tensile yield strength is absent; the modulus of elasticity in flexure is 220 MPa.

Example 7 (comparative)

The composition according to Example 1 is provided, save that a blend of two polymer components PP-Daelim XP9200 instead of a triple blend of PP-Engage 8452- Daelim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2 16) is 1 1.0 g/10 min; haze of 1 mm of a surface is 65.1%; mold shrinkage after holding an article for 2 hours is 1.6%; mold shrinkage after holding an article for 24 hours is 1.7%; tensile yield strength is 21.2 MPa; the modulus of elasticity in flexure is 750 MPa.

Example 8

The composition according to Example 1 is provided, save that analogous Engage 8200 instead of the Engage 8452 elastomer is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 16.0 g/10 min; haze of 1 mm of a surface is 20.74%; mold shrinkage after holding an article for 2 hours is 0.6%; mold shrinkage after holding an article for 24 hours is 0.7%; tensile yield strength is 18.1 MPa; the modulus of elasticity in flexure is 650 MPa.

Example 9

The composition according to Example 1 is provided, save that analogous Engage 8842 instead of the Engage 8452 elastomer is used.

Key properties of the resultant composition are: the melt flow index (MFI230 _/ 2 _. 16) is 10.0 g/10 min; haze of 1 mm of a surface is 35.0%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.7%; tensile yield strength is 17.7 MPa; the modulus of elasticity in flexure is 590 MPa.

Example 10

The composition according to Example 1 is provided, save that analogous Engage 8137 instead of the Engage 8452 elastomer is used, and more easily flowable Daelim XP9400 instead of the Daeilim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI _{230/2 16} ) is 18.7 g/10 min; haze of 1 mm of a surface is 21.4%; mold shrinkage after holding an article for 2 hours is 0.6%; mold shrinkage after holding an article for 24 hours is 0.6%; tensile yield strength is 18.1 MPa; the modulus of elasticity in flexure is 670 MPa.

Example If

The composition according to Example 1 is provided, save that analogous Lucene 670 instead of the Engage 8452 elastomer is used, and more easily flowable Daelim XP9400 instead of the Daeilim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2 16) is 15.7 g/10 min; haze of 1 mm of a surface is 20.9%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.7%; tensile yield strength is 17.9 MPa; the modulus of elasticity in flexure is 660 MPa.

Example 12

The composition according to Example 1 is provided, save that analogous Engage 8200 instead of the Engage 8452 elastomer is used, and a PE 51 18Q LLDPE instead of the Daeilim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 15.0 g/10 min; haze of 1 mm of a surface is 35.0%; mold shrinkage after holding an article for 2 hours is 0.6%; mold shrinkage after holding an article for 24 hours is 0.6%; tensile yield strength is 17.5 MPa; the modulus of elasticity in flexure is 590 MPa.

Example 13

The composition according to Example 1 is provided, save that more easily flowable PPH350GP instead of the PPH270GP polypropylene is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 20.0 g/10 min; haze of 1 mm of a surface is 26.7%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.8%; tensile yield strength is 18.1 MPa; the modulus of elasticity in flexure is 650 MPa.

Example 14

The composition according to Example 1 is provided, save that even more easily flowable PPH450GP instead of the PPH270GP polypropylene is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 28.8 g/10 min; haze of 1 mm of a surface is 28.0%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.8%; tensile yield strength is 17.4 MPa; the modulus of elasticity in flexure is 635 MPa.

Example 15 (comparative)

The composition according to Example 1 is provided, save that a carbon-chain hydrocarbon elastomer, which is a Vistamax 6202 random propylene-ethylene-butene- 1 copolymer (a propylene-based elastomer), instead of an elastomer representing a random ethylene-octene-1 copolymer (the Engage and Lucene grades - ethylene-based elastomers) is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2.16) is 17.8 g/10 min; haze of 1 mm of a surface is 58.1%; mold shrinkage after holding an article for 2 hours is 0.9%; mold shrinkage after holding an article for 24 hours is 1.0%; tensile yield strength is 16.5 MPa; the modulus of elasticity in flexure is 450 MPa.

Example 16 (comparative)

The composition according to Example 1 is provided, save that a carbon-chain hydrocarbon elastomer, which is a Royalene 563 random copolymer of ethylene, propylene and nonconjugated diene (EPDM), instead of an elastomer representing a random ethylene-octene-1 copolymer (the Engage and Lucene grades - ethylene-based elastomers) is used. Key properties of the resultant composition are: the melt flow index (MFI230 _/ 2 _. 16) is 8.7 g/10 min; haze of 1 mm of a surface is 65.0%; mold shrinkage after holding an article for 2 hours is 0.9%; mold shrinkage after holding an article for 24 hours is 1.0%; tensile yield strength is 17.2 MPa; the modulus of elasticity in flexure is 550 MPa.

Example 17 (comparative)

The composition according to Example 1 is provided, save that a LDPE- 158020 low-density polyethylene instead of the Daelim XP9200 LLDPE is used.

Key properties of the resultant composition are: the melt flow index (MFI230/2 10) is 15.0 g/10 min; haze of 1 mm of a surface is 51.7%; mold shrinkage after holding an article for 2 hours is 0.7%; mold shrinkage after holding an article for 24 hours is 0.7%; tensile yield strength is 16.7 MPa; the modulus of elasticity in flexure is 580 MPa.

As follows from the experimental data given above, the claimed easily flowable polypropylene composition has decreased shrinkage and high optical characteristics, in particular, reduced haze and excellent physical and mechanical properties, especially tensile yield strength and modulus of elasticity in flexure.

Table 1. Formulations and properties of the polypropylene compositions for 3d-printing

¹ p stands for Partial Break; h stands for Hinge Break (translator’s note).

Continuation of Table 1

As demonstrated in Table 1 , the composition obtained by the process of the present invention according to Examples 1 to 3 and 8 to 14 has a complex of optical and physical-mechanical properties, in particular, it exhibits:

- haze of 1 mm of a surface of molded samples of less than 35%;

- mold shrinkage of from 0.6 to 0.8%;

- a melt flow index (MFI230 _/ 2 _. 16) from 10.0 to 27.8 g/10 min;

- tensile yield strength from 15.5 to 20.5 MPa;

- a modulus of elasticity in flexure from 450 to 750 MPa;

- a Vicat temperature, 10H, of at least 105°C;

- notched Izod impact strength from 456 to 725 (partial break) J/m (at 23°C), from 100 to 785 (partial break) J/m (at 0°C).

Therefore, the composition obtained by the process according to the present invention may be used to manufacture articles not only by injection moulding, but also through 3d-printing by the Fused Deposition Modelling (FDM) method. An article made from the presently claimed composition by 3d-printing is shown in Figure.

The comparative examples (Examples 4 to 7, 15 to 17) have explicitly shown that the use of the components of different nature or the use of the claimed polymer components (A, B, C) beyond the claimed ranges results in considerable deterioration of the complex of optical and physical-mechanical properties, which does not permit using such compositions for 3d-printing.

Specifically, Comparative Examples 4 and 5 have made it clear that the provision of compositions, in which the content of the crystalline isotactic propylene homopolymer (component A) is outside the claimed ranges, leads to significant deterioration of shrinkage, flowability, as well as strength, mechanical, and optical properties of the produced compositions.

Moreover, Comparative Examples 6 and 7 have revealed unattainability of the technical result when a composition is provided that consists not of three polymer components (A, B and C) but only of two polymer components: (A, B) or (A, C).

It has also been demonstrated that the technical result cannot be achieved when elastomers of a different nature are used, i.e. elastomers other than the elastomeric ethylene-a-olefm copolymers. In particular, Examples 15 and 16 show that the use of elastomers based on propylene or copolymers of ethylene with propylene and non- conjugated diene (EPDM) adversely affects the complex of optical and physical- mechanical properties, which make the use of such compositions in 3d-printing impossible.

It should also be pointed out that it is essential to use one or more copolymers of ethylene with a-olefms comprising 3 to 10 carbon atoms, preferably an LLDPE, as the thermoplastic polymer (component C). Thus, Example 17 shows worsening of the complex of properties when other highly branched commercial grades of LDPE produced under high pressure and radical initiation conditions, such as LDPE-158020, are used together with the LLDPE.