阅读说明：本技术 纺制微原纤化纤维素 (Spun microfibrillated cellulose ) 是由 G.库尼亚 H.萨克赛尔 于 2018-12-20 设计创作，主要内容包括：提供制备交联的微原纤化纤维素的纤维材料(优选毡或长丝)的方法。磷酸化的微原纤化纤维素被纺制成纤维材料；并且然后所述纤维材料被后处理(例如通过热处理)以提供磷酸化的微原纤化纤维素之间的交联。还描述了纤维材料(比如长丝或毡)以及包含这样的材料的卫生产品。(A process for preparing a fibrous material, preferably a felt or filament, of crosslinked microfibrillated cellulose is provided. Phosphorylated microfibrillated cellulose is spun into a fibrous material; and then the fiber material is post-treated (e.g. by heat treatment) to provide cross-linking between the phosphorylated microfibrillated cellulose. Fibrous materials (such as filaments or felts) and hygiene products comprising such materials are also described.)

1. A method of preparing a fibrous material of crosslinked microfibrillated cellulose, the method comprising the steps of:

i. spinning a cellulose composition comprising or consisting of phosphorylated microfibrillated cellulose (P-MFC) into a fiber material;

heat treating the fiber material to provide cross-linking of phosphorylated microfibrillated cellulose.

2. The method of claim 1, wherein the fibrous material is a filament.

3. The method of claim 1, wherein the fibrous material is a felt.

4. The method according to any one of the preceding claims, wherein the cellulose composition additionally comprises unmodified microfibrillated cellulose.

5. The method according to any of the preceding claims, wherein the cellulose composition additionally comprises chemically modified microfibrillated cellulose, such as e.g. dialdehyde-MFC or TEMPO-MFC.

6. The method according to any of the preceding claims, wherein the cellulosic composition comprises more than 25 wt.%, preferably more than 50 wt.%, such as e.g. more than 75 wt.% of P-MFC.

7. The method according to any of the preceding claims, wherein the heat treatment is carried out at a temperature between 60 and 200 ℃, preferably between 70 and 120 ℃.

8. The method according to any of the preceding claims, wherein the heat treatment is carried out for a time between 10 and 180 minutes.

9. The method of any one of the preceding claims, wherein crosslinking is performed in the absence of any additional crosslinking agent.

10. The process according to any one of the preceding claims, wherein the spinning is selected from wet spinning, electrospinning and dry spinning, preferably dry spinning.

11. The method according to any one of the preceding claims, wherein the phosphorylated microfibrillated cellulose (P-MFC) is obtained by; providing a suspension of cellulose pulp fibers in water, and phosphorylating the cellulose pulp fibers in said aqueous suspension with a phosphorylating agent, followed by fibrillation.

12. The method according to any one of the preceding claims, further comprising the step of drying the fibrous material prior to the heat treatment step.

13. The method according to any one of the preceding claims, further comprising a step of hydrating the fibrous material with water after the heat treatment step.

14. A spun felt or spun filament obtained by the process of any of the preceding claims.

15. A spun felt or spun filament comprising crosslinked phosphorylated microfibrillated cellulose.

16. A method of making a web of spun filaments, the method comprising: preparing spun filaments of cross-linked phosphorylated microfibrillated cellulose according to any one of the preceding claims, and; laying the spun filaments to provide a web.

17. A web comprising spun filaments, wherein the spun filaments are spun filaments according to any one of claims 14-15.

18. The web of claim 17, or the method of claim 16, wherein the web comprises additional filaments or fibers, such as, for example, synthetic filaments, wood fibers, or spun filaments of unmodified MFC.

19. The web of any one of claims 17-18, wherein the web is woven or non-woven.

20. A water-absorbing material comprising the felt or filament according to any one of claims 14-15.

21. Hygiene product comprising a felt or filament according to any one of claims 14-15 and/or a water absorbing material according to claim 20.

22. The hygiene product of claim 21, selected from the group consisting of disposable diapers, sanitary napkins, wipes, tampons, absorbent dressings, and disposable paper napkins.

23. A method of providing a hygiene product, the method comprising preparing a fibrous material of cross-linked microfibrillated cellulose according to any one of claims 1-13, and; introducing the felt or filament into a hygiene product.

Background

Microfibrillated cellulose (MFC) includes partially or fully fibrillated cellulose or lignocellulose fibers. The diameter of the released fibrils is less than 100nm, while the actual fibril diameter or particle size distribution and/or aspect ratio (length/width) depends on the source and manufacturing method. The smallest fibrils are called base fibrils (primary fibrils) and are about 2-4nm in diameter (see e.g. Chinga-carasco, g., Nanoscale research letters 2011,6:417), whereas it is common that base fibrils in aggregated form (which are also defined as microfibrils) are the main products obtained when manufacturing MFC, e.g. by using an extended refining process or a pressure drop decomposition process (see Fengel, d., Tappi j., March 1970, Vol53, No. 3.). The length of the fibrils may vary from about 1 to greater than 10 microns depending on the source and method of manufacture. The coarse MFC grade may contain a substantial part of fibrillated fibres, i.e. protruding fibrils from the tracheids (cellulose fibres), and a certain amount of fibrils released from the tracheids (cellulose fibres).

MFC has different acronyms, such as cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, fibril aggregates, nano-sized cellulose fibrils, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibrillar aggregates and cellulose microfibril aggregates. MFC may also be characterized by various physical or physicochemical properties, such as a large surface area or its ability to form a gel-like material at low solids (1-5 wt%) when dispersed in water.

MFC exhibits useful chemical and mechanical properties. Chemical surface modification of MFC has the potential to improve the properties of MFC itself, as well as the properties of filaments spun from MFC, such as mechanical strength, water absorption and elasticity/flexibility.

In a recent review article, Lundahl et al ind. Among other things, filaments obtained from spinning TEMPO-oxidized MFC showed weaker than filaments spun from untreated MFC.

An additional problem with chemically modified MFC is that its water absorption is increased due to its chemical load when compared to unmodified MFC and may start to lose integrity on contact with water. It may be difficult to achieve a balance of mechanical strength and water absorption.

Other documents in the art include US4,256,111 and US6,027,536.

There is therefore a need to improve the properties of mats or filaments spun from MFC; in particular, (wet) strength, water absorption and elastic/flexible properties. Suitably, the improvement can be achieved in a straightforward manner without the use of external modifiers such as cross-linking agents.

Disclosure of Invention

The present inventors have found that fibrous materials (e.g. felt or filaments) having the desired elasticity and water absorption can be formed from a cellulose composition comprising phosphorylated microfibrillated cellulose (P-MFC).

There is thus provided a process for preparing a fibrous material (e.g. filament or felt) of crosslinked microfibrillated cellulose, said process comprising the steps of:

i. forming a cellulose composition comprising or consisting of phosphorylated microfibrillated cellulose (P-MFC) into a fiber material;

heat treating the fiber material to provide cross-linking of phosphorylated microfibrillated cellulose.

Also provided is a spun fibrous material, such as a spun felt or spun filament, obtained by the process described herein. Additionally, a spun fiber material of cross-linked phosphorylated microfibrillated cellulose is provided, which is a spun felt or a spun filament. Also provided are webs containing such spun filaments, such as water absorbent materials comprising the spun fibrous materials. In another aspect, a hygiene product comprising the spun fibrous material and/or water absorbent material is provided.

Further aspects of the invention are provided in the following and in the dependent claims.

Detailed Description

In a first aspect, the present invention provides a method of preparing a fibrous material of crosslinked microfibrillated cellulose (MFC). The term "fibrous material" is used herein to include both felt and filaments, preferably filaments.

In the context of the present patent application, microfibrillated cellulose (MFC) or so-called Cellulose Microfibrils (CMF) shall mean nano-scale cellulose particle fibers or fibrils with at least one dimension smaller than 100 nm. MFC comprises partially or fully fibrillated cellulose or lignocellulose fibers. The cellulose fibres are preferably fibrillated to such an extent that the final specific surface area of the MFC formed, when the freeze-dried material is measured by the BET method, is from about 1 to about 300m²G, e.g. 1 to 200m²In g or more preferably in the range from 50 to 200m²/g。

There are various methods of manufacturing MFC, such as single or multiple refining, prehydrolysis followed by refining or high shear disintegration or fibril release. One or several pre-treatment steps are usually required to make MFC manufacture both energy efficient and sustainable. Thus, the cellulose fibers of the pulp to be supplied may be subjected to enzymatic or chemical pretreatment, for example to reduce the amount of hemicellulose or lignin. The cellulose fibers may be chemically modified prior to fibrillation, wherein the cellulose molecules contain functional groups other than (or more than) those found in the original cellulose. These groups include, in particular, carboxymethyl (CMC), aldehyde and/or carboxyl groups (cellulose obtained by N-oxyl-mediated oxidation, for example "TEMPO"), or quaternary ammonium (cationic cellulose). After modification or oxidation in one of the above-mentioned methods, it is easier to decompose the fibers into MFC or NFC.

The nanofibrillar cellulose may contain some hemicellulose; the amount depends on the plant source. The mechanical disintegration of the pretreated fibers, for example hydrolyzed, preswollen or oxidized cellulose raw materials, is carried out using suitable apparatuses, for example refiners, grinders, homogenizers, colloid discharge devices (colloiders), friction grinders, ultrasonic sonicators, single-or twin-screw extruders, fluidizers, such as microfluidizers, macrofluidizers or fluidizer-type homogenizers. Depending on the MFC manufacturing process, the product may also contain fine particles or nanocrystalline cellulose or other chemicals present e.g. in wood fibre or paper making processes. The product may also contain various amounts of micron-sized fiber particles that are not effectively fibrillated.

MFC can be made from lignocellulosic fibers, including both hardwood or softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made of pulp, including pulp from virgin fibers, e.g., mechanical, chemical, and/or thermomechanical pulp. It can also be made of broke or recycled paper.

The above definition of MFC includes, but is not limited to, TAPPI standard W13021 proposed on cellulose nano-or microfibrils (CMF), which defines a cellulose nanofibrous material containing a plurality of base fibrils, having both crystalline and amorphous regions, having a high aspect ratio, a width of 5-30nm and an aspect ratio typically larger than 50.

Phosphorylated microfibrillated cellulose (P-MFC) is typically obtained by: cellulose pulp fibers are reacted with a phosphorylating agent, such as phosphoric acid, and the fibers are subsequently fibrillated into P-MFC. One particular method involves providing a suspension of cellulose pulp fibers in water and phosphorylating the cellulose pulp fibers in the aqueous suspension with a phosphorylating agent, followed by fibrillation by methods common in the art. Suitable phosphorylating agents include phosphoric acid, phosphorus pentoxide, phosphorus oxychloride, diammonium phosphate and sodium dihydrogen phosphate.

In the reaction to form P-MFC, the alcohol function (-OH) in the cellulose is converted to a phosphate group (-OPO)₃ ^2-). In this manner, the crosslinkable functional group (phosphate group) is introduced into the pulp fiber or microfibrillated cellulose.

In a first general step of the method, a cellulose composition comprising or consisting of phosphorylated microfibrillated cellulose (P-MFC) is spun into a fiber material.

In case the cellulosic composition consists of P-MFC, no components other than P-MFC are present in the composition. Where the cellulosic composition comprises P-MFC, components other than P-MFC may be present in the composition. However, the cellulosic composition suitably comprises more than 25 wt%, preferably more than 50 wt%, such as for example more than 75 wt% of P-MFC. In a preferred aspect, the cellulose composition comprising P-MFC may additionally comprise unmodified (natural) MFC. By "unmodified" or "natural" MFC is meant microfibrillated cellulose which is the direct product (result) of fibrillation of natural cellulose fibres, i.e. there is no chemical treatment before or after fibrillation.

Suitably, the cellulosic composition therefore consists of P-MFC and MFC. Alternatively or additionally, the cellulose composition comprising P-MFC may additionally comprise chemically modified microfibrillated cellulose, such as for example dialdehyde-MFC or TEMPO-MFC (i.e. MFC oxidised with 2,2,6, 6-tetramethylpiperidin-1-yl) oxy (oxidinyl). Additional components of the cellulosic composition may include natural or synthetic filaments or natural or synthetic staple fibers.

In a second general step of the method, the fiber material from the first step is heat treated to provide cross-linking of the phosphorylated microfibrillated cellulose. The crosslinking is suitably carried out without the use of any additional crosslinking agent; i.e. crosslinks are formed directly between the phosphate moieties (moieties) and the other components of the cellulosic composition.

The heat treatment in the second general step of the process is suitably carried out at a temperature of between 60 and 200 ℃, for example at a temperature of between 70 and 120 ℃. Such temperatures are not only sufficient to obtain cross-linking, but also limit the potential degradation of MFC. It has been determined that the heat treatment is suitably carried out for a time of between 10 and 180 minutes, depending on the temperature used and the initial solids content of the material to be heat treated. The heat treatment may be performed in an oven, but other heat treatment methods may also be used.

The fibrous material is preferably filaments and the forming method is spinning. General methods for spinning filaments from MFC are described in, for example, Lundahl et al, ind. Suitable spinning methods may be selected from wet spinning, electrostatic spinning and dry spinning. The preferred spinning method for phosphorylated microfibrillated cellulose is dry spinning, as this technique avoids the need for an additional coagulation bath and makes it easier to handle the filaments and to create a pattern (e.g. a grid).

The fibrous material may also be a felt. If the fibrous material is a felt, the composition is spun (i.e., a spun felt). "spun felt" means that, unlike spinning individual filaments, an interconnected structure (body) made from filaments can be directly spun.

The general steps of the process (spinning followed by heat treatment) can be carried out in the absence of any intermediate (interlacing) process steps. Alternatively, one or more intermediate process steps may be performed between the spinning step and the heat treatment step. In a particular aspect, the fibrous material can be dried before or during the heat treatment step. Drying may suitably be carried out at ambient conditions (e.g. 25 ℃). It has been found that cross-linking can be triggered in a fibre material which has previously been dried under ambient conditions, for example by placing the dried fibre material according to the invention in an oven. This means that in principle it is possible to dry the material at ambient conditions (without crosslinking) and then to trigger the crosslinking at a later stage by heat treatment, if desired.

Alternatively, the step of drying the fibrous material (felt or filament) may be performed during the heat treatment step. In this alternative, a dry, crosslinked fibrous material is obtained which can have advantageous water absorption properties and strength properties under both dry and wet conditions.

If a hydrated fibrous material is desired, a further step of hydrating the fibrous material with water may be performed after the heat treatment step.

It is believed that insufficient water is removed from the sample at room temperature (i.e., drying at RT); crosslinking requires heat treatment. Furthermore, it is considered surprising that a certain stretchability/elasticity behavior can be obtained after soaking the heat-treated material in water.

The general process of the present invention can be used to provide spun filaments of crosslinked phosphorylated microfibrillated cellulose. The spun filaments may then be used to prepare a web of spun filaments by laying the spun filaments to provide a web. The present invention thus provides a web comprising spun filaments, wherein the spun filaments are as described herein.

The web may comprise additional filaments or fibers, such as, for example, synthetic filaments, wood fibers, or spun filaments of unmodified MFC or other types of modified MFC. The web may be woven or non-woven. The web may be an air laid, meltblown or spun laid nonwoven web.

The invention also provides a spun felt or a spun filament, preferably a spun filament, obtained by the process described herein. Additionally provided is a spun felt or spun filament of crosslinked phosphorylated microfibrillated cellulose. The cross-linking of phosphate groups present between MFC fibrils can be determined spectroscopically, for example³¹P NMR。

The spun felt or filament described herein can be used as a water absorbent material due to a particular combination of strength (particularly wet strength) and water absorbency. Thus, a hygiene product is provided comprising the spun felt or filament of the invention and/or a water-absorbing material comprising said spun felt or filament. The sanitary product may be selected from the group consisting of disposable diapers, sanitary napkins, wipes (wipes), tampons, absorbent dressings and disposable paper towels. There is also provided a method of providing a hygiene product, the method comprising: preparing a mat or filament of cross-linked phosphorylated microfibrillated cellulose according to the invention, and; introducing the felt or filament into a hygiene product. The standard methods of constructing hygiene products and incorporating felts or filaments into such products are known to those skilled in the art.