NL2015319B1

NL2015319B1 - Paper fiber based products.

Info

Publication number: NL2015319B1
Application number: NL2015319A
Authority: NL
Inventors: Wilhelmus Maria Van Tol Martinus; Gerardus Jacobus Wesselman Marinus
Original assignee: Wp Trading Alphen Aan Den Rijn B V
Priority date: 2015-08-19
Filing date: 2015-08-19
Publication date: 2017-03-07

Abstract

The invention is in the field of biodegradable products and methods for the production thereof. In particular, the invention is directed to a three dimensionally shaped biodegradable product that is based on paper fibers. The method of the invention comprises blending aqueous paper pulp and a resin composition; suction-molding of the composite slurry thus obtained; pressing the composite slurry to obtain a three dimensionally shaped pre-product; and heating the pre-product to obtain the three dimensionally shaped biodegradable product.

Description

Title: Paper fiber based products

The invention is in the field of biodegradable products and methods for the production thereof. In particular, the invention is directed to a three dimensionally shaped biodegradable product that is based on paper fibers.

The use of plastic product based on e.g. polypropylene comes with well known disadvantages. For instance, the plastic material is often based on fossil resources and is not biodegradable, resulting in the accumulation of plastic waste. This is in particular the case for disposable products that have a short use lifetime, such as plastic bags, disposable pallets and plastic pots for e.g. plants. Therefore, considerable effort has been made in recent years to replace plastic materials for bio-based and biodegradable materials, for examples materials based on lactic acid, starches, cellulose, and other biopolymers.

However, due to the low costs of both the production and the feedstock, the cost price of plastics such a polypropylene is much lower than most bio-based and biodegradable materials.

In order to (more) effectively compete with the traditional plastic products and the production methods thereof, it is desired to use bio-based and biodegradable materials that are readily available and preferably have the same or a lower cost price than plastic. It is further particularly preferred that these materials can be shaped into products by a production process that can be implemented in existing industrial infrastructures to keep the initial investment costs low.

The present inventors found that a composite material based on a fibrous filler and a polyester that is derived from an ahphatic polyalcohol with 2-15 carbon atoms and a tricarboxylic acid such as described in WO 2012/140237 (which is incorporated herein in its entirety) would particularly be suitable for use a base material for disposable products. Moreover, in case the fibrous fillers are paper fibers, the cost prize is kept low while beneficial properties such as a biological origin and biodegradability are retained.

Paper fiber based products are typically made from paper pulp. Paper pulp is a hgnocellulosic fibrous material prepared by chemically and/or mechanically separating cellulose fibers from wood, fiber crops or waste paper. When forming products from paper pulp, the pulp is blended in water to obtain aqueous paper pulp with a content of about 90-99 wt.% water. A drawback of aqueous paper pulp for use in the composite material described in WO 2012/140237 for the production of shaped products is i.a. the low viscosity of the aqueous paper pulp, even when the aliphatic polyalcohol and the tricarboxylic acid are mixed with the aqueous paper pulp. The formation of three-dimensionally shaped products is therefore difficult,. Moreover, the high water content of the aqueous paper pulp required the removal of large amounts water when or after the product has been shaped.

The present inventors found that these problems can be solved by a method for the production of a three dimensionally shaped biodegradable product comprising the steps of - blending aqueous paper pulp and a resin composition comprising a polyalcohol with 2-15 carbon atoms and a tricarboxylic acid to obtain a composite slurry; - suction-molding of the composite slurry on a first mold thereby draining water from the composite slurry; - pressing the composite slurry in between the first mold and a second mold that is complementarily shaped to the first mold to obtain a three dimensionally shaped pre-product; - heating the pre-product at a temperature in the range of 140 - 200 °C.

The method of the invention thus comprises blending aqueous paper pulp and a resin composition; suction-molding of the composite slurry thus obtained; pressing the composite slurry to obtain a three dimensionally shaped pre-product; and heating the pre-product to obtain the three dimensionally shaped biodegradable product.

Blending the aqueous paper pulp and the resin composition should be understood broadly. The paper pulp may for instance first be mixed with one or more components present in the resin composition before water is added, or one component may be mixed with the aqueous paper pulp before the further component(s) is added. Hence, the polyalcohol and the tri-carboxylic acid in the resin composition can be blended at once or sequentially with the (aqueous) paper pulp in any suitable order. In a preferred embodiment however, the resin composition as a whole is added to the aqueous paper pulp.

The composite slurry typically comprises 8 - 20 vol% of the resin mixture and/or 80 - 92 vol% aqueous paper pulp.

In the suction-molding step the composite slurry is applied on or in the first mold and sequentially or simultaneously suction is applied from the side of the mold surface not in contact with the composite slurry so that liquid (water and resin composition) is drained from the composite slurry through the mold. This ensures that the composite slurry is not only located on the lower parts of the mold, but that the entire relevant surface of the mold is covered by the drained composite slurry. Hence, also a slurry with a low viscosity can be used to shape and obtained three dimensionally shaped products. The first mold is shaped to the contour of the product to be made and is typically of a mesh material. Alternatively, a plurahty of small holes are located in the solid surface of the mold to drain the water through.

In a preferred embodiment, at least part of the liquid that is drained from the mold, which contains water and resin composition, is recycled to be used as a source for the resin composition. After or simultaneous with the suction-molding step, pressure can be applied by using a second mold that is complementarily shaped to the first mold.

In a particular embodiment, by applying suction on the first mold, the second mold is drawn toward the first mold such that pressure is applied. The pressure between the first and the second mold may therefore be achieved by the negative pressure from the suction. Hence, it may be appreciated that the steps of suction-molding and pressuring may in fact be one operational step.

Suction-molding and pressing are known from other fields such as egg trays manufacturing as described in e.g. US2704439 and US3166467. Production of egg trays is typically done by using an aqueous paper pulp and subjecting this to suction-molding, pressing and drying. It may be appreciated that for the known production of egg trays, no resin mixture is present.

Preferably, the steps of suction-molding and pressing in accordance with the present invention are performed with an apparatus that is adapted for the production of paper egg trays. Examples of such an apparatus are also described in US2704439 and US3166467. The use of such existing facilities is beneficial since it minimizes initial investments costs. Moreover, the high abundance of pulp molding facilities throughout the world may limit the need of transportation and the concomitant costs and environmental effects thereof.

Hence, a particular aspect of the present invention is the use of an egg trays production apparatus for the production of three dimensionally shaped biodegradable product in accordance with the present invention. In may be appreciated that the products in accordance with the present invention are entirely different, than molded pulp (i.e. the material of egg trays) in terms of mechanical properties.

For instance, the product in accordance with the present invention typically has a flexural strength of between 1 to 20 MPa, preferably from 1.5-10 MPa, more preferably 2-5 MPa. For comparison, plywood has a flexural strength of around 3.7 MPa. A typical pot, or other container, made in accordance with the present invention has sufficient strength to support a load, such as a plant, of 5-20 kg, preferably 8-15 kg, for instance about 10 kg, without resulting in any loss of structural integrity, i.e. without permanent deformation or breakage.

The density of the products produced in accordance with the present invention depend on the amount of resin apphed, which may vary from 10 to 60 wt.%, preferably 12 to 55 wt.%. When a product is made using 50 wt.% resin, the density is typically higher than 1 kg/dm3. When lower amounts of resin are used the densities may be lower, e.g. between 0.8 and 0.95 kg/dm3.

Heating the pre-product typically takes place at a temperature of 140 - 200 °C, preferably in the range of 160 - 180 °C. This are typical temperatures that are involved in common pulp molding processes. A minimal difference between the standard drying temperature used for pulp molding and the heating temperature used for the present invention is preferred since no alternative drying apparatus would then be required for the present invention. In fact, such a minimal difference in drying temperature allows for a facile process change between the traditional pulp molding and the process of the present invention. The time for drying the pre-product (i.e. the drying time) is typically between 5 minutes to 24 hours. The drying time mostly depends on the amount of remaining water in the pre-product and the set temperatures. For instance, when the temperature is 200 °C drying/curing times of 0.5-2 hours may be sufficient, preferably about 1 hour.

By heating the pre-product water evaporates and/or the resin composition reacts to form the resin (hardening or curing). The formation of the resin is described in more detail in WO 2012/140237.

An aspect of the present invention is a three dimensionally shaped biodegradable product comprising 10 - 98 wt.% of paper fibers and at least 2 wt.% of a resin derived from a resin composition comprising an aliphatic polyalcohol with 2-15 carbon atoms and a tricarboxylic acid.

An advantage of this product is that it can be disposed of as organic waste. Both the resin and the paper fibers degrade in water and/or a biological environment. Hence, the product can be discard of a land-fill and no special waste treatment is required.

The paper fibers are present in the product according to the invention as filler. If the amount of paper fibers is less than 10 wt.% (dry weight, based on the combined total weight of the dry paper fibers and the resin), a composite material with the desired properties may be difficult to obtain. If the amount of paper fibers is above 98 wt.%, the amount of resin (polyester) matrix will be too low to provide the product with adequate properties.

In one embodiment, the paper fibers are present in an amount of at least 20 wt.%, in particular at least 40 wt.%, more in particular at least 50% (dry weight, based on the combined total weight of the paper fibers and the resin). In some embodiments, the amount of paper fibers may be at most 95%, more in particular at most 90%. The resin is present in an amount of at least 2 wt.%. It may be preferred for the polyester to be present in an amount of at least 5 wt.%, still more in particular at least 10 wt.%.

The resin composition comprises an aliphatic polyalcohol with 2-15 carbon atoms and a tricarboxylic acid. Typically, the resin composition comprises more than 80 wt.%, preferably more than 90 wt.% of the aliphatic polyalcohol with 2-15 carbon atoms and the tricarboxyhc acid, based on the total weight of the resin composition.

The polyalcohol used in the present invention does preferably not contain aromatic structures, N and/or S heteroatoms. More in particular the polyalcohol is an ahphatic polyalkanol containing only carbon, hydrogen, and oxygen atoms. The polyalcohol used in the present invention comprises typically at least two hydroxyl groups, in particular at least three hydroxyl groups. In general, the number of hydroxyl groups will be 10 or less, more in particular 8 or less, or even 6 or less. The polyalcohol has 2-15 carbon atoms. More in particular, the polyalcohol has 3-10 carbon atoms.

It is preferred for the polyalcohol to contain only hydrocarbon and hydroxyl groups. It is preferred for the alcohol to contain no heteroatoms, including oxygen, in its backbone. In a preferred embodiment of the present invention the polyalcohol contains a relatively large number of hydroxyl groups in comparison with its number of carbon atoms. For example, the ratio between the number of hydroxyl groups and the number of carbon atoms ranges from 1:4 (i.e. one hydroxyl group per four carbon atoms, or 8 carbon atoms for a dialcohol} to 1:1 (i.e. one hydroxyl groups per carbon atom). Compounds wherein the ratio of hydroxyl groups to carbon atoms is 1:1 are considered especially preferred.

Examples of suitable polyalcohols include glycerol, sorbitol, xylitol, and mannitol, and, from the group of dialcohols 1,2-propane diol, 1,3-propane diol, and 1,2-ethane diol. The use of compounds selected from the group of glycerol, sorbitol, xylitol, and mannitol, is preferred, with the use of glycerol being particularly preferred.

It is preferred that all the polyalcohol in the resin comprise at least 50 mol% glycerol, xyhtol, sorbitol, and/or mannitol, in particular glycerol, preferably at least 70 mol%, more in particular at least 90 mol%, or even at least 95 mol%. In one embodiment the alcohol consists essentially (i.e. more than 98 mol%) of glycerol.

The tricarboxylic acid does preferably not contain aromatic structures, N and/or S heteroatoms. More in particular the tricarboxylic acid is an aliphatic tricarboxylic acid containing only C, H, and O atoms. It is preferred for the tricarboxyhc acid to contain no other functional groups than carboxylic acid groups. It is preferred for the tricarboxyhc acid to contain no heteroatoms, including oxygen, in its backbone.

The tricarboxylic acid may be any tricarboxylic acid which has three carboxylic acid groups and, in general, at most 15 carbon atoms. Examples include citric acid, isocitric acid, aconitic acid (both cis and trans), and 3-carboxy-cis,cis-muconic acid. The use of citric acid is considered preferable, both for reasons of costs and of availabihty.

The molar ratio between the polyalcohol and the tricarboxylic acid will be governed by the ratio between the number of reacting groups in the polyalcohol and tricarboxylic acid.

In general, the ratio between the number of OH groups and the number of acid groups is between 5:1 and 1:5. More in particular, the ratio may between 2:1 and 1:2, more specifically between 1.5:1 and 1:1.5, more preferably between 1.1:1 and 1:1.1. The theoretical molar ratio is 1:1.

The molar ratio between the polyalcohol and the tricarboxylic acid will be governed by the ratio between the number of reacting groups in the alcohol(s) and acid used.

The product of the present invention is particular suitable for the storage and/or containment of plants and the like. Hence, in a particular advantageous embodiment of the invention the product is a container. The container may either be a singular pot (i.e. not attached to any other pots) or a tray to e.g. contain the pots with plants therein or to directly contain a plurality of plants.

The shape and of the container is preferable identical to commonly used pots for plants. Hence, the container has a bottom plate and one or more side walls having an a internal volume of 50 mm3 to 2 dm3. Moreover, the angle between the bottom plate and the side wall is preferably between 95° and 120°.

The products of the present invention can have a variety of shapes. Egg trays and plant pots are examples thereof. The products can be further treated to obtain desirable properties. In one embodiment the products are treated with bnseed oil to improve watertightness, while keeping the product 100% biobased.

The cured products of the present invention have shown to maintain watertight for a long period of time, for instance several weeks, preferably 5-10 days.

When subjected to degrading conditions, which can be simulated by covering the products in moist soil or submerging them in water, the products will degrade typically in about 10-14 months.

For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

Claims

A method for the production of a three-dimensionally formed biodegradable product, comprising the steps of: mixing aqueous paper pulp and a resin composition comprising a polyalcohol of 2-15 carbon atoms and a tricarboxylic acid to obtain a composite slurry; - suctioning the composite slurry to a first shape wherein water is drained from the composite slurry; pushing the composite slurry between the first mold and the second mold that is complementary to the first mold to obtain a three-dimensional molded preproduct; and - heating the preproduct to a temperature in the range of 140 to 200 ° C to obtain the three-dimensionally shaped biodegradable product.

The method of claim 1, wherein the composite slurry contains 8-20% by volume of the resin blend and preferably 80-92% by volume of aqueous paper pulp.

Method according to any one of the preceding claims, wherein the preproduct contains 50 vol%, preferably more than 75 vol% less water than the composite slurry.

Method according to any one of the preceding claims, wherein the drying of the preproduct takes place at a temperature in the range of 160 to 180 ° C.

A method according to any one of the preceding claims, wherein the suction forming and pushing steps are performed with an apparatus adapted for the production of paper eggshells.

The method of any one of the preceding claims, wherein the resin composition consists essentially of glycerol and citric acid.

A three-dimensional shaped biodegradable product obtainable by the method of any one of the preceding claims, comprising 10-98% by weight of paper fibers and at least 2% by weight of a resin derived from a resin composition comprising an aliphatic polyalcohol of 2 -15 carbon atoms and a tricarboxylic acid.

A three-dimensional shaped biodegradable product according to claim 7 which is a container.

A three-dimensionally shaped biodegradable product that is a container according to claim 8, with an internal volume of 50 mm 3 to 2 dm 3.

The three-dimensional biodegradable product of any one of claims 7 to 9, wherein the entire aliphatic polyalcohol in the resin contains at least 50 mole% glycerol and the entire tricarboxylic acid contains at least 50 mole% citric acid.

The product of any one of claims 7 to 10, wherein the resin composition consists essentially of glycerol and citric acid.

Use of the container according to one of claims 7 to 11 for the storage of plants.