Soft butene-1 copolymer for pipes

Abstract

The present disclosure relates to copolymers of butene-1 and hexene-1 that are particularly suitable for the manufacture of pipes and have the following characteristics: [Solution] 1) The content of hexene-1 comonomer units is 2 to 4 wt %, and 2) The melting temperature TmI is 115°C or higher.

Description

Technical Field

[0001] The present invention relates to a butene-1 / hexene-1 copolymer having a low flexural modulus, which is useful for the production of pipes, particularly underfloor heating pipes (UFH pipes).

Background Art

[0002] The butene-1 polymers of the present invention are known to those skilled in the art and have a wide range of applicability. In particular, butene-1 polymers with a high degree of crystallinity generally have good properties in terms of pressure resistance, creep resistance, and impact strength, and can be used for the production of pipes to replace metal pipes.

[0003] One of the important requirements for their use in the field of UFH pipes is an excellent combination of flexibility (low flexural modulus) and a sufficiently high degree of crystallinity and melting point, which provides pressure resistance and heat resistance.

[0004] A butene-1 / propylene / ethylene terpolymer that meets such requirements is disclosed in WO2008132035.

Summary of the Invention

Problems to be Solved by the Invention

[0005] It has been found that a specific copolymer of butene-1 and hexene-1 further improves the balance of flexibility, melting point, and degree of crystallinity.

[0006] Therefore, the present disclosure provides a copolymer of butene-1 and hexene-1 (hereinafter referred to as "copolymer") having the following characteristics. 1) The content of hexene-1 comonomer units is 2 to 4% by weight, preferably 2 to 3.5% by weight, particularly 2.2 to 4% by weight or 2.2 to 3.5% by weight 2) The melting temperature TmI is 115°C or higher, preferably 117°C or higher

[0007] The amount of the hexene-1 comonomer unit refers to the total weight of the copolymer.

[0008] In addition to a high melting point, the copolymer of the present invention has a high crystallinity and a relatively low flexural modulus, which means good flexibility.

Embodiments for Carrying Out the Invention

[0009] The copolymer of the present invention may contain other olefin comonomer units, provided that the TmI does not have a value of less than 115°C in addition to hexene-1.

[0010] Therefore, as used herein, the term "copolymer" also includes polymers containing two or more monomer units other than butene-1.

[0011] However, a copolymer in which the hexene-1 unit is the only comonomer unit (no other comonomer units are present) is preferred.

[0012] Examples of any comonomer units in the present copolymer include comonomer units selected from α-olefins having 7 to 10 carbon atoms such as ethylene, propylene, pentene-1, and octene-1.

[0013] The copolymer of the present invention preferably has a TmI of 115 to 120°C, more preferably 117 to 120°C.

[0014] The melting temperature TmI is the melting temperature resulting from the crystalline form I of the copolymer.

[0015] To measure TmI, after melting a copolymer sample, it is cooled to 20°C at a cooling rate of 10°C / min, stored at room temperature for 10 days, cooled to -20°C, and then heated to 200°C at a scanning rate corresponding to 10°C / min to perform differential scanning calorimetry (DSC) analysis. In this heating operation, the highest temperature peak value in the thermogram is taken as the melting temperature (TmI).

[0016] Preferably, the copolymer of the present invention has at least one of the following additional DSC characteristics.

[0017] The melting temperature TmII measured in the second DSC heating scan performed at a scanning rate of -10 °C / min is 105 °C to 109 °C

[0018] - The crystallization temperature T c measured by DSC at a scanning rate of 10 °C / min is 68 °C to 75 °C

[0019] The TmII temperature value is determined after one melting cycle (second DSC heating scan).

[0020] Therefore, since these are measured during the heating operation performed after first melting the polymer sample, such TmII temperature values are due to the crystalline form II of this copolymer.

[0021] When one or more peaks of melting or crystallization are detected, the temperature of the strongest peak is taken as TmII or T c respectively.

[0022] Preferably, the MIE of the copolymer of the present invention is 0.1 to 10 g / 10 min, more preferably 0.1 to 1 g / 10 min, where MIE is the melt flow index measured at 190 °C / 2.16 kg in accordance with ISO 1133-2:2011.

[0023] The copolymer of the present invention may preferably have at least one of the following additional characteristics. - The X-ray crystallinity is 48% to 53% - The content of the fraction soluble in xylene at 0 °C is 8% by weight or less, more preferably 6% by weight or less, and in all cases the lower limit is 3.2% by weight, and said amount is based on the total weight of the copolymer.

[0024] The molecular weight distribution (MWD) of the copolymer of the present invention can generally be included in a wide range. However, in order to achieve an optimal balance between ease of processing in pipe preparation and final mechanical properties, when the MWD value measured by GPC analysis is represented by Mw / Mn (Mw is the weight average molecular weight and Mn is the number average molecular weight), it is preferably 4 or more, particularly 5 or more, 5.8 or more, 6 or more.

[0025] In any case, the upper limit of the value of Mw / Mn is preferably 9.

[0026] A value of Mw / Mn greater than 5 generally corresponds to a broad MWD.

[0027] The copolymer preferably has, alone or in combination with the value of Mw / Mn, an Mz value of 1,000,000 to 2,500,000 g / mol, where Mz is the z average molecular weight measured by GPC analysis.

[0028] The copolymer of the present invention preferably has an Mz / Mw value of 2 to 4.

[0029] Optionally, the ethylene polymer A) may have at least one of the following further additional features: - The flexural modulus measured in accordance with standard ISO 178:2019 for the compression plaque 30 days after molding is 200 to 300 MPa, more preferably 220 to 280 MPa - The Izod impact resistance at 23 °C measured in accordance with ISO 180:2000 for the compression plaque in accordance with ISO 8986-2:2009 30 days after molding is 30 to 65 kJ / m 2 Particularly 35 to 60 kJ / m 2 is - The Izod impact resistance at 0 °C measured in accordance with ISO 180:2000 for the compression plaque in accordance with ISO 8986-2:2009 30 days after molding is 20 to 50 kJ / m 2 Particularly 20 to 45 kJ / m 2 is - The elongation at break measured in accordance with ISO 527-1:2019 for the compression plaque is 250% to 350% 30 days after forming.

[0030] The copolymer of the present invention can be obtained by polymerizing butene-1 and hexene-1 (and any additional comonomers) using a Ziegler-Natta catalyst based on the low-pressure coordination polymerization of butene-1, in particular a titanium halogenated compound (in particular, TiCl4) supported on magnesium chloride and a cocatalyst (in particular an aluminum alkyl compound).

[0031] In particular, the copolymer of the present invention can be produced by polymerizing monomers in the presence of a stereospecific catalyst comprising (i) a solid component containing a titanium compound and an internal electron donor compound supported on MgCl2, (ii) an alkylaluminum compound, and (iii) an external electron donor compound.

[0032] As the carrier, magnesium dichloride in the active form is preferably used. As is well known from the patent literature, magnesium dichloride in the active form is particularly suitable as a carrier for Ziegler-Natta catalysts. In particular, USP 4,298,718 and USP 4,495,338 were the first to describe the use of these compounds in Ziegler-Natta catalysts. As can be seen from these patents, the magnesium dihalide in the active form used as a carrier or cocarrier in the catalyst component for polymerizing olefins is characterized by an X-ray spectrum, where the strongest diffraction line appearing in the spectrum of the inert halide is replaced by a halo with reduced intensity and the maximum intensity shifted to a lower angle relative to the maximum intensity of a stronger line.

[0033] The titanium compounds used in the catalyst component (i) are preferably TiCl4 and TiCl3, and it is also possible to use titanohaloalkoxides represented by the formula Ti(OR) n-y X y (wherein n is the valence of titanium, X is a halogen, preferably chlorine, and y is a number in the range of 1 to n).

[0034] The internal electron-donating compound is preferably selected from esters, more preferably from alkyl, cycloalkyl or aryl esters of monocarboxylic acids (such as benzoic acid) or polycarboxylic acids (such as phthalic acid, succinic acid, glutaric acid), where the alkyl, cycloalkyl or aryl has 1 to 18 carbon atoms. Examples of the electron-donating compound include diisobutyl phthalate, diethyl phthalate, dihexyl phthalate, diethyl 3,3-dimethylglutarate or diisobutyl. Usually, the molar ratio of the internal electron-donating compound to MgCl2 is 0.01 to 1, preferably 0.05 to 0.5.

[0035] The alkyl-Al compound (ii) is preferably selected from trialkylaluminum compounds such as triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, etc. A mixture of a trialkylaluminum compound and an alkylaluminum halide, alkylaluminum hydride or alkylaluminum sesquichloride such as AlEt2Cl and Al2Et3Cl3 may also be used.

[0036] The external electron-donating compound (iii) is R a 1 R b 2 Si(OR 3 ) c (wherein a and b are integers from 0 to 2, c is an integer from 1 to 3, (a + b + c) is 4, and R 1 , R 2 and R 3 are alkyl, cycloalkyl or aryl having 1 to 18 carbon atoms which may contain a heteroatom.). It is preferably selected from silicon compounds. A particularly preferred group of silicon compounds is where a is 0, c is 3, b is 1, R 2 is a branched alkyl or cycloalkyl which may contain a heteroatom, and R 3is methyl. Examples of such preferred silicon compounds include cyclohexyltrimethoxysilane, tert-butyltrimethoxysilane, diisopropyltrimethoxysilane, and hexyltrimethoxysilane. Particularly preferably, hexyltrimethoxysilane is used.

[0037] The amount of the electron-donating compound (iii) used is such that the molar ratio of the organoaluminum compound to the electron-donating compound (iii) is 0.1 to 500, preferably 1 to 300, more preferably 3 to 100.

[0038] In order to make the catalyst particularly suitable for the polymerization step, the catalyst can be prepolymerized in the prepolymerization step. The prepolymerization may be carried out in a liquid (slurry or solution) or in the gas phase, usually at a temperature of less than 100 °C, preferably 20 to 70 °C. The prepolymerization step is carried out with a small amount of monomer for the time required to obtain the polymer in an amount of 0.5 to 2000 g, preferably 5 to 500 g, more preferably 10 to 100 g per 1 g of the solid catalyst component.

[0039] The polymerization method can be carried out according to known techniques such as slurry polymerization using a liquid inert hydrocarbon as a diluent or solution polymerization using, for example, liquid butene-1 as a reaction medium. Further, the polymerization process may be carried out in the gas phase, and the operation is carried out in one or more fluidized bed or mechanically stirred bed reactors. The polymerization is very preferably carried out in liquid butene-1 as a reaction medium.

[0040] The preferred polymerization temperature is 20 to 120 °C, particularly 40 to 90 °C, especially when the polymerization is carried out in liquid butene-1.

[0041] To control the molecular weight, a molecular weight regulator, particularly hydrogen, is supplied to the polymerization environment.

[0042] Examples of the polymerization catalyst and method are disclosed in WO99 / 45043 and WO2004048424.

[0043] Copolymers having a broad MWD can be obtained in several ways. One way is to use a catalyst that can produce a substantially broad MWD copolymer when copolymerizing butene-1. Another possible way is to mechanically blend butene-1 polymers having sufficiently different molecular weights using a conventional mixing device.

[0044] Also, it is possible to operate according to a multi-stage polymerization method in which butene-1 polymers having different molecular weights are successively produced in two or more reactors with different reaction conditions such as the concentration of a molecular weight regulator supplied to each reactor.

[0045] It is clear that the copolymer of the present invention can also include additives commonly used in the art, such as stabilizers, antioxidants, preservatives, processing aids, nucleating agents, pigments, organic fillers, and inorganic fillers.

[0046] As described above, a preferred use of the copolymer of the present invention is in the production of pipes, particularly UHF pipes. Generally, it can be advantageously used in any application that requires improved thermal and mechanical properties.

[0047] Examples and advantages of the various embodiments, compositions, and methods provided herein are disclosed in the following examples. These examples are merely illustrative and are not intended to limit the scope of the invention in any way.

[0048] Copolymer monomer content

[0049] 13 Determined by 13C NMR.

[0050] 13 The 13C NMR spectrum was acquired on a Bruker AV-600 spectrometer equipped with a cryoprobe operating at 150.91 MHz in Fourier transform mode.

[0051] T ((The carbon peak (nomenclature of C. J. Carman, R. A. Harrington, and C. E. Wilkes, <Macromolecules>, 10, 3, 536 (1977)) is utilized at 37.24 ppm as an internal reference. The sample is dissolved in 1,1,2,2-tetrachloroethane-d2 at 120 °C at a concentration of 8% wt / v. Each spectrum is acquired with a 90° pulse, with a 15-second delay between pulses and 1 H- 13 C coupling removed. Using a spectral window of 9000 Hz, approximately 512 transients are stored in 32K data points.

[0052] The diad distribution is calculated from S((carbon (see Table 1) according to the following relationship. HH = A / Σ BH = B / Σ BB = C / Σ where (Σ = A + B + C

[0053] The total amount (mol%) of 1-butene and 1-hexene is calculated using the following relationship for the diad. [H] = (HH + 0.5 HB) * 100 [B] = (BB + 0.5 HB) * 100

[0054] Next, the molar composition is converted to a weight composition using the monomer molecular weights.

Table 1

[0055] Melting and crystallization temperatures by differential scanning calorimetry (DSC)

[0056] Differential scanning calorimetry (DSC) data were acquired using a Perkin Elmer DSC-7 instrument with a weighed sample (5 - 10 mg) encapsulated in an aluminum disk.

[0057] To determine the melting temperature of polybutene-1 crystalline form I (TmI), the sample was heated to 200 °C at a scanning rate equivalent to 10 °C / min, held at 200 °C for 5 minutes, and then cooled to 20 °C at a cooling rate of 10 °C / min. Thereafter, the sample was stored at room temperature for 10 days. After 10 days, the sample was subjected to DSC, cooled to -20 °C, and then heated to 200 °C at a scanning rate equivalent to 10 °C / min. In this heating operation, the highest temperature peak in the thermogram, i.e., the first peak temperature from the higher temperature side in the thermogram, was taken as the melting temperature (TmI).

[0058] Melting temperature and crystallization temperature T of polybutene-1 crystalline form II (TmII) c To determine them, the sample was heated to 200 °C at a scanning rate equivalent to 10 °C / min, held at 200 °C for 5 minutes to completely melt all the microcrystals and remove the thermal history of the sample. Subsequently, it was cooled to -20 °C at a scanning rate equivalent to 10 °C / min, and the peak temperature was taken as the crystallization temperature (T c ), and the area was taken as the crystallization enthalpy. After standing at -20 °C for 5 minutes, the sample was subjected to a second heating up to 200 °C at a scanning rate equivalent to 10 °C / min. In this second heating operation, the peak temperature was taken as the melting temperature (TmII) of polybutene-1 crystalline form II, and the area was taken as the melting enthalpy (ΔHfII).

[0059] Determination of X-ray crystallinity

[0060] The X-ray crystallinity was measured using an X-ray diffractometer for powder diffraction that collected spectra at 0.1° steps every 6 seconds between diffraction angles 2Θ = 5° and 2Θ = 35° using Cu-Kα1 radiation with a fixed slit.

[0061] The measurement was performed on disk-shaped compression-molded specimens approximately 1.5 to 2.5 mm thick and approximately 2.5 to 4.0 cm in diameter. These specimens were obtained by compression molding in a press at a temperature of 200 °C ± 5 °C for 10 minutes without applying any particular pressure, and then a pressure of about 10 kg / cm 2 was applied for about several seconds, and the last operation was repeated 3 times.

[0062] Using the diffraction pattern, an appropriate linear baseline was defined across the spectrum, and all the components necessary for crystallinity were derived by calculating the total area (Ta) (expressed in counts / second·2Θ) between the spectral profile and the baseline. Next, an appropriate amorphous profile that separates the amorphous region and the crystalline region according to a two-phase model was defined along the entire spectrum. Thus, the amorphous region (Aa) expressed in counts / second·2Θ may be calculated as the region between the amorphous profile and the baseline, and the crystalline region (Ca) expressed in counts / second·2Θ may be calculated as Ca = Ta - Aa.

[0063] Next, the crystallinity of the sample was calculated based on the following formula.

[0064] %Cr = 100×Ca / Ta

[0065] Fraction soluble and insoluble in xylene at 0 °C (XS-0 °C)

[0066] 2.5 g of the polymer sample was stirred at 135 °C and dissolved in 250 ml of xylene. After 30 minutes, the solution was cooled to 100 °C with stirring, then placed in an ice-water bath and cooled to 0 °C. Then, the solution was precipitated in the ice-water bath for 1 hour. The precipitate was filtered through filter paper. During filtration, the flask was placed in an ice-water bath to keep the temperature inside the flask as close to 0 °C as possible. After filtration, the filtrate temperature was maintained at 25 °C, and the volumetric flask was immersed in a water bath for about 30 minutes, and then 50 ml of the aliquot was divided into two. The solution aliquot was evaporated in a nitrogen gas stream and the residue was dried in vacuo at 80 °C until a constant weight was reached. The weight difference between the two residues must be less than 3%. Otherwise, the test needs to be repeated. Therefore, the weight percentage of the polymer soluble matter (xylene soluble matter at 0 °C = XS 0 °C) was calculated from the average weight of the residues. The insoluble fraction in o-xylene at 0 °C (xylene insoluble matter at 0 °C = XI%0 °C) is as follows.

[0067] XI%0 °C = 100 - XS%0 °C.

[0068] MIE

[0069] It was determined at 190 °C under a load of 2.16 kg in accordance with ISO 1133-2:2011.

[0070] Intrinsic viscosity

[0071] It was determined in tetralin at 135 °C in accordance with standard ASTM D 2857-16.

[0072] Determination of Mw, Mn and Mz by gel permeation chromatography (GPC)

[0073] Using a GPC-IR instrument from PolymerChar, the average values Mn, Mw, Mz and Mw / Mn derived therefrom were measured by gel permeation chromatography (GPC) in 1,2,4-trichlorobenzene (TCB). This instrument is equipped with a column set consisting of four PLgel Olexis mixed layers (Polymer Laboratories) and an IR5 infrared detector (PolymerChar). The column dimensions are 300×7.5 mm and the particle size is μm. The mobile phase flow rate is maintained at 1.0 mL / min. All measurements are carried out at 150 °C. The solution concentration is 2.0 mg / ml (150 °C), and 0.3 g / L of 2,6-dibutyl-p-cresol is added to prevent degradation. For GPC calculations, a universal calibration curve is obtained using 12 polystyrene (PS) standard samples (peak molecular weight range 266 - 1220000) provided by PolymerChar. Cubic polynomial fitting is used to interpolate the experimental data to obtain the corresponding calibration curve. Data collection and processing are performed using Empower 3 (Waters).

[0074] The Mark-Houwink relationship was used to determine the average molecular weight related to the molecular weight distribution. The respective K values for PS and polybutene (PB) are K PS = 1.21×10 -4 dL / g and K PB = 1.78×10 -4It is dL / g, and the Mark-Houwink exponent a = 0.706 for PS and a = 0.725 for PB are used.

[0075] Flexural modulus

[0076] It was determined by measuring the compression plaque 30 days after molding in accordance with standard ISO 178:2019.

[0077] Tensile stress and elongation at yield and at break

[0078] It was determined by measuring the compression plaque 30 days after molding in accordance with standard ISO 527-1:2019.

[0079] Izod impact resistance at 23 °C and 0 °C It was determined by measuring the compression plaque conforming to ISO 180:2000 in accordance with ISO 8986-2:2009 30 days after molding.

[0080] Polydispersity index

[0081] This property is closely related to the molecular weight distribution of the measured polymer. In particular, it is inversely proportional to the creep resistance of the polymer in the molten state. This resistance, called modulus separation at a low modulus value (500 Pa), was determined at a temperature of 200 °C using an RMS-800 type parallel plate rheometer sold by RHEOMETRICS (USA) operating at an oscillation frequency increased from 0.1 rad / s to 100 rad / s. From the modulus separation, P.I. can be derived by the following equation. P.I := 54.6 x (modulus separation) -1.76 The modulus separation is defined as follows. Modulus separation = frequency at G' = 500 Pa / frequency at G'' = 500 Pa Here, G' is the storage modulus and G'' is the loss modulus.

[0082] Example 1 and Example 2, and Comparative Example 1

[0083] Production of Solid Catalyst Component

[0084] At 0 °C, 225 ml of TiCl4 was introduced into a 500 ml four-necked round-bottom flask purged with nitrogen gas. While stirring, microspherical MgCl2 (prepared as described in Example 2 of USP 4,399,054 except that it operates at 3,000 rpm instead of 10,000 rpm) was added. The flask was heated to 40 °C, and 4.4 mmol of diisobutyl phthalate was added. After raising the temperature to 100 °C and holding for 2 hours, stirring was stopped to precipitate the solid, and the supernatant was siphoned off.

[0085] 200 ml of fresh TiCl4 was added and reacted at 120 °C for 1 hour. Then, the supernatant was siphoned off, and the obtained solid was washed 6 times with anhydrous hexane (6 × 100 ml) at 60 °C and then dried under vacuum. The catalyst component contains 2.8 wt% titanium and 12.3 wt% phthalate ester.

[0086] Polymerization

[0087] Polymerization was carried out continuously after a pre-contact step in two liquid-phase stirred reactors connected in series in which liquid butene-1 constitutes the liquid medium. In the pre-contact step, the solid catalyst component, the aluminalkyl compound triisobutylaluminum, and the external donor ethyltrimethoxysilane were pre-mixed in the relative amounts shown in Table 2. The catalyst system was injected into the first reactor, and polymerization was carried out under the conditions reported in Table 2.

[0088] After the first polymerization step, the contents of the first reactor were transferred to the second reactor, and polymerization was continued in the second reactor under the same conditions shown in Table 2. Polymerization was stopped by deactivating the catalyst and transferring the polymer substance in a devolatilization step.

[0089] A detailed description of this method is described in International Patent Application WO2004000895.

[0090] The results of characterizing the obtained copolymer are shown in Table 3.

Table 2

Table 3

Claims

1. A copolymer of butene-1 and hexene-1 having the following characteristics. 1) The content of hexene-1 comonomer units is 2 to 4% by weight. 2) The melting temperature TmI is 115°C or higher. 3) The value of Mw / Mn is 4 or higher, where Mw is the weight-average molecular weight measured by GPC analysis and Mn is the number-average molecular weight measured by GPC analysis.

2. The copolymer according to claim 1, wherein MIE is 0.1 to 10 g / 10 min, and MIE is the melt flow index measured at 190°C / 2.16 kg in accordance with ISO 1133-2:2011.

3. The copolymer according to claim 1 or 2, wherein the X-ray crystallinity is 48% to 53%.

4. The copolymer according to claim 1 or 2, wherein the crystallization temperature Tc measured by DSC at a scanning rate of 10°C / min is 68 to 75°C.

5. The copolymer according to claim 1 or 2, wherein the content of the fraction soluble in xylene at 0°C is 8% by weight or less based on the total weight of the copolymer.

6. The copolymer according to claim 1 or 2, wherein the Mz value is 1,000,000 to 2,500,000 g / mol, and Mz is the z-average molecular weight measured by GPC analysis.

7. The copolymer according to claim 1 or 2, wherein the Mz / Mw value is 2 to 4.

8. The copolymer according to claim 1 or 2, wherein the flexural modulus measured for a compression plaque in accordance with standard ISO 178:2019 30 days after molding is 200 to 300 MPa.

9. The Izod impact strength at 0 °C measured in accordance with standard ISO 180:2000 for compression plaques conforming to ISO 8986-2:2009, 30 days after molding, is 20 to 50 kJ / m ２ The copolymer according to claim 1 or 2, wherein the Izod impact strength is as defined above.

10. An article comprising the copolymer according to any one of claims 1 to 9.

11. The article according to claim 10, which is in the form of a pipe.

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