Liquid lignin composition, lignin-based resin, and method of increasing the solubility of lignin

Abstract

The present invention relates to a liquid lignin mixture comprising 3-50 wt % methanol, 12-50 wt % lignin and 5-85 wt % aqueous alkali solution wherein the concentration of said aqueous alkali solution is 1 to 50 wt % of alkali in water, based on the weight of said alkali solution prior to mixing with the other components of the mixture. The liquid lignin mixture can be used to manufacture lignin-based phenolic resins, which are particularly useful in the manufacture of laminates.

Claims

1. A mixture comprising 3-50 wt % methanol, 12-50 wt % lignin and 5-85 wt % aqueous alkali solution, wherein the concentration of said aqueous alkali solution is 1 to 50 wt % of alkali in water, based on the weight of said alkali solution prior to mixing with the other components of the mixture.

2. A mixture according to claim 1, comprising 40-50 wt % aqueous alkali solution.

3. A mixture according to claim 1, comprising 35-50 wt % lignin.

4. A mixture according to claim 3, comprising 40-50 wt % lignin.

5. A mixture according to claim 1, wherein the alkali is sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide or a mixture thereof.

6. A mixture according to claim 1, comprising 3-30 wt % methanol.

7. A mixture according to claim 6, comprising 3-12 wt % methanol.

8. A mixture according to claim 1, wherein said mixture has been heated at a temperature of 30-95 C.

9. A resin obtainable by adding phenol and formaldehyde to a mixture according to claim 1 and heating at a temperature of 70-90 C. for 2-8 hours.

10. A laminate manufactured using a resin according to claim 9.

Description

EXAMPLES

Example 1

(1) To a mixture of methanol, water and an aqueous sodium hydroxide solution (concentration: 50 wt % of NaOH in water), was added kraft lignin. The mixture was stirred for approximately 5 minutes and subsequently heated in an oven at 55 C. for 1-21 hours. The viscosities of lignin solutions were measured at 25 C. using a Brookfield DV-II+LV viscometer. Viscosity values are illustrated in Table 1.

(2) TABLE-US-00001 TABLE 1 Aq sol NaOH, Lignin Methanol 50 wt % Viscosity [wt %] [wt %] [wt %] H.sub.2O [cP] 35 0 16 49 254 35 10 16 39 103 37.5 0 16 46.5 758.8 37.5 10 16 36.5 501.5 40 0 16 44 1993 40 10 16 34 1108

Example 2

(3) Phenolic resin was synthesized with a phenol replacement level of 25%. In the first step, lignin solution was prepared by mixing of 105 g of kraft lignin (solid content 95%), 160 g of water, 31.2 g of methanol and 23.2 g of 50% sodium hydroxide solution in a 1 liter glass reactor equipped with overhead stirrer, condenser and temperature control unit. Lignin solution was heated to 80 C. and continued heating at 80 C. for one hour. Then, the temperature of the lignin solution was decreased to 45 C.

(4) In the second step, 304 g of phenol and 271.6 g of formalin (concentration 52.5%) were added to the lignin solution. The temperature was increased to 85 C. The reaction was monitored by measuring the viscosity using the Brookfield DV-II+LV viscometer. The reaction mixture was continuously heated at the temperature at 85 C. until the viscosity was about 106 cP at 25 C.

(5) The resin was analyzed and the results of the analysis are given in Table 2.

(6) TABLE-US-00002 TABLE 2 Resin Properties S.C (%) 57.2 Visc. (cP) 106 @25 C. pH 9.0 Gel time (min) 76 @100 C.

(7) The gel time was measured by adding 10 g of the resin in a glass tube with a stamper made of aluminium. The glass tube was heated at 100 C. in an oil bath. The stamper was moving up and down until the resin became gel. The time until the resin become gel was measured as gel time.

(8) It can be seen in the Table 2 that the solid content, pH, viscosity and gel time of the resin is on a suitable level for the phenolic resin used for laminates.

(9) In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.