阅读说明：本技术 用于纤维水泥屋顶应用的在碱性环境中具有增强的分散性的表面上具有亲水性聚合物的双组分微纤维 (Bicomponent microfibers with hydrophilic polymers on surface with enhanced dispersibility in alkaline environments for fiber cement roofing applications ) 是由 E·克鲁兹 M·J·拉德勒尔 A·C·鲁埃达内里 P·K·乔格 G·F·比洛维茨 J·D· 于 2020-03-24 设计创作，主要内容包括：本发明提供用于增强混凝土的双组分核-壳聚合物微纤维,所述聚合物微纤维包含作为第一组分(壳)的乙烯-乙烯醇(EVOH)聚合物和至少一种增塑剂,优选聚乙二醇,以及作为第二组分(核)的聚合物,所述聚合物选自聚酰胺；聚酯,例如聚对苯二甲酸乙二酯；以及聚烯烃和酸酐接枝的聚烯烃的聚合物共混物,并且具有300至1000的长度与直径或当量直径的长径比(L/D)。所述双组分聚合物微纤维包含5重量％至45重量％的所述第一组分,易于加工,并且在相对低的微纤维负载下提供具有改进的机械性能的纤维水泥。(The present invention provides a two-component core-shell polymer microfiber for reinforcing concrete, said polymer microfiber comprising as a first component (shell) an ethylene vinyl alcohol (EVOH) polymer and at least one plasticizer, preferably polyethylene glycol, and as a second component (core) a polymer selected from the group consisting of polyamides; polyesters, such as polyethylene terephthalate; and a polymer blend of a polyolefin and an anhydride grafted polyolefin, and having an aspect ratio of length to diameter or equivalent diameter (L/D) of from 300 to 1000. The bi-component polymer microfibers include from 5 to 45 weight percent of the first component, are easy to process, and provide a fiber cement with improved mechanical properties at relatively low microfiber loading.)

1. A composition comprising a bi-component polymer microfiber for reinforcing concrete, said bi-component polymer microfiber having as an outer or first component or shell an ethylene vinyl alcohol (EVOH) polymer having from 30 to 50 mole% ethylene, and at least one plasticizer, and as a second component or core a polymer selected from polyamides; a polyester; and a polymer blend of a polyolefin on the one hand and an anhydride-grafted polyolefin on the other hand, the bicomponent polymer microfiber having an aspect ratio of length to diameter or equivalent diameter (L/D) of from 300 to 1000.

2. A composition of bicomponent polymer microfibers according to claim 1, wherein the at least one plasticizer is a polyalkylene glycol, a methoxypolyalkylene glycol or mixtures thereof, and wherein the microfibers have an equivalent diameter <0.3mm or less than 30 micrometers according to ASTM D7580/D7580M (2015).

3. The composition of bicomponent polymer microfibers of claim 1, wherein the total amount of the plasticizer in the first component is in a range of 1 to 10 weight percent, based on the total weight of the first component of the bicomponent polymer microfibers.

4. The composition of bicomponent polymer microfibers of claim 1,

wherein the second component comprises a polymer blend of a polyolefin and an ethylenically unsaturated anhydride grafted olefin polymer.

5. The composition of bicomponent polymer microfibers of claim 1, wherein the second component comprises a polymer blend of polypropylene and maleic anhydride grafted polypropylene.

6. The composition of bicomponent polymer microfibers of claim 1, wherein the second component is a polymer blend of polypropylene and polypropylene grafted with maleic anhydride, and the proportion of maleic anhydride is in the range of 0.01 weight percent to 0.3 weight percent, based on the total weight of the polymer blend solids of the second component.

7. The composition of bicomponent polymer microfibers of claim 1, wherein the EVOH polymer has a Melt Flow Rate (MFR) of 6.4 to 38g/10min at 210 ℃, 2.16Kg (ASTM D1238-13(2013)), and further wherein the second component comprises the polymer blend, wherein the polyolefin is a polypropylene having a melt flow rate of 12 to 24g/10min at 230 ℃ and 2.16Kg (ASTM D1238-13 (2013)).

8. The composition of bicomponent polymer microfibers of claim 1, wherein the bicomponent polymer microfibers have a second component (core) to first component (shell) ratio of 55 wt% to 95 wt% to 5 wt% to 45 wt% (or 95: 5 to 55: 45), all weights based on the total weight of microfiber solids.

9. The composition of bicomponent polymer microfibers of claim 1, wherein the bicomponent polymer microfibers comprise a ratio of second component (core) to first component (shell) of from 60 to 90 weight percent to from 10 to 40 weight percent (or from 60: 40 to 90: 10), all weights based on the total weight of microfiber solids.

10. The composition of bicomponent polymer microfibers of claim 1, wherein the composition comprises a wet fiber cement composition of the bicomponent polymer microfibers, and further comprises water, hydraulic cement, limestone aggregate, and cellulosic fibers.

Disclosure of Invention

The present invention provides bicomponent polymer microfibers having a core-shell structure with an ethylene vinyl alcohol (EVOH) polymer shell and an olefin, polyamide or polyester core, and which are highly dispersible in fiber cement compositions as well as wet cement compositions used to make cement fiberboard.

Preferred bicomponent fibers of the invention comprise microfibers comprising polypropylene (PP) in the core and maleated PP (PP-g-MAH) in the core, which is a blend of the material in the core and an outer layer or shell of ethylene vinyl alcohol (EVOH) that reacts by esterification with the PP (PP-g-MAH) to maintain the two layers bonded. Preferred bicomponent fibers of the invention have an equivalent diameter of <0.3mm or less than 30 microns according to ASTM D7580/D7580M (2015). Preferred bicomponent fibers of the invention have an aspect ratio of length to diameter or equivalent diameter (L/D) of from 300 to 1000.

In preferred bicomponent fibers of the invention, the (EVOH) polymer has from 30 to 50 mole%, or preferably from 38 to 48 mole% of ethylene.

In the first component or sheath of the preferred bicomponent fibers of the present invention, the EVOH polymer comprises an ethylene vinyl acetate polymer wherein the vinyl acetate portion is 85% or more hydrolyzed, or preferably 97% or more hydrolyzed, or more preferably fully hydrolyzed.

Preferred bicomponent fibers of the present invention comprise at least one plasticizer, preferably a polyalkylene glycol, a methoxypolyalkylene glycol or mixtures thereof, or more preferably polyethylene glycol (PEG), in the outer component.

In preferred bicomponent fibers of the invention, the total amount of plasticizer of the first component or sheath is in the range of from 0.75 to 15 weight percent, or preferably from 1 to 10 weight percent, or more preferably from 1.5 to 7.5 weight percent, all weight percents being based on the total weight of the first component of the bicomponent polymeric microfiber.

Preferred bicomponent fibers of the invention comprise a polymer blend of a polyolefin and an anhydride grafted olefin polymer, or more preferably an ethylenically unsaturated anhydride grafted olefin polymer, in the second component or core, wherein the unsaturated anhydride is selected from the group consisting of maleic anhydride, itaconic anhydride and fumaric anhydride, or more preferably maleic anhydride.

In preferred bicomponent fibers of the invention, the ratio of the second component (core) to the first component (sheath) is in the range of 55 to 95 wt.% to 5 to 45 wt.% (or 95: 5 to 55: 45), or preferably 60 to 90 wt.% to 10 to 40 wt.% (or 60: 40 to 90: 10), or more preferably 70 to 85 wt.% to 15 to 30 wt.% (or 70: 30 to 85: 15), all weights being based on the total weight of the microfiber solids.

Preferred bicomponent fibers of the invention comprise a polymer blend of polypropylene and polypropylene grafted with an ethylenically unsaturated anhydride (preferably maleic anhydride) in the second component or core and the ethylenically unsaturated anhydride proportion is in the range of from 0.01 to 0.3 wt%, or preferably from 0.02 to 0.15 wt%, or more preferably from 0.02 to 0.08 wt%, or even more preferably from 0.05 to 0.08 wt% of maleic anhydride, based on the total weight of the polymer blend solids of the second component.

Most preferred bicomponent fibers of the present invention comprise a polymer blend of polypropylene and maleic anhydride grafted polypropylene in a second component or core.

In a second aspect according to the invention, the composition comprises the preferred bi-component polymer micro fibers of the invention for reinforcing concrete.

1. In a second aspect according to the invention, the composition of the two-component polymer microfiber for reinforcing concrete comprises as an external or first component, preferably as a shell, an ethylene-vinyl alcohol (EVOH) polymer having from 30 to 50 mole% or preferably from 38 to 48 mole% of ethylene, and at least one plasticizer, preferably a polyalkylene glycol, a methoxypolyalkylene glycol or a mixture thereof, or more preferably a polyethylene glycol (PEG), and as an internal or second component, or a core, a polymer selected from polyamides; polyesters, such as polyethylene terephthalate; or a polymer blend of a polyolefin, Preferably Polypropylene (PP) or polyethylene on the one hand, or more preferably polypropylene and an anhydride-grafted polyolefin, preferably polypropylene grafted with maleic anhydride (PP-g-MAH) on the other hand, wherein the bicomponent polymer microfiber has an aspect ratio of length to diameter or equivalent diameter (L/D) of from 300 to 1000.

2. The composition of bi-component polymer microfibers of item 1 above, wherein the total amount of plasticizer in the first component or shell is in the range of 0.75 to 15 weight percent, or preferably 1 to 10 weight percent, or more preferably 1.5 to 7.5 weight percent, all weight percents being based on the total weight of the first component of the bi-component polymer microfiber.

3. The composition of bicomponent polymer microfibers according to any one of claims 1 or 2 above, wherein in the first component or shell the EVOH polymer comprises an ethylene vinyl acetate polymer, wherein the vinyl acetate moieties are 85% or more hydrolyzed, or preferably 97% or more hydrolyzed, or more preferably fully hydrolyzed.

4. The composition of bicomponent polymer microfibers according to any one of items 1, 2 or 3 above, wherein the EVOH polymer has a Melt Flow Rate (MFR) of 6.4 to 38g/10min at 210 ℃, 2.16Kg (ASTM D1238-13(2013)), and further wherein the second component or core comprises the polymer blend, wherein the polyolefin is a polypropylene having a melt flow rate of 12 to 24, or preferably 15 to 21g/10min at 230 ℃ and 2.16Kg (ASTM D1238-13 (2013)).

5. The bicomponent polymer microfiber composition of any of above items 1, 2, 3 or 4 wherein said second component or core comprises a polymer blend of a polyolefin and an anhydride grafted olefin polymer, or preferably an ethylenically unsaturated anhydride grafted olefin polymer, wherein said unsaturated anhydride is selected from the group consisting of maleic anhydride, itaconic anhydride and fumaric anhydride, or more preferably maleic anhydride.

6. The bicomponent polymer microfiber composition of any of above items 1, 2, 3, 4 or 5, wherein said second component or core comprises a polymer blend of polypropylene and maleic anhydride grafted polypropylene.

7. The two-component polymer microfiber composition of any of above 1, 2, 3, 4, 5 or 6 wherein said second component or core is a polymer blend of polypropylene and polypropylene grafted with an ethylenically unsaturated anhydride, preferably maleic anhydride, and said ethylenically unsaturated anhydride proportion is in the range of 0.01 to 0.3 wt%, or preferably 0.02 to 0.15 wt%, or more preferably 0.02 to 0.08 wt%, or even more preferably 0.05 to 0.08 wt% maleic anhydride, based on the total weight of the polymer blend solids of the second component.

8. The composition of bicomponent polymer microfibers according to any one of above 1, 2, 3, 4, 5, 6, or 7, wherein the bicomponent polymer microfibers have a second component (core) to first component (shell) ratio of 55 to 95 weight percent to 5 to 45 weight percent (or 95: 5 to 55: 45), or preferably 60 to 90 weight percent to 10 to 40 weight percent (or 60: 40 to 90: 10), or more preferably 70 to 85 weight percent to 15 to 30 weight percent (or 70: 30 to 85: 15), all weights based on the total weight of microfiber solids.

9. A composition of bicomponent polymer microfibers according to any one of items 1, 2, 3, 4, 5, 6, 7 or 8 above, or any preferred bicomponent fiber of the present invention, wherein the composition comprises a wet fiber cement composition of the bicomponent polymer microfibers, preferably having EVOH as a first component or shell and polyolefin as a second component or core, preferably a polymer blend of polypropylene with ethylenically unsaturated anhydride grafted polyolefin, preferably maleic anhydride grafted polypropylene, and further comprising water, hydraulic cement, limestone aggregate and cellulose fibers.

10. The wet fiber cement composition according to item 9 above,

wherein the composition further comprises one or more of a filler (preferably silica or clay), a thickener, a plasticizer or a pigment or a colorant.

11. The wet fiber cement composition according to any one of the above 9 or 10, or any preferred bicomponent fiber of the present invention, wherein said wet composition comprises from 0.05 to 3.0 wt.%, or preferably from 0.1 to 1.25 wt.%, or more preferably from 0.15 to 1.0 wt.% of said bicomponent polymer microfibers in solid form, based on the total weight of said wet composition.

12. According to another aspect of the invention, the fiber cement article comprises a composition of said preferred bicomponent fibers or bicomponent polymeric microfibers of the invention, said composition having as an external or first component an ethylene-vinyl alcohol (EVOH) polymer having from 32 to 50 mole% or preferably from 38 to 48 mole% of ethylene, and at least one plasticizer, preferably a polyalkylene glycol, a methoxypolyalkylene glycol, or more preferably a polyethylene glycol (PEG), and as a second component a polymer selected from polyamides; polyesters, such as polyethylene terephthalate; and on the one hand polyolefins, preferably polypropylene or polyethylene, or more preferably polypropylene, and on the other hand anhydride-grafted polyolefins, preferably polypropylene grafted with maleic anhydride, and cured hydraulic cements.

13. The fiber cement article according to item 12 above, wherein said second component comprises a polymer blend of a polyolefin and an anhydride grafted olefin polymer, or preferably an ethylenically unsaturated anhydride grafted olefin polymer, wherein said unsaturated anhydride is selected from the group consisting of maleic anhydride, itaconic anhydride and fumaric anhydride, or more preferably maleic anhydride.

14. The fiber cement article according to any one of the above items 12 or 13,

wherein the article further comprises limestone aggregate and cellulosic fibers.

15. The fiber cement article according to item 14 above, wherein said article further comprises one or more of a filler (preferably silica or clay), a thickener, a plasticizer or a pigment or a colorant.

16. According to yet another aspect of the present invention, a method of making the bicomponent polymer microfiber of any one of items 1 to 9 above comprises coextruding the first component and the second component without blending them.

17. The method of item 16, wherein upon coextrusion, the fibers are shaped and stretched to an aspect ratio of length to diameter or equivalent diameter (L/D) of 300 to 1000, or preferably 450 to 700.

Conditions of temperature and pressure are ambient temperature and standard pressure, unless otherwise indicated. All ranges recited are inclusive and combinable.

Unless otherwise indicated, any term containing parentheses or alternatively refers to the entire term as if no parentheses were present and no parentheses were present, as well as combinations of each alternative. Thus, the term "(poly) ethylene glycol" refers to ethylene glycol, polyethylene glycol, or mixtures thereof.

All ranges are inclusive and combinable. For example, the term "a range of 0.06 to 0.25 wt.%, or preferably 0.06 to 0.08 wt.%" will include each of 0.06 to 0.25 wt.%, 0.06 to 0.08 wt.%, and 0.08 to 0.25 wt.%.

As used herein, the term "ASTM" refers to a publication of the ASTM International standard organization (ASTM International, West Conshohocken, PA) by West concheshoken, pennsylvania.

As used herein, the term "aspect ratio" or "L/D" refers to the ratio of the total length of the cut fiber to its cross-sectional width, where the length is measured by sliding a small bundle of fibers into a slot of a fiber clamp and compressing the fiber by inserting a tab from a mating piece of the clamp into the slot, then cutting the fiber by sliding a sharp blade across the surface of the clamp, and then measuring the cross-section of the fiber with a digital camera by optical microscopy. If the cross-section of the fiber is not perfectly circular, the major and minor axis dimensions of the fiber are measured as ovals and then the average is taken as the cross-sectional dimension or equivalent diameter. Fiber samples were randomly selected and the reported aspect ratio is the average of the equivalent diameters determined from twenty (20) randomly selected fibers.

As used herein, the term "fiber cement" is interchangeable with "cement fiberboard" or "fiberboard" and means the same thing as "cement fiberboard" or "fiberboard". However, as used herein, the term "wet fiber cement" refers to a hydraulic binder composition used to make fiber cement or fiber board.

As used herein, the term "equivalent diameter" refers to the average cross-sectional diameter of a fiber used to determine the aspect ratio of the fiber, i.e., the average cross-section of the major and minor axes of a fiber in which the fiber is not perfectly round. Fiber samples were randomly selected and the reported equivalent diameters are the average of the equivalent diameters determined from twenty (20) randomly selected fibers.

As used herein, the term "diameter" refers to the diameter of a microfiber having a circular cross-section. Fiber samples were randomly selected and the reported diameters are the average of the diameters determined from twenty (20) randomly selected fibers.

As used herein, the term "macrofiber" means a fiber having an average linear density greater than or equal to 580 denier and an equivalent diameter greater than or equal to 0.3mm or greater than or equal to 30 microns according to ASTM D7508/D7508M (2015) standard specification for polyolefin chopped strands used in concrete.

As used herein, the term "microfiber" means a fiber having a linear density of less than 580 denier and an equivalent diameter of <0.3mm or less than 30 microns according to ASTM D7580/D7580M (2015) standard specification for polyolefin chopped strands used in concrete.

As used herein, the term "polymer" includes homopolymers and copolymers formed from two or more different monomer reactants or comprising two different repeat units.

As used herein, the term "surfactant" is intended to mean a composition containing a hydrophilic phase (e.g., an oligoethoxylate) and a hydrophobic group or a hydrophobic phase (e.g., C)₈Alkyl or alkaryl).

As used herein, the term "total solids" refers to all materials in a given composition except for solvent, liquid carrier, non-reactive volatiles (including volatile organic compounds or VOCs), ammonia, and water.

As used herein, the term "weight average molecular weight" or MW refers to the weight average of the molecular weight distribution of a polymer or plasticizer material, as determined at room temperature using Gel Permeation Chromatography (GPC) of polymer dispersions in water or suitable solvents for the analyte polymer or plasticizer and using suitable conventional polyethylene glycol, vinyl, or styrene polymer standards.

As used herein, the term "weight average particle size" refers to the weight average of the particle size distribution particle size of a given material as determined by light scattering or another equivalent method.

As used herein, the phrase "wt%" means weight percent.

The present invention provides bicomponent microfibers and compositions containing them for use as reinforcing agents in fiber cements where the adhesion between the second component or core and the outer component or first component polymer, e.g., core to sheath or core to shell, improves fiber cement performance. Furthermore, the present invention enables a practical method of manufacturing microfibers according to the present invention. Furthermore, since ethylene vinyl alcohol (EVOH) forms a strong bond with cement, the present invention allows the preparation of bicomponent polymer microfibers that improve the fiberboard containing them, for example in terms of its ductility.

The inventors found that microfibers having an equivalent diameter of 10 to 29.5 microns, unlike large fibers having an equivalent diameter of 300 to 1000 microns, pose significantly greater difficulties with respect to spinnability and gel formation. Because EVOH is a brittle and tough hydrophilic material, microfiber spinning or extrusion processes with EVOH in the desired proportions can pose problems as opposed to macrofiber formation. A composition of EVOH material gelled during spinning or extrusion with an 50/50(w/w /) ratio of the first component and the second component; furthermore, bicomponent polymer microfibers made from 50% by weight of the first component EVOH polymer composition give insufficient ductility for practical use and are not strong enough from the standpoint of tensile strength. At the desired EVOH concentration, e.g. 20 wt% of the total microfiber forming composition, a viscosity develops high enough to enable extrusion or spinning, while having a smaller equivalent diameter causes problems and the microfibers break during the lower viscosity. Thus, either the microfibers are too brittle and gel or form clusters on the microfibers in processing, or they cannot be processed when they have a lower EVOH content. Thus, the inventors have found that the addition of a plasticizer in the shell of the first component forming the EVOH composition enables successful spinning to produce EVOH or bicomponent polymer microfibers having an equivalent diameter of 15 microns and a sufficiently low proportion of the first component to ensure sufficient fiber ductility and tensile strength in use.

EVOH provides excellent dispersibility in the alkaline environment (pH 10-13) of cement matrices. Furthermore, EVOH allows good interaction or adhesion between the bicomponent polymer microfibers and the cement matrix, achieving the performance of polyvinyl alcohol (PVOH) fibers in use. This adhesion between the cement matrix and the microfibrils remains critical for fiber cements produced by the Hatschek process (Hatschek process), which requires dehydration of the composition without loss of materials other than water. In the haake process, a combination of microfibers, cement, any filler (e.g., silica), thickener, and limestone are dispersed in water at a solids concentration of 150 to 200 grams solids per liter prior to dewatering.

In addition, according to the present invention, a bicomponent polymeric microfiber reinforcement for fiber cement can improve dispersion and mechanical properties in microfiber-containing compositions. For example, according to the invention, bicomponent microfibers having a blend of a first component (shell) of EVOH and PP as a second component (core) and grafted with maleic anhydride, having a diameter of 10 to 15 microns and a length of 9 to 12mm, provide fiber cement composites having better physicochemical properties than existing asbestos-free fiber cement composites comprising polypropylene fibers (also known as "fiber cement NT").

Suitable bicomponent polymer microfibers according to the present invention have a polyamide core or a second component of a polymer blend of polypropylene (PP) further comprising PP grafted with maleic anhydride (PP-g-MAH).

Bicomponent polymer microfibers according to the present invention can have any shaped cross-section including, for example, circular, oval, ellipsoidal, triangular, rhomboidal, rectangular, square, polygonal (having more than 3 sides), twisted ribbon, ribbon or filament, and multi-lobal.

Suitable bicomponent polymer microfibers have an aspect ratio or L/D ratio of from 300 to 1000, or preferably from 450 to 700. In one example, the bicomponent polymer microfiber has dimensions of 15 micron equivalent diameter and 9mm length to give an L/D ratio of about 600. Bicomponent microfibers having larger or smaller equivalent diameters may be cut longer or shorter to maintain the desired aspect ratio.

In accordance with the bicomponent polymer microfiber compositions of the present invention, the combination of one or more plasticizers, such as polyethylene glycol (PEG), in the shell or first component with the EVOH polymer allows for good spinnability at the first component/second component ratios suitable for forming the bicomponent polymer microfibers of the present invention.

Suitable plasticizers include polyalkylene glycols, such as polyethylene glycol (PEG) or polypropylene glycol (PPG) and methoxypolyalkylene glycols, any of which has a weight average molecular weight MW of 300 to 10,000, or preferably 6000 to 9000. Preferably, according to the present invention, the plasticizer comprises one or more polyethylene glycols (PEGs).

In the bicomponent polymeric microfibers and compositions used to make the microfibers of the present invention, the plasticizer forms a portion of the EVOH or the first component. Suitable amounts of plasticizer are sufficient to enable the first component to be spun, but not so much as to prevent pressure build-up in the extruder, such as is required to form fibers.

The total amount of plasticizer ranges from 0.75 wt% to 15 wt%, or preferably from 1 wt% to 10 wt%, or more preferably from 1.5 wt% to 7.5 wt%, all weight percentages being based on the total weight of the first component of the bicomponent polymeric microfiber.

According to a first component of the bicomponent polymer microfibers of the present invention, the polymer of the first component or shell comprises an ethylene vinyl alcohol (EVOH) polymer. Suitable EVOH polymers may comprise ethylene vinyl acetate polymers wherein the vinyl acetate portion is 85% or more, or preferably 97% or more, or more preferably fully hydrolyzed.

The first component may comprise an ethylene vinyl alcohol (EVOH) polymer of any molecular weight sufficiently high to ensure formation of EVOH fibers, for example 50,000 or higher, or preferably 70,000 or higher, and a weight average Molecular Weight (MW) of up to 10,000,000 as determined by gel permeation chromatography using conventional vinyl or styrene polymer standards. It is not a wax.

The first component ethylene vinyl alcohol (EVOH) polymer may comprise 32 to 48 wt% ethylene, preferably 38 to 48 mol% ethylene, based on the total solids weight of the EVOH polymer. If the amount of ethylene is too low, the EVOH polymer will be too sensitive or too absorbent to water and will have too strong adhesion to the concrete, and delamination of the fibers from the concrete is a desirable failure mode. If the amount of ethylene is too high, adhesion of the EVOH polymer to the concrete and the polymer of the second component will be impaired.

Suitable EVOH polymers preferably comprise from 32 to 48 wt% of ethylene, based on the total weight of the reactants used to prepare the polymer, of the first component of the bicomponent polymer microfiber according to the present invention.

In order to ensure that the EVOH polymer of the first component or shell of the bicomponent polymer microfibers according to the invention flows sufficiently to enable fiber formation to enable the production of bicomponent polymer microfibers, EVOH has a Melt Flow Rate (MFR) of 6.4 to 38g/10min at 210 ℃ and 2.16Kg (ASTM D123813). Generally, the higher the ethylene content, the lower the MFR.

EVOH polymers with excess vinyl alcohol repeat units are more difficult to process and may break when the fiber is drawn. Preferably, the ethylene vinyl alcohol (EVOH) polymer according to the present invention comprises 30 to 48 wt% ethylene, for example 32 to 48 wt% ethylene, based on the total weight of the reactants used to prepare the polymer, and has a vinyl acetate fraction that is 85% or more hydrolyzed, or preferably 97% or more, or more preferably fully hydrolyzed, having a Melt Flow Rate (MFR) at 210 ℃, 2.16Kg (ASTM D1238-13(2013)) of 6.4 to 38g/10 min. Such suitable EVOH polymers are not waxes. Examples of suitable EVOH polymers include those having an ethylene content of 48% by weight and an MFR of 6.1g/10min at 210 ℃ and 2.16Kg, those having an ethylene content of 44% by weight and an MFR of 12g/10min at 210 ℃ and 2.16Kg, and those having an ethylene content of 32% and an MFR of 21g/10min at 210 ℃ and 2.16 Kg.

Bicomponent polymer microfibers according to the present invention provide the best Average Residual Strength (ARS) results and have as a second component or core an amide polymer, a polyester polymer such as polyethylene terephthalate (PET), or a polymer blend of a polyolefin, preferably polypropylene, and only a minor amount of a polyolefin grafted with an unsaturated anhydride, preferably a polymer blend, or more preferably a polypropylene grafted with maleic anhydride, of a polymer blend.

The second component or core of the bicomponent polymeric microfibers according to the present invention comprise at least one polyamide, such as polyhexamethylene adipamide; at least one polyester, such as polyethylene terephthalate (PET); or a polymer blend of a polyolefin on the one hand, such as polypropylene (PP), Polyethylene (PE) and on the other hand an anhydride grafted polyolefin selected from ethylenically unsaturated anhydride grafted PP, ethylenically unsaturated anhydride grafted Polyethylene (PE), such as an anhydride modified High Density Polyethylene (HDPE) resin, an anhydride modified Linear Low Density Polyethylene (LLDPE) resin or an anhydride modified Low Density Polyethylene (LDPE) resin, or preferably a polymer blend, or more Preferably Polypropylene (PP) with ethylenically unsaturated anhydride grafted PP, or even more preferably PP with maleic anhydride grafted PP.

Suitable polyolefins for the second component according to the invention include polypropylene having a Melt Flow Rate (MFR) at 230 ℃ and 2.16Kg (ASTM D1238-13(2013)) of from 12 to 24, or preferably from 15 to 21g/10 min. Low MFR polyolefins should be processed at higher temperatures.

Suitable acid anhydrides for the anhydride-grafted olefin polymer used to prepare the polymer blend of the second component according to the present invention are any ethylenically unsaturated anhydrides, such as maleic anhydride, itaconic anhydride and fumaric anhydride, preferably maleic anhydride.

In the second component polymer blend according to the present invention, if the amount of grafted anhydride polymer is too low, the resulting microfibers will suffer from insufficient adhesion to the first component polymer; if the amount of grafted anhydride is too high, the second component fiber-forming polymer will be too cohesive to consistently form microfibers; and will be unevenly or non-uniformly distributed into the bicomponent polymer microfiber product.

The polymer blend of the second component of the bicomponent polymer microfiber according to the present invention, the ethylenically unsaturated anhydride used for grafting comprises a proportion of from 0.01 to 0.3 wt.%, or preferably from 0.01 to 0.2 wt.%, such as preferably from 0.02 to 0.15 wt.% of unsaturated anhydride, such as preferably from 0.02 to 0.08 wt.%, or more preferably in an amount of from 0.02 to 0.08 wt.% of maleic anhydride, or even more preferably from 0.05 to 0.08 wt.% of maleic anhydride, all amounts being based on the total weight of the polymer blend solids of the second component.

The polymer blend of the second component of the bicomponent polymer microfiber according to the present invention comprises 80 to 99 wt.%, or preferably 90 to 97 wt.%, of the polyolefin and the graft polymer in the remainder of the polymer blend, based on the total weight of polymer blend solids.

In the bicomponent polymer microfibers according to the present invention, the ratio of the second component (core) to the first component (shell) is from 55 wt% to 95 wt% to 5 wt% to 45 wt% (or 95: 5 to 55: 45), or preferably from 60 wt% to 90 wt% to 10 wt% to 40 wt% (or 60: 40 to 90: 10), or more preferably from 70 wt% to 85 wt% to 15 wt% to 30 wt% (or 70: 30 to 85: 15), all weights being based on the total weight of the microfiber solids. In preferred polymer blends of the second component or core according to the invention, the polymer blend comprises from 1 wt% to 20 wt%, or preferably from 3 to 10 wt%, based on polymer blend solids, of an unsaturated anhydride grafted olefin, such as polypropylene grafted with maleic anhydride (PP-g-MAH). In one example, a core of a bicomponent polymer microfiber thus comprising PP (core) and EVOH (shell) or a core-shell bicomponent polymer microfiber without PP-g-MAH in the second component does not adequately disperse or improve the ductility of the fiber cement containing them. They do not show adhesion between the core and the shell.

In another aspect, the invention includes a wet fiber cement composition for use in making cement fiberboard. The wet composition comprising the bicomponent polymeric microfibers according to the present invention further comprises a material for forming a fibrous cement, such as a wet mix of hydraulic cement, e.g. ordinary portland cement, cellulose or cellulose fibers, as a screen to retain solids upon dewatering, e.g. from eucalyptus or pine, limestone or calcium carbonate, and, if desired, a thickener or rheology modifier.

According to the dry solids of the fiber cement composition of the present invention suitable for making fiberboard, the composition comprises from 0.15 wt% to 3.0 wt%, or preferably from 0.3 wt% to 2.5 wt%, or more preferably from 0.5 wt% to 2.2 wt% bi-component polymer microfiber solids by weight. Water typically occupies one-half to two-thirds of the wet mix used to make the fiberboard. Thus, according to the wet cement composition of the present invention suitable for use in making fiberboard, the composition comprises from 0.05 wt% to 1.5 wt%, or preferably from 0.1 wt% to 1.25 wt%, or more preferably from 0.15 wt% to 1.0 wt% bi-component polymer microfiber solids by weight. When the microfibers contain more EVOH that is denser than the fibers of the second component, a greater weight percentage of microfibers will be needed so that the total microfiber volume can be kept constant. Thus, the bicomponent polymer microfibers of the present invention provide a savings in microfiber loading in fiber cement applications.

Other additives useful in forming concrete, such as those known in the art, may also be added according to the wet fiber cement composition of the present invention. Examples include superplasticizers, water reducers, rheology modifiers, fumed silica, slag, air entraining agents, corrosion inhibitors, and polymer emulsions. To ensure a uniform fiberboard product, the weight average particle size of the filler or additive should be 300 micrometers or less. Thus, the wet fiber cement composition according to the present invention consists essentially of a material having a weight average particle size of 300 microns or less.

In yet another aspect according to the present invention, a method of making a wet fiber cement composition according to the present invention comprises mixing a hydraulic cement with the bi-component polymer microfibers of the present invention for at least 10 seconds up to 20 minutes to form a wet fiber cement composition and, if desired, curing under heat. Preferably, the mixing time is at least 30 seconds, or more preferably at least 1 minute and at most 10 minutes, or most preferably from 1 to 5 minutes.

In accordance with yet another aspect of the present invention, the process of forming the bicomponent polymeric microfibers includes well known processes such as melt spinning or extrusion, wet spinning or composite spinning. Any known fiber forming process will work so long as the process will melt the material used to form the microfibers and thereafter not damage the microfibers in the process. In processing, the fibers are shaped, formed, and drawn, such as by melt extrusion through a die to shape the fibers, and through a spinneret to form elongated fibers, which can then be drawn, such as around a set of draw-placed rollers, to a particular length to diameter or equivalent diameter aspect ratio (L/D). Preferably, the bicomponent polymer microfibers may be stretched to an aspect ratio of 300 to 1000. Thus, the amount of the more rigid first component in the bicomponent polymer microfiber remains limited to 45 weight percent or less, or preferably 10 weight percent to 40 weight percent, or more preferably 15 weight percent to 30 weight percent, based on the total solids weight of the bicomponent polymer microfiber.

Preferably, according to the present invention, the method comprises co-extruding the first component and the second component and does not include blending a vinyl alcohol polymer and an anhydride, such as Maleic Anhydride (MAH), a grafted polyolefin, or a polypropylene polymer. The polymers of the first and second components react at the interface and form chemical bonds, thereby increasing the interlayer adhesion between the first and second components of the microfiber.

When the second component is a polymer blend according to the first component, the method of preparing the polymer blend comprises mixing the polymers making up the polymer blend to form the second component prior to coextrusion, or it comprises masterbatching a portion of the anhydride grafted polyolefin greater than its amount in the second component with the polyolefin to form a masterbatch, and subsequently melt blending the masterbatch with the polyolefin to form a melt of the second component.

Bicomponent polymer microfibers can be formed having a variety of configurations with a core of the second component and a shell of the first component, including, for example, core/sheath microfilament microfibers. For example, the bicomponent polymer microfibers of the present invention may be extruded in any size, shape, or length desired. They may be extruded in any desired shape, for example cylindrical, cross, trilobal or ribbon-like cross-sections. Regardless of their configuration, the bicomponent polymer microfibers of the present invention may have a cross-section of any shape that accommodates both the second component and the first component as microfibers with the first component on the exterior of the fibers. For example, in a bicomponent polymer microfiber having an islands-in-the-sea configuration, a bicomponent polymer microfiber having a circular cross-section can accommodate more islands of a second component than a bicomponent polymer microfiber having a ribbon-like cross-section.

Core/shell bicomponent polymer microfibers, with the second component completely surrounding those microfibers of the first component. The most common method of producing core/shell microfibers is a technique in which two polymer component melts are separately introduced in close proximity to the orifice and then coaxially extruded in the core/shell form. In the case of concentric fibers, the orifice supplying the second component is in the center of the spinning orifice outlet, and the flow conditions of the core polymer fluid are tightly controlled to maintain concentricity of the two components while spinning. The improvement of the spinning orifice enables one to obtain cores or/and shells of different shapes within the microfiber cross section.

Other processes for producing core/sheath bicomponent fibers are described in U.S. patent nos. 3,315,021 and 3,316,336.

Examples: the following examples are intended to illustrate the invention without limiting it to these examples. Unless otherwise indicated, all temperatures are ambient (21-23 ℃) and all pressures are 1 atmosphere.

The microfibers of the present invention shown in examples 1A, 2 and 3 below, the comparative polymer blend microfibers of example 4 below, and the comparative bi-component polymer blend microfibers of example 5 below were extruded, shaped and drawn by a melt spinning process. In this process, all the specified components are melted in an extruder or, in the case of coextrusion, one component in each of two different extruders and then pumped into a die having a plate designed to flow one component or, in the case of two components, an inner and an outer material having a two-component core/shell configuration. Downstream of the die, the resulting fibers are drawn to a desired aspect ratio. The apparatus comprises a Hills, inc. (West Melbourne, FL) extruder device with a temperature profile of 185-200 ℃, a flow rate of 800mpm and a denier of 5.9den, wherein the extruder die is configured in case of co-extrusion such that the second component flows through a circular die with a diameter of 0.25 mm. In one-component extrusion, the components are passed through a circular die having a diameter of 0.25 mm. The spinneret is located downstream of the coextrusion apparatus.

In coextrusion, the first component is coextruded coaxially around the second component through an annular die having an inner diameter matching the outer diameter of the circular die. The spun fibers were then drawn to form bicomponent polymer microfibers having an average diameter of about 15 microns, with the sheath of the first component forming loops having a thickness of 1 to 2 microns.

In extrusion, one component is extruded through a circular die and the spun fibers are then drawn into polymer microfibers having an average diameter of about 15 microns.

The component ratios are shown in the following examples. The inventive ratios of the first component and the second component of the bicomponent polymer microfibers were selected to target a core/shell bicomponent microfiber having an 80/20 ratio (w/w /) of the second component or core to the first component or shell. The first component, EVOH, is very difficult to extrude, shape and stretch into microfibers. Thus, the polyethylene glycols indicated in the examples below are included in the melt of the first component; and bicomponent polymer microfibers are produced by a melt spinning process. During extrusion, the amounts of the first component and the second component are varied in the process to reduce the proportion of the first component as much as possible. If possible, the proportion of the first component is reduced to 20% by weight, based on the total weight of the bicomponent polymer microfiber solids. In the event that it is not possible to reduce the first component proportion to 20% by weight, the specified proportion of the first component in the bi-component polymer microfibers is the lowest proportion of the first component that is obtained prior to breaking of the resulting microfibers when stretched to form microfibers.

All fibers in the following examples and comparative examples had an L/D of 600, a diameter of 15 microns and a length of 9 mm.

The materials used in the examples are as follows:

ethylene vinyl alcohol copolymer or EVOH: SOARNOL^TMA4412 ethylene vinyl alcohol copolymer having an ethylene content of 44 mol%, a Melt Flow Rate (MFR) (210 ℃, 2.16Kg, as determined by melt index) of 12g/10minTester) at 23 ℃ of 1.14g/cm³Density (Micromeritics GAs densitometer Micromeritics Instrument core, Norcross, GA) and melting point of 164 ℃ (DSC heating and cooling rate of 10 ℃/min) (sorus LLC, Arlington Heights, IL).

Polyethylene glycol or PEG: MW from 7000 to 9000, density 1.07 (g/cm)³(ii) a 70 ℃); heat of fusion 41 (Cal/g); average number of oxyethylene repeat units 181.

Maleic anhydride grafted polypropylene or PP-g-MAH: POLYBOND^TM3150 maleic anhydride grafted polypropylene having a maleic anhydride content of 0.7 wt.%, a Melt Flow Rate (MFR) of 52g/10min (230 ℃, 2.16Kg, by melt index tester) and 0.91g/cm at 23 ℃³(iii) density (additive corporation, Danbury, CT). Various PP-g-MAH materials and their polymer blends are given in tables 2A and 2B below.

Polypropylene or PP: polypropylene D180M PP, MFR 18g/10min at 230 ℃ and 2.16Kg (Braskem USA, Philadelphia, Pa.). Has a melting point MP (DSC) of 160 ℃, a density of 0.905g/cc and an MFR of 18g/10min at 230 ℃ and 2.16 Kg. The various PP materials and their polymer blends are given in table 2 below.

Polyvinyl alcohol (PVOH) microfibers: high-toughness and high-modulus PVA fiber W16 mm is from Anhui Wanweii Updated Hirightech Material Industrial Co.Ltd., Chao hu, Anhui, China, Anhui, An. PVOH fiber characteristics are presented in table 1 below.

PP microfibers: PP monofilament 1.10dtex X9mm (Saint Gobain do Brasil products Ind. e para const. Ltda-Brasil Cia.). The PP fiber characteristics are presented in table 2A below.

MB 2: the compositions shown in Table 2B below were prepared by extrusion in a 26mm twin screw extruder (44L/D and 30Hp) having eleven (11) barrels and equipped with a 3mm, 2 hole strand die. Using a Ktron^TMA single screw feeder (Coperion GmbH, Stuttgart, DE) feeds the pellets of each of PP and PP-g-MAH into the extruder. The material was fed into the main feed throat (barrel #1) along with nitrogen in the feed throat. Make the thread materialGranulation was performed through a 3.048 meter water bath and using a Conair strand cutter (Conair, Stamford, CT). The total feed rate was 18.14Kg/h and the screw speed was 300 RPM. The temperature set point in zone 1 of barrel #2 was 60 deg.C, and 180 deg.C in the remaining zones.

Table 1: PVOH fiber characteristics

Characteristics of	Value of
		Line Density (dtex)	2
Tenacity (cN/dtex)	12.2
		Elongation (%)	6.8
Hot Water solubility (90 ℃, 1h)	0.7
		Dispersion rating (grade)	1
Length (mm)	6

Table 2A: characteristics of PP fiber

Characteristics of	Value of	Specification of
			Title	1.12dtex	≤1.20dtex
Toughness	10.18cN/dtex	≥9.50cN/dtex
			Elongation percentage	19.42％	≤25％
Water content	2％	1.5-2.5％
			Final content	0.68％	0.6-0.7％
Grade of dispersion	3	Grade 2 to 3

Table 2B: a second component

Table 2C: acid content of the second component

Material	Acid content (% by weight)
		MB2	0.14
A second component	0.035
		If the second component is diluted 3X with pure PP	0.012

The test method comprises the following steps:

the following test methods were used to evaluate the examples. The specified aqueous dispersions of each specified bicomponent polymer microfiber were tested for dispersibility in water. Separately, the bicomponent polymer microfibers shown in examples C1, C2, 1A, 2, 3, 4, and 5 below were made into cement fiberboard and tested for mechanical properties by the methods given above.

DispersibilityEvaluation was carried out by stirring 0.02g of the bicomponent polymer microfibers in 1 l of alkaline water (pH 10-11, ammonium OH) for 3 minutes, and then filtering it through a black polyester cloth (for comparison) by applying a vacuum (200 to 300 mmHg). The solution was then poured onto filter paper (Whatman, 80 g/cm) with a multi-well plate²10cm diameter, Merck Millipore, Burlington, MA) upstream of the buchner funnel and dark fabric (to achieve visual assessment). After removal of water, the graph made of the fibers was evaluatedTo evaluate their dispersibility. Fiber dispersion was visually graded using the following rating scale as follows:

level 1: the (fully dispersed) microfibers were uniformly distributed over the entire area of the filter paper without agglomerated fibers;

and 2, stage: from 5% to 10% by weight of microfibers clump after filtration testing;

and 3, level: 20-30 wt% of the microfibers clump after the filtration test;

4, level: (poor dispersibility) most of the microfibers agglomerate; the filter paper area is poorly distributed.

The dispersion results are reported in table 3 below.

Mechanical properties:cement fiberboard a wet composition using bicomponent polymer microfibers was prepared in the manner shown in the following examples. After completion of the curing period, fiber cement boards (160mm x40mm x5mm) were cut and evaluated for mechanical properties according to the RILEM 49 TFR: test methods for fiber cement based composites, France, (1984). In particular, by using INSTRON^TM5565 a load tester (Instron, Norwood, Ma) equipped with a 5kgf load cell and a 5mm/min load ratio on four steel cylindrical bending points, an upper distance between points of 45mm and a lower distance between points of 135mm, with two point centers placed on a platform below the cement fiberboard and flush with each edge of the 40mm wide underside of the fiberboard, tensile tests were performed on the specified fiber cement board to generate a stress-strain curve; and the other two bending points are placed below the platform a distance of Lmm a such that the load cell is centered between each pair of bending points. Tensile testing produces stress-strain curves from which various mechanical properties are derived. The mechanical results are shown in Table 4 below.

Stress-strain curve: the cement fiberboard containing microfibers prepared according to the illustrated examples were subjected to mechanical testing by varying the stress, load or force generated thereon and measuring the strain caused by each stress level. The test was used to generate a stress-strain curve. From the stress-strain curve during the tensile strength test.

Obtained from stress-strain curves generated during tensile testingMOR or modulus of ruptureReported as the maximum stress supported by the composite matrix during the stress-strain test and calculated as the ultimate load reached during the test divided by the area of the fiberboard sample. MOR is given by equation 1 below and is the average result reported from five (5) cement fiberboards randomly selected. An acceptable modulus of rupture is at least 2.0MPa, or preferably at least 3.0 MPa.

Wherein:

F₂maximum load applied in N:

l is the maximum distance in mm between the two lower bearing points of the illustrated cement fiberboard placed across its width on the two bearing points centered on top of the wider bearing member supported by the two lower bearing points;

b is the cement fiberboard width in mm;

d is the cement fiberboard thickness in mm.

Obtained from the stress-strain curve generated during the tensile test,proportional Limit (LOP)Is the area corresponding to elastic deformation in the stress-strain curve and is proportional to the applied load. The LOP is calculated from the load at which the load-strain curve deviates from linearity, which is the onset of a plastic deformation state, as shown in equation 2 below. An acceptable limit for the ratio is at least 2.0MPa, or preferably at least 2.5 MPa.

Wherein:

F₁the load applied in the LOP is in N:

l is the maximum distance in mm between the two lower bearing points of the illustrated cement fiberboard placed across its width on the two bearing points centered on top of the wider bearing member supported by the two lower bearing points;

b is the sample width in mm;

d is the sample thickness in mm.

Obtained from stress-strain curves generated during bending deformation testsModulus of elasticity (MOE)Or young's modulus as the slope of the stress-strain curve in the elastically deformed state (see Callister, d.w., Rethwish g.d.,Materials Science and Engineering：An Introduction8 th edition, John Wiley&Sons inc., chapter 6, page 157, 2012).

The higher the MOE, the more rigid the cement fiberboard and the lower its elastic deformation, where stress is proportional to deformation. An acceptable elastic modulus is at least 2.5 GPa.

Obtained from stress-strain curves generated during bending deformation testsSpecific Energy (SE)Defined as the energy absorbed during the stress-strain test and calculated by integrating the area under strain with the curve load, see equation 3 below. The higher the SE value, the better the fiber reinforcement. An acceptable specific energy is at least 2.5kJ/m²Or preferably at least 3.5kJ/m²。

Wherein:

the energy absorbed is calculated as above.

b is the sample width in mm;

d is the sample thickness in mm.

Comparative example 1 (C1): polyvinyl alcohol (PVOH) microfibers

As a reference standard, cement fiberboard was made with PVOH microfibers and then evaluated. A cement fiberboard was prepared by dispersing ordinary portland cement (64 wt%), limestone (31.1 wt%), cellulose fibers (3 wt%), and PVOH fibers (1.9 wt%) in water. Thereafter, the water was removed by a dehydration method using a molding chamber and applying a vacuum (200-. The fiber cement board was cast into 4 layers. Each layer was pressed at 3.2MPa for 2 min. Finally, one layer is placed on top of the other. Finally, the resulting plate was pressed at 3.2MPa for 5 min. The method approximately mimics the hascheck method. The fiber cement board was then "plastic sealed" (wrapped) in a polyvinylidene fluoride wrap and placed in an oven at 50 ℃ for 24 h; after this period, the cement fiberboard was removed from the oven and left to cure at room temperature (6 d/23. + -. 2 ℃). After completion of the curing period, fiber cement boards (160mm x40mm x5mm) were cut and evaluated for mechanical properties.