US-12624482-B2 - Nonwoven fabrics comprising polylactic acid and surface-treated calcium carbonate

US12624482B2US 12624482 B2US12624482 B2US 12624482B2US-12624482-B2

Abstract

A process for the production of a nonwoven fabric. In particular, it relates to the production of a nonwoven fabric having desirable tactile and haptic as well as mechanical properties, as well as to the nonwoven fabric itself. The process requires the selection of specific polylactic acid polymers and corresponding process conditions.

Inventors

Martin Brunner
Christophe Roux
Simon FREMEAUX

Assignees

OMYA INTERNATIONAL AG

Dates

Publication Date: 20260512
Application Date: 20210112
Priority Date: 20200129

Claims (7)

1 . A process for producing a nonwoven fabric, the process comprising the following steps: a) providing a surface-treated calcium carbonate-containing filler material, the surface-treated calcium carbonate-containing filler material being a calcium carbonate-containing filler material and a surface-treatment layer on at least a part of the surface of said calcium carbonate-containing filler material, wherein the surface-treatment layer is formed by contacting the calcium carbonate-containing filler material with a surface treatment agent, wherein the surface treatment agent comprises at least one mono-substituted succinic anhydride and/or mono-substituted succinic acid and/or a salt thereof; b) providing a first polylactic acid polymer; c) providing a second polylactic acid polymer being different from the first polylactic acid polymer; d) forming a masterbatch consisting of the surface-treated calcium carbonate-containing filler material of step a) in an amount of from 20 to 80 wt.-%, based on the total weight of the masterbatch, with the first polylactic acid polymer of step b); e) mixing the masterbatch of step d) with the second polylactic acid polymer of step c) to obtain a mixture, the mixture consisting of the masterbatch of step d) and the second polylactic acid polymer of step c); f) forming the mixture of step e) into fibers; g) forming a fibrous web from the fibers of step f); and h) forming the non-woven fabric by calendering or hydroentanglement of the fibrous web of step g).
2 . The process of claim 1 , wherein the calcium carbonate-containing filler material has prior to the surface treatment i) a weight median particle size (d 50 ) value in the range from 0.1 μm to 7 μm, ii) a top cut (d 98 ) value of 15 μm or less, iii) a specific surface area (BET) from 0.5 to 120 m 2 /g, as measured by the BET method, and/or iv) a residual total moisture content from 0.01 wt.-% to 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material.
3 . The process of claim 1 , wherein the mixture of step e) has a surface-treated calcium carbonate-containing filler material content in the range of 5 to 25 wt.-%, based on the total weight of the mixture.
4 . The process of claim 1 , wherein the fibers formed in step f) are filaments having an average fiber diameter in the range from 9 to 25 μm, and/or a titer in the range from 1 to 6 dtex, as measured by EN ISO 2062:2009, and/or are formed from the mixture of step e) by spunbonding.
5 . The process of claim 1 , wherein the fibers formed in step f) are staple fibers having an average fiber diameter in the range from 9 to 25 μm, and/or a titer in the range from 1 to 6 dtex, as measured by EN ISO 2062:2009 and/or a staple fiber length in the range from 30 to 90 mm.
6 . The process of claim 1 , wherein the non-woven fabric is formed in step h) by hydroentanglement.
7 . The process of claim 1 , wherein the non-woven fabric is formed in step h) by calendering.

Description

The present invention relates to a process for producing a nonwoven fabric comprising a polylactic acid polymer and a surface-treated calcium carbonate-containing filler material, a nonwoven fabric comprising a polylactic acid polymer and a surface-treated calcium carbonate-containing filler material, the use of a surface-treated calcium carbonate-containing filler material for the manufacture of a nonwoven fabric comprising a polylactic acid polymer, and an article comprising the nonwoven fabric. Nonwoven fabrics are flexible sheet or web structures, which are composed of an interlocked network of staple fibers and/or filaments, which are used in a variety of consumer and industrial applications, such as in absorbent hygiene products, agriculture and horticulture, clothing and footwear, filtration, geotextiles and the like. Due to their absorbent properties, they are frequently used in personal care products, such as absorbent hygiene products, baby wipes, cleansing wipes, or antibacterial wipes. Today, nonwoven fabrics are mainly produced from synthetic thermoplastic polymers, such as polypropylene, polyethylene, polyesters, e.g., polyethylene terephthalate, or polyamides. These materials typically originate from non-renewable sources, such as fossil fuels, and are non-biodegradable. As a consequence, the utilization of nonwoven fabrics formed from synthetic polymers at their end of life typically is limited to energetic recycling, i.e., the materials have to be burned. Furthermore, if such nonwovens are used in geotextiles or are discarded in nature, they may remain permanently in the soil without decomposing, thus representing a threat for the environment. In recent years, biodegradable polymers emerged as a viable alternative to fossil-fuel derived conventional polymers. Biodegradable polymers are specific types of polymers that decompose after having fulfilled their intended purpose, yielding natural byproducts such as gases, water, biomass, and inorganic salts. These polymers can be derived from both natural and synthetic sources, and typically comprise ester-, amide-, and ether-containing repeating groups. Representative materials are known in the prior art. One known bio-degradable polymer is polylactic acid or polylactide (PLA). PLA is a bio-degradable thermoplastic aliphatic polyester derived from renewable resources, such as corn starch, tapioca roots, chips or starch, or sugarcane. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist. For example, poly-L-lactide (PLLA) is the product resulting from polymerization of L,L-lactide (also known as L-lactide). In 2019, PLA had the second highest production volume of bioplastic worldwide. Depending on their intended field of application, nonwoven fabrics may show a range of desirable material properties, i.e., mechanical properties (such as high tensile strength, both in machine direction (MD) and cross direction (CD), tear resistance, high puncture resistance, flexibility, and abrasion resistance), haptic properties (such as smoothness, softness, or a “cotton-feel”), and other properties (such as absorbency and breathability). In order to improve one or more of these material properties of nonwoven fabrics, it was suggested to incorporate inorganic fillers, such as particulate calcium carbonate, into the fibers of the nonwoven fabric. However, the incorporation can lead to lower tensile strength of the fibers, which causes processing issues, such as fiber breakages, pressure buildup at the die, or “sticky” fibers, and deteriorates the mechanical properties of the nonwoven fabric. Furthermore, there are specific issues associated with the incorporation of calcium carbonate fillers in a PLA fiber. In particular, calcium carbonate may catalyze the cleavage of the ester moieties in the PLA, leading to a deterioration of the mechanical properties or fiber breakages during spinning. This effect is more pronounced at elevated temperatures, such as those temperatures occurring during filament extrusion, which effectively limits the processability of calcium carbonate-filled PLA fibers. In the production process of nonwoven fabrics, the obtained fibers finally have to be consolidated in a web bonding step to yield a nonwoven fabric having a suitable strength for the intended applications. Commonly employed methods include thermobonding, also called calendering, or chemical bonding. Alternative processes may be needle-punching or hydroentanglement. Needlepunching tends to impart significant material stress to the nonwoven fabric, and may lead to fiber breakage and deterioration of mechanical strength of the material. Hydroentangling, also known as spunlacing, is a process, which employs high pressure water jets to entangle fibers in a loose web, thereby creating a fabric held together by frictional forces between said fibers. There is a need for processes, which allow for the formation of a bio-based, biodegradable nonwoven fabr