BIAXIALLY ORIENTED PIPE

Abstract

The disclosure relates to a biaxially oriented pipe made of a polymer composition comprising a propylene-based polymer, wherein the pipe is made by a process comprising the steps of: •a) forming the polymer composition having a melting temperature Tm (° C.) into a tube, •b) heating the tube such that the tube has a drawing temperature Td (° C.) and •c) stretching the tube of step a) in the axial direction and in the peripheral direction at Td to obtain the biaxially oriented pipe, wherein Td is equal to or higher than Tm, wherein •i) the propylene-based polymer comprises (A1) a heterophasic propylene copolymer, wherein the heterophasic propylene copolymer consists of (a1) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene copolymer consisting of at least 70 wt % of propylene monomer units and at most 30 wt % of ethylene and/or α-olefin monomer units, based on the total weight of the propylene-based matrix and (a2) a dispersed ethylene-α-olefin copolymer, wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100 wt %, wherein the amount of (a2) with respect to the propylene-based polymer is 2.0 to 30 wt % or ii) the propylene-based polymer comprises (B) a random copolymer of propylene and a comonomer which is ethylene and/or an α-olefin having 4 to 10 carbon atoms, wherein when the pipe has an outer diameter of less than 40 mm, the propylene-based polymer comprising (B) has a comonomer content of 0.1 to 3.8 wt % based on the propylene-based polymer.

Claims

1. A biaxially oriented pipe made of a polymer composition comprising a propylene-based polymer, wherein the pipe is made by a process comprising the steps of: a) forming the polymer composition having a melting temperature Tm (° C.) into a tube, b) heating the tube such that the tube has a drawing temperature Td (° C.) and c) stretching the tube of step a) in the axial direction and in the peripheral direction at Td to obtain the biaxially oriented pipe, wherein Td is equal to or higher than Tm, wherein i) the propylene-based polymer comprises (A1) a heterophasic propylene copolymer, wherein the heterophasic propylene copolymer consists of (a1) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene copolymer consisting of at least 70 wt % of propylene monomer units and at most 30 wt % of ethylene and/or α-olefin monomer units, based on the total weight of the propylene-based matrix and (a2) a dispersed ethylene-α-olefin copolymer, wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100 wt %, wherein the amount of (a2) with respect to the propylene-based polymer is 2.0 to 30 wt % or ii) the propylene-based polymer comprises (B) a random copolymer of propylene and a comonomer which is ethylene and/or an α-olefin having 4 to 10 carbon atoms, wherein when the pipe has an outer diameter of less than 40 mm, the propylene-based polymer comprising (B) has a comonomer content of 0.1 to 3.8 wt % based on the propylene-based polymer.

2. The pipe according to claim 1, wherein Td is higher than Tm.

3. The pipe according to claim 1, wherein Td≥Tm+0.1° C.

4. The pipe according to claim 1, wherein Td≤Tm+15.0° C., Td≤Tm+13.0° C., Td≤Tm+10.0° C., Td≤Tm+8.0° C. or Td≤Tm+5.0° C.

5. The pipe according to claim 1, wherein Tm+1.0° C.≤Td≤Tm+15.0° C.

6. The pipe according to claim 1, wherein Tm is 150 to 165° C. and Td is 150 to 170° C., wherein Tm≤Td≤Tm+15.0° C.

7. The pipe according to claim 1, wherein the pipe has a shrinkage of at most 2.0%, wherein shrinkage=(L1−L2)/L1×100, L2 is the length of the pipe after placing the pipe in a preheated air oven at 120° C. for 1 hour and cooling the pipe heated in the oven to room temperature, L1 is the length of the pipe before the heating at 120° C.

8. The pipe according to claim 1, wherein the pipe has a time to failure of at least 100 hours, preferably at least 400 hours, more preferably at least 1000 hours, according to ISO 1167-1 determined at a stress level of 20 MPa and a temperature of 20° C.

9. The pipe according to claim 1, wherein when the pipe has an outer diameter of less than 40 mm, the propylene-based polymer comprising (B) has a comonomer content of 0.1 to 3.4 wt % based on the propylene-based polymer.

10. The pipe according to claim 1, wherein the propylene-based polymer comprising (B) has a comonomer content of 0.1 to 3.8 wt % based on the propylene-based polymer when the pipe has an outer diameter of less than 40 mm and when the pipe has an outer diameter of at least 40 mm.

11. The pipe according to claim 1, wherein the polymer composition comprises the propylene-based polymer.

12. The pipe according to claim 10, wherein the propylene-based polymer has a Melt Flow Index of 0.1 to 10.0 g/10 min measured according to ISO1133-1:2011 at 230° C./2.16 kg.

13. The pipe according to claim 10, wherein the propylene-based polymer comprises (A1) the heterophasic propylene copolymer.

14. The pipe according to claim 12, wherein the amount of (a2) with respect to A) is 2.0 to 40 wt %.

15. The pipe according to claim 10, wherein ii) the propylene-based polymer comprises (B) the random copolymer.

Description

[0133] In some embodiments, (B1) consists of one type of the low comonomer random copolymer.

[0134] In some embodiments, (B1) consists of at least two types of the low comonomer random copolymer wherein the comonomer contents and/or the melt flow index measured according to ISO1133-1:2011 (230° C./2.16 kg) of the at least two types of the low comonomer random copolymer are different from each other. It will be appreciated that the comonomer content and the melt flow index of (B1) is determined by the weight ratio of the components in (B1).

[0135] In some embodiments, (B2) consists of one type of the high comonomer random copolymer.

[0136] In some embodiments, (B2) consists of at least two types of the high comonomer random copolymer wherein the comonomer contents and/or the melt flow index measured according to ISO1133-1:2011 (230° C./2.16 kg) of the at least two types of the high comonomer random copolymers are different from each other.

[0137] In some embodiments, (B3) consists of one type of the propylene homopolymer.

[0138] In some embodiments, (B3) consists of at least two types of the propylene homopolymer wherein the melt flow index measured according to ISO1133-1:2011 (230° C./2.16 kg) of the at least two types of the propylene homopolymer are different from each other.

[0139] In some preferred embodiments, the propylene-based polymer consists of (B1), wherein

[0140] (B1) consists of one type of the low comonomer random copolymer,

[0141] wherein the comonomer of the low comonomer random copolymer is ethylene and the propylene-based polymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0142] In some preferred embodiments, the propylene-based polymer consists of (B1), wherein (B1) consists of at least two types of the low comonomer random copolymer, wherein the comonomer of each of the at least two types of the low comonomer random copolymer is ethylene and

[0143] the propylene-based polymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0144] In some preferred embodiments, the propylene-based polymer consists of (B1) and (B2), wherein

[0145] (B1) consists of one type of the low comonomer random copolymer,

[0146] (B2) consists of one type of the high comonomer random copolymer the comonomer of the low comonomer random copolymer and the high comonomer random copolymer is ethylene, the low comonomer random copolymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg),

[0147] the high comonomer random copolymer has a melt flow index of 1.1 to 10.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg), the weight ratio of A) to B) is 1:10 to 10:1,

[0148] the propylene-based polymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0149] In some preferred embodiments, the propylene-based polymer consists of (B1) and (B3), wherein

[0150] (B1) consists of one type of the low comonomer random copolymer,

[0151] (B3) consists of one type of the propylene homopolymer,

[0152] the comonomer of the low comonomer random copolymer is ethylene, the low comonomer random copolymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg),

[0153] the propylene homopolymer has a melt flow index of 0.1 to 10.0 g/10 min, measured according to ISO1133-1:2011 (230° C./2.16 kg), the weight ratio of A) to C) is 1:10 to 10:1,

[0154] the propylene-based polymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0155] In some preferred embodiments, the propylene-based polymer consists of (B2) and (B3), wherein

[0156] (B2) consists of one type of the high comonomer random copolymer

[0157] (B3) consists of one type of the propylene homopolymer,

[0158] the comonomer of the high comonomer random copolymer is ethylene,

[0159] the high comonomer random copolymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg),

[0160] the propylene homopolymer has a melt flow index of 0.1 to 10.0 g/10 min, measured according to ISO1133-1:2011 (230° C./2.16 kg), the weight ratio of (B2) to (B3) is 1:10 to 10:1,

[0161] the propylene-based polymer has a melt flow index of 0.1 to 1.0 g/10 min measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0162] Polymer Composition Comprising Ethylene-Based Polymer

[0163] In some embodiments, the polymer composition comprises the ethylene-based polymer.

[0164] Preferably, the ethylene-based polymer has a Melt Flow Index of 0.1 to 10.0 g/10 min, preferably 0.1 to 4.0 g/10 min, more preferably 0.1 to 1.0 g/10 min, measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0165] Preferably, when the polymer composition comprises the ethylene-based polymer, the amount of the ethylene-based polymer with respect to the total amount of polymers in the polymer composition is at least 95 wt %, at least 98 wt %, at least 99 wt % or 100 wt %.

[0166] Preferably, the pipe made of the polymer composition comprising the ethylene-based polymer has a time to failure of at least 100 hours, preferably at least 400 hours, more preferably at least 1000 hours, according to ISO 1167-1 determined at a stress level of 20 MPa and a temperature of 20° C.

[0167] Additives

[0168] Preferably, the polymer composition comprising the propylene-based polymer or the ethylene-based polymer essentially comprises no further polymers other than said propylene-based polymer or ethylene-based polymer. The total amount of the propylene-based polymer and the ethylene-based polymer with respect to the total amount of polymers in the polymer composition may be at least 95 wt %, at least 98 wt %, at least 99 wt % or 100 wt %.

[0169] Preferably, the polymer composition has a Melt Flow Index of 0.1 to 10.0 g/10 min, preferably 0.1 to 4.0 g/10 min, more preferably 0.1 to 1.0 g/10 min, measured according to ISO1133-1:2011 (230° C./2.16 kg).

[0170] Preferably, when the polymer composition comprises the propylene-based polymer, the amount of the propylene-based polymer with respect to the total amount of polymers in the polymer composition is at least 95 wt %, at least 98 wt %, at least 99 wt % or 100 wt %.

[0171] The polymer composition may comprise components other than the propylene-based polymer and the ethylene-based polymer, such as additives and fillers.

[0172] Examples of the additives include nucleating agents; stabilisers, e.g. heat stabilisers, anti-oxidants, UV stabilizers; colorants, like pigments and dyes; clarifiers; surface tension modifiers; lubricants; flame-retardants; mould-release agents; flow improving agents; plasticizers; anti-static agents; external elastomeric impact modifiers; blowing agents; and/or components that enhance interfacial bonding between polymer and filler, such as a maleated polyethylene. The amount of the additives is typically 0 to 5 wt %, for example 1 to 3 wt %, with respect to the total composition.

[0173] Examples of fillers include glass fibers, talc, mica, nanoclay. The amount of fillers is typically 0 to 40 wt %, for example 5 to 30 wt % or 10 to 25 wt %, with respect to the total composition.

[0174] Accordingly, in some embodiments, the polymer composition further comprises 0 to 5 wt % of additives and 0 to 40 wt % of fillers.

[0175] The polymer composition may be obtained by melt-mixing the polyolefin with any other optional components.

[0176] Preferably, the total amount of the propylene-based polymer and the optional additives and the optional fillers is 100 wt % with respect to the total composition.

[0177] Preferably, the pipe has a time to failure of at least 100 hours, preferably at least 400 hours, more preferably at least 1000 hours, according to ISO 1167-1 determined at a stress level of 20 MPa and a temperature of 20° C.

[0178] Preferably, the pipe has a shrinkage of at most 2.0%,

wherein shrinkage=(L1−L2)/L1×100,

[0179] L2 is the length of the pipe after placing the pipe in a preheated air oven at 120° C. for 1 hour and cooling the pipe heated in the oven to room temperature,

[0180] L1 is the length of the pipe before the heating at 120° C.

[0181] It is noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

[0182] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product/composition comprising certain components also discloses a product/composition consisting of these components. The product/composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product/composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

[0183] When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0184] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0185] Materials:

[0186] rPP1: propylene-ethylene copolymer with comonomer content of 1.5 wt % and MFR 230° C./2.16 kg of 0.3 g/10 minutes. Tm=156° C.

[0187] IPC1: heterophasic propylene copolymer consisting of 91.0 wt % of propylene homopolymer (MFI 230° C./2.16 kg of 0.43 dg/min) and 9.0 wt % of ethylene-propylene copolymer, wherein the amount of ethylene derived units in the ethylene-propylene copolymer is 58 wt %, MFI 230° C./2.16 kg of 0.3 dg/min. Tm=163° C.

[0188] Production of Biaxially Oriented Pipe:

[0189] rPP1 or IPC1 was made into granules using a twin screw extruder. Processing temperature and screw profile were of standard polypropylene compounding. Standard additives for a propylene based pipe were added in making the granules.

[0190] These compounded granules were used to produce thick tubular profiles of approximate dimensions of an outer diameter of about 32 mm and an inner diameter of about 16 mm. These thick tubes were drawn over an expanding conical mandrel of exit diameter of 32 mm and semi angle 15 degree at temperature as shown in table 1. Tubes were drawn very uniformly in thickness and could be drawn to low axial draw ratios.

[0191] These thick tubes were drawn over an expanding conical mandrel of exit diameter of 61-65 mm and semi angle 15 degree at temperature shown in table 1 at a draw speed of 100 mm/min. Axial draw ratio was 3 and the average hoop draw ratio was 1.3.

[0192] The draw stress, shrinkage at 120° C. and yield stress in hoop direction were measured and shown in Table 1.

[0193] Draw force was measured by a load cell attached to the haul-off device, which pulls the biaxially oriented pipe over the mandrel. Draw stress was calculated by dividing the drawing force by the cross-sectional area of the biaxially drawn pipe.

[0194] Biaxially oriented pipes of 1 m lengths drawn at different temperatures were placed in a preheated air oven at 120° C. for an hour. After one hour these pipes were taken out and cooled down to room temperature of around 20° C. Shrinkage percentage were determined by measuring the change in length of pipes before and after heating.

[0195] Hoop yield strength of pipes were measured using the split disk method according to ASTM D2290.

TABLE-US-00001 TABLE 1 Draw Yield stress in PP (Tm stress Shrinkage hoop direction in ° C.) Td (MPa) (%) (MPa) CEx 1 rPP1 (156) 150 4.5 7.6 32 CEx 2 rPP1 (156) 155 3.5 4.0 34 Ex 3 rPP1 (156) 160 1.3 1.5 37.5 CEx 4 IPC1 (163) 150 7.6 7.9 28.7 CEx 5 IPC1 (163) 160 5.3 4.0 29.8 CEx 6 IPC1 (163) 165 3.3 2.5 — Ex 7 IPC1 (163) 170 1.9 0.9 32.1

[0196] It can be understood that drawing at a temperature higher than the melting temperature requires a lower draw stress for biaxial drawing and results in a lower shrinkage an a higher yield stress of the produced pipe.