Phenolic resin obtained by polycondensation of formaldehyde, phenol and lignin

Abstract

A lignin-phenol-formaldehyde resin, which is obtained by polycondensation of formaldehyde, phenol and lignin in the presence of a basic or acidic catalyst, is characterized in that the lignin is a lignin that is not chemically modified at the available functional groups. This lignin has a low molecular mass and includes available functional groups chosen from the group including aliphatic hydroxyls and phenolic hydroxyls. The degree of substitution by weight of phenol with the lignin is between 50% and 60%. The weight proportion of the lignin and of phenol in the resin is equal to the weight proportion of phenol in a lignin-free phenol-formaldehyde (PF) resin.

Claims

1. A thermosetting synthetic resin, known as a lignin-phenol-formaldehyde resin, or LPF resin, which is obtained by polycondensation of formaldehyde, phenol and lignin in the presence of a basic or acidic catalyst, wherein the lignin is a lignin that is not chemically modified at the available functional groups, and said available functional groups comprising aliphatic hydroxyls and phenolic hydroxyls.

2. The resin according to claim 1, wherein the lignin has a low molecular mass whose Mw is between 700 g/mol and 2000 g/mol.

3. The resin according to claim 1, wherein the aliphatic hydroxyls are present in a proportion of from 1.5 mmol/g to 3.0 mmol/g.

4. The resin according to claim 1, wherein the phenolic hydroxyls are present in a proportion of from 1.1 mmol/g to 2.0 mmol/g.

5. The resin according to claim 1, wherein the resin comprises a degree of substitution by weight of phenol with the lignin which is between 50 and 70%.

6. The resin according to claim 5, wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) between 35 and 60%.

7. The resin according to claim 2, wherein the lignin has a low molecular mass whose Mw is equal to 1500 g/mol.

8. The resin according to claim 4, wherein the phenolic hydroxyls are present in a proportion not less than 1.5 mmol/g.

9. The resin according to claim 5, wherein the degree of substitution by weight of phenol with the lignin which is between 50% and 60%.

10. The resin according to claim 6, wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) between 45 and 50%.

11. The resin according to claim 10, wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) of 47%.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention proposes a thermosetting synthetic resin, known as LPF, or lignin-phenol-formaldehyde, which is obtained by polycondensation of formaldehyde, phenol and lignin in the presence of a basic or acidic catalyst, characterized in that the lignin is a lignin that is not chemically modified at the available functional groups. In the present invention lignin that is not chemically modified at the available functional groups means a lignin known as Biolignin or CIMV Lignin as defined and characterized according to the teachings of the documents mentioned previously.

(2) The said lignin has a low molecular mass whose Mw is between 700 g/mol and 2000 g/mol and preferably equal to 1500 g/mol.

(3) The said lignin comprises available functional groups chosen from the group comprising aliphatic hydroxyls and phenolic hydroxyls.

(4) The aliphatic hydroxyls are present in a proportion of from 1.0 mmol/g to 3.0 mmol/g, and preferably in a proportion of from 1.5 mmol/g to 3.0 mmol/g.

(5) The phenolic hydroxyls are present in a proportion of from 1.1 mmol/g to 2.0 mmol/g and preferably in a proportion of a content not less than 1.5 mmol/g.

(6) The resin has a degree of substitution by weight of the phenol with the said lignin which is between 50 and 70%, and preferably between 50% and 60%.

(7) The weight proportion of the said lignin and of the phenol in the resin is equal to the weight proportion of phenol in a phenol-formaldehyde (PF) resin not containing lignin.

(8) The production of this novel LPF resin is similar to that of a phenoplast or phenol-formaldehyde PF resin of the prior art, or of an LPF resin of the prior art with a low degree of substitution or replacement by weight of the phenol with a lignin.

(9) The said particular lignin known as Biolignin, or CIMV Lignin, is used by predispersing it in phenol, the phenol-CIMV Biolignin mixture then being used in the same manner as lignin-free phenol in a PF resin.

(10) The weight proportion of the said lignin in the composition of the resin is equal to the weight proportion of phenol in a standard phenol-formaldehyde PF resin.

(11) The resin is synthesised with a formaldehyde to phenol and lignin ratio (F/(P+L)) between 35 and 60%, preferably between 45 and 50%, and optimally of 47%.

(12) The said lignin or Biolignin or CIMV Lignin is produced according to the CIMV processes and by means of a CIMV installation as described previously. For example, said lignin or Biolignin or CIMV Lignin is extracted from wheat straw.

(13) It can be characterized by its physicochemical properties: molecular weight, dry matter, acidity, ashes, Lignin Klason and residual hemicelluloses contents. An example of such lignin can be:

(14) TABLE-US-00001 TABLE 1 example of Biolignin Composition Molecular weight Mn 890 g/mol, Mw 1720 g/mol Dry matter .sup.95% Acidity 3.22% Ashes content 1.22% Klason content 88.5% Residual hemicelluloses content 5.15% Protein contents 8.4%

(15) This lignin is supplied for its use for the industrial preparation of the novel resin according to the invention under entirely satisfactory conditions, especially in the form of a powder that is able to be dispersed in phenol.

(16) The term degree of substitution by weight refers herein to the weight proportion of phenol of a phenol-formaldehyde PF resin, substituted with Biolignin or CIMV Lignin.

(17) By way of examples, the functional groups of Biolignin or CIMV Lignin may be quantified in the following manner.

EXAMPLE 1 (2012)

(18) TABLE-US-00002 TABLE 2 Quantification of a first example of Biolignin Molecular weight of the Biolognin = 1500 g/mol Aldehyde Acetyl Hydroxyls Total Hydroxyls (phenolic + aliphatic) 0.60 0.50 2.90 4.00 Phenolic hydroxyls 0.20 0.05 0.85 1.10 Aliphatic hydroxyls 0.40 0.45 2.05 2.90 (mmol/g of Biolignin)

EXAMPLE 2

(19) TABLE-US-00003 TABLE 3 example of Biolignin of Quantification of functional groups of Biolignin by NMR analysis Aliphatic formylated hydroxyl 0.41 mmol/g of Biolignin Aliphatic acetylated hydroxyl 0.46 mmol/g of Biolignin Total Aliphatic hydroxyl 1.11 mmol/g of Biolignin Total phenolic hydroxyl 1.74 mmol/g of Biolignin

(20) In this second example of Biolognin, the total free phenolic hydroxyls can be distributed in the three units (p-hydroxyphenyl, guaacyl and syringyl) constituting the lignin as follows:

(21) TABLE-US-00004 TABLE 4 Repartition of the phenolic hydroxyls groups in the three monomeric units p- Phenolic Syringyl Guaacyl Hydroxyphenyl hydroxyl unit units units Biolignin 1.74 mmol/g 0.70 mmol/g 0.86 mmol/g 0.18 mmol/g

(22) 1.5 mmol of phenolic hydroxyls of Biolignin or CIMV Lignin allows a degree of substitution of the phenol with lignin equal to about 50% by weight.

(23) Fives resins PF (phenol-formaldehyde resins) and LPF (Lignin-phenol-formaldehyde resins) were synthesized with different phenol substitution contents by lignin (w/w).

(24) The reaction time at 90 C. was set in order to reach a specified viscosity. The higher was the substitution of phenol by Biolignin, the shorter was the reaction time.

(25) The characteristics of four resins LPF1, LPF2, LPF3 and LPF4) and the standard resin (PF1) are shown in the following table. These resins reached the viscosity, dry matter and pH requirements for industrial PF

(26) TABLE-US-00005 TABLE 5 Characteristics of different PF and LPF synthesized from the same formulation with different substitution rate. Reaction substitution time Viscosity P Dry rate (min) pH (25 C.) Matter industrial 11-12 300-800 cP.sup. >45% requirements of an ad- hesive resin PF1 0% 52 min 11.8 3.1 P 47.0% reference LPF1 20% 45 min 11.6 4.2 P 47.3% LPF2 30% 35 min 11.7 4.7 P 47.4% LPF3 50% 15 min 11.4 4.1 P 47.9% LPF4 60% 12 min 11.5 4.8 P 47.1%

(27) Preferably the residual free formaldehyde content of the resins has to be under 0.2% to respect industrial requirements.

(28) The formaldehyde to (phenol+lignin) ratio (F/(P+L)) is between 35 and 60%, preferably between 45 and 50% and optimally 47% for a 50 to 70%, preferably 50 to 60% Biolignin-based resin.

(29) Table 6 presents the characteristics of 50% substituted LPF synthesized with different formaldehyde to phenol and lignin ratio. The reaction time was fixed at 15 min. Each one of the six LPF resins reaches the standard resin requirements in terms of pH and viscosity. Moreover, with initial formaldehyde to phenol and Lignin ratio between 35 and 60%, the substituted resins present characteristics which are closed to all industrial requirements.

(30) TABLE-US-00006 TABLE 6 Evolution of residual formaldehyde according initial mass ratio formaldehyde/(Phenol + Lignin) Initial F/(P + L) Viscosity Residual (w/w) pH (25 C.) formaldehyde LPF 5 79.8% 11.7 2.5 P 8.1% LPF 3 64.0% 11.4 4.1 P 4.4% LPF 6 56.6% 11.6 3.2 P 2.7% LPF 7 49.7% 11.5 4.1 P 1.1% LPF 8 47.1% 11.5 5.2 P 0.5% LPF 9 39.9% 11.7 5.5 P 0.2%

(31) By way of example, the characteristics of an optimized LPF resin (LPF 10) according to the invention with a degree of substitution of 50% by weight and a formaldehyde to (phenol+lignin) ratio of 47% are as follows:

(32) TABLE-US-00007 TABLE 7 Characteristics of an optimized LPF resin (LPF 10) residual substitution F/ reaction Dry Viscosity formal- content (P + L) time matter (25 C.) pH dehyde 50% 47% 21 min 48.10% 3.4 P 11.9 0.18%

(33) By way of example, the composition, expressed on a weight basis, of an LPF resin according to the invention with a degree of substitution of 50% by weight is as follows:

(34) TABLE-US-00008 TABLE 8 Formulation of an example of LPF resin Water Urea Phenol Biolignin NaOH Formaldehyde 48% 2.7% 12.1% 12.1% 7.3% 17.2%

(35) The LPF resins according to the invention based on Biolignin or CIMV Lignin have the same thermomechanical profile as a PF industrial resin (reference).

(36) Thus, as non-limiting examples of such a composition:

(37) TABLE-US-00009 TABLE 9 Comparative tests performed on wood panels by means of resin according to the invention Reference Biolignin/phenol Resin PF 60%/40% LPF 10 Maximum 1500 1314 1720 Young's modulus (MPa) Temperature 139 150 143 ( C.)

(38) Comparative tests performed on wood panels (particle boards) by means of a resin according to the invention reveal results, characteristics and performance qualities at least equal to those obtained with a standard industrial adhesive/PF resin.

(39) By way of non-limiting example, the optimized LPF 10 resin was tested in particle board manufacturing. Panels have been characterized and compared with industrial requirements. Results are as follow in Table 10. The mechanical properties of the panels obtained reach the industrial requirements for particle boards, especially in terms of traction, flexion and module.

(40) TABLE-US-00010 TABLE 10 Biolignin based particle boards characteristics compared with industrials requirements % pressing traction Flexion dry temperature Den- (N/ (N/ Module resin ( C.) sity mm.sup.2) mm.sup.2) (MPa) LPF10 9% 190 C. 681 0.39 13.8 2337 Require- 0.3 13 2050 ments