TW201309734A - Polypropylene resin suitable for soft nonwoven applications - Google Patents

Abstract

A polypropylene impact copolymer is disclosed. The propylene impact copolymer composition comprises from 60 to 90 percent by weight of the impact copolymer composition of a matrix phase, which can be a homopolymer polypropylene or random polypropylene copolymer having from 0.1 to 7 mol percent of units derived from ethylene or C4-C10 alpha olefins. The propylene impact copolymer composition also comprises from 10 to 40 percent by weight of the impact copolymer composition of a dispersed phase, which comprises a propylene/alpha-olefin copolymer having from 6 to 40 mol percent of units derived from ethylene or C4-C10 alpha olefins, wherein the dispersed phase has a comonomer content which is greater than the comonomer content in the matrix phase. The propylene impact copolymer composition is further characterized by having the beta/alpha ratio being 1.2 or less. The polypropylene impact copolymers of the present invention are well suited for making spunbond fibers which can be used to make nonwoven fabrics having good haptics.

Description

Polypropylene resin for soft non-woven applications Field of invention

The present invention relates to a novel polypropylene impact copolymer composition which is ideally suited for the production of spunbonds having improved softness and good tensile strength (spunbond) ) Not woven. The composition comprises a plurality of matrix phases comprising a homopolymer polypropylene or a random polypropylene copolymer having a fraction of 0.1 to 7 moles derived from ethylene or A unit of a C ₄ -C ₁₀ alpha-olefin, and a minority of a dispersed phase comprising a propylene/α-olefin copolymer having units having an alpha-olefin content ranging from 6 to 40 mole percent. The impact copolymer has a characteristic that the ratio of the substrate MFR to the dispersed phase MFR is 1.2 or less.

Background of the invention

Polypropylene (PP) spunbonded non-woven fabric (SBNW) materials are very large for the global nonwovens market, exceeding the total global volume of 1700 kT, and are distributed in market segments such as sanitary, furniture, medical, and industrial. In addition to noise and drape improvements, one of the most important properties desired for absorbent sanitary materials and medical nonwovens produced from PP is improved to softness or feel. Polypropylene is a polymer choice in the spin-bonding process due to its high tensile and abrasion resistance properties, ease of processing, and low cost and high availability in the history of polymers. However, the haptics of polypropylene fabrics are not ideal in terms of perched air softness.

There are now many possible solutions to the introduction of softness or cloth-like feel on spunbonded nonwovens. These include the use of a two-component spin-bonding process, the use of a blend of propylene/ethylene plastic and PP, and the spinning of a random copolymer which is a random copolymer of polypropylene with 2-4% by weight and units derived from ethylene. Silk, and/or a slip additive that changes the coefficient of friction (COF) of the PP surface. Furthermore, in order to change the surface of the fabric and thus make it feel softer, manufacturing modifications can be implemented. Although these methods have been so successfully proven, they increase the cost or inefficiency of the process. Thus, new polypropylene materials can be spun into fibers and produce soft fabrics in a spunbonding process.

Summary of invention

A special impact copolymer that has historically been considered to be unspun has been found to be capable of meeting at least some of the desired properties. Thus, in one aspect of the invention, there is provided a polypropylene impact copolymer which can be spun into fibers using conventional spunbonding processes, and which will form polypropylene fibers and a fabric forming a fabric having improved softness. In one embodiment, the invention is a polypropylene impact copolymer composition comprising from 60 to 90% by weight of a substrate phase of the impact copolymer composition comprising a homopolymer polypropylene or random polypropylene a copolymer having from 0.1 to 7 mole percent of units derived from ethylene or a C ₄ -C ₁₀ alpha-olefin; and from 10 to 40% by weight of the impact copolymer composition dispersed, preferably a partially miscible phase comprising a propylene/α-olefin copolymer having an alpha olefin content ranging from 6 to 40 mole percent, wherein the comonomer content of the dispersed phase is greater than the comonomer of the substrate phase Body content. Although partial miscibility is required, the difference must be sufficient to result in at least two distinct phases. While the specific amount of comonomer must be different in order to ensure that the differentiated phases differ depending on the molecular weight of the polymer, it is generally preferred that the comonomer content of the dispersed phase is at least greater than 10 mole percent (absolute), More preferably, it is at least greater than 12 mole percent. The impact copolymer of this specific example further has a characteristic that the ratio of the substrate MFR to the dispersed phase MFR (also associated with the β/α value) is 1.2 or less.

A second aspect of the invention is a fiber produced from the impact copolymer of the first aspect of the invention. This fiber can be melt spun into 0.2 to 10 denier or 0.5 to 2.0 denier on a conventional spinning apparatus and will have a wide bonding window.

Another aspect of the invention is a spunbonded nonwoven fabric produced from the fibers of the second aspect of the invention. The spunbonded nonwoven fabric of the specific example of the present invention has a lower adhesion temperature of at least 5 ° C, preferably at least 10 ° C lower than comparable non-woven fabrics made of hPP fibers, as measured by the calender oil temperature; Improved softness measured according to the handle-o-meter and an evaluation of the sensory test on the improvement of non-woven fabrics such as smoothness, garment-like feel, stiffness and noise, and hPP fibers. (sensory testing panel) results.

Simple illustration

Figure 1 is a transmission electron microscope image of an immiscible propylene impact copolymer system; Figure 2 is a transmission electron microscope image of a partially miscible propylene impact copolymer system; Figure 3 is a bar graph depicting The results of the softness tester of several embodiments and comparative examples of the present invention; FIG. 4 is a view showing the tensile strength versus the bonding temperature of the several embodiments and comparative examples of the present invention in the machine direction; FIG. 5 is a view showing The transverse tensile strength versus bonding temperature of several embodiments and comparative examples of the present invention; FIG. 6 is a diagram showing the elongation versus the bonding temperature in the machine direction of several embodiments and comparative examples of the present invention; and FIG. The graph shows the elongation in the transverse direction versus the bonding temperature for several examples and comparative examples of the present invention.

Detailed description of the preferred embodiment

The following definitions and analytical methods are used in the present invention: The term "polymer" as used herein refers to a polymeric compound prepared by polymerization of a plurality of monomers of the same or different types. The generic term polymer includes the term "homopolymer", generally used to refer to a polymer prepared from a single type of monomer, and "copolymer" refers to a preparation of two or more different monomers. polymer.

"Polypropylene" shall mean a polymer comprising more than 50% by weight of units derived from propylene monomers. This includes polypropylene homopolymers or copolymers (meaning units derived from two or more comonomers).

Density is determined in accordance with ASTM D792.

It also means that the "melt flow rate" as "MFR" is determined in accordance with ASTM D1238 (230 ° C, 2.16 kg).

The term molecular weight distribution or "MWD" is defined as the ratio of the weight average molecular weight to the number average molecular weight (M _w /M _n ). M _w and M _n are measured using a method based on common gel permeation chromatography (GPC) of the known art.

"E _m " refers to the percentage of moles of comonomer (represented by ethylene) in the substrate phase.

"E _tot " means the total weight percentage of comonomer (represented by ethylene) in the propylene impact copolymer, and is determined by S. Di Martino and M. Kelchtermans "Determination of the Composition of Ethylene-Propylene Rubbers Using 13C- Measured by a conventional method described in NMR Spectroscopy "J. of Applied Polymer Science, v56, 1781-1787 (1995).

"F _c " means the weight percentage of the dispersed rubber phase in the total impact copolymer. In general, F _c may be readily determined by mass balance, i.e., equal to the ratio of the total amount of material of the material produced in the second reactor produced. For a typical impact copolymer, the rubber content of the impact copolymer can be evaluated by measuring the amount of material that remains soluble in xylene at room temperature. For substrates having a low ethylene content (e.g., less than about 2 mole percent) of the phase, the xylene solubles of the method may be applied to estimate the F _c. The xylene solubles (XS) were measured according to the following procedure: 0.4 g of the polymer was stirred at 130 ° C for 30 minutes and dissolved in 20 ml of xylene; the solution was then cooled to 25 ° C and filtered to remove insoluble after 30 minutes. The polymer part. The resulting filtrate was analyzed by flow injection polymer analysis using a Viscotek ViscoGEL H-100-3078 column with a flow rate of 1.0 ml/min THF. The column is connected to a Viscotek Model 302 triple detector array with a light scattering, viscometer and refractometer detector operating at 45 °C. Instrument calibration was maintained with Viscotek PolyCAL ^TM polystyrene standards. The amount of xylene solubles measured by the Viscotek method corresponds to the amount of dispersed rubber phase (F _c ) in the impact copolymer. For purposes of the present invention unless and otherwise specified, the mass balancing method to be used to determine F _c.

"E _c " refers to the weight percentage of the ethylene content in the dispersed phase and is calculated by E _c = [E _{tot -} E _m (1-F _c )] / F _c .

The "bonding window" is determined by the surface temperature of the calendar roll and the smooth roll or the range of the heated oil temperature, which can be used in the bonding process for manufacturing the spunbonded nonwoven fabric to obtain the The physical properties of the fabric (eg tensile strength, abrasion resistance and elongation) are balanced.

The "softness meter" is an instrument available from Thwing-Albert. The softness meter measures a "handle" which is a combination of elasticity and surface friction of, for example, a non-woven sheet material. In this test, the smaller the value, the more desirable the fabric.

The following steps were used to generate tensile test data for the nonwoven fabric of the present invention. The basis weight can be determined by measuring the weight of the fabric of a known area. For example, the basis weight (g/m ² ) can be determined in accordance with ASTM D 3776.

The tensile test is based on the following criteria, namely the EDANA test method:

a) ERT 60.2-99 standard conditions; b) ERT 130.2-89 non-woven sampling; c) ERT 20.2-89 and Iso test methods a) ISO 554-76(E) b) ISO 186: 1985.

The breaking force and elongation of the non-woven material were measured by the following procedure. This test method describes two steps for completing the tensile test of a non-woven material, A-IST 110.4-02 and B-ERT 20.2-89. These steps used two specimens, selected for A-25 mm (1.0 in.) strip fabric tensile and B-50 mm (2.0 in.) strip fabric tensile. A test specimen was clamped in a tensile test machine at a jaw spacing of 200 mm, and a force was applied at a rate of 100 mm/min to stretch the test specimen until it broke. The breaking force values and elongation values of the test specimens were obtained via a computer interface.

The breaking force (ie, the breaking stress) is the maximum force applied before a material breaks. Brittle materials usually break at maximum force. Soft materials usually experience a maximum force before breaking. The maximum tensile strength is the strength when a material is subjected to a tensile test. It is a stress that a material can withstand without breaking or tearing. High-precision electronic test instruments are used to measure the elongation and tensile strength of materials when tensile forces are applied to the material. The force exerted on the sample is read directly from the test machine or from the drawing during the test step. At least 5 samples were tested for each sample and the average was calculated and used to observe the fracture force of the sample. This average is called maximum breaking force or maximum tensile strength.

The elongation (i.e., the strain at break) is the deformation caused by the tension of the primary force in the direction of the load. Elongation is expressed as a percentage of the length of the stretched material and the length of the unstretched material. Elongation at break is determined at the point at which the stretched material breaks. The apparent elongation is determined by the increase in length from the beginning of the force-extension curve to a point corresponding to the breaking force or other specified force. The surface elongation is calculated from the calculated length (L ₀ ) as a percentage of the length increase.

"Abrasion resistance" was measured as follows. A non-woven fabric or sheet was worn using a Sutherland 2000 friction tester to determine the fuzz level. A lower degree of fluff is required, which means that the fabric has a higher resistance to wear. According to ISO POR 01 106 (attach a 2 lb of alumina 320-gravel laundry sandpaper and rub 20 cycles at a rate of 42 cycles per minute) wear a 11.0 cm x 4.0 cm non-woven fabric with sandpaper to allow the spread The fibers accumulate on the surface of the fabric. The scattered fibers were collected with tape and the weight was measured. The degree of fluff is then determined by dividing the total weight of the dispersed fibers by the area of the fiber sample (44.0 cm ² ).

"β/α" (b/a) is conceptually the ratio of the molecular weight of the dispersed phase (ethylene propylene rubber, that is, EPR) to the molecular weight of the substrate phase. It is generally measured by dividing the intrinsic viscosity (IV) of the dispersed phase by the IV of the homopolymer or random copolymer substrate. However, to a practical extent, as used for the production of impact copolymer polypropylene products, b/a is defined as the melt flow of the homopolymer/random copolymer reactor (first reactor) product and the total impact. The ratio of the product of the copolymer reactor (second reactor) was measured on a stable powder sample according to the following formula. For the impact copolymer produced in the reactor, when β/α is maintained within the specified range, the product gel content can be minimized and the rubber area size can be minimized.

β/α=[(MFR ₁ /MFR ₂ ) ^0.213 -1]/[(Fc/100)+1]

Wherein MFR ₁ is the first reactor (substrate phase only) and MFR ₂ is the second reactor (total ICP).

The "miscibility" of the dispersed phase in the substrate phase was measured by a transmission electron microscope ("TEM") according to the following method. As seen in the comparison between Figure 1 (showing a completely immiscible system) and Figure 2 (showing a partially miscible system), the sign of immiscibility is the darkening and transformation of the crystalline sheet structure in the modified formulation via the rubber. Observed by the appearance of the big. This darkening, that is, the relatively brighter region of the appearance of the "dirty sheet" is a sign of partial miscibility and mixing of the elastomer has occurred (see, for example, the area in the circle). Because of the lower density components (such as elastomers), the higher density components are more strongly dyed, so these darker, speckled diffusion regions are identified and elastomers in the crystalline homopolymer polypropylene. Partial miscibility in the substrate is associated. Therefore, materials containing such dirty sheets in TEM images are referred to as "partially miscible".

The TEM method was as follows: Samples were prepared from pellets and fabrics. The extruded sheet sample is trimmed such that the cut portion can be collected centrally and the cut portion is perpendicular to the extruded stream. The fabric sample is embedded in an epoxy resin to make the fiber strong and provide stability during cutting. Prior to dyeing, the trimmed sample was cryopolished at -60 °C by removing the cut portion from the block to avoid the elastomer phase being rubbed. The cryogenically polished agglomerates were dyed with a vapor phase of 2% aqueous osmium tetroxide at ambient temperature for 3 hours. The staining solution was prepared by weighing 0.2 gm of ruthenium (III) chloride hydrate (RuCl3 x H2O) in a glass bottle with a screw cap and adding 10 ml of a 5.25% aqueous sodium hypophosphite solution to the bottle. The samples were placed in a glass vial using a glass slide with double-sided tape. The slide was placed in the bottle in order to bring the agglomerate about 1 inch above the dyeing solution. A nearly 90 nm thick cut portion was collected at ambient temperature using a diamond knife on a Leica EM UC6 slicer and placed on an unused TEM grid of 600 mesh for viewing. JEOL JEM-1230 was operated at 100 kV accelerating voltage to collect images and collected with a Gatan-791 and 794 digital camera. Process images with Adobe Photoshop 7.0. Size distribution analysis: Image analysis was performed from TEM images using Leica Qwin Pro V2.4 software. The magnification is selected based on the number and size of features being analyzed. In order to take into account the binary image generation of the elastomer distribution, manual depiction of the elastomeric region was performed using TEM photographs using black Sharpie markers. The depicted TEM images were scanned using Hewlett Packard Scan Jet 4c and imported into Adobe Photoshop 7.0. The image is enhanced by adjusting the brightness and contrast to more clearly reveal the features of interest. The digital image is imported into the Leica Qwin Pro V2.4 analysis program and converted to a binary image by setting a gray-level threshold to include the feature of interest. Once a binary image is produced, the image is edited with other processing tools prior to image analysis. Some features include the removal of edge features, acceptance or exclusion of features, and the need to separate features for manual cutting. Once the features in the image are measured, the size data is exported to an Excel spreadsheet that produces a range of bins for the demand feature. Using the histogram function, the size data is placed into the appropriate bin range and a histogram of the equivalent circular diameter to the frequency percentage is generated. Report the circle diameter minimum, maximum and average size and standard deviation parameters. The same binary image was used for size distribution analysis to determine the area percentage analysis occupied by the elastomeric region in the PP substrate. This value can be reported as the percentage of the elastomeric area occupied in the two-dimensional space.

The propylene impact copolymer of the present invention (sometimes referred to as "ICPs") comprises at least two main components: a substrate and a dispersed phase. The substrate phase comprises from 60 to 90% by weight, preferably from 65 to 85% by weight of the impact copolymer composition. The substrate phase may be a homopolymer polypropylene or a random polypropylene copolymer having from 0.1 to 7 mole percent, preferably from 0.5 to 3 mole percent, derived from ethylene or a C ₄ -C ₁₀ alpha-olefin Unit. Generally, the substrate preferably comprises a propylene/[alpha]-olefin copolymer and ethylene is the preferred comonomer.

Particularly for high speed spinning processes, such as for spunbond applications, the substrate phase propylene homopolymer or random copolymer should have from 0.5 to about 10 g/10 min, preferably from 1.0 to about 7 g/10 More preferably, the melt flow rate is in the reactor (i.e., prior to cracking) in the range of from about 1.2 to about 4 g/10 min. These materials can be advantageously cracked to give a higher melt flow rate, for example by reaction with a peroxide. This cleavage typically occurs in the post reactor and may advantageously increase the MFR at a cleavage ratio of from 7 to 35, preferably from 8 to 30, more preferably from 10 to 25 such that the MFR is 7 for the total ICP obtained. It is in the range of 350 g/10 min, preferably 10 to 150 g/10 min, more preferably 15 to 100 g/10 min or even more preferably 25 to 65 g/10 min.

This MFR can be as high as 2000 g/10 min for total ICP (whether lysed or from the reactor) for meltblowing applications. For staple fiber applications, the MFR can range from 8 to 35 g/10 min or 12 to 18 g/10 min for total ICP. For other applications, such as blown or cast film, the MFR may be lower, including the MFR of the fraction (ie, the MFR is less than one).

For high speed spinning applications, the propylene impact copolymer should have a narrow molecular weight distribution (Mw/Mn), such as less than 3.5 or preferably less than 3. This can be achieved, for example, by using a single site catalyst or by utilizing cleavage.

The dispersed phase of the propylene impact copolymer of the present invention comprises 10 to 40% by weight, preferably 15 to 35% by weight, of the impact copolymer. The dispersed phase comprises a propylene/α-olefin copolymer having an α-olefin content ranging from 6 to 40 mole percent, preferably from 7 to 30 percent, and even more preferably from 8 to 18 percent, wherein the dispersed phase The comonomer content is greater than the comonomer content of the substrate phase. While partial miscibility is required, the difference in comonomer content of the substrate phase from the dispersed phase should be sufficient to result in at least two distinct phases being present. While the specific amount of comonomer must be different in order to ensure that the differentiated phases differ depending on the molecular weight of the polymer and the relative amounts of the different phases, it is generally preferred that the comonomer content of the dispersed phase is at least greater than 10 moles. The percentage (absolute), more preferably at least greater than 12 mole percent. For the dispersed phase, the α-olefin as a comonomer may be ethylene or a C ₄ -C ₁₀ α-olefin. Although not intended to be bound by theory, it is assumed that when the dispersed phase is partially soluble in the substrate phase, the softness of the resulting fiber or nonwoven fabric can be enhanced. Specifically, it is generally preferred that the comonomer used in the dispersed phase be the same as the comonomer (if any) used in the substrate phase, as this is believed to help increase miscibility. Thus, ethylene is also a preferred comonomer for the dispersed phase.

When the impact copolymer of the present invention further has a ratio of the substrate MFR (before any cracking) to the dispersed phase MFR (also associated with the β/α value) of 1.2 or less, preferably 1.0, or even When the characteristics are 0.9 or less, it is found that the softness of the obtained fiber and/or nonwoven fabric is improved. Furthermore, it is believed that having a similar melt flow ratio helps the dispersed phase to be more mutually soluble in the substrate phase, which is inferred to result in improved softness and high speed spinnability.

As previously stated, it is believed that when the dispersed phase is partially soluble in the phase of the substrate, the softness will be enhanced. The mutual solubility is measured according to the above method.

The impact copolymer of the present invention preferably has a total comonomer (preferably ethylene) content of from 0.6 to 20.2.

When these impact polypropylene products can be produced by melt synthesis of individual polymer components, it is preferably produced in a reactor. This is produced by polymerizing propylene in a first reactor as a substrate polymer and transferring from the first reactor to a second reactor, and in the presence of a highly crystalline material, propylene and ethylene (or other Copolymerization) is conveniently achieved by copolymerization. Such "reactor grade" products can theoretically be interpolymerized in one reactor, but are preferably formed in series using two reactors. The impact copolymers of the present invention can be conveniently prepared via conventional (for impact copolymer) polymerization processes such as a two-step process, although it is conceivable to produce in a single reactor. Each step can be carried out separately in one of a gas phase or a liquid slurry phase. For example, the first step can be carried out in a gas phase or a liquid slurry phase. The dispersed phase is preferably polymerized in a second gas phase reactor.

In an alternative embodiment, to obtain a variable melt flow fraction, the polymeric material for the substrate is made in at least two reactors. This was found to increase the processability of the impact copolymer. This can be particularly applied to the production of staple fibers via a short spinning process.

As is generally known in the art, hydrogen can be added to any reactor to control molecular weight, intrinsic viscosity, and melt flow rate (MFR). The composition of the dispersed rubber phase is controlled via the ethylene/propylene ratio and the amount of hydrogen (typically in the second reactor).

For example, the final impact copolymer obtained from the reactor can be blended with various other ingredients including other polymers. As is generally known in the art, various additives can be incorporated into the impact copolymer for various purposes. Such additives include, for example: stabilizing agents, antioxidants (e.g., hindered (hindered) phenols, such as from Ciba-Geigy Corp. of Irgafos ^TM 1010), phosphites (e.g., from Ciba-Geigy Corp. of Irgafos ^TM 168), adhesion agent (cling additives) (e.g. polyisobutylene), polymeric processing aids (such as from Dyneon under the Dynamar ^TM 5911 from General Electric company or Silquest ^TM PA-1), fillers, colorants, antiblocking agents, acid Remover, wax, antimicrobial, uv stabilizer, nucleating agent and antistatic agent. In particular, it has been found that the addition of a slip agent, such as erucamide, enhances the perceived softness of the fibers and/or nonwovens made from the impact copolymer.

The impact copolymers of the present invention are quite suitable for use in fiber strands that are commonly used in the art. Fibers having a thickness of from 0.5 to 15 denier, preferably from about 1.5 to 3 denier, can be advantageously produced. The melt blown fibers may range in diameter from 200 nanometers to 10 microns. The impact copolymer can be spun at a high speed, for example, a filament rate of from 1000 to 5000 m/min.

Such a fiber, whether made into a monocomponent or a bicomponent type, can be advantageously used to make a nonwoven fabric. As used herein, "non-woven" or "non-woven" or "non-woven material" means single-component and/or bi-component fibers (eg, core/sheath, islands in the sea, side-by-side). A combination of side-by side, segmented pie, etc., is connected together in a random web, for example via mechanical interlocking or via melting at least a portion of the fibers. Nonwovens can be made by a variety of methods generally known in the art. The fibers produced by the melt spinning process, including staple fibers (including long-spinning, short-spinning), spunbonding, melt-blown or multiple combinations thereof, can be formed in a web, followed by bonding techniques such as carding Carded thermal bonding, wetlaid, airlaid, air through bonding, calendar thermal bonding, hydro entanglement, needle sticking (needlepunching), adhesive bonding, or any combination thereof forms a nonwoven fabric. These various fiber processing techniques are well known to those skilled in the art and are described very accurately in documents such as Chapters IV and V of "Synthetic Fibers-Machines and Equipment Manufacture and Properties" by Fourne.

In one aspect, the impact copolymers of the present invention are used to make single component and/or bicomponent staple fibers in accordance with methods commonly used in the art. These staple fibers can be used in the production of fibers with a carding line.

Alternatively, the impact copolymers of the present invention can be used in a spunbond non-woven process. As is generally known in the art, in this process, long continuous single component and/or bicomponent fibers are produced and randomly stacked on a continuous conveyor belt in the form of a web. This is followed by methods known in the art, such as hot-roll calendering or by passing the web through a saturated vapor chamber under pressure or by entanglement or hot air with water or by needle or the like. Bonding can be done. The fibers of the present invention are particularly suitable for the manufacture of a spunbonded nonwoven material and multilayer composites, various optimized linear structures such as SMS, SMMS, SMMMS, SSMMS, SSMMMS, SXXXXXXS, X which may be produced via a melt spinning process. Any arrangement.

Fabrics made from single component and/or bicomponent fibers comprising the impact copolymers of the present invention are found to have characteristics that are good to feel.

Although the touch is not easily quantified, it can be evaluated using a sensory panel. The sensory panelist can be asked to sort various samples based on attributes such as "smoothness", "feeling", "stiffness" and "noise intensity".

A more objective test involves the use of a commercially available known "softness meter". This device evaluates the surface friction and stiffness of the fabric. Preferably, the nonwoven fabric of the present invention has a hand of 4 g or less, more preferably 3 g or less, when a single layer of 6 吋 x 6 吋 sample is evaluated using a 100 gm bundle combination and a 10 mm slit width.

Fabrics can also be evaluated against tensile strength, abrasion resistance and elongation. The nonwoven fabric of the present invention preferably has a tensile strength (for 20 gsm fabric) ranging from more than 25, preferably 30 N/5 cm, more preferably 40 N/5 cm in both MD and CD. The nonwoven fabric of the present invention preferably has abrasion in the range of less than 0.5 mg/cm ² , more preferably 0.4, 0.3. The nonwoven fabric of the present invention preferably has an elongation in the range of more than 40%, more preferably more than 60%, still more preferably more than 75%.

The nonwoven fabric of the present invention can be used to make a wide variety of end use articles. Such items include sanitary absorbent products (such as baby diapers, adult incontinence or feminine hygiene products), medical non-woven fabrics (such as surgical gowns, surgical covers or masks), protective clothing (such as face masks or tights), and wipes.

In addition to the composite structure of fibers and nonwovens or fibers, the compositions of the present invention can also be used to make other processed articles such as oriented cast films, non-oriented cast films, thermoformed articles, injection molded articles, oriented Blown film, non-directional blown film and blow molded articles.

Example

The first series of propylene impact copolymers are made in a dual reactor unit, the substrate polymer is produced in a first gas phase reactor, and then the contents of the first reactor are moved to A second gas phase reactor. The ethylene content in the substrate (Em) and the dispersed phase (Ec), and the amount (Fc) of the dispersed phase and the β/α were measured for each ICP according to the above test method, and are shown in Table 1. The resulting impact copolymer was treated with peroxide cracking for the total melt flow rate as described in Table 1. Comparative Example 1 is a polyethylene fiber having a melt index (190 ° C / 2.16 kg) of 30 g / 10 min and a density of 0.955 g / cc. Each of Comparative Examples 2 and 3 is a propylene impact copolymer having a β/α value outside the range of the present invention, showing a decrease in the ability of the spun fiber.

These materials were then evaluated on a Hills fiber spinning line. First, the samples were evaluated to determine the Ramp to Break. In this test, the fiber strands were wound at a bottom spinning roll of a Hills fiber spinning line at 500 m/min. No spinning is exhausted. Next, the rolls were accelerated from 500 m/min to 5000 m/min for 2 min in increments of 100 m/min. The point of break occurs when a large fracture of the sputum is observed (usually 5 or more than 5 rupture). For the example in which the fracture slope is described as ">5000", no break point was observed.

Fibers can also be evaluated for the Stick point. The test was carried out as follows: as used in the fracture ramp test, the fibers were wound around the same bottom spinning roll, forcing a glass stir bar to gently lean against the fibers at the bottom and slowly move upward until the fibers adhered and the crucible broke. . The sticking point is recorded as the height of the glass rod at the moment of a large break (5 or more).

A series of non-woven fabrics were made using the resin described in Table 2 from Reifenh The user Gruppe manufacture of spun bonding techniques Reicofil ^TM 4. (Note that Examples 10 and 12 are the same as Examples 9 and 11, respectively, and 500 ppm of erucamide eramide is additionally added). The machine used for this confirmation is a 1.2 m line width, 180 kg/h/m throughput operation, 150 m/min line speed operation and use between an embossed roll and a smooth roll. The hot rolled optical bonding was carried out at a nip pressure of 70 N/mm and at various temperatures indicated in Table 2 or in the following comparative examples. All fabrics were made at a basis weight of about 20 g/m ² (20 GSM).

These materials are compared to non-woven fabrics made of the following resins: for the purposes of the present invention, as is generally known in the art, "adhesion temperature" refers to the oil temperature used for the calender rolls, which may be comparable to the surface temperature of the fabric. A few degrees above. Comparative Example 4 is a homopolymer polypropylene (230°/2.16 kg) having a melt flow rate of 35 from a homopolymer polypropylene having a melt flow rate of 3-4 g/10 min (adhesion temperature 150/148). °C). Comparative Example 5 is a random polypropylene copolymer ("RCP") having 3.2% ethylene and a melt flow rate of 35 g/10 min (bonding temperature 145/143 ° C). Comparative Example 6 is a 30% (by weight) having a melt flow rate of 25g / 10min and a density of 0.876 g / cc of a polypropylene based plastic is available from Dow Chemical Company VERSIFY ^TM 4200 plastic, and 70% Comparative Example 4 a blend of the homopolymer polypropylene (adhesion temperature 135/133 ° C). Comparative Example 7 is a two-component (core-sheath) fiber produced at a machine speed of 240 kg/h and operated at a line speed of 175 m/min, and utilized between an embossing roll and a smooth roll. Hot-rolling optical bonding at a calender roll oil temperature of 140 °C. The bicomponent fiber of Comparative Example 7 contained 50% by weight of the core of the homopolymer polypropylene described in Comparative Example 4 and 50% by weight of the sheath of the polyethylene material described in Comparative Example 1.

If the difference in feel and hearing between several samples can be detected, it is determined using a sensory panel test. The panelists were asked to sort the non-woven samples according to the attributes of "smoothness", "clothing", "stiffness" and "noise intensity". The steps used are as follows: Cut A4 size non-woven sheets half. one of them 吋x The enamel sheet is used for the attributes "smoothness" and "class clothing" and the other 吋x The enamel sheet is used for the attributes "stiffness" and "noise intensity".

The attributes "smoothness" and "clothing" are analyzed using non-woven covered napkins. Four napkins are stacked on top of one another and non-woven sheets are placed on top of the napkins. Adhered to the bottom edge of the sheets as a mark with a three-digit blinding code.

The attributes "stiffness" and "noise intensity" are analyzed on a counter table using a single piece of non-woven fabric. Three-digit blind codes are written at the bottom of the sheets.

The samples were placed in a random order (Williams Design) and presented in a small compartment of the panelists.

The panel of judges used in the evaluation is a trained panel. It consists of insiders (Dow Chemical Company employees) who have been trained in the evaluation of the tactile properties of polyolefin products. They have learned how to focus on one attribute at a time without being overwhelmed by all the characteristics of the material. They have the ability to measure very small differences between samples and have exercised a variety of hand-feeling techniques that require reliable, reproducible data.

Each attribute was analyzed using F-statistic in the Variance Analysis (ANOVA) to determine if there were any significant differences between the multiple comparative samples. The F-ratio in ANOVA indicates a significantly different sample, thereby calculating Fisher's Least Significant Difference (LSD) to determine a one-at-a-time complex comparison. Fisher's LSD test is used to compare pairs when a significant F-value has been obtained. When the significance level is > 5%, it is considered that there is no significant difference.

The data in the table below is the average of these attributes. Lower numbers indicate better/better values. The letter characters next to the average indicate statistical differences at 5% level. Different letters indicate that the samples are statistically different. The same letter indicates that there is no statistical difference in these samples. An item with a plural letter (eg, "item") means that there is no statistical difference between that particular sample and any of the groups. In the examples of the smoothness ranking of Table 1 below, there is no statistical difference between Example 10 and either Example 11 or Example 12; however, Examples 11 and 12 are statistically different from each other.

A single 6 吋 x 6 吋 sample of each of these fabrics was also evaluated for "feel" (i.e., a stiffness-friction measurement) using a 100 gm bundle combination and a 10 mm slit width machine setting according to a softness tester. The results of this test are presented in Figure 3.

These fabrics were also evaluated against tensile strength (both in machine and transverse directions). The results of this test are presented in Figures 4 and 5.

These fabrics were also evaluated for elongation (both in machine direction and in landscape direction). The results of this test are presented in Figures 6 and 7.

Figure 1 is a transmission electron microscope image of an immiscible propylene impact copolymer system;

Figure 2 is a transmission electron microscope image of a partially miscible propylene impact copolymer system;

Figure 3 is a bar graph depicting the results of a softness tester of several embodiments and comparative examples of the present invention;

Figure 4 is a diagram showing the tensile strength versus bonding temperature in the machine direction of several embodiments and comparative examples of the present invention;

Figure 5 is a view showing the tensile strength versus bonding temperature in the transverse direction of several embodiments and comparative examples of the present invention;

Figure 6 is a diagram showing the elongation versus adhesion temperature in the machine direction of several embodiments and comparative examples of the present invention;

Figure 7 is a graph showing the elongation in the transverse direction versus the bonding temperature for several examples and comparative examples of the present invention.

Claims (18)

A polypropylene impact copolymer composition comprising: a) from 60 to 90% by weight of a substrate phase of the impact copolymer composition, the substrate phase comprising a homopolymer polypropylene or a random polypropylene copolymer The random polypropylene copolymer has a unit derived from ethylene or a C ₄ -C ₁₀ α-olefin in an amount of 0.1 to 7 mol%; and b) a dispersed phase of 10 to 40% by weight of the impact copolymer composition The dispersed phase comprises a propylene/α-olefin copolymer having from 6 to 40 mole percent of units derived from ethylene or a C ₄ -C ₁₀ alpha-olefin, wherein the dispersed phase has a comonomer content greater than the The comonomer content of the substrate phase; wherein the impact copolymer is characterized by having a β/α ratio of 1.2 or less. The polypropylene impact copolymer of claim 1, wherein the substrate phase comprises from 65 to 85% by weight of the impact copolymer composition. The polypropylene impact copolymer of claim 1, wherein the dispersed phase is partially soluble in the substrate phase. The polypropylene impact copolymer of claim 1, wherein the substrate phase comprises a random polypropylene copolymer having a molar percentage of 0.5 to 3 moles derived from ethylene or C ₄ - Unit of C ₁₀ alpha-olefin. The polypropylene impact copolymer of claim 1, wherein the dispersed phase comprises from 15 to 35 wt% of the impact copolymer composition. The polypropylene impact copolymer of claim 1, wherein the dispersed phase comprises a propylene/α-olefin copolymer having an α-olefin content of from 8 to 18 mole percent. The polypropylene impact copolymer of claim 1, wherein the impact copolymer has a β/α ratio of less than 1.0. The polypropylene impact copolymer of claim 1, wherein the dispersed phase comprises a propylene/ethylene copolymer. The polypropylene impact copolymer of claim 1, wherein the impact copolymer is subsequently cleaved by a peroxide. The polypropylene impact copolymer of claim 1, wherein the dispersed phase has a comonomer content of at least 10% (absolute) greater than the comonomer content of the substrate phase. The polypropylene impact copolymer of claim 1 further comprises at least one slip additive. The polypropylene impact copolymer of claim 11, wherein the slip additive is erucamide, and is present in an amount of from 100 to 2000 ppm. The polypropylene impact copolymer of claim 12, wherein the erucamide is present in an amount of from 250 to 750 ppm. The polypropylene impact copolymer of claim 1 further has a melt flow rate ranging from 25 to 65 g/10 min. The polypropylene impact copolymer of claim 14, wherein the impact copolymer is cleaved by a peroxide. A composition comprising a polypropylene impact copolymer and at least one slip agent, when the composition is used to produce a spunbonded web composed of a single constituent fiber, at a basis weight of 20 gsm, Production of a non-woven fabric having a hand rating of less than 4 g. The polypropylene impact copolymer of claim 16 wherein the feel is less than 3 g. A composition comprising at least one slip agent and a polypropylene impact copolymer composition comprising: a) 65 to 80% by weight of a substrate of the impact copolymer composition Phase, the substrate phase comprises a random polypropylene copolymer having from 0.5 to 3 mole percent of units derived from ethylene or butene; and b) one of the impact copolymer compositions Up to 35% by weight of the dispersed phase, the dispersed phase comprising a propylene/α-olefin copolymer having from 8 to 18 mole percent of units derived from ethylene or butene, wherein the dispersed phase has a comonomer content greater than The comonomer content of the substrate phase; wherein the impact copolymer is characterized by having a β/α ratio of 1.0 or less.