FI20225173A1

FI20225173A1 - Fiber-reinforced material, composite and laminate structure and methods for manufacturing the same and the use thereof

Info

Publication number: FI20225173A1
Application number: FI20225173A
Authority: FI
Inventors: Juha Salmela
Original assignee: Spinnova Oy
Priority date: 2022-02-25
Filing date: 2022-02-25
Publication date: 2023-08-26

Abstract

Described herein is fiber-reinforced material that comprise a reinforcement structure and a binder matrix, wherein the binder matrix comprises a layer of random, microfibrillated cellulose fibers (MFC), and wherein the reinforcement structure comprises cellulose monofilaments permeated by the binder matrix. Also described herein are a composite material and a laminate structure and methods of manufacturing the fiber-reinforced material, composite material and laminate structure and the uses thereof.

Description

FIBER-REINFORCED MATERIAL, COMPOSITE AND LAMINATE STRUCTURE

AND METHODS FOR MANUFACTURING THE SAME AND THE USE THEREOF

Technical field

The present invention relates to a method of manufacturing fiber-reinforced materials, a method of manufacturing composite materials and a method of manufacturing laminate structures. Further, the invention relates to fiber-reinforced materials, composite materials, and laminate structures obtainable by said methods, as well as uses of said fiber-reinforced materials, composite materials and laminate structures.

Background

There exists a variety of different fiber-based reinforcements for a polymer matrix in composite materials. In such reinforcements, fibers of glass, carbon, aramid, or basalt have traditionally been used. In recent years, the application of recyclable natural cellulosic fibers such as long fibers of hemp, flax, kanaf, cotton, jute, sisal and coconut and shorter plant fibers, mainly derived from wood pulp, has also received increasing attention due to increasing environmental consciousness.

The type of the reinforcement fiber is one of the most contributory factors impacting on performance of the composite material. For instance, carbon fiber reinforcements are commonly used in the composites wherever high strength-to- weight ratio and stiffness are required. One drawback of carbon fiber material is its environmental impact; it is notoriously difficult to recycle, energy-intensive to produce and it does not biodegrade, for instance. In recent years, microfibrillated cellulose (MFC) has been gaining attention as a reinforcement material due to

MFC's potentiality to provide high strength-to-weight ratio reinforcement for

N 25 composites in environmentally friendly manner.

O

N However, there are various challenges related to the known solutions that utilize

Q MFC in the context of composite materials. For instance, high volume fraction of

O the cellulose microfibrils within the polymer matrix that is necessary to produce a

I stiff and strong composite, remains challenging and energy-intensive to achieve. A a 30 known problem of laminate structures that comprise fiber reinforcements

O embedded in polymer matrix or plastic materials is the large difference in stiffness jo between the fibers and plastic. Reinforcement fibers have considerable higher

N Young's modulus compared to polymer matrix such as epoxy resin, which may

N cause problems of delamination when different layers of composite materials are bonded together with resins. A further known problem is that fiber-reinforced materials comprising unidirectional fibers have very low stiffness and strength at right angles to the fiber direction.

Consequently, there exists a demand for improved MFC fiber reinforcements, composites and laminate structures, and simple methods for manufacturing the

MFC reinforcements, composites and laminate structures.

Summary

Based on the above, it is an aim of the present invention to at least alleviate one or more of the above drawbacks or challenges associated with the existing solutions in the context of composite materials, such as especially MFC reinforcement materials, and composites and laminate structures comprising said reinforcement material.

The aims of the invention are obtained with a fiber-reinforced material and a composite material and laminate structure comprising said fiber-reinforced material, methods for producing said fiber-reinforced material, composite material and laminate structure, and uses thereof, which are characterized in what is presented in the independent claims. Some advantageous embodiments of the invention are presented in the dependent claims.

According to a first aspect of the present invention there is provided a fiber- reinforced material that comprises a reinforcement structure and a binder matrix, wherein the binder matrix comprises a layer of random (i.e. arranged in a random manner), microfibrillated cellulose (MFC) fibers. Further, the reinforcement structure comprises cellulose monofilaments permeated at least partially by the binder matrix.

In the fiber-reinforced material the binder matrix is absorbed into the reinforcement structure. The fibers of the binder matrix are bonded with the cellulose monofilaments. Since the cellulose monofilaments are permeated by the binder matrix there is no clear interface of different types of materials between the binder

N matrix and the reinforcement structure. In other words, the fiber-reinforced material

N is devoid of substantial difference in stiffness between the fibers of the binder

N matrix and reinforcement structure. Still in other words, a plurality of the fibers of

S the binder matrix are permeated inside and bonded with cellulose monofilaments

O 30 of the reinforcement structure. This improves fatigue resistance of the fiber-

I reinforced material and fatigue resistance (damping performance) of the a composite material comprising the fiber-reinforced material.

O

= The fiber-reinforced material is preferably a layer, film or sheet comprising a first a surface and a second surface opposing the first surface. The thickness of the

S 35 material may vary depending on the application.

Preferably each of the cellulose monofilaments of the reinforcement structure comprises an elongate internal structure comprising interlocked cellulose fibers and extending generally along the longitudinal dimension of the cellulose monofilament.

Preferably at least part of the monofilaments of the reinforcement structure comprises MFC fibers.

Preferably the cellulose fibers of at least one of the binder matrix and the reinforcement structure or the cellulose fibers of both the binder matrix and the reinforcement structure comprise plant based natural, non-regenerated cellulose fibers.

Alternatively, the cellulose fibers of the binder matrix comprise non-regenerated cellulose fibers and the cellulose fibers of the reinforcement structure comprise a mixture of non-regenerated and regenerated cellulose fibers. The regenerated cellulose fibers may improve tensile strength and stretch of the fibrous monofilament. The regenerated cellulose fibers mixed with the other fibers forming the monofilament of the reinforcement structure may hence be used to tailor further mechanical properties of the structure. These regenerated cellulose fibers may be man-made cellulosic fibers (for example Lyocell, viscose or modal).

Preferably the reinforcement structure comprises mixture of MFC fibers and man- made cellulosic fibers. The reinforcement structure may comprise at least 40 wt.%

MFC fibers and at least 20 wt.% man-made cellulosic fibers. Alternatively, the reinforcement structure may comprise at least 50 wt.% MFC fibers and at least 30 wt.% man-made cellulosic fibers. Alternatively, the reinforcement structure may comprise at least 55 wt.% MFC fibers and at least 35 wt.% man-made cellulosic fibers

Alternatively, the reinforcement structure may comprise between 50 and 60 wt.% of MFC fibers and between 30 and 40 wt.% of man-made cellulosic fibers.

N Alternatively, the reinforcement structure may comprise between 55 and 70 wt.% < of MFC fibers and between 30 and 45 wt.% of man-made cellulosic fibers.

N

<Q Preferably man-made cellulosic fibers are Lyocell fibers. Preferably the

S reinforcement structure may comprise at least 40 wt.% MFC fibers and at least 20

I 30 wt% Lyocell fibers. Alternatively, the reinforcement structure may comprise at + least 50 wt.% MFC fibers and at least 30 wt.% Lyocell fibers. Alternatively, the 2 reinforcement structure may comprise between 50 and 60 wt.% wt.% of MFC jo fibers and between 30 and 40 wt.% of Lyocell fibers.

QA

N Alternatively, the reinforcement structure may comprise between 55 and 70 wt.% wt.%of MFC fibers and between 30 and 45 wt.% of Lyocell fibers.

Preferably most of the cellulose monofilaments of the reinforcement structure have a cross-sectional aspect ratio in a range of 30-300 x10-6 m / 5-30 x10-6 m or in a range of 30-200 x10-6 m / 5-20 x10-6 m or in a range of 30—120 x10-6m / 5-10 x10-6 m. In this context by a term “majority” is meant more than 50 % of the monofilaments.

The reinforcement structure may consist of one or more portions. A plurality of portions may be similar and/or dissimilar with each other, depending on the application.

Preferably the reinforcement structure has a portion whose cellulose —monofilaments are oriented substantially parallel to one another along their length.

Preferably the reinforcement structure has a portion where the cellulose monofilaments being formed into a woven or knitted fabric.

Preferably the reinforcement structure has a portion where the cellulose monofilaments being formed into a non-woven fabric.

Preferably the cellulose monofilaments in the woven fabric and in the non-woven fabric are spun into yarns having a linear density in a range of 10-100 tex or in a range of 20-30 tex or in a range of 30-40 tex.

Preferably the woven fabric and/or the nonwoven fabric has a weight in a range of 10-500 g/m2 or in a range 50-350 g/m2 or in a range 100-300 g/m2.

Preferably the cellulose monofilaments of the portion of the woven fabric and/or the non-woven fabric are staple fibers having an average length in a range of 3— 160 mm or in a range of 10-80 mm or in a range of 30-60 mm.

Preferably the cellulose monofilaments have a linear density in a range of 1-10

N dtex or in a range of 2—8 dtex or in a range of 3—5 dtex.

QA

N 25 Preferably the fiber-reinforced material has a generally average density in a range

N approximately 1000 kg/m3 to approximately 1600 kg/m3 or in a range

LO approximately 1100 kg/m3 to approximately 1500 kg/m3 or in a range - approximately 1150 kg/m3 to approximately 1400 kg/m3 o in a range

T approximately 1200 kg/m3 to approximately 1300 kg/m3. 2 30 According to a second aspect of the present invention there is provided a (D composite material comprising the fiber-reinforced material of the first aspect of o the present invention and a polymer matrix impregnated in the fiber-reinforced material.

Preferably the polymer matrix encapsulates at least one of two opposing surfaces (i.e., at least one of the first and second surfaces) of the fiber-reinforced material.

Preferably the polymer matrix is selected from the list of thermosets consisting of epoxy, polyurethanes, phenolic and amino resins, bismaleimides (BMI, 5 polyimides), polyester, and polyamides or mixtures thereof. Alternatively, or additionally, the polymer matrix is selected from the list consisting of acrylic, ABS, nylon, PLA, polybenzimidazole, polycarbonate, polyether sulfone, polyoxymethylene, polyether ether ketone, polyetherimide, polyethylene, polyphenylene oxide, polyphenylene sulfide, polypropylene, and polystyrene or mixtures thereof.

When a polymer matrix is impregnated in the fiber-reinforced material forming mutually a composite material, the fiber-reinforced material ensures good stress transfer through the polymer matrix to the fiber-reinforced material so providing the composite material with the desired stiffness, strength, and toughness properties.

According to a third aspect of the present invention there is provided a laminate structure comprising two or more layers wherein at least one of the two or more layers comprise fiber-reinforced material according to the first aspect of the present invention.

Preferably the structure further comprises one or more layers of one or more polymer matrix disposed between the two or more layers.

The polymer matrix of the composite material or laminate structure may be hydrophobic resin. The hydrophobic resin comprises an epoxy such Bisphenol-A or modified Bisphenol A epoxy. Alternatively, or additionally, the hydrophobic resin comprises a resin selected from the group comprising siloxanes, polyurethanes, phenolic resins, and acrylics.

N According to a fourth aspect of the present invention there is provided a method

O for manufacturing a fiber-reinforced material. The method comprises the steps of:

N a) contacting a reinforcement fiber structure comprising cellulose monofilaments

LO with an aqueous suspension comprising discontinuous cellulose fibers; and

N 30 b) removing the water of the agueous suspension to form a layer of binder matrix

I

T from the agueous suspension. 2 Preferably the step of removing the water (i.e. step b) comprises heating the

S contacted reinforcement fiber structure and agueous suspension.

QA

O

N Preferably the step of removing the water (i.e. step b) comprises pressurizing the contacted reinforcement fiber structure and aqueous suspension, which pressurizing may optionally result in a desired shaped preform of the fiber- reinforced material.

Additionally, or alternatively, the step of contacting a reinforcement fiber structure (i.e. step a) is preferably preceded by a step of arranging a plurality of cellulose monofilaments substantially parallel to one another along their length to form at least a portion of the reinforcement fiber structure.

Additionally, or alternatively, the step of contacting a reinforcement fiber structure (i.e. step a) is preferably preceded by steps of cutting a plurality of cellulose monofilaments to generally the same length fibers, spinning yarn and weaving the — yarn into at least one fabric sheet to form at least a portion of the reinforcement fiber structure.

Additionally, or alternatively, the step of contacting a reinforcement fiber structure (i.e. step a) is preferably preceded by steps of cutting a plurality of cellulose monofilaments to generally the same length fibers, arranging randomly the fibers in a sheet, layer or web, and optionally consolidating the arranged fibers, to form at least a portion of the reinforcement fiber structure.

According to a fifth aspect of the present invention there is provided a method for manufacturing composite material. The method comprises a step of providing the fiber-reinforced material according to the first aspect of the present invention or the fiber-reinforced material manufactured according to the fourth aspect of the present invention and a further step of impregnating a polymer matrix into the fiber-reinforced material.

According to a sixth aspect of the present invention there is provided a method for manufacturing a laminate structure. The method comprises a step of providing two or more layers wherein at least one of the two or more layers comprise a fiber- reinforced material according to the first aspect of the present invention or the

N fiber-reinforced material manufactured according to the fourth aspect of the

N present invention.

N

7 Preferably the method further comprises steps of impregnating one or more layers

N 30 of one or more polymer matrix between the two or more layers.

I a + According to a seventh aspect of the present invention there is provided a use of 2 an aqueous suspension comprising MFC fibers as a binder matrix within a fiber- jo reinforced material.

QA

N According to an eight aspect of the present invention there is provided a use of the fiber-reinforced material according to the first aspect of the present invention or the fiber-reinforced material manufactured according to the fourth aspect of the present invention as a reinforcing member, construction, decorative, packing, transport or insulating material.

According to a ninth aspect of the present invention there is provided a use of the composite material according to the second aspect of the present invention or the composite material manufactured according to the fifth aspect of the present invention as a sports equipment, construction, decorative, packing or transport material.

According to a tenth aspect of the present invention there is provided use of the laminate structure according to the third aspect of the present invention as a — sports equipment, construction, decorative, packing or transport material.

Description of Preferred Embodiments

Hereinafter, the present invention will be described in detail.

As briefly discussed above, the present invention generally achieves novel fiber- reinforced material and composite and laminate structure comprising the same — with combination of properties selected from strength, fatigue resistance (damping performance), mechanical stability, strength-to-weight ratio, and recyclability.

The microfibrillated cellulose (MFC), a.k.a. microfibrous cellulose, in the present invention is a cellulose fiber or an elongated element having a far smaller width than a pulp fiber that is used for ordinary paper-manufacturing. The MFC is a collection of cellulose molecules in a crystal state, and the crystal structure thereof is the I-type, i.e., parallel chain. The width of the MFC is preferably between approximately 2 nm to approximately 1000 nm, more preferably 2 nm to 500 nm, and still more preferably 4 nm to 100 nm under suitable microscopic observation.

When the width of the fiber is less than 2 nm, the cellulose is dissolved in water in 3 25 a molecular form, and therefore, it becomes difficult for the cellulose to exhibit the a favorable properties of an elementary fibril or microfiber such as strength or rigidity

N or dimensional stability, for instance. Said favorable properties cannot be obtained

LO either when the width of the fiber exceeds 1000 nm in which case such a fiber is

N simply an element included in ordinary pulp.

I

S 30 In the present disclosure a “fiber” refers to elongated fibrous filaments and staple 2 fibers. Fibers including natural cellulose fibrils refer to fibers including plurality of jo natura! cellulose fibrils, which are interlocked together through hydrogen bonds

N and exhibit crystalline structure of cellulose I. Cellulose fibrils originate from refined

N pulp or other plant-based material.

In the present disclosure a “polymer matrix’ refers generally to any thermoset or thermoplastic known in the art that is used together with a reinforcement to construct a composite material.

In the present disclosure a “natural cellulose fibril’ i.e., fibrous element of natural cellulose has not undergone chemical or physical modification of its macromolecular structure. Cellulose fibrils in native form refer to natural cellulose fibrils. Natural cellulose fibrils may originate from plant based raw material. Plant based raw material may be wood or non-wood material. The wood material can be based on softwood tree, such as spruce, pine, fir, larch, Douglas-fir or hemlock, or hardwood tree, such as birch, aspen, poplar, alder, eucalyptus or acacia, or any mixture of above. The non-wood material may be based on, such as cotton, hemp, flax, sisal, jute, kenaf, bamboo, peat, or coconut. Non-wood based natural cellulose fibrils may also be from agricultural residues, grasses, or other plant substances such as straw, leaves, bark, seeds, hulls, flowers, vegetables or fruits.

Natural cellulose fibrils may be wood based. Wood based natural cellulose fibrils may originate from chemical pulp, thermomechanical pulp, mechanical pulp, or waste-paper pulp. Wood based natural cellulose fibrils are non-regenerated.

Crystalline cellulose structure of non-regenerated natural cellulose fibrils consists of cellulose I, which is native form of cellulose. Natural cellulose fibrils may have gone through mechanical or chemical treatment known in the art to increase firer fibrillation and to separate microfibrils from pulp fibers.

The method for manufacturing MFC is not particularly limited. MFC may be isolated from cellulose fibers through high pressure, high temperature and high velocity impact homogenization, for instance. The homogenization process is used to delaminate or disintegrate the cell walls of the fibers and to liberate their sub- structural fibrils and micro fibrils. Enzymatic and/or mechanical pre-treatments of wood fibers may also be used.

N Preferably cellulose fibers are processed into MFC in a mechanical operation such

S as crushing. Preferably such as a grinder (an ultra-fine friction grinder or the like),

A 30 a high-pressure homogenizer or ultrahigh-pressure homogenizer, a high-pressure 7 impact grinder, a disc-type refiner, or a conical refiner, is used.

N

I In the present disclosure an “aqueous suspension comprising MFC fibers” is a understood to mean any suspension comprising water and MFC fibers.

O

= The agueous suspension may be manufactured as disclosed in patent publications a 35 WO201815099 A1, WO 2016/174307 A1 or WO2013/034814 A1, for instance.

S The cellulose monofilaments may be manufacture as disclosed in those publications, accordingly, or any other method of manufacturing cellulose monofilament known in the art.

The aqueous suspension may comprise 80-98 wt.% of water and 2-20 wt.% of

MFC. Alternatively, the aqueous suspension may comprise 85-98 wt.% of water and 2-15 wt.% of MFC. In addition the aqueous suspension may comprise 0-5 wt. % of dispersion agent and/or rheology modifier.

The water content of the aqueous suspension may vary depending on the method for applying the aqueous suspension when manufacturing the fiber-reinforced material. Additionally, or alternatively, the water content may vary depending on characteristics such as porosity of the reinforcement structure.

The dispersion agent may be a cellulose derivative such as one or any mixture selected from the list consisting of: Carboxymethylcellulose (CMC), Hydroxyethyl cellulose (HEC), Ethyl hydroxyethyl cellulose (EHEC), Methyl cellulose (MC),

Hydroxypropyl methyl cellulose (HPMC) Hydroxyethyl methyl cellulose (HEMC),

Hydroxyethyl cellulose (HEC), Ethyl HEC (EHEC), Methyl EHEC (MEHEC),

Hydroxypropyl cellulose (HPC), Ethyl cellulose (EC), and starch. Alternatively, or additionally, the dispersing agent is selected from the list consisting of Polyacrylic acid, Polymethacrylic acid, Polyphosphoric acid, Polystyrene sulfonic acid,

Polyvinyl amine, Polyvinyl alcohol, Polyacrylamide, Polyethylene oxide (PEO), copolymer of Acrylamide, Acrylic acid, and any mixtures thereof.

Rheology modifier comprises a compound or agent arranged to modify the viscosity, yield stress and/or thixotropy of the suspension. Rheology modifier may comprise high molecular weight polymers. Rheology modifier is arranged to modify aqueous suspension rheology by adjusting gel strength and yield point of it.

The fiber-reinforced material and composites and laminate structures comprising the same and the methods for manufacturing said material, composite and laminate structure will be discussed below in greater detail. However, generally it can be noted that the fiber-reinforced material comprises a reinforcement structure and a binder matrix, wherein the binder matrix comprises a layer of random,

N discontinuous MFC fibers, and wherein the reinforcement structure comprises

S cellulose monofilaments permeated by the binder matrix.

S 30 Manufacturing method of fiber-reinforced material

LO

- The fiber-reinforced material may be formed in a method comprising the steps of: a > a) contacting a reinforcement fiber structure comprising cellulose

C monofilaments with an agueous suspension comprising discontinuous MFC n cellulose fibers; and

N 35 b) removing the water of the agueous suspension to form a layer of binder

N matrix from the agueous suspension.

In the water removing step the binder layer is cured. The water removing step or curing step may be enhanced by heating and drying the contacted structure and suspension which may be carried out at a temperature of 70°C to 130°C such as 80°C. The water removing step may be carried out by methods utilizing vacuum, mechanical pressing, convection, conduction, or radiation of heat, by any suitable heating means such as heated airflow, IR, or contact with heated surface, for instance.

Alternatively, or additionally, a method in which the free water of the aqueous suspension is dehydrated (i.e. dewatered) using preferably methods that are generally used for papermaking such as a method of Fourdrinier, a cylinder mold, an inclined wire, or the like, and then dehydrated using a roll press is preferred. In addition, ordinary methods used for papermaking can be used as the drying method, and methods using, for example, a cylinder dryer, a Yankee dryer, hot air drying, or an infrared heater are preferred. Meanwhile, the drying temperature is preferably about 70°C to 130°C.

Pressure need not be applied to the formed fiber-reinforced material during curing, but it can be advantageous in reducing imperfections in the cured material. One or a plurality of layers can be built up by this method (e.g., reinforcement fiber structure/aqueous suspension/reinforcement fiber structure/aqueous suspension) before drying and curing, or each material layer comprising reinforcement fiber structure and aqueous suspension can be cured first before the addition of optional further layers.

The method for applying the aqueous suspension in the contacting step is not particularly limited, and an ordinary method, such as bar coating, die coating, curtain coating, air knife coating, blade coating, rod coating, Gravure coating, spray coating, size press coating, and gate roll coating, may be used.

In the method the reinforcement structure is advantageously disposed on a metal surface from which the formed fiber-reinforced material can be removed. The surface may alternatively comprise or consists of other suitable material known to

N those skilled in the art, like plastic material can be used. Advantageously the

S surface comprises a hydrophobic external surface. The removal of the fiber-

A 30 reinforced material may be further improved by applying oil or wax to the surface 7 contacting with the structure.

N

I When the reinforcement structure is contacted with the aqueous suspension the a water of the suspension penetrates the cellulose monofilaments of the

O reinforcement structure resulting in expansion of the monofilaments of the n 35 reinforcement structure and hence permitting the MFC fibers of the suspension to

N enter inside the monofilaments. When the wetted, i.e., moist, reinforcement

N structure is dried the monofilaments shrink and the fibers of the reinforcement structure and penetrated MFC fibers of the suspension contact each other forming bonds such as hydrogen bonds between them. The MFC fibers originating from the suspension distribute randomly manner forming the binder matrix in a form of layer or film. Consequently, there are MFC fibers connected each other also in the possible openings of the reinforcement structure. In other words, the formed fiber- reinforcement material comprises one-material phase of cellulose extending through the material. Such a one-material phase provides various positive effects to mechanical properties of the reinforcement material. For instance, it improves stress and vibration distribution within the material. In other words, the formed structure of the reinforcement material comprises a fused phase of the cellulose fibers extending through the material where the strength and stiffness of the material originate from the nature of the elementary fibrils of MFC distributed through the material. This enables improvement in the strength-to-weight ratio compared to reinforce material known in the art.

One further advantage of the formed reinforce material, compared to reinforce material known in the art, is that the stiffness and strength properties can also be improved at right angles to the fiber direction and monofilament direction of the reinforcement structure.

Advantageously at least part of the monofilaments of the reinforcement structure comprises MFC fibers. When the monofilaments of the reinforcement structure comprise MFC fibers the reinforcement structure turns in its wetted state in the manufacturing process to gel-like form. This may further improve bonding between and fusion and absorption of the fibers of the reinforcement structure and the aqueous suspension, which in turn improve the mechanical properties of the dried, formed fiber-reinforcement material.

In one embodiment a major part of the cellulose fibers of the reinforcement structure are MFC fibers.

When less than 10 % of the fibers of the reinforcement structure are MFC fibers there is a concern that the reinforcement structure does not turn preferred gel-like in its wetted state, which may not be preferable for formation of bonding between

N the fibers of the reinforcement structure and the agueous suspension in the

S manufacturing process.

S 30 In one embodiment at least 70 % of the cellulose fibers of the reinforcement

S structure are MFC fibers. In another embodiment at least 80 % of the cellulose

T fibers of the reinforcement structure are MFC fibers. Still another embodiment at & least 90 % of the cellulose fibers of the reinforcement structure are MFC fibers.

O

= One advantage of the method is that it enables a simple, energy effective way to a 35 manufacture fiber-reinforcement material which fibers may consists mainly or

S optionally totally of MFC fibers. Still another advantage of the method is that it may be actuated environmentally friendly manner, for instance, there is no need for organic solvents.

The applied amount of aqueous suspension in the manufacturing process is not particularly limited, but the applied amount is preferably 10 g/m2 to 500 g/m2, more preferably 50 g/m2 to 400 g/m2, and particularly preferably 100 g/m2 to 300 g/m2. When the applied amount is less than 10 g/m2, there is a concern that the properties of strength, and fatigue resistance (damping performance) may not become as good as desired due to insufficient amount of MFC fibers for forming uniform layer of fused MFC fibers extending through the material, which is not preferable.

The content and/or dimensions of the reinforcement structure may be varied depending on the application. In an embodiment, the cellulose monofilaments of the reinforcement structure comprise an elongate internal structure comprising interlocked cellulose fibers and extending generally along the longitudinal dimension of the cellulose monofilament.

In an embodiment, most of the cellulose monofilaments of the reinforcement structure have a cross-sectional aspect ratio in a range of 30-300 x10-6 m / 5-30 x10-6 m or in a range of 30-200 x10-6 m / 5-20 x10-6 m or in a range of 30-120 x10-6M/5—10 x10-6 m.

When the cross-sectional aspect ratio of the cellulose monofilaments of the reinforcement structure is non-spherical, such as 5:120 or 10:100 or 20:80, the

MFC fiber matrix of the aqueous suspension can penetrate further in the direction of the cross section of the monofilament, which may improve the mechanical properties of the dried, formed fiber-reinforcement material and enable formation of an even thinner fiber-reinforce material.

There are various forms of the reinforcement structure. Which dimensions and — directions of the monofilament are used depend on the application and use case of the reinforcement structure. For instance, if the reinforcement structure is employed in a ski the reinforcement structure advantageously comprises a portion

N where the cellulose monofilaments are oriented substantially parallel to one

S another along their length. It will be apparent to those skilled in the art that the

A 30 reinforcement structure can be employed into a desired form, including variables 7 how many layers and directions of the monofilaments in the layer there are

N employed, to obtain a performance to the product comprising the structure that is

E desired. Respectively, when the reinforcement structure is employed in packing or 0 insulating material, for instance, the reinforcement structure advantageously ~ 35 comprises a portion where the cellulose monofilaments are oriented substantially a randomly.

N In an embodiment, the reinforcement structure has a portion whose cellulose monofilaments are oriented substantially parallel to one another along their length.

Generally, in this disclosure a “portion” of the reinforcement structure refers an area or a through cut area of the reinforcement structure. Furthermore, the portion may cover in a certain use cases or applications the whole reinforcement structure. Alternatively, the whole reinforcement structure may comprise a plural of different portions so that there can be mutually similar or dissimilar portions in the reinforcement structure, depending on the application.

In an embodiment, the reinforcement structure has a portion where the cellulose monofilaments being formed into a woven or knitted fabric.

In an embodiment, the reinforcement structure has a portion where the cellulose monofilaments being formed into a non-woven fabric.

It will be apparent to those skilled in the art that woven or knitted fabric has varying porosity whereas the porosity of non-woven fabric is generally uniform, and the porosity of the reinforcement structure impacts on the absorption of the MFC fibers of the aqueous suspension to the reinforcement structure.

In an embodiment, the cellulose monofilaments in the woven fabric and/or in the non-woven fabric are spun into yarns having a linear density in a range of 10-100 tex or in a range of 20-50 tex or in a range of 30-40 tex, which tex relates to an amount of mass per unit length (1 tex = 1 g/1000 m; and 1 decitex = 1 dtex = 1 g/10000 m).

What linear mass density of the cellulose monofilaments in the reinforcement structure is used depends on the application. The linear mass density may have an impact on stiffness of the fiber-reinforced material.

In an embodiment, the woven fabric and/or the nonwoven fabric has a weight in a range of 10-500 g/m2 or in a range 50-350 g/m2 or in a range 100-300 g/m2.

Whatfabric weight is used in the fabric of the reinforcement structure depends on

N the application.

N In an embodiment, the cellulose monofilaments of the portion of the woven fabric

O or the non-woven fabric are staple fibers having an average length in a range of 3—

O 160 mm or in a range of 10-80 mm or in a range of 30-60 mm. z 30 In an embodiment the reinforcement structure comprises a portion whose cellulose 0 monofilaments are oriented substantially parallel to one another along their length, = the cellulose monofilaments of such a portion have a linear density in a range of

N 1—10 dtex or in a range of 2—8 dtex or in a range of 3-5 dtex.

O

N In an embodiment, the fiber-reinforced material has a generally average density in a range approximately 1000 kg/m3 to approximately 1600 kg/m3 or in a range approximately 1100 kg/m3 to approximately 1500 kg/m3 or in a range approximately 1150 kg/m3 to approximately 1400 kg/m3 or in a range approximately 1200 kg/m3 to approximately 1300 kg/m3.

In addition to fibrous elements the fibrous monofilament and/or aqueous suspension may comprise additive(s). For example, polysaccharide additive(s) such as binders, cation active reagent(s), crosslinking agent(s), dispersion agent(s), pigment(s), and/or other modifier(s). Total amount of additive(s) in the fibrous monofilament may be between 0.01 and 30 wt.%, between 0.05 and 20 wt. %, preferably between 0.1 and 15 wt. %.

According to an embodiment, the fibers of the fiber-reinforced material may include crosslinking chemicals, such as sodium alginate and di- or trivalent cations. Additionally, or instead, fibers may include polycarboxylic acids and/or sodium hypophosphite to generate crosslinking. Crosslinking chemicals may increase wet strength of the fibers. According to an example, the fibers may include PEO, APAM, cationic polyacrylamide (CPAM). An amount of additives may be between 1 and 15 %. These additives may have effect on strength of the structure.

An additive may comprise polysaccharide additives, such as alginate, alginic acid, pectin, carrageenan or nanocellulose, or a combination of such. During manufacturing of the structure, the polysaccharide additive, such as an alginate, may have effect on forming hydrogel. The polysaccharide additive may be arranged to react with at least one reagent, for example a cation active agent. The reagent may comprise salt, like calcium chloride or magnesium sulfite. The chemical reaction between the polysaccharide additive and the reagent provides rapid increase on viscosity and yield stress of the aqueous suspension. Increase of viscosity of the aqueous suspension, in turn, may have effect of increasing strength of the structure. In addition, the polysaccharide additives, such as alginate, may act as a binder agent(s) in the structure. Alginate may cause crosslinking, which may have effect on binding of fibers.

N

O According to an embodiment, the agueous suspension comprises polyethylene

A 30 oxide (PEO), carboxymethyl cellulose (CMC) and/or starch. These may have 7 effect on mechanical properties of the fibers, such as stretch and strength.

N

I According to another embodiment, the aqueous suspension includes between 50 a and 99 wt.%, or between 70 and 99 wt.%, or preferably between 90 and 99 wt.%

O of natural MFC fibers, and further optionally between 0.1 and 10 wt% of o 35 dispersion agent and/or rheology modifier.

O A further advantage of the fiber-reinforced material is that it is free from any additional binder, specifically the fiber-reinforced material is free from resin-based binder including plastic, glass, or mixtures thereof.

Manufacturing method of composite material

The composite material comprising the aforedescribed fiber-reinforced material may be formed in a method comprising the steps of: a) the reinforcement fiber structure is applied to a surface; b) a polymer matrix is applied to the reinforcement fiber structure and allowed to impregnate into the structure; and c) curing the formed layer to form a layer of composite material comprising the fiber-reinforced material.

The curing step of the method may comprise any suitable drying or curing method described hereinabove and/or known in the art.

Suitable polymer matrix used in the method are described hereinabove.

A further function of the polymer matrix such as epoxy, or any other suitable hydrophobic resin, is that it effectively encapsulates the cellulose fragments of the fiber-reinforced material, so rendering the formed composite material impermeable — to water.

Manufacturing method of laminate structure

The composite material comprising the aforedescribed fiber-reinforced material may be formed in a method comprising the steps of: a) thereinforcement fiber structure is applied to a surface; and b) a polymer matrix is applied to the reinforcement fiber structure and allowed to impregnate into the structure; c) a layer of fiber-reinforced material is applied on top of the laminated material; d) a polymer matrix is applied on top of the layer applied in step c) and allowed to spread and impregnate into the layer of the fiber-reinforced material;

N e) steps c) and d) are repeated until the laminated structure is of the desired

S weight and/or thickness; and

N f) the formed laminate structure is pressed together in a press and heated to <Q 30 cure the polymer matrix.

LO

- The pressing and curing step of the method may comprise any suitable pressing = and drying/curing method described hereinabove and/or known in the art.

O

= The surface whereto reinforcement fiber structure is applied in the manufacturing a the composite material or laminate structure (i.e., in step a in the aforementioned

S 35 manufacturing methods) is advantageously such a surface which enables successful removal of the formed material or structure. The surface may be made from metal or plastic, for instance. Advantageously the surface comprises a hydrophobic external surface. The removal of the composite material or laminate structure may be further improved by applying oil or wax to the external surface contacting with the reinforcement fiber structure.

Another surface can be used to sandwich the formed composite or laminate structure to be pressed in a press.

The polymer matrix applied in manufacturing of the composite material or laminate structure can be hydrophobic resin. The hydrophobic resin may comprise an epoxy. Alternatively, or additionally, the hydrophobic resin comprises urethane.

The composite material and laminate structure described above exhibit several unique features over those materials described in the prior art. In the first instance they exhibit damping performance, stiffness and tensile strength parameters that are favorably comparable with any fiber-reinforced composites and laminates known in the art.

Furthermore, the described material and structure have the significant advantage that it is also impermeable to water so allowing its range of applications to be extensively increased. In particular, the described material may be employed to produce skis, snowboards, surfboards, skateboards, etc., or tubular items such as ski poles, fishing rods, bicycle frames, for instance.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

N The features recited in various embodiments hereinabove and dependent claims

N are mutually freely combinable unless otherwise explicitly stated.

S

: = a

R

LO

N

Claims

1. A fiber-reinforced material, the material comprising a reinforcement structure and a binder matrix, wherein the binder matrix comprises a layer of random, microfibrillated cellulose (MFC) fibers, and wherein the reinforcement structure comprises cellulose monofilaments at least partially permeated by the binder matrix.

2. The fiber-reinforced material according to claim 1, wherein each of the cellulose monofilaments of the reinforcement structure comprises an elongate internal structure comprising interlocked cellulose fibers and extending generally along the longitudinal dimension of the cellulose monofilament.

3. The fiber-reinforced material according to claim 1 or 2, wherein at least part of the monofilaments of the reinforcement structure comprises MFC fibers.

4. The fiber-reinforced material according to any of the preceding claims, wherein the cellulose fibers of the binder matrix and/or the cellulose fibers of the cellulose monofilaments of the reinforcement structure comprise plant based natural, non-regenerated cellulose fibers.

5. The fiber-reinforced material according to any of the preceding claims, wherein most of the cellulose monofilaments of the reinforcement structure have a cross-sectional aspect ratio in a range of 30-300 x10-6 m / 5-30 x10-6 m or in a range of 30-200 x10-6m / 5-20 x10-6 m or in a range of 30-120 x10-6 m / 5-10 x10-6 m.

6. The fiber-reinforced material according to any of the preceding claims, wherein the reinforcement structure has a portion whose cellulose monofilaments are oriented substantially parallel to one another along their length.

7. The fiber-reinforced material according to any of the preceding claims, wherein the reinforcement structure has a portion where the cellulose monofilaments N being formed into a woven or knitted fabric. N

N 8. Thefiber-reinforced material according to any of the preceding claims, wherein LO 30 the reinforcement structure has a portion where the cellulose monofilaments N being formed into a non-woven fabric. I Ao

- 9. The fiber-reinforced material according to claim 7 or 8, wherein the cellulose O monofilaments in the woven fabric of claim 7 and in the non-woven fabric of n claim 8 being spun into yarns having a linear density in a range of 10-100 tex N 35 or in arange of 20—50 tex or in a range of 30—40 tex. N

10. The fiber-reinforced material according to claim 7 or 9, wherein the woven fabric of claim / and/or the nonwoven fabric of claim 8 has a weight in a range of 10-500 g/m? or in a range 50-350 g/m? or in a range 100-300 g/m?.

11. The fiber-reinforced material according to any of claims 7 to 10, wherein the cellulose monofilaments of the portion of the woven fabric of claim 7 or the non-woven fabric of claim 8 are staple fibers having an average length in a range of 3—160 mm or in a range of 10-80 mm or in a range of 30-60 mm.

12. The fiber-reinforced material according to any of the preceding claims, wherein the cellulose monofilaments have a linear density in a range of 1-10 dtex or in a range of 2-8 dtex or in a range of 3-5 dtex.

13. The fiber-reinforced material according to any of the preceding claims, wherein the fiber-reinforced material has a generally average density in a range approximately 1000 kg/m3 to approximately 1600 kg/m3 or in a range approximately 1100 kg/m? to approximately 1500 kg/m? or in a range approximately 1150 kg/m? to approximately 1400 kg/m? or in a range approximately 1200 kg/m? to approximately 1300 kg/m3.

14. A composite material comprising a fiber-reinforced material according to any of the preceding claims and a polymer matrix impregnated in the fiber- reinforced material.

15. The composite material according to claim 14, wherein the polymer matrix encapsulates at least one of two opposing surfaces of the fiber-reinforced material.

16. The composite material according to claim 14 or 15, wherein the polymer matrix is selected from the list of thermosets consisting of epoxy, polyurethanes, phenolic and amino resins, bismaleimides (BMI, polyimides), polyester, and polyamides or is selected from the list consisting of acrylic, ABS, nylon, PLA, polybenzimidazole, polycarbonate, polyether sulfone, polyoxymethylene, polyether ether ketone, polyetherimide, polyethylene, polyphenylene oxide, polyphenylene sulfide, polypropylene, and polystyrene.

17. A laminate structure comprising two or more layers wherein at least one of the N two layers comprise a fiber-reinforced material according to any of claims 1 to & 13. N 7 30

18. The laminate structure according to claim 17, wherein the structure further N comprises one or more layers of a polymer matrix disposed between the two = or more layers. a O

19. A method of manufacturing a fiber-reinforced material, the method comprising 5 the steps of: N S 35 a) contacting a reinforcement fiber structure comprising cellulose monofilaments with an agueous suspension comprising discontinuous cellulose fibers; and b) removing the water of the aqueous suspension to form a layer of binder matrix from the aqueous suspension.

20. The method according to claim 19, wherein the step b) comprises heating the contacted reinforcement fiber structure and aqueous suspension.

21. The method according to any of claims 19 to 20, wherein the step b) comprises pressurizing the contacted reinforcement fiber structure and aqueous suspension.

22. The method according to any of claims 19 to 21, wherein the step a) is preceded by a step of arranging a plurality of cellulose monofilaments substantially parallel to one another along their length to form at least a portion of the reinforcement fiber structure.

23. The method according to any of claims 19 to 21, wherein the step a) is preceded by steps of cutting a plurality of cellulose monofilaments to generally the same length fibers, spinning yarn and weaving the yarn into at least one fabric sheet to form at least a portion of the reinforcement fiber structure.

24. The method according to any of claims 19 to 21, wherein the step a) is preceded by steps of cutting a plurality of cellulose monofilaments to generally the same length fibers, arranging randomly the fibers in a sheet or web to form at least a portion of the reinforcement fiber structure.

25. A method of manufacturing composite material, wherein the method comprises a step of providing a fiber-reinforced material according to any of claims 1 to 13 or a fiber-reinforced material manufactured according to any of claims 19 to 24 and a further step of impregnating a polymer matrix into the fiber-reinforced material.

26. A method of manufacturing a laminate structure, wherein the method comprises a step of providing two or more layers wherein at least one of the N two layers comprise a fiber-reinforced material according to any of claims 1 to < 13 or a fiber-reinforced material manufactured according to any of claims 19 to N 24. <Q 3 30

27. The method according to claim 26, wherein the method further comprises I steps of impregnating one or more layers of a polymer matrix between the two a or more layers. R =

28. Use of an aqueous suspension comprising MFC fibers as a binder matrix N within a fiber-reinforced material. O N 35

29. Use of the fiber-reinforced material according to any of claims 1 to 13 or of the fiber-reinforced material manufactured according to any of claims 19 to 24 as a reinforcing member, construction, decorative, packing, transport or insulating material.

30. Use of the composite material according to any of claims 14 to 16 or of the composite material manufactured according to claim 25 as a sports equipment, construction, decorative, packing or transport material.

31. Use of the laminate structure according to claims 17 or 18 or the laminate structure manufactured according to claims 26 or 27 as a sports equipment, construction, decorative, packing or transport material. N QA O N N <Q LO N I Ao a O NS LO N N O N