A COMPOSITION FORMED FROM A CALCIUM CARBONATE-COMPRISING MATERIAL AND A GRAFTED POLYMER

Abstract

A composition includes a calcium carbonate-comprising material and from 0.1 to 8 wt.-%, based on the total weight of the calcium carbonate-comprising material, of at least one grafted polymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer including butadiene units and optionally styrene units and/or salty reaction products thereof a polyester mixture including the composition, a polyester product prepared from the polyester mixture, a process for preparing the polyester product as well as the use of the at least one grafted polymer to decrease the melt flow rate of such a polyester product and an article formed from the polyester product.

Claims

1. A composition comprising a calcium carbonate-comprising material selected from among ground calcium carbonate (GCC), precipitated calcium carbonate (PCC) and mixtures thereof, and from 0.1 to 8 wt.-%, based on the total weight of the calcium carbonate-comprising material, of at least one grafted polymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer comprising butadiene units and optionally styrene units and/or salty reaction products thereof.

2. The composition according to claim 1, wherein the ground calcium carbonate (GCC) is selected from the group consisting of marble, limestone, dolomite, chalk and mixtures thereof, or the precipitated calcium carbonate (PCC) is selected from the group consisting of the aragonitic, vateritic and calcitic mineralogical crystal forms, colloidal PCC, and mixtures thereof.

3. The composition according to claim 1, wherein the calcium carbonate-comprising material has i) a weight median particle size d.sub.50 value measured by the sedimentation method in the range from 0.1 μm to 10 μm, and/or ii) a top cut (d.sub.98) measured by the sedimentation method of ≤45 μm, and/or iii) a specific surface area (BET) of from 0.5 to 150 m.sup.2/g as measured using nitrogen and the BET method according to ISO 9277:2010, and/or iv) a residual total moisture content of ≤2 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

4. The composition according to claim 1, wherein the at least one grafted polymer comprises at least one unsubstituted succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer comprising butadiene units and/or salty reaction products thereof.

5. The composition according to claim 1, wherein the at least one grafted polymer is a) a grafted polybutadiene homopolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene homopolymer and having i) a number average molecular weight Mn measured by gel permeation chromatography from 1,000 to 20,000 g/mol, and/or ii) a number of functional groups per chain in the range from 2 to 12, and/or iii) an anhydride equivalent weight in the range from 400 to 2,200, or b) a grafted polybutadiene-styrene copolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene-styrene copolymer and having a 1,2 vinyl content from 20 to 80 mol.-%, based on the total weight of the grafted polybutadiene-styrene copolymer.

6. The composition according to claim 1, wherein the composition comprises the at least one calcium carbonate-comprising material and the at least one grafted polymer and/or the salty reaction products thereof as physical mixture and/or in that the at least one grafted polymer and/or the salty reaction products thereof are present on the surface of the at least one calcium carbonate-comprising material in form of a treatment layer.

7. A polyester mixture comprising a) a polyester resin, and b) from 3 to 82 wt.-%, based on the total weight of the mixture, of the composition according to claim 1, wherein the composition is dispersed in the polyester resin.

8. The polyester mixture according to claim 7, wherein the polyester resin consists of one or more saturated polyester resins selected from the group comprising polylactic acid, polylactic acid-based polymer, aliphatic polyester such as polyhydroxyalkanoates, e.g. polyhydroxybutyrate, poly-3-hydroxybutyrate (P3HB), polyhydroxyvalerate, polyhydroxybutyrate-polyhydroxyvalerate copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate); polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutyrate-adipate-terephthalate (PBAT), polyglycolide, poly(dioxanone) and mixtures thereof.

9. The polyester mixture according to claim 7, wherein the polyester resin has i) a number average molecular weight Mn measured by gel permeation chromatography from 5,000 to 200,000 g/mol, and/or ii) a specific gravity measured according to ASTM D782 from 0.5 to 5, and/or iii) a glass transition temperature Tg measured by differential scanning calorimetry (DSC) in the range from 35 to 90° C.

10. The polyester mixture according to claim 7, wherein the polyester resin consists of polylactic acid, based on the total weight of the polylactic acid.

11. The polyester mixture according to claim 7, wherein the mixture further comprises additives such as colouring pigments, fibers, e.g. cellulose, glass or wood fibers, dyes, waxes, lubricants, oxidative- and/or UV-stabilizers, antioxidants and other fillers, such as carbon black, TiO.sub.2, mica, clay, precipitated silica, talc or calcined kaolin.

12. A polyester product formed from the polyester mixture of claim 7.

13. A process for preparing a polyester product as defined in claim 12, wherein the process comprises the steps of a) providing a polyester resin, b) providing from 3 to 82 wt.-%, based on the total weight of the polyester product, of at least one calcium carbonate-comprising material as filler, c) providing from 0.1 to 8 wt.-%, based on the total weight of the calcium carbonate-comprising material, of at least one grafted polymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer comprising butadiene units d) providing further additives such as colouring pigments, fibers, dyes, waxes, lubricants, oxidative- and/or UV-stabilizers, antioxidants, e) contacting the components of step a), step b), step c) and step d) in any order, and f) forming the mixture of step e) such that a polyester product is obtained.

14. The process according to claim 13, wherein in contacting step e) firstly the at least one calcium carbonate-comprising material of step b) is contacted under mixing, in one or more steps, with the at least one grafted polymer of step c) such that a treatment layer comprising the at least one grafted polymer and/or salty reaction product(s) thereof is formed on the surface of said at least one calcium carbonate-comprising material of step b), and secondly this surface-treated calcium carbonate-comprising material is contacted under mixing, in one or more steps, with the polyester resin of step a).

15. The process according to claim 13, wherein contacting step e) is carried out during forming step f) in that the at least one grafted polymer is contacted under mixing with the polyester resin of step a) before or after adding the at least one calcium carbonate-comprising material.

16. A method of preparing a polyester product formed from a polyester mixture comprising a polyester resin and at least one calcium carbonate-comprising material as filler, the method comprising using at least one grafted polymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer comprising butadiene units to decrease the melt flow rate of such a polyester product by at least 5%, measured according to DIN EN ISO 1133-1:2011, in comparison to the same polyester product formed from the same polyester mixture comprising the polyester resin and at least one calcium carbonate-comprising material but without the at least one grafted polymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a homo- or copolymer comprising butadiene.

17. An article formed from a polyester product according to claim 12, wherein the article is selected from the group comprising hygiene products, medical and healthcare products, filter products, geotextile products, agriculture and horticulture products, clothing, footwear and baggage products, household and industrial products, packaging products, construction products, automotive parts, bottles, cups, and the like.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0332] FIG. 1 shows the results for the melt flow rates of a series of compounded polymer compositions

[0333] The scope and interest of the invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the present invention and are non-limitative.

EXAMPLES

1. Measurement Methods

[0334] In the following, measurement methods implemented in the examples are described.

Particle Size Distribution

[0335] The weight median particle size d.sub.50(wt) and weight top cut particle size d.sub.98(wt) is determined by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph™ 5120, Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and sonicated.

[0336] The processes and instruments are known to the skilled person and are commonly used to determine the particle size of fillers and pigments.

Specific Surface Area (SSA)

[0337] The specific surface area was measured via the BET method according to ISO 9277:2010 using nitrogen as adsorbing gas on a Micromeritics ASAP 2460 instrument from Micromeritics. The samples were pretreated in vacuum (10.sup.−5 bar) by heating at 150° C. for a period of 60 min prior to measurement.

Amount of Surface-Treatment Layer

[0338] The amount of the treatment layer on the calcium carbonate-comprising material is calculated theoretically from the values of the BET of the untreated calcium carbonate-comprising material and the amount of the one or more compound(s) that is/are used for the surface-treatment. It is assumed that 100% of the one or more compound(s) are present as surface treatment layer on the surface of the calcium carbonate-comprising material.

Molecular Weight

[0339] The number-average molecular weight Mn is measured by gel permeation chromatography, according to ISO 16014-1:2019 and ISO 16014-2/2019.

Acid Number

[0340] The acid number is measured according to ASTM D974-14.

Iodine Number

[0341] The iodine number is measured according to DIN 53241/1.

Melt Flow Rate

[0342] The “melt flow rate” was measured on a CEAST Melt Flow modular line instrument from Instron. The instruments and the measuring method are known to the skilled person. The melt flow rate was measured according to DIN EN ISO 1133-1:2011 by using procedure A. The polymer samples to be measured were in the form of granules or pellets with a length of 1 mm to 5 mm. An amount between 6 to 9 g was used for the measurements. Measurement of the samples was made at 210° C. with a nominal load of 2.16 kg using a capillary die having an inner diameter of 2.095 mm and a length of 8.00 mm. The preheating without load was performed for 300 seconds and the measure length is 20 mm.

[0343] The melt flow rate was obtained under standard conditions. The term “standard conditions” according to the present invention refers to standard ambient temperature and pressure (SATP) which refers to a temperature of 298.15 K (25° C.) and an absolute pressure of exactly 100000 Pa (1 bar, 14.5 psi, 0.98692 atm). All measurements were performed on samples that have been stored under similar conditions after preparation.

Total Residual Moisture Content

[0344] The residual total moisture content was determined by thermogravimetric analysis (TGA). The equipment used to measure the TGA was the Mettler-Toledo TGA/DSC1 (TGA 1 STARe System) and the crucibles used were aluminium oxide 900 μl. The method consists of several heating steps under air (80 mL/min). The first step was a heating from 25 to 105° C. at a heating rate of 20° C./minute (step 1), then the temperature was maintained for 10 minutes at 105° C. (step 2), then heating was continued at a heating rate of 20° C./minute from 105 to 400° C. (step 3). The temperature was then maintained at 400° C. for 10 minutes (step 4), and finally, heating was continued at a heating rate of 20° C./minute from 400 to 600° C. (step 5). The residual total moisture content is the cumulated weight loss aftersteps 1 and 2.

2. Materials Used

[0345] The materials used for the present invention had the characteristics set out in the following.

Treatment A

[0346] Treatment A was a grafted polybutadiene homopolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene homopolymer (Mn=3100 Da, viscosity (25° C.)=6500 cPs+/−3500, functional groups/chain=2, anhydride equivalent weight 1238; acid number: 40.1-51.5 meq KOH/g, total acid: 7-9 wt.-%, microstructure (molar % of butadiene): 20-35% 1-2 vinyl functional groups) commercially available from Cray Valley under the trade name RICON®130MA8 (Cray Valley).

Treatment B

[0347] Treatment B was a grafted polybutadiene homopolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene homopolymer (Mn=5000 Da, Brookfield viscosity (25° C.)=48000 cPs, functional groups/chain=5, anhydride equivalent weight 981) commercially available from Cray Valley under the trade name RICON®131MA10.

Treatment C

[0348] Treatment C was a grafted polybutadiene homopolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene homopolymer (Mn=2500 Da, Brookfield viscosity (55° C.)=140000 cPs, functional groups/chain=3, anhydride equivalent weight 583) commercially available from Cray Valley under the trade name RICON®156MA17.

Treatment D

[0349] Treatment D was a low molecular weight grafted polybutadiene-styrene copolymer comprising at least one succinic anhydride group obtained by grafting maleic anhydride onto a polybutadiene-styrene copolymer (Mn=9900 Da, Brookfield viscosity (45° C.)=170000 cPs, functional groups/chain=6, anhydride equivalent weight 1651, acid number=28.5-40 meqKOH/g, Styrene amount: 17-27 wt %) commercially available from Cray Valley under the trade name RICON® 184MA6.

Treatment E

[0350] Treatment E was a mono-substituted alkenyl succinic anhydride (2,5-Furandione, dihydro-, mono-C.sub.15-20-alkenyl derivs., CAS No. 68784-12-3), which was a blend of mainly branched octadecenyl succinic anhydrides (CAS #28777-98-2) and mainly branched hexadecenyl succinic anhydrides (CAS #32072-96-1). More than 80% of the blend was branched octadecenyl succinic anhydrides. The purity of the blend was >95 wt %. The residual olefin content was below 3 wt %.

Treatment F

[0351] Treatment F was a fatty acid mixture 2, which was a 1:1 mixture of stearic acid and palmitic acid.

Calcium Carbonate-Comprising Filler Material 1 (Powder 1)

[0352] Powder 1 was a dry ground calcium carbonate from Italy (d.sub.50(wt)=3.4 μm, d.sub.98(wt)=14 μm, BET specific surface area=2.6 m.sup.2/g). The material obtained had a residual total moisture content of 0.21 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Calcium Carbonate-Comprising Filler Material 2 (Powder 2)

[0353] Powder 2 was a stearic acid-surface treated dry ground calcium carbonate from Italy (d.sub.50(wt)=3.4 μm, d.sub.98(wt)=14 μm, BET specific surface area=2.6 m.sup.2/g). The material obtained had a residual total moisture content of 0.09 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface Treated Calcium Carbonate-Comprising Filler Material 3 (Powder 3)

[0354] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.8 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment A (7.2 g) was added to the mixture. Stirring and heating was then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 3). The material obtained had a residual total moisture content of 0.15 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface Treated Calcium Carbonate-Comprising Filler Material 4 (Powder 4)

[0355] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.8 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment B (7.2 g) was added to the mixture. Stirring and heating was then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 4). The material obtained had a residual total moisture content of 0.16 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface Treated Calcium Carbonate-Comprising Filler Material 5 (Powder 5)

[0356] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.8 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment C (7.2 g) was added to the mixture. Stirring and heating was then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 5).

Surface Treated Calcium Carbonate-Comprising Filler Material 6 (Powder 6)

[0357] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.8 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment D (7.2 g) was added to the mixture. Stirring and heating was then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 6).

Surface Treated Calcium Carbonate-Comprising Filler Material 7 (Powder 7)

[0358] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.4 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment A (3.6 g) and 0.4 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment F (3.6 g) were added directly one after another in the given order to the mixture. Stirring and heating is then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 7). The material obtained had a residual total moisture content of 0.12 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface Treated Calcium Carbonate-Comprising Filler Material 8 (Powder 8)

[0359] 900 g of powder 1 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (2000 rpm, 120° C.). After that time, 0.4 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment A (3.6 g) and 0.4 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment E (3.6 g) were added directly one after another in the given order to the mixture. Stirring and heating was then continued for another 20 minutes (120° C., 2000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 8).

Calcium Carbonate-Comprising Filler Material 9 (Powder 9)

[0360] Powder 9 was a wet ground and subsequently dried ground calcium carbonate (GCC, marble) from Norway treated with treatment F (0.6%) and treatment A (2.5%) (d.sub.50(wt)=0.3 μm, d.sub.98(wt)=1.4 μm, BET specific surface area=14.4 m.sup.2/g). The material obtained had a residual total moisture content of 0.16 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Precipitated Calcium Carbonate-Comprising Filler Material 10 (Powder 10)

[0361] Powder 10 was a precipitated calcium carbonate (colloidal PCC) from Austria (d.sub.50(wt)=1.5 μm, d.sub.98(wt)=8 μm, BET specific surface area=34.4 m.sup.2/g). The material obtained had a residual total moisture content of 0.60 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface-Treated Precipitated Calcium Carbonate-Comprising Filler Material 11 (Powder 11)

[0362] Powder 11 was prepared by surface-treating powder 10 with 2.5 wt % of treatment A. To carry out the treatment, the treatment A (25 g) was first dispersed in 200 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0363] A suspension of powder 11 (1.00 kg in 7 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then transferred to a metallic tray and dried in an oven (110° C.). The dried cake was then deagglomerated using a Retsch SR300 rotor beater mill. The material obtained had a residual total moisture content of 0.48 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Precipitated Calcium Carbonate-Comprising Filler Material 12 (Powder 12)

[0364] Powder 12 was a precipitated calcium carbonate (colloidal PCC) from Austria (d.sub.50(wt)=2.7 μm, d.sub.98(wt)=3.9 μm, BET specific surface area=70.8 m.sup.2/g). The material had a residual total moisture content of 1.22 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface-Treated Precipitated Calcium Carbonate-Comprising Filler Material 13 (Powder 13)

[0365] Powder 13 was prepared by surface-treating powder 12 with 2.5 wt % of treatment A. To carry out the treatment, the treatment A (25 g) was first dispersed in 200 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0366] A suspension of powder 13 (1.00 kg in 7 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then transferred to a metallic tray and dried in an oven (110° C.). The dried cake was then deagglomerated using a Retsch SR300 rotor beater mill. The material obtained had a residual total moisture content of 0.96 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface-Treated Precipitated Calcium Carbonate-Comprising Filler Material 14 (Powder 14)

[0367] Powder 14 was prepared by surface-treating powder 12 with 5 wt % of treatment A. To carry out the treatment, the treatment A (45 g) was first dispersed in 300 mL of deionized water, heated to 60° C. and neutralized to pH 10 with NaOH solution.

[0368] A suspension of powder 14 (0.9 kg in 7 L deionized water) was prepared in a 10 L ESCO batch reactor and heated to 85° C. The pH was adjusted to 10 with Ca(OH).sub.2 and the neutralized treatment agent was then added under vigorous stirring. Mixing was continued at 85° C. for 45 minutes, and the suspension was then transferred to a metallic tray and dried in an oven (110° C.). The dried cake was then deagglomerated using a Retsch SR300 rotor beater mill.

Calcium carbonate-comprising filler material 15 (powder 15)

[0369] Powder 15 was an untreated wet ground spray dried limestone from France (d.sub.50(wt)=0.7 μm, d.sub.98(wt)=2.9 μm, BET SSA=7.9 m.sup.2/g)

Surface-Treated Calcium Carbonate-Comprising Filler Material 16 (Powder 16)

[0370] 1000 g of powder 15 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 5 minutes (700 rpm, 145° C.). After that time, 1.8 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment A (18 g) were added to the mixture. Stirring and heating was then continued for another 15 minutes (145° C., 700 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 16). The material obtained had a residual total moisture content of 0.05 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Calcium Carbonate-Comprising Filler Material 17 (Powder 17)

[0371] Powder 17 was a wet ground and spray dried calcium carbonate (marble) from Italy (sedigraph: d.sub.50(wt)=1.8 μm, d.sub.98(wt)=6.1 μm; BET=3.3 m.sup.2/g). The material obtained had a residual total moisture content of 0.06 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

Surface-Treated Calcium Carbonate-Comprising Filler Material 18 (Powder 18)

[0372] 1100 g of powder 17 was placed in a high speed mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes (1000 rpm, 120° C.). After that time, 1.0 parts by weight relative to 100 parts by weight CaCO.sub.3 of Treatment A (11 g) was added to the mixture. Stirring and heating was then continued for another 15 minutes (120° C., 1000 rpm). After that time, the mixture was allowed to cool and the free-flowing powder was collected (powder 18). The material obtained had a residual total moisture content of 0.04 wt.-%, based on the total dry weight of the at least one calcium carbonate-comprising material.

3. Examples

Polymer Component

[0373] As polymer component polylactic acid was used which is commercially available from NatureWorks under the trade name Biopolymer 2003D. The polylactic acid is a PDLLA comprising 4.6 wt.-% of D isomers, based on the total weight of the polylactic acid. Furthermore, the PDLLA has a specific gravity of 1.24 and a glass transition temperature from 55 to 60° C. The PDLLA has residual monomer content of 0.21 wt.-%, based on the total weight of the polylactic acid.

Polymer Compounding Preparations

[0374] The compounded polymer compositions were prepared in a two-step synthesis.

[0375] In a first step, the polymer component polylactic acid was added to a twin roll mill (Collin 150, Walzwerk 150×400, Germany) followed by the addition of the calcium carbonate-comprising filler material after the PLA has been melted. The at least one grafted polymer was present on the surface of the calcium carbonate-comprising material and/or was added separately afterwards during compounding. The compounding of the composition was carried out with a total amount of 120 g of material (calcium carbonate-comprising material+polymer component+at least one grafted polymer) using the conditions given in table 1 below.

TABLE-US-00001 TABLE 1 Compounding conditions Composition Calcium carbonate comprising material Various amounts Polylactic acid as polymer component Various amounts at least one grafted polymer optional Roll speed 20 rpm Speed −40% difference (typical) Thickness: 0.6 mm Temperature 200° C.

[0376] After obtaining a homogeneous mixture, the melt was removed from the rolls and added again (operation repeated 3 times) for a total compounding time on the roll mill of 11 minutes (unless indicated otherwise).

[0377] In a second step, the compounded polymer composition was treated in a press (Collin P 300 P, Dr. Collin, Germany). Approx. 90 g of the compounded polymer composition were cut in pieces and pressed between 2 metal plates to obtain sheets of the following dimensions: 169×169×2 mm.sup.3. The used press program is given in table 2 below.

TABLE-US-00002 TABLE 2 Press conditions Temperature Time Pressure [° C.] [s] [bar] 210 60  20 210 90 200 cooling 90 200

[0378] The compounding was performed in a room at 25±2 00 at 40-50% rH.

[0379] The amounts of the used materials and the formulation of the compounded polymer compositions is given in table 3 below. As especially the melt flow rate of the referenced material, i.e. unfilled polymer component, may vary with time, comparative examples were made for each series of test.

TABLE-US-00003 TABLE 3 Compounded polymer compositions Calcium Polymer carbonate component comprising in weight material in grafted polymer in Example parts weight parts weight parts CE1 100 — — CE2 100 Powder 1 (20) — CE3 100 Powder 2 (20) — E1 100 Powder 3 (20) * E2 100 Powder 4 (20) * E3 100 Powder 5 (20) * E4 100 Powder 6 (20) * E5 100 Powder 7 (20) * E6 100 Powder 8 (20) * E7 100 Powder 1 (20) Treatment A.sup.# (0.16) * The grafted polymer was present on the surface of the calcium carbonate-comprising material .sup.#The grafted polymer was added directly during compounding, i.e. the grafted polymer is not present on the surface of the calcium carbonate-comprising material

[0380] The melt flow rates of a series of compounded polymer compositions are presented in Table 4 below. The analysis were performed on samples produced at the same moment to minimize the effect of aging on the analysis results. Table 4 shows the melt flow rate of comparative examples CE1 to CE3 and inventive example E1 to E7.

TABLE-US-00004 TABLE 4 melt flow rate of the compounded polymer compositions MFR % reduction vs Example (g/10 min) comparative example CE1 15.2 / CE2 29.4 / CE3 44.3 / E1 18.4 37.4% (CE2) E2 15.5 47.3% (CE2) E3 12.1 58.8% (CE2) E4 16.3 44.6% (CE2) E5 23.2 21.1% (CE2) E6 17.8 39.5% (CE2) E7 20.7 29.6% (CE2)

[0381] As can be seen from the examples by the use of the at least one grafted polymer before or during compounding of a polymer composition comprising polylactic acid as polymer component and at least one calcium carbonate-comprising material as filler, it was possible to decrease the melt flow rate of such a compounded polymer composition. More precisely, it was possible to decrease the melt flow rate between 21.1% to 58.8% in comparison to the same polymer composition that has been treated the same way but without using the at least one grafted polymer. The measured results also are graphically visualized in FIG. 1.