A METHOD OF MAKING A THERMOPLASTIC FIBER COMPOSITE MATERIAL AND WEB

Abstract

A method for forming a thermoplastic composite material in a papermaking machine, wherein the method comprises the steps of: forming an aqueous fiber material suspension; bringing said fiber suspension in contact with at least one additive, said additive being introduced into said fiber suspension, whereby said additive reacts to form a precipitation product onto or into the fibers, thereby forming an intermediate suspension, introducing, after the formation of the intermediate suspension, a plastic material into said intermediate suspension, thereby forming a plastic fiber composite suspension.

Claims

1. A method for forming a thermoplastic composite material, wherein the method comprises the steps of: forming an aqueous fiber material suspension; bringing said fiber suspension in contact with at least one additive, said additive being introduced into said fiber suspension, whereby said additive reacts to form a precipitation product onto or into the fibers, thereby forming an intermediate suspension, introducing, after the formation of the intermediate suspension, a plastic material into said intermediate suspension, thereby forming a composite material.

2. The method as claimed in claim 1, wherein the thermoplastic composite material comprises a web material formed in a fibrous web papermaking machine.

3. The method as claimed in claim 1, wherein the plastic material comprises any one of a plastic particle material, a plastic fiber material or a mixture thereof.

4. The method as claimed in claim 1, wherein the method comprises introducing said at least one additive in a liquid flow of a short circulation of a fibrous web forming process of a fibrous web machine, in an in-line production method for forming said reaction agent onto or into the fibers of the fiber suspension.

5. The method as claimed in claim 1, wherein, when there are two or more additives, the method further comprises allowing these to react with one another to form the precipitation product onto or into the fibers.

6. The method as claimed in claim 1, wherein the precipitation product comprises a crystallized filler, and wherein the additives are carbon dioxide and lime milk, said carbon dioxide and lime milk being fed to the short circulation separately or simultaneously, wherein said precipitation product or filler is allowed to precipitate onto or into the fibers of the fiber suspension, thereby forming the intermediate suspension, comprising precipitated calcium carbonate onto or into said fibers.

7. The method as claimed in claim 1, wherein a coupling agent is introduced into the intermediate suspension simultaneously with, or substantially directly after, the introduction of said additive.

8. The method as claimed in claim 1, wherein said method further comprises, before the step of bringing said fiber suspension in contact with at least one additive, separating said fiber suspension into two separate flows, a first flow which is subsequently brought into contact with said additive, and a second flow, which is subsequently re-introduced into the intermediate suspension.

9. The method as claimed in claim 1, wherein the fiber is an organic fiber comprising at least one of a natural fiber, wood fiber, bleached kraft fiber, dissolving pulp fiber, microfibrillated cellulose, or inorganic fibers such as glass fibers, metal fibers, plastic fibers, thermo treated fibers.

10. The method according to claim 1, wherein the plastic material is a plastic selected from the group of polyethylene (PE), polypropylene (PP), ethylene/propylene copolymer, polycarbonate (PC), polystyrene (PS), polyethylene terephthalate (PET), polylactic acid (PLA), polyhydroxybutylate, acrylonitrile/butadiene/styrene copolymer (ABS), styrene/acrylonitrile copolymer (SAN), polyoxymethylene (POM), biodegradable thermoplastics, starch-based thermoplastics, their derivatives and/or mixtures thereof.

11. The method as claimed in claim 1, wherein the plastic fiber composite suspension is dewatered and pressed to a product in the paper machine.

12. The method as claimed in claim 1, wherein the plastic fiber composite suspension is dewatered and thereafter extruded to form a product.

13. The method as claimed in claim 1, wherein the plastic fiber composite suspension is dewatered in a mould after which an object is formed.

14. The method as claimed in claim 1, wherein said plastic fiber composite suspension is transferred to a headbox of a fiber web machine.

15. A plastic fiber composite material obtained by the method as claimed in claim 1.

16. The method as claimed in claim 1, wherein the liquid flow comprises at least one of the following components: virgin pulp suspension, recycled pulp suspension, additive suspension and solids-containing filtrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the present solution will now be described, by way of example, with reference to the accompanying schematic drawings.

[0037] FIG. 1 shows schematically a short circulation arrangement according to prior art.

[0038] FIG. 2 shows schematically a short circulation arrangement according to one embodiment of the invention.

[0039] FIGS. 3a-b shows schematically a short circulation arrangement according to one alternative embodiment of the invention.

[0040] FIG. 4 shows schematically a short circulation arrangement according to yet an alternative embodiment of the invention.

[0041] FIG. 5 shows schematically a short circulation arrangement according to yet another alternative embodiment of the invention.

[0042] FIG. 6 shows a schematic flow scheme of the present invention.

[0043] FIGS. 7a and 7b are a schematic side views of a conventional paper making machine.

DESCRIPTION OF EMBODIMENTS

Definition of Precipitated Calcium Carbonate (PCC)

[0044] Almost all PCC is made by direct carbonation of hydrated lime, known as the milk of lime process. The lime is slaked with water to form Ca(OH).sub.2 and in order to form the precipitated calcium carbonate (insoluble in water) the slaked lime is combined with the (captured) carbon dioxide. The PCC may then be used in paper industry as a filler or pigmentation, mineral or coating mineral or in plastic or barrier layers. It can also be used as filler in plastics or as additive in home care products, tooth pastes, food, pharmaceuticals, paints, inks etc.

Definition of in-Line Precipitated Calcium Carbonate Process

[0045] By in-line production is meant that the precipitated calcium carbonate (PCC) is produced directly into the flow of the paper making stock, i.e. the captured carbon dioxide is combined with slaked lime milk inline, instead of being produced separately from the paper making process. Separate production of PCC further requires the use of retention chemicals to have the PCC adsorbed or fixed onto the fibers. An in-line PCC process is generally recognized as providing a clean paper machine system, and there is a reduced need of retention chemicals. An in-line PCC process is for instance disclosed in WO2011/110744.

[0046] FIG. 1 shows a prior art method for inline production of precipitated calcium carbonate, as disclosed in US2011/0000633 and a schematic process arrangement for a paper making machine 2. The white water F, is carried to e.g. a mixing tank or filtrate tank 4, to which various fibrous components are introduced for the paper making stock preparation. From fittings at least one of virgin pulp suspension (long-fiber pulp, short-fiber pulp, mechanical pulp, chemomechanical pulp, chemical pulp, microfiber pulp, nanofiber pulp), recycled pulp suspension (recycled pulp, reject, fiber fraction from the fiber recovery filter), regenerated cellulose, dissolving pulp, additive suspension and solids-containing filtrate is carried to the mixing tank, and from there conveyed by a mixing pump 14 to a vortex cleaner 16, where heavier particles are separated. The accept of the vortex cleaning continues to a gas separation tank 18, where air and/or other gases are removed from the paper making stock. The paper making stock is then transported to a feed pump 20 of the headbox, which pumps the paper making stock to a so-called headbox screen 22, where large sized particles are separated from the paper making stock. The accept faction is carried to the paper making machine 2 through its headbox. The short circulation of fiber web machines producing less demanding end products may, however, not have a vortex cleaner, gas separation plant and/or headbox.

[0047] In the prior art process the PCC production is performed in the short circulation of the paper making machine, before the vortex cleaning plant 16. The carbon dioxide (CO.sub.2) is injected on the pressure side of the vortex cleaner and the lime milk (MoL) is injected a few meters after the carbon dioxide has dissolved in the same pipe. It is however conceivable that this PCC production could take place closer to the headbox, or that the distance between the injectors is very small, virtually injecting carbon dioxide and lime milk at the same location in the short circulation. This depends on the requirements of the end product and the design of the paper making machine.

[0048] Where two or more additives are fed into the short circulation these are preferably allowed to react with one another, which means that they are fed into the short circulation in a manner which allows for the additives to react, in the case of lime milk and carbon dioxide, such that precipitated calcium carbonate is formed onto or into the fibers as the reaction agent.

[0049] According to one embodiment of the present invention, an in-line PCC process is combined with the dosage of fibers into the in-line PCC process.

[0050] In one embodiment of the present invention, lime milk, carbon dioxide and fiber solution are injected separately into the short circulation and fibrous web of the paper making machine.

[0051] In an alternative embodiment, the fiber solution is provided e.g. in the preparation of the paper making stock, and thus is present in the paper making stock and the carbon dioxide and lime milk are injected separately or simultaneously into the short circulation.

[0052] In all of the above described embodiments it is to be understood that the order of injection of the additives, i.e. lime milk, carbon dioxide, fiber solution and possibly other additives may occur in a different order or at a different stage in the short circulation. It is conceivable that the injection occurs very close to the headbox, or that the fiber solution dosage is prior to the addition of the carbon dioxide or that the distances between the injection points is shorter or longer than described above. Thus the fiber solution, lime milk and carbon dioxide may be injected into the short circulation substantially at the same injection point.

[0053] The point or point where the injection takes place thus forms a PCC reaction zone.

[0054] In one embodiment of the present invention, as shown in FIG. 2 lime milk, carbon dioxide and fiber solution are injected separately into the short circulation and fibrous web of the paper making machine.

[0055] In an alternative embodiment, as shown in FIGS. 3a and 3b the fibers are provided e.g. in the preparation of the paper making stock, and thus is present in the paper making stock and the carbon dioxide and lime milk are injected separately or simultaneously into the short circulation.

[0056] In yet an alternative embodiment, as shown in FIG. 4 the lime milk and the fibers are mixed before the injection into the short circulation and the carbon dioxide is injected separately from this mixture.

[0057] In yet another alternative embodiment, as shown in FIG. 5, the fibers are mixed with other additives and this mixture is injected separately from the lime milk and carbon dioxide.

[0058] Alternatively other fillers may be used, such as silicate, calcium silicate, or other types of fillers based on alkaline earth carbonates, such as magnesium carbonate.

[0059] The first additive may be sodium silicate and the second additive an acidic media thereby forming silica.

[0060] The first additive may be calcium hydroxide, CaOH, and the second additive may be carbon dioxide CO2, and a third additive may be sodium silicate thereby forming calcium silicate.

[0061] The first additive may be another hydroxide of an alkaline earth metal (e.g. MgOH), and the second additive may be carbon dioxide, CO2, thereby forming other types of fillers based on alkaline earth carbonates, such as e.g. magnesium carbonate.

[0062] In FIG. 6 an overview of the method is shown. In step A a fiber material suspension is provided. This suspension may comprise any of the aforementioned fibers. The fiber suspension is then contacted with one or more additives, either as an in-line process or in a batch operation. In step B the formed intermediate suspension comprises the fibers and the additives, where the additives may be a precipitation agent, such as PPC which may have been formed onto the fibers of the fiber suspension.

[0063] In step C the intermediate suspension is contacted with a plastics material, which may be any of the aforementioned materials. The resulting material is a suspension comprising a composite of plastic and fiber, which may then be further processed, for instance as described below. If the process is an in-line production method all of these steps may be performed more or less simultaneously. It is however preferred that the intermediate suspension, i.e. the precipitation product is formed before the plastics material is added. In the in-line production method the formation of the intermediate suspension can be very rapid, thus allowing for a very efficient way to form the plastics fiber composite.

[0064] According to one alternative the method provides for a separation of material or suspension flows, such that in step A before the fiber suspension is contacted with with at least one additive, the fiber suspension is separated into two separate flows, a first flow which is subsequently brought into contact with said additive, and a second flow, which is subsequently re-introduced into the intermediate suspension. According to this alternative it may further be possible to precipitate the PCC only on one fraction such as nanofibers, whereas large fibers (normal) are remain untreated by the process.

[0065] In the present disclosure different types of plastics materials may be used to form the thermoplastic composite material. Such materials include the aforementioned materials, but may also include a fiber type of thermoplastic material or mixture of two or several thermoplastic materials. The material may also contain a coupling agent that improves the adhesion between fibers or fiber-filler and plastic.

[0066] Alternatively the additive may be introduced into the fiber suspension in for instance a mixing tank prior to the introduction into the papermaking machine, or headbox of a fibrous web machine. According to yet an alternative the fiber suspension, additive and plastic material are all mixed in a headbox of a papermaking machine.

[0067] According to one embodiment a thermoplastic web according to the present disclosure may be produced in a conventional type of paper making machine. An example of such a paper machine 60 is shown in FIGS. 7a and 7b, where FIG. 7b is a continuation of FIG. 7a.

[0068] FIG. 7a illustrates a forming section 65 or the so called wet end of the paper making machine and a pressing or wet pressing section 66. In the head box 62 a stock solution or suspension 4 is usually provided and prepared. The stock solution 64 may for instance be heated to a desired temperature, or run through sieves to remove impurities etc. In the head box 62 different types of paper making additives or chemical aid may also be added to the stock solution, for instance, but not limited to additives such as retention chemicals, fillers and surface active agents or polymers.

[0069] In the present invention the plastic fiber composite solution may be transferred to the headbox 62.

[0070] Other types of additives that may be added in the wet end or size press may be additives such as starch, PVOH, CMC, or latex (SB, SA), cross-linkers, optical brighteners or colorants, biocides, fixatives, lubricants, preservatives, dispersants, etc.

[0071] The stock suspension 64, containing the plastic fiber composite solution, is provided onto a wire 63 in the forming section 65. A wet web 63 is thereby formed on the wire. An arrow 64 indicates the direction of the web or the machine direction.

[0072] After the forming section 65 the web passes through a pressing section 66, or a wet pressing section. The pressing operation may be performed by passing the wet web 63 through a series of nips, which are formed by rolls 67 pressing against each other, and are aided by press felts 68 which absorb the pressed water from the web.

[0073] After the wet pressing operation the web or sheet material 63, may be passed through a drying section 69. The drying may be performed in many different manners, but one way is to use drying cylinders 70 and steam. After the drying section 69 the web or sheet 63 may pass through a calender section and a series of calenders (heavy steel rolls) 72 to smooth the sheet, and finally rolled onto a roll or reel 73.