阅读说明：本技术 聚烯烃压力管树脂 (Polyolefin pressure pipe resin ) 是由 S·D·梅塔 N·N·迪奥 于 2020-05-12 设计创作，主要内容包括：描述了具有改善的长期流体静力强度,由双峰高分子量高密度聚乙烯制成的下一代管树脂的组合物和方法。(Compositions and methods of next generation pipe resins made from bimodal high molecular weight high density polyethylene having improved long term hydrostatic strength are described.)

1. A high strength resin comprising:

a. a bimodal, high molecular weight, high density polyethylene base polymer having a density of 0.947g/cm³And 0.952g/cm³And are prepared from

b. Color masterbatch comprising a carrier resin and carbon black, said color masterbatch having a density of 1.1g/cm³And 1.4g/cm³Wherein the carbon black has a particle size range of less than 55 nm;

wherein the high strength resin has a Minimum Required Strength (MRS) of at least 11.2 MPa.

2. The high strength resin of claim 1 wherein the color masterbatch is 55-65 weight percent carrier resin and 35-45 weight percent carbon black.

3. The high strength resin of claim 1 wherein the carrier resin is polyethylene or high density polyethylene.

4. The high strength resin of claim 1, wherein the base polymer has a density of 0.9490g/cm³And 0.9520g/cm³In the meantime.

5. The high strength resin of claim 1 wherein the final concentration of the color masterbatch in the high strength resin is 4.5-6.5 wt%.

6. The high strength resin of claim 1, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.19g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

7. The high strength resin of claim 1, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.12g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

8. A method, comprising:

a. in the presence of a masterbatch comprising a carrier resin and carbon black, the density is adjusted to 0.947g/cm³And 0.952g/cm³Extruding bimodal, high molecular weight, high density polyethylene base polymer, the density of the color masterbatch being 1.1g/cm³And 1.4g/cm³Wherein the carbon black has a particle size range of less than 55 nm;

b. pressure pipes with a Minimum Required Strength (MRS) of 11.2MPa were formed.

9. The process of claim 8 wherein the color masterbatch is 55-65% by weight of the carrier resin and 35-45% by weight of the carbon black.

10. The method of claim 8, wherein the base polymer has a density of about 0.949g/cm³。

11. The method of claim 8, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.19g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

12. The method of claim 8, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.12g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

13. A pressure pipe having a Minimum Required Strength (MRS) of 11.2MPa prepared by a process comprising:

a. in the presence of a masterbatch comprising a carrier resin and carbon black, the density is adjusted to 0.947g/cm³And 0.952g/cm³Extruding bimodal, high molecular weight, high density polyethylene base polymer, the density of the color masterbatch being 1.1g/cm³And 1.4g/cm³Wherein the carbon black has a particle size range of less than 55 nm; and

b. forming a pressure tube.

14. The process of claim 13, wherein the color masterbatch is 55-65% of a carrier resin and 35-45% of carbon black.

15. The method of claim 13, wherein the base polymer has a density of about 0.949g/cm³。

16. The method of claim 13, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.19g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

17. The method of claim 13, wherein the base polymer has a density of 0.949g/cm³The density of the color master batch is 1.12g/cm³The carbon black has a particle size of less than 25nm and the color masterbatch has a carbon loading of 40%.

Technical Field

The present disclosure relates to polyolefin pipes, and more particularly to bimodal polyethylene resins and color concentrates for improving the strength, processability and production of high performance pipes.

Background

Polyolefins have often been used in commercial plastic applications due to excellent performance and cost characteristics. These polymers can be amorphous or highly crystalline, and their properties can be like thermoplastics, thermoplastic elastomers, or thermosets. Thus, by appropriate selection of its molecular structure and molecular weight distribution, polyolefins are readily designed and modified for selected applications to achieve an appropriate balance of Slow Crack Growth Resistance (SCGR), impact strength, and processability during extrusion. Accordingly, polyolefins are widely used in a variety of products, including grocery bags, containers, food storage, toys, adhesives, household appliances, engineering plastics, automotive parts, medical devices including prosthetic implants, and medical applications.

Polyethylene (PE) has become one of the most widely used and recognized polyolefins. The polyethylene composition may comprise low molecular weight, high molecular weight, and ultra-high molecular weight polymer chains, or a combination of relatively higher and lower molecular weight components, to create a multimodal Molecular Weight Distribution (MWD). In addition, the density of the polyethylene or the amount of branching in the monomer can be controlled to expand the utility of PE in various commercial and consumer applications.

Polyethylene is generally highly industrialized for demanding applications because it is strong, extremely hard, and very durable. For example, multimodal High Density Polyethylene (HDPE) has found use in high performance pressure pipe applications due to its chemical and physical elasticity, e.g., its impact strength, slow crack growth resistance, sag resistance, and its ability to withstand thermal extremes. The strength of the final tube is determined by balancing three key properties: minimum Required Strength (MRS), slow crack growth resistance, and fast crack propagation resistance. This results in a lighter weight and longer length pipe, which saves considerable labor and equipment when installing HDPE pipes.

Despite advances in modifying HDPE for high performance applications, there remains a need to develop PE resins with enhanced strength and stress crack resistance to extend the long term durability and reduce the cost of pipes made therefrom. What is needed in the art, therefore, is a method to improve the physical properties of HDPE resins for use in pipe applications (especially thick wall pipes) without increasing production costs, sacrificing pipe weight, or durability.

Disclosure of Invention

The present disclosure provides a novel pressure pipe resin comprising High Density Polyethylene (HDPE), wherein the pipe has improved physical properties compared to contemporary high density polyethylene pipes. Specifically, one or more variables of the high density polyethylene base polymer and/or color masterbatch of the pipe resin are optimized to improve strength and performance to create next generation pressure pipes. This optimization increases the Minimum Required Strength (MRS) and creep performance of the resulting pipe.

In more detail, the present disclosure is a newly formulated base polymer and/or carbon black masterbatch for use in PE100 pipe to create a new generation of pipe resin that is stronger, lighter weight, and easier to process to form PE112 rated pipe. Any combination of the following may be made to improve the physical properties and performance of the resin:

the density and/or molecular weight of the base polymer is varied to be used with the same color masterbatch as in contemporary pressure pipes. The density, molecular weight, or both of the base polymer may be increased to achieve PE112 identification.

The density and/or molecular weight of the carrier resin in the color masterbatch is varied without changing the carbon black characteristics for use with the same base polymer in contemporary pressure pipes. As with the base polymer above, the density, molecular weight, or both of the carrier resin may be increased to achieve PE112 labeling.

Once modified, the base polymer and color masterbatch can be mixed to form a resin that can be extruded as a next generation tube.

Embodiments and methods disclosed herein include any one or more of the following in combination:

a high strength resin with MRS of at least 11.2MPa comprising a bimodal, high molecular weight, high density polyethylene base polymer having a density of 0.947g/cm and a color masterbatch³And 0.952g/cm³The color masterbatch comprises a carrier resin and carbon black. The density of the color master batch is 1.1g/cm³And 1.4g/cm³And the particle size range of the carbon black is less than 55 nm.

A method of forming a pressure pipe having 11.2MPa of MRS comprising including a carrierIn the presence of color master batch of resin and carbon black, the density is adjusted to be 0.947g/cm³And 0.952g/cm³Bimodal, high molecular weight, high density polyethylene base polymer extrusion. The density of the color master batch is 1.1g/cm³And 1.4g/cm³And the particle size range of the carbon black is less than 55 nm.

A pressure pipe having 11.2MPa of MRS prepared by a process comprising bringing the density to 0.947g/cm in the presence of a masterbatch comprising a carrier resin and carbon black³And 0.952g/cm³In between, extruding and forming a pressure tube from a bimodal, high molecular weight, high density polyethylene base polymer, wherein the masterbatch has a density of 1.1g/cm³And 1.4g/cm³And the particle size range of the carbon black is less than 55 nm.

In any of the above embodiments, wherein the base polymer has a density of 0.9490g/cm³And 0.9520g/cm³In the meantime.

Any of the above embodiments, wherein the color masterbatch is 55 to 65 weight percent carrier resin and 35 to 45 weight percent carbon black. Any of the above embodiments, wherein the final concentration of the color masterbatch in the high strength resin is 4.5 to 6.5 weight percent.

In one embodiment thereof, the present invention provides a pipe resin comprising a bimodal, high molecular weight HDPE extruded with a color masterbatch having a carbon black loading of 35 to 45 weight percent and a high density polymeric carrier resin, the final pipe resin having 4.5 to 6.5 weight percent of the color masterbatch (about 2.5 to 4.2 weight percent of the carrier resin) and 93.5 to 95 weight percent of the bimodal, high molecular weight HDPE. The masterbatch improves the properties of pipes made with the same bimodal high molecular weight HDPE to obtain the pipe identification of PE 112.

In another embodiment thereof, the present invention provides a pipe resin comprising a bimodal high molecular weight HDPE extruded with a color masterbatch having a 40% carbon black loading using carbon particles less than 25nm and a masterbatch density of about 1.19g/cm³The lower predicted limit of the tube is 11.24MPa with a MRS of 11.2MPa on the ISO9080 creep rupture curve at 20 ℃ and 50 years.

In one embodiment thereof, the present invention provides a pipe resin comprising a bimodal high molecular weight high density polyethylene mixed with a color masterbatch comprising 35 to 45 weight percent carbon black such that the color masterbatch comprises 5 to 6.5 weight percent of the final resin. The resin may then be extruded into a pipe having a minimum required strength of 11.2MPa and/or a long term hydrostatic strength between 11.2MPa and 12.5MPa based on the ISO9080 creep rupture curve.

In another embodiment thereof, the present invention provides a pipe resin comprising a bimodal high molecular weight high density polyethylene extruded with a color masterbatch having a 40% carbon black loading using carbon particles less than 25nm and a masterbatch density of about 1.12g/cm³The lower predicted limit of the tube is 11.30MPa at 20 ℃ and 50 years of the ISO9080 creep rupture curve, which has an MRS of 11.2 MPa.

Any of the above embodiments also include extruding the resin as a pressure tube having a uniform thickness of about 0.05 inches (0.13cm) to 4 inches (10.2cm) or more, an outer diameter ranging from about 1 inch (2.54 cm) to about 8 feet (2.43 meters) or more, and identified as PE112 without changing the extrusion process.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to be used as an aid in limiting the scope of the claimed subject matter.

Further, various ranges and/or numerical limitations may be expressly stated throughout the disclosure and the detailed description. It should be understood that the endpoints are interchangeable unless otherwise indicated. Any range includes iterative ranges of similar magnitude falling within the explicitly stated ranges or limits.

Drawings

Figure 1 shows the hoop stress testing of one embodiment of the resin of the present disclosure (example 1) at 20 ℃, 60 ℃ and 80 ℃. The LPL value at 50 hours on the 20 ℃ regression line (circumferential direction) was 11.24 MPa.

Figure 2 shows the hoop stress testing of one embodiment of the resin of the present disclosure (example 2) at 20 ℃, 60 ℃ and 80 ℃. The LPL value at 50 hours on the 20 ℃ regression line (circumferential direction) was 11.30 MPa.

Definition and testing method

A "material designation code" is used to identify the resin and tube as discussed herein. High performance HDPE resins are identified by material identification codes based on pressure test procedures from ASTM or international organization for standardization (ISO). The final tube may have a different identity from the resin and is tested separately. The disclosed method is directed to forming a pipe having a PE112 identification.

Two pressure rating methods for HDPE pipes are ASTM D2837 and ISO 9080. The ASTM pressure rating method was tested using pipe samples at constant temperature extrapolated to 100,000 hours (11 years) using a linear logarithmic stress-logarithmic time regression line, while ISO was tested using pipe samples at three different temperatures extrapolated to 480,000 hours (50 years) using a linear logarithmic stress-logarithmic time 20 ℃ regression line. However, both standard test methods are widely accepted in the industry. Unless otherwise specified, for the pipe samples made with the resins disclosed herein, ISO 9080: the 2012 protocol tests the performance.

The ISO designation (e.g., PE100 or PE112) informs the user of the pipe material and the long-term performance or life of the pipe based on creep rupture data and curve prediction to determine the allowable hoop stress (circumferential stress) that the pipe can withstand without failure. This is called long term hydrostatic strength (LTH). The lower confidence level of the extrapolated value in the ISO9080 test is referred to as the lower predictive limit of long-term hydrostatic strength (LPL), and the classification value of LPL is referred to as the Minimum Required Strength (MRS). For a given set of end-use conditions, MRS simply refers to the long-term hydrostatic strength of the classification made in the circumferential or hoop direction.

Thus, "ISO designation" is the name of the polymer (referred to herein as PE), MRS × 10. Thus, a polyethylene resin having an LPL falling between 11.2MPa and 12.5MPa on the creep rupture curve (11.2. ltoreq. sigma.)_LPL< 12.5) has a classification value of 11.2 and an MRS rating of 11.2, with PE112 identification.

According to ISO9080 using a 32mm outside diameter inch pipe sample with a standard dimension ratio (SDR ═ outside diameter/minimum wall thickness) ═ 11: 2012 method, assay systemLPL and subsequent MRS rating of the prepared exemplary pipes. The tube sample was sealed with a predetermined internal pressure and immersed in a water bath at a specific temperature. The target designation for the resins and pipes disclosed herein is PE112, which has an LPL value of 11.2 ≦ σ at 20 ℃ and 50 years_LPL＜12.5MPa。

The term "color masterbatch" as used herein refers to a solid or liquid additive to a plastic resin used to impart other properties to the resin. Color concentrates include additives such as carbon black, encapsulated in a carrier resin during heating, which is then cooled and cut into granular or pellet shapes. Since the color concentrates are already pre-mixed compositions, their use alleviates the problem of caking or inadequate dispersion of the additive.

The addition of the carbon black masterbatch to the base polymer in the disclosed composition can be carried out by tumble mixing the pellets of the components (base resin and carbon black masterbatch) such that the final resin color masterbatch concentration is 4.5-6.5 wt%, and then adding the components to the feed hopper of the tube extruder. Alternatively, the carbon black masterbatch can be added to the base polymer while the composition is being extruded such that the carbon black is uniformly distributed throughout the resin. In another alternative, the carbon black masterbatch may be added directly to the base resin during granulation of the base polymer.

As used herein, the term "improved processability" may mean that extrudability (as measured by extruder head pressure and AMPS, or shear viscosity) is improved or remains the same as compared to a similar unmodified resin and/or PE100 rating tree.

Another property used to distinguish the current generation resin from the next generation resin prepared by the process described herein may be the molecular weight of the extruded bimodal high molecular weight high density polyethylene, measured as High Load Melt Index (HLMI). The HLMI of the extruded HDPE can be in the range of about 5dg/min to about 15dg/min, or in the range of about 6dg/min to about 10dg/min, or in the range of about 6dg/min to about 8.5dg/min, or in the range of about 6dg/min to about 8 dg/min.

All concentrations herein are in weight percent ("wt%") unless otherwise indicated.

The use of the words "a" or "an" when used in conjunction with the term "comprising" in the claims or the specification means one or more unless the context dictates otherwise.

The term "about" means that the value is plus or minus a margin of measurement error, if no method of measurement is specified, plus or minus 10%.

The term "or" as used in the claims means "and/or" unless explicitly indicated to refer to only one option or to both options as being mutually exclusive.

The terms "comprising", "having", "including" and "containing" (and variants thereof) are open-ended linking verbs and allow the addition of other elements when used in the claims.

The phrase "consisting of" is closed and excludes all additional elements.

The phrase "consisting essentially of" does not include additional material elements, but allows for the inclusion of non-material elements that do not substantially alter the nature of the disclosed compositions and/or methods.

The term "effective" as used in the specification and/or claims means a result sufficient to achieve a desired, expected, or objective result.

The above definitions supersede any conflicting definition in any reference cited herein. However, the fact that certain terms are defined should not be taken as an indication that any undefined terms are undefined. Rather, all terms used are to be considered as descriptive terms for the appended claims so as to be understood by those of ordinary skill.

The following abbreviations are used herein:

Detailed Description

Illustrative embodiments of the subject matter claimed below will now be disclosed. In the interest of clarity, not all functions implemented in practice are described in this specification. Various combinations may be made within the scope of the disclosure herein, and embodiments of the compositions and/or methods may include combinations of features other than those expressly claimed.

The present disclosure provides pipe resin compositions having improved physical properties compared to other high density polyethylene pipe resins (e.g., contemporary PE100 rated pipes). The extruded resin can be used to form the following tubes: MRS rating 11.2 MPa; or based on ISO 9080: 2012 creep rupture curve with lower prediction limit between 11.2MPa and 12.5MPa at 20 ℃ and 50 years; or with PE112 identification. Furthermore, the extruded resin can be used to make pipes about 10% lower than the thickness of an equivalent PE100 for a given nominal pressure.

The modern HDPE pressure pipe resin combines high molecular weight HDPE basic polymer and carbon black master batch. The resulting pipe has the ISO material identification code of PE100, which means that the pipe consists of PE and has a Minimum Required Strength (MRS) rating of 10.0MPa, i.e. its Lower Predicted Limit (LPL) at 20 ℃ and 50 years is between 10MPa and 11.2MPa, based on the ISO9080 creep rupture curve. The resin tends to create flexible, non-corrosive pipes with a service life of up to 100 years. However, improvements are always needed to create stronger and longer lasting tubes.

The pipe resins disclosed herein comprise a bimodal, high molecular weight, high density polyethylene as the base polymer and a carbon black loaded high density polyethylene color masterbatch. One or both of these components have been optimized to increase the MRS rating of the resulting pipe to PE112 and to improve other performance of the pressure pipe while allowing the user to lighten its pipe weight. The PE112 pipe designation implies an MRS rating of 11.2MPa and an LPL of between 11.2MPa and 12.5 MPa.

The method disclosed by the invention modifies the base polymer and/or the carbon black master batch used in the PE100 pipe so as to change the density and/or the molecular weight of the base polymer without changing the master batch used in the modern pressure pipe; or by changing the density and/or molecular weight of the carrier resin in the color masterbatch while remaining the same as the carbon black and base polymer used in contemporary pressure pipes. Any combination of these variations to the base polymer or carrier resin may also result in a resin capable of producing the desired PE112 pipe.

The color masterbatch can be modified instead of the base polymer to create a new generation of pipe, as this allows the user to make pressure pipes with "standard" properties as well as the next generation of pipes without the need to develop a new reactor grade of base polymer.

Base polymer: as noted above, the base polymer used in the pipe resins disclosed herein is a bimodal high molecular weight high density polyethylene. Bimodal polymers are resins based on a combination of two polymers, a high molecular weight polymer and a low molecular weight polymer. Polyethylene (PE) resin compositions, consisting of relatively higher and lower molecular weight components, have a bimodal Molecular Weight Distribution (MWD) and have been disclosed for pipe applications. Such resins produced using various tandem polymerization processes have an acceptable balance of strength, stiffness, stress crack resistance and processability as a result of the contributions of different molecular weight PE species.

The density of the base bimodal high molecular weight HDPE used in the practice of this disclosure is 0.942g/cm³And 0.956g/cm³(at 23 ℃) or at 0.947g/cm³And 0.952g/cm³(at 23 ℃) or 0.949g/cm³(at 23 ℃). The bimodal HDPE base polymer may have a PE3608 or PE4710 pipe material designation as standard for plastic pipe research. The bimodal HDPE base may also have an HLMI (190 ℃/21.6kg) of between about 6.0g/min and 4.0 g/min.

Bimodal high molecular weight HDPE base polymers can also be prepared as described in U.S. patent No. 9,249,286, the disclosure of which is incorporated herein by reference for all purposes. Alternatively, commercially available from Lyondellbasell (houston, TX) may be usedThe product is used as a base polymer. These products have a density in the range of about0.947-0.9520g/cm³。L4904 can be used in the present compositions.L4904 has a melt index (190 deg.C/2.16 kg) of about 0.04g/10min, an HLMI (190 deg.C/21.6 kg) of about 7.0g/min, and a density of about 0.949g/cm³(23 ℃), a flexural modulus of about 146,000psi (1007 MPa; 2% secant), a tensile stress at break of about 5100psi, a tensile stress at yield of about 3500psi, and a tensile elongation at break of about 800%. In contrast to a standard rating,l4904 exhibits improved melt strength and slow crack growth resistance. In addition to this, the present invention is,l4904 has been used in PE100 rating pipes and can be combined with the color masterbatch described herein to produce a resin with a PE112 rating without changing reactor variables.

Color master batch: the carbon black masterbatch in the disclosed pipe resin has a nominal carbon black loading of about 35-45% by weight, with the remaining 55-65% of the component being a polymeric carrier resin. Ideally, the final pipe resin is 5-6.5 weight percent color masterbatch (with a carrier resin of about 2.5-4.2%) and 93.5-95 weight percent base polymer. Thus, the carrier resin in the color base particles can be selected to match the base polymer of the pipe. Alternatively, the carrier resin does not match the base polymer, but still blends well with the bimodal HDPE. Desirably, the carrier resin is HDPE, linear low density polyethylene or medium density polyethylene. Alternatively, the carrier resin may be a high density polyethylene having a high molecular weight.

The resin of the present invention may comprise a masterbatch having a density at least 1% higher than the density of the masterbatch used in the PE100 rating pipe. Alternatively, the density may be at least 1.5% higher or 2% higher than the color masterbatch used in the PE100 rating pipe resin.

Any carbon black may be used in the color masterbatch. In one aspect, the carbon black particles can be "p-type," which is a specialty black with stringent product specifications to meet the stringent performance requirements of critical applications requiring exceptional purity. The graded carbon black has a particle size of 20-25nm, excellent Ultraviolet (UV) weathering and low Composite Moisture Absorption (CMA), with very low sulfur, ash and grit, ensuring optimum performance in pressure-regulated pipes. It is also widely approved for food contact and drinking water applications. Other types of carbon black particles, such as RCF and HAF, may also be used in the color concentrates described herein.

In one aspect, the carbon black particles are less than 55nm in size. Alternatively, they may be between 10nm and 30 nm. In another alternative, the carbon black is less than 25 nm.

While any number of the above variables can be modified to produce improved pressure pipes, optimization of the color masterbatch variables is preferred because it allows the user to prepare pressure pipes with "standard" properties or PE100 designation, as well as the next generation of pressure pipes with improved properties, without the need to develop new reactor grades of the base polymer.

Examples

The following examples are included to demonstrate embodiments of the appended claims. It will be appreciated by those of skill in the art that various changes can be made in the specific embodiments disclosed without departing from the spirit and scope of the disclosure. The following examples should not be read to limit or define the scope of the appended claims in any way.

The base polymer and color masterbatch in the following examples were tumble mixed so that the final resin had a color masterbatch concentration of 4.5% to 6.5%. The resin was then added to the feed hopper of a tube extruder and extruded into tube samples, nominal dimensions 32 x 3mm, for further characterization.

Example 1

By mixing a commercially available bimodal high molecular weight HDPE base polymer: (L4904; LyondellBasell, houston, TX) with a commercial masterbatch with 40% carbon black loading (r: (r) ((r))HD 277; cabot corp., Boston, MA) were mixed to create example 1. The amount of color masterbatch in example 1 was 5.90 wt%, the remainder 94.1 wt% being base polymer.

This base polymer was chosen because it has been used in contemporary PE100 pipe and its use in this disclosure would not require the creation of new reactor grades. L4904 has a tensile strength of about 3500psi at yield, an elongation at break of > 700%, a flexural modulus of 146,000psi (2% secant, 16: 1 span: depth, 0.5 inch/min), and PENT slow crack growth of > 500 hours, all of which make L4904 an ideal polymer for pressure pipes.

The selected master batch uses HDPE carrier resin, so that the HDPE carrier resin is well mixed with polyethylene-based pipe resin, and the density of the master batch is 1.19g/cm³HLMI is 40g/10min (at 21.6kg/190 ℃). The size of carbon particles in the selected color master batch is less than 25 nm. The density of the masterbatch carrier resin is higher than the medium density masterbatch used in the PE100 rating resin.

Multiple tube samples from the example 1 resin were extruded through a die for further testing.

First, the reaction according to ISO 1167 was carried out on example 1 tube samples: hydrostatic test of 2006. The method uses deionized water on the inside and outside of the tube samples to test their response to pressure, including resistance to internal pressure at constant temperatures of 20 ℃, 60 ℃ and 80 ℃. The accuracy of temperature and pressure were maintained at. + -. 1 ℃ and + 2/-1%, respectively. The wall thickness measurements were accurate to within 0.01mm and the diameter was accurate to within 0.1 mm. No unusual behavior was observed during hydrostatic testing of the sample of example 1, nor was problematic failure found.

Next, according to ISO 9080: 2012 were subjected to a series of hoop stress tests to determine the strength and long term behavior of example 1. ISO9080 is used for long-term prediction of the properties of pipe resins. This test measures the ability of a pipe sample to withstand various hoop stresses without fracturing at different temperatures and lengths of time. Regression is then applied to the data to infer an estimate of the amount of stress that can be sustained in the future. Although the tests were performed under the ISO9080 protocol for a number of temperatures and times, a 50 year test at 20 ℃ was used to determine the rating or identity of the pipe.

The results of the hoop tests at 20 ℃, 60 ℃ and 80 ℃ are shown in FIG. 1, along with standard extrapolated regression plots of LTH and LPL. Regression equations and constants are in ISO 9080: 2012 and need not be repeated here.

Fig. 1 shows the stress results for the On test (open data points) and the ductile failure (solid points) at each temperature. Only the data points used in the regression are shown. Using Pipeson (Sweden)The software performs multiple linear regression analysis of LPL and LTH. The regression method allows prediction of service life at a given stress and temperature, and specifies minimum required strength ratings for PE resins of 50 years and 20 ℃.

Since the LPL value at 20 ℃ and 50 years (black circles) was 11.24MPa, the sample of example 1 was determined to have an MRS rating of 11.2 MPa. Thus, according to ISO 12162: 2009, the resin is identified as PE 112.

Table 1 shows the LTHS extrapolated intensity values and estimated LPLs of example 1 at selected times of three temperatures, with the MRS rated LPLs shown in bold.

Table 1: extrapolated intensity values of example 1

From example 1, it was determined that PE112 rated pressure pipe may use the same base polymer as lower strength rated pipes (e.g., PE80 and PE 100). This may save time and cost, i.e. tubes of different intensity ratings may be created without changing the reactor grade. Instead, color masterbatch or other additives may be added during extrusion to quickly lift the resin into the PE112 tube leaving downstream machinery unaffected.

Example 2

To confirm whether the same base polymer of PE100 pipe could be used to create PE112 pipe, the same bimodal high molecular weight HDPE of example 1 (r), (b), (c), (d) and (d) in a) and (d) were combinedL4904) with different color masterbatches (PECB 4025A; beijing beihuagaokou new technologies, ltd). The amount of color masterbatch in example 2 was 5.70 wt%, the remainder 94.3 wt% being base polymer.

The color masterbatch selected in example 2 had a nominal carbon black loading of 40% and the size of the carbon particles was less than 25 nm.

The masterbatch also uses a HDPE carrier resin so it will be well mixed with the L4904 base polymer. The second selected color masterbatch had a density of 1.12g/cm³The HLMI value was 60g/10min (at 21.6kg/190 ℃). Thus, this masterbatch would increase the ability to extrude example 2 while retaining the ability to form higher strength PE112 pipe.

This masterbatch was also chosen because it was specifically designed for use in making black PE80 and PE100 pipe compounds. However, it is believed that the higher density of the carrier resin will allow the creation of PE112 pipe using a bimodal high molecular weight HDPE such as L4904.

Multiple tube samples of the resulting example 2 resin were extruded and tested according to ISO 1167: 2006 and ISO 9080: 2012 further pressure and strength tests.

The results of the hoop tests at 20 ℃, 60 ℃ and 80 ℃ are shown in fig. 2, along with the standard regression of the LTH and LPL estimates. Example 2 was also determined to have an MRS rating of 11.2MPa by virtue of its LPL value of 11.30MPa at 20 ℃ and 50 years (black circles). It can also be according to ISO 12162: 2009 is identified as PE 112.

Table 2 shows the extrapolated intensity values and estimated LPL for the LTHS of example 2 at selected times at three temperatures. For comparison, applicants note that the LPL of example 2 at 20 ℃ decreases at a slower rate than that of example 1. Over 100,000h, example 1 dropped to 11.464MPa, while example 2 was 11.504 MPa.

The above examples show that a standard PE100 base polymer can be used to create stronger improved pipe resins by varying the density and molecular weight of the color masterbatch. A series of color concentrates with these combinations can be developed for the L4904 base polymer. The color concentrate and the properties of the carbon particles in the color concentrate can be tailored to obtain an improved resin having a PE112 rating.

In addition, increasing the molecular weight and density of the base polymer also increased the strength rating of the pipe resin to PE 112. Although there are considerations in creating a new base polymer, i.e., the reactor must be changed to switch to a new polymer, with a slightly higher density (L4904 is 0.949 g/cm)³The bimodal HDPE was 0.952g/cm³) Or slightly lower HLMI (7 g/min to 6g/min at 190 ℃/21.6kg) also allows for improved pipe resin identification. These base polymers can also be used with commercially available color masterbatches for use in PE100 pipe.

The following references are incorporated herein by reference in their entirety.

U.S.Pat.No.9,249,286

ISO 11420：1996，“Method for the assessment of the degree of carbon black dispersion in polyolefin pipes，fittings and compounds”

ISO 9080：2012，“Plastics piping and ducting systems-Determination of the long-term hydrostatic strength of thermoplastics materials in pipe form by extrapolation”

ISO 1167：2006，“Thermoplastics pipes，fittings and assemblies for the conveyance of fluids--Determination of the resistance to internal pressure”

ISO 12162：2009，“Thermoplastics materials for pipes and fittings for pressure applications--Classification，designation and design coefricient”

ASTM D2837-13e1，“Standard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials or Pressure Design Basis for Thermoplastic Pipe Products”.