Additive for heat-treated foamable polypropylene

Abstract

There is provided a composition comprising a first polypropylene having at least 90 wt% propylene, based on the weight of the first polypropylene, an alpha nucleation inhibitor, and a beta nucleation additive. Methods of making the foamable polypropylene composition are also provided. The present invention relates to a process for preparing a polypropylene blend comprising the steps of: a) compounding a first polypropylene comprising at least 90 wt% propylene, based on the weight of the first polypropylene, with an alpha nucleation inhibitor to form a polypropylene blend; b) mixing the polypropylene blend with a blowing agent to form a pre-annealing polypropylene composition; and c) annealing the pre-annealing polypropylene composition at an annealing temperature Ta for an annealing time ta to form the foamable polypropylene composition. The foamable polypropylene composition has a first melting peak T1 and a second melting peak T2 measured by differential scanning calorimetry at a heating rate of 20 DEG C / min.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Patent Application No. 17 / 964,430, filed on October 12, 2022, the disclosure of which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] The present invention relates to polypropylene compositions useful in foamable applications. Background Art

[0004] Expanded polypropylene (EPP) is an engineered plastic foam that can be used in a variety of applications. Polypropylene offers many properties that make it preferred in some engineered plastic foam applications. Compared with other polymers such as polyethylene and polystyrene, its high temperature resistance, high energy absorption, low weight and high thermal stability are some attractive properties. If certain polymers (such as polystyrene) become less ideal due to regulatory restrictions, cost and / or recycling challenges, these properties may become more important. Other desirable properties of foamed polypropylene include: high weight to energy absorption ratio, excellent repeated impact performance, excellent high temperature resistance, high durability, and easy recycling. In addition, polypropylene can include recycled materials, low or zero VOC content; non-toxic, suitable for contact with food; oil-resistant, chemical-resistant, weather-resistant, flexible, recovers to its original shape after static or dynamic loads, i.e., creep-resistant, its foaming ratio can be easily adjusted, its water absorption rate is low, and it is an insulator for both heat and electricity.

[0005] Typical methods for generating EPP include:

[0006] 1) Adding a blowing agent to polypropylene and producing small plastic beads incorporating the blowing agent. The blowing agent is typically carbon dioxide or a low molecular weight alkane, such as n-butane or n-pentane. This incorporation process is accomplished by applying heat, pressure, and a gas (e.g., carbon dioxide or an alkane) to polypropylene pellets in an autoclave to form small plastic beads infused with the gas.

[0007] 2) These gas-infused beads are then placed into a mold and placed into a steam box to heat the beads, thereby sintering them, producing a foamed part molded into a complex shape.

[0008] The key to the process is the first step, the autoclaving step, because it transforms the crystalline morphology of polypropylene. Conventional EPP uses random propylene / ethylene copolymer PP (RCP), which has a single melting point at about 145°C (see Figure 1By keeping the RCP at a constant temperature and pressure and subsequently cooling it, the melting point shifts to two separate peaks, usually around 140°C and 160°C (see Figure 2 ). The lower melting peak is attributed to the beta crystallites (crystallites) and the higher melting peak is attributed to the alpha crystallites. This "twin crystal structure" or "twin peak" technology is required for good sintering in the second step in the steam box. The low melting beta material is needed to produce good adhesion between the beads, while the high melting temperature alpha crystals maintain the overall foam structure during the sintering process. Therefore, the steam chamber temperature is between the local minima (between the two melting peaks).

[0009] However, current methods of producing EPP have at least two disadvantages. First, the autoclave step is expensive and slow, making bead production an expensive proposition. If the gas could be incorporated more quickly (e.g., by melt compounding and then only annealing the beads to provide bimodal melting behavior without the need for an autoclave), bead production would be more efficient. Second, the greater the temperature difference between the two melting peaks, the less thermal control required in the second steam chamber step, providing a more flexible and robust production process for EPP foamed parts. Summary of the invention

[0010] The present inventors have solved these problems by providing a polypropylene composition comprising both a beta nucleation additive and an alpha nucleation inhibitor. The polypropylene composition provides at least two melting peaks with a wide interval between the peaks. The present inventors have also provided a method for producing a polypropylene composition having (at least) bimodal melting behavior which does not require the use of an autoclave but can be produced by other (including more traditional) polymer compounding techniques followed by annealing.

[0011] A composition is provided that includes a first polypropylene including at least 90 weight percent propylene as a polymerized monomer, based on the weight of the first polypropylene, an alpha nucleation inhibitor, and a beta nucleation additive.

[0012] A method for preparing a foamable polypropylene composition is also provided. The method comprises the following steps:

[0013] a) compounding a first polypropylene with an alpha nucleation inhibitor to form a polypropylene blend, wherein the first polypropylene comprises at least 90 wt% propylene as a polymerized monomer, based on the weight of the first polypropylene;

[0014] b) compounding the polypropylene blend with a blowing agent to form a pre-annealed polypropylene composition; and

[0015] c) annealing the pre-annealing polypropylene composition at an annealing temperature Ta for an annealing time of ta to form the foamable polypropylene composition. The foamable polypropylene composition has a first melting peak T1 and a second melting peak T2 as measured by differential scanning calorimetry at a heating rate of 20°C / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The melting behavior of unannealed random copolymer polypropylene (RCP) is shown;

[0017] Figure 2 The melting behavior of annealed random copolymer polypropylene (RCP) is shown;

[0018] Figure 3 shows the secondary DSC traces of Comparative Example 1 at different annealing temperatures;

[0019] Figure 4 shows the secondary melting DSC traces of Example 1 at different annealing temperatures;

[0020] Figure 5 shows an enlarged view of the DSC trace of the higher melting peak between 160°C and 190°C in Example 1;

[0021] Figure 6 shows the secondary melting DSC traces of Example 2 at different annealing temperatures;

[0022] Figure 7 shows the secondary melting DSC traces of Example 3 at different annealing temperatures;

[0023] Figure 8 The secondary melting DSC traces of Comparative Example 1 and Examples 1, 2 and 3 at an annealing temperature of 150° C. are shown;

[0024] Fig. 9 The secondary melting DSC traces of Examples 1, 2 and 3 at an annealing temperature of 160° C. are shown, wherein the endset melting temperature of Comparative Example 1 is shown for reference;

[0025] Fig.10 Comparative Example 2 shows the annealed Ziegler-Natta catalyzed random copolymer (propylene / ethylene copolymer) alone;

[0026] Fig.11 The annealed secondary melt DSC trace of Example 4 is shown;

[0027] Fig.12 The secondary melting DSC traces of Comparative Example 2 and Example 4 annealed at 150°C are shown;

[0028] Fig.13 The annealed secondary melt DSC trace of Example 5 is shown;

[0029] Fig.14 The secondary melting DSC traces of Comparative Example 2 and Example 5 annealed at 150°C are shown;

[0030] Fig.15 The annealed secondary melt DSC trace of Example 6 is shown;

[0031] Fig.16 The secondary melting DSC traces of Comparative Example 2 and Example 6 annealed at 150°C are shown;

[0032] Fig.17 The secondary melting DSC traces of Example 4 and Example 6 annealed at 130°C are shown;

[0033] Fig.18 The annealed secondary melt DSC trace of Example 7 is shown;

[0034] Fig.19 The secondary melting DSC traces of Comparative Example 2 and Example 7 annealed at 150°C are shown;

[0035] Fig. 20 The secondary melt DSC traces of Comparative Example 2 and Example 7 annealed at 140°C are shown;

[0036] Fig.21 shows the annealed secondary melt DSC trace of Example 8; and

[0037] Fig. 22 A diagram showing a method for determining the onset temperature and the end temperature is shown. DETAILED DESCRIPTION

[0038] Composition :

[0039] A composition for producing expanded polypropylene (EPP) is provided. The composition comprises:

[0040] a first polypropylene comprising, as polymerized monomer, at least 90 wt. % propylene, based on the weight of the first polypropylene,

[0041] alpha nucleation inhibitors, and

[0042] Beta nucleating additives.

[0043] The first polypropylene is not particularly limited. Non-limiting examples of the first polypropylene are: polypropylene homopolymer, isotactic polypropylene, or syndiotactic polypropylene. The first polypropylene may also contain: one or more of ethylene, butene, pentene, hexene or a combination thereof as a polymerized monomer up to 6 wt % based on the weight of the first polypropylene. The first polypropylene may be a random copolymer of propylene and ethylene, which contains up to 6 wt % of ethylene based on the weight of the first polypropylene.

[0044] The melt flow index of the first polypropylene may be 0.1 to 500 g / 10 min, as measured according to ISO-1133-1. For example, the melt flow index of the first polypropylene may be at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, or at least 475 g / 10 min, as measured according to ISO-1133-1. 150, 125, 100, 75, 50, 25, 20, 15 or at most 10 475 g / 10 min measured according to ISO-1133-1.

[0045] The molecular weight distribution [also known as polydispersity (Mw / Mn)] of the first polypropylene may be 2.0 to 15.0. The molecular weight Mw of the first polypropylene may be 10,000 g / mol to 1,000,000 g / mol or more as measured using gel permeation chromatography and polystyrene standards.

[0046] For example, the first polypropylene can have a weight average molecular weight of at least 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, 110,000, 115,000, 120,000, 125,000, 130,000, , 135,000, 140,000, 145,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,0 00, 390,000, 400,000, 410,000, 420,000, 430,000, 440,000, 450,000, 455,000, 460,000, 470,000, 480,000, 490,000, 500,000, 510,000, 520,000, 530,000, 540,000, 560,000, 570,000, 580,000, 590,000, 600,000, 610,000, 620,000, 630,000, 640,000, 65 , 840,000, 850,000, 860,000, 870,000, 880,000, 890,000, or at least 900,000 g / mol.For example, the first polypropylene can have a weight average molecular weight of 2,000,000, 1,900,000, 1,800,000, 1,700,000, 1,600,000, 1,500,000, 1,400,000, 1,300,000, 1,200,000, 1,100,000, 1,000,000, 950,000, or more. ,000, 900,000, 850,000, 800,000, 750,000, 700,000, 650,000, 600,000, 550,000, 500,000, 450,000, 400,000, 350,000, 300,000, 250,000, 200,000, 150,000, or up to 100,000 gm / mol.

[0047] For example, the first polypropylene can have a number average molecular weight of at least 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, 110,000, 115,000, 120,000, 125,000, 130,000, , 135,000, 140,000, 145,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,0 00, 390,000, 400,000, 410,000, 420,000, 430,000, 440,000, 450,000, 455,000, 460,000, 470,000, 480,000, 490,000, 500,000, 510,000, 520,000, 530,000, 540,000, 560,000, 570,000, 580,000, 590,000, 600,000, 610,000, 620,000, 630,000, 640,000, 65 , 840,000, 850,000, 860,000, 870,000, 880,000, 890,000, or at least 900,000 g / mol.For example, the first polypropylene can have a number average molecular weight of 2,000,000, 1,900,000, 1,800,000, 1,700,000, 1,600,000, 1,500,000, 1,400,000, 1,300,000, 1,200,000, 1,100,000, 1,000,000, 950,000, or 1,000,000. 0,000, 1,000, 2,000, 3,000, 5,000, 6,000, 7,000, 8,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 5,000, 0,000,

[0048] The polydispersity of the first polypropylene may be at least 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2 , 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, 13.6, 13.8, or at least 14.0. The polydispersity of the first polypropylene may be at most 15.0, 14.8, 14.6, 14.4, 14.2, 14.0, 13.8, 13.6, 13.4, 13.2, 13.0, 12.8, 12.6, 12.4, 12.2, 12.0, 11.8, 11.6, 11.4, 11.2, 11.0, 10.8, 10.6, 10.4, 10.2, 10. 0, 9.8, 9.6, 9.4, 9.2, 9.0, 8.8, 8.6, 8.4, 8.2, 8.0, 7.8, 7.6, 7.4, 7.2, 7.0, 6.8, 6.6, 6.4, 6.2, 6.0, 5.8, 5.6, 5.4, 5.2, 5.0, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, 3.2, or at most 3.0.

[0049] The first polypropylene can be produced, for example, using a metallocene catalyst or using a Ziegler-Natta catalyst. The first polypropylene can be produced in a gas phase, a suspension, a solution or a melt. The molecular weight distribution can be reduced by post-reactor thermal or chemical treatment, for example by degradation with peroxide ("visbreaking"). The molecular weight can be determined by gel permeation chromatography (GPC) as described in the examples.

[0050] The first polypropylene used in the present invention may be a homopolymer or a random copolymer of propylene and one or more comonomers. The comonomer may be ethylene or a C4-C28 alpha-olefin, such as butene-1, pentene-1, hexene-1, octene-1 or 4-methyl-pentene-1. According to one embodiment, the random copolymer is a copolymer of propylene and ethylene. The random copolymer of the first polypropylene of the present invention may contain at least 0.1 wt %, or at least 0.2 wt %, or at least 0.5 wt % of comonomer, based on the weight of the first polypropylene. They may contain up to 6.0 wt %, or up to 5.0 wt %, or up to 4.0 wt % of comonomer, based on the weight of the first polypropylene.

[0051] The alpha nucleation inhibitor may comprise potassium stearate.

[0052] Non-limiting examples of the beta-nucleating additive are: quinacridone dye in gamma crystalline form; aluminum salt of 6-quinazirin sulfonic acid; disodium phthalate; isophthalic acid or its derivatives; terephthalic acid or its derivatives; N',N'-dicyclohexyl-2,6-naphthalene dicarboxamide; blends of organic dibasic acids with oxides, hydroxides or acids of Group II metals; or combinations thereof.

[0053] The composition may further include up to 5 wt % of a second polypropylene, based on the weight of the composition. The second polypropylene is different from the first polypropylene and includes at least 99 wt % of propylene as a polymerized monomer, based on the weight of the second polypropylene. Importantly, the second polypropylene is a high crystallinity polypropylene and has a crystallinity of at least 50 wt %, based on the weight of the second polypropylene. The crystallinity of the second polypropylene may be at least 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 48, 85, 86, 87, 88, 89 or at least 90 wt %, based on the weight of the second polypropylene. The weight % crystallinity is measured as described in the example section. The second polypropylene is not particularly limited in addition. Non-limiting examples of the second polypropylene are: polypropylene homopolymer, isotactic polypropylene, or syndiotactic polypropylene. The second polypropylene may further comprise one or more of ethylene, butene, pentene, hexene or a combination thereof as a polymerized monomer at most 1 wt %, based on the weight of the second polypropylene. The second polypropylene may be a random copolymer of propylene and ethylene, comprising at most 1 wt % of ethylene, based on the weight of the second polypropylene. The melt flow index of the second polypropylene may be 0.1 to 500 g / 10 min, measured according to ISO-1133-1. For example, the second polypropylene may have a melt flow index of at least 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400 or at least 475 g / 10 min as measured according to ISO-1133-1. 125, 100, 75, 50, 25, 20, 15 or at most 10 g / 10 min measured according to ISO-1133-1.

[0054] The molecular weight distribution (Mw / Mn) of the second polypropylene may be 2.0 to 15.0. The molecular weight Mw of the second polypropylene may be 10,000 g / mol to 1,000,000 g / mol or more as measured using gel permeation chromatography and polystyrene standards. For example, the second polypropylene can have a weight average molecular weight of at least 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, 110,000, 115,000, 120,000, 125,000, 130,000, , 135,000, 140,000, 145,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,0 00, 390,000, 400,000, 410,000, 420,000, 430,000, 440,000, 450,000, 455,000, 460,000, 470,000, 480,000, 490,000, 500,000, 510,000, 520,000, 530,000, 540,000, 560,000, 570,000, 580,000, 590,000, 600,000, 610,000, 620,000, 630,000, 640,000, 65 , 840,000, 850,000, 860,000, 870,000, 880,000, 890,000, or at least 900,000 g / mol.For example, the weight average molecular weight of the second polypropylene can be 2,000,000, 1,900,000, 1,800,000, 1,700,000, 1,600,000, 1,500,000, 1,400,000, 1,300,000, 1,200,000, 1,100,000, 1,000,000, 950,000, or 1,000,000. 0,000, 1,000, 2,000, 3,000, 5,000, 6,000, 7,000, 8,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 5,000, 0,000,

[0055] For example, the second polypropylene can have a number average molecular weight of at least 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, 110,000, 115,000, 120,000, 125,000, 130,000, , 135,000, 140,000, 145,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,0 00, 390,000, 400,000, 410,000, 420,000, 430,000, 440,000, 450,000, 455,000, 460,000, 470,000, 480,000, 490,000, 500,000, 510,000, 520,000, 530,000, 540,000, 560,000, 570,000, 580,000, 590,000, 600,000, 610,000, 620,000, 630,000, 640,000, 65 , 840,000, 850,000, 860,000, 870,000, 880,000, 890,000, or at least 900,000 g / mol.For example, the second polypropylene can have a number average molecular weight of 2,000,000, 1,900,000, 1,800,000, 1,700,000, 1,600,000, 1,500,000, 1,400,000, 1,300,000, 1,200,000, 1,100,000, 1,000,000, 950,000, or 1,000,000. 0,000, 1,000, 2,000, 3,000, 5,000, 6,000, 7,000, 8,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 0,000, 1,000, 0,000, 1,000, 0,000, 9,000, 1,000, 2,000, 3,000, 5,000, 5,000, 0,000,

[0056] The polydispersity of the second polypropylene may be at least 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2 , 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, 10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, 13.6, 13.8, or at least 14.0. The polydispersity of the second polypropylene may be at most 15.0, 14.8, 14.6, 14.4, 14.2, 14.0, 13.8, 13.6, 13.4, 13.2, 13.0, 12.8, 12.6, 12.4, 12.2, 12.0, 11.8, 11.6, 11.4, 11.2, 11.0, 10.8, 10.6, 10.4, 10.2, 10. 0, 9.8, 9.6, 9.4, 9.2, 9.0, 8.8, 8.6, 8.4, 8.2, 8.0, 7.8, 7.6, 7.4, 7.2, 7.0, 6.8, 6.6, 6.4, 6.2, 6.0, 5.8, 5.6, 5.4, 5.2, 5.0, 4.8, 4.6, 4.4, 4.2, 4.0, 3.8, 3.6, 3.4, 3.2, or at most 3.0.

[0057] The second polypropylene can be produced, for example, using a metallocene catalyst or a Ziegler-Natta catalyst. The second polypropylene can be produced in a gas phase, a suspension, a solution or a melt. The molecular weight distribution of the second polypropylene can be reduced by post-reactor heat or chemical treatment, for example by degradation ("visbreaking") with peroxides. The molecular weight can be measured by gel permeation chromatography (GPC) as described in the examples.

[0058] The second polypropylene used in the present invention may be a homopolymer or a random copolymer of propylene and one or more comonomers. The comonomer may be ethylene or a C4-C28 alpha-olefin, such as butene-1, pentene-1, hexene-1, octene-1 or 4-methyl-pentene-1. According to one embodiment, the random copolymer is a copolymer of propylene and ethylene. The random copolymer of the second polypropylene of the present invention may contain at least 0.1 wt%, or at least 0.2 wt% or at least 0.5 wt% of comonomer, based on the weight of the second polypropylene. They contain up to 1.0 wt%, or up to 0.3 wt% or up to 0.5 wt% of comonomer, based on the weight of the second polypropylene.

[0059] After annealing at an annealing temperature Ta for an annealing time ta, the composition has a first melting peak T1 and a second melting peak T2 as measured by differential scanning calorimetry at a heating rate of 20°C / min. According to some embodiments, the annealing temperature Ta may be 90°C to 200°C. According to some embodiments, the annealing temperature may be 100°C to 180°C or 120°C to 160°C. According to some embodiments, the annealing temperature Ta may be at least 90°C, at least 95°C, at least 100°C, at least 105°C, at least 110°C, at least 115°C, at least 120°C, at least 125°C, at least 130°C, at least 135°C, at least 140°C, at least 145°C, at least 150°C, at least 155°C, at least 160°C, at least 165°C, or at least 175°C. According to some embodiments, the annealing temperature may be at most 200°C, or at most 195°C, at most 190°C, at most 185°C, at most 180°C, at most 175°C, at most 170°C, at most 165°C, at most 160°C, at most 155°C, at most 150°C, at most 145°C, at most 140°C, at most 135°C, at most 130°C, or at most 125°C. According to some embodiments, the first melting peak T1 may be 110°C to 165°C. According to some embodiments, the first melting peak T1 may be 135°C to 165°C, or 140°C to 155°C. According to some embodiments, the second melting peak T2 is 150°C to 180°C. According to some embodiments, the second melting peak is 155°C to 175°C, or 160°C to 170°C. According to one embodiment, the composition may have a third melting peak T3. The third melting peak T3 may be 160° C. to 180° C., or 165° C. to 175° C. The measurement of the melting peak is as described in the Examples.

[0060] The composition has an overall degree of crystallinity of at least 25 wt.-%, based on the total weight of the first polypropylene, measured as described in the Examples.

[0061] The composition may further comprise a blowing agent. Non-limiting examples of suitable blowing agents are gases such as CO2, nitrogen, small alkanes such as n-butane or n-pentane, and combinations thereof.

[0062] The composition may be in the form of a masterbatch. A masterbatch is a concentrated composition for accurately distributing additives into the polypropylene composition. The carrier of the masterbatch may be the first polypropylene, or the second polypropylene, or other polymers or polypropylenes. In the masterbatch, the alpha nucleation inhibitor and the beta nucleation additive together account for 0.1 to 80 weight percent, based on the total weight of the masterbatch composition.

[0063] method:

[0064] A method for preparing a foamable polypropylene composition is provided. The method comprises the following steps:

[0065] a) compounding a first polypropylene with an alpha nucleation inhibitor to form a polypropylene blend, wherein the first polypropylene comprises at least 90 wt% propylene as a polymerized monomer, based on the weight of the first polypropylene;

[0066] b) compounding the polypropylene blend with a blowing agent to form a pre-annealing polypropylene composition; and

[0067] c) annealing the pre-annealing polypropylene composition at an annealing temperature Ta for an annealing time ta to form the foamable polypropylene composition, wherein the foamable polypropylene composition has a first melting peak T1 and a second melting peak T2 as measured by differential scanning calorimetry at a heating rate of 20°C / min.

[0068] According to one embodiment, the polypropylene before annealing may have a third melting peak T3.

[0069] According to another embodiment, step a) of the method may further comprise: compounding a beta nucleating additive with the first polypropylene and the alpha nucleating inhibitor to form the polypropylene blend. According to one embodiment, at least one of the beta nucleating additive and the alpha nucleating inhibitor may be in the form of a masterbatch. According to one embodiment, step a) and step b) may be performed in a single mixing operation.

[0070] According to another embodiment, step b) may further comprise: pelletizing the pre-annealing polypropylene composition.

[0071] A method for preparing a foamable polypropylene composition is provided. The method comprises: heating the foamable polypropylene composition to a foaming temperature higher than T1 and lower than T2. ​​The heating step can be carried out at a pressure lower than 1 atm. For example, the pressure can be 0.95 atm, or 0.90 atm, 0.85 atm, 0.80 atm, 0.75 atm, 0.70 atm, 0.65 atm, 0.60 atm, 0.55 atm or 0.50 atm or lower.

[0072] Example

[0073] method :

[0074] Differential Scanning Calorimetry (DSC) : DSC experiments were performed on 5 to 7 mg samples by a Discovery 250 instrument manufactured by TA Instruments. The samples were run under nitrogen and the instrument was calibrated using indium standards as described in the examples.

[0075] For non-isothermal testing, ASTM 3418-21 was followed. Specifically, the sample was equilibrated at 50°C for one minute, ramped to 210°C at 10°C / min, held at 210°C for five minutes, cooled to 50°C at -10°C / min, held at 50°C for one minute, reheated to 190°C at 10°C / min, then cooled to 50°C to end the test. This method provides crystallization data, such as crystallization temperature and enthalpy in the cooling trace. The second heating trace provides melting temperature and melting enthalpy data.

[0076] For DSC tests annealed at different temperatures, an in-house procedure was used. Details of the procedure are given below.

[0077] Compound : In preparation for compounding, the reactor polypropylene powder was blended with the additives and subsequently introduced into the extruder. Blending was performed on a high intensity mixer for one minute. The high intensity mixer was a Prodex Corporation model 18JSS.

[0078] After the powder is blended, add 1 1 / 4" single screw extruder. The extruder was an American Kuhne, model AK125 24AC 5HP ULT. The extruder temperatures were set to 410°F / 420°F / 420°F / 430°F / 430°F / 430°F for Zone 1 (feed) / Zone 2 / Zone 3 / Clamp / Die 1 / Die 2. The extruder was equipped with a 100 mesh screenpack. After the die, the strands were passed through a water bath maintained at room temperature and pelletized.

[0079] Melt Flow Index (MFI) : MFI measurements were performed according to ASTM-D1238-20. The test equipment was a Tinius Olsen plastometer, model MP600 or MP1200. About 7 grams of pellets were consumed per test. All MFI tests were performed according to ASTM standards at 230°C, using an orifice with a diameter of 2.095 mm and a length of 8.00 mm. The melt temperature was 230°C.

[0080] Mw、Mn:The weight average molecular weight and number average molecular weight (Mw, Mn) were determined by gel permeation method. The GPC instrument used was a Polymer Char GPC-IR equipped with three chromatographic columns. The first two chromatographic columns were Shodex AT-80M / S (Part No. 34200) linear chromatographic columns. The third chromatographic column was a Waters Ultrastyragel high temperature linear chromatographic column (Part No. 35554). 16 mg of sample was placed in a 10 ml vial, and the GPC-IR automatic sampler automatically added 8 ml of trichlorobenzene (TCB) solvent thereto. The sample was run at 135-145°C. The eluate was analyzed by an infrared detector. Polystyrene samples were used.

[0081] Percent crystallinity : The percentage crystallinity is determined by measuring the heat of fusion of each sample and then dividing the result by the heat of fusion of a 100% crystalline sample of polypropylene. The value for 100% crystalline polypropylene used herein is 207 J / g. The heat of fusion of each sample is determined using non-isothermal testing according to ASTM 3418-21 or under a heating ramp after annealing.

[0082] End melting point and start melting point :The onset and end melting points are determined under non-isothermal heating ramps. They are determined by extending the baseline and tangent lines from the melting curve, and these temperatures are defined by the intersection of the two lines. Fig. 9 An example of the termination temperature is illustrated. Fig. 22 Instructions for determining the starting and ending melting points are also provided.

[0083] Unless otherwise indicated, all percentages are by weight.

[0084] Unless otherwise indicated, all parts, such as parts per million (ppm), are parts by weight.

[0085] Examples 1-3, Comparative Example 1: Effects of β-nucleating additives and α-nucleating inhibitors on the melting behavior of high crystalline polypropylene Influence

[0086] The four compositions shown in Table 1 below were prepared using a polypropylene homopolymer (TotalEnergies 3270) having a melt flow index MFI of 2 gm / 10 min (measured according to ASTM D1238-20) as the base polymer.

[0087]

[0088] 1010 (BASF) is the trade name of pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate. The Chemical Abstracts Service number (CAS number) is 6683-19-8. 168 (BASF) is the trade name of tris(2,4-di-tert-butylphenyl)phosphite, and its CAS number is 31570-04-4. Calcium stearate CAS number is 1592-23-0. Potassium stearate CAS number is 593-29-3. NJ Star NU-100 (New Japan Chemical Co.) is N,N-dicyclohexyl-2,6-naphthalene dicarboxamide. Its CAS number is 153250-52-3.

[0089] DSC tests were conducted as follows to determine the effects of beta nucleating additives and alpha nucleating inhibitors (alone or in combination) on the melt behavior of polypropylene.

[0090] 1. Ramp temperature to 210°C at 20°C / min. Hold for 5 minutes.

[0091] 2. Ramp temperature from -20°C / min to 50°C and hold for 1 minute.

[0092] 3. Ramp the temperature to 120°C at 20°C / min. Maintain for 15 minutes. This is 120°C annealing.

[0093] 4. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0094] 5. Ramp temperature to 190°C at 20°C / min. Hold for 1 minute.

[0095] 6. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0096] 7. Ramp the temperature to 130°C at 20°C / min. Maintain for 15 minutes. This is 130°C annealing.

[0097] 8. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0098] 9. Ramp temperature to 190°C at 20°C / min. Hold for 1 minute.

[0099] 10. Ramp to 23°C at -20°C / min. Hold for 1 minute.

[0100] 11. Ramp the temperature to 140°C at 20°C / min. Maintain for 15 minutes. This is 140°C annealing.

[0101] 12. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0102] 13. Ramp temperature to 190°C at 20°C / min. Hold for 1 minute.

[0103] 14. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0104] 15. Ramp the temperature to 150°C at 20°C / min. Maintain for 15 minutes. This is 150°C annealing.

[0105] 16. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0106] 17. Ramp temperature to 190°C at 20°C / min. Hold for 1 minute.

[0107] 18. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0108] 19. Ramp the temperature to 160°C at 20°C / min. Maintain for 15 minutes. This is 160°C annealing.

[0109] 20. Ramp to 23°C at -20°C / min. Hold for 1 minute.

[0110] 21. Ramp temperature to 190°C at 20°C / min. Hold for 1 minute.

[0111] 22. Cool to room temperature and end the test.

[0112] like Figure 3 As shown, the DSC results of Comparative Example 1 show the response of the baseline polymer (high crystallinity polypropylene resin) to the annealing step at each holding temperature. All annealing temperatures do not produce the expected bimodal behavior that can be used to produce polypropylene foam. On the contrary, the result is that the endothermic lower melting part moves to a higher temperature. This forms a more obvious shoulder on the left part of the DSC trace and gradually pushes into the main body of the peak. This behavior changes with annealing at 160°C, which increases the peak melting temperature while maintaining a single peak shape. This shows that the annealing of high crystallinity polypropylene does not produce bimodal behavior, which is typical in random copolymer polypropylene used for foaming polypropylene grades. At all annealing temperatures, it seems that the unmelted material present at 190°C is negligible. The development of the higher melting peak can be quantified relative to the increase in the amount of higher melting point material (relative to the gradually increasing temperature). Quantification can be defined by the "termination melting temperature (Tes)", which is similar to the initial melting temperature. The termination melting temperature is determined by taking the intersection temperature between the slope of the melting curve and the baseline. The change in peak melting temperature is shown in Table 2. As shown in Table 2, annealing temperatures from 120°C to 150°C only shifted the peak by a total of about 1°C. However, annealing at 160°C increased the melting temperature by nearly 4°C.

[0113]

[0114] Table 1 also shows that the end melting temperature also changes similarly. The annealing temperature from 120°C to 150°C causes the end temperature (Tes) to increase by slightly more than 1°C. When the annealing temperature increases from 150°C to 160°C, the change is close to 6°C.

[0115] like Figure 4 As shown, the introduction of 2000ppm of the beta nucleating additive in Example 1 produces a bimodal melting endotherm when the sample is annealed at a temperature of 120°C to 150°C. In addition, these data show that the size and shape of the two melting peaks and their shapes vary with the annealing temperature. The higher the annealing temperature, the higher the second higher melting peak. In addition, the higher annealing temperature also leads to a larger area under the second melting peak, which means that the amount of high melting point crystals is greater. The second higher melting peak itself also moves to a higher melting point. Obviously, all of these effects are due to the presence of the beta nucleating additive. Figure 5 is with Figure 4 The same DSC data, but plotted for a smaller temperature range, to more clearly show the effect of the beta nucleating additive on the second melting peak at different annealing temperatures. These higher melting point species are important in EPP (expanded polypropylene) processing. Without wishing to be bound by any particular theory, these high melting point crystallites can create physical crosslinks, thereby providing a framework to maintain the foam structure even at higher temperatures.

[0116] Table 2 lists the properties of the melting peaks for the polymer containing the beta nucleating additive (Example 1). The spread of the two peaks (lower melting point and higher melting point) is from about 12°C to about 13°C. This spread is narrower than the typical spread of 20°C for random copolymers of propylene and ethylene, but is still significant, and importantly, is not present at all in the same polymer annealed in the same manner but without the beta nucleating additive, as shown in Comparative Example 1 above.

[0117] Example 1.

[0118]

[0119] The end melting temperatures of Comparative Example 1 and Example 1 were also measured to evaluate the effect of adding a beta nucleating additive. Unexpectedly, it was found that the addition of a beta nucleating additive promoted the formation of higher melting point species, rather than just helping to generate lower melting point species within the typical range of beta grains. This effect is very important for a variety of applications requiring high temperature resistance, including the steam chamber portion of the EPP process. Table 3 lists the data supporting this. As can be seen from Table 3, the beta nucleating additive is more effective in generating high melting point species at higher annealing temperatures of 150°C and 160°C.

[0120]

[0121]

[0122] Next, in Example 2, the effect of adding an α nucleation inhibitor on the annealing temperature response was determined. The DSC curves of Example 2 compared with Comparative Example 1 are shown in FIG. Figure 5 As shown in . Figure 5 It can be seen that annealing at 120°C provides a unimodal curve. However, unexpectedly, annealing at 130°C, 140°C and 150°C produces a bimodal melting endotherm. As the annealing temperature rises, the second melting peak becomes a peak temperature that moves to a higher temperature. Finally, as in Example 1 where a β-nucleating additive is added, the peak becomes a unimodal at an annealing temperature of 160°C. However, it has a very strong lower temperature shoulder.

[0123] Similar to the addition of the β-nucleating additive in Example 1, when the α-nucleating inhibitor was added in Example 2, more higher melting point materials were produced compared to Comparative Example 1 at an annealing temperature of 160°C.

[0124] Figure 5 The properties of these melting peaks shown in Table 4 are listed. The difference between the two peaks is about slightly more than 13°C. This difference is narrower than the typical 20°C for random copolymer polypropylene, but it is still significant, and importantly, this difference is not seen in the comparative examples that do not contain the alpha nucleation inhibitor.

[0125]

[0126] like Figure 5 As shown in the DSC traces in Table 4, the addition of α nucleation Inhibitors lead to Form more Higher Melting Point Material. This result was unexpected since the alpha grains have a higher melting point than the beta grains and is important for many applications requiring high temperature resistance including especially the steam chamber portion of the EPP process.

[0127] Data showing this effect are listed in Table 6. Table 6 shows that the effect of more higher melting point species in the presence of an alpha nucleation inhibitor is greater at higher annealing temperatures of 150°C and 160°C.

[0128]

[0129] Example 3 includes both a beta nucleation additive and an alpha nucleation inhibitor. Figure 7 The effect of an alpha nucleation inhibitor and a beta nucleation additive together on the melting behavior is shown. As shown, the two additives can be used together to produce the desired bimodal melting endothermic melting shape. The properties of these melting peaks are listed in Table 7. The difference between the two peaks is greater than 11.5°C to slightly greater than 12.5°C. This difference is less than the 20°C typical of random copolymer polypropylene, but is still quite large, and this difference is not seen in high crystallinity polypropylene homopolymers.

[0130]

[0131] The effect of using a beta nucleating additive together with an alpha nucleating inhibitor on the termination temperature at these different annealing temperatures is discussed below.

[0132] Unexpectedly, the alpha nucleation inhibitor was added together with the beta nucleation additive. Promoted Formation of higher melting point species. This result was unexpected because the alpha form of the grains has a higher melting point than the beta grains. This effect is important for many applications that require high temperature resistance, including the steam chamber portion of the EPP process. Table 8 lists the data to support this. As shown in Table 8, the enhancement of the alpha nucleation inhibitor is stronger at the higher annealing temperatures of 150°C and 160°C.

[0133]

[0134] Figure 8 Visual assessments of each of Comparative Example 1 and Examples 1-3 annealed at 150°C are shown. Interestingly, the peak heights of both the first and second peaks of the peak intensity for Example 3 are between those of Example 1 with only the beta nucleating additive and Example 2 with only the alpha nucleating inhibitor. Thus, the combination of the beta nucleating additive and the alpha nucleating inhibitor unexpectedly work together to provide the desired dual melting peak behavior. The combination of the beta nucleating additive and the alpha nucleating inhibitor can be used to adjust the crystallization behavior to an optimal level for industry.

[0135] The second finding is that at an annealing temperature of 150°C, the alpha nucleation inhibitor provides a more balanced peak size between the first and second melting peaks. The strength of this response relative to the beta nucleation additive highlights that the crystallization kinetics between these two additives may be different and provides practitioners with two independent tools to modify and optimize the performance of a given annealing process. For example, the optimal process for, for example, an expanded polypropylene EPP process may be completely different when annealing a slit film yarn.

[0136] Fig. 9 The effects of alpha nucleation inhibitors, beta nucleation additives, and the combination of the two in forming higher melting point grains are illustrated. The end melting temperature of the baseline TotalEnergies 3270 of Comparative Example 1 (no beta nucleation additive and no alpha nucleation inhibitor) is 179.96°C. Meanwhile, the higher melting endothermic peaks of Examples 1-3 are 179.08°C to 179.45°C. Clearly, these additives together produce a large amount of crystalline material that melts above 180°C and crystalline material that melts above 185°C.

[0137] As known in the art, grains can be used as physical crosslinking. Therefore, at high temperatures, these preparations of Examples 1-3 can better resist deformation, which will produce higher Vicat softening points and higher heat distortion temperatures. This will also make these preparations more viscous than the baseline comparative example 1 preparation, because the residual grains can greatly increase the flow resistance of the melt. This attribute is desirable in foaming processes such as EPP, because high melting point materials are needed to help maintain the structural integrity in the steam chamber molding process. It is expected that high melting point grains can be used to soften polymers with other processes for further molding, such as thermoforming and injection stretch blow molding of preforms.

[0138] Comparative Example 2 and Examples 4-8. Addition of high crystallinity PP and β-nucleation additives and α-nucleation inhibitors to the zigzag Effect of Lennart-Natta Catalysis on the Melting Behavior of Random Copolymers (Propylene / Ethylene Copolymers)

[0139] Test materials and conditions

[0140] TotalEnergies 6575 was used as the base polymer powder for the preparation of the six compounds listed in Table 9 below. This polymer is an 8 MFR Ziegler-Natta polypropylene. Its melting temperature is about 145°C. This MFR and melting temperature are typical for RCP used in EPP applications. All six compounds contain 1000 ppm of 1010 and 1000 ppm 168 as an antioxidant. The compound numbers and descriptions are shown in Table 9 below.

[0141]

[0142] The DSC test of the composition shown in Table 9 was carried out as follows:

[0143] 1. Ramp temperature to 210°C at 20°C / min. Hold for 5 minutes.

[0144] 2. Ramp temperature from -20°C / min to 50°C and hold for 1 minute.

[0145] 3. Ramp the temperature to 120°C at 10°C / min. Maintain for 15 minutes. This is 120°C annealing.

[0146] 4. Ramp temperature to 23°C at -10°C / min. Hold for 1 minute.

[0147] 5. Ramp temperature to 210°C at 20°C / min. Hold for 1 minute.

[0148] 6. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0149] 7. Ramp the temperature to 130°C at 10°C / min. Maintain for 15 minutes. This is 130°C annealing.

[0150] 8. Ramp to 23°C at -10°C / min. Hold for 1 minute.

[0151] 9. Ramp temperature to 210°C at 20°C / min. Hold for 1 minute.

[0152] 10. Ramp to 23°C at -20°C / min. Hold for 1 minute.

[0153] 11. Ramp the temperature to 140°C at 10°C / min. Maintain for 15 minutes. This is 140°C annealing.

[0154] 12. Ramp to 23°C at -10°C / min. Hold for 1 minute.

[0155] 13. Ramp temperature to 210°C at 20°C / min. Hold for 1 minute.

[0156] 14. Ramp temperature to 23°C at -20°C / min. Hold for 1 minute.

[0157] 15. Ramp the temperature to 150°C at 10°C / min. Maintain for 15 minutes. This is 150°C annealing.

[0158] 16. Ramp to 23°C at -10°C / min. Hold for 1 minute.

[0159] 17. Ramp temperature to 210°C at 20°C / min. Hold for 1 minute.

[0160] 18. Ramp temperature to 50°C at -20°C / min. Hold for 1 minute.

[0161] 19. Cool to room temperature and end the test.

[0162] result

[0163] The analysis begins with how the baseline Comparative Example 2 (TotalEnergies 6575) responds to the annealing step at each annealing temperature. Fig.10 As shown, the melting endotherm shifts within the annealing temperature range of 120°C to 150°C.

[0164] Annealing at 120°C forms a broad lower melting shoulder from about 125°C to about 135°C, which then rises to a peak at 145°C.

[0165] Annealing at 130°C and 140°C causes the lower melting shoulder to become less pronounced. It also increases the peak height and pushes back the end peak temperature, especially at 140°C annealing.

[0166] Annealing at 150°C is transformational. A small peak is formed above 160°C, which qualitatively meets the requirements of the bimodal technology. The lower melting peak is bimodal and very broad.

[0167] These results show that although some aspects of the melting behavior of Comparative Example 2 (TotalEnergies 6575) are similar to those of Figure 3 The melting behavior of Comparative Example 1 (TotalEnergies 3270) seen in Figure 1 is similar, but the random copolymer polypropylene of Comparative Example 2 also has some distinctive features. Specifically, no formation of a trimodal melting endotherm was observed when testing Comparative Example 1 TotalEnergies 3270 up to an annealing temperature of 160°C. Since the results of Comparative Example 2 indicate that a trimodal melting peak is possible, the term "multimodal" will be used to refer to such behavior. "Multimodal" as used herein means a melting endotherm that exhibits two or more melting temperatures.

[0168] The complexity of the melting endotherm of Comparative Example 2 is shown in Table 10. The initial melting temperature increases with increasing annealing temperature until the annealing temperature is 150°C, after which the initial melting temperature drops to slightly above 111°C. Within the same range of 120°C to 140°C, the terminal melting temperature increases, but not as rapidly. Therefore, the melting temperature width (i.e., the difference between the terminal Tm and the initial Tm) becomes narrower. At an annealing temperature of 150°C, the behavior changes. The melting temperature width increases to over 55°C, the terminal Tm increases to nearly 167°C, and a clear melting peak appears at a position above 160°C. This melting point above 160°C is important in EPP processing because the crystalline material that melts around 160°C is important for maintaining the overall foaming structure, as can be seen from the bimodal melting behavior of polypropylene.

[0169]

[0170] In Example 4, the introduction of a beta nucleating additive to TotalEnergies 6575 produced an additional melting endotherm. This indicates the presence of a strong interaction ( Fig.11 ). The qualitative observation results of Example 4 and Comparative Example 2 baseline include:

[0171] The low melting peak / shoulder is more obvious in Example 4.

[0172] • The melting endotherms at 130°C and 140°C are broader in Example 4. This means a more robust processing window for EPP.

[0173] Annealing at 150°C produces a more obvious high melting peak above 160°C ( Fig.12 ).

[0174] These features should be attractive in processes that use annealing in general, such as EPP, because the inclusion of beta nucleating additives changes the melting behavior. In addition, the formation of more higher melting point species at elevated annealing temperatures ensures that crystalline species are present to help maintain the foamed structure in EPP.

[0175] The complexity of the melting endotherms of Example 4 is shown in Table 11. Unlike Comparative Example 2, three of the four annealing temperatures produced multi-peak melting endotherms. The peak melting temperature in Example 4 tended to be lower than that in Comparative Example 2. In addition, the end melting temperature of Example 4 tended to be higher. As a result, the expected melting temperature width of Example 4 increased within the annealing temperature range tested.

[0176]

[0177] Example 5 shows that the effect of introducing an alpha nucleation inhibitor into TotalEnergies 6575 is less than that of a beta nucleation additive ( Fig.13 ). The qualitative observations for Example 5 are almost identical to those for Comparative Example 2 baseline, with one exception. Example 5 annealed at 150°C produces a more pronounced high melting point peak above 160°C ( Fig.14 This could be attractive for some EPP processes. This suggests that RCP containing an alpha nucleation inhibitor could be processed in a very similar manner to a standard RCP grade, but with more of the high melting point material needed to maintain the EPP foam structure.

[0178] The melting endotherm data for Example 5 are shown in Table 12. The data are almost identical to those for Comparative Example 2. This result is encouraging because it demonstrates that the DSC testing technique has excellent reproducibility. It also provides strong confidence that Fig.14 The larger (greater than 160°C) melting peak shown in is real and not a test artifact.

[0179]

[0180]

[0181] Example 6 Combining an alpha nucleation inhibitor and a beta nucleation additive in TotalEnergies 6575 has a synergistic effect on the melting behavior ( Fig.12 ). The qualitative observation results of Example 6 and Comparative Example 2 include:

[0182] • All DSC traces exhibit multimodal melting exotherms.

[0183] • A more pronounced low melting peak / shoulder is observed.

[0184] Broader melting endotherms at 130°C and 140°C are observed. This provides a desired wider processing window for EPP.

[0185] Like the compositions of Examples 4 and 5, the composition of Example 6 produced a more obvious high melting peak above 160°C when annealed at 150°C ( Fig.13 ).

[0186] The general trends of Example 6 are similar to those of Example 4, but not a direct replication; the alpha nucleation inhibitor together with the beta nucleation additive provides a different melting behavior than either alone.

[0187] The melting endotherm data for Example 6 shown in Table 13 behaves similarly to Example 4. The breadth of the melting temperatures at each annealing temperature is very similar, as are most of the peak melting temperatures. The melting behavior is different from pure Comparative Example 2.

[0188]

[0189] Fig.14 Secondary melting DSC traces of Example 4 and Example 6 after annealing at 130°C are shown. Fig.14 This shows how the beta nucleating additive and alpha nucleating inhibitor in Total Energies 6575 work synergistically compared to using only the beta nucleating additive. Example 6 has a lower first peak and forms a distinct second peak, such as Fig.15 This result is counterintuitive; one skilled in the art would not expect to add α-nucleating Inhibitors meeting Enhancement The formation of higher melting point species, because α crystallites are the higher melting point species in polypropylene.

[0190] In contrast, Example 4 has only a distinct shoulder, rather than a distinct second peak (ie, the tangent line behind the first peak is never equal to zero indicating a local minimum that would provide a mathematically defined dividing line between the first and second peaks).

[0191] In a further experiment, Example 7 was prepared by compounding 5% of high crystallinity polypropylene TotalEnergies 3270 into TotalEnergies 6575 as a resin modifier.

[0192] It can be seen that after annealing at 150°C, the introduction of 5% TotalEnergies 3270 into TotalEnergies 6575 has an effect on the melting behavior ( Fig.18 , Fig.19 ). The high melting peak above 160°C dominates the shape of the DSC trace. Therefore, the small addition of high crystallinity PP (such as TotalEnergies 3270) enhances the size of this high melting peak.

[0193] Other effects of adding high crystallinity PP are as follows. After annealing at 140°C, the addition of high crystallinity PP resulted in a transition to a higher melting point material ( Fig. 20 ). This transition to higher temperatures can also be replicated at lower annealing temperatures. This behavior may prove useful in applications outside of EPP, such as medical applications, where the article needs to be autoclaved at high temperatures without part deformation.

[0194] Table 14 shows the case of adding 5% of TotalEnergies 3270. The most important thing is to move the end melting temperature higher. This feature is useful by itself because it provides a higher annealing temperature without eliminating high melting point grains. This feature can provide a more robust annealing temperature range in the EPP process. This shift also increases the melting temperature width because the starting temperature tends to remain similar to that of the base TotalEnergies 6575 resin.

[0195]

[0196] Next, Example 8 was compounded with 5% TotalEnergies 3270 and 2000 ppm of an alpha nucleation inhibitor. If there is no complementary behavior, Example 8 should perform similarly to Example 7. Deviations from Example 7 would support a synergistic effect, especially if they are qualitatively similar to the trends of the other compounds in Examples 4-6.

[0197] The initial DSC results for Example 8 followed the general pattern seen in Example 7N21053-5 ( Fig.18 When annealed at 150°C, Example 8 produced a very strong melting peak at greater than 160°C ( Fig.21 ). At lower annealing temperatures, the peak melting temperature decreases and a lower melting shoulder is formed.

[0198] As in Example 8 and Fig.21 As shown, formulating TotalEnergies 6575 with TotalEnergies 3270 and a beta nucleation inhibitor produced a subtle but consistent effect. The ending melting temperature was consistently higher than the Example 7 (TotalEnergies 6575 / TotalEnergies 3270 - 95 / 5%) composition. The starting melting temperature remained consistent between Example 7 and Example 8, but the melting temperature breadth of the Example 8 formulation also increased.

[0199]

[0200]

[0201]

[0202] The present disclosure relates to modifying the melting behavior of random copolymer polypropylene (RCP) by annealing at different temperatures and adding small amounts of β-nucleating additives, α-nucleating inhibitors and high crystallinity polypropylene. By using these additives / modifiers, the following beneficial properties can be achieved:

[0203] • The amount of higher melting point (≥160°C) melted material increases after annealing, which is visually shown by the size of the melting endotherm compared to the pure RCP baseline.

[0204] The end melting temperature is usually shifted to a higher temperature.

[0205] Compared with the pure RCP baseline, a multimodal melting endotherm is generated.

[0206] • The melting temperature breadth (defined as the end melting temperature minus the onset melting temperature) increases.

[0207] Taken together, these results indicate that RCP thermal properties are improved to better suit end-use applications with high temperature conditioning / annealing steps. The production of expanded polypropylene (EPP) is a commercial example of its practice. Other applications are articles subjected to high temperature sterilization (e.g., autoclave and steam sterilization), and other polypropylene processing techniques where the article is reheated for further shaping (e.g., thermoforming of sheets, or injection stretch blow molding of preforms).

[0208] In some embodiments, the invention herein can be interpreted as not including any element or method that does not materially affect the basic and novel characteristics of the composition or method. In addition, in some embodiments, the invention can be interpreted as not including any element or method not specified herein.

[0209] Although the invention is shown and described herein with reference to particular embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the range and equivalents of the claims without departing from the invention.

Claims

1. A composition comprising: a first polypropylene comprising, as polymerized monomer, at least 90 wt. % propylene, based on the weight of the first polypropylene, alpha nucleation inhibitors, and Beta nucleating additives. 2 . The composition of claim 1 , wherein after annealing at an annealing temperature Ta for an annealing time ta, the composition has a first melting peak T1 and a second melting peak T2 as measured by differential scanning calorimetry at a heating rate of 20° C. / min.

3. The composition according to claim 2, wherein The composition has a third melting peak T3 as measured by differential scanning calorimetry at a heating rate of 20°C / min.

4. The composition of claim 1, wherein the alpha nucleation inhibitor comprises potassium stearate.

5. The composition according to claim 1, wherein The beta-nucleating additive comprises at least one of the following: a quinacridone dye in a gamma crystalline form; an aluminum salt of 6-quinizarin sulfonic acid; disodium phthalate; isophthalic acid or its derivatives; terephthalic acid or its derivatives; N',N'-dicyclohexyl-2,6-naphthalene dicarboxamide; a blend of an organic dibasic acid and an oxide, hydroxide or acid of a Group II metal; or a combination thereof.

6. The composition of claim 1, wherein the composition further comprises up to 5 wt% of a second polypropylene, based on the weight of the composition, wherein the polypropylene polymer is different from the first polypropylene and comprises at least 99 wt% propylene as a polymerized monomer, based on the weight of the second polypropylene, and has a crystallinity of at least 50 wt%, based on the weight of the second polypropylene.

7. The composition of claim 1, wherein the first polypropylene comprises isotactic polypropylene.

8. The composition of claim 1, wherein the first polypropylene comprises syndiotactic polypropylene.

9. The composition of claim 1, wherein the first polypropylene further comprises as polymerized monomers up to 6 wt% of one or more of ethylene, butene, pentene, hexene, or a combination thereof, based on the weight of the first polypropylene.

10. The composition according to claim 1, wherein The composition has a degree of crystallinity of at least 25 wt% based on the total weight of the first polypropylene as measured by NMR.

11. The composition of claim 1, further comprising a blowing agent.

12. The composition of claim 1 in the form of a masterbatch, wherein the alpha nucleation inhibitor and the beta nucleation additive together comprise 0.1 to 80 weight percent, based on the total weight of the composition.

13. A method for preparing a foamable polypropylene composition, the method comprising: a) compounding a first polypropylene with an alpha nucleation inhibitor to form a polypropylene blend, wherein the first polypropylene comprises at least 90 weight percent propylene as a polymerized monomer, based on the weight of the first polypropylene; b) mixing the polypropylene blend with a blowing agent to form a pre-annealing polypropylene composition; and c) annealing the pre-annealing polypropylene composition at an annealing temperature Ta for an annealing time ta to form the foamable polypropylene composition, wherein the foamable polypropylene composition has a first melting peak T1 and a second melting peak T2 as measured by differential scanning calorimetry at a heating rate of 20°C / min.

14. The method of claim 13, wherein: The polypropylene composition before annealing has a third melting peak T3 measured by differential scanning calorimetry at a heating rate of 20°C / min.

15. The method of claim 13, wherein step a) further comprises: A beta nucleation additive is compounded with the first polypropylene and the alpha nucleation inhibitor to form a polypropylene blend.

16. The method of claim 15, wherein at least one of the beta nucleation additive and the alpha nucleation inhibitor is in the form of a masterbatch.

17. The method of claim 13, wherein steps a) and b) are performed in a single compounding operation.

18. The method of claim 13, wherein step b) further comprises: The pre-annealing polypropylene composition is pelletized.

19. A method for preparing a foamed polypropylene composition, the method comprising: The foamable polypropylene composition according to claim 1 is heated to a foaming temperature higher than T1 and lower than T2.

20. The method of claim 19, further comprising: The pressure was reduced to below 1 atm during heating.

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