Silicone composition, method of manufacturing the same, and cable made therefrom

Abstract

The composition includes a peroxide-crosslinked or condensation-crosslinked organopolysiloxane material. The composition includes a silicone polymer. The composition also includes at least one of a metal oxide, a metal-containing compound, boric acid, or zinc borate. The metal oxide is selected from the group consisting of magnesium oxide, aluminum oxide, tin oxide, calcium oxide, titanium oxide, and barium oxide. The metal-containing compound generates a metal oxide from the group upon heating. The composition includes a platinum complex containing at least one unsaturated group and 33 to 100 parts by weight of mica based on 100 parts by weight of the organopolysiloxane material. The composition generates a ceramic material at temperatures of 610°C or higher.

Description

[Technical Field]

[0001] The present invention relates generally to silicone compositions, and also to methods for making the silicone compositions and components made therefrom. [Background technology]

[0002] Silicone materials are used in many applications, including insulation and fire safety applications. In some fire safety applications, it is desirable for the materials used to be resilient. However, these materials typically do not exhibit high heat reflectivity. Alternatively, materials used to provide good heat reflectivity in such applications are often rigid. Furthermore, materials known for use in such applications are often difficult to process. Summary of the Invention [Problem to be solved by the invention]

[0003] It would therefore be desirable to provide a composition that overcomes the aforementioned deficiencies. [Means for solving the problem]

[0004]

[0010] Provided herein are embodiments of compositions. In one embodiment, the composition comprises a peroxide-crosslinked or condensation-crosslinked organopolysiloxane material. The composition includes a silicone polymer. The composition also includes at least one of a metal oxide, a metal-containing compound, boric acid, or zinc borate. When present, the metal oxide is selected from the group consisting of magnesium oxide, aluminum oxide, tin oxide, calcium oxide, titanium oxide, and barium oxide. When present, the metal-containing compound yields a metal oxide of said group upon heating. The composition includes a platinum complex containing at least one unsaturated group and 33 to 100 parts by weight of mica based on 100 parts by weight of the organopolysiloxane material. The composition forms a ceramic material at temperatures of 610°C or higher.

[0005] In some embodiments, the organopolysiloxane material includes a peroxide crosslinker, hi other embodiments, the organopolysiloxane material is an elastomer and includes a vinyl-functional organopolysiloxane and a hydroxyl-functional organopolysiloxane.

[0006] In other embodiments, the mica is of the formula KAl2(F,OH)2 or (KF)2(Al2O3)3(SiO2)6).

[0007] In yet another embodiment, the silicone polymer is vinylmethylpolydimethylsiloxane.

[0008] In some embodiments, the platinum complex is a platinum-vinylsiloxane complex. In one such embodiment, the platinum-vinylsiloxane complex is a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex.

[0009] In certain embodiments, the metal oxide is aluminum oxide. In embodiments where the metal oxide is aluminum oxide, the platinum complex is a platinum-vinylsiloxane complex.

[0010] In certain embodiments, the composition further comprises a reinforcing filler, a non-reinforcing filler, or a mixture thereof. In embodiments, the reinforcing filler comprises silica.

[0011] Also provided are embodiments of methods of preparing the compositions. In one such embodiment, the method comprises mixing the components of the composition.

[0012] Additionally provided are cable and profile embodiments, each comprising the composition. DETAILED DESCRIPTION OF THE INVENTION

[0013] It is to be understood that the present invention may assume various alternative compositions and step sequences, unless expressly stated to the contrary. It is also to be understood that the specific components, materials, and methods described in the following specification are merely exemplary embodiments of the inventive concepts. Accordingly, specific properties, conditions, or other physical characteristics related to the disclosed embodiments are not to be considered limiting, unless expressly stated.

[0014] In embodiments, compositions are provided. In some embodiments, the compositions are ceramizable. For example, the compositions can form ceramic materials at high temperatures, preferably 610°C or higher. The compositions are suitable for use in fire safety applications, such as insulation for conductors. However, the compositions are also suitable for other applications, such as for use in profiles or to form other components.

[0015] Preferably, the composition comprises an organopolysiloxane material. In some embodiments, the organopolysiloxane material can be comprised of units of general formula (I):

[0016] [ka] wherein R may be the same or different and is an unsubstituted or substituted hydrocarbon group; r is 0, 1, 2 or 3, and has an average value of 1.9 to 2.1.

[0017] Examples of hydrocarbon radicals R are alkyl radicals, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or tert-pentyl radicals, hexyl radicals such as n-hexyl radical, heptyl radicals such as n-heptyl radical, octyl radicals such as n-octyl radical and isooctyl radicals such as 2,2,4-trimethylpentyl radical, nonyl radicals such as n-nonyl radical, decyl radicals such as n-decyl radical, n-dodecyl radical, groups such as dodecyl groups, octadecyl groups such as n-octadecyl groups, cycloalkyl groups such as cyclopentyl, cyclohexyl and cycloheptyl groups and methylcyclohexyl groups, aryl groups such as phenyl, biphenyl, naphthyl, anthryl and phenanthryl groups, alkaryl groups such as o-, m- or p-tolyl, xylyl and ethylphenyl groups, and aralkyl groups such as benzyl and α- and β-phenylethyl groups.

[0018] Examples of substituted hydrocarbon groups R are halogenated alkyl groups such as 3-chloropropyl, 3,3,3-trifluoropropyl and perfluorohexylethyl groups, and halogenated aryl groups such as p-chlorophenyl and p-chlorobenzyl groups.

[0019] Other examples of radicals R are vinyl, allyl, methallyl, 1-propenyl, 1-butenyl and 1-pentenyl, as well as 5-hexenyl, butadienyl, hexadienyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, ethynyl, propargyl and 1-propynyl.

[0020] The group R is preferably a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, particularly preferably a methyl group. In some embodiments, the group R may be preferably an alkenyl group having 2 to 8 carbon atoms, particularly preferably a vinyl group. Among unsubstituted or substituted hydrocarbon groups having 1 to 8 carbon atoms, a methyl group, a vinyl group, a phenyl group, or a 3,3,3-trifluoropropyl group is particularly preferred.

[0021] Preferably, alkyl groups, especially methyl groups, are bonded to at least 70 mol % of the Si atoms present in the organopolysiloxane material composed of units of formula (I). When the organopolysiloxane material contains Si-bonded vinyl and / or phenyl groups in addition to Si-bonded methyl and / or 3,3,3-trifluoropropyl groups, the amount of these latter is preferably 0.001 to 30 mol %.

[0022] Preferably, the organopolysiloxane material may be composed primarily of diorganosiloxane units. The terminal groups of the organopolysiloxane may be trialkylsiloxy groups, particularly trimethylsiloxy groups or dimethylvinylsiloxy groups. However, it is also possible for one or more of these alkyl groups to be substituted with hydroxyl groups or alkoxy groups such as methoxy or ethoxy groups. In some embodiments, the organopolysiloxane material may comprise a mixture of organosiloxanes. For example, in certain embodiments, the organopolysiloxane material may comprise a vinyl-functional organopolysiloxane and a hydroxyl-functional organopolysiloxane.

[0023] The organopolysiloxane material can be a liquid or a high viscosity material. 3 ~10 8 mm 2 It is preferred that the viscosity of the coating be 0.015 g / sec.

[0024] The organopolysiloxane material is crosslinked by peroxide or condensation crosslinking. A suitable crosslinking agent is used to crosslink the organopolysiloxane material. In some embodiments, a peroxide crosslinking agent is utilized to crosslink the organopolysiloxane material. Suitable peroxide crosslinking agents include peroxides such as dibenzoyl peroxide, bis(2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, or 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, or mixtures thereof, preferably bis(2,4-dichlorobenzoyl) peroxide or 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Preferably, the crosslinking agent comprises a mixture of bis(4-methylbenzoyl) peroxide (PMBP) and 2,5-dimethyl-2,5-di-tert-butylhexane peroxide (DHBP) in a ratio of 1:0.4 to 0.5:1, preferably 1:0.4.

[0025] The organopolysiloxane (A) according to the present invention also preferably comprises a reinforcing filler and / or a non-reinforcing filler. Examples of reinforcing fillers include those having a BET specific surface area of ​​at least 50 m 2 The silica filler may be pyrogenic or precipitated silica, with a % SiO 2 content of 1 / g. The silica filler may have hydrophilic properties or may be hydrophobized by known methods, such as those described in U.S. Pat. No. 5,057,151. In such cases, hydrophobization is generally carried out using 1 to 20% by weight of hexamethyldisilazane and / or divinyltetramethyldisilazane and 0.5 to 5% by weight of water, in each case based on the total weight of the organopolysiloxane material. These reagents are advantageously fed into a suitable mixing device, such as a kneader or internal mixer, in which an initial charge of the organopolysiloxane material is made, before gradually incorporating the reinforcing filler.

[0026] Examples of non-reinforcing fillers are powdered quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolite, metal oxide powders such as aluminum oxide, titanium oxide, iron oxide, or zinc oxide, barium silicate, barium sulfate, calcium carbonate, gypsum, and synthetic polymer powders such as polyacrylonitrile powder or polytetrafluoroethylene powder. The fillers used may also contain fibrous components such as glass fibers or synthetic polymer fibers. The BET specific surface area of ​​these fillers is greater than 50 m. 2 / g or less is preferred.

[0027] The amount of filler present in the organopolysiloxane material is preferably from 1 to 200 parts by weight, particularly preferably from 30 to 100 parts by weight, in each case based on 100 parts by weight of organopolysiloxane material.

[0028] Depending on the specific application, additives such as processing aids, e.g., plasticizers, pigments, or stabilizers, e.g., heat stabilizers, can be added to the organopolysiloxane material, which can then be crosslinked or vulcanized to obtain an elastomer. Examples of plasticizers that can be used as additives include polydimethylsiloxane terminated with trimethylsilyl groups or silanol groups, or vinylsiloxane and diphenylsilanediol. Combinations of the above plasticizers can also be used. Examples of heat stabilizers that can be used as additives include transition metal salts of fatty acids, such as iron octoate, transition metal silanolates, e.g., iron silanolate, and cerium(IV) compounds. The organopolysiloxane material used can be a conventional condensation-crosslinked organopolysiloxane, as described, for example, in EP 0 359 251, or other known addition-crosslinked materials.

[0029] Each component used to prepare the organopolysiloxane material may be a single type of material or a mixture of two or more different materials that together form the component. In some embodiments, the organopolysiloxane material does not contain any additional components other than those listed above. For example, in one such embodiment, the organopolysiloxane material does not contain hydrophobic metal nitrides and carbides.

[0030] Preferably, the composition comprises a silicone polymer. Preferably, the silicone polymer is vinylmethylpolydimethylsiloxane. In certain embodiments, the silicone polymer comprises at least one vinyldimethylsiloxane terminal unit. In these embodiments, the vinylmethylpolydimethylsiloxane can be of the following formula:

[0031] [ka] wherein Y is 1000 to 10,000 siloxane units, preferably about 7500 to 10,000 units. In other embodiments, the silicone polymer includes at least one vinylmethylsiloxane unit included in the main polymer chain. In these embodiments, the vinylmethylpolydimethylsiloxane can be of the formula:

[0032] [ka] where X + Y is equal to about 500-10,000 siloxane units, preferably about 7,500-10,000 units. In yet other embodiments, the silicone polymer comprises at least one vinyldimethylsiloxane terminal unit and at least one vinylmethylsiloxane unit in the main polymer chain. In these embodiments, the vinylmethylpolydimethylsiloxane can be of the formula:

[0033] [ka] wherein X + Y is equal to about 500 to 10,000 siloxane units, preferably about 7,500 to 10,000 units. Mixtures of the above vinylmethylpolydimethylsiloxanes can also be utilized. Preferably, in these embodiments, a vinyl group is provided for every 500 to 10,000 siloxane units. In some embodiments, a vinyl group is provided for every 1,000 to 5,000 siloxane units. In one such embodiment, a vinyl group is provided for every 1,200 siloxane units. In other embodiments, the silicone polymer is a dimethylpolydimethylsiloxane containing at least one saturated terminal unit. In these embodiments, the dimethylpolydimethylsiloxane can be of the formula:

[0034] [ka] In the formula, Y is 1,000 to 10,000 siloxane units, preferably about 7,500 to 10,000 units.

[0035] The composition includes at least one of a metal oxide, a metal-containing compound, boric acid, or zinc borate. When present, the metal oxide is selected from the group consisting of magnesium oxide, aluminum oxide, tin oxide, calcium oxide, titanium oxide, and barium oxide. When present, the metal-containing compound generates a metal oxide of the group upon heating. Examples of such metal-containing compounds include, for example, metal hydroxides. In some embodiments, the above components are provided in the composition in an amount of 1.5 to 40 wt. %, preferably 10 to 20 wt. %, always based on the total weight of the composition. Mixtures of at least one of the above metal oxides, metal-containing compounds, boric acid, and zinc borate can also be used.

[0036] The composition includes a platinum complex containing at least one unsaturated group. Preferably, the unsaturated group is a hydrocarbon group. Examples of preferred platinum complexes include platinum-olefin complexes, platinum-aldehyde complexes, platinum-ketone complexes, platinum-vinylsiloxane complexes, or platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes (with or without detectable organic halogen content), platinum-norbornadiene-methylacetonate complexes, bis(gamma-picoline)platinum dichloride, trimethylenedipyridine platinum dichloride, dicyclopentadiene platinum dichloride, (dimethyl sulfoxide)(ethylene)platinum(II) dichloride, and the reaction products of platinum tetrachloride with an olefin and a primary amine, a secondary amine, or both a primary amine and a secondary amine, such as the reaction product of sec-butylamine and platinum tetrachloride dissolved in 1-octene. In certain embodiments, the platinum complex is a platinum-vinylsiloxane complex. Preferably, the platinum-vinylsiloxane complex is a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex. However, other platinum-vinylsiloxane complexes may be suitable. The amount of platinum complex used is 5 to 200 ppm, preferably 10 to 100 ppm. This amount is based on elemental platinum. It is also possible to use a mixture of platinum complexes in the composition.

[0037] The composition includes mica. The mica can be of the muscovite or phlogopite variety. Preferably, the mica is a muscovite variety. In these embodiments, the mica can be of the formula KAl2(F,OH)2 or (KF)2(Al2O3)3(SiO2)6. In some embodiments, the composition includes at least 33 parts by weight of mica based on 100 parts by weight of organopolysiloxane material. In one such embodiment, the composition includes 33 to 100 parts by weight of mica based on 100 parts by weight of organopolysiloxane material. In another embodiment, the composition includes 50 to 100 parts by weight of mica based on 100 parts by weight of organopolysiloxane material. In another embodiment, the composition includes 65 to 100 parts by weight of mica based on 100 parts by weight of organopolysiloxane material.

[0038] Preferably, the mica is provided as a fine powder. In some embodiments, the mica can have a D50 value of 1 to 75 μm, which represents the particle size distribution of the mica. In one such embodiment, the mica can have a D50 value of 25 μm. The mica can also have a desirable aspect ratio (Jennings factor). For example, the mica can have an aspect ratio of 80.

[0039] In certain embodiments, the composition can be formed by a method comprising mixing the above-described components. The components can be mixed in an apparatus such as, for example, an internal mixer or another suitable mixing device. In these embodiments, it is preferred to add the mica to the mixture in two or more portions. For example, in certain embodiments, the mica can be added to the mixture in equal portions. In other embodiments, the portions of mica added to the mixture can be unequal. In these embodiments, the mica can be added in portions corresponding to 1 to 30 parts per 100 parts of the mixture. In some embodiments, the mixture can already contain the other components described above before the mica is added. In these embodiments, the mica can be added in portions of 10 kilograms (kg) or less or in portions greater than 10 kg.

[0040] After mixing, the mixture is cured. The mixture is cured for a predetermined period of time. In some embodiments, the composition is formed by curing the mixture at ambient temperature. Heating the mixture can shorten the time it takes for the mixture to cure. In certain embodiments, the mixture can be heated to a temperature of 25 to 250°C for curing. Preferably, the mixture is cured at a temperature ranging from about 40°C to about 200°C. Other curing mechanisms, such as moisture curing, peroxide curing, and radiation curing, can also be used to form the composition.

[0041] Preferably, curing results in an elastomeric composition. Furthermore, after curing, the composition can initiate sintering at temperatures as low as 610°C. In certain embodiments, this property allows the composition to form a ceramic material at temperatures above 610°C. The ceramic material can be formed as a layer, which may allow the composition to retain its functionality when exposed to fire. When the composition exhibits low density, especially when exposed to high temperatures such as temperatures above 900°C, the composition also exhibits higher levels of mechanical properties, better heat aging properties, and greater insulating capabilities than conventional silicone compositions. Furthermore, the ceramic material formed during fire is significantly more resistant to impact and shock than the mixtures described in the prior art. This simply forms a stable ash layer.

[0042] The composition can exhibit the same electrical and heat aging properties as known silicone rubber compositions. Furthermore, the composition exhibits excellent mechanical properties. For example, in certain embodiments, the composition exhibits a tensile strength of 400 psi or greater. In one such embodiment, the composition exhibits a tensile strength of 400 to 1200 psi. The tensile strength of the composition can be measured in accordance with ASTM D412 using a tensile tester. An example of a tensile tester suitable for use in measuring the tensile strength of the composition in accordance with ASTM D412 is the TensiTech III tester manufactured by Tech-Pro, Inc. In some embodiments, the composition exhibits an elongation at break of 100% or greater. In other embodiments, the composition exhibits an elongation at break of 200% or greater. Preferably, the composition exhibits an elongation at break of 200 to 400%. The elongation of the composition can be measured in accordance with ASTM D412 and when measuring tensile strength. In some embodiments, the composition exhibits a Shore A hardness of 50 or greater. In these embodiments, the composition can exhibit a Shore A hardness of 70 or greater. Preferably, the composition exhibits a Shore A hardness of 70 to 100. The Shore A hardness of the composition can be measured in accordance with ASTM D2240 using a hardness tester. An example of a hardness tester suitable for measuring Shore A hardness in accordance with ASTM D2240 is the Portable Hardness Tester Type A sold by Instron. In yet other embodiments, the composition exhibits a tear strength of 100 N / mm or greater. In these embodiments, the composition can exhibit a tear strength of 100 to 150 pounds per inch. The tear strength of the composition can be measured in accordance with ASTM D624, Test Die B specimens, using a TensiTech III tester manufactured by Tech-Pro, Inc. Additionally, the composition can exhibit a desirable specific gravity, for example, of 1.40 to 1.60. The specific gravity of the composition can be measured in accordance with ASTM D792 using a hydrostatic specific gravity tester. An example of a hydrostatic specific gravity tester suitable for measuring specific gravity in accordance with ASTM D792 is the SECURA 224-1S analytical scale equipped with a density analytical balance kit manufactured and sold by Sartorius Group.

[0043] As described above, the composition exhibits good mechanical properties, heat aging properties, and insulating properties. Furthermore, the composition may also exhibit excellent elastomeric and / or heat-reflective properties. Thus, the composition has a wide range of uses, including fire safety applications. The composition is also processable and easy to use, even in known processes, such as extrusion processes. Because of these properties, the composition can be utilized to form cables and profiles, which may include the composition. The cable can be a communications cable or an energy cable. The profile can be a foam or compact gasket for fire screening for rooms, cabinets, or safety, or a layer for ablation control in the lining of rocket engines or other aerospace systems. [Example]

[0044] The following examples are presented solely for the purpose of further illustrating and disclosing composition embodiments. Example 2 set forth below illustrates an embodiment of a composition within the scope of the present invention.

[0045] [Example 1] It is end-capped with trimethylsiloxy groups and is composed of 99.93 mole percent dimethylsiloxane units and 0.07 mole percent vinylmethylsiloxane units, and has a viscosity of 8*10 at 25°C. 6 100 parts of a diorganopolysiloxane having a viscosity of 1000 psi mPa*s was first thermally decomposed into the gas phase in a kneader operated at 150°C, and then mixed with 200 ml of 2 / g, then 1 part dimethylpolysiloxane end-capped with trimethylsiloxy groups and having a viscosity of 96 mPa*s at 25°C, then 7 parts dimethylpolysiloxane having a SiC-bonded hydroxy group at each end unit and having a viscosity of 40 mPa*s at 25°C, 36 parts aluminum oxide having a particle size >10μ and an alkali metal oxide content <0.5 wt% and 0.3 wt% platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex.

[0046] [Example 2] Next, 85 parts by weight of Example 1 were mixed with 15 parts by weight of ELASTOSIL® V 1200 A. Mixing was performed using an internal 75 L mixer, a Kneader Machinery model KD75-250 manufactured and sold by Wacker Chemie AG. Sufficient mixing time was applied to achieve a uniform blend. 70 parts by weight of mica (IMERYS Suzorite® 325-HK) and 0.6 parts by weight of a peroxide crosslinker (Varox® DBPH, Vanderbilt Chemicals) were also added. The mica was added in three equal portions over time, with mixing between each addition. After all the mica was added to the mixture, the crosslinker was added and the composition was mixed until uniform.

[0047] The composition of Example 2 was cured for 10 minutes at 350°F. After curing, the composition of Example 2 exhibited a specific gravity of 1.48, a tensile strength of 562 psi, an elongation at break of 252%, a Shore A hardness of 75, and a break strength of 122 lb / in. The specific gravity, tensile strength at break, elongation at break, Shore A hardness, and tear strength were determined according to the methods set forth above.

[0048] It will be apparent from the foregoing detailed description that various modifications, additions, and other alternative embodiments are possible without departing from the true scope and spirit of the present invention. The embodiments discussed herein have been chosen and described to best illustrate the principles of the present invention and to provide a practical application thereof so as to enable those skilled in the art to use the invention in various embodiments and to make various modifications suited to the particular use intended. It is to be recognized that all such modifications and variations are within the scope of the present invention.

Claims

1. 1. A composition comprising: (a) a peroxide-crosslinked or condensation-crosslinked organopolysiloxane material containing a reinforcing filler; (b) a crosslinkable silicone polymer that is an organopolysiloxane material; (c) at least one of a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, tin oxide, calcium oxide, titanium oxide, and barium oxide, a metal-containing compound that generates a metal oxide of said group upon heating, boric acid, or zinc borate; (d) a platinum complex containing at least one unsaturated group, and (e) 33 to 100 parts by weight of mica based on 100 parts by weight of component (a) and component (b). which, after curing, produces a ceramic material at a temperature of 610°C or greater.

2. The composition of claim 1 , wherein the organopolysiloxane material comprises a peroxide crosslinker.

3. The mica has the formula KAl ２ (F, OH) ２ or (KF) ２ (Al ２ O ３ ) ３ (SiO ２ ) ６ 2. The composition of claim 1 , wherein

4. The composition of claim 1 wherein the silicone polymer is vinylmethylpolydimethylsiloxane.

5. The composition of claim 1, wherein the platinum complex is a platinum-vinyl siloxane complex.

6. The composition of claim 5, wherein the platinum-vinyl siloxane complex is a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex.

7. 10. The composition of claim 1, wherein the organopolysiloxane material is elastomeric and comprises a vinyl-functional organopolysiloxane and a hydroxyl-functional organopolysiloxane.

8. The composition of claim 1 wherein the metal oxide is aluminum oxide.

9. The composition of claim 8, wherein the metal oxide is aluminum oxide and the platinum complex is a platinum-vinylsiloxane complex.

10. The composition of claim 1 , wherein the reinforcing filler comprises silica.

11. 2. The composition of claim 1, comprising 50 to 100 parts by weight of mica per 100 parts by weight of component (a) and component (b).

12. The composition of claim 1, wherein the composition exhibits a specific gravity of 1.40 to 1.

60.

13. A method for preparing the composition of claim 1 comprising mixing components (a) through (e).

14. A cable in which the insulation of a conductor comprises the composition of claim 1.

15. A cable comprising the composition of claim 1.

16. The composition of claim 1, wherein the mica is added in two or more portions.