JPS6162574A - Lignin adhesive composition - Google Patents

Abstract

PURPOSE:The titled composition for wood, etc., comprising lignin as an adhesive base, not using formaldehyde, wherein lignin extracted from wood is acidified by ion exchange treatment, etc., and cured by oxidation reaction. CONSTITUTION:Lignin extracted from wood (e.g., ligninsulfonate, thiolignin, etc.) is acidified by ion exchange treatment, or membrane permeation treatment. Then it is directly cured by oxidation reaction, or it is mixed with an oxidizing agent, and, if necessary, a water resistance imparting substance and cured by oxidation reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition characterized by curing water-extracted lignin through an oxidative reaction.

Today, urea formaldehyde resin and melamine formaldehyde, which are used as wood adhesives, all rely on petroleum resources for their raw materials.
For this reason, there are concerns about its future in terms of depletion of petroleum resources or international instability in supply and demand, and the conversion of adhesive raw materials to reproducible natural resources other than petroleum has become an important issue.

For this reason, research has recently begun on adhesives that use wood-extracted lignin, which is a natural phenol that can be collected from plants. Since it is a resin, it is no more than an imitation of the current synthetic resin adhesive, and the possibility of formaldehyde emission from adhesive products, which has become a social issue in recent years, remains as a drawback, and its performance is not good enough. It has not gone beyond the level of quality.

From this perspective, the present inventors have conducted intensive studies on an adhesive composition that uses lignin obtained from water conservancy as an adhesive base, and that cures the lignin through an oxidative reaction without using formaldehyde, and has developed the present invention. completed.

As the wood-extracted lignin in the present invention, any known wood-extracted lignin can be used without being limited to the tree species or extraction method from which it is extracted, as long as it is water-soluble lignin. For example, lignin sulfonate contained in sulfide pulp wastewater, thiolignin contained in kraft pulp black liquor and its sulfonated products, and other water-soluble lignins obtained by decomposition and extraction of wood can all be used.

Acidic groups such as phenolic hydroxyl groups that exist in naturally occurring lignin, or acidic groups such as sulfone groups and carboxyl groups introduced into the lignin of wood components when wood is extracted or treated with an aqueous solution containing sulfites, are ionized. It is made into a free state (hydrogen form) by membrane permeation treatment such as exchange treatment, dialysis, and ultrafiltration, and then heated as it is or by adding an oxidizing agent in an amount of 2.0 to 0.005 oxidation equivalents per 100.9 of the lignin solid content. Then, it hardens through an oxidative reaction,
The adhesive composition has water resistance.

The oxidizing agents used at this time include hydrogen peroxide, hydrogen peroxide and ferrous sulfate, hydrogen peroxide and copper sulfate, hydrogen peroxide and potassium ferrocyanide, hydrogen peroxide and potassium ferricyanide,
Examples include ammonium persulfate, ammonium persulfate and ferrous sulfate, ammonium persulfate and copper sulfate, potassium or sodium dichromate salt, potassium or sodium dichromate salt and manganese sulfate, and sodium hypochlorite. The amount of oxidizing agent used is lignin solid content 1009 a
92.0 to 0.005 oxidation equivalent, preferably 1
．． 2 to 0.01 oxidation equivalent.

After acidic groups such as phenolic hydroxyl groups, carboxyl groups, or sulfonic groups are made into a free state (hydrogen form) by a pretreatment operation such as ion exchange, or these acidic groups are converted into sodium salts, carmine salts, ammonium salts, etc. In the case of the salt type, lignin is made acidic by adding 15 to 150 mmol of acid such as sulfuric acid or nitric acid per 100 g of lignin, and then an insoluble crosslinked polymer gel is produced by reaction with an acid or an oxidizing agent. Additives such as polyvinyl alcohol and furfuryl alcohol are added to the wood extracted lignin in an amount of 1 to 30 g (wt%) and heated.
When cured by an oxidative reaction, the water resistance of the cured product is significantly improved.

As a pretreatment for wood-extracted lignin, molecular weight fractionation such as dialysis, ultrafiltration, or fractional precipitation is performed to reduce the molecular weight to 50.
When the low molecular weight segment of 0 to 20,000 or less is removed, the resin is more easily cured by oxidative reaction than the case where the low molecular weight segment is not removed, and the water resistance of the cured product is also improved.

Next, the present invention will be explained in more detail by showing examples.

Example 1 Rig°72/l/ ;t″′′ contained in acid salt
) The waste pulp waste liquid is cation-exchanged using a cation-exchange resin (An-(-Lai) IR12OB) to make acidic groups such as sulfone groups free (hydrogen form), and a solution with a solid content concentration of 50% is prepared. was prepared. This solution was used as it was (Experiment 1), or as an oxidizing agent, 15% of hydrogen peroxide and 0.01% of ferrous sulfate (each % by weight based on the solid content of the drained liquid) were added as an adhesive solution (Experiment 2). And so. Flake-like particles made from cedar wood were sprayed with 15% (solid weight %) of these adhesive liquids, then molded and heat-pressed at 150°C for 7 minutes to produce particle boards. The strength properties were measured according to JIS A 5908 after curing for 7 days or more. 1 shows the case where it was used as an adhesive liquid.In addition, in Control 2, a solution made by adding 55 mmol of sulfuric acid per 100 g of solid content to the sulfide pulp waste liquid to make it acidic (PH 1, 2) was used as an adhesive liquid as it was. The case is shown in which Experiments 1 and 2 of the invention are superior to Controls 1 and 2, especially in terms of water resistance.

Example 2 Cation exchange was performed using a cation exchange resin (Amberlite I-120B) to convert acidic groups such as sulfone groups into free forms (hydrogen forms) to produce sulfide pulp wastewater with a solid content concentration of 50%. , polyvinyl alcohol (molecular weight 500
Adhesive liquid (experiment 1) to which 10% (added as an aqueous solution) (weight % of additive to solid content) was added, or solid content concentration 50 to which 50 mmol of sulfuric acid was added per 100 g of solid content of sulfide pulp effluent. Adhesive liquids (Experiment 2) were prepared by adding 10% (% based on solid content) of furfuryl alcohol to the sulfide pulp waste liquid (Experiment 2). Additionally, 15% hydrogen peroxide and 0.2% ferrous sulfate (each relative to the solid content) were added to the adhesive solution prepared in the same manner as in Experiments 1 and 2. 3. Experiment 4) was prepared. Particle boards were manufactured using these adhesive liquids in the same manner as in Example 1, and their properties were investigated. The results are shown in Table 2. The properties of the board are further improved when the oxidizing agent and additives are used together.

Example 3j Dialysis using a cellophane tube or ultrafiltration using a membrane filter with a cutoff molecular weight of 500 to remove low molecular weight fractions was followed by cation exchange or cation exchange in the same manner as in Example 2. Sulfuric acid was added to prepare a sulfide pulp effluent with a solid content concentration of 50%.

To these solutions, 10% polyvinyl alcohol or furfuryl alcohol was added as an additive as shown in Table 3.
(Weight % based on the solid content of the effluent) Added as is or as an oxidizing agent: 15% hydrogen peroxide and 0.05% ferrous sulfate (each % by weight based on the solid content of the effluent)
Each of the added adhesive liquids was prepared. Particle boards were manufactured in the same manner as in Example 1 using the adhesive liquids shown in Table 3, and their properties were investigated.

The results are shown in Table 4. In addition, the values shown as a control are
These are the properties of a board manufactured from the same cedar wood particles as in the example using an area resin adhesive commercially available for particle boards.

All of the examples of the present invention exhibited superior adhesion performance compared to this control example.

Table 4

Claims (3)

[Claims] (1) An adhesive composition in which wood-extracted lignin is made acidic by ion exchange treatment or membrane permeation treatment, and then cured by an oxidative reaction either as is or by adding an oxidizing agent. (2) In the method described in claim 1, an additive that imparts water resistance to the cured product is added to lignin that has been subjected to ion exchange treatment or membrane permeation treatment, or lignin that has been subjected to acid addition treatment. An adhesive composition with improved water resistance that is cured by an oxidative reaction either as it is or by adding an oxidizing agent. (3) In the method according to claims 1 and 2, an adhesive composition in which wood-extracted lignin is subjected to a pretreatment operation to remove low-molecular weight fractions, and then cured by an oxidative reaction.