Two-component natural polymeric water-based glues, obtained from derivatives of cork

Abstract

The present invention is related to a new method to produce natural water-based glues made of two components, designed to glue lignocellulosic surfaces, mainly cork and wood. The mentioned process comprises the extraction of the aqueous phase of a mixture resulting from liquefying cork dust and/or cork granules, process that is commonly referred to as depolimerization process of cork; evaporation of the aqueous phase, therefore obtaining a first component consisting of a gel composed by the soluble components of the liquefying mixture; mixing and homogenizing of this gel with the second component that consists of a curing aliphatic compound; and, optionally, addition and mixture to cork dust to the previously mentioned mix.

Claims

1. A process for preparing two-component natural polymeric water-based glues, suitable for gluing lignocellulosic surfaces, comprising the following steps: (a) extraction of the aqueous phase resulting from a mixture resulting from the liquefaction of cork dust and/or granules, (b) evaporation of aqueous phase to remove the water and to obtain a first component which consists of a gel composed of the soluble components of the liquefaction mixture, (c) mixing and homogenization of the gel with a second component which consists of an aliphatic crosslinking agent in water, thereby creating a formulated mixture, and optionally (d) addition and mixture of cork dust to said formulated mixture.

2. The process according to claim 1, wherein the aqueous phase extracted at step (a) contains oligosaccharides and oligomers from suberin and lignin, obtained by liquid-liquid extraction from polymerization of cork.

3. The process according to claim 1, wherein the evaporation at step (b) is carried out to reach a reduction of water contents above 95%, by weight.

4. The process according to claim 1, wherein at step (c) the two components, the gel and the cross-linking agent, prepared separately, are blended together upon application, with a pot life between 30 minutes to 2 hours.

5. The process according to claim 4, wherein at step (c) the gel, containing oligosaccharides and oligomers, is mixed with the cross-linking agent in a ratio, by weight, of crosslinking agent:gel from 1:6 to 4:6, and with distilled water in a ratio, by weight, of distilled water:gel from 4:1 to 12:1.

6. The process according to claim 5, wherein the cross-linking agent is present in a ratio, by weight, from 2:6 to 4:6, and the distilled water is present in a ratio, by weight, from 4:1 to 8:1.

7. The process according to claim 1, wherein the aliphatic cross-linking agent is dispersible in water and with an isocyanate reactive functionality.

8. The process according to claim 7, wherein the aliphatic cross-linking agent has an isocyanate content between 5 and 25%, by weight.

9. The process according to claim 8, wherein the aliphatic cross-linking agent has an isocyanate content between 15 and 24%, by weight.

10. The process according to claim 1 wherein the two component glue obtained at step (c) has a water content above 90%, by weight.

11. The process according to claim 1 wherein the two component glue obtained at step (c) has a viscosity between 1 and 10 mPas.

12. The process according to claim 1 wherein at step (d) the two component glue is mixed with cork dust upon application on lignocellulosic surfaces, with a pot life between 30 minutes and 2 hours.

13. The process according to claim 12, wherein the cork dust has a particle size below 0.5 mm, and is present in an amount from 0.1% to 0.6%, by weight, in relation to the total weight of the mixture.

14. The process according to claim 13, wherein the cork dust is present in an amount from 0.1% to 0.2%, by weight, in relation to the total weight of the mixture.

15. The process according to claim 1, wherein the lignocellulosic surfaces are cork and wood.

16. The process according to claim 4, wherein the mixture occurred at room temperature.

17. The process according to claim 1, wherein the gluing temperature occurs between 15 C. and 30 C.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 illustrates two cork stoppers glued top to top by using the glue prepared according to the current invention

(2) FIG. 2 Illustrates an agglomerated cork composite obtained by gluing with natural water based glue: (a) top image with size 19.5 cm19.5 cm; (b) detail from the side packing.

(3) FIG. 3 Illustrates two cylindrical wood blocks glued top to top by using the glue prepared according to the current invention

(4) FIG. 4 Illustrates collated cork stoppers by using the glue prepared according to the current invention.

SUMMARY OF THE INVENTION

(5) The present invention is related to a new production method of natural-based glues, with an adhesive power potential (maximum cutting forces are 9.410-3 N/m2 when gluing Cork surfaces).

(6) The formulations are developed through acid liquefaction of lignocellulosic derivatives, in particular cork, from where one extracts two phases: a polyols liquid, which is one of the components in the formulation of glues in conjunction with an aliphatic isocyanate component (with preferentially levels of NCO in the rage of 15-25%), water and cork dust; and an organic phase, that presents an attractive economic and environmental nature as fuel, this can be used as an alternative to similar compounds obtained by petrochemical sources. The formulated glues are suitable for the gluing of lignocellulosic materials surfaces, such as cork and/or wood at room temperature (15-30 C.). On the other hand, they are also suitable for the preparation of agglomerated cork at low temperatures (50-80 C.).

DETAILED DESCRIPTION OF THE INVENTION

(7) Based on what has been explained, this invention aims at solving the technical issues not solved or only partially solved by prior knowledge, namely applying a modified liquefying process, this being a thermochemical conversion process using organic solvent agents, from cork based materials, from which there is the extraction of polyol compounds used for the formulation of ecological glues used for a range of applications, such as gluing lignocellulosic materials.

(8) The term liquefaction according to the present invention, should be understood as a thermochemical process related to the depolymerization of a solid material, with concomitant dissolution in a solvent.

(9) The current formulations of glues claim their applicability in a high diversity of systems. These include the surface adhesion of lignocellulosic materials and/or the clogging of the material pores. This results in the covering of materials such as the Cork and wood. On the other hand, the process allows for obtaining two intermediate products, an aqueous solution (polyol liquid) and an organic phase (non soluble components). These products show economical as well as environmental potential, both of which can be used as an alternative to similar compounds obtained by petrochemical sources. The organic phase can be used as fuel in combustion systems. The phase which contains polyols can be used in the formulation of glues, as well as in the formulation and synthesis of polymers, such as polyesters and polyurethanes, their application can be further extended to several sectors, such as: food, pharmaceutical, furniture, civil engineering, automobile and polymer industries.

(10) For obtaining new formulations of glues claimed in this document it is necessary the use of an aliphatic cross linker of isocyanate, which as very useful in combination polymers from lignocellulosic and cellulosic nature to achieve a stronger binding between lignocellulosic surfaces upon the gluing process. Examples of these cross-linkers are the DESMODUR DA-L and DESMODUR DN, used in illustrative examples of this patent. These compounds penetrate in lignocellulosic network of polyols, acting moderately at room temperature, revealing an excellent compatibility with the hydroxyl groups present in lignocellulosic-based polymers. This promotes the achievement of natural glues with very promising properties through a simple and low-cost process.

(11) The process here claimed is adequate to the gluing of lignocellulosic materials, surfaces and clusters of natural base such as cork-based. Taking into account what was mentioned above, it should be noted that the developed formulations include the addition of cork particles (dust<250 m), as promoter of the gluing mechanical properties, but also as an adherence promoter of the glue to the gluing surface, essentially when this is also made of Cork. These particles act not only as load, but also as a mechanic ligand in filling the porosity inherent to the surface. Regarding the glue formulation, and taking in consideration that it is obtained from cork's own components, the interfacial adhesion of these particles is favoured, ensuring the uniformity of its mechanical properties. One should note that the novel process here claimed in order to obtain adhesives, and in the particular case of application in the preparation of compound clusters of cork, it allows the gluing process to occur at relatively low temperatures, 50-80 C. It is also worth to mention that the viscosities obtained in formulated glues are very close to water, preferably in the range of 1 to 5 MPa.Math.s, as a result of high water contents (>90%), which favours the mixing operation with the corks granules. This allows a reduction of the economic effort in using the glue, and also does not avoid the consequent appearance of pores, due to the glue contraction. The latter would provoke the appearance of air bubbles that would affect the coarse grain properties.

(12) The claimed invention presents as potential markets: Construction sector, production of panels for acoustic and thermal insulation. The footwear sector as soles, heels and insoles. Current market Sector of clusters and paintings. Cork Industry for gluing corks, cork discs or panels. In the same industry in colmating natural stoppers.

(13) In conclusion, the added value of the invention can be listed as: Obtaining a natural glue without solvents in its composition and adhesive power at room temperature; Obtaining a versatile natural glue that can be applied in lignocellulosic materials, even in the form of particles/grainy, allowing their agglomeration and formation of composites; Obtaining a natural glue compatible with Cork particles, allowing a good interfacial adhesion, with concomitant improvement of their mechanical properties after curing (ex: ductility), with a consequent increase of its resistance and endurance to cracking when subject to stress forces; Environmental and Economic Advantages that is a reflection from the use a waste from cork industry, as cork dust and cork granules.

(14) The proposed method includes the extraction of an aqueous phase resulting from the fixture liquefaction, commonly referred to as cork depolymerization. This is performed using distilled water which acts as an extracting agent for the liquefied soluble components (polyols).

(15) The resulting aqueous solution is then subjected to a controlled evaporation process in order to remove the water from the mixture leading to the formation of a gel.

(16) Following step relates to mining the gel with distilled water, in order to adjust the water contents in the formulation together with the aliphatic cross-linking isocyanate.

(17) This mixture is then homogenized under specific proportions, depending on the desired viscosity, as well as the desired gluing power of the resulting glue.

(18) Before the application of the resulting glue, cork dust is still added to the mix followed by a new homogenization process thus leading to a better performing water-based glue formulation.

(19) The final application of the glue is suitable to be carried out at room temperature, preferably between 15-30 C., being advisable to apply amounts between 1 and 2 L/m.sup.2 in the surface. Gluing process is accomplished in a recommended interval of time within the range of 30 min to 180 min.

OBJECT OF INVENTION

(20) To be more precise, the current invention refers to a process for preparing two-component natural polymeric water-based glues, suitable for gluing lignocellulosic surfaces, specifically cork and wood, comprising the following steps: (a) extraction of the aqueous phase resulting from a mixture resulting from the liquefaction of cork dust and/or granules, which is usually designated by cork depolymerization. (b) evaporation of aqueous phase to remove the water and to obtain a first component which consists of a gel composed by the soluble components of the liquefaction mixture. (c) mixing and homogenization of the gel with a second component which consists of an aliphatic crosslinking agent in water. and optionally (d) addition and mixture of cork dust to the previously formulated mixture.

(21) Preferably, the aqueous phase obtained from step a) contains oligosaccharides and oligomers from suberin and lignin, obtained by liquid-liquid extraction from depolimerization of cork.

(22) Normally, the evaporation at step (b) is carried out to reach a reduction of water contents above 95%, by weight.

(23) Preferably, at step e) the two components, the gel and the cross-linking agent, prepared separately, are blended together upon-application, with a pot life between 30 minutes to 2 hours.

(24) At step (c) the gel, containing oligosaccharides and oligomers, is commonly mixed with the cross-linking agent in a ratio, by weight, of crosslinking agent:gel from 1:6 to 4:6, preferably from 2:6 to 4:6, and with distilled water in a ratio, by weight, of distilled water:gel from 4:1 to 12:1, preferably from 4:1 to 8:1.

(25) The aliphatic cross-linking agent is dispersible in water and with an isocyanate reactive functionality, usually with a contents of isocyanate between 5 and 25%, especially between 15 and 24%, by weight.

(26) The two component glue obtained at step (c) has normally a water contents above 90%, by weight, and a viscosity between 1 and 10 mPa.Math.s.

(27) At step (d) the two component glue is mixed with cork dust upon application on ligno-cellulosic surfaces, with a typical pot life between 30 minutes and 2 hours.

(28) Preferably the cork dust has a particle size below 0.5 mm, and is present in an amount from 0.1% to 0.6%, by weight, specially from 0.1% to 0.2%, by weight, in relation to the total weight of the mixture.

(29) These glues are intended to be appropriate glues for gluing lignocellulosic surfaces, with a natural or synthetic structure, at room temperature, between 8 and 30 C., preferably between 15 and 30 C.

(30) These glues are also appropriate glues for gluing lignocellulosic materials, under the shape of agglomerated particles, in particular of cork, allowing the formation of composed clusters, in a range of temperatures between 50 to 100 C., preferably between 50 and 80 C., under pressure for 8 to 24 hours, preferably 8 to 10 hours.

EXAMPLES

Example 1

(31) As a first example the preparation of water-based glue and its formulation for the gluing corks top to top is described.

(32) In a first phase one proceeded to the liquefaction process of the cork dust in a similar way to the one presented in the patent WO2012/150043. The classification of the cork dusts according to their source in the cork transformation process is presented in Table 1 (example 1).

(33) TABLE-US-00001 TABLE 1 Properties of different types of cork Type of Volumic Moisture Ash higher Granulometric Cork mass (% contents contents calorific fraction (<0.25 dust m/m) (% m/m) (% m/m) value (MJ kg.sup.1) mm % m/m) A 261 14 3.7 18.87 30.2 B 328 20 6.0 15.91 4.0 C 306 11 3.3 18.93 20.3 D 115 3 0.9 27.71 35.0 E 82 5 0.9 26.76 27.3 F 73 8 2.0 100 G 60 3 1.6 ~29.29 ~10 H 233 12 49.9 1-Adapted from L. Gil, Biomass & Bioenergy 13 (1-2), p. 59, 1997. Where: A. Grinding dust (pre-crushing and granulation) B. Cleaning dust (removal of impurities) C. Dust from particle size separation D. Finishing dust from agglomerates panels. E. Finishing dust from stoppers and cluster disks. F. Finishing dust from natural cork stoppers and disks. G. Finshing dust from cork insulating boards. H. Fuel dust (mixtures of A, B and C)

(34) After applying the liquefaction process, one proceeds with multiple washings of the filtered mix with distilled water. Subsequently, the resulting aqueous solution is driven to an evaporation process of the entire extracting agent, in order to obtain a gel which included the liquefied soluble constituents (polyols).

(35) In order to obtain the glue, one proceeds to the mixture of 1.5 g of this gel with 10 ml distilled water and 0.6 g of Desmodur DA. The proportions of the components included in this glue formulation depend on the viscosity and adhesive power required for the glue. In this particular application, the values are suggested in order to obtain a preferential optimum.

(36) Before the application of the resulting glue, 0.1 g (m/m) of cork dust is still added to the mixture, suffering new homogenization, leading therefore to the claimed water-based glue formulations.

(37) The results for the cutting forces for the set A and B are of 5.710-3 and 7.4110-3 N/m2, respectively. For the torsion angle the respective values were: for set A 54.3 and for set B 57.9. Taking into account these results the claimed invention presents a high glue power for both sets.

Example 2

(38) The formulation of natural water based glue obtained from Cork derivatives is performed under the same conditions as in the previous example.

(39) We proceeded to the application of the claimed invention for the preparation of cork agglomerate. For this purpose, one proceeds with the mixture of 40 g of water based glue with 200 g of cork granules. The next step involved the filling cubic mold with the glue. The mold was constituted by a removable lid and bottom, presenting the following dimensions: 19.519.5 cm. To the previous system a compression force of 1000 psi was applied with heating (temperature of 80 C.) for about 30 min, after which it was left to cool down gradually until it reached the room temperature followed by unmolding.

(40) The obtained module is represented in FIG. 2.

Example 3

(41) The formulation of natural water based glue obtained from Cork derivatives is performed by mixing 1.5 g of this gel with 10 mL of distilled water and 1 g of Desmodur DA, followed by homogenization. The proportions of the components included in this formulation are dependent on the viscosity and adhesive power required for the glue. And for this particular application, the values suggested are preferential.

(42) Before the application of the resulting glue, it was added to the mixture 0.5 g (m/m in the mix) of cork dust, followed by new homogenization, leading to the claimed water-based natural glue formulations.

(43) The application of glue is held at a temperature of 25 C., by applying 1 mL on top of a wood cylinder. Optimum gluing is achieved in a time interval of 3 h. It is recommended, in order to increase the efficiency of the gluing process, a pretreatment of the wood surface in order to increase its roughness.

(44) A representative image of glued cylinders top to top with the claimed water-based glue is presented in FIG. 3.

Example 4

(45) The formulation of the glue retrieved from Cork derivatives is performed by mixing 150 g of gel with 1 L of distilled water and 60 g of Desmodur DA-L followed by homogenization.

(46) The formulation was applied in a pilot-scale for cork colmation under the conditions presenting in table for 200 corks.

(47) TABLE-US-00002 ENSATO Step 1 2 3 4 5 6 7 1 product Glue Dust Dust End volume 150 100 100 (mL) time (min) 5 10 7 7 rpm (%) 100 10 10 10 2 product Glue Glue Dust Dust End volume 50 150 100 100 (mL) time (min) 5 10 10 10 rpm (%) 100 10 10 10 3 product Dust Glue Glue Glue Dust Dust End volume 100 50 100 100 100 100 (mL) time (min) 10 5 10 10 10 10 rpm (%) 10 100 10 10 10 10

(48) Similar products were obtained with this procedure to the ones existing in currant market as it is illustrated.